Energy storage system and control method of energy storage system

Abstract

The application discloses an energy storage system and a control method thereof, and relates to the technical field of energy storage. The energy storage system comprises an energy storage circuit, a first switch circuit, a power conversion circuit and a 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 direct-current bus. The first end of the power conversion circuit is electrically connected with the at least one direct-current bus, and the second end of the power conversion circuit is used for being connected with a power grid. The power conversion circuit is used for inverting and outputting direct-current electricity on the direct-current bus to the power grid. The control circuit is electrically connected with the controlled end of the first switch circuit and the power conversion circuit. The application aims to improve the most effective recycling of regenerated energy of equipment and reduce the power consumption.

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, etc. The current energy source of these equipment is commercial power. According to statistics, the annual average power consumption of elevators nationwide is 26 billion degrees of electricity. When the commercial 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 renewable energy in the form of heat by consuming resistors, 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 and reuse of renewable energy of 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:

[0005] an energy storage circuit;

[0006] 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;

[0007] a power conversion circuit, a first end of the power conversion circuit being electrically connected with the 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;

[0008] 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;

[0009] the control circuit being used for controlling the first switching circuit to be turned on to charge the energy storage circuit by 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 when the total renewable power is greater than the total power consumption;

[0010] The control circuit is further configured to control the first switch circuit to be turned on to enable the energy storage circuit to discharge the DC bus and / or control the power conversion circuit to output the DC power on the DC bus to the power grid when the total regenerated power is not greater than the total power consumption.

[0011] In an embodiment, the first switch circuit comprises:

[0012] a first switch component and a unidirectional conduction circuit, a first end of the first switch component and an output end of the unidirectional conduction circuit are electrically connected to the energy storage circuit, and a second end of the first switch component and an input end of the unidirectional conduction circuit are electrically connected to at least one DC bus.

[0013] In an embodiment, the energy storage system further comprises at least one second switch component, a first end of the second switch component is connected to an output end of the first switch circuit, a second end of the second switch component is electrically connected to a DC bus, and a controlled end of the second switch component is electrically connected to the control circuit.

[0014] The present application further provides a control method of an energy storage system, which is applied to any one of the above-mentioned energy storage systems, and the control method comprises:

[0015] obtaining total regenerated power and total power consumption on at least one DC bus;

[0016] controlling the first switch circuit to be turned on to enable the DC bus to charge the energy storage circuit and / or controlling the power conversion circuit to output the DC power on the DC bus to the power grid when the total regenerated power is greater than the total power consumption;

[0017] controlling the first switch circuit to be turned on to enable the energy storage circuit to discharge the DC bus and / or controlling the power conversion circuit to output the DC power on the DC bus to the power grid when the total regenerated power is not greater than the total power consumption.

[0018] In an embodiment, the controlling the first switch circuit to be turned on to enable the DC bus to charge the energy storage circuit and / or controlling the power conversion circuit to output the DC power on the DC bus to the power grid when the total regenerated power is greater than the total power consumption comprises:

[0019] obtaining a chargeable amount of the energy storage circuit, and comparing a difference between the total regenerated power and the total power consumption with the chargeable amount;

[0020] 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.

[0021] 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.

[0022] In one embodiment, there are multiple DC buses, and the power conversion circuit includes multiple power conversion modules, each connected to one of the multiple DC buses. When the difference between the total regenerated power and the total power consumption is greater than the rechargeable capacity, controlling the first switching circuit to conduct so that the DC buses charge the energy storage circuit, and controlling the power conversion circuit to invert the DC power on the DC buses before outputting it to the power grid includes:

[0023] 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.

[0024] 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.

[0025] 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.

[0026] In one embodiment, 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:

[0027] 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;

[0028] 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 grid.

[0029] In a 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 so as to make the energy storage circuit discharge the DC bus.

