Power supply circuit and power supply device

Abstract

To provide a power supply circuit capable of converting a DC power supply into an AC power supply at low cost.SOLUTION: A power supply circuit comprises: a first switch connected between a first power supply line and a first connection point; a second switch connected between the first connection point and a second connection point; a third switch connected between the second connection point and a third connection point; a fourth switch connected between the third connection point and a second power supply line; a first power supply part comprising a first DC power supply and a reactor that are connected in series, and having one end connected to the second connection point and the other end connected to a fourth connection point; a second DC power supply in which a positive electrode side terminal is connected to the first connection point and a negative electrode side terminal is connected to the third connection point; an H bridge comprising a fifth switch connected between the first power supply line and the fourth connection point and a sixth switch connected between the fourth connection point and the second power supply line, and having a high potential side connected to the first power supply line and a low potential side connected to the second power supply line; and an input capacitor connected between the first power supply line and the second power supply line.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a power supply circuit and a power supply device. [Background technology]

[0002] Conventionally, bidirectional DC / DC converters have been widely used, which control the output voltage of a DC power supply and exchange power with a DC power storage device of a different voltage. In such DC / DC converters, the DC power supply and the DC power storage device each normally require separate reactors, but a flying capacitor DC / DC converter that achieves a similar function using a single reactor has been reported (see, for example, Non-Patent Document 1). [Prior art documents] [Non-patent literature]

[0003] [Non-Patent Document 1] Miyashita et al., "Operational Verification of Battery Management System Using Flying Capacitor DC-DC Converter Applying Discontinuous Current Mode," Institute of Electrical Engineers of Japan, Semiconductor Power Conversion Study Group, 2019 Summary of the Invention [Problem to be solved by the invention]

[0004] In the case of power sources such as solar cells, whose output voltage and load capacity change depending on certain conditions, a DC / DC converter may be connected to an energy storage device such as a battery or capacitor. Many load devices, such as home appliances, operate on single-phase AC, converting the DC power supply to AC using an inverter. Therefore, when using a DC power supply with a fluctuating output voltage to convert it into an AC power supply, a DC / DC converter may be connected to an inverter. When a flying capacitor type DC / DC converter such as the one described above is connected to an inverter device, it is composed of a large number of power conversion switching elements and reactors, and as an emergency power source, there are issues with making the entire device smaller, more efficient, and less expensive.

[0005] The present invention has been made in view of the above circumstances, and has as its object to provide a power supply circuit capable of converting DC power to AC power at low cost. [Means for solving the problem]

[0006] A power supply circuit according to one aspect of the present invention includes a first switch that controls a current flowing between a first power supply line and a first connection point to be in a conductive state or a non-conductive state, a second switch that controls a current flowing between the first connection point and a second connection point to be in a conductive state or a non-conductive state, a third switch that controls a current flowing between the second connection point and a third connection point to be in a conductive state or a non-conductive state, a fourth switch that controls a current flowing between the third connection point and a second power supply line to be in a conductive state or a non-conductive state, and a first DC power supply and a reactor connected in series, one end of which is connected to the second connection point and the other end of which is connected to the second connection point. a first power supply unit having a positive terminal connected to the first connection point and a negative terminal connected to the third connection point; a fifth switch that controls a current flowing between the first power supply line and the fourth connection point to be in a conductive state or a non-conductive state; and a sixth switch that controls a current flowing between the fourth connection point and the second power supply line to be in a conductive state or a non-conductive state, the sixth switch including an H-bridge having a high potential side connected to the first power supply line and a low potential side connected to the second power supply line; and an input capacitor connected between the first power supply line and the second power supply line. The energy stored in the reactor is supplied to the input capacitor through a path connecting the first DC power supply and the second DC power supply in series, and the voltage across the input capacitor is substantially the same as the output voltage of the first DC power supply. .

[0007] In the power supply circuit according to an aspect of the present invention, a load is connected to the H-bridge, and both the first power supply unit and the load are grounded at the fourth connection point.

[0008] In the power supply circuit according to one aspect of the present invention, the voltage across the input capacitor is greater than the output voltage of either the first DC power supply or the second DC power supply.

[0009] Furthermore, a power supply device according to one embodiment of the present invention includes a power supply circuit and a control unit that controls the conduction state of each of the first switch, the second switch, the third switch, the fourth switch, the fifth switch, and the sixth switch.

[0010] In addition, in a power supply device according to one embodiment of the present invention, the control unit controls the conductive states of the first switch, the second switch, the third switch, and the fourth switch according to whether the fifth switch is controlled to a conductive state or whether the sixth switch is controlled to a conductive state.

[0011] In addition, in the power supply device according to one aspect of the present invention, the control unit controls the current flowing through the reactor in a predetermined cycle, and within the cycle there is a period during which the current flowing through the reactor becomes zero.

[0012] In a power supply device according to one aspect of the present invention, the control unit controls the potential at the fourth connection point as follows: The potential at approximately the center of the potentials across the input capacitor The fifth switch and the sixth switch are controlled so that

[0013] In the power supply device according to an aspect of the present invention, the control unit controls the first switch, the second switch, the third switch, and the fourth switch in response to control of the fifth switch and the sixth switch. [Effects of the Invention]

[0014] According to the present invention, it is possible to provide a power supply circuit capable of converting DC power to AC power at low cost. [Brief explanation of the drawings]

[0015] [Figure 1] 1 is a circuit diagram showing an example of a circuit configuration of a power supply device according to an embodiment; [Figure 2] 3 is a diagram for explaining a current path when power is supplied from a first DC power supply and a second DC power supply to a single-phase inverter of the power supply device according to the embodiment. FIG. [Figure 3] 10 is a diagram for explaining a current path when power is supplied from a second DC power supply to a first DC power supply in a power supply device according to an embodiment, and the first DC power supply supplies power to a single-phase inverter. FIG. [Figure 4] 4A and 4B are diagrams showing examples of current waveforms of a first DC power supply and a second DC power supply according to an embodiment, where Fig. 4A shows the current waveform of Fig. 2, and Fig. 4B shows the current waveform of Fig. 3. [Figure 5] FIG. 10 is a diagram showing simulation conditions according to the embodiment. [Figure 6] FIG. 5 is a diagram showing the current waveform of the first DC power supply and the current waveform of the second DC power supply obtained as a result of the simulation related to FIG. 4(A). [Figure 7] FIG. 5 is a diagram showing the current waveform of the first DC power supply and the current waveform of the second DC power supply obtained as a result of the simulation related to FIG. 4(B). [Figure 8] FIG. 4 is a diagram showing current waveforms of a first DC power supply and a second DC power supply at the time of mode switching, obtained as a result of a simulation according to the embodiment. [Figure 9] FIG. 10 is a diagram showing a voltage waveform of a capacitor obtained as a result of a simulation according to an embodiment. [Figure 10] FIG. 10 is a diagram showing an output current waveform obtained as a result of a simulation according to the embodiment. [Figure 11] FIG. 1 is a diagram showing an example of a circuit diagram in which a flying capacitor converter circuit and a single-phase inverter circuit according to the prior art are combined; DETAILED DESCRIPTION OF THE INVENTION

[0016] [Prior art] 11 shows an example of a circuit diagram in which a conventional flying capacitor converter circuit and a single-phase inverter circuit are combined. Problems with the conventional technology will be described with reference to this diagram. The circuit 90 is a combination of a conventional flying capacitor converter circuit 91 and a conventional single-phase inverter circuit 92.

[0017] The flying capacitor converter circuit 91 includes a battery 911, a reactor 912, a solar cell 913, a switch 914, a switch 915, a switch 916, and a switch 917. The flying capacitor converter circuit 91 exchanges power between the battery 911 and the solar cell 913 by causing the switches 914, 915, 916, and 917 to perform switching operations at predetermined timings. Note that the battery 911 and the solar cell 913 may be any devices capable of transmitting and receiving power.

[0018] The single-phase inverter circuit 92 includes an H-bridge configured with a switch 923, a switch 924, a switch 925, and a switch 926, a reactor 921, and a load 922. The single-phase inverter circuit 92 controls the H-bridge to convert the DC power supplied from the flying capacitor converter circuit 91 into single-phase AC power.

[0019] The single-phase inverter circuit 92 includes a capacitor 927 as an input capacitor. Typically, a large-capacity electrolytic capacitor is used as the input capacitor for a single-phase inverter circuit. Electrolytic capacitors have the disadvantages of being large in size and having a short lifespan. To compensate for these disadvantages, a small-capacity film capacitor is used as the capacitor 927 included in the single-phase inverter circuit 92. For this reason, it is necessary to increase the voltage applied to the capacitor 927 and impart a pulsation to the input voltage of the single-phase inverter circuit 92 that is twice the power supply frequency (i.e., the frequency of the power output by the single-phase inverter circuit 30).

[0020] The circuit 90 includes a reactor 93, a switch 94, and a switch 95 connected between a flying capacitor converter circuit 91 and a single-phase inverter circuit 92. The circuit 90 controls the current flowing through the reactor 93 by switching the switches 94 and 95 at predetermined timings, thereby controlling the voltage applied as the input voltage to the single-phase inverter circuit 92.

[0021] As described above, the prior art requires a reactor 93, a switch 94, and a switch 95 to connect the flying capacitor converter circuit 91 and the single-phase inverter circuit 92. In particular, the reactor 93, which constitutes the chopper, is heavy, resulting in an increase in the weight and size of the entire system. Furthermore, when DC power from the solar cell 913 is connected to the capacitor 927, which serves as a single-phase AC power source, or when the DC power is supplied to the single-phase load 922, power pulsation with a frequency component twice the power supply frequency occurs in the PV panel of the solar cell 913. From the perspective of MPPT (Maximum Power Point Tracking), it is desirable for the power extracted from the solar cell 913 to be a constant output according to the power supply cycle. To suppress this power pulsation, a large-capacity electrolytic capacitor is generally used as the capacitor 927. However, electrolytic capacitors have issues such as their large size and short lifespan. Furthermore, using an electrolytic capacitor increases system size, increases costs, and increases the frequency of maintenance.

