Patent ID: 12261516

DETAILED DESCRIPTION

The present disclosure will now be described with reference to the Figures, which in general relate to electric power circuits that may be used, for example, in an electric vehicle. For example, circuits described here may be used for charging a battery from an external source and for controlling power to drive an electric motor using the battery.

EV power systems are sensitive to component dimension, weight, and converter efficiency. Main stream power converter designs using conventional metal-oxide-semiconductor field-effect transistor (MOSFET) and insulated-gate bipolar transistor (IGBT) have hit their performance limits, and new-generation power devices such as Gallium Nitride (GaN) and Silicon Carbide (SiC) MOSFET transistors are being adopted for efficiency, dimension and weight benefits. Also, using shared hardware circuitry to perform different functions such as driving a motor and charging a battery is efficient and may save costs; and integrating motor drives and battery charging systems may provide further gains in cost and dimensions.

Generally, EVs should be able to charge their batteries from at least two different power sources, e.g., DC power from a charging station, and AC power from the utility AC grid. Therefore, EV on-board power systems may include both DC and AC charging circuits, in addition to an inverter circuit that operates the EV motor during a drive mode or a traction mode.

Charging of EV batteries may include use of an on-board charging circuit. Power from the battery may be used to power one or more electric motors through an inverter to propel the electric vehicle. In some cases, certain components may be shared by these circuits, which may reduce costs and promote efficiency. Integration of the on board charging circuit and the inverter circuit using an advanced high-frequency circuit topology and using common power converter stages (e.g. power bridges) between the on-board charger and the inverter may reduce the overall cost, size, and weight of the EV power system. However, any integrated solutions also need to address those technology challenges brought about by different power ratings, isolation requirements, and a wide voltage range.

It is understood that the present embodiments of the disclosure may be implemented in many different forms and that the claim scope should not be construed as being limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete and will fully convey the inventive embodiment concepts to those skilled in the art. Indeed, the disclosure is intended to cover alternatives, modifications and equivalents of these embodiments, which are included within the scope and spirit of the disclosure as defined by the appended claims. Furthermore, in the following detailed description of the embodiments of the disclosure, numerous specific details are set forth in order to provide a thorough understanding. However, it will be clear to those of ordinary skill in the art that the embodiments of the disclosure may be practiced without such specific details.

FIG.1Aillustrates a concept diagram of a multibridge converter100, comprising a multibridge110(which consists of two switching bridges, i.e., phase-A bridge111and phase-B bridge112, but may also consist of more than two switching bridges, as desired in various embodiments) connected to a DC bus130and coupled with an isolation transformer120having a primary winding connected between an output (i.e. port A) of the phase-A bridge111and an output (i.e. port B) of the phase-B bridge112. With a controller140generating and providing different PWM gate control signals to the multibridge converter100, the multibridge converter100can be operated in at least two different modes including: (i) a non-isolated operation mode where the two switching bridges are operated in a parallel mode, and power is delivered from the DC bus130to the non-isolated ports A and B, and (ii) an isolated operation mode where the two switching bridges are operated in a full bridge mode, and power is delivered from the DC bus130to the isolated ports E and F though the isolation transformer120. In general, the multibridge converter100can be used in DC-to-DC or DC-to-AC inverter systems.

FIG.1B illustrates an example of switching waveforms for the non-isolated operation mode of the multibridge converter100. For simplicity all the deadtime in each bridge's PWM signals are neglected, and that is true with all the other example waveforms throughout this disclosure. The two switching bridges111and112are synchronized in gate on-off signals to generate the same PWM voltage waveforms with no phase shift across the primary winding of the transformer120, therefore the primary winding of the transformer120is not excited with any significant differential voltages (i.e., voltage VAB, representing the voltage between the port A and the port B) and power is delivered mainly from the DC bus to the non-isolated ports A and B, with the capability of bidirectional power flow. The rule of switching in the non-isolated operation mode is that the phase-A bridge111and the phase-B bridge112are fully synchronized in phase and switching devices S1and S2(such as IGBT, Silicon MOSFET, and Silicon-carbide MOSFET) in the phase-A bridge111are turned on and off by the same gating signals as switching devices S3and S4(such as IGBT, Silicon MOSFET, and Silicon-carbide MOSFET) in the phase-B bridge112. In other words, the phase-A and phase-B bridges111and112work in perfect synchronization usually because they are controller by the same PWM gating signals. And the common PWM gating signals are typically generated by a multivariable input-to-output close-loop regulations in terms of duty cycle control or space-vector modulations of the converter100. The result is that the primary winding of the transformer120is excited by the identical voltage waveforms of the voltage VA from the phase-A bridge111and the voltage VB from the phase-B bridge112, and therefore the voltage VEF across the secondary winding of the transformer120will be flat, ideally standing at “0” voltage. So power is delivered from the DC bus130to the non-isolated ports A and B, but not to the isolated ports E and F. It is note that, in this non-isolated operation mode with non-perfect gate signal synchronization, the switching devices of the phase-A bridge111and the phase-B bridge112may not turn on and off at the same timing, and short voltage pulses or glitches may be seen at the secondary ports E and F of the transformer120, but those short pulses can be tolerated due to the fact they will not deliver any significant portion of the total power flow.

