An energy storage system and an energy storage system control method

Abstract

The application provides a kind of energy storage system and energy storage system control method, energy storage system includes multiple battery clusters, with the power converter corresponding to the connection of battery cluster and main controller, main controller is used to when the carrying capacity of power grid drops greater than or equal to the first threshold or the carrying capacity of power grid improves greater than or equal to the second threshold, control j power converters in one or more power converters stop power output, and control k power converters other than j power converters output reactive power, and the reactive power output by k power converters is greater than or equal to the reactive power absorbed by j power converters from power grid, to avoid energy storage system in standby state to pull down power grid voltage.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of power electronics, and particularly relates to an energy storage system and an energy storage system control method. BACKGROUND

[0002] The energy storage system can be applied to large photovoltaic power stations, industrial and commercial distributed power stations, household photovoltaic power systems, electric vehicles and many other fields.

[0003] The energy storage system can temporarily store the electricity generated by the power generation system, and output the stored electricity to the load when the power generation capacity of the power generation system decreases, so as to ensure the power demand of the load, wherein the load can also be a power grid. The energy storage system can make up for the disadvantage of unstable power generation capacity of the new energy power generation system, and combine the new energy power generation system into a whole power supply system, for example, a light storage system, which couples the photovoltaic power generation system and the energy storage system to supply power to the load together, so as to ensure the stability of the power supply of the load. At this time, due to the working state of the energy storage system, the working state of the energy storage system will be affected by the power generation state of the new energy power generation system, and the energy storage system needs to be kept in standby state at any time, which causes the power loss of the energy storage system when it is not working, and reduces the efficiency of the energy storage system. How to improve the efficiency of the energy storage system and reduce the standby power consumption is an important problem to be solved. SUMMARY

[0004] The present application provides an energy storage system and an energy storage system control method, compared with the traditional energy storage system design, the design of the energy storage system or the energy storage system control method can make the standby loss of the energy storage system low and the overall system efficiency high.

[0005] In a first aspect, the application provides an energy storage system, comprising n battery clusters, n power converters connected to the n battery clusters respectively, and a main controller, wherein a direct current end of the power converter is connected to the corresponding battery cluster, and an output end of the power converter is used to be connected to a power grid; the main controller is used to control one or more of the power converters to input power from the power grid to the corresponding battery cluster when a load capacity of the power grid is greater than a power demand of the load, or to output power from the corresponding battery cluster to the power grid when the load capacity of the power grid is less than the power demand of the load; the main controller is further used to control j power converters of the one or more power converters to stop power output, and control k power converters other than the j power converters to output reactive power when a load capacity decrease of the power grid is greater than or equal to a first threshold or a load capacity increase of the power grid is greater than or equal to a second threshold, and the k power converters output reactive power greater than or equal to reactive power absorbed by the j power converters from the power grid, and j+k≤n; wherein the power converter comprises a filter capacitor used to filter ripple current in alternating current output by the power converter; and the size of the reactive power absorbed by the j power converters from the power grid is positively correlated with the size of the filter capacitor in the j power converters.

[0006] In the foregoing embodiment, the power converter in the energy storage system can timely adjust the working state according to the demand of the power grid, and when the load capacity of the power grid is strong, the power converter stops working to reduce unnecessary power output, the power devices in the power converter that stops working do not perform switching action and do not generate switching loss, and a reasonable number of power converters perform reactive power output to ensure that the energy storage system provides stable reactive power support for the power grid and maintains the stability of the voltage of the power grid.

[0007] In an embodiment, the power converter comprises a relay used to control the power converter to be connected to or disconnected from the power grid by being turned on or turned off; and the main controller is further used to control the relay in the j power converters and the k power converters to be turned off when the duration for which the j power converters stop power output is greater than or equal to a time threshold.

[0008] In the foregoing embodiment, when the power converter in the energy storage system does not provide power to the power grid for a long time, the power converter is disconnected from the power grid, and the relay does not need to continue to be attracted, so that the coil of the relay does not consume power, thereby reducing the power loss of the power converter in the energy storage system due to the power consumption caused by the power converter being connected to the power grid, and reducing the operating energy consumption of the energy storage system.