[0022] [Embodiment] Hereinafter, this embodiment will be described with reference to the drawings.

[0023] [Power supply circuit configuration] 1 is a circuit diagram showing an example of the circuit configuration of a power supply device according to an embodiment. With reference to the diagram, an example of the circuit configuration of the power supply device 1 will be described. The power supply device 1 includes a power supply circuit 2 and a control unit 50. The power supply circuit 2 includes a first DC power supply 11, a reactor 12, a first switch S1, a second switch S2, a third switch S3, a fourth switch S4, a second DC power supply 21, an input capacitor 40, an H-bridge circuit 33, a reactor 31, and a load 32. In the following description, the configuration including the first DC power supply 11 and the reactor 12 may be referred to as a first power supply unit 10.

[0024] The input capacitor 40 is connected between a first power supply line PL1 connected to the high-potential side of the H-bridge circuit 33 and a second power supply line PL2 connected to the low-potential side of the H-bridge circuit 33. The input capacitor 40 is a small-capacity film capacitor. Here, the small capacity may be, for example, about 88 μF (microfarads). The voltage across the input capacitor 40 is greater than the output voltage of the first DC power supply 11 and greater than the output voltage of the second DC power supply 21. Specifically, the capacitance of the input capacitor 40 is set so that the voltage across the input capacitor 40 is greater than the output voltage of both the first DC power supply 11 and the second DC power supply 21.

[0025] For example, when the output voltage of the first DC power supply 11 becomes larger than the voltage across the input capacitor 40, the DC power stored in the first DC power supply 11 flows to the input capacitor 40 via the parasitic diode component of the second switch S2 and the parasitic diode component of the first switch S1. Therefore, the output voltage of the first DC power supply 11 and the voltage across the input capacitor 40 become substantially the same. Here, the "substantially the same" range refers to a range that takes into consideration voltage drops due to the reactor 12, the parasitic diode component of the second switch S2, and the parasitic diode component of the first switch S1.

[0026] Similarly, when the output voltage of the second DC power supply 21 becomes larger than the voltage across the input capacitor 40, the power stored in the second DC power supply 21 flows to the input capacitor 40 via the parasitic diode component of the first switch S1 and the parasitic diode component of the fourth switch S4. Therefore, the output voltage of the second DC power supply 21 and the voltage across the input capacitor 40 become substantially the same. Here, the "substantially the same" range refers to a range that takes into account the voltage drops due to the parasitic diode components of the first switch S1 and the fourth switch S4.

[0027] The first DC power supply 11 is a power supply capable of outputting DC power. The first DC power supply 11 may be a power supply with a unidirectional power flow such as a solar cell, or a power supply with a bidirectional power flow such as a battery. 。 R The reactor 12 is connected in series to the first DC power supply 11. The reactor 12 is connected in series to the positive terminal side of the first DC power supply 11. The reactor 12 may also be connected in series to the negative terminal side of the first DC power supply 11. The first DC power supply 11 and the reactor 12 (that is, the first power supply unit 10) connected in series have one end connected to the second connection point P2 and the other end connected to the fourth connection point P4.

[0028] The first switch S1 controls the current flowing between the first power line PL1 and the first connection point P1 to be in a conductive state or a non-conductive state. The second switch S2 controls the current flowing between the first connection point P1 and the second connection point P2 to be in a conductive state or a non-conductive state. The third switch S3 controls the current flowing between the second connection point P2 and the third connection point P3 to be in a conductive state or a non-conductive state. The fourth switch S4 controls the current flowing between the third connection point P3 and the second power line PL2 to a conductive state or a non-conductive state.

[0029] The first switch S1, the second switch S2, the third switch S3, and the fourth switch S4 may be, for example, field effect transistors (FETs). When the first switch S1, the second switch S2, the third switch S3, and the fourth switch S4 are FETs, the control unit 50 controls the gate voltage of each switch, thereby controlling the conduction state or the current value of the current flowing between the collector and the emitter.

[0030] The second DC power supply 21 has a positive terminal and a negative terminal. The positive terminal is connected to the first connection point P1, and the negative terminal is connected to the third connection point P3. The second DC power supply 21 may be a power supply with a unidirectional power flow, such as a solar cell, or a power supply with a bidirectional power flow, such as a battery. 。

[0031] The H-bridge circuit 33 has a high potential side connected to the first power supply line PL1 and a low potential side connected to the second power supply line PL2. The H-bridge circuit 33 includes a fifth switch S5, a sixth switch S6, a seventh switch S7, and an eighth switch S8 as components. The fifth switch S5 controls the current flowing between the first power line PL1 and the fourth connection point P4 to be in a conductive state or a non-conductive state. The sixth switch S6 controls the current flowing between the fourth connection point P4 and the second power line PL2 to a conductive state or a non-conductive state. The seventh switch S7 controls the current flowing between the first power line PL1 and the fifth connection point P5 to be in a conductive state or a non-conductive state. The eighth switch S8 controls the current flowing between the fifth connection point P5 and the second power line PL2 to a conductive state or a non-conductive state. The reactor 31 and the load 32 are connected to an H-bridge circuit 33. Specifically, the reactor 31 and the load 32 are connected in series between a fourth connection point P4 and a fifth connection point P5.

[0032] The fifth switch S5, the sixth switch S6, the seventh switch S7, and the eighth switch S8 may be, for example, FETs. When the fifth switch S5, the sixth switch S6, the seventh switch S7, and the eighth switch S8 are FETs, the control unit 50 controls the gate voltage of each switch, thereby controlling the value of the current flowing between the collector and the emitter.

[0033] The control unit 50 controls the conduction states of the first switch S1, the second switch S2, the third switch S3, the fourth switch S4, the fifth switch S5, the sixth switch S6, the seventh switch S7, and the eighth switch S8 (hereinafter simply referred to as switches). Specifically, the control unit 50 controls the conduction states of the switches so as to exchange power between the first DC power source 11 and the second DC power source 21. Furthermore, the control unit 50 converts power stored in at least one of the first DC power source 11 or the second DC power source 21 into single-phase AC power by controlling the conduction states of the switches.

[0034] Here, the DC converter circuit and the single-phase inverter circuit included in the power supply circuit 2 are grounded to a common ground point at the fourth connection point P4. Specifically, the first power supply unit 10 included in the DC converter circuit and the load 32 connected to the single-phase inverter circuit are both grounded at the fourth connection point P4. Therefore, the switching operation for operating the DC converter circuit and the switching operation for operating the single-phase inverter circuit influence each other, and therefore the control unit 50 needs to control the switches so as to transfer the DC power of the first DC power source 11 and the second DC power source 21 to the input capacitor 40, and to supply the DC power stored in the input capacitor 40 to the load 32 as single-phase AC power.

[0035] [Power supply operating mode] Next, we will explain the current paths in the power supply device 1. Here, the control unit 50 controls the conduction state of each switch to control the supply and receipt of power among the first DC power supply 11, the second DC power supply 21, the reactor 12, and the input capacitor 40. In the following description, the term "current path" refers to a path through which power moves. The four current paths of the power supply device 1, ie, the first current path R1 to the fourth current path R4, will be described below.

[0036] The first current path R1 supplies power from the first DC power supply 11 to the reactor 12. The second current path R2 supplies power from the first DC power supply 11 and the reactor 12 to the input capacitor 40. The third current path R3 supplies power from the first DC power supply 11, the reactor 12, and the second DC power supply 21 to the input capacitor 40. The fourth current path R4 supplies power from the second DC power supply 21 to the first DC power supply 11. The control unit 50 controls the state of any one of the first current path R1 to the fourth current path R4, thereby controlling the exchange of power.

[0037] The power supply device 1 has two current path switching modes: an upper arm mode and a lower arm mode. In the upper arm mode, power can be extracted from the first DC power supply 11 when the fifth switch S5 of the H-bridge circuit 33 is controlled to a conductive state. In the lower arm mode, power can be extracted from the first DC power supply 11 when the sixth switch S6 of the H-bridge circuit 33 is controlled to a conductive state. The control unit 50 controls the first switch S1, the second switch S2, the third switch S3, and the fourth switch S4 in accordance with the control of the fifth switch S5 and the sixth switch S6. That is, the power supply device 1 switches between the upper arm mode and the lower arm mode in accordance with the control status of the inverter circuit, so that it can extract power from the second DC power supply 21 regardless of whether the upper or lower switch of the H-bridge is on.

[0038] The control unit 50 calculates the average value I of the current flowing into the input capacitor 40. dc_ave and the average value I of the current flowing out from the second DC power supply 21 pv_dc The current in each part is controlled according to the magnitude relationship. Specifically, the power supply device 1 includes a current value acquisition unit (not shown) to acquire an average value I of the current flowing into the input capacitor 40.dc_ave and the average value I of the current flowing out from the second DC power supply 21 pv_dc The current value comparison unit (not shown) compares the obtained current values ​​and determines whether the mode is a first mode or a second mode defined below.

[0039] More specifically, when the following formula (1) is satisfied, the control unit 50 controls the switch in the first mode. This means that power is supplied to the capacitor 40 from both the first DC power supply 11 and the second DC power supply 21.

