Energy storage converter and multi-machine parallel system
By introducing a first controller into the energy storage converter system, power equalization among multiple units is achieved, which solves the risk of zero-sequence circulating current caused by individual converter derating and ensures stable system operation and device safety.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- SHENZHEN HOPEWIND ELECTRIC CO LTD
- Filing Date
- 2026-01-19
- Publication Date
- 2026-04-21
AI Technical Summary
In a multi-unit AC/DC parallel system of energy storage converters, individual energy storage converters may trigger derating events, leading to power imbalance and zero-sequence circulating current risk. Existing technologies make it difficult to achieve power equality among multiple units.
By introducing a first controller into the system, the desired power is issued and the status information of the energy storage converter is obtained. The converter that needs to be derated is determined, and the minimum derated limit value is issued as a temporary setting value to all converters to ensure that all converters exit the derated event synchronously and achieve power equalization.
It achieves power equalization in multi-unit energy storage converter systems, reduces the risk of zero-sequence circulating current, avoids imbalance caused by derating of individual converters, and protects device lifespan and current distortion.
Smart Images
Figure CN121906591A_ABST
Abstract
Description
Technical Field
[0001] This application relates to the field of energy storage technology, and in particular to an energy storage converter and a multi-machine parallel system. Background Technology
[0002] With the large-scale development of smart grids and new energy power generation technologies, and the increasing demand for energy storage system capacity, the parallel connection of multiple energy storage converters in AC / DC configurations is becoming increasingly widespread in energy storage systems. This parallel connection method connects the DC and AC buses of the energy storage converters in parallel, improving the overall system capacity ratio and flexibility. It is also simple to assemble and easy to expand. While the application of parallel connection of multiple energy storage converters in AC / DC configurations offers many advantages, uneven power distribution among the multiple units can easily lead to zero-sequence circulating current. Excessive zero-sequence circulating current can cause uneven stress on switching devices, leading to damage to power devices. It can also cause problems such as current distortion, high harmonics, and DC bias in the output current of the energy storage converter. Therefore, power balance is a critical requirement in parallel connection systems of multiple energy storage converters in AC / DC configurations.
[0003] In some cases, such as when the heat sink of an energy storage converter overheats, power derating is necessary to reduce the heat generated during energy conversion and prevent damage to the devices or shorten their lifespan. In multi-unit AC / DC parallel energy storage converter systems, if one or more converters trigger a derating event, power imbalance will occur among the converters, leading to significant zero-sequence circulating current and its associated effects. Therefore, achieving power equality among multiple converters in a multi-unit AC / DC parallel energy storage converter system and avoiding the risk of zero-sequence circulating current caused by power imbalance due to derating of individual converters is a pressing problem in this field. Summary of the Invention
[0004] In view of this, the purpose of this application is to provide an energy storage converter and a multi-unit parallel system to achieve power equalization among multiple units in a multi-unit AC / DC parallel system of energy storage converters, thereby reducing the risk of zero-sequence circulating current caused by power imbalance due to derating of individual energy storage converters.
[0005] The technical solution adopted in this application to solve the above-mentioned technical problems is as follows:
[0006] This application provides a multi-machine parallel system, which includes n energy storage converters connected in parallel between an energy storage battery and the power grid, where n≥2; the DC side of each energy storage converter is connected to the DC side of the other energy storage converters and then connected to the energy storage battery, and the AC side of each energy storage converter is connected to the AC side of the other energy storage converters and then connected to the power grid; the multi-machine parallel system also includes a first controller that is communicatively connected to the n energy storage converters.
[0007] The first controller is configured to send the desired power to all the energy storage converters so that all the energy storage converters execute the desired power; acquire the status information uploaded by all the energy storage converters; if it is determined based on the status information that any one of the energy storage converters needs power derating, then the smallest derating limit value among all the energy storage converters is taken as a temporary power setting value and sent to all the energy storage converters so that all the energy storage converters exit the derating event.
[0008] Another aspect of this application provides an energy storage converter, wherein the DC side of the energy storage converter is connected to the DC side of other energy storage converters and then connected to an energy storage battery, and the AC side of the energy storage converter is connected to the AC side of other energy storage converters and then connected to the power grid.
