Power conversion device

Abstract

Provided is a power conversion device in which a plurality of power conversion units are mounted in the same cabinet. The plurality of power conversion units are connected by common DC wiring, and are classified into two groups according to the magnitude of a control time constant of each power conversion unit. Among the two groups, the plurality of power conversion units belonging to the group having a smaller control time constant are disposed adjacent to each other in the cabinet.

Description

Power Conversion Device

[0001] The present invention relates to a power conversion device including a plurality of power conversion units with different control time constants.

[0002] Against the backdrop of decarbonization, the introduction of renewable energy power (renewable energy power) such as solar power generation and electric vehicles (EVs) is progressing. Furthermore, the introduction of stationary storage batteries is also progressing with the aim of effectively utilizing renewable energy. When installing these devices in buildings such as buildings, the installation space may be limited, so miniaturization of the devices is required. One method for achieving device miniaturization is to integrate the functions of a solar power generator, EV charger, and stationary storage battery into a single power conversion device. In this case, the main circuits for AC / DC conversion (converting three-phase AC to DC), non-isolated DC / DC conversion (converting DC power from solar panels and storage batteries), and isolated DC / DC conversion (charging EV batteries) may be implemented in separate units, and these units may be combined to form a power conversion device with integrated functions. For example, Patent Document 1 describes a method for connecting these power conversion units.

[0003] Japanese Patent Application Laid-Open No. 2022-77968

[0004] The aforementioned Patent Document 1 describes the arrangement of units inside a power converter and a method of connecting them to busbar wiring in order to reduce the size of the power converter. Consider, for example, a power converter incorporating a non-isolated DC / DC converter for solar power generation or stationary storage batteries, an isolated DC / DC converter for EV charging, and an AC / DC converter that converts three-phase AC to DC. In EV charging, a current is output based on a command value from the EV to charge the EV's internal storage battery. Because this operation is controlled by changing the command value according to the storage battery's state of charge, the output current does not change suddenly, and the control time constant does not need to be very small.

[0005] Here, the control time constant is an index that indicates the response speed in a control system, and represents the time it takes for the output to reach approximately 63% of the input. Generally, if the output is OUT, the input is IN, and the time constant is T, it can be expressed by the following formula: OUT = IN x (1 - e EXP (-t / T)) From this formula, we can see that the larger the time constant T, the slower the rate at which the output value increases, i.e., the slower the response speed.

[0006] As mentioned above, while EV charging has a large control time constant, solar power generation must continue even when the weather changes suddenly, such as from sunny to cloudy, so its control time constant is smaller than that of EV charging.When stationary storage batteries are used for power energy management in buildings and factories, there are also large changes in the input and output power from the storage battery to respond to sudden changes in load, so the control time constant is smaller than that of EV charging.

[0007] As described above, power from solar power generation systems and stationary storage batteries is exchanged with a grid or three-phase AC distribution system within a facility through AC / DC conversion, but if the non-isolated DC / DC conversion unit for solar power generation systems or stationary storage batteries, which has a small time constant, is located away from the AC / DC conversion unit, the following problem can occur: If the power from the non-isolated DC / DC conversion unit for solar power generation systems or stationary storage batteries changes suddenly, the impedance of the bus bar wiring connecting these units can cause the DC voltage to fluctuate, potentially resulting in an unstable output voltage.

[0008] The present invention has been made in view of the above-mentioned problems, and its object is to provide a power conversion device that has a built-in AC / DC conversion unit that converts three-phase AC to DC or vice versa, a non-insulated DC / DC conversion unit for solar power generation or stationary storage batteries, or an insulated DC / DC conversion unit for EV charging, which suppresses fluctuations in the internal DC voltage even when the power from the solar power generation or stationary storage batteries changes suddenly.

[0009] In order to solve the above problems, the power conversion device of the present invention is a power conversion device in which multiple power conversion units are mounted in the same cabinet, and the multiple power conversion units are connected by common DC wiring and classified into two groups according to the magnitude of the control time constant of each power conversion unit, and the multiple power conversion units belonging to the group with the smaller control time constant of the two groups are arranged adjacent to each other within the cabinet.

[0010] According to the present invention, it is possible to suppress fluctuations in DC voltage in a power conversion device even when the power from a solar power generation system or a stationary storage battery changes suddenly. Further features related to the present invention will become apparent from the description of this specification and the accompanying drawings. In addition, the problems, configurations, and effects other than those described above will become apparent from the following description of the embodiments.

