Control device for bidirectional isolated DC-DC converter

Abstract

To provide a control device of a bidirectional insulation type DC-DC converter which improves a current response by reducing an error to a pulse width and a phase difference command value due to a dead time.SOLUTION: A control device of a bidirectional insulation type DC-DC converter comprises: an imaginary axis component V1q calculation unit 32 which obtains an imaginary axis component V1q of the output voltage V1 of an inverter on a side on which the DC voltage is high; a real axis component V2d calculation unit 33 which obtains a real axis component V2d of the output voltage V2 of the inverter on a side on which the DC voltage is low from a pulse width command value W2 on which the DC voltage is low and the DC voltage Vdc2; a phase difference command value θ calculation unit 34 which obtains a phase difference command value θ of the two inverters from the output of the calculation units 32, 33; a pulse width command value W1 calculation unit 35 which obtains a pulse width command value W1 on a side on which the DC voltage is high from the DC voltage Vdc1 on a side on which the DC voltage is high and the output from the calculation units 32, 33; and a pulse width command value compensation unit 40 which compensates for the pulse width command value W1 by adding a dead time error obtained from the product of a switching frequency of the inverter and a dead time Td to W1.SELECTED DRAWING: Figure 7

Description

[Technical Field]

[0001] The present invention relates to a control technique for suppressing a decrease in current response due to dead time in a Dual Active Bridge (hereinafter referred to as DAB) converter that transmits power bidirectionally while isolating the input and output. [Background technology]

[0002] In bidirectional isolated DC-DC converters, the output or input current is controlled by controlling the phase difference between the output voltages of the two inverters, but there is a problem that the 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 the output voltage of each inverter, as described in Non-Patent Document 1 and Patent Document 1.

[0003] However, the dead time causes errors in the actual measured values relative to the pulse width and phase difference command values, which causes the problem of being unable to follow the current command value and resulting in a decrease in response. Non-Patent Document 3 describes a method to solve this problem, but it requires calculations for each mode, making it very complicated.

[0004] The configuration of a DAB converter to which the control method of the present invention is applied is shown in Figure 1. In Figure 1(a), which shows a configuration in which a reactor is 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.

[0005] 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.

[0006] 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.

[0007] The semiconductor switching elements S1 to S8 are configured by, for example, IGBTs, and switching control is performed by gate signals generated by a gate signal generating unit of the control device, which will be described later.

[0008] The positive terminal of the DC side of the primary single-phase inverter 1 is connected to the primary positive terminal P1, and the negative terminal is connected to the primary negative terminal N1. A primary capacitor C is connected between the positive and negative terminals. in The positive terminal of the DC side of the secondary single-phase inverter 2 is connected to the secondary positive terminal P2 via the reactor 4, and the negative terminal is connected to the secondary negative terminal N2. A secondary capacitor C is connected between the positive and negative terminals of the DC side of the secondary single-phase inverter 2. out is connected.

[0009] V in is the input DC voltage (primary side capacitor C in voltage), V out is the output DC voltage (secondary capacitor C out 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.

[0010] i pr is 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, and i se is 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 10 indicates the load current between the reactor 4 and the secondary side positive terminal P2 detected by the current detector 6.

[0011] A DC power supply (not shown) is connected between the primary positive terminal P1 and the primary negative terminal N1, and a load (not shown) is connected between the secondary positive terminal P2 and the secondary negative terminal N2.

[0012] In Figure 1(b), which shows a configuration in which a reactor is connected to the primary side, instead of the reactor 4 in Figure 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, and the other parts are configured in the same way as in Figure 1(a).

[0013] Figure 2 shows the operating waveforms of the pulse width control method. The period during which the output voltage is zero is set by simultaneously turning on two semiconductor switching elements on the upper arm (S1 and S3 on the primary side as an example) or two semiconductor switching elements on the lower arm (S2 and S4 on the primary side as an example) of each inverter 1 and 2 (pulse widths W1 and W2 shown). In the figure, θ is the phase difference.

[0014] A method is being considered for expanding the soft switching range using this pulse width control even when the difference between the primary and secondary DC voltages is large. The control of this embodiment can be applied to square wave, single-sided, or double-sided pulse width control.

[0015] The general configuration of pulse width control is shown in Figure 3. This configuration consists of the following two blocks:

[0016] Pulse width and phase difference calculation block 11 Input DC voltage value V in , output DC voltage value V out , power command value P ref This is a block that calculates each pulse width W1, W2 and the phase difference command value θ from the above. As an example of pulse width calculation, for example, a technique disclosed in Patent Document 1 has been proposed.

