Power conversion system

Abstract

This reduces unused power capacity, enabling system miniaturization, while also maintaining power input and output even when switching to a priority power source. [Solution] The system includes first and second fixed power converters 10 and 20 connected to first and second power sources 1 and 2, a variable power converter 100 connected to either the first or second power source 1 or 2, and a route switch A that switches the connection between the variable power converter 100 and the power source. The variable power converter 100 is connected to the power source with the higher priority among the power sources. When the priority of the power sources changes, the power supply capacity of at least the variable power converter 100 among the fixed power converters 10 and 20 and the variable power converter 100 is changed, and the route switch A is switched without interrupting the power at the output terminals of the fixed power converters 10 and 20 and the variable power converter 100.

Description

Technical Field

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[0003]

[0001] The present disclosure relates to a power conversion system.

Background Art

[0002] For the purposes of system stabilization, backup during power outages, peak shifting, etc., power sources such as storage batteries are connected to the power transmission and distribution system. In addition to stationary battery equipment, batteries mounted on moving bodies such as electric vehicles or plug-in hybrid vehicles are also connected to the power transmission and distribution system to exchange charge and discharge power.

[0003] Normally, for a set of storage batteries (power sources), a set of power converters is used, and the capacity of the power converter is determined from the output-capable capacity of the storage battery (power source) or the input / output power required by the system from the storage battery (power source).

[0004] In a system including two or more storage batteries (power sources), when operating the storage batteries (power sources) according to the usage priority, there are times when no power exchange is performed with the non-priority storage batteries (power sources), or only a small amount of power exchange is performed. In this case, the system has a large amount of unused power converter power capacity (surplus power capacity), and the system becomes larger by the amount of the surplus power capacity.

[0005] In Patent Document 1 below, in a system having a plurality of power sources such as a plurality of storage batteries and a plurality of power conversion units, when the priority power source is changed to another power source, by switching the path connecting the power source and the power converter, the capacity of the power conversion unit connected to the priority power source is improved by connecting the power conversion units corresponding to the non-priority power sources to the priority power source.

Prior Art Documents

Patent Documents

[0006]

Patent Document 1

Summary of the Invention

[0007] In Patent Document 1, when the priority power source is changed and the connection of the power conversion unit is switched, it is necessary to stop the power input and output to perform the switch, which may prevent the system from outputting the power required by the load connected to it.

[0008] This disclosure provides technology to solve the above-mentioned problems, and aims to provide a power conversion system that reduces the unused power capacity of a power conversion system equipped with multiple power sources, thereby enabling system miniaturization, and that can maintain power input and output even when switching priority power sources. [Means for solving the problem]

[0009] The power conversion system of this disclosure is n power supplies (where n is an integer greater than or equal to 2), Each of the aforementioned power supplies is connected to n fixed power conversion units, A variable power converter connected to one of the aforementioned power supplies, The system includes a path switch that switches the connection between one of the aforementioned power sources and the variable power conversion unit, The output terminal of the fixed power converter and the output terminal of the variable power converter are connected. The variable power conversion unit is connected to the power supply with the highest priority among the power supplies. If the priority of the aforementioned power supply is changed, The power supply capacity of at least the variable power conversion unit among the fixed power conversion unit and the variable power conversion unit is changed, and the switching operation of the route switch is performed without interrupting the power at the output terminal. [Effects of the Invention]

[0010] According to this disclosure, it is possible to reduce the unused power capacity of a power conversion system equipped with multiple power sources, thereby enabling miniaturization of the system, while also maintaining power input and output even when switching to a priority power source.

Brief Description of the Drawings

[0011] [Figure 1] It is a schematic configuration diagram showing a power conversion system according to Comparative Example 1. [Figure 2] It is a schematic configuration diagram showing a power conversion system according to Embodiment 1. [Figure 3] It is a diagram for explaining the reduction of the power capacity of the power conversion system according to Embodiment 1. [Figure 4] It is a schematic configuration diagram showing the conversion module of the power conversion system according to Embodiment 1. [Figure 5] It is a diagram for explaining the switching operation of the priority power supply according to Embodiment 1. [Figure 6] It is a schematic configuration diagram showing the power supply monitoring unit according to Embodiment 1. [Figure 7] It is a schematic configuration diagram showing a power conversion system according to Comparative Example 2. [Figure 8] It is a schematic configuration diagram showing a power conversion system according to Embodiment 2. [Figure 9] It is a diagram for explaining the switching operation of the priority lending grid according to Embodiment 2. [Figure 10] It is a schematic configuration diagram showing a power conversion system according to Comparative Example 3. [Figure 11] It is a schematic configuration diagram showing a power conversion system according to Embodiment 3. [Figure 12] It is a diagram for explaining the switching operation of the priority power supply according to Embodiment 3. [Figure 13] It is a diagram showing an example of the hardware of the management device according to the embodiment.

Modes for Carrying Out the Invention

[0012] Embodiment 1. [Power Conversion System of Comparative Example 1] Before explaining the power conversion system of Embodiment 1, the power conversion system of Comparative Example 1 will be explained based on FIG. FIG. 1 is a schematic configuration diagram of a power conversion system according to Comparative Example 1. As shown in FIG. 1, in the power conversion system according to Comparative Example 1, a first power supply system 1000 and a second power supply system 2000 are connected to a power line 40. The first power supply system 1000 includes a first power supply 1 and a first fixed power conversion unit 10. One of the input / output terminals of the first fixed power conversion unit 10 is connected to the first power supply 1, and the other input / output terminal is connected to the power line 40 in order to perform power conversion between the first power supply 1 and the power line 40. Similarly, the second power supply system 2000 includes a second power supply 2 and a second fixed power conversion unit 20. One of the input / output terminals of the second fixed power conversion unit 20 is connected to the second power supply 2, and the other input / output terminal is connected to the power line 40 in order to perform power conversion between the second power supply 2 and the power line 40.