FIG.1C illustrates an example of switching waveforms for the isolated operation mode of the multibridge converter100. In this mode, the two switching bridges111and112are operated in a full bridge mode, the PWM switching signals are phase shifted with 180° and exactly in opposite phase between the two bridges, therefore the winding of the transformer120is excited with intended significant differential voltages and power is delivered mainly from the DC bus130to the isolated outputs (i.e. the isolated ports E and F) through the transformer120, with the capability of bidirectional power flow. The phase-A bridge111and the phase-B bridge112are out of phase and not turned on and off by the same gate timing signals. In fact, the two bridges111and112can be operated in the opposite phase, where the switching device S1of the phase-A bridge111and the switching device S4of the phase-B bridge112are typically turned on at the same time, while the switching device S2of the phase-A bridge111and the switching device S3of the phase-B bridge112are typically turned on at the same time, without any intended phase shift. The result is that the isolated ports E and F of the transformer120generate a square-shape waveform or alike, and therefore power is mainly delivered from the DC bus130to the isolated ports E and F. It is worth noting that in this isolated operation mode, the purpose is to minimize the power flow to the non-isolated ports A and B, and to achieve that goal, some caution or special arrangements may be needed with the load wirings or load configurations connected to the non-isolated ports A and B.

FIG.1D illustrates another example of switching waveforms for the isolated operation mode of the multibridge converter100. Here the two switching bridges operate in full bridge mode with an intended phase shift on the PWM switching signals, (i.e., S1/S2vs. S3/S4) between the two phase bridges. For simplicity the deadtime in each bridge's PWM signals is neglected. As a result, the PWM voltage output across the transformer primary winding VAB has a bipolar waveform, i.e., having positive and negative DC bus voltage alternatively with zero voltage transition in the middle. And that same bipolar waveform will appear in the transformer secondary winding voltage VEF, neglecting all the parasitic effects. In fact, the active duty cycle or pulse width of the positive-negative voltage waveform depends on the phase shift angle; therefore, adjusting this phase shift angle between the two bridges' PWM gating signals will regulate the power flow to the isolated load through the transformer. The detailed gate timing is usually dependent on the close-loop regulation method of the converter100, such as PWM, frequency modulation, phase shift control, etc. In fact it is operated the same way like a conventional full-bridge phase-shift or LLC converter.

FIGS.2A-2Billustrate an example of a multibridge converter and its operation waveforms in accordance with various embodiments of the present disclosure. Circuits inFIGS.2A and2Bare almost identical as that inFIG.1A, but merely differ from that inFIG.1in that an additional disconnect switch250, namely Kc, is connected between the output port A or B of the multibridge210and the isolated port E or F across the transformer220, and this disconnect switch Kc can be in series with the transformer either on the primary winding side as shown inFIG.2Aor on the secondary winding side inFIG.2B. With the help of this disconnect switch Kc, the purpose is to introduce a phase shift angle in the synchronized PWM signals and achieve the PWM interleaving operation among the two bridges211and212of the multibridge converter200during the non-isolated operation in parallel mode. This disconnect switch Kc can be anything like contactor, relay, or semiconductor device switches. Parallel bridge PWM interleaving is well known for the benefit of increasing the effective PWM frequency on the output terminal and hence reducing the output voltage and current ripple and potentially mitigating electromagnetic emissions (EMI) and audible noises.

FIG.2Cshows an example of PWM interleaved switching waveforms in the non-isolated operation mode of the multibridge converters200. In this mode, the disconnect switch Kc remains open and therefore the isolation transformer is not active in the circuit functions. Across the two switching bridges211and212, there is a 180° phase-shift angle between their synchronized PWM gating signals. As such, the load output voltage VAB will cause the effective PWM switching frequency to double, leading to a smaller PWM switching ripple and lower EMI noises across the load etc.

FIG.2Dshows that in the isolated operation mode of the multibridge converters200while the disconnect switch Kc remains closed, circuit operations of the multibridge converter200are the same as in full bridge mode and the output waveforms are identical to the case inFIGS.1A to1C without disconnect switch Kc. In essence,FIGS.2A to2Dare under the same circuit concept ofFIGS.1A to1C, with an additional feature on PWM phase-shift interleaving and improved performance.

FIG.3Aillustrates a concept circuit diagram of a three-level multibridge converter300as an example. A multibridge310connected to a DC bus330consists of two switching bridges (i.e. a phase-A bridge311and a phase-B bridge312) using diode NPC three-level topology. Similarly, the same concept can be applied to other multilevel topologies such as ANPC, flying capacitor, or hybrid multilevel converters. A primary winding of an isolation transformer320is connected across an output of the phase-A bridge311and an output of the phase-B bridge312, namely, ports A and B. The secondary winding of the transformer320provides an isolated output at ports E and F.

With the controller340generating different PWM gating signals, the three-level multibridge converter300can be operated in at least two different modes including: (i) a non-isolated operation mode where the two switching bridges are operated in a parallel mode, the PWM switching signals are synchronized in phase between the two bridges, and power is delivered from the DC bus330to the non-isolated ports A and B, and (ii) an isolated operation mode where the two switching bridges are operated in a full bridge mode, the PWM switching signals are phase shifted and out of phase between the two bridges, and thus power is delivered from the DC bus330to the isolated ports E and F though the isolation transformer320. The three-level multibridge converter300can be used in DC-to-DC or DC-to-AC inverter systems.

FIG.3Billustrates an example of switching waveforms in the non-isolated operation mode of the multibridge converter300. The rule of switching in the non-isolated operation mode is that the phase-A bridge311and phase-B bridge312are fully synchronized in phase and work in perfect parallel with the same PWM gate signals. The result is that the primary winding of the transformer320is excited by the identical voltage waveforms from the port A and the port B, and therefore the secondary winding of the transformer320will remain at “0” voltage. So power is mainly delivered from the DC bus330to the non-isolated ports A and B, but not to the isolated ports E and F. Note that, in this non-isolated operation mode with non-perfect gate signal synchronization, switching devices S1to S4of the phase-A bridge311and switching devices S5to S8of the phase-B bridge312may not turn on and off at exactly the same timing, and short voltage pulses or glitches may be seen at the secondary ports E and F of the transformer320. But such short voltage pulses can be tolerated due to the fact they will not deliver any significant portion of the total power flow.

