Energy storage system and control method thereof

Abstract

The invention discloses an energy storage system and a control method of the energy storage system, and relates to the technical field of energy storage. The first end of the first switch circuit is electrically connected with the energy storage circuit, and the second end of the first switch circuit is electrically connected with at least one direct current bus; the first end of the power conversion circuit is electrically connected with the at least one direct current bus, the second end of the power conversion circuit is used for being connected into a power grid, and the power conversion circuit is used for inverting the direct current on the direct current bus and then outputting the direct current to the power grid; the control circuit is electrically connected with the controlled end of the first switching circuit and the power conversion circuit respectively; the invention aims to realize the most effective recycling of the regenerated energy of the equipment and reduce the power utilization cost to the greatest extent.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of energy storage, in particular to an energy storage system and a control method thereof. BACKGROUND

[0002] At present, various production and manufacturing equipment are changing and upgrading to new energy saving and power saving. The present application mainly relates to equipment capable of generating renewable energy, including elevators, hoisting machinery and oil pumping machines. The current energy source of these devices is mains power. According to statistics, the annual power consumption of elevators nationwide is up to 26 billion degrees of electricity. When the mains power is off, the equipment cannot operate reliably and stably, affecting the daily operation of the equipment. At the same time, when the equipment operates to drive the main circuit, renewable energy is generated. The current common processing method is to dissipate the heat energy in the form of consumption resistance, and there is a lack of effective recycling scheme, so there is a lot of energy waste. SUMMARY

[0003] The main purpose of the present application is to provide an energy storage system and a control method thereof, which aims to improve the most effective recycling of renewable energy of the equipment and reduce the power consumption cost as much as possible.

[0004] To achieve the above purpose, the present application provides an energy storage system, which comprises: an energy storage circuit; a first switching circuit, a first end of the first switching circuit being electrically connected with the energy storage circuit, and a second end of the first switching circuit being electrically connected with at least one DC bus; a power conversion circuit, a first end of the power conversion circuit being electrically connected with at least one DC bus, and a second end of the power conversion circuit being used for connecting to a power grid, the power conversion circuit being used for inverting and outputting the DC power on the DC bus to the power grid; a control circuit, the control circuit being electrically connected with a controlled end of the first switching circuit and the power conversion circuit respectively, and the control circuit being used for acquiring total renewable power and total power consumption on the DC bus; the control circuit being used for controlling the first switching circuit to be turned on to charge the energy storage circuit with the DC bus and / or controlling the power conversion circuit to invert and output the DC power on the DC bus to the power grid in the case that the total renewable power is greater than the total power consumption; the control circuit being further used for controlling the first switching circuit to be turned on to discharge the DC bus with the energy storage circuit and / or controlling the power conversion circuit to invert and output the DC power on the DC bus to the power grid in the case that the total renewable power is not greater than the total power consumption.

[0005] In an embodiment, the first switching circuit comprises: The first switch assembly and the unidirectional conduction circuit are electrically connected with the energy storage circuit, and the second end of the first switch assembly and the input end of the unidirectional conduction circuit are electrically connected with at least one DC bus.

[0006] In an embodiment, the energy storage system further comprises at least one second switch assembly, the first end of the second switch assembly is connected with the output end of the first switch circuit, the second end of the second switch assembly is electrically connected with a DC bus, and the controlled end of the second switch assembly is electrically connected with the control circuit.

[0007] The application further provides a control method of an energy storage system, which is applied to the energy storage system as described in any one of the preceding items, and the control method comprises the following steps: obtaining total regenerated electric quantity and total electric quantity on at least one DC bus; in the case that the total regenerated electric quantity is greater than the total electric quantity, controlling the first switch circuit to be conductive, so that the DC bus charges the energy storage circuit, and / or controlling the power conversion circuit to output DC power on the DC bus to the power grid after inversion processing; in the case that the total regenerated electric quantity is not greater than the total electric quantity, controlling the first switch circuit to be conductive, so that the energy storage circuit discharges the DC bus, and / or controlling the power conversion circuit to output DC power on the DC bus to the power grid after inversion processing.

[0008] In an embodiment, the step of, in the case that the total regenerated electric quantity is greater than the total electric quantity, controlling the first switch circuit to be conductive, so that the DC bus charges the energy storage circuit, and / or controlling the power conversion circuit to output DC power on the DC bus to the power grid, comprises the following steps: obtaining chargeable quantity of the energy storage circuit, and comparing the difference between the total regenerated electric quantity and the total electric quantity with the chargeable quantity; in the case that the difference between the total regenerated electric quantity and the total electric quantity is greater than the chargeable quantity, controlling the first switch circuit to be conductive, so that the DC bus charges the energy storage circuit, and also controlling the power conversion circuit to output DC power on the DC bus to the power grid after inversion processing; in the case that the difference between the total regenerated electric quantity and the total electric quantity is not greater than the chargeable quantity, controlling the first switch circuit to be conductive, so that the DC bus charges the energy storage circuit.

[0009] In an embodiment, the number of DC buses is multiple, the power conversion circuit includes multiple power conversion modules, and the multiple power conversion modules are connected in one-to-one correspondence with the multiple DC buses. In the case where the difference between the total regenerated power and the total power consumption is greater than the chargeable amount, the first switch circuit is controlled to be turned on to enable the DC bus to charge the energy storage circuit, and the power conversion circuit is controlled to output DC power on the DC bus to the power grid after being inverted. The regenerated energy on the multiple DC buses is sorted from large to small, and the first number of DC buses corresponding to the power conversion modules are selected from large to small. According to the rated power of the first number of power conversion modules and the difference between the total regenerated power and the total power consumption, the first duration required for the first number of power conversion modules to release the discharge amount to the power grid when operating at the rated power is calculated. The first number of power conversion modules are controlled to continuously output DC power on the DC bus to the power grid after being inverted based on the first duration at the respective rated power.

[0010] In an embodiment, in the case where the total regenerated power is not greater than the total power consumption, the first switch circuit is controlled to be turned on to enable the energy storage circuit to discharge the DC bus, and / or the power conversion circuit is controlled to output DC power on the DC bus to the power grid after being inverted. The dischargeable amount of the energy storage circuit is obtained, and the difference between the total regenerated power and the total power consumption is compared with the dischargeable amount. In the case where the difference between the total power consumption and the total regenerated power is less than the dischargeable amount, the first switch circuit is controlled to be turned on to enable the energy storage circuit to discharge the DC bus, and the power conversion circuit is controlled to output DC power on the DC bus to the power grid after being inverted. In the case where the difference between the total power consumption and the total regenerated power is not less than the dischargeable amount, the first switch circuit is controlled to be turned on to enable the energy storage circuit to discharge the DC bus.