[0017] Gate, dead time generation block 12 Pulse width command values W1, W2, phase difference command value θ, dead time command value T d is input, a dead time is added, and gate signals for the semiconductor switching elements S1 to S8 of the inverters 1 and 2 are output. Non-Patent Document 2, for example, has proposed an example of a gate generator.

[0018] The input DC voltage value V in and the output DC voltage value V out In the case of a DAB converter that has an operating mode in which the magnitude relationship between the input and output is reversed, the input DC voltage value V is 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 a higher DC voltage" described later. in , output DC voltage value V out Enter each one.

[0019] Figure 4 shows the fundamental component model of the DAB converter used to calculate the pulse width. In Figure 4, the fundamental wave model of the output voltage of each inverter is composed of voltage sources V1 and V2 of the fundamental component of a three-level voltage including a square wave or zero voltage, and the combined inductance L(I L ,V L )

[0020] 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 plotted on the real axis (d axis) V d component, imaginary axis (q-axis V q ) components. 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.

[0021] An example of the construction of a pulse width control block is shown in Figure 6. The construction 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).

[0022] In FIG. 6(a), 21 is the input DC voltage value V in is a divider that divides the current 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).

[0023] The output of the divider 21 is led to an input terminal 22 a of a selection switch 22 , an input terminal 23 b of a selection switch 23 , and one input terminal of a voltage comparator 24 .

[0024] Output DC voltage V out are respectively 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.

[0025] The voltage comparator 24 compares the magnitude of the voltages fed to one input terminal with the magnitude of the other input terminal, and switches the selection switches 22 and 23 depending on the comparison result. in >V out When 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. in ≦V out When this condition is met (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.

[0026] This allows V in V out When the DC voltage V of the primary inverter 1 set at the output terminal 22c of the selection switch 22 is higher than dc1 V in is assigned to the output terminal of the selection switch 23, and the DC voltage V dc2 V out Also, V in V out When the following occurs, the DC voltage V of the primary inverter 1 dc1 V out is assigned, and the DC voltage V of the secondary inverter 2 dc2 V in is assigned.

[0027] In FIG. 6(b) showing the phase difference and pulse width command derivation block, 31 is the power command value P ref and the input DC voltage V in Or output DC voltage V out The quotient is taken to obtain the current command value (I load ) is a divider that calculates

[0028] 32 is the calculated current command value (I load ) and (13) based on the equations (1), (2), (3), and (12) described below, calculate the imaginary axis component V of the output voltage V1 of the inverter with the higher DC voltage. 1q The imaginary axis component V 1q This is the calculation unit.

[0029] 33 is the pulse width command value W2 of the output voltage of the inverter on the side with a lower DC voltage, which is set to a fixed value close to 1, for example, approximately 0.7 to 0.95, and the DC voltage V of the inverter on the side with a lower DC voltage, which is assigned by the voltage magnitude relationship derivation block (voltage detection comparison unit) in FIG. 6(a). dc2 Using this, calculate the equation (15) described later, and calculate the real axis component V of the output voltage V2 of the inverter with the lower DC voltage. 2d Real axis component V to be calculated 2d This is the calculation unit.

[0030] 34 is the V obtained when the fundamental wave power factor cosγ of the inverter on the side with the lower DC voltage, expressed by equations (4) and (5) described later, is 1. 1d =V 2d Based on this, the real axis component V 2d V calculated by the calculation unit 33 2d The real axis component V of the output voltage V1 of the inverter with the higher DC voltage 1d and the real axis component V 1d and the imaginary axis component V 1q The imaginary axis component V of the output voltage V1 of the inverter with the higher DC voltage calculated by the calculation unit 32 1q and calculates equation (16) described later using the above to obtain a phase difference command value θ between the output voltages of the inverter on the side with a higher DC voltage and the inverter on the side with a lower DC voltage.

[0031] In Non-Patent Document 1, the fundamental power factor of the inverter on the side with a lower DC voltage is determined to be 1.

[0032] 35 is the real axis component V of the output voltage V1 of the inverter on the side with the higher DC voltage determined above. 1d and the imaginary axis component V 1qThe imaginary axis component V of the output voltage V1 of the inverter with the higher DC voltage calculated by the calculation unit 32 1q and the DC voltage V of the inverter with the higher DC voltage assigned in the voltage magnitude relationship derivation block (voltage detection comparison unit) in FIG. 6(a). dc1 and a pulse width command value W1 calculation unit that calculates equation (14) below using the above to obtain a pulse width command value W1 of the output voltage of the inverter on the side with a higher DC voltage.

