Patent ID: 12249937

DESCRIPTION OF EMBODIMENTS

An embodiment of a rotating electrical machine control device that controls, through two inverters, drive of a rotating electrical machine having open-end windings of a plurality of phases that are independent of each other will be described below based on the drawings.FIG.1is a schematic block diagram of a rotating electrical machine control system100including a rotating electrical machine control device1(MG-CTRL). A rotating electrical machine80serves as, for example, a drive power source for wheels of a vehicle such as an electric vehicle or a hybrid vehicle. The rotating electrical machine80is an open-end winding type rotating electrical machine having stator coils8(open-end windings) of a plurality of phases (three phases in the present embodiment) that are independent of each other. Inverters10that are controlled independently of each other to convert electric power between direct current and alternating currents of a plurality of phases (here, three phases) each are connected to each end side of the stator coils8. That is, a first inverter11(INV1) is connected to a one-end side of the stator coils8, and a second inverter12(INV2) is connected to an other-end side of the stator coils8. In the following description, when the first inverter11and the second inverter12do not need to be distinguished from each other, the first inverter11and the second inverter12are simply referred to as the inverters10.

The inverters10each are configured to include a plurality of switching elements3. For the switching elements3, insulated gate bipolar transistors (IGBTs) or power metal oxide semiconductor field effect transistors (MOSFETs) are used.FIG.1exemplifies a mode in which IGBTs are used as the switching elements3. In the present embodiment, the first inverter11and the second inverter12are the inverters10of the same circuit configuration that use the same type of switching elements3.

In the two inverters10, each arm3A for one alternating-current phase includes a series circuit of an upper-stage-side switching element3H and a lower-stage-side switching element3L. Each switching element3has a freewheeling diode35provided in parallel thereto, with a direction going from a negative polarity FG to a positive polarity P (a direction going from a lower-stage side to an upper-stage side) being a forward direction. Note that in the arms3A of a plurality of phases, a side that includes the upper-stage-side switching elements3H is referred to as upper-stage-side arms, and a side that includes the lower-stage-side switching elements3L is referred to as lower-stage-side arms.

In addition, in the present embodiment, the two inverters10are connected to direct-current power supplies6that are independent of each other. That is, a first floating ground FG1which is the negative polarity FG of the first inverter11and a second floating ground FG2which is the negative polarity FG of the second inverter12are independent of each other. In addition, a direct-current link capacitor (smoothing capacitor4) that smooths direct-current voltage is provided between each inverter10and a corresponding direct-current power supply6. In addition, between the positive and negative polarities on the direct-current side of each inverter10there is provided a discharge resistor40in parallel to a smoothing capacitor4.

Specifically, a first smoothing capacitor41is connected to a direct-current side of the first inverter11in which an arm3A for one alternating-current phase includes a series circuit of a first upper-stage-side switching element31H and a first lower-stage-side switching element31L, and the first inverter11is connected on its direct-current side to a first direct-current power supply61and connected on its alternating-current side to the one-end side of the stator coils8of a plurality of phases, to convert electric power between direct current and alternating currents of a plurality of phases. A second smoothing capacitor42is connected to a direct-current side of the second inverter12in which an arm3A for one alternating-current phase includes a series circuit of a second upper-stage-side switching element32H and a second lower-stage-side switching element32L, and the second inverter12is connected on its direct-current side to a second direct-current power supply62and connected on its alternating-current side to the other-end side of the stator coils8of a plurality of phases, to convert electric power between direct current and alternating currents of a plurality of phases.

In the present embodiment, the first direct-current power supply61and the second direct-current power supply62are direct-current power supplies having equal ratings of voltage, etc., and the first smoothing capacitor41and the second smoothing capacitor are capacitors having equal ratings of capacitance, etc. The rated voltage of the direct-current power supplies6is about 48 volts to 400 volts. The direct-current power supplies6include, for example, secondary batteries (batteries) such as nickel-hydrogen batteries or lithium-ion batteries, or electric energy storage devices such as electric double-layer capacitors. The rotating electrical machine80can function as both an electric motor and a generator. The rotating electrical machine80converts electric power from the direct-current power supplies6into mechanical power through the inverters10(powering). Alternatively, the rotating electrical machine80converts rotary drive power transmitted from the wheels, etc., into electric power to charge the direct-current power supplies6through the inverters10(regeneration).

As shown inFIG.1, the inverters10are controlled by the rotating electrical machine control device1(control part). The rotating electrical machine control device1can control the first inverter11and the second inverter12using control schemes that are independent of each other (details of the control schemes will be described later). The rotating electrical machine control device1is constructed using a logic circuit such as a microcomputer, as a core member. For example, the rotating electrical machine control device1controls the rotating electrical machine80through the inverters10by performing current feedback control that uses a vector control method, based on target torque (torque instruction) of the rotating electrical machine80that is provided from other control devices, etc., such as a vehicle control device which is not shown.

Between the direct-current power supply6, and the inverter10and the smoothing capacitor4there is provided a contactor9that establishes and cuts off an electrical connection therebetween. Specifically, a first contactor91is provided between the first inverter11and the first smoothing capacitor41, and the first direct-current power supply61, and a second contactor92is provided between the second inverter12and the second smoothing capacitor42, and the second direct-current power supply62. The contactor9is controlled by the above-described vehicle control device which is not shown or the rotating electrical machine control device1to electrically connect the direct-current power supply6to the inverter10and the smoothing capacitor4in a closed state (CLOSE) of the contactor9, and to cut off the electrical connection therebetween in an open state (OPEN) of the contactor9. The contactor9includes, for example, a relay.

An actual current flowing through a stator coil8of each phase of the rotating electrical machine80is detected by a current sensor15, and a magnetic pole position at each time point of a rotor of the rotating electrical machine80is detected by a rotation sensor13such as a resolver. The rotating electrical machine control device1performs current feedback control using results of detection by the current sensor15and the rotation sensor13. The rotating electrical machine control device1is configured to include various functional parts to perform current feedback control, and each functional part is implemented by cooperation of hardware such as a microcomputer and software (program). In addition, a direct-current link voltage Vdc which is a voltage on the direct-current side of each inverter10is detected by a voltage sensor which is not shown, and can be obtained by the rotating electrical machine control device1. The rotating electrical machine control device1obtains a first direct-current link voltage Vdc1which is a voltage on the direct-current side of the first inverter11and a second direct-current link voltage Vdc2which is a voltage on the direct-current side of the second inverter12.

A block diagram ofFIG.2shows some functional parts of the rotating electrical machine control device1in a simplified manner. In a vector control method, feedback control is performed by coordinate-transforming actual currents (a U-phase current Iu, a V-phase current Iv, and a W-phase current Iw) flowing through the rotating electrical machine80into vector components (a d-axis current Id and a q-axis current Iq) on a d-axis indicating a direction of a magnetic field (magnetic flux) generated by permanent magnets disposed in the rotor of the rotating electrical machine80and on a q-axis indicating a direction orthogonal to the d-axis (a direction advanced by an electrical angle of π/2 relative to the direction of the magnetic field). In the rotating electrical machine control device1, a three-to-two phase coordinate-transforming part55performs coordinate transformation, based on a result of detection (θ: a magnetic pole position and an electrical angle) by the rotation sensor13.

A current feedback control part5(FB) performs feedback control on the rotating electrical machine80based on deviation between current instructions (a d-axis current instruction Id* and a q-axis current instruction Iq*) issued based on a torque instruction for the rotating electrical machine80and the actual currents (the d-axis current Id and the q-axis current Iq) in a d-q-axis orthogonal vector coordinate system, thereby computing voltage instructions (a d-axis voltage instruction Vd* and a q-axis voltage instruction Vq*). The rotating electrical machine80is driven through the two inverters10, the first inverter11and the second inverter12. Hence, the d-axis voltage instruction Vd* and the q-axis voltage instruction Vq* are divided, by a dividing part53(DIV), into a first d-axis voltage instruction Vd1* and a first q-axis voltage instruction Vq1* for the first inverter11and a second d-axis voltage instruction Vd2* and a second q-axis voltage instruction Vq2* for the second inverter12.

As described above, the rotating electrical machine control device1can control the first inverter11and the second inverter12using control schemes that are independent of each other, and includes two voltage control parts7each including a three-phase voltage instruction computing part73and a modulating part74(MOD). Namely, the rotating electrical machine control device1includes a first voltage control part71that generates switching control signals (Su1, Sv1, and Sw1) for the respective U-phase, V-phase, and W-phase of the first inverter11; and a second voltage control part72that generates switching control signals (Su2, Sv2, and Sw2) for the respective U-phase, V-phase, and W-phase of the second inverter12. Though details will be described later, voltage instructions (Vu1**, Vv1**, and Vw1**) for the first inverter11and voltage instructions (Vu2**, Vv2**, and Vw2**) for the second inverter12differ from each other in phase by “π”. Hence, a value obtained by subtracting “n” from a result of detection (θ) by the rotation sensor13is inputted to the second voltage control part72.

Note that as will be described later, modulation schemes include synchronous modulation that is synchronized with rotation of the rotating electrical machine80; and asynchronous modulation that is independent of rotation of the rotating electrical machine80. In general, a generation block (a generation flow in a case of software) for switching control signals by synchronous modulation differs from a generation block for switching control signals by asynchronous modulation. The above-described voltage control parts7generate switching control signals based on voltage instructions and a carrier that is not synchronized with rotation of the rotating electrical machine80, but in the present embodiment, for simplification of description, description will be made assuming that switching control signals by synchronous modulation (e.g., switching control signals for a case of rectangular-wave control which will be described later) are also generated by the voltage control parts7.

