Energy storage heating control method, energy storage system and photovoltaic storage system

Abstract

The present invention relates to an energy storage heating control method, an energy storage system and a photovoltaic storage system. The energy storage system includes a controller and a plurality of battery packs connected in parallel. The battery pack includes: a cell pack, a temperature sensing module, a temperature control module and a BMS. Among them, the temperature sensing module is used to detect the temperature of the energy storage battery, the temperature control module is used to heat the energy storage battery, and the BMS is used to send a heating request and the SOC of the corresponding battery pack to the controller. The controller determines the number of battery packs that can turn on the temperature control module according to the difference between the DC bus voltage and the reference value of the charging voltage of the energy storage system, and determines the priority of the battery pack that turns on the temperature control module according to the SOC of the battery pack. The present invention makes full use of the power generation power of the photovoltaic array. Without affecting the normal power scheduling of the photovoltaic array, it not only avoids the waste of photovoltaic power generation power at low temperatures, but also avoids using the energy of the energy storage system itself to heat the battery pack.

Description

Technical Field

[0001] The present application relates to the field of solar energy storage technology, and in particular to a solar energy storage system energy storage heating method and a solar energy storage system. Background Art

[0002] In recent years, the demand for household photovoltaic energy storage systems has gradually emerged, and household energy storage systems are experiencing explosive growth. For safety reasons, energy storage systems are generally installed outdoors. Therefore, when the temperature drops at night, the temperature of the battery cells in the energy storage system may be below zero degrees.

[0003] At present, lithium-ion batteries are widely used in photovoltaic storage systems due to their advantages such as high power density, long cycle life, low self-discharge rate, and no memory effect. However, under low temperature conditions, the electrochemical performance of lithium-ion batteries is poor. This is mainly due to the following three reasons: (1) The viscosity of the electrolyte in the lithium-ion battery increases, and it may even partially solidify, resulting in a decrease in the conductivity of the electrolyte; (2) The compatibility between the electrolyte and the negative electrode and the separator deteriorates; (3) The diffusion coefficient of lithium ions in the positive and negative active materials decreases, and the charge transfer impedance (Rct) increases significantly. Moreover, even if the temperature rises during the day, the charging power of the battery cells of the energy storage system may be limited or even unable to be charged due to the large heat capacity and slow temperature rise of lithium-ion batteries, resulting in a waste of photovoltaic power generation. Therefore, when the charging capacity of the energy storage system is limited due to low temperature, it is necessary to heat the battery cells through a heating device to increase the battery cell temperature, thereby increasing the rechargeable power of the energy storage system and reducing photovoltaic waste. However, the industry usually uses the energy storage system's own power to heat the heating device, which easily leads to a decrease in the energy storage's own power. Summary of the invention

[0004] At present, in order to solve the problem of low cell temperature and poor charging effect in energy storage systems under low temperature, the industry usually heats the cells with a fixed power. When the cell temperature rises to the corresponding heating exit temperature, the heating is turned off. However, this technology needs to ensure that the power for heating the cell is sufficient. Among them, the source of heating the cell can come from outside the energy storage system or from the energy storage system itself. When the photovoltaic power generation outside the energy storage system is insufficient, it is generally necessary to use the energy storage system's own power, which can easily lead to a reduction in the energy storage system's power.

[0005] In view of this, the embodiments of the present application provide an energy storage heating control method, an energy storage system, and a photovoltaic storage system to fully utilize the power generation power of the photovoltaic array under low temperature conditions, heat the energy storage cells in the energy storage system, improve the rechargeable capacity of the energy storage cells, avoid the waste of photovoltaic power generation power and the reduction of the power of the energy storage cells themselves.

[0006] In the first aspect, an embodiment of the present application provides a method for controlling energy storage heating, which is applied to a photovoltaic storage system, wherein the photovoltaic storage system includes a photovoltaic array, an inverter, and an energy storage system. The photovoltaic array is composed of a plurality of photovoltaic modules connected in series and parallel. The inverter includes a DC bus, a DC / DC converter, and a DC / AC converter. The DC / DC converter is connected to the DC / AC converter via a DC bus. The DC / DC converter is also connected to the photovoltaic array, and performs maximum power point tracking (MPPT) on the power generated from the photovoltaic array. The DC / AC converter is also connected to a load and / or a power grid. The energy storage system includes a plurality of battery packs connected in parallel and a controller, wherein the parallel connection points of the plurality of battery packs are connected to the controller or the DC bus. It is worth mentioning that when the controller is a separate device, the parallel connection points of the plurality of battery packs are connected to the controller, and the controller is connected to the DC bus. When the controller is integrated into the inverter, the parallel connection points of the battery packs are connected to the DC bus. The battery pack includes a cell pack, a temperature control module, a temperature sensing module and a battery management system (BMS). The cell pack is used to store and release electrical energy, the temperature control module is used to heat the battery pack, the temperature sensing module is used to detect the temperature of the battery pack, and the BMS is used to receive, manage and send information such as the battery pack's temperature, current, voltage and state of charge (SOC).

[0007] The method is as follows: a controller receives a heating request of a battery pack and a state of charge SOC of the battery pack, and the controller adjusts the number N of battery packs whose temperature control modules are to be turned on according to the difference between the DC bus voltage and the reference value of the charging voltage of the energy storage system, where N is an integer greater than or equal to 1. The controller determines the priority of turning on the temperature control modules of the multiple battery packs according to the SOCs of the multiple battery packs, and turns on the temperature control modules of N battery packs among the multiple battery packs.

[0008] It should be noted that the DC bus voltage is mainly related to the power generation of the photovoltaic array, the charging power of the battery pack in the energy storage system, and the output power of the inverter. The charging voltage reference value of the energy storage system is mainly related to the input voltage of the photovoltaic array, the grid voltage, and the battery pack voltage. The size of the difference between the DC bus voltage and the charging voltage reference value of the energy storage system represents whether the power generation of the photovoltaic array is sufficient. Specifically, when the difference between the DC bus voltage and the charging voltage reference value of the energy storage system is positive, it means that the power generation of the photovoltaic array is large, and the power generation of the photovoltaic array can not only charge the battery pack of the energy storage system, but also have a part of surplus. When the difference between the DC bus voltage and the charging voltage reference value of the energy storage system is zero, it means that the power generation of the photovoltaic array can meet the charging demand of the battery pack of the energy storage system, but there is no surplus. When the difference between the DC bus voltage and the charging voltage reference value of the energy storage system is negative, it means that the power generation of the photovoltaic array is small, and the power generation of the photovoltaic array is not enough to charge the battery pack of the energy storage system, and there is no surplus. Based on this, if the power generated by the photovoltaic array is sufficient to charge the battery pack of the energy storage system, and there is a surplus, the energy storage system will use this surplus energy to heat the battery pack to increase the chargeable power of the battery pack and avoid the waste of photovoltaic power generation. At the same time, in order to better avoid the "short board effect", that is, to convert as much power generated by the photovoltaic array as possible into energy stored in the battery pack, the energy storage controller of the energy storage system will determine the priority of the battery pack that turns on the temperature control module based on the SOC of the battery pack, so as to make better use of the power generated by the photovoltaic array.

