Power conversion device

Abstract

The power conversion device of the present invention has a plurality of multi-phase converters connected in parallel with a chopper circuit, the chopper circuit having a switching element and an inductor connected to the switching element, and is characterized in that it has: a single current sensor, which is arranged on the primary side of the chopper circuit, and detects the phase current flowing in each of the inductors when the switching elements are in both the on state and the off state; and a bias current detection unit, which detects the bias current of the phase current in the multi-phase converter based on the phase current detected by the current sensor, and the current sensor detects the phase current so that the directions of the phase current flowing in each of the inductors are the same direction as each other.

Description

Technical Field

[0001] The present invention relates to a power conversion device.

[0002] This application claims the benefit of priority based on Tokugan Application No. 2018-115547 filed in Japan on June 18, 2018, the contents of which are incorporated herein by reference. Background Art

[0003] Patent Document 1 below discloses a multiphase converter in which two chopper circuits each of which is a combination of a switching element and a reactor are connected in parallel. The chopper circuit includes a first chopper circuit and a second chopper circuit.

[0004] The multiphase converter detects a current imbalance (hereinafter referred to as "bias current") between the first chopper circuit and the second chopper circuit using a single current sensor. The multiphase converter controls switching of each switching element to reduce the bias current detected by the single current sensor.

[0005] The single current sensor detects that a first current from the reactor of the first chopper circuit toward the switching element and the diode and a second current from the reactor of the second chopper circuit toward the switching element and the diode are in opposite directions, respectively. Thus, the single current sensor can detect the difference between the first current and the second current, i.e., the bias current.

[0006] Prior art literature

[0007] Patent Literature

[0008] Patent Document 1: Japanese Patent No. 5734441 Summary of the invention

[0009] Problems to be solved by the invention

[0010] The current detected by the single current sensor is a sum of the first current and the second current flowing in the opposite direction to the first current. Therefore, the first current and the second current cancel each other out. Therefore, the current value detected by the single current sensor may become smaller, and the detection accuracy of the bias current may decrease.

[0011] The present invention has been made in view of the above circumstances, and an object of the present invention is to improve the detection accuracy of bias current in a multi-phase converter.

[0012] Solutions to Solve Problems

[0013] (1) One aspect of the present invention is a power conversion device having a plurality of multi-phase converters connected in parallel with a chopper circuit, the chopper circuit having a switching element and an inductor connected to the switching element, characterized in that the power conversion device comprises: a single current sensor, which is arranged on the primary side of the chopper circuit, and detects the phase current flowing in each of the inductors when the switching elements are both in an on state and an off state; and a bias current detection unit, which detects the bias current of the phase current in the multi-phase converter based on the phase current detected by the current sensor, the current sensor detecting the phase current so that the directions of the phase current flowing in each of the inductors are the same direction as each other.

[0014] (2) As the power conversion device of (1) above, the bias current detection unit may detect the bias current based on a phase current detected by the current sensor when the phase current changes from increasing to decreasing, that is, a change-point phase current.

[0015] (3) As the power conversion device of (2) above, the bias current detection unit may acquire the phase current detected by the current sensor when each of the switching elements is switched from an on state to an off state as the change-point phase current.

[0016] (4) As the power conversion device of the above-mentioned (2) or (3), it may also have a delay unit that delays the phase current input from the current sensor to the bias current detection unit by only a specified time, and the bias current detection unit obtains the phase current from the current sensor at a first timing, and the specified time is set to the difference between the second timing when the switching element is switched from the on state to the off state and the first timing.

[0017] (5) As the power conversion device of any one of (2) to (4) above, the bias current detection unit may detect a current difference among the plurality of phase currents at the change points detected by the current sensor as the bias current.

[0018] (6) In the power conversion device according to any one of (1) to (5) above, the reactors may be magnetically coupled to each other.

[0019] (7) As the power conversion device according to any one of (1) to (6) above, the multi-phase converter may be a two-phase converter in which two chopper circuits are connected in parallel.

[0020] Effects of the Invention

[0021] As described above, according to the present invention, the detection accuracy of the bias flow can be improved. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 This is a diagram showing an example of a schematic configuration of the PCU 1 according to the present embodiment.

