power supply

Abstract

To provide a power source device that can increase the efficiency of power transmission between two direct-current power sources.SOLUTION: A power source device A1 includes: a transformer 3 having a winding L1 and a winding L2; an input-output terminal pair T1 for connecting a direct-current power source B1; an input-output terminal pair T2 for connecting a direct-current power source B2; an inverter 1 electrically intervening between the input-output terminal pair T1 and the winding L1, in which a plurality of switching elements Q11 to Q14 is full-bridge connected in the inverter 1; an inverter 2 electrically intervening between the input-output terminal pair T2 and the winding L2, in which a plurality of switching elements Q21 to Q24 is full-bridge connected in the inverter 2; and a lifting pressure chopper circuit 4 including switching elements Q31, Q32. The lifting pressure chopper circuit 4 is connected between the inverter 2 and the input-output terminal pair T2.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present disclosure relates to a power supply device. [Background technology]

[0002] Conventionally, bidirectional DC / DC converters that perform bidirectional power conversion between two DC power sources have been known. For example, Patent Document 1 discloses a DAB (Dual Active Bridge) bidirectional DC / DC converter. Hereinafter, a DAB bidirectional DC / DC converter will be referred to as a "DAB circuit." The DAB circuit described in Patent Document 1 includes an isolation transformer, two full-bridge circuits, and two input / output terminal pairs. The two full-bridge circuits are connected to the primary and secondary sides of the isolation transformer, respectively. For example, DC power sources are connected to each of the two input / output terminal pairs. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2017-204998 Summary of the Invention [Problem to be solved by the invention]

[0004] In the DAB circuit described in Patent Document 1, in order to transfer power between two input / output terminal pairs (two DC power supplies) with high efficiency, it is preferable to perform soft switching (zero-voltage switching) when switching between the two full-bridge circuits to reduce switching losses. For example, by optimally designing the turns ratio and inductor of the isolation transformer according to the rated input voltage and rated output voltage (rated output current), soft switching is possible when switching in each full-bridge circuit at these rated voltages. However, because the circuit is designed to enable soft switching at these rated voltages, soft switching may become impossible if the voltage applied to each input / output terminal pair deviates from the rated value and becomes larger (smaller). In other words, voltage fluctuations in the two DC power supplies may prevent soft switching in each full-bridge circuit. Therefore, conventional DAB circuits have room for improvement in the power transfer efficiency between two DC power supplies.

[0005] The present disclosure has been made in view of the above circumstances, and has as its object to provide a power supply device that can achieve high efficiency in power transmission between two DC power sources. [Means for solving the problem]

[0006] The power supply device of the present disclosure includes a transformer having a first winding and a second winding, a first input / output terminal pair for connecting a first DC power supply, a second input / output terminal pair for connecting a second DC power supply, a first inverter electrically interposed between the first input / output terminal pair and the first winding and having a plurality of first switching elements connected in a full bridge configuration, a second inverter electrically interposed between the second input / output terminal pair and the second winding and having a plurality of second switching elements connected in a full bridge configuration, and a buck-boost chopper circuit including a third switching element, and the buck-boost chopper circuit is connected between the second inverter and the second input / output terminal pair.

[0007] In a preferred embodiment of the power supply device, the power supply device further includes a first voltage detector that detects a first DC voltage applied to a DC terminal of the first inverter, a second voltage detector that detects a second DC voltage applied to a DC terminal of the second inverter, and a first control unit that controls the step-up / step-down chopper circuit, wherein the first control unit controls the switching operation of the third switching element so that the first DC voltage and the second DC voltage are equal to each other.

[0008] In a preferred embodiment of the power supply device, the power supply device further includes a current detector that detects a first DC current flowing in a DC terminal of the second inverter, a third voltage detector that detects a third DC voltage (VE2) applied to the second input / output terminal pair, and a second control unit that controls the first inverter and the second inverter, wherein the second control unit has a setting unit that sets the second DC current flowing in the second input / output terminal pair, and controls the switching operations of the plurality of first switching elements and the plurality of second switching elements so that the first DC current becomes a calculated value obtained by multiplying a value obtained by dividing the third DC voltage by the second DC voltage by a set value of the second DC current.

[0009] In a preferred embodiment of the power supply device, the transformer has a turns ratio of the first winding to the second winding of 1:1.

