Patent Description:
In recent years, electric vehicles equipped with a large-capacity battery have been developed. Although such an electric vehicle has a long cruising range, it has a problem that it takes a long time to charge. Therefore, development on quick charging is underway.

When high-voltage power (for example, <NUM>,600V) is drawn from a commercial power source in order to implement quick charging, a high-voltage power receiving facility (cubicle) is required, which is a heavy burden in terms of size and cost. Moreover, when it is attempted to store energy equivalent to that of an existing gas station with electric power, a required site becomes very large, which is not realistic.

Therefore, <CIT> proposes to use a flywheel as an energy storage device to store kinetic energy instead of electrical energy.

<CIT> discloses a charging system which charges a power storage device mounted on a moving object, comprising: an electric power conversion device configured to convert electric power supplied from a commercial power supply; a kinetic energy storage device configured to store kinetic energy; and a rotary electric machine that is electrically connected to the electric power conversion device and is mechanically connected to the kinetic energy storage device.

<CIT> shows a charging system according to the preamble of claim <NUM>. There, each of the electrical storage units has a DC/AC converter.

However, there is room for improvement when trying to use the one described in <CIT> commercially.

The present invention provides a charging system capable of efficiently charging in a limited space.

According to an aspect of the present invention, there is provided a charging system according to claim <NUM>.

According to the features of claim <NUM>, by storing the electric power supplied from the commercial power supply as kinetic energy in the kinetic energy storage device, it is possible to store energy appropriately in a limited space as compared with the case of storing electrical energy. As a result, the power storage device mounted on the vehicle can be efficiently charged.

According to the features of claim <NUM>, since a plurality of rotary electric machines are connected in parallel to the electric power conversion device, the charging system can be miniaturized as compared with the case where the electric power conversion device is connected to each of the rotary electric machines.

According to the features of claim <NUM>, even when the plurality of rotary electric machines are connected in parallel to the electric power conversion device, the plurality of rotary electric machines can be appropriately controlled by the phase matching control.

According to the further features of claim <NUM>, the rotor phases can be made uniform even when the rotor phases are different in the plurality of rotary electric machines.

According to the features of claim <NUM>, the electric power supplied from the commercial power supply has a voltage of <NUM> V or more and <NUM> V or less. Therefore, no special power receiving facility such as a high-voltage power receiving facility (cubicle) is required and the site for introducing the charging system can be small. As a result, the introduction cost can be suppressed.

According to the features of claim <NUM>, a highly versatile electric power conversion device can be used.

According to the features of claim <NUM>, by intermittently applying torque to each phase, a gentle reaction force acts on the rotor when the torque is released, and thus the phase matching operation of the rotor is promoted.

According to the features of claim <NUM>, the phase matching control can be easily performed.

According to the features of claim <NUM>, the current peak can be lowered, and thus the cost increase of the boost converter can be suppressed.

According to the features of claim <NUM>, since the auxiliary power source such as a solar cell is electrically connected to the electric power conversion device, natural energy can be effectively utilized.

Hereinafter, examples not covered by the claims and embodiments of a charging system of the present invention will be described with reference to the drawings.

As illustrated in <FIG>, a charging system <NUM> is a charging system that charges a battery BAT mounted on a vehicle V, which is a moving object. The vehicle V may be a vehicle equipped with the battery BAT and is, for example, a hybrid vehicle, a plug-in hybrid vehicle, an electric vehicle, or a fuel cell vehicle.

The charging system <NUM> includes an inverter <NUM> that converts electric power supplied from a commercial power supply PS, a flywheel <NUM> that stores kinetic energy, a motor generator <NUM> that is electrically connected to the inverter <NUM> and is mechanically connected to the flywheel <NUM>, a quick charger <NUM> that is electrically connected to the motor generator <NUM> and supplies electric power to the battery BAT of the vehicle V, and a control device <NUM> that controls the inverter <NUM> and the quick charger <NUM>. The flywheel <NUM> and the motor generator <NUM> form a kinetic energy storage unit <NUM>.

A voltage of the electric power supplied from the commercial power supply PS (hereinafter, referred to as "introduced electric power") is preferably an AC voltage of <NUM> V or more and <NUM> V or less and is, for example, a three-phase three-wire AC <NUM> V When the voltage of the introduced electric power is high, a dedicated power receiving facility such as a high-voltage power receiving facility (cubicle) is required, but when the voltage of the introduced electric power is low, a special power receiving facility such as a high-voltage power receiving facility (cubicle) is not required. In addition, when the voltage of the introduced electric power is low, a large site for installing a high-voltage power receiving facility (cubicle) is not required, and thus an introduction cost can be suppressed. When the site has a margin, a high-voltage power receiving facility (cubicle) capable of receiving an AC voltage of <NUM>,<NUM> V and receiving an electric power of <NUM> kW to <NUM> kW may be installed.