[0011] In an embodiment, the number of DC buses is multiple, the power conversion circuit includes multiple power conversion modules, and the multiple power conversion modules are connected in one-to-one correspondence with the multiple DC buses. In the case where the difference between the total power consumption and the total regenerated power is less than the dischargeable amount, the first switch circuit is controlled to be turned on to enable the energy storage circuit to discharge the DC bus, and the power conversion circuit is controlled to output DC power on the DC bus to the power grid after being inverted. acquire an actual electricity price of a current period, and calculate a remaining dischargeable amount of the dischargeable amount under a condition that electricity consumption of a plurality of DC bus connected loads is met, in a case where the actual electricity price is greater than a preset electricity price; acquire rated power sizes of a plurality of the power conversion modules, and sort them from large to small; sort out a second number of the power conversion modules from large to small, and determine a second time length required for discharge amounts released to a power grid by the second number of the power conversion modules operating at respective rated powers to reach the remaining dischargeable amount; control the second number of the power conversion modules to continuously output DC power on the DC bus to the power grid after inverting processing of the DC power based on the second time length at the respective rated powers.

[0012] In an embodiment, the control method further comprises: determining a maximum current flowing to the energy storage circuit on a plurality of DC buses within a preset time period based on historical operation data; determining a rated power of the energy storage circuit according to the maximum current and a rated voltage of the DC bus; determining a total rated power of a plurality of the power conversion modules as a difference between a sum of rated powers of a plurality of frequency converters connected to the DC buses and the rated power of the energy storage circuit, and determining a rated power of each of the power conversion modules according to the total rated power and the rated powers of the plurality of frequency converters.

[0013] In an embodiment, the determining of the maximum current flowing to the energy storage circuit on the plurality of DC buses within the preset time period based on the historical operation data comprises: determining a maximum number k of electric machines in a power generation state and a number l of electric machines in a power consumption state within a preset time period based on historical power generation data and historical power consumption data of a plurality of electric machines, wherein k+l=n, and n is a total number of the electric machines; determining a first maximum DC side current of each of the k electric machines in the power generation state, and determining a second maximum DC side current of each of the l electric machines in the power consumption state; adding the first maximum DC side current of each of the electric machines and the second maximum DC side current of each of the electric machines to calculate the maximum current flowing to the energy storage circuit on the plurality of DC buses.

[0014] In an embodiment, the first switching circuit comprises: a first switching component and a unidirectional conduction circuit, a first end of the first switching component and an output end of the unidirectional conduction circuit are both electrically connected to the energy storage circuit, a second end of the first switching component and an input end of the unidirectional conduction circuit are both electrically connected to at least one DC bus, and the control method further comprises: acquire a current power of the energy storage circuit; in a case that the current power is less than a preset full discharge threshold, control the first switch assembly to be turned off, so that the DC bus charges the energy storage circuit through the unidirectional conduction circuit; in a case that the power of the energy storage circuit reaches a preset full charge threshold, control the first switch assembly to be turned on.

[0015] The energy storage system comprises an energy storage circuit, a first switch circuit, a control circuit, a power conversion circuit and the control circuit. The first end of the first switch circuit is electrically connected with the energy storage circuit, and the second end of the first switch circuit is electrically connected with at least one DC bus. The first end of the power conversion circuit is electrically connected with at least one DC bus, and the second end of the power conversion circuit is used for connecting to a power grid. The power conversion circuit is used for inverting the DC power on the DC bus and outputting to the power grid, so as to discharge the power grid. The control circuit is used for determining that there is residual regenerative power on the DC bus in a case that the total regenerative power is greater than the total power consumption, and controlling the first switch circuit to be turned on, so that the DC bus charges the energy storage circuit, thereby storing and recycling the regenerative power generated by the regenerative device, and / or controlling the power conversion circuit to invert the DC power on the DC bus and output to the power grid, thereby obtaining the electricity selling income. The control circuit is also used for determining that the energy consumed by the regenerative device is greater than or equal to the energy generated in a case that the total regenerative power is not greater than the total power consumption, and the external supplement may be needed. Therefore, the first switch circuit is controlled to be turned on, so that the energy storage circuit discharges the DC bus, so that the device on the DC bus can work by using the excess power of the energy storage circuit 10, thereby reducing the power obtained from the power grid, thereby saving the corresponding electricity fee, and / or controlling the power conversion circuit to invert the DC power on the DC bus and output to the power grid, thereby obtaining the electricity selling income.

[0016] By such an arrangement, compared with the prior art, the energy storage system can not only release the regenerative power generated by the device to the power grid to obtain the electricity selling income, but also store the regenerative power to the energy storage circuit. The energy storage circuit can discharge to the DC bus when the device needs external supplement of power, thereby reducing the power obtained from the power grid, thereby saving the corresponding electricity fee, and / or releasing to the power grid, thereby further improving the income. Therefore, the energy storage system not only guarantees the operation reliability, but also realizes the efficient recycling of regenerative energy and comprehensively reduces the comprehensive power consumption cost. BRIEF DESCRIPTION OF DRAWINGS

[0017] In order to make the technical solutions in the embodiments of the present application or the prior art clearer, the accompanying drawings needed in the embodiments or prior art description will be briefly introduced. Obviously, the accompanying drawings in the following description only need to be some embodiments of the present application, and for those skilled in the art, other drawings can be obtained without creative labor.

[0018] Figure 1 The circuit structure schematic diagram of an embodiment of the present application; Figure 2 The circuit structure schematic diagram of another embodiment of the present application; Figure 3 The circuit structure schematic diagram of still another embodiment of the present application; Figure 4 The flowchart schematic diagram of an embodiment of the present application; Figure 5 The flowchart schematic diagram of another embodiment of the present application; Figure 6 The flowchart schematic diagram of still another embodiment of the present application; Figure 7 The flowchart schematic diagram of yet another embodiment of the present application; Figure 8 The flowchart schematic diagram of still another embodiment of the present application; Figure 9 The flowchart schematic diagram of another embodiment of the present application; Figure 10 The flowchart schematic diagram of still another embodiment of the present application; Figure 11 The flowchart schematic diagram of yet another embodiment of the present application.

[0019] Explanation of the accompanying drawings: 10, energy storage circuit; 20, first switch circuit; 21, first switch component; 22, unidirectional conduction circuit; 30, power conversion circuit; 31, power conversion module; 40, control circuit; 50, second switch component.

[0020] The implementation, functional features and advantages of the present application will be further described with reference to the embodiments and the accompanying drawings. DETAILED DESCRIPTION

[0021] The technical solutions in the embodiments of the present application will be described clearly and completely with reference to the accompanying drawings in the embodiments of the present application. Obviously, the described embodiments are only some embodiments of the present application, but not all the embodiments. Based on the embodiments in the present application, all the other embodiments obtained by those skilled in the art without creative labor belong to the protection scope of the present application.

[0022] It should be noted that if the embodiments of the present application involve directional indications (such as up, down, left, right, front, back, etc.), the directional indications are only used to explain the relative position relationship, motion condition, etc. between components in a certain posture, and if the certain posture changes, the directional indications will also change accordingly.