[0011] Fig. 1 is a diagram showing the circuit configuration of an AC / DC conversion unit according to each embodiment of the present invention. Fig. 2 is a diagram showing the circuit configuration of a non-insulated DC / DC conversion unit for photovoltaic power generation according to each embodiment of the present invention. Fig. 3 is a diagram showing the circuit configuration of a non-insulated DC / DC conversion unit for a stationary storage battery according to each embodiment of the present invention. Fig. 4 is a diagram showing the circuit configuration of an insulated DC / DC conversion unit for EV charging according to each embodiment of the present invention. Fig. 5 is a diagram showing the unit configuration of a power conversion device according to Example 1 of the present invention. Fig. 6 is a diagram showing the unit configuration of a power conversion device according to Example 2 of the present invention. Fig. 7 is a diagram showing the unit configuration of a power conversion device according to a modified example of the present invention.

[0012] Hereinafter, embodiments will be described with reference to the drawings. [Embodiment 1] First, embodiment 1 will be described with reference to Figs. 1 to 5. Fig. 1 shows an example of the circuit configuration of an AC / DC conversion unit 101 that converts three-phase AC to DC (or the reverse conversion). The AC / DC conversion unit 101 includes a three-phase full-bridge circuit 102, DC wiring 103, a capacitor 104, a filter circuit 105, a gate drive circuit and its control circuit 106, and input / output terminals 107 and 108. The time constant of the AC / DC conversion unit 101 is relatively small.

[0013] The three-phase full-bridge circuit 102 is a known bridge circuit that converts three-phase AC to DC or DC to three-phase AC. A capacitor 104 stabilizes the voltage of the DC wiring 103. A filter circuit 105 is made up of a reactor and a capacitor. A gate drive circuit and its control circuit 106 drive the three-phase full-bridge circuit 102. Input / output terminals 107 are terminals for three-phase AC, and input / output terminals 108 are DC terminals connected to the DC wiring 502 of the power conversion device described below.

[0014] 2 shows an example of the circuit configuration of a non-insulated DC / DC conversion unit 201 used for solar power generation. The non-insulated DC / DC conversion unit 201 includes a switching circuit 202, an inductor 203, a gate drive circuit and its control circuit 204, DC wiring 205, a capacitor 206, and input / output terminals 207 and 208. The time constant of the non-insulated DC / DC conversion unit 201 used for solar power generation is relatively small, similar to that of the AC / DC conversion unit 101.

[0015] The switching circuit 202 includes a known switching element and, together with an inductor 203, converts the DC voltage obtained by the solar power generation device into a voltage that is easy to use. A gate drive circuit and its control circuit 204 drive the switching circuit 202. A capacitor 206 functions to stabilize the voltage of the DC wiring 205. An input / output terminal 207 is connected to the DC wiring 502 of the power conversion device, and an input / output terminal 208 is connected to the DC load of the solar panel.

[0016] 3 shows an example of the circuit configuration of a non-insulated DC / DC conversion unit 301 used in a stationary storage battery. The non-insulated DC / DC conversion unit 301 includes a switching circuit 302, an inductor 303, a gate drive circuit and its control circuit 304, DC wiring 305, a capacitor 306, and input / output terminals 307 and 308. The time constant of the non-insulated DC / DC conversion unit 301 used in a stationary storage battery is relatively small, similar to the above two units.

[0017] The switching circuit 302 includes a known switching element and, together with an inductor 303, converts the DC voltage output from the stationary storage battery into a voltage that is easy to use. A gate drive circuit and its control circuit 304 drive the switching circuit 302. A capacitor 306 functions to stabilize the voltage of the DC wiring 305. An input / output terminal 307 is connected to the DC wiring 502 of the power conversion device, and an input / output terminal 308 is connected to the DC load of the stationary storage battery.

[0018] 4 shows an example of the circuit configuration of an isolated DC / DC conversion unit 401 used in an EV charger. Isolated DC / DC conversion unit 401 includes single-phase full-bridge circuits 402 and 403, a transformer 404, capacitors 405 and 406, a gate drive circuit and its control circuit 407, and input / output terminals 408 and 409. Furthermore, the time constant of isolated DC / DC conversion unit 401 used in an EV charger is relatively large compared to the above three units.