[0009] The energy storage converter also includes a second controller, which is configured to receive a desired power from a host computer and execute the desired power; upload the status information of the energy storage converter to the host computer; and execute the temporary power setting value if a temporary power setting value is received from the host computer; wherein the temporary power setting value is used to cause the energy storage converter to exit the derating event.
[0010] The energy storage converter and multi-unit parallel system provided in this application synchronously perform power derating among multiple units when the energy storage converter triggers power derating. On the one hand, the minimum derating limit can meet the derating requirements of all energy storage converters, and on the other hand, it ensures that the power of all energy storage converters is equal, avoiding the generation of large circulating currents. Attached Figure Description
[0011] Figure 1 This is a schematic diagram of a multi-machine parallel system provided in an embodiment of this application;
[0012] Figure 2 This is a schematic diagram of the preset relationship curve between radiator temperature and derating limit provided in the embodiments of this application;
[0013] Figure 3 This is a schematic diagram of the control flow of a multi-machine parallel system provided in an embodiment of this application;
[0014] Figure 4 This is another control flow diagram of a multi-machine parallel system provided in an embodiment of this application.
[0015] The realization of the purpose, functional features and advantages of this application will be further explained in conjunction with the embodiments and with reference to the accompanying drawings. Detailed Implementation
[0016] To make the technical problems, technical solutions, and beneficial effects to be solved by this application clearer and more understandable, the following detailed description is provided in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of this application and are not intended to limit this application.
[0017] like Figure 1 As shown in the figure, an embodiment of this application provides a multi-machine parallel system, which includes n energy storage converters (PCS1~PCSn in the figure) connected in parallel between the energy storage battery and the power grid, where n≥2; the DC side of each energy storage converter is connected to the DC side of the other energy storage converters and then connected to the energy storage battery, and the AC side of each energy storage converter is connected to the AC side of the other energy storage converters and then connected to the power grid.
[0018] It should be noted that the specific structure of the aforementioned energy storage converter is not limited here.
[0019] In some examples, after the AC side of each of the energy storage converters is connected to the AC side of the other energy storage converters, it is connected to the power grid through a grid-connected transformer T1 and a grid-connected switch K1. The grid-connected switch K1 includes, but is not limited to, a contactor and a circuit breaker.
[0020] In some examples, the multi-machine parallel system also includes a first controller that is communicatively connected to the n energy storage converters (as shown by the dashed lines in the figure). The first controller may be an energy management system (EMS) and may be integrated into any one of the energy storage converters or independent of any one of the energy storage converters.
[0021] Based on the above multi-machine parallel system, in some examples, the first controller is configured to send the desired power to all the energy storage converters so that all the energy storage converters execute the desired power; obtain the status information uploaded by all the energy storage converters; if it is determined based on the status information that any one of the energy storage converters needs power derating, then the smallest derating limit value among all the energy storage converters is taken as the temporary power setting value and sent to all the energy storage converters so that all the energy storage converters exit the derating event.
[0022] In some examples, the status information includes a comprehensive depreciation flag;
[0023] The first controller is configured to determine that if the comprehensive derating flag uploaded by one of the energy storage converters is a first preset value, then the energy storage converter needs power derating; if the comprehensive derating flag uploaded by one of the energy storage converters is a second preset value, then the energy storage converter does not need power derating.
[0024] For example, if the overall derating flag uploaded by one of the energy storage converters is "1", it is determined that the energy storage converter requires power derating. If the overall derating flag uploaded by one of the energy storage converters is "0", it is determined that the energy storage converter does not require power derating. It should be noted that if the overall derating flags uploaded by all the energy storage converters are "0", it is determined that all the energy storage converters do not require power derating or have exited the derating event.
[0025] In some examples, the status information includes a derating limit value;
[0026] The first controller is configured to determine the smallest derating limit among all the energy storage converters based on the derating limit values uploaded by all the energy storage converters.
[0027] For example, find the minimum value among the derating limits uploaded by the n energy storage converters. This minimum value is the smallest derating limit among all the energy storage converters.
[0028] In some examples, the first controller is configured to reissue the desired power to all the energy storage converters after all the energy storage converters exit the derating event, so that all the energy storage converters perform the reissued desired power.
[0029] In some examples, the status information includes fault signals;
[0030] The first controller is configured to issue a shutdown command to the other energy storage converters if it is determined based on the fault signal that one of the energy storage converters has failed to shut down, so that all the other energy storage converters shut down.
