Distributed Power Systems

Abstract

To provide a distributed power supply system capable of supplying single-phase AC power with reduced distortion when supplying power to a single-phase load and a three-phase load during self-sustained operation.SOLUTION: The distributed power supply system includes a power conversion device that converts DC power output from a distributed power supply into single-phase AC power, and supplies single-phase AC power to a single-phase load and supplies three-phase AC power to a three-phase load during self-sustained operation. The distributed power supply system further includes: a three-phase AC power generator that generates the three-phase AC power on the basis of the DC power output from the distributed power supply; and a distortion suppression mechanism that suppresses the distortion of the AC voltage supplied to the single-phase load.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a distributed power system that is connected to a commercial power grid and includes a power conversion device that can supply power from a distributed power source to a three-phase load and a single-phase load during stand-alone operation. [Background technology]

[0002] Conventionally, a distributed power supply system has been proposed that combines a single-phase power conditioner that converts DC power output from a distributed power supply such as a storage battery or a solar cell into single-phase AC power, and a single-phase to three-phase converter that converts single-phase AC power into three-phase AC power, to supply power to a single-phase load and a three-phase load when connected to a commercial power grid or during stand-alone operation (see, for example, Patent Documents 1 and 2).

[0003] However, in such a distributed power system, when power is supplied to three phases, the single-phase to three-phase converter has characteristics as a nonlinear load when viewed from the single-phase power conditioner, which results in large distortion in the output voltage of the single-phase power conditioner, i.e., the voltage applied to the single-phase load, which may lead to malfunctions and failures of equipment connected as single-phase loads, and may limit the equipment that can be connected as single-phase loads. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Patent No. 4536027 [Patent Document 2] Japanese Patent Application Laid-Open No. 2008-295133 Summary of the Invention [Problem to be solved by the invention]

[0005] The present invention has been made in consideration of the above-mentioned problems, and has an object to provide a distributed power system that can supply single-phase AC power with little distortion when supplying power to single-phase loads and three-phase loads during stand-alone operation. [Means for solving the problem]

[0006] To solve the above problems, the present invention provides: A distributed power supply system including a power conversion device that converts DC power output from a distributed power supply into single-phase AC power, and that supplies single-phase AC power to a single-phase load and three-phase AC power to a three-phase load during stand-alone operation, a three-phase AC power generation device that generates the three-phase AC power based on the DC power output from the distributed power source; a distortion suppression mechanism for suppressing distortion of the AC voltage supplied to the single-phase load; The present invention is characterized by the following features.

[0007] According to this, even if the three-phase AC power generation device has characteristics as a nonlinear load, the distortion suppression mechanism is provided, and therefore distortion occurring in the AC voltage supplied to the single-phase load from the power conversion device connected to the three-phase AC power generation device during stand-alone operation is suppressed. Therefore, when the power conversion device and the three-phase AC power generation device are combined to supply three-phase AC power to the three-phase load during stand-alone operation, single-phase AC power with little distortion can be supplied to the single-phase load. As the distributed power source, various power sources such as storage batteries, solar cells, and fuel cells can be used.

[0008] In addition, in the present invention, The distortion suppression mechanism includes: the three-phase AC power generation device that generates the three-phase AC power by converting the single-phase AC power output from the power conversion device into the three-phase AC power; a smoothing device that smoothes the voltage of the three-phase AC power generated by the three-phase AC power generation device; a first single-phase power supply line that supplies the AC power of any one phase of the three-phase AC power, the voltage of which has been smoothed by the smoothing device, to the single-phase load; The above formula may be used.

[0009] In this way, when the power conversion device and the three-phase AC power generation device are combined to supply three-phase AC power to a three-phase load during stand-alone operation, the single-phase load is supplied with AC power of any one phase of the three-phase AC power smoothed by the smoothing device, so that single-phase AC power with little distortion can be supplied.

[0010] In addition, in the present invention, the power conversion device includes: a converter that converts power output from the distributed power source into DC power; an inverter that converts the DC power into single-phase AC power and outputs the single-phase AC power; and a DC current path that inputs the DC power output from the converter to the inverter; The distortion suppression mechanism includes: a second single-phase power supply path that supplies the single-phase AC power output from the power conversion device to the single-phase load; the three-phase AC power generation device that generates the three-phase AC power by converting the DC power branched off from the DC power line and input into the three-phase AC power; The above formula may be used.