[0019] Single-phase full-bridge circuits 402 and 403 are connected to the DC wiring side of the power conversion device, which is the primary side, and the EV side, which is the secondary side, respectively. A transformer 404 is installed between these two full-bridge circuits and transforms the voltage. Capacitors 405 and 406 function to stabilize the voltage on both the primary and secondary DC wiring sides. A gate drive circuit and its control circuit 407 drive the single-phase full-bridge circuits 402 and 403. In addition, an input / output terminal 408 is connected to the DC wiring 502 of the power conversion device, and an input / output terminal 409 is connected to a DC load of the EV's storage battery.

[0020] 5 shows how the above-described AC / DC conversion unit 101, non-insulated DC / DC conversion unit 201 for solar power generation, non-insulated DC / DC conversion unit 301 for stationary storage batteries, and insulated DC / DC conversion unit 401 for EV charging are mounted on a converter panel. The converter panel includes a cabinet 501 in which the above-described units are mounted, and DC wiring 502 installed along the back surface of the cabinet 501. The converter panel also includes three-phase AC wiring 503 at the lower back surface of the cabinet 501, DC wiring 504 connected to the solar panels, and DC wiring 505 connected to the stationary storage batteries. In addition, DC wiring 506 for connection to an EV is provided at the upper back surface of the cabinet 501.

[0021] The AC / DC conversion unit 101 is disposed at the bottom of the cabinet 501. A three-phase AC input / output terminal 107 on the back of the AC / DC conversion unit 101 is connected to three-phase AC wiring 503 inside the cabinet 501. A DC input / output terminal 108 on the back of the AC / DC conversion unit 101 is connected to DC wiring 502 inside the cabinet 501.

[0022] Non-insulated DC / DC conversion unit 201 for solar power generation is placed immediately above AC / DC conversion unit 101 within cabinet 501. DC input / output terminal 207 on the back of non-insulated DC / DC conversion unit 201 for solar power generation is connected to DC wiring 502 within cabinet 501. Similarly, terminal 208 on the back of non-insulated DC / DC conversion unit 201 for solar power generation, which is connected to a DC load of a solar panel, is connected to DC wiring 504 which is connected to the solar panel within cabinet 501.

[0023] The non-insulated DC / DC conversion unit 301 for a stationary storage battery is disposed immediately above the non-insulated DC / DC conversion unit 201 for photovoltaic power generation within the cabinet 501. A DC input / output terminal 307 on the back of the non-insulated DC / DC conversion unit 301 for a stationary storage battery is connected to DC wiring 502 within the cabinet 501. Similarly, an input / output terminal 308 on the back of the non-insulated DC / DC conversion unit 301 for a stationary storage battery is connected to DC wiring 505 within the cabinet 501, which is connected to the stationary storage battery.

[0024] In FIG. 5 , the AC / DC conversion unit 101, the non-insulated DC / DC conversion unit 201 for solar power generation, and the non-insulated DC / DC conversion unit 301 for a stationary storage battery are mounted in this order from the bottom of the cabinet 501. However, the order of these three types of power conversion units may be arbitrary. In other words, these units, which have relatively small control time constants, only need to be arranged adjacent to each other, and the order does not matter. This configuration shortens the length of the DC wiring 502 connecting the units, thereby suppressing increases in impedance and DC voltage. Furthermore, only one of the non-insulated DC / DC conversion unit 201 for solar power generation and the non-insulated DC / DC conversion unit 301 for a stationary storage battery may be mounted.

[0025] An isolated DC / DC conversion unit 401 for EV charging is mounted on the top of cabinet 501. DC input / output terminals 408 on the back of isolated DC / DC conversion unit 401 for EV charging are connected to DC wiring 502 inside cabinet 501. Similarly, input / output terminals 409 on the back of isolated DC / DC conversion unit 401 for EV charging are connected to DC wiring 506 for connection to the EV inside cabinet 501. In this way, isolated DC / DC conversion unit 401 for EV charging, which has a larger control time constant than the three types of power conversion units described above, is placed adjacent to the power conversion unit with a smaller control time constant that is placed at the farthest end. Furthermore, all of the above units are connected by common DC wiring.