Note that as described above, each arm3A of the inverters10includes a series circuit of an upper-stage-side switching element3H and a lower-stage-side switching element3L. Though not distinguished inFIG.2, a switching control signal for each phase is outputted as two types of control signals, an upper-stage switching control signal and a lower-stage switching control signal. For example, a first U-phase switching control signal Su1for performing switching control on the U-phase of the first inverter11is outputted as two signals, a first U-phase upper-stage-side switching control signal Su1+ which is added with “+” at the end and a first U-phase lower-stage-side switching control signal Su1− which is added with “−” at the end. Note that when an upper-stage-side switching element3H and a lower-stage-side switching element3L that are included in an arm3A simultaneously go into on state, the arm3A goes into a short-circuited state. To prevent this short circuit, there is provided dead time during which both an upper-stage-side switching control signal and a lower-stage-side switching control signal for each arm3A go into an inactive state. The dead time is also added by the voltage control parts7.

As shown inFIG.1, a control terminal (a gate terminal in a case of an IGBT or a FET) of each switching element3included in the inverters10is connected to the rotating electrical machine control device1through a corresponding drive circuit2(DRV), and switching control is individually performed on the switching elements3. High-voltage system circuits (systems connected to the direct-current power supplies6) for driving the rotating electrical machine80, such as the inverters10, and low-voltage system circuits (systems with an operating voltage of about 3.3 volts to 5 volts) such as the rotating electrical machine control device1that uses a microcomputer, etc., as a core greatly differ from each other in operating voltage (the power supply voltage of the circuits). The drive circuits2increase each of drive capabilities (e.g., capabilities to allow a circuit at a subsequent stage to operate, such as voltage amplitude and output current) of a drive signal (switching control signal) for each switching element3, and relay the drive signal. A first drive circuit21relays switching control signals to the first inverter11, and a second drive circuit22relays switching control signals to the second inverter12.

As switching pattern modes (modes of voltage waveform control) of the switching elements3included in the first inverter11and the second inverter12, the rotating electrical machine control device1can perform, for example, two types of control, pulse width modulation (PWM) control in which a plurality of pulses with different patterns are outputted in one cycle of electrical angle, and rectangular-wave control (single-pulse control (1-Pulse)) in which one pulse is outputted in one cycle of electrical angle. Namely, the rotating electrical machine control device1can perform pulse width modulation control and rectangular-wave control as control schemes for the first inverter11and the second inverter12. Note that as described above, the rotating electrical machine control device1can control the first inverter11and the second inverter12using control schemes that are independent of each other.

In addition, pulse width modulation has schemes such as continuous pulse width modulation (CPWM: continuous PWM), e.g., sinusoidal pulse width modulation (SPWM: sinusoidal PWM) and space vector pulse width modulation (SVPWM: space vector PWM), and discontinuous pulse width modulation (DPWM: discontinuous PWM). Thus, the pulse width modulation control that can be performed by the rotating electrical machine control device1includes, as control schemes, continuous pulse width modulation control and discontinuous pulse width modulation.

The continuous pulse width modulation is a modulation scheme in which pulse width modulation is continuously performed for all arms3A of a plurality of phases, and the discontinuous pulse width modulation is a modulation scheme in which pulse width modulation is performed including a period during which switching elements in an arm(s)3A of one or more of the plurality of phases are fixed to on state or off state. Specifically, in the discontinuous pulse width modulation, for example, the signal levels of switching control signals for an inverter that correspond to one phase out of three-phase alternating-current electric power are sequentially fixed, and the signal levels of switching control signals corresponding to the other two phases are changed. In the continuous pulse width modulation, all phases are modulated without thus fixing switching control signals corresponding to any of the phases. These modulation schemes are determined based on operating conditions such as rotational speed and torque that are required for the rotating electrical machine80, and a modulation index (a ratio of the root-mean-square value of line-to-line three-phase alternating-current voltages to a direct-current voltage) required to satisfy the operating conditions.

In the pulse width modulation, pulses are generated based on a magnitude relationship between the amplitude of an alternating-current waveform which is a voltage instruction and the amplitude of a waveform of a triangle wave (including a sawtooth wave) carrier (CA) (seeFIGS.5to10). There is also a case in which a PWM waveform is directly generated by digital computation instead of comparison with the carrier, but even in that case, the amplitude of an alternating-current waveform which is an instruction value and the amplitude of a virtual carrier waveform have a correlation.

In pulse width modulation by digital computation, a carrier is determined based on a control cycle of the rotating electrical machine control device1, e.g., a computation cycle of the microcomputer or a duty cycle of an electronic circuit. That is, even when alternating-current electric power of a plurality of phases is used to drive the alternating-current rotating electrical machine80, a carrier has a cycle that is not constrained by (a cycle that is not synchronized with) the rotational speed or rotational angle (electrical angle) of the rotating electrical machine80. Thus, neither the carrier nor each pulse generated based on the carrier is synchronized with the rotation of the rotating electrical machine80. Thus, modulation schemes such as sinusoidal pulse width modulation and space vector pulse width modulation may be referred to as asynchronous modulation. On the other hand, a modulation scheme in which pulses are generated in synchronization with the rotation of the rotating electrical machine80is referred to as synchronous modulation. For example, in rectangular-wave control (rectangular-wave modulation), one pulse is outputted per electrical angle cycle of the rotating electrical machine80, and thus, the rectangular-wave modulation is synchronous modulation.

As described above, as an index indicating a conversion rate from direct-current voltage to alternating-current voltage, there is a modulation index indicating a ratio of the root-mean-square value of line-to-line alternating-current voltages of a plurality of phases to a direct-current voltage. In general, the maximum modulation index for sinusoidal pulse width modulation is about 0.61 (≈0.612) and the maximum modulation index for space vector pulse width modulation control is about 0.71 (≈0.707). A modulation scheme having a modulation index exceeding about 0.71 is considered a modulation scheme whose modulation index is higher than normal, and is referred to as “overmodulation pulse width modulation”. The maximum modulation index for the “overmodulation pulse width modulation” is about 0.78. The value “0.78” is a physical (mathematical) limit value for electric power conversion from direct current to alternating current. In the overmodulation pulse width modulation, when the modulation index reaches 0.78, rectangular-wave modulation (single-pulse modulation) in which one pulse is outputted in one cycle of electrical angle is performed. In the rectangular-wave modulation, the modulation index is fixed to about 0.78 which is a physical limit value. Note that the values of modulation indices exemplified here are physical (mathematical) values that do not take into account dead time.

Overmodulation pulse width modulation whose modulation index is less than 0.78 can be implemented by using a principle of any of a synchronous modulation scheme and an asynchronous modulation scheme. A representative modulation scheme for the overmodulation pulse width modulation is discontinuous pulse width modulation. The discontinuous pulse width modulation can be implemented by using a principle of any of a synchronous modulation scheme and an asynchronous modulation scheme. For example, when the synchronous modulation scheme is used, in rectangular-wave modulation, one pulse is outputted in one cycle of electrical angle, whereas in discontinuous pulse width modulation, a plurality of pulses are outputted in one cycle of electrical angle. When there are a plurality of pulses in one cycle of electrical angle, a pulse active period decreases correspondingly, reducing the modulation index. Thus, not only a modulation index that is fixed to about 0.78, but also any modulation index less than 0.78 can be implemented by the synchronous modulation scheme. For example, it is also possible to perform multi-pulse modulation (Multi-Pulses) such as 9-pulse modulation (9-Pulses) in which nine pulses are outputted in one cycle of electrical angle or 5-pulse modulation (5-Pulses) in which five pulses are outputted in one cycle of electrical angle.

In addition, the rotating electrical machine control device1can perform shutdown control (SDN) or active short-circuit control (ASC) as fail-safe control performed when an abnormality is detected in an inverter10or the rotating electrical machine80. The shutdown control is control in which an inverter10is brought into off state by bringing switching control signals for all switching elements3included in the inverter10into an inactive state. The active short-circuit control is control in which one side, a set of upper-stage-side switching elements3H in arms3A of all of the plurality of phases or a set of lower-stage-side switching elements3L in the arms3A of all of the plurality of phases, is brought into on state and the other side is brought into off state. Note that a case in which the upper-stage-side switching elements3H in the arms3A of all of the plurality of phases are brought into on state and the lower-stage-side switching elements3L in the arms3A of all of the plurality of phases are brought into off state is referred to as upper-stage-side active short-circuit control (ASC-H). Note also that a case in which the lower-stage-side switching elements3L in the arms3A of all of the plurality of phases are brought into on state and the upper-stage-side switching elements3H in the arms3A of all of the plurality of phases are brought into off state is referred to as lower-stage-side active short-circuit control (ASC-L).

As in the present embodiment, in a case in which each inverter10is connected to each end side of the stator coils8, when one inverter10is short-circuited by active short-circuit control, the stator coils8of a plurality of phases are short-circuited in the one inverter10. That is, the one inverter10serves as a neutral point and the stator coils8are Y-connected. Hence, the rotating electrical machine control device1can implement a mode in which the rotating electrical machine control device1controls the open-end winding type rotating electrical machine80through the two inverters10and a mode in which the rotating electrical machine control device1controls the Y-connected rotating electrical machine80through one inverter10(one of the inverters10on which active short-circuit control is not performed).

