Multi-phase converter control device

Abstract

A multiphase converter control device of the present application PWM-controls driving of a multiphase converter. The multiphase converter is configured so that a plurality of converters connected in parallel with each other respectively have reactors that are magnetically coupled with each other and generate a boosted voltage by boosting an input voltage. The multiphase converter control device has a feedback control section that performs feedback control so that the boosted voltage becomes a target voltage, a PWM control section that generates a PWM signal based on a voltage command value output from the feedback control section, and a driving section that drives the multiphase converter based on the PWM signal. The feedback control section calculates a boost ratio of the multiphase converter and changes a control gain in the feedback control based on the boost ratio.

Description

Technical Field

[0001] This invention relates to a multiphase converter control device.

[0002] This application claims priority based on Japanese Special Purpose Application No. 2020-037623 filed with Japan on March 5, 2020, the contents of which are incorporated herein by reference. Background Technology

[0003] Japanese Patent No. 5734441 discloses a converter control device for performing PWM control on a multiphase converter consisting of a first converter and a second converter connected in parallel. This converter control device performs feedback control so that the boost voltage of the multiphase converter becomes the target voltage.

[0004] However, in the case of magnetic coupling between the reactors of the first and second converters of a multiphase converter, which are the objects of control, the plant model (the model described by a mathematical model) of the multiphase converter is composed of two plant models with different step-up ratios. Therefore, in order to control the multiphase converter with magnetic coupling between its reactors, a control device is provided for each plant model with a different step-up ratio. Summary of the Invention

[0005] The problem that the invention aims to solve

[0006] However, if a control device is set up for each device model with different boost ratios, the device becomes large-scale. Therefore, the inventors have come up with the idea of ​​approximating two device models with different boost ratios into one device model and controlling the multiphase converter with a single control device.

[0007] However, if a feedback control device is used, the control gain may be inconsistent within a certain boost ratio range, causing the boost voltage of the multiphase converter to oscillate (hunt). As a result, the controllability of the multiphase converter may be reduced.

[0008] The present invention was made in view of the following circumstances, and its object is to provide a multiphase converter control device that improves the controllability of multiphase converters.

[0009] Methods for solving problems

[0010] (1) One aspect of the present invention is a multiphase converter control device that performs PWM control on the drive of a multiphase converter. The multiphase converter is configured such that multiple converters connected in parallel each have reactors, the reactors are magnetically coupled to each other, and boost the input voltage to generate a boost voltage. The multiphase converter control device includes: a feedback control unit that performs feedback control to make the boost voltage a target voltage; a PWM control unit that generates a PWM signal based on a voltage command value output from the feedback control unit; and a drive unit that drives the multiphase converter based on the PWM signal. The feedback control unit calculates the boost ratio of the multiphase converter and changes the control gain in the feedback control based on the boost ratio.

[0011] (2) The multiphase converter control device described in (1) above can also be configured as follows: The feedback control unit includes: a voltage control unit that generates a current command value by applying PI control to the deviation between the boost voltage and the target voltage; a current control unit that generates the voltage command value by applying PI control to the deviation between the current command value and the phase current input to the multiphase converter; and a boost ratio calculation unit that calculates the boost ratio; the voltage control unit changes the control gain used to generate the current command value based on the boost ratio.

[0012] (3) In the multiphase converter control device of (2) above, the voltage control unit may also include: a storage unit that stores a proportional gain diagram showing the correspondence between the boost ratio and the proportional gain, and an integral gain diagram showing the correspondence between the boost ratio and the integral gain; an acquisition unit that acquires the proportional gain corresponding to the boost ratio calculated by the boost ratio calculation unit from the proportional gain diagram, and acquires the integral gain corresponding to the boost ratio from the integral gain diagram; and an arithmetic unit that uses the proportional gain and the integral gain acquired by the acquisition unit to perform the PI control.

[0013] (4) In any one of the multiphase converter control devices described in (1) to (3) above, when the boost ratio is below a predetermined boost ratio, the feedback control unit may also change the control gain in the feedback control based on the boost ratio.