[0026] By using the mounting structure of each power conversion unit shown in Figure 5, the non-isolated DC / DC conversion unit 201 for photovoltaic power generation and the non-isolated DC / DC conversion unit 301 for a stationary storage battery, which experience abrupt changes in DC power, are located near the AC / DC conversion unit 101, thereby suppressing fluctuations in DC voltage within the power conversion device. For example, if a power conversion unit with a large control time constant is sandwiched between power conversion units with a small control time constant, abrupt changes in power would increase impedance at the power conversion unit with the large control time constant, causing large fluctuations in DC voltage before it reaches the adjacent power conversion unit with a small control time constant, resulting in unstable operation of the power conversion unit. However, by adopting the configuration of this embodiment, such problems can be avoided.

[0027] To summarize the configuration of this embodiment, the power conversion device shown in Figure 5 is a power conversion device in which multiple power conversion units 101, 201, 301, and 401 are mounted in the same cabinet 501, and these power conversion units are connected by a common DC wiring 502 and classified into two groups according to the magnitude of their time constants, with the power conversion units 101, 201, and 301 belonging to the group with the smaller time constant being arranged adjacent to each other in the cabinet 501.

[0028] In this embodiment, the power conversion units having small control time constants are AC / DC conversion unit 101, non-insulated DC / DC conversion unit 201 for solar power generation, and non-insulated DC / DC conversion unit 301 for stationary storage batteries, and the power conversion unit having large control time constants is insulated DC / DC conversion unit 401 for EV charging. However, the power conversion units are not limited to these. For example, other power conversion units having small time constants include inverter circuit units that rotate various motors, and power conversion units having large time constants include power supply units that supply power to loads such as air conditioners. Furthermore, it is preferable that the average time constant in the group having large time constants is at least twice the average time constant in the group having small time constants.

[0029] [Example 2] Next, a power conversion device according to Example 2 of the present invention will be described with reference to Fig. 6. In Fig. 6, the same reference numerals as in Figs. 1 to 5 indicate the same components, and therefore repeated description will be omitted. In Example 1, only one each of the AC / DC conversion unit 101, the non-insulated DC / DC conversion unit 201 for photovoltaic power generation, the non-insulated DC / DC conversion unit 301 for a stationary storage battery, and the insulated DC / DC conversion unit 401 for EV charging was implemented, but Example 2 differs from Example 1 in that a configuration in which multiple of each of these units are implemented is used.

[0030] 6 shows a configuration in which multiple AC / DC conversion units 101, multiple non-insulated DC / DC conversion units 201 for solar power generation, multiple non-insulated DC / DC conversion units 301 for stationary storage batteries, and multiple isolated DC / DC conversion units 401 for EV charging are installed. From the bottom, multiple AC / DC conversion units 101, multiple non-insulated DC / DC conversion units 201 for solar power generation, and multiple non-insulated DC / DC conversion units 301 for stationary storage batteries are arranged in the lower part of a power converter cabinet 501. As in the first embodiment, these three types of power conversion units only need to be arranged adjacent to each other, and the order of arrangement may be arbitrary. Furthermore, only one of the non-insulated DC / DC conversion units 201 for solar power generation and the non-insulated DC / DC conversion units 301 for stationary storage batteries may be installed.

[0031] A plurality of isolated DC / DC conversion units 401 for charging EVs are arranged on top of the power converter cabinet 501 .

[0032] By using the mounting structure of each power conversion unit shown in Figure 6, even if multiple AC / DC conversion units 101, non-insulated DC / DC conversion units 201 for solar power generation, non-insulated DC / DC conversion units 301 for stationary storage batteries, and insulated DC / DC conversion units 401 for EV charging are mounted, the non-insulated DC / DC conversion units 201 for solar power generation and the non-insulated DC / DC conversion units 301 for stationary storage batteries, in which DC power changes sharply, are placed near the AC / DC conversion units 101, so fluctuations in DC voltage within the power conversion device can be suppressed as in Example 1.

[0033] [Modification] FIG. 7 is a diagram showing the configuration of a power conversion device according to a modification of Example 2. As in FIG. 6 , FIG. 7 also shows a configuration in which a plurality of AC / DC conversion units 101, a non-insulated DC / DC conversion unit 201 for photovoltaic power generation, a non-insulated DC / DC conversion unit 301 for a stationary storage battery, and an insulated DC / DC conversion unit 401 for EV charging are mounted. In this modification, one AC / DC conversion unit 101, one non-insulated DC / DC conversion unit 201 for photovoltaic power generation, and one non-insulated DC / DC conversion unit 301 for a stationary storage battery are arranged vertically from the center of the lower part of a cabinet 501 of the power converter. As in Examples 1 and 2, these three types of power conversion units may be arranged adjacent to each other, and the order of arrangement may be arbitrary. Furthermore, only one of the non-insulated DC / DC conversion unit 201 for photovoltaic power generation and the non-insulated DC / DC conversion unit 301 for a stationary storage battery may be mounted.