[0031] Thus, in a multi-unit parallel system, the states of all energy storage converters are synchronized. After the first controller issues a start command, all energy storage converters start simultaneously; after the first controller issues power, all energy storage converters load and execute simultaneously; when at least one energy storage converter fails, the first controller detects the fault information of the energy storage converter and immediately issues a stop command, and the other energy storage converters stop simultaneously.
[0032] In some examples, any one of the energy storage converters includes a second controller configured to receive a desired power from a host computer (e.g., the aforementioned first controller) and execute the desired power; upload the status information of the energy storage converter to the host computer; and execute the temporary power setting if a temporary power setting value is received from the host computer; wherein the temporary power setting value is used to cause the energy storage converter to exit the derating event.
[0033] In some examples, the second controller is configured to execute the retransmission of the desired power if it receives the desired power retransmitted by the host computer.
[0034] In some examples, the second controller is configured to determine the derating limit value when a derating event is triggered; if the derating limit value is lower than the desired power, then set the overall derating flag to a first preset value; if the derating limit value is higher than the desired power, then set the overall derating flag to a second preset value; and / or,
[0035] The second controller is configured to set the comprehensive derating flag to a second preset value when no derating event is triggered.
[0036] For example: if the derating limit is lower than the expected power, it means that the energy storage converter needs to be drated, and the overall derating flag is "1". If the derating limit is higher than the expected power, it means that power derating is not required at this time, and the power derating is stopped to continue maintaining the expected power, and the overall derating flag is "0".
[0037] It should be noted that "lower than" and "higher than" can refer to "less than or equal to" or "greater than", or they can refer to "less than" or "greater than or equal to".
[0038] In some examples, the energy storage converter includes a heat sink;
[0039] The second controller is configured to determine whether to trigger a derating event based on the temperature of the heat sink and a preset temperature range; when a derating event is triggered, the derating limit value is determined based on the temperature of the heat sink and a preset relationship between the heat sink temperature and the derating limit value.
[0040] by Figure 2 For example, Figure 2This diagram illustrates the preset relationship between radiator temperature and derating limit. The vertical axis represents the derating limit, and the horizontal axis represents the radiator temperature, with a preset temperature range of 81℃ to 91℃. When the radiator temperature is below (less than or equal to) 81℃, the energy storage converter does not trigger an over-temperature derating event; when the radiator temperature is between 81℃ and 91℃, the energy storage converter triggers an over-temperature derating event. For example, when the collected radiator temperature is 86℃, the energy storage converter derating limit is 75% * rated power; when the collected radiator temperature is 91℃, the energy storage converter derating limit is 50% * rated power. The derating limit limits the output power to protect internal components from damage. The derating limit can be applied to the apparent output power, the active charging or discharging power, or the capacitive or inductive reactive power.
[0041] In some examples, the status information uploaded by the energy storage converter also includes temperature information.
[0042] In some examples, the second controller is configured to shut down the energy storage converter when the energy storage converter fails or when a shutdown command is received from the host computer.
[0043] The following combination Figures 3-4 Explanation:
[0044] like Figure 3 As shown, the control flow of a multi-machine parallel system includes the following steps:
[0045] S101, The first controller sends the desired power.
[0046] S102, All energy storage converters operate and deliver the desired power.
[0047] S103. All energy storage converters upload status information, including derating limit value, comprehensive derating flag, temperature information, and fault signals.
[0048] S104. The first controller receives the status information uploaded by all energy storage converters.
[0049] S105. Based on the uploaded status information, the first controller determines that any one of the energy storage converters needs power derating. For example, the comprehensive derating flag is "1".
[0050] S106. The first controller takes the smallest derating limit value among all the energy storage converters as the temporary power setting value and sends it to all the energy storage converters.
[0051] S107. All energy storage converters execute temporary power settings.
[0052] S108. All energy storage converters upload status information again.
[0053] S109, the first controller receives the status information uploaded by all energy storage converters again.
[0054] S110. Based on the status information uploaded here, the first controller determines that all the energy storage converters have exited the derating event. For example, the overall derating flag of all the energy storage converters is "0".
[0055] S111, the first controller reissues the desired power.
[0056] S112, All energy storage converters operate and execute the reissued desired power.
[0057] like Figure 4 As shown, the control flow of a multi-machine parallel system includes the following steps:
[0058] S201, The first controller sends the desired power.