[0023] Figure 2 1 is a diagram showing an example of a waveform of the total phase current IPN detected by the current sensor 26 according to the present embodiment.

[0024] Figure 3 2 is a schematic diagram of the structure of the bias current detection unit 52 according to the present embodiment.

[0025] Figure 4 It is a schematic configuration diagram of the control unit 51 of this embodiment. DETAILED DESCRIPTION

[0026] Hereinafter, the power conversion device according to the present embodiment will be described with reference to the drawings.

[0027] Figure 1 1 is a diagram showing an example of a schematic structure of a power conversion device 1 according to the present embodiment. The power conversion device 1 is mounted on a vehicle that runs with a motor M as a power source. For example, the power conversion device 1 is mounted on a vehicle such as a hybrid vehicle and an electric vehicle. For example, the power conversion device 1 is a PCU (Power Control Unit).

[0028] like Figure 1 As shown, the power conversion device 1 includes a multi-phase converter 2 , an inverter 3 , a delay unit 4 , and a control device 5 .

[0029] The multi-phase converter 2 is, for example, a multi-phase DC / DC converter for vehicle use. The multi-phase converter 2 boosts the DC voltage VB input from the DC power supply E to a predetermined voltage Vc (hereinafter referred to as "boosted voltage") and outputs it to the inverter 3. Furthermore, in this embodiment, the multi-phase converter 2 is described as a two-phase DC / DC converter, but the present invention is not limited to this. If the number of phases is two or more, it is not particularly limited. The specific structure of the multi-phase converter 2 of this embodiment is described below.

[0030] The multi-phase converter 2 has a primary-side capacitor 21 , chopper circuits 22 , 23 , a secondary-side capacitor 24 , a voltage detection unit 25 , and a current sensor 26 .

[0031] The primary side capacitor 21 has a first end connected to the positive terminal of the DC power source E, and a second end connected to the negative terminal of the DC power source E. The primary side capacitor 21 is a smoothing capacitor that smoothes the DC voltage VB output from the DC power source E.

[0032] The chopper circuits 22 and 23 are connected in parallel to each other between the DC power supply E and the inverter 3. In the present embodiment, the chopper circuits 22 and 23 are described as step-up chopper circuits, but the present invention is not limited thereto, and for example, they may be step-down chopper circuits or step-up step-down chopper circuits.

[0033] The chopper circuit 22 includes a reactor L1 and a power module P1 .

[0034] The reactor L1 has a first end connected to a first end of the primary-side capacitor 21 , and a second end connected to the power module P1 .

[0035] The power module P1 includes a switching element Q1 and a switching element Q2 connected in series. In the present embodiment, the switching element Q1 and the switching element Q2 are described as IGBTs (Insulated Gate Bipolar Transistors), but the present invention is not limited thereto, and for example, they may be FETs (Field Effective Transistors) or the like.

[0036] The collector terminal of the switching element Q1 is connected to the first end of the secondary side capacitor 24 , and the emitter terminal is connected to the collector terminal of the switching element Q2 .

[0037] The emitter terminal of the switching element Q2 is connected to the negative terminal of the DC power source E.

[0038] A connection point between the emitter terminal of the switching element Q1 and the collector terminal of the switching element Q2 is connected to the second end of the reactor L1 . Gate terminals of the switching element Q1 and the switching element Q2 are connected to the control device 5 , respectively.

[0039] The chopper circuit 23 includes a reactor L2 and a power module P2.

[0040] The first end of the reactor L2 is connected to the first end of the primary-side capacitor 21, and the second end is connected to the power module P2. The reactor L1 and the reactor L2 are magnetically coupled to each other.

[0041] The power module P2 includes a switching element Q3 and a switching element Q4 connected in series. In the present embodiment, the switching element Q3 and the switching element Q4 are described as IGBTs, but the present invention is not limited thereto, and for example, they may be FETs.

[0042] The collector terminal of the switching element Q3 is connected to the first end of the secondary side capacitor 24 , and the emitter terminal is connected to the collector terminal of the switching element Q4 .

[0043] The emitter terminal of the switching element Q4 is connected to the negative terminal of the DC power source E.

[0044] A connection point between the emitter terminal of the switching element Q3 and the collector terminal of the switching element Q4 is connected to the second end of the reactor L2 . The gate terminals of the switching element Q3 and the switching element Q4 are connected to the control device 5 , respectively.