In addition, when back electromotive force generated by rotation of the rotating electrical machine80is large, even if all switching elements3are controlled to off state by shutdown control, freewheeling diodes35connected in parallel to the switching elements3are turned on. This may result in a case in which an inverter10on which the shutdown control is performed is short-circuited, implementing the Y-connected rotating electrical machine80.

FIG.3exemplifies a vector diagram for one operating point of the rotating electrical machine80in a d-q-axis vector coordinate system. In the drawing, “V1” represents a first voltage vector indicating the voltage of the first inverter11and “V2” represents a second voltage vector indicating the voltage of the second inverter12. Voltage that appears in the stator coils8which are open-end windings through the two inverters10corresponds to the difference “V1-V2” between the first voltage vector V1and the second voltage vector V2. “Va” in the drawing represents a combined voltage vector that appears in the stator coils8. In addition, “Ia” represents current flowing through the stator coils8of the rotating electrical machine80. As shown inFIG.3, when the first inverter11and the second inverter12are controlled such that the vector directions of the first voltage vector V1and the second voltage vector V2differ from each other by 180 degrees, the combined voltage vector Va is a vector obtained by adding the magnitude of the second voltage vector V2to the direction of the first voltage vector V1.

In the present embodiment, a plurality of control regions R based on the operating conditions of the rotating electrical machine80(seeFIG.4) are set, and the rotating electrical machine control device1controls the inverters10using control schemes set for each control region R.FIG.4shows an example of a relationship between the rotational speed and torque of the rotating electrical machine80. For example, as shown inFIG.4, as the control regions R of the rotating electrical machine80, there are set a first speed region VR1, a second speed region VR2in which the rotational speed of the rotating electrical machine80is higher than that in the first speed region VR1with the same torque, and a third speed region VR3in which the rotational speed of the rotating electrical machine80is higher than that in the second speed region VR2with the same torque.

As described above, the rotating electrical machine control device1can control each of the first inverter11and the second inverter12using a plurality of control schemes with different switching patterns. The control schemes include pulse width modulation control (PWM) in which a plurality of pulses with different patterns are outputted in one cycle of electrical angle; and mixed pulse width modulation control (MX-PWM) in which control is performed such that a plurality of pulses with different patterns are outputted during a first period T1(seeFIG.5, etc.) which is a ½ cycle (half cycle) of electrical angle (full cycle) and an inactive state continues during a second period T2(seeFIG.5, etc.) which is the other ½ cycle (half cycle) (described later with reference toFIGS.5to8). In the first speed region VR1and the second speed region VR2, the rotating electrical machine control device1controls both inverters, the first inverter11and the second inverter12, by mixed pulse width modulation control.

The mixed pulse width modulation control (MX-PWM) includes mixed continuous pulse width modulation control (MX-CPWM) and mixed discontinuous pulse width modulation control (MX-DPWM). Though details will be described later, in the mixed continuous pulse width modulation control, during a second period T2, control is performed such that an inactive state continues, and during a first period T1, pulse width modulation is continuously performed for all arms3A of a plurality of phases (described later with reference toFIGS.5and7). Likewise, though details will be described later, in the mixed discontinuous pulse width modulation control, during a second period T2, control is performed such that an inactive state continues, and during a first period T1, pulse width modulation is performed including a period during which switching elements3in an arm(s)3A of one or more of the plurality of phases are fixed to on state or off state (described later with reference toFIGS.6and8).

In the mixed pulse width modulation control, since switching control signals are in an inactive state during the second period T2, too, loss in the inverters10decreases, and harmonic current resulting from switching also decreases, also reducing loss (iron loss) in the rotating electrical machine80. That is, by performing the mixed pulse width modulation control, system loss can be reduced.

For example, as shown in the following table 1, in the first speed region VR1, the rotating electrical machine control device1controls both inverters10, the first inverter11and the second inverter12, by mixed continuous pulse width modulation control (MX-CPWM) which will be described later. In addition, in the second speed region VR2, the rotating electrical machine control device1controls both inverters10, the first inverter11and the second inverter12, by mixed discontinuous pulse width modulation control (MX-DPWM) which will be described later. In addition, in the third speed region VR3, the rotating electrical machine control device1controls both inverters10, the first inverter11and the second inverter12, by rectangular-wave control. Mi_sys, Mi_inv1, and Mi_inv2in the table will be described later.

TABLE 1RMi_sysINV1Mi_inv1INV2Mi_inv2VR1M < aMX-CPWMM < aMX-CPWMM < aVR2a ≤ M <MX - PWMa ≤ M <MX - DPWMa ≤ M <0.780.780.78VR3M = 0.781 - PulseM = 0.781 - PulseM = 0.78

It is preferred that boundaries between the control regions R (boundaries between the first speed region VR1, the second speed region VR2, and the third speed region VR3) be set based on at least either one of the rotational speed of the rotating electrical machine80based on the torque of the rotating electrical machine80and a ratio of the root-mean-square value of line-to-line alternating-current voltages of a plurality of phases to a direct-current voltage (which may be an instruction value or may be an equivalent from an output voltage).

As exemplified inFIG.4, the operating conditions of the rotating electrical machine80are often defined by a relationship between rotational speed and torque. The control regions R may be set based on rotational speed which is one parameter. Here, the rotational speed that defines boundaries between the control regions R can be set to be constant regardless of torque, but it is further preferred that the rotational speed that defines boundaries between the control regions R be set to a value that varies depending on the torque. By doing so, drive of the rotating electrical machine80can be controlled with high efficiency, based on the operating conditions of the rotating electrical machine80.

In addition, for example, when the rotating electrical machine80requires high output (high rotational speed or high torque), a voltage-type inverter implements the requirement by increasing direct-current voltage or increasing a rate at which direct-current voltage is converted into alternating-current voltage. When direct-current voltage is constant, by increasing a rate at which the direct-current voltage is converted into alternating-current voltage, the requirement can be implemented. The rate can be represented as a ratio of the root-mean-square value of three-phase alternating-current electric power to direct-current electric power (in a case of a voltage-type inverter, it is equivalent to a ratio of the root-mean-square value of three-phase alternating-current voltages to a direct-current voltage). As described above, control schemes for controlling the inverters10include various schemes from a scheme in which the ratio is low to a scheme in which the ratio is high.

As shown in table 1, when the control regions R are set based on the ratio of the root-mean-square value of three-phase alternating-current electric power to direct-current electric power (modulation index) which is determined based on a requirement for the rotating electrical machine80, drive of the rotating electrical machine80can be controlled with high efficiency, based on the operating conditions of the rotating electrical machine80. Note that in the table, “Vi_inv1” represents the modulation index of the first inverter11, “Mi_inv2” represents the modulation index of the second inverter12, and “Mi_sys” represents the modulation index of the entire system.

The above-described table 1 exemplifies modulation indices for each control region R. In the present embodiment, a terminal-to-terminal voltage “E1” of the first direct-current power supply61and a terminal-to-terminal voltage “E2” of the second direct-current power supply62are identical (both are voltages “E”). When the root-mean-square value on the alternating-current side of the first inverter11is “Va_inv1” and the root-mean-square value on the alternating-current side of the second inverter12is “Va_inv2”, the modulation index “Mi_inv1” of the first inverter11and the modulation index “Mi_inv2” of the second inverter12are as shown in the following equations (1) and (2). In addition, the modulation index “Mi_sys” of the entire system is as shown in the following equation (3).
Mi_inv1=Va_inv1/E1=Va_inv1/E(1)
Mi_inv2=Va_inv2/E2=Va_inv2/E(2)
Mi_sys=(Va_inv1+Va_inv2)/(E1+E2)=(Va_inv1+Va_inv2)/2E(3)

For the instantaneous value of voltage, an instantaneous vector needs to be considered, but when only the modulation index is simply considered, the modulation index “Mi_sys” of the entire system is “(Mi_inv1+Mi_inv2)/2” from equations (1) to (3). Note that table 1 shows, as rated values, modulation indices for each control region R. Hence, upon actual control, taking into account hunting occurring when a control scheme changes between control regions R, etc., modulation indices for each control region R may include an overlapping range.

Note that the modulation index “a” shown in table 1 and the modulation index “b” shown in table 2 which will be described later are set based on a theoretical upper limit value of a modulation index for each modulation scheme, and further taking into account dead time. For example, “a” is about 0.5 to 0.6, and “b” is about 0.25 to 0.3.

Now, with reference toFIGS.5to8, mixed pulse width modulation control (MX-PWM) will be described by showing exemplary waveforms of U-phase voltage instructions (Vu1** and Vu2**) and U-phase upper-stage-side switching control signals (Su1+ and Su2+). Note that depiction of a second U-phase lower-stage-side switching control signal Su2− and the V-phase and the W-phase is omitted.FIGS.5and7show exemplary waveforms for mixed continuous pulse width modulation control (MX-CPWM) andFIGS.6and8show exemplary waveforms for mixed discontinuous pulse width modulation control (MX-DPWM).

