Control device for power conversion circuit

Abstract

The present invention provides a control device for a power conversion circuit, which can maintain a detection value of a second voltage at a target value of the second voltage without relying on feedback control when a first voltage fluctuates. The control device (30) of the power conversion circuit changes a control value X through feedback control so that the detection value V2sen of the second voltage approaches the target value V2ref of the second voltage, corrects the control value X based on the detection value V1sen of the first voltage, and performs feedforward correction on the change of the control value caused by the change of the first voltage when the control value is not corrected, thereby calculating a control value D for control, and performing on-off control of a switching element based on the control value D.

Description

Technical Field

[0001] The present application relates to a control device for a power conversion circuit. Background Art

[0002] Patent Document 1 discloses a control device for a power conversion circuit that controls a power conversion circuit including a switching element and a reactor and performs power conversion between a first terminal and a second terminal.

[0003] In the technology of Patent Document 1, a calculation value X is changed by feedback control based on the deviation between the second terminal voltage, i.e., the detected value of the second voltage, and the target value of the second voltage, and damping control based on the reactor current, and the calculation value X is corrected based on the detected value Vin of the first voltage to calculate the duty cycle Duty of the switching element.

[0004] Prior art literature

[0005] Patent Literature

[0006] Patent Document 1: Japanese Patent No. 6153144 Summary of the Invention

[0007] Technical problem to be solved by the invention

[0008] However, when the first voltage, which is the first terminal voltage, fluctuates for some reason, the duty cycle of the switching element needs to be changed in order to maintain the detected value of the second voltage at the target value. However, when the duty cycle is changed by feedback control, a follow-up delay is generated due to the feedback control, causing the detected value of the second voltage to deviate from the target value of the second voltage. When the second voltage exceeds the protection threshold, the on-off control of the switching element is stopped by the overvoltage protection function provided in the control device or the power conversion circuit, and the power conversion of the power conversion circuit may be stopped. In order to reduce the rise of the second voltage when the first voltage fluctuates, it is necessary to lower the target value of the second voltage or increase the capacitance of the smoothing capacitor on the second terminal side, which will lead to a decrease in output voltage and an increase in the size of the device.

[0009] In the technology of Patent Document 1, the calculated value X calculated through feedback control is corrected based on the detected value Vin of the first voltage, so that the gain of the transfer function of the duty cycle Duty with respect to the calculated value X does not change due to changes in the resonant frequency. However, the technology of Patent Document 1 does not take into account fluctuations in the first voltage. In the embodiments of the present application, as described using equations (4) and (5), when the first voltage fluctuates, the calculated value X must be changed through feedback control in order to ensure that the detected value of the second voltage follows the target value of the second voltage. Therefore, the technology of Patent Document 1 cannot solve the above-mentioned problem.

[0010] Therefore, an object of the present application is to provide a control device for a power conversion circuit that can maintain a detected value of a second voltage at a target value of the second voltage without relying on feedback control when a first voltage fluctuates.

[0011] Technical means for solving technical problems

[0012] The control device of a power conversion circuit involved in the present application controls the power conversion circuit, wherein the power conversion circuit includes a single or multiple switching elements connected in parallel with a second terminal, and a reactor connected at one end to a first terminal and at the other end to the switching element, and performs power conversion between the first terminal and the second terminal. The control device of the power conversion circuit includes:

[0013] a second voltage detection unit configured to detect a second voltage as a voltage of the second terminal;

[0014] a first voltage detection unit configured to detect a first voltage as a voltage of the first terminal;

[0015] a control value calculation unit configured to change a control value through feedback control so that the detected value of the second voltage approaches a target value of the second voltage;

[0016] a control value correction unit that corrects the control value based on the detected value of the first voltage so as to perform feedforward correction on a change in the control value caused by a change in the first voltage when the control value correction is not performed, thereby calculating a control value for control; and

[0017] A switch control unit performs on-off control of the switching element based on the control value.

[0018] Effects of the Invention

[0019] According to the control device for a power conversion circuit of the present application, when the first voltage fluctuates, the control value for control is changed based on the detected value of the first voltage, thereby performing feedforward correction for changes in the control value caused by the change in the first voltage. Therefore, when the detected value of the first voltage fluctuates, the detected value of the second voltage can be maintained at the target value of the second voltage, even without changing the control value through feedback control. Consequently, when the first voltage fluctuates, the following delay caused by feedback control can be eliminated, and the deviation between the second voltage and the target value of the second voltage can be reduced. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 This is a schematic configuration diagram of a power conversion circuit and a control device according to the first embodiment.

[0021] Figure 2 This is a block diagram of the control device according to the first embodiment.

[0022] Figure 3 This is a hardware configuration diagram of the control device according to the first embodiment.

[0023] Figure 4 This is a timing chart for explaining on-off control of a switching element based on a duty ratio according to the first embodiment.

[0024] Figure 5 This is a timing chart for explaining the control operation during the first voltage fluctuation according to the comparative example.

[0025] Figure 6 This is a timing chart for explaining the control operation during the first voltage fluctuation according to the first embodiment.

[0026] Figure 7 1 is a Bode plot of the transfer function of the second voltage with respect to the control value at two different boosting ratios according to the first embodiment.

[0027] Figure 8 4 is a Bode plot of the transfer function of the second voltage with respect to the control value at two different boosting ratios according to the first embodiment.

[0028] Figure 9 3 is a Bode plot of transfer functions of different PI controllers according to the first embodiment.

[0029] Figure 10 This is a diagram for explaining the setting of the proportional gain and the integral gain according to the boost ratio according to the first embodiment.

[0030] Figure 11 3 is a Bode plot of the open-loop transfer function of the second voltage with respect to the voltage deviation at two different boosting ratios according to the first embodiment.