FIG.3Cillustrates an example of switching waveforms in the isolated operation mode of the multibridge converter300. In this mode, the phase-A bridge311and the phase-B bridge312are phase shifted and out of phase and not turned on and off by the same gate timing signals. The result is that the isolated ports E and F of the transformer320generate a multi-step square-shape waveform or alike, and therefore power is mainly delivered from the DC bus330to the isolated ports E and F. In fact, the two bridges311and312are operated much like a conventional three-level full-bridge phase-shift or LLC converter. The detailed gate timing is usually dependent on the close-loop regulation method of the converter300, such as PWM, frequency modulation, phase shift control, etc. It is worth noting that in this isolated operation mode, the purpose is to minimize the power flow to the non-isolated ports A and B, and to achieve that goal, some special arrangements may be needed with the load configurations connected to the non isolated ports A and B.

FIG.4Aillustrates a concept circuit diagram of a three-bridge multibridge converter410connected to two separate isolation transformers420and421. There are three switching bridges connected to the DC bus, namely a phase-A bridge411with an output port A, a phase-B bridge412with an output port B, and a phase-C bridge413with an output port C. A primary winding of the isolation transformer420is connected across the port A and the port B, and a primary winding of the isolation transformer421is connected across the port C and the port B. The secondary windings of the two transformers420and421provide isolated outputs at ports E and F and at ports G and H, respectively. Note the polarities of the multiple transformer windings need to be arranged in the same way as shown in order to match the switching waveforms illustrated below.

FIG.4Billustrates a concept diagram of a three-bridge multibridge converter410connected to one integrated transformer422. The only difference betweenFIG.4AandFIG.4Blies in the isolation transformer, but both of the isolation transformers ofFIGS.4A and4Bbasically work in the same way. It is worth noting the polarities of the multiple transformer windings need to be arranged in the same way as shown in order to match the switching waveforms illustrated below.

FIG.4Cillustrates an example of switching waveforms in the non-isolated operation mode of the circuit ofFIG.4A. The rule of switching in the non-isolated operation mode is that a phase-A bridge411, a phase-B bridge412and a phase-C bridge413are fully synchronized and work in perfect parallel with the same PWM gate signals. The result is that primary windings of the two transformers420and421connected to voltages VA and VB at the ports A and B and voltages Vc and VB at the ports C and B are excited by the identical voltage waveforms, and therefore the output voltage VEF at the isolated ports E and F of the secondary winding of the transformer420and the output voltage VGH at the isolated ports G and FI of the secondary winding of the transformer421will stand still at “0” voltage. So power is mainly delivered from the DC bus to the non isolated ports A and B and the non-isolated ports C and B, but not to the isolated ports E and F, or ports G and FI. Note in this non-isolated operation mode with non-perfect gate signal synchronization, the phase-A, phase-B and phase-C bridges may not turn on or off at the same timing, and short voltage pulses or glitches may be seen at the ports E and F and the ports G and FI of the transformers420and421. But the short voltage pulses can be tolerated due to the fact they will not deliver any significant portion of the total power flow.

FIG.4Dillustrates an example of switching waveforms in the isolated operation mode of the circuit ofFIG.4A. In this mode, the phase-A bridge411and the phase-B bridge412are out of phase and not turned on and off by the same gate timing signals. At the same time, the phase-C bridge413and the phase-B bridge412are out of phase as well. The result is that square-shape waveforms or alike are generated at the isolated ports E and F and the isolated ports G and FI of the transformers420and421, and therefore power is mainly delivered from the DC bus to the isolated ports E and F and the isolated ports G and FI. In fact, the three bridges411,412and413are operated much like a conventional full-bridge phase-shift or LLC converter. The detailed gate timing is usually dependent on the close-loop regulation method of the converter, such as PWM, frequency modulation, phase shift control, etc. It is worth noting that in this isolated operation mode, the purpose is to minimize the power flow to the non-isolated ports A, B and C, and to achieve that goal, some special arrangements may be needed with the load wirings or load configurations connected to the non-isolated ports A, B and C.

FIG.5Aillustrates an embodiment of a multibridge converter-based single phase inverter integrated with a battery charging system. There are two multibridges510and520connected to the DC bus, each multibridge510or520having two switching bridges. The multibridge510includes a phase1A bridge and a phase1B bridge, and the multibridge520includes a phase2A bridge and a phase2B bridge. The two multibridges510and520form a non-isolated single-phase output with port1A of the phase1A bridge and port2A of the phase2A bridge, and a parallel single-phase non-isolated output with port1B of the phase1B bridge and port2B of the phase2B bridge. The multibridges510and520are connected to isolation transformers530and531, respectively. Power converters550and551are connected to the secondary windings of the transformers530and531and function as a rectifier to generate a DC voltage for charging up the battery570through an optional contactor K2. The same battery570is also connected to the DC bus through a main contactor K1. Typically, battery570is packed with many modules of multiple cells having a battery management system (BMS)570for electric safety and thermal protections. In addition, there is also a PFC rectifier580connected between the DC bus and an external AC power source. A controller590controls gate timing of the phase bridges of the multibridges510and520according to two different operation modes. Note both the inverter drive operation and the battery charging operation are featured by the bidirectional power flow capability.

