A seamless switching system and method for an energy storage inverter based on a large-capacity VSG

Abstract

The present invention relates to a seamless switching system and method for an energy storage inverter based on a large-capacity VSG. The system includes an external network, an energy management cabinet, and an energy storage inverter that are interconnected. The energy management cabinet includes a load power distribution cabinet, a first external network switch, a first energy control switch, and a second energy control switch that are connected in sequence. The load power distribution cabinet is connected between the connection lines of the first energy control switch and the second energy control switch, and a synchronous switch terminal voltage sampling circuit is connected in parallel at both ends of the first energy control switch. The energy storage inverter includes a plurality of AC inverter units connected in parallel with each other, and each AC inverter unit is connected to the second energy control switch through an energy storage inverter switch. Compared with the prior art, the present invention can complete the switching process of the external network and the microgrid, as well as the microgrid and the external network. The entire structure is more stable and reliable, realizes seamless switching, avoids the problem of short-term power outage, and improves the stability and reliability of the load operation.

Description

Technical Field

[0001] The present invention relates to the technical field of power grid switching, and in particular to a seamless switching system and method for an energy storage inverter based on a large-capacity VSG. Background Art

[0002] With the rise of clean energy, energy storage technology has also played an increasingly important role in the power grid. At present, for the power supply of terminal equipment, the power grid supply and the energy storage equipment supply can be adopted simultaneously. However, in the process of energy switching between the power grid and the energy storage equipment, the existing technologies all require short-term power outages, which affect the stable operation of the equipment side and cause losses to production applications. Summary of the Invention

[0003] The purpose of the present invention is to overcome the defect that in the process of energy switching between the power grid and the energy storage equipment in the existing technologies, short-term power outages are required and seamless switching cannot be achieved, and to provide a seamless switching system and method for an energy storage inverter based on a large-capacity VSG.

[0004] The purpose of the present invention can be realized by the following technical solutions:

[0005] A seamless switching system for an energy storage inverter based on a large-capacity VSG includes an external network, an energy management cabinet, and an energy storage inverter that are connected to each other. The energy management cabinet includes a load power distribution cabinet, a first external network switch, a first energy control switch, and a second energy control switch that are connected in sequence. The load power distribution cabinet is connected between the connection lines of the first energy control switch and the second energy control switch. A synchronous switch terminal voltage sampling circuit is connected in parallel at both ends of the first energy control switch;

[0006] The energy storage inverter includes a plurality of AC inverter units connected in parallel with each other, and each AC inverter unit is connected to the second energy control switch through an energy storage inverter switch.

[0007] Further, the external network is connected to the first external network switch, and an external network voltage monitoring circuit is also connected between the connection lines of the external network and the first external network switch.

[0008] Further, a microgrid voltage and current monitoring circuit is also connected between the connection lines of the energy storage inverter and the second energy control switch.

[0009] Further, the synchronous switch terminal voltage sampling circuit, the external network voltage monitoring circuit, and the microgrid voltage and current monitoring circuit are all communicatively connected to a controller.

[0010] Further, the first external network switch, the first energy control switch, the second energy control switch, and the energy storage inverter switch are all contactors.

[0011] Further, the controller includes an external grid and microgrid control circuit. The microgrid and external grid control circuit includes a first data synchronization device, an analog-to-digital conversion circuit, a comparator, and a first level signal output device connected in sequence. The first data synchronization device is also respectively connected to the synchronization switch terminal voltage sampling circuit and the external grid voltage monitoring circuit. The first data synchronization device and the microgrid voltage and current monitoring circuit are respectively connected to the input end of the comparator through the analog-to-digital conversion circuit. The output end of the comparator is connected to the first level signal output device, and the first level signal output device is also connected to the first energy control switch.

[0012] Further, the controller also includes a microgrid and external grid control circuit, which includes a second data synchronization device and a second level signal output device connected in sequence. The second data synchronization device is respectively connected to the energy management cabinet and the energy storage inverter, and the second level signal output device is also connected to the energy storage inverter switch.