[0009] In an embodiment, the power converters comprise relays for controlling the on or off of the power converters with the grid; the main controller is configured to control the relays in the j power converters and the k power converters to be off when the duration of the j power converters stopping power output is greater than or equal to a time threshold and the power loss of the energy storage system is greater than or equal to a system loss threshold.

[0010] In the foregoing embodiment, the power converters in the energy storage system are disconnected from the grid in the case of long-term non-provision of power to the grid, and are kept connected to the grid in the case of short-term non-provision of power to the grid, so as to reduce the power loss of the power converters in the energy storage system due to the electrical connection with the grid, and reduce the operating energy consumption of the energy storage system, while maintaining the ability of the energy storage system to respond to the demand of the grid.

[0011] In an embodiment, the main controller is configured to control the relays in one or more of the j power converters and the k power converters to be on and control the one or more of the j power converters and the k power converters to input the power of the grid to the corresponding battery cluster when the load-carrying capacity of the grid increases by more than or equal to a third threshold after the main controller controls the relays in the j power converters and the k power converters to be off; or the main controller is configured to control the relays in one or more of the j power converters and the k power converters to be on and control the one or more of the j power converters and the k power converters to input the power of the corresponding battery cluster to the grid when the load-carrying capacity of the grid decreases by more than or equal to a fourth threshold after the main controller controls the relays in the j power converters and the k power converters to be off.

[0012] In an embodiment, the demand response time limit of the grid is greater than or equal to a demand response threshold; the main controller controls the relays in the one or more power converters to be on and controls the one or more power converters to start inputting the power of the grid to the battery cluster in a time less than or equal to the demand response threshold after the main controller controls the relays in the j power converters and the k power converters to be off; or the main controller controls the relays in the one or more power converters to be on and controls the one or more power converters to start outputting the power of the battery cluster to the grid in a time less than or equal to the demand response threshold after the main controller controls the relays in the j power converters and the k power converters to be off.

[0013] In an embodiment, the power converter comprises a master controller and a slave controller, the master controller is configured to send control instructions to the slave controller to control the slave controller to control the power conversion circuit to work or stop working to achieve the power output or stop the power output of the power converter, and to send control instructions to the slave controller to control the slave controller to control the relay to turn on or turn off.

[0014] In an embodiment, each of the power converters and the corresponding battery cluster is located in the same energy storage container.

[0015] In a second aspect, the application provides a method for controlling an energy storage system, the method comprising: controlling one or more power converters to input power from a power grid to a corresponding battery cluster when the load carrying capacity of the power grid is greater than the power demand of a load, or to output power from the corresponding battery cluster to the power grid when the load carrying capacity of the power grid is less than the power demand of the load; controlling j power converters among the one or more power converters to stop power output and k power converters among the one or more power converters to output reactive power when the load carrying capacity of the power grid decreases by more than or equal to a first threshold or the load carrying capacity of the power grid increases by more than or equal to a second threshold, and the k power converters output reactive power that is greater than or equal to the reactive power absorbed by the j power converters from the power grid, and j+k≤n, where n is the number of power converters in the energy storage system; wherein the power converter comprises a filter capacitor configured to filter out ripple current in the alternating current output by the power converter; and wherein the amount of reactive power absorbed by the j power converters from the power grid is positively correlated to the size of the filter capacitor in the j power converters.

[0016] In an embodiment, the relay in the j power converters and the k power converters is turned off when the duration of the power output stoppage of the j power converters is greater than or equal to a time threshold; wherein the relay is configured to control the power converter to turn on or turn off by turning on or turning off.

[0017] In an embodiment, the relay in the j power converters and the k power converters is turned off when the duration of the power output stoppage of the j power converters is greater than or equal to a time threshold and the power loss of the energy storage system is greater than or equal to a system loss threshold; wherein the relay is configured to control the power converter to turn on or turn off by turning on or turning off.

