Power Conversion Equipment

Abstract

To provide an electric power conversion device capable of equalizing a voltage by moving an electric charge between battery cells or battery blocks without separately providing a voltage adjustment device such as a step-up converter and a step-down converter.SOLUTION: An electric power conversion device 1 comprises: an electric power source 2 having an upper battery block 2a and a lower battery block 2b; a plurality of capacitors 7 and 8 serially connected between a positive electrode and a negative electrode of the electric power source; a rotational machine having a plurality of phased coils 3u, 3v, and 3w; a connection point 9 between the capacitors 7 and 8; upper arm elements Q1, Q3, and Q5 provided between the positive electrode of the electric power source 2 and each of the coils 3u, 3v, and 3w; and lower arm elements Q2, Q4, and Q6 provided between the negative electrode of the electric power source 2 and each of the coils 3u, 3v, and 3w. In the electric power conversion device, an intermediate terminal 4 between the upper battery block 2a and the lower battery block 2b is connected to the connection point 9.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a power conversion device that converts power output from a power supply. [Background technology]

[0002] Patent Document 1 describes a voltage equalizer that includes a battery pack formed by connecting multiple battery cells in series and that can equalize the voltages of the battery cells or battery blocks by transferring charge between the battery cells or between battery blocks each consisting of a set of a predetermined number of battery cells. In order to transfer charge between the battery cells or battery blocks in this way, a balancing circuit is formed that connects the positive terminal of one battery cell (battery block) and the negative terminal of the other battery cell (battery block) among adjacent battery cells (battery blocks).

[0003] The balancing circuit is provided with two switch elements, and the midpoint of the switch elements is connected to an intermediate terminal between the negative terminal of one battery cell (battery block) and the positive terminal of the other battery cell (battery block) via a coil. In other words, a step-up / step-down converter is provided between the battery cells or battery blocks.

[0004] Therefore, by controlling the on / off of the switch elements of the balancing circuit configured as described above, the voltage of one side can be increased or decreased, thereby transferring charges between adjacent battery cells (battery blocks). [Prior art documents] [Patent documents]

[0005] [Patent Document 1] JP 2013-247690 A Summary of the Invention [Problem to be solved by the invention]

[0006] The voltage equalizer described in Patent Document 1 forms a balancing circuit for transferring charges between battery cells or battery blocks. In other words, it is equipped with a voltage regulator composed of coils and switch elements for transferring charges. Therefore, a power conversion device including a battery pack in which a plurality of battery cells are connected, a motor to which power is supplied from the battery pack, and an inverter that converts the power supplied from the battery pack to the motor may become large. In addition, if the coils and switch elements are made smaller in size to prevent the power conversion device from becoming large, the current ratings of the coils and switch elements will be lowered, and this may limit the charges that can be transferred between battery cells or battery blocks.

[0007] This invention has been made in light of the above-mentioned technical problems, and aims to provide a power conversion device that can transfer charge between battery cells or battery blocks to equalize voltages, without the need for a separate voltage adjustment device such as a step-up converter or step-down converter. [Means for solving the problem]

[0008] In order to achieve the above object, the present invention provides a power conversion device including: a power source formed by connecting a plurality of battery cells in series; a rotating machine having a plurality of phase coils and a neutral point to which one terminal of the coils of the plurality of phases is connected; a plurality of capacitors connected in series between a positive electrode of the power source and a negative electrode of the power source; a plurality of intermediate switch elements connecting a connection point between a positive electrode side capacitor and a negative electrode side capacitor of the plurality of capacitors and each of the coils of the plurality of phases; an upper arm element having a plurality of positive electrode side switch elements provided between each of the coils of the plurality of phases and the positive electrode of the power source; a lower arm element having a plurality of negative electrode side switch elements provided between each of the coils of the plurality of phases and the negative electrode of the power source; and a controller for controlling the upper arm element, the lower arm element, and the intermediate switch element. It is a placeThe power source includes an upper battery block on the positive electrode side and a lower battery block on the negative electrode side, and an intermediate terminal between the upper battery block and the lower battery block is connected to the connection point. the controller is configured to execute equalization control for controlling the upper arm element, the lower arm element, and the intermediate switch element so that the power consumption of the upper battery block and the lower battery block are the same, or for controlling the upper arm element, the lower arm element, and the intermediate switch element so that the remaining charge amount of the upper battery block and the lower battery block are the same, and is configured to supply power from one side of the upper battery block and the lower battery block to the other side by switching operation of the positive side switch and the negative side switch connected without passing through the neutral point to a predetermined coil of the multiple phase coils in which the supply of power from the power source via the intermediate switch element is cut off by being put into the non-conductive state when there is no request to drive the rotating machine. The present invention is characterized in that

[0009] In addition, this invention a rotating machine having a power source formed by connecting a plurality of battery cells in series, a plurality of coils of a plurality of phases, and a neutral point to which one terminal of the coils of the plurality of phases is connected, a plurality of capacitors connected in series between a positive electrode of the power source and a negative electrode of the power source, a plurality of intermediate switch elements connecting a connection point between a positive electrode side capacitor and a negative electrode side capacitor of the plurality of capacitors and each of the coils of the plurality of phases, an upper arm element having a plurality of positive electrode side switch elements provided between each of the coils of the plurality of phases and the positive electrode of the power source, a lower arm element having a plurality of negative electrode side switch elements provided between each of the coils of the plurality of phases and the negative electrode of the power source, and a controller for controlling the upper arm element, the lower arm element, and the intermediate switch element, and an intermediate terminal between the upper battery block and the lower battery block is connected to the connection point, and the controller is configured to execute equalization control to control the upper arm elements, the lower arm elements, and the intermediate switch elements so that the power consumption of the upper battery block and the lower battery block is the same, or to control the upper arm elements, the lower arm elements, and the intermediate switch elements so that the remaining charge of the upper battery block and the lower battery block is the same, and the controller determines a rotating machine voltage to be applied to the multi-phase coils in accordance with the power required for the rotating machine, adds a difference in SOC voltage values ​​output from the upper battery block and the lower battery block determined by the equalization control to the rotating machine voltage, determines a modulation factor based on a total voltage obtained by adding the difference in SOC voltage values ​​to the rotating machine voltage, and controls the upper arm elements, the lower arm elements, and the intermediate switch elements based on the modulation factor. In addition, in this invention, the controller may control the upper arm element, the lower arm element, and the intermediate switch element so that the power consumption of the upper battery block or the lower battery block which has a greater remaining charge is greater than the power consumption of the upper battery block or the lower battery block which has a lesser remaining charge. In addition, the present invention relates to the above A high-voltage auxiliary may be connected to at least one of the upper battery block and the lower battery block.

[0010] In the present invention, the high voltage auxiliary may be configured to be driven at a voltage lower than the output voltage of the power supply.

[0011] In the present invention, the high voltage auxiliary device may include a DC-DC converter and an electric compressor connected to the positive and negative terminals of the one of the battery blocks.

[0023] In addition, this invention a rotating machine having a power source formed by connecting a plurality of battery cells in series, a plurality of coils of a plurality of phases, and a neutral point to which one terminal of the coils of the plurality of phases is connected, a plurality of capacitors connected in series between a positive electrode of the power source and a negative electrode of the power source, a plurality of intermediate switch elements connecting a connection point between a positive electrode side capacitor and a negative electrode side capacitor of the plurality of capacitors and each of the coils of the plurality of phases, an upper arm element having a plurality of positive electrode side switch elements provided between each of the coils of the plurality of phases and the positive electrode of the power source, a lower arm element having a plurality of negative electrode side switch elements provided between each of the coils of the plurality of phases and the negative electrode of the power source, and a controller for controlling the upper arm element, the lower arm element, and the intermediate switch element, The controller sets a low voltage mode in which a voltage applied to the coils of the multiple phases is relatively low when a voltage required for the coils of the multiple phases is equal to or higher than a predetermined voltage or a current value required for the coils of the multiple phases is equal to or higher than a predetermined current value, and sets a high voltage mode in which a voltage applied to the coils of the multiple phases is relatively high when a voltage required for the coils of the multiple phases is less than a predetermined voltage or a current value required for the coils of the multiple phases is less than a predetermined current value. The present invention is characterized in that it determines

[0024] In the present invention, the predetermined voltage may include a voltage at which partial discharge occurs.

[0025] In addition, this invention a rotating machine having a power source formed by connecting a plurality of battery cells in series, a plurality of coils of a plurality of phases, and a neutral point to which one terminal of the coils of the plurality of phases is connected, a plurality of capacitors connected in series between a positive electrode of the power source and a negative electrode of the power source, a plurality of intermediate switch elements connecting a connection point between a positive electrode side capacitor and a negative electrode side capacitor of the plurality of capacitors and each of the coils of the plurality of phases, an upper arm element having a plurality of positive electrode side switch elements provided between each of the coils of the plurality of phases and the positive electrode of the power source, a lower arm element having a plurality of negative electrode side switch elements provided between each of the coils of the plurality of phases and the negative electrode of the power source, and a controller for controlling the upper arm element, the lower arm element, and the intermediate switch element,The controller sets a two-level mode in which, when the rotation speed of the rotating machine is less than a predetermined rotation speed or the output torque of the rotating machine is less than a predetermined torque, the voltage applied to the coils of the multiple phases is controlled to two voltage levels, 0 V and the output voltage of the power source, and sets a three-level mode in which, when the rotation speed of the rotating machine is equal to or greater than the predetermined rotation speed or the output torque of the rotating machine is equal to or greater than the predetermined torque, the voltage applied to the coils of the multiple phases is controlled to three voltage levels, namely, a midpoint voltage of the voltage of the power source and a voltage obtained by adding / reducing a voltage that is 1 / 2 the voltage of the power source to / from the midpoint voltage. The present invention is characterized in that it determines