[0033] Next, we will explain the operation of the phase difference and pulse width command derivation block in Figure 6(b). First, consider the fundamental wave components of the inverter output voltages in the DAB converters in Figures 4 and 5. As shown in Figure 4, the two sinusoidal voltage sources V1 and V2 connected by inductor L are expressed by equation (1).

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[0035] Applied voltage V across inductor L L , current I L is expressed as equation (2).

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[0037] Next, the apparent power S2 and power factor cosγ on the output voltage V2 side of the inverter with the lower DC voltage can be calculated using equations (3) and (4), respectively.

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[0040] 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, and V 1d is the real axis component of V1, V 2d is the real axis component of V2, V L is the applied voltage across the inductor L of the isolation transformer, and I L is the current flowing through the inductor L, S2 is the apparent power of the inverter on the side with the lower DC voltage, I load is the current command value (load current), P2 is the active power of the inverter on the side with the lower DC voltage, and Q2 is the reactive power of the inverter on the side with the lower DC voltage.

[0041] Also, equation (4) is V 1d When we solve for

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[0043] When the inverter with the lower DC voltage is driven at a power factor of 1, V 2d =V 1d This is applied to a square wave. The DC voltage on the primary side is V DC1 , the DC voltage on the secondary side is V DC2 When the firing angles are α1 and α2, the inverter output voltages v1 and v2 are expressed as in the following equations (6) and (7).

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[0046] However, the firing angles α1 and α2 are expressed in the range of 0 to 1 using the pulse widths W1 and W2 of the inverter output voltages.

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[0049] When v1 is expanded into a Fourier series,

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[0051] Therefore, the effective value V of the fundamental wave component of the output voltage v1 of the primary side single-phase inverter 1 11rms is expressed as equation (11).

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[0053] Therefore, the real axis component of V2, V 2d 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 the low voltage side pulse width design from the viewpoint of efficiency requires very complicated calculations for each load current and DC voltage condition, it is set to a fixed value determined by pre-calculation, etc. Next, the primary and secondary side pulse widths and phase difference are calculated from the desired current command value and power factor. First, the load current I load (Current command value) is expressed as Equation (12) using Equation (3).

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[0055] This is V 1q Solving for this gives equation (13).

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[0057] 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.

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[0060] 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, and this 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):

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[0062] [Non-Patent Document 1] 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 Application Conference and Expesition, 2014, pp.1020-1025 [Non-patent document 2] Higa Jun, 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," Institute of Electrical Engineers of Japan Annual Convention 2020, No. 4, Vol. 052, 2021, pp. 89-90 [Non-patent document 3] Kengo Kawachi, Jun Higa, Daiki Watanabe, Keisuke Kusaka, Junichi Ito; "Current Effective 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 documents]

[0063] [Patent Document 1] Patent No. 6785304 Summary of the Invention [Problem to be solved by the invention]

[0064] In the basic configuration shown in Fig. 6, the inductor current (I in Fig. 4) is calculated 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. L However, if the fundamental 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, which causes a dead time error as shown in Non-Patent Document 3, and reduces the response of the input or load current.

[0065] The present invention is devised to solve the above-mentioned problems, and an object of the present invention is to provide a control device for an isolated bidirectional DC-DC converter that can reduce errors in pulse width and phase difference command values due to dead time and improve current response. [Means for solving the problem]

[0066] 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 The imaginary axis component V of the output voltage V1 of the inverter with the higher DC voltage of the primary side single-phase inverter and the secondary side single-phase inverter. 1q and the real axis component V 1d 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 side with a higher DC voltage and the inverter on the side with a lower DC voltage, based on the phase difference command value θ; The DC voltage V of the inverter with the higher DC voltage dc1 and the imaginary axis component V of the output voltage V1 of the inverter with the higher DC voltage. 1q and the real axis component V 1d a pulse width command value W1 calculation unit that calculates a pulse width command value W1 of the output voltage of the inverter with a higher DC voltage from the above; 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 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 a higher DC voltage compensated by the pulse width command value compensation unit, the 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 the dead time command value T d The present invention is characterized in that 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 above.

