JP7722228B2 - Control device for bidirectional isolated DC-DC converter - Google Patents

Description

The present invention relates to a control technology that suppresses the degradation of current response due to dead time in a Dual Active Bridge (DAB) converter, which transmits power bidirectionally while isolating the input and output.

In bidirectional isolated DC-DC converters, output or input current is controlled by controlling the phase difference between the output voltages of the two inverters, but there is a problem in that power conversion efficiency decreases when the input and output DC voltages change. Therefore, there are methods for improving efficiency by controlling the pulse width of each inverter's output voltage, as described in Non-Patent Document 1 and Patent Document 1.

However, dead time causes errors in the actual measured values relative to the pulse width and phase difference command values, which can lead to an issue of being unable to follow the current command value and resulting in a decrease in response. Non-patent document 3 proposes a method to solve this problem, but it requires calculations for each mode, making it extremely complicated.

Figure 1 shows the configuration of a DAB converter to which the control method of the present invention is applied. In Figure 1(a), which shows a configuration with a reactor connected to the output side, reference numeral 1 denotes a primary-side single-phase inverter in which semiconductor switching elements S1, S2, S3, and S4 are bridge-connected, and reference numeral 2 denotes a secondary-side single-phase inverter in which semiconductor switching elements S5, S6, S7, and S8 are bridge-connected.

The common connection point of semiconductor switching elements S1 and S2 is connected to the common connection point of semiconductor switching elements S3 and S4 via reactor _L1 , primary winding 3a of insulating transformer 3, and reactor _L2 .

The common connection point of semiconductor switching elements S5 and S6 is connected to the common connection point of semiconductor switching elements S7 and S8 via reactor _L3 , secondary winding 3b of insulating transformer 3, and reactor _L4 .

The semiconductor switching elements S1 to S8 are configured, for example, as IGBTs, and switching is controlled by gate signals generated by a gate signal generation unit of the control device, which will be described later.

The positive terminal of the DC side of the primary single-phase inverter 1 is connected to the primary positive terminal _P1 , the negative terminal is connected to the primary negative terminal _N1 , and a primary capacitor _Cin is connected between the positive and negative terminals. The positive terminal of the DC side of the secondary single-phase inverter 2 is connected to the secondary positive terminal _P2 via a reactor 4, and the negative terminal is connected to the secondary negative terminal _N2 . A secondary capacitor _Cout is connected between the positive and negative terminals of the DC side of the secondary single-phase inverter 2.

_Vin indicates the input DC voltage (voltage of the primary side capacitor _Cin ), _Vout indicates the output DC voltage (voltage of the secondary side capacitor _Cout ), _V1 indicates the output voltage of the primary side single-phase inverter 1, and _V2 indicates the output voltage of the secondary side single-phase inverter 2.

i _pr denotes the current between the reactor _L2 and the common connection point of the semiconductor switching elements S3 and S4, detected by the current detector 5a; i _se denotes the current between the reactor _L4 and the common connection point of the semiconductor switching elements S7 and S8, detected by the current detector 5b; and I _load denotes the load current between the reactor L4 and the secondary-side positive terminal _P2 , detected by the current detector 6.

A DC power supply (not shown) is connected between the primary positive terminal P ₁ and the primary negative terminal N ₁ , and a load (not shown) is connected between the secondary positive terminal P ₂ and the secondary negative terminal N ₂ .

In FIG. 1(b), which shows a configuration in which a reactor is connected to the primary side, instead of the reactor 4 in FIG. 1(a), a reactor 7 is connected between the primary side positive terminal _P1 and the positive terminal on the DC side of the primary side single-phase inverter 1, and the current flowing through the reactor 7 is detected by a current detector 6, with the other parts being configured in the same way as in FIG. 1(a).

Figure 2 shows the operating waveforms of the pulse width control method. Two upper arm semiconductor switching elements (S1 and S3 on the primary side, for example) or two lower arm semiconductor switching elements (S2 and S4 on the primary side, for example) of each inverter 1 and 2 are simultaneously turned ON (pulse widths _W1 and _W2 shown in the figure) to set a period during which the output voltage is zero. In the figure, θ is the phase difference.

A method is being considered for using this pulse width control to expand the soft switching range even when the difference in DC voltage between the primary and secondary sides is large. The control in this embodiment can be applied to square wave, single-sided, or double-sided pulse width control.

Figure 3 shows the general configuration of pulse width control. This configuration consists of the following two blocks:

Pulse width and phase difference calculation block 11
This block calculates the pulse widths _W1 , _W2 and the phase difference command value θ from the input DC voltage value _Vin , the output DC voltage value _Vout , and the power command value _Pref . An example of pulse width calculation is proposed in Patent Document 1.

Gate and dead time generation block 12
It receives pulse width command values _W1 , _W2 , a phase difference command value θ, and a dead time command value _Td as inputs, adds dead time, and outputs gate signals for the semiconductor switching elements S1 to S8 of the inverters 1 and 2. Non-patent document 2, for example, proposes an example of a gate generator.

In the case of a DAB converter that has an operating mode in which the magnitude relationship between the input DC voltage value _Vin and the output DC voltage value _Vout is reversed, the input DC voltage value Vin and the output DC voltage value Vout are input to the "gate and dead time generation block ₁₂ " in Figure 3 in order to determine whether to assign a gate signal based on the "pulse width _W1 of the inverter output voltage on the side with the higher DC voltage" described below to the input _{or output} .