[0011] In this way, the three-phase AC power generation device is connected to a DC current path connecting the converter of the power conversion device and the inverter, while the single-phase AC power output from the power conversion device, i.e., the inverter, is supplied to the single-phase load through the second single-phase power supply path. In this way, the three-phase AC power generation device does not affect the single-phase power output from the power conversion device, so when the power conversion device and the three-phase AC power generation device are combined to supply three-phase AC power to the three-phase load during stand-alone operation, single-phase AC power with little distortion can be supplied to the single-phase load.

[0012] In addition, in the present invention, The distortion suppression mechanism includes: the three-phase AC power generating device; a second power conversion device connected to a stage preceding the three-phase AC power generation device and configured to convert the single-phase AC power output from the power conversion device into input power to be input to the three-phase AC power generation device; a power supply path that supplies the single-phase AC power output from the power conversion device to the second power conversion device; a third single-phase power supply line branching from the power supply line and supplying the single-phase AC power to the single-phase load; The above formula may be used.

[0013] In this way, the single-phase AC power output from the power conversion device is supplied to the second power conversion device disposed in front of the three-phase AC power generation device through the power supply path, and is also supplied to the single-phase load through a third single-phase power supply path branching from this power supply path. When the power conversion device and the three-phase AC power generation device are combined to supply three-phase AC power to the three-phase load during stand-alone operation, the third single-phase power supply path that supplies single-phase power to the single-phase load branches off from the power supply path. Since the three-phase power generating device is not directly connected to the line but is connected via the second power conversion device, single-phase AC power with little distortion can be supplied.

[0014] In addition, in the present invention, The second power conversion device may be a high power factor converter.

[0015] In addition, in the present invention, The distortion suppression mechanism includes: the three-phase AC power generating device; a second smoothing device connected to a stage preceding the three-phase AC power generation device and smoothing the single-phase AC power output from the power conversion device; a power supply path that supplies the single-phase AC power output from the power conversion device to the second smoothing device; a third single-phase power supply line branching from the power supply line and supplying the single-phase AC power to the single-phase load; The above formula may be used.

[0016] In this way, the single-phase AC power output from the power conversion device is supplied through the power supply path to the second smoothing device arranged upstream of the three-phase AC power generation device, and is also supplied to the single-phase load through a third single-phase power supply path branching off from this power supply path. When the power conversion device and the three-phase AC power generation device are combined to supply three-phase AC power to the three-phase load during stand-alone operation, the three-phase power generation device is not directly connected to the power supply path into which the third single-phase power supply path that supplies single-phase power to the single-phase load branches off, but is connected via the second smoothing device, so that single-phase AC power with little distortion can be supplied.

[0017] In addition, in the present invention, The three-phase AC power generating device may be a variable voltage variable frequency converter. [Effects of the Invention]

[0018] According to the present invention, it is possible to provide a distributed power system that can supply single-phase AC power with little distortion when supplying power to a single-phase load and a three-phase load during stand-alone operation. [Brief explanation of the drawings]

[0019] [Figure 1] 1 is a diagram showing a schematic configuration of a distributed power supply system according to a first embodiment of the present invention. [Figure 2] FIG. 2 is a diagram illustrating an example of a smoothing filter circuit according to the first embodiment of the present invention. [Figure 3] FIG. 4 is a diagram illustrating another example of a smoothing filter circuit according to the first embodiment of the present invention. [Figure 4] FIG. 4 is a diagram illustrating another example of a smoothing filter circuit according to the first embodiment of the present invention. [Figure 5] FIG. 4 is a diagram illustrating another example of a smoothing filter circuit according to the first embodiment of the present invention. [Figure 6] FIG. 2 is a diagram illustrating an example of a smoothing circuit according to the first embodiment of the present invention. [Figure 7] FIG. 10 is a diagram showing a schematic configuration of a distributed power supply system according to a second embodiment of the present invention. [Figure 8]FIG. 10 is a diagram showing a schematic configuration of a distributed power supply system according to a third embodiment of the present invention. [Figure 9] FIG. 10 is a diagram illustrating an example of a smoothing filter circuit according to a modified example of the third embodiment of the present invention. [Figure 10] 1 is a diagram showing a schematic configuration of a distributed power supply system according to a reference example of the present invention; DETAILED DESCRIPTION OF THE INVENTION

[0020] [Application example] Hereinafter, application examples of the present invention will be described with reference to the drawings.