[0067] 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, The DC voltage of the inverter with the higher DC voltage among the primary side single-phase inverter and the secondary side single-phase inverter is V dc1 , the DC voltage of the inverter with the lower DC voltage is V dc2is defined as the input DC voltage value V of the bidirectional isolated DC-DC converter. in and V out Compare V in V out When V is higher than in V dc1 To, V 0ut V dc2 V in V out When V is in V dc2 To, V 0ut V dc1 a voltage detection and comparison unit for respectively allocating the voltages to the The fundamental wave components of the output voltages of the primary-side single-phase inverter and the secondary-side single-phase inverter are separated into real axis (d-axis) components and imaginary axis (q-axis) components, respectively, and the power command value P ref The imaginary axis component V of the output voltage V1 of the inverter with the higher DC voltage is calculated based on the current command value obtained from the quotient of the input DC voltage value or the output DC voltage value and equation (13) based on equations (1), (2), (3), and (12). 1q The imaginary axis component V 1q A calculation unit;

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[0073] (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, V 1d is the real axis component of V1, V 2d is the real axis component of V2, V L is the applied voltage across the inductor L of the isolation transformer, and I L is the current flowing through the inductor L, S2 is the apparent power of the inverter on the side with the lower DC voltage, I load is the current command value (load current), P2 is the active power of the inverter on the side with the lower DC voltage, and Q2 is the reactive power of the inverter on the side with the lower DC voltage. The pulse width command value W2 of the output voltage of the inverter with the lower DC voltage set and the DC voltage V of the inverter with the lower DC voltage allocated by the voltage detection comparison unit dc2 Using this, calculate equation (15) and calculate the real axis component V of the output voltage V2 of the inverter with the lower DC voltage. 2d Real axis component V to be calculated 2d a calculation unit,

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[0075] The phase difference command value θ calculation unit calculates V when the fundamental wave power factor cosγ of the inverter on the side with the lower DC voltage expressed by equations (4) and (5) is 1. 1d =V 2d Based on this, the real axis component V 2d V calculated by the calculation section 2d The real axis component V of the output voltage V1 of the inverter with the higher DC voltage 1d and the real axis component V 1d and the imaginary axis component V 1q The imaginary axis component V of the output voltage V1 of the inverter with the higher DC voltage calculated by the calculation unit 1q (16) is calculated using the above to obtain the phase difference command value θ between the output voltages of the inverter with the higher DC voltage and the inverter with the lower DC voltage.

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[0079] The pulse width command value W1 calculation unit calculates the real axis component V of the output voltage V1 of the inverter on the side where the DC voltage is higher. 1d and the imaginary axis component V 1q The imaginary axis component V of the output voltage V1 of the inverter with the higher DC voltage calculated by the calculation unit 1q and the DC voltage V of the inverter with the higher DC voltage allocated by the voltage detection comparison unit. dc1 The pulse width command value W1 of the output voltage of the inverter on the side with a higher DC voltage is calculated using equation (14).

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[0081] 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 The imaginary axis component V of the output voltage V1 of the inverter with the higher DC voltage among the primary side single-phase inverter and the secondary side single-phase inverter. 1q and the real axis component V of the output voltage V2 of the inverter with the lower DC voltage 2d From the fundamental wave power factor cosγ of the inverter on the side with a lower DC voltage, which is set to 1 or less, the real axis component V of the output voltage V1 of the inverter on the side with a higher DC voltage is calculated. 1d Real axis component V to be calculated 1dA calculation unit; The imaginary axis component V of the output voltage V1 of the inverter with the higher DC voltage 1q and the real axis component V 1d The real axis component V calculated by the calculation section 1d 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 side with a higher DC voltage and the inverter on the side with a lower DC voltage; The real axis component V 1d The real axis component V calculated by the calculation section 1d and the imaginary axis component V of the output voltage V1 of the inverter with the higher DC voltage 1q and the DC voltage V of the inverter with the higher DC voltage dc1 and a pulse width command value W1 calculation unit for calculating a pulse width command value W1 of the output voltage of the inverter having a higher DC voltage. 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 a higher DC voltage calculated by the pulse width command value W1 calculation unit, the 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 the dead time command value T d The present invention is characterized in that 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 above.

[0082] 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, The DC voltage of the inverter with the higher DC voltage among the primary side single-phase inverter and the secondary side single-phase inverter is V dc1 , the DC voltage of the inverter with the lower DC voltage is V dc2 is defined as the input DC voltage value V of the bidirectional isolated DC-DC converter. in and V out Compare V in V out When V is higher than in V dc1 To, V 0ut V dc2 V in V out When V is in Vdc2 To, V 0ut V dc1 a voltage detection and comparison unit for respectively allocating the voltages to the The fundamental wave components of the output voltages of the primary-side single-phase inverter and the secondary-side single-phase inverter are separated into real axis (d-axis) components and imaginary axis (q-axis) components, respectively, and the power command value P ref The imaginary axis component V of the output voltage V1 of the inverter with the higher DC voltage is calculated based on the current command value obtained from the quotient of the input DC voltage value or the output DC voltage value and equation (13) based on equations (1), (2), (3), and (12). 1q The imaginary axis component V 1q A calculation unit;