FIGS.5and6show examples of a first carrier CA1which is a carrier CA for the first inverter11, a second carrier CA2which is a carrier CA for the second inverter12, a common U-phase voltage instruction Vu** which is a U-phase voltage instruction common to the first inverter11and the second inverter12, a first U-phase upper-stage-side switching control signal Su1+, and a second U-phase upper-stage-side switching control signal Su2+. Depiction of a first U-phase lower-stage-side switching control signal Su1−, a second U-phase lower-stage-side switching control signal Su2−, and the V-phase and the W-phase is omitted (the same also applies to other control schemes).

For example, the first carrier CA1can change between “0.5<CA1<1”, the second carrier CA2can change between “0<CA2<0.5”, and the voltage instruction (V**) can change between “0≤V**≤I”. A carrier CA (the first carrier CA1and the second carrier CA2) is compared with a voltage instruction (V**), and when the voltage instruction is greater than or equal to the carrier CA, a switching control signal is “1”, and when the voltage instruction is less than the carrier CA, the switching control signal is “0”. Comparative logic between the carrier CA and the voltage instruction (V**) is also the same in the following description.

As shown inFIGS.5and6, the amplitudes of the first carrier CA1and the second carrier CA2are half of an amplitude allowed for the voltage instruction (V**). In general pulse width modulation, the amplitude of the carrier CA is equal to an amplitude allowed for a voltage instruction, and the carrier CA for mixed pulse width modulation can be referred to as half carrier. By using such a half carrier, during a first period T1(half cycle) which is a ½ cycle of electrical angle (full cycle), such a half carrier crosses the voltage instruction (V**), and thus, a plurality of pulses with different patterns are outputted as a switching control signal. During a second period T2(half cycle) which is the other ½ cycle, the half carrier does not cross the voltage instruction (V**), and thus, the switching control signal is outputted such that an inactive state continues.

Note that in mixed discontinuous pulse width modulation control, as shown inFIG.6, during the second period T2, too, pulses that are partially in an active state are outputted as a switching control signal. This results from the fact that the modulation index for discontinuous pulse width modulation which serves as the basis is large compared to that for continuous pulse width modulation. Points where the pulses in an active state are outputted during the second period T2are near the center of the amplitude of the voltage instruction (V**) and in the neighborhood of inflection points of the voltage instruction (V**). As shown inFIG.6, it can be said that in the mixed discontinuous pulse width modulation control, too, an inactive state is continuously outputted during the second period T2. In addition, when the second period T2is only a period during which the switching control signal is in an inactive state (a period less than a ½ cycle), and is set to a period in one cycle other than the second period T2(a period greater than or equal to a ½ cycle), mixed pulse width modulation can also be defined as follows. It can also be said that in the mixed pulse width modulation control, control is performed such that a plurality of pulses with different patterns are outputted during the first period T1which is a ½ cycle or more of electrical angle, and an inactive state continues during the second period T2which is the other period of one cycle of electrical angle.

FIGS.7and8exemplify a different mode of mixed continuous pulse width modulation control and mixed discontinuous pulse width modulation control than that inFIGS.5and6. Switching control signals to be generated are the same.FIGS.7and8show examples of a first carrier CA1which is a carrier CA for the first inverter11, a second carrier CA2which is a carrier CA for the second inverter12, a first U-phase voltage instruction Vu1** which is a U-phase voltage instruction for the first inverter11, a second U-phase voltage instruction Vu2** which is a U-phase voltage instruction for the second inverter12, a first U-phase upper-stage-side switching control signal Su1+, and a second U-phase upper-stage-side switching control signal Su2+. For example, the first carrier CA1and the second carrier CA2can change between “0.5<CA1<1” and voltage instructions (V**) can change between “0≤V**≤1”. The first carrier CA1and the second carrier CA2differ from each other in phase by 180 degrees (π). In addition, the first U-phase voltage instruction Vu1** and the second U-phase voltage instruction Vu2** also differ from each other in phase by 180 degrees (π).

As shown inFIGS.7and8, the amplitudes of the first carrier CA1and the second carrier CA2are half of an amplitude allowed for the voltage instructions (V**). Thus, carriers CA in the mode shown inFIGS.7and8each are also a half carrier. By using such a half carrier, during a first period T1which is a ½ cycle (or a ½ cycle or more) of electrical angle, such a half carrier crosses a voltage instruction (V**), and thus, a plurality of pulses with different patterns are outputted as a switching control signal. During a second period T2which is the other period of the cycle, the half carrier does not cross the voltage instruction (V**), and thus, the switching control signal is outputted such that an inactive state continues.

The mode exemplified inFIGS.5and6is a scheme in which modulation is performed using two half carriers and one common reference voltage instruction (V**), and thus can be said to be a double half-carrier and single reference scheme. On the other hand, the mode exemplified inFIGS.7and8is a scheme in which modulation is performed using two half carriers and two voltage instructions (V**), and thus can be said to be a double half-carrier and double reference scheme.

As described above with reference toFIGS.5to8, in the mixed pulse width modulation control, a plurality of pulses are generated based on a half carrier (the first carrier CA1and the second carrier CA2) which is a carrier CA with the ½ wave height of a variable range of an instruction value (a voltage instruction; in the above-described examples, the U-phase voltage instruction (Vu**(Vu**=Vu1**=Vu2**), Vu1**, and Vu2**)), and the instruction value. In the present embodiment, as schemes for the mixed pulse width modulation control, two schemes are exemplified: the double half-carrier and single reference scheme and the double half-carrier and double reference scheme.

In the double half-carrier and single reference scheme, as described with reference toFIGS.5and6, pulses for the first inverter11are generated based on a first half carrier (the first carrier CA1) that is set, as a half carrier, on one of a higher voltage side and a lower voltage side (here, the higher voltage side) than the center of the amplitude of an instruction value (the common U-phase voltage instruction Vu**), and the instruction value (the common U-phase voltage instruction Vu**) common to the first inverter11and the second inverter12. In addition, in this scheme, pulses for the second inverter12are generated based on a second half carrier (the second carrier CA2) that has the same phase as the first half carrier (the first carrier CA1) and that is set on the other one of the higher voltage side and the lower voltage side (here, the lower voltage side) than the center of the amplitude of the instruction value (the common U-phase voltage instruction Vu**), and the instruction value (the common U-phase voltage instruction Vu**).

In the double half-carrier and double reference scheme, as described with reference toFIGS.7and8, pulses for the first inverter11are generated based on a first half carrier (the first carrier CA1) that is set, as a half carrier, on one of a higher voltage side and a lower voltage side (here, the higher voltage side) than the centers of the amplitudes of instruction values (the first U-phase voltage instruction Vu1** and the second U-phase voltage instruction Vu2**), and a first instruction value for the first inverter11(the first U-phase voltage instruction Vu1**). In addition, in this scheme, pulses for the second inverter12are generated based on a second half carrier (the second carrier CA2) that differs in phase by 180 degrees from the first half carrier (the first carrier CA1) and that is set on the same side (the higher voltage side) as the first half carrier (the first carrier CA1), and a second instruction value for the second inverter12(the second U-phase voltage instruction Vu2**) that differs in phase by 180 degrees from the first instruction value (the first U-phase voltage instruction Vu1**).

Note that as will be described later with reference to table 2, in the first speed region VR1and the second speed region VR2, the inverters10may be controlled by pulse width modulation instead of mixed pulse width modulation.FIG.9shows an example of a first U-phase voltage instruction Vu1**, a second U-phase voltage instruction Vu2**, a carrier CA, a first U-phase upper-stage-side switching control signal Su1+, and a second U-phase upper-stage-side switching control signal Su2+ for a case in which in the first speed region VR1, both the first inverter11and the second inverter12are controlled by continuous pulse width modulation control. In addition,FIG.10shows an example of a first U-phase voltage instruction Vu1**, a second U-phase voltage instruction Vu2**, a carrier CA, a first U-phase upper-stage-side switching control signal Su1+, and a second U-phase upper-stage-side switching control signal Su2+ for a case in which in the second speed region VR2, both the first inverter11and the second inverter12are controlled by discontinuous pulse width modulation control.

When switching control is performed on both the first inverter11and the second inverter12, the first U-phase voltage instruction Vu1** and the second U-phase voltage instruction Vu2** have phases different from each other by approximately 180 degrees. For example, the maximum amplitude of U-phase voltage is “(4/3)E” and the maximum amplitude of line-to-line voltage is “2E” (see also the vector diagram ofFIG.3). Note that the first direct-current power supply61and the second direct-current power supply62are independent of each other, and a first voltage E1of the first direct-current power supply61and a second voltage E2of the second direct-current power supply62may have different values. For example, to be precise, the maximum amplitude of U-phase voltage is “((⅔)E1)+(⅔)E2”, but for easy understanding, in this specification, “E1=E2=E”. To the rotating electrical machine80is supplied equal electric power from the two inverters10. At this time, identical voltage instructions (V**) with phases different from each other by 180 degrees (π) are provided to both inverters10.

Meanwhile, when switching control is performed on the inverters10, ripple components superimposed on an alternating-current fundamental may generate noise in an audio frequency band. When the two inverters10are controlled by pulses having different modes, a ripple based on each pulse occurs, which may increase noise in the audio frequency band. Particularly, when the rotational speed of the rotating electrical machine80is low, the possibility of inclusion of the frequency of ripple components (or sideband frequencies thereof) in the audio frequency band increases. It is desirable to appropriately set control schemes for the rotating electrical machine80, i.e., control schemes for the inverters10, based on operating conditions so that both of operation with high system efficiency and a reduction in audible noise can be achieved.