[0013] The first power supply 1 and the second power supply 2 use a DC power generation device such as a solar cell, an AC power generation device such as a generator, a DC power storage device such as a storage battery, or an AC power storage device such as a flywheel.

[0014] The first fixed power conversion unit 10 is composed of a conversion module 31 that performs unidirectional or bidirectional power conversion. The conversion module 31 may be a single unit, but as shown in FIG. 1, it is possible to increase the power capacity by connecting a plurality of them in parallel. For example, when connecting a plurality in parallel, the power capacity of a single conversion module 31 and the number of conversion modules 31 connected in parallel are determined according to the power capacity required for the first fixed power conversion unit 10, or cost and size. [[ID=1...]]The conversion module 31 has an AC / DC conversion or DC / DC conversion or DC / AC conversion function, and may have an insulation function or may not have an insulation function.

[0015] Similarly, the second fixed power conversion unit 20 is composed of conversion modules 32 that perform unidirectional or bidirectional power conversion. The conversion modules 32 can be used individually, but their power capacity can be increased by using multiple modules in parallel. For example, when using multiple modules in parallel, the power capacity of a single conversion module 32 and the number of conversion modules 32 used in parallel are determined by the power capacity required for the second fixed power conversion unit 20, or by cost and size. The conversion module 32 has AC / DC conversion, DC / DC conversion, or DC / AC conversion functions, and may or may not have isolation functions.

[0016] The control device 50 sets the operating modes of the first fixed power converter 10 and the second fixed power converter 20, and sets the input / output current or power values, based on the priority order of use of the first power supply 1 and the second power supply 2.

[0017] [Configuration of the power conversion system in Embodiment 1] Figure 2 is a schematic diagram of the power conversion system according to Embodiment 1. This section will primarily describe the differences between the power conversion system according to Embodiment 1 in Figure 2 and the power conversion system in Comparative Example 1 in Figure 1. The power conversion system according to Embodiment 1 in Figure 2, compared to the power conversion system according to Comparative Example 1 in Figure 1, shares a portion of the conversion module 31 included in the first fixed power conversion unit 10 connected to the first power supply 1 and a portion of the conversion module 32 included in the second fixed power conversion unit 20 connected to the second power supply 2, and newly provides a variable power conversion unit 100. That is, the variable power conversion unit 100 includes a conversion module 33, one of the input / output terminals of the variable power conversion unit 100 is connected to the path switching unit A, and the other is connected to the power line 40.

[0018] The path switching unit A includes switches 1A and 2A, connecting the first power supply 1 and the variable power conversion unit 100 via switch 1A, and connecting the second power supply 2 and the variable power conversion unit 100 via switch 2A. For example, when switch 1A is turned on and switch 2A is turned off, the variable power conversion unit 100 is connected to the first power supply 1. In this case, the first fixed power conversion unit 10 and the variable power conversion unit 100 are connected to the first power supply 1, and the second fixed power conversion unit 20 is connected to the second power supply 2. Furthermore, when switch 1A is turned off and switch 2A is turned on, the variable power conversion unit 100 is connected to the second power supply 2. In this case, the second fixed power conversion unit 20 and the variable power conversion unit 100 are connected to the second power supply 2, and the first fixed power conversion unit 10 is connected to the first power supply 1.

[0019] The control device 51 sets the operating modes of the first fixed power converter 10, the second fixed power converter 20, and the variable power converter 100, sets the input / output current or power values, and sets on / off commands for switches 1A and 2A of the path switching unit A, based on the priority order of use of the first power supply 1 and the second power supply 2. The path switching unit A switches switches 1A and 2A on and off based on the information received from the control device 51.

[0020] [Operation of the power conversion system in Embodiment 1] The miniaturization of the power conversion system by this embodiment will be explained by comparing it with Comparative Example 1, based on Figure 3. In Case 1 of the power conversion system in Comparative Example 1 (Figure 1), if the amount of power required by the first power source 1 and the second power source 2 is 100kW each, the power capacity of the first fixed power conversion unit 10 will be 100kW and the power capacity of the second fixed power conversion unit 20 will be 100kW, so the total power capacity of the power conversion system will be 200kW.

[0021] In contrast, in case 2 of the power conversion system according to this embodiment (Figure 2), the power capacity of the first fixed power conversion unit 10 can be set to 50kW, the power capacity of the second fixed power conversion unit 20 to 50kW, and the power capacity of the variable power conversion unit 100 to 50kW. When the first power supply 1 has a high priority for use, the first fixed power conversion unit 10 and the variable power conversion unit 100 are connected to the first power supply 1 to achieve a total power capacity of 100kW. When the second power supply 2 has a high priority for use, the second fixed power conversion unit 20 and the variable power conversion unit 100 are connected to the second power supply 2 to achieve a total power capacity of 100kW. In this case, the total power capacity of the power conversion system will be 150kW, which is 50kW less than the 200kW power capacity of the power conversion system in Comparative Example 1 (Figure 1), thus enabling miniaturization of the power conversion system.

[0022] The combination of power capacities of the first fixed power conversion unit 10, the second fixed power conversion unit 20, and the variable power conversion unit 100 can be realized in cases other than Case 2. For example, in Case 3 of Figure 3, the power capacity of the first fixed power conversion unit 10 can be set to 60kW, the power capacity of the second fixed power conversion unit 20 to 60kW, and the power capacity of the variable power conversion unit 100 to 40kW. In this case, the total power capacity of the power conversion system becomes 160kW, which is a reduction of 40kW compared to the power conversion system in Comparative Example 1 (Figure 1).