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[0088] (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, V 1d is the real axis component of V1, V 2d is the real axis component of V2, V L is the applied voltage across the inductor L of the isolation transformer, and I L is the current flowing through the inductor L, S2 is the apparent power of the inverter on the side with the lower DC voltage, I loadis the current command value (load current), P2 is the active power of the inverter on the side with the lower DC voltage, and Q2 is the reactive power of the inverter on the side with the lower DC voltage. The pulse width command value W2 of the output voltage of the inverter with the lower DC voltage set and the DC voltage V of the inverter with the lower DC voltage allocated by the voltage detection comparison unit dc2 Using this, calculate equation (15) and calculate the real axis component V of the output voltage V2 of the inverter with the lower DC voltage. 2d Real axis component V to be calculated 2d a calculation unit,

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[0090] The real axis component V 1d The calculation unit calculates the imaginary axis component V 1q The imaginary axis component V of the output voltage V1 of the inverter with the higher DC voltage calculated by the calculation unit 1q and the real axis component V 2d The real axis component V of the output voltage V2 of the inverter with the lower DC voltage calculated by the calculation unit 2d Using the fundamental wave power factor cosγ of the inverter on the side with a lower DC voltage, which is set to 1 or less, calculate equation (5) based on equations (3) and (4) to obtain the real axis component V of the output voltage V1 of the inverter on the side with a higher DC voltage. 1d Seeking

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[0094] The phase difference command value θ calculation unit calculates the imaginary axis component V1q The imaginary axis component V of the output voltage V1 of the inverter with the higher DC voltage calculated by the calculation unit 1q and the real axis component V 1d The real axis component V of the output voltage V1 of the inverter with the higher DC voltage calculated by the calculation unit 1d Using the above, the equations (3), (4), (5), (13), (15), and (16) are calculated to determine the phase difference command value θ between the output voltages of the inverter with the higher DC voltage and the inverter with the lower DC voltage,

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[0101] The pulse width command value W1 calculation unit calculates the real axis component V 1d The real axis component V of the output voltage V1 of the inverter with the higher DC voltage calculated by the calculation unit 1d and the imaginary axis component V 1q The imaginary axis component V of the output voltage V1 of the inverter with the higher DC voltage calculated by the calculation unit 1qand the DC voltage V of the inverter with the higher DC voltage allocated by the voltage detection comparison unit. dc1 The pulse width command value W1 of the output voltage of the inverter on the side with a higher DC voltage is calculated using equation (14).

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[0103] (1) According to the inventions set forth 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, so that 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. [Brief explanation of the drawings]

[0104] [Figure 1] The circuit configuration of a DAB converter is shown in (a) with inductor L connected to the output side, and (b) with inductor L connected to the input side. [Figure 2] FIG. 10 is an operational waveform diagram of a pulse width control method. [Figure 3] General configuration diagram of pulse width control. [Figure 4] FIG. 1 is an explanatory diagram of an equivalent circuit model using the fundamental wave component of a DAB converter. [Figure 5] Feather diagram of the output voltage of each inverter when the equivalent circuit model is applied. [Figure 6] FIG. 10 is a block diagram showing an example of the construction of a pulse width control block. [Figure 7] FIG. 2 is a control block diagram according to the first embodiment of the present invention. [Figure 8] FIG. 10 is a block diagram showing the configuration of each control system in a second embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0105] Hereinafter, embodiments of the present invention will be described with reference to the drawings, but the present invention is not limited to the following embodiments. [Example]

[0106] Fig. 7 shows a control block 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 on the side with a higher DC voltage; other parts are configured in the same way as Fig. 6(b).

[0107] The pulse width command value compensator 40 has a dead time T d The inverter switching frequency is 2f sw This is a multiplier that multiplies the dead time by 1 to obtain the ratio of the dead time to the switching period, i.e., the dead time error.

[0108] 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.

[0109] 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 on the side with a 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 on the side with a lower DC voltage set as described above, and the dead time command value T d 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 above.

[0110] In the configuration of Example 1 in Fig. 7, a function is added to the basic configuration 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. In addition, compensation must not be made for the inverter on the side with a lower DC voltage.

[0111] 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.

[0112] According to the first embodiment, the dead time error can be reduced as in the prior art, and the current response can be improved, thereby improving the stability of the control.

[0113] Furthermore, in addition to the conventional pulse width control configuration, this can be achieved 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. [Example]

[0114] 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.

[0115] FIG. 8 shows the configuration of each control system in the second embodiment, and the same parts as those in FIG. 6(b) are denoted by the same reference numerals.

[0116] 51 is the imaginary axis component V 1qThe imaginary axis component V of the output voltage V1 of the inverter on the side with a higher DC voltage, calculated by the calculation unit 32, 1q and the real axis component V 2d The real axis component V of the output voltage V2 of the inverter with the lower DC voltage calculated by the calculation unit 33 2d Using the fundamental wave power factor cosγ of the inverter on the side with a lower DC voltage, which is set to 1 or less, calculate equation (5) based on equations (3) and (4) to obtain the real axis component V of the output voltage V1 of the inverter on the side with a higher DC voltage. 1d Real axis component V to be calculated 1d This is the calculation unit.

[0117]

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[0118]

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[0119]

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[0120] 52 is the imaginary axis component V 1q The imaginary axis component V of the output voltage V1 of the inverter on the side with a higher DC voltage, calculated by the calculation unit 32, 1q and the real axis component V 1d The real axis component V of the output voltage V1 of the inverter on the side with a higher DC voltage, calculated by the calculation unit 51, 1d and a phase difference command value θ calculation unit that calculates equations (3), (4), (5), (13), (15), and (16) using the above to find a phase difference command value θ between the output voltages of the inverter on the side with a higher DC voltage and the inverter on the side with a lower DC voltage.

[0121]

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[0122]

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[0123]

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[0124]

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[0125]

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[0126]

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[0127] 53 is the real axis component V 1d The real axis component V of the output voltage V1 of the inverter on the side with a higher DC voltage calculated by the calculation unit 51 1d and the imaginary axis component V 1q The imaginary axis component V of the output voltage V1 of the inverter with the higher DC voltage calculated by the calculation unit 32 1q and the DC voltage V of the inverter on the side where the DC voltage allocated by the voltage detection comparison unit 24 is higher. dc1 and calculates equation (14) using the above to obtain a pulse width command value W1 for the output voltage of the inverter on the side with a higher DC voltage.

[0128]

number

[0129] 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 on the side with a 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 on the side with a lower DC voltage calculated by the pulse width command value W1 calculation unit 54, and the dead time command value T dThe 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 above.

[0130] In the second embodiment, the voltage difference is large for each operating condition and the power command value P ref When is small, the power factor is set to cosγ=1 to make the reactive current almost zero, and the voltage difference is reduced or the power command value P ref By reducing the power factor cosγ as the capacitance increases, it is possible to reduce both the reactive current and the dead time error.

[0131] According to the second embodiment, the dead time error can be reduced as in the prior art, and the current response can be improved, thereby improving the stability of the control.

[0132] Furthermore, because the power factor can be controlled for each operating condition, under conditions where no dead time error occurs, the inverter can be driven with a fundamental wave power factor of 1, achieving both improved efficiency and reduced dead time error. [Explanation of symbols]

[0133] 1...Primary side single-phase inverter 2...Secondary side single-phase inverter 3...Isolation transformer 11...Pulse width and phase difference calculation block 21, 31...divider 22, 23...Selection switch 24...Voltage comparator 32...Imaginary axis component V 1q Arithmetic unit 33...Real axis component V 2d Arithmetic unit 34, 52...Phase difference command value θ calculation section 35, 53...Pulse width command value W1 calculation unit 40...Pulse width command value compensation unit 51...Real axis component V 1d Arithmetic unit

Claims

1. 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 The output voltage V of the inverter having a higher DC voltage among the primary-side single-phase inverter and the secondary-side single-phase inverter 1 The imaginary axis component V 1q and the real axis component V 1d 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 side with a higher DC voltage and the inverter on the side with a lower DC voltage, based on the phase difference command value θ; The DC voltage V of the inverter on the side where the DC voltage is higher dc1 and the output voltage V of the inverter with the higher DC voltage 1 The imaginary axis component V 1q and the real axis component V 1d Therefore, the pulse width command value W of the output voltage of the inverter with the higher DC voltage is 1 The pulse width command value W 1 A calculation unit; The dead time error calculated from the product of the inverter switching frequency and the dead time is used as the pulse width command value W 1 The pulse width command value W obtained by the calculation unit 1 The pulse width command value W of the output voltage of the inverter with the higher DC voltage is added to 1 a pulse width command value compensation unit that compensates for The phase difference command value θ calculated by the phase difference command value θ calculation unit, the pulse width command value W of the output voltage of the inverter on the side with a higher DC voltage compensated by the pulse width command value compensation unit 1 , the set pulse width command value W of the output voltage of the inverter on the side with the lower DC voltage 2 and the dead time command value T d A control device for a bidirectional isolated DC-DC converter, characterized in that each semiconductor switching element of a primary side single-phase inverter and a secondary side single-phase inverter is controlled by a gate signal generated using the above.