[0018] It should be understood that the implementation and beneficial effects of the above aspects of the present application can be mutually referred to. BRIEF DESCRIPTION OF DRAWINGS

[0019] Figure 1 is a schematic diagram of an energy storage system architecture provided by the present application;

[0020] Figure 2 is a schematic diagram of an internal structure of a power converter provided by the present application;

[0021] Figure 3 is a schematic diagram of another internal structure of a power converter provided by the present application;

[0022] Figure 4 is a schematic diagram of still another internal structure of a power converter provided by the present application;

[0023] Figure 5 is a schematic diagram of a control flow of a power converter provided by the present application. DETAILED DESCRIPTION

[0024] In order to make the above objectives, features and advantages of the present application more apparent and comprehensible, the present application will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0025] The term “one embodiment” or “an embodiment” as used herein means that a particular implementation can include a particular feature, structure, or characteristic, but every embodiment can not necessarily include the particular feature, structure, or characteristic. The appearances of the term “in one embodiment” or “in an embodiment” in various places in the specification are not necessarily all referring to the same embodiment, nor are they necessarily mutually exclusive of one another. Unless otherwise specifically stated, the terms “connected,” “coupled,” or “in communication” as used in the specification, can range from being directly connected or in direct communication to being indirectly connected or in indirect communication through one or more other devices, components, wires, buses, networks, etc.

[0026] Hereinafter, the terms “first”, “second”, etc. are used only for descriptive purposes and should not be construed as indicating or implying relative importance or a specific number of the technical features indicated. Therefore, the features defined with “first”, “second”, etc. can explicitly or implicitly include one or more of the features. In the description of the present application, the meaning of “a plurality of” is two or more, unless otherwise specified.

[0027] The technical solutions provided by the embodiments of the present application can be applied to different application scenarios, such as large-scale photovoltaic power stations, industrial and commercial distributed power stations, and household photovoltaic power systems.

[0028] In order to facilitate the understanding of the technical solutions provided by the embodiments of the present application, the specific application of the technical solutions provided by the embodiments of the present application will be described below by selecting one type of scenario.

[0029] Reference Figure 1A schematic diagram of an energy storage system is provided for the embodiments. As shown in Figure 1 The energy storage system 100 includes a controller 110, a plurality of battery clusters 120, and n power converters 130, where the power converter 130 is also referred to as a PCS (Power Conversion System). The plurality of battery clusters 120 are connected to the n power converters 130 in a corresponding manner, and it should be understood that the corresponding connection relationship between the battery cluster 120 and the power converter 130 can be one-to-one, many-to-one, one-to-many, etc. In one possible embodiment, the battery cluster 120 and the power converter 130 are placed in the same energy storage container, and in another possible embodiment, the battery cluster 120 and the power converter 130 are placed in different locations. The DC end of the power converter 130 is connected to the corresponding battery cluster 120, and the AC end of the power converter 130 is used to connect to the power grid. The controller 110 can be used to control one or more power converters 130 to input the power of the power grid to the battery cluster 120 when the load capacity of the power grid is greater than the power demand of the load, that is, when the power grid has redundant power. Alternatively, when the load capacity of the power grid is less than the power demand of the load, for example, when the load connected to the power grid has a large power demand and the current power grid does not have enough capacity to provide stable power to the load, the energy storage system 100 needs to output power to the power grid to improve the load capacity of the power grid. At this time, the controller 110 can control one or more power converters 130 to output the power of the corresponding battery cluster 120 to the power grid to ensure that the power grid can provide enough power to the load.

[0030] It should be noted that as the power demand of the load connected to the power grid fluctuates, the working state of the energy storage system needs to be adjusted in a timely manner to improve the operating efficiency of the energy storage system and the power supply stability of the power grid.

[0031] In one embodiment provided by the present application, the power converter 130 used in the energy storage system 100 is a bidirectional power converter. When charging through the power grid, the power output of the power converter 130 is received by the battery cluster 120, and the power supply for the power output of the power converter 130 is sourced from the power grid, thereby storing excess power in the battery cluster 120 when the power supply capacity of the power grid is redundant. When the load capacity of the power grid is insufficient, the power output of the power converter 130 is received by the power grid, and the power supply for the power output of the power converter 130 is sourced from the battery cluster 120, thereby outputting the power stored in the battery cluster 120 to the power grid.