[0014] The effects of the invention

[0015] As explained above, the controllability of the multiphase converter can be improved according to the various methods described above. Attached Figure Description

[0016] Figure 1 This is a circuit diagram showing the schematic structure of a power conversion device 1 having a multiphase converter control device according to an embodiment of the present invention.

[0017] Figure 2 This is a schematic structural diagram of the control unit 11 in the same embodiment.

[0018] Figure 3 This is a schematic structural diagram of the voltage control unit 22 in the same embodiment.

[0019] Figure 4 These are examples of proportional gain maps and integral gain maps representing the same implementation.

[0020] Figure 5 This is a diagram showing a device model 100 that describes the multiphase converter 2 of the same implementation using a mathematical model.

[0021] Figure 6A This is a timing diagram of the switches in the multiphase converter 2 of the same implementation, showing the case where the boost ratio P exceeds "2".

[0022] Figure 6B This is a timing diagram of the switches in the multiphase converter 2 of the same embodiment, showing the case where the boost ratio P is "2" or less.

[0023] Figure 7 This is a diagram showing an example of the waveform of the phase current iL detected by the current sensor 10 of the same embodiment.

[0024] Explanation of reference numerals in the attached figures

[0025] 2. Multiphase converter

[0026] 4. Control device (multiphase converter control device)

[0027] 6a First Converter (Converter)

[0028] 6b Second Converter (Converter)

[0029] 11 Control Department

[0030] 12 Drive Unit

[0031] 20 Feedback Control Department

[0032] 21 Boost Ratio Calculation Unit

[0033] 22 Voltage Control Unit

[0034] 23 Current Control Unit

[0035] 30 Storage Department

[0036] 31 Acquisition Department

[0037] 32. Arithmetic Unit

[0038] 50 PWM Control Unit Detailed Implementation

[0039] Hereinafter, a multiphase converter control device according to an embodiment of the present invention will be described with reference to the accompanying drawings.

[0040] Figure 1 This diagram illustrates an example of the schematic structure of a power conversion device (e.g., a PCU (Power Control Unit)) 1 equipped with a multiphase converter control device according to this embodiment. The power conversion device 1 is mounted in a vehicle such as a hybrid electric vehicle or an electric vehicle that uses an electric motor M as its power source.

[0041] However, the electric motor M can also be an electric generator. That is, the electric motor M can also function as a generator driven by the vehicle's engine. For example, the electric motor M is a three-phase (U, V, W) brushless electric motor.

[0042] like Figure 1 As shown, the power conversion device 1 includes a multiphase converter 2, an inverter 3, and a control device 4. The control device 4 is an example of the "multiphase converter control device" of the present invention.

[0043] The multiphase converter 2 is configured, for example, as a multiphase DC / DC converter for automotive use. The multiphase converter 2 boosts the DC voltage VB input from the DC power supply E to a predetermined voltage Vc (hereinafter referred to as the "boost voltage") and outputs it to the inverter 3. In this embodiment, the multiphase converter 2 is described as a two-phase DC / DC converter, but the present invention is not limited thereto, and there is no particular limitation as long as the number of phases is two or more. The specific structure of the multiphase converter 2 in this embodiment will be described below. Furthermore, the DC voltage VB is an example of the "input voltage" of the present invention.

[0044] The multiphase converter 2 includes a primary-side capacitor 5, converters 6a and 6b, a secondary-side capacitor 7, a first voltage sensor 8, a second voltage sensor 9, and a current sensor 10.

[0045] One end of the primary-side capacitor 5 is connected to the positive terminal of the DC power supply E, and the other end of the primary-side capacitor 5 is connected to the negative terminal of the DC power supply E. The primary-side capacitor 5 is a smoothing capacitor that smooths the DC voltage VB output from the DC power supply E.

[0046] Converters 6a and 6b are connected in parallel between the DC power supply E and the inverter 3. Furthermore, in this embodiment, converters 6a and 6b are described as boost converters, but the invention is not limited to this; for example, they could also be buck converters or buck-boost converters.

[0047] The converter 6a (first converter) includes a reactor L1 (first reactor) and a power module P1.

[0048] One end of reactor L1 is connected to one end of primary capacitor 5, and the other end of reactor L1 is connected to power module P1.