[0009] In some possible implementations, as mentioned above, when the DC bus voltage is greater than the reference value of the charging voltage of the energy storage system, that is, the power generated by the photovoltaic array can charge the battery pack of the energy storage system, and there is a part of energy remaining, at this time, the controller controls the temperature control modules of the first N battery packs in the energy storage system to turn on in order of SOC from low to high, so as to increase the temperature of the N battery packs. With this arrangement, the battery packs with low SOC can be heated first, thereby increasing their chargeable power and better converting and storing the electric energy generated by the photovoltaic array. Among them, it is worth mentioning that the reference value of the charging voltage of the energy storage system will change with the grid voltage, the photovoltaic array input voltage and the battery pack voltage, and the reference value of the charging voltage of the energy storage system is greater than the grid voltage and the photovoltaic array input voltage.

[0010] In some possible implementations, when the DC bus voltage is greater than the reference value of the charging voltage of the energy storage system, but the power generation power of the photovoltaic array becomes smaller, the difference between the DC bus voltage and the reference value of the charging voltage of the energy storage system becomes smaller (the difference is still positive), and the input voltage of the battery pack decreases. As the input voltage of the battery pack decreases, the power generation power of the photovoltaic array cannot both charge the battery pack of the energy storage system and keep the temperature control modules of the N battery packs turned on. Therefore, under this condition, in order to maintain the temperature control modules in the N battery packs turned on, the battery packs in the battery packs will automatically supply power to the temperature control modules. However, as mentioned above, if the battery cells of the battery pack discharge to the temperature control module, the energy of the battery pack itself will be consumed. Therefore, in order to avoid using the battery pack's own power, when the controller receives a signal that the battery pack discharges to the temperature control module, the controller turns off the temperature control modules corresponding to all battery packs to avoid consuming the battery pack's own power. Similarly, the input voltage of the battery pack being lower than a preset value also indirectly reflects that the power generation power of the photovoltaic array cannot both charge the battery pack of the energy storage system and keep the temperature control modules of N battery packs turned on. Therefore, when the controller receives a signal that the input voltage of the battery pack is lower than a preset value, the controller will also turn off the temperature control modules corresponding to all the battery packs in the aforementioned multiple battery packs to avoid consuming the battery pack's own power, and the energy storage system will enter the next heating cycle.

[0011] Further, in the next heating cycle, when the temperature control modules of all the aforementioned battery packs are in the off state and the DC bus voltage is greater than the charging voltage reference value of the energy storage system, the controller again controls the temperature control modules of the first L battery packs in the energy storage system to be turned on according to the SOC of the battery pack that issued the heating request, in the order of SOC from low to high, so as to increase the temperature of the L battery packs, where L is a positive integer less than N. For example, L = N-1, L = N-2, etc. That is to say, in this heating cycle, the number of battery packs with temperature control modules turned on in the energy storage system is reduced. In this way, the battery pack with a higher SOC in the last heating cycle can be preferentially exited from heating, avoiding too many temperature control modules from being turned on at the same time, so as to better match the power generation power of the photovoltaic array at that moment. For example, if the power generation power of the photovoltaic array continues to decrease, the energy storage system will continue to enter a new heating cycle, and the number of battery packs in the energy storage system that can turn on the temperature control module will continue to decrease until the temperature control modules of all battery packs in the aforementioned multiple battery packs in the energy storage system are turned off.

[0012] It is worth mentioning that if the temperature control modules of all the battery packs in the aforementioned multiple battery packs in the energy storage system are turned off, the power generation power of the photovoltaic array continues to decrease, the DC bus voltage will be lower than the charging voltage reference value of the energy storage system, and the power generation power of the photovoltaic array will not be able to charge the battery pack.

[0013] In some possible implementations, after the controller controls the temperature control modules of N battery packs to turn on, when the power generation power of the photovoltaic array increases, that is, when the difference between the DC bus voltage and the reference value of the charging voltage of the energy storage system increases (the difference is a positive value), the input voltage of the battery pack will gradually increase. As the input voltage of the battery pack increases, the power generation power of the photovoltaic array can charge the battery pack of the energy storage system and keep the temperature control modules of N battery packs turned on, and at the same time, there is still some power remaining. Therefore, under this condition, in order to better adapt to the changes in the power generation power of the photovoltaic array, the energy storage system will enter the next heating cycle. Specifically, when the controller receives a signal that the input voltage of the battery pack is higher than a preset value, or when the controller receives a signal that the battery pack has not received a signal that the battery pack supplies power to the temperature control module within a period of time (for example, ten minutes), the controller will control the energy storage system to enter the next heating cycle.

[0014] Furthermore, in the next heating cycle, the controller again controls the temperature control modules of the first M battery packs in the energy storage system to turn on according to the SOC of the battery pack that issued the heating request, in order from low to high SOC, to increase the temperature of the M battery packs, where M is an integer greater than N. For example, M=N+1 or M=N+2. That is to say, in this heating cycle, the number of battery packs with temperature control modules turned on in the energy storage system has increased. With such a setting, the temperature control modules of more battery packs with lower SOC can be turned on to make more full use of the power generation power of the photovoltaic array and increase the chargeable power of the energy storage system. For example, if the power generation power of the photovoltaic array continues to increase, the energy storage system will continue to enter new heating cycles, and the number of battery packs in the energy storage system that can turn on the temperature control modules will continue to increase until the temperature control modules of all battery packs in the aforementioned multiple battery packs in the energy storage system are turned on.

[0015] It is worth mentioning that if the temperature control modules of all battery packs in the energy storage system are turned on, the power generation power of the photovoltaic array continues to increase. The DC / DC converter in the inverter will adjust the power generation power of the photovoltaic array to avoid charging damage to the battery pack.

