JP7677128B2 - Control device and control method for bidirectional isolated DC-DC converter - Google Patents

Description

The present invention relates to a control device for a bidirectional isolated DC-DC converter, and to the control of a method of connecting multiple DAB converters in series and parallel in a Dual Active Bridge (hereinafter referred to as DAB) converter that transmits power in both directions while isolating the input and output.

When controlling multiple DAB converters in a series-parallel connection, capacitor voltage balance control on the series-connected side is required. In some cases, current control, voltage control, and damping control may be added to suppress DC voltage oscillations and resonance when a separate reactor is connected.

In Patent Document 1, one of two DABs is connected in series and the other in parallel, and the phase difference is controlled to achieve capacitor voltage balance control on the series-connected side.

In addition, Non-Patent Documents 1 and 2 discuss capacitor voltage balance control and output voltage control in a configuration in which three or more DABs are connected in series and parallel.

In a DC-DC converter equipped with multiple DAB converters, conventional technology for determining the pulse width of the semiconductor switching elements in each converter is well known , and a conventional technology for generating gate signals for the semiconductor switching elements from a pulse width command value, a phase command value, etc. is described in, for example, Patent Document 2.

P. Zumel et al. , “Modular Dual-Active Bridge Converter Architecture,” in IEEE Transactions on Industry Applications, vol. 52, no. 3, pp. 2444-2455.2016 F. Deng. X. Znang. X. Li, T. Lei and T. Wang, “Decoupling Control Strategy for Input-Series Output-Parallel Systems Based on Dual Active Bridge dc-dc Converters, “2018 9th IEEE International Symposium on Power Electronics for Distributed Generation Systems (PEDG), 2018, PP. 1-8 B. Zhao, Q. Song, W. Liu and Y. Sun. “Overview of Dual-Active-Bridge Isolated Bidirectional DC-DC Converter for High-Frequency-Link Power-Conversion System”in IEEE Transactions on Power Electronics. vol. 29. no. 8. pp. 4091-4106. Aug. 2014 Tsuboi, Tsuji, and Yamada, "Instability of a Chopper System with an Input LC Filter and Its Countermeasures," Journal of Electrical Engineering D, Vol. 120, No. 10, pp. 1171-1181 (2000)

Patent No. 6674171 Patent No. 6785304

However, the capacitor voltage balance control discussed in Patent Document 1 cannot be applied to three or more converters. In addition, it is unclear how to change the control system if the number of converters increases.

In addition, in the non-patent documents 1 and 2, when current control is applied, if the voltage control installed in each DAB converter is simply replaced with current control, high-response current control is attempted even when the current detection value changes suddenly, so information on the current detection value needs to be communicated at high speed between the DAB converters. Even in applications where a slow response speed of current control is acceptable, high-speed communication or a large filter is required if it is necessary to reduce current ripple.

The present invention aims to solve the above problems, and its purpose is to provide a control device and control method for a bidirectional isolated DC-DC converter that reduces the communication load between multiple converters and simplifies control changes when changing the number of converters.

In order to solve the above problem, a control device for a bidirectional isolated DC-DC converter according to claim 1 comprises:
A plurality of DAB (Dual Active Bridge) converters are provided, the DAB converters including a primary single-phase inverter having an AC side connected to a primary winding of an insulating transformer, a secondary single-phase inverter having an AC side connected to a secondary winding of the insulating transformer, a primary capacitor connected between positive and negative terminals of a DC side of the primary single-phase inverter, and a secondary capacitor connected between positive and negative terminals of a DC side of the secondary single-phase inverter,
A control device for a bidirectional isolated DC-DC converter, the control device being configured by connecting the positive and negative terminals of each of the primary side single-phase inverters of the plurality of DAB converters in series between the positive and negative terminals of a first DC power source, and connecting the positive and negative terminals of each of the secondary side single-phase inverters of the plurality of DAB converters in parallel between the positive and negative terminals of a second DC power source,
The control device includes:
a current control unit that outputs a phase difference command value that causes a current flowing through the first DC power supply or the second DC power supply to follow a set current command value;
a capacitor voltage balance control unit which receives as input the voltage of the primary capacitor of the first DAB converter or an average voltage value obtained by dividing the voltage of the first DC power supply by the number of installed DAB converters and the voltage of the primary capacitor of an n-th DAB converter (n is a positive number of 2 or more), and outputs a phase command value for reducing the deviation of the voltage of the primary capacitor of the n-th DAB converter;
a gate signal generating unit that generates gate signals for the primary single-phase inverter and the secondary single-phase inverter based on command values for gate pulse widths of the primary single-phase inverter and the secondary single-phase inverter of the multiple DAB converters, which are determined from a voltage of a primary capacitor of the multiple DAB converters, a voltage of a secondary capacitor, a turn ratio between a primary winding and a secondary winding of an insulating transformer, and a power command value, and a phase command value determined by feedback control;
The gate signal generating unit generates a gate signal for a first DAB converter based on a phase difference command value and a gate pulse width command value fed back from the current control unit, and generates a gate signal for an n-th DAB converter based on a phase command value and a gate pulse width command value fed back from the capacitor voltage balance control unit.