[0021] FIG. 1 is a diagram showing a schematic configuration of a distributed power system 1 according to an application example of the present invention. The distributed power system 1 is equipped with a single-phase power conditioner 20 including a converter 12 connected to a storage battery 11 and an inverter 10. The converter 12 converts the voltage of DC power discharged from the storage battery 11 to a predetermined voltage and outputs it. The inverter 10 converts the DC power input from the converter 12 into single-phase AC power and outputs it from output terminals 101a and 101b. In the distributed power system 1, during grid-connected operation, single-phase three-wire AC power is supplied from the commercial power system 1a to the single-phase loads 2 and 3 via the output of the inverter 10, and power due to the single-phase voltage of the inverter 10 is supplied to the single-phase loads 2 and 3. During grid-connected operation, three-phase three-wire AC power is supplied from the commercial power system 1b to the three-phase load 9.

[0022] During stand-alone operation, relays 5a and 5b on the inverter 10 side are disconnected, relays 7a and 7b are connected from their disconnected state, and a variable voltage variable frequency inverter (VVVF inverter) 13 is connected to the inverter 10. Single-phase AC power is input to the VVVF inverter 13 from a power conditioner 20. The VVVF inverter 13 converts the single-phase AC power and outputs three-phase, three-wire AC power, which is input to a smoothing filter circuit 14. The smoothing filter circuit 14 smoothes the three-phase AC power output from the VVVF inverter 13. The three-phase AC power output from the smoothing filter circuit 14 is supplied to a three-phase load 9 via relays SW8a, 8b, and 8c. The VVVF inverter 13 is an inverter whose voltage and frequency can be freely controlled.

[0023] Power lines 106a and 106b branching from power lines 105a and 105c, respectively, which connect the smoothing filter circuit 14 and the three-phase load 9, are connected to the primary side of a transformer Tr. Power lines 107a, 107b, and 107b connected to the secondary side of the transformer Tr are connected to the single-phase loads 2 and 3 via relays SW6a, 6b, and 6c. During independent operation, the relays SW6a, 6b, and 6c are switched from the commercial power system 1a side to the transformer Tr side, and AC power output from the power conditioner 20 is also supplied to the single-phase loads 2 and 3 via the VVVF inverter 13, the smoothing filter circuit 14, and the transformer Tr.

[0024] 10 is a diagram showing a schematic configuration of a distributed power system 41 according to a reference example of the present invention. Components common to the distributed power system 1 are denoted by the same reference numerals and detailed description thereof will be omitted.

[0025] In the distributed power system 41, power lines 103a and 103b connected to the power conditioner 20 via the relays 7a and 7b are connected on the secondary side of the transformer Tr to the single-phase loads 2 and 3 via power lines 107a, 107b, and 107c on the one hand, and to the VVVF inverter 13 via power lines 110a and 110b on the other hand. In this way, in the distributed power system 41 as well, AC power is supplied from the power conditioner 20 to the single-phase loads 2 and 3 and the three-phase load 9 during independent operation.

[0026] When the VVVF inverter 13 is connected to the output terminals 101a and 101b of the power conditioner 20 and power is supplied to the three-phase load 9 via the VVVF inverter 13, as in the distributed power system 41, the VVVF inverter 13 operates as a nonlinear load, resulting in significant distortion in the output voltage of the power conditioner 20. As a result, a significantly distorted voltage is applied to the single-phase loads 2 and 3 from the power lines 103a and 103b, the transformer Tr, and the power lines 110a and 110b connecting the VVVF inverter 13 and the output terminals 101a and 101b of the power conditioner 20, through the power lines 107a, 107b, and 107c branching off from the secondary side of the transformer Tr. This may cause malfunction or failure of the devices connected as the single-phase loads 2 and 3, and limits the types of devices that can be connected as single-phase loads.

[0027] As described above, in the distributed power supply system 1 shown in FIG. 13 is similarly connected to output terminals 101a, 101b of power conditioner 20. However, in distributed power system 1, power lines 107a, 107b, 107c and transformer Tr that supply power to single-phase loads 2, 3 during islanded operation are connected to power lines 106a, 106b branching from two of power lines 105a, 105b, 105c that connect smoothing filter circuit 14 downstream of VVVF inverter 13 and three-phase load 9, thereby suppressing distortion of the AC voltage supplied to single-phase loads 2, 3. This relaxes restrictions on devices that can be connected as single-phase loads in distributed power system 1 during islanded operation.

[0028] Example 1 A distributed power system 1 according to a first embodiment of the present invention will be described in more detail below with reference to the drawings.

[0029] FIG. 1 is a diagram showing a schematic configuration of a distributed power system 1 according to a first embodiment of the present invention. The distributed power system 1 is equipped with a single-phase power conditioner 20 including a converter 12 connected to a storage battery 11 and an inverter 10. The converter 12 converts the voltage of DC power discharged from the storage battery 11 to a predetermined voltage and outputs it to the inverter 10 via DC buses 120a and 120b equipped with capacitors. The inverter 10 converts the DC power input via the DC buses 120a and 120b into single-phase AC power and outputs it from output terminals 101a and 101b. In this example, during grid-connected operation, relays 5a and 5b are connected to the output of the inverter 10, and relays SW6a, 6b, and 6c are connected to the commercial power system 1a side, so that single-phase three-wire AC power from the commercial power system 1a and power generated by the single-phase voltage of the inverter 10 are supplied to the single-phase loads 2 and 3. During grid-connected operation, relays SW8, 8b, and 8c are connected to the commercial power system 1b, and three-phase, three-wire AC power is supplied from the commercial power system 1b to the three-phase load 9 through three-phase power lines 4d, 4e, and 4f. Here, the storage battery 11 corresponds to a distributed power source of the present invention. The converter 12, the inverter 10, and the DC buses 120a and 120b correspond to a converter, an inverter, and a DC current circuit of the present invention, respectively. The power conditioner 20 corresponds to a power conversion device of the present invention.

[0030] During grid-connected operation, single-phase three-wire AC power (single-phase power) is supplied from commercial power system 1a to single-phase loads 2 and 3 via power lines 4a, 4b, and 4c. That is, a voltage of 100 V is applied between power lines 4a and 4b, a voltage of 100 V between power lines 4b and 4c, and a voltage of 200 V between power lines 4a and 4c. Power lines 4a, 4b, and 4c are connected to single-phase loads 2 and 3 via relays SW6a, 6b, and 6c, respectively. Furthermore, during grid-connected operation, output terminals 101a and 101b of inverter 10 are connected to power lines 4a, 4b, and 4c via relays 5a and 5b. At this time, power lines 102a and 102b connected to output terminals 101a and 101b of inverter 10 are connected to power lines 4a and 4c, respectively, and power line 102c connected to the midpoint of two capacitors connected in series between power lines 102a and 102b connected to output terminals 101a and 101b, respectively, is connected to power line 4b.

[0031] During stand-alone operation, relays 5a and 5b on the inverter 10 side are disconnected, and relays 7a and 7b are connected from their disconnected state, connecting variable voltage variable frequency inverter (VVVF inverter) 13 to inverter 10. This cuts off the connections between inverter 10 and single-phase loads 2 and 3 via power lines 102a, 102b, and 102c and power lines 4a, 4b, and 4c during grid-connected operation. Here, VVVF inverter 13 corresponds to the three-phase AC power generation device of the present invention.

[0032] During the stand-alone operation, the VVVF inverter 13 is supplied with a single-phase power through the power lines 103a and 103b connected to the output terminals 101a and 101b by the relays 7a and 7b, respectively. AC power is input to the VVVF inverter 13, which is an inverter capable of variably controlling the output voltage and frequency. Here, the VVVF inverter 13 also functions as a single-phase to three-phase converter that converts single-phase AC power to three-phase AC power. Three-phase, three-wire AC power is output from the VVVF inverter 13 and input to the smoothing filter circuit 14 via power lines 104a, 104b, and 104c. Because the three-phase AC power output from the VVVF inverter 13 is generally a quasi-sine wave pulse voltage, the smoothing filter circuit 14 smooths it to generate a sine wave. The three-phase AC power output from the smoothing filter circuit 14 is supplied to the three-phase load 9 via power lines 105a, 105b, and 105c via relays SW8a, 8b, and 8c, which are switched to the power conditioner 20 side. Here, the smoothing filter circuit 14 corresponds to the smoothing device of the present invention.

[0033] 2 to 5 show specific examples of the smoothing filter circuit 14. Fig. 2(A) shows the configuration of a smoothing filter circuit 141, Fig. 2(B) shows the configuration of a smoothing filter circuit 142, Fig. 3 shows the configuration of a smoothing filter circuit 143, Fig. 4(A) shows the configuration of a smoothing filter circuit 144, Fig. 4(B) shows the configuration of a smoothing filter circuit 145, Fig. 5(A) shows the configuration of a smoothing filter circuit 146, and Fig. 5(B) shows the configuration of a smoothing filter circuit 147.

[0034] Next, the configuration of the smoothing filter circuit 141 will be described with reference to FIG. 2(A). Resistor R1, inductor L1, resistor R4, and inductor L4 are connected in series to power line 104a connected to the VVVF inverter 13, in that order from the VVF inverter 13 side, with one end of capacitor C1 connected between inductor L1 and resistor R4. Resistor R2, inductor L2, resistor R5, and inductor L5 are connected in series to power line 104b connected to the VVVF inverter 13, in that order from the VVF inverter 13 side, with one end of capacitor C2 connected between inductor L2 and resistor R5. Resistor R3, inductor L3, resistor R6, and inductor L6 are connected in series to power line 104c connected to the VVVF inverter 13, in that order from the VVF inverter 13 side, with one end of capacitor C3 connected between inductor L3 and resistor R6. The other ends of capacitors C1, C2, and C3 are connected to each other.