[0040]

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[0041] Furthermore, when the following formula (2) is satisfied, the control unit 50 controls the switch in the second mode. This means that power is supplied from the second DC power supply 21 to the first DC power supply 11, and power is supplied from the first DC power supply 11 to the capacitor 40.

[0042]

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[0043] 2 is a diagram illustrating a current path in the first mode of the power supply device according to the embodiment. The current path in the first mode will be described with reference to the same figure. Note that the arrows in the figure indicate the direction of current flow. Fig. 2(A) shows the current path according to the first current path R1. Fig. 2(B) shows the current path according to the third current path R3. Fig. 2(C) shows the current path according to the second current path R2. The first mode includes the first current path R1, the third current path R3, and the second current path R2, as well as a zero current period during which the current is zero.

[0044] In the first mode, first, energy is stored in the reactor 12 from the first DC power supply 11 via the first current path R1. Next, power from the first DC power supply 11 and power from the second DC power supply 21 are supplied to the input capacitor 40 via the third current path R3. Finally, power is supplied from the first DC power supply 11 alone to the input capacitor 40 via the second current path R2. Thereafter, the control unit 50 controls the conductive state of all the switches in the first leg leg1 to a non-conductive state, resulting in a zero current period.

[0045] 3 is a diagram for explaining a current path in the second mode of the power supply device according to the embodiment. The current path in the second mode will be explained with reference to the same figure. Note that the arrows shown in the figure indicate the direction of current flow. Fig. 3(A) shows the current path according to the fourth current path R4. Fig. 3(B) shows the current path according to the first current path R1. Fig. 3(C) shows the current path according to the third current path R3. The second mode includes the fourth current path R4, the first current path R1, and the third current path R3, as well as a zero current period during which the current becomes zero.

[0046] In the second mode, the current flowing through the first DC power supply 11 changes between positive and negative during one carrier period. First, the power of the second DC power supply 21 is charged to the first DC power supply 11 via the fourth current path R4. Next, energy is stored in the reactor 12 from the first DC power supply 11 via the first current path R1. Finally, the power of the first DC power supply 11 and the power of the second DC power supply 21 are supplied to the input capacitor 40 via the third current path R3. Thereafter, the control unit 50 controls the conductive state of all switches in the first leg leg1 to a non-conductive state, resulting in a zero current period.

[0047] Here, in both the first mode and the second mode, the control unit 50 controls the switch so that the potential at the fourth connection point P4 is approximately 50% of the voltage across the input capacitor 40. Approximately 50% may be, for example, a range according to the allowable characteristics of the AC waveform of the AC power supply generated by the inverter circuit. If the potential at the fourth connection point P4 is close to 50% of the voltage across the input capacitor 40, the voltage utilization rate will be low, but a more suitable AC waveform can be generated.

[0048] 4 is a diagram showing the current waveform of the first DC power supply and the current waveform of the second DC power supply according to the embodiment. The diagram also shows the current for one cycle when the control unit 50 performs repetitive control. With reference to the diagram, the current i of the first DC power supply when the switches are controlled in the first mode and the second mode is shown. bat and the current waveform of the second DC power supply i pv The current waveform of the first DC power supply i bat indicates a current flowing out of the first DC power supply 11 or a current flowing into the first DC power supply 11. The current i pv indicates a current flowing out from the second DC power supply 21 or a current flowing into the second DC power supply 21. FIG. 4(A) shows the current waveform when the switch is controlled in the first mode, and FIG. 4(B) shows the current waveform when the switch is controlled in the second mode. The horizontal axis indicates time [s (seconds)], and the vertical axis indicates current value [A (amperes)].

[0049] 4A, periods D1, D2, and D3 indicate the periods during which a current flows through the first current path R1, the third current path R3, and the second current path R2, respectively. sw indicates a period obtained by adding a zero current period to periods D1 to D3.

[0050] First, the current i of the first DC power supply bat This article explains: During the period D1, energy is stored in the reactor 12 from the first DC power supply 11, so that the current i bat increases. During the period D2, the power of the first DC power supply 11 and the power of the second DC power supply 21 are supplied to the input capacitor 40, so that the current i bat decreases slowly. During period D3, power is supplied from the first DC power supply 11 alone to the input capacitor 40, so the voltage decreases more steeply than during period D2. Finally, a zero current period is provided, so that the conduction state of all the switches in the first leg (leg1) is controlled to a non-conduction state, and the current i bat becomes zero.

[0051] Next, the current i of the second DC power supply pv This article explains: During the periods D1 and D3, the current path does not pass through the second DC power supply 21, so the current i pv is zero. During the period D2, the power of the second DC power supply 21 is taken out to the input capacitor 40, and the current i pv The current i of the second DC power supply during the period D2 pv The value of is a value according to the amount of power generated by the second DC power source 21.

[0052] 4B, periods D1, D2, and D3 respectively indicate the period during which a current flows through the fourth current path R4, the period during which a current flows through the first current path R1, and the period during which a current flows through the third current path R3. The switching period Tsw indicates the period obtained by adding the zero-current period to periods D1 to D3.