[0010] In a preferred embodiment of the power supply device, the DC voltage applied to the first input / output terminal pair is greater than the DC voltage applied to the second input / output terminal pair. [Effects of the Invention]

[0011] In the power supply device of the present disclosure, the buck-boost chopper circuit is connected between the second inverter and the second input / output terminal pair, so that the DC voltage applied to the second inverter can be controlled to a constant voltage. This reduces the influence of voltage fluctuations occurring in the second DC power supply connected to the second input / output terminal pair, making it possible to perform soft switching in the first inverter or the second inverter. In other words, the power supply device of the present disclosure can achieve high efficiency in power transmission between two DC power supplies. [Brief explanation of the drawings]

[0012] [Figure 1] 1 is a circuit configuration diagram illustrating a power supply device according to the present disclosure. [Figure 2] FIG. 10 is a waveform diagram showing a simulation result of the power supply device of the present disclosure. [Figure 3] FIG. 10 is a waveform diagram showing a simulation result of a conventional DAB circuit that does not include a step-up / step-down chopper circuit. [Figure 4] FIG. 10 is a circuit diagram showing a power supply device according to a modified example of the present disclosure. DETAILED DESCRIPTION OF THE INVENTION

[0013] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A preferred embodiment of the power supply device of the present disclosure will be described below with reference to the drawings. In the following, identical or similar components will be designated by the same reference numerals and redundant description will be omitted.

[0014] 1 shows a power supply device A1 according to one embodiment. The power supply device A1 includes two input / output terminal pairs T1 and T2, two inverters 1 and 2, a transformer 3, a step-up / step-down chopper circuit 4, an inductor L4, multiple voltage detectors 51, 52, and 53, a current detector 61, and two control units 7 and 8.

[0015] The power supply device A1 is electrically connected between two DC power supplies B1 and B2. The DC power supply B1 is connected to an input / output terminal pair T1, and the DC power supply B2 is connected to an input / output terminal pair T2. Each of the two input / output terminal pairs T1 and T2 includes a high-potential side connection terminal and a low-potential side connection terminal. The power supply device A1 transmits power bidirectionally between these two input / output terminal pairs T1 and T2. In this embodiment, the power supply voltage of the DC power supply B1 is higher than the power supply voltage of the DC power supply B2. Therefore, when power is input from the DC power supply B1, the power supply device A1 steps down the input voltage from the DC power supply B1 and outputs it to the DC power supply B2. On the other hand, when power is input from the DC power supply B2, the power supply device A1 steps up the input voltage from the DC power supply B2 and outputs it to the DC power supply B1. Hereinafter, the power supply voltage and power supply current of the DC power supply B1 will be referred to as the "first power supply voltage E1" and "first power supply current I E1 ", and the power supply voltage and power supply current of DC power supply B2 are called "second power supply voltage E2" and "second power supply current I E2 Therefore, the first power supply voltage E1 is applied to the input / output terminal pair T1, and the first power supply current I E1 A second power supply voltage E2 is applied to the input / output terminal pair T2, and a second power supply current I E2 The first power supply voltage E1 is, for example, 300 V or more and 400 V or less, and the second power supply voltage E2 is, for example, 24 V or more and 60 V or less. Note that the first power supply voltage E1 and the second power supply voltage E2 are not limited to these examples.

[0016] The power supply device A1 is incorporated into, for example, a charge / discharge device. In this example, a DC power supply B1, for example, a system power supply (DC power transmission system) or a solar power generation device, is connected to the input / output terminal pair T1. Also, a storage battery or a capacitor, for example, is connected to the input / output terminal pair T2 as the DC power supply B1. The power supply device A1 converts the power input from, for example, the system power supply and outputs it to the storage battery, thereby charging the storage battery. On the other hand, the power supply device A1 converts the power input from the storage battery and outputs it to the system power supply, thereby discharging the storage battery. When charging the storage battery, the second power supply current I E2becomes a positive value, and when discharging the storage battery, the second power supply current I E2 These positive and negative values ​​may be reversed.

[0017] As will be understood from the configuration described in detail later, the two inverters 1 and 2 and the transformer 3 form a DAB bidirectional DC / DC converter (DAB circuit). As shown in Fig. 1, the inverter 1 is connected to the DC power supply B1 (input / output terminal pair T1) side of the transformer 3, and the inverter 2 is connected to the DC power supply B2 (input / output terminal pair T2) side of the transformer 3.

[0018] The transformer 3 is electrically connected between the two inverters 1 and 2. The transformer 3 includes two physically insulated windings L1 and L2. The two windings L1 and L2 are magnetically coupled to each other. In this embodiment, the turns ratio between the windings L1 and L2 (the turns ratio of the transformer 3) is, for example, 1:1. The turns ratio between the windings L1 and L2 is not limited to 1:1 and may be appropriately set based on the voltages applied to the two inverters 1 and 2. The transformer 3 transfers power input to the winding L1 to the winding L2 and transfers power input to the winding L2 to the winding L1. At this time, the transformer 3 performs a voltage transformation according to the turns ratio between the windings L1 and L2. In the example shown in FIG. 1, an inductor L4 is connected to one connection terminal of the winding L1. Unlike the example shown in FIG. 1, the inductor L4 may be omitted and replaced with the leakage inductance of the transformer 3. Also, unlike the example shown in FIG. 1, an additional inductor may be connected to one of the connection terminals of the winding L2.