[0023] If we let P1 be the power capacity required for the first power supply 1, P2 be the power capacity required for the second power supply 2, P10 be the power capacity of the first fixed power conversion unit 10, P20 be the power capacity of the second fixed power conversion unit 20, and P100 be the power capacity of the variable power conversion unit 100, then we select a combination of power capacities such that the following relationship holds. P10+P20≧P1 (Formula 1) P10+P20≧P2 (Formula 2) P10+P100≧P1...(Formula 3) P20+P100≧P2··(Formula 4) From (Equation 1) to (Equation 4), the following (Equation 5) holds true. (3 / 2)×(P10+P20)+P100≧P1+P2 (Formula 5)

[0024] [Power capacity of the variable power converter] Here, we will explain the power capacity of the variable power conversion unit. The power capacity of the variable power converter is set such that, when there are n power sources (n≧2), the sum of the value obtained by multiplying the total power capacity of the fixed power converter by (n+1) / 2 and the value obtained by multiplying the power capacity of the variable power converter by n / 2 is equal to or greater than the power capacity required by the n power sources. In Embodiment 1, there are two power supplies, a first power supply 1 and a second power supply 2. Therefore, in Case 2 of Figure 3, the total capacity of the fixed power conversion unit is the sum of the power capacity P10 = 50kW of the first fixed power conversion unit 10 and the power capacity P20 = 50kW of the second fixed power conversion unit 20, and the power capacity P100 = 50kW of the variable power conversion unit 100. 3 / 2 × (50kW + 50kW) + 2 / 2 × 50kW = 200kW ... (Equation 6). Since the power capacities of the first power source 1 and the second power source 2 (P1 and P2) are 100kW each, 100kW(P1) + 100kW(P2) = 200kW (Equation 7). Therefore, from (Equation 6) and (Equation 7), 200kW = 200kW, and the above setting conditions are met.

[0025] Furthermore, in the case of Case 3 in Figure 3, the total capacity of the fixed power conversion unit is the sum of the power capacity P10 = 60kW of the first fixed power conversion unit 10 and the power capacity P20 = 60kW of the second fixed power conversion unit 20, and the power capacity P100 = 40kW of the variable power conversion unit 100, 3 / 2 × (60kW(P10) + 60kW(P20)) + 40kW(P100) = 220kW ... (Equation 8). Since the power capacities of the first power source 1 and the second power source 2 (P1 and P2) are 100kW each, 100kW(P1) + 100kW(P2) = 200kW (Equation 9). Therefore, from (Equation 8) and (Equation 9), 220kW > 200kW, and the above setting conditions are met.

[0026] [Description of the conversion module] Next, using Figure 4, we will describe the conversion module 31 of the first fixed power conversion unit 10, the conversion module 32 of the second fixed power conversion unit, and the conversion module 33 of the variable power conversion unit 100 in Embodiment 1. Since conversion modules 31, 32, and 33 have similar configurations, conversion module 31 will be described as a representative example. The conversion module 31 consists of a circuit section 300 that performs power conversion and voltage or current detection, and a converter control section 400 that drives and controls the circuit section 300. The circuit unit 300 consists of a conversion circuit unit 302 that performs power conversion, a sensor unit 301 that detects voltage or current on the first power supply 1 side, and a sensor unit 303 that detects voltage or current on the power line 40 side.

[0027] The converter control unit 400 includes a voltage control unit 402 that generates a current command value Iin_ref based on the voltage Vo measured by the sensor unit 303 and the voltage command value Vo_ref, and a current control unit 401 that issues an operation command to the conversion circuit unit 302 based on the current Iin measured by the sensor unit 301 and the current command value Iin_ref. Here, the voltage command value Vo_ref may be held internally as a constant by the converter control unit 400, received as a command value from an external source, or generated by calculation within the converter control unit 400. Furthermore, the voltage command value Vo_ref is input to the voltage control unit 402 via a command value filter to suppress abrupt changes in the voltage command value Vo_ref, and a limiter to restrict the upper and lower limits of the voltage command value Vo_ref. Similarly, a filter and limiter are set for the current command value Iin_ref to limit the input and output currents.

[0028] Furthermore, the converter control unit 400 includes an input / output power control unit 403 that generates a current command value Iin_ref based on the input / output power command value of the first power supply 1 and the voltage and current of the first power supply 1 measured by the sensor unit 301. Either the voltage control unit 402 or the input / output power control unit 403 must be enabled so that the current command value Iin_ref does not conflict. The input / output power command values ​​may be received as command values ​​from an external source, or they may be generated by the converter control unit 400 through calculation. Furthermore, filters and limiters are set on the input / output power command values ​​to limit the available input / output current.

[0029] In this embodiment 1, the case where the circuit unit 300 and the converter control unit 400 correspond one-to-one is described as an example. However, it is also possible to adopt a configuration in which multiple conversion modules containing only the circuit unit 300 are arranged in parallel, and conversion modules containing both the circuit unit 300 and the converter control unit 400 are arranged in parallel, so that all the circuit units 300 are driven by a single converter control unit 400.

[0030] [Explanation of priority power switching operation] Next, Figure 5 will be used to explain the priority power supply switching operation of the power conversion system of Embodiment 1. In Embodiment 1, the first power supply 1 and the second power supply 2 are DC energy storage devices, and the conversion modules 31, 32, and 33 have DC / DC conversion functions. The explanation will focus on the case where DC power is output to the power line 40 from either the first power supply 1 or the second power supply 2.

[0031] First, during the period t1 in which the first power supply 1 is given priority, switch 1A of the path switching unit A is on and switch 2A is off, and the variable power conversion unit 100 is connected to the first power supply 1. The first fixed power conversion unit 10 and the variable power conversion unit 100 are controlled to keep the output voltage to the power line 40 constant. Since the second power supply 2 is not a priority power supply, the second fixed power converter 20 is either inactive or controlled to keep the output voltage to the power line 40 constant, but the output current is limited to zero by the limiter of the converter control unit 400. In addition, when the second fixed power converter 20 controls the input power or current to the second power supply 2 to keep it constant in order to charge the second power supply 2, or when controlling the output voltage to keep it constant, it may set the output voltage lower than that of the first fixed power converter 10 or variable power converter 100 and set the input current value to zero or more (the output current value to zero or less), but here the input and output power values ​​are assumed to be zero.