[0016] In the second aspect, an embodiment of the present application provides an energy storage system, which includes a controller and a plurality of battery packs connected in parallel, wherein the parallel connection points of the plurality of battery packs are connected to the controller or the DC bus. The battery pack includes a cell pack, a temperature control module, a temperature sensing module and a BMS. Among them, the cell pack is electrically connected to the temperature control module and the BMS, the temperature sensing module is electrically connected to the BMS, and the BMS is electrically connected to the controller. In addition, the cell pack is used to store and release electric energy, the temperature control module is used to generate heat to increase the temperature of the battery pack, the temperature sensing module is used to detect the temperature of the battery pack, the BMS is used to receive, manage and send information such as the temperature, current, voltage and SOC of the battery pack, the controller is used to receive the heating request of the battery pack and the state of charge SOC of the battery pack, and the controller adjusts the number N of battery packs whose temperature control modules are to be turned on according to the difference between the DC bus voltage and the reference value of the charging voltage of the energy storage system, wherein N is an integer greater than or equal to 1. The controller determines the priority of turning on the temperature control modules of the plurality of battery packs according to the SOC of the plurality of battery packs, and turns on the temperature control modules of N battery packs in the plurality of battery packs.

[0017] It should be noted that the DC bus voltage is mainly related to the power generation power of the photovoltaic array, the charging power of the battery pack in the energy storage system, and the output power of the inverter. The charging voltage reference value of the energy storage system is mainly related to the input voltage of the photovoltaic array, the grid voltage, and the battery pack voltage. The difference between the DC bus voltage and the charging voltage reference value of the energy storage system represents whether the photovoltaic storage system has sufficient photovoltaic power generation. When the difference between the DC bus voltage and the charging voltage reference value of the energy storage system is positive, it means that the power generation power of the photovoltaic array is large, and the power generation power of the photovoltaic array can not only charge the battery pack of the energy storage system, but also have a part of surplus. When the difference between the DC bus voltage and the charging voltage reference value of the energy storage system is zero, it means that the power generation power of the photovoltaic array can meet the charging of the battery pack of the energy storage system, but there is no surplus. When the difference between the DC bus voltage and the charging voltage reference value of the energy storage system is negative, it means that the power generation power of the photovoltaic array is small, and the power generation power of the photovoltaic array is not enough to charge the battery pack of the energy storage system, and there is no surplus. Based on this, if the power generated by the photovoltaic array is sufficient to charge the energy storage, and there is a surplus, the energy storage system will use this surplus energy to heat the battery pack to increase the chargeable power of the battery pack and avoid the waste of photovoltaic power generation. At the same time, in order to better avoid the "short board effect" and convert as much power generated by the photovoltaic array as possible into energy stored in the battery pack, the energy storage controller in the energy storage system will determine the priority of the battery pack that turns on the temperature control module based on the SOC value of the battery pack, so as to make better use of the power generated by the photovoltaic array.

[0018] In some possible implementations, as mentioned above, when the DC bus voltage is greater than the charging voltage reference value of the energy storage system, the power generation of the photovoltaic array can charge the battery pack of the energy storage system, and there is a part of energy remaining. At this time, the controller controls the temperature control modules of the first N battery packs in the energy storage system to turn on in order of SOC from low to high, so as to increase the temperature of the N battery packs. With this arrangement, the battery packs with low SOC can be heated first, thereby increasing their chargeable power and better converting and storing the electric energy generated by the photovoltaic array. Among them, it is worth mentioning that the charging voltage reference value of the energy storage system will change with the grid voltage, the photovoltaic array input voltage and the battery pack voltage, and the charging voltage reference value of the energy storage system is greater than the grid voltage and the photovoltaic array input voltage.

[0019] In some possible implementations, when the power generation of the photovoltaic array becomes smaller, the difference between the DC bus voltage and the reference value of the charging voltage of the energy storage system becomes smaller (the difference is a positive value), and the input voltage of the battery pack will decrease (without considering the influence of the power grid). As the input voltage of the battery pack decreases, the power generation of the photovoltaic array cannot both charge the battery pack of the energy storage system and keep the temperature control modules of the N battery packs turned on. Therefore, under this condition, in order to maintain the temperature control modules in the N battery packs turned on, the battery packs in the battery packs will automatically supply power to the temperature control modules. However, as mentioned above, if the battery cells of the battery pack discharge to the temperature control module, the battery pack's own power will be consumed. Therefore, in order to avoid using the battery pack's own power, when the controller receives a signal that the battery pack is discharging to the temperature control module, the controller turns off the temperature control modules corresponding to all battery packs. Similarly, the input voltage of the battery pack is lower than a preset value, which indirectly reflects that the power generation of the photovoltaic array cannot charge the battery pack of the energy storage system and keep the temperature control modules of N battery packs turned on. Therefore, when the controller receives a signal that the input voltage of the battery pack is lower than a preset value, the controller turns off the temperature control modules corresponding to all the battery packs in the aforementioned multiple battery packs to avoid the reduction of the battery pack power. The energy storage system enters the next heating cycle.

[0020] Further, in the next heating cycle, when the temperature control modules of all the battery packs in the aforementioned multiple battery packs are in the off state and the DC bus voltage is greater than the charging voltage reference value of the energy storage system, the controller again controls the temperature control modules of the first L battery packs in the energy storage system to be turned on according to the SOC of the battery pack that issued the heating request, in the order of SOC from low to high, so as to increase the temperature of the L battery packs, where L is an integer less than N. For example, L = N-1 or L = N-2, etc., that is, the controller reduces the number of battery packs with temperature control modules turned on in the energy storage system. In this way, the battery pack with a higher SOC in the last heating cycle can be preferentially exited from heating, avoiding too many temperature control modules from being turned on at the same time, so as to better match the power generation power of the photovoltaic array at that moment. For example, if the power generation power of the photovoltaic array continues to decrease, the energy storage system will continue to enter a new heating cycle, and the number of battery packs in the energy storage system that can turn on the temperature control module will also continue to decrease until the temperature control modules of all the battery packs in the aforementioned multiple battery packs in the energy storage system are turned off.

[0021] It is worth mentioning that if the temperature control modules of all the battery packs in the aforementioned multiple battery packs in the energy storage system are turned off, the power generation power of the photovoltaic array continues to decrease, the DC bus voltage will be lower than the charging voltage reference value of the energy storage system, and the power generation power of the photovoltaic array will no longer be able to charge the battery pack.

