An energy storage system

Abstract

The application discloses an energy storage system, comprising a controller, a DC / AC conversion circuit, at least one battery unit and a corresponding first transmission branch, and a battery heating circuit, the battery heating circuit is powered by a DC bus, the controller controls the operation of each first transmission branch and the DC / AC conversion circuit, so that each battery unit realizes the conversion and transmission of electric energy between the power grid and / or the load, and when the temperature of at least one battery unit is lower than a preset temperature value, the heating power of the corresponding battery heating circuit is adjusted, so that the battery heating circuit generates Joule heat, and the Joule heat is used to heat the corresponding battery unit. Since the battery heating circuit in the application directly obtains the power supply voltage from the DC bus, and the voltage of the DC bus can be provided by the battery unit, the whole process is not affected by the alternating current power grid, thereby improving the user experience.

Description

TECHNICAL FIELD

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

[0002] The storage and conversion of clean energy are of great significance to solving global warming. Lithium-ion batteries have been widely studied and focused on due to their advantages such as large power, high energy density, low self-discharge rate, no memory effect, long cycle life, and environmental friendliness.

[0003] However, the external characteristics of lithium-ion power batteries are easily affected by environmental temperature, especially in low-temperature environments, the capacity decreases, and when charging at low temperature, the battery cannot be fully charged, which will cause damage to the battery, reduce the service life of the battery, and reduce the effective capacity of the battery. Therefore, before use, the battery needs to be preheated to reach the normal working temperature range.

[0004] In the traditional battery preheating method, a battery heating circuit is generally arranged at the position of the battery, and the battery heating circuit is controlled by logic to heat the battery. Since the traditional battery heating circuit directly obtains the supply voltage from the AC power grid, when the AC power grid has no power and the DC side energy is insufficient to establish the AC power grid, or when the off-grid AC load is too heavy to establish the AC power grid, the battery heating circuit will stop working and cannot heat the battery, thereby causing the battery to be unable to start and affecting user use. SUMMARY

[0005] Therefore, the present application discloses an energy storage system to solve the problem that the battery heating circuit stops working and cannot heat the battery due to the lack of power in the AC power grid.

[0006] An energy storage system, comprising: a controller, a DC / AC conversion circuit, at least one battery unit and a corresponding first transmission branch, and a battery heating circuit;

[0007] Each of the battery units is connected to the DC bus of the DC / AC conversion circuit through the corresponding first transmission branch;

[0008] Each of the battery heating circuits is arranged at a preset heating position of the corresponding battery unit and is connected to the DC bus;

[0009] The AC side of the DC / AC conversion circuit is connected to the power grid and / or the load;

[0010] The controller is configured to control the operation of each of the first transmission branches and the DC / AC conversion circuit, so that each of the battery units realizes the conversion and transmission of electric energy between the power grid and / or the load; and the controller is further configured to adjust the heating power of the corresponding battery heating circuit when the temperature of at least one of the battery units is lower than a preset temperature value, so as to heat the corresponding battery unit.

[0011] Optionally, the energy storage system further comprises at least one photovoltaic string and a corresponding second transmission branch.

[0012] Each of the photovoltaic strings is connected to the DC bus through the corresponding second transmission branch.

[0013] The controller is configured to control the operation of each of the second transmission branches and the DC / AC conversion circuit, so that each of the photovoltaic strings realizes the conversion and transmission of electric energy between the power grid and / or the load.

[0014] Optionally, when the controller is configured to adjust the heating power of the corresponding battery heating circuit to heat the corresponding battery unit, the controller is specifically configured to:

[0015] dynamically control the voltage of the DC bus to adjust the heating power of the battery heating circuit to heat the corresponding battery unit.

[0016] Optionally, the first transmission branch comprises a first DC / DC conversion circuit.

[0017] The controller is configured to dynamically control the voltage of the DC bus, and specifically configured to:

[0018] control the corresponding first DC / DC conversion circuit to perform reverse rectification to control the voltage of the DC bus.

[0019] Optionally, when the energy storage system simultaneously comprises the first transmission branch and the second transmission branch, the first transmission branch comprises a first DC / DC conversion circuit, and the second transmission branch comprises a second DC / DC conversion circuit.

[0020] The controller is configured to dynamically control the voltage of the DC bus, and specifically configured to:

[0021] When the electric energy of the photovoltaic string is higher than a first energy threshold, the corresponding second DC / DC conversion circuit is preferentially controlled to dynamically control the voltage of the DC bus.

[0022] When the electric energy of the photovoltaic string is lower than a second energy threshold, the corresponding first DC / DC conversion circuit is preferentially controlled to perform reverse rectification to dynamically control the voltage of the DC bus.