[0049] The power module P1 includes a switching element Q1 and a switching element Q2 (the first switching element) connected in series. In this embodiment, the switching elements Q1 and Q2 are described as IGBTs (Insulated Gate Bipolar Transistors), but the invention is not limited to this; for example, they could also be FETs (Field Effective Transistors).

[0050] The collector terminal of switching element Q1 is connected to one end of the secondary capacitor 7, and the emitter terminal of switching element Q1 is connected to the collector terminal of switching element Q2.

[0051] The emitter terminal of the switching element Q2 is connected to the negative terminal of the DC power supply E.

[0052] Furthermore, the connection point between the emitter terminal of switching element Q1 and the collector terminal of switching element Q2 is connected to the other end of reactor L1. The gate terminals of switching elements Q1 and Q2 are respectively connected to control device 4.

[0053] Converter 6b (second converter) includes reactor L2 (second reactor) and power module P2.

[0054] One end of reactor L2 is connected to one end of primary-side capacitor 5, and the other end of reactor L2 is connected to power module P2. Additionally, reactors L1 and L2 are magnetically coupled to each other.

[0055] In addition, when reactor L1 and reactor L2 are not distinguished from each other, they are referred to as reactor L.

[0056] The power module P2 includes switching elements Q3 and Q4 connected in series. Furthermore, this embodiment describes the case where switching elements Q3 and Q4 (the second switching element) are IGBTs, but the invention is not limited thereto; for example, they could also be FETs.

[0057] The collector terminal of the switching element Q3 is connected to one end of the secondary capacitor 7, and the emitter terminal of the switching element Q3 is connected to the collector terminal of the switching element Q4.

[0058] The emitter terminal of the switching element Q4 is connected to the negative terminal of the DC power supply E.

[0059] Furthermore, the connection point between the emitter terminal of switching element Q3 and the collector terminal of switching element Q4 is connected to the other end of reactor L2. The gate terminals of switching elements Q3 and Q4 are respectively connected to control device 4.

[0060] The secondary capacitor 7 is a smooth capacitor with one end connected to the collector terminals of the switching elements Q1 and Q3, and the other end connected to the negative terminal of the DC power supply E.

[0061] The first voltage sensor 8 is connected between the terminals of the DC power supply E to detect the DC voltage VB output from the DC power supply E. In other words, the first voltage sensor 8 is a sensor installed between the terminals of the primary-side capacitor 5 to detect the voltage (hereinafter referred to as "primary-side voltage") Vp on the primary side of the multiphase converter. The primary-side voltage Vp is equivalent to the voltage between the terminals (one end and the other end) of the primary-side capacitor 5, representing the same value as the DC voltage VB. The first voltage sensor 8 outputs the detected primary-side voltage Vp to the control device 4.

[0062] The second voltage sensor 9 detects the potential difference across the secondary-side capacitor 7, which is the boosted voltage Vc after being boosted by converters 6a and 6b. This boosted voltage Vc is the voltage on the secondary side of the multiphase converter. The second voltage sensor 9 outputs the detected boosted voltage Vc to the control device 4. Furthermore, the boosted voltage Vc detected by the second voltage sensor 9 is referred to as the "secondary-side voltage Vs". The second voltage sensor 9 outputs the detected secondary-side voltage Vs to the control device 4.

[0063] A current sensor 10 is installed on the primary side of converters 6a and 6b. It is a single sensor that detects the phase currents of the first phase current iLa and the second phase current iLb, which have the same flow direction. That is, the current sensor 10 outputs the detected phase current iL to the control device 4. The current directions of the phase currents (first phase current iLa and second phase current iLb) of the phase current iL detected by the current sensor 10 are in the same direction. In addition, the primary side of converters 6a and 6b refers to the connection point between the positive terminal of the power supply E and the emitter terminal of the switching element Q1 and the collector terminal of the switching element Q2, and the connection point between the positive terminal of the power supply E and the emitter terminal of the switching element Q3 and the collector terminal of the switching element Q4.

[0064] Inverter 3, under the control of control device 4, converts the boost voltage Vc output from multiphase converter 2 into AC voltage and supplies it to motor M.