[0031] Figure 12 This is a schematic configuration diagram of a power conversion circuit and a control device according to the second embodiment.

[0032] Figure 13 This is a block diagram of a control device according to the second embodiment.

[0033] Figure 14 4 is a Bode plot of the transfer function of the second voltage with respect to the control value under damping control according to the second embodiment.

[0034] Figure 15 This is a Bode plot of the open-loop transfer function of the second voltage with respect to the voltage deviation according to the second embodiment.

[0035] Figure 16 This is a diagram for explaining the setting of the proportional gain, the integral gain, and the attenuation gain according to the on / off control frequency according to the second embodiment. DETAILED DESCRIPTION

[0036] 1. Implementation Method 1

[0037] A power conversion circuit 10 and a control device 30 for the power conversion circuit (hereinafter simply referred to as the control device 30 ) according to the first embodiment will be described with reference to the drawings. Figure 1 1 is a schematic configuration diagram of the power conversion circuit 10 and the control device 30 according to the present embodiment.

[0038] 1-1. Power Conversion Circuit 10

[0039] The power conversion circuit 10 includes a switching element and a reactor 15, and performs power conversion between a first terminal 11 and a second terminal 12. A DC power supply or a load is connected to the first terminal 11, and a DC power supply or a load is connected to the second terminal 12. In the present embodiment, a DC power supply 21 is connected to the first terminal 11, and a load 22 is connected to the second terminal 12. A DC power supply whose output voltage varies depending on its internal state is used for the DC power supply 21. For example, a power storage device is used for the DC power supply 21, and the output voltage, which becomes the first voltage V1, varies depending on the charge state of the power storage device. Alternatively, a voltage variable device such as a DC-DC converter is also provided in the DC power supply 21, and the output voltage varies depending on the operating state of the voltage variable device. The load 22 is configured as an inverter or a motor.

[0040] In this embodiment, the power conversion circuit 10 is a DC-DC converter that converts DC power and a boost carrier circuit that boosts a DC voltage from a first terminal 11 to a second terminal 12 .

[0041] The power conversion circuit 10 includes a single or multiple switching elements connected in parallel with the second terminal 12, and a reactor 15 having one end connected to the high-potential side of the first terminal 11 and the other end connected to the switching element. In this embodiment, two switching elements 13a and 13b connected in series are connected in parallel with the second terminal 12. That is, the high-potential switching element 13a and the low-potential switching element 13b are connected in series between the high-potential side and the low-potential side of the second terminal 12. The other end of the reactor 15 is connected to the connection point of the two switching elements 13a and 13b. Alternatively, a diode may be used instead of the high-potential switching element 13a.

[0042] The switching element may be an IGBT (Insulated Gate Bipolar Transistor) with a diode connected in reverse parallel, or a MOSFET (Metal Oxide Semiconductor Field Effect Transistor) that functions as a diode connected in reverse parallel. Alternatively, various switching elements may be used, such as a SiC (Silicon Carbide) MOSFET, a GaN (Gallium Nitride) FET, or a GaN-HEMT (High Electron Mobility Transistor).

[0043] Gate drive signals Gt1 and Gt2 output from the control device 30 are input to gate terminals of the switching elements 13 a and 13 b , respectively. The switching elements 13 a and 13 b are turned on and off according to the gate drive signals Gt1 and Gt2 .

[0044] The high potential side of the first terminal 11 is connected to the connection point of the two switching elements 13a and 13b via the reactor 15. The low potential side of the first terminal 11 is connected to the low potential side of the second terminal 12.

[0045] The circuit includes a second-terminal-side smoothing capacitor 16 connected in parallel with the second terminal 12. The second-terminal-side smoothing capacitor 16 is provided closer to the second terminal 12 than the two switching elements 13a and 13b. The circuit includes a first-terminal-side smoothing capacitor 17 connected in parallel with the first terminal 11. The first-terminal-side smoothing capacitor 17 is provided closer to the first terminal 11 than the reactor 15.

[0046] The second voltage detection circuit 18 is provided to detect a second voltage V2 as the voltage of the second terminal 12. The second voltage detection circuit 18 detects the voltage across the smoothing capacitor 16 on the second terminal side. The output signal of the second voltage detection circuit 18 is input to the control device 30.

[0047] The first voltage detection circuit 19 is provided to detect a first voltage V1 at the first terminal 11. The first voltage detection circuit 19 detects the voltage across the smoothing capacitor 17 on the first terminal side. The output signal of the first voltage detection circuit 19 is input to the control device 30.

[0048] 1-2. Control device 30

[0049] The control device 30 controls the power conversion circuit 10. Figure 2 As shown in FIG. 3 , the control device 30 includes a first voltage detection unit 31, a second voltage detection unit 32, a control value calculation unit 33, a control gain setting unit 34, a control value correction unit 35, and a switch control unit 36. Each function of the control device 30 is realized by a processing circuit provided by the control device 30. Specifically, the control device 30 is as follows. Figure 3 As shown, the processing circuit includes an operation processing device 90 (computer) such as a CPU (Central Processing Unit), a storage device 91 connected to the operation processing device 90 via a signal line such as a bus, an input circuit 92 for inputting external signals to the operation processing device 90, and an output circuit 93 for outputting signals from the operation processing device 90 to the outside.

[0050] The processing unit 90 may include an ASIC (Application Specific Integrated Circuit), an IC (Integrated Circuit), a DSP (Digital Signal Processor), an FPGA (Field Programmable Gate Array), various logic circuits, and various signal processing circuits. Furthermore, the processing unit 90 may include multiple processing units of the same or different types to share the execution of various processes.