FIG.5Billustrates the equivalent active circuit portion of the circuit shown inFIG.5Ain the non-isolated operation mode, together with example switching waveforms. In this non-isolated operation mode, the battery570supplies power to the DC bus with K1closed, and the multibridges510and520provide a pair of single-phase outputs at the ports1A and2A and the ports1B and2B, which are in parallel as single phase inverter outputs. As shown in the example switching waveforms, a phase-1A bridge and a phase-1B bridge of the multibridge510are fully synchronized with the same gate timing signals; and also a phase-2A bridge and a phase-2B bridge of the multibridge520are fully synchronized with the same gate timing signals. Therefore, the phase-1A bridge and the phase-1B bridge generate identical PWM voltage waveforms across the primary winding of the transformer530, therefore the secondary winding of the transformer530will have “0” voltage VEF at the ports E and F with no power flow under ideal conditions. The same thing is true with the transformer531, of which the secondary winding will produce a flat voltage VGH staying at “0” at the ports G and H. Note in this non-isolated operation mode with non-perfect gate signal synchronization, the phase-1A and phase-1B bridges, as well as the phase-2A and phase-2B bridges, may not turn on or off at the same timing, and short voltage pulses or glitches may be seen at the secondary ports E and F of the transformer530and the secondary ports G and FI of the transformer531. But the short voltage pulses can be tolerated due to the fact they will not deliver any significant portion of the total power flow.

FIG.5Cillustrates the equivalent active circuit portion of the circuit shown inFIG.5Ain the isolated operation mode with example switching waveforms. In this mode, the PFC rectifier580is actively working to support the DC bus by drawing power from the external AC source. Multibridges510and520are operate in opposite phase and thus the isolation transformers530and531are excited with square-shape voltage waveforms and power is delivered across the isolation transformers to charge up the battery570. However, the non-isolated output ports1A and2A or ports1B and2B of the single-phase multibridge510or520will not have any significant power flow as shown in the example switching waveforms. The phase-1A bridge of the multibridge510and the phase-2A bridge of the multibridge520are fully synchronized with the same gate timing signals, and so are the phase-1B bridge of the multibridge510and the phase-2B bridge of the multibridge520fully synchronized. Therefore, the phase-1A bridge and the phase-2A bridge generate identical PWM voltage waveforms and therefore result in “0” differential voltage across the non-isolated ports1A and2A. The same thing is true with the phase-1B bridge and the phase-2B bridge which generate “0” differential voltage across the non-isolated ports1B and2B. It is worth noting that in this isolated operation mode, the purpose is to minimize the power flow to the non-isolated ports1A and2A and ports1B and2B, and to achieve that goal, some special arrangements may be needed with the load configurations connected to the non-isolated ports1A and2A and ports1B and2B.

FIG.6Aillustrates an example circuit diagram of a three-phase inverter system based on the multibridge converter in accordance with various embodiments of the present disclosure. There are three multibridge converters610,611, and612which are configured for driving a double winding AC motor660, and coupled with three isolation transformers620,621, and622and their rectifiers630,631,632for charging the battery670. A PFC rectifier640and an EMI filter650are connected between the DC bus and the external AC source. There is also a plug port for the external DC source for charging. With a controller680,FIG.6Ashows an example of EV on-board integrated circuits that can perform functions of battery charging and inverter motor drives in an efficient manner. By sharing the main power components (i.e. the same multibridges610,611,612hardware), between the battery charging mode and the drive mode, component costs, sizes and weights of the circuit are reduced. Both the inverter drive operation and the battery charging operation are featured by the bidirectional power flow capability. Also, disconnect switches Kc1, Kc2and Kc3are connected in series with the primary windings of transformers T1, T2and T3, respectively. And during non-isolated operation in parallel mode, these disconnect switches will allow the multibridge converter to operate in PWM phase interleaving to increase the effective switching frequency of the PWM voltages across the motor terminals. The benefits include reduced motor torque ripple and audible noise etc.

FIG.6Billustrates an example of switching waveforms for a non-isolated operation mode of the three-phase inverter system based on the multibridge converter shown inFIG.6A. In this non-isolated operation mode, i.e. a motor drive mode, a main contactor switch K1for the battery is closed and the three multibridge converters610,611,612work together and function as a three-phase inverter, which is controlled by PWM or space-vector modulation (SVM) according to the motor speed and torque close-loop regulations in real time. Within each multibridge converter, the pair of two phase-bridges (e.g.,1A and1B,2A and2B, or3A and3B) are synchronized in phase and always gated on and off at the same timing so that the PWM output voltages

(i.e., ViA=ViB, V2A=V2B, V3A=V3B) are identical in the same waveforms. Even without the disconnect switches (e.g., Kc1, Kc2, Kc3) there will be virtually “0” differential voltages applied across the three transformer primary windings. Therefore, as a result, the differential voltages across the secondary windings of the isolation transformers (namely, voltages VEF, VGH, and VJK) will also remain at “0”. Therefore, battery power is mainly delivered to drive the motor through its double windings; and no significant power flow will be delivered across the three isolation transformers.

FIG.6Cillustrates an example of switching waveforms for an isolated operation mode of the three-phase inverter system based on the multibridge converter shown inFIG.6A. In this isolated operation mode, i.e. a battery charging mode, the main contactor switch K1for the battery stays open and the phase bridges of each multibridge converters610,611, or612are not switched on or off at the same timing. In fact, each multibridge operates like a standard LLC or phase-shift full-bridge converter and PWM regulation or frequency modulation is typically used to regulate the battery charging DC voltage and charging current. The charging power for the battery can be supplied by the PFC rectifier from the AC source, or by an external DC source.