The control device for a bidirectional isolated DC-DC converter according to claim 2 comprises:
A plurality of DAB (Dual Active Bridge) converters are provided, the DAB converters including a primary single-phase inverter having an AC side connected to a primary winding of an insulating transformer, a secondary single-phase inverter having an AC side connected to a secondary winding of the insulating transformer, a primary capacitor connected between positive and negative terminals of a DC side of the primary single-phase inverter, and a secondary capacitor connected between positive and negative terminals of a DC side of the secondary single-phase inverter,
A control device for a bidirectional isolated DC-DC converter, the control device being configured by connecting the positive and negative terminals of each of the primary side single-phase inverters of the plurality of DAB converters in series between the positive and negative terminals of a first DC power source, and connecting the positive and negative terminals of each of the secondary side single-phase inverters of the plurality of DAB converters in parallel between the positive and negative terminals of a second DC power source,
The control device includes:
a current control unit that outputs a phase difference command value that causes a current flowing through the first DC power supply or the second DC power supply to follow a set current command value;
a capacitor voltage balance control unit which receives as input the voltage of the primary capacitor of the first DAB converter or an average voltage value obtained by dividing the voltage of the first DC power supply by the number of installed DAB converters and the voltage of the primary capacitor of an n-th DAB converter (n is a positive number of 2 or more), and outputs a phase command value for reducing the deviation of the voltage of the primary capacitor of the n-th DAB converter;
a phase difference/pulse width calculation unit that calculates gate pulse width command values and phase differences of the primary single-phase inverter and the secondary single-phase inverter of the multiple DAB converters from the voltage of the primary capacitor, the voltage of the secondary capacitor, the turns ratio of the primary winding and the secondary winding of the insulating transformer of the first DAB converter, and a power command value;
a gate signal generating unit that generates gate signals for the primary side single-phase inverters and the secondary side single-phase inverters of the plurality of DAB converters based on a command value of the gate pulse width calculated by the phase difference/pulse width calculating unit and a phase difference command value obtained by subtracting a phase command value determined by feedback control from the phase difference calculated by the phase difference/pulse width calculating unit,
The gate signal generating unit generates a gate signal for a first DAB converter based on a phase difference command value that is the difference between the phase difference command value fed back from the current control unit and the phase difference calculated by the phase difference/pulse width calculation unit, and a gate pulse width command value, and generates a gate signal for an n-th DAB converter based on a phase difference command value that is the difference between the phase difference command value fed back from the capacitor voltage balance control unit and the phase difference calculated by the phase difference/pulse width calculation unit, and a gate pulse width command value.

The control device for a bidirectional isolated DC-DC converter according to claim 3 comprises:
A plurality of DAB (Dual Active Bridge) converters are provided, the DAB converters including a primary single-phase inverter having an AC side connected to a primary winding of an insulating transformer, a secondary single-phase inverter having an AC side connected to a secondary winding of the insulating transformer, a primary capacitor connected between positive and negative terminals of a DC side of the primary single-phase inverter, and a secondary capacitor connected between positive and negative terminals of a DC side of the secondary single-phase inverter,
A control device for a bidirectional isolated DC-DC converter, the control device being configured by connecting the positive and negative terminals of each of the primary side single-phase inverters of the plurality of DAB converters in series between the positive and negative terminals of a first DC power source, and connecting the positive and negative terminals of each of the secondary side single-phase inverters of the plurality of DAB converters in parallel between the positive and negative terminals of a second DC power source,
The control device includes:
a current control unit that outputs a phase difference command value that causes a current flowing through the first DC power supply or the second DC power supply to follow a set current command value;
a capacitor voltage balance control unit which receives as input the voltage of the primary capacitor of the first DAB converter or an average voltage value obtained by dividing the voltage of the first DC power supply by the number of installed DAB converters and the voltage of the primary capacitor of an n-th DAB converter (n is a positive number of 2 or more), and outputs a phase command value for reducing the deviation of the voltage of the primary capacitor of the n-th DAB converter;
a phase difference/pulse width calculation unit that calculates a gate pulse width command value and a phase difference of a primary side single-phase inverter and a secondary side single-phase inverter of a first DAB converter from an average voltage value obtained by dividing the voltage of the first DC power source by the number of installed DAB converters, the voltage of the second DC power source, a turns ratio of a primary winding and a secondary winding of an insulating transformer, and a power command value;
a gate signal generating unit that generates gate signals for the primary side single-phase inverters and the secondary side single-phase inverters of the plurality of DAB converters based on a command value of the gate pulse width calculated by the phase difference/pulse width calculating unit and a phase difference command value obtained by subtracting a phase command value determined by feedback control from the phase difference calculated by the phase difference/pulse width calculating unit,
The gate signal generating unit generates a gate signal for the first DAB converter based on a phase difference command value which is the difference between the phase difference command value of the first DAB converter fed back from the current control unit and the phase difference calculated by the phase difference/pulse width calculation unit, and the gate pulse width command value, and generates a gate signal for the nth DAB converter based on a phase difference command value which is the difference between the phase difference command value of the nth DAB converter fed back from the capacitor voltage balance control unit and the phase difference calculated by the phase difference/pulse width calculation unit, and the gate pulse width command value.