The fundamental component model of the DAB converter used for pulse width calculation is shown in Fig. 4. In Fig. 4, the fundamental wave model of the output voltage of each inverter has voltage sources _V1 and _V2 of the fundamental wave components of a square wave or a three-level voltage including zero voltage, and a combined inductance L (I _L , V _L ) of the leakage inductance of the high-frequency transformer (insulation transformer 3) and the additional inductors (reactors L ₁ to L ₄ ).

Figure 5 shows a feather diagram of the output voltages of the inverters 1 and 2. By using the fundamental wave component of the inverter output voltage, the voltage is separated into a real axis (d-axis) _Vd component and an imaginary axis (q-axis _Vq ) component. The side with the lower DC voltage is defined as the secondary side, and the inverter output voltage _V2 on the secondary side is used as the reference.

Figure 6 shows an example of how a pulse width control block is constructed. The example in Figure 6 is divided into a voltage magnitude relationship derivation block (voltage detection and comparison unit) in Figure 6(a) and a phase difference and pulse width command derivation block in Figure 6(b).

In FIG. 6(a), reference numeral 21 denotes a divider that divides the input DC voltage value _Vin by 1/N (N is the ratio of the number of turns of the primary winding 3a and the secondary winding 3b of the insulating transformer 3 in FIG. 1).

The output of the divider 21 is connected to the input terminal 22a of the selection switch 22, the input terminal 23b of the selection switch 23, and one input terminal of the voltage comparator 24.

The output DC voltage _Vout is led to an input terminal 22b of the selection switch 22, an input terminal 23a of the selection switch 23, and the other input terminal of the voltage comparator 24, respectively.

The voltage comparator 24 compares the magnitude of the voltages introduced to one and the other input terminals, and switches the selection switches 22 and 23 according to the comparison result. That is, when _NVin > _Vout (the input DC voltage is higher than the output DC voltage), the selection switches 22 and 23 are switched to the input terminals 22a and 23a, respectively, and when _NVin ≦ _Vout (the input DC voltage is equal to or lower than the output DC voltage), the selection switches 22 and 23 are switched to the input terminals 22b and 23b, respectively.

As a result, when _Vin is higher than _Vout , Vin is allocated to the DC voltage _Vdc1 of the primary inverter 1 set at the output terminal 22c of the selection switch 22, and _Vout is allocated to the DC voltage _Vdc2 of the secondary inverter 2 set at the output terminal of the selection switch 23. Furthermore, when _Vin is equal to or lower than _Vout , _Vout is allocated to the DC voltage _Vdc1 of the primary inverter 1, _{and Vin is} allocated to the DC voltage _Vdc2 of the secondary inverter 2.

In FIG. 6B showing the phase difference and pulse width command derivation block, 31 is a divider that calculates a current command value (I _load ) by taking the quotient of the power command value _Pref and the input DC voltage _Vin or the output DC voltage _Vout .

Reference numeral 32 denotes an imaginary axis component V1q calculation unit that calculates equation (13) based on the calculated current command value ( _Iload ) and equations (1), (2), (3), and (12 ₎ described below, to find the imaginary axis component _V1q of the output voltage _V1 of the inverter on the side with a higher DC voltage.

Reference numeral 33 denotes a real axis component V2d calculation unit that calculates equation (15) described below using a pulse width command value _W2 of the output voltage of the inverter on the lower DC voltage side, which is set to a fixed value close to 1, for example, approximately 0.7 to 0.95, and the DC voltage _Vdc2 of the inverter on the lower DC voltage side, which is assigned in the voltage magnitude relationship derivation block (voltage detection and comparison unit ₎ in FIG. 6( a), to find a real axis component _V2d of the output voltage _V2 of the inverter on the lower DC voltage side.

Reference numeral 34 denotes a phase difference command value θ calculation unit that determines V2d calculated by the real axis component V2d calculation unit 33 as the real axis component _V1d of the output voltage _V1 of the inverter on the higher DC voltage side based on _V1d = _V2d obtained when the fundamental wave power factor cos _γ of the inverter on the lower DC voltage side, which is expressed by equations (4) and (5) described below, is ₁ , and calculates equation ( ₁₆ ) described below using this real axis component _V1d and the imaginary axis component _V1q of the output voltage _V1 of the inverter on the higher DC voltage side calculated by the imaginary axis component V1q calculation unit 32 to calculate a phase difference command value θ between the output voltages of the inverter on the higher DC voltage side and the inverter on the lower DC voltage side.

In addition, in Non-Patent Document 1, the fundamental power factor of the inverter with the lower DC voltage is determined to be 1.

Reference numeral 35 denotes a pulse width command value W1 calculation unit that calculates equation (14) described later using the real axis component _V1d of the output voltage _V1 of the inverter having the higher DC voltage determined above, the imaginary axis component _V1q of the output voltage _V1 of the inverter having the higher DC voltage calculated by the imaginary axis component _V1q calculation unit 32, and the DC voltage _Vdc1 of the inverter having the higher DC voltage assigned by the voltage magnitude relationship derivation block (voltage detection and comparison unit) shown in FIG. 6( a) to determine the pulse width command value _W1 of the output voltage of the inverter having the higher _DC voltage.

Next, the operation of the phase difference and pulse width command derivation block in Fig. 6(b) will be explained. First, consider the fundamental wave components of the inverter output voltages in the DAB converters in Fig. 4 and Fig. 5. As shown in Fig. 4, two sinusoidal voltage sources _V1 and _V2 connected by an inductor L are expressed by equation (1).

The applied voltage V _L and current _IL of the inductor L are given by equation (2).