[0032] The controller 110 is further configured to control the one or more power converters 130 to be clamped when the capacity of the power grid decreases by more than or equal to a certain amount, for example, when the capacity of the power grid decreases by more than or equal to a first threshold value. In particular, assuming that the first threshold value is set to 200 kW and the maximum power of the one power converter 130 is 200 kW, it means that when the capacity of the power grid decreases by more than or equal to 200 kW, at least one power converter 130 is controlled to stop power output. If the capacity of the power grid decreases by 600 kW, three power converters 130 are required to stop power output.

[0033] Similarly, the controller 110 is further configured to control the one or more power converters 130 to be clamped when the capacity of the power grid increases by more than or equal to a certain amount, for example, when the capacity of the power grid increases by more than or equal to a second threshold value. In particular, assuming that the second threshold value is also set to 200 kW and the maximum power of the one power converter 130 is 200 kW, it means that when the capacity of the power grid increases by more than or equal to 200 kW, at least one power converter 130 is controlled to stop power output. If the capacity of the power grid increases by 600 kW, three power converters 130 are required to stop power output.

[0034] With reference to Figure 2 The power conversion of the power converter 130 is realized by switching of the switching tubes in the power conversion circuit 131. Figure 2 The switching tubes 1311, 1312, 1313 and 1314 shown in the figure are a commonly used connection and combination of switching tubes in an inverter bridge arm. In an embodiment provided in the present application, there are usually three similar inverter bridge arms in the power conversion circuit 131, and the switching tubes in the inverter bridge arms are switched to convert the alternating current of the power grid into direct current output to the battery cluster 120, or convert the direct current output by the battery cluster 120 into alternating current output to the power grid. The power converter 130 further comprises a filter capacitor C, which forms an LC filter circuit with a filter inductor L and is connected between the alternating current output end of the power conversion circuit 131 and the power grid. The filter capacitor C can filter the ripple current output by the power conversion circuit 131, so that the alternating current output by the power converter 130 to the power grid is smoother.

[0035] It should be noted that when the power converter 130 stops power output, that is, the switching tube in the power conversion circuit 131 stops switching action, the energy exchange between the battery cluster 120 and the power grid will stop. However, due to the presence of the filter capacitor C, the reactive power in the power grid will be absorbed by the power converter 130, and the size of the reactive power absorbed by the power converter 130 is positively correlated with the size of the filter capacitor C. At this time, the reactive support in the power grid will decrease, causing the power grid voltage to decrease, resulting in fluctuations in the power grid voltage. To avoid this adverse effect, the energy storage system 100 can be configured to allow the other power converters 130 except the power converter 130 that stops power output to output reactive power, and the power converter 130 that stops power output to absorb reactive power, thereby stabilizing the reactive support of the power grid and maintaining the stability of the power grid voltage.

[0036] In an embodiment provided in the present application, the controller 110 is further configured to control the k power converters 130 to output reactive power when the j power converters 130 among the one or more power converters 130 stop power output, and the reactive power output by the k power converters 130 is greater than or equal to the reactive power absorbed by the j power converters 130 from the power grid. It can be understood that when there are n power converters 130 in the energy storage system 100, j+k≤n.

[0037] For example, to meet the discharge demand of the power grid, it is assumed that there are 8 power converters 130 in the energy storage system 100, and each power converter corresponds to one battery cluster 120, and the maximum power output of each power converter 130 is 200kw. When the load capacity of the power grid decreases, at least one power converter 130 needs to perform power output to output the electrical energy released by the power grid to the battery cluster 120. If the redundant load capacity of the power grid is initially 1600kw, then the 8 power converters 130 all perform full-power power conversion. When the load capacity of the power grid decreases to 600kw, the controller 110 controls 5 power converters 130 to stop power output. At this time, 5 power converters 130 will absorb the reactive power of the power grid, causing the power grid to drop. At this time, 1, 2 or 3 power converters 130 among the 5 power converters 130 can be selected to output reactive power to compensate for the reactive power absorbed by the remaining 4, 3 or 2 power converters 130. The number of power converters 130 that need to output reactive power can be determined according to the size of the reactive power absorbed by each power converter 130 and the reactive power output capability of the power converter 130, as long as the total reactive power output by the energy storage system 100 to the power grid is greater than or equal to the value of the reactive power absorbed from the power grid.