[0013] Further, an external grid main switch is also provided in the connection line between the external grid and the first external grid switch, and the external grid voltage monitoring circuit is connected in the connection line between the external grid main switch and the first external grid switch.

[0014] Further, the external grid main switch is a contactor.

[0015] Further, the energy management cabinet is communicatively connected to the energy storage inverter.

[0016] The present invention also provides a switching method for a seamless switching system of an energy storage inverter based on a large-capacity VSG as described above, including the following steps:

[0017] External grid and microgrid control step: When the energy storage inverter switch is closed, the first energy control switch is open, and the second energy control switch is closed, the synchronization switch terminal voltage sampling circuit collects the grid information at both ends of the first energy control switch. After synchronizing with the grid information collected by the external grid voltage monitoring circuit, it is transmitted to the energy storage inverter; the energy storage inverter adjusts its own microgrid parameters according to the synchronized grid information, so that when the microgrid information collected by the microgrid voltage and current monitoring circuit is synchronized with the grid information, the first energy control switch is closed to complete the connection of the external grid and the microgrid;

[0018] Microgrid and external grid control step: When the energy storage inverter switch is open, the first energy control switch is closed, and the second energy control switch is open, the energy storage inverter synchronizes the microgrid information collected by the microgrid voltage and current monitoring circuit with the grid information collected by the synchronization switch terminal voltage sampling circuit. After the synchronization is completed, the energy storage inverter switch is closed to complete the connection of the microgrid and the external grid;

[0019] Steps for seamless switching when the external network and the microgrid work simultaneously: When the energy storage inverter switch is closed, the first energy control switch is closed, and the second energy control switch is closed, the external network and the energy storage inverter supply power continuously at the same time.

[0020] Further, both the grid information and the microgrid information include frequency, phase, and amplitude.

[0021] Compared with the prior art, the present invention has the following advantages:

[0022] The present invention realizes the conduction and disconnection of the external network, the load distribution cabinet, and the energy storage inverter by setting the first external network switch, the second energy control switch, and the energy storage inverter switch respectively, realizes the synchronization of the external network information in the external network and the external network information in the energy management cabinet through the first energy control switch, and then realizes the synchronization of the external network information in the energy management cabinet and the microgrid information in the energy storage inverter through the microgrid voltage and current monitoring circuit, and then completes the switching process of the external network and the microgrid, as well as the microgrid and the external network. The whole structure is more stable and reliable, realizes seamless switching, avoids the problem of short-time power outage, and improves the stability and reliability of the load operation. Description of the Drawings

[0023] Figure 1 It is a schematic structural diagram of a seamless switching system of an energy storage inverter based on a large-capacity VSG provided in an embodiment of the present invention;

[0024] In the figure, 1 is the external network, 2 is the energy management cabinet, 201 is the first external network switch, 202 is the first energy control switch, 203 is the synchronous switch terminal voltage sampling circuit, 204 is the load distribution cabinet, 205 is the second energy control switch, 3 is the energy storage inverter, 301 is the energy storage inverter switch, and 302 is the AC inverter unit. Specific Embodiments

[0025] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are some, but not all, of the embodiments of the present invention. Usually, the components of the embodiments of the present invention described and illustrated herein can be arranged and designed in various different configurations.

[0026] Therefore, the following detailed description of the embodiments of the present invention provided in the drawings is not intended to limit the scope of the present invention claimed, but merely represents selected embodiments of the present invention. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts fall within the scope of protection of the present invention.

[0027] It should be noted that: Similar reference numerals and letters denote similar items in the following drawings. Therefore, once an item is defined in one drawing, it does not need to be further defined and explained in subsequent drawings.