[0032] If the charge level of the first power supply 1 decreases due to its use during period t1 and falls below a threshold, the management device 51 switches the preferred power supply to the second power supply 2. As shown in Figure 6, the management device 51 receives information such as the remaining power capacity, power generation status, and degradation status of each power source from the power supply monitoring unit 52, which monitors the status of the first power source 1 and the second power source 2. Based on the information received from the power supply monitoring unit 52 and the elapsed time, the management device 51 can determine which power source to prioritize for use.

[0033] Period t2 begins when the preferred power source is switched. During period t2, the operating mode of the second fixed power converter 20 is first changed from normal operating mode to switching operating mode by a command from the management device 51. In switching operating mode, it is possible to set the power conversion operation to pause and to set the control target (constant output voltage control or constant input / output power control). When the second fixed power converter 20 enters switching operating mode, the control target is set to be the same as that of the first fixed power converter 10 (constant output voltage), and the output power value is also changed to the same value as that of the first fixed power converter 10.

[0034] Next, the operating mode of the variable power converter 100 is changed to the switching operation mode, the power conversion operation is paused, and the output power value is set to zero. For example, considering the case where a load is connected to the power line 40, in period t1, power was supplied to the load only from the first power source 1, whereas in period t2, power is supplied from both the first power source 1 and the second power source 2. In period t2, the power that was supplied from the first power source 1 via the variable power converter 100 is changed to be supplied from the second power source 2 via the second fixed power converter 20, and there is no change in the power supplied to the load itself.

[0035] When the setting of the variable power conversion unit 100 is switched, period t3 begins, and the second fixed power conversion unit 20 changes from switching operation mode to normal operation mode. Also, the management device 51 sends an on / off switching command to the route switching unit A for switches 1A and 2A. Upon receiving the on / off switching command, the route switching unit A switches switch 1A to off and switch 2A to on. At this time, because the input voltage becomes zero for a period when switch 1A is turned off, the abnormality detection function of the variable power conversion unit 100 is masked to prevent the output of an error. Note that power is supplied to the load connected to the power line 40 from the first power source 1 via the first fixed power conversion unit 10 and from the second power source 2 via the second fixed power conversion unit 20, as in period t2, so the route switching of the variable power conversion unit 100 does not affect the power supply to the load.

[0036] After the switching of switch 1A and switch 2A is complete, period t4 begins, the variable power converter 100 resumes power conversion operation, the output power value is set to the same as in period t1, and the system switches to normal operation mode. Subsequently, the output power of the first fixed power converter 10 is set to zero. At this time, the operation mode may be changed to switching operation mode, and the control target may be set. Thus, power is supplied to the load connected to the power line 40 only from the second power source 2 via the fixed power converter 20 and the variable power converter 100.

[0037] After the settings are changed, the first fixed power conversion unit 10 switches to normal operation mode, and period t5 begins. During period t5, the priority power supply switching is complete and the power conversion system is operating normally.

[0038] [Closing] Thus, according to the power conversion system of this embodiment 1, by switching switches 1A and 2A of the path switching unit A while changing the output power values ​​of the first fixed power conversion unit 10, the second fixed power conversion unit 20, and the variable power conversion unit 100 during periods t2, t3, and t4, the priority power source is switched without interrupting the power supply from the first power source 1 and the second power source 2 to the power line 40, thereby reducing the total power capacity of the power conversion system and enabling miniaturization of the power conversion system.

[0039] [Effects of Embodiment 1] As described above, the power conversion system according to Embodiment 1 is n power supplies (where n is an integer greater than or equal to 2), Each of the aforementioned power supplies is connected to n fixed power conversion units, A variable power converter connected to one of the aforementioned power supplies, The system includes a path switch that switches the connection between one of the aforementioned power sources and the variable power conversion unit, The output terminal of the fixed power converter and the output terminal of the variable power converter are connected. The variable power conversion unit is connected to the power supply with the highest priority among the power supplies. If the priority of the aforementioned power supply is changed, By changing the power supply capacity of at least the variable power conversion unit among the fixed power conversion unit and the variable power conversion unit, the switching operation of the route switch is performed without interrupting the power at the output terminal, This reduces unused power capacity, enabling system miniaturization, while also maintaining power input and output even when switching to a priority power source.

[0040] Furthermore, in changing the power supply capacity, Before the switching operation of the aforementioned route switcher, The fixed power conversion unit of the non-priority power supply is configured to increase its power supply capacity. The aforementioned variable power conversion unit is modified to have zero power supply capacity. After the switching operation of the aforementioned route switcher, The variable power conversion unit is set to increase the power supply capacity, This allows for route switching while maintaining power supply capacity.

[0041] Furthermore, the variable power conversion unit includes a switching operation mode for path switching. In the aforementioned switching operation mode, power conversion operation and abnormality detection are stopped. The variable power conversion unit changes its operation to the switching operation mode before the switching operation of the route switcher. Since the operation is changed from the switching operation mode to the normal operation mode after the connection switching is completed at the aforementioned route switch, This allows for smooth switching of the connections of the variable power conversion unit.

[0042] Furthermore, a management device that commands the priority of the power supply, The system includes a power supply monitoring unit that measures and monitors the state of the power supply, The management device is configured to determine the priority of the power supply based on the information from the power supply monitoring unit. The management device and the power supply monitoring unit can determine the priority of the power supply.

[0043] Furthermore, the power capacity of the variable power conversion unit is If the number of power supplies is the n, The value obtained by multiplying the total power capacity of the fixed power converter by (n+1) / 2 and adding the value obtained by multiplying the power capacity of the variable power converter by n / 2 is set to be equal to or greater than the power capacity required by the n power supplies. This enables miniaturization of power conversion systems.

[0044] Furthermore, if the fixed power conversion unit and the variable power conversion unit are DC / DC converters that input and output DC power, The aforementioned path switcher offers the advantage of eliminating the need to consider phase or frequency during switching.