Furthermore, there is another important thing to note here inFIG.6Con the battery charging mode. The phase-A bridges of all three multibridge converters610,611and612(i.e. the phase-1A bridge, the phase-2A bridge and the phase-3A bridge) are synchronized in phase, and the output voltages (namely, VIA=V2A=V3A) of these phase-A bridges are the same in PWM waveforms. So is true that output voltages (namely, VIB=V2B=AB) of the phase-B bridges of all three multibridge converters610,611and612have the same waveforms. The result is that motor windings are not excited with any significant differential voltages that may cause circulating currents, especially with the two sets of motor double windings being separate from each other.

FIG.6Dillustrates another embodiment of a three-phase multibridge inverter with two isolation transformers for a battery charging system. Here LLC converters with resonant capacitors Cr1and Cr2are explicitly shown in the circuit of the three-phase multibridge inverter. This circuit works in the same way as the three-transformer version inFIG.6A, and the only difference therebetween is the reduced rating for battery charging power capacity. Both the inverter drive operation and the battery charging operation are featured by the bidirectional power flow capability.

FIG.6Eillustrates another embodiment of a three-phase multibridge inverter with one isolation transformer for a battery charging system. Here an LLC converter with a resonant capacitor Cr1is explicitly shown in the circuit of the three-phase multibridge inverter. This circuit works in the same way as the three-transformer version inFIG.6Aor the two-transformer version inFIG.6D, and the only difference therebetween is the further reduced rating for battery charging power capacity. Both the inverter drive operation and the battery charging operation are featured by the bidirectional power flow capability.

As pointed earlier, all the example circuits shown in this disclosure can be configured to be LLC resonant converter, although the resonant capacitors may not be explicitly shown in all the circuit drawings. In fact, throughout the examples in the present disclosure, the isolated DC-DC charging circuit is illustrated as a full-bridge phase-shift converter, an LLC converter, or a dual active bridge (DAB) converter. It should be understood that other isolated DC-DC topologies or a combination of different topologies are also applicable and may be well suitable for implementations of the multibridge converter circuit. And such modifications using other different topologies do not depart from the spirit and scope of the present disclosure as set forth in the appended claims.

FIG.7Aillustrates another embodiment of a three-phase multibridge inverter using one isolation transformer720with three coupled primary windings for a battery charging system. This circuit of the three-phase multibridge inverter works in the same way as the three-transformer version shown inFIG.6A, and the only difference therebetween is on the design of the magnetic transformer. Alternatively, on the secondary winding of the isolation transformer720, it is shown that a passive rectifier730can be used for battery charging, and the main benefit would be the lower cost compared to an active switching rectifier630. Note both the inverter drive operation and the battery charging operation are featured by the bidirectional power flow capability.

FIG.7Billustrates another embodiment of a three-phase multibridge inverter using one isolation transformer721with two coupled primary windings for a battery charging system. This circuit of the three-phase multibridge inverter works in the same way as the two-transformer version inFIG.6D, and the only difference therebetween is on the design of the magnetic transformer. Alternatively, it is shown that a Vienna rectifier741is used for the Boost PFC converter to draw power from an external AC source, obtaining a benefit of the lower cost due to reduced voltage stress and current on the active switching devices.

FIG.8Aillustrates an embodiment of a three-phase multibridge inverter without additional PFC rectifier hardware. Instead, a phase bridge812is used as a Boost PFC rectifier operating in reverse power flow and winding inductance of a motor860is used as Boost inductors. This would further cut down the charging hardware cost.FIG.8Ashows two isolation transformers820and821and two rectifiers830and831for battery charging. A single-phase AC source is connected through an EMI filter850to the neutral points of the double windings of the EV motor860. In an EV drive mode, the circuits shown inFIG.8Awork in the same way as previously described, and within each multibridge the two phase bridges operate in parallel mode. The difference is on the battery charging mode due to the fact there is no additional PFC rectifier. During battery charging in the isolated operation mode, within each multibridge the two phase bridges operate in a full bridge mode. In addition, the PWM duty cycles of each multibridge in full bridge mode still need to be modulated by the AC voltage reference waveform for power factor correction functions. This is basically the same way how congenital single-stage PFC-enable isolated DC-DC converter works. And the drawback is that the isolated transformer magnetic core size will be bigger due to the AC current envelop riding on top of PWM switching ripples. When the phase bridges810,811,812operate as a PFC rectifier to draw current through motor windings, they need to coordinate together in terms of PWM gate timing synchronization in order to minimize the motor winding circulating currents. Caution is also needed in the control design to reduce the motor pulsating torque and not to allow the rotor to move during charging. Note both the inverter drive operation and the battery charging operation are featured by the bidirectional power flow capability.

FIG.8Billustrates another embodiment of a three-phase multibridge inverter without additional PFC rectifier hardware. Similarly, phase bridges810,811and812are used as Boost PFC rectifiers operating in reverse power flow and winding inductance of a motor860is used as Boost inductors. An AC source is connected through an EMI filter850to the two neutral points of the dual windings of the motor860.FIG.8Bshows one isolation transformer820for a battery charging system. During battery charging in the isolation mode, the phase bridges810,811and812operate as single-stage PFC-enable DC-DC converter, the same way as inFIG.8A. Also the gate timing controls for the phase bridges810,811and812need to be synchronized in phase to minimize the motor winding circulating currents. Caution is also needed in the control design to reduce the motor pulsating torque and not to allow the rotor to move during charging. Other than that, this circuit of the three-phase multibridge inverter basically works in the same way as that inFIG.8A. Note both the inverter drive operation and the battery charging operation are featured by the bidirectional power flow capability.