[0028] In the description of the present invention, it should be noted that the orientation or positional relationship indicated by the terms "center", "upper", "lower", "left", "right", "vertical", "horizontal", "inner", "outer", etc. is based on the orientation or positional relationship shown in the drawings, or the orientation or positional relationship in which the inventive product is customarily placed during use. It is only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and thus should not be construed as a limitation on the present invention.

[0029] It should be noted that the terms "first" and "second" are only used for descriptive purposes and should not be construed as indicating or implying relative importance or implicitly specifying the quantity of the indicated technical features. Thus, the features defined with "first" and "second" may explicitly or implicitly include one or more of such features. In the description of this application, "a plurality of" means two or more unless otherwise specifically defined.

[0030] In addition, terms such as "horizontal" and "vertical" do not mean that the components are required to be absolutely horizontal or hanging vertically, but may be slightly inclined. For example, "horizontal" only means that its direction is more horizontal relative to "vertical", and does not mean that the structure must be completely horizontal, but may be slightly inclined.

[0031] Embodiment 1

[0032] As Figure 1 shown, this embodiment provides a seamless switching system for an energy storage inverter based on a large-capacity VSG, including an external network 1, an energy management cabinet 2, and an energy storage inverter 3 that are connected to each other. The energy management cabinet 2 includes a load power distribution cabinet 204, a first external network switch 201, a first energy control switch 202, and a second energy control switch 205 that are connected in sequence. The load power distribution cabinet 204 is connected between the connection lines of the first energy control switch 202 and the second energy control switch 205. A synchronous switch terminal voltage sampling circuit 204 is connected in parallel at both ends of the first energy control switch 202;

[0033] The energy storage inverter 3 includes a plurality of AC inverter units 302 connected in parallel with each other. Each AC inverter unit 302 is connected to the second energy control switch 205 through an energy storage inverter switch 301.

[0034] The external network 1 is connected to the first external network switch 201, and an external network voltage monitoring circuit 102 is also connected in parallel to the connection line between the external network 1 and the first external network switch 201. A microgrid voltage and current monitoring circuit is also connected in parallel to the connection line between the energy storage inverter 3 and the second energy control switch 205.

[0035] The synchronous switch terminal voltage sampling circuit 204, the external network voltage monitoring circuit 102, and the microgrid voltage and current monitoring circuit are all communicatively connected to a controller.

[0036] The first external network switch 201, the first energy control switch 202, the second energy control switch 205, and the energy storage inverter switch 301 are all contactors. The first external network switch 201 can also be a circuit breaker.

[0037] The controller includes an external network and microgrid control circuit. This microgrid and external network control circuit includes a first data synchronization device, an analog-to-digital conversion circuit, a comparator, and a first level signal output device connected in sequence. The first data synchronization device is also respectively connected to the synchronous switch terminal voltage sampling circuit 204 and the external network voltage monitoring circuit 102. The first data synchronization device and the microgrid voltage and current monitoring circuit are respectively connected to the input end of the comparator through the analog-to-digital conversion circuit. The output end of the comparator is connected to the first level signal output device, and the first level signal output device is also connected to the first energy control switch 202.

[0038] The controller also includes a microgrid and external network control circuit, which is a second data synchronization device and a second level signal output device connected in sequence. The second data synchronization device is respectively connected to the energy management cabinet 2 and the energy storage inverter 3, and the second level signal output device is also connected to the energy storage inverter switch 301.

[0039] This embodiment also provides a switching method for a seamless switching system of an energy storage inverter based on a large-capacity VSG as described above, including the following steps:

[0040] External network and microgrid control step: When the energy storage inverter switch is closed, the first energy control switch is open, and the second energy control switch is closed, the synchronous switch terminal voltage sampling circuit collects the grid information at both ends of the first energy control switch. After synchronizing with the grid information collected by the external network voltage monitoring circuit, it is transmitted to the energy storage inverter. The energy storage inverter adjusts its own microgrid parameters according to the synchronized grid information. When the microgrid information collected by the microgrid voltage and current monitoring circuit is synchronized with the grid information, the first energy control switch is closed to complete the connection of the external network to the microgrid.