The control device for a bidirectional isolated DC-DC converter according to claim 4 includes any one of claims 1 to 3,
an inductor connected in series to the first DC power source between the first DC power source and the DC side of each of the primary single-phase inverters of the plurality of DAB converters, or connected in series to the second DC power source between the second DC power source and the DC side of each of the secondary single-phase inverters of the plurality of DAB converters;
a damping control section that performs damping control based on a current flowing through the inductor, or based on a voltage of a secondary capacitor of the first DAB converter when the inductor is connected in series to a second DC power source, and based on a voltage of the first DC power source or a voltage of a primary capacitor of the first DAB converter when the inductor is connected in series to a first DC power source, and outputs a phase difference that suppresses resonance generated by the inductor and the capacitor;
The gate signal generating unit generates a gate signal by using a phase command value that is fed back by subtracting the phase difference output by the damping control unit from the phase difference command value output by the current control unit, instead of the phase difference command value fed back from the current control unit.

A control method for a bidirectional isolated DC-DC converter according to claim 5,
The present invention is characterized by comprising a step of executing the operation of each part of the control device for a bidirectional isolated DC-DC converter according to any one of claims 1 to 4.

(1) According to the invention described in claims 1 to 5, the control is divided among multiple DAB converters, so the communication load required between each DAB converter is reduced. In addition, there are few changes required when changing the number of DAB converters installed, which makes it possible to shorten the design time.
(2) According to the invention as recited in claim 2, a phase difference and pulse width calculation section is provided, so that the responsiveness of power control is improved.
(3) According to the invention described in claim 3, the average value of the first DC power supply voltage (average input voltage value) is used to calculate the phase difference and pulse width. Therefore, the same phase difference and pulse width can be used in the control systems of all the DAB converters regardless of the unbalance rate of the capacitor voltage. This reduces disturbance to the capacitor voltage balance control section due to fluctuations in the capacitor voltage, improving responsiveness.
(4) According to the invention as recited in claim 4, a damping control section is provided, so that LC resonance caused by the inductor and the primary side capacitor or the secondary side capacitor can be suppressed.

1A shows a bidirectional isolated DC-DC converter according to the present invention, in which FIG. 1A is a configuration diagram in which an inductor is connected to the secondary side, and FIG. 1B is a configuration diagram in which an inductor is connected to the primary side. 2 is an operation waveform diagram of a pulse width control method for semiconductor switching elements of the primary side single-phase inverter and the secondary side single-phase inverter of FIG. 1 . FIG. 2 is a control block diagram according to the first embodiment of the present invention. FIG. 11 is a configuration diagram of each control system according to a second embodiment of the present invention. 13A and 13B show the configuration of each control system in a third embodiment of the present invention, where FIG. 13A is a control block diagram of a first DAB converter, and FIG. 5A and 5B show the configuration of a control unit in each embodiment of the present invention, where FIG. 5A is a configuration diagram when an inductor is connected to the secondary side, and FIG. 5B is a configuration diagram when an inductor is connected to the primary side.

The following describes an embodiment of the present invention with reference to the drawings, but the present invention is not limited to the following embodiment. Figure 1 shows the configuration of a bidirectional isolated DC-DC converter according to this embodiment.

In FIG. 1(a), which shows a configuration in which an inductor (L) is connected to the secondary side, 1 is a primary side single-phase inverter in which semiconductor switching elements S11, S21, S31, and S41 are bridge-connected, and 2 is a secondary side single-phase inverter in which semiconductor switching elements S51, S61, S71, and S81 are bridge-connected.

The common connection point of the semiconductor switching elements S11 and S21 is connected to the common connection point of the semiconductor switching elements S31 and S41 via a reactor _L1 and a primary winding ₃₁ of an insulating transformer 3.

The common connection point of the semiconductor switching elements S51 and S61 is connected to the common connection point of the semiconductor switching elements S71 and S81 via a reactor _L2 and a secondary winding ₃₂ of an insulating transformer 3.

The primary winding ₃₁ and the secondary winding ₃₂ of the isolation transformer 3 are insulated from each other, and the turns ratio thereof is _N1 : _N2 .

The semiconductor switching elements S11, S21, S31, S41, S51, S61, S71, and S81 are composed of, for example, IGBTs, and switching control is performed by a gate signal generated by a gate signal generating unit of the control device described later.

V _acp1 indicates the voltage at the common connection point of semiconductor switching elements S11 and S21, and V _acs1 indicates the voltage at the common connection point of semiconductor switching elements S51 and S61.

A primary side capacitor _Cin is connected between the positive and negative terminals on the DC side of the primary side single-phase inverter 1, and a secondary side capacitor _Cout is connected between the positive and negative terminals on the DC side of the secondary side single-phase inverter 2.

_Vin1 indicates the voltage of the primary side capacitor _Cin , and _Vout indicates the voltage of the secondary side capacitor _Cout .

The first DAB converter _10-1 is constituted by the primary side single-phase inverter 1, primary side capacitor C _in , insulating transformer 3, secondary side single-phase inverter 2, and secondary side capacitor C _out , and n DAB converters _10-1 to _{10 -n} each having the same configuration as DAB converter 10-1 are provided.

Reference numeral 11 denotes a first DC power source, between whose positive and negative terminals the positive and negative terminals of each of the primary side single-phase inverters 1 of n DAB converters 10 ₁ to 10 _n are connected in series in sequence.