[0026] And this invention a rotating machine having a power source formed by connecting a plurality of battery cells in series, a plurality of coils of a plurality of phases, and a neutral point to which one terminal of the coils of the plurality of phases is connected, a plurality of capacitors connected in series between a positive electrode of the power source and a negative electrode of the power source, a plurality of intermediate switch elements connecting a connection point between a positive electrode side capacitor and a negative electrode side capacitor of the plurality of capacitors and each of the coils of the plurality of phases, an upper arm element having a plurality of positive electrode side switch elements provided between each of the coils of the plurality of phases and the positive electrode of the power source, a lower arm element having a plurality of negative electrode side switch elements provided between each of the coils of the plurality of phases and the negative electrode of the power source, and a controller for controlling the upper arm element, the lower arm element, and the intermediate switch element, The controller sets a two-level mode in which, when the temperature of the intermediate switching element is equal to or higher than a predetermined temperature, the voltage applied to the coils of the multiple phases is controlled to two voltage levels, 0 V and the output voltage of the power source, and sets a three-level mode in which, when the temperature of the intermediate switching element is lower than the predetermined temperature, the voltage applied to the coils of the multiple phases is controlled to three voltage levels, the midpoint voltage of the voltage of the power source, and a voltage obtained by adding / reducing a voltage that is 1 / 2 the voltage of the power source to / from the midpoint voltage. The present invention is characterized in that it determines Effect of the Invention

[0027] According to this invention, the capacitors connected in series are connected to the positive and negative poles of the power source, and the intermediate switch element is provided to connect the connection point of the capacitors to the coils of each phase. Therefore, by controlling the intermediate switch element, the positive side switch element, and the negative side switch element, the voltage applied to the rotating machine can be controlled to a multi-stage voltage, thereby controlling the torque of the rotating machine. In addition, by connecting the intermediate terminal of the power source to the connection point of the capacitor, the power consumption of the upper battery block on one side of the intermediate terminal and the lower battery block on the other side can be independently controlled regardless of whether the rotating machine is stopped or driven. That is, it is possible to move charge from one battery block to the other battery block, or to make the power consumption of the upper battery block and the lower battery block equal. That is, it is possible to equalize the power of the upper battery block and the lower battery block. In other words, since there is no need to separately provide a reactor or a capacitor for moving charge between the battery blocks, it is possible to suppress the size of the power conversion device from increasing. [Brief description of the drawings]

[0028] [Figure 1] 1 is a configuration diagram for explaining an example of a power conversion device according to an embodiment of the present invention. [Diagram 2] FIG. 13 is a diagram for explaining a configuration in which a high-voltage auxiliary device is connected to a lower battery block. [Diagram 3] 10 is a diagram for explaining a configuration in which high-voltage auxiliary equipment is connected to an upper battery block and a lower battery block. FIG. [Figure 4] FIG. 2 is a diagram for explaining a configuration in which a high-voltage auxiliary device is connected to an upper battery block. [Diagram 5] 11 is a flowchart illustrating a control example for determining a modulation rate by equalization control. [Figure 6] FIG. 11 is an equivalent circuit diagram showing a simplified circuit state in a stop equalization mode. [Figure 7] FIG. 7 is an equivalent circuit diagram showing a further simplified circuit state of the circuit shown in FIG. 6. [Figure 8]FIG. 11 is a control block diagram for explaining an example of control for determining a switch signal by PMW control in a stop equalization mode. [Figure 9] FIG. 1(a) is a diagram for explaining an example of a modulation rate that is set when power is applied from the upper battery block to the lower battery block, and FIG. 1(b) is a diagram for explaining an example of a modulation rate that is set when power is applied from the lower battery block to the upper battery block. [Figure 10] This figure shows the current values ​​of each coil and the power consumption of the upper battery block and the lower battery block when the same power is output from the upper battery block and the lower battery block and controlled to supply power to a high-voltage auxiliary connected to the lower battery block. [Figure 11] 1A is an equivalent circuit diagram when the motor is driven only by power from the upper battery block, and FIG. 1B is an equivalent circuit diagram when the motor is driven only by power from the lower battery block. [Figure 12] FIG. 11 is a control block diagram for explaining a control example in which a modulation rate is determined according to an SOC when a motor is driven. [Figure 13] FIG. 13(a) is a diagram showing the phase current, modulation rate, and power consumption of the upper battery block and the lower battery block when the modulation rate is determined based on the control example shown in FIG. 12, and FIG. 13(b) is a diagram showing the phase current, modulation rate, and power consumption of the upper battery block and the lower battery block when the modulation rate is determined based only on the power required by the motor. [Figure 14] FIG. 11 is a control block diagram for explaining a control example for offsetting a modulation rate. [Figure 15] FIG. 15(a) is a diagram showing the phase current, modulation rate, and power consumption of the upper battery block and the lower battery block when the modulation rate is determined based on the control example shown in FIG. 14; FIG. 15(b) is a diagram showing the phase current, modulation rate, and power consumption of the upper battery block and the lower battery block when the modulation rate is not offset; and FIG. 15(c) is a diagram showing the effect of reducing power loss by offsetting the modulation rate. [Figure 16]FIG. 11 is a control block diagram for explaining a control example for changing the modulation rate to an overmodulation region. [Figure 17] FIG. 17A is a diagram showing the phase current and the modulation factor when the modulation factor is determined based on the control example shown in FIG. 16, FIG. 17B is a diagram showing the phase current and the modulation factor when the modulation factor is not changed to the offset and overmodulation region, and FIG. 17C is a diagram showing the effect of reducing power loss by offsetting the modulation factor and changing it to the overmodulation region. [Figure 18] FIG. 4 is a diagram showing the relationship between atmospheric pressure and partial discharge inception voltage. [Figure 19] 10 is a flowchart illustrating an example of control for changing a method for determining a modulation factor in response to a request for protecting an insulating portion of a motor. [Figure 20] FIG. 1A is a diagram showing the phase current, modulation factor, and line voltage of the motor when the MG insulation protection mode is set, and FIG. 1B is a diagram showing the phase current, modulation factor, and line voltage of the motor when the motor drive mode is set. [Figure 21] FIG. 1A is an equivalent circuit diagram showing a schematic diagram of the connection state between the upper battery block and the motor when the modulation rate is offset, and FIG. 1B is an equivalent circuit diagram showing a schematic diagram of the connection state between the power supply and the motor when the modulation rate is not offset. [Figure 22] 5 is a flowchart illustrating an example of control for switching between a two-level mode and a three-level mode depending on the operating state of the motor. [Diagram 23] FIG. 1A is a diagram showing phase currents and line voltages when a two-level mode is set, FIG. 1B is a diagram showing phase currents and line voltages when a three-level mode is set, and FIG. 1C is a diagram showing the effect of reducing power loss by setting the two-level mode. [Figure 24] FIG. 1 is a configuration diagram for explaining an example of a power conversion device that controls a five-phase AC motor. [Diagram 25] FIG. 11 is a configuration diagram for explaining another example of a power conversion device. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0029] A configuration for explaining an example of a power conversion device according to an embodiment of the present invention is shown in Fig. 1. The power conversion device 1 shown in Fig. 1 converts the electric power passing between a power source 2 and a motor 3, which corresponds to the "rotating machine" in the embodiment of the present invention.

[0030] The power source 2 is configured by arranging multiple battery cells Bc, each of which is a secondary battery such as a lithium ion battery or a nickel-metal hydride battery, in series. That is, the power source 2 is configured as a battery pack. The power source 2 shown in FIG. 1 is divided into an upper battery block 2a on the upper side and a lower battery block 2b on the lower side in FIG. 1. Specifically, an intermediate terminal 4 is provided between the upper battery block 2a and the lower battery block 2b.

[0031] The motor 3 is configured in the same manner as a motor provided as a driving force source for a conventional electric vehicle or hybrid vehicle. The motor 3 is a star-connected AC motor having coils of two or more phases. In the example shown in Fig. 1, the motor 3 is configured as a synchronous motor having three-phase coils 3u, 3v, and 3w of U-phase, V-phase, and W-phase.

[0032] A positive busbar 5 is connected to the positive terminal of the power source 2, and a negative busbar 6 is connected to the negative terminal of the power source 2. A first capacitor 7 and a second capacitor 8 are connected between the positive busbar 5 and the negative busbar 6. Specifically, the positive terminal of the first capacitor 7 is connected to the positive busbar 5, the negative terminal is connected to the positive terminal of the second capacitor 8, and the negative terminal of the second capacitor 8 is connected to the negative busbar 6. That is, the first capacitor 7 and the second capacitor 8 are connected in series. In addition, the intermediate terminal 4 is connected to a connection point 9 between the first capacitor 7 and the second capacitor 8. The first capacitor 7 corresponds to the "positive side capacitor" in the embodiment of the present invention, and the second capacitor 8 corresponds to the "negative side capacitor" in the embodiment of the present invention.

[0033] An upper arm switch (element) 10 and a lower arm switch (element) 11 are further provided between the positive bus bar 5 and the negative bus bar 6. Specifically, the collector which is the high potential side terminal of the upper arm switch 10 is connected to the positive bus bar 5, the emitter which is the low potential side terminal is connected to the collector which is the high potential side terminal of the lower arm switch 11, and the emitter which is the low potential side terminal of the lower arm switch 11 is connected to the negative bus bar 6. That is, the upper arm switch 10 and the lower arm switch 11 are connected in series.