[0019] Each of the two inverters 1 and 2 converts between DC voltage and AC voltage. In this embodiment, when power is supplied from DC power supply B1 to DC power supply B2, inverter 1 converts the DC voltage to AC voltage, and inverter 2 converts the AC voltage to DC voltage (rectification). On the other hand, when power is supplied from DC power supply B2 to DC power supply B1, inverter 2 converts the DC voltage to AC voltage, and inverter 1 converts the AC voltage to DC voltage (rectification).

[0020] The inverter 1 is electrically interposed between the input / output terminal pair T1 and the winding L1. The inverter 1 includes a DC end 11 and an AC end 12. As shown in FIG. 1, the DC end 11 and the AC end 12 each have a pair of connection terminals. The DC end 11 is connected to the input / output terminal pair T1, and the AC end 12 is connected to the winding L1 via an inductor L4 (note that the inductor L4 is connected between one connection terminal of the AC end 12 and one connection terminal of the winding L1). Hereinafter, the DC voltage applied to (the pair of connection terminals of) the DC end 11 will be referred to as the "first bus line voltage V BUS1 ", the DC current flowing through the DC terminal 11 (a pair of connection terminals) is referred to as "first bus line current I BUS1 In this embodiment, the DC terminal 11 is connected to the input / output terminal pair T1, so that the first bus line voltage V BUS1 and the first power supply voltage E1 have approximately the same value, and the first bus line current I BUS1 and the first power supply current I E1 are approximately the same value.

[0021] The inverter 1 includes multiple switching elements Q11 to Q14, which are connected in a full-bridge configuration. Each of the switching elements Q11 to Q14 switches between an ON state and an OFF state in response to a drive signal (e.g., a PWM signal) input from the control unit 8. As shown in FIG. 1, multiple diodes D11 to D14 are connected in anti-parallel to each of the switching elements Q11 to Q14. For ease of explanation, the parallel circuit of the switching element Q11 and the diode D11 is referred to as the switching unit SW11. Similarly, the parallel circuits of the switching elements Q12 to Q14 and the diodes D12 to D14 are referred to as the switching units SW12 to SW14, respectively. During DC-AC conversion, the inverter 1 alternately switches between an ON state and an OFF state for the pair of switching elements Q11 and Q14 and the pair of switching elements Q12 and Q13. During AC-DC conversion, the inverter 1 turns off each of the switching elements Q11 to Q14, and appropriately turns on each of the diodes D11 to D14.

[0022] The inverter 2 is electrically interposed between the input / output terminal pair T2 and the winding L2. The inverter 2 includes a DC end 21 and an AC end 22. As shown in FIG. 1, the DC end 21 and the AC end 22 each have a pair of connection terminals. The DC end 21 is connected to the step-up / step-down chopper circuit 4, and the AC end 22 is connected to the winding L2. Hereinafter, the DC voltage applied to the DC end 21 (the pair of connection terminals thereof) will be referred to as the "second bus line voltage V BUS2 ", and the DC current flowing through the DC terminal 21 (a pair of connection terminals) is referred to as "second bus line current I BUS2 "

[0023] The inverter 2 includes multiple switching elements Q21-Q24, which are connected in a full-bridge configuration. Each of the switching elements Q21-Q24 switches between an ON state and an OFF state in response to a drive signal (e.g., a PWM signal) input from the control unit 8. As shown in FIG. 1, multiple diodes D21-D24 are connected in anti-parallel to each of the switching elements Q21-Q24. For ease of explanation, the parallel circuit formed by the switching element Q21 and the diode D21 is referred to as the switching unit SW21. Similarly, the parallel circuits formed by the switching elements Q22-Q24 and the diodes D22-D24 are referred to as the switching units SW22-SW24, respectively. During DC-AC conversion, the inverter 2 alternately switches between an ON state and an OFF state for the pair of switching elements Q21, Q24 and the pair of switching elements Q22, Q23. During AC-DC conversion, the inverter 2 has a plurality of switching elements Q21 to Q24 each in an OFF state, and the diodes D21 to D24 appropriately conducting.