[0038] Through the above control mode, the energy storage system 100 can not only ensure to provide power for the power grid at any time, but also maintain the stability of the power grid voltage when stopping power output.

[0039] With reference to the foregoing Figure 3 , the power converter 130 further comprises a grid-connected switch S1, and the grid-connected switch S1 is connected between the LC filter circuit and the alternating-current output end of the power converter 130. The grid-connected switch S1 controls the on or off of the power converter 130 and the power grid by being turned on or off.

[0040] In an embodiment provided in the present application, the grid-connected switch S1 is a relay. When the duration of the j power converters 130 stopping power output is greater than or equal to the time threshold, the controller 110 controls the relay in the j power converters 130 and the k power converters 130 to be turned off. Specifically, when the power converter 130 stops power output, keeping the relay closed can enable the power converter 130 to output power at any time when the power grid's discharge demand or power demand recovers, thereby ensuring the response capability of the power converter 130. However, if the relay is kept closed for a long time, the coil of the relay will be continuously powered, which will consume a certain amount of power. If the load-carrying capacity of the power grid remains low for a long time, or if the power grid has a low deficiency, so that multiple power converters 130 remain in the state of being connected to the power grid, it will increase the system power consumption of the energy storage system 100, causing unnecessary energy consumption. Therefore, when one or more power converters 130 stop power output for a duration greater than or equal to the time threshold, the controller 110 controls the relay in these power converters 130 to be turned off. In the foregoing embodiment, when a part of the power converters 130 stop power output, another part of the power converters 130 provide reactive power output. When the power converters 130 that stop power output are disconnected from the power grid, these power converters 130 no longer absorb reactive power from the power grid, so other power converters 130 no longer need to provide reactive power compensation. Therefore, the controller 110 also controls the relay in the power converters 130 that provide reactive power compensation to be turned off.

[0041] In another embodiment provided in the present application, the controller 110 controls the relays in the j power converters 130 and the k power converters 130 to be opened when the duration that the j power converters stop power output is greater than or equal to the time threshold and the power loss of the energy storage system 100 is greater than the system loss threshold. In this embodiment, the design of the energy storage system 100 not only considers the time of the power converters 130, but also sets a threshold on the power loss of the system to avoid disconnecting the power converters 130 from the grid in the case of low loss, sacrificing the speed of some power converters 130 to respond to the demand of the grid. The controller 110 controls the relays in one or more power converters 130 to be opened when the duration that the power converters 130 stop power output is greater than or equal to the time threshold and the power loss of the energy storage system 100 is greater than or equal to the system loss threshold, while controlling the relays in other power converters 130 that provide reactive power compensation to be opened.

[0042] It should be noted that, whether the power converters 130 are disconnected from the grid due to the increase or decrease of the load carrying capacity of the grid, or the energy storage system 100 has not started to supply power to the grid or receive redundant power from the grid, when the load carrying capacity of the grid is less than the power demand of the load or the load carrying capacity of the grid is greater than the power demand of the load, the relays in one or more power converters 130 are first controlled to be turned on, and then the power converters 130 are controlled to output the power of the battery cluster 120 to the grid or the power converters 130 are controlled to output the power of the grid to the battery cluster 120.