FIG.8Cillustrates an embodiment of a three-phase multibridge inverter with two isolation transformers820and821used for charging. Again there is no additional PFC rectifier hardware used here. Instead, a phase bridge812is used as a Boost PFC rectifier operating in reverse power flow and two inductors La and Lb are used as Boost inductors. Three multibridge converters formed by the phase bridges810,811and812are used for driving a double winding motor860; and two isolation transformers820and821and two rectifiers830and831are used for charging the battery870. A single-phase AC source is connected through an EMI filter850to the double winding terminals3A and3B of the EV motor860through the inductors La, Lb. In the EV drive mode, the circuits shown inFIG.8Cwork in the same way as previously described. During battery charging in the isolated operation mode, the phase bridge812operates as a PFC rectifier to draw current from the external AC source, and the other phase bridges810and811need to coordinate with the phase bridge812in terms of PWM gate timing in order to minimize the winding circulating currents of the motor860. Ideally with gate timing synchronized among three multibridges, PWM output voltage at port1A,2A, and3A will be the same and motor860phase-A winding will not have any circulating current. Similarly, PWM output voltage at1B,2B, and3B will be the same and thus the phase-B winding of motor860will not have any circulating current. Therefore the rotor of the motor860will not move during battery charging. Note both the inverter drive operation and the battery charging operation are featured by the bidirectional power flow capability.

FIG.8Dillustrates another embodiment of a three-phase multibridge inverter with one isolation transformer820used for charging. Similarly, there is no additional PFC rectifier hardware used here. Instead, phase bridge812are used as Boost PFC rectifiers operating in reverse power flow and two inductors La and Lb are used as Boost inductors. For the same reason, PWM gate timing of all three multibridges are synchronized and the same PWM output voltage are generate across motor860phase A windings (namely, port1A,2A,3A) and across phase B winding (namely, port1B,2B,3B). Although AC voltages are applied across winding terminals3A and3B of the motor860, no circulating current through the windings of the motor860is excited and therefore the rotor of the motor860will not move during battery charging. During battery charging in the isolation mode, while the phase bridge812operates as PFC rectifiers, the PWM gate timing for the phase bridges810,811and812need to be synchronized in phase to minimize the motor winding circulating currents so that motor will not move during charging. Note both the inverter drive operation and the battery charging operation are featured by the bidirectional power flow capability.

FIG.9Aillustrates an embodiment of a three-phase multibridge inverter driving two Ac motors960and961. There is no additional PFC rectifier hardware used here. Instead, a phase bridge912is used as a Boost PFC rectifier operating in reverse power flow and two inductors La and Lb are used as Boost inductors. There are two isolation transformers920and921and two rectifiers930and931for charging the battery970. A single-phase AC source is connected through an EMI filter950to winding terminals3A and3B of the motors960and961through the inductors La and Lb. Another inductor Lc is connected to the middle point of the DC bus to form a third line of the AC input, either as three-phase AC or split single-phase AC. In the EV drive mode, the circuits shown inFIG.9Awork in the same way as previously described. During battery charging in the isolated operation mode, the phase bridge912mainly operates as a PFC rectifier to draw current from the external AC source, and the other phase bridges910and911need to coordinate with the phase bridge912in terms of PWM gate timing synchronization in order to minimize the circulating currents through the windings of the motors960and961. Here again although AC voltage is applied across winding terminals3A and3B of the motors960and961, no circulating current through the windings of the motors960and961is excited and therefore the rotors of the motors960and961will not move during battery charging. Note both the inverter drive operation and the battery charging operation are featured by the bidirectional power flow capability.

FIG.9Billustrates another embodiment of a three-phase multibridge inverter driving two AC motors960and961, with one isolation transformer920used for battery charging. Similarly, there is no additional PFC rectifier hardware used here. Instead, a phase bridge912is used as a Boost PFC rectifier operating in reverse power flow and two inductors La and Lb are used as Boost inductors. Another inductor Lc is connected to the middle point of the DC bus to form a third line of the AC input, either as three-phase AC or split single-phase AC. For the same reason, although AC voltages are applied across winding terminals3A and3B of the motors960and961, no circulating current through the windings of the motors960and961is excited and therefore the motors960and961will not move during battery charging. Caution is needed in the design to coordinate the gate timing controls of the phase bridges910,911and912in order to minimize any high-frequency part of circulating current through the windings of the motors960and961. Note both the inverter drive operation and the battery charging operation are featured by the bidirectional power flow capability.

FIG.10Aillustrates an example circuit of a multibridge-based DC-DC boost converter and a battery charging system in accordance with various embodiments of the present disclosure. A multibridge1010having two phase bridges1011and1012is shown as a boost converter that converts the DC voltage of a battery1070to a higher voltage for the DC Bus to drive an inverter1040to support an AC load (for example, an AC motor load for EV tractions). Two Boost inductors1060, namely L1and L2, are connected between the main contactor K1for the battery1070and non-isolated output ports A and B of the phase bridges1011and1012, respectively. The inductors1060can also be coupled inductors. A bidirectional PFC rectifier1030is provided to draw current from an external AC source to supply the DC bus while charging. The primary winning of an isolation transformer1020is connected across the output ports A and B of the multibridge1010. At the output formed by the ports E and F of the secondary winding of the transformer1020, a bidirectional power converter1050is used to regulate an AC voltage from the transformer1020to a DC voltage and charge up the battery1070. Note both the inverter operation mode and the battery charging mode are featured by the bidirectional power flow capability.

FIG.10Billustrates the equivalent active switching circuit of the circuit shown inFIG.10Ain a non-isolated operation mode with example switching waveforms. During an inverter operation in the non-isolated mode, the battery contactor K1is closed and the external source is disconnected, the multibridge1010works as a DC-DC boost converter. Phase bridges1011and1012of the multibridge1010are operated in a parallel mode with their PWM gate switching signals synchronized in phase. Therefore, the same PWM voltage waveforms are generated across the primary winding of an isolation transformer1020, and the transformer winding is not excited with any significant differential voltages. So that power flow is mainly delivered to the inverter1040and further to the AC load, but not much power flow across the isolation transformer1020except for some transformer core losses. Also short pulses or voltage glitches may be seen at the secondary ports E and F of the transformer, but those short pulses can be tolerated due to the fact they will not deliver any significant portion of the total power flow.