[0023] In addition, if the embodiments of the present application involve descriptions such as "first", "second", etc., the descriptions of "first", "second", etc. are only for description purposes and cannot be understood as indicating or implying the relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features limited by "first" and "second" can explicitly or implicitly include at least one of the features. In addition, "and / or" or "and / or" appearing throughout the text means that the three parallel schemes are included, for example, "A and / or B" includes A scheme, or B scheme, or A and B are satisfied at the same time. In addition, the technical solutions of each embodiment can be combined with each other, but it must be based on the realization of ordinary skilled in the art, when the combination of technical solutions appears contradictory or unachievable, it should be considered that the combination of technical solutions does not exist, nor within the scope of protection claimed by the present application.

[0024] At present, various types of production and manufacturing equipment are changing and upgrading to new energy saving and energy saving. The present scheme mainly relates to equipment capable of generating renewable energy, including elevators, hoisting machinery and oil pumping machines, etc. The current energy source of these devices is the power supply. According to statistics, the annual power consumption of elevators nationwide is 26 billion degrees, and when the power supply is cut off, the equipment cannot be reliably and stably operated, affecting the daily operation of the equipment. At the same time, when the equipment is operating and driving the main circuit, it will generate renewable energy. The current common processing method is to dissipate the heat energy in the form of heat by consuming resistance, and there is a lack of effective recovery scheme, so there is a lot of energy waste.

[0025] To solve the above technical problems, the present application provides an energy storage system, in an embodiment, referring to Figure 1 The energy storage system comprises: An energy storage circuit 10; A first switching circuit 20, a first end of the first switching circuit 20 is electrically connected with the energy storage circuit 10, and a second end of the first switching circuit 20 is electrically connected with at least one DC bus; A power conversion circuit 30, a first end of the power conversion circuit 30 is electrically connected with at least one DC bus, and a second end of the power conversion circuit 30 is used for connecting to a power grid, and the power conversion circuit 30 is used for inverting the DC power on the DC bus and outputting to the power grid; A control circuit 40 is electrically connected to the controlled end of the first switching circuit 20 and the power conversion circuit 30, respectively, and is configured to obtain total regenerated power and total power consumption on at least one DC bus. The control circuit 40 is configured to control the first switching circuit 20 to be turned on to charge the DC bus to the energy storage circuit 10 and / or control the power conversion circuit 30 to output DC power on the DC bus to the grid after inversion processing in the case that the total regenerated power is greater than the total power consumption. The control circuit 40 is further configured to control the first switching circuit 20 to be turned on to discharge the DC bus to the energy storage circuit 10 and / or control the power conversion circuit 30 to output DC power on the DC bus to the grid after inversion processing in the case that the total regenerated power is not greater than the total power consumption.

[0026] In the embodiment, the number of DC buses can be one or more, and the device is connected to the grid through a DC / AC module, a DC bus and an AC / DC module in sequence, wherein the DC / AC module, the DC bus and the AC / DC module constitute a frequency converter.

[0027] In the embodiment, the energy storage circuit 10 is configured to store and release electric energy, and can be implemented by a plurality of series-connected batteries, which can be various chemical substances such as supercapacitors, lithium batteries, storage batteries and sodium batteries.

[0028] In the embodiment, the first switching circuit 20 can be implemented by at least one switching tube such as a MOS tube, an IGBT tube, a thyristor, a triode and a power tube, and / or at least one switching device such as a contactor, a circuit breaker and a relay.

[0029] In the embodiment, the power conversion circuit 30 can be implemented by one power conversion module, which is a DC / AC module and is connected to the energy storage circuit 10 and all DC buses to realize centralized inversion and grid connection of energy. The power conversion circuit 30 can also be implemented by a plurality of power conversion modules, the number of which is less than the total number of DC buses, at least one power conversion module is connected in parallel to two or more DC buses, and the cost and partial redundancy capability are considered. Figure 2 The power conversion circuit 30 can also be implemented by the same number of power conversion modules 31 as the number of DC buses to realize one-to-one independent connection, improve system flexibility, scalability and fault isolation capability.

[0030] In the embodiment, the control circuit 40 can be implemented by a master control module, a voltage detection module and a current detection module. The master control module can be implemented by, for example, an MCU (Microcontroller Unit), a DSP (Digital Signal Process), an FPGA (Field Programmable Gate Array), an SOC (System On Chip), etc. The voltage detection circuit is used to detect the voltage on the DC bus, the current detection circuit is used to detect the current on the DC bus, and the master control module is used to calculate the instantaneous power of each DC bus according to the voltage on the DC bus and the current on the DC bus. When the instantaneous power is negative, it indicates that the device on the DC bus is generating regenerative electric energy. The control circuit 40 adds the regenerative electric energy generated by each device in the power generation state to obtain the total regenerative energy. When the instantaneous power is positive, it indicates that the device on the DC bus is consuming electric energy. The control circuit 40 adds the electric energy consumed by each device in the power consumption state to obtain the total power consumption.

[0031] In the embodiment, the control circuit 40 is used to determine that there is residual regenerative electric energy on the DC bus when the total regenerative electric energy is greater than the total power consumption, and control the first switch circuit 20 to be turned on so as to charge the energy storage circuit 10 by the DC bus, thereby storing and recycling the regenerative electric energy generated by the regenerative device, and / or control the power conversion circuit 30 to output the DC power on the DC bus to the power grid after inversion processing, thereby obtaining the electricity selling benefit. The control circuit 40 is also used to determine that the energy consumed by the regenerative device is greater than or equal to the energy generated when the total regenerative electric energy is not greater than the total power consumption, which may need external supplement. Therefore, the first switch circuit 20 is controlled to be turned on so as to discharge the energy storage circuit 10 to the DC bus, so that the device on the DC bus can work by using the excess electric energy of the energy storage circuit 10, thereby reducing the electric energy obtained from the power grid and saving the corresponding electricity fee, and / or the power conversion circuit 30 is controlled to output the DC power on the DC bus to the power grid after inversion processing, thereby obtaining the electricity selling benefit.

[0032] In this way, compared with the prior art, the energy storage system of the present application not only releases the regenerative electric energy generated by the device to the power grid to obtain the electricity selling benefit, but also stores the regenerative electric energy to the energy storage circuit 10. The energy storage circuit 10 can discharge to the DC bus when the device needs external supplement of electric energy, thereby reducing the electric energy obtained from the power grid and saving the corresponding electricity fee, and / or releasing to the power grid, thereby further improving the benefit. Therefore, the energy storage system of the present application not only guarantees the operation reliability, but also realizes the efficient recycling of regenerative energy and comprehensively reduces the comprehensive power consumption cost.