Next, the apparent power S2 and power factor cos γ on the output voltage _V2 side of the inverter with the lower DC voltage can be calculated by equations (3) and (4), respectively.

where _V1 is the output voltage of the inverter with the higher DC voltage, _V2 is the output voltage of the inverter with the lower DC voltage, _V1d is the real axis component of _V1 , _V2d is the real axis component of _V2 , _VL is the applied voltage to inductor L of the isolation transformer, _IL is the current flowing through inductor L, _S2 is the apparent power of the inverter with the lower DC voltage, _Iload is the current command value (load current), _P2 is the active power of the inverter with the lower DC voltage, and _Q2 is the reactive power of the inverter with the lower DC voltage.

Furthermore, solving equation (4) for V _1d gives

When the inverter with the lower DC voltage is driven at a power factor of 1, _V2d = _V1d . This applies to square waves. If the primary side DC voltage is _VDC1 , the secondary side DC voltage is _VDC2 , and the firing angles are _α1 and _α2 , the inverter output voltages _v1 and _v2 are expressed by the following equations (6) and (7).

However, the firing angles α ₁ and α ₂ are expressed in the range of 0 to 1, and the pulse widths W ₁ and W ₂ of the inverter output voltages are expressed as follows:

When v ₁ is expanded in a Fourier series,

Therefore, the effective value V _11rms of the fundamental wave component of the output voltage v ₁ of the primary side single-phase inverter 1 is given by equation (11).

Therefore, the real axis component _V2d of _V2 is the AC end voltage amplitude on the low voltage side, and the voltage amplitude can be changed by changing the pulse width _W2 . Since designing the low voltage side pulse width from the viewpoint of efficiency requires very complex calculations for each load current and DC voltage condition, a fixed value determined by pre-calculation or the like is used. Next, the primary and secondary side pulse widths and phase differences are calculated from the desired current command value and power factor. First, the load current _Iload (current command value) is obtained from equation (3) as equation (12).

Solving this for V _1q gives equation (13).

When this is solved for the pulse width _W1 of the inverter output voltage on the side where the DC voltage is higher, equations (14) and (15) are obtained.

Taking into account the turns ratio of the isolation transformer 3, the pulse width of the inverter on the side with the lower DC voltage is set to _W2 , which is a constant value in this control system. Efficiency can be improved by changing this depending on the voltage and load conditions. Finally, from equations (5), (13), and (15), the phase difference θ between the output voltages of the inverters on the high and low DC voltage sides can be calculated using the following equation (16).

J. Itoh, H. Higa and T. Nagano, “A Novel Control Method focusing on reactive power for a dual active bridge converter”, 2014 International Power Electronics and Applications Conference and Expesition, 2014, pp. 1020-1025 Higa Shun, Morita Kazunori, Oi Kazunobu, Urushibata Shota, Tadano Yugo, "A Method for Suppressing DC Superposition in Transformer Current in Dual Active Bridge Systems Using Pulse Width Control," IEEJ National Convention 2020, No. 4, Vol. 052, 2021, pp. 89-90 Kengo Kawachi, Jun Higa, Daiki Watanabe, Keisuke Kusaka, and Junichi Ito, "Effective Current Value of Dual Active Bridge Converter in Compensation Method for Nonlinear Power Error Due to Dead Time," IEEJ Transactions on Power Systems, Vol. 140, No. 3, pp. 1-9 (2020)

Patent No. 6785304

In the basic configuration shown in Fig. 6, the amplitude of the inductor current (IL in Fig. 4) is minimized by calculating the phase difference θ and the pulse width _W1 of the inverter output voltage on the side with a higher DC voltage so that the fundamental wave power factor on the side with a lower _DC voltage is 1. However, when the fundamental wave power factor is 1, the dead time of the inverter output voltage and the zero crossing of the inductor current are close to each other, so a dead time error occurs as shown in Non-Patent Document 3, and the response of the input or load current deteriorates.

The present invention aims to solve the above problems by providing a control device for a bidirectional isolated DC-DC converter that can reduce errors in pulse width and phase difference command values due to dead time and improve current response.

In order to solve the above problem, a control device for a bidirectional isolated DC-DC converter according to claim 1 comprises:
A control device for a bidirectional isolated DC-DC converter including a primary-side single-phase inverter having an AC side connected to a primary winding of an isolated transformer, and a secondary-side single-phase inverter having an AC side connected to a secondary winding of the isolated transformer,
The control device
a phase difference command _value θ calculation unit that calculates a phase difference command value θ between the output voltages of the inverter having a higher DC voltage and the inverter having a lower DC voltage from an imaginary axis component _V1q and a real axis component _V1d of the output voltage V1 of the inverter having a higher DC voltage, out of the primary side single-phase inverter and the secondary side single-phase inverter;
a pulse width command value W1 calculation unit that calculates a pulse width command value _W1 of the output voltage of the inverter having the higher DC voltage, based on the DC voltage _Vdc1 of the inverter having the higher DC voltage and an imaginary axis component _V1q and a real axis component _V1d of the output voltage _V1 of the inverter having the _higher DC voltage;
a pulse width command value compensating unit that adds a dead time error calculated from the product of the switching frequency and the dead time of the inverter to the pulse width command value _W1 calculated by the pulse width command value _W1 calculation unit, thereby compensating for the pulse width command value _W1 of the output voltage of the inverter having a higher DC voltage;
The semiconductor switching elements of the primary-side single-phase inverter and the secondary-side single-phase inverter are controlled by gate signals generated using the phase difference command value θ calculated by the phase difference command value _{θ calculation unit, the pulse width command value W1 of} the output voltage of the inverter with the higher DC voltage compensated by the pulse width command value compensation unit, the set pulse width command value W2 of the output voltage of the inverter with the lower DC voltage, and the dead time command value _Td .

The control device for a bidirectional isolated DC-DC converter according to claim 2 is the control device for a bidirectional isolated DC-DC converter according to claim 1,
a voltage detection and comparison unit that defines the DC voltage of one of the primary-side single-phase inverter and the secondary-side single-phase inverter having a higher DC voltage as _Vdc1 and the DC voltage of the other of the inverter having a lower DC voltage as _Vdc2 , compares input DC voltage values _Vin and _{Vout of the bidirectional isolated DC-DC converter, and allocates Vin to Vdc1} and _Vout to _Vdc2 when _Vin is higher than _Vout , and _{allocates Vin} to _Vdc2 and _Vout to _Vdc1 when Vin is equal to or lower than Vout;
an imaginary axis component V1q calculation unit that separates and handles the fundamental wave components of the output voltages of the primary-side single-phase inverter and the secondary-side single-phase inverter into a real axis (d-axis) component and an imaginary axis (q-axis) component, and calculates equation (13) based on equations (1), (2), (3), and (12) and a current command value obtained from the quotient of the power command value _Pref and the input DC voltage value or the output DC voltage value, to determine an imaginary axis component _V1q of the output voltage _V1 of the inverter on the side with a higher DC _voltage ;

( _V1 is the output voltage of the inverter with the higher DC voltage, _V2 is the output voltage of the inverter with the lower DC voltage, _V1d is the real axis component of _V1 , _V2d is the real axis component of _V2 , _VL is the applied voltage to inductor L of the isolation transformer, _IL is the current flowing through inductor L, _S2 is the apparent power of the inverter with the lower DC voltage, _Iload is the current command value (load current), _P2 is the active power of the inverter with the lower DC voltage, and _Q2 is the reactive power of the inverter with the lower DC voltage.)
a real axis component V2d calculation unit that calculates equation (15) using the set pulse width command value _W2 of the output voltage of the inverter having the lower DC voltage and the DC voltage _Vdc2 of the inverter having the lower DC voltage allocated by the voltage detection comparison unit, to determine a real axis component _V2d of the output voltage _V2 of the inverter having the lower _DC voltage;

The phase difference command value θ calculation unit determines V2d calculated by the real axis component V2d calculation unit as the real axis component _V1d of the output voltage V1 of the inverter on the higher DC voltage side based on _V1d = _V2d obtained when the fundamental wave power factor cos γ of the inverter on the lower DC voltage side, which is expressed by equations (4) and (5), _{is 1 ,} and calculates equation ( ₁₆ ) using the real axis component _V1d and the imaginary axis component _V1q of the output voltage _V1 of the inverter on the higher DC voltage side calculated by the imaginary axis component _V1q calculation unit to calculate a phase difference command value θ between the output voltages of the inverter on the higher DC voltage side and the inverter on the lower DC voltage side;

The pulse width command value _W1 calculation unit calculates equation (14) using the real axis component _V1d of the output voltage _V1 of the inverter having the higher DC voltage, the imaginary axis component _V1q of the output voltage _V1 of the inverter having the higher DC voltage calculated by the imaginary axis component _V1q calculation unit, and the DC voltage _Vdc1 of the inverter having the higher DC voltage allocated by the voltage detection comparison unit, to calculate the pulse width command value _W1 of the output voltage of the inverter having the higher DC voltage.

The control device for a bidirectional isolated DC-DC converter according to claim 3 comprises:
A control device for a bidirectional isolated DC-DC converter including a primary-side single-phase inverter having an AC side connected to a primary winding of an isolated transformer, and a secondary-side single-phase inverter having an AC side connected to a secondary winding of the isolated transformer,
The control device
a real axis component V1d calculation unit that calculates a real axis component V1d of the output voltage _V1 of the inverter with a higher DC voltage from an imaginary axis component _V1q of the output voltage _V1 of the inverter with a higher DC voltage out of the primary side single-phase inverter and the secondary side single-phase inverter, a real axis component _V2d of the output voltage _V2 of the inverter with a lower DC voltage, and a fundamental wave power factor cos _γ of the inverter with the lower DC voltage set to _{1 or less} ;
a phase difference command value _θ calculation unit that calculates a phase difference command value θ between the output voltages of the inverter on the _higher DC voltage side _and the inverter on the lower DC voltage side, based on the imaginary axis component _V1q of the output voltage V1 of the inverter on the higher DC voltage side and the real axis component V1d calculated by the real axis component V1d calculation unit;
a pulse width command value _W1 calculation unit that calculates a pulse width command value _W1 of the output voltage of the inverter having the higher DC voltage, from the real axis component _V1d calculated by the real axis component V1d calculation unit, an imaginary axis component _V1q of the output voltage _V1 of the inverter having the higher _DC voltage, and a DC voltage _Vdc1 of the inverter having the higher DC voltage,
The semiconductor switching elements of the primary-side single-phase inverter and the secondary-side single-phase inverter are controlled by gate signals generated using the phase difference command value θ calculated by the phase difference command value _θ calculation unit, the pulse width command value _{W1 of} the output voltage of the inverter on the side with the higher DC voltage calculated by the pulse width command value W1 calculation unit, the set pulse width command value W2 of the output voltage of the inverter on the side with the lower DC voltage, and the dead time command value _Td .

The control device for a bidirectional isolated DC-DC converter according to claim 4 is the control device for a bidirectional isolated DC-DC converter according to claim 3,
a voltage detection and comparison unit that defines the DC voltage of one of the primary-side single-phase inverter and the secondary-side single-phase inverter having a higher DC voltage as _Vdc1 and the DC voltage of the other of the inverter having a lower DC voltage as _Vdc2 , compares input DC voltage values _Vin and _{Vout of the bidirectional isolated DC-DC converter, and allocates Vin to Vdc1} and _Vout to _Vdc2 when _Vin is higher than _Vout , and _{allocates Vin} to _Vdc2 and _Vout to _Vdc1 when Vin is equal to or lower than Vout;
an imaginary axis component V1q calculation unit that separates and handles the fundamental wave components of the output voltages of the primary-side single-phase inverter and the secondary-side single-phase inverter into a real axis (d-axis) component and an imaginary axis (q-axis) component, and calculates equation (13) based on equations (1), (2), (3), and (12) and a current command value obtained from the quotient of the power command value _Pref and the input DC voltage value or the output DC voltage value, to determine an imaginary axis component _V1q of the output voltage _V1 of the inverter on the side with a higher DC _voltage ;

( _V1 is the output voltage of the inverter with the higher DC voltage, _V2 is the output voltage of the inverter with the lower DC voltage, _V1d is the real axis component of _V1 , _V2d is the real axis component of _V2 , _VL is the applied voltage to inductor L of the isolation transformer, _IL is the current flowing through inductor L, _S2 is the apparent power of the inverter with the lower DC voltage, _Iload is the current command value (load current), _P2 is the active power of the inverter with the lower DC voltage, and _Q2 is the reactive power of the inverter with the lower DC voltage.)
a real axis component V2d calculation unit that calculates equation (15) using the set pulse width command value _W2 of the output voltage of the inverter having the lower DC voltage and the DC voltage _Vdc2 of the inverter having the lower DC voltage allocated by the voltage detection comparison unit, to determine a real axis component _V2d of the output voltage _V2 of the inverter having the lower _DC voltage;

The real axis component _V1d calculation unit calculates equation ( ₅₎ based on equations (3) and (4) using the imaginary axis component _V1q of the output voltage _V1 of the inverter on the higher DC voltage side calculated by the imaginary axis component _V1q calculation unit, the real axis component _V2d of the output voltage _V2 of the inverter on the lower DC voltage side calculated by the real axis component V2d calculation unit, and the fundamental wave power factor cos γ of the inverter on the lower DC voltage side set to 1 or less, to calculate the real axis component _V1d of the output voltage _V1 of the inverter on the higher DC voltage side;

the phase difference command value θ calculation unit calculates equations (3), (4), (5), (13), (15), and _{(16) using} the imaginary axis component _V1q of the output voltage _V1 of the inverter having the higher DC voltage calculated by the imaginary axis component _V1q calculation unit and the real axis component _V1d of the output voltage V1 of the inverter having the higher DC voltage calculated by the real axis component V1d calculation unit to calculate a phase difference command value θ between the output voltages of the inverter having the higher DC voltage and the inverter having the lower DC voltage;

The pulse width command value _W1 calculation unit calculates equation ₍₁₄₎ using the real axis component V1d of the output voltage _V1 of the inverter having the higher DC voltage calculated by the real axis component _V1d calculation unit, the imaginary axis component _V1q of the output voltage _V1 of the inverter having the higher DC voltage calculated by the imaginary axis component _V1q calculation unit, and the DC voltage _Vdc1 of the inverter having the higher DC voltage allocated by the voltage detection comparison unit, to calculate the pulse width command value _W1 of the output voltage of the inverter having the higher DC voltage.

(1) According to the inventions described in claims 1 to 4, the dead time error can be reduced and the current response is improved, thereby improving the stability of control.
(2) According to the inventions described in claims 1 and 2, the pulse width command value _W1 can be compensated for simply by adding the dead time error to the pulse width command value of the output voltage of the inverter on the side with the higher DC voltage, thereby enabling implementation at low cost.
(3) According to the inventions described in claims 3 and 4, the power factor can be controlled for each operating condition. Therefore, under conditions where no dead time error occurs, the inverter can be driven with a fundamental power factor of 1, thereby achieving both improved efficiency and reduced dead time error.

1A and 1B show the circuit configuration of a DAB converter, where FIG. 1A is a circuit diagram in which an inductor L is connected to the output side, and FIG. 1B is a circuit diagram in which an inductor L is connected to the input side. FIG. 10 is an operational waveform diagram of a pulse width control method. General configuration diagram of pulse width control. FIG. 10 is an explanatory diagram of an equivalent circuit model using the fundamental wave component of a DAB converter. Feather diagram of the output voltage of each inverter when the equivalent circuit model is applied. FIG. 10 is a block diagram showing an example of the construction of a pulse width control block. FIG. 2 is a control block diagram according to the first embodiment of the present invention. FIG. 10 is a block diagram showing the configuration of each control system in a second embodiment of the present invention.

Embodiments of the present invention will be described below with reference to the drawings, but the present invention is not limited to the following embodiments.

Fig. 7 shows a control block diagram in the embodiment 1. Fig. 7 differs from Fig. 6(b) in that it includes a pulse width command value compensator 40 that adds a dead time error calculated from the product of the inverter switching frequency and the dead time to the pulse width command value _W1 calculated by the pulse width command value _W1 calculation unit 35, thereby compensating for the pulse width command value _W1 of the output voltage of the inverter having the higher DC voltage; other parts are configured in the same way as Fig. 6(b).