[0035] Next, the configuration of the smoothing filter circuit 142 will be described with reference to FIG. 2(B). Elements that are the same as those in the smoothing filter circuit 141 are assigned the same reference numerals, and their description will be omitted. The smoothing filter circuit 142 differs from the smoothing filter circuit 141 in the way capacitors C4, C5, and C6 are connected. That is, in the smoothing filter circuit 142, one end of capacitor C4 is connected between inductance L1 and resistor R4, and the other end of capacitor C4, one end of capacitor C5, and one end of capacitor C6 are connected between inductance L2 and resistor R5, respectively. The other end of capacitor C5 and the other end of capacitor C6 are connected between inductance L3 and resistor R6.

[0036] Next, the configuration of the smoothing filter circuit 143 will be described with reference to Fig. 3. The same elements as those in the smoothing filter circuit 141 are denoted by the same reference numerals, and description thereof will be omitted. Except for the fact that the resistors R1, R2, R3, R4, R5, and R6 are omitted from the smoothing filter circuit 141, the smoothing filter circuit 143 has the same configuration as the smoothing filter circuit 141. That is, the smoothing filter circuit 143 is composed of inductors L1, L2, L3, L4, L5, and L6 and capacitors C1, C2, and C3.

[0037] Next, the configuration of the smoothing filter circuit 144 will be described with reference to Fig. 4(A). The same elements as those in the smoothing filter circuit 141 are denoted by the same reference numerals, and a description thereof will be omitted. The smoothing filter circuit 144 has the same configuration as the smoothing filter circuit 141, except that the resistors R4, R5, and R6 and the inductors L4, L5, and L6 are omitted from the smoothing filter circuit 141. That is, the smoothing filter circuit 144 has the resistors R1, R2, and R3, the inductors It consists of transistors L1, L2, and L3 and capacitors C1, C2, and C3.

[0038] Next, the configuration of the smoothing filter circuit 145 will be described with reference to Fig. 4(B). The same elements as those in the smoothing filter circuit 141 are denoted by the same reference numerals, and description thereof will be omitted. Except for the fact that the resistors R1, R2, R3, R4, R5, and R6 and the inductors L4, L5, and L6 are omitted from the smoothing filter circuit 141, the smoothing filter circuit 145 has the same configuration as the smoothing filter circuit 141. That is, the smoothing filter circuit 145 is composed of inductors L1, L2, and L3 and capacitors C1, C2, and C3.

[0039] Next, the configuration of the smoothing filter circuit 146 will be described with reference to Fig. 5(A). The same elements as those in the smoothing filter circuit 141 are denoted by the same reference numerals, and description thereof will be omitted. Except for the fact that the resistors R4, R5, R6, inductors L4, L5, L6, and capacitors C1, C2, C3 are omitted from the smoothing filter circuit 141, the smoothing filter circuit 146 has the same configuration as the smoothing filter circuit 141. That is, the smoothing filter circuit 146 is composed of resistors R1, R2, R3 and inductors L1, L2, L3.

[0040] Next, the configuration of the smoothing filter circuit 147 will be described with reference to Fig. 5(B). The same elements as those in the smoothing filter circuit 141 are denoted by the same reference numerals, and description thereof will be omitted. Except for the fact that the resistors R1, R2, R3, R4, R5, and R6 and the inductors L1, L2, L3, L4, L5, and L6 are omitted from the smoothing filter circuit 141, the smoothing filter circuit 146 has the same configuration as the smoothing filter circuit 141. That is, the smoothing filter circuit 146 is composed of capacitors C1, C2, and C3.

[0041] 6 shows the configuration of a smoothing circuit 16 that has the same function as the smoothing filter circuit 14 but a different configuration. The smoothing circuit 16 is used in place of the smoothing filter circuit 14 in FIG. 1. The smoothing circuit 16 includes a PFC converter 161 and a three-phase inverter 162. In the smoothing circuit 16, the PFC converter 161 is connected to the output side of the VVVF inverter 13, and the three-phase inverter 162 is connected downstream of the PFC converter 161. The smoothing circuit 16 having such a configuration functions as a sine wave output AC / AC converter, and has the function of smoothing the output from the VVVF inverter 13, similar to the smoothing filter circuit. In this case, the smoothing circuit 16 corresponds to the smoothing device of the present invention.