The rotating electrical machine control device1of the present embodiment has, as control modes of the rotating electrical machine80, a loss reduction priority mode (efficiency priority mode) and a noise reduction priority mode in a switchable manner. In the loss reduction priority mode, as described above with reference to table 1, the rotating electrical machine control device1performs switching control on the inverters10using mixed pulse width modulation control. In the noise reduction priority mode, as exemplified in the following table 2, the rotating electrical machine control device1performs switching control on the inverters10using pulse width modulation control.

TABLE 2RMi_sysINV1Mi_inv1INV2Mi_inv2VR1M < bCPWMM < bCPWMM < bVR2-2b ≤ M <DPWMb ≤ M <DPWMb ≤ M <0.780.780.78VR3M = 0.781-PulseM = 0.781-PulseM = 0.78

When switching control is performed on the inverters10, ripple components superimposed on an alternating-current fundamental may generate noise in the audio frequency band. Particularly, when the rotational speed of the rotating electrical machine80is low, the possibility of inclusion of the frequency of ripple components (or sideband frequencies thereof) in the audio frequency band increases. In mixed pulse width modulation, as shown inFIGS.5to8, during a half cycle of electrical angle, the two inverters10are controlled using different modes of pulses, and thus, a ripple based on each pulse occurs, and there is a possibility of increase in noise in the audio frequency band. In the first speed region VR1and the second speed region VR2in which the rotational speed of the rotating electrical machine80is relatively low, sound associated with travel of the vehicle (traveling sound such as sound of tires contacting a road surface) is also small, and thus, when noise outputted from one inverter10to be driven is noise in the audio frequency band, there is a possibility that the noise is likely to be audible to a user.

For example, it is preferred that upon the start of the vehicle or upon deceleration to make a stop, taking into account the fact that noise in the audio frequency band is likely to be audible to the user, the noise reduction priority mode be selected, and upon steady-state driving where the vehicle travels in a steady state, the loss reduction priority mode be selected. Note that these modes may be selected by a user's operation (a setting switch (also including input from a touch panel, etc.)).

In the noise reduction priority mode, in the first speed region VR1and the second speed region VR2in which the rotational speed of the rotating electrical machine80is relatively low, the first inverter11and the second inverter12are controlled by pulse width modulation control instead of mixed pulse width modulation control. In the two inverters10that allow currents to flow through the stator coils8, the phases of the currents differ from each other by substantially 180 degrees, and thus, the phases of the currents including ripple components differ from each other by substantially 180 degrees. Thus, at least some of the ripple components can cancel each other out, enabling a reduction in noise in the audio frequency band.

As described above, the rotating electrical machine80having open-end windings of a plurality of phases that are independent of each other is appropriately controlled by the rotating electrical machine control device1that can control the first inverter11and the second inverter12independently of each other. Meanwhile, as described above, in the rotating electrical machine control system100, between a direct-current power supply6connected to each inverter10, and the inverter10and a smoothing capacitor4there is provided a contactor9such as a relay for establishing and cutting off an electrical connected between the direct-current power supply6, and the inverter10and the smoothing capacitor4. If the contactor9goes into a state of cutting off an electrical connection (a state in which an open failure has occurred) due to a failure, etc., with the rotating electrical machine80rotating, then supply of electric power from the direct-current power supply6to the inverter10may be interrupted, or a terminal-to-terminal voltage of the smoothing capacitor4may rise because back electromotive force of the rotating electrical machine80cannot be regenerated to the direct-current power supply6.

As described above, the rotating electrical machine control device1can control the first inverter11and the second inverter12independently of each other, and if, for example, an open failure has occurred in either one of the contactors9, then the rotating electrical machine control device1cannot control the rotating electrical machine80by performing switching control on an inverter10connected to the contactor9having the failure. However, as described above, by performing active short-circuit control on one of the inverters10, the inverter10is short-circuited, creating a neutral point of the stator coils8, by which as a rotating electrical machine having the Y-connected stator coils8, drive of the rotating electrical machine80can be controlled (single-inverter torque control mode). To do so, it is desirable to identify a contactor9having a failure, and to ease, at an early stage, a transitional state occurring due to occurrence of the failure to appropriately perform a single-inverter torque control mode.

In the rotating electrical machine control system100of the present embodiment, the rotating electrical machine control device1identifies a contactor9having a failure, and appropriately performs fail-safe control according to a control state, etc., at the time based on the failure of the contactor9. Here, the fail-safe control refers to control in which a transitional state occurring due to occurrence of an open failure in a contactor9is eased at an early stage to appropriately perform a single-inverter torque control mode.

As described above, the rotating electrical machine control system100that controls drive of the rotating electrical machine80having open-end windings (the stator coils8) of a plurality of phases that are independent of each other includes the first inverter11connected to the one-end side of the open-end windings: the second inverter12connected to the other-end side of the open-end windings; the first direct-current power supply61to which the first inverter11is connected; the second direct-current power supply62to which the second inverter12is connected; the first smoothing capacitor41connected in parallel to the first direct-current power supply61; the second smoothing capacitor42connected in parallel to the second direct-current power supply62; the first contactor91that establishes and cuts off an electrical connection between the first inverter11and the first smoothing capacitor41, and the first direct-current power supply61; the second contactor92that establishes and cuts off an electrical connection between the second inverter12and the second smoothing capacitor42, and the second direct-current power supply62; and the rotating electrical machine control device1(control part) that controls each of the first contactor91and the second contactor92and can control the first inverter11and the second inverter12independently of each other.

Though details will be described later with reference toFIGS.11to23, when a voltage (first direct-current link voltage Vdc1) at both ends of the first smoothing capacitor41is higher than a first upper limit voltage VrefH1or lower than a first lower limit voltage VrefL1and a current (first battery current Ib1) flowing through the first direct-current power supply61is less than or equal to a predefined first lower limit current Iref1, the rotating electrical machine control device1determines that the first contactor91is in an open state. In addition, when a voltage (second direct-current link voltage Vdc2) at both ends of the second smoothing capacitor42is higher than a second upper limit voltage VrefH2or lower than a second lower limit voltage VrefL2and a current (second battery current Ib2) flowing through the second direct-current power supply62is less than or equal to a predefined second lower limit current Iref2, the rotating electrical machine control device1determines that the second contactor92is in an open state. Here, these determination processes are referred to as contactor open determination processes. In addition, one of the contactors9, the first contactor91or the second contactor92, that is determined to be in an open state in a contactor open determination process is considered a failed contactor, and the other contactor9is considered a normal contactor.

Note that the first upper limit voltage VrefH1is set to a value larger than a voltage fluctuation range of the first direct-current power supply61. For example, when the rated voltage of the first direct-current power supply61is 300 [V] and a voltage fluctuation of ±25% is allowed, the voltage fluctuation range is 220 [V] to 380 [V]. Thus, the first upper limit voltage VrefH1is set to, for example, 400 [V]. The first lower limit voltage VrefL1is set to a value smaller than the voltage fluctuation range of the first direct-current power supply61. In the aforementioned example, the first lower limit voltage VrefL1is set to a value less than 220 [V] and is set to, for example, 200 [V]. Likewise, the second upper limit voltage VrefH2is set to a value larger than a voltage fluctuation range of the second direct-current power supply62, and the second lower limit voltage VrefL2is set to a value smaller than the voltage fluctuation range of the second direct-current power supply62. In the present embodiment, the first direct-current power supply61and the second direct-current power supply62have the same rated voltage and the same specifications, and the first upper limit voltage VrefH1and the second upper limit voltage VrefH2are set to the same value. In addition, the first lower limit voltage VrefL1and the second lower limit voltage VrefL2are also set to the same value. In such a case, the first upper limit voltage VrefH1and the second upper limit voltage VrefH2may be simply referred to as upper limit voltage VrefH without distinguishing therebetween, and the first lower limit voltage VrefL1and the second lower limit voltage VrefL2may be simply referred to as lower limit voltage VrefL without distinguishing therebetween, Needless to say, the first upper limit voltage VrefH1and the second upper limit voltage VrefH2may be set to different values, and the first lower limit voltage VrefL1and the second lower limit voltage VrefL2may be set to different values.

With reference toFIGS.11to23, detection of an open failure of a contactor and fail-safe control will be specifically described below. A flowchart ofFIG.11shows an example of a procedure of detection of an open failure of a contactor and fail-safe control. Timing charts ofFIGS.12to23show examples of operation performed upon detection of an open failure of a contactor and fail-safe control.FIGS.12to15show an example case in which the rotational speed of the rotating electrical machine80is a relatively high rotational speed (e.g., 13000 [rpm] or more),FIGS.20to23show an example case in which the rotational speed of the rotating electrical machine80is a relatively low rotational speed (e.g., less than 5000 [rpm]), andFIGS.16to19show an example in which the rotational speed of the rotating electrical machine80is an intermediate rotational speed between the relatively high rotational speed and the relatively low rotational speed (e.g., around 9000 [rpm]).FIGS.12,13,16,17,20, and21show an example case in which the rotating electrical machine80is performing regenerative operation, andFIGS.14,15,18,19,22, and23show an example case in which the rotating electrical machine80is performing powering operation. In addition,FIGS.12,14,16,18,20, and22show an example in which fail-safe control is performed with a normal contactor maintaining a closed state, andFIGS.13,15,17,19,21, and23show an example in which fail-safe control is performed with the normal contactor being also in an open state. The flowchart shown inFIG.11shows an example in which fail-safe control is performed with the normal contactor being also in an open state.