[0051] The storage device 91 includes volatile and nonvolatile storage devices such as RAM (Random Access Memory), ROM (Read Only Memory), and EEPROM (Electrically Erasable Programmable ROM). The input circuit 92 is connected to various sensors and switches such as the first voltage detection circuit 19 and the second voltage detection circuit 18, and includes an A / D converter that inputs the output signals of these sensors and switches to the processing unit 90. The output circuit 93 is connected to electrical loads such as gate drive circuits that turn switching elements on and off, and includes a drive circuit that outputs control signals from the processing unit 90 to these electrical loads.

[0052] Furthermore, the functions of the control units 31 to 36 and the like included in the control device 30 are realized by the arithmetic processing unit 90 executing software (programs) stored in a storage device 91, such as a ROM, in cooperation with other hardware of the control device 30, such as the storage device 91, the input circuit 92, and the output circuit 93. Furthermore, setting data such as control gains used by the control units 31 to 36 and the like is stored as part of the software (programs) in the storage device 91, such as the ROM. The functions of the control device 30 will be described in detail below.

[0053] 1-2-1. Voltage detection unit

[0054] The second voltage detection unit 32 detects the second voltage V2 as the voltage of the second terminal 12. In the present embodiment, the second voltage detection unit 32 detects the second voltage V2 based on the output signal of the second voltage detection circuit 18.

[0055] The first voltage detection unit 31 detects a first voltage V1 that is a voltage at the first terminal 11. In the present embodiment, the first voltage detection unit 31 detects the first voltage V1 based on an output signal of the first voltage detection circuit 19.

[0056] 1-2-2. Control Value Calculation Unit 33

[0057] The control value calculation unit 33 changes the control value X through feedback control so that the detected value V2sen of the second voltage approaches the target value V2ref of the second voltage. Based on the deviation ΔV2 between the detected value V2sen of the second voltage and the target value V2ref of the second voltage, the control value calculation unit 33 performs at least proportional control and integral control as feedback control. In this embodiment, proportional control and integral control, or PI control, are performed. In addition to proportional control and integral control, differential control, or PID control, may also be performed. The target value V2ref of the second voltage may be calculated within the control device 30 or transmitted from outside the control device 30.

[0058] Specifically, as shown in the following equation, the control value calculation unit 33 subtracts the detected value V2sen of the second voltage from the target value V2ref of the second voltage to calculate a deviation ΔV2, multiplies the deviation ΔV2 by the proportional gain Kp to calculate a proportional control value Xp, integrates the value obtained by multiplying the deviation ΔV2 by the integral gain Ki to calculate an integral control value Xi, and adds the proportional control value Xp and the integral control value Xi to calculate the control value X. The control gain setting unit 34 for setting the proportional gain Kp and the integral gain Ki will be described later.

[0059] [Mathematical formula 1]

[0060] ΔV2=V2 ref -V2 sen

[0061] X p =K p ×ΔV2

[0062]

[0063] X=X p +X i …(1)

[0064] In equation (1), s is the Laplace operator, and 1 / s represents the integral operation of a continuous system. In this embodiment, the control value calculation unit 33 is configured to perform the operation for each operation cycle ΔT. The calculation of the integral control value Xi in equation (1) (3) is actually performed using the following discretized equation. Here, (m) represents the calculated value for the current operation cycle, and (m-1) represents the calculated value for the previous operation cycle.

[0065] [Mathematical formula 2]

[0066] X i (m) = X i (m-1)+K i ×ΔV2×ΔT…(2)

[0067] 1-2-3. Switch Control Unit 36

[0068] The switch control unit 36 ​​controls the switching elements on and off based on the control value D calculated by the control value correction unit 35, described later. Based on the control value D, the switch control unit 36 ​​generates gate drive signals Gt1 and Gt2 for the high- and low-potential switching elements 13a and 13b, respectively, through PWM (Pulse Width Modulation) control. In this embodiment, the control value D serves as the on-duty ratio for the low-potential switching element 13b and the off-duty ratio for the high-potential switching element 13a. When the low-potential switching element 13b is on, the high-potential switching element 13a is off. A dead time is provided between the on-period of the high-potential switching element 13a and the on-period of the low-potential switching element 13b, during which both switching elements 13a and 13b are off. This ensures that both switching elements 13a and 13b are on simultaneously, preventing a short circuit between the high-potential and low-potential sides.

[0069] For example, Figure 4 As shown, the switch control unit 36 ​​compares the control value D with the carrier Vcr to generate gate drive signals Gt1 and Gt2 for each switching element. The carrier Vcr is a triangular wave that oscillates between 0 and 1 with an on-off control period (PWM control period). When the control value D is greater than the carrier Vcr, the switch control unit 36 ​​sets the low-potential gate drive signal Gt2 to a high level. When the control value D is less than the carrier Vcr, the switch control unit 36 ​​sets the low-potential gate drive signal Gt2 to a low level. Furthermore, when the duty ratio D+ΔDt, obtained by adding the value ΔDt corresponding to the dead zone to the control value D, is greater than the carrier Vcr, the switch control unit 36 ​​sets the high-potential gate drive signal Gt1 to a low level. When the added duty ratio D+ΔDt is less than the carrier Vcr, the switch control unit 36 ​​sets the high-potential gate drive signal Gt1 to a high level. The carrier Vcr can use a sawtooth wave or an inverse sawtooth wave.

[0070] 1-2-4. Control Value Correction Unit 35

[0071] <Technical Problems in the Case Where the Control Value Correction Unit 35 Is Not Provided>

[0072] First, the correction principle of the control value X will be described. Ideally, the following equation holds true between the control value D for controlling the on-duty ratio of the switching element 13 b on the low potential side and the first and second voltages V1 and V2 .

[0073] [Mathematical formula 3]

[0074]

[0075] As can be seen from equation (3), the control value D (the on-duty ratio on the low-potential side) changes according to the second voltage V2 and also changes according to the first voltage V1. Therefore, if the first voltage V1 fluctuates for some reason, the control value D (the on-duty ratio on the low-potential side) must be changed. In the comparative example where the control value correction unit 35, described later, does not perform feedforward correction on the control value X, the control value calculation unit 33 must use feedback control to change the control value X. Therefore, when the first voltage V1 fluctuates, a follow-up delay occurs due to feedback control, causing the second voltage V2 to deviate from the target value V2ref of the second voltage.

[0076] Will use Figure 5 The control operation for a comparative example without the control value correction unit 35 will be described. By time T01, the first voltage V1 is stabilized at a constant value, the second voltage detection value V2sen follows the second voltage target value V2ref, which is set to a constant value, and the control value X and the control value D for directly setting the control value X are stabilized at constant values.

[0077] At time T01, for some reason, the first voltage V1 suddenly increases. As a result, the second voltage detection value V2sen rises above the second voltage target value V2ref. Feedback control gradually decreases the control value X so that the second voltage detection value V2sen approaches the second voltage target value V2ref. However, between time T01 and time T02, due to a follow-up delay in feedback control, the second voltage detection value V2sen deviates from the second voltage target value V2ref.

[0078] At this time, if the detected value V2sen of the second voltage exceeds the protection threshold, the on / off control of the switching element is stopped by the overvoltage protection function provided in the control device 30 or the power conversion circuit 10, and the boost operation of the power conversion circuit 10 may be stopped. In the comparative example, in order to reduce the rise of the second voltage V2 when the first voltage V1 fluctuates, it is necessary to lower the target value V2ref of the second voltage or increase the capacitance of the smoothing capacitor 16 on the second terminal side, which will lead to a decrease in the output voltage and an increase in the size of the device. Therefore, it is necessary to suppress the fluctuation of the second voltage V2 when the first voltage V1 fluctuates without causing a decrease in the output voltage and an increase in the size of the device.

[0079] In Patent Document 1, the control value X calculated by feedback control is obtained from the equation (2) and Figure 2 After correction, the control value D for control is calculated.

[0080] [Formula 4]

[0081] In the case of Patent Document 1

[0082]

[0083] Substituting equation (4) into equation (3) and rearranging the control value X yields equation (5). As can be seen from equation (5), in the technology of Patent Document 1, the control value D is calculated by correcting the control value X using equation (4). However, the control value X fluctuates due to fluctuations in the first voltage V1, and feedback control is required to change the control value X. Therefore, even in the technology of Patent Document 1, a follow-up delay due to feedback control occurs when the first voltage V1 fluctuates, causing the second voltage V2 to deviate from the target value V2ref of the second voltage.

[0084] [Formula 5]

[0085] In the case of Patent Document 1

[0086]

[0087] <Configuration of Control Value Correction Unit 35>

[0088] Therefore, the control value corrector 35 corrects the control value X based on the first voltage detection value V1sen so as to perform feedforward correction on the change in the control value caused by the change in the first voltage V1 when the control value X is not corrected, thereby calculating the control value D for control.

[0089] With this configuration, when the first voltage V1 fluctuates, the control value D changes based on the first voltage detection value V1sen, thereby performing feedforward correction of changes in the control value caused by changes in the first voltage V1. Therefore, when the first voltage detection value V1sen fluctuates, there is no need to use feedback control to change the control value X. Consequently, when the first voltage V1 fluctuates, tracking delays caused by feedback control can be avoided, and the deviation between the second voltage V2 and the second voltage target value V2ref can be reduced.

[0090] In the present embodiment, the control value correction unit 35 calculates the control value D using the following equation.

[0091] [Formula 6]

[0092]

[0093] Substituting equation (6) into equation (3) and rearranging the control value X yields equation (7). Equation (7) shows that the control value X is independent of fluctuations in the first voltage V1 and is the second voltage V2. Consequently, the control value X remains unchanged by fluctuations in the first voltage V1, eliminating any follow-up delay caused by feedback control and ensuring that the second voltage V2 does not deviate from the target second voltage value V2ref.

[0094] [ 数 Mathematical formula 7]

[0095]

[0096] use Figure 6 The control operation of this embodiment in which the control value correction unit 35 is provided will be described. Figure 5 The same situation is as in the case of , until time T11, the detection value V1sen of the first voltage is stabilized at a constant value, the detection value V2sen of the second voltage follows the target value V2ref of the second voltage set to a constant value, and the control value X and the control value D are stabilized at a constant value.

[0097] At time T11, for some reason, the first voltage detection value V1sen increases abruptly. After time T11, the control value X is corrected based on the increased first voltage detection value V1sen, so that the change in the control value caused by the change in the first voltage V1 is feedforward corrected to calculate the control value D, which then decreases abruptly. As a result, even without changing the control value X through feedback control, the control value D can be feedforward-varied based on the first voltage detection value V1sen, preventing the second voltage detection value V2sen from deviating from the second voltage target value V2ref. As a result, as in the comparative example, a decrease in output voltage and an increase in device size can be suppressed without lowering the second voltage target value V2ref or increasing the capacitance of the smoothing capacitor 16 on the second terminal side to account for fluctuations in the first voltage V1. However, in reality, due to the influence of the detection error of the first voltage caused by the sensor error, the detection delay of the change of the first voltage caused by the operation cycle, etc., errors will occur in the feedforward correction, and the second voltage V2 will change slightly from the target value V2ref of the second voltage, so feedback control is required.

[0098] 1-2-5. Control Gain Setting Unit 34

[0099] The control gain setting unit 34 sets the proportional gain Kp and the integral gain Ki. While these values ​​can be fixed, in this embodiment, they are variable based on the voltage step-up ratio Rbst, which is the ratio of the second voltage to the first voltage, to improve feedback responsiveness and stability. This will be described in detail below.

[0100] <Transfer function of controlled object>

[0101] The transfer function of the second voltage V2 with respect to the control value D (duty ratio D) can be expressed as follows.

[0102] [Formula 8]

[0103]

[0104]

[0105] Here, ILave is the average value of the oscillating reactor current IL, L is the inductance of the reactor 15 , ω0 is the resonance angular frequency, and C2 is the electrostatic capacitance of the smoothing capacitor 16 on the second terminal side.

[0106] As shown in equation (3), when the first voltage V1 and the second voltage V2 change, the control value D (duty cycle D) changes, and thus the resonant angular frequency ω0 changes, as shown in the second equation of equation (8). Specifically, the control value D (duty cycle D) changes according to the ratio of the second voltage V2 to the first voltage V1, that is, the step-up ratio Rbst (V2 / V1), and the resonant angular frequency ω0 changes.

[0107] Figure 7 The following figure shows the Bode plot of the transfer function of Equation (8) for two different boost ratios Rbst. For each boost ratio Rbst, the gain increases at the resonant angular frequency ω0, and the phase is delayed by 180 degrees. When the boost ratio Rbst is relatively large, the control value D (duty cycle D) increases, the resonant angular frequency ω0 decreases, and the gain below the resonant angular frequency ω0 increases. When the boost ratio Rbst is relatively small, the control value D (duty cycle D) decreases, the resonant angular frequency ω0 increases, and the gain below the resonant angular frequency ω0 decreases.

[0108] In this embodiment, the control value X and the control value D (duty ratio D) have the relationship shown in equation (6). Therefore, the transfer function of the second voltage V2 with respect to the control value X can be expressed as shown in the following equation.

[0109] [Formula 9]

[0110]

[0111]

[0112] Figure 8 The Bode plots of the transfer function of equation (9) for two different boost ratios Rbst are shown. Even if the boost ratio Rbst is different, it can be seen from equation (9) that at an angular frequency lower than the resonant angular frequency ω0, V2(s) / X(s) becomes 1 and the gain [db] becomes 0. On the other hand, if the boost ratio Rbst is different, then the same as equations (8) and Figure 7 Similarly, the resonant angular frequency ω0 changes. Specifically, when the boost ratio Rbst is relatively large, the control value D (duty cycle D) increases, lowering the resonant angular frequency ω0. However, the gain below the resonant angular frequency ω0 remains unchanged. When the boost ratio Rbst is relatively small, the control value D (duty cycle D) decreases, raising the resonant angular frequency ω0. However, the gain below the resonant angular frequency ω0 remains unchanged.

[0113] <Control gain setting>

[0114] like Figure 8 As shown in Figure 1, as the boost ratio Rbst increases, the resonant angular frequency ω0 decreases, and the frequency of a 180-degree phase reversal decreases. Therefore, regardless of the boost ratio Rbst, using the same control gain may not ensure equivalent closed-loop stability and responsiveness despite changes in the boost ratio Rbst.

[0115] If the inflection point angular frequency ωip of the PI controller is set lower than the resonant angular frequency ω0, the stability of the closed loop can be ensured.

[0116] like Figure 9 As shown in the Bode plot of the PI controller, the PI controller's inflection point angular frequency ωip is the angular frequency at the boundary between the integral element and the proportional element, and is expressed as ωip = Ki / Kp. As shown in the following equation, the integral gain Ki and the proportional gain Kp can be adjusted so that the inflection point angular frequency ωip is lower than the resonant angular frequency ω0. The resonant angular frequency ω0 varies inversely with the voltage step-up ratio Rbst (= V2 / V1). Thus, the control gain setting unit 34 can set the proportional gain Kp and the integral gain Ki based on the voltage step-up ratio Rbst so that the PI controller's inflection point angular frequency ωip, obtained by dividing the integral gain Ki by the proportional gain Kp, is lower than the resonant angular frequency ω0, which varies inversely with the voltage step-up ratio Rbst.

[0117] [Formula 10]

[0118]

[0119] To maintain closed-loop stability, the inflection point angular frequency ωip (=Ki / Kp) can be reduced as the boost ratio Rbst increases and the resonant angular frequency ω0 decreases. As shown in the following equation (10) regarding the proportional gain Kp, if the integral gain Ki is not changed, the proportional gain Kp can be increased as the boost ratio Rbst increases and the resonant angular frequency ω0 decreases.

[0120] [Mathematical formula 11]

[0121]

[0122] Therefore, if Figure 10 As shown, the control gain setting unit 34 is configured to increase the proportional gain Kp as the ratio of the second voltage V2 to the first voltage V1, that is, the voltage step-up ratio Rbst (= V2 / V1 ), increases, while setting the integral gain Ki to a constant value without increasing it.

[0123] According to this structure, the proportional gain Kp increases as the boost ratio Rbst increases, thereby maintaining the stability of the closed loop by reducing the inflection point angular frequency ωip of the PI controller according to the reduced resonant angular frequency ω0, and the integral gain Ki does not change. Therefore, regardless of changes in the boost ratio Rbst, the responsiveness of the closed loop can be maintained.

[0124] For example, the control gain setting unit 34 uses equation (10) to calculate the resonance angular frequency ω0 based on the boost ratio Rbst, and calculates the proportional gain Kp by multiplying the value obtained by dividing the integral gain Ki by the resonance angular frequency ω0 by a coefficient α greater than 1 as shown in the following equation.

[0125] [Mathematical formula 12]

[0126]

[0127] Alternatively, the control gain setting unit 34 may refer to proportional gain setting map data that predefines the relationship between the boost ratio Rbst and the proportional gain Kp, and calculate the proportional gain Kp corresponding to the current boost ratio Rbst.

[0128] In addition, if Figure 9 、 Figure 11As shown in the following equation, if the integral gain Ki is set to be less than the inflection point angular frequency ωip (= Ki / Kp), the angular frequency at which the gain of the PI controller's transfer function crosses to 0 (the gain crossover angular frequency) can be set as the integral gain Ki. The gain above the gain crossover angular frequency becomes less than 0. By placing the inflection point angular frequency ωip and the resonant angular frequency ω0 above the gain crossover angular frequency, the gain of the transfer function of the second voltage V2 at the resonant angular frequency ω0 can be attenuated, ensuring stability. Therefore, the proportional gain Kp can be set to less than 1.

[0129] [Mathematical formula 13]

[0130]

[0131] Figure 11 As shown in Figure 10 The following figure shows a Bode plot of the open-loop transfer function from deviation ΔV2 to the second voltage detection value V2sen at two different boost ratios Rbst, with the control gain set. Based on the decrease in resonant angular frequency ω0 due to the increase in boost ratio Rbst, the PI controller's breakpoint angular frequency ωip can be appropriately lowered, the gain of the open-loop transfer function at the resonant angular frequency ω0 can be appropriately lowered to below 0, and phase delay can be suppressed.

[0132] By the correction of the control value correction unit 35, the gain of the transfer function of the second voltage V2 with respect to the control value X becomes 0 at a resonance angular frequency ω0 or less (see Figure 8 ), in addition, since the integral gain Ki does not change, Figure 11 As shown, the characteristics of the open-loop transfer function below the inflection point angular frequency ωip, including the gain crossover angular frequency (=Ki), remain constant, and the closed-loop responsiveness remains constant. This ensures equivalent closed-loop stability and responsiveness regardless of changes in the boost ratio Rbst and resonant angular frequency ω0.

[0133] exist Figure 10 In the entire boost ratio Rbst, the proportional gain Kp increases as the boost ratio Rbst increases, but it is also possible to make the proportional gain Kp a constant value and not change in a part of the boost ratio Rbst interval regardless of the increase in the boost ratio Rbst.

[0134] Furthermore, if it is desired to vary the closed-loop responsiveness based on the boost ratio Rbst, the control gain setting unit 34 may also vary the integral gain Ki based on the boost ratio Rbst. For example, the control gain setting unit 34 may increase the proportional gain Kp and the integral gain Ki as the boost ratio Rbst increases. Increasing the integral gain Ki increases the gain of the open-loop transfer function in the low-frequency band as the boost ratio Rbst increases, and the closed-loop responsiveness can be improved as the boost ratio Rbst increases. In this case, the proportional gain Kp and the integral gain Ki may be set based on the boost ratio Rbst so that the PI controller's breakpoint angular frequency ωip, obtained by dividing the integral gain Ki by the proportional gain Kp, is less than the resonant angular frequency ω0. In this case, one or both of the proportional gain Kp and the integral gain Ki may be constant and unchanged regardless of increases in the boost ratio Rbst within a certain range of the boost ratio Rbst. The interval in which the boost ratio Rbst is set to a constant value may be different between the proportional gain Kp and the integral gain Ki.

[0135] Furthermore, as long as the required closed-loop stability and responsiveness can be ensured, the proportional gain Kp can be a constant value regardless of changes in the boost ratio Rbst. Furthermore, in addition to proportional and integral control, other control methods such as differential control can be employed, or only integral control can be employed without proportional control.

[0136] <Calculation of Boost Ratio>

[0137] As shown in the following equation, control gain setting unit 34 calculates boost ratio Rbst by dividing second voltage detection value V2sen or second voltage target value V2ref by first voltage detection value V1sen. Second voltage detection value V2sen and first voltage detection value V1sen may use detection values ​​detected in the previous calculation cycle, or smoothed values ​​such as low-pass filtered values ​​or moving average values ​​of the detection values.

[0138] [Mathematical formula 14]

[0139]

[0140] <Control gain update cycle>

[0141] Control gain setting unit 34 updates the control gain at n / 2 times the on / off control period (PWM control period) (n is an integer greater than or equal to 1), in synchronization with the on / off control period. A smaller n allows for more responsive control depending on the state of boost ratio Rbst. A larger n reduces the risk of oscillation and external disturbances, ensuring robustness.

[0142] 2. Implementation Method 2

[0143] Next, the power conversion circuit 10 and control device 30 according to Embodiment 2 will be described with reference to the accompanying drawings. Descriptions of the same components as those in Embodiment 1 will be omitted. The basic configuration and processing of the power conversion circuit 10 and control device 30 according to this embodiment are the same as those in Embodiment 1.

[0144] <Damping Control>

[0145] Figure 12 1 is a schematic structural diagram of the power conversion circuit 10 and the control device 30 according to this embodiment. Figure 13 This is a block diagram of the control device 30 according to this embodiment. In this embodiment, the power conversion circuit 10 includes a reactor current sensor 14 that detects the reactor current IL flowing through the reactor 15. The reactor current sensor 14 is provided on the wire connecting the high-potential side of the first terminal 11 to the reactor 15. The reactor current sensor 14 is a Hall element, a shunt resistor, or the like. The output signal of the reactor current sensor 14 is input to the control device 30.

[0146] The control device 30 includes a reactor current detection unit 37 that detects a reactor current IL flowing through the reactor 15 . The reactor current detection unit 37 detects the reactor current IL based on an output signal of the reactor current sensor 14 .

[0147] In this embodiment, the control value calculation unit 33 performs damping control in addition to proportional control and integral control. As shown in equations 1 through 3 of equation (1), the control value calculation unit 33 calculates a deviation ΔV2 by subtracting the detected second voltage value V2sen from the target second voltage value V2ref. It then multiplies the deviation ΔV2 by the proportional gain Kp to calculate the proportional control value Xp. Finally, it integrates the value obtained by multiplying the deviation ΔV2 by the integral gain Ki to calculate the integral control value Xi.