[0045] A first end of the secondary side capacitor 24 is connected to the collector terminals of the switching elements Q1 and Q2 , and a second end thereof is connected to the negative terminal of the DC power source E. The secondary side capacitor 24 is a smoothing capacitor.

[0046] The voltage detection unit 25 detects a potential difference across the secondary capacitor 24. The voltage difference across the secondary capacitor 24 is a boosted voltage Vc boosted by the chopper circuits 22 and 23. The voltage detection unit 25 outputs the detected boosted voltage Vc to the control device 5.

[0047] The current sensor 26 is provided on the primary side of the chopper circuits 22 and 23, and detects the phase currents of the first phase current IL1 and the second phase current IL2, which flow in the same direction. The current sensor 26 is a single current sensor. The current sensor 26 detects the total phase current (hereinafter referred to as "total phase current") IPN of the first phase current IL1 and the second phase current IL2 and outputs it to the bias current detection unit 52. The primary side of the chopper circuits 22 and 23 is between the positive terminal of the current power supply E and the connection point with the emitter terminal of the switching element Q1 and the collector terminal of the switching element Q2, and between the positive terminal of the current power supply E and the connection point with the emitter terminal of the switching element Q3 and the collector terminal of the switching element Q4.

[0048] The inverter 3 is controlled by the control device 5 and converts the boosted voltage Vc output from the multi-phase converter 2 into an AC voltage. The inverter 3 supplies the converted AC voltage to the motor M.

[0049] The delay unit 4 delays the output from the current sensor 26 by a predetermined time and transmits the output to the control device 5. For example, the delay unit 4 is a low-pass filter.

[0050] The control device 5 includes a control unit 51 and a bias current detection unit 52 .

[0051] The control unit 51 controls the driving of the chopper circuits 22 and 23. Specifically, the control unit 51 controls the switching of a pair of switching elements Q1 and Q2 and a pair of switching elements Q3 and Q4 at different timings. As a result, currents of different phases (e.g., a phase difference of 180°) flow through the chopper circuits 22 and 23.

[0052] The control unit 51 controls the switching element Q2 to be in the on state so that the current flows through the reactor L1, the switching element Q2, and the negative terminal of the DC power source E, thereby accumulating energy in the reactor L1. Then, the control unit 51 controls the switching element Q2 to be in the off state, and supplies the energy accumulated in the reactor L1 to the secondary side capacitor 24 through the switching element Q1, thereby boosting the DC power source VB. The current (hereinafter referred to as "phase current") flowing through the reactor L1 when the switching element Q2 is in both the on state and the off state is referred to as the first phase current IL1.

[0053] The control unit 51 controls the switch element Q4 to be in the on state so that the current flows through the reactor L2, the switch element Q4, and the negative terminal of the DC power source E, thereby accumulating energy in the reactor L2. Then, the control unit 51 controls the switch element Q4 to be in the off state, and supplies the energy accumulated in the reactor L2 to the secondary side capacitor 24 through the switch element Q3 to boost the DC power source VB. The current (hereinafter referred to as "phase current") flowing in the reactor L2 when the switch element Q4 is in both the on state and the off state is referred to as the second phase current IL2.

[0054] The multiphase converter 2 operates as a two-phase DC / DC converter. For this reason, the first phase current IL1 and the second phase current IL2 flow in the same direction. That is, when the first phase current IL1 flows from the DC power supply E through the reactor L1 to the power module P1, the second phase current IL2 flows from the DC power supply E through the reactor L2 to the power module P2.

[0055] The control unit 51 performs PWM (Pulse Width Modulation) control on the switches of the switching elements Q1, Q2 and the switching elements Q3, Q4 to reduce the current difference (hereinafter referred to as "bias current") between the first phase current IL1 and the second phase current IL2. Specifically, the control unit 51 outputs a first PWM signal to the switching elements Q1, Q2, and outputs a second PWM signal whose phase is 180° different from the first PWM signal to the switching elements Q3, Q4. As a result, the multi-phase converter 2 can generate a stable boost voltage Vc with less pulsation.