FIG.10Cillustrates the equivalent active switching circuit ofFIG.10Ain an isolated operation mode with example switching waveforms. During a battery charging operation in the isolated mode, the battery contactor kl is open and the external AC or DC source is connected, the two phase bridges1011and1012of the multibridge1010are operated in a full bridge mode. The PWM gate switching signals are phase shifted and out of phase between the two bridges. In fact, the two bridges1011and1012can be regulated as a normal LLC or DAB converter with PWM regulation, frequency modulation or phase-shift control, so that power from the AC source is mainly delivered to the isolated output (i.e. the isolated ports E and F) through the transformer1020.

FIG.10Dillustrates a modified example circuit with an additional switch being added to the circuit shown inFIG.10A. Particularly,FIG.10Dshows the revised equivalent active switching circuit in a non-isolated operation mode along with example switching waveforms. The circuit inFIG.10Dmerely differs from that inFIG.10Ain that a transformer disconnect switch, namely Kc, is connected between an output of the multibridge1010and a winding terminal of the transformer1020. With the help of this disconnect switch Kc, the purpose is to introduce a phase shift angle in the synchronized PWM signals and achieve the interleaved operation between the switching bridges1011and1012during the non-isolated operation mode. This disconnect switch Kc can be anything like contactor, relay, or semiconductor device switches. Also, this disconnect switch Kc can be in series with the transformer either on the side of the primary winding as shown inFIG.10Dor on the side of the secondary winding (not shown). Parallel bridge interleaving is well known for the benefit of increasing the effective PWM frequency across the load, therefore reducing the load voltage and current ripple and potentially mitigating electromagnetic emissions (EMI) and audible noises.

FIG.11Aillustrates another example circuit of a multibridge-based DC-to-DC boost converter and a battery charging system in accordance with various embodiments of the present disclosure. Unlike the previous circuit shown inFIG.10A, here a battery1180, a main DC contactor K1, an inductor L1, and the mid-point of the primary winding of an isolation transformer1120are connected in series. During an EV drive operation in the non-isolated operation mode, the primary winding of the transformer1120is used as a coupled Boost inductor. When the inductance of the transformer1120is properly design, the inductor L1may not be needed or it can be indicated as parasitic inductance of wirings and cabling, etc.

FIG.11B illustrates the equivalent active switching circuit of the circuit shown inFIG.11Ain the non-isolated operation mode with example switching waveforms. During an inverter operation in the non-isolated operation mode, the contactor K1is closed and the external source is disconnected, multibridge1110operates as a DC-DC boost converter. Similarly to the case inFIG.10B, the two phase bridges are operated in a parallel mode and their gate switching signals synchronized in phase. Therefore the same PWM voltage waveforms are generated across the primary winding of the transformer1120, and the transformer winding is not excited with any significant differential voltages. So that power flow is mainly delivered to the inverter1150and further to the AC load (e.g. an AC motor1160as shown), but not much across the isolation transformer1120except for the transformer core loss and other parasitic losses.

FIG.11C illustrates the equivalent active switching circuit ofFIG.11Ain an isolated operation mode with example switching waveforms. During a battery charging operation in the isolated mode, the contactor kl is open and the external AC or DC source is connected. Similarly to the case inFIG.10C, the two phase bridges of the multibridge1110are operated in full bridge mode and the PWM switching signals are phase shifted and out of phase between the two bridges. In fact, the two phase bridges can be operated as a normal LLC or DAB converter with PWM regulation, frequency modulation, or phase-shift control, so that power is transferred between the DC bus and the isolated outputs (i.e. the isolated ports E and F) through the transformer1120.

FIG.11D illustrates a modified example circuit with an additional switch being added to the circuit shown inFIG.11A. Particularly,FIG.11D shows the revised equivalent active switching circuit in a non-isolated operation mode along with example switching waveforms. The circuit inFIG.11D merely differs from that inFIG.11A in that a transformer disconnect switch, namely Kc, is connected to an output terminal of the secondary winding of the transformer1120. With the help of this disconnect switch Kc, the purpose is to introduce a phase shift angle in the synchronized PWM signals and achieve the interleaved operation between the two phase bridges during the non-isolated Boost mode. This disconnect switch Kc can be anything like contactor, relay, or semiconductor device switches. Parallel bridge interleaving is well known for the benefit of increasing the effective PWM frequency on the load, therefore reducing the load current and voltage ripple, and potentially mitigating electromagnetic emissions (EMI) and audible noises.

FIG.12illustrates another example circuit of a multibridge-based DC-DC boost converter and a battery charging system in accordance with various embodiments of the present disclosure. A PWM inverter1230is provided for driving an AC traction motor1240, and the motor winding neutral point is connect to an AC source, with a reference return to DC bus middle point. Here connected across the DC bus is a voltage-doubler circuit1260, which includes two diodes D1and D2, and split capacitors C1and C2in series with a contactor switch Q2. By the controller1290selectively closing the contactor switch Q2, a voltage doubling function may be enabled (i.e. when the switch Q2is closed, voltage doubling is enabled and when the switch Q2is open, voltage doubling is disabled). This provides additional flexibility in accommodating a wide range of AC source voltages. The effect of using the voltage doubler1260is to provide the same stable high voltage on the DC bus in both low-AC and high-AC input cases. The voltage doubler1260should be disabled in the inverter operation. Note both the inverter drive mode and the battery charging mode are featured by the bidirectional power flow capability. Alternatively, a passive rectifier can be used at the output of the secondary winding of the isolation transformer1220in place of the active switching rectifier1270for cost saving.