In addition, in the timing charts ofFIGS.12to23, a case of the contactor9being in an open state is represented as “OPEN” and a case of the contactor9being in a closed state is represented as “CLOSE”. For the control modes of the first inverter11and the second inverter12, as described with reference to tables 1 and 2 andFIGS.1to10, a control mode in which the inverters10are driven by pulse width modulation control (also including rectangular-wave modulation control) based on a torque instruction is represented as a “torque mode”. In addition, as described above, shutdown control is represented as “SDN” and active short-circuit control is represented as “ASC”. The voltage values of the first direct-current link voltage Vdc1and the second direct-current link voltage Vdc2at normal times are a first normal voltage Vtyp1and a second normal voltage Vtyp2, respectively. At ratings, the first normal voltage Vtyp1and the second normal voltage Vtyp2are identical voltages, and when the first normal voltage Vtyp1and the second normal voltage Vtyp2are not distinguished from each other, the first normal voltage Vtyp1and the second normal voltage Vtyp2are simply referred to as normal voltage Vtyp. As will be described later, the value of the direct-current link voltage Vdc varies depending on the open/close of the contactor9, etc. InFIGS.12to23, the voltage value of the direct-current link voltage Vdc is represented as V52, V38, V48, etc. The larger number indicates a higher voltage. In addition, for the rotational speed of the rotating electrical machine80, too, likewise, inFIGS.12to23, the rotational speed is represented as R15, R3, etc. For the rotational speed, too, the larger number indicates a higher rotational speed. Note that though details will be described later, MD1represents a dual-inverter torque control mode, MD2represents a shutdown control mode (non-torque control mode), and MD3represents a single-inverter torque control mode.

As shown inFIG.11, the rotating electrical machine control device1first detects a voltage (first direct-current link voltage Vdc1) at both ends of the first smoothing capacitor41, a voltage (second direct-current link voltage Vdc2) at both ends of the second smoothing capacitor42, a current (first battery current Ib1) flowing through the first direct-current power supply61, and a current (second battery current Ib2) flowing through the second direct-current power supply62(#1). The first direct-current link voltage Vdc1and the second direct-current link voltage Vdc2(collectively referred to as direct-current link voltages Vdc) each are detected by being measured by a voltage sensor which is not shown inFIG.1, etc., and obtained by the rotating electrical machine control device1through an in-vehicle network, e.g., a controller area network (CAN). The first battery current Ib1and the second battery current Ib2each are also detected by being measured by a current sensor which is not shown inFIG.1, etc., and obtained by the rotating electrical machine control device1through an in-vehicle network, e.g., the CAN. The rotating electrical machine control device1detects the first direct-current link voltage Vdc1, the second direct-current link voltage Vdc2, the first battery current Ib1, and the second battery current Ib2based on a control cycle of vector control. When a detection period is long, resolution decreases, and when the detection period is too short, the capacity of a temporary storage device such as a memory is consumed and a computing load increases. Thus, it is preferred that the first direct-current link voltage Vdc1, the second direct-current link voltage Vdc2, the first battery current Ib1, and the second battery current Ib2be detected, for example, once every control cycle of vector control.

Then, the rotating electrical machine control device1determines whether the first direct-current link voltage Vdc1is higher than the first upper limit voltage VrefH1or the first direct-current link voltage Vdc1is lower than the first lower limit voltage VrefL1, and the first battery current Ib1is less than or equal to the first lower limit current Iref1(#2a). When these conditions are satisfied, the rotating electrical machine control device1determines that the first contactor91has an open failure, and sets the first contactor91as a failed contactor and sets the second contactor92which is the other one as a normal contactor. In addition, the first inverter11which is one of the inverters10to which the first contactor91, the failed contactor, is connected is set as a failure-side inverter, and the second inverter12which is one of the inverters10to which the second contactor92, the normal contactor, is connected is set as a normal-side inverter (#3a).

Likewise, the rotating electrical machine control device1determines whether the second direct-current link voltage Vdc2is higher than the second upper limit voltage VrefH2or the second direct-current link voltage Vdc2is lower than the second lower limit voltage VrefL2, and the second battery current Ib2is less than or equal to the second lower limit current Iref2(#2b). When these conditions are satisfied, the rotating electrical machine control device1determines that the second contactor92has an open failure, and sets the second contactor92as a failed contactor and sets the first contactor91which is the other one as a normal contactor. In addition, the second inverter12which is one of the inverters10to which the second contactor92, the failed contactor, is connected is set as a failure-side inverter, and the first inverter11which is one of the inverters10to which the first contactor91, the normal contactor, is connected is set as a normal-side inverter (#3b).

Note that although the flowchart exemplified inFIG.11exemplifies a mode in which if the conditions are not satisfied at step #3a, then step #3bis performed, they may be performed in reversed order. When steps #2aand #2bare collectively referred to, they are referred to as step #2, and when steps #3aand #3bare collectively referred to, they are referred to as step #3. Step #2corresponds to the above-described contactor open determination process. In addition, the first lower limit current Iref1and the second lower limit current Iref2each are set to a value close to zero and larger than the maximum value of an error of a current sensor that measures the battery currents Ib.

Here, the timing charts ofFIGS.12to23are referred to. At first, the first contactor91and the second contactor92are in a closed state (CLOSE), and the inverters10and the smoothing capacitors4are electrically connected to their corresponding direct-current power supplies6, which is common toFIGS.12to23. The first inverter11(INV1) and the second inverter12(INV2) both are controlled by a torque mode (dual-inverter torque control mode). The first direct-current link voltage Vdc1and the second direct-current link voltage Vdc2are the first normal voltage Vtyp1and the second normal voltage Vtyp2, respectively, and are both the normal voltages Vtyp.

In addition, when the rotating electrical machine80is performing regenerative operation, negative torque is outputted (FIGS.12,13,16,17,20, and21), and when the rotating electrical machine80is performing powering operation, positive torque is outputted (FIGS.14,15,18,19,22, and23). The rotational speed rises to R15in a case of the high rotational speed (FIGS.12to15), rises to R9in a case of the intermediate rotational speed (FIGS.16to19), and rises to R3in a case of the low rotational speed (FIGS.20to23). Here, at time t1, an open failure occurs in the second contactor92and the second contactor92goes into an open state (OPEN), which is common toFIGS.12to23.

If the second contactor92goes into an open state, then when the rotating electrical machine80is performing regenerative operation, generated electric power is not regenerated to the second direct-current power supply62, and thus, the second smoothing capacitor42is charged. Hence, the second direct-current link voltage Vdc2which is the voltage at both ends of the second smoothing capacitor42rises from the second normal voltage Vtyp2(FIGS.12,13,16,17,20, and21). As is clear from a comparison ofFIGS.12,16, and20and a comparison ofFIGS.13,17, and21, the higher the rotational speed of the rotating electrical machine80, the larger the rising voltage. At time t21(t2), the rising second direct-current link voltage Vdc2reaches the second upper limit voltage VrefH2. Though not shown in the timing charts, by the second contactor92going into an open state, the second battery current Ib2reaches substantially zero, and thus, the condition that the second battery current Ib2is less than or equal to the second lower limit current Iref2is satisfied. When the second direct-current link voltage Vdc2reaches the second upper limit voltage VrefH2, the conditions at step #2(#2b) ofFIG.11are satisfied.

On the other hand, when the rotating electrical machine80is performing powering operation, supply of electric power from the second direct-current power supply62to the rotating electrical machine80is interrupted, and the rotating electrical machine80performs powering using electric power stored in the second smoothing capacitor42. That is, electric power is supplied from the second smoothing capacitor42to the rotating electrical machine80, and the second direct-current link voltage Vdc2which is the voltage at both ends of the second smoothing capacitor42drops from the second normal voltage Vtyp2(FIGS.14,15,18,19,22, and23). At time t22(t2), the dropping second direct-current link voltage Vdc2reaches less than or equal to the second lower limit voltage VrefL2. Though not shown in the timing charts, by the second contactor92going into an open state, the second battery current Ib2reaches substantially zero, and thus, the condition that the second battery current Ib2is less than or equal to the second current lower limit value is satisfied. When the second direct-current link voltage Vdc2reaches less than or equal to the second lower limit voltage VrefL2, the conditions at step #2(#2b) ofFIG.11are satisfied.

When the conditions at step #2ofFIG.11are satisfied, i.e., when an open failure of a contactor9is detected, the rotating electrical machine control device1performs shutdown control on both the first inverter11and the second inverter12(#4). Namely, at time t2, the operating mode of the first inverter11and the second inverter12transitions from the torque control mode (dual-inverter torque control mode MD1) to the shutdown control mode MD2(non-torque control mode), which is common toFIGS.12to23.