[0030] In an embodiment, the number of DC buses is multiple, the power conversion circuit includes multiple power conversion modules, the multiple power conversion modules are connected in one-to-one correspondence with the multiple DC buses, and the control of the first switch circuit to be turned on so as to make the energy storage circuit discharge the DC bus and the control of the power conversion circuit to output the DC power on the DC bus to the power grid after the DC power is inverted include:

[0031] An actual price of a current period is obtained, and in a case where the actual price is greater than a preset price, a remaining dischargeable amount of the dischargeable amount in a case where the power consumption of the multiple DC buses connected loads is met is calculated;

[0032] The rated power sizes of the multiple power conversion modules are obtained and sorted in descending order;

[0033] The second number of power conversion modules are filtered out in descending order, and a second time length required for the discharge amount released to the power grid by the second number of power conversion modules operating at respective rated powers to reach the remaining dischargeable amount is determined;

[0034] The second number of power conversion modules are controlled to output the DC power on the DC bus to the power grid after the DC power is inverted based on the second time length and at respective rated powers.

[0035] In an embodiment, the control method further includes:

[0036] Based on historical operation data, a maximum current flowing to the energy storage circuit from the multiple DC buses in a preset time period is determined;

[0037] The rated power of the energy storage circuit is determined according to the maximum current and a rated voltage of the DC bus;

[0038] The difference between the sum of rated powers of multiple frequency converters connected to the multiple DC buses and the rated power of the energy storage circuit is 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 powers of the multiple frequency converters.

[0039] In an embodiment, the determination of the maximum current flowing to the energy storage circuit from the multiple DC buses in the preset time period based on the historical operation data includes:

[0040] determining a maximum number k of the motors in the power generation state and a number l of the motors in the power consumption state in a preset time period based on historical power generation data and historical power consumption data of the motors, wherein k+l=n, n being a total number of the motors;

[0041] determining a first maximum DC side current of each motor in the k motors in the power generation state, and determining a second maximum DC side current of each motor in the l motors in the power consumption state;

[0042] adding the first maximum DC side current of each motor and the second maximum DC side current of each motor to calculate a maximum current flowing to the energy storage circuit on the plurality of DC buses.

[0043] In an embodiment, the first switching circuit comprises:

[0044] 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:

[0045] obtaining a current electric quantity of the energy storage circuit;

[0046] in a case where the current electric quantity is less than a preset full discharge threshold, controlling the first switching component to be turned off, so that the DC bus charges the energy storage circuit through the unidirectional conduction circuit;

[0047] in a case where the electric quantity of the energy storage circuit reaches a preset full charge threshold, controlling the first switching component to be turned on.

[0048] 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, and the power conversion circuit is used for inverting and outputting the DC power on the DC bus to the power grid to discharge the power grid; the control circuit is used for determining that there is residual regenerative power on the DC bus when 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 and output the DC power on the DC bus to the power grid, thereby obtaining 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 when the total regenerative power is not greater than the total power consumption, and external supplement may be needed, so 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, reducing the power obtained from the power grid, thereby saving the corresponding electricity fee, and / or controlling the power conversion circuit to invert and output the DC power on the DC bus to the power grid, thereby obtaining electricity selling income.

[0049] 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 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 power supplement, thereby reducing the power obtained from the power grid, saving the corresponding electricity fee, and / or releasing to the power grid, further improving the income, so that 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

[0050] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the following will briefly introduce the drawings needed to be used in the embodiments or the prior art description. Obviously, the drawings in the following description are only some embodiments of the present application, and other drawings can also be obtained according to the structures shown in the drawings without creative labor for those skilled in the art.

[0051] Figure 1 It is a circuit structure schematic diagram of an embodiment of the present application;

[0052] Figure 2 It is a circuit structure schematic diagram of another embodiment of the present application;

[0053] Figure 3Circuit structure schematic diagram of another embodiment of the present application;

[0054] Figure 4 Flowchart schematic diagram of an embodiment of the present application;

[0055] Figure 5 Flowchart schematic diagram of another embodiment of the present application;

[0056] Figure 6 Flowchart schematic diagram of another embodiment of the present application;

[0057] Figure 7 Flowchart schematic diagram of another embodiment of the present application;

[0058] Figure 8 Flowchart schematic diagram of another embodiment of the present application;

[0059] Figure 9 Flowchart schematic diagram of another embodiment of the present application;

[0060] Figure 10 Flowchart schematic diagram of another embodiment of the present application;

[0061] Figure 11 Flowchart schematic diagram of another embodiment of the present application.

[0062] Brief Description of the Drawings:

[0063] 10, energy storage circuit; 20, first switch circuit; 21, first switch component; 22, unidirectional conducting circuit; 30, power conversion circuit; 31, power conversion module; 40, control circuit; 50, second switch component.