[0033] If the system continues to be in the net power consumption state (i.e., the total power consumption continues to be greater than the total renewable power, and the net energy flow is from the energy storage circuit 10 to the DC bus to the load), and the initial energy of the energy storage circuit 10 is already low (e.g., the terminal voltage is close to or lower than the preset full discharge threshold), then continuous discharging will cause deep over-discharge, which may cause accelerated capacity degradation, increased internal resistance, and even irreversible damage or safety risks of the energy storage circuit 10.

[0034] In an embodiment of the present application, referring to Figure 2 , the first switching circuit 20 comprises: A first switching component 21 and a unidirectional conduction circuit 22, the first end of the first switching component 21 and the output end of the unidirectional conduction circuit 22 are both electrically connected to the energy storage circuit 10, and the second end of the first switching component 21 and the input end of the unidirectional conduction circuit 22 are both electrically connected to at least one DC bus. Wherein, the first switching component 21 can be realized by a switching tube, such as MOS tube, IGBT tube, thyristor, triode, power tube, etc., and / or realized by a switching device, such as contactor, circuit breaker and relay.

[0035] In the present embodiment, the unidirectional conduction circuit 22 can be realized by at least one diode, the cathode of the diode as the output end of the unidirectional conduction circuit 22, and the anode as the input end of the unidirectional conduction circuit 22.

[0036] In the present embodiment, the control circuit 40 can control the first switching component 21 to be turned off when it is detected that the energy of the energy storage circuit 10 is lower than the preset full discharge threshold. Due to the unidirectional conduction characteristic of the unidirectional conduction circuit 22, only a unidirectional charging path is reserved between the DC bus and the energy storage circuit 10 (the current can flow from the DC bus to the energy storage circuit 10 through the unidirectional conduction circuit 22, but cannot flow in the opposite direction), so that the energy storage circuit 10 can only draw power from the DC bus, but cannot discharge the DC bus. Wherein, the preset full discharge amount is the lowest safe energy limit value that the energy storage circuit 10 allows to discharge, and discharging below this value may cause irreversible damage.

[0037] In this way, the unidirectional conduction circuit 22 effectively blocks the discharge path of the energy storage circuit 10 to the DC bus, avoiding deep over-discharge due to continuous power supply to the outside in a low energy state. If there is renewable energy in the DC bus, it can passively flow into the energy storage circuit 10 for supplementary charging, promoting the energy of the energy storage circuit 10 to rise to the full charge state, and significantly improving the safety and cycle life of the energy storage circuit 10.

[0038] In an embodiment of the present application, referring to Figure 3The energy storage system further comprises at least one second switch assembly 50, a first end of the second switch assembly 50 is connected with an output end of the first switch circuit 20, a second end of the second switch assembly 50 is connected with a DC bus, and a controlled end of the second switch assembly 50 is connected with the control circuit 40. The second switch assembly 50 can be realized by at least one switch tube, such as a MOS tube, an IGBT tube, a thyristor, a triode, a power tube, etc., and / or at least one switch device, such as a contactor, a circuit breaker and a relay.

[0039] In the embodiment, when any one device is detected to be faulty, the control circuit 40 can control the second switch assembly 50 connected with the DC bus to which the device is connected to be disconnected, so as to avoid the energy storage circuit 10 from discharging to the faulty device and causing an accident.

[0040] The application further provides a control method of an energy storage system, which is applied to any one of the energy storage systems, and in an embodiment, with reference to Figure 4 The control method comprises the following steps. Step S100: acquiring total regenerated power and total power consumption on at least one DC bus; Step S200: in a case where the total regenerated power is greater than the total power consumption, controlling the first switch circuit 20 to be turned on, so as to charge the DC bus to the energy storage circuit 10, and / or controlling the power conversion circuit 30 to output DC power on the DC bus to a power grid after inverting the DC power; In a case where the total regenerated power is not greater than the total power consumption, controlling the first switch circuit 20 to be turned on, so as to discharge the energy storage circuit 10 to the DC bus, and / or controlling the power conversion circuit 30 to output DC power on the DC bus to a power grid after inverting the DC power.

[0041] Specifically, the control method is used to determine that there is surplus renewable energy on the DC bus in the case that the total renewable energy is greater than the total power consumption, and control the first switch circuit 20 to be turned on to enable the DC bus to charge the energy storage circuit 10, so as to store and recycle the renewable energy generated by the renewable device, and / or control the power conversion circuit 30 to output the DC power on the DC bus to the power grid after inverting the DC power, so as to obtain the electricity selling income; the control method is also used to determine that the energy consumed by the renewable device is greater than or equal to the energy generated in the case that the total renewable energy is not greater than the total power consumption, and external supplement may be needed, so the first switch circuit 20 is controlled to be turned on to enable the energy storage circuit 10 to discharge the DC bus, so that the device on the DC bus can work by using the excess energy of the energy storage circuit 10, thereby reducing the energy obtained from the power grid, so as to save the corresponding electricity fee, and / or the power conversion circuit 30 is controlled to output the DC power on the DC bus to the power grid after inverting the DC power, so as to obtain the electricity selling income.

[0042] In this way, compared with the prior art, the energy storage system of the present application not only releases the renewable energy generated by the device to the power grid to obtain the electricity selling income, but also stores the renewable energy to the energy storage circuit 10, which can discharge to the DC bus when the device needs external power supplement, thereby reducing the energy obtained from the power grid and saving the corresponding electricity fee, and / or releasing to the power grid to further improve the income. Therefore, the energy storage system of the present application not only ensures the operation reliability, but also realizes the efficient recycling of renewable energy and reduces the comprehensive power consumption cost.

[0043] It is worth noting that since the control method of the energy storage system of the present application is based on the above-mentioned energy storage system, the embodiments of the control method of the energy storage system of the present application include all the technical solutions of all the embodiments of the above-mentioned energy storage system, and the technical effects achieved are also completely the same, which will not be repeated here.

[0044] In an embodiment of the present application, with reference to Figure 5 , the control of the first switch circuit 20 to be turned on to enable the DC bus to charge the energy storage circuit 10 and / or the control of the power conversion circuit 30 to output the DC power on the DC bus to the power grid after inverting the DC power in the case that the total renewable energy is greater than the total power consumption includes: Step S210: obtaining the chargeable amount of the energy storage circuit 10, and comparing the difference between the total renewable energy and the total power consumption with the chargeable amount; Step S220: in the case that the difference between the total renewable energy and the total power consumption is greater than the chargeable amount, controlling the first switch circuit 20 to be turned on to enable the DC bus to charge the energy storage circuit 10, and also controlling the power conversion circuit 30 to output the DC power on the DC bus to the power grid after inverting the DC power; In the case that the difference between the total regenerated electric quantity and the total electric quantity is not greater than the chargeable quantity, the first switch circuit 20 is controlled to be turned on so as to charge the energy storage circuit 10 by the DC bus.

[0045] It should be noted that the chargeable quantity is the difference between the current electric quantity of the energy storage circuit 10 and the preset full charge quantity, and the preset full charge quantity is the highest safe electric quantity limit value that the energy storage circuit 10 can reach, and the continuous charging beyond the value may cause risks such as thermal runaway, lithium precipitation and bulging.