[0056] The bias current detection unit 52 detects the bias current between the first phase current IL1 and the second phase current IL2 based on the total current IPN detected by the current sensor 26. Figure 2 A method of detecting a bias current according to the present embodiment will be described. Figure 2 1 is a diagram showing an example of the waveform of the total phase current IPN detected by the current sensor 26 .

[0057] like Figure 2As shown, the waveform of the total current IPN detected by the current sensor 26 has roughly two types of change points A and B. The change points A and B are points where the total phase current IPN changes from increasing to decreasing.

[0058] For example, the change point A indicates the timing (time t1) when the switch element Q2 is switched from the on state to the off state. Therefore, the total phase current IPN at the change point A indicates the maximum value of the first phase current IL1. The change point B indicates the timing (time t2) when the switch element Q4 is switched from the on state to the off state. Therefore, the total phase current IPN at the change point B indicates the maximum value of the second phase current IL2.

[0059] Reactor L1 and reactor L2 have the characteristic that the self-inductance decreases when the current flowing in the phase increases. For this reason, the larger the phase current, the larger the pulsating current of the phase current. Therefore, in the waveform of the total phase current, the maximum value of the total phase current deviates at the change point A and the change point B according to the bias current. In the present embodiment, the phase difference between the switching of the switching elements Q1, Q2 and the switching elements Q3, Q4 is 180°, so the change point A and the change point B occur alternately every 180°.

[0060] The bias current detection unit 52 detects bias current based on the total phase current (hereinafter referred to as "change point phase current") when the total phase current IPN detected by the current sensor 26 changes from increasing to decreasing. That is, the bias current detection unit 52 detects the difference between the total phase current IPN at the change point A, i.e., the change point phase current IA, and the total phase current IPN at the change point B, i.e., the change point phase current IB, among the total phase current IPN detected by the current sensor 26 as bias current.

[0061] The method of acquiring the change point phase current IA and the change point phase current IB in the bias current detection unit 52 is not particularly limited, but for example, they can be acquired by any of the following methods (a) and (b).

[0062] (a) The bias current detection unit 52 obtains the change point phase current A and the change point phase current B by obtaining the total phase current IPN detected by the current sensor 26 when the total phase current IPN changes from increasing to decreasing within a predetermined period.

[0063] (b) The bias current detection unit 52 acquires the total phase currents IPN output from the current sensor 26 as the change point phase current A and the change point phase current B when the switch elements Q2 and Q4 are switched from the on state to the off state.

[0064] In the above (b), the bias current detection unit 52 obtains the change point phase current A and the change point phase current B by synchronizing the timing of obtaining the total phase current IPN from the current sensor 26 (hereinafter referred to as "obtaining timing") with the timing of turning off the switching elements Q2 and Q4.

[0065] However, when the acquisition timing of the bias current detection unit 52 and the respective timings of turning off the switching elements Q2 and Q4 cannot be synchronized, the bias current detection unit 52 can be set to the delay unit 4 in the power conversion device 1. Figure 3 In the structure shown, the bias current detection unit 52 can obtain the change point phase current IA and the change point phase current IB according to the method (b) above.

[0066] The situation where the acquisition timing of the bias current detection unit 52 and the timing of the disconnection of the switch elements Q2 and Q4 cannot be synchronized refers to the situation where, for example, the acquisition timing of the bias current detection unit 52 is not the timing of the disconnection of the switch elements Q2 and Q4, but the timing of the peak and trough of the carrier (triangular wave). Furthermore, in the above (b), when the acquisition timing of the bias current detection unit 52 and the timing of the disconnection of the switch elements Q2 and Q4 can be synchronized without the delay unit 4, the delay unit 4 is not a necessary structure of the power conversion device 1. The following describes Figure 3 The structure of the bias current detection unit 52 is shown.

[0067] like Figure 3 As shown, the bias current detection unit 52 includes a first acquisition unit 521 , a second acquisition unit 522 , and a bias current calculation unit 523 .