[0064] 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

[0065] The technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all the embodiments of the present application. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative work fall within the protection scope of the present application.

[0066] 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, movement condition, etc. between components in a certain posture, and if the certain posture changes, the directional indications also change accordingly.

[0067] In addition, if the description of "first", "second" and the like is involved in the embodiments of the present application, the description of "first", "second" and the like is only for the purpose of description, and cannot be understood as indicating or implying the relative importance of the indicated technical features or implicitly indicating the number of the indicated technical features. Therefore, the features limited by "first", "second" can be explicitly or implicitly included at least one of the features. In addition, if "and / or" or "and / or" appears throughout the text, it means that the three parallel schemes are included, for example, "A and / or B" includes A scheme, or B scheme, or A and B scheme. In addition, the technical solutions of each embodiment can be combined with each other, but it must be based on the realization of the 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 in the protection scope required by the present application.

[0068] At present, various 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 power supply. According to statistics, the annual power consumption of elevators nationwide is up to 26 billion degrees, and when the power supply is cut off, the equipment cannot be reliably and stably operated, which affects the daily operation of the equipment. At the same time, when the equipment operation drives the main circuit, it will generate renewable energy. The current common processing method is to dissipate the heat energy in the form of consumption resistance, and there is a lack of effective recovery scheme, so there is a lot of energy waste.

[0069] To solve the above technical problems, the present application provides an energy storage system, in one embodiment, referring to Figure 1 , the energy storage system comprises:

[0070] Energy storage circuit 10;

[0071] The first switch circuit 20, the first end of the first switch circuit 20 is electrically connected with the energy storage circuit 10, and the second end of the first switch circuit 20 is electrically connected with at least one DC bus;

[0072] The power conversion circuit 30, the first end of the power conversion circuit 30 is electrically connected with at least one DC bus, and the second end of the power conversion circuit 30 is used for connecting to the power grid. The power conversion circuit 30 is used for inverting the direct current on the DC bus and outputting to the power grid;

[0073] The control circuit 40, the control circuit 40 is electrically connected with the controlled end of the first switch circuit 20 and the power conversion circuit 30 respectively, and the control circuit 40 is used for acquiring the total renewable power and the total power consumption on at least one DC bus;

[0074] The control circuit 40 is configured to control the first switch circuit 20 to be turned on to charge the energy storage circuit 10 by the DC bus and / or control the power conversion circuit 30 to output the DC power on the DC bus to the power grid after being inverted, when the total regenerated power is greater than the total power consumption.

[0075] The control circuit 40 is further configured to control the first switch circuit 20 to be turned on to discharge the DC bus by the energy storage circuit 10 and / or control the power conversion circuit 30 to output the DC power on the DC bus to the power grid after being inverted, when the total regenerated power is not greater than the total power consumption.

[0076] In the embodiment, the number of DC buses can be one or more, and the device is connected to the power 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.

[0077] 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.

[0078] In the embodiment, the first switch circuit 20 can be implemented by at least one switch 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.

[0079] 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.

[0080] In this embodiment, the control circuit 40 can be implemented using a main control module, a voltage detection module, and a current detection module. The main control module can be implemented using, for example, an MCU (Microcontroller Unit), a DSP (Digital Signal Processor), an FPGA (Field Programmable Gate Array), or a SOC (System-on-Chip). The voltage detection circuit is used to detect the voltage on the DC bus, and the current detection circuit is used to detect the current on the DC bus. The main control module is used to calculate the instantaneous power of each DC bus based on the voltage and current on the DC bus. When the instantaneous power is negative, it indicates that the devices on the DC bus are generating regenerative energy. The control circuit 40 adds up the regenerative energy generated by each device in the generating state to obtain the total regenerative energy. When the instantaneous power is positive, it indicates that the devices on the DC bus are consuming energy. The control circuit 40 adds up the energy consumed by each device in the consuming state to obtain the total power consumption.