[0046] When the difference between the total regenerated electric quantity and the total electric quantity is greater than the chargeable quantity of the energy storage circuit 10, it indicates that the regenerated energy still has a surplus after meeting the maximum charging demand of the energy storage circuit 10; at this time, the control method of the present application can be executed synchronously: (1) the first switch circuit 20 is turned on to charge the energy storage circuit 10 by the DC bus; (2) the power conversion circuit 30 is started to convert the surplus electric energy on the DC bus into alternating current and feed into the power grid, realizing efficient utilization of energy and maximization of electricity sales revenue.

[0047] When the difference between the total regenerated electric quantity and the total electric quantity is not greater than the chargeable quantity of the energy storage circuit 10, it indicates that the total regenerated electric quantity is sufficient but does not exceed the current receiving capacity of the energy storage circuit 10. At this time, the control method can only turn on the first switch circuit 20 to preferentially store the regenerated electric energy to the energy storage circuit 10, and temporarily not start the power grid feedback, so as to improve the energy utilization efficiency and reduce the electric energy conversion loss.

[0048] In an embodiment of the present application, referring to Figure 2 and Figure 6 , the number of DC buses is multiple, the power conversion circuit 30 comprises multiple power conversion modules 31, the multiple power conversion modules 31 are connected in one-to-one correspondence with the multiple DC buses, and in the case that the difference between the total regenerated electric quantity and the total electric quantity is greater than the chargeable quantity, the first switch circuit 20 is controlled to be turned on so as to charge the energy storage circuit 10 by the DC bus, and the power conversion circuit 30 is further controlled to output the DC power on the DC bus to the power grid after inverting processing. Step S221: The sizes of the regenerated energy on the multiple DC buses are sorted from large to small, and the first number of DC buses corresponding to the power conversion modules 31 are selected from large to small; Step S222: According to the rated power of the first number of power conversion modules 31 and the difference between the total regenerated electric quantity and the total electric quantity, the first duration required for the discharge quantity released to the power grid by the first number of power conversion modules 31 working at the rated power to reach the difference between the total regenerated electric quantity and the total electric quantity is calculated; Step S223: Control the first number of power conversion modules 31 to output the direct current on the direct current bus to the power grid based on the first duration after inverting processing.

[0049] It should be noted that when the regenerative energy of part of the direct current bus is small, if it is inverted and connected to the grid by the power conversion module 31, it may be directly consumed by the power consumption process of the device itself before the inversion is completed, resulting in a decrease in energy scheduling efficiency. Therefore, the control method sorts the regenerative energy of each direct current bus in real time in descending order, and preferentially selects the first number of direct current buses with higher regenerative energy to be connected to the corresponding power conversion module 31 for inversion output, thereby improving the effectiveness of energy feedback and system response efficiency.

[0050] It should be noted that in the process of selecting the first number of power conversion modules 31, the control method judges the working state of each power conversion module 31, and if any module is in an abnormal state (such as over-temperature, over-current, communication interruption or fault alarm), it is automatically excluded and does not participate in scheduling, ensuring safe and reliable operation of the system. The control method can set a minimum energy threshold that can effectively feedback to the grid, select direct current buses with regenerative energy greater than the minimum energy threshold, and set the total number selected as the first number.

[0051] It should be noted that in the case where the specifications of the plurality of power conversion modules 31 are different, the rated power of each power conversion module 31 can be set according to the historical maximum current on the corresponding connected direct current bus and the corresponding direct current bus voltage, thereby ensuring that it has sufficient inversion capacity and reliably and efficiently feeds the regenerative energy back to the grid. In the case where the specifications of the plurality of power conversion modules 31 are the same, the rated power of each power conversion module 31 can be calculated according to the service life of each power conversion module 31.

[0052] In this embodiment, the control method can calculate the first duration according to the following formula:

[0053] wherein, is the difference between the total regenerative power and the total power consumption, is the rated power of the jth power conversion module 31 of the first number of power conversion modules 31, t1 is the first duration, and k is the first number.

[0054] After calculating the first duration, the control method controls the first number of power conversion modules 31 to output the direct current on the direct current bus to the power grid based on the first duration after inverting processing, so that the power conversion circuit 30 can accurately release the remaining regenerative energy on the direct current bus to the power grid, without more or less, achieving efficient recovery of regenerative electric energy.

[0055] Further, with reference to Figure 7 , the control of the first switch circuit 20 to be turned on to make the energy storage circuit 10 discharge to the DC bus and / or the control of the power conversion circuit 30 to output the DC on the DC bus to the grid after inversion processing includes: Step S230: Obtain the dischargeable amount of the energy storage circuit 10, and compare the difference between the total regenerated power and the total power consumption with the dischargeable amount; Step S240: In the case where the difference between the total power consumption and the total regenerated power is less than the dischargeable amount, control the first switch circuit 20 to be turned on to make the energy storage circuit 10 discharge to the DC bus, and control the power conversion circuit 30 to output the DC on the DC bus to the grid after inversion processing; In the case where the difference between the total power consumption and the total regenerated power is not less than the dischargeable amount, control the first switch circuit 20 to be turned on to make the energy storage circuit 10 discharge to the DC bus.

[0056] It should be noted that the dischargeable amount is the difference between the current amount of the energy storage circuit 10 and the preset full discharge amount, and the preset full discharge amount is the lowest safe amount limit that the energy storage circuit 10 can discharge to, and below this value, continued discharge will cause irreversible damage.

[0057] When the difference between the total power consumption and the total regenerated power is less than the dischargeable amount, it indicates that the energy storage circuit 10 still has surplus capacity after meeting the power demand of the device. At this time, the control method executes a double optimization strategy: control the first switch circuit 20 to be turned on to make the energy storage circuit 10 discharge to the DC bus, preferentially meet the power demand of the device, reduce the power taken from the grid by the device, and reduce the power consumption cost; simultaneously enable the power conversion circuit 30 to invert the surplus power (from the discharge of the energy storage circuit 10) on the DC bus into alternating current and feed it into the grid, realize the on-grid of surplus power under the premise of guaranteeing local power supply, and obtain the power selling revenue.

[0058] When the difference between the total power consumption and the total regenerated power is not less than the dischargeable amount, it indicates that the energy storage energy can completely cover the current power demand of the device, but is insufficient to over-supply. At this time, the control method only turns on the first switch circuit 20 to make the energy storage circuit 10 discharge to the DC bus, preferentially on-site consumption, to efficiently meet the load demand and avoid unnecessary grid interaction or energy conversion loss.