[0034] As described above, since the motor 3 shown in FIG. 1 is a three-phase AC motor, the upper arm switch 10 and the lower arm switch 11 are each composed of three switches. Specifically, the upper arm switch 10 is composed of a first switch Q1 connected to the U-phase coil 3u, a third switch Q3 connected to the V-phase coil 3v, and a fifth switch Q5 connected to the W-phase coil 3w. The lower arm switch 11 is composed of a second switch Q2 connected to the U-phase coil 3u, a fourth switch Q4 connected to the V-phase coil 3v, and a sixth switch Q6 connected to the W-phase coil 3w. The first switch Q1, the third switch Q3, and the fifth switch Q5 correspond to the "positive pole side switch element" in the embodiment of the present invention, and the second switch Q2, the fourth switch Q4, and the sixth switch Q6 correspond to the "negative pole side switch element" in the embodiment of the present invention.

[0035] Each of these switches Q1 to Q6 is formed of a conventionally known insulated gate bipolar transistor (IGBT), and a flywheel diode D1 to D6 is connected in anti-parallel to each of the IGBTs. Note that each of the switches Q1 to Q6 is not limited to an IGBT, and may be formed of other switch elements such as a metal oxide semiconductor field effect transistor (MOSFET).

[0036] One end of the U-phase coil 3u is connected to the connection point between the first switch Q1 and the second switch Q2, one end of the V-phase coil 3v is connected to the connection point between the third switch Q3 and the fourth switch Q4, and one end of the W-phase coil 3w is connected to the connection point between the fifth switch Q5 and the sixth switch Q6. The other ends of the U-phase coil 3u, the V-phase coil 3v, and the W-phase coil 3w are connected, and the point where the coils 3u, 3v, and 3w are connected forms a neutral point 12.

[0037] In addition, an intermediate switch 13 is provided for connecting the intermediate terminal 4 of the power source 2 and the connection point 9 of the first capacitor 7 and the second capacitor 8 to each of the coils 3u, 3v, and 3w. The intermediate switch 13 is composed of a seventh switch Q7 to a twelfth switch Q12, and the collectors of the seventh switch Q7, the ninth switch Q9, and the eleventh switch Q11 are connected to the connection point 9 between the first capacitor 7 and the second capacitor 8. In addition, the emitter of the seventh switch Q7 is connected to the emitter of the eighth switch Q8, and the collector of the eighth switch Q8 is connected to the connection point between the first switch Q1 and the second switch Q2. Similarly, the emitter of the tenth switch Q10 is connected to the emitter of the ninth switch Q9, and the collector of the tenth switch Q10 is connected to the connection point between the third switch Q3 and the fourth switch Q4. Furthermore, the emitter of the eleventh switch Q11 is connected to the emitter of the twelfth switch Q12, and the collector of the twelfth switch Q12 is connected to the connection point between the fifth switch Q5 and the sixth switch Q6.

[0038] The seventh switch Q7 to the twelfth switch Q12 are configured by IGBTs like the first switch Q1 to the sixth switch Q6 described above, and flywheel diodes D7 to D12 are connected in anti-parallel to the switches Q7 to Q12, respectively. The switches Q7 to Q12 are not limited to IGBTs, and may be configured by other switch elements such as MOSFETs or reverse blocking IGBTs (RB-IGBTs).

[0039] The above-mentioned power conversion device 1 is provided with an ammeter 14 that detects the current flowing through each of the coils 3u, 3v, 3w, and a cell monitoring unit 15 that monitors the state of charge (SOC), state of health (SOH), temperature, voltage, etc. of the power source 2. Furthermore, an inverter control device (controller) 16 is provided that controls each of the switches Q1 to Q12 based on data detected by the ammeter 14 and cell monitoring unit 15.

[0040] The power conversion device 1 configured as described above can function as a three-level inverter (hereinafter simply referred to as the inverter) 17 that controls the output voltage to three voltage levels, namely, the midpoint voltage Vdc / 2 of the voltage Vdc of the power supply 2 as a reference, the midpoint voltage Vdc / 2, and a voltage obtained by adding or subtracting 1 / 2 times the voltage Vdc of the power supply 2 to or from the midpoint voltage Vdc / 2, by controlling the first switch Q1 to the twelfth switch Q12. Specifically, by controlling the upper arm switch 10 to the on state, the voltage that can be output becomes Vdc / 2 based on the midpoint voltage Vdc / 2 (i.e., the voltage Vdc of the power supply 2 based on 0V), by controlling the lower arm switch 11 to the on state, the voltage that can be output becomes -Vdc / 2 based on the midpoint voltage Vdc / 2 (i.e., 0V based on 0V), and by controlling the middle switch 13 to the on state, the voltage that can be output becomes 0 based on the midpoint voltage Vdc / 2 (i.e., Vdc / 2 based on 0V).

[0041] In addition, in the power conversion device 1 according to an embodiment of the present invention, a high-voltage auxiliary device such as an electric compressor that operates at a voltage lower than the output voltage of the power source 2 may be connected to at least one of the upper battery block 2a and the lower battery block 2b via a DC-DC converter.

[0042] Figure 2 shows an example in which a high-voltage auxiliary device 18 is connected to the lower battery block 2b. In the example shown in Figure 2, an electric compressor 19 and a DC-DC converter 20 are connected in parallel to the intermediate terminal 4 (i.e., the positive terminal of the lower battery block 2b) and the negative busbar 6, and an auxiliary battery 21 is connected to the DC-DC converter 20.

[0043] FIG. 3 shows an example in which high-voltage auxiliary equipment 18 is connected to the upper battery block 2a and the lower battery block 2b. In the example shown in FIG. 3, an electric compressor 19 is connected to the positive bus bar 5 and the intermediate terminal 4, a DC-DC converter 20 is connected to the intermediate terminal 4 and the negative bus bar 6, and an auxiliary battery 21 is connected to the DC-DC converter 20.

[0044] Figure 4 shows an example in which a high-voltage auxiliary device 18 is connected to the upper battery block 2a. In the example shown in Figure 2, an electric compressor 19 and a DC-DC converter 20 are connected in parallel to the positive busbar 5 and the intermediate terminal 4 (i.e., the negative terminal of the upper battery block 2a), and an auxiliary battery 21 is connected to the DC-DC converter 20.

[0045] In the example shown in Figures 2 to 4, the power source 2 and the motor 3 are connected in the same manner as in the example shown in Figure 1, so the components connecting the power source 2 and the motor 3 are given the same reference symbols and their descriptions are omitted.

[0046] The power conversion device 1 configured as described above is configured to transfer charge between the upper battery block 2a and the lower battery block 2b, and to make the power consumption of the upper battery block 2a and the lower battery block 2b different. A flow chart for explaining an example of the control is shown in FIG. 5. In the control example shown in FIG. 5, first, it is determined whether or not there is a request to execute the equalization control (step S1). This equalization control controls each switch Q1 to Q12 so as to reduce the difference in the remaining charge (SOC) between the upper battery block 2a and the lower battery block 2b, or to suppress an increase in the SOC difference. That is, each switch Q1 to Q12 is controlled so that the remaining charge of the upper battery block 2a and the lower battery block 2b becomes the same. Therefore, for example, the voltage of the upper battery block 2a and the SOC of the lower battery block 2b are measured, and if the difference in SOC is equal to or greater than a predetermined difference, it is determined that there is a request to execute the equalization control. Also, if there is a request to make the power consumption of the upper battery block 2a and the lower battery block 2b the same, it is similarly determined that there is a request to execute the equalization control.

[0047] If the answer to step S1 is negative because there is no request to execute equalization control, the normal drive mode or standby mode is set (step S2), and this routine ends once. The normal drive mode is a mode in which the switches Q1 to Q12 are controlled according to the power required for the motor 3, similar to a conventional power conversion device equipped with a three-level inverter. The standby mode is a mode in which the switches Q1 to Q12 are stopped without outputting gate signals to them. In other words, power control is performed in the same manner as in the conventional method, without considering the relationship between the power consumption of the upper battery block 2a and the lower battery block 2b.

[0048] On the other hand, if the answer to step S1 is affirmative because there is a request to execute equalization control, it is determined whether there is a request to drive the motor 3 in order to determine the gate signals of each switch Q1 to Q12, in other words, to determine the voltage values ​​to be applied to each coil 3u, 3v, 3w (step S3).

[0049] If the answer to step S3 is negative because there is no request to drive the motor 3, the vehicle-stopped equalization mode is set (step S4). This vehicle-stopped equalization mode is a mode in which electric charge is transferred between the upper battery block 2a and the lower battery block 2b, and power is supplied from one battery block 2a (2b) having a higher SOC to the other battery block 2b (2a) having a lower SOC to charge the other battery block 2b (2a), or the upper battery block 2a and the lower battery block 2b output the same power to supply power to the high-voltage auxiliary device 18 connected to the power conversion device 1, or the power consumption of the battery block 2a (2b) having a higher SOC is made greater than the power consumption of the other battery block 2b (2a).

[0050] Therefore, when step S4 is executed and the vehicle-parked equalization mode is set, the voltage of one of the battery blocks 2a (2b) is increased or decreased to match the voltage of the other battery block 2b (2a), and the other battery block 2b (2a) is charged, or power is supplied from each of the battery blocks 2a, 2b to the high-voltage auxiliary device 18 connected to the other battery block 2b. That is, the inverter 17 is made to function as a step-up converter or a step-down converter. Therefore, following step S4, first, a conductive state is established between the connection point 9 and one or two of the U-phase coil 3u, the V-phase coil 3v, and the W-phase coil 3w. That is, one of the intermediate switches 13 is set to ON (step S5). The other intermediate switches 13 are made non-conductive.

[0051] FIG. 6 shows a simplified equivalent circuit diagram when the seventh switch Q7 is turned on. For convenience of explanation, in FIG. 6, the U-phase coil 3u and the V-phase coil 3v are shown as one coil, and the W-phase coil 3w is not shown. As shown in FIG. 6, by turning on the seventh switch Q7, the intermediate terminal 4 is connected in series with the U-phase coil 3u and the V-phase coil 3v, and the other ends of the coils 3u and 3v are connected to the third switch Q3 and the fourth switch Q4. Similarly, the intermediate terminal 4 is connected in series with the U-phase coil 3u and the W-phase coil 3w, and the other ends of the coils 3u and 3w are connected to the fifth switch Q5 and the sixth switch Q6.