[0042] A power line 106a branching from power line 105a and a power line 106b branching from power line 105c are connected to the primary side of a transformer Tr. Power lines 107a, 107b, and 107c are connected to the secondary side of this transformer Tr. One-phase AC power of the three-phase AC voltage output from the smoothing filter circuit 14 is extracted by the power line 106a and the power line 106b. The extracted single-phase AC voltage is converted into a single-phase three-wire AC voltage by the transformer Tr. During stand-alone operation, relays SW6a, 6b, and 6c are switched from the commercial power system 1a side to the transformer Tr side, and the AC power output from the power conditioner 20 is also supplied to the single-phase loads 2 and 3 via the VVVF inverter 13, the smoothing filter circuit 14, and the transformer Tr. The transformer Tr is used to convert single-phase two-wire 200V AC power to single-phase three-wire 100V, and may be omitted depending on the combination of the rated voltage of the single-phase loads 2 and 3 and the output voltage of the power conditioner 20 (this also applies to the following embodiments). Here, the power lines 106a and 106b, the transformer Tr, and the power lines 107a to 107c correspond to the first single-phase power supply path of the present invention. Furthermore, the VVVF inverter 13, the power lines 104a to 104c, the smoothing filter circuit 14, the power lines 105a to 105c, the power lines 106a and 106b, the transformer Tr, and the power lines 107a to 107c constitute the distortion suppression mechanism of the present invention.

[0043] In this way, the power conditioner 20 capable of supplying single-phase AC power as an independent operation output is In a distributed power supply system combined with a VVVF inverter 13 that converts single-phase AC power to three-phase AC power, the three-phase AC voltage output from the VVVF inverter 13 is smoothed by a smoothing filter circuit 14 and supplied to a three-phase load 9, and one phase of the AC voltage is extracted and supplied to the single-phase loads 2 and 3, thereby suppressing distortion of the AC voltage supplied to the single-phase loads 2 and 3. This relaxes restrictions on devices that can be connected as single-phase loads during stand-alone operation.

[0044] Example 2 Second Embodiment A distributed power supply system 21 according to a second embodiment of the present invention will be described in detail below with reference to FIG.

[0045] Fig. 7 is a diagram showing a schematic configuration of a distributed power supply system 21. Components common to the distributed power supply system 1 shown in Fig. 1 are designated by the same reference numerals and detailed description thereof will be omitted.

[0046] In the distributed power supply system 21, the method of connecting the VVVF inverter 13 and the single-phase loads 2 and 3 to the power conditioner 20 is different from that in the distributed power supply system 1. In the distributed power system 21, the VVVF inverter 13 is connected to DC buses 120a and 120b that connect the converter 12 and the inverter 10 of the power conditioner 20. That is, in the distributed power system 21, the DC power output from the converter 12 to the inverter 10 is also input to the VVVF inverter 13 via power lines 108a and 108b branching off from the DC buses 120a and 120b. The input DC power is converted to three-phase, three-wire AC power in the VVVF inverter 13 and output to power lines 109a, 109b, and 109c. During independent operation, the relays SW8a, 8b, and 8c that connect the power lines 109a, 109b, and 109c to the three-phase load 9 are switched from the commercial power system 1b side to the VVVF inverter 13 side, and three-phase AC power is supplied from the power conditioner 20 to the three-phase load 9 via the VVVF inverter 13.

[0047] Power lines 103a and 103b, which are connected to output terminals 101a and 101b of inverter 10 via relays 7a and 7b, are connected to the primary side of transformer Tr. Power lines 107a, 107b, and 107c are connected to the secondary side of transformer Tr, and these are connected to single-phase loads 2 and 3 via relays SW6a, 6b, and 6c. During independent operation, relays 7a and 7b are closed, and relays SW6a, 6b, and 6c are switched from the commercial power system 1a side to the power conditioner 20 side, and single-phase three-wire AC power is supplied from power conditioner 20 to the single-phase loads 2 and 3 via transformer Tr. Here, power lines 103a and 103b, transformer Tr, and power lines 107a to 107c correspond to a second single-phase power supply path of the present invention. Furthermore, power lines 108a and 108b, VVVF inverter 13, power lines 103a and 103b, transformer Tr, and power lines 107a to 107c constitute a distortion suppression mechanism of the present invention.

[0048] Here, the VVVF inverter 13 is not connected to the output terminals 101a and 101b that supply AC power from the power conditioner 20 to the single-phase loads 2 and 3, so distortion caused by the VVVF inverter 13 in the output voltage of the power conditioner 20 does not occur, and a stable AC voltage can be supplied to the single-phase loads 2 and 3. This relaxes the restrictions on devices that can be connected as single-phase loads during stand-alone operation.

[0049] Example 3 Third Embodiment A distributed power supply system 31 according to a third embodiment of the present invention will be described in detail below with reference to FIG.

[0050] Fig. 8 is a diagram showing a schematic configuration of a distributed power supply system 31. Components common to the distributed power supply system 1 shown in Fig. 1 are designated by the same reference numerals and detailed description thereof will be omitted.

[0051] In the distributed power system 31, the method of connecting the VVVF inverter 13 and the single-phase loads 2 and 3 to the power conditioner 20 differs from that in the distributed power system 1, and a high power factor converter (PFC converter) 15 is provided in front of the VVVF inverter 13. In the distributed power system 31, power lines 103a and 103b, which are connected to output terminals 101a and 101b of an inverter 10 via relays 7a and 7b, are connected to the primary side of a transformer Tr. The secondary side of the transformer Tr is connected to power lines 110a and 110b, which are connected to a high-PFC converter 15, and to a power line 107b, which is connected to single-phase loads 2 and 3 via a relay SW6b. The power line 110a is connected to a power line 107a, which is connected to a single-phase load 2 via a relay SW6a. The power line 110b is connected to a power line 107c, which is connected to a single-phase load 3 via a relay SW6c. Here, the PFC converter 15 corresponds to a second power conversion device of the present invention. The transformer Tr and the power lines 107a to 107c correspond to a third single-phase power supply path of the present invention.

[0052] PFC converter 15 converts single-phase AC power into DC power (input power) and improves the power factor of the AC power. PFC converter 15 improves the power factor by switching the input single-phase AC current to approximate a sine wave, thereby suppressing distortion of the single-phase voltage. It stabilizes the AC output of VVVF inverter 13. Single-phase AC power input to PFC converter 15 via power lines 110a and 110b is converted into DC power, which is then input to VVVF inverter 13 via power lines 111a and 111b. VVVF inverter 13 converts the input DC power into three-phase AC power, which is then supplied to three-phase load 9 via power lines 109a, 109b, and 109c and relays SW8a, 8b, and 8c. Here, power lines 103a and 103b, transformer Tr, and power lines 110a and 110b correspond to the power supply path of the present invention.

[0053] Here, power lines 110a and 110b, which are connected to a PFC converter 15, and power lines 107a, 107c, and power line 107b branching from these are connected to the secondary side of transformer Tr, which is connected to the isolated output of power conditioner 20. That is, VVVF inverter 13 is connected to power conditioner 20 and transformer Tr via PFC converter 15. This makes it possible to suppress distortion in the single-phase AC voltage supplied to single-phase loads 2 and 3 via transformer Tr. This alleviates restrictions on devices that can be connected as single-phase loads during isolated operation. Here, power lines 103a and 103b, transformer Tr, power lines 110a and 110b, PFC converter 15, power lines 111a and 111b, VVVF inverter 13, and power lines 107a to 107c constitute a distortion suppression mechanism of the present invention.

[0054] (Variation) Next, smoothing filter circuits 17 and 18 will be described, which are arranged in front of the VVVF inverter 13 and have the same function as the PFC converter 15 shown in Fig. 8. The smoothing filter circuits 17 and 18 are each used in place of the PFC converter 15 shown in Fig. 8. Fig. 9(A) shows the configuration of the smoothing filter circuit 17, and Fig. 9(B) shows the configuration of the smoothing filter circuit 18.

[0055] In the smoothing filter circuit 17, a resistor R7, an inductor L7, and one end of a capacitor C4 are connected in series between a power line 17a connected to the transformer Tr and the VVVF inverter 13, in that order from the transformer Tr side. One end of the capacitor C4 is connected between a power line 17c connected to the transformer Tr and the VVVF inverter 13. This smoothing filter circuit 17 also makes it possible to make the output current closer to a sine wave and suppress distortion of the single-phase voltage. Here, the smoothing filter circuit 17 corresponds to the second smoothing device of the present invention.

[0056] The smoothing filter circuit 18 has the same configuration as the smoothing filter circuit 17, except that the capacitor C4 is omitted from the smoothing filter circuit 17, and therefore a detailed description thereof will be omitted. Such a smoothing filter circuit 18 can also make the output current closer to a sine wave and suppress distortion of the single-phase voltage. Here, the smoothing filter circuit 18 corresponds to the second smoothing circuit of the present invention.