[0059] Further, with reference to Figure 2 and Figure 8, the number of the DC buses is multiple, the power conversion circuit 30 comprises multiple power conversion modules 31, the multiple power conversion modules 31 are connected in one-to-one correspondence with the multiple DC buses, in the case that the difference between the total power consumption and the total regenerated power is less than the dischargeable amount, the first switch circuit 20 is controlled to be turned on, so that the energy storage circuit 10 discharges the DC bus, and the power conversion circuit 30 is controlled to output the DC on the DC bus to the power grid after inverting the DC. Step S241: acquiring an actual electricity price of a current period, and in the case that the actual electricity price is greater than a preset electricity price, calculating a remaining dischargeable amount of the dischargeable amount in the case that the dischargeable amount meets the power consumption of the multiple DC bus connected loads; Step S242: acquiring the rated power size of the multiple power conversion modules 31, and sorting them in descending order; Step S243: screening out a second number of the power conversion modules 31 in descending order, and according to the second number of the power conversion modules 31 working at respective rated powers, the discharge amount released to the power grid reaches a second time length required by the remaining dischargeable amount of the energy storage circuit 10; Step S244: controlling the second number of the power conversion modules 31 to output the DC on the DC bus to the power grid after inverting the DC based on the second time length and at respective rated powers.

[0060] It should be noted that in the case that the difference between the total power consumption and the total regenerated power is less than the dischargeable amount, the power conversion circuit 30 can be controlled to output the DC on the DC bus to the power grid after inverting the DC, so as to obtain electricity selling revenue. In order to obtain higher electricity selling revenue, the discharge to the power grid can be performed at a high electricity price period, i.e., when the actual electricity price of the current period is greater than the preset electricity price, so as to obtain electricity selling revenue at a high electricity price.

[0061] In the embodiment, the remaining dischargeable amount of the energy storage circuit 10 is:

[0062] wherein, is the remaining dischargeable amount, is the total power consumption, is the total regenerated power, is the dischargeable amount.

[0063] It should be noted that due to the difference in driving power of different devices, the regeneration capacity and the rated power of the matching power conversion module 31 are also different. When multiple power conversion modules 31 simultaneously invert the electrical energy released by the energy storage circuit 10, the increase in the number of modules will result in an increase in the total loss of the system. Therefore, the rated power of multiple power conversion modules 31 can be sorted in descending order to select the first second number of power conversion modules 31, so that the second number of power conversion modules 31 inverts the electrical energy released by the energy storage circuit 10. It can be understood that the larger the rated power, the higher the conversion efficiency and the greater the capacity, which is suitable for being used for inverting the electrical energy released by the energy storage circuit 10. In this way, unnecessary power conversion modules 31 can be avoided to reduce the loss generated when the power conversion circuit 30 is working.

[0064] It should be noted that in the process of screening the second number of power conversion modules 31, the control method judges the working state of each power conversion module 31. If any module is in an abnormal state (such as over-temperature, over-current, communication interruption or fault alarm), it is automatically excluded and does not participate in scheduling to ensure safe and reliable operation of the system. Among them, the control method can set a minimum rated power threshold that can effectively invert direct current, select a direct current bus with a rated power greater than the minimum rated power threshold, and set the total number selected as the second number.

[0065] In this embodiment, the calculation formula of the second duration can be:

[0066] Among them, is the remaining dischargeable amount, f is the second number, is the rated power of the jth power conversion module 31 of the second number of power conversion modules 31, and t2 is the second duration.

[0067] After calculating the second duration, the control method controls the second number of power conversion modules 31 to invert the direct current on the direct current bus based on the second duration and the respective rated power, and then outputs to the power grid, so that the power conversion circuit 30 can accurately release the remaining dischargeable amount of the energy storage circuit 10 to the power grid, neither more nor less. In this way, not only can the electricity selling revenue be maximized during the high electricity price period, but also the idle electricity can be avoided, and the over-discharge state of the energy storage circuit 10 caused by the release of too much electricity by the energy storage circuit 10 can be avoided, and the safety and cycle life of the battery can be ensured.

[0068] It should be noted that when the second time period exceeds the remaining time period during which the actual electricity price is greater than the preset electricity price, the second time period can be the remaining time period during which the actual electricity price is greater than the preset electricity price, so as to store the remaining unreleased electric energy of the energy storage circuit 10, and release it at the next time period during which the actual electricity price is greater than the preset electricity price, so as to improve the electricity selling income.

[0069] In an embodiment of the present application, with reference to Figure 9 , the control method further comprises: Step S300: determining the maximum current flowing from the plurality of DC bus bars to the energy storage circuit 10 in a preset time period based on historical operation data; Step S400: determining the rated power of the energy storage circuit 10 according to the maximum current and the rated voltage of the DC bus bar; Step S500: taking the difference between the sum of the rated powers of the frequency converters connected to the plurality of DC bus bars and the rated power of the energy storage circuit 10 as the total rated power of the plurality of power conversion modules 31, and determining the rated power of each power conversion module 31 according to the total rated power and the rated power of the plurality of frequency converters.

[0070] It should be noted that the preset time period can be more than one year, or can be set according to actual needs. The control method can detect the current flowing from the plurality of DC bus bars to the energy storage circuit 10 in real time, and when the time window of the current is detected, the sum of the currents flowing from the plurality of DC bus bars to the energy storage circuit 10 is calculated and stored. The control method compares the plurality of current sums stored in the preset time period to determine the maximum current flowing from the plurality of DC bus bars to the energy storage circuit 10 in the preset time period.

[0071] After the maximum current flowing to the energy storage circuit 10 is calculated, the maximum current and the rated voltage of the DC bus bar are multiplied to calculate the rated power of the energy storage circuit 10. In this way, the user can select the composition structure of the energy storage circuit 10 according to the rated power, for example, select the combination of the battery cells of the energy storage circuit 10 according to the rated power, so that the rated power can reach the calculated rated power, so as to ensure that the energy storage circuit 10 can absorb all the regenerated energy under the most severe working condition, and avoid triggering the braking resistor.

[0072] The calculation formula for calculating the total rated power of the plurality of power conversion modules 31 is:

[0073] wherein, P x is the rated power of the xth frequency converter of the n frequency converters, P is the rated power of the energy storage circuit 10, and n is the number of frequency converters.

[0074] The calculation formula of the rated power of each power conversion module 31 is:

[0075] wherein, Py is the rated power of the yth power conversion module 31, P is the total rated power of the plurality of power conversion modules 31, Pf is the rated power of the yth frequency converter.

[0076] Taking an embodiment as an example, it is assumed that the rated powers of three frequency converters are 30 kW, 20 kW and 10 kW respectively, P is 36 kW, then = (30 + 20 + 10) - 36 = 24 kW, the rated power of the first power conversion module 31 is 24 x 30 ÷ 60 = 12 kW, the rated power of the second power conversion module 31 is 24 x 20 ÷ 60 = 8 kW, and the rated power of the third power conversion module 31 is 24 x 10 ÷ 60 = 4 kW.