[0022] In some possible implementations, after the controller controls the temperature control modules of N battery packs to turn on, when the power generation power of the photovoltaic array increases, that is, when the difference between the DC bus voltage and the reference value of the charging voltage of the energy storage system increases, the input voltage of the battery pack will gradually increase. As the input voltage of the battery pack increases, the power generation power of the photovoltaic array can charge the battery pack of the energy storage system and keep the temperature control modules of N battery packs turned on, and there is a part of power remaining. Therefore, under this condition, in order to better adapt to the changes in the power generation power of the photovoltaic array, the energy storage system will enter the next heating cycle. Specifically, when the controller receives a signal that the input voltage of the battery pack is higher than a preset value, or when the controller receives a signal that the battery pack has not received a discharge signal from the battery pack to the temperature control module within a period of time (for example, ten minutes), the controller will control the energy storage system to enter the next heating cycle.

[0023] Furthermore, in the next heating cycle, the controller again controls the temperature control modules of the first M battery packs in the energy storage system to turn on according to the SOC of the battery pack that issued the heating request, in order of SOC from low to high, so as to increase the temperature of the M battery packs, where M is an integer greater than N. For example, M=N+1 or M=N+2, etc. That is to say, in this heating cycle, the number of battery packs with temperature control modules turned on in the energy storage system has increased. With such a setting, the temperature control modules of more battery packs with lower SOC can be turned on to make more full use of the power generation power of the photovoltaic array and increase the chargeable power of the energy storage system. For example, if the power generation power of the photovoltaic array continues to increase, the energy storage system will continue to enter new heating cycles, and the number of battery packs in the energy storage system that can turn on the temperature control modules will continue to increase until the temperature control modules of all battery packs in the energy storage system are turned on.

[0024] It is worth mentioning that if the temperature control modules of all the battery packs in the aforementioned multiple battery packs in the energy storage system are turned on, the power generation power of the photovoltaic array continues to increase. The DC / DC converter in the inverter will adjust the power generation power of the photovoltaic array to avoid charging damage to the battery pack.

[0025] In a third aspect, an embodiment of the present application provides a photovoltaic storage system, which includes the energy storage system and an inverter as described in any one of the second aspects. The inverter includes a DC / DC converter, a DC / AC converter, and a DC bus, and the energy storage system is connected to the inverter via the DC bus.

[0026] The photovoltaic storage system energy storage heating method, energy storage system and photovoltaic storage system provided in the embodiments of the present application can enable the energy storage system or photovoltaic storage system to heat the stored energy without consuming the power of the energy storage system itself. That is, according to the power generation power of the photovoltaic array, the number of opened temperature control modules in the energy storage system and the opening priority are automatically adjusted, and the waste of photovoltaic power at low temperatures is avoided without affecting the normal power scheduling of the photovoltaic storage system, and the problem of reducing the stored energy power due to heating the stored energy by using the power of the energy storage system itself is avoided. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 A schematic diagram of the structure of a photovoltaic storage system provided in an embodiment of the present application.

[0028] Figure 2 A schematic flow chart of a method for controlling energy storage heating of a photovoltaic storage system provided in an embodiment of the present application; DETAILED DESCRIPTION

[0029] Against the backdrop of carbon peak and carbon neutrality, the installed capacity ratio of new energy sources has gradually increased. Among them, "photovoltaic + energy storage" has gradually become the standard for photovoltaic development. Combining photovoltaics with energy storage can provide more sustainable development momentum for photovoltaic power generation. Generally speaking, the photovoltaic storage system mainly includes photovoltaic arrays, inverters and energy storage systems. When there is sufficient sunlight, the photovoltaic storage system can store the electrical energy generated by the photovoltaic array in the energy storage system. At the same time, the direct current generated by the photovoltaic array can also be supplied to the load or the power grid through the inverter. When there is insufficient sunlight, the energy storage system can output direct current, which continues to provide electrical energy to the load after being inverted by the inverter.

[0030] In household solar-storage scenarios, the battery pack of the energy storage system is generally installed outdoors, which makes its charge and discharge power susceptible to the influence of ambient temperature. Specifically, the battery pack is generally a lithium-ion battery. When the outdoor temperature is low, the viscosity of the electrolyte in the lithium-ion battery increases, the impedance increases, and the charge and discharge power decreases. Therefore, it is very important to increase the temperature of the battery pack in time and restore the charge and discharge power of the battery pack.

[0031] Based on this, the embodiments of the present application provide a method for controlling energy storage heating of a photovoltaic storage system, an energy storage system, and a photovoltaic storage system. The method can automatically adjust the number of temperature control modules that are turned on and the priority of turning on the temperature control modules in the energy storage system according to the power generation power of the photovoltaic array. Without affecting the normal power scheduling of the photovoltaic storage system, it not only avoids the waste of photovoltaic power at low temperatures, but also avoids the problem of using the power of the energy storage system to heat the energy storage, thereby reducing the energy storage power.

[0032] In order to enable those skilled in the art to better understand the technical solution of the present application, the embodiments of the present application will be described below in conjunction with the drawings of the embodiments.

[0033] See also Figure 1 , Figure 1 Schematic diagram of the structure of the optical storage system provided in the embodiment of the present application. Figure 1 As shown, the photovoltaic storage system includes a photovoltaic array 101, an inverter 102 and an energy storage system 103. The photovoltaic array 101 is composed of one or more photovoltaic modules connected in series and in parallel, and is used to convert solar radiation energy into direct current. The inverter 102 includes a DC / DC (direct current / direct current) converter, a DC / AC (direct current / alternating current) converter and a DC bus. The energy storage system 103 includes a plurality of battery packs 105 connected in parallel and an energy storage controller 104. When the energy storage controller 104 is a separate device (such as Figure 1The parallel connection points of multiple battery packs 105 are connected to the energy storage controller 104, and the energy storage controller 104 is connected to the DC bus. When the energy storage controller 104 is integrated into the inverter 102 (not shown in the figure), the parallel connection points of the battery packs 105 are connected to the DC bus. The battery pack 105 includes a temperature control module, a battery pack, a BMS, and a temperature sensing module (not shown in the figure).

[0034] For example, the photovoltaic modules in the photovoltaic array 101 include one or more of monocrystalline silicon solar modules, polycrystalline silicon solar modules, amorphous silicon solar modules, cadmium telluride thin film modules, gallium arsenide thin film modules, copper indium gallium selenide thin film modules, cadmium sulfide thin film modules, dye-sensitized solar modules, organic flexible solar modules and perovskite thin film modules, but the present application does not limit this.