[0024] The buck-boost chopper circuit 4 is connected between the inverter 2 and the input / output terminal pair T2. In this embodiment, the buck-boost chopper circuit 4 steps down the voltage input from the inverter 2 and outputs it to the input / output terminal pair T2. The buck-boost chopper circuit 4 also steps up the voltage input from the input / output terminal pair T2 and outputs it to the inverter 2.

[0025] As shown in FIG. 1, the buck-boost chopper circuit 4 includes two switching elements Q31 and Q32, two diodes D31 and D32, an inductor L3, and a capacitor C. The two switching elements Q31 and Q32 are switched between an ON state and an OFF state in response to a drive signal input from the control unit 7. The two switching elements Q31 and Q32 are connected in series and connected to the DC terminal 21 of the inverter 2. In the example shown in FIG. 1, the switching element Q31 is connected to the high-potential side of the DC terminal 21 of the inverter 2, and the switching element Q32 is connected to the low-potential side. The diode D31 is connected in anti-parallel to the switching element Q31, and the diode D32 is connected in anti-parallel to the switching element Q32. The inductor L3 is connected to the connection point of the two switching elements Q31 and Q32 and the high-potential side connection terminal of the input-output terminal pair T2. The capacitor C is connected in parallel to the series circuit of the two switching elements Q31 and Q32. The step-up / step-down chopper circuit 4 is not limited to the above configuration.

[0026] When switching element Q32 is off, switching element Q31 performs switching operation, causing step-up / step-down chopper circuit 4 to function as a step-down circuit.When switching element Q31 is off, switching element Q32 performs switching operation, causing step-up / step-down chopper circuit 4 to function as a step-up circuit.

[0027] 1, the switching elements Q11 to Q14, Q21 to Q24, Q31, and Q32 are bipolar transistors. Alternatively, the switching elements Q11 to Q14, Q21 to Q24, Q31, and Q32 may be other transistors such as MOSFETs (Metal-Oxide-Semiconductor Field-Effect Transistors) and IGBTs (Insulated Gate Bipolar Transistors).

[0028] The voltage detector 51 detects the DC voltage (first bus line voltage V BUS1The voltage detector 51 detects the detected first bus line voltage V BUS1 is output to the control unit 7.

[0029] The voltage detector 52 detects the DC voltage (second bus line voltage V BUS2 The voltage detector 52 detects the detected second bus line voltage V BUS2 are output to the respective control units 7 and 8.

[0030] The voltage detector 53 detects the DC voltage (second power supply voltage E2) applied to the input / output terminal pair T2. The voltage detector 53 outputs the detected second power supply voltage E2 to the control unit 8.

[0031] The current detector 61 detects the DC current flowing through the DC terminal 21 of the inverter 2 (i.e., the second bus line current I BUS2 1, the current detector 61 is disposed on a connection line connected to a connection terminal on the low potential side of the DC end 21, but unlike this example, the current detector 61 may be disposed on a connection line connected to a connection terminal on the high potential side of the DC end 21. The current detector 61 detects the second bus line current I BUS2 is output to the control unit 8.

[0032] The control unit 7 controls the step-up / step-down chopper circuit 4 by inputting drive signals to the multiple switching elements Q31 and Q32. In an example where the turns ratio of the transformer 3 is 1:1, the control unit 7 controls the first bus line voltage V BUS1 and the second bus line voltage V BUS2 and V are equal to each other. In a configuration in which the turns ratio of the transformer 3 is not 1:1, the following formula (1) becomes an formula corresponding to the turns ratio of the transformer 3. Specifically, if the number of turns of the winding L1 is Np and the number of turns of the winding L2 is Ns (i.e., the turns ratio of the transformer 3 is Np:Ns), the control unit 7 calculates Ns×V BUS1 = Np × V BUS2 The step-up / step-down chopper circuit 4 is controlled so as to satisfy the following.

number

[0033] For example, as shown in Fig. 1, the control unit 7 includes a differentiator 71 and a driver 72. The differentiator 71 calculates the first bus line voltage V BUS1 and the second bus line voltage V BUS2 Hereinafter, the calculation result (difference) of the differentiator 71 will be referred to as the "first difference." In this embodiment, as shown in FIG. 1, the differentiator 71 calculates the difference between the first bus line voltage V BUS1 to the second bus line voltage V BUS2 In a configuration in which the turns ratio of the transformer 3 is not 1:1, the differentiator 71 calculates the first difference by taking into account the turns ratio of the transformer 3. For example, the differentiator 71 calculates the first difference by subtracting the first bus line voltage V BUS1 The second bus line voltage V is calculated by multiplying the value of V by the number of turns Ns of the winding L2. BUS2 and the number of turns Np of winding L1, and then subtract the product of these to calculate a first difference. Driver 72 generates drive signals for switching elements Q31, Q32 so that the first difference input from differentiator 71 becomes 0 (zero). Driver 72 outputs the generated drive signals to switching elements Q31, Q32.