[0052] A further simplified version of this circuit is shown in Figure 7, in which a step-up converter or step-down converter circuit is formed with coils 3u, 3v as reactors, as shown in Figure 7. Therefore, by controlling the on / off of the third switch Q3 and the fourth switch Q4, the voltage of one of the battery blocks 2a (2b) can be increased or decreased, and charge can be transferred between the upper battery block 2a and the lower battery block 2b.

[0053] Therefore, following step S5, the modulation factors (=voltage command value / carrier wave amplitude) Mv, Mw according to the power required for the upper battery block 2a are determined (step S6), and then the first switch Q1 to the sixth switch Q6 are PWM (on / off) controlled based on the modulation factors Mv, Mw determined in step S6 (step S7), and this routine is temporarily terminated. Specifically, the positive pole side switch (here, the third switch Q3 and the fifth switch Q5) and the negative pole side switch (here, the fourth switch Q4 and the sixth switch Q6) connected to a predetermined coil (here, the V-phase coil 3v and the W-phase coil 3w) that is not turned on in step S5 among the first switch Q1 to the sixth switch Q6 and thus the supply of power from the power source 2 via the intermediate switch 13 is cut off are PWM-controlled (switching operation).

[0054] Fig. 8 shows a control block diagram for determining the gate signals of the switches that are PWM controlled by setting the stationary equalization mode. The example shown in Fig. 8 shows a case where the seventh switch Q7 is turned on in step S5. In this case, the eighth switch Q8 is turned off, but is in a conductive state via the eighth diode D8, so in Fig. 8, the eighth switch Q8 is shown as being on.

[0055] 8, the first switch Q1, the second switch Q2, the ninth switch Q9 to the twelfth switch Q12 are turned off, that is, the switches Q1, Q2, Q9 to Q12 are in a non-conducting state.

[0056] On the other hand, in order to perform PWM control on the third switch Q3 to the sixth switch Q6, first, a required current value Iu_req to be passed through the U-phase coil 3u is calculated. For example, the SOCs of the upper battery block 2a and the lower battery block 2b are compared, and the required current value Iu_req can be calculated based on the power passed from one battery block 2a (2b) to the other battery block 2b (2a) in order to reduce the difference in SOC. In addition, when power is supplied to something other than the motor 3, such as when a high-voltage auxiliary device 18 is connected to the lower battery block 2b as shown in FIG. 2, the SOCs of the upper battery block 2a and the lower battery block 2b are compared, and the required current value Iu_req can be calculated based on the difference in SOC so that the power consumption of the battery block 2a (2b) with the higher SOC is increased.

[0057] Next, the current passing through the U-phase coil 3u is detected by the ammeter 14, and the difference between the requested current value Iu_req and the feedback value Iu_fe, which is the detected current value, is input to the PI controller 22. Then, a target current value to be passed through the U-phase coil 3u is calculated based on the difference between the requested current value Iu_req and the feedback value Iu_fe, and a target voltage value V_tgt for passing a current of this target current value through the U-phase coil 3u is calculated and output from the PI controller 22. Note that the target voltage value V_tgt corresponds to the "rotating machine voltage" in this embodiment of the present invention.

[0058] In the control example shown here, the duty ratio of each switch Q3 to Q6 is determined by a conventionally known triangular wave comparison method. Therefore, in the example shown in FIG. 8, first, the target voltage value V_tgt output from the PI controller 22 is normalized. That is, the target voltage value V_tgt is divided by a value that is 1 / 2 the voltage value of the power source 2. By normalizing the target voltage value V_tgt in this way, the maximum and minimum voltage values ​​of the carrier wave (carrier wave) to be compared with the normalized target voltage value V_tgt become ±1. That is, at the point in time when the target voltage value V_tgt is normalized, the modulation factors (=voltage command value / amplitude of the carrier wave) Mv and Mw are substantially found.

[0059] 9(a) shows the modulation factors Mv and Mw of the command values ​​of the voltages applied to the V-phase coil 3v and the W-phase coil 3w determined as described above when power is supplied from the upper battery block 2a to the lower battery block 2b to charge the lower battery block 2b, or when more power is supplied from the upper battery block 2a to the high-voltage auxiliary device 18 connected to the lower battery block 2b than from the lower battery block 2b. Also, FIG. 9(b) shows the modulation factors Mv and Mw of the command values ​​of the voltages applied to the V-phase coil 3v and the W-phase coil 3w determined as described above when power is supplied from the lower battery block 2b to the upper battery block 2a to charge the upper battery block 2a, or when more power is supplied from the lower battery block 2b to the high-voltage auxiliary device 18 connected to the upper battery block 2a than from the upper battery block 2a. Here, the current values ​​flowing through the coils 3u, 3v, and 3w toward the neutral point 12 are shown as positive values. That is, the example shown in Figure 9(a) shows the modulation factors Mv, Mw when the required current value Iu_req is set to a positive value, and the example shown in Figure 9(b) shows the modulation factors Mv, Mw when the required current value Iu_req is set to a negative value.

[0060] As shown in FIG. 9(a), when power is supplied from the upper battery block 2a to the lower battery block 2b, the voltage value output from the PI controller 22 is a positive value, so the modulation factors Mv, Mw of the V-phase coil 3v and the W-phase coil 3w are set to be greater than 0. That is, the modulation factors Mv, Mw are set to be offset to the positive side. Similarly, as shown in FIG. 9(b), when power is supplied from the lower battery block 2b to the upper battery block 2a, the voltage value output from the PI controller 22 is a negative value, so the modulation factors Mv, Mw of the V-phase coil 3v and the W-phase coil 3w are set to be smaller than 0. That is, the modulation factors Mv, Mw are set to be offset to the negative side.

[0061] Then, the modulation factors Mv, Mw and the carrier wave are input to a comparator 23, which determines the duty ratio of a signal to be output to each of the switches Q3 to Q6. Then, based on the duty ratio determined by the comparator 23, a signal is output from a PWM output unit 24 to each of the switches Q3 to Q6.

[0062] Figure 10 shows the current values ​​passing through each coil 3u, 3v, 3w and the power consumption of each battery block 2a, 2b when high-voltage auxiliary equipment 18 is connected to the lower battery block 2b as shown in Figure 2 and the power required by the high-voltage auxiliary equipment 18 is controlled so as to be shared equally between the upper battery block 2a and the lower battery block 2b.

[0063] As shown in Fig. 10, a positive current flows through the U-phase coil 3u, and a negative current flows through the V-phase coil 3v and the W-phase coil 3w. The upper battery block 2a and the lower battery block 2b consume the same amount of power. That is, the power of the upper battery block 2a and the lower battery block 2b can be used equally to supply power to the high-voltage auxiliary device 18.

[0064] On the other hand, if the answer to step S3 is affirmative because there is a request to drive the motor 3, the motor drive equalization mode is set (step S8). This motor drive equalization mode is a mode in which the switches Q1 to Q12 are controlled so that the power consumption of the upper battery block 2a and the lower battery block 2b is the same when supplying power to the motor 3 and the high-voltage auxiliary equipment 18, or the power consumption of the battery block 2a (2b) with the higher SOC is greater than the power consumption of the other battery block 2b (2a).

[0065] Therefore, following step S7, the modulation rate determined based on the power required for the motor 3 is modified (changed) in accordance with the power consumption required for the upper battery block 2a and the lower battery block 2b (step S9).

[0066] As shown in the equivalent circuit diagrams in simplified form in Fig. 11(a) and Fig. 11(b), the above-described power conversion device 1 can drive the motor 3 using the upper battery block 2a as a power source, or can drive the motor 3 using the lower battery block 2b as a power source. Specifically, as shown in Fig. 11(a), the first switch Q1, the third switch Q3, the fifth switch Q5, and the seventh switch Q7 to the twelfth switch Q12 can be controlled to control the power supplied from the upper battery block 2a to the motor 3. Also, as shown in Fig. 11(b), the second switch Q2, the fourth switch Q4, the sixth switch Q6, and the seventh switch Q7 to the twelfth switch Q12 can be controlled to control the power supplied from the lower battery block 2b to the motor 3. That is, the power consumption of the upper battery block 2a and the lower battery block 2b can be controlled to be the same, or the power consumption of the upper battery block 2a can be controlled to be different from the power consumption of the lower battery block 2b.

[0067] Therefore, in step S9, the modulation factors Mu, Mv, and Mw of the U-phase coil 3u, the V-phase coil 3v, and the W-phase coil 3w are determined based on the power supplied to the motor 3 according to the required torque and the power supplied to the high-voltage auxiliary device 18. A control block for determining the modulation factors Mu, Mv, and Mw is shown in FIG. 12. In the example shown in FIG. 12, first, the difference between the d-axis required current value Id_req according to the required torque of the motor 3 and the d-axis feedback current value Id_fe is input to the d-axis PI controller 25, and the d-axis target current value Id_tgt to be supplied to the d-axis is calculated based on these values. Next, the d-axis target voltage value Vd_tgt required to supply the d-axis target current value Id_tgt is calculated and output from the d-axis PI controller 25.

[0068] Similarly, the difference between the q-axis required current value Iq_req according to the required torque of the motor 3 and the q-axis feedback current value Iq_fe is input to the q-axis PI controller 26, and the q-axis target current value Iq_tgt to be supplied to the q-axis is calculated based on these values. Next, the q-axis target voltage value Vq_tgt required to supply the q-axis target current value Iq_tgt is calculated and output from the q-axis PI controller 26.