[0053] First, the current i of the first DC power supply bat This article explains: During the period D1, the power of the second DC power supply 21 is charged into the first DC power supply 11, and the current i bat decreases. During the period D2, energy is stored in the reactor 12 from the first DC power supply 11, so that the current i bat increases. During period D3, the power of the first DC power supply 11 and the power of the second DC power supply 21 are supplied to the input capacitor 40, and therefore, the power decreases. Finally, a zero current period is provided, so that the conduction state of all the switches in the first leg (leg1) is controlled to a non-conduction state, and the current i bat becomes zero.

[0054] Next, the current i of the second DC power supply pv This article explains: During a period D1, the power of the second DC power supply 21 is extracted to the first DC power supply 11 via the reactor 12, and then during a period D3, the power of the second DC power supply 21 is again extracted to the input capacitor 40. Therefore, the current i pv increases in the period D1 and decreases in the period D3. The current i of the second DC power supply in the period D1 and the period D3 pv The slope of the curve is a value that corresponds to the amount of power generated by the second DC power source 21. During the period D2, the current path does not pass through the second DC power supply 21, so the current i pv is zero.

[0055] [Calculating the duty ratio] Next, a method for determining the switching period of the duty ratio in each of the first and second modes will be described. In the current path in the first mode described with reference to Figure 2, the relationship between the voltage across both ends of reactor 12 and the current is expressed by the following equation (3) according to Faraday's law.

[0056]

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[0057] Here, inductance L is the inductance of reactor 12, dt is the time during which current flows through reactor 12, and load current I L indicates the AC load current. From the above equation (3), the peak current of the inductor in each mode is shown in the following equation (4).

[0058]

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[0059] Here, the periods D1, D2, and D3 are periods in the first and second modes, respectively. sw is the period obtained by adding the zero current period to the periods D1 to D3. pk1 is the peak current value at the end of the period D1, and the peak current I pk2 is the peak current value at the end of period D2. Peak current I pk1 and peak current I pk2 This is also shown in Figure 4. The average current I of the second DC power supply 21 pv_ave and the average value I of the current flowing into the input capacitor 40 dc_ave is expressed by the following equation (5) from the peak current and conduction period in FIG. 4(A).

[0060]

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[0061] From the above equations (4) and (5), each duty ratio can be calculated using the following equation (6): Equation (6) is the duty applied to leg 1 and leg 2 when operating in the first mode.

[0062]

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[0063] Furthermore, for each current path in the second mode of operation, the duty ratio shown in the following equation (7) can be calculated using a similar calculation flow. Equation (7) is the duty applied to leg 1 and leg 2 when operating in the second mode.

[0064]

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[0065] The duty ratios of the above equations (6) and (7) are given to each switch as shown in the below equation (8).

[0066]

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[0067] [Power supply control method] The power supply device 1 outputs single-phase AC power from a first DC power supply 11 through a power conversion circuit having a three-leg configuration. Here, the first leg (leg1) performs switching for inductor sharing and simultaneously controls the voltage of the input capacitor 40. The second leg (leg2) and the third leg (leg3) operate as single-phase inverters. The control unit 50 must determine the current path taking into consideration the on / off state of the switch of the second leg leg2, and therefore applies a duty to the second leg leg2 so that the current path is as shown in FIGS.

[0068] The pulsating component appearing in the DC input current is absorbed by the voltage compensation method and the current compensation method. The power P buf is twice the AC frequency. This magnitude is shown as the second term on the right side of equation (9) below.

[0069]

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[0070] In this embodiment, the pulsation is absorbed by a small-capacity film capacitor, so the detected v buf The control circuit controls only the DC component by eliminating the double frequency with a band-stop filter (BEF). buf It is preferable to set the average voltage applied to the inverter to a high value. The feedback control of the average voltage is performed by the first leg (leg1). The subsequent current control is performed by controlling the input power P in =V bat i bat and the power P that is charged and discharged by the input capacitor 40buf =V buf i c From the equivalent relationship, the output of the AVR (Automatic Voltage Regulator) (current command value i c ) to the ACR (Automatic Current Regulator) input (current command value i bat ) conversion is performed.

[0071]

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[0072] As a result, the current i that would normally flow into the input capacitor 40 c However, according to the power supply circuit 2, the current i flowing through the reactor 12 bat By controlling the voltage, the voltage is indirectly controlled. This operation eliminates the need to add a compensation inductor to the APD circuit, allowing for a reduction in the number of elements.

[0073] The third leg (leg3), which performs inverter control, is given a sinusoidal control input via PWM, while the second leg (leg2) is given a control input with the duty ratio shown in equation (8) above. Therefore, to prevent control interference, the control input of the second leg (leg2) is added to the control input of the third leg (leg3).

[0074] [simulation] Next, a simulation according to this embodiment will be described with reference to FIGS. 5 is a diagram showing simulation conditions according to the embodiment. In the simulation, the output rating was set to 500 [W (watts)]. Furthermore, in the simulation, grid interconnection was not performed, and a grid interconnection inductor and a resistive load of 20 [Ω (ohms)] were used. The input capacitor 40 for pulsation compensation was assumed to be a film capacitor and set to 100 [μF (microfarads)].

[0075] Specifically, the output power P of single-phase AC power outis 1500 [VA], and the voltage v of the first DC power supply 11 bat is 60 [V], and the voltage v of the second DC power supply 21 pv is 90[V], and the voltage v applied across the input capacitor 40 buf is set to 300 [V], and the inductance L of the reactor 31 a is 30 [μH], and the capacitance C of the input capacitor 40 buf is set to 100 [μH], the resistance value R of the load 32 is set to 6.67 [Ω], and the inductance L of the interconnection inductor b is 20 [mH], and the output voltage of single-phase AC power v out is set to 100 [Vrms] and 50 [Hz], and the switching frequency f sw was set to 10[kHz].

[0076] 6 is a diagram showing the current waveforms of the first DC power supply and the second DC power supply in the first mode obtained as a result of a simulation according to the embodiment, where the horizontal axis represents time [s] and the vertical axis represents current value [A]. As shown in the figure, a current discontinuous period in which the current value becomes zero can be confirmed every cycle.

[0077] 7 is a diagram showing the current waveforms of the first DC power supply and the second DC power supply in the second mode obtained as a result of a simulation according to the embodiment, where the horizontal axis represents time [s] and the vertical axis represents current value [A]. As shown in the figure, a current discontinuous period in which the current value becomes zero can be confirmed every cycle.

[0078] 8 is a diagram showing the current waveforms of the first DC power supply and the second DC power supply at the time of mode switching, obtained as a result of a simulation according to the embodiment, where the horizontal axis represents time [s] and the vertical axis represents current value [A]. The figure shows the current waveforms of the first DC power supply and the second DC power supply when operated in the first and second modes. It can be seen that in both the first and second modes, the APD circuit is able to reduce the pulsation that appears at double the frequency.

[0079] 9 is a diagram showing a voltage waveform of a capacitor obtained as a result of a simulation according to the embodiment, where the horizontal axis represents time [s] and the vertical axis represents voltage value [V]. The voltage applied across the input capacitor 40, v buf is stabilized at 300 [V] and is controlled to include the double frequency of 100 [Hz], thereby compensating for pulsation. As a result, as shown in Figure 8, the pulsation that appears at the double frequency can be reduced.

[0080] 10 is a diagram showing an output current waveform obtained as a result of a simulation according to the embodiment, where the horizontal axis represents time [s] and the vertical axis represents current value [A]. As shown in the figure, the output current i out This resulted in a clean waveform without distortion. This confirmed that the power supply device 1 operated properly. It was also confirmed that the pulsation component was properly compensated for by the single-phase power pulsation compensation.

[0081] [Summary of the embodiment] As described above, the power supply circuit 2 includes a DC / DC converter circuit and a single-phase AC inverter circuit, and these circuits are interconnected without the need for an interconnection reactor. Therefore, the power supply circuit 2 does not require the interconnection reactor (reactor 93 in FIG. 11) that was required in the prior art, and it is also possible to eliminate two switching elements (switches 94 and 95 in FIG. 11). Therefore, according to this embodiment, it is possible to prevent the power supply circuit 2 from becoming too large and increasing in cost.

[0082] Furthermore, according to this embodiment, the DC / DC converter circuit and the single-phase AC inverter circuit are grounded at the fourth connection point P4 in the power supply circuit 2. Therefore, according to this embodiment, the DC / DC converter circuit and the single-phase AC inverter circuit can be made to have a common ground level, so they can be connected to a common ground point (for example, the chassis of the vehicle on which the power supply device 1 is mounted), making them resistant to noise.

[0083] Furthermore, according to this embodiment, in the power supply circuit 2, the voltage across the input capacitor 40 is higher than the output voltage of either the first DC power supply 11 or the second DC power supply 21. Therefore, according to this embodiment, since the voltage across the input capacitor 40 is high, even if the voltage utilization rate drops due to switching, the low voltage utilization rate does not become a constraint on generating single-phase AC power.

[0084] Furthermore, according to this embodiment, the power supply device 1 includes the power supply circuit 2 and the control unit 50. Therefore, the power supply circuit 2 can be suitably controlled by the control unit 50.

[0085] Furthermore, according to this embodiment, the control unit 50 controls the switch in either the first mode or the second mode. Therefore, even when the DC / DC converter circuit and the single-phase AC inverter circuit are interconnected at the same ground point, the control unit 50 can perform either the DC converter operation or the single-phase AC inverter operation. Furthermore, according to the present embodiment, by controlling the conduction states of the first switch S1, the second switch S2, the third switch S3, and the fourth switch S4 in accordance with each mode, it is possible to share power from the first DC power supply 11 to the input capacitor 40 regardless of the conduction states of the fifth switch S5 and the sixth switch S6.