[0035] The DC / DC converter and DC / AC converter of the inverter 102 can be integrated into one device or divided into multiple devices. Under the discharge condition, the DC input side of the DC / DC converter is connected to the photovoltaic array 101, and the DC power output by the photovoltaic array 101 is converted into a suitable DC power to meet the working requirements of the DC / AC converter. At the same time, the maximum power point tracking MPPT is performed on the DC power output by the photovoltaic array 101, so as to obtain the maximum power generation power of the photovoltaic array 101, and the DC power is output from the DC output side of the DC / DC converter. The DC output side of the DC / DC converter is connected to the DC input side of the DC / AC converter, and the DC / AC converter converts the received DC power into AC power and outputs it from the AC output side of the DC / AC converter. The coupling point between the DC output side of the DC / DC converter and the DC input side of the DC / AC converter is the DC bus. In other words, the DC bus refers to the positive and negative poles between the DC / DC converter and the DC / AC converter. In the grid-connected scenario, the DC power generated by the photovoltaic array 101 is inverted into AC power by the inverter 102 and transmitted to the grid. In an off-grid scenario, the direct current generated by the photovoltaic array 101 and / or delivered by the energy storage system 103 is delivered to the load via the inverter 102 .

[0036] The energy storage system 103 includes a plurality of battery packs 105 and an energy storage controller 104. The plurality of battery packs 105 are connected in parallel with each other. As an external device, the battery pack 105 can be connected to the bus of the inverter 102, that is, the battery pack 105 can be connected between the DC / DC converter and the DC / AC converter. Furthermore, the battery cell pack in the battery pack 105 is used to store electrical energy from the power grid or photovoltaic components, the temperature control module is used to increase / lower the temperature of the battery cell, the temperature sensing module is used to detect the temperature of the battery cell, and report the temperature information of the battery cell to the BMS in the battery pack, and the BMS is used to receive, manage and send the temperature, current, voltage and SOC information of the battery cell pack. In addition, the battery cell pack is electrically connected to the temperature control module, the temperature control module is electrically connected to the DC bus and the BMS, the temperature sensing module is electrically connected to the BMS, and the BMS is electrically connected to the energy storage controller 104.

[0037] For example, the battery cells in the battery pack may include one or more of lithium iron phosphate battery cells, lithium cobalt oxide battery cells, lithium manganese oxide battery cells, nickel cobalt aluminum battery cells, lithium titanate battery cells, nickel cobalt manganese battery cells, lead-carbon battery cells, nickel-metal hydride battery cells, nickel-cadmium battery cells and lead-acid battery cells.

[0038] For example, the temperature control module may include various types of heating devices, such as PTC (Positive Temperature Coefficient, positive temperature coefficient (large components)), heating wire, heating film and thermoelectric cooler. Among them, the heating film includes a translucent polyester film that can generate heat after being energized, which is made of a special conductive ink and a metal current-carrying strip that is processed and hot-pressed between insulating polyester films. The heating film is soft and has a large heating area, which can fit the battery module well and provide a faster heating rate. The heating wire is mainly made of materials such as iron-chromium-aluminum and nickel-chromium alloy. The heating wire is relatively cheap and can reduce system costs. The thermoelectric cooler is a device that can both cool and heat by using the Peltier effect of semiconductor materials. The conversion of cooling or heating can be achieved by simply changing the direction of the DC current passing through it. Since the thermoelectric cooler can both cool and heat, the electric heating device can also cool the battery module when the temperature of the battery module is too high.

[0039] For example, the temperature sensing module is a sensing device for detecting the temperature of the battery cells in the battery pack 105. The sensing device includes one or more temperature sensors, and the temperature sensors include thermocouple type or resistor type. The temperature sensing module is generally attached to various positions on the surface of the battery to detect the temperature of the battery cells in the battery pack 105 in real time and report the temperature information of the battery cells to the BMS.

[0040] In some possible implementations, the temperature sensing module of each battery pack 105 in the energy storage system 103 detects the temperature information of the battery pack in real time and reports the temperature information of the battery pack to the BMS. When the temperature of the battery pack is lower than a certain threshold, the BMS of the battery pack 105 sends a heating request to the energy storage controller 104 and reports the SOC of the corresponding battery pack 105 to the energy storage controller 104.

[0041] The energy storage controller 104 receives the heating request and SOC of the battery pack 105, determines the number of battery packs 105 for turning on the temperature control module according to the difference between the DC bus voltage and the charging voltage reference value of the energy storage system 103, and determines the priority of the battery pack 105 for turning on the temperature control module according to the SOC of the battery pack 105 that issues the heating request.

[0042] It should be noted that the DC bus voltage is mainly related to the power generation of the photovoltaic array 101, the charging power of the battery pack 105 in the energy storage system 103, and the output power of the inverter, and the charging voltage reference value of the energy storage system 103 is mainly related to the input voltage of the photovoltaic array 101, the grid voltage, and the battery pack voltage. The difference between the DC bus voltage and the charging voltage reference value of the energy storage system 103 represents whether the power generation of the photovoltaic array 101 is sufficient. Specifically, when the difference between the DC bus voltage and the charging voltage reference value of the energy storage system 103 is positive, it means that the power generation of the photovoltaic array 101 is large, and the power generation of the photovoltaic array 101 can not only charge the battery pack 105 of the energy storage system 103, but also have a part of surplus. When the difference between the DC bus voltage and the charging voltage reference value of the energy storage system 103 is zero, it means that the power generation of the photovoltaic array 101 can meet the charging demand of the battery pack 105 of the energy storage system 103, but there is no surplus. When the difference between the DC bus voltage and the reference value of the charging voltage of the energy storage system 103 is negative, it means that the power generation of the photovoltaic array 101 is small, and the power generation of the photovoltaic array 101 is not enough to charge the battery pack 105 of the energy storage system 103, and there is no surplus. Based on this, if the power generation of the photovoltaic array 101 is sufficient to charge the battery pack 105 of the energy storage system 103, the energy storage system 103 will use this part of the surplus energy to heat the battery pack 105 to increase the chargeable power of the battery pack 105 and avoid the waste of the power generation of the photovoltaic array 101. At the same time, in order to better avoid the "short board effect", that is, to convert as much power generation of the photovoltaic array 101 as possible into energy stored in the battery pack 105, the energy storage controller 104 of the energy storage system 103 will determine the priority of the battery pack 105 to turn on the temperature control module according to the SOC of the battery pack 105, so as to make more full use of the power generation of the photovoltaic array 101.