Reference numeral 12 denotes a second DC power source, between whose positive and negative terminals the positive and negative terminals of the secondary single-phase inverters 2 of the n DAB converters 10 ₁ to 10 _n are connected in parallel.

An inductor 22 (L) is connected between the positive terminal of the secondary-side single-phase inverter 2 of the first DAB converter ₁₀₁ and the positive terminal of the second DC power source 12. Note that the second DC power source 12 is connected to, for example, a load (not shown).

_Vcc indicates the voltage of the first DC power supply 11, and _Vload indicates the voltage of the second DC power supply 12.

FIG. 1(b) shows a configuration in which an inductor (L) is connected to the primary side. Instead of the inductor 22 in FIG. 1(a), an inductor 21 (L) is connected between the positive terminal of the primary-side single-phase inverter 1 of the first DAB converter _10-1 and the positive terminal of the first DC power source 11. The other parts are configured in the same way as in FIG. 1(a).

In addition, the inductors 21 and 22 may not be connected.

In the following specification, each of the DAB converters (10 ₁ to 10 _n ) may be referred to as a cell. The current and voltage of each part in Figures 1(a) and 1(b) are detected by current detectors and voltage detectors, respectively, not shown.

Figure 2 shows the operating waveforms of the pulse width control method in the control device of this embodiment. Two upper arm semiconductor switching elements (S11, S31 for the primary side) or two lower arm semiconductor switching elements (S21, S41 for the primary side) of the inverters 1 and 2 in each DAB converter (10 ₁ to 10 _n ) are simultaneously turned on (pulse widths W ₁₁ and W ₂₁ shown) to set a period during which the output voltage becomes zero. A method is being considered for expanding the soft switching range using this pulse width control even when the difference between the DC voltages on the primary and secondary sides is large. The control of this embodiment can be applied to square wave, one-sided or both-sided pulse width control.

In this embodiment, the control system is divided for each DAB converter, and there are three examples shown below from the standpoint of control responsiveness and efficiency during transient operation.

The control device in the first embodiment includes the control blocks shown in Fig. 3 and Fig. 6. In Fig. 3, 30 denotes a gate signal generating unit that generates gate signals ( _S1 (n), S2(n), S3( _{n )} , S4(n), S5(n), _{S6(n), S7(n)} , S8(n)) of the primary single-phase inverter 1 and the secondary single-phase inverter 2 of each of the n DAB converters ₁₀₁ to _10n based on gate pulse width command values W1 _{(n )} , W2(n) (pulse widths _W11 , _W21 for simultaneously turning on the upper arm semiconductor switching elements or the lower arm semiconductor switching elements of each inverter, as shown in the operation waveforms in Fig. 2 _{) and a} phase command value _{θFB (n )} determined by feedback control _, which will be described later.

The pulse width command values W1 _(n) and W2 _(n) are determined by a method based on known technology from the input voltage (voltage Vin _(n) of primary capacitor _Cin ), output voltage _Vout (voltage of secondary capacitor _Cout ) of the nth cell of each DAB converter, turns ratio _N1 / _N2 of insulating transformer 3, and power command value P ^* .

The phase command value θ _FB(n) determined by the feedback control is generated by the control block in Fig. 6. Fig. 6(a) is applied to the device in Fig. 1(a) in which the inductor 22 is connected to the secondary side, and Fig. 6(b) is applied to the device in Fig. 1(b) in which the inductor 21 is connected to the primary side.

In FIG. 6( a ), reference numeral 61 denotes a current control unit that receives as input a detected value of the current (secondary side DC current) I _load flowing through the inductor 22 and a set current command value I _load ^* , and outputs a phase difference command value θ _acr by performing PI control on the difference between the inputs to cause the detected value to follow the current command value.

Reference numeral 62 denotes a damping control section that receives the voltage V _out of the secondary side capacitor C _out of the first DAB converter 10 ₁ as an input and outputs a phase difference θ _dump1 that suppresses resonance generated by the inductor ( 22 ) and the secondary side capacitor C _out .

Incidentally, the current (secondary side DC current) I _load flowing through the inductor 22 may be used as the input to the damping control section 62 .

The damping control unit 62 and the damping control unit 66 described below use, for example, the damping circuit shown in Figure 2 of Non-Patent Document 4.

Reference numeral 63 denotes a subtractor that subtracts the output (phase difference θ _dump1 ) of the damping control unit 62 from the output (phase difference command value θ _acr ) of the current control unit 61 to output a phase command value θ _FB1 for the first cell.

In addition, if there is no inductor 22 and there is no risk of resonance, or if resonance is tolerable, the damping control unit 62 may be omitted.

Reference numeral 64 denotes a capacitor voltage balance control unit that receives as input the voltage _Vin1 of the primary capacitor _Cin of the first cell DAB converter ₁₀₁ and the voltage Vin _(n) of the primary capacitor _Cin of the nth cell DAB converter _10n , amplifies the difference between the two using a controller, and outputs a phase command value θFB _(n) (=phase difference θbal _(n) ) that reduces the deviation of the capacitor voltage of the nth cell.

In addition, instead of the voltage _Vin1 of the primary side capacitor _Cin of the first cell, an average voltage value ( _Vcc / _Ncell ) obtained by dividing the voltage _Vcc of the first DC power source 11 by the number of cells (the number of installed DAB converters) may be input.