Reference numeral 41 in the pulse width command value compensator 40 denotes a multiplier that multiplies the dead time _Td by the switching frequency _2fsw of the inverter to obtain the ratio of the dead time to the switching period, that is, the dead time error.

An adder 42 adds the dead time error, which is the output of the multiplier 41, to the pulse width _W1 of the output voltage of the inverter on the side of the higher DC voltage, which is calculated by the pulse width command value _W1 calculation unit.

The semiconductor switching elements of the primary-side single-phase inverter 1 and the secondary-side single-phase inverter 2 are controlled by gate signals generated using the phase difference command value θ calculated by the phase difference command value θ calculation unit ₃₄ , the pulse width command value _W1 of the output voltage of the inverter with the higher DC voltage compensated by the pulse width command value compensation unit 40, the pulse width command value W2 of the output voltage of the inverter with the lower DC voltage set as above, and the dead time command value _Td .

In the configuration of the first embodiment shown in Fig. 7, a function is added to the basic configuration shown in Fig. 6 to add a dead time for the switching period to the pulse width command value _W1 of the inverter output voltage on the side with a higher DC voltage. Also, compensation should not be made for the inverter on the side with a lower DC voltage.

Although the current amplitude increases in this first embodiment, the dead time error can be reduced by compensating for the pulse width command value _W1 of the inverter output voltage on the side with the higher DC voltage. However, since the difference in output DC voltage is large and a large third harmonic is superimposed on the AC current, and a certain amount of current flows even during the dead time, the output voltage does not become unstable and no dead time error occurs, so excess reactive current is generated, which increases the conduction loss of magnetic components and the conduction loss of semiconductors, thereby reducing the efficiency of the DAB converter.

This embodiment 1 reduces dead time errors and improves current response, similar to conventional technology, thereby improving control stability.

Furthermore, in addition to the conventional pulse width control configuration, this can be realized simply by adding the dead time error to the pulse width command value _W1 of the inverter output voltage on the side with a higher DC voltage, so it can be implemented at low cost.

In the second embodiment, the pulse width _W1 and phase difference θ of the inverter output voltage on the side where the DC voltage is higher are calculated using equation (5) described later so that the fundamental wave power factor of the inverter output voltage on the side where the DC voltage is lower is 1 or less, thereby shifting the timing of the inductor current zero crossing and the dead time period, thereby reducing the dead time error.

Figure 8 shows the configuration of each control system in Example 2, with the same parts as in Figure 6(b) being designated by the same reference numerals.

Reference numeral 51 denotes a real axis component _V1d calculation unit that calculates equation (5) based on equations (3) and (4) using the imaginary axis component _V1q of the output voltage _V1 of the inverter on the higher DC voltage side calculated by the imaginary axis component _V1q calculation unit ₃₂ , the real axis component _V2d of the output voltage V2 of the inverter on the lower DC voltage side calculated by the real axis component _V2d calculation unit ₃₃ , and the fundamental wave power factor cos _{γ of the inverter on the lower DC voltage side, which is set to 1 or less} .

Reference numeral 52 denotes a phase difference command value _θ calculation unit that calculates equations (3), (4), (5), (13), (15), and ( ₁₆ ) using the imaginary axis component _V1q of the output voltage _V1 of the inverter on the higher DC voltage side calculated by the imaginary axis component _V1q calculation unit ₃₂ and the real axis component V1d of the output voltage V1 of the inverter on the higher DC voltage side calculated by the real axis component V1d calculation unit 51 to calculate a phase difference command value θ between the output voltages of the inverter on the higher DC voltage side and the inverter on the lower DC voltage side.

Reference numeral 53 denotes a pulse width command value _W1 calculation unit that calculates equation (14) using the real axis component _V1d of the output voltage _V1 of the inverter on the higher DC voltage side calculated by the real axis component _V1d calculation unit 51, the imaginary axis component _V1q of the output voltage _V1 of the inverter on the higher DC voltage side calculated by the imaginary axis component V1q calculation unit 32, and the DC voltage _Vdc1 of the inverter on the higher DC voltage side allocated by the voltage detection comparison unit ₂₄ , to calculate a pulse width command value _W1 of the output voltage of the inverter on the higher DC voltage side.

The semiconductor switching elements of the primary side single-phase inverter 1 and the secondary side single-phase inverter ₂ are controlled by gate signals generated using the phase difference command value θ calculated by the phase difference command value θ calculation unit 52, the pulse width command value _W1 of the output voltage of the inverter with the higher DC voltage calculated by the pulse width command value _W1 calculation unit 53, the pulse width command value W2 of the output voltage of the inverter with the lower DC voltage set as above, and the dead time command value _Td .

In the second embodiment, when the voltage difference is large and the power command value _Pref is small for each operating condition, the power factor cosγ is set to 1 to make the reactive current almost zero, and as the voltage difference decreases or the power command value _Pref increases, the power factor cosγ is made smaller, thereby making it possible to reduce both the reactive current and the dead time error.

This second embodiment reduces dead time errors and improves current response, similar to conventional technology, thereby improving control stability.

Furthermore, since the power factor can be controlled for each operating condition, under conditions where no dead time error occurs, it can be operated with a fundamental wave power factor of 1, achieving both improved efficiency and reduced dead time error.