[0081] In this embodiment, the control circuit 40 is used to determine that there is residual regenerated electrical energy on the DC bus when the total regenerated electricity is greater than the total electricity consumption, and to control the first switching circuit 20 to conduct so that the DC bus charges the energy storage circuit 10, thereby storing and recovering the regenerated electrical energy generated by the regeneration equipment, and / or to control the power conversion circuit 30 to invert the DC power on the DC bus and output it to the grid, thereby obtaining electricity sales revenue; the control circuit 40 is also used to determine that the energy consumed by the regeneration equipment is greater than or equal to the energy generated when the total regenerated electricity is not greater than the total electricity consumption, and external supplementation may be required, so to control the first switching circuit 20 to conduct so that the energy storage circuit 10 discharges to the DC bus, so that the equipment on the DC bus can use the excess electrical energy of the energy storage circuit 10 to work, reduce the amount of electricity obtained from the grid, thereby saving corresponding electricity costs, and / or to control the power conversion circuit 30 to invert the DC power on the DC bus and output it to the grid, thereby obtaining electricity sales revenue.

[0082] With this configuration, compared to existing technologies, the energy storage system of the present invention can not only release the regenerated electrical energy generated by the equipment to the power grid to obtain electricity sales revenue, but also store the regenerated electrical energy in the energy storage circuit 10. The energy storage circuit 10 can discharge to the DC bus when the equipment needs external power replenishment, reducing the need to obtain electrical energy from the power grid, thereby saving corresponding electricity costs, and / or releasing it to the power grid to further increase revenue. Thus, the energy storage system of the present invention achieves efficient recovery of regenerated energy while ensuring operational reliability, and comprehensively reduces the overall cost of electricity.

[0083] 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.

[0084] In an embodiment of the present application, referring to Figure 2 , the first switching circuit 20 comprises:

[0085] The first switching component 21 and the unidirectional conduction circuit 22, the first end of the first switching component 21 and the output end of the unidirectional conduction circuit 22 are 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 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.

[0086] 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.

[0087] 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 of the energy storage circuit 10 allowed to discharge, and below this value, continuous discharging may 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 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 to rise to the full charge state, and significantly improving the safety and cycle life of the energy storage circuit 10.

[0089] 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.

[0090] In the embodiment, when detecting that any one device fails, 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 device that fails and causing an accident.

[0091] The application further provides a control method of an energy storage system, which is applied to the energy storage system and in an embodiment, with reference to any one of the energy storage systems, Figure 4 The control method comprises the following steps.

[0092] S100: acquiring total regenerated power and total power consumption on at least one DC bus;

[0093] 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.

[0094] 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.

[0095] Specifically, the control method is used to determine that there is surplus renewable energy on the DC bus when the total renewable energy is greater than the total power consumption, and control the first switch circuit 20 to be turned on to charge the energy storage circuit 10 by the DC bus, 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, 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 when 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 discharge the energy storage circuit 10 to 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 power obtained from the power grid, thereby 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 inverting, thereby obtaining the electricity selling income.

[0096] 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 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 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 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.

[0097] 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.

[0098] In an embodiment of the present application, with reference to Figure 5 , the control method comprises the following steps:

[0099] Step S210: Obtain the chargeable amount of the energy storage circuit 10, and compare the difference between the total renewable energy and the total power consumption with the chargeable amount;

[0100] Step S220: in the case that the difference between the total regenerated electric quantity and the total electric quantity consumed is greater than the chargeable quantity, the first switch circuit 20 is controlled to be turned on so as to make the DC bus charge the energy storage circuit 10, and the power conversion circuit 30 is also controlled to output the DC power on the DC bus to the power grid after inverting the DC power;

[0101] In the case that the difference between the total regenerated electric quantity and the total electric quantity consumed is not greater than the chargeable quantity, the first switch circuit 20 is controlled to be turned on so as to make the DC bus charge the energy storage circuit 10.

[0102] 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.

[0103] When the difference between the total regenerated electric quantity and the total electric quantity consumed 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 application can be executed synchronously: (1) turn on the first switch circuit 20 to make the DC bus charge the energy storage circuit 10; (2) start the power conversion circuit 30 to invert the excess electric energy on the DC bus into alternating current and feed it into the power grid, realizing efficient utilization of energy and maximization of electricity sales revenue.

[0104] When the difference between the total regenerated electric quantity and the total electric quantity consumed is not greater than the remaining 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.