[0077] In this way, the user can accurately match the specifications of the power conversion modules 31 according to the calculated rated power. The maximum carrying capacity of the power conversion modules 31 can simultaneously cover the requirements of the maximum current of the DC bus and the rated power of the frequency converter, thereby avoiding excessive equipment cost caused by excessive power margin while preventing system overload problems caused by insufficient power, achieving the unity of system economy and reliability.

[0078] Further, with reference to Figure 10 , the determination of the maximum current flowing to the energy storage circuit 10 on the plurality of DC buses in the preset time period based on historical operation data comprises: Step S310: based on the historical power generation data and historical power consumption data of the plurality of motors, determining the maximum number k of motors in the power generation state in the preset time period, and the number l of motors in the power consumption state, wherein k + l = n, n is the total number of motors; Step S320: for the k motors in the power generation state, determining the first maximum DC side current of each motor, and for the l motors in the power consumption state, determining the second maximum DC side current of each motor; Step S330: adding the first maximum DC side current of each motor and the second maximum DC side current of each motor to calculate the maximum current flowing to the energy storage circuit 10 on the plurality of DC buses.

[0079] It should be noted that the motor is the motor inside the equipment connected with the DC bus. When the motor speed direction is opposite to the electromagnetic torque direction (for example, the motor rises), the motor generates electricity (regenerative braking). When the motor speed direction is the same as the electromagnetic torque direction (for example, the motor falls), the motor consumes electricity (electric drive).

[0080] The first maximum DC side current is the historical maximum positive bus current (i.e. feedback current peak) of each motor in the power generation state, which is a direct manifestation of the motor regenerative ability. The second maximum DC side current is the historical maximum negative bus current (i.e. driving current peak) of each motor in the power consumption state, which is a manifestation of the motor consumption ability.

[0081] The calculation formula of the maximum current is:

[0082] Among them, is the maximum current, is the first maximum DC side current of the i-th motor, is the second maximum DC side current of the j-th motor.

[0083] Taking an embodiment as an example, the number of motors is 5, and the historical data shows that a maximum of 4 motors generate electricity at the same time, and the other 1 motor consumes electricity at the same time. The maximum currents of the 4 motors generating electricity are 30A, 28A, 25A and 22A respectively → total = 105A, and the maximum current of the 1 motor consuming electricity is 18A, then the maximum current = 105A - 18A = 87A.

[0084] By setting in this way, the overestimation problem of the traditional method can be effectively avoided: if the maximum charging current is estimated according to the sum of the maximum regenerative currents of all motors, the natural offset effect of the power consumption load on the regenerative current in actual operation is not considered, which will lead to the virtual high demand of the calculated energy storage demand, and then the rated power of the power conversion module 31 is redundantly configured; the control method of the present application is based on historical working condition data, accurately identifies the coexistence state of the power generation and power consumption motors, and takes the net charging current (the sum of the maximum power generation currents the sum of the maximum power consumption currents) as the design basis, so as to ensure that the capacity of the power conversion module 31 can meet the real demand of the system, significantly reduce the equipment selection cost, and at the same time ensure the safe and reliable operation of the system.

[0085] If the system continues to be in the net power consumption state (i.e. the total power consumption is greater than the total regenerative power, and the net energy flow is from the energy storage circuit 10 to the DC bus to the load), and the initial energy of the energy storage circuit 10 is already low (such as the terminal voltage is close to or lower than the preset full discharge threshold), then continuous discharging will lead to deep overdischarge, which may cause the capacity of the energy storage circuit 10 to accelerate attenuation, the internal resistance to increase, and even cause irreversible damage or safety risk.

[0086] In an embodiment of the present application, referring to Figure 2 , the first switch circuit 20 comprises: a first switch component 21 and a unidirectional conduction circuit 22, a first end of the first switch component 21 and an output end of the unidirectional conduction circuit 22 are electrically connected with the energy storage circuit 10, a second end of the first switch component 21 and an input end of the unidirectional conduction circuit 22 are electrically connected with at least one DC bus, referring to Figure 11 , the control method further comprises: Step S500: obtaining the current power of the energy storage circuit 10; Step S600: in the case that the current power is less than a preset full discharge threshold, controlling the first switch component 21 to be turned off, so that the DC bus charges the energy storage circuit 10 through the unidirectional conduction circuit; In the case that the power of the energy storage circuit 10 reaches a preset full charge threshold, the first switch component 21 is controlled to be turned on.

[0087] In the present embodiment, the control method can determine the current power of the energy storage circuit 10 by detecting the voltage of the energy storage circuit 10, and the control method can control the first switch component 21 to be turned off in the case that the power of the energy storage circuit 10 is detected to be lower than the preset full discharge threshold. Due to the unidirectional conduction characteristic of the unidirectional conduction circuit 22, only one unidirectional charging path is reserved between the DC bus and the energy storage circuit 10 (the current can flow from the DC bus to the energy storage circuit 10 through the unidirectional conduction circuit, but cannot flow in the opposite direction), so that the energy storage circuit 10 can only draw power from the DC bus and cannot discharge the DC bus. The preset full discharge power is the lowest safe power limit value that the energy storage circuit 10 allows to discharge, and discharging below this value will cause irreversible damage.

[0088] In this way, the unidirectional conduction circuit 22 effectively blocks the discharge path of the energy storage circuit 10 to the DC bus, avoiding the situation that the energy storage circuit 10 is deeply over-discharged due to continuous power supply to the outside in a low power state. If there is regenerative energy in the DC bus, it can passively flow into the energy storage circuit 10 for supplementary charging, promoting the power of the energy storage circuit 10 to rise to a full charge state, and significantly improving the safety and cycle life of the energy storage circuit 10.

[0089] The above only describes exemplary embodiments of the present application, and does not limit the patent scope of the present application. Any equivalent structural transformation made based on the technical concept of the present application, or direct / indirect application in other related technical fields, is included in the patent protection scope of the present application.

Claims

1. An energy storage system, characterized in that, include: Energy storage circuit; A first switching circuit, wherein a first terminal of the first switching circuit is electrically connected to the energy storage circuit, and a second terminal of the first switching circuit is electrically connected to at least one DC bus. A power conversion circuit, wherein a first terminal of the power conversion circuit is electrically connected to at least one DC bus, a second terminal of the power conversion circuit is used to connect to the power grid, and the power conversion circuit is used to invert the DC power on the DC bus and output it to the power grid; A control circuit is electrically connected to the controlled terminal of the first switching circuit and the power conversion circuit, respectively. The control circuit is used to obtain the total regenerated power and total power consumption on the DC bus. The control circuit is used to control the first switching circuit to conduct when the total regenerated power is greater than the total power consumption, so as to charge the energy storage circuit by the DC bus, and / or control the power conversion circuit to invert the DC power on the DC bus and output it to the grid. The control circuit is also used to control the first switching circuit to conduct when the total regenerated power is not greater than the total power consumption, so as to allow the energy storage circuit to discharge to the DC bus, and / or control the power conversion circuit to invert the DC power on the DC bus and output it to the power grid.