As illustrated in <FIG>, the inverter <NUM> includes a first power conversion unit INV1 which converts the three-phase AC power (hereinafter, sometimes referred to as a first three-phase AC power), which is the introduced electric power, into DC power and a second power conversion unit INV2 which converts the DC power converted by the first power conversion unit INV1 into a three-phase AC power (hereinafter, sometimes referred to as a second three-phase AC power) different from the first three-phase AC power, which is suitable for driving the motor generator <NUM>. The first power conversion unit INV1 and the second power conversion unit INV2 have the same structure and are connected in series to each other with a first smoothing capacitor <NUM> interposed therebetween.

Each of the first power conversion unit INV1 and the second power conversion unit INV2 includes a bridge circuit formed of a plurality of bridge-connected switching elements. For example, the switching element is a transistor such as an Insulated Gate Bipolar Transistor (IGBT) or a Metal Oxide Semi-conductor Field Effect Transistor (MOSFET). For example, in the bridge circuit, paired high-side arm and low-side arm U-phase transistors UH and UL, paired high-side arm and low-side arm V-phase transistors VH and VL, and paired high-side arm and low-side arm W-phase transistors WH and WL are respectively bridge-connected.

Respective transistors UH, VH, and WH of the high side arm have collectors connected to positive electrode terminals PI to form a high side arm. In each phase, each positive electrode terminal PI of the high side arm is connected to a positive electrode connection line 50p.

Respective transistors UL, VL, and WL of the low side arm have emitters connected to negative electrode terminals NI to form a low side arm. In each phase, each negative electrode terminal NI of the low side arm is connected to a negative electrode connection line 50n.

In each phase, the emitters of respective transistors UH, VH, and WH of the high side arm are connected to the collectors of respective transistors UL, VL, and WL of the low side arm at connection points TI.

In each phase of the first power conversion unit INV1, the connection point TI is connected to the commercial power supply PS by a first connection line <NUM>. In each phase of the second power conversion unit INV2, the connection point TI is connected to the motor generator <NUM> by a second connection line <NUM>.

The bridge circuit includes a diode connected between the collector and the emitter of respective transistors UH, UL, VH, VL, WH, and WL so as to be in a forward direction from the emitter to the collector.

Each of the first power conversion unit INV1 and the second power conversion unit INV2 switches ON (conduction) and OFF (disconnection) of each phase transistor pair based on a gate signal which is a switching command input to a gate of each of the transistors UH, VH, WH, UL, VL, and WL. The first power conversion unit INV1 converts the first three-phase AC power input from the commercial power supply PS into DC power, and the second power conversion unit INV2 converts the DC power input from the first power conversion unit INV1 into the second three-phase AC power.

The first smoothing capacitor <NUM> smoothes voltage fluctuation generated by an ON and OFF switching operation of each of the transistors UH, UL, VH, VL, WH, and WL of each of the first power conversion unit INV1 and the second power conversion unit INV2.

The motor generator <NUM> is a three-phase AC type motor generator. During energy filling, the flywheel <NUM> is rotated by power running drive using the electric power input from the inverter <NUM>. Further, during battery charging, kinetic energy of the flywheel <NUM> is converted into electric energy by regenerative drive and electric power is supplied to the quick charger <NUM>.

As illustrated in <FIG>, the quick charger <NUM> includes a third power conversion unit INV3 which converts the three-phase AC power generated by the motor generator <NUM> into DC power, a fourth power conversion unit INV4 which converts the DC power converted by the third power conversion unit INV3 into single-phase AC power, a high-frequency transformer <NUM> which transforms the single-phase AC power input from the fourth power conversion unit INV4, and a fifth power conversion unit INV5 which converts the single-phase AC power input from the high-frequency transformer <NUM> into DC power. A second smoothing capacitor <NUM> is provided between the third power conversion unit INV3 and the fourth power conversion unit INV4 and a third smoothing capacitor <NUM> is provided on a downstream side of the fifth power conversion unit INV5. The fourth power conversion unit INV4, the high frequency transformer <NUM>, and the fifth power conversion unit INV5 form a boost converter <NUM> which boosts the electric power supplied from the motor generator <NUM> during battery charging.