[0045] Embodiment 2. [Configuration of the power conversion system in Comparative Example 2] Before describing the power conversion system of Embodiment 2, the power conversion system of Comparative Example 2 will be described based on Figure 7. Comparative Example 2 in Figure 7 differs from Comparative Example 1 in Figure 1 in the following ways. In Comparative Example 1 in Figure 1, the first power supply 1 and the second power supply 2 correspond to the first power grid G1 and the second power grid G2 in Comparative Example 2 in Figure 7. The third power grid G3 is connected to the power line 40. The third power grid G3 exchanges power with the first power grid G1 and the second power grid G2. The management device 50 receives power exchange commands between each power grid from the energy management system (hereinafter abbreviated as EMS) 7, which manages each power grid, and sets power command values ​​for the first fixed power conversion unit 10 and the second fixed power conversion unit 20.

[0046] The first fixed power conversion unit 10 is composed of a conversion module 31 that performs unidirectional or bidirectional power conversion. The conversion module 31 has AC / DC conversion, DC / DC conversion, or DC / AC conversion functions, and may or may not have isolation functions.

[0047] Similarly, the second fixed power conversion unit 20 is also composed of a conversion module 32 that performs unidirectional or bidirectional power conversion. The conversion module 32 has AC / DC conversion, DC / DC conversion, or DC / AC conversion functions, and may or may not have isolation functions.

[0048] The control device 50 sets the operating modes of the first fixed power converter 10 and the second fixed power converter 20, and sets the input / output current or power values, based on the usage priority of the first power grid G1 and the second power grid G2.

[0049] [Configuration of the power conversion system in Embodiment 2] Figure 8 is a schematic diagram of the power conversion system according to Embodiment 2. Here, we will mainly explain the differences between the power conversion system according to Embodiment 2 shown in Figure 8 and the power conversion system in Comparative Example 2 shown in Figure 7. The power conversion system according to Embodiment 2 in Figure 8, compared to the power conversion system according to Comparative Example 2 in Figure 7, includes a first fixed power conversion unit 10 connected to the first power grid G1 and having a conversion module 31, a second fixed power conversion unit 20 connected to the second power grid G2 and having a conversion module 32, and a newly added variable power conversion unit 100. Specifically, the variable power conversion unit 100 includes a conversion module 33, one of the input / output terminals of the variable power conversion unit 100 is connected to the path switching unit A, and the other is connected to the power line 40.

[0050] The route switching unit A includes switches 1A and 2A, and connects the first power grid G1 and the variable power conversion unit 100 via switch 1A, and connects the second power grid G2 and the variable power conversion unit 100 via switch 2A. For example, when switch 1A is turned on and switch 2A is turned off, the variable power conversion unit 100 is connected to the first power grid G1. In this case, the first fixed power conversion unit 10 and the variable power conversion unit 100 are connected to the first power grid G1, and the second fixed power conversion unit 20 is connected to the second power grid G2. Furthermore, when switch 1A is turned off and switch 2A is turned on, the variable power conversion unit 100 is connected to the second power grid G2. In this case, the second fixed power conversion unit 20 and the variable power conversion unit 100 are connected to the second power grid G2, and the first fixed power conversion unit 10 is connected to the first power grid G1.

[0051] The control device 51 sets the operating modes of the first fixed power converter 10, the second fixed power converter 20, and the variable power converter 100, sets the input / output current or power values, and sets on / off commands for switches 1A and 2A of the route switching unit A, based on the usage priority of the first power grid G1 and the second power grid G2. The route switching unit A switches switches 1A and 2A on and off based on the information received from the control device 51.

[0052] In this second embodiment, the power PG1 that can be exchanged between the third power grid G3 and the first power grid G1 is different from the power PG2 that can be exchanged between the third power grid G3 and the second power grid G2, and the case where PG1 > PG2 is treated as an example. However, the power capacity of the first fixed power conversion unit 10 is P10, the power capacity of the second fixed power conversion unit 20 is P20, and the power capacity of the variable power conversion unit 100 is P100.

[0053] In this case, let PG1 be 100kW and PG2 be 60kW. P10+P20≧PG1 (Formula 10) P10+P20≧PG2 (Formula 11) P10+P100≧PG1 (Formula 12) P20+P100≧PG2 (Formula 13) From equations 10 to 13, the following equation 14 holds true. (3 / 2)×(P10+P20)+P100≧PG1+PG2 (Formula 14)

[0054] The power capacity P10 of the first fixed power conversion unit 10, the power capacity P20 of the second fixed power conversion unit, and the power capacity P100 of the variable power conversion unit 100 are selected such that equations (10) to (14) hold true. For example, it becomes possible to select a power capacity P10 of the first fixed power conversion unit 10 as 70kW, a power capacity P20 of the second fixed power conversion unit 20 as 30kW, and a power capacity P100 of the variable power conversion unit 100 as 30kW, resulting in a total power capacity of 130kW for the power conversion system. In the case of the power conversion system in Comparative Example 2 shown in Figure 7, the total power capacity is PG1 + PG2 = 160 kW, so it is possible to reduce the power capacity by 30 kW and miniaturize the power conversion system. Furthermore, in Embodiment 2, the case in which the first fixed power conversion unit 10, the second fixed power conversion unit 20, and the variable power conversion unit 100 are controlled to maintain a constant output power will be described as an example.

[0055] [Description of the operation of Embodiment 2] The operation of this second embodiment will be explained using Figure 9. First, during period t1, the variable power converter 100 is connected to the first power grid G1, with an output power command value of 100kW for the first power grid G1 and -10kW for the second power grid G2. 90kW of power is output to the third power grid G3.