[0034] The control unit 8 controls the two inverters 1 and 2 by inputting drive signals to the switching elements Q11 to Q14 and Q21 to Q24. The control unit 8 controls the second bus line current I BUS2 The second power supply voltage E2 is the second bus line voltage V BUS2 The second power supply current I E2 Setting value I E2 _ ref The switching operations of the switching elements Q11 to Q14 and Q21 to Q24 are controlled so that the second power supply current I E2 Setting value I E2_ref is set by a setting unit 81, which will be described later.

number

[0035] 1, the control unit 8 includes a setting unit 81, a divider 82, a multiplier 83, a differentiator 84, and a driving unit 85. The setting unit 81 controls the second power supply current I E2 Setting value I E2 _ ref and set the second power supply current I E2 Setting value I E2 _ ref 1, the setting unit 81 may not be included in the control unit 8, but may be provided separately from the control unit 8. The divider 82 divides the second power supply voltage E2 by the second bus line voltage V BUS2 The divider 82 divides the result of the division (E2 / V BUS2 ) to the multiplier 83. The multiplier 83 multiplies the division result of the divider 82 by the second power supply current I E2 Setting value I E2 _ ref The multiplier 83 multiplies the result of the multiplication ((E2 / V BUS2 )×I E2 _ ref ) to the differentiator 84. The differentiator 84 outputs the multiplication result of the multiplier 83 and the second bus line current I BUS2 Hereinafter, the calculation result (difference) of the differentiator 84 will be referred to as the "second difference." In this embodiment, as shown in FIG. 1, the differentiator 84 calculates the second bus line current I BUS2 The second difference is calculated by subtracting the second difference from the first difference. The driver 85 generates drive signals for the switching elements Q11 to Q14 and Q21 to Q24 so that the second difference input from the differentiator 84 becomes 0 (zero). The driver 85 outputs the generated drive signals to the switching elements Q11 to Q14 and Q21 to Q24.

[0036] Next, an example of the switching operation of inverter 1 in power supply device A1 when power is supplied from DC power supply B1 to DC power supply B2 will be described with reference to Fig. 2. Fig. 2 shows the results of simulating the switching operation of inverter 1 in power supply device A1. In the simulation of power supply device A1, assuming a case where voltage fluctuation occurs in first power supply voltage E1, the first power supply voltage E1 was varied by ±10% based on a base case where first power supply voltage E1 was 320 V, and simulations were performed for three cases where first power supply voltage E1 was 320 V, 288 V (320 V - 10%), and 352 V (320 V + 10%). 2(a) shows the simulation results when the first power supply voltage E1 is 288V (-10% of 320V), FIG. 2(b) shows the simulation results when the first power supply voltage E1 is 320V, and FIG. 2(c) shows the simulation results when the first power supply voltage E1 is 352V (+10% of 320V). That is, FIG. 2(b) shows the simulation results for an ideal case where there is no fluctuation in the first power supply voltage E1, FIG. 2(a) shows the simulation results when the first power supply voltage E1 decreases, and FIG. 2(c) shows the simulation results when the first power supply voltage E1 increases. In addition, in the simulation of the power supply device A1, the second power supply voltage E2 was set to 48V, the second power supply current I E2 was set to 22A, the turns ratio of transformer 3 was 1:1 (the number of turns of winding L1 was 320, and the number of turns of winding L2 was 320), the excitation inductance of winding L1 of transformer 3 was 1mH, and the inductance of inductor L4 was 30μH.

[0037] Furthermore, as a comparison with the power supply device A1, a similar simulation was performed on a configuration (e.g., a conventional DAB circuit) that did not include the buck-boost chopper circuit 4. Figure 3 shows the results of a simulation of the switching operation of the inverter 1 in a configuration that does not include the buck-boost chopper circuit 4. In the simulation of the configuration that does not include the buck-boost chopper circuit 4, as in the simulation of the power supply device A1, voltage fluctuations in the first power supply voltage E1 were assumed, and simulations were performed for three cases in which the first power supply voltage E1 was changed. Unlike the simulation of the power supply device A1, in the simulation of the configuration that does not include the buck-boost chopper circuit 4, the turns ratio of the transformer 3 was not 1:1, but rather the number of turns of the winding L1 was 320 and the number of turns of the winding L2 was 48. The other values ​​were the same as those in the simulation of the power supply device A1.

[0038] 2(a) to 2(c) and 3(a) to 3(c) show switching waveforms in switching unit SW11 of inverter 1. In each of FIGS. 2(a) to 2(c) and 3(a) to 3(c), the upper part shows a waveform indicating a drive signal (PWM signal) input to switching unit SW11 (switching element Q11), the middle part shows a waveform of a voltage (hereinafter referred to as "switching voltage") applied to switching unit SW11, and the lower part shows a waveform of a current (hereinafter referred to as "switching current") flowing through switching unit SW11. Note that the waveforms in switching unit SW14 are the same as those in switching unit SW11, and the waveforms in switching units SW12 and SW13 are phase-shifted but have substantially the same shape as those in switching unit SW11 (for example, the waveforms are inverted versions of those in switching unit SW11).

[0039] In power supply device A1, in all of FIGS. 2(a) to 2(c), the switching voltage of switching unit SW11 is 0V at time t2 when switching element Q11 turns on (switches from an off state to an on state). This is because diode D11 is conductive at time t1, before time t2, so the switching voltage is 0V. In each of FIGS. 2(a) to 2(c), the switching current of switching unit SW11 indicates a negative value at time t1, which indicates that diode D11 is conductive. Therefore, in power supply device A1, even if the first power supply voltage E1 changes, the switching unit turns on when the switching voltage is 0V, so it can be seen that soft switching is being performed.

[0040] On the other hand, in a configuration that does not include the buck-boost chopper circuit 4, as shown in Figures 3(b) and (c), at time t2 when the switching element Q11 turns on (switches from the off state to the on state), the switching voltage of the switching unit SW11 is 0V, so soft switching is performed, just like in the power supply device A1. However, in Figure 3(a), the switching element Q11 is turned on when the switching voltage of the switching unit SW11 is not 0V. In other words, in a configuration that does not include the buck-boost chopper circuit 4, soft switching may not occur when the first power supply voltage E1 changes.

[0041] Therefore, as can be seen from Figures 2 and 3, in a configuration that does not include a step-up / step-down chopper circuit 4, soft switching may not be possible if voltage fluctuations occur in the first power supply voltage E1, but it can be seen that in the power supply device A1, soft switching is possible even if voltage fluctuations occur in the first power supply voltage E1.

[0042] In the above simulation of power supply device A1, an example was shown in which first power supply voltage E1 fluctuated, but when second power supply voltage E2 fluctuates, soft switching is similarly performed on switching elements Q11-Q14 of inverter 1. Furthermore, in the above simulation of power supply device A1, a case was shown in which power is supplied from DC power supply B1 to DC power supply B2 (for example, when a storage battery is being charged), but conversely, soft switching is similarly performed on switching elements Q21-Q24 of inverter 2 when power is supplied from DC power supply B2 to DC power supply B1 (for example, when a storage battery is being discharged).

[0043] The power supply device A1 has the following functions and effects.

[0044] In the power supply device A1, the two inverters 1 and 2 and the transformer 3 form a DAB bidirectional DC / DC converter. The buck-boost chopper circuit 4 is connected between the inverter 2 and the input / output terminal pair T2. With this configuration, the buck-boost chopper circuit 4 can step up or step down the voltage between the inverter 2 and the input / output terminal pair T2. Therefore, even if voltage fluctuations occur in the second power supply voltage E2 (the power supply voltage of the DC power supply B2) applied to the input / output terminal pair T2, the buck-boost chopper circuit 4 can control the DC voltage applied to the inverter 2 (the voltage applied to the DC terminal 21) to a constant voltage. This reduces the impact of voltage fluctuations in the second power supply voltage E2 on the two inverters 1 and 2 and the transformer 3 (DAB circuit). In other words, the power supply device A1 is capable of soft switching even if voltage fluctuations occur in the second power supply voltage E2, thereby enabling high-efficiency power transmission between the two input / output terminal pairs T1 and T2.

[0045] The power supply device A1 includes a control unit 7 that controls the step-up / step-down chopper circuit 4. The control unit 7 controls the first bus line voltage V BUS1 and the second bus line voltage V BUS2 According to this configuration, the switching elements Q31 and Q32 are controlled so that the second bus line voltage V BUS2 is the first bus line voltage VBUS1 Therefore, the potential difference between both ends (DC terminals 11, 21) of the DAB circuit (two inverters 1, 2 and transformer 3) is constant regardless of voltage fluctuations of the two DC power supplies B1, B2. Therefore, even if voltage fluctuations occur in the first power supply voltage E1 and the second power supply voltage E2, the first bus line voltage V BUS1 and the second bus line voltage V BUS2 and are equal to each other, maintaining a state that is favorable for soft switching of each of inverters 1 and 2. That is, power supply device A1 is capable of soft switching in the DAB circuit without being affected by voltage fluctuations of DC power supplies B1 and B2, and therefore it is possible to achieve high efficiency in power transmission between the two input / output terminal pairs T1 and T2.