FIG.13illustrates another example circuit of a multibridge-based DC-DC boost converter and a battery charging system in accordance with various embodiments of the present disclosure. There are two AC traction motors1350and1351driven by two inverters1330and1331. A single-phase AC source1340is connected across the winding neutral points of the two motors1350and1351and the two inverters1330and1331are both used for charging with bidirectional power capability. Due to the balanced charging currents among the three-phase motor windings, no significant rotating magnetic force would be generated in the motors1350and1351and the motor pulsating torque would be negligible. Other than that, the multibridge circuit shown inFIG.13basically works in the same way as inFIG.11.

FIG.14illustrates another embodiment of a multibridge DC-DC boost converter and a transformer-isolated battery charging system. The circuit shown inFIG.14is different in that two inverters1430and1431drive an AC traction motor1450with double windings in conventional Y-configuration. A single-phase AC source is connected through an EMI filter1460to two neutral points of the double windings of the motor1450for charging with bidirectional power capability. Due to the balanced charging currents among each set of the three-phase motor windings, no significant rotating magnetic force would be generated in the motor1450and the motor pulsating torque would be negligible. And the circuit works the same way as other circuits previously described.

FIG.15Aillustrates another example circuit of a multibridge-based DC boost converter and a transformer-isolated battery charging system in accordance with various embodiments of the present disclosure. The circuit shown inFIG.15Ais different in that two inverters1530and1531drive an AC traction motor1550with open winding configuration. A three-phase AC source is connected through an EMI filter1560and an AC contact switch Q1to three middle points of windings of the motor1550for charging with bidirectional power capability. During charging of the battery1580, both inverters1530and1531operate as Boost PFC rectifiers and draw evenly distributed currents among all three phase winding of the motor1550. As a result of these balance currents, the motor windings will not generate any significant rotating magnetic force and the motor pulsating torque would be negligible. Other than that, the multibridge circuit inFIG.15Aworks the same way as that inFIG.11.

FIG.15Billustrates another embodiment of a multibridge DC boost converter, with a three-phase or split-phase AC input connected to open winding middle points of a motor1550for battery charging. The circuit shown inFIG.15Bis different in that the AC contactor switch Q1is configured with a common neutral point that can change the motor windings into double Y-configurations when enabled. With the common neutral point connected, the double Y-configurations have the flexibility of operating the motor in a 6-phase mode vs. 3-phase double winding mode. The difference is the relative current phase relationship among the motor windings in terms of space vector control. The benefit would be reducing the back EMF voltage reflected across the DC bus at the high motor speed of the motor and increase the motor current capability at lower motor speed.

FIG.15Cillustrates another embodiment of a multibridge DC-DC boost converter, with a single-phase AC input connected to a three-phase motor1550at its open winding middle points for battery charging. Note only two motor windings have the mid points connected to the AC input, which is typical with single-phase AC source. In this case, the motor needs to have a special type and commonly seen dual-section winding motor, where each phase winding basically has two half windings with two layers of conducting wires overlapped in the same slots at the same current direction. With the winding mid points injecting equal current into both half windings the induced magnetic forces are always balanced and cancelled. Therefore, balanced motor winding currents during PFC rectifier operation will not cause any significant pulsating torque or vibration issue.

Aspects of the present technology may be applied to a wide range of electric motors in a variety of arrangements (e.g. multiple motors in an EV). A few examples are illustrated here but it will be understood that these are not limiting and that the present technology is applicable to many more types of electric motors in many more configurations.

Aspects of the present technology are not limited to any single type of electric motor and may be used with different electric motor designs including single winding motors, dual winding motors, and open winding motors and with any number of motors (either of the same type or different types).

For purposes of this document, it should be noted that the dimensions of the various features depicted in the figures may not necessarily be drawn to scale.

For purposes of this document, reference in the specification to “an embodiment,” “one embodiment,” “some embodiments,” or “another embodiment” may be used to describe different embodiments or the same embodiment.

For purposes of this document, a connection may be a direct connection or an indirect connection (e.g., via one or more other parts). In some cases, when an element is referred to as being connected or coupled to another element, the element may be directly connected to the other element or indirectly connected to the other element via intervening elements. When an element is referred to as being directly connected to another element, then there are no intervening elements between the element and the other element. Two devices are “in communication” if they are directly or indirectly connected so that they can communicate electronic signals between them.

For purposes of this document, the term “based on” may be read as “based at least in part on.”

For purposes of this document, without additional context, use of numerical terms such as a “first” object, a “second” object, and a “third” object may not imply an ordering of objects, but may instead be used for identification purposes to identify different objects.

Although the present disclosure has been described with reference to specific features and embodiments thereof, it is evident that various modifications and combinations can be made thereto without departing from scope of the disclosure. The specification and drawings are, accordingly, to be regarded simply as an illustration of the disclosure as defined by the appended claims, and are contemplated to cover any and all modifications, variations, combinations or equivalents that fall within the scope of the present disclosure.

The foregoing detailed description has been presented for purposes of illustration and description. It is not intended to be exhaustive or to limit the subject matter claimed herein to the precise form(s) disclosed. Many modifications and variations are possible in light of the above teachings. The described embodiments were chosen in order to best explain the principles of the disclosed technology and its practical application to thereby enable others skilled in the art to best utilize the technology in various embodiments and with various modifications as are suited to the particular use contemplated. It is intended that the scope be defined by the claims appended hereto.