In FIG. 6(b), reference numeral 65 denotes a current control unit that receives as input the detected value of the current (primary side DC current) _Iin flowing through the inductor 21 and a set current command value _Iin ^* , and outputs a phase difference command value _θacr by performing PI control on the difference between the inputs to cause the detected value to follow the current command value.

Reference numeral 66 denotes a damping control section which receives the voltage _Vin1 of the primary side capacitor _Cin of the first DAB converter ₁₀₁ and outputs a phase difference _θdump1 for suppressing resonance generated by the inductor (21) and the primary side capacitor _Cin .

As an input to the damping control section 66, either or both of the current (primary side DC current) _Iin flowing through the inductor 21 and the voltage (input voltage) _Vcc of the first DC power supply 11 may be used.

Reference numeral 67 denotes a subtractor that subtracts the output (phase difference θ _dump1 ) of the damping control unit 66 from the output (phase difference command value θ _acr ) of the current control unit 65 to output a phase command value θ _FB1 for the first cell.

In addition, if there is no inductor 21 and there is no risk of resonance, or if resonance is tolerable, the damping control unit 66 may be omitted.

64 is a capacitor voltage balance control unit configured in the same manner as the capacitor voltage balance control unit 64 in FIG. 6(a).

The subtraction outputs θ _FB1 (phase command value) of the subtractors 63 and 67 and the output θ _FB(n) (phase command value) of the capacitor voltage balance control unit 64 are input to the gate signal generating unit 30 as the phase command value (θ _FB(n) ) determined by feedback control.

In controlling the first cell (DAB converter 10 ₁ ), the outputs of current control units 61 and 65 (because in this embodiment the power supply voltage is considered to be constant) which control the input power or output power, and the outputs of damping control units 62 and 66 which suppress LC resonance are applied.

That is, the gate signal generating unit 30 generates a gate signal for the first cell DAB converter 101 from the phase command value _θFB1 that is fed back by subtracting the phase difference _θdump1 output from the damping control unit 62, 66 from the phase difference command value θacr output from the current control unit 61 _{or 65} in a subtractor 63 or 67, and the gate pulse width command values W1 _(n) , W2 _(n) .

In the control of the second cell and thereafter (DAB converter ₁₀₂ and thereafter), the balance control of the capacitor voltage of each cell is applied. That is, the gate signal generating unit 30 generates a gate signal for the DAB converter 10n of the nth cell based on the phase command value θFB _(n) fed back from the capacitor voltage balance control unit ₆₄ and the gate pulse width command values W1 _(n) and W2 _(n) .

By dividing the control among the cells as described above, the only communication required between cells to achieve the desired control is the input voltage value and the detected capacitor voltage value. Because only the first cell performs current control, high-speed communication of current detection value information between each cell is not required. Also, when the input is capacitive, the input voltage value does not change rapidly, reducing the communication load between cells.

In addition, the present invention can be applied regardless of the number of installed cells, and there are few changes to the control when changing the number of cells, making it possible to shorten the design time. Furthermore, the present invention is not limited to parallel side power control, but can also be applied to series side power control.

As described above, according to the first embodiment, the signals communicated between cells are input/output voltages and capacitor voltages that do not fluctuate significantly, so the communication load can be reduced. Therefore, the control system can be constructed using optical cables or wireless communication, which is difficult to apply when the communication load is high, and wiring can be reduced.

The control device in the second embodiment includes the control blocks shown in Figs. 4 and 6. The second embodiment is characterized in that it calculates the command values for the pulse width and phase difference in advance to improve the responsiveness of the power control.

In Figure 4, reference numeral 41 denotes a phase difference/ _pulse width calculation unit that calculates pulse _width command values _{W1 (n)} , W2(n) (pulse widths W11, ^W21 for simultaneously turning _ON the upper arm semiconductor switching elements or _lower arm semiconductor switching elements of each inverter, as shown by the operating waveforms in Figure _{2 )} and phase difference θFF _(n) from the input voltage (voltage of primary capacitor Cin) Vin _{( n)} , output voltage (voltage of secondary capacitor Cout) Vout, power command value P* and turns ratio N1/N2 of the insulating transformer 3 of multiple DAB converters _{101 to 10n} .

The phase difference/pulse width calculation unit 41 performs calculations using known techniques from the input voltage ( voltage Vin _(n) of the _primary capacitor Cin), the output voltage ( voltage Vout of the secondary capacitor Cout) _of the _nth cell of each DAB converter, the turns ratio N1/N2 of the insulating transformer 3 _, and _the power command value P ^* .

Reference numeral 42 denotes a subtractor that subtracts a phase command value θ _{FB (n)} determined by the feedback control of each control unit in FIG. 6 from the phase difference θ FF(n) calculated by the phase difference/pulse width calculation unit 41, and outputs a phase difference command value θ _(n) .

In this manner, in the subtractor 42, the difference between the phase command value θ _FB of the feedback control and the phase difference θ _FF calculated by the phase difference/pulse width calculation unit 41 is calculated, whereby the error between the transmission power and the power command value P ^* due to deviations in the circuit constants, detection errors, etc. is corrected.