2. The DC voltage of the inverter having a higher DC voltage among the primary side single-phase inverter and the secondary side single-phase inverter is V dc1 , the DC voltage of the inverter with the lower DC voltage is V dc2 The input DC voltage value V of the bidirectional isolated DC-DC converter is defined as in and V out Compare V in V out When V is higher than in V dc1 To V 0ut V dc2 V in V out When V is in V dc2 To V 0ut V dc1 a voltage detection and comparison unit for respectively allocating the voltages to the The fundamental wave components of the output voltages of the primary-side single-phase inverter and the secondary-side single-phase inverter are separated into a real axis (d-axis) component and an imaginary axis (q-axis) component, respectively, and the power command value P ref and the input DC voltage value or the output DC voltage value, and the equation (13) is calculated based on the equations (1), (2), (3), and (12), and the output voltage V of the inverter on the side with a higher DC voltage is calculated. 1 The imaginary axis component V 1q The imaginary axis component V 1q A calculation unit; [Equation 1] [Equation 2] [Equation 3] [0012] [0013] (V 1 is the output voltage of the inverter with the higher DC voltage, V 2 is the output voltage of the inverter with the lower DC voltage, V 1d is V 1 The real axis component of V 2d is V 2 The real axis component of V L is the applied voltage of the inductor L of the isolation transformer, I L is the current flowing through the inductor L, S 2 is the apparent power of the inverter with the lower DC voltage, I load is the current command value (load current), P 2 is the active power of the inverter with the lower DC voltage, Q 2 is the reactive power of the inverter with the lower DC voltage) The set pulse width command value W of the output voltage of the inverter with the lower DC voltage 2 and the DC voltage V of the inverter with the lower DC voltage assigned by the voltage detection comparison unit. dc2 Using this, the equation (15) is calculated, and the output voltage V of the inverter with the lower DC voltage is calculated. 2 The real axis component V 2d The real axis component V 2d a calculation unit, [Equation 15] The phase difference command value θ calculation unit calculates V obtained when the fundamental wave power factor cos γ of the inverter on the side with the lower DC voltage expressed by equations (4) and (5) is 1. 1d =V 2d Based on this, the real axis component V 2d V calculated by the calculation unit 2d The output voltage V of the inverter with the higher DC voltage 1 The real axis component V 1d and the real axis component V 1d and the imaginary axis component V 1q The output voltage V of the inverter with the higher DC voltage calculated by the calculation unit 1 The imaginary axis component V 1q and calculate the equation (16) using the above to obtain a phase difference command value θ between the output voltages of the inverter with the higher DC voltage and the inverter with the lower DC voltage. [Equation 4] [Equation 5] [0016] The pulse width command value W 1 The calculation unit calculates the output voltage V of the inverter on the side where the DC voltage is higher. 1 The real axis component V 1d and the imaginary axis component V 1q The output voltage V of the inverter with the higher DC voltage calculated by the calculation unit 1 The imaginary axis component V 1q and the DC voltage V of the inverter on the side where the DC voltage allocated by the voltage detection comparison unit is higher. dc1 and calculate the equation (14) using the above to obtain the pulse width command value W of the output voltage of the inverter with the higher DC voltage. 1 2. The control device for a bidirectional isolated DC-DC converter according to claim 1, wherein the following is obtained: [0014]

3. 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 The output voltage V of the inverter having a higher DC voltage among the primary-side single-phase inverter and the secondary-side single-phase inverter 1 The imaginary axis component V 1q and the V of the output voltage of the inverter with the lower DC voltage 2 The real axis component V 2d and the fundamental wave power factor cos γ of the inverter on the side with a lower DC voltage, which is set to 1 or less, the output voltage V of the inverter on the side with a higher DC voltage. 1 The real axis component V 1d The real axis component V 1d A calculation unit; Output voltage V of the inverter with the higher DC voltage 1 The imaginary axis component V 1q and the real axis component V 1d The real axis component V calculated by the calculation unit 1d 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 side with a higher DC voltage and the inverter on the side with a lower DC voltage; The real axis component V 1d The real axis component V calculated by the calculation unit 1d and the output voltage V of the inverter with the higher DC voltage 1 The imaginary axis component V 1q and the DC voltage V of the inverter with the higher DC voltage dc1 Therefore, the pulse width command value W of the output voltage of the inverter with the higher DC voltage is 1 The pulse width command value W 1 a calculation unit, The phase difference command value θ calculated by the phase difference command value θ calculation unit, the pulse width command value W 1 The pulse width command value W of the output voltage of the inverter with the higher DC voltage calculated by the calculation unit 1 , the set pulse width command value W of the output voltage of the inverter on the side with the lower DC voltage 2 and the dead time command value T d A control device for a bidirectional isolated DC-DC converter, characterized in that each semiconductor switching element of a primary side single-phase inverter and a secondary side single-phase inverter is controlled by a gate signal generated using the above.