[0041] Microgrid and external network control step: When the energy storage inverter switch is open, the first energy control switch is closed, and the second energy control switch is open, the microgrid information collected by the energy storage inverter through the microgrid voltage and current monitoring circuit is synchronized with the grid information collected by the synchronous switch terminal voltage sampling circuit. After synchronization is completed, the energy storage inverter switch is closed to complete the connection of the microgrid to the external network.

[0042] Seamless switching steps when the external network and the microgrid work simultaneously: When the energy storage inverter switch is closed, the first energy control switch is closed, and the second energy control switch is closed, the external network and the energy storage inverter supply power continuously at the same time.

[0043] Both the power grid information and the microgrid information include frequency, phase, and amplitude.

[0044] The basic working principle of seamless switching of the energy management cabinet is as follows: The first external network switch 201 is normally fully closed. For the seamless process of the external network and the microgrid: When the microgrid is supplying power normally, that is, the AC inverter unit 302 is closed, the first energy control switch 202 is open, and the second energy control switch 205 is closed, the sampling circuit inside collects the grid information such as frequency, phase, and amplitude at both ends of the synchronous contactor K1 for the data required for synchronization during the seamless connection of the external power grid. The ARM in the energy management cabinet will send the external network information such as frequency, phase, and amplitude to the energy storage inverter. After receiving the relevant signals and the external network information such as frequency, phase, and amplitude, the energy storage inverter adjusts its own microgrid parameters to make the grid on the microgrid side approach the external power grid parameters such as frequency, phase, and amplitude. When the energy management cabinet detects that the external power grid and the microgrid frequencies, phases, and amplitudes are synchronized, it closes the contactor K1 on the external power grid side to complete the seamless switching process of the external power grid and the microgrid.

[0045] Seamless process of the microgrid connecting to the external network: When the power grid is supplying power normally, that is, the first external network switch 201 is open, the first energy control switch 202 is closed, and the second energy control switch 205 is open, the ARM in the energy management cabinet issues an instruction to control the VSG of the energy storage inverter to start. The energy storage inverter itself collects the grid information for synchronization. After synchronization is completed, the contactor K is closed to complete the seamless process of the microgrid connecting to the external network.

[0046] Seamless switching when the power grid and the microgrid work simultaneously: When both the power grid and the microgrid are supplying power, that is, the first external network switch 201 is closed, the first energy control switch 202 is closed, and the second energy control switch 205 is closed, when the external power grid suddenly loses power, the energy storage inverter will continue to supply power as a voltage source to ensure that the load does not lose power.

[0047] There is also an external network main switch 101 in the connection line between the external network 1 and the first external network switch 201. The external network voltage monitoring circuit 102 is connected in parallel in the connection line between the external network main switch 101 and the first external network switch 201. The external network main switch 101 is a contactor or a circuit breaker. The energy management cabinet 2 is communicatively connected to the energy storage inverter 3. In this embodiment, communication is carried out through the Modbus485 protocol.

[0048] The preferred specific embodiments of the present invention have been described in detail above. It should be understood that those of ordinary skill in the art can make many modifications and variations based on the concept of the present invention without creative efforts. Therefore, all technical solutions that can be obtained by those skilled in the art in this technical field based on the concept of the present invention through logical analysis, reasoning, or limited experiments on the basis of the prior art should fall within the protection scope determined by the claims.