DESCRIPTION OF SYMBOLS 1... Primary side single-phase inverter 2... Secondary side single-phase inverter 3... Insulation transformer 11... Pulse width, phase difference calculation block 21, 31... Divider 22, 23... Selection switch 24... Voltage comparator 32... Imaginary axis component _V1q calculation unit 33... Real axis component _V2d calculation unit 34, 52... Phase difference command value θ calculation unit 35, 53... Pulse width command value _W1 calculation unit 40... Pulse width command value compensation unit 51... Real axis component _V1d calculation unit

Claims (4)

A control device for a bidirectional isolated DC-DC converter including a primary-side single-phase inverter having an AC side connected to a primary winding of an isolated transformer, and a secondary-side single-phase inverter having an AC side connected to a secondary winding of the isolated transformer,
The control device
a phase difference command _value θ calculation unit that calculates a phase difference command value θ between the output voltages of the inverter having a higher DC voltage and the inverter having a lower DC voltage from an imaginary axis component _V1q and a real axis component _V1d of the output voltage V1 of the inverter having a higher DC voltage, out of the primary side single-phase inverter and the secondary side single-phase inverter;
a pulse width command value W1 calculation unit that calculates a pulse width command value _W1 of the output voltage of the inverter having the higher DC voltage, based on the DC voltage _Vdc1 of the inverter having the higher DC voltage and an imaginary axis component _V1q and a real axis component _V1d of the output voltage _V1 of the inverter having the _higher DC voltage;
a pulse width command value compensating unit that adds a dead time error calculated from the product of the switching frequency and the dead time of the inverter to the pulse width command value _W1 calculated by the pulse width command value _W1 calculation unit, thereby compensating for the pulse width command value _W1 of the output voltage of the inverter having a higher DC voltage;
a phase difference command value θ calculated by the phase difference command value θ calculation unit, a pulse width command value _W1 of the output voltage of the inverter on the side with a higher DC voltage compensated by the pulse width command value compensation unit, a pulse width command value W2 of the output voltage of the inverter on the side with a lower DC voltage that has been set, and a dead time command value Td, which controls each semiconductor switching element of the primary-side single-phase inverter and the secondary-side single-phase inverter by means of gate signals generated using the phase difference command value θ calculated by the phase difference command value _θ calculation unit, a pulse width command value _W1 of the output voltage of the inverter on the side with a higher DC voltage compensated by the pulse width command value compensation unit, a pulse width command value W2 of the output voltage of the inverter on the side with a lower DC voltage that has been set, and a dead time command value Td. a voltage detection and comparison unit that defines the DC voltage of one of the primary-side single-phase inverter and the secondary-side single-phase inverter having a higher DC voltage as _Vdc1 and the DC voltage of the other of the inverter having a lower DC voltage as _Vdc2 , compares input DC voltage values _Vin and _{Vout of the bidirectional isolated DC-DC converter, and allocates Vin to Vdc1} and _Vout to _Vdc2 when _Vin is higher than _Vout , and _{allocates Vin} to _Vdc2 and _Vout to _Vdc1 when Vin is equal to or lower than Vout;
an imaginary axis component V1q calculation unit that separates and handles the fundamental wave components of the output voltages of the primary-side single-phase inverter and the secondary-side single-phase inverter into a real axis (d-axis) component and an imaginary axis (q-axis) component, and calculates equation (13) based on equations (1), (2), (3), and (12) and a current command value obtained from the quotient of the power command value _Pref and the input DC voltage value or the output DC voltage value, to determine an imaginary axis component _V1q of the output voltage _V1 of the inverter on the side with a higher DC _voltage ;
( _V1 is the output voltage of the inverter with the higher DC voltage, _V2 is the output voltage of the inverter with the lower DC voltage, _V1d is the real axis component of _V1 , _V2d is the real axis component of _V2 , _VL is the applied voltage to inductor L of the isolation transformer, _IL is the current flowing through inductor L, _S2 is the apparent power of the inverter with the lower DC voltage, _Iload is the current command value (load current), _P2 is the active power of the inverter with the lower DC voltage, and _Q2 is the reactive power of the inverter with the lower DC voltage.)
a real axis component V2d calculation unit that calculates equation (15) using the set pulse width command value _W2 of the output voltage of the inverter having the lower DC voltage and the DC voltage _Vdc2 of the inverter having the lower DC voltage allocated by the voltage detection comparison unit, to determine a real axis component _V2d of the output voltage _V2 of the inverter having the lower _DC voltage;
The phase difference command value θ calculation unit determines V2d calculated by the real axis component V2d calculation unit as the real axis component _V1d of the output voltage V1 of the inverter on the higher DC voltage side based on _V1d = _V2d obtained when the fundamental wave power factor cos γ of the inverter on the lower DC voltage side, which is expressed by equations (4) and (5), _{is 1 ,} and calculates equation ( ₁₆ ) using the real axis component _V1d and the imaginary axis component _V1q of the output voltage _V1 of the inverter on the higher DC voltage side calculated by the imaginary axis component _V1q calculation unit to calculate a phase difference command value θ between the output voltages of the inverter on the higher DC voltage side and the inverter on the lower DC voltage side;
2. The control device for a bidirectional isolated DC-DC converter according to claim ₁ , wherein the pulse width command value W1 calculation unit calculates equation ( ₁₄ ) using the real axis component _V1d of the output voltage _V1 of the inverter having the higher DC voltage, the imaginary axis component _V1q of the output voltage _V1 of the inverter having the higher DC voltage calculated by the imaginary axis component _V1q calculation unit, and the DC voltage Vdc1 of the inverter having the higher DC voltage allocated by the voltage detection comparison unit, to determine the pulse width command value _W1 of the output voltage of the inverter having the higher DC voltage.