[0059] S202, All energy storage converters operate and deliver the desired power.
[0060] S203. All energy storage converters upload status information, including derating limit value, comprehensive derating flag, temperature information, and fault signals.
[0061] S204. The first controller receives the status information uploaded by all energy storage converters.
[0062] S205. Based on the uploaded status information, the first controller determines that one of the energy storage converters has failed and stopped, for example, by receiving a fault signal.
[0063] S206. The first controller sends a shutdown command to the other energy storage converters.
[0064] S207, all other energy storage converters mentioned above must be shut down.
[0065] The preferred embodiments of this application have been described above with reference to the accompanying drawings, but this does not limit the scope of the claims. Any modifications, equivalent substitutions, and improvements made by those skilled in the art without departing from the scope and spirit of this application shall be within the scope of the claims.
Claims
1. A multi-machine parallel system, characterized in that, The multi-machine parallel system includes n energy storage converters connected in parallel between the energy storage battery and the power grid, where n≥2; the DC side of each energy storage converter is connected to the DC side of the other energy storage converters and then connected to the energy storage battery, and the AC side of each energy storage converter is connected to the AC side of the other energy storage converters and then connected to the power grid. The multi-machine parallel system also includes a first controller that is communicatively connected to the n energy storage converters. The first controller is configured to send the desired power to all the energy storage converters so that all the energy storage converters execute the desired power; acquire the status information uploaded by all the energy storage converters; if it is determined based on the status information that any one of the energy storage converters needs power derating, then the smallest derating limit value among all the energy storage converters is taken as a temporary power setting value and sent to all the energy storage converters so that all the energy storage converters exit the derating event.
2. The multi-machine parallel system according to claim 1, characterized in that, The first controller is configured to reissue the desired power to all energy storage converters after all energy storage converters exit the derating event, so that all energy storage converters execute the reissued desired power.
3. The multi-machine parallel system according to claim 1, characterized in that, The status information includes a comprehensive reduction indicator; The first controller is configured to determine that if the comprehensive derating flag uploaded by one of the energy storage converters is a first preset value, then the energy storage converter needs power derating; if the comprehensive derating flag uploaded by one of the energy storage converters is a second preset value, then the energy storage converter does not need power derating.
4. The multi-machine parallel system according to claim 1, characterized in that, The status information includes the reduction limit value; The first controller is configured to determine the smallest derating limit among all the energy storage converters based on the derating limit values uploaded by all the energy storage converters.
5. The multi-machine parallel system according to claim 1, characterized in that, The status information includes fault signals; The first controller is configured to issue a shutdown command to the other energy storage converters if it is determined based on the fault signal that one of the energy storage converters has failed to shut down, so that all the other energy storage converters shut down.
6. An energy storage converter, characterized in that, The DC side of the energy storage converter is connected to the DC side of other energy storage converters and then connected to the energy storage battery. The AC side of the energy storage converter is connected to the AC side of other energy storage converters and then connected to the power grid. The energy storage converter also includes a second controller, which is configured to receive a desired power from a host computer and execute the desired power; upload the status information of the energy storage converter to the host computer; and execute the temporary power setting value if a temporary power setting value is received from the host computer; wherein the temporary power setting value is used to cause the energy storage converter to exit the derating event.
7. The energy storage converter according to claim 6, characterized in that, The second controller is configured to execute the retransmission of the desired power if it receives the desired power retransmitted by the host computer.
8. The energy storage converter according to claim 6, characterized in that, The status information includes the reduction limit value and the comprehensive reduction flag; The second controller is configured to, upon triggering a derating event, determine the derating limit value; if the derating limit value is lower than the desired power, set the overall derating flag to a first preset value; if the derating limit value is higher than the desired power, set the overall derating flag to a second preset value; and / or, The second controller is configured to set the comprehensive derating flag to a second preset value when no derating event is triggered.
9. The energy storage converter according to claim 8, characterized in that, The energy storage converter includes a heat sink; The second controller is configured to determine whether to trigger a derating event based on the temperature of the heat sink and a preset temperature range; When a derating event is triggered, the derating limit is determined based on the temperature of the radiator and the preset relationship between the radiator temperature and the derating limit.
10. The energy storage converter according to claim 6, characterized in that, The status information includes fault signals; The second controller is configured to control the energy storage converter to shut down when the energy storage converter fails or when a shutdown command is received from the host computer.