[0069] The target voltage values ​​Vd_tgt, Vq_tgt determined by the d-axis PI controller 25 and the q-axis PI controller 26 are input to a converter 27. This converter 27 determines motor voltage values ​​Vu, Vv, Vw to be applied to the U-phase coil 3u, V-phase coil 3v, and W-phase coil 3w from the d-axis target voltage value Vd_tgt and the q-axis target voltage value Vq_tgt by conventionally known vector control. That is, the voltages to be applied to the coils 3u, 3v, 3w are determined according to the power required of the motor 3 (i.e., the power to be supplied).

[0070] Also, the output voltage of the upper battery block 2a required to reduce the difference in SOC between the upper battery block 2a and the lower battery block 2b is calculated. That is, the output voltage of the upper battery block 2a required to equalize the SOC between the upper battery block 2a and the lower battery block 2b is calculated. For this reason, in the example shown in Fig. 11, the difference in SOC between the upper battery block 2a and the lower battery block 2b is input to the remaining charge PI controller 28, and the remaining charge PI controller 28 calculates the SOC voltage value Vsoc to be applied to each coil 3u, 3v, 3w to reduce the SOC difference, and outputs the SOC voltage value Vsoc.

[0071] Then, the SOC voltage value Vsoc is added to the motor voltage values ​​Vu, Vv, Vw, and the summed voltage value is normalized (divided by 1 / 2 the voltage value Vdc of the power source 2) to obtain the modulation factors Mu, Mv, Mw. Based on the modulation factors Mu, Mv, Mw thus obtained, the duty ratios of the switches Q1 to Q6 are determined in the same manner as in the example shown in Fig. 7. Note that, since the inverter 17 functions as a multilevel inverter here, the comparator 23 compares the modulation factors Mu, Mv, Mw with two carrier waves to determine the duty ratio, in the same manner as in conventionally known multilevel inverter control.

[0072] Based on the modulation factors Mu, Mv, Mw (more specifically, the duty ratios of the switches Q1 to Q12) determined as described above, the switches Q1 to Q12 are PWM (on / off) controlled (step S10), and this routine is temporarily terminated.

[0073] Fig. 13(a) shows the current values ​​passing through the coils 3u, 3v, 3w, the modulation factors Mu, Mv, Mw of each phase, and the power consumption of each battery block 2a, 2b when the switches Q1-Q12 are controlled based on the above-mentioned control example so that the power required for the high-voltage auxiliary machine 18 connected to the lower battery block 2b and the motor 3 is output evenly from the upper battery block 2a and the lower battery block 2b. Fig. 13(b) shows the current values ​​passing through the coils 3u, 3v, 3w, the modulation factors Mu, Mv, Mw of each phase, and the power consumption of each battery block 2a, 2b when the modulation factors Mu, Mv, Mw are determined only by the current required for the motor 3.

[0074] As shown in Fig. 13(a), by executing control to equalize the power consumption of the upper battery block 2a and the lower battery block 2b, the modulation factors Mu, Mv, and Mw are set higher than when the control is not executed. As a result, the power consumption of each battery block 2a, 2b can be made the same. Even if the modulation factors Mu, Mv, and Mw are set in this way, the current value passed through each coil 3u, 3v, and 3w does not change, as shown in Fig. 13(a) and Fig. 13(b).

[0075] As described above, by connecting the intermediate terminal 4 of the power source 2 to the connection point 9 of the first capacitor 7 and the second capacitor 8 in the power conversion device functioning as a three-level inverter, the power consumption of the upper battery block 2a on one side of the intermediate terminal 4 and the lower battery block 2b on the other side can be controlled independently regardless of whether the motor 3 is stopped or driven. That is, it is possible to transfer charge from one battery block 2a (2b) to the other battery block 2b (2a) and to equalize the power consumption of the upper battery block 2a and the lower battery block 2b. That is, it is possible to equalize the power of the upper battery block 2a and the lower battery block 2b. In other words, since there is no need to separately provide a reactor or a capacitor for transferring charge between the battery blocks 2a and 2b, it is possible to suppress the size of the power conversion device 1 from increasing.

[0076] Furthermore, by connecting a DC-DC converter 20 and a compressor 19 to the upper battery block 2a and the lower battery block 2b, the power supply 2 of the power conversion device 1, which is a high-voltage system, can be used as a power supply for the compressor 19 and the like that operates at a lower voltage than the voltage of the power supply 2. As a result, there is no need to separately provide another power supply or power conversion device, and the device can be made smaller.

[0077] Furthermore, in the power conversion device 1 configured as described above, in a region where the modulation rate of the voltage applied to each of the coils 3u, 3v, 3w is low, such as when the motor 3 is rotating at a low rotation speed or when the torque required by the motor 3 is small, a mode occurs in which a current circulates between the intermediate switch 13 and each of the coils 3u, 3v, 3w. In such a circulating mode, the conduction loss of the intermediate switch 13 increases, resulting in a large power loss.

[0078] Therefore, the power conversion device 1 in this embodiment of the present invention is configured to suppress the flow of current through the intermediate switch 13 by changing the modulation factors Mu, Mv, and Mw in the operating region of the motor 3 in which the above-mentioned freewheel mode occurs.

[0079] A control block for explaining an example of the control is shown in Fig. 14. In the example shown in Fig. 14, similarly to the control example shown in Fig. 12, motor voltage values ​​Vu, Vv, Vw to be applied to each coil 3u, 3v, 3w are calculated according to the torque required by the motor 3. Specifically, first, the difference between the d-axis requested current value Id_req according to the torque required by the motor 3 and the d-axis feedback current value Id_fe is input to the d-axis PI controller 25, and the d-axis target current value Id_tgt to be applied to the d-axis is calculated based on these values. Next, the d-axis target voltage value Vd_tgt for applying the d-axis target current value Id_tgt is calculated and output from the d-axis PI controller 25.

[0080] Similarly, the difference between the q-axis required current value Iq_req according to the required torque of the motor 3 and the q-axis feedback current value Iq_fe is input to the q-axis PI controller 26, and the q-axis target current value Iq_tgt to be supplied to the q-axis is calculated based on these values. Next, the q-axis target voltage value Vq_tgt for supplying the q-axis target current value Iq_tgt is calculated and output from the q-axis PI controller 26.

[0081] The target voltage values ​​Vd_tgt, Vq_tgt calculated by the d-axis PI controller 25 and the q-axis PI controller 26 are input to a converter 27. This converter 27 calculates motor voltage values ​​Vu, Vv, Vw to be applied to the U-phase coil 3u, V-phase coil 3v, and W-phase coil 3w from the d-axis target voltage value Vd_tgt and the q-axis target voltage value Vq_tgt by conventionally known vector control.

[0082] Next, in order to change (offset) the modulation factors Mu, Mv, Mw, a predetermined voltage is added (or subtracted) to the motor voltage values ​​Vu, Vv, Vw obtained as described above. Here, a voltage ¼ times the output voltage Vdc of the power supply 2 is added. Then, in order to normalize the value to which the predetermined voltage is added, it is divided by a value ½ times the voltage Vdc of the power supply 2 to obtain the modulation factors Mu, Mv, Mw of the voltages to be applied to the coils 3u, 3v, 3w. Based on the modulation factors Mu, Mv, Mw obtained in this way, the comparator 23 compares the modulation factors Mu, Mv, Mw with the two carrier waves, as in the example shown in FIG. 12, and determines the duty ratio of each of the switches Q1 to Q12.

[0083] Fig. 15(a) shows the phase current, modulation factors Mu, Mv, Mw, and power consumption of each battery block 2a, 2b when the modulation factors Mu, Mv, Mw are determined based on the control block shown in Fig. 14. Fig. 15(b) shows the phase current, modulation factor, and power consumption when the modulation factor is not changed. Fig. 15(c) shows the result of comparing the power loss when the modulation factors Mu, Mv, Mw are controlled as shown in Fig. 15(a) with the power loss when the modulation factors Mu, Mv, Mw are controlled as shown in Fig. 15(b).

[0084] In the example shown in Fig. 15(a), the motor 3 is driven using the power of the lower battery block 2b until a predetermined time t1. That is, the modulation factors Mu, Mv, Mw are determined by adding a negative value as a voltage for changing the modulation factors Mu, Mv, Mw in the control block shown in Fig. 14. In contrast, after the predetermined time t1, the motor 3 is driven using the power of the upper battery block 2a. That is, the modulation factors Mu, Mv, Mw are determined by adding a positive value as a voltage for changing the modulation factors in the control block shown in Fig. 14.

[0085] As shown in Fig. 15(a) and Fig. 15(b), even if the modulation factors Mu, Mv, and Mw are changed, the phase current does not change. That is, the torque required by the motor 3 can be output. Also, in Fig. 15(a), before the predetermined time t1, all of the power required by the motor 3 is output from the lower battery block 2b, and after the predetermined time t1, all of the power required by the motor 3 is output from the upper battery block 2a. In contrast, in Fig. 15(b), the same power is always output from each of the battery blocks 2a and 2b, and the total power is the power required by the motor 3. That is, regardless of which control is executed, the actual power consumption by driving the motor 3 is almost the same.

[0086] However, as shown in Fig. 15(c), the power loss during driving of the motor 3 can be reduced by about 10% when the modulation factors Mu, Mv, Mw are controlled as shown in Fig. 15(a) compared to when the modulation factors Mu, Mv, Mw are controlled as shown in Fig. 15(b). This is because the upper arm switch 10 and the lower arm switch 11 are on / off controlled by offsetting the modulation factors Mu, Mv, Mw to the positive or negative side, and as a result, the occurrence of the above-mentioned freewheel mode can be suppressed.

[0087] It is also known that in the overmodulation region where the modulation factors Mu, Mv, Mw are equal to or greater than a predetermined value (0.61), the number of times the gate signal is switched on and off can be reduced, and the loss in the switch can be reduced. Therefore, in addition to offsetting the modulation factors Mu, Mv, Mw as shown in FIG. 14, or instead of offsetting the modulation factors Mu, Mv, Mw, the modulation factors Mu, Mv, Mw may be changed to the overmodulation region. A control block for explaining an example of such control is shown in FIG. 16. Note that in the example shown in FIG. 16, in addition to offsetting the modulation factors Mu, Mv, Mw, as in the example shown in FIG. 14, the modulation factors are changed to the overmodulation region.

[0088] In the example shown in Fig. 16, similarly to the control example shown in Fig. 14, the motor voltage values ​​Vu, Vv, Vw to be applied to the coils 3u, 3v, 3w are calculated according to the required torque of the motor 3, and a predetermined voltage (Vdc / 4) for changing the modulation factors Mu, Mv, Mw is added (or subtracted) to the motor voltage values ​​Vu, Vv, Vw. Next, in order to set the motor voltage values ​​Vu, Vv, Vw to the overmodulation region, the sum of the predetermined voltage for changing the modulation factors Mu, Mv, Mw is multiplied by a predetermined coefficient K. This predetermined coefficient K is a coefficient for increasing the motor voltage values ​​Vu, Vv, Vw to the overmodulation region, and therefore can be determined based on the motor voltage values ​​Vu, Vv, Vw.

[0089] Then, in order to normalize the value multiplied by the predetermined coefficient K as described above, similar to the example shown in Fig. 14, the modulation factors Mu, Mv, Mw of the voltages applied to the coils 3u, 3v, 3w are obtained by dividing the value by 1 / 2 the value of the voltage Vdc of the power supply 2. Based on the modulation factors Mu, Mv, Mw thus obtained, similar to the examples shown in Fig. 12 and Fig. 14, the comparator 23 compares the modulation factors Mu, Mv, Mw with the two carrier waves to determine the duty ratio of each of the switches Q1 to Q12.

[0090] Fig. 17(a) shows the phase current and the modulation factors Mu, Mv, Mw when the modulation factors Mu, Mv, Mw are determined based on the control block shown in Fig. 16. Fig. 17(b) shows the phase current and the modulation factors Mu, Mv, Mw when the modulation factors Mu, Mv, Mw are not offset and are not changed to the overmodulation region. Fig. 17(c) shows the result of comparing the power loss when the modulation factors Mu, Mv, Mw are controlled as shown in Fig. 17(a) with the power loss when the modulation factors Mu, Mv, Mw are controlled as shown in Fig. 17(b).

[0091] By determining the modulation factors Mu, Mv, Mw based on the control block of FIG. 16, the amplitude of the modulation factors Mu, Mv, Mw becomes large as shown in FIG. 17(a). On the other hand, although the ratio of the power supplied from the upper battery block 2a to the motor 3 increases by offsetting the modulation factor, the voltage applied to each coil 3u, 3v, 3w has a magnitude based on the required value. Therefore, as shown in FIG. 17(a) and FIG. 17(b), the phase currents of each coil 3u, 3v, 3w are the same. However, by changing the modulation factors Mu, Mv, Mw to increase the overmodulation region, the period during which each switch Q1 to Q12 is turned on can be extended, in other words, the number of times the switches Q1 to Q12 are switched on and off can be reduced. As a result, the power loss caused by the on / off switching of each switch Q1 to Q12 can be reduced by about 25% as shown in FIG. 17(c).

[0092] In the above example, after offsetting the modulation factors Mu, Mv, Mw, a predetermined coefficient K is further multiplied to make them into the overmodulation region. However, the modulation factors Mu, Mv, Mw may be changed by multiplying them by a predetermined coefficient K without offsetting them.

[0093] Moreover, the power conversion device 1 configured as shown in FIG. 1 insulates the motor 3 (specifically, each of the coils 3u, 3v, 3w). Meanwhile, partial discharge occurs in the electric circuit depending on the atmospheric pressure, the coil (winding) temperature, and the like. FIG. 18 shows an example in which the voltage at which partial discharge occurs (PDIV: partial discharge inception voltage) changes depending on the atmospheric pressure, and as shown by the dashed line in FIG. 18, the lower the atmospheric pressure, the lower the PDIV. Therefore, it is preferable to reduce the voltage applied to the motor 3 when the PDIV is low. A flowchart for explaining an example of such control is shown in FIG. 19.

[0094] In the control example shown in Fig. 19, first, it is determined whether or not there is a request to drive the motor 3 (step S11). This step S11 can be determined based on the accelerator opening degree by the driver, etc.

[0095] If the answer to step S11 is NO because there is no request to drive the motor 3, the standby mode is set (step S12) and this routine ends once. In the standby mode, the switches Q1 to Q12 are stopped without outputting gate signals thereto.

[0096] On the other hand, if the answer to step S11 is YES because there is a request to drive the motor 3, it is determined whether there is a request to protect the insulating portion of the motor (MG) 3 (step S13). This step S13 is determined YES when the PDIV is equal to or lower than a predetermined value and the conditions are such that partial discharge is likely to occur. In other words, it is determined whether there is a request to reduce the voltage applied to the motor 3.

[0097] Specifically, step S13 is determined based on a predetermined parameter that affects (is related to) the change in PDIV, such as when the atmospheric pressure detected by an atmospheric pressure sensor or the like is equal to or lower than a predetermined pressure, or when the temperature of the winding detected by a temperature sensor or the like is equal to or higher than a predetermined temperature. Similarly, partial discharge occurs when the voltage applied to the winding becomes equal to or higher than the PDIV. Therefore, step S13 is determined based on a parameter that causes the voltage applied to the winding to increase, such as when the terminal voltage of the power source 2 is equal to a predetermined voltage, or when the phase current of each of the coils 3u, 3v, and 3w is equal to or higher than a predetermined current. That is, step S13 can be determined based on whether or not the environment is one in which partial discharge may occur, whether or not the motor is in an operating state, etc.

[0098] More specifically, when the maximum voltage is output from the upper battery block 2a and the lower battery block 2b as shown in FIG. 18, the atmospheric pressure at which the voltage value applied to each coil 3u, 3v, 3w is equal to or less than PDIV is defined as the predetermined pressure Pth, and if the atmospheric pressure is less than the predetermined pressure Pth, a positive judgment is made in step S13.

[0099] If the answer to step S13 is negative because there is no request to protect the insulation of the motor 3, in other words, the condition is such that the possibility of partial discharge occurring is low, the motor drive mode is set (step S14). This step S14 is a mode in which the motor 3 is normally driven, and if there is a request for equalization control based on the control example shown in FIG. 5, the modulation factors Mu, Mv, and Mw are determined based on the SOC of the upper battery block 2a and the lower battery block 2b, and if there is no request for equalization control, the switches Q1 to Q12 are controlled according to the power required for the motor 3, similar to a power conversion device equipped with a conventional three-level inverter. In other words, the voltage applied to the coils 3u, 3v, and 3w is controlled to a magnitude based on the output voltage of the power source 2, and a mode is set in which a higher voltage is applied than when the MG insulation protection mode described later is set.

[0100] Next, modulation factors Mu, Mv, Mw are determined based on the accelerator operation amount, etc., and the switches Q1 to Q12 are PWM-controlled based on the determined modulation factors Mu, Mv, Mw (step S15), after which this routine is temporarily terminated.

[0101] On the other hand, if the answer of step S13 is affirmative due to a request to protect the insulation of the motor 3, the MG insulation protection mode is set (step S16). This MG insulation protection mode is a mode for protecting insulation such as the coating of the winding, and is a mode for lowering or limiting the peak voltage applied to the winding. Therefore, when step S16 is executed and the MG insulation protection mode is set, the motor 3 is driven using the power of either the upper battery block 2a or the lower battery block 2b. That is, the modulation factors Mu, Mv, and Mw are offset or limited (step S17). Specifically, the modulation factors Mu, Mv, and Mw are calculated after adding ±Vdc / 2 to a voltage value determined based on the required d-axis current and q-axis current. By determining the modulation factors Mu, Mv, Mw in this manner, the voltage of one battery block 2a (2b) is applied to the motor 3, resulting in a low voltage mode in which the voltage applied to the coils 3u, 3v, 3w is lower than when the above-mentioned motor drive mode is set. In other words, the above-mentioned motor drive mode corresponds to the "high voltage mode" in this embodiment of the present invention, and the MG insulation protection mode corresponds to the "low voltage mode" in this embodiment of the present invention.

[0102] Then, the switches Q1 to Q12 are PWM-controlled based on the modulation factors Mu, Mv, and Mw that have been offset or limited in step S17 (step S15), and this routine is temporarily terminated.

[0103] Figure 20(a) shows the phase current, modulation factors Mu, Mv, Mw, and line voltage of motor 3 when the MG insulation protection mode is set, and Figure 20(b) shows the phase current, modulation factors Mu, Mv, Mw, and line voltage of motor 3 when the motor drive mode is set.

[0104] When the air pressure is less than a predetermined pressure Pth and it is required to protect the insulating part of the motor 3, the MG insulation protection mode is set, and the modulation factors Mu, Mv, Mw are offset to the positive side as shown in Fig. 20(a). In the example shown here, the modulation factors Mu, Mv, Mw when the motor drive mode is set are increased by 0.5 to obtain the modulation factors Mu, Mv, Mw. By adding 0.5 to the modulation factors Mu, Mv, Mw when the motor drive mode is set in this way, the lower arm switch 11 is controlled to the off (stopped) state.

[0105] By offsetting the modulation factors Mu, Mv, and Mw in this way, an electric circuit is formed that connects the upper battery block 2a and the motor 3 as shown in Fig. 21(a) in schematic form. That is, the maximum value of the voltage applied to each of the coils 3u, 3v, and 3w is limited to a value based on the maximum value of the output voltage of the upper battery block 2a.