[0043] In an embodiment provided in the present application, after the controller 110 controls the relays in the j power converters 130 and the k power converters 130 to be turned off, when the load carrying capacity of the power grid increases by more than or equal to a third threshold value, the controller 110 controls the relays in one or more of the j power converters 130 and the k power converters 130 to be turned on, and controls the one or more of the j power converters 130 and the k power converters 130 to input the power from the power grid to the corresponding battery cluster 120; or, after the controller 110 controls the relays in the j power converters 130 and the k power converters 130 to be turned off, when the load carrying capacity of the power grid decreases by more than or equal to a fourth threshold value, the controller 110 controls the relays in one or more of the j power converters 130 and the k power converters 130 to be turned on, and controls the one or more of the j power converters 130 and the k power converters 130 to input the power from the corresponding battery cluster 120 to the power grid. For example, for simplicity, the third threshold value and the fourth threshold value are also 200kw, and in actual applications, the first threshold value, the second threshold value, the third threshold value, and the fourth threshold value can all be different values. When the load carrying capacity of the power grid redundancy increases from 600kw to 1000kw, and the maximum power output of each power converter 130 is 200kw, then among the power converters 130 that have stopped power output, three of them are selected to perform power output. After the power converters 130 that have stopped power output resume power output, they stop absorbing the reactive power of the power grid, and the power converters 130 that need to output the reactive power also decrease. The controller 110 continues to use the foregoing control logic to retain a certain number of power converters 130 to output the reactive power, as long as the total amount of the reactive power output by the power converters 130 is greater than or equal to the total amount of the reactive power absorbed by the other power converters 130 that have stopped power output.

[0044] In another embodiment provided in the present application, in addition to the foregoing power converters 130 that have stopped power output, there are other power converters 130 in the energy storage system 100, and the controller 110 controls any one or more of the power converters 130 that have stopped power output and the other power converters 130 to perform power output to meet the load carrying demand of the power grid.

[0045] It should be understood that after the controller 110 receives the demand of the power grid, the process of controlling the relay in the power converter 130 to be turned on and then controlling the power converter 130 to output power needs a certain time, and the power grid usually has a certain requirement on the response time of its demand, for example, the power grid has a higher requirement on the response time of the energy storage system 100 in the frequency modulation scenario of energy storage, that is, the speed of the response of the energy storage system 100 is required to be faster, and the power grid has a lower requirement on the response time of the energy storage system 100 in the peak regulation scenario, that is, the speed of the response of the energy storage system 100 is required to be lower. Therefore, in different application scenarios, the time required for the controller 110 to control the relay in the power converter 130 to be turned on and then control the power converter 130 to start inputting the power of the power grid to the battery cluster 120, or the time required for the controller 110 to control the relay in the power converter 130 to be turned on and then control the power converter 130 to start inputting the power of the battery cluster 120 to the power grid, can be less than or equal to the demand response threshold of the power grid.

[0046] With reference back to Figure 4 In an embodiment provided by the present application, the power converter 130 also has a controller 132, and the controller 110 is a master controller, also called a data collector, which can be used to collect information such as the load demand of the power grid and the voltage of the power grid, and can be used to send working instructions to the controller 132. The controller 132 is a slave controller, which is responsible for receiving instructions from the controller 110 and controlling the power conversion circuit 131 in the power converter 130 and the specific control of the turning on and off of the relay. Through the functional division of the master controller and the slave controller and the reasonable allocation of the computing power of the controllers, the response efficiency of the energy storage system 100 can be higher.

[0047] In an embodiment provided by the present application, the power converter 130 and the corresponding battery cluster 120 are placed in the same battery cabinet to form an energy storage unit, and the energy storage units are combined to form the energy storage system 100. In this way, each energy storage unit in the energy storage system 100 is an independent working unit, and each power converter 130 and the corresponding battery cluster 120 cooperate to independently control the power output of the energy storage unit.

[0048] With reference back to Figure 5 A control process of the power converter 130 provided in an embodiment of the present application.

[0049] When the energy storage system 100 is in a state of being connected to the power grid, if the load carrying capacity of the power grid is insufficient or redundant, step S101 is performed.

[0050] S101: controlling one or more power converters 130 to output / input electric energy. That is, when the grid generates power demand, controlling one or more power converters 130 to output electric energy in the battery cluster 120 to the grid, and when the grid generates discharge demand, controlling one or more power converters 130 to output electric energy in the grid to the battery cluster 120.