[0086] Furthermore, according to this embodiment, in the cycle in which the control unit 50 controls the switch, there is a period in which the current flowing through the reactor 12 becomes zero in both the first mode and the second mode. According to this embodiment, by using the discontinuous current mode having a period in which the current flowing through the reactor 12 becomes zero, it is possible to reduce the size of the reactor 12.

[0087] Furthermore, according to this embodiment, the control unit 50 controls the switch so that the potential at the fourth connection point P4 becomes approximately 50% of the voltage across the input capacitor 40. Furthermore, according to this embodiment, in the power supply circuit 2, the voltage across the input capacitor 40 is greater than the output voltages of both the first DC power supply 11 and the second DC power supply 21. Therefore, according to this embodiment, even if the voltage utilization rate is approximately 50%, this does not become a constraint on generating single-phase AC power.

[0088] Furthermore, according to this embodiment, the first leg leg 1 is controlled in response to the control of the second leg leg 2. Therefore, even if the DC / DC converter circuit and the single-phase AC inverter circuit are connected via a common ground point, the AC power waveform is not distorted by the switching required for conversion.

[0089] The above describes an embodiment of the present invention with reference to the drawings, but the specific configuration is not limited to the above-described embodiment, and design changes and the like are also included within the scope that does not deviate from the gist of the present invention. [Explanation of symbols]

[0090] REFERENCE SIGNS LIST 1...power supply device, 10...first power supply unit, 11...first DC power supply, 12...reactor, 20...DC converter circuit, 21...second DC power supply, 30...single-phase inverter circuit, 31...reactor, 32...load, 33...H-bridge circuit, 40...input capacitor, 50...control unit, S1...first switch, S2...second switch, S3...third switch, S4...fourth switch, S5...fifth switch, S6...sixth switch, S7...seventh switch, S8...eighth switch, PL1...first power supply line, PL2...second power supply line, P1...first connection point, P2...second connection point, P3...third connection point, P4...fourth connection point, 91...flying capacitor type converter circuit, 92...single-phase inverter circuit

Claims

1. a first switch that controls a current flowing between the first power supply line and the first connection point to a conductive state or a non-conductive state; a second switch that controls a current flowing between the first connection point and the second connection point to a conductive state or a non-conductive state; a third switch that controls a current flowing between the second connection point and the third connection point to a conductive state or a non-conductive state; a fourth switch that controls a current flowing between the third connection point and the second power line to a conductive state or a non-conductive state; a first power supply unit including a first DC power supply and a reactor connected in series, one end of which is connected to the second connection point and the other end of which is connected to the fourth connection point; a second DC power supply having a positive terminal connected to the first connection point and a negative terminal connected to the third connection point; an H-bridge including a fifth switch that controls a current flowing between the first power supply line and the fourth connection point to be in a conductive state or a non-conductive state, and a sixth switch that controls a current flowing between the fourth connection point and the second power supply line to be in a conductive state or a non-conductive state, the H-bridge having a high potential side connected to the first power supply line and a low potential side connected to the second power supply line; an input capacitor connected between the first power supply line and the second power supply line; Equipped with the energy stored in the reactor is supplied to the input capacitor through a path connecting the first DC power supply and the second DC power supply in series; a frequency of the voltage across the input capacitor is twice the frequency of the voltages output by the first DC power supply and the second DC power supply; power circuit.

2. A load is connected to the H-bridge, The first power supply unit and the load are both grounded at the fourth connection point.

2. The power supply circuit according to claim 1.

3. The voltage across the input capacitor is greater than the output voltage of either the first DC power supply or the second DC power supply.

3. The power supply circuit according to claim 1.

4. The power supply circuit according to any one of claims 1 to 3; a control unit that controls the conduction state of each of the first switch, the second switch, the third switch, the fourth switch, the fifth switch, and the sixth switch; A power supply device comprising:

5. 5. The power supply device according to claim 4, wherein the control unit controls the conduction states of the first switch, the second switch, the third switch, and the fourth switch according to whether the fifth switch is controlled to a conductive state or whether the sixth switch is controlled to a conductive state.

6. 6. The power supply device according to claim 5, wherein the control unit controls the current flowing through the reactor in a predetermined cycle, and the cycle includes a period during which the current flowing through the reactor becomes zero.

7. The control unit controls the fifth switch and the sixth switch so that the potential at the fourth connection point becomes a potential approximately at the center of the potentials at both ends of the input capacitor. The power supply device according to any one of claims 4 to 6.

8. The control unit controls the first switch, the second switch, the third switch, and the fourth switch in response to control of the fifth switch and the sixth switch. The power supply device according to any one of claims 4 to 7.

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