[0056] The control device 51 receives information from the EMS7 regarding changes in the output power command values ​​of the first power grid G1 and the second power grid G2, changes the priority grid, and period t2 begins. Here, the output power command values ​​of each power grid after the priority grid switch are set to 30kW for the first power grid G1 and 60kW for the second power grid G2. During period t2, the output power command value of the first fixed power conversion unit 10 is simultaneously changed from 100kW to 60kW by the control device 51, the output power command value of the second fixed power conversion unit 20 is changed from -10kW to 30kW, and the output power command value of the variable power conversion unit 100 is changed from 30kW to 0kW. By gradually changing the output power command value and aligning the start and completion times of the change in the output power command value of each power conversion unit, the output power to the third power grid G3 can be kept constant. After the output power command value of the variable power conversion unit 100 is set to 0kW, it is changed from normal operation mode to switching operation mode by a command from the management device 51. In switching operation mode, power conversion operation is suspended and the abnormality detection function is masked.

[0057] When the operating mode of the variable power conversion unit 100 is switched, period t3 begins, and the path switching unit A switches switch 1A to off and switch 2A to on. After the switching of switch 1A and switch 2A is complete, period t4 begins, and the variable power converter 100 is switched to normal operation mode. Subsequently, the output power command value of the first fixed power converter 10 is changed from 60kW to 30kW, and the output power command value of the variable power converter 100 is changed from 0kW to 30kW simultaneously.

[0058] After the settings are changed, period t5 begins. During period t5, the switch to the preferred grid is complete.

[0059] [Closing] Thus, according to this second embodiment, when a power conversion system that exchanges power between power grids receives a command from an EMS7 that manages multiple power grids and switches to a grid to which power will be preferentially supplied, it gradually changes the output power command values ​​of the first fixed power conversion unit 10, the second fixed power conversion unit 20, and the variable power conversion unit 100, and by aligning the start time and end time of the change, it is possible to switch to the preferred grid while keeping the power output to the third power grid G3 constant.

[0060] [Effects of Embodiment 2] As described above, Embodiment 2 provides the effects described in Embodiment 1, as well as the following effects. In other words, in changing the power supply capacity, The power supply capacity of the fixed power conversion unit and the variable power conversion unit is set to change in stages, and the start time and end time of the staged change of the fixed power conversion unit and the variable power conversion unit are set to be the same. This allows for route switching while maintaining the system's overall power supply capacity.

[0061] Furthermore, the power source is the power grid. The output terminals of the fixed power conversion unit and the output terminals of the variable power conversion unit are connected to a power grid. The management device receives power exchange commands between each power grid and sets the output power values ​​of the fixed power conversion unit and the variable power conversion unit, and switches the connection destination of the variable power conversion unit. This enables smooth power exchange between power grids and provides a compact power conversion system.

[0062] Embodiment 3. In the power conversion system of Embodiment 1, the power supply consisted of two components. Embodiment 3 describes a case where, in addition to the first power supply 1 and the second power supply 2, there is a third power supply 3.

[0063] [Configuration of the power conversion system in Comparative Example 3] Before describing the power conversion system of Embodiment 3, the power conversion system of Comparative Example 3 will be described based on Figure 10. In Comparative Example 3 of Figure 10, compared to the configuration of Comparative Example 1 of Figure 1, a third power supply 3 is added in addition to the first power supply 1 and the second power supply 2. A third fixed power conversion unit 30, which has a conversion module 34, is connected to the third power supply 3, and a power line 40 is connected to the third fixed power conversion unit 30. The control device 50 sets the operating modes of the first fixed power converter 10, the second fixed power converter 20, and the third fixed power converter 30, and sets the input / output current or power values, based on the priority order of use of the first power supply 1, the second power supply 2, and the third power supply 3.

[0064] [Configuration of the power conversion system in Embodiment 3] Figure 11 is a schematic diagram of the power conversion system according to Embodiment 3. In the power conversion system of Embodiment 3 shown in Figure 11, in addition to the first fixed power conversion unit 10, second fixed power conversion unit 20, and third fixed power conversion unit 30, a variable power conversion unit 100 having a conversion module 33 is provided, compared to the configuration of Comparative Example 3 shown in Figure 10. The variable power conversion unit 100 is connected to the first power supply 1 via switch 1A in the path switching unit AA, to the second power supply 2 via switch 2A, and to the third power supply 3 via switch 3A. The control device 51 sets the operating modes of the first fixed power conversion unit 10, the second fixed power conversion unit 20, the third fixed power conversion unit 30, and the variable power conversion unit 100, sets the input / output current or power values, and sets on / off commands for switches 1A, 2A, and 3A to the path switching unit AA.

[0065] In this third embodiment, we will explain using the case where output is taken only from the power supply with the highest priority among the three power supplies as an example. In this case, if the power capacity required for the third power supply 3 is P3 and the power capacity of the third fixed power conversion unit 30 is P30, then a combination of power capacities is selected such that the following relationship holds. Furthermore, let P1 be the power capacity required for the first power supply 1, P2 be the power capacity required for the second power supply 2, P10 be the power capacity of the first fixed power conversion unit 10, P20 be the power capacity of the second fixed power conversion unit 20, and P100 be the power capacity of the variable power conversion unit 100.

[0066] P10+P20+P30≧P1 (Formula 15) P10+P20+P30≧P2 (Formula 16) P10+P20+P30≧P3 (Formula 17) P10+P100≧P1 (Formula 18) P20+P100≧P2 (Formula 19) P30+P100≧P3 (Formula 20) From (Equations 15) to (Equations 20), the following (Equation 21) holds. 2×(P10+P20+P30)+(3 / 2)×P100≧P1+P2+P3 (12) (Formula 21)

[0067] In the case where P1=P2=P3=100kW, we can choose P10=P20=P30=35kW and P100=65kW. In this case, the total power capacity of the power conversion system is 170kW, which is 130kW less than the total power capacity of the power conversion system in Comparative Example 3 (300kW, P10=P20=P30=100kW), making it possible to miniaturize the power conversion system. In Embodiment 3, the first fixed power conversion unit 10, the second fixed power conversion unit 20, the third fixed power conversion unit 30, and the variable power conversion unit 100 are each set to maintain a constant output voltage to the power line 40.