[0068] The delay unit 4 delays the output from the current sensor 26 by a predetermined time, so that the first timing at which the first acquisition unit 521 acquires the total phase current IPN is synchronized with the second timing at which the switching elements Q2 and Q4 are turned off. For example, the delay unit 4 sets the difference between the timing of the peak of the carrier (triangular wave) and the timing of the rise of the above-mentioned first PWM signal to the delay time Δt, and delays the total phase current IPN output from the first acquisition unit 521 by the delay time Δt and inputs it to the bias current calculation unit 523. The delay unit 4 may also set the difference between the timing of the trough of the carrier (triangular wave) and the timing of the rise of the above-mentioned second PWM signal to the delay time Δt, and delay the total phase current IPN output from the first acquisition unit 521 by the delay time Δt and input it to the bias current calculation unit 523.

[0069] The first timing refers to the timing of the peak and the trough of the carrier wave (triangular wave) for generating the first PWM signal and the second PWM signal.

[0070] The first acquisition unit 521 acquires the total phase current IPN from the delay unit 4 at the first timing. The first acquisition unit 521 outputs the total phase current IPN acquired by the delay unit 4 at the first timing to the bias current calculation unit 523.

[0071] The second acquisition unit 522 acquires the total phase current IPN from the current sensor 26 at the first timing without passing through the delay unit 4 , and outputs the acquired total phase current IPN to the control device 5 .

[0072] The bias current calculation unit 523 obtains the total phase current IPN as the change point phase currents A and B by obtaining the total phase current IPN delayed by the delay unit 4 by the delay time Δt. In this way, the bias current calculation unit 523 can obtain the change point phase currents A and B at the first timing by delaying the total phase current IPN by the delay unit 4 by the delay time Δt.

[0073] Then, the bias current calculation unit 523 calculates the bias current from the acquired change point phase currents A and B and outputs it to the control device 5 .

[0074] Below, use Figure 4 The configuration of the control unit 51 of this embodiment will be described.

[0075] The control unit 51 includes a voltage control unit 41 , a current control unit 42 , a correction unit 43 , a carrier generation unit 44 , a phase shift unit 45 , and comparison units 46 and 47 .

[0076] The voltage control unit 41 performs a PI operation on the deviation between the boosted voltage Vc detected by the voltage detection unit 25 and a preset target voltage, thereby calculating a current command value for bringing the deviation close to zero.

[0077] The current control unit 42 performs PI operation on the deviation between the current command value calculated by the voltage control unit 41 and the total phase current IPN acquired from the second acquisition unit 522 , thereby calculating a switching command value D which is a signal for bringing the deviation close to zero.

[0078] The correction unit 43 corrects the switch command value D calculated by the current control unit 42 to a switch command value D′ for suppressing the bias current so as to suppress the bias current detected by the bias current detection unit 52. For example, the correction unit 43 generates a switch command value D′ (D1′) by adding a value obtained by multiplying the bias current detected by the bias current detection unit 52 by a predetermined coefficient to the switch command value D, and outputs the value to the comparison unit 46. In addition, the correction unit 43 generates a switch command value D′ (D2′) by subtracting a value obtained by multiplying the bias current detected by the bias current detection unit 52 by a predetermined coefficient from the switch command value D, and outputs the value to the comparison unit 47.

[0079] The carrier wave generating unit 44 generates the carrier wave and outputs the carrier wave to the phase shifting unit 45 and the comparing unit 47 .

[0080] The phase shifter 45 shifts the phase of the carrier from the carrier generator 44 by, for example, 180°. Thus, the switch element Q2 and the switch element Q4 are controlled to be alternately turned on. The phase shifter 45 outputs the phase-shifted carrier to the comparison unit 46 .

[0081] The comparison unit 46 generates a first PWM signal by comparing the switching command value D1' with the carrier wave output from the phase shift unit 45, and outputs the first PWM signal to the power module P1. Thus, the control unit 51 can perform PWM control on the switching elements Q1 and Q2.

[0082] The comparison unit 47 generates a second PWM signal by comparing the switching command value D2' with the carrier wave outputted from the carrier wave generation unit 44, and outputs the second PWM signal to the power module P2. Thus, the control unit 51 can perform PWM control on the switching elements Q3 and Q4.

[0083] As described above, the power conversion device 1 of the present embodiment has a single current sensor 26 and a bias current detection unit 52. The single current sensor 26 is provided on the primary side of the chopper circuits 22 and 23, and detects the phase current flowing in each of the reactors L1 and L2 when both the switching elements Q2 and Q4 are in the on state and the off state. The bias current detection unit 52 detects the bias current of the phase current flowing in the reactor L1 and the phase current flowing in the reactor L2 based on the phase current detected by the current sensor 26. Then, the current sensor 26 detects the phase current so that the directions of the phase currents flowing in the reactors L1 and L2 are the same direction as each other.