Reference numeral 43 denotes a gate signal generation unit that generates gate signals (S1 _(n) , S2(n), S3 _(n) , S4(n), S5(n), S6(n), S7 _{(n), S8(n)) for} the primary side single-phase inverter 1 and the secondary side single-phase inverter 2 of each of the DAB converters _10-1 to 10- _n , based on the pulse widths W1 _{(n )} , W2 _{(n) calculated} by the phase _difference/ pulse _width calculation unit 41 and the phase command value θ _(n ) output from the subtractor 42.

The subtraction output θ _FB1 (phase command value) of the subtractors 63 and 67 in FIG. 6 and the output θ _FB(n) (phase command value) of the capacitor voltage balance control unit 64 are input to the subtractor 42 in FIG. 4 as a phase command value (θ _FB(n) ) determined by feedback control, and a deviation from the phase difference θ _FF(n) is calculated.

In the control of the first cell (DAB converter 10 ₁ ), the outputs of the current control sections 61 and 65 and the outputs of the damping control sections 62 and 66 are applied in the same manner as in the first embodiment.

That is, the gate signal generating unit 43 generates a gate signal for the first cell DAB converter 101 using the phase command value θ _{( n) obtained by subtractor 42 calculating the deviation between the phase command value θFB1} to which the output of the subtractor 63 or ₆₇ is fed back and the phase difference θFF( _n) calculated by the phase difference/pulse width calculating unit 41, and the gate pulse width command values _W1(n) , W2 _(n) .

In the control of the second cell and thereafter (DAB converter ₁₀₂ and thereafter), the balance control of the capacitor voltage of each cell is applied. That is, the gate signal generating unit 43 generates a gate signal for the DAB converter 10n of the nth cell by the phase command value θ _(n) obtained by subtracting the deviation between the phase command value _θFB(n) fed back from the capacitor voltage balance control unit 64 and the phase difference θFF _(n ) calculated by the phase difference and pulse width calculating unit ₄₁ , and the gate pulse width command values W1 _(n) and W2 _(n) .

As described above, the responsiveness of power control can be improved by calculating the pulse width and phase difference in a feedforward manner in the phase difference/pulse width calculation unit 41. However, due to cell losses, dead time, gate driver delays, etc., the pulse width and phase difference are not output according to the calculated values, and deviations occur in the power from the command value. Therefore, feedback control is performed only on the difference between the detected value and the command value (current control units 61, 65). Therefore, there is no need to speed up the response of feedback control.

Furthermore, since the aforementioned deviation occurs only under transient conditions, its impact on the accuracy of power control is low.

As described above, according to the second embodiment, the phase difference and pulse width calculation unit is added, so that the responsiveness of the power control can be improved. Furthermore, since the pulse width of each cell is changed according to the imbalance rate of the capacitor voltage (according to the output of the capacitor voltage balance control unit 64), the power conversion efficiency in the transient state of the capacitor voltage balance control can be improved.

The control device in the third embodiment includes the control blocks in Fig. 5 and Fig. 6. In the third embodiment, some of the input parameters of the phase difference/pulse width calculation unit 41 in the second embodiment are changed to calculate the pulse width command and phase difference θ _FF for the first cell, and the pulse width command and phase difference θ _FF for the first cell are used to control the DAB converters of the second cell and onward.

In Figure 5 (a) showing the control block of the first cell, 51 is a phase difference/pulse width calculation unit that receives as input the average voltage value _Vcc / _Ncell (average input voltage value) obtained by dividing the voltage _Vcc of the first DC power supply 11 by the number of installed DAB converters _Ncell , the voltage _Vload of the second DC power supply 12, the power command value P ^* , and the turns ratio _N1 / _N2 of the primary winding and secondary winding of the insulating transformer 3, and calculates the pulse widths _W11 , _W21 and phase difference _θFF1 of the inverters 1 and ₂ of the first cell DAB converter 101.

A subtractor 52 subtracts a phase command value θ _FB1 determined by feedback control of each control unit in FIG. 6 from the phase difference θ _FF1 calculated by the phase difference/pulse width calculation unit 51, and outputs a phase difference command value θ ₁ .

Reference numeral 53 denotes a gate signal generating unit that generates gate signals (S11, S21, _S31 , _S41 , S51, S61, S71, S81) for the primary side single-phase inverter ₁ and the secondary side single-phase inverter 2 of the first cell DAB converter ₁₀₁ based on the pulse widths W11, W21 calculated by the phase difference/pulse width calculating unit 51 and the phase command value θ1 output from the subtractor 52.

In FIG. 5(b) showing the control block of the DAB converter for the second cell onward, reference numeral 54 denotes a subtractor that subtracts the phase command value θ FB(n) for the second cell onward determined by the feedback control of each control unit in FIG. 6 from the phase difference θ _FF1 of the first cell calculated by the phase difference/pulse width calculation unit 51 in FIG. 5 _(a) to output the phase difference command value θ _(n) for the second cell onward.

The gate signal generating unit 53 in FIG. 5(b) generates gate signals (S1(n), S2(n), S3(n), _S4 (n), _S5(n) , S6 _{(n), S7(n} ), S8 ₍ n)) for the primary side single-phase inverter 1 and the secondary side single-phase inverter 2 of the DAB converters 10 ₂ to 10 _n of the second cell and thereafter, based on the pulse widths W 11 and _W 21 of the first cell _{calculated by the} phase difference _/ pulse width calculating _unit 51 and the phase _{difference command value θ} (n ₎ which is the output of the subtractor ₅₄ .