[0023] when the electrical energy of the photovoltaic string is higher than the second energy threshold and lower than the first energy threshold, simultaneously controlling the first DC / DC conversion circuit and the second DC / DC conversion circuit to dynamically control the voltage of the DC bus;

[0024] wherein the first energy threshold is greater than the second energy threshold.

[0025] Optionally, the controller is configured to dynamically control the voltage of the DC bus, and specifically configured to:

[0026] when the temperature of at least one of the battery units is higher than a preset minimum temperature limit and lower than the preset temperature value, controlling the voltage of the DC bus to be no less than a preset voltage value.

[0027] Optionally, the controller is configured to dynamically control the voltage of the DC bus, and specifically configured to:

[0028] when the temperature of at least one of the battery units is lower than a preset minimum temperature limit, controlling the voltage of the DC bus to be increased, and increasing the heating power of the corresponding battery heating circuit to rapidly heat the corresponding battery unit, wherein the preset minimum temperature limit is less than the preset temperature value.

[0029] when the temperature of the corresponding battery unit is increased from the preset minimum temperature limit to a first temperature value and is lower than the preset temperature value, controlling the voltage of the DC bus to be decreased, and decreasing the heating power of the corresponding battery heating circuit to slowly heat the corresponding battery unit.

[0030] Optionally, the controller is configured to adjust the heating power of the corresponding battery heating circuit to heat the corresponding battery unit, and specifically configured to:

[0031] controlling the heating impedance of the corresponding battery heating circuit to adjust the heating power of the battery heating circuit to heat the corresponding battery unit.

[0032] Optionally, the battery heating circuit comprises a first heating impedance, a first circuit total switch, and at least one first battery heating branch, and each of the first battery heating branches comprises a second heating impedance and a controllable switch connected in series with the second heating impedance.

[0033] the first heating impedance and each of the first battery heating branches are connected in parallel, and a total circuit composed of the first heating impedance and each of the first battery heating branches is connected in series with the first circuit total switch.

[0034] Optionally, the controller controls the heating impedance of the corresponding battery heating circuit, specifically for:

[0035] When the voltage across the first heating impedance is higher than a first voltage threshold, or the temperature of at least one of the battery cells is higher than the maximum temperature limit, the controller controls the controllable switches in the first battery heating branches to be off, so that the impedance of the battery heating circuit equals to the first heating impedance, and the heating power of the corresponding battery heating circuit is reduced.

[0036] Optionally, the controller controls the heating impedance of the corresponding battery heating circuit, specifically for:

[0037] When the temperature of at least one of the battery cells is lower than the minimum temperature limit, the controller controls the controllable switches in the first battery heating branches to be on, so that the impedance of the battery heating circuit equals to the parallel total impedance of the first heating impedance and the second heating impedances, and the heating power of the corresponding battery heating circuit is increased.

[0038] Optionally, the battery heating circuit comprises a third heating impedance, a second circuit total switch, and at least one second battery heating branch, each of the second battery heating branches comprises a fourth heating impedance and a controllable switch connected in series with the fourth heating impedance.

[0039] The third heating impedance is connected in series with the second circuit total switch through the series connection of each of the second battery heating branches.

[0040] Optionally, the controller controls the heating impedance of the corresponding battery heating circuit, specifically for:

[0041] When the voltage across the third heating impedance is higher than a first voltage threshold, or the temperature of at least one of the battery cells is higher than the maximum temperature limit, the controller controls the controllable switches in the second battery heating branches to be off, so that the impedance of the battery heating circuit equals to the series total impedance of the third heating impedance and the fourth heating impedances, and the heating power of the corresponding battery heating circuit is reduced.

[0042] Optionally, the controller controls the heating impedance of the corresponding battery heating circuit, specifically for:

[0043] When the temperature of at least one of the battery cells is lower than the minimum temperature limit, the controller controls the controllable switches in the second battery heating branches to be on, so that the impedance of the battery heating circuit equals to the third heating impedance, and the heating power of the corresponding battery heating circuit is increased.

[0044] Or, when the voltage of the DC bus is greater than a preset value, the controller controls each controllable switch in each second battery heating branch to be turned off, so that the impedance of the battery heating circuit is equal to the total impedance of the series connection of the third heating impedance and each fourth heating impedance, and the heating power of the corresponding battery heating circuit is reduced.

[0045] Optionally, the battery heating circuit comprises a fifth heating impedance and a third circuit total switch.

[0046] The fifth heating impedance and the third circuit total switch are connected in series.

[0047] The controller controls the size of the heating impedance of the corresponding battery heating circuit, and is specifically used for:

[0048] The third circuit total switch is controlled to be turned on and turned off according to a preset on-off period, so as to control the size of the impedance of the battery heating circuit.

[0049] From the above technical solution, the application discloses a kