Control method for power conversion apparatus

Abstract

To restrain rotation of a rotary machine at a control start time.SOLUTION: A power conversion apparatus 1 includes capacitors 7a and 7b which are connected in series between a positive electrode and a negative electrode of a battery 2, switch elements Q1 to Q12, a control device 9 that controls the switch elements Q1 to Q12, and a charging relay 13 that can connect a charging stand 14 for charging the battery 2 between the negative electrode-side terminal of the capacitor 7b and a node Nm where the capacitors 7a and 7b are connected. The control device 9 includes a voltage control unit 15 that controls the voltage at the node Nm to fall under the range of output voltage of the charging stand 14 by lowering the voltage of the battery 2. The control device 9 is configured to perform PWM control on driving of the switch elements Q1 to Q6, and to control an initial duty which is a duty at a control start time of the voltage control unit 15, to be equal to the ratio between the voltage of the battery 2 and the voltage of the capacitor 7b.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a control device for a power conversion device that converts electric power flowing between a power source and a rotating machine. [Background technology]

[0002] Currently, while 800V charging stations are beginning to be installed, their penetration rate is low, with 400V charging stations being the mainstream. BEV is an abbreviation for Battery Electric Vehicle. In order to charge a BEV equipped with an 800V battery at a 400V charging station, a voltage regulator such as a boost converter dedicated to charging that converts 400V to 800V is required.

[0003] Patent Document 1 discloses a technology for boosting the voltage of a charging stand by operating a three-level inverter and a motor as a boost converter. Hereinafter, the technology disclosed in Patent Document 1 will be simply referred to as the prior art. According to the prior art, it is possible to charge a battery, which is a power source, by adjusting the voltage of the charging stand, which is a charger, without providing a separate voltage adjustment device such as a boost converter. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2022-160202 A Summary of the Invention [Problem to be solved by the invention]

[0005] In the conventional technology, a system main relay is actually provided between the battery and the inverter, which switches between power on and off between the battery and the inverter. In this specification, the system main relay is sometimes abbreviated as SMR. Therefore, in the conventional technology, a flow is provided to turn on the SMR before control starts. When the SMR is turned on, two capacitors connected in series between the positive and negative electrodes of the battery are charged to the battery voltage, which is the voltage of the battery. For example, in an 800V three-level inverter, one capacitor is charged with 400V.

[0006] In conventional technology, the drive of the switch elements constituting the inverter is controlled by PWM, but if control is started from a duty of 0, the charged capacitor will discharge and an uncontrollable current will flow to the motor, which may result in torque being generated and the vehicle moving. In this specification, unless otherwise specified, "duty" refers to the ratio of the on-time Ton of the switch elements constituting the upper arm of the inverter to the carrier period T, that is, "Ton / T".

[0007] The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a control device for a power conversion device that can suppress the rotation of a rotating machine at the start of control. [Means for solving the problem]

[0008] The control device of a power conversion device described in claim 1 is used in a power conversion device that converts electric power passing between a power source (2) and a rotating machine (3) having multiple phase coils (3u, 3v, 3w) and a neutral point (6) to which one terminal of the multiple phase coils is connected. The power conversion device includes a plurality of capacitors (7a, 7b) connected in series between the positive electrode of the power source and the negative electrode of the power source, a plurality of intermediate switch elements (Q7 to Q12, D1 to D6) provided between an intermediate terminal (Nm) to which the plurality of capacitors are connected and each of the coils of the multiple phases, a plurality of positive side switch elements (Q1, Q3, Q5) provided between each of the coils of the multiple phases and the positive electrode of the power source, a plurality of negative side switch elements (Q2, Q4, Q6) provided between each of the coils of the multiple phases and the negative electrode of the power source, a control device (9) that controls the intermediate switch elements, the positive side switch elements, and the negative side switch elements, and a connection unit (13) that can connect a charger (14) for charging the power source between the intermediate terminal and the positive terminal or the negative terminal of the capacitor.

[0009] The control device includes a voltage control unit (15) that controls the voltage of the intermediate terminal within a range of the output voltage of the charger by stepping down the voltage of the power source, and a phase current control unit (16) that determines an input phase from the multiple phases through which the current of the charger is passed to the rotating machine and controls a current ratio that is a ratio of currents flowing through two phases other than the input phase among the multiple phases. In the above configuration, a three-level inverter is configured by the multiple intermediate switching elements, the multiple positive side switching elements, and the multiple negative side switching elements.

[0010] In such a configuration, the voltage control unit of the control device can control the voltage of the intermediate terminal within the range of the output voltage of the charger by stepping down the three-level inverter. As will be described in detail later, in the above configuration, the torque of the motor can be made zero and the rotation can be suppressed by skillfully adjusting the current ratio. Therefore, in the above configuration, the phase current control unit of the control device can suppress the rotation of the motor by controlling the current ratio to a predetermined value that makes the torque zero.

[0011] In the above configuration, the control device is configured to PWM-control the drive of the positive-side switch element and the negative-side switch element, and the initial duty, which is the duty at the start of control by the voltage control unit, is set to the ratio of the voltage of the power supply to the voltage of the negative-side capacitor, which is the capacitor connected between the intermediate terminal and the negative-side terminal. In this way, at the start of control, the output voltage of the three-level inverter, i.e., the voltage of the intermediate terminal, can be made to match the voltage of the negative-side capacitor, and as a result, the discharge of the negative-side capacitor is suppressed, so that an uncontrollable current does not flow in the rotating machine and generate torque. Therefore, with the above configuration, an excellent effect of suppressing the rotation of the rotating machine at the start of control is obtained. [Brief description of the drawings]

[0012] [Figure 1] FIG. 1 is a diagram showing a schematic configuration of a power conversion device according to an embodiment; [Diagram 2] FIG. 11 is a waveform diagram showing the relationship between the electrical angle and the current ratio of the motor when stopped according to an embodiment; [Diagram 3] FIG. 1 is a diagram showing a configuration example in which an inverter according to an embodiment is operated as a step-down converter to charge a battery. [Figure 4] FIG. 2 shows a configuration example in which an inverter according to an embodiment is operated as a step-down converter to charge a battery. [Diagram 5] FIG. 2 is a diagram showing an example of a specific configuration of a control device according to an embodiment; [Figure 6] FIG. 13 is a diagram showing an example of a determination result by an input phase determination unit according to an embodiment; [Figure 7] FIG. 2 is a diagram showing an example of a specific configuration of a current ratio calculation unit according to an embodiment; [Figure 8] FIG. 13 is a diagram showing an example of a determination result of a maximum value determination unit and a current ratio calculation formula according to an embodiment; [Figure 9] FIG. 4 is a diagram showing an example of a specific configuration of a switch signal selection unit according to an embodiment; [Figure 10] FIG. 2 is a diagram showing an example of a specific configuration related to PI control and PWM control provided in a control device according to an embodiment; [Figure 11] FIG. 2 is a diagram showing a flow of operations performed by a control device at the start of control according to an embodiment; [Figure 12] FIG. 1 is a diagram for explaining a current path in a power conversion device at the start of charging control according to an embodiment. [Figure 13] FIG. 2 is a diagram for explaining a current path in a power conversion device at the start of charging control according to an embodiment. [Figure 14] FIG. 1 is a schematic diagram illustrating an example of an operational waveform of each part when the power conversion device is operated as a step-down converter in an embodiment and a comparative example. [Figure 15] FIG. 1 is a schematic diagram illustrating a configuration of a modified example of an inverter according to an embodiment; [Figure 16] FIG. 13 is a diagram for explaining an example of a current path when an inverter according to a modified example is operated as a step-down converter. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0013] Hereinafter, an embodiment of a control device for a power converter will be described with reference to the drawings. <Overall composition> As shown in Fig. 1, a power conversion device 1 of this embodiment is mounted on a vehicle such as a BEV, and converts power flowing between a battery 2 and a motor 3 also mounted on the vehicle. The battery 2 supplies a DC voltage to the power conversion device 1, and corresponds to a power source. The battery 2 can be configured as a battery pack in which secondary batteries such as lithium ion batteries are connected in series in multiple stages.

[0014] Each terminal of the battery 2 is connected to a pair of DC power supply lines 4, 5 via the SMR 30. Specifically, the positive electrode of the battery 2 is connected to the DC power supply line 4 via a contact 30a of the SMR 30, and the negative electrode is connected to the DC power supply line 5 via a contact 30b of the SMR 30. The SMR 30 is a relay provided to switch between energization and cutoff between the battery 2 and the power conversion device 1, and the contacts 30a, 30b are turned on before control starts.

[0015] The motor 3 corresponds to a rotating machine and has multiple phases, specifically, three-phase coils 3u, 3v, and 3w, and a neutral point 6 to which one terminal of the coils 3u, 3v, and 3w is connected. In other words, the motor 3 is a star-connected three-phase AC motor. The motor 3 serves as a drive source for running the vehicle. The power conversion device 1 includes multiple capacitors 7a, 7b, an inverter 8, a control device 9, current sensors 10a, 10b, voltage sensors 11a, 11b, a rotor position sensor 12, a charging relay 13, and the like.

[0016] The positive terminal of the capacitor 7a is connected to the DC power supply line 4, and its negative terminal is connected to the node Nm. The positive terminal of the capacitor 7b is connected to the node Nm, and its negative terminal is connected to the DC power supply line 5. That is, the multiple capacitors 7a, 7b are connected in series between the positive electrode of the battery 2 and the negative electrode of the battery 2 via the SMR 30. The node Nm is a node where the multiple capacitors 7a, 7b are connected to each other, and functions as an intermediate terminal. The capacitor 7a is connected between the positive electrode of the battery 2 and the node Nm, and functions as a positive side capacitor. The capacitor 7b is connected between the node Nm and the negative electrode of the battery 2, and functions as a negative side capacitor.

[0017] The inverter 8 is a T-type NPC three-level inverter and includes switch elements Q1 to Q12. Each of the switch elements Q1 to Q12 is configured with an N-channel MOSFET. Each of the switch elements Q1 to Q12 includes a body diode connected between the drain and source with the source side serving as the anode. The switch elements Q1 to Q12 may also be configured with other semiconductor switching elements such as IGBTs. The switch elements Q1 to Q6 are connected between DC power supply lines 4 and 5 to form a three-phase full-bridge circuit.

[0018] That is, the drains of the switching elements Q1, Q3, and Q5 are connected to a DC power supply line 4, and the sources of the switching elements Q2, Q4, and Q6 are connected to a DC power supply line 5. The source of the switching element Q1 and the drain of the switching element Q2 are connected to a node Nu. The source of the switching element Q3 and the drain of the switching element Q4 are connected to a node Nv. The source of the switching element Q5 and the drain of the switching element Q6 are connected to a node Nw.

[0019] The node Nu functions as a U-phase output terminal of the inverter 3 and is connected to the other terminal of the U-phase coil 3u of the motor 3. The node Nv functions as a V-phase output terminal of the inverter 3 and is connected to the other terminal of the V-phase coil 3v of the motor 3. The node Nw functions as a W-phase output terminal of the inverter 3 and is connected to the other terminal of the W-phase coil 3w of the motor 3.

[0020] In the above configuration, the switch elements Q1, Q3, and Q5 are provided between the three-phase coils 3u, 3v, and 3w of the motor 3 and the positive electrode of the battery 2, and correspond to a plurality of positive-side switch elements. Also, in the above configuration, the switch elements Q2, Q4, and Q6 are provided between the three-phase coils 3u, 3v, and 3w of the motor 3 and the negative electrode of the battery 2, and correspond to a plurality of negative-side switch elements. In the following description, the switch elements Q1, Q3, and Q5 may be collectively referred to as the positive-side switch elements, and the switch elements Q2, Q4, and Q6 may be collectively referred to as the negative-side switch elements.

[0021] The switch elements Q7 and Q8 are provided so as to be able to open and close between the node Nm and the node Nu. Specifically, the sources of the switch elements Q7 and Q8 are connected in common. The drain of the switch element Q7 is connected to the node Nm, and the drain of the switch element Q8 is connected to the node Nu. The switch elements Q9 and Q10 are provided so as to be able to open and close between the node Nm and the node Nv. Specifically, the sources of the switch elements Q9 and Q10 are connected in common. The drain of the switch element Q9 is connected to the node Nm, and the drain of the switch element Q10 is connected to the node Nv.

[0022] The switch elements Q11 and Q12 are provided so as to be capable of opening and closing between the node Nm and the node Nw. Specifically, the sources of the switch elements Q11 and Q12 are commonly connected. The drain of the switch element Q11 is connected to the node Nm, and the drain of the switch element Q12 is connected to the node Nw. In the above configuration, the switch elements Q7 to Q12 are provided between the node Nm and each of the three-phase coils 3u, 3v, and 3w of the motor 3, and correspond to a plurality of intermediate switch elements. In the following description, the switch elements Q7 to Q12 may be collectively referred to as intermediate switch elements.

[0023] The control device 9 includes various functional blocks, and controls the intermediate switch elements, the positive side switch elements, and the negative side switch elements by the operation of these functional blocks. The control device 9 performs PWM control of the drive of the positive side switch elements and the negative side switch elements. Note that PWM is an abbreviation for Pulse Width Modulation. The control device 9 generates switch signals that drive each of the switch elements Q1 to Q12. The switch signals generated by the control device 9 are provided to the gates of the switch elements Q1 to Q12. In this way, the control device 9 controls the on / off of the switch elements Q1 to Q12.

[0024] The current sensor 10a detects the U-phase current of the motor 3, and outputs a detection signal corresponding to the detection value Iu to the control device 9. In FIG. 1 and other figures, each signal may be indicated with a symbol corresponding to the value represented by the signal. The current sensor 10b detects the V-phase current of the motor 3, and outputs a detection signal corresponding to the detection value Iv to the control device 9. In this embodiment, the U-phase current and the V-phase current of the three-phase current of the motor 3 are detected, but it is sufficient to detect the currents of any two phases of the three-phase current. Alternatively, a configuration in which all three-phase currents are detected may be used.

[0025] The voltage sensor 11a detects a first voltage which is the voltage of the battery 2. The voltage sensor 11a outputs a detection signal corresponding to a detection value VH of the first voltage to the control device 9. The voltage sensor 11b detects a second voltage which is the voltage between the node Nm and the negative electrode of the battery 2, that is, the terminal-to-terminal voltage of the capacitor 7b. The voltage sensor 11b outputs a detection signal corresponding to a detection value VL of the second voltage to the control device 9. In the following description, the first voltage may be referred to as a battery voltage, and the second voltage may be referred to as an intermediate terminal voltage.

[0026] The rotor position sensor 12 detects the rotation angle of the motor 3, specifically the mechanical angle, and outputs a detection signal corresponding to the detected value θm to the control device 9. The power conversion device 1 is configured to be connected to a current output charging stand 14, which is equipment provided outside the vehicle, and to charge the battery 2 by stepping down the voltage of the battery 2 and regenerating the current of the charging stand 14. The charging relay 13 is provided to connect the charging stand 14 to the power conversion device 1. The contact 13a of the charging relay 13 is provided so as to be able to open and close between one output terminal of the charging stand 14 and the node Nm. The contact 13b of the charging relay 13 is provided so as to be able to open and close between the other output terminal of the charging stand 14 and the DC power supply line 5.

[0027] In the above configuration, the charging stand 14 functions as a charger for charging the battery 2. Also, in the above configuration, the charging relay 13 functions as a connection unit that can connect the charging stand 14 for charging the battery 2 between the node Nm and the negative terminal of the capacitor 7b. The power conversion device 1 configured as above is configured such that when the charging stand 14 is connected, the contacts 13a, 13b of the charging relay 13 are closed.

[0028] The control device 9 includes a voltage control unit 15 and a phase current control unit 16 as part of its functional blocks. The voltage control unit 15 controls the voltage of the node Nm to be within the range of the output voltage of the charging stand 14 by stepping down the voltage of the battery 2. An intermediate terminal voltage command representing an intermediate terminal voltage command value VL* transmitted from a higher-level ECU (not shown) is input to the control device 9. The voltage control unit 15 controls the voltage of the node Nm, i.e., the intermediate terminal voltage, based on the intermediate terminal voltage command. The phase current control unit 16 determines an input phase from among the three phases for passing the current of the charging stand 14 to the motor 3, and controls a current ratio that is a ratio of currents flowing through the two phases other than the input phase among the three phases.

[0029] The voltage control unit 15 is adapted to perform calculations for controlling the voltage of the node Nm within the range of the output voltage of the charging stand 14. The phase current control unit 16 obtains three-phase currents by performing coordinate conversion using the electrical angle when the rotation of the motor 3 is stopped and the d-axis current value and the q-axis current value at which the torque of the motor 3 is equal to or less than a predetermined threshold torque. The phase current control unit 16 determines, as an input phase, a phase corresponding to a maximum current value, which is the maximum absolute value among the calculated current values, which are the values ​​of the currents of the three phases obtained. In the following description, the phase corresponding to the maximum current value among the calculated current values ​​may be referred to as the absolute maximum phase.

[0030] The phase current control unit 16 determines the current ratio of the two phases other than the input phase as the absolute value of the value obtained by dividing each of the calculated current values ​​of the three phases by the maximum current value, and multiplies the current ratio by the calculation result of the voltage control unit 15 to obtain the current command for the three phases. In this case, the threshold torque is set to a value lower than the holding force of the parking brake provided on the vehicle. In addition, in this case, the phase current control unit 16 performs coordinate conversion with the value of the q-axis current set to 0.

[0031] The principle by which the torque of the motor 3 becomes 0 in the above configuration will be described below. First, the torque T of the motor 3 is expressed by the torque formula such as the following formula (1). Here, p is the number of pole pairs, id is the d-axis current, iq is the q-axis current, φm is the permanent magnet flux linkage, Ld is the d-axis inductance, and Lq is the q-axis inductance.

[0032]

number

[0033] According to (1) above, if the value of the q-axis current is 0, in other words, "iq = 0", the torque T will be 0. Therefore, the three-phase currents for which "iq = 0" are found. The U-phase current Iu, V-phase current Iv, and W-phase current Iw are expressed by the uvw / dq coordinate transformation equation such as the following equation (2).

[0034]

number

[0035] When the above formula (2) is expanded, it becomes the following formulas (3), (4), and (5). Note that in each of the following formulas, √(2 / 3) represents the square root of 2 / 3, √3 represents the square root of 3, and * represents multiplication.

[0036] Iu=√(2 / 3)*{Id*cosΘ+Iq*sinΘ} …(3) Iv=√(2 / 3)*{Id*cos(Θ-2π / 3)+Iq*sin(Θ-2π / 3)} =√(2 / 3)*[Id*{cosΘcos(2π / 3)+sinΘsin(2π / 3)}+Iq*{sinΘcos(2π / 3)-cosΘsin(2π / 3)}] =√(2 / 3)*{Id*(-1 / 2*cosΘ+√3 / 2*sinΘ)+Iq*(-1 / 2*sinΘ-√3 / 2*cosΘ)} …(4) Iw=√(2 / 3)*{Id*cos(Θ+2π / 3)+Iq*sin(Θ+2π / 3)} =√(2 / 3)*[Id*{cosΘcos(2π / 3)-sinΘsin(2π / 3)}+Iq*{sinΘcos(2π / 3)+cosΘsin(2π / 3)}] =√(2 / 3)*{Id*(-1 / 2*cosΘ-√3 / 2*sinΘ)+Iq*(-1 / 2*sinΘ+√3 / 2*cosΘ)} …(5)

[0037] By substituting "Iq = 0" into equations (3), (4), and (5), and using the addition theorem (cos(Θ-α)=cosΘcosα+sinΘsinα), the three-phase currents are expressed by the following equations (6), (7), and (8).

[0038] Iu = √(2 / 3) * Id * cosΘ … (6) Iv=√(2 / 3)*Id*(-1 / 2cosΘ+√3 / 2sinΘ) =√(2 / 3)*Id*cos(Θ-2π / 3) …(7) Iw=√(2 / 3)*Id*(-1 / 2*cosΘ-√3 / 2*sinΘ) =√(2 / 3)*Id*cos(Θ-4π / 3) …(8)

[0039] In equations (6) to (8), the terms before cos represent coefficients, and the terms after cos represent current ratios. The coefficients are proportional to the current of the charging stand 14, that is, "coefficient ∝ current of the charging stand 14". In this way, the three-phase currents Iu, Iv, and Iw for which "Iq = 0" can be expressed as cosine waves with a phase shift of 2π / 3. That is, the current ratio of the three-phase currents Iu, Iv, and Iw can be expressed as a waveform as shown in FIG. 2. In FIG. 2, the horizontal axis represents the electrical angle [deg] of the motor 3 when stopped, and the vertical axis represents the current ratio. In this way, the torque of the motor 3 can be made zero by controlling the three-phase currents Iu, Iv, and Iw to have a current ratio as shown in FIG. 2 according to the electrical angle when stopped.

[0040] The power conversion device 1 configured as described above can operate the inverter 8 as a step-down converter that steps down the voltage of the battery 2. When the control device 9 operates the inverter 8 as a step-down converter, the control device 9 controls each switch element of the input phase, which is one of the three phases, and the control phase, which is two phases other than the input phase, as follows. That is, the control device 9 fixes the middle switch element of the input phase to ON, fixes the middle switch element of the control phase, the positive side switch element of the input phase, and the negative side switch element of the input phase to OFF, and then PWM controls the ON / OFF of the positive side switch element and the negative side switch element of the control phase, thereby stepping down the voltage of the battery 2.

[0041] For example, as shown in Figures 3 and 4, when the input phase is the W phase and the control phases are the U phase and the V phase, switch elements Q11 and Q12 are fixed ON and switch elements Q5 to Q10 are fixed OFF, and then the ON / OFF of switch elements Q1 to Q4 is PWM controlled to step down the voltage of battery 2 and regenerate the current of charging stand 14. Note that, compared to Figure 3, Figure 4 omits the illustration of configuration that does not directly contribute to the operation as a step-down converter.

[0042] <Control device configuration> A specific configuration of the control device 9 is, for example, as shown in Fig. 5. The voltage control unit 15 includes a subtractor 17 that subtracts the detection value VL of the voltage sensor 11b from the command value VL* of the intermediate terminal voltage, and a PI controller 18 that outputs a signal corresponding to the current command IL* by performing PI control on the output signal of the subtractor 17. In this way, the voltage control unit 15 performs PI control from the command value VL* of the intermediate terminal voltage and the detection value VL of the voltage sensor 11b to calculate the current command IL*.

[0043] The electrical angle calculation unit 19 converts the detection value θm of the rotor position sensor 12 into an electrical angle θe. Such a conversion can be performed as "electrical angle θe = detection value θm of mechanical angle × number of pole pairs of the motor 3". The phase current control unit 16 includes an input phase determination unit 20, a current ratio calculation unit 21, a phase current command calculation unit 22, a W-phase current calculation unit 23, and a PI control unit 24. The input phase determination unit 20 performs ON / OFF fixation determination of each of the switch elements Q1 to Q12 from the electrical angle θe.

[0044] Based on the result of the ON / OFF fixation determination, the input phase determination unit 20 outputs positive and negative switch signals Su2, Sv2, and Sw2, which are switch signals corresponding to the positive and negative switch elements, and intermediate switch signals Snu, Snv, and Snw, which are switch signals corresponding to the intermediate switch elements. In the following description, the positive and negative switch signals and intermediate switch signals may be simply referred to as switch signals. Each switch signal is a binary signal, with a high level corresponding to a level that turns on the switch element and a low level corresponding to a level that turns off the switch element.

[0045] In this specification, the high level of a binary signal may be referred to as "1," and its low level may be referred to as "0." For each switch signal, the input phase determination unit 20 regards the signal as "0" when the corresponding switch element is fixed to OFF, and as "1" when the corresponding switch element is fixed to ON, or when the corresponding switch element is not fixed to ON or OFF.

[0046] The result of the ON / OFF fixation determination by the input phase determination unit 20 is as shown in Fig. 6. Fig. 6 corresponds to a table in which the current ratios of the three-phase currents shown in Fig. 2 are quantified. For example, when the electrical angle θe is "0 to less than 30°", the phase with the maximum absolute value is the "U phase", the switch signal Su2 is "0", the switch signals Sv2 and Sw2 are "1", the switch signal Snu is "1", and the switch signals Snv and Snw are "0". When the electrical angle θe is "30 to less than 90°", the phase with the maximum absolute value is the "W phase", the switch signal Sw2 is "0", the switch signals Su2 and Sv2 are "1", the switch signal Snw is "1", and the switch signals Snu and Snv are "0".

[0047] At the boundary of the electrical angle θe, that is, when the electrical angle θe is "30°+60°×n", there are two maximum absolute value phases, and either of these two phases may be set as the maximum absolute value phase, where n is an integer. When the electrical angle θe is 30°, there are two maximum absolute value phases, the U phase and the W phase, but in this embodiment, the W phase is set as the maximum absolute value phase.

[0048] The current ratio calculation unit 21 calculates current ratios Ru, Rv, and Rw representing the respective ratios of the U-phase current, the V-phase current, and the W-phase current of the motor 3 from the electrical angle θe. The phase current command calculation unit 22 includes a multiplier 22u that multiplies the current command IL* by the current ratio Ru to output a signal corresponding to the phase current command Iu* of the U-phase, a multiplier 22v that multiplies the current command IL* by the current ratio Rv to output a signal corresponding to the phase current command Iv* of the V-phase, and a multiplier 22w that multiplies the current command IL* by the current ratio Rw to output a signal corresponding to the phase current command Iw* of the W-phase. In this way, the phase current command calculation unit 22 multiplies the current command IL* by the current ratios Ru, Rv, and Rw to calculate the phase current commands Iu*, Iv*, and Iw*.

[0049] The W-phase current calculation unit 23 is composed of a subtractor that subtracts the detection value Iv of the current sensor 10b from a value obtained by inverting the sign of the detection value Iu of the current sensor 10a and outputs a signal corresponding to the calculated value Iw of the W-phase current. In this manner, the W-phase current calculation unit 23 calculates the W-phase current from the U-phase current and the V-phase current. Specifically, the W-phase current calculation unit 23 calculates the W-phase current as "Iw=-Iu-Iv".

[0050] The PI control unit 24 includes a subtractor 25u that subtracts the detection value Iu from the phase current command Iu*, and a PI controller 26u that outputs a signal corresponding to a phase voltage command Vu* of the U phase by performing PI control on the output signal of the subtractor 25u. The PI control unit 24 also includes a subtractor 25v that subtracts the detection value Iv from the phase current command Iv*, and a PI controller 26v that outputs a signal corresponding to a phase voltage command Vv* of the V phase by performing PI control on the output signal of the subtractor 25v.

[0051] Furthermore, the PI control unit 24 includes a subtractor 25w that subtracts a calculated value Iw from the phase current command Iw*, and a PI controller 26w that outputs a signal corresponding to a phase voltage command Vw* of the W phase by performing PI control on an output signal of the subtractor 25w. In this manner, the PI control unit 24 performs PI control on the phase current commands Iu*, Iv*, Iw*, the detection values ​​Iu, Iv of the current sensors 10a, 10b, and the calculated value Iw obtained as a result of the calculation by the W-phase current calculation unit 23, to calculate the phase voltage commands Vu*, Vv*, Vw*.

[0052] The duty calculation / PWM modulation units 27u, 27v, 27w calculate duties from the phase voltage commands Vu*, Vv*, Vw* and the detection value VH of the voltage sensor 11a. The duty calculation / PWM modulation units 27u, 27v, 27w PWM-modulate the calculated duties to calculate positive and negative switch signals Su1, Sv1, Sw1 which are switch signals corresponding to the positive and negative switch elements.

[0053] The switch signal selection unit 28 transmits to the inverter 8 a signal obtained by taking the logical product, that is, AND, of the positive and negative switch signals Su1, Sv1, Sw1 transmitted from the duty calculation / PWM modulation units 27u, 27v, 27w and the positive and negative switch signals Su2, Sv2, Sw2 transmitted from the input phase determination unit 20. In addition, the switch signal selection unit 28 transmits the intermediate switch signals Snu, Snv, Snw transmitted from the input phase determination unit 20 to the inverter 8 as is.

[0054] <Configuration of current ratio calculation section> As a specific configuration of the current ratio calculation unit 21, for example, a configuration example as shown in Fig. 7 can be adopted. The current ratio calculation unit 21 of the configuration example shown in Fig. 7 includes a dq / uvw coordinate conversion unit 31, an absolute value conversion unit 32, and a maximum value determination unit 33. The dq / uvw coordinate conversion unit 31 performs dq / uvw coordinate conversion using the electrical angle θe, the d-axis current Id, and the q-axis current Iq. At this time, the value of the d-axis current Id is set to 1, that is, "Id=1", and the value of the q-axis current Iq is set to 0, that is, "Iq=0". Note that as long as "Iq=0", the value of the d-axis current Id may be any value.

[0055] An absolute value conversion unit 32 converts the calculated current value Iru of the U phase, the calculated current value Irv of the V phase, and the calculated current value Irw of the W phase, which are the calculation results of the dq / uvw coordinate transformation, into absolute values ​​|Iru|, |Irv|, and |Irw|, respectively. A maximum value determination unit 33 determines, from the electrical angle θe, the phase having the maximum absolute value among the calculated current values ​​Iru, Irv, and Irw, which are the calculation results of the dq / uvw coordinate transformation, and calculates the current ratios Ru, Rv, and Rw from a current ratio calculation formula.

[0056] The result of the determination by maximum value determination unit 33 and the current ratio calculation formula are as shown in Fig. 8. The current ratio calculation formula used in this case is expressed by division with the absolute value corresponding to the maximum absolute value phase as the denominator and the absolute values ​​corresponding to each of the phases as the numerator. For example, when the electrical angle θe is 15°, the phase with the maximum absolute value is the "U phase", so the current ratio calculation formula is expressed by division with the absolute value |Iru| as the denominator and the absolute values ​​|Iru|, |Irv|, |Irw| corresponding to each of the phases as the numerators, as shown in the following formulas (9), (10), and (11). Ru = |Iru| / |Iru| …(9) Rv = |Irv| / |Iru| …(10) Rw = |Irw| / |Iru| …(11)

[0057] In this case, as in the case of fixed ON / OFF judgment, when the electrical angle θe is at the boundary between the electrical angles θe, that is, when the electrical angle θe is "30° + 60° × n", there will be two phases with maximum absolute values, and either of these two phases may be determined to be the phase with maximum absolute value.

[0058] <Configuration of switch signal selection section> As a specific configuration of the switch signal selection unit 28, for example, a configuration example as shown in Fig. 9 can be adopted. The switch signal selection unit 28 of the configuration example shown in Fig. 9 includes AND circuits 34, 35, and 36. The AND circuit 34 receives the switch signal Su1 output from the duty calculation / PWM modulation unit 27u and the switch signal Su2 output from the input phase determination unit 20, and outputs a signal representing the logical AND of these input signals.

[0059] The AND circuit 35 receives the switch signal Sv1 provided from the duty operation · PWM modulation unit 27v and the switch signal Sv2 provided from the input phase determination unit 20, and outputs a signal representing the logical product of these input signals. The AND circuit 36 receives the switch signal Sw1 provided from the duty operation · PWM modulation unit 27w and the switch signal Sw2 provided from the input phase determination unit 20, and outputs a signal representing the logical product of these input signals. The switch signal selection unit 28 outputs the output signals of the AND circuits 34 to 36 to the positive-side switch element and the negative-side switch element of the inverter 8. Further, the switch signal selection unit 28 outputs the switch signals Snu, Snv, and Snw provided from the input phase determination unit 20 to the intermediate switch element of the inverter 8.

[0060] <Configuration related to PI control and PWM control> Among the configurations provided in the control device 9, as specific configurations of each part related to PI control and PWM control, specifically, the voltage control unit 15, the phase current control unit 16, and the duty operation · PWM modulation units 27u, 27v, and 27w, for example, a configuration example as shown in FIG. 10 can be adopted. In FIG. 10, only the configuration corresponding to the U phase is shown among the configurations of each part, but the same configuration as that of the U phase can also be adopted for the configurations corresponding to the V phase and the W phase.

[0061] The voltage control unit 15 includes the PI controller 18 as described above, and is configured to perform PI control, that is, proportional-integral control. The PI controller 18 includes an adder 41, an integrator 42, and the like. The integrator 42 integrates and outputs a signal obtained by applying an integration gain to the output signal of the subtractor 17. The adder 41 adds a signal obtained by applying a proportional gain to the output signal of the subtractor 17 and the output signal of the integrator 42. In this case, the output signal of the adder 41 becomes the current command IL*.

[0062] As described above, the phase current control unit 16 includes the PI control unit 24, and is configured to perform PI control, that is, proportional-integral control. The PI controller 26u of the PI control unit 24 includes an adder 43, an integrator 44, and the like. The integrator 44 integrates a signal obtained by adding an integral gain to the output signal of the subtractor 25u, and outputs the integrated signal. The integrator 44 is configured to set an initial value based on a signal provided from the outside. The adder 43 adds the signal obtained by adding a proportional gain to the output signal of the subtractor 25u, and the output signal of the integrator 44. In this case, the output signal of the adder 43 becomes the phase voltage command Vu*.

[0063] The duty calculation / PWM modulation unit 27u includes a divider 45, a comparator 46, and a carrier generator 47. The divider 45 divides the phase voltage command Vu* by the detection value VH of the voltage sensor 11a. The output signal of the divider 45 represents the duty and is input to the non-inverting input terminal of the comparator 46. The carrier generator 47 generates and outputs a carrier which is a triangular wave. The carrier output from the carrier generator 47 is input to the inverting input terminal of the comparator 46. In this case, the output signal of the comparator 46 becomes the switch signal Su1.

[0064] In such a configuration, the control device 9 sets the initial duty, which is the duty when the voltage control unit 15 starts control, to the ratio between the voltage of the battery 2 and the voltages of the node Nm and capacitor 7b. The control device 9 also determines the initial duty so that the initial voltage, which is the voltage of the node Nm when the voltage control unit 15 starts control, matches the voltage of the capacitor 7b.

[0065] Specifically, the control device 9 derives the initial duty from a state averaging equation in a steady state. When the power conversion device 1 is made to function as a step-down converter, a state averaging equation for the output voltage of the step-down converter is expressed as the following formula (12). In this case, the W phase is the input phase, and the U phase and the V phase are the control phases. Note that Vout is the output voltage of the step-down converter (= intermediate terminal voltage), ru is the resistance value obtained by adding the motor winding resistance of the U phase to the element resistance, rv is the resistance value obtained by adding the motor winding resistance of the V phase to the element resistance, Du is the duty of the U phase, Dv is the duty of the V phase, Vin is the input voltage of the step-down converter (= battery voltage), and Io is the output current of the step-down converter.

[0066]

number

[0067] By substituting the following equations (13), (14), and (15), which are conditions at the start of control by voltage control unit 15, into equation (12), the following equation (16) is obtained, where Vc is the voltage of capacitor 7b, and Dini is the initial duty. Vout = Vc … (13) Io=0 …(14) Du=Dv=Dini …(15)

[0068]

number

[0069] By solving equation (16) for the initial duty Dini, equation (17) is obtained.

[0070]

number

[0071] As shown in equation (17), according to this derivation method, the initial duty Dini is the value obtained by dividing the voltage Vc of the capacitor 7b by the input voltage Vin. In other words, the initial duty Dini is the ratio between the battery voltage (=input voltage Vin) and the voltage Vc of the capacitor 7b.

[0072] When such a method of deriving the initial duty Dini is realized by each functional block included in the control device 9, the following method can be adopted. That is, when the voltage control unit 15 starts control, the voltage control unit 15 sets a command value VL*, which is a voltage command representing a command value of the voltage of the node Nm for performing PI control, to the detection value VL of the voltage sensor 11b. Also, when the voltage control unit 15 starts control, the phase current control unit 16 sets an initial value of the integrator 44 for performing PI control to the detection value VL of the voltage sensor 11b. The above method will be described in detail below.

[0073] First, the idea is as follows: That is, by substituting the values ​​in each functional block of the control device 9 into the above formula (17), the following formula (18) is derived. From formula (18), the initial duty Dini can be obtained by setting the phase voltage command Vu* to the initial voltage Vc. Dini = Vc / Vin = Vu* / VH …(18)

[0074] In the configuration of this embodiment, the input of the PI controller 26u of the PI control section 24, that is, the value obtained by subtracting the detection value Iu of the current sensor 10a from the phase current command Iu*, is set to 0, and the initial value of the integrator 44 is set to an initial voltage Vc, thereby making it possible to establish equation (18), that is, to obtain the initial duty Dini shown in equation (17). A specific method for obtaining the initial duty Dini based on this concept is as follows.

[0075] That is, in the initial state, no current flows from the charging stand 14, so the detection value Iu of the current sensor 10a is 0 A, and therefore it is necessary to set the phase current command Iu* to 0. Therefore, the command value VL* is set to the detection value VL. This makes the phase current command Iu* 0, and as a result, the output of the subtractor 25u, that is, the input to the PI controller 26u, becomes 0. Also, the initial value of the integrator 44 of the PI controller 26u is set to the detection value VL. This makes the phase voltage command Vu* become the initial voltage Vc, and as a result, the duty represented by the output signal of the divider 45 of the duty calculation / PWM modulation unit 27u becomes the initial duty Dini shown in equation (17).

[0076] Next, the operation of the above configuration will be described. The flow of operations by the control device 9 at the start of control is shown in a flowchart in Fig. 11. In this case, seven processes from step S101 to S107 are executed in order. As shown in Fig. 11, in step S101, the SMR 30 is turned on. This causes the capacitors 7a and 7b to be precharged from the battery 2.

[0077] In step S102, after completion of precharging, the intermediate terminal voltage is detected by the voltage sensor 11b. In step S103, a command value VL* is set to the detection value VL of the voltage sensor 11b. In step S104, an initial value of the integrator 44 of the PI controller of the phase current control unit 16 is set to the detection value VL of the voltage sensor 11b. In step S105, control of the inverter 8 is started. In step S106, the charging relay 13 is turned on. This electrically connects the charging stand 14 and the inverter 8. In step S107, charging is started. After execution of step S107, this series of operations is terminated.

[0078] According to the present embodiment described above, the following effects can be obtained. In the power conversion device 1 configured as above, the inverter 8, which is a three-level inverter, is configured by a plurality of intermediate switch elements, a plurality of positive pole side switch elements, and a plurality of negative pole side switch elements. In such a configuration, the voltage control unit 15 of the control device 9 can control the intermediate terminal voltage to be within the range of the output voltage of the charging stand 14 by stepping down the inverter 8. As described above, according to the present embodiment, since it is possible to control the intermediate terminal voltage to a desired value, even when the charging stand 14 with a current output is connected, there is no risk of a malfunction such as the voltage of the capacitors 7a, 7b fluctuating and making it impossible to charge, or a malfunction such as a voltage exceeding the withstand voltage being applied to the capacitors 7a, 7b.

[0079] In the above configuration, the torque of the motor 3 can be made zero and the rotation can be suppressed by appropriately adjusting the current ratio. Therefore, in the above configuration, the phase current control unit 16 of the control device 9 can suppress the rotation of the motor 3 by controlling the current ratio to a predetermined value that makes the torque zero. Therefore, according to this embodiment, the rotation of the motor 3 can be suppressed regardless of the stop angle of the motor 3 during charging of the battery 2, and as a result, it is possible to prevent the occurrence of a situation in which the vehicle moves during charging.

[0080] However, in the power conversion device 1 having the above configuration, when the power conversion device 1 is operated as a step-down converter, if the duty is low at the start of control, that is, at the start of charging control, the capacitor 7b may be discharged, causing an uncontrollable current to flow through the motor 3, generating torque. Therefore, in this embodiment, the initial duty Dini is set as described above to prevent such a problem from occurring. Below, the effects obtained by this embodiment will be described in comparison with a comparative example in which the initial duty Dini is set to 0.

[0081] First, the current path at the start of control when the power conversion device 1 configured as described above is operated as a step-down converter, that is, at the start of charging control, will be described with reference to Fig. 12 and Fig. 13. In this case, the W phase is the input phase, and the U phase and the V phase are the control phases. The power conversion device 1 operates as a step-down converter by alternately repeating a first operating state shown in Fig. 12 and a second operating state shown in Fig. 13, with the switching elements Q11 and Q12 fixed to ON and the switching elements Q5 to Q10 fixed to OFF.

[0082] In the first operating state, the switch elements Q2 and Q4, which are negative-side switch elements constituting the lower arm of the inverter 8, are turned on, so that a current flows through a path as shown by the thick arrow in Fig. 12, discharging the capacitor 7b. In the second operating state, the switch elements Q1 and Q3, which are positive-side switch elements constituting the upper arm of the inverter 8, are turned on, so that a current flows through a path as shown by the thick arrow in Fig. 13, charging the capacitor 7b.

[0083] If the duty is low at the start of charging control, the time during which the power conversion device 1 is in the first operating state becomes longer than the time during which the power conversion device 1 is in the second operating state, and the capacitor 7b may be discharged, causing an uncontrollable current to flow to the motor 3, resulting in the generation of torque. In the comparative example, since the initial duty Dini is 0, the time during which the power conversion device 1 is in the first operating state becomes relatively long at the start of charging control, and as a result, the capacitor 7b may be discharged and torque may be generated. In contrast, in the present embodiment, since the initial duty Dini is a value (=Vc / Vin) greater than 0, the time during which the power conversion device 1 is in the first operating state becomes shorter than in the comparative example at the start of charging control, and as a result, the discharge of the capacitor 7b may be suppressed to prevent the generation of torque.

[0084] The effect obtained by this embodiment is also clear from the simulation result shown in Fig. 14. Fig. 14 shows an example of the operating waveforms of each part when the power conversion device 1 is operated as a step-down converter in this embodiment and the comparative example. In Fig. 14, the current (=input current) of the charging stand 14 is called the charging stand current, and the current of the battery 2 is called the battery current. In Fig. 14, the actual current, which is the current that actually flows, and the command representing the command value are shown for the charging stand current, but since they are the same value, they are shown as one waveform. In Fig. 14, the duty of the U phase and the duty of the V phase are shown, but since they are the same value, they are shown as one waveform.

[0085] FIG. 14 shows the simulation results under the following conditions. <Condition> Battery voltage → 800V Initial intermediate terminal voltage (= initial voltage Vc) → 400V Charging station 14 current (=input current) → 0A Intermediate terminal voltage command value → 400V

[0086] 14, in the comparative example, the initial duty Dini is 0, so that the transient peak value of the battery current, that is, the current contributing to the discharge of the capacitor 7b, is relatively large at the start of the charging control. Therefore, in the comparative example, the transient peak value of the torque of the motor 3 is relatively large at the start of the charging control, and there is a possibility that the vehicle will move.

[0087] In contrast, in this embodiment, since the initial duty Dini is 0.5 (=400V / 800V), the transient peak value of the battery current, that is, the current contributing to the discharge of the capacitor 7b, is relatively small at the start of the charging control. Therefore, in this embodiment, the transient peak value of the torque of the motor 3 is relatively small at the start of the charging control, and it is possible to prevent the occurrence of a situation in which the vehicle moves.

[0088] In this manner, in this embodiment, since the initial duty Dini is set to the ratio between the battery voltage and the voltage Vc of the capacitor 7b, it is possible to make the output voltage of the inverter 8, i.e., the intermediate terminal voltage, equal to the voltage Vc of the capacitor 7b when the charging control starts, and as a result, the discharge of the capacitor 7b is suppressed, so that an uncontrollable current does not flow to the motor 3 and generate torque. Therefore, according to this embodiment, it is possible to obtain the excellent effect of suppressing the rotation of the motor 3 when the control starts.

[0089] <Modifications of the inverter circuit configuration> The circuit configuration of the inverter is not limited to a T-type NPC three-level inverter, but may be an NPC three-level inverter, such as inverter 8A shown in Fig. 15. Inverter 8A differs from inverter 8 shown in Fig. 1 in the connection form of switch elements Q7 to Q12 and in the addition of diodes D1 to D6. In this case, switch elements Q7 to Q12 and diodes D1 to D6 form an intermediate switch element.

[0090] The source of the switching element Q7 is connected to the node Nu, and its drain is connected to the source of the switching element Q1. The drain of the switching element Q8 is connected to the node Nu, and its source is connected to the drain of the switching element Q2. The anode of the diode D1 is connected to the node Nm, and its cathode is connected to the drain of the switching element Q7. The cathode of the diode D2 is connected to the node Nm, and its anode is connected to the source of the switching element Q8.

[0091] The source of the switching element Q9 is connected to the node Nv, and its drain is connected to the source of the switching element Q3. The drain of the switching element Q10 is connected to the node Nv, and its source is connected to the drain of the switching element Q4. The anode of the diode D3 is connected to the node Nm, and its cathode is connected to the drain of the switching element Q9. The cathode of the diode D4 is connected to the node Nm, and its anode is connected to the source of the switching element Q10.

[0092] The source of the switching element Q11 is connected to the node Nw, and its drain is connected to the source of the switching element Q5. The drain of the switching element Q12 is connected to the node Nw, and its source is connected to the drain of the switching element Q6. The anode of the diode D5 is connected to the node Nm, and its cathode is connected to the drain of the switching element Q11. The cathode of the diode D6 is connected to the node Nm, and its anode is connected to the source of the switching element Q12.

[0093] When the inverter 8A having the above configuration is used, the inverter 8A can function as a step-down converter by turning on the middle switch element of the input phase and synchronously switching the positive switch element, negative switch element and middle switch element of the control phase, which are two phases other than the input phase. In this case, the current flows through the path shown by the thick arrow in FIG. 16.

[0094] The inverter 8, which is a T-type NPC three-level inverter, and the inverter 8A, which is an NPC three-level inverter, each have the following features. First, the inverter 8 has the advantage that the number of elements can be reduced by six compared to the inverter 8A, although only the elements connected to the neutral point can use low-voltage elements with a relatively low withstand voltage, while the elements constituting the bridge must use high-voltage elements with a relatively high withstand voltage. In contrast, the inverter 8A has a greater number of elements than the inverter 8, but has the advantage that all elements can be low-voltage elements.

[0095] (Other embodiments) The present invention is not limited to the embodiments described above and shown in the drawings, and can be modified, combined, or expanded in any manner without departing from the spirit and scope of the present invention. The numerical values ​​and the like shown in the above embodiment are merely examples and are not intended to be limiting.

[0096] The positive side capacitor, which is a capacitor connected between the positive electrode of the battery 2 and the node Nm, is not limited to being composed of one capacitor 7a, and may be composed of, for example, two or more capacitors connected in parallel. Also, the negative side capacitor, which is a capacitor connected between the node Nm and the negative electrode of the battery 2, is not limited to being composed of one capacitor 7b, and may be composed of, for example, two or more capacitors connected in parallel.

[0097] Although the present disclosure has been described based on the embodiment, it is understood that the present disclosure is not limited to the embodiment or structure. The present disclosure also includes various modifications and modifications within the equivalent range. In addition, various combinations and forms, and other combinations and forms including only one element, more than one element, or less than one element, are also within the scope and concept of the present disclosure. [Explanation of symbols]

[0098] 1...power conversion device, 2...battery, 3...motor, 3u, 3v, 3w...coil, 6...neutral point, 7a, 7b...capacitor, 9...control device, 11b...voltage sensor, 13...charging relay, 14...charging stand, 15...voltage control unit, 16...phase current control unit, 44...integrator, D1 to D6...diodes, Nm...node, Q1, Q3, Q5...positive side switching element, Q2, Q4, Q6...negative side switching element, Q7 to Q12...intermediate switching element.

Claims

1. A control device used in a power conversion device that converts electric power passing between a power source (2) and a rotating machine (3) having multiple phase coils (3u, 3v, 3w) and a neutral point (6) to which one terminal of the multiple phase coils is connected, comprising: The power conversion device is A plurality of capacitors (7a, 7b) connected in series between the positive terminal of the power supply and the negative terminal of the power supply; a plurality of intermediate switch elements (Q7 to Q12, D1 to D6) provided between intermediate terminals to which the plurality of capacitors are connected and the coils of the plurality of phases, respectively; A plurality of positive pole side switch elements (Q1, Q3, Q5) provided between each of the coils of the plurality of phases and a positive pole of the power source; A plurality of negative pole side switch elements (Q2, Q4, Q6) provided between each of the coils of the plurality of phases and the negative pole of the power source; The control device (9) controls the intermediate switch element, the positive switch element, and the negative switch element; a connection portion (13) capable of connecting a charger (14) for charging the power source between the intermediate terminal and the positive terminal or the negative terminal of the capacitor; Equipped with The control device includes: a voltage control unit (15) that controls the voltage of the intermediate terminal to be within a range of an output voltage of the charger by stepping down the voltage of the power source; a phase current control unit (16) that determines an input phase for passing a current of the charger to the rotating machine from among the multiple phases, and controls a current ratio that is a ratio of currents flowing through two phases other than the input phase among the multiple phases; Equipped with The driving of the positive side switch element and the negative side switch element is PWM controlled, A control device for a power conversion device that sets an initial duty, which is the duty when control by the voltage control unit starts, to the ratio of the voltage of the power supply to the voltage of a negative side capacitor (7b), which is the capacitor connected between the intermediate terminal and the negative electrode of the power supply.

2. The control device for a power conversion device according to claim 1 , wherein the control device determines the initial duty so that an initial voltage, which is a voltage at the intermediate terminal when control by the voltage control unit starts, coincides with a voltage of the negative electrode side capacitor.

3. Further, a voltage sensor (11b) is provided for detecting the voltage of the negative electrode side capacitor, The voltage control unit and the phase current control unit each perform proportional-integral control, the voltage control unit sets a voltage command representing a command value of a voltage at the intermediate terminal for performing the proportional-integral control to a detection value of the voltage sensor when the voltage control unit starts control; 3. The control device for a power conversion device according to claim 2, wherein the phase current control unit sets an initial value of an integrator (44) for performing the proportional-integral control to the detection value of the voltage sensor when the control by the voltage control unit starts.

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