During the transient operation of the capacitor voltage balance control unit 64 in FIG. 6, there is a deviation in the capacitor voltage, so the pulse width and phase difference change. Since the change in pulse width becomes a disturbance to the capacitor voltage balance control and damping control, if the capacitor voltage fluctuates significantly, the responsiveness of the capacitor voltage balance control and damping control deteriorates.

To solve this problem, in this embodiment 3, the input voltage average value ( _Vcc / _Ncell ) is used to calculate the phase difference and pulse width, and the same phase difference and pulse width ( _θFF1 , _W11 , _W21 ) are used in the control systems of all cells regardless of the capacitor voltage imbalance rate. This reduces disturbances to the capacitor voltage balance control unit 64 and damping control units 62 and 66 caused by fluctuations in the capacitor voltage, improving responsiveness.

In this way, the responsiveness of the voltage balance control is improved, allowing the input capacitor capacity to be reduced, making it possible to miniaturize the device.

REFERENCE SIGNS LIST 1...Primary side single-phase inverter 2...Secondary side single-phase inverter 3...Insulating transformer 10 ₁ to 10 _n ...DAB converter 11...First DC power supply 12...Second DC power supply 21, 22...Inductor 30, 43, 53...Gate signal generator 41, 51...Phase difference and pulse width calculator 42, 52, 54, 63, 67...Subtractor 61, 65...Current controller 62, 66...Damping controller 64...Capacitor voltage balance controller

Claims (5)