[0148] As shown in the following equation, the control value calculation unit 33 calculates the attenuation control value Xdp by multiplying the attenuation gain Kdp by the detected value ILsen of the reactor current. The control value calculation unit 33 then calculates the control value X by adding the proportional control value Xp and the integral control value Xi and subtracting the attenuation control value Xdp.

[0149] [Mathematical formula 15]

[0150] X dp =K dp ×IL sen …(15)

[0151] X=Xp +X i -X dp

[0152] Alternatively, as the reactor current detection value ILsen used for damping control, the reactor current detection value ILsen detected in the previous calculation cycle or a smoothed value such as a low-pass filtered value or a moving average value of the reactor current detection value ILsen may be used.

[0153] <Control gain setting>

[0154] Figure 14 The Bode diagram of the transfer function of the second voltage V2 with respect to the control value X in the case of the present embodiment in which the damping control is performed is shown. Figure 14 , for comparison, the transfer function of the first embodiment in which damping control is not performed is also shown.

[0155] In the transfer function with damping control, the peak value of the gain at the resonance angular frequency ω0 is lower and the phase delay at the resonance angular frequency ω0 is gentler than in the case without damping control. In other words, the resonance can be attenuated by damping control.

[0156] Figure 15 , which is a Bode diagram of the open-loop transfer function from the deviation ΔV2 to the second voltage detection value V2sen when the PI control with the same control gain is performed with and without damping control. Figure 15 ] shows the Bode plot of the open-loop transfer function when the control gain is increased with damping control.

[0157] With damping control, the peak value of the gain at the resonant angular frequency ω0 is lower than without damping control. Therefore, the gain at the resonant angular frequency ω0 can be kept below 0 [dB], and the control gain can be increased while maintaining closed-loop stability. Furthermore, if the peak value of the gain at the resonant angular frequency ω0 is sufficiently low due to damping control, as in Embodiment 1, the proportional gain Kp and the integral gain Ki may be set based on the boost ratio Rbst so that the inflection point angular frequency ωip (=Ki / Kp) is less than the resonant angular frequency ω that varies with the boost ratio Rbst, rather than based on the boost ratio Rbst. Alternatively, the proportional gain Kp and the integral gain Ki may be set based on the boost ratio Rbst so that the inflection point angular frequency ωip (=Ki / Kp) is less than the resonant angular frequency ω that varies with the boost ratio Rbst.

[0158] In this embodiment, the control gain setting unit 34 sets the proportional gain Kp, the integral gain Ki and the attenuation gain Kdp as follows: Figure 16As shown, the control gain setting unit 34 increases the proportional gain Kp, integral gain Ki, and attenuation gain Kdp as the on-off control frequency (PWM control frequency) of the switching element increases. The higher the on-off control frequency, the more the phase delay caused by the control delay changes toward the high frequency side. According to the above structure, even when the phase delay caused by the control delay changes under different on-off control frequency conditions, each control gain can be made variable to set the inflection point angular frequency ωip of the PI controller, thereby improving the responsiveness of the control. In addition, it is also possible to make one or more of the proportional gain Kp, integral gain Ki, and attenuation gain Kdp constant and unchanged in a part of the on-off control frequency interval regardless of the increase in the on-off control frequency. The interval of the on-off control frequency set to a constant value can be different for the proportional gain Kp, integral gain Ki, and attenuation gain Kdp.

[0159] Alternatively, the control gain setting unit 34 may increase one or more of the proportional gain Kp, the integral gain Ki, and the attenuation gain Kdp as the on / off control frequency (PWM control frequency) increases. In this case, the proportional gain Kp, the integral gain Ki, or the attenuation gain Kdp that is not increased does not increase regardless of the increase in the on / off control frequency and is set to a constant value.

[0160] Furthermore, as control for reducing the peak value of the gain at the resonance angular frequency ω0, various controls such as current control may be performed instead of damping control.

[0161] [Other embodiments]

[0162] (1) In each of the above embodiments, the first voltage detection unit 31 detects the first voltage V1 based on the output signal of the first voltage detection circuit 19. However, the first voltage detection unit 31 may also calculate the first voltage detection value V1sen based on the second voltage detection value V2sen and the past control value Dold. For example, the following formula is used. As the past control value Dold, the control value D calculated in the previous calculation cycle, or a smoothed value such as a low-pass filtered value or a moving average value of the control value D is used.

[0163] [Mathematical formula 16]

[0164] V1 sns =V2 sns ×(1-D old )…(16)

[0165] (2) In each of the above embodiments, the power conversion circuit 10 is described as a boost carrier circuit that boosts a DC voltage from the first terminal 11 to the second terminal 12. However, the embodiments of the present application are not limited thereto. That is, if the power conversion circuit 10 is a circuit that includes a switching element and performs power conversion between the first terminal 11 and the second terminal 12, various power converters can be used. For example, the power conversion circuit 10 can be a bidirectional carrier circuit that is a combination of a boost carrier circuit that boosts a DC voltage from the first terminal 11 to the second terminal 12 and a buck carrier circuit that bucks a DC voltage from the second terminal 12 to the first terminal 11.

[0166] (3) In the above embodiments, the DC power supply 21 is connected to the first terminal 11, and the load 22 such as an inverter or a motor is connected to the second terminal 12. However, the power supply or the load only needs to be connected to the first terminal 11, and the power supply or the load only needs to be connected to the second terminal 12, and various power supplies and loads can be used.

[0167] (4) In the above embodiments, the control value calculation unit 33 uses PI control as feedback control. However, the control value calculation unit 33 may use various control methods other than PI control as feedback control to calculate the control value X. Even in this case, the control gain setting unit 34 may change the control gain based on the boost ratio Rbst so that the closed-loop stability and responsiveness can be maintained with respect to changes in the boost ratio Rbst.