[0065] Control device 4 controls the driving of converters 6a and 6b. Specifically, control device 4 controls the switching of a pair of switching elements Q1 and Q2 and a pair of switching elements Q3 and Q4 at different timings, so that currents with different phases (e.g., a phase difference of 180°) flow through converters 6a and 6b. That is, control device 4 generates a first PWM signal, drives and controls converter 6a based on the first PWM signal, generates a second PWM signal, drives and controls converter 6b based on the second PWM signal. The phases of the first PWM signal and the second PWM signal are exactly 180 degrees apart. Thus, multiphase converter 2 can generate a stable boost voltage Vc with less ripple.

[0066] The structure of the control device 4 in this embodiment will be described below.

[0067] The control device 4 includes a control unit 11 and a drive unit 12.

[0068] The control unit 11 generates the first PWM signal and the second PWM signal.

[0069] The driver 12 controls converters 6a and 6b based on the first PWM signal and the second PWM signal. That is, the driver 12 outputs a gate signal based on the first PWM signal to converter 6a and outputs a gate signal based on the second PWM signal to converter 6b. For example, the driver 12 is a gate drive circuit.

[0070] The following uses Figure 2 The structure of the control unit 11 in this embodiment will be explained. Figure 2 This is a schematic structural diagram of the control unit 11 in this embodiment.

[0071] The control unit 11 includes a feedback control unit 20 and a PWM (Pulse Width Modulation) control unit 50.

[0072] Feedback control unit 20 generates a voltage command value VL', which is used to make the boost voltage Vc of multiphase converter 2 follow the target voltage Vth.

[0073] The PWM control unit 50 generates a first PWM signal and a second PWM signal based on the voltage command value VL' output from the feedback control unit 20. Here, the first PWM signal and the second PWM signal are signals with a phase difference of 180 degrees. The PWM control unit 50 generates one or more carrier waves (triangular waves) and generates the first PWM signal and the second PWM signal by comparing the carrier wave with the voltage command value VL'. For example, the PWM control unit 50 generates a first carrier wave and a second carrier wave with a phase difference of 180 degrees relative to the first carrier wave. Moreover, the PWM control unit 50 can also generate the first PWM signal by comparing the first carrier wave with the voltage command value VL', and generate the second PWM signal by comparing the second carrier wave with the voltage command value VL'.

[0074] Next, the feedback control unit 20 of this embodiment will be described.

[0075] The feedback control unit 20 includes a boost ratio calculation unit 21, a voltage control unit 22, and a current control unit 23.

[0076] The boost ratio calculation unit 21 calculates the boost ratio P of the multiphase converter 2.

[0077] For example, the boost ratio calculation unit 21 acquires the primary-side voltage Vp detected by the first voltage sensor 8, the secondary-side voltage Vs detected by the second voltage sensor 9, and the phase current iL detected by the current sensor 10. A combined resistance rz is pre-stored in the boost ratio calculation unit 21. The combined resistance rz is the combined resistance of the resistive component rL in the reactor L within the multiphase converter 2 and the resistive component rsw of the switching element when the phase current iL flows within the multiphase converter 2. Reactors L1 and L2 each have the same resistive component rL.

[0078] For example, the boost ratio calculation unit 21 calculates the boost ratio P based on the primary side voltage Vp, the secondary side voltage Vs, the phase current iL, and the combined resistor rz. Specifically, the boost ratio calculation unit 21 calculates the boost ratio P by substituting the primary side voltage Vp, the secondary side voltage Vs, the phase current iL, and the combined resistor rz into the following equation (1).

[0079] The boost ratio P = (Vs - iL × rz) / Vp…(1)

[0080] The boost ratio calculation unit 21 outputs the calculated boost ratio P to the voltage control unit 22.

[0081] The voltage control unit 22 calculates the current command value iL' to bring the voltage deviation ΔVs close to zero by performing feedback control based on PI control or PID control on the deviation between the secondary side voltage Vs and the preset target voltage Vth.

[0082] The current control unit 23 performs feedback control based on PI or PID control on the deviation between the current command value iL' calculated by the voltage control unit 22 and the phase current iL, i.e., the current deviation ΔIL, to calculate the voltage command value VL' to make the current deviation ΔIL approach zero. The current control unit 23 outputs the calculated voltage command value VL' to the PWM control unit 50.