[0084] According to such a configuration, the value of the phase current detected by the current sensor 26 does not decrease. Therefore, the power conversion device 1 of the present embodiment can improve the detection accuracy of the bias current.

[0085] In addition, the current sensor 26 may be provided on the primary side of the chopper circuits 22 and 23. For this purpose, the current sensor 26 detects the phase current before being stepped up by the chopper circuits 22 and 23, and calculates the bias current based on the detected phase current. Thus, the bias current detection unit 52 can detect the bias current with higher accuracy without being affected by the switching loss generated when the switching elements Q1 to Q4 are driven.

[0086] For example, if the current sensor 26 is provided on the high voltage side of the chopper circuits 22 and 23, the switching element of the inverter 3 is driven according to the driving state of the vehicle, and there is a case where the AC component of the current flowing during the driving affects the current sensor 26. Therefore, if the current sensor 26 is provided on the high voltage side of the chopper circuits 22 and 23, there is a case where the current sensor 26 cannot correctly detect the current flowing in the reactors L1 and L2. The current sensor 26 of this embodiment can also be provided on the low voltage side, that is, the primary side, of the chopper circuits 22 and 23. Therefore, the AC component of the above-mentioned current does not affect the current sensor 26. Therefore, the current sensor 26 of this embodiment can correctly detect the current flowing in the reactors L1 and L2.

[0087] The control device 5 of this embodiment detects the current value and bias value of a single current sensor 26. The current control unit 42 of the control device 5 obtains the switch command value D based on the current command value and the current value. The correction unit 43 of the control device 5 corrects the switch command value D to the switch command value D′ for suppressing its bias. That is, the control device 5 uses a single current sensor 26 to perform current control of the phase current and suppress bias. For this reason, compared with the case where the control device 5 uses multiple current sensors to perform current control of the phase current and suppress bias, the detection sensitivity difference (deviation) of the components caused by using multiple current sensors can be eliminated. The control device 5 can control the bias with higher accuracy than the structure using multiple current sensors. The case where multiple current sensors are used to perform current control of the phase current and suppress bias refers to, for example, the case where the control device performs current control based on the measurement value of the first current sensor and suppresses bias based on the measurement value of the second current sensor different from the first current sensor.

[0088] Furthermore, the reactors L1 and L2 are magnetically coupled to each other, so they have a DC superposition characteristic. Therefore, a significant difference occurs between the maximum value of the total phase current IPN detected by the current sensor 26, that is, the change point phase current IA and the change point phase current IB. Therefore, the power conversion device 1 can calculate the current deviation based on the values ​​of the change point phase current IA and the change point phase current IB, and can detect the bias current with higher accuracy.

[0089] As mentioned above, although the embodiment of the present invention is described in detail with reference to the drawings, the specific structure is not limited to this embodiment, and also includes the design etc. within the scope which does not deviate from the meaning of the present invention.

[0090] For example, in the above embodiment, the current control means 42 may make the proportional gain of the PI operation variable based on the self-inductance component and the mutual inductance component of the reactors L1 and L2 . Thus, the current control means 42 may improve the responsiveness of the current sensor 26 .

[0091] In the above embodiment, when the total phase current IPN detected by the current sensor 26 exceeds a predetermined value, the control device 5 may determine that the current output from the multiphase converter 2 is an overcurrent. Thus, the power conversion device 1 does not need to have a separate current sensor for detecting overcurrent.

[0092] In the above embodiment, the current sensor 26 is configured so as to detect the phase current flowing in the wiring (e.g., busbar) connecting the inductors L1, L2 and the power modules P1, P2, but the present invention is not limited thereto. For example, it may be provided between the positive terminal of the DC power supply E and the connection point between the first end of the reactor L1 and the first end of the reactor L2. That is, as long as the current sensor 26 can obtain the current flowing in the reactors L1, L2, it may be provided at any position on the primary side of the multi-phase converter 2.

[0093] In the above-mentioned embodiment, the bias current detection unit 52 and the control unit 51 may be integrally formed or mechanically formed as a single body. For example, the power conversion device 1 of this embodiment has a bias current detection device that is separate from the control device 5, and the bias current detection device may also have the function of the bias current detection unit 52, and the control device 5 may also have the function of the control unit 51.

[0094] Industrial Applicability

[0095] According to the above-described power conversion device, it is possible to improve the detection accuracy of the bias current in the multi-phase converter.

[0096] Description of symbols

[0097] 1 Power conversion device

[0098] 2 Multiphase Converter

[0099] 5. Control Device

[0100] 22, 23 Chopper circuit

[0101] L1, L2 reactor

[0102] P1, P2 power modules

[0103] Q1~Q4 switching elements

[0104] 26 Current sensor

[0105] 52 Bias current detection unit

Claims

1. A power conversion device comprising a multiphase converter in which two chopper circuits are connected in parallel, the chopper circuit comprising a switching element and a reactor connected to the switching element, characterized in that: The power conversion device has: a single current sensor provided on the primary side of the chopper circuit, detecting a phase current flowing in each of the reactors in both an on state and an off state of each of the switching elements; a bias current detection unit, which detects a bias current of a phase current in the multi-phase converter based on the phase current detected by the current sensor; a voltage detection unit for detecting a boosted voltage boosted by the two chopper circuits; as well as A control unit controls driving of the two chopper circuits. The current sensor detects a phase current obtained by summing a first phase current flowing in a first reactor and a second phase current flowing in a second reactor among the reactors, that is, a total phase current, so that the direction of the first phase current and the direction of the second phase current are the same direction. The power conversion device further comprises: a delay unit that delays the total phase current from the current sensor by a predetermined time, The bias current detection unit has: A first acquisition unit, which acquires the total phase current after being delayed for a predetermined time; a second acquisition unit that acquires the total phase current from the current sensor without passing through the delay unit; and a bias current calculation unit, which obtains the total phase current obtained by the first acquisition unit as a change point phase current, and calculates a bias current based on the obtained change point phase current, The control unit has: a voltage control unit that calculates a current command value for making the deviation between the boosted voltage detected by the voltage detection unit and a preset target voltage approach zero by performing a PI operation on the deviation between the boosted voltage detected by the voltage detection unit and the preset target voltage; a current control unit that calculates a first switching command value, which is a signal for bringing the deviation close to zero, by performing a PI operation on the deviation between the current command value calculated by the voltage control unit and the total phase current acquired from the second acquisition unit; a correction unit that generates a second switch command value by adding a value obtained by multiplying the bias current detected by the bias current detection unit by a predetermined coefficient to the first switch command value, and generates a third switch command value by subtracting a value obtained by multiplying the bias current detected by the bias current detection unit by a predetermined coefficient from the first switch command value; A carrier generation unit, generating a carrier; a phase shifting unit, which shifts the phase of the carrier from the carrier generating unit; a first comparing unit that generates a first control signal for controlling one of the two chopper circuits by comparing the second switch command value with the carrier wave output from the phase shifting unit; and The second comparing unit generates a second control signal for controlling the other of the two chopper circuits by comparing the third switching command value with the carrier wave output from the carrier wave generating unit.

2. The power conversion device according to claim 1, characterized in that: The bias current detection unit detects the bias current based on a phase current at a time when the total phase current detected by the current sensor changes from increasing to decreasing, ie, a change-point phase current.

3. The power conversion device according to claim 2, characterized in that: The bias current detection unit acquires the total phase current detected by the current sensor when each of the switching elements is switched from an on state to an off state as the change-point phase current.

4. The power conversion device according to claim 2 or 3, characterized in that: The bias current detection unit acquires the total phase current from the current sensor at a first timing, The predetermined time is set to a time difference between a second timing at which the switching element is switched from an on state to an off state and the first timing.

5. The power conversion device according to claim 2 or 3, characterized in that: The bias current detection unit detects a current difference among the plurality of change-point phase currents detected by the current sensor as the bias current.

6. The power conversion device according to any one of claims 1 to 3, characterized in that: The reactors are magnetically coupled to each other.

7. The power conversion device according to any one of claims 1 to 3, characterized in that: The multiphase converter is a two-phase converter in which two chopper circuits are connected in parallel.

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