[0046] The power supply device A1 includes a control unit 8 that controls the two inverters 1 and 2. In the power supply device A1, if the power supplied (consumed) from the DAB circuit (the two inverters 1 and 2 and the transformer 3) to the buck-boost chopper circuit 4 is equal to the power consumed (supplied) by the DC power supply B2, the second bus line voltage V BUS2 and the second bus line current I BUS2 The power due to the second power supply voltage E2 and the second power supply current I E2 Therefore, there is no excess or deficiency in the power due to the second bus line voltage V BUS2 is controlled to be constant, and the second bus line current I BUS2 If the second power supply current I E2 Therefore, in the power supply device A1, the control unit 8 controls the second bus line current I so as to satisfy the above formula (2). BUS2 The second power supply voltage E2 is the second bus line voltage V BUS2 The second power supply current I E2 Setting value I E2 _ ref Therefore, the power supply device A1 controls the switching operations of the switching elements Q11 to Q14 and Q21 to Q24 so that the second bus line current I BUS2 By controlling the second power supply current I E2Therefore, when the DC power supply B2 is a storage battery, the power supply device A1 can perform constant current control of the charging current and discharging current of the storage battery.

[0047] In the power supply device A1, the transformer 3 has a turns ratio of 1:1 between the windings L1 and L2. In the power supply device A1, the voltage transformation between the two input / output terminal pairs T1 and T2 (i.e., mutual conversion between the first power supply voltage E1 and the second power supply voltage E2) is performed by the voltage step-up or step-down operation of the buck-boost chopper circuit 4. Alternatively, it is possible to change the turns ratio of the transformer 3 and perform voltage transformation between the two input / output terminal pairs T1 and T2 by the transformer 3's transformation action. In this configuration, the buck-boost chopper circuit 4 primarily functions to suppress the effects of voltage fluctuations in the first power supply voltage E1 and the second power supply voltage E2. Therefore, in the power supply device disclosed herein, the turns ratio of the transformer 3 does not need to be 1:1. However, in a configuration in which the voltage transformation between the two input / output terminal pairs T1 and T2 is performed by the transformer 3's transformation action, the turns ratio of the transformer 3 needs to be designed according to the first power supply voltage E1 and the second power supply voltage E2. Furthermore, if the turns ratio of the transformer 3 is 1:1, it is easier to bring the coupling coefficient closer to 1 than if the turns ratio of the transformer 3 is not 1:1, and it is therefore possible to reduce the leakage magnetic flux in the transformer 3. Therefore, in the power supply device A1, by making the turns ratio of the transformer 3 1:1, it is possible to simplify the design of the transformer 3 and further improve the efficiency of power transmission between the two input / output terminal pairs T1 and T2.

[0048] Note that the provision of the buck-boost chopper circuit 4 in the power supply device A1 may increase the overall power loss of the power supply device A1 by the amount of power loss in the buck-boost chopper circuit 4. However, the power supply device A1 has the following advantages. First, the buck-boost chopper circuit 4 does not use an isolation transformer, so it does not need to operate at a higher frequency than when the transformer 3 is used to step up or step down the voltage, and can operate at a lower frequency (e.g., 5 kHz to 10 kHz). In other words, the power supply device A1 can reduce switching loss in the buck-boost chopper circuit 4. Second, even when there is a significant potential difference, such as when the first power supply voltage E1 is 400 V and the second power supply voltage E2 is 24 V, the power supply device A1 can configure the transformer 3 with a turns ratio of 1:1. As described above, configuring the transformer 3 with a turns ratio of 1:1 simplifies transformer design and enables the coupling coefficient to approach 1. Third, power supply device A1 can constantly keep the current crest factor in the DAB circuit close to 1, thereby reducing losses in each of windings L1 and L2. Considering the above, even if power loss occurs in the buck-boost chopper circuit 4, there are significant advantages to providing the buck-boost chopper circuit 4 in the DAB circuit.

[0049] In the above embodiment, an example has been shown in which the buck-boost chopper circuit 4 is connected between the inverter 2 and the input / output terminal pair T2, but different from this example, the buck-boost chopper circuit 4 may be connected between the inverter 1 and the input / output terminal pair T1. Two buck-boost chopper circuits 4 may be provided, one connected between the inverter 1 and the input / output terminal pair T1 and the other connected between the inverter 2 and the input / output terminal pair T2. Fig. 4 shows an example in which the buck-boost chopper circuit 4 is connected between the inverter 1 and the input / output terminal pair T1.