Claims

1. A seamless switching system for an energy storage inverter based on a large-capacity VSG, characterized in that It includes an interconnected external network (1), an energy management cabinet (2), and a energy storage inverter (3). The energy management cabinet (2) includes a load power distribution cabinet (204), a first external network switch (201), a first energy control switch (202), and a second energy control switch (205) connected in sequence. The load power distribution cabinet (204) is connected between the connection lines of the first energy control switch (202) and the second energy control switch (205). A synchronous switch terminal voltage sampling circuit (203) is connected in parallel at both ends of the first energy control switch (202); The energy storage inverter (3) includes a plurality of AC inverter units (302) connected in parallel with each other. Each AC inverter unit (302) is connected to the second energy control switch (205) through an energy storage inverter switch (301); The external network (1) is connected to the first external network switch (201), and an external network voltage monitoring circuit (102) is also connected between the connection lines of the external network (1) and the first external network switch (201); The synchronous switch terminal voltage sampling circuit (203), the external network voltage monitoring circuit (102), and the microgrid voltage and current monitoring circuit are all communicatively connected to a controller; The first external network switch (201), the first energy control switch (202), the second energy control switch (205), and the energy storage inverter switch (301) are all contactors; The controller includes an external network and microgrid control circuit. This external network and microgrid control circuit includes a first data synchronization device, an analog-to-digital conversion circuit, a comparator, and a first level signal output device connected in sequence. The first data synchronization device is also respectively connected to the synchronous switch terminal voltage sampling circuit (203) and the external network voltage monitoring circuit (102). The first data synchronization device and the microgrid voltage and current monitoring circuit are respectively connected to the input end of the comparator through the analog-to-digital conversion circuit. The output end of the comparator is connected to the first level signal output device, and the first level signal output device is also connected to the first energy control switch (202); The controller also includes a microgrid and external network control circuit. This microgrid and external network control circuit includes a second data synchronization device and a second level signal output device connected in sequence. The second data synchronization device is respectively connected to the energy management cabinet (2) and the energy storage inverter (3), and the second level signal output device is also connected to the energy storage inverter switch (301).

2. The seamless switching system of an energy storage inverter based on a large-capacity VSG according to claim 1, characterized in that, A microgrid voltage and current monitoring circuit is also connected between the connection lines of the energy storage inverter (3) and the second energy control switch (205).

3. A seamless switching system for an energy storage inverter based on a large-capacity VSG according to claim 1, characterized in that, An external network main switch (101) is also provided in the connection line between the external network (1) and the first external network switch (201), and the external network voltage monitoring circuit (102) is connected between the connection lines of the external network main switch (101) and the first external network switch (201).

4. A switching method for a seamless switching system of an energy storage inverter based on a large-capacity VSG as described in any one of claims 1 to 3, characterized in that, It includes the following steps: External network and microgrid control steps: When the energy storage inverter switch (301) is closed, the first energy control switch (202) is open, and the second energy control switch (205) is closed, the synchronous switch terminal voltage sampling circuit (203) collects the grid information at both ends of the first energy control switch (202). After synchronizing with the grid information collected by the external network voltage monitoring circuit (102), it is transmitted to the energy storage inverter (3); the energy storage inverter (3) adjusts its own microgrid parameters according to the synchronized grid information. When the microgrid information collected by the microgrid voltage and current monitoring circuit is synchronized with the grid information, the first energy control switch (202) is closed to complete the connection of the external network to the microgrid; Microgrid and external network control steps: When the energy storage inverter switch (301) is open, the first energy control switch (202) is closed, and the second energy control switch (205) is open, the microgrid information collected by the energy storage inverter (3) through the microgrid voltage and current monitoring circuit is synchronized with the grid information collected by the synchronous switch terminal voltage sampling circuit (203). After synchronization is completed, the energy storage inverter switch (301) is closed to complete the connection of the microgrid to the external network; Seamless switching steps when the external network and the microgrid work simultaneously: When the energy storage inverter switch (301) is closed, the first energy control switch (202) is closed, and the second energy control switch (205) is closed, the external network (1) and the energy storage inverter (3) supply power continuously at the same time.

5. The method according to claim 4, wherein Both the grid information and the microgrid information include frequency, phase, and amplitude.

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