2. The energy storage system as described in claim 1, characterized in that, The first switching circuit includes: A first switching assembly and a unidirectional conduction circuit, wherein a first terminal of the first switching assembly and an output terminal of the unidirectional conduction circuit are both electrically connected to the energy storage circuit, and a second terminal of the first switching assembly and an input terminal of the unidirectional conduction circuit are both electrically connected to at least one DC bus.

3. The energy storage system as described in claim 1, characterized in that, The energy storage system further includes at least one second switching component, the first end of which is connected to the output end of the first switching circuit, the second end of which is electrically connected to the DC bus, and the controlled end of which is electrically connected to the control circuit.

4. A control method for an energy storage system, applied to the energy storage system as described in any one of claims 1 to 3, characterized in that, The control method includes: Obtain the total regenerative power and total power consumption on at least one DC bus; When the total regenerated power is greater than the total power consumption, the first switching circuit is controlled to be turned on so that the DC bus charges the energy storage circuit, and / or the power conversion circuit is controlled to invert the DC power on the DC bus and output it to the power grid. If the total regenerated power is not greater than the total power consumption, the first switching circuit is controlled to be turned on so that the energy storage circuit discharges to the DC bus, and / or the power conversion circuit is controlled to invert the DC power on the DC bus and output it to the power grid.

5. The control method for the energy storage system as described in claim 4, characterized in that, When the total regenerated power is greater than the total power consumption, controlling the first switching circuit to conduct so that the DC bus charges the energy storage circuit, and / or controlling the power conversion circuit to invert the DC power on the DC bus and output it to the power grid includes: Obtain the rechargeable amount of the energy storage circuit, and compare the difference between the total regenerated power and the total power consumption with the rechargeable amount; When the difference between the total regenerated power and the total power consumption is greater than the rechargeable amount, the first switching circuit is controlled to be turned on so that the DC bus charges the energy storage circuit. The power conversion circuit is also controlled to invert the DC power on the DC bus and output it to the power grid. If the difference between the total regenerated power and the total power consumption is not greater than the rechargeable amount, the first switching circuit is controlled to be turned on so that the DC bus charges the energy storage circuit.

6. The control method for the energy storage system as described in claim 5, characterized in that, The system has multiple DC buses, and the power conversion circuit includes multiple power conversion modules, each connected to a corresponding DC bus. When the difference between the total regenerated power and the total power consumption is greater than the rechargeable power, the system controls the first switching circuit to conduct, allowing the DC buses to charge the energy storage circuit. The system also controls the power conversion circuit to invert the DC power from the DC buses and output it to the power grid, including: The regenerative energy on multiple DC buses is sorted from largest to smallest, and the power conversion modules connected to the first number of DC buses are selected from largest to smallest. Based on the rated power of the first number of power conversion modules and the difference between the total regenerated power and the total power consumption, a first time is calculated that the discharge amount released to the grid by the first number of power conversion modules when operating at rated power reaches the difference between the total regenerated power and the total power consumption. The first number of power conversion modules are controlled to continuously invert the DC power on the DC bus and output it to the power grid according to their respective rated power and based on the first duration.

7. The control method for the energy storage system as described in claim 4, characterized in that, The step of controlling the first switching circuit to conduct when the total regenerated power is not greater than the total power consumption, so as to allow the energy storage circuit to discharge to the DC bus, and / or controlling the power conversion circuit to invert the DC power on the DC bus and output it to the power grid includes: Obtain the discharge capacity of the energy storage circuit, and compare the difference between the total regenerated power and the total power consumption with the discharge capacity; If the difference between the total power consumption and the total regenerated power is less than the dischargeable amount, the first switching circuit is controlled to be turned on so that the energy storage circuit discharges to the DC bus, and the power conversion circuit is controlled to invert the DC power on the DC bus and output it to the power grid. If the difference between the total power consumption and the total regenerated power is not less than the dischargeable amount, the first switching circuit is controlled to be turned on so that the energy storage circuit discharges to the DC bus.

8. The control method for the energy storage system as described in claim 7, characterized in that, The number of DC buses is multiple, and the power conversion circuit includes multiple power conversion modules, each connected to a corresponding DC bus. When the difference between the total power consumption and the total regenerated power is less than the dischargeable amount, controlling the first switching circuit to conduct, so that the energy storage circuit discharges onto the DC bus, and controlling the power conversion circuit to invert the DC power on the DC bus and output it to the power grid includes: Obtain the actual electricity price for the current period, and if the actual electricity price is greater than the preset electricity price, calculate the remaining dischargeable amount of the dischargeable amount to meet the power consumption of the loads connected to multiple DC buses; Obtain the rated power of multiple power conversion modules and sort them from largest to smallest; A second number of power conversion modules are selected from largest to smallest, and a second time is required for the discharge amount released to the grid by the second number of power conversion modules when they are operating at their respective rated power to reach the remaining discharge capacity. The second number of power conversion modules are controlled to continuously invert the DC power on the DC bus and output it to the power grid according to their respective rated power and based on the second duration.

9. The control method for the energy storage system as described in claim 6 or 8, characterized in that, The control method further includes: Based on historical operating data, determine the maximum current flowing to the energy storage circuit on multiple DC buses within a preset time period; The rated power of the energy storage circuit is determined based on the maximum current and the rated voltage of the DC bus. The sum of the rated power of the multiple inverters connected to the DC bus and the difference between the rated power of the energy storage circuit are taken as the total rated power of the multiple power conversion modules, and the rated power of each power conversion module is determined according to the total rated power and the rated power of the multiple inverters.

10. The control method for the energy storage system as described in claim 9, characterized in that, The determination of the maximum current flowing to the energy storage circuit on multiple DC buses within a preset time period based on historical operating data includes: Based on historical power generation and power consumption data of multiple motors, determine the maximum number k of motors in power generation state within a preset time period, and the corresponding number l of motors in power consumption state, where k+l=n, and n is the total number of motors. For k motors in the generating state, determine the first maximum DC side current of each motor; for l motors in the consuming state, determine the second maximum DC side current of each motor. The first maximum DC-side current and the second maximum DC-side current of each motor are added together to calculate the maximum current flowing to the energy storage circuit on multiple DC buses.

11. The control method for the energy storage system according to any one of claims 4 to 8, characterized in that, The first switching circuit includes: A first switching assembly and a unidirectional conduction circuit, wherein a first terminal of the first switching assembly and an output terminal of the unidirectional conduction circuit are both electrically connected to the energy storage circuit, and a second terminal of the first switching assembly and an input terminal of the unidirectional conduction circuit are both electrically connected to at least one DC bus, the control method further includes: Obtain the current power level of the energy storage circuit; When the current power level is less than the preset full discharge threshold, the first switch component is controlled to turn off so that the DC bus charges the energy storage circuit through the unidirectional conduction circuit. When the energy storage circuit reaches a preset full charge threshold, the first switching component is controlled to turn on.

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