[0168] Although this application describes various exemplary embodiments and examples, the various features, methods, and functions described in one or more embodiments are not limited to the application of specific embodiments and can be applied to the embodiments individually or in various combinations. Therefore, it can be considered that countless variations not illustrated are also included in the technical scope disclosed in this application specification. For example, it is set to include the case where at least one component is deformed, added, or omitted, and the case where at least one component is extracted and combined with the components of other embodiments.

[0169] Description of labels

[0170] 10 Power Conversion Circuit

[0171] 11 Terminal 1

[0172] 12 Terminal 2

[0173] 13a High potential side switching element

[0174] 13b Low potential side switching element

[0175] 14 Reactor current sensor

[0176] 15 Reactor

[0177] 18. Second voltage detection circuit

[0178] 19. First voltage detection circuit

[0179] 30. Control device for power conversion circuit

[0180] 31 First voltage detection unit

[0181] 32 Second voltage detection unit

[0182] 33 Control value calculation unit

[0183] 34 Control gain setting unit

[0184] 35 Control value correction unit

[0185] 36 Switch control unit

[0186] D Control value

[0187] Ilsen reactor current detection value

[0188] Kdp attenuation gain

[0189] Ki integral gain

[0190] Kp proportional gain

[0191] Rbst step-up ratio

[0192] V1sen Detection value of the first voltage

[0193] V2ref Target value of the second voltage

[0194] V2sen Second voltage detection value

[0195] X control value

[0196] Xdp attenuation control value

[0197] Xi integral control value

[0198] Xp proportional control value

[0199] ΔV2 deviation

[0200] ω0 resonant angular frequency.

Claims

1. A control device for a power conversion circuit, wherein the control device controls the power conversion circuit, wherein the power conversion circuit includes a single or multiple switching elements connected in parallel with a second terminal, and a reactor having one end connected to a first terminal and the other end connected to the switching element, and performs power conversion between the first terminal and the second terminal, the control device for the power conversion circuit comprising: a second voltage detection unit configured to detect a second voltage as a voltage of the second terminal; a first voltage detection unit configured to detect a first voltage as a voltage of the first terminal; a control value calculation unit configured to change a control value through feedback control so that the detected value of the second voltage approaches a target value of the second voltage; a control value correction unit that corrects the control value based on the detected value of the first voltage so as to perform feedforward correction on a change in the control value caused by a change in the first voltage when the control value correction is not performed, thereby calculating a control value for control; and a switch control unit that controls the switching element to be turned on or off based on the control value; The control value correction unit sets the control value as X, the detected value of the first voltage as V1sen, and the control value for control as D, and calculates the value by the formula D=(X-V1sen) / X, Calculating the control value for the control, The switching control unit performs on-off control of the switching element using a duty ratio corresponding to the control value.

2. The control device for a power conversion circuit according to claim 1, wherein: The first voltage detection unit calculates the first voltage detection value based on the second voltage detection value and the past control value.

3. The control device for a power conversion circuit according to claim 1 or 2, wherein: The control value calculation unit performs at least proportional control and integral control as the feedback control based on a deviation between the detected value of the second voltage and the target value of the second voltage.

4. The control device for a power conversion circuit according to claim 1 or 2, wherein: A control gain setting unit is included, wherein the control gain setting unit sets a proportional gain and an integral gain, The control value calculation unit calculates a proportional control value by multiplying the proportional gain by a deviation between the detected value of the second voltage and the target value of the second voltage, calculates an integral control value by integrating a value obtained by multiplying the integral gain by the deviation, and calculates the control value by adding at least the proportional control value and the integral control value. The control gain setting unit increases one or both of the proportional gain and the integral gain as a ratio of the second voltage to the first voltage, ie, a voltage step-up ratio, increases.

5. The control device for a power conversion circuit according to claim 1 or 2, wherein: A control gain setting unit is included, wherein the control gain setting unit sets a proportional gain and an integral gain, The control value calculation unit calculates a proportional control value by multiplying the proportional gain by a deviation between the detected value of the second voltage and the target value of the second voltage, calculates an integral control value by integrating a value obtained by multiplying the integral gain by the deviation, and calculates the control value by adding at least the proportional control value and the integral control value. The resonant angular frequency of the transfer function of the second voltage with respect to the control value changes in inverse proportion to the ratio of the second voltage to the first voltage, that is, the voltage step-up ratio. The control gain setting unit sets the proportional gain and the integral gain based on the voltage step-up ratio so that a value obtained by dividing the integral gain by the proportional gain becomes smaller than the resonant angular frequency.

6. The control device for a power conversion circuit according to claim 1 or 2, wherein: include: a reactor current detection unit configured to detect a reactor current flowing through the reactor; as well as a control gain setting unit that sets a proportional gain, an integral gain, and an attenuation gain, The control value calculation unit calculates a proportional control value by multiplying the proportional gain by the deviation between the detected value of the second voltage and the target value of the second voltage, calculates an integral control value by integrating the value obtained by multiplying the integral gain by the deviation, calculates an attenuation control value by multiplying the attenuation gain by the detected value of the reactor current, and calculates the control value by at least adding the proportional control value and the integral control value and subtracting the attenuation control value.

7. The control device for a power conversion circuit according to claim 6, wherein: The control gain setting unit increases one or more of the proportional gain, the integral gain, and the attenuation gain as the on / off control frequency of the switching element increases.

8. The control device for a power conversion circuit according to claim 1 or 2, wherein: comprising a control gain setting unit for setting a control gain used in the control value calculation unit, The control gain setting unit updates the control gain in synchronization with the on-off control period at n / 2 times the on-off control period, where n is an integer greater than or equal to 1.

9. The control device for a power conversion circuit according to claim 1 or 2, wherein: A DC power supply whose output voltage varies according to an internal state is connected to the first terminal.

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