[0057] <Appendix 1> A distributed power system (1, 21, 31) includes a power conversion device (20) that converts DC power output from a distributed power source (11) into single-phase AC power, and supplies single-phase AC power to single-phase loads (2, 3) and three-phase AC power to a three-phase load (9) during stand-alone operation, a three-phase AC power generation device (13) that generates the three-phase AC power based on DC power output from the distributed power source (11); a distortion suppression mechanism (14, 106a, 106b, 107a, 107b, 107c, 108a, 108b, 15, 110a, 110b) for suppressing distortion of the AC voltage supplied to the single-phase load (2, 3); A distributed power system (1, 21, 31) comprising: [Explanation of symbols]

[0058] 1, 21, 31, 41: Distributed power systems 1a, 1b: Commercial power system 2, 3: Single-phase load 9: Three-phase load 11: Storage battery 13: VVVF inverter 14: Smoothing filter circuit 20: Power conditioner 103a, 103b, 103c: Power line 105a, 105b, 105c: Power line 106a, 106b Tr: transformer

Claims

1. A distributed power system comprising a power conversion device that converts DC power output from a distributed power source into single-phase AC power, and that supplies single-phase AC power to single-phase loads and three-phase AC power to three-phase loads during stand-alone operation, a three-phase AC power generation device that generates the three-phase AC power based on the DC power output from the distributed power source; a distortion suppression mechanism for suppressing distortion of the AC voltage supplied to the single-phase load; Equipped with The distortion suppression mechanism includes: the three-phase AC power generation device that generates the three-phase AC power by converting the single-phase AC power output from the power conversion device into the three-phase AC power; a smoothing device that smoothes the voltage of the three-phase AC power generated by the three-phase AC power generation device; a first single-phase power supply line that supplies the AC power of any one phase of the three-phase AC power, the voltage of which has been smoothed by the smoothing device, to the single-phase load; A distributed power generation system comprising:

2. A distributed power system comprising a power conversion device that converts DC power output from a distributed power source into single-phase AC power, and that supplies single-phase AC power to single-phase loads and three-phase AC power to three-phase loads during stand-alone operation, a three-phase AC power generation device that generates the three-phase AC power based on the DC power output from the distributed power source; a distortion suppression mechanism for suppressing distortion of the AC voltage supplied to the single-phase load; Equipped with the power conversion device includes: a converter that converts power output from the distributed power source into DC power; an inverter that converts the DC power into single-phase AC power; and a DC current path that inputs the DC power output from the converter to the inverter; The distortion suppression mechanism includes: a second single-phase power supply for supplying the single-phase AC power output from the power conversion device to the single-phase load; A power supply line; the three-phase AC power generation device that generates the three-phase AC power by converting the DC power branched off from the DC power line and input into the three-phase AC power; A distributed power generation system comprising:

3. A distributed power supply system comprising a power conversion device that converts DC power output from a distributed power supply into single-phase AC power, and that supplies single-phase AC power to single-phase loads and three-phase AC power to three-phase loads during stand-alone operation, a three-phase AC power generation device that generates the three-phase AC power based on the DC power output from the distributed power source; a distortion suppression mechanism for suppressing distortion of the AC voltage supplied to the single-phase load; Equipped with The distortion suppression mechanism includes: the three-phase AC power generating device; a second power conversion device connected to a stage preceding the three-phase AC power generation device and configured to convert the single-phase AC power output from the power conversion device into input power to be input to the three-phase AC power generation device; a power supply path that supplies the single-phase AC power output from the power conversion device to the second power conversion device; a third single-phase power supply line branching from the power supply line and supplying the single-phase AC power to the single-phase load; A distributed power generation system comprising:

4. 4. The distributed power system according to claim 3, wherein the second power conversion device is a high power factor converter.

5. A distributed power system comprising a power conversion device that converts DC power output from a distributed power source into single-phase AC power, and that supplies single-phase AC power to a single-phase load and three-phase AC power to a three-phase load during stand-alone operation, a three-phase AC power generation device that generates the three-phase AC power based on the DC power output from the distributed power source; a distortion suppression mechanism for suppressing distortion of the AC voltage supplied to the single-phase load; Equipped with The distortion suppression mechanism includes: the three-phase AC power generating device; a second smoothing device connected to a stage preceding the three-phase AC power generation device and smoothing the single-phase AC power output from the power conversion device; a power supply path that supplies the single-phase AC power output from the power conversion device to the second smoothing device; a third single-phase power supply line branching from the power supply line and supplying the single-phase AC power to the single-phase load; A distributed power generation system comprising:

6. 6. The distributed power system according to claim 1, wherein the three-phase AC power generating device is a variable voltage variable frequency inverter.

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