[0068] [Power capacity of the variable power converter] Here, we will explain the power capacity of the variable power conversion unit. As described in Embodiment 1, the power capacity of the variable power converter is set such that, when the number of power sources is n (n≧2), the sum of the value obtained by multiplying the total power capacity of the fixed power converter by (n+1) / 2 and the value obtained by multiplying the power capacity of the variable power converter by n / 2 is equal to or greater than the power capacity required by the n power sources. In Embodiment 3, there are three power supplies: a first power supply 1, a second power supply 2, and a third power supply 3. The total capacity of the fixed power conversion unit is the sum of the power capacity P10 = 35kW of the first fixed power conversion unit 10, the power capacity P20 = 35kW of the second fixed power conversion unit 20, and the power capacity P20 = 35kW of the third fixed power conversion unit 30, and the power capacity P100 = 65kW of the variable power conversion unit 100. Therefore, 4 / 2 × (35kW + 35kW + 35kW) + 3 / 2 × (65kW) = 307.5kW (Equation 22). Since the power capacities of the first power supply 1, the second power supply 2, and the third power supply 3 (P1, P2, P3) are each 100kW, 100kW + 100kW + 100kW = 300kW (Equation 23). Therefore, from (Equation 22) and (Equation 23), 307.5kW > 300kW, and the above setting conditions are met.

[0069] [Operation of the power conversion system in Embodiment 3] The operation of the power conversion system of Embodiment 3 will be explained with reference to Figure 12. First, during period t1, the priority power source is the first power source 1, so the variable power converter 100 is connected to the first power source 1. The output power of the first fixed power converter 10 is set to 35kW, the output power of the variable power converter 100 is set to 65kW, and the output power of the second fixed power converter 20 and the third fixed power converter 30 is set to 0kW. When the priority power source is switched to the third power source 3 by the management device 51, period t2 begins.

[0070] During period t2, the output power of the second fixed power converter 20 is first changed to 30kW, and the output power of the third fixed power converter 30 is changed to 35kW. Next, the output power of the variable power converter 100 is changed from 65kW to 0kW, and the operating mode is changed from normal operation mode to switching operation mode, which pauses power conversion operation and masks abnormality detection.

[0071] When the operating mode of the variable power conversion unit 100 is switched, period t3 begins, and the path switching unit AA switches switch 1A from on to off, keeps switch 2A in the off state, and switches switch 3A from off to on. After the switching between switch 1A and switch 3A is complete, period t4 begins, the variable power converter 100 switches to normal operation mode, and the output power is set to 65kW. Subsequently, the output power of the first fixed power converter 10 and the second fixed power converter 20 is set to 0kW. After the settings are changed, period t5 begins and the switchover of the priority power supply is completed. In the operation example shown in Figure 12, during period t5, the first fixed power conversion unit 10 and the second fixed power conversion unit 20 enter a switching operation mode to reduce conversion losses and suspend power conversion operations.

[0072] [Closing] As described above, according to this embodiment 3, in a power conversion system with three power sources, when switching the priority power source, in addition to the fixed power conversion unit connected to the newly prioritized power source and the fixed power conversion unit connected to the previous priority power source, the output power of the fixed power conversion units connected to the other power sources is also temporarily set to a higher level. This makes it possible to switch the priority power source while preventing a decrease in the system's output power due to the switching of the connection destination of the variable power conversion unit. Furthermore, it becomes possible to reduce the total power capacity of the power conversion system and make it more compact.

[0073] [Effects of Embodiment 3] As described above, the power conversion system according to Embodiment 3 achieves the effects described in Embodiments 1 and 3, and also provides the following benefits. In other words, three power supplies, Three fixed power converters connected to each of the aforementioned power supplies, A variable power converter connected to one of the aforementioned power supplies, The system includes a path switch that switches the connection between one of the aforementioned power sources and the variable power conversion unit, The output terminal of the fixed power converter and the output terminal of the variable power converter are connected. The variable power conversion unit is connected to the power supply with the highest priority among the power supplies. If the priority of the aforementioned power supply is changed, By changing the power supply capacity of at least the variable power conversion unit among the fixed power conversion unit and the variable power conversion unit, the switching operation of the route switch is performed without interrupting the power at the output terminal, In a power conversion system equipped with three power sources, unused power capacity is reduced, enabling system miniaturization, while also maintaining power input and output even when switching priority power sources.

[0074] In embodiments 1 to 3, the management device 51 consists of a processor 5100 and a storage device 5101, as shown in Figure 13, as an example of the hardware. The storage device 5101 includes a volatile storage device such as random access memory (not shown) and a non-volatile auxiliary storage device such as flash memory. Alternatively, a hard disk may be provided as an auxiliary storage device instead of flash memory. The processor 5100 executes the program input from the storage device 5101. In this case, the program is input to the processor 5100 from the auxiliary storage device via the volatile storage device. The processor 5100 may also output data such as calculation results to the volatile storage device of the storage device 5101, or it may save the data to the auxiliary storage device via the volatile storage device.

[0075] While this disclosure describes various exemplary embodiments and examples, the various features, aspects, and functions described in one or more embodiments are not limited to the application of a particular embodiment, but are applicable individually or in various combinations to the embodiments. Accordingly, countless variations not illustrated are conceivable within the scope of the art disclosed in this specification. These include, for example, modifying, adding or omitting at least one component, or even extracting at least one component and combining it with components of other embodiments.

[0076] The various aspects of this disclosure are summarized below as an appendix.