[0051] When the grid's carrying capacity decreases by more than or equal to a first threshold value / the grid's carrying capacity increases by more than or equal to a second threshold value, step S102 is performed, otherwise S101 is continued.

[0052] S102: controlling j power converters 130 to be blocked and k power converters 130 to output reactive power. It should be understood that here controlling j power converters 130 to be blocked means controlling one or more power converters 130 in the one or more power converters 130 in step S101 to stop power output, and controlling k power converters 130 to output reactive power means controlling k power converters 130 to output reactive power. That is, when the grid's carrying capacity decreases by more than or equal to a first threshold value, among the one or more power converters 130 that output electric energy in the grid to the corresponding battery cluster 120, one or more are selected to stop outputting electric energy in the grid to the corresponding battery cluster 120, and among the power converters 130 other than the power converters 130 that stop power output, one or more are selected to output reactive power to provide reactive compensation for the grid; when the grid's carrying capacity increases by more than or equal to a second threshold value, among the one or more power converters 130 that output electric energy in the battery cluster 120 to the grid, one or more are selected to stop outputting electric energy in the battery cluster 120 to the grid, and among the power converters 130 other than the power converters 130 that stop power output, one or more are selected to output reactive power to provide reactive compensation for the grid, to ensure the stability of the grid voltage.

[0053] When the time for j power converters 130 to be blocked is greater than or equal to a time threshold value, S103 is performed.

[0054] S103: disconnecting the relays of j+k power converters 130. That is, when the time for the power converters 130 that stop power output in step S102 to stop working is greater than or equal to a time threshold value, the relays of j and k power converters 130 are controlled to be disconnected. That is, when the time for the power converters 130 that stop power output in step S102 to stop working is greater than or equal to a time threshold value, the relays of the power converters 130 that stop power output and the power converters 130 that output reactive power compensation are controlled to be disconnected, to reduce the power loss of the system.

[0055] In another embodiment provided by the application, the trigger condition for performing S103 is relaxed, not only considering time, but also considering the current system loss, i.e., when the duration of the j power converters 130 stopping power output is greater than or equal to the time threshold and the power loss of the energy storage system 100 exceeds the system loss threshold, performing step S103 to balance the power loss of the energy storage system 100 and the response demand of the energy storage system 100 to the power grid.

[0056] In addition, in an embodiment provided by the application, when the load carrying capacity of the power grid changes again after part of the power converters 130 stop power output due to the change of the load carrying capacity of the power grid, the power converter 130 that stops power output is controlled to resume power output; in another embodiment provided by the application, in addition to the power converter 130 that stops power output, there are other power converters 130 in the energy storage system 100, and the controller 110 controls any one or more of the power converter 130 that stops power output and the other power converters 130 to output power to meet the load carrying demand of the power grid.

[0057] The preferred embodiments of the application disclosed above are only used to help explain the application. The preferred embodiments do not describe all the details and limit the application to the specific embodiments described. Obviously, many modifications and changes can be made according to the content of the embodiments of the application. The application selects and describes these embodiments in order to better explain the principles and practical applications of the application, so that those skilled in the art can well understand and utilize the application. The application is limited only by the claims and their full scope and equivalents.

Claims

1. An energy storage system, characterized by, The power converter includes a relay for controlling the power converter and the power grid by turning on or off; The main controller is configured to control one or more of the power converters to input power from the power grid to the corresponding battery cluster when the load capacity of the power grid is greater than the power demand of the load, or to control one or more of the power converters to output power from the corresponding battery cluster to the power grid when the load capacity of the power grid is less than the power demand of the load; The main controller is further configured to control j of the power converters to stop power output and k of the power converters to output reactive power when the load capacity of the power grid decreases by more than or equal to a first threshold or the load capacity of the power grid increases by more than or equal to a second threshold, and the k power converters output reactive power greater than or equal to the reactive power absorbed by the j power converters from the power grid, j+k≤n. The power converter includes a filter capacitor for filtering out ripple current in the AC power output by the power converter, and the amount of reactive power absorbed by the j power converters from the power grid is positively correlated with the size of the filter capacitor in the j power converters.