[0105] In an embodiment of the 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, and the multiple power conversion modules 31 are connected in one-to-one correspondence with the multiple DC buses; the control of the first switch circuit 20 to be turned on so as to make the DC bus charge the energy storage circuit 10 and 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 difference between the total regenerated electric quantity and the total electric quantity consumed is greater than the chargeable quantity comprises:

[0106] Step S221: the sizes of the regenerated energy on the multiple DC buses are sorted from large to small, and the power conversion modules 31 corresponding to the first number of DC buses are selected from large to small;

[0107] Step S222: According to the rated power of the first number of power conversion modules 31 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 31 to release the discharge amount to the power grid at the rated power to reach the difference between the total regenerated power and the total power consumption is calculated.

[0108] 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 after inverting processing based on the first duration according to the respective rated power.

[0109] It should be noted that when the renewable 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 renewable energy of each direct current bus in real time in descending order, and preferentially selects the first number of direct current buses with high renewable 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.

[0110] 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 power grid, select direct current buses with renewable energy greater than the minimum energy threshold, and set the total number selected as the first number.

[0111] 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 renewable energy back to the power 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.

[0112] In this embodiment, the control method can calculate the first duration according to the following formula:

[0113]

[0114] wherein, is the difference between the total regenerated 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.

[0115] After calculating the first time length, 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 after inverting processing based on the first time length at the respective rated power, so that the power conversion circuit 30 can accurately release the remaining regenerative electric energy on the direct current bus to the power grid, not more or less, and realize efficient recovery of regenerative electric energy.

[0116] Further, with reference to Figure 7 , in the case that the total regenerative electric quantity is not greater than the total electric quantity, the control of the first switch circuit 20 to be turned on to make the energy storage circuit 10 discharge the direct current bus, and / or the control of the power conversion circuit 30 to output the direct current on the direct current bus to the power grid after inverting processing includes:

[0117] Step S230: Obtain the dischargeable quantity of the energy storage circuit 10, and compare the difference between the total regenerative electric quantity and the total electric quantity with the dischargeable quantity;

[0118] Step S240: In the case that the difference between the total electric quantity and the total regenerative electric quantity is less than the dischargeable quantity, control the first switch circuit 20 to be turned on to make the energy storage circuit 10 discharge the direct current bus, and control the power conversion circuit 30 to output the direct current on the direct current bus to the power grid after inverting processing;

[0119] In the case that the difference between the total electric quantity and the total regenerative electric quantity is not less than the dischargeable quantity, control the first switch circuit 20 to be turned on to make the energy storage circuit 10 discharge the direct current bus.

[0120] It should be noted that the dischargeable quantity is the difference between the current electric quantity of the energy storage circuit 10 and the preset full discharge quantity, and the preset full discharge quantity is the lowest safe electric quantity limit value that the energy storage circuit 10 allows to discharge to, and below this value, continued discharge will cause irreversible damage.

[0121] When the difference between the total electric quantity and the total regenerative electric quantity is less than the dischargeable quantity, it indicates that the energy storage circuit 10 still has surplus capacity after meeting the device electric demand. 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 direct current bus, preferentially meet the device electric demand, reduce the device power from the power grid, and reduce the electric cost; simultaneously enable the power conversion circuit 30 to invert the surplus electric energy (from the discharge of the energy storage circuit 10) on the direct current bus into alternating current and feed into the power grid, realize the surplus electricity on the Internet under the premise of guaranteeing local power supply, and obtain the electricity selling income.

[0122] When the difference between the total power consumption and the total renewable power is not less than the dischargeable amount, it indicates that the energy storage energy can completely cover the current shortage of power demand of the equipment, but is insufficient to over-supply. At this time, the control method only turns on the first switch circuit 20, so that the energy storage circuit 10 discharges to the DC bus, and preferentially on-site consumption, to efficiently meet the load demand, and avoid unnecessary grid interaction or energy conversion loss.

[0123] Further, with reference to Figure 2 and Figure 8 , the number of DC buses is multiple, the power conversion circuit 30 includes multiple power conversion modules 31, multiple power conversion modules 31 are connected one by one with multiple DC buses, and the control of the first switch circuit 20 is turned on to make the energy storage circuit 10 discharge to the DC bus under the condition that the difference between the total power consumption and the total renewable power is less than the dischargeable amount, and the power conversion circuit 30 includes:

[0124] Step S241: acquiring the actual electricity price of the current period, and calculating the remaining dischargeable amount of the dischargeable amount under the condition that the multiple DC bus connected loads meet the power consumption amount when the actual electricity price is greater than the preset electricity price;

[0125] Step S242: acquiring the rated power size of multiple power conversion modules 31, and sorting them from large to small;

[0126] Step S243: screening out the second number of power conversion modules 31 from large to small, and according to the second number of power conversion modules 31 working at the respective rated power, the discharge amount released to the grid reaches the second duration required by the remaining dischargeable amount of the energy storage circuit 10;

[0127] Step S244: controlling the second number of power conversion modules 31 to continuously output the DC power on the DC bus to the grid after inverting processing according to the respective rated power based on the second duration.

[0128] It should be noted that in the case that the difference between the total power consumption and the total renewable power is less than the dischargeable amount, the power conversion circuit 30 can be controlled to output the DC power on the DC bus to the grid after inverting processing, so as to obtain the electricity selling income. In order to obtain higher electricity selling income, the discharge to the grid can be carried out at the 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 the electricity selling income of high electricity price.

[0129] In this embodiment, the remaining dischargeable amount of the energy storage circuit 10 is:

[0130]

[0131] wherein, is the remaining dischargeable amount, is the total power consumption, is the total regenerated power, is the dischargeable amount.

[0132] It should be noted that due to the difference in driving power of different devices, the regeneration capacity and the rated power of the supporting 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 bearing 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.

[0133] It should be noted that in the process of screening the second number of power conversion modules 31, the control method can judge 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 will be automatically excluded and not participate in scheduling to ensure safe and reliable operation of the system. The control method can set a minimum rated power threshold for effectively inverting 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.

[0134] In this embodiment, the calculation formula of the second duration can be:

[0135]

[0136] wherein, 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.

[0137] After the second duration is calculated, the control method controls the second number of power conversion modules 31 to output the direct current on the direct current bus to the power grid after the direct current on the direct current bus is inverter processed based on the second duration according to the respective rated power, so that the power conversion circuit 30 can accurately release the remaining dischargeable amount of the energy storage circuit 10 to the power grid, not more or less. In this way, not only can the electricity selling revenue be maximized during the high electricity price period, and the idle electricity can be avoided, but also the over-discharge of the energy storage circuit 10 caused by the release of too much electricity can be avoided, and the safety and cycle life of the battery can be ensured.

[0138] It should be noted that when the second duration exceeds the remaining time period during which the actual electricity price is greater than the preset electricity price, the second duration can be valued as the remaining time period during which the actual electricity price is greater than the preset electricity price, so as to store the remaining unreleased electrical energy of the energy storage circuit 10, and release it during the next time period during which the actual electricity price is greater than the preset electricity price, so as to improve the electricity selling revenue.

[0139] In an embodiment of the present application, with reference to Figure 9 , the control method further comprises:

[0140] Step S300: determining the maximum current flowing to the energy storage circuit 10 on the plurality of direct current buses within a preset time period based on historical operation data;

[0141] Step S400: determining the rated power of the energy storage circuit 10 according to the maximum current and the rated voltage of the direct current bus;

[0142] Step S500: taking the difference between the sum of the rated powers of the frequency converters connected to the plurality of direct current buses 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.

[0143] It should be noted that the preset time period can be valued as more than one year, or can be set according to actual needs. The control method can detect the current flowing to the energy storage circuit 10 from the plurality of direct current buses in real time, and when a time window of the current is detected, the sum of the plurality of currents flowing to the energy storage circuit 10 from the plurality of direct current buses is calculated and stored. The control method compares the plurality of stored sums of currents to determine the maximum current flowing to the energy storage circuit 10 from the plurality of direct current buses within the preset time period.

[0144] After the maximum current flowing to the energy storage circuit 10 is calculated, the maximum current and the rated voltage of the DC bus are multiplied to calculate the rated power of the energy storage circuit 10, so that 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 thereof can reach the calculated rated power, 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.

[0145] The calculation formula for calculating the total rated power of the plurality of power conversion modules 31 is:

[0146]

[0147] wherein, Pxi 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.

[0148] The calculation formula for calculating the rated power of each power conversion module 31 is:

[0149]

[0150] 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, Pxi is the rated power of the yth frequency converter.

[0151] Taking an embodiment as an example, it is assumed that the rated powers of the 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.

[0152] 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, so as to avoid the problem of system overload caused by insufficient power while avoiding the problem of excessive cost of equipment caused by excessive power margin, and realize the unity of system economy and reliability.