The rotating electrical machine control device1then determines whether the operating region of the rotating electrical machine80is a high-rotation region (#5). If the operating region of the rotating electrical machine80is a high-rotation region, then the normal contactor which is, in this case, the first contactor91is brought into an open state (OPEN) (#6andFIGS.13,15,17,19,21, and23).FIGS.14,16,18,20, and22exemplify a case in which the first contactor91does not go into an open state (OPEN). For example,FIGS.20and22exemplify a case of the low rotational speed, and exemplifies a case in which it is determined at step #5ofFIG.11that the operating region is not a high-rotation region. Though details will be described later, a mode can also be adopted in which even if the operating region of the rotating electrical machine80is a high-rotation region, the normal contactor is not brought into an open state (OPEN).FIGS.14and16(also includingFIGS.18and20which are timing charts for the intermediate rotational speed) exemplify such a mode. In addition,FIGS.21and23show, as a comparative example, an example case in which when the rotational speed of the rotating electrical machine80is the low rotational speed, too, the normal contactor is brought into an open state.

For example, whenFIG.13in which the first contactor91goes into an open state at time t2(time t21) is compared withFIG.12in which the first contactor91continues to be in a closed state (CLOSE) at time t2(t22), too, for the second direct-current link voltage Vdc2, “V52” ofFIG.12in which the first contactor91continues to be in a closed state is higher than “V48” ofFIG.13in which the first contactor91is also in an open state. When the first contactor91goes into an open state, regenerative electric power flows through the first smoothing capacitor41and the second smoothing capacitor42, charging the two smoothing capacitors4. In the closed state of the first contactor91, only the second smoothing capacitor42is charged, and thus, a voltage rise in the second direct-current link voltage Vdc2increases.

As shown inFIGS.14and15, when the rotating electrical machine80is performing powering operation, too, the smoothing capacitors4are charged by back electromotive force, and thus, the same phenomenon is observed. Note that as is clear from a comparison ofFIGS.12and13withFIGS.16and17andFIGS.20and21, and a comparison ofFIGS.14and15,FIGS.18and19, andFIGS.22and23, the lower the rotational speed of the rotating electrical machine80, the smaller the voltage rise in the second direct-current link voltage Vdc2.

Although the above description is made of a case in which the rotating electrical machine80performs regenerative operation, the same also applies to a case in which the rotating electrical machine80performs powering operation, and a person skilled in the art can easily understand by referring toFIGS.14,15,18,19,22, and23, and thus, a detailed description thereof is omitted. In addition, the determination at step #5may be performed based on the operating region of the rotating electrical machine80, or may be performed, as with step #7which will be described later, by a comparison of the rotational speed of the rotating electrical machine80with a speed threshold value ωth.

At time t2, shutdown control is performed on both the first inverter11and the second inverter12, by which the rotational speed of the rotating electrical machine80decreases by so-called braking torque. The timing charts ofFIGS.12to19that exemplify cases in which the rotational speed of the rotating electrical machine80is the high rotational speed and the intermediate rotational speed (a rotational speed higher than or equal to the speed threshold value ωth exemplified at step #7ofFIG.11) exemplify a mode in which the rotational speed starts to decrease from time t3. In the timing charts ofFIGS.20to23in which the rotational speed of the rotating electrical machine80is the low rotational speed, upon the determination at step #5, too, the rotational speed is less than the speed threshold value ωth, and thus, even if the control mode goes into the shutdown control mode MD2, the rotational speed does not decrease.

For a process subsequent to step #5, first, control for the high-rotation region (a case of transitioning from step #5→step #6) will be described below. When the rotational speed of the rotating electrical machine80decreases and the rotational speed (represented by “w” inFIG.11) reaches less than the speed threshold value ωth at time t4(#7), thereafter, the rotating electrical machine control device1controls the second inverter12which is the failure-side inverter by active short-circuit control (#8a(#8)). Thereafter, the rotating electrical machine control device1controls the first inverter11which is the normal-side inverter by pulse width modulation control (#9(#9a)).

As shown inFIG.13, etc., at time t4, the rotational speed reaches R3(here, the speed threshold value ωth>R3), and the second inverter12is controlled by active short-circuit control from time t5later than time t4. Then, the rotating electrical machine control device1controls the first inverter11which is the normal-side inverter by pulse width modulation control from time t6later than time t5.

Here, when the first contactor91which is the normal contactor is controlled to an open state, the first smoothing capacitor41is also charged and thus the first direct-current link voltage Vdc1is higher than the first normal voltage Vtyp1(FIGS.13,15,17,19, (21), and (23)). Hence, by providing a discharge torque instruction TQ1to the first inverter11which is the normal-side inverter and driving the first inverter11by pulse width modulation control, the first smoothing capacitor41is discharged (#10). The discharge torque instruction TQ1is less than or equal to 1% of maximum torque provided to the rotating electrical machine80and is, for example, very small torque of about 1 [Nm]. By driving the rotating electrical machine80so as to output very small torque, a smoothing capacitor4can be discharged without providing a large load to the rotating electrical machine80.

By pulse width modulation control by the discharge torque instruction TQ1, the first smoothing capacitor41is discharged, and at time t7, the first direct-current link voltage Vdc1decreases to the first normal voltage Vtyp1. The rotating electrical machine control device1brings the first contactor91which is the normal contactor back to a closed state, and brings the torque instruction to zero (#11). Namely, an instruction by the discharge torque instruction TQ1is terminated. Then, at time t8later than time t7, the rotating electrical machine control device1starts to provide a normal torque instruction to the first inverter11, and drives the rotating electrical machine80by a torque control mode (single-inverter torque control mode MD3) (#12). Note that since pulse width modulation control based on the discharge torque instruction TQ1is performed, the control mode from time t6corresponds to the single-inverter torque control mode MD3.

When the operating region of the rotating electrical machine80is not the high-rotation region, i.e., when step #5transitions to step #8b, as shown inFIGS.20and22, at time t5, the second inverter12is controlled by active short-circuit control (#8b). Furthermore, the rotating electrical machine control device1controls the first inverter11which is the normal-side inverter by pulse width modulation control from time t6later than time t5(#9(#9b)).

Meanwhile, in the flowchart exemplified inFIG.11, a mode is exemplified and described in which the normal contactor is controlled to an open state based on whether the operating region of the rotating electrical machine80is the high-rotation region or whether the rotational speed of the rotating electrical machine80is less than the speed threshold value ωth. However, as described above with reference toFIGS.12and13, the reason that the normal contactor is brought into an open state is to suppress a rise in the voltage at both ends of a smoothing capacitor4connected to the failed contactor, i.e., the direct-current link voltage Vdc. Thus, when the rise in the direct-current link voltage Vdc does not exceed the withstanding voltages of the smoothing capacitor4and the inverter10, even if the operating region is the high-rotation region, the normal contactor may be maintained in a closed state. That is, even if the operating region is the high-rotation region, the normal contactor may be maintained in a closed state as shown inFIGS.12and14, instead of bringing the normal contactor into an open state as shown inFIGS.13and15.

For example, in a case in which the rotating electrical machine control device1performs shutdown control with the rotational speed of the rotating electrical machine80being a preset maximum rotational speed and with one of the first contactor91and the second contactor92being in an open state and the other one being in a closed state, when a voltage at both ends of a smoothing capacitor4connected to a contactor9that is in an open state is less than or equal to the withstanding voltage of a corresponding inverter10, even if the rotational speed of the rotating electrical machine80is greater than or equal to the defined speed threshold value ωth when it is determined that one of the first contactor91and the second contactor92is a failed contactor, a normal contactor which is the other one may be maintained in a closed state without bringing the normal contactor into an open state.

When the normal contactor is brought into an open state from a closed state, a voltage at both ends of a smoothing capacitor4connected to the normal contactor also rises, requiring control for reducing the risen voltage. Even if a voltage at both ends of a smoothing capacitor4connected to the failed contactor rises, if the voltage does not exceed the withstanding voltages of the smoothing capacitor4and an inverter10to which the smoothing capacitor4is connected, then there is a low necessity to distribute back electromotive force of the rotating electrical machine80to the two smoothing capacitors4. Thus, fail-safe control can be performed by simple control.

As described above, when an open failure has occurred in either one of the contactors9, the rotating electrical machine control device1can control drive of the rotating electrical machine80using only an inverter10to which the other contactor9having no failure is connected. However, since the rotating electrical machine80that is normally driven through the two inverters10is driven by one inverter10, it is difficult to perform usual output. Thus, it is preferred that when the rotating electrical machine control device1determines that one of the first contactor91and the second contactor92is in an open state, the rotating electrical machine control device1limit torque and rotational speed that can be outputted from the rotating electrical machine80within a defined range. In addition, it is preferred that a driver of the vehicle be alerted of occurrence of a failure in the contactor9.

By limiting the torque and rotational speed within the defined range, travel of the vehicle can be continued even under certain limitations. In addition, since the driver of the vehicle is alerted, the driver recognizes a failure in the vehicle based on the alert, and allows the vehicle to travel even under certain limitations and can allow the vehicle to travel to a safe location such as a road shoulder to stop the vehicle. Alternatively, the driver can allow the vehicle to travel to a service garage, a location where roadside assistance is received, etc., to have the vehicle fixed promptly. Namely, so-called limp home is possible.

As described above, according to the present embodiment, when a failure has occurred in one of the smoothing capacitors provided for the respective two inverters each provided at each end side of the open-end windings, the failed smoothing capacitor can be identified.

SUMMARY OF THE EMBODIMENT

A summary of the rotating electrical machine control system (100) described above will be briefly described below.