By controlling the switching of the first power conversion unit INV1 and the second power conversion unit INV2 of the inverter <NUM> and controlling the switching of the third power conversion unit INV3, the fourth power conversion unit INV4, and the fifth power conversion unit INV5 of the quick charger <NUM>, the control device <NUM> performs energy filling of the flywheel <NUM> and performs charging of the battery BAT mounted on the vehicle V.

The charging system <NUM> configured in such a way can be installed in a car dealer, a convenience store, a supermarket, or the like. The flywheel <NUM> stores kinetic energy until the flywheel <NUM> is fully filled by power running driving the motor generator <NUM> which receives the electric power supplied from the commercial power supply PS via the inverter <NUM>. The charging system <NUM> having the flywheel <NUM> in a fully filled state can be recognized by a user (driver) of the vehicle V through a mobile terminal such as a car navigation system or a smartphone. As illustrated in <FIG>, one charging station may be provided with two charging systems <NUM> or three or more charging systems <NUM>. When the vehicle V needs to be charged, the user can charge the battery BAT mounted on the vehicle V by stopping at one of the nearby charging systems <NUM> in the fully filled states. As a result, it is possible to shorten or eliminate the waiting time.

Each charging system <NUM> may be capable of supplying the energy required to charge the battery BAT for one vehicle. Here, it is assumed that the vehicle V is an electric vehicle having a cruising range of <NUM>. In order to secure the cruising range of <NUM>, the electric energy amount of the battery BAT needs to be about <NUM> kWh. When it is assumed that the output of the quick charger <NUM> is <NUM> MW, charging of the electric vehicle can be achieved in about one minute as similar to that of an existing gasoline vehicle until the charging is completed. When the output of the inverter <NUM> is about <NUM> kW, it may be sufficient to have a space of <NUM><NUM> as an installation space of the inverter <NUM>. Also, when the energy storage capacity of the flywheel <NUM> is <NUM> kWh, it may be sufficient to have a space of <NUM><NUM> as an installation space of the flywheel <NUM>. Further, when the output of the quick charger <NUM> is <NUM> MW, it may be sufficient to have a space of <NUM><NUM> as an installation space of the quick charger <NUM>. When the output of the inverter <NUM> is <NUM> kW, the flywheel <NUM> having an energy storage capacity of <NUM> kWh can be fully filled in about sixty minutes.

<FIG> is a graph illustrating changes in the charging power (kW: left vertical axis) of the quick charger <NUM> and the kinetic energy filling rate (%: right vertical axis) of the flywheel <NUM> with respect to time (min: horizontal axis) when it is assumed that the voltage of the introduced electric power is AC <NUM> V, the output of the inverter <NUM> is <NUM> kW, the output of the quick charger <NUM> is <NUM> MW, and the energy storage capacity of the flywheel <NUM> is <NUM> kWh.

According to <FIG>, since the introduced electric power is a low voltage, it takes a predetermined time to fully fill the flywheel <NUM> with the kinetic energy, but the charging is completed in an extremely short time. Therefore, the user can charge the vehicle V in the similar time as that of an existing gasoline vehicle. It is not preferable to completely stop the flywheel <NUM> during charging, and for example, it is preferable to complete charging when the kinetic energy filling rate reaches <NUM>% to <NUM>%.

As described above, according to the charging system <NUM> of the present embodiment, since a relatively small space is sufficient for installation, the degree of freedom of installation is high and many charging stations can be provided to users.

Next, a charging system <NUM> of a second example on will be described with reference to <FIG>.

In the charging system <NUM> of the second example, a solar cell <NUM> is electrically connected to the inverter <NUM> as an auxiliary power source in the charging system <NUM> of the first example. In the present example and other examples and embodiments described below, the same configuration as that of the charging system <NUM> of the first example is designated by the same reference numerals and letters and the description thereof will be omitted.

The charging system <NUM> of the present example is configured such that the solar cell <NUM> is electrically connected to the inverter <NUM> as an auxiliary power source via an auxiliary power source inverter <NUM> and the electric power generated by the solar cell <NUM> can be used as needed. The auxiliary power source inverter <NUM> converts the DC power generated by the solar cell <NUM> into three-phase AC power. In <FIG> and <FIG>, the solid arrow indicates AC power and the dotted arrow indicates DC power (the same applies to <FIG>).

Specifically, when the flywheel <NUM> is not fully filled, as illustrated in <FIG>, in addition to the electric power supplied from the commercial power supply PS, the electric power generated by the solar cell <NUM> is supplied to the motor generator <NUM> via the inverter <NUM>, and then the motor generator <NUM> which receives these electric powers is driven by power running to store kinetic energy in the flywheel <NUM> until the flywheel <NUM> is fully filled. On the other hand, when the flywheel <NUM> is fully filled, as illustrated in <FIG>, the electric power generated by the solar cell <NUM> can be sold via a power supply path of the commercial power supply PS. As a result, the natural energy can be effectively utilized and the economic burden on an operator of the charging system <NUM> can be reduced. The auxiliary power source is not limited to the solar cell <NUM>, but may be wind power generation, geothermal power generation, wave power generation, or the like.

Next, a charging system <NUM> of an embodiment of the present invention will be described with reference to <FIG>. In the charging system <NUM> of the first example, one kinetic energy storage unit <NUM> composed of the flywheel <NUM> and the motor generator <NUM> is provided. However, in the charging system <NUM> of the embodiment, a plurality of kinetic energy storage units <NUM> are provided between the inverter <NUM> and the quick charger <NUM>.

More specifically, in the charging system <NUM> of the present embodiment, a plurality of (for example, eight) motor generators <NUM> are electrically connected each other, and electrically connected in parallel between the inverter <NUM> and the quick charger <NUM>. Each motor generator <NUM> forms the kinetic energy storage unit <NUM> and the flywheel <NUM> is connected to each motor generator <NUM>. When driving the plurality of motor generators <NUM> with one inverter <NUM>, it is necessary to match phases of all the motor generators <NUM>. Therefore, before driving all the motor generators <NUM>, as illustrated in <FIG>, a phase matching control in which direct current is passed through all the motor generators <NUM> for a predetermined time is performed in advance. By the phase matching control, all the motor generators <NUM> can be drawn to any position, and as a result, the phases of all the motor generators <NUM> can be matched.

Here, the phase matching control will be described more specifically with reference to <FIG> illustrate a case where n (n is an integer of one or more) motor generators <NUM> are electrically connected each other, and electrically connected to the inverter <NUM> in parallel. M/Gn is an n-th motor generator <NUM>. Also, n-R is an R-phase coil of the n-th motor generator <NUM>, n-S is an S-phase coil of the n-th motor generator <NUM>, and n-T is a T-phase coil of the n-th motor generator <NUM>. In <FIG>, the three phases of the three-phase AC power are the R phase, the S phase, and the T phase, which are synonymous with the U phase, the V phase, and the W phase in <FIG>.

As illustrated on the left side of <FIG>, when the rotor phases of the motor generators <NUM> (M/G1, M/G2,. M/Gn) are different, even when the alternating current output from the inverter <NUM> is energized as it is, rotors of respective motor generators <NUM> (M/G1, M/G2,. M/Gn) do not rotate appropriately. Therefore, as illustrated in <FIG>, an instantaneous value (in the example of <FIG>, the value at the zero phase of the R phase current) of the three-phase alternating current is applied to the S phase and the T phase with direct current. In this case, as illustrated in <FIG>, it is preferable to intermittently execute DC energization by repeating energization (ON) and stop (OFF) for a predetermined period. By intermittently applying torque to at least a part of the phases in such a way, a gentle reaction force acts on the rotor when the torque is released, and thus the phase matching operation of the rotor is promoted. Phase matching control is not limited to the case where DC energization is executed for the remaining two phases of the three phases when any one of the three phases is zero phase and DC energization may be executed for all three phases.

After the phase matching operation illustrated on the right side of <FIG> is completed, as illustrated in <FIG> and <FIG>, all the flywheels <NUM> can be filled with kinetic energy by supplying AC power to all the motor generators <NUM>.

When a plurality of motor generators <NUM> are electrically connected each other and electrically connecter to the quick charger <NUM> in parallel, the inductance of the boost converter <NUM> during charging changes depending on the number of motor generators <NUM>. When the number n of the motor generators <NUM> increases, the effective current value becomes n times and the inductance becomes <NUM> / n, so that the peak value of the ripple current becomes n times. Therefore, since the current peak is the sum of the effective current value and the peak value of the ripple current (hereinafter, simply referred to as the ripple current), the current peak becomes n times as the number n of the motor generators <NUM> increases. When the current peak becomes large, it is necessary to use a component having a high withstand voltage, which leads to an increase in cost of the boost converter <NUM>.

For example, assuming a situation where <NUM> to <NUM> motor generators <NUM> can be connected, when the voltage is constant, the time for which the current rises in one ON time is <NUM> to <NUM> times, and thus the ripple current is also <NUM> to <NUM> times. <FIG> is a graph illustrating a relationship between the number of motor generators <NUM>, and the current peak and ripple current.