[0043] In some possible implementations, as mentioned above, when the DC bus voltage is greater than the charging voltage reference value of the energy storage system 103, the power generation of the photovoltaic array 101 can charge the battery pack 105 of the energy storage system 103, and there is a part of energy remaining. At this time, the energy storage controller 104 controls the temperature control modules of the first N battery packs 105 in the energy storage system 103 to turn on in the order of SOC from low to high, so as to increase the temperature of the N battery packs 105. In this way, the battery pack 105 with a low SOC can be heated first, thereby increasing its chargeable power and better converting and storing the electric energy generated by the photovoltaic array 101. Among them, it is worth mentioning that the charging voltage reference value of the energy storage system 103 will change with the grid voltage, the photovoltaic array input voltage and the battery pack voltage, and the energy storage system charging voltage reference value is greater than the grid voltage and the photovoltaic array input voltage.

[0044] It should be noted that the sampling value of the DC bus voltage can be obtained by a bus voltage controller (not shown in the figure). The bus voltage controller can be a separate device or integrated in the inverter 102. The charging voltage reference value of the energy storage system 103 is generally affected by the grid voltage, the input voltage of the photovoltaic array 101 and the voltage of the battery pack 105, and the charging voltage reference value of the energy storage system 103 is greater than the grid voltage and the input voltage of the photovoltaic array 101.

[0045] In some possible implementations, the DC bus voltage is greater than the reference value of the charging voltage of the energy storage system 103, but the power generation of the photovoltaic array 101 becomes smaller, that is, the difference between the DC bus voltage and the reference value of the charging voltage of the energy storage system 103 becomes smaller, and the input voltage of the battery pack 105 will gradually decrease. As the input voltage of the battery pack 105 decreases, the power generation of the photovoltaic array 101 cannot both charge the battery pack 105 of the energy storage system 103 and keep the temperature control modules of the N battery packs 105 turned on. Therefore, under this condition, in order to maintain the opening of the temperature control modules in the N battery packs 105, the battery packs in the battery pack 105 will automatically supply power to the temperature control module. However, as mentioned above, if the battery cells of the battery pack 105 discharge to the temperature control module, the energy of the battery pack 105 itself will be consumed. Therefore, in order to avoid using the power of the battery pack 105 itself, when the energy storage controller 104 receives the signal that the battery cell pack discharges to the temperature control module, the energy storage controller 104 turns off the temperature control modules corresponding to all battery packs 105. Similarly, the input voltage of the battery pack 105 being lower than a preset value indirectly reflects that the power generation power of the photovoltaic array 101 cannot both charge the battery pack 105 of the energy storage system 103 and keep the temperature control modules of N battery packs 105 turned on. Therefore, when the energy storage controller 104 receives that the input voltage of the battery pack 105 is lower than a preset value, the energy storage controller 104 will also turn off the temperature control modules corresponding to all battery packs 105 to avoid consuming the battery pack 105's own power, and the energy storage system 103 is ready to enter the next heating cycle.

[0046] Further, in the next heating cycle, when the temperature control modules of all battery packs 105 in the aforementioned multiple battery packs are in the off state and the DC bus voltage is greater than the charging voltage reference value of the energy storage system 103, the energy storage controller 104 again controls the temperature control modules of the first L battery packs 105 in the energy storage system 103 to turn on according to the SOC of the battery pack 105 that issued the heating request, in the order of SOC from low to high, so as to increase the temperature of the L battery packs 105, where L is a positive integer less than N. For example, L=N-1, L=N-2, etc. That is to say, in this heating cycle, the number of battery packs 105 with temperature control modules turned on in the energy storage system 103 is reduced compared with the previous heating cycle. With such a setting, the battery packs 105 with higher SOC in the previous heating cycle can be preferentially exited from heating, avoiding too many temperature control modules from being turned on at the same time, so as to better match the power generation power of the photovoltaic array 101 at that moment.

[0047] For example, if the power generation power of the photovoltaic array 101 continues to decrease, the energy storage system 103 will continue to enter a new heating cycle, and the number of battery packs 105 in the energy storage system 103 that can turn on the temperature control modules will continue to decrease until the temperature control modules of all battery packs 105 in the aforementioned multiple battery packs in the energy storage system 103 are turned off.

[0048] It is worth mentioning that if the temperature control modules of all battery packs 105 in the aforementioned multiple battery packs in the energy storage system 103 are turned off, the power generation power of the photovoltaic array 101 continues to decrease, the DC bus voltage will be lower than the charging voltage reference value of the energy storage system 103, and the power generation power of the photovoltaic array 101 will no longer be able to charge the battery pack 105.

[0049] In some possible implementations, the power generation of the photovoltaic array 101 increases, that is, the difference between the DC bus voltage and the reference value of the charging voltage of the energy storage system 103 increases (the difference is a positive value), and the input voltage of the battery pack 105 gradually increases. As the input voltage of the battery pack 105 increases, the power generation of the photovoltaic array 101 can charge the battery pack 105 of the energy storage system 103 and keep the temperature control modules of N battery packs 105 turned on, and there is a part of power remaining. Therefore, under this condition, in order to better adapt to the change of the power generation of the photovoltaic array 101, the energy storage system 103 will enter the next heating cycle. Specifically, when the energy storage controller 104 receives a signal that the input voltage of the battery pack 105 is higher than a preset value, or when the energy storage controller 104 receives that the battery pack 105 has not received a signal that the battery pack discharges to the temperature control module within a period of time (for example, ten minutes), the energy storage controller 104 will control the energy storage system 103 to enter the next heating cycle.

[0050] Furthermore, in the next heating cycle, the energy storage controller 104 again controls the temperature control modules of the first M battery packs 105 in the energy storage system 103 to turn on according to the SOC of the battery pack 105 that issued the heating request, in order of SOC from low to high, so as to increase the temperature of the M battery packs 105, where M is a positive integer greater than N. For example, M=N+1, M=N+2, etc. That is to say, in this heating cycle, the number of battery packs 105 with temperature control modules turned on in the energy storage system 103 has increased. With such a setting, the temperature control modules of more battery packs 105 with lower SOC can be turned on to more fully utilize the power generation power of the photovoltaic array 101 and increase the chargeable power of the energy storage system 103.

[0051] For example, if the power generation power of the photovoltaic array 101 continues to increase, the energy storage system 103 will continue to enter a new heating cycle, and the number of battery packs 105 in the energy storage system 103 that can turn on the temperature control module will continue to increase until the temperature control modules of all battery packs 105 in the aforementioned multiple battery packs in the energy storage system 103 are turned on.

[0052] It is worth mentioning that if the temperature control modules of all battery packs 105 in the energy storage system 103 are turned on, the power generation power of the photovoltaic array 101 continues to increase. The DC / DC converters in the aforementioned multiple battery packs in the inverter 102 will adjust the power generation power of the photovoltaic array 101 to avoid charging damage to the battery packs 105.