[0083] The following uses Figure 3 The general structure of the voltage control unit 22 in this embodiment will be explained. Figure 3 This is a schematic structural diagram of the voltage control unit 22 in this embodiment.

[0084] like Figure 3 As shown, the voltage control unit 22 includes a storage unit 30, an acquisition unit 3, and an arithmetic unit 32.

[0085] The storage unit 30 stores a proportional gain diagram that represents the correspondence between the boost ratio P and the proportional gain Kp, and an integral gain diagram that represents the correspondence between the boost ratio P and the integral gain Kg. Figure 4 These are examples of proportional gain plots and integral gain plots. Figure 4 In the example shown, the proportional gain map and the integral gain map are stored as a single map in the storage unit 30, but this is not a limitation. That is, the proportional gain map and the integral gain map can be stored as separate maps in the storage unit 30.

[0086] The proportional gain plot can be determined experimentally or theoretically, allowing the proportional gain Kp to be determined based on the boost ratio P. For example, the proportional gain plot can also be a table showing each boost ratio P and the proportional gain Kp associated with each boost ratio P. However, it is not limited to this structure; the proportional gain plot can be any information showing the correspondence between the boost ratio P and the proportional gain Kp, and is not limited to the table mentioned above; it can also be a mathematical expression.

[0087] The integral gain plot can be determined experimentally or theoretically, allowing the integral gain Kg to be determined based on the boost ratio P. For example, the integral gain plot can also be a table showing each boost ratio P and the integral gain Kg associated with that boost ratio P. However, it is not limited to this structure; the integral gain plot can be any information showing the correspondence between the boost ratio P and the integral gain Kg, and is not limited to the table mentioned above; it can also be a mathematical expression.

[0088] The acquisition unit 31 acquires the boost ratio P calculated by the boost ratio calculation unit 21. Then, referring to the proportional gain diagram, the acquisition unit 31 acquires the proportional gain Kp corresponding to the boost ratio P calculated by the boost ratio calculation unit 21 from the proportional gain diagram. Then, the acquisition unit 31 outputs the proportional gain Kp acquired from the proportional gain diagram to the proportional gain multiplication unit 41.

[0089] Furthermore, the acquisition unit 31 refers to the integral gain diagram and obtains the integral gain Kg corresponding to the boost ratio P calculated by the boost ratio calculation unit 21. Then, the acquisition unit 31 outputs the integral gain Kg obtained from the integral gain diagram to the integral gain multiplication unit 42.

[0090] The arithmetic unit 32 includes: a subtractor 40, a proportional gain multiplier 41, an integral gain multiplier 42, an integrator 43, and an adder 44.

[0091] Subtractor 40 calculates the voltage deviation ΔVs by subtracting the secondary voltage Vs from the target voltage Vth.

[0092] The proportional gain multiplier 41 multiplies the voltage deviation ΔVs by the proportional gain Kp output from the acquisition unit 31 and outputs it to the adder 44.

[0093] The integral gain multiplier 42 multiplies the voltage deviation ΔVs by the integral gain Kg output from the acquisition unit 31 and outputs it to the integrator 43.

[0094] Integrator 43 calculates the integral value by integrating the output from the integral gain multiplication unit 42, and outputs the integral value to adder 44. Additionally, Figure 3 The s shown is the operator of the Laplace transform, where s means differential and 1 / s means integral.

[0095] Adder 44 calculates the voltage command value Vz' by adding the output from proportional gain multiplier 41 and the integral value from integrator 43.

[0096] Next, use Figure 5 The device model 100 of the multiphase converter 2 is described using a mathematical model. The device model 100 of the multiphase converter 2 is a model that approximates two device models with different boost ratios (e.g., a device model with a boost ratio of "2" and a device model with a boost ratio lower than "2") and represents them with a single mathematical model.

[0097] Block 101 is a block obtained by modeling the switching elements Q1-Q4, and multiplying the duty cycle D by the secondary side voltage Vs, which is equivalent to the boost voltage.