[0034] An insulated DC / DC conversion unit 401 for charging an EV is disposed at each of the top and bottom of the power converter cabinet 501 .

[0035] By using the mounting structure of each power conversion unit shown in Figure 7, even if a plurality of AC / DC conversion units 101, non-insulated DC / DC conversion units 201 for solar power generation, non-insulated DC / DC conversion units 301 for stationary storage batteries, and isolated DC / DC conversion units 401 for EV charging are mounted, the non-insulated DC / DC conversion units 201 for solar power generation and the non-insulated DC / DC conversion units 301 for stationary storage batteries, in which DC power changes sharply, are placed near the AC / DC conversion unit 101, so fluctuations in DC voltage within the power conversion device can be suppressed as in Examples 1 and 2.

[0036] The above-described embodiment of the present invention provides the following advantageous effects.

[0037] (1) The power conversion device of the present invention is a power conversion device in which multiple power conversion units are mounted in the same cabinet, and the multiple power conversion units are connected by common DC wiring and classified into two groups according to the magnitude of the control time constant of each power conversion unit, and multiple power conversion units belonging to the group with the smaller control time constant of the two groups are arranged adjacent to each other in the cabinet.

[0038] With the above configuration, fluctuations in DC voltage within the power conversion device can be suppressed even when the power from photovoltaic power generation or a stationary storage battery changes suddenly.

[0039] (2) The multiple power conversion units include at least an AC / DC conversion unit that converts between three-phase and direct current, a solar power generation unit, a stationary storage battery unit, and an EV charging unit. These units are the power conversion units that have been widely used in recent years.

[0040] (3) Of the two groups, the group with the smallest control time constant includes AC / DC conversion units, solar power generation units, and stationary battery units, while the group with the largest control time constant includes EV charging units. By dividing the devices into two groups based on their control time constants, the above-described effects of the present invention can be achieved.

[0041] (4) The average time constant of the power conversion units belonging to the one with the larger time constant of the two groups is at least twice the time constant of the power conversion units belonging to the one with the smaller time constant. This is the preferred setting of the time constant threshold for dividing the groups.

[0042] It should be noted that the present invention is not limited to the above-described embodiments, and various modifications are possible. For example, the above-described embodiments have been described in detail to clearly explain the present invention, and the present invention is not necessarily limited to embodiments that include all of the described configurations. Furthermore, it is possible to replace part of the configuration of one embodiment with the configuration of another embodiment. It is also possible to add the configuration of another embodiment to the configuration of one embodiment. It is also possible to delete part of the configuration of each embodiment, or to add or replace other configurations.

[0043] 101...AC / DC conversion unit, 201...non-insulated DC / DC conversion unit for solar power generation, 301...non-insulated DC / DC conversion unit for stationary storage battery, 401...insulated DC / DC conversion unit for EV charger, 501...power conversion device cabinet, 502...DC wiring in power conversion device cabinet

Claims

1. A power conversion device in which a plurality of power conversion units are mounted in the same cabinet, the plurality of power conversion units are connected by common DC wiring and classified into two groups according to the magnitude of the control time constant of each power conversion unit, and the plurality of power conversion units belonging to the group with the smaller control time constant of the two groups are arranged adjacent to each other in the cabinet.

2. A power conversion device as described in claim 1, characterized in that the multiple power conversion units include at least an AC / DC conversion unit that performs conversion between three-phase and direct current, a solar power generation unit, a stationary storage battery unit, and an EV charging unit.

3. A power conversion device as described in claim 2, wherein, of the two groups, the group having a smaller control time constant includes the AC / DC conversion unit, the solar power generation unit, and the stationary storage battery unit, and the group having a larger control time constant includes the EV charging unit.

4. A power conversion device as described in claim 1, characterized in that the average time constant of the power conversion units belonging to the one of the two groups having the larger time constant is at least twice the time constant of the power conversion units belonging to the one of the two groups having the smaller time constant.

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