[0050] In the example shown in FIG. 4, the voltage detector 53 detects the DC voltage (i.e., the first power supply voltage E1) applied to the input / output terminal pair T1. The current detector 61 detects the DC current (i.e., the first bus line current I BUS14, the current detector 61 is disposed on a connection line connected to a connection terminal on the low potential side of the DC end 11, but may also be disposed on a connection line connected to a connection terminal on the high potential side of the DC end 11. The setting unit 81 detects the second power supply current I E2 Setting value I E2 _ ref Instead, the first power supply current I E1 Setting value I E1_ref Then, each of the control units 7 and 8 performs calculations similar to the above equations (1) and (2) using the detected values ​​of the voltage detectors 51 to 53 and the current detector 61 and the set value of the setting unit 81. For example, the control unit 7 controls the switching operations of the multiple switching elements Q31 and Q32 so as to satisfy the above equation (1), similar to the control unit 7 of the power supply device A1. The control unit 8 calculates the first bus line current I BUS1 The first power supply voltage E1 is the first bus line voltage V BUS1 The value divided by is the first power supply current I E1 Setting value I E1_ref The switching operations of the multiple switching elements Q11 to Q14 and the multiple switching elements Q21 to Q24 are controlled so that the calculated value obtained by multiplying the above equations is equal to the calculated value obtained by multiplying the above equations, that is, so that the following equation (3) is satisfied.

number

[0051] 4, similarly to the power supply device A1, even if voltage fluctuations occur in the first power supply voltage E1 and the second power supply voltage E2, soft switching of the inverters 1 and 2 is possible. Furthermore, in the example shown in Fig. 4, the voltage supplied to the DAB circuit (the two inverters 1 and 2 and the transformer 3) is low, so that elements with low withstand voltages can be used.

[0052] In the examples shown in FIGS. 1 and 4, the power supply voltage (first power supply voltage E1) of DC power supply B1 is greater than the power supply voltage (second power supply voltage E2) of DC power supply B2, but conversely, the power supply voltage (second power supply voltage E2) of DC power supply B2 may be greater than the power supply voltage (first power supply voltage E1) of DC power supply B1.

[0053] The power supply device according to the present disclosure is not limited to the above-described embodiment, and the specific configuration of each part of the power supply device according to the present disclosure can be freely modified in various ways. [Explanation of symbols]

[0054] A1: power supply unit, 1, 2: inverter, 11, 21: DC terminal, 12, 22: AC terminal, 3: transformer, L1, L2: winding, 4: step-up / step-down chopper circuit, 51, 52, 53: voltage detector, 61: current detector, 7, 8: control unit, T1, T2: input / output terminal pair, B1, B2: DC power supply, Q11 to Q14, Q21 to Q24, Q31, Q32: switching elements, L3, L4: inductor

Claims

1. a transformer having a first winding and a second winding; a first input / output terminal pair for connecting a first DC power supply; a second input / output terminal pair for connecting a second DC power supply; a first inverter electrically interposed between the first input / output terminal pair and the first winding, the first inverter including a plurality of first switching elements connected in a full bridge configuration; a second inverter electrically interposed between the second input / output terminal pair and the second winding, the second inverter including a plurality of second switching elements connected in a full bridge configuration; a step-up / step-down chopper circuit including a third switching element; a first voltage detector that detects a first DC voltage applied to a DC terminal of the first inverter; a second voltage detector that detects a second DC voltage applied to a DC terminal of the second inverter; a third voltage detector that detects a third DC voltage applied to the second input / output terminal pair; a current detector that detects a first DC current flowing through a DC terminal of the second inverter; a first control unit that controls the step-up / step-down chopper circuit; a second control unit that controls the first inverter and the second inverter; Equipped with the step-up / step-down chopper circuit is connected between the second inverter and the second input / output terminal pair, the first control unit controls a switching operation of the third switching element so that the first DC voltage and the second DC voltage are equal to each other; the second control unit has a setting unit that sets a second DC current flowing through the second input / output terminal pair, and controls the switching operations of the plurality of first switching elements and the plurality of second switching elements so that the first DC current becomes a calculated value obtained by multiplying a value obtained by dividing the third DC voltage by the second DC voltage by a set value of the second DC current.

2. 2. The power supply device according to claim 1, wherein the transformer has a turns ratio between the first winding and the second winding of 1:

1.

3. 3. The power supply device according to claim 1, wherein the DC voltage applied to the first pair of input / output terminals is greater than the DC voltage applied to the second pair of input / output terminals.

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