[0098] The output of the second block 102 is the voltage generated in the reactor L through which the phase current iL flows, namely the reactor voltage VL. That is, the second block 102 models the formula for obtaining the reactor voltage VL by subtracting the primary side voltage Vp from the output Va of the first block 101.

[0099] Block 3, 103, is a model of the magnetically coupled reactors L1 and L2. r2 is the equivalent series resistance. L is the self-inductance of reactors L1 and L2, and M is the mutual inductance.

[0100] Block 4 104 outputs the current (hereinafter referred to as "secondary current") from multiphase converter 2 by multiplying the phase current iL output from block 3 103 by the duty cycle D.

[0101] Block 5 (105) represents the secondary-side capacitor 7. The charging and discharging phenomenon of the secondary-side capacitor 7 is modeled based on the difference between the secondary-side current ic output from block 4 (104) and the load current is flowing through the load (motor M) connected to the multiphase converter 2. Block 5 (105) takes the secondary-side current ic and the load current is as inputs and outputs the secondary-side voltage Vs.

[0102] Next, the operation flow of the control device 4 in this embodiment will be explained.

[0103] Control device 4 generates a voltage command value VL' for making the boost voltage Vc of multiphase converter 2 follow the target voltage Vth via PI control. Then, control device 4 calculates the duty cycle D for controlling multiphase converter 2 based on this voltage command value VL' and outputs a drive signal (gate signal) for duty cycle D to multiphase converter 2. At this time, control device 4 sets the control gain for PI control to a variable value instead of a fixed value. Specifically, control device 4 calculates the boost ratio P of multiphase converter 2 and changes the control gain based on this boost ratio P. For example, if the boost ratio P exceeds a predetermined boost ratio, the feedback control unit 20 sets the control gain to a predetermined fixed value; if the boost ratio P is below the predetermined boost ratio, the control gain is changed to a value higher than the fixed value. In this way, the feedback control unit 20 performs control such that the control gain in the feedback control differs when the boost ratio P exceeds the predetermined boost ratio and when the boost ratio P is below the predetermined boost ratio. Therefore, the control device 4 can prevent the boost voltage of the multiphase converter 2 from oscillating, thereby improving the controllability of the multiphase converter 2. The control gain modified based on the boost ratio P can be a proportional gain, an integral gain, or both. That is, the control gain modified based on the boost ratio P is at least one of the proportional gain and the integral gain.

[0104] Figure 6A as well as Figure 6B This is a timing diagram of the switches in a 2-phase multiphase converter 2. Figure 6A This indicates a boost ratio P exceeding "2". Figure 6B This indicates a boost ratio P of 2 or less. For example... Figure 6A As shown, when the boost ratio P exceeds "2", the periods during which the switching element Q2 in the lower arm is in the on state and the periods during which the switching element Q4 is in the on state do not overlap. On the other hand, as... Figure 6BAs shown, when the boost ratio P is 2 or less, there is an overlap between the period during which the switching element Q2 in the lower arm is in the conducting state and the period during which the switching element Q4 is in the conducting state. This overlap is one of the main causes of oscillation in the boost voltage Vc. Therefore, as an example, in the 2-phase multiphase converter 2, the feedback control unit 20 suppresses the oscillation of the boost voltage Vc by changing the control gain to a higher value when the boost ratio P is 2 or less. Specifically, in the 2-phase multiphase converter 2, the feedback control unit 20 sets the control gain to a first gain when the boost ratio P exceeds 2, and sets the control gain to a second gain, which is higher than the first gain, when the boost ratio P is 2 or less. In addition, the feedback control unit 20 can continuously change the control gain between the first gain and the second gain, or it can do so in stages.

[0105] The above description, with reference to the accompanying drawings, details one embodiment of the present invention. However, the specific structure is not limited to this embodiment and may include design changes that do not depart from the spirit of the present invention.

[0106] For example, the following variations relative to the above embodiments may also be used. Furthermore, in the following description, the differences from the above embodiments will be mainly explained; other aspects will be assumed to be the same as the above embodiments, and repeated descriptions will be omitted.