[0053] See also Figure 2 , Figure 2 This is a flow chart of a method for controlling energy storage heating of a photovoltaic storage system provided in this application. The control method comprises the following steps:

[0054] Step S201: the battery pack 105 issues a heating request.

[0055] When the temperature of the battery pack 105 is lower than a certain threshold, the BMS of the battery pack 105 sends a heating request to the energy storage controller 104 to increase the temperature of the battery pack 105 and increase its chargeable power.

[0056] Step S202 : the energy storage controller 104 receives a heating request of the battery pack 105 and the SOC of the battery pack 105 .

[0057] The energy storage controller 104 determines the priority of the battery pack 105 for turning on the temperature control module according to the SOC of the battery pack 105 that issues the heating request.

[0058] Step S203 : the energy storage controller 104 determines whether the DC bus voltage is greater than a charging voltage reference value of the energy storage system 103 .

[0059] If the DC bus voltage is greater than the charging voltage reference value of the energy storage system 103, it means that the power generation of the photovoltaic array 101 is large, and the power generation of the photovoltaic array 101 can not only charge the battery pack 105 of the energy storage system 103, but also have a part of surplus. If the DC bus voltage is equal to the charging voltage reference value of the energy storage system 103, it means that the power generation of the photovoltaic array 101 can meet the charging demand of the battery pack 105 of the energy storage system 103, but there is no surplus. If the DC bus voltage is less than the charging voltage reference value of the energy storage system 103, it means that the power generation of the photovoltaic array 101 is insufficient to charge the battery pack 105 of the energy storage system 103, and there is no surplus.

[0060] Step S204: If the DC bus voltage is greater than the charging voltage reference value of the energy storage system 103, the energy storage controller 104 controls the temperature control modules of the first N battery packs 105 that issue heating requests to turn on in order of SOC values ​​from low to high, so as to increase the temperature of the battery pack 105 and increase the chargeable power of the battery pack 105.

[0061] Wherein, N is the number of corresponding battery packs 105 whose heating modules are allowed to be turned on by the energy storage system 103 in this heating cycle, and N generally corresponds to different values ​​in different heating cycles.

[0062] With such configuration, the temperature control module of the low SOC battery pack 105 can be turned on first, the temperature of the battery pack 105 rises, thereby increasing its chargeable power and better converting and storing the electrical energy generated by the photovoltaic array 101.

[0063] In one embodiment, when the SOC values ​​of two or more battery packs 105 are the same, the temperature control modules corresponding to the battery packs 105 can be turned on or off according to the SN code order of the battery packs 105. The embodiment of the present application does not limit the SN code priority order of the battery packs 105.

[0064] Step S205: the energy storage controller 104 determines whether the cell pack in the battery pack 105 is discharged to the temperature control module, or whether the input voltage of the battery pack 105 is lower than a preset value.

[0065] When the energy storage controller 104 receives a signal that the battery pack in the battery pack 105 discharges to the temperature control module, or when the energy storage controller 104 receives a signal that the input voltage of the battery pack 105 is lower than a preset value, it means that the power generation power of the photovoltaic array 101 cannot both charge the battery pack 105 in the energy storage system 103 and keep the temperature control modules of N battery packs 105 turned on.

[0066] If the energy storage controller 104 receives a signal within a period of time (for example, ten minutes) that the battery packs in the battery pack 105 are not discharging to the temperature control module, or receives a signal that the input voltage of the battery pack 105 is higher than a preset value, it means that the power generated by the photovoltaic array 101 is not only enough to charge the battery packs 105 in the energy storage system 103 and keep the temperature control modules of N battery packs 105 turned on, but also has a portion of power left.

[0067] Step S206: If the energy storage controller 104 receives a signal that the battery pack in the battery pack 105 discharges to the temperature control module, or receives a signal that the input voltage of the battery pack 105 is lower than a preset value, the energy storage controller 104 controls the temperature control modules of all battery packs 105 in the aforementioned multiple battery packs in the energy storage system 103 to turn off, and re-determines the N value corresponding to the next heating cycle, that is, N', where N'=N-1 or N'=N-2, etc., and the present application does not impose any restrictions on this.

[0068] That is, in the next heating cycle, the number of battery packs 105 whose temperature control modules are turned on by the energy storage controller 104 is reduced. Subsequently, the energy storage system 103 will enter the next heating cycle, and the energy storage controller 104 will re-determine the relative size of the DC bus voltage and the reference value of the charging voltage of the energy storage system 103.

[0069] For example, if the power generation power of the photovoltaic array 101 continues to decrease, but the DC bus voltage is still greater than the charging voltage reference value of the energy storage system 103, the energy storage system 103 will continue to enter a new heating cycle, and the number of battery packs 105 in the energy storage system 103 that can turn on the temperature control module will continue to decrease until the temperature control modules of all battery packs 105 in the aforementioned multiple battery packs in the energy storage system 103 are turned off.

[0070] It is worth mentioning that if the temperature control modules of all battery packs 105 in the aforementioned multiple battery packs in the energy storage system 103 are turned off, the power generation power of the photovoltaic array 101 continues to decrease, the DC bus voltage will be lower than the charging voltage reference value of the energy storage system 103, and the power generation power of the photovoltaic array 101 will no longer be able to charge the battery pack 105.

[0071] In one embodiment, after the energy storage controller 104 re-determines the N value (i.e., N') corresponding to the next heating cycle, it delays for a period of time (for example, five minutes), and the energy storage system 103 enters the next heating cycle to avoid frequent changes in the N value. At the same time, it can also try to ensure that the output power of the photovoltaic array 101 after the change is relatively stable.

[0072] Step S207: If the energy storage controller 104 does not receive a signal from the battery cell in the battery pack 105 discharging to the temperature control module within a period of time (for example, ten minutes), or the energy storage controller 104 receives a signal that the input voltage of the battery pack 105 is higher than a preset value, the energy storage controller 104 re-determines the corresponding N value in the next heating cycle, that is, N', where N'=N+1 or N'=N+2, etc., and the present application does not impose any restrictions on this.

[0073] That is, in the next heating cycle, the number of battery packs 105 whose temperature control modules are turned on by the energy storage controller 104 increases. Subsequently, the energy storage system 103 will enter the next heating cycle, and the energy storage controller 104 will re-determine the relative size of the DC bus voltage and the reference value of the charging voltage of the energy storage system 103.

[0074] For example, if the power generation of the photovoltaic array 101 continues to increase, in order to better utilize the power generation of the photovoltaic array 101, the energy storage system 103 will continue to enter a new heating cycle, and the number of battery packs 105 in the energy storage system 103 that can turn on the temperature control module will also continue to increase until the temperature control modules of all battery packs 105 in the energy storage system 103 are turned on.