[0153] Further, referring to Figure 10The determination of the maximum current flowing to the energy storage circuit 10 on multiple DC buses within a preset time period based on historical operating data includes:

[0154] Step S310: Based on the historical power generation data and historical 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.

[0155] Step S320: 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.

[0156] Step S330: Add 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 multiple DC buses.

[0157] It should be noted that the motor is an internal motor of the equipment connected to the DC bus. When the direction of the motor speed is opposite to the direction of the electromagnetic torque (e.g., the motor is rising), the motor generates electricity (regenerative braking). When the direction of the motor speed is the same as the direction of the electromagnetic torque (e.g., the motor is falling), the motor consumes electricity (electric drive).

[0158] The first maximum DC-side current is the historical maximum forward bus current (i.e., peak feedback current) of each motor in generating mode during power generation, directly reflecting the strength of the motor's regenerative capability. The second maximum DC-side current is the historical maximum reverse bus current (i.e., peak drive current) of each motor in consuming power during power consumption, reflecting the motor's power consumption capability.

[0159] The formula for calculating the maximum current is:

[0160]

[0161] in, For the maximum current, For the i-th first maximum DC-side current, This is the j-th second maximum DC-side current.

[0162] To illustrate with an example, consider a scenario where there are 5 motors. Historical data shows that a maximum of 4 motors can generate electricity simultaneously, while another motor consumes electricity. The maximum currents of the 4 generating motors are 30A, 28A, 25A, and 22A respectively, totaling 105A. The maximum current of the consuming motor is 18A. Therefore, the maximum current... =105A-18A=87A.

[0163] Thus, 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 the motors, the natural offset effect of the electric load on the regenerative current in actual operation is not considered, which will lead to the virtual overestimation of the calculated energy storage demand, and then the redundant configuration of the rated power of the power conversion module 31; the control method of the present application accurately identifies the coexistence state of the power generation and power consumption motors based on historical working condition data, 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.

[0164] 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 being close to or lower than the preset full discharge threshold), then continuous discharging will lead to deep overdischarge, which may cause accelerated capacity decay and increased internal resistance of the energy storage circuit 10, and even cause irreversible damage or safety risks.

[0165] In an embodiment of the present application, with reference to Figure 2 , the first switching circuit 20 comprises:

[0166] 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 electrically connected to the energy storage circuit 10, the second end of the first switching component 21 and the input end of the unidirectional conduction circuit 22 are electrically connected to at least one DC bus, with reference to Figure 11 , the control method further comprises:

[0167] Step S500: acquiring the current energy of the energy storage circuit 10;

[0168] Step S600: in the case that the current energy is less than the preset full discharge threshold, controlling the first switching component 21 to be turned off, so that the DC bus charges the energy storage circuit 10 through the unidirectional conduction circuit;

[0169] In the case that the energy of the energy storage circuit 10 reaches the preset full charge threshold, the first switching component 21 is controlled to be turned on.

[0170] In the 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 assembly 21 to be turned off when it is detected that the power of the energy storage circuit 10 is lower than the preset full discharge threshold. Due to the one-way conduction characteristic of the one-way conduction circuit 22, only one one-way 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 one-way 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 of the energy storage circuit 10 that allows discharging, and discharging below this value will cause irreversible damage.

[0171] In this way, the one-way 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 discharged due to continuous power supply 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 charging, so as to restore the power of the energy storage circuit 10 to the full charge state, thereby significantly improving the safety and cycle life of the energy storage circuit 10.

[0172] The above description is only an exemplary embodiment of the present application, and does not limit the patent scope of the present application. Any equivalent structural transformation, direct / indirect application in other related technical fields, or use of the content of the present application specification and drawings within the technical concept of the present application are 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 turn on 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 power grid. The control circuit is also used to control the first switching circuit to turn on when the total regenerated power is not greater than the total power consumption, so that the energy storage circuit discharges 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 capacity, the first switching circuit is controlled 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, When the total regenerated power is not greater than the total power consumption, controlling the first switching circuit to conduct so that the energy storage circuit discharges 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 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 power consumption and the total regenerated power is less than the dischargeable amount, the system controls the first switching circuit to conduct, allowing the energy storage circuit to discharge onto the DC buses. 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: 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 switching 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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