A plurality of DAB (Dual Active Bridge) converters are provided, the DAB converters including a primary single-phase inverter having an AC side connected to a primary winding of an insulating transformer, a secondary single-phase inverter having an AC side connected to a secondary winding of the insulating transformer, a primary capacitor connected between positive and negative terminals of a DC side of the primary single-phase inverter, and a secondary capacitor connected between positive and negative terminals of a DC side of the secondary single-phase inverter,
A control device for a bidirectional isolated DC-DC converter, the control device being configured by connecting the positive and negative terminals of each of the primary side single-phase inverters of the plurality of DAB converters in series between the positive and negative terminals of a first DC power source, and connecting the positive and negative terminals of each of the secondary side single-phase inverters of the plurality of DAB converters in parallel between the positive and negative terminals of a second DC power source,
The control device includes:
a current control unit that outputs a phase difference command value of a phase difference between a voltage of a primary side single-phase inverter and a voltage of a secondary side single-phase inverter, the phase difference command value being used to make a current flowing through the first DC power source or the second DC power source follow a set current command value;
a capacitor voltage balance control unit which receives as input the voltage of the primary capacitor of the first DAB converter or an average voltage value obtained by dividing the voltage of the first DC power source by the number of installed DAB converters, and the voltage of the primary capacitor of an n-th DAB converter (n is a positive number of 2 or more), and outputs a phase command value for reducing the deviation of the voltage of the primary capacitor of the n-th DAB converter;
a gate signal generating unit that generates gate signals for the primary single-phase inverter and the secondary single-phase inverter based on a command value for gate pulse widths of the primary single-phase inverter and the secondary single-phase inverter of the multiple DAB converters, the command values being determined from a voltage of a primary capacitor of the multiple DAB converters, a voltage of a secondary capacitor, a turns ratio between a primary winding and a secondary winding of an insulating transformer, and a power command value, and a phase command value calculated from a phase difference command value determined by feedback control based on a difference between the current command value and a current detection value in the current control unit,
The control device for a bidirectional isolated DC-DC converter, characterized in that the gate signal generating unit generates a gate signal for a first DAB converter based on a phase difference command value and a gate pulse width command value fed back from the current control unit, and generates a gate signal for an n-th DAB converter based on a phase command value and a gate pulse width command value fed back from the capacitor voltage balance control unit. A plurality of DAB (Dual Active Bridge) converters are provided, the DAB converters including a primary single-phase inverter having an AC side connected to a primary winding of an insulating transformer, a secondary single-phase inverter having an AC side connected to a secondary winding of the insulating transformer, a primary capacitor connected between positive and negative terminals of a DC side of the primary single-phase inverter, and a secondary capacitor connected between positive and negative terminals of a DC side of the secondary single-phase inverter,
A control device for a bidirectional isolated DC-DC converter, the control device being configured by connecting the positive and negative terminals of each of the primary side single-phase inverters of the plurality of DAB converters in series between the positive and negative terminals of a first DC power source, and connecting the positive and negative terminals of each of the secondary side single-phase inverters of the plurality of DAB converters in parallel between the positive and negative terminals of a second DC power source,
The control device includes:
a current control unit that outputs a phase difference command value of a phase difference between a voltage of a primary side single-phase inverter and a voltage of a secondary side single-phase inverter, the phase difference command value being used to make a current flowing through the first DC power source or the second DC power source follow a set current command value;
a capacitor voltage balance control unit which receives as input the voltage of the primary capacitor of the first DAB converter or an average voltage value obtained by dividing the voltage of the first DC power source by the number of installed DAB converters, and the voltage of the primary capacitor of an n-th DAB converter (n is a positive number of 2 or more), and outputs a phase command value for reducing the deviation of the voltage of the primary capacitor of the n-th DAB converter;
a phase difference/pulse width calculation unit that calculates gate pulse width command values and phase differences of the primary single-phase inverter and the secondary single-phase inverter of the multiple DAB converters from the voltage of the primary capacitor of the first DAB converter, the voltage of the secondary capacitor, the turns ratio of the primary winding and the secondary winding of the insulating transformer, and a power command value;
a gate signal generating unit that generates gate signals for a primary side single-phase inverter and a secondary side single-phase inverter of the plurality of DAB converters based on a command value of a gate pulse width calculated by the phase difference/pulse width calculating unit and a phase difference command value obtained by subtracting a phase command value determined by feedback control based on a difference between the current command value and a current detection value in the current control unit from the phase difference calculated by the phase difference/pulse width calculating unit,
The control device for a bidirectional isolated DC-DC converter, characterized in that the gate signal generating unit generates a gate signal for a first DAB converter based on a phase difference command value that is the difference between the phase difference command value fed back from the current control unit and the phase difference calculated by the phase difference/pulse width calculation unit, and a command value for the gate pulse width, and generates a gate signal for an n-th DAB converter based on a phase difference command value that is the difference between the phase difference command value fed back from the capacitor voltage balance control unit and the phase difference calculated by the phase difference/pulse width calculation unit, and a command value for the gate pulse width. A plurality of DAB (Dual Active Bridge) converters are provided, the DAB converters including a primary single-phase inverter having an AC side connected to a primary winding of an insulating transformer, a secondary single-phase inverter having an AC side connected to a secondary winding of the insulating transformer, a primary capacitor connected between positive and negative terminals of a DC side of the primary single-phase inverter, and a secondary capacitor connected between positive and negative terminals of a DC side of the secondary single-phase inverter,
A control device for a bidirectional isolated DC-DC converter, the control device being configured by connecting the positive and negative terminals of each of the primary side single-phase inverters of the plurality of DAB converters in series between the positive and negative terminals of a first DC power source, and connecting the positive and negative terminals of each of the secondary side single-phase inverters of the plurality of DAB converters in parallel between the positive and negative terminals of a second DC power source,
The control device includes:
a current control unit that outputs a phase difference command value of a phase difference between a voltage of a primary side single-phase inverter and a voltage of a secondary side single-phase inverter, the phase difference command value being used to make a current flowing through the first DC power source or the second DC power source follow a set current command value;
a capacitor voltage balance control unit which receives as input the voltage of the primary capacitor of the first DAB converter or an average voltage value obtained by dividing the voltage of the first DC power source by the number of installed DAB converters, and the voltage of the primary capacitor of an n-th DAB converter (n is a positive number of 2 or more), and outputs a phase command value for reducing the deviation of the voltage of the primary capacitor of the n-th DAB converter;
a phase difference/pulse width calculation unit that calculates a gate pulse width command value and a phase difference of a primary side single-phase inverter and a secondary side single-phase inverter of a first DAB converter from an average voltage value obtained by dividing the voltage of the first DC power source by the number of installed DAB converters, the voltage of the second DC power source, a turns ratio of a primary winding and a secondary winding of an insulating transformer, and a power command value;
a gate signal generating unit that generates gate signals for a primary side single-phase inverter and a secondary side single-phase inverter of the plurality of DAB converters based on a command value of a gate pulse width calculated by the phase difference/pulse width calculating unit and a phase difference command value obtained by subtracting a phase command value determined by feedback control based on a difference between the current command value and a current detection value in the current control unit from the phase difference calculated by the phase difference/pulse width calculating unit,
The gate signal generating unit generates a gate signal for the first DAB converter based on a phase difference command value, which is the difference between the phase difference command value of the first DAB converter fed back from the current control unit and the phase difference calculated by the phase difference/pulse width calculation unit, and a gate pulse width command value, and generates a gate signal for the nth DAB converter based on a phase difference command value, which is the difference between the phase difference command value of the nth DAB converter fed back from the capacitor voltage balance control unit and the phase difference calculated by the phase difference/pulse width calculation unit, and a gate pulse width command value. an inductor connected in series to the first DC power source between the first DC power source and the DC side of each of the primary single-phase inverters of the plurality of DAB converters, or connected in series to the second DC power source between the second DC power source and the DC side of each of the secondary single-phase inverters of the plurality of DAB converters;
a damping control section that performs damping control based on a current flowing through the inductor, or based on a voltage of a secondary capacitor of the first DAB converter when the inductor is connected in series to a second DC power source, and based on a voltage of the first DC power source or a voltage of a primary capacitor of the first DAB converter when the inductor is connected in series to a first DC power source, and outputs a phase difference that suppresses resonance generated by the inductor and the capacitor;
4. The control device for a bidirectional isolated DC-DC converter according to claim 1, wherein the gate signal generation unit generates a gate signal by using a phase command value that is fed back by subtracting the phase difference output by the damping control unit from the phase difference command value output by the current control unit, instead of the phase difference command value fed back from the current control unit. A method for controlling a bidirectional isolated DC-DC converter, comprising a step of executing the operation of each part of a control device for a bidirectional isolated DC-DC converter according to any one of claims 1 to 4.

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