A control device for a bidirectional isolated DC-DC converter including a primary-side single-phase inverter having an AC side connected to a primary winding of an isolated transformer, and a secondary-side single-phase inverter having an AC side connected to a secondary winding of the isolated transformer,
The control device
a real axis component V1d calculation unit that calculates a real axis component V1d of the output voltage _V1 of the inverter with a higher DC voltage from an imaginary axis component _V1q of the output voltage _V1 of the inverter with a higher DC voltage out of the primary side single-phase inverter and the secondary side single-phase inverter, a real axis component _V2d of the output voltage _V2 of the inverter with a lower DC voltage, and a fundamental wave power factor cos _γ of the inverter with the lower DC voltage set to _{1 or less} ;
a phase difference command value _θ calculation unit that calculates a phase difference command value θ between the output voltages of the inverter on the _higher DC voltage side _and the inverter on the lower DC voltage side, based on the imaginary axis component _V1q of the output voltage V1 of the inverter on the higher DC voltage side and the real axis component V1d calculated by the real axis component V1d calculation unit;
a pulse width command value _W1 calculation unit that calculates a pulse width command value _W1 of the output voltage of the inverter having the higher DC voltage, from the real axis component _V1d calculated by the real axis component V1d calculation unit, an imaginary axis component _V1q of the output voltage _V1 of the inverter having the higher _DC voltage, and a DC voltage _Vdc1 of the inverter having the higher DC voltage,
a phase difference command value θ calculated by the phase difference command value θ calculation unit, a pulse width command value _W1 of the output voltage of the inverter on the side with a higher DC voltage calculated by the pulse width command value W1 calculation unit, a pulse width command value _W2 of the output voltage of the inverter on the side with a _lower DC voltage that has been set, and a dead time command value Td, which controls each semiconductor switching element of the primary-side single-phase inverter and the secondary-side single-phase inverter using gate signals generated using the phase difference command value _θ calculated by the phase difference command value θ calculation unit, a pulse width command value W1 of the output voltage of the inverter on the side with a lower DC voltage that has been set, and a dead time command value Td. a voltage detection and comparison unit that defines the DC voltage of one of the primary-side single-phase inverter and the secondary-side single-phase inverter having a higher DC voltage as _Vdc1 and the DC voltage of the other of the inverter having a lower DC voltage as _Vdc2 , compares input DC voltage values _Vin and _{Vout of the bidirectional isolated DC-DC converter, and allocates Vin to Vdc1} and _Vout to _Vdc2 when _Vin is higher than _Vout , and _{allocates Vin} to _Vdc2 and _Vout to _Vdc1 when Vin is equal to or lower than Vout;
an imaginary axis component V1q calculation unit that separates and handles the fundamental wave components of the output voltages of the primary-side single-phase inverter and the secondary-side single-phase inverter into a real axis (d-axis) component and an imaginary axis (q-axis) component, and calculates equation (13) based on equations (1), (2), (3), and (12) and a current command value obtained from the quotient of the power command value _Pref and the input DC voltage value or the output DC voltage value, to determine an imaginary axis component _V1q of the output voltage _V1 of the inverter on the side with a higher DC _voltage ;
( _V1 is the output voltage of the inverter with the higher DC voltage, _V2 is the output voltage of the inverter with the lower DC voltage, _V1d is the real axis component of _V1 , _V2d is the real axis component of _V2 , _VL is the applied voltage to inductor L of the isolation transformer, _IL is the current flowing through inductor L, _S2 is the apparent power of the inverter with the lower DC voltage, _Iload is the current command value (load current), _P2 is the active power of the inverter with the lower DC voltage, and _Q2 is the reactive power of the inverter with the lower DC voltage.)
a real axis component V2d calculation unit that calculates equation (15) using the set pulse width command value _W2 of the output voltage of the inverter having the lower DC voltage and the DC voltage _Vdc2 of the inverter having the lower DC voltage allocated by the voltage detection comparison unit, to determine a real axis component _V2d of the output voltage _V2 of the inverter having the lower _DC voltage;
The real axis component _V1d calculation unit calculates equation ( ₅₎ based on equations (3) and (4) using the imaginary axis component _V1q of the output voltage _V1 of the inverter on the higher DC voltage side calculated by the imaginary axis component _V1q calculation unit, the real axis component _V2d of the output voltage _V2 of the inverter on the lower DC voltage side calculated by the real axis component V2d calculation unit, and the fundamental wave power factor cos γ of the inverter on the lower DC voltage side set to 1 or less, to calculate the real axis component _V1d of the output voltage _V1 of the inverter on the higher DC voltage side;
the phase difference command value θ calculation unit calculates equations (3), (4), (5), (13), (15), and _{(16) using} the imaginary axis component _V1q of the output voltage _V1 of the inverter having the higher DC voltage calculated by the imaginary axis component _V1q calculation unit and the real axis component _V1d of the output voltage V1 of the inverter having the higher DC voltage calculated by the real axis component V1d calculation unit to calculate a phase difference command value θ between the output voltages of the inverter having the higher DC voltage and the inverter having the lower DC voltage;
4. The control device of a bidirectional isolated DC-DC converter according to claim 3, wherein the pulse width command value _W1 calculation unit calculates equation ( _{14 )} using the real axis component _V1d of the output voltage _V1 of the inverter having the higher DC voltage calculated by the real axis component _V1d calculation unit, the imaginary axis component _V1q of the output voltage _V1 of the inverter having the higher DC voltage calculated by the imaginary axis component V1q calculation unit, and the DC voltage Vdc1 of the inverter having the higher DC voltage allocated by the voltage detection comparison unit, to calculate the pulse width command value _W1 of the output voltage of the inverter having the higher DC voltage.