[0077] (Note 1) n power supplies (where n is an integer greater than or equal to 2), Each of the aforementioned power supplies is connected to n fixed power conversion units, A variable power converter connected to one of the aforementioned power supplies, The system includes a path switch that switches the connection between one of the aforementioned power sources and the variable power conversion unit, The output terminal of the fixed power converter and the output terminal of the variable power converter are connected. The variable power conversion unit is connected to the power supply with the highest priority among the power supplies. If the priority of the aforementioned power supply is changed, A power conversion system that changes the power supply capacity of at least the variable power conversion unit among the fixed power conversion unit and the variable power conversion unit, and performs the switching operation of the route switcher without interrupting the power at the output terminal. (Note 2) In changing the aforementioned power supply capacity, Before the switching operation of the aforementioned route switcher, The fixed power conversion unit of the non-priority power supply is configured to increase its power supply capacity. The aforementioned variable power conversion unit is modified to have zero power supply capacity. After the switching operation of the aforementioned route switcher, The power conversion system described in Appendix 1, wherein the variable power conversion unit is configured to increase the power supply capacity. (Note 3) In changing the aforementioned power supply capacity, The power supply capacity of the fixed power conversion unit and the variable power conversion unit is set to change in stages, and the start time and end time of the staged change of the fixed power conversion unit and the variable power conversion unit are set to be the same. (Note 4) The variable power conversion unit includes a switching operation mode for path switching, In the aforementioned switching operation mode, power conversion operation and abnormality detection are stopped. The variable power conversion unit changes its operation to the switching operation mode before the switching operation of the route switcher. The power conversion system described in Appendix 2 or Appendix 3, which changes its operation from the switching operation mode to the normal operation mode after the connection switching is completed at the aforementioned route switch. (Note 5) A management device that commands the priority of the aforementioned power supply, The system includes a power supply monitoring unit that measures and monitors the state of the power supply, The power conversion system described in any one of the appendices 1 to 3, wherein the management device determines the priority of the power supply based on information from the power supply monitoring unit. (Note 6) The power capacity of the variable power converter is If the number of power supplies is the n, The power conversion system according to any one of the appendices 1 to 5, wherein the value obtained by adding the value obtained by multiplying the total power capacity of the fixed power conversion unit by (n+1) / 2 to the value obtained by multiplying the power capacity of the variable power conversion unit by n / 2 is set to be equal to or greater than the power capacity required by the n power sources. (Note 7) The aforementioned power source is the power grid, The output terminals of the fixed power conversion unit and the output terminals of the variable power conversion unit are connected to a power grid. The power conversion system described in Appendix 5, wherein the management device receives power exchange commands between each power grid, sets the output power values ​​of the fixed power conversion unit and the variable power conversion unit, and switches the connection destination of the variable power conversion unit. (Note 8) The power conversion system according to any one of the appendices 1 to 7, wherein the fixed power conversion unit and the variable power conversion unit are DC / DC converters that input and output DC power. [Explanation of symbols]

[0078] 1 1st power supply, 2 2nd power supply, 3 3rd power supply, 7 Energy Management System (EMS), 10 First Fixed Power Conversion Unit, 20 Second fixed power conversion unit, 30 Third fixed power conversion unit, 31, 32, 33, 34 Conversion modules, 40 Power lines, 51 Control devices, 52 Power supply monitoring unit, 100 Variable power conversion unit, 300 Circuit unit, 302 Conversion circuit unit, 301, 303 Sensor section, 400 Converter control section, 401 Current control section, 402 Voltage control unit, 403 Input / output power control unit, A, AA Path switching unit, G1: Power grid 1, G2: Power grid 2, G3: Power grid 3.

Claims

1. n power supplies (where n is an integer greater than or equal to 2), Each of the aforementioned power supplies is connected to n fixed power conversion units, A variable power converter connected to one of the aforementioned power supplies, The system includes a path switch that switches the connection between one of the aforementioned power sources and the variable power conversion unit, The output terminal of the fixed power converter and the output terminal of the variable power converter are connected. The variable power conversion unit is connected to the power supply with the highest priority among the power supplies. If the priority of the aforementioned power supply is changed, A power conversion system that changes the power supply capacity of at least the variable power conversion unit among the fixed power conversion unit and the variable power conversion unit, and performs the switching operation of the route switcher without interrupting the power at the output terminal.

2. In changing the aforementioned power supply capacity, Before the switching operation of the aforementioned route switcher, The fixed power conversion unit of the non-priority power supply is configured to increase its power supply capacity. The aforementioned variable power conversion unit is modified to have zero power supply capacity. After the switching operation of the aforementioned route switcher, The power conversion system according to claim 1, wherein the variable power conversion unit is configured to increase the power supply capacity.

3. In changing the aforementioned power supply capacity, The power supply capacity of the fixed power conversion unit and the variable power conversion unit is set to change in stages, and the start time and end time of the staged change of the fixed power conversion unit and the variable power conversion unit are set to be the same.

4. The variable power conversion unit includes a switching operation mode for path switching, In the aforementioned switching operation mode, power conversion operation and abnormality detection are stopped. The variable power conversion unit changes its operation to the switching operation mode before the switching operation of the route switcher. The power conversion system according to claim 2 or 3, wherein the operation is changed from the switching operation mode to the normal operation mode after the connection switching is completed at the route switch.

5. A management device that commands the priority of the aforementioned power supply, The system includes a power supply monitoring unit that measures and monitors the state of the power supply, The power conversion system according to any one of claims 1 to 3, wherein the management device determines the priority of the power supply based on information from the power supply monitoring unit.

6. The power capacity of the variable power converter is If the number of power supplies is n, The power conversion system according to any one of claims 1 to 3, wherein the value obtained by adding the value obtained by multiplying the total power capacity of the fixed power conversion unit by (n+1) / 2 to the value obtained by multiplying the power capacity of the variable power conversion unit by n / 2 is set to be equal to or greater than the power capacity required by the n power sources.

7. The aforementioned power source is the power grid, The output terminals of the fixed power converter and the output terminals of the variable power converter are connected to a power grid. The power conversion system according to claim 5, wherein the management device receives power exchange commands between each power grid, sets the output power values ​​of the fixed power conversion unit and the variable power conversion unit, and switches the connection destination of the variable power conversion unit.

8. The power conversion system according to any one of claims 1 to 3, wherein the fixed power conversion unit and the variable power conversion unit are DC / DC converters that input and output DC power.

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