2. The energy storage system of claim 1, wherein, The power converter includes a relay for controlling the power converter and the power grid by turning on or off; The main controller is further configured to control the relays in the j power converters and the k power converters to turn off when the duration of the j power converters stopping power output is greater than or equal to a time threshold.

3. The energy storage system of claim 1, wherein, The power converter includes a relay for controlling the power converter and the power grid by turning on or off; The main controller is configured to control the relays in the j power converters and the k power converters to turn on and control one or more of the j power converters and the k power converters to input power from the power grid to the corresponding battery cluster when the load capacity of the power grid increases by more than or equal to a third threshold after the relays in the j power converters and the k power converters are controlled to turn off; or 4. An energy storage system according to claim 2 or 3, characterised in that, The main controller is configured to control the relays in the j power converters and the k power converters to turn on and control one or more of the j power converters and the k power converters to input power from the power grid to the corresponding battery cluster when the load capacity of the power grid increases by more than or equal to a third threshold after the relays in the j power converters and the k power converters are controlled to turn off; or The main controller is configured to control the relays in one or more of the j power converters and the k power converters to turn on after the relays in the j power converters and the k power converters are controlled to turn off, and the load-carrying capacity of the power grid decreases by more than or equal to a fourth threshold value, and control the one or more power converters to input the electrical energy of the corresponding battery cluster to the power grid.

5. The energy storage system of claim 4, wherein, The demand response time limit of the power grid is greater than or equal to a demand response threshold value; The main controller controls the relays in the one or more power converters to turn on and controls the one or more power converters to start inputting the electrical energy of the power grid to the battery cluster after the relays in the j power converters and the k power converters are controlled to turn off, and the time required is less than or equal to the demand response threshold value; Or The main controller controls the relays in the one or more power converters to turn on and controls the one or more power converters to start outputting the electrical energy of the battery cluster to the power grid after the relays in the j power converters and the k power converters are controlled to turn off, and the time required is less than or equal to the demand response threshold value.

6. The energy storage system of any of claims 1-3 or 5, wherein, The power converter comprises a slave controller and a power conversion circuit, and the main controller is configured to send control instructions to the slave controller to control the slave controller to control the power conversion circuit to work or stop working to realize the power output or stop power output of the power converter, and send control instructions to the slave controller to control the relay to turn on or turn off.

7. The energy storage system of claim 6, wherein, Each of the power converters and the corresponding battery cluster is located inside the same energy storage container.

8. A method of controlling an energy storage system, the method comprising: One or more power converters are controlled to input the electrical energy of the power grid to the corresponding battery cluster when the load-carrying capacity of the power grid is greater than the power demand of the load, or output the electrical energy of the corresponding battery cluster to the power grid when the load-carrying capacity of the power grid is less than the power demand of the load; When the load-carrying capacity of the power grid decreases by more than or equal to a first threshold value or the load-carrying capacity of the power grid increases by more than or equal to a second threshold value, j of the one or more power converters are controlled to stop power output, and k of the power converters other than the j power converters are controlled to output reactive power, and the reactive power output by the k power converters is greater than or equal to the reactive power absorbed by the j power converters from the power grid, j+k≤n, where n is the number of power converters in the energy storage system; Wherein, the power converter comprises a filter capacitor, and the filter capacitor is configured to filter out the ripple current in the alternating current output by the power converter; the size of the reactive power absorbed by the j power converters from the power grid is positively related to the size of the capacitance value of the filter capacitor in the j power converters.

9. The energy storage system control method of claim 8, wherein, when the duration of the j power converters stopping power output is greater than or equal to a time threshold, controlling a relay in the j power converters and the k power converters to open; wherein the relay is configured to control the power converter to turn on or off by turning on or off.

10. The energy storage system control method of claim 8, wherein, when the duration of the j power converters stopping power output is greater than or equal to a time threshold and the power loss of the energy storage system is greater than or equal to a system loss threshold, controlling a relay in the j power converters and the k power converters to open; wherein the relay is configured to control the power converter to turn on or off by turning on or off.

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