Here, it is preferable that the control device <NUM> variably controls a switching cycle of the boost converter <NUM>. <FIG> illustrates the current when the control device <NUM> controls the boost converter <NUM> at a constant switching frequency regardless of the number of motor generators <NUM> electrically connected in parallel to the quick charger <NUM>. In the <FIG> indicate the number of motor generators <NUM>. Further, the up and down of the current value is caused by the up and down of the ripple current, and the current peak is a value when the ripple current takes a peak value. From <FIG>, when the switching frequency is set to a constant value regardless of the number of motor generators <NUM>, the effective current value increases as the number of motor generators <NUM> increases, and further, the ripple current also increases as the number of motor generators <NUM> increases, and thus the current peak increases.

On the other hand, <FIG> illustrates the current peak when the boost converter <NUM> is controlled in a set switching cycle by appropriately setting the switching frequency according to the number of motor generators <NUM> electrically connected in parallel to the quick charger <NUM>. In an example of <FIG>, the switching frequency is set so that the ripple current becomes a constant value regardless of the number of motor generators <NUM>. According to this, although the effective current value increases as the number of motor generators <NUM> increases, the current peak becomes smaller because the ripple current is a constant value. The ripple current does not have to be a constant value and the switching frequency may be set so that the ripple current is equal to or less than a predetermined value.

In such a way, the current peak can be lowered by the control device <NUM> switching the switching frequency of the boost converter <NUM> so that the ripple current becomes equal to or less than a predetermined value according to the number of motor generators <NUM>. As a result, it is possible to suppress the cost increase of the boost converter <NUM>.

When the control device <NUM> does not know the number of motor generators <NUM> electrically connected in parallel to the quick charger <NUM> at the start of operation of the boost converter <NUM>, the boost converter <NUM> can be operated in a predetermined switching cycle and the number of motor generators <NUM> can be acquired from a gradient of the input and output voltage and current of the boost converter <NUM>. A relationship between the gradient of the input and output voltage and current of the boost converter <NUM> and the number of motor generators <NUM> may be measured in advance and stored as a table, or may be calculated as appropriate.

The control device <NUM> may acquire the number of motor generators <NUM> from the gradient of the input and output voltage and current of the boost converter <NUM> and may switch the switching frequency based on the acquired number of motor generators <NUM>. Also, the control device <NUM> may switch the switching frequency directly from the gradient of the input and output voltage and current of the boost converter <NUM>.

<FIG> illustrates the current peak and ripple current when the switching cycle is constant (fixed frequency) and the current peak and ripple current when the switching cycle is switched (variable frequency). As is clear from <FIG>, the current peak of the boost converter <NUM> can be suppressed by switching the switching frequency based on the number of motor generators <NUM>.

Next, a charging system <NUM> of a third example will be described with reference to <FIG>.

In the charging system <NUM> of the first example, one set of the inverter <NUM>, the kinetic energy storage unit <NUM>, and the quick charger <NUM> (hereinafter, the one set of the inverter <NUM>, the kinetic energy storage unit <NUM>, and the quick charger <NUM> may be referred to as a charging unit <NUM>) is configured to be able to supply the energy required to charge the battery BAT for one vehicle. However, in the charging system <NUM> of the third example, three sets of the charging units <NUM> are configured to be able to supply the energy required to charge the battery BAT for one vehicle. As a result, each of the inverter <NUM>, the kinetic energy storage unit <NUM>, and the quick charger <NUM> can be miniaturized. It is clear that a person skilled in the art can come up with various modifications to the embodiments within the scope of the claims and it is understood that they also naturally belong to the technical scope of the present invention.

Claim 1:
A charging system (<NUM>) configured to charge a power storage device (BAT) mounted on a moving object (V), comprising:
an electric power conversion device (<NUM>) configured to convert electric power supplied from a commercial power supply (PS);
a control device (<NUM>) configured to control the electric power conversion device (<NUM>);
a kinetic energy storage device (<NUM>) configured to store kinetic energy; and
a rotary electric machine (<NUM>) that is electrically connected to the electric power conversion device and is mechanically connected to the kinetic energy storage device, wherein
the kinetic energy storage device and the rotary electric machine are configured to form a kinetic energy storage unit (<NUM>),
the charging system has a plurality of the kinetic energy storage units (<NUM>), and
a plurality of the rotary electric machines (<NUM>) are electrically connected to each other
and electrically connected to the electric power conversion device (<NUM>) in parallel, characterized in that the control device (<NUM>) is configured to perform phase matching control for matching rotational phases of rotors of the plurality of rotary electric machines (<NUM>) before starting storage of kinetic energy of the kinetic energy storage device by the plurality of rotary electric machines, and the phase matching control is performed so that at least a part of a plurality of phases is energized with direct current.