[0075] It is worth mentioning that if the temperature control modules of all battery packs 105 in the energy storage system 103 are turned on, the power generation power of the photovoltaic array 101 continues to increase, and the DC / DC converter in the inverter 102 will adjust the power generation power of the photovoltaic array 101 to avoid charging damage to the battery pack 105.

[0076] In one embodiment, after the energy storage controller 104 re-determines the N value (i.e., N') corresponding to the next heating cycle, there is a delay of a period of time (for example, ten minutes), and the energy storage system 103 enters the next heating cycle to avoid frequent changes in the N value. At the same time, it can also try to ensure that the output power of the photovoltaic array 101 after the change is relatively stable.

[0077] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or replace some or all of the technical features therein by equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for controlling energy storage heating, characterized in that: The method is applied to a photovoltaic storage system, which includes a photovoltaic array, an inverter and an energy storage system. The inverter includes a DC / DC converter and a DC / AC converter connected via a DC bus. The DC / DC converter is connected to the photovoltaic array and performs maximum power point tracking (MPPT) on the power generated from the photovoltaic array. The DC / AC converter is connected to a load and / or a power grid. The energy storage system includes a plurality of battery packs connected in parallel and a controller. The parallel connection points of the plurality of battery packs are connected to the controller or the DC bus. The battery pack includes a cell pack, a temperature control module, a temperature sensing module and a battery management system (BMS). The method includes: The controller receives a heating request of each of the plurality of battery packs and a state of charge (SOC) of each of the plurality of battery packs; The controller adjusts the number N of the battery packs to be powered on of the temperature control module according to the difference between the DC bus voltage and the reference value of the charging voltage of the energy storage system, where N is an integer greater than or equal to 1; The controller determines a priority for turning on the temperature control modules of each of the multiple battery packs according to the SOCs of the multiple battery packs, and turns on the temperature control modules of N of the multiple battery packs.

2. The energy storage heating control method according to claim 1, characterized in that: The method comprises: In response to the DC bus voltage being greater than a charging voltage reference value of the energy storage system, the controller turns on the temperature control modules of the first N battery packs among the multiple battery packs in order of the SOCs of the multiple battery packs from low to high.

3. The energy storage heating control method according to claim 2, characterized in that: After the controller turns on the temperature control modules of the first N battery packs among the multiple battery packs in the order of the SOCs of the multiple battery packs from low to high, the method further includes: In response to the input voltage of the multiple battery packs being less than a first preset value, or the cell packs in the N battery packs of the temperature control module being turned on to supply power to the temperature control module, the controller turns off the temperature control modules corresponding to the multiple battery packs.

4. The energy storage heating control method according to claim 3, characterized in that: After the controller turns off the temperature control modules corresponding to the multiple battery packs, the method further includes: The controller turns on the temperature control modules corresponding to the first L battery packs among the multiple battery packs in order of the SOCs of the multiple battery packs from low to high, where L is a positive integer less than N.

5. The energy storage heating control method according to claim 2, characterized in that: After the controller turns on the temperature control modules of the first N battery packs among the multiple battery packs in order of the SOCs of the multiple battery packs from low to high, the method further includes: In response to the input voltage of the battery pack being greater than a first preset value, the controller turns on the temperature control modules corresponding to the first M battery packs among the multiple battery packs in order of the SOCs of the multiple battery packs from low to high, where M is an integer greater than N.

6. An energy storage system, characterized in that: The energy storage system includes a controller and a plurality of battery packs connected in parallel, wherein the parallel connection points of the plurality of battery packs are connected to the controller or the DC bus, wherein the battery pack includes a battery pack, a temperature control module, a temperature sensing module and a BMS, the battery pack is electrically connected to the temperature control module and the BMS, the temperature sensing module is electrically connected to the BMS, the BMS is electrically connected to the controller, the temperature control module is used to generate heat to increase the temperature of the battery pack, the temperature sensing module is used to detect the temperature of the battery pack, and the BMS is used to receive, manage and send the temperature, current, and voltage of the battery pack. The controller is used to receive a heating request of each of the multiple battery packs and the state of charge SOC of each of the multiple battery packs. The controller adjusts the number N of the battery packs whose temperature control modules are to be turned on according to the difference between the DC bus voltage and the charging voltage reference value of the energy storage system, where N is an integer greater than or equal to 1. The controller determines the priority of turning on the temperature control modules of each of the multiple battery packs according to the SOCs of the multiple battery packs, and turns on the temperature control modules of N of the multiple battery packs.

7. The energy storage system according to claim 6, characterized in that: In response to the DC bus voltage being greater than a charging voltage reference value of the energy storage system, the controller turns on the temperature control modules of the first N battery packs among the multiple battery packs in order of the SOCs of the multiple battery packs from low to high.

8. The energy storage system according to claim 7, characterized in that: After the controller turns on the temperature control modules of the first N battery packs among the multiple battery packs in order of the SOCs of the multiple battery packs from low to high, the controller turns off the temperature control modules corresponding to the multiple battery packs in response to the input voltage of the multiple battery packs being less than a first preset value, or the battery cell packs among the N battery packs that have the temperature control modules turned on supplying power to the temperature control module.

9. The energy storage system according to claim 8, characterized in that: After the controller turns off the temperature control modules corresponding to the multiple battery packs, the controller turns on the temperature control modules corresponding to the first L battery packs among the multiple battery packs in order of the SOCs of the multiple battery packs from low to high, where L is a positive integer less than N.

10. The energy storage system according to claim 7, characterized in that: After the controller turns on the temperature control modules of the first N battery packs among the multiple battery packs in order of the SOCs of the multiple battery packs from low to high, in response to the input voltage of the battery pack being greater than a first preset value, the controller turns on the temperature control modules corresponding to the first M battery packs among the multiple battery packs in order of the SOCs of the multiple battery packs from low to high, where M is an integer greater than N.

11. A solar energy storage system, characterized in that: The photovoltaic storage system includes the energy storage system and the inverter according to any one of claims 6 to 10, wherein the inverter includes a DC / DC converter, a DC / AC converter and a DC bus, the energy storage system is connected to the inverter via the DC bus, the DC / AC converter is connected to the high-voltage DC side of the DC / DC converter, and the DC / AC converter is used to realize bidirectional conversion between AC and DC, converting the DC from the DC / DC converter or the energy storage system into AC and transmitting the AC to the power grid or the load, or converting the AC from the power grid into DC to charge the battery pack of the energy storage system.

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