4. The DC voltage of the inverter having a higher DC voltage among the primary side single-phase inverter and the secondary side single-phase inverter is V dc1 , the DC voltage of the inverter with the lower DC voltage is V dc2 The input DC voltage value V of the bidirectional isolated DC-DC converter is defined as in and V out Compare V in V out When V is higher than in V dc1 To V 0ut V dc2 V in V out When V is in V dc2 To V 0ut V dc1 a voltage detection and comparison unit for respectively allocating the voltages to the The fundamental wave components of the output voltages of the primary-side single-phase inverter and the secondary-side single-phase inverter are separated into a real axis (d-axis) component and an imaginary axis (q-axis) component, respectively, and the power command value P ref and the input DC voltage value or the output DC voltage value, and the equation (13) is calculated based on the equations (1), (2), (3), and (12), and the output voltage V of the inverter on the side with a higher DC voltage is calculated. 1 The imaginary axis component V 1q The imaginary axis component V 1q A calculation unit; [Equation 1] [Equation 2] [Equation 3] [0012] [0013] (V 1 is the output voltage of the inverter with the higher DC voltage, V 2 is the output voltage of the inverter with the lower DC voltage, V 1d is V 1 The real axis component of V 2d is V 2 The real axis component of V L is the applied voltage of the inductor L of the isolation transformer, I L is the current flowing through the inductor L, S 2 is the apparent power of the inverter with the lower DC voltage, I load is the current command value (load current), P 2 is the active power of the inverter with the lower DC voltage, Q 2 is the reactive power of the inverter with the lower DC voltage) The set pulse width command value W of the output voltage of the inverter with the lower DC voltage 2 and the DC voltage V of the inverter with the lower DC voltage assigned by the voltage detection comparison unit. dc2 Using this, the equation (15) is calculated, and the output voltage V of the inverter with the lower DC voltage is calculated. 2 The real axis component V 2d The real axis component V 2d a calculation unit, [Equation 15] The real axis component V 1d The calculation unit calculates the imaginary axis component V 1q The output voltage V of the inverter with the higher DC voltage calculated by the calculation unit 1 The imaginary axis component V 1q and the real axis component V 2d The output voltage V of the inverter with the lower DC voltage calculated by the calculation unit 2 The real axis component V 2d Using the fundamental wave power factor cos γ of the inverter on the side with a lower DC voltage, which is set to 1 or less, equation (5) is calculated based on equations (3) and (4), and the output voltage V of the inverter on the side with a higher DC voltage is calculated. 1 The real axis component V 1d Seeking [Equation 3] [Equation 4] [Equation 5] The phase difference command value θ calculation unit calculates the imaginary axis component V 1q The output voltage V of the inverter with the higher DC voltage calculated by the calculation unit 1 The imaginary axis component V 1q and the real axis component V 1d The output voltage V of the inverter with the higher DC voltage calculated by the calculation unit 1 The real axis component V 1d Using the above, the equations (3), (4), (5), (13), (15), and (16) are calculated to determine a phase difference command value θ between the output voltages of the inverter on the side with a higher DC voltage and the inverter on the side with a lower DC voltage, [Equation 3] [Equation 4] [Equation 5] [0013] [Equation 15] [0016] The pulse width command value W 1 The calculation unit calculates the real axis component V 1d The output voltage V of the inverter with the higher DC voltage calculated by the calculation unit 1 The real axis component V 1d and the imaginary axis component V 1q The output voltage V of the inverter with the higher DC voltage calculated by the calculation unit 1 The imaginary axis component V 1q and the DC voltage V of the inverter on the side where the DC voltage allocated by the voltage detection comparison unit is higher. dc1 and calculate the equation (14) using the above to obtain the pulse width command value W of the output voltage of the inverter with the higher DC voltage. 1 4. The control device for a bidirectional isolated DC-DC converter according to claim 3, wherein the following is obtained: [0014]

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