[0107] (Modified Example)

[0108] In this embodiment, the control unit 11 can also detect the bias current iLab between the first phase current iLa and the second phase current iLb based on the phase current iL detected by the current sensor 10. Hereinafter, using... Figure 7 This section describes the method for detecting the bias flow in the iLab of this modified example. Figure 7 This is a graph showing an example of the waveform of the phase current iL detected by the current sensor 10, and it is a curve with time on the horizontal axis and the total phase current on the vertical axis. For example... Figure 7 As shown, the waveform of the phase current iL detected by the current sensor 10 has approximately two points of change, A and B. These points of change A and B are the points where the phase current iL changes from increasing to decreasing.

[0109] For example, change point A represents the timing (time t1) when switch element Q2 switches from the on state to the off state. Therefore, the phase current iL at change point A becomes the maximum value representing the first phase current iLa. On the other hand, change point B represents the timing (time t2) when switch element Q4 switches from the on state to the off state. Therefore, the phase current iL at change point B becomes the maximum value representing the second phase current iLb. Furthermore, reactors L1 and L2 have the characteristic that when the current flowing through their respective phases increases, the self-inductance decreases, resulting in a larger pulsating current in the phase with the larger current. Therefore, in the waveform of the total phase current, a deviation occurs at the maximum value of the total phase current at change points A and B, depending on the bias current. Here, in this modified example, similar to the above embodiment, since the phase difference between the switching elements Q1, Q2 and Q3, Q4 is 180°, change points A and B alternate every 180° phase.

[0110] Therefore, the control unit 11 detects the bias current iLab based on the value of the phase current iL detected by the current sensor 10 when it changes from increasing to decreasing (hereinafter referred to as the "change point phase current"). That is, the control unit 11 detects the difference between the phase current iL at change point A (i.e., change point phase current IA) and the phase current iL at change point B (i.e., change point phase current IB) as the bias current iLab from the phase current iL detected by the current sensor 10.

[0111] Furthermore, there are no particular limitations on the methods for obtaining the phase current IA and phase current IB at the changing point in the control unit 11. For example, they can be obtained by the following methods (a) and (b).

[0112] (a) The control unit 11 acquires the phase currents IA and IB at the point of change by acquiring the phase current iL detected by the current sensor 10 when the phase current iL changes from increasing to decreasing within a specified period.

[0113] (b) The control unit 11 acquires the phase current iL output from the current sensor 10 when each switching element Q2 and Q4 switches from the on state to the off state, and uses it as the phase current IA and IB at the change point.

[0114] Furthermore, the above method (b) can be achieved by synchronizing the following timings: the timing at which the control unit 11 acquires the phase current iL from the current sensor 10 (hereinafter referred to as the "acquisition timing"), and the timings at which the switching elements Q2 and Q4 are respectively disconnected.

[0115] However, if it is not possible to synchronize the timing of the acquisition by the control unit 11 with the timing of disconnecting the switching elements Q2 and Q4 respectively, the following method can be used instead. That is, by providing a delay unit in the control device 4 that delays the output from the current sensor 10 by a predetermined time, the changing point phase current IA and the changing point phase current IB can be acquired using the method described above (b). The output of the current sensor 10 delayed by the delay unit is a different output from the phase current iL used in the feedback control unit 20. For example, the output of the current sensor 10 can be branched into two, with one output used for bias current detection and the other output used for the feedback control unit 20.

[0116] Here, the situation where the acquisition timing of the control unit 11 cannot be synchronized with the timing of disconnecting the switching elements Q2 and Q4 respectively, is, for example, when the acquisition timing of the control unit 11 is not the timing of disconnecting the switching elements Q2 and Q4, but the timing of the peaks and troughs of the carrier wave C generated within the control device 4. Furthermore, in (b) above, even without the aforementioned delay unit, if the acquisition timing of the control unit 11 and the timing of disconnecting the switching elements Q2 and Q4 can be synchronized, the aforementioned delay unit is not a necessary structure of the control device 4.