In one aspect, a rotating electrical machine control system (100) that controls drive of a rotating electrical machine (80) having open-end windings (8) of a plurality of phases that are independent of each other includes a first inverter (11) connected to a one-end side of the open-end windings (8); a second inverter (12) connected to an other-end side of the open-end windings (8); a first direct-current power supply (61) to which the first inverter (11) is connected; a second direct-current power supply (62) to which the second inverter (12) is connected; a first smoothing capacitor (41) connected in parallel to the first direct-current power supply (61); a second smoothing capacitor (42) connected in parallel to the second direct-current power supply (62); a first contactor (91) that establishes and cuts off an electrical connection between the first inverter (11) and the first smoothing capacitor (41), and the first direct-current power supply (61); a second contactor (92) that establishes and cuts off an electrical connection between the second inverter (12) and the second smoothing capacitor (42), and the second direct-current power supply (62); and a control part (1) that controls each of the first contactor (91) and the second contactor (92) and can control the first inverter (11) and the second inverter (12) independently of each other, and in the first inverter (11) and the second inverter (12), an arm (3A) for one alternating-current phase includes a series circuit of an upper-stage-side switching element (3H) and a lower-stage-side switching element (3L), the control part (1) can control each of the first inverter (11) and the second inverter (12) by active short-circuit control that brings all of the upper-stage-side switching elements (3H) into off state and brings all of the lower-stage-side switching elements (3L) into on state, or brings all of the upper-stage-side switching elements (3H) into on state and brings all of the lower-stage-side switching elements (3L) into off state, and by shutdown control that brings all switching elements (3) of a plurality of phases into off state, and using a first upper limit voltage (VrefH1) set to a value larger than a voltage fluctuation range of the first direct-current power supply (61), a first lower limit voltage (VrefL1) set to a value smaller than a voltage fluctuation range of the first direct-current power supply (61), a second upper limit voltage (VrefH2) set to a value larger than a voltage fluctuation range of the second direct-current power supply (62), and a second lower limit voltage (VrefL2) set to a value smaller than a voltage fluctuation range of the second direct-current power supply (62), the control part (1) determines that the first contactor (91) is in an open state, when a voltage (Vdc1) at both ends of the first smoothing capacitor (41) is higher than the first upper limit voltage (VrefH1) or lower than the first lower limit voltage (VrefL1), and a current (Ib1) flowing through the first direct-current power supply (61) is less than or equal to a first lower limit current (Iref1) defined in advance; determines that the second contactor (92) is in an open state, when a voltage (Vdc2) at both ends of the second smoothing capacitor (42) is higher than the second upper limit voltage (VrefH2) or lower than the second lower limit voltage (VrefL2), and a current (Ib2) flowing through the second direct-current power supply (62) is less than or equal to a second lower limit current (Iref2) defined in advance; considers one of contactors (9) that is determined to be in an open state a failed contactor and considers the other one of the contactors (9) a normal contactor, the contactors (9) being the first contactor (91) and the second contactor (92); controls both the first inverter (11) and the second inverter (12) by shutdown control and brings both the first contactor (91) and the second contactor (92) into an open state, in a state in which a rotational speed of the rotating electrical machine (80) is greater than or equal to a speed threshold value (ωth) defined in advance; after the rotational speed of the rotating electrical machine (80) reaches less than the speed threshold value (ωth), controls a failure-side inverter by the active short-circuit control and maintains the normal contactor in an open state, and drives a normal-side inverter using discharge torque of a normal-side smoothing capacitor, the failure-side inverter being an inverter (10) connected to the failed contactor, the normal-side inverter being an inverter (10) connected to the normal contactor, and the normal-side smoothing capacitor being a smoothing capacitor (4) connected to the normal-side inverter; and after a rise in a voltage (Vdc) at both ends of the normal-side smoothing capacitor is eliminated, controls the normal contactor to a closed state and controls drive of the rotating electrical machine (80) by the normal-side inverter.

According to this configuration, when the rotating electrical machine (80) is performing regenerative operation, occurrence of a failure in a contactor (9) can be detected by a current (Ib) of a direct-current power supply that stops flowing due to the contactor (9) going into an open state and by a voltage (Vdc) at both ends of a smoothing capacitor (4) that rises by a regenerative current. In addition, when the rotating electrical machine (80) is performing powering operation, occurrence of a failure in a contactor (9) can be detected by a current (Ib) of a direct-current power supply that stops flowing due to the contactor (9) going into an open state and by a voltage (Vdc) at both ends of a smoothing capacitor (4) that drops due to being discharged to drive the rotating electrical machine (80). Furthermore, according to the configuration, after both inverters (10) are controlled by shutdown control, one of the inverters (10) to which a failed contactor (9) is connected is short-circuited by active short-circuit control, and the rotating electrical machine (80) is driven by the other inverter (10). At this time, when the rotational speed of the rotating electrical machine (80) is greater than or equal to the speed threshold value (ωth), a contactor (9) having no failure is also controlled to an open state. By this, back electromotive force from the rotating electrical machine (80) is absorbed by the two smoothing capacitors (4), enabling suppression of a rise in a voltage (VDc) at both ends of a smoothing capacitor (4) connected to the failed contactor. In this case, a voltage (Vdc) at both ends of a normal-side smoothing capacitor connected to a normal-side inverter also rises, but the normal-side smoothing capacitor is discharged by driving the normal-side inverter using discharge torque (TQ1). When the rise in the voltage (Vdc) at both ends of the normal-side smoothing capacitor is eliminated, drive of the rotating electrical machine (80) is controlled by the normal-side inverter. As such, according to the configuration, when a failure has occurred in one of the contactors (9) each provided between one of the direct-current power supplies (6) connected to the respective two inverters (10) each provided at each end side of the open-end windings (8), the failed contactor (9) is identified and drive of the rotating electrical machine (80) can be controlled.

In addition, it is preferred that in a case in which the control part (1) performs the shutdown control with a rotational speed of the rotating electrical machine (80) being a maximum rotational speed set in advance and with one of the first contactor (91) and the second contactor (92) being in an open state and the other one being in a closed state, when a voltage (Vdc) at both ends of a smoothing capacitor (4) connected to one of the contactors (9) that is in an open state is less than or equal to a withstanding voltage of a corresponding one of the inverters (10), even if a rotational speed of the rotating electrical machine (80) is greater than or equal to a defined speed threshold value (ωth) when it is determined that one of the first contactor (91) and the second contactor (92) is the failed contactor, the control part (1) maintain the normal contactor which is the other one in a closed state without bringing the normal contactor into an open state.

When a normal contactor is brought into an open state from a closed state, a voltage (Vdc) at both ends of a smoothing capacitor (4) connected to the normal contactor also rises, requiring control for reducing the risen voltage. Even if a voltage (Vdc) at both ends of a smoothing capacitor (4) connected to a failed contactor rises, if the voltage (Vdc) does not exceed the withstanding voltages of the smoothing capacitor (4) and an inverter (10) to which the smoothing capacitor (4) is connected, then there is a low necessity to distribute back electromotive force of the rotating electrical machine (80) to the two smoothing capacitors (4). Thus, fail-safe control can be performed by simple control.

In addition, it is preferred that the rotating electrical machine (80) be a drive power source that is mounted on a vehicle to drive wheels of the vehicle, and when the control part (1) determines that one of the first contactor (91) and the second contactor (92) is in an open state, the control part (1) limit torque and rotational speed that can be outputted from the rotating electrical machine (80) within a defined range, and alert a driver of the vehicle.

By limiting the torque and rotational speed within the defined range, travel of the vehicle can be continued even under certain limitations. In addition, since the driver of the vehicle is alerted, the driver recognizes a failure in the vehicle based on the alert, and allows the vehicle to travel even under certain limitations and can allow the vehicle to travel to a safe location such as a road shoulder to stop the vehicle. Alternatively, the driver can allow the vehicle to travel to a service garage, a location where roadside assistance is received, etc., to have the vehicle fixed promptly. Namely, so-called limp home is possible.

In addition, it is preferred that the discharge torque (TQ1) be less than or equal to 1% of maximum torque.

By driving a normal-side inverter (10) by, for example, pulse width modulation control so that the normal-side inverter (10) outputs discharge torque (TQ1), a smoothing capacitor (4) connected to the normal-side inverter is discharged. When the discharge torque (TQ1) is less than or equal to 1% of maximum torque of the rotating electrical machine (80), it is very small torque. By driving the rotating electrical machine (80) so as to output such very small torque, the smoothing capacitor (4) can be discharged without providing a large load to the rotating electrical machine (80).

REFERENCE SIGNS LIST

1: Rotating electrical machine control device (control part),3: Switching element,3A: Arm,3H: Upper-stage-side switching element,3L: Lower-stage-side switching element,4: Smoothing capacitor,6: Direct-current power supply,8: Stator coil (open-end winding),9: Contactor,10: Inverter,11: First inverter,12: Second inverter,41: First smoothing capacitor,42: Second smoothing capacitor,61: First direct-current power supply,62: Second direct-current power supply,80: Rotating electrical machine,91: First contactor,92: Second contactor,100: Rotating electrical machine control system, Ib: Battery current, Ib1: First battery current (current flowing through the first direct-current power supply), Ib2: Second battery current (current flowing through the second direct-current power supply), Iref1: First lower limit current, Iref2: Second lower limit current, TQ1: Discharge torque instruction, VrefH1: First upper limit voltage, VrefH2: Second upper limit voltage, VrefL1: First lower limit voltage, VrefL2: Second lower limit voltage, and ωth: Speed threshold value