[0106] On the other hand, when the motor drive mode is set because the air pressure is equal to or higher than the predetermined pressure Pth, and the modulation factors Mu, Mv, and Mw are not offset as shown in Fig. 20(b), the electric circuit connecting the power supply 2 and the motor 3 is formed as shown in Fig. 21(b). That is, the maximum value of the voltage applied to each of the coils 3u, 3v, and 3w is a value based on the maximum value of the output voltage of the power supply 2.

[0107] As a result, when the modulation factors Mu, Mv, Mw are not offset, the line voltage of the motor 3 increases instantaneously as shown in Fig. 20(b), whereas when the modulation factors Mu, Mv, Mw are offset, the line voltage of the motor 3 can be prevented from becoming excessively high as shown in Fig. 20(a). In other words, the occurrence of partial discharge can be prevented, and the durability of the motor 3 can be prevented from decreasing.

[0108] In addition, in the power conversion device 1 equipped with the intermediate switch 13 as described above, when the rotation speed of the motor 3 is low, a current flows back between the intermediate switch 13 and each of the coils 3u, 3v, 3w as described above, and when the output torque of the motor 3 is high, the copper loss of the intermediate switch 13 increases, and power loss may increase. Therefore, the power conversion device 1 in the embodiment of the present invention is configured to control the voltage applied to each of the coils 3u, 3v, 3w by selecting from a two-level mode and a three-level mode according to the operating point of the motor 3. Similarly, since the durability of the intermediate switch 13 may decrease with an increase in power loss as described above, the power conversion device 1 is configured to control by selecting from a two-level mode and a three-level mode according to the temperature of the intermediate switch 13.

[0109] A flow chart for explaining an example of this control is shown in Fig. 22. In the control example shown in Fig. 22, first, it is determined whether or not there is a request to drive the motor 3 (step S21). This step S21 is the same as the above-mentioned step S11, and can be determined based on the accelerator opening degree by the driver, etc.

[0110] If the answer to step S21 is NO because there is no request to drive the motor 3, the standby mode is set (step S22) and this routine ends once. This step S22 is the same as step S12 described above, and the switches Q1 to Q12 are stopped without being outputting gate signals thereto.

[0111] On the other hand, if the answer to step S21 is YES because there is a request to drive the motor 3, it is determined whether the rotation speed Nm of the motor (MG) 3 is equal to or greater than a predetermined rotation speed Nth, or whether the output torque Tm of the motor 3 is less than a predetermined torque Tth (step S23). This step S23 can be determined based on, for example, a detection value of a rotation speed sensor such as a resolver that detects the rotation speed of the motor 3, a required driving force based on the accelerator opening, or the like.

[0112] If the rotation speed Nm of the motor 3 is equal to or greater than the predetermined rotation speed Nth, or the output torque Tm of the motor 3 is less than the predetermined torque Tth, the process advances to step S24, where it is determined whether the temperature TE of the intermediate switch 13 is less than a predetermined temperature TEth. The predetermined temperature TEth is a temperature that is set in advance so that the durability of the intermediate switch 13 is not reduced.

[0113] If the temperature TE of the intermediate switch 13 is lower than the predetermined temperature TEth and therefore the answer to step S24 is affirmative, the three-level mode is set (step S25) and this routine ends once. That is, the switches Q1 to Q12 are PWM-controlled based on the modulation wave corresponding to the required torque and rotation speed.

[0114] On the other hand, if the rotation speed Nm of the motor 3 is less than the predetermined rotation speed and the output torque Tm of the motor 3 is equal to or greater than the predetermined torque Tth, and therefore the result of step S23 is negative, or if the temperature TE of the intermediate switch 13 is equal to or greater than the predetermined temperature TEth, and therefore the result of step S24 is negative, the power loss is reduced and the intermediate switch 13 is prevented from excessively increasing in temperature and decreasing in durability. Specifically, the intermediate switch 13 is set to OFF (step S26). By setting the intermediate switch 13 to OFF in this way, the power conversion device 1 can function only as a two-level inverter, so the two-level mode is set as the control mode (step S27), and this routine is temporarily terminated. That is, the first switch Q1 to the sixth switch Q6 are PWM-controlled based on a modulation wave according to the required torque and rotation speed.

[0115] Fig. 23(a) shows the phase current and line voltage when the two-level mode is set, and Fig. 23(b) shows the phase current and line voltage when the three-level mode is set. As shown in Fig. 23(a) and Fig. 23(b), the line voltage is increased by setting the two-level mode.

[0116] 23(c) shows a comparison result of power loss when the motor 3 is controlled in the 2-level mode and when the motor 3 is controlled in the 3-level mode, when the rotation speed Nm of the motor 3 is less than the predetermined rotation speed Nth and the output torque of the motor 3 is equal to or greater than the predetermined torque Tth. As shown in FIG. 23(c), when the motor 3 is controlled in the 2-level mode, the power loss can be reduced by about 10% compared to when the motor 3 is controlled in the 3-level mode.

[0117] The power conversion device according to the embodiment of the present invention is not limited to one that controls a three-phase AC motor, and may be configured to control a multi-phase AC motor such as a five-phase AC motor. Fig. 24 shows an example of a power conversion device 1 that controls a five-phase AC motor, in which a thirteenth switch Q13 to a twentieth switch Q20, an X-phase coil 3x, and a Y-phase coil 3y are additionally provided to the power conversion device 1 shown in Fig. 1.

[0118] Specifically, the collector of the thirteenth switch Q13 is connected to the positive bus bar 5, the emitter is connected to the collector of the fourteenth switch Q14, and the emitter of the fourteenth switch Q14 is connected to the negative bus bar 6. Similarly, the collector of the fifteenth switch Q15 is connected to the positive bus bar 5, the emitter is connected to the collector of the sixteenth switch Q16, and the emitter of the sixteenth switch Q16 is connected to the negative bus bar 6. One end of the X-phase coil 3x is connected to the connection point between the thirteenth switch Q13 and the fourteenth switch Q14, one end of the Y-phase coil 3y is connected to the connection point between the fifteenth switch Q15 and the sixteenth switch Q16, and the other ends of the coils 3x, 3y are connected to the neutral point 12.

[0119] Also, the collector of the seventeenth switch Q17 is connected to the junction 9 between the first capacitor 7 and the second capacitor 8, the emitter of the seventeenth switch Q17 is connected to the emitter of the eighteenth switch Q18, and the collector of the eighteenth switch Q18 is connected to the junction of the thirteenth switch Q13 and the fourteenth switch Q14. Similarly, the emitter of the nineteenth switch Q19 is connected to the emitter of the twentieth switch Q20, and the collector of the twentieth switch Q20 is connected to the junction of the fifteenth switch Q15 and the sixteenth switch Q16.

[0120] Each of the switches Q13 to Q20 is formed of an IGBT, and a flywheel diode D13 to D20 is connected in anti-parallel to each of the switches Q13 to Q20.

[0121] Furthermore, the power conversion device in the embodiment of the present invention is not limited to a so-called A-NPC type multilevel inverter circuit. Fig. 25 shows a power conversion device 1 having another configuration. Note that the description of the same configuration as in Fig. 1 will be omitted. In the power conversion device 1 shown in Fig. 25, the collector of the 21st switch Q21 is connected to the emitter of the first switch Q1, the collector of the 22nd switch Q22 is connected to the emitter of the 21st switch Q21, and the collector of the 22nd switch Q22 is further connected to the emitter of the 22nd switch Q22.

[0122] Similarly, the collector of the 23rd switch Q23 is connected to the emitter of the 3rd switch Q3, the collector of the 24th switch Q24 is connected to the emitter of the 23rd switch Q23, and the collector of the 4th switch Q4 is connected to the emitter of the 24th switch Q24. Furthermore, the collector of the 25th switch Q25 is connected to the emitter of the 5th switch Q5, the collector of the 26th switch Q26 is connected to the emitter of the 26th switch Q26, and the collector of the 6th switch Q6 is connected to the emitter of the 26th switch Q26.

[0123] Each of these switches Q21 to Q26 is configured by an IGBT like the above-mentioned first switch Q1 to sixth switch Q6, and flywheel diodes D21 to D26 are connected in anti-parallel to each of the switches Q21 to Q26.

[0124] The connection point 9 between the first capacitor 7 and the second capacitor 8 and the connection point between the first switch Q1 and the 21st switch Q21 are connected via a 27th diode D27, and the connection point 9 between the first capacitor 7 and the second capacitor 8 and the connection point between the 22nd switch Q22 and the second switch Q2 are connected via a 28th diode D28. Similarly, the connection point 9 between the first capacitor 7 and the second capacitor 8 and the connection point between the third switch Q3 and the 23rd switch Q23 are connected via a 29th diode D29, and the connection point 9 between the first capacitor 7 and the second capacitor 8 and the connection point between the 24th switch Q24 and the 4th switch Q4 are connected via a 30th diode D30. Furthermore, the connection point 9 between the first capacitor 7 and the second capacitor 8 and the connection point between the fifth switch Q5 and the twenty-fifth switch Q25 are connected via a thirty-first diode D31, and the connection point 9 between the first capacitor 7 and the second capacitor 8 and the connection point between the twenty-sixth switch Q26 and the sixth switch Q6 are connected via a thirty-second diode D32.

[0125] One end of the U-phase coil 3u is connected to the connection point between the 21st switch Q21 and the 22nd switch Q22, one end of the V-phase coil 3v is connected to the connection point between the 23rd switch Q23 and the 24th switch Q24, and one end of the W-phase coil 3w is connected to the connection point between the 25th switch Q25 and the 26th switch Q26.

[0126] Furthermore, the power conversion device 1 that can be the target of the control example shown in Fig. 22 described above is not limited to the configurations shown in Fig. 1, Fig. 24, and Fig. 25, and the intermediate terminal 4 and the connection point 9 may not be connected. In other words, it is sufficient if the power conversion device has an intermediate switch and has a function as a two-level inverter and a function as a three-level inverter. [Explanation of symbols]

[0127] 1 Power conversion device 2 power supply 2a Upper battery block 2b Lower battery block 3 Motor 3u, 3v, 3w, 3x, 3y coils 4 Intermediate terminal 5 Positive busbar 6 Negative bus bar 7,8 Capacitors 9 Connection points 10 Upper arm switch 11 Lower arm switch 12 Neutral point 13 Intermediate switch 16 Inverter control device 17 Inverter 18 High voltage auxiliary equipment 19 Electric Compressor 20 Converter 22,25,26,28 PI controller 23 Comparator 24 Output section 27 Converter Bc Battery Cell D1~D32 Diodes Q1~Q26 Switch

Claims

1. A power source configured by connecting a plurality of battery cells in series; A rotating machine having coils of multiple phases and a neutral point to which one terminal of the coils of the multiple phases is connected; a plurality of capacitors connected in series with each other between the positive terminal of the power source and the negative terminal of the power source; a plurality of intermediate switch elements connecting connection points between positive and negative capacitors of the plurality of capacitors and coils of the plurality of phases; an upper arm element having a plurality of positive-side switch elements provided between each of the coils of the plurality of phases and a positive electrode of the power source; a lower arm element having a plurality of negative-side switch elements provided between each of the coils of the plurality of phases and a negative electrode of the power source; a controller for controlling the upper arm element, the lower arm element, and the intermediate switch element; A power conversion device comprising: The power supply includes an upper battery block on a positive electrode side and a lower battery block on a negative electrode side, an intermediate terminal between the upper battery block and the lower battery block is connected to the connection point; The controller: an equalization control is performed to control the upper arm element, the lower arm element, and the intermediate switch element so that the power consumption of the upper battery block and the power consumption of the lower battery block are the same, or to control the upper arm element, the lower arm element, and the intermediate switch element so that the remaining charge amount of the upper battery block and the lower battery block are the same, When there is no request to drive the rotating machine, at least one of the intermediate switch elements is brought into a conductive state and the other switch elements are brought into a non-conductive state; The positive electrode side switch and the negative electrode side switch are connected to a predetermined coil of the multiple phase coils, which is in the non-conductive state and thereby the supply of power from the power source via the intermediate switch element is cut off, without passing through the neutral point, to perform a switching operation to pass power from one side of the upper battery block and the lower battery block to the other side. A power conversion device comprising:

2. A power source configured by connecting a plurality of battery cells in series; A rotating machine having coils of multiple phases and a neutral point to which one terminal of the coils of the multiple phases is connected; a plurality of capacitors connected in series with each other between the positive terminal of the power source and the negative terminal of the power source; a plurality of intermediate switch elements connecting connection points between positive and negative capacitors of the plurality of capacitors and coils of the plurality of phases; an upper arm element having a plurality of positive-side switch elements provided between each of the coils of the plurality of phases and a positive electrode of the power source; a lower arm element having a plurality of negative-side switch elements provided between each of the coils of the plurality of phases and a negative electrode of the power source; a controller for controlling the upper arm element, the lower arm element, and the intermediate switch element; A power conversion device comprising: The power supply includes an upper battery block on a positive electrode side and a lower battery block on a negative electrode side, an intermediate terminal between the upper battery block and the lower battery block is connected to the connection point; The controller: an equalization control is performed to control the upper arm element, the lower arm element, and the intermediate switch element so that the power consumption of the upper battery block and the power consumption of the lower battery block are the same, or to control the upper arm element, the lower arm element, and the intermediate switch element so that the remaining charge amount of the upper battery block and the lower battery block are the same, determining a rotating machine voltage to be applied to the coils of the plurality of phases in accordance with the electric power required for the rotating machine; adding a difference between SOC voltage values ​​output from the upper battery block and the lower battery block, the difference being determined by the equalization control, to the rotating machine voltage; determining a modulation factor based on a total voltage obtained by adding the difference in the SOC voltage value to the rotating machine voltage; The upper arm element, the lower arm element, and the intermediate switch element are controlled based on the modulation factor. A power conversion device comprising:

3. The power conversion device according to claim 1 or 2, The controller: The upper arm element, the lower arm element, and the intermediate switch element are controlled so that the power consumption of the battery block having a larger remaining charge among the upper battery block and the lower battery block is greater than the power consumption of the battery block having a smaller remaining charge among the upper battery block and the lower battery block. A power conversion device comprising:

4. The power conversion device according to any one of claims 1 to 3, A high-voltage auxiliary device is connected to at least one of the upper battery block and the lower battery block. A power conversion device comprising:

5. The power conversion device according to claim 4, The high voltage auxiliary is configured to be driven at a voltage lower than the output voltage of the power supply. A power conversion device comprising:

6. The power conversion device according to claim 4 or 5, The high voltage auxiliary device includes a DC-DC converter and an electric compressor connected to the positive and negative terminals of the one of the battery blocks. A power conversion device comprising:

7. A power source configured by connecting a plurality of battery cells in series; A rotating machine having coils of multiple phases and a neutral point to which one terminal of the coils of the multiple phases is connected; a plurality of capacitors connected in series with each other between the positive terminal of the power source and the negative terminal of the power source; a plurality of intermediate switch elements connecting connection points between positive and negative capacitors of the plurality of capacitors and coils of the plurality of phases; an upper arm element having a plurality of positive-side switch elements provided between each of the coils of the plurality of phases and a positive electrode of the power source; a lower arm element having a plurality of negative-side switch elements provided between each of the coils of the plurality of phases and a negative electrode of the power source; a controller for controlling the upper arm element, the lower arm element, and the intermediate switch element; A power conversion device comprising: The power supply includes an upper battery block on a positive electrode side and a lower battery block on a negative electrode side, an intermediate terminal between the upper battery block and the lower battery block is connected to the connection point; The controller: When the voltage required for the coils of the multiple phases is equal to or greater than a predetermined voltage, or when the current value required for the coils of the multiple phases is equal to or greater than a predetermined current value, a low voltage mode is set in which the voltage applied to the coils of the multiple phases is relatively low, and when the voltage required for the coils of the multiple phases is less than a predetermined voltage, or when the current value required for the coils of the multiple phases is less than a predetermined current value, a high voltage mode is set in which the voltage applied to the coils of the multiple phases is relatively high. A power conversion device comprising:

8. The power conversion device according to claim 7, The predetermined voltage includes a voltage at which partial discharge occurs. A power conversion device comprising:

9. A power source configured by connecting a plurality of battery cells in series; A rotating machine having coils of multiple phases and a neutral point to which one terminal of the coils of the multiple phases is connected; a plurality of capacitors connected in series with each other between the positive terminal of the power source and the negative terminal of the power source; a plurality of intermediate switch elements connecting connection points between positive and negative capacitors of the plurality of capacitors and coils of the plurality of phases; an upper arm element having a plurality of positive-side switch elements provided between each of the coils of the plurality of phases and a positive electrode of the power source; a lower arm element having a plurality of negative-side switch elements provided between each of the coils of the plurality of phases and a negative electrode of the power source; a controller for controlling the upper arm element, the lower arm element, and the intermediate switch element; A power conversion device comprising: The power supply includes an upper battery block on a positive electrode side and a lower battery block on a negative electrode side, an intermediate terminal between the upper battery block and the lower battery block is connected to the connection point; The controller: A two-level mode is set in which, when the rotation speed of the rotating machine is less than a predetermined rotation speed or the output torque of the rotating machine is less than a predetermined torque, the voltage applied to the coils of the multiple phases is controlled to two voltage levels, 0 V and the output voltage of the power source, and when the rotation speed of the rotating machine is equal to or greater than the predetermined rotation speed or the output torque of the rotating machine is equal to or greater than the predetermined torque, a three-level mode is set in which, with a midpoint voltage of the voltage of the power source as a reference, the voltage applied to the coils of the multiple phases is controlled to three voltage levels, the midpoint voltage and a voltage obtained by adding / reducing a voltage that is 1 / 2 the voltage of the power source to / from the midpoint voltage. A power conversion device comprising:

10. A power source configured by connecting a plurality of battery cells in series; A rotating machine having coils of multiple phases and a neutral point to which one terminal of the coils of the multiple phases is connected; a plurality of capacitors connected in series with each other between the positive terminal of the power source and the negative terminal of the power source; a plurality of intermediate switch elements connecting connection points between positive and negative capacitors of the plurality of capacitors and coils of the plurality of phases; an upper arm element having a plurality of positive-side switch elements provided between each of the coils of the plurality of phases and a positive electrode of the power source; a lower arm element having a plurality of negative-side switch elements provided between each of the coils of the plurality of phases and a negative electrode of the power source; a controller for controlling the upper arm element, the lower arm element, and the intermediate switch element; A power conversion device comprising: The power supply includes an upper battery block on a positive electrode side and a lower battery block on a negative electrode side, an intermediate terminal between the upper battery block and the lower battery block is connected to the connection point; The controller: When the temperature of the intermediate switching element is equal to or higher than a predetermined temperature, a two-level mode is set in which the voltage applied to the coils of the multiple phases is controlled to two voltage levels, 0 V and the output voltage of the power source, and when the temperature of the intermediate switching element is lower than the predetermined temperature, a three-level mode is set in which the voltage applied to the coils of the multiple phases is controlled to three voltage levels, namely, a midpoint voltage of the voltage of the power source and a voltage obtained by adding / reducing a voltage that is 1 / 2 the voltage of the power source to / from the midpoint voltage, with the midpoint voltage as a reference. A power conversion device comprising:

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