[0117] Then, the control unit 11 corrects the voltage command value VL' to make the detected bias current iLab disappear. For example, the control unit 11 can also perform PI control or PID control on the bias current iLab, calculate the command value V* to make the bias current iLab approach zero, and perform correction by adding or subtracting V* from the voltage command value VL'. Alternatively, the control unit 11 can calculate a coefficient corresponding to the bias current iLab and perform correction by multiplying the bias current voltage command value VL' by the coefficient. Alternatively, the control unit 11 can calculate two coefficients corresponding to the bias current iLab, multiply one of them by the voltage command value used to generate the first PWM signal, and multiply the other coefficient by the voltage command value used to generate the second PWM signal, thereby performing correction.

[0118] As explained above, the control device 4 in the above embodiment changes the control gain in the feedback control based on the boost ratio P of the multiphase converter 2, which is magnetically coupled to reactors L1 and L2.

[0119] Based on this structure, when two device models with different boost ratios are approximated as a single device model and controlled by a single control device, control gain mismatch is less likely to occur, and the boost voltage Vc oscillation of the multiphase converter 2 can be suppressed. As a result, the controllability of the multiphase converter 2 is improved. For example, using a mathematical model representing a device model with a first boost ratio and a device model with a second boost ratio lower than the first boost ratio, and controlling the multiphase converter 2 with a single control device, if the control gain is adjusted to the first boost ratio, then when the multiphase converter 2 has the second boost ratio, boost voltage Vc oscillation occurs.

[0120] In this embodiment, the control device 4 makes the control gain variable according to the boost ratio P, so the boost voltage Vc will not oscillate, and the controllability of the multiphase converter 2 is improved.

[0121] Alternatively, all or part of the control device 4 described above can be implemented using a computer. In this case, the computer may include a processor such as a CPU or GPU, and a computer-readable recording medium. Furthermore, it can be implemented by recording a program for implementing all or part of the functions of the control device 4 by the computer on the computer-readable recording medium, and then having the processor read and execute the program recorded on the recording medium. Here, "computer-readable recording medium" refers to removable media such as flexible disks, optical disks, ROMs, CD-ROMs, and storage devices such as hard disks built into a computer system. Additionally, "computer-readable recording medium" may also include media that dynamically maintains a program for a short period of time, such as communication lines used when sending programs via networks such as the Internet or telephone lines, and media that maintain a program for a certain period of time, such as volatile memory inside a computer system acting as a server or client. Furthermore, the program may be a program for implementing a portion of the functions described above, a program that can implement the functions by combining with a program already recorded in the computer system, or a program implemented using a programmable logic device such as an FPGA.

Claims

1. A multiphase converter control device, characterized in that, The multiphase converter is driven by PWM control. The multiphase converter is configured such that multiple converters connected in parallel each have a reactor. The reactors are magnetically coupled to each other and boost the input voltage to generate a boost voltage. The multiphase converter control device includes: The feedback control unit generates a voltage command value for feedback control, so that the boosted voltage becomes the target voltage; The PWM control unit generates a PWM signal based on the voltage command value output from the feedback control unit; as well as The driving unit drives the multiphase converter based on the PWM signal. The feedback control unit includes: The voltage control unit generates a current command value by applying PI control to the deviation between the boost voltage and the target voltage; The current control unit generates the voltage command value by applying PI control to the deviation between the current command value and the phase current input to the multiphase converter. as well as The boost ratio calculation unit calculates the boost ratio. The feedback control unit calculates the boost ratio of the multiphase converter and adjusts the control gain in the feedback control based on the boost ratio. The voltage control unit changes the control gain used to generate the current command value based on the boost ratio.

2. The multiphase converter control device as described in claim 1, characterized in that, The voltage control unit includes: The storage unit stores a proportional gain graph showing the correspondence between the boost ratio and the proportional gain, and an integral gain graph showing the correspondence between the boost ratio and the integral gain. The acquisition unit acquires the proportional gain corresponding to the boost ratio calculated by the boost ratio calculation unit from the proportional gain graph, and acquires the integral gain corresponding to the boost ratio from the integral gain graph; and The arithmetic unit performs the PI control using the proportional gain and integral gain acquired by the acquisition unit.

3. The multiphase converter control device as described in claim 1 or 2, characterized in that, When the boost ratio is below a predetermined boost ratio, the feedback control unit changes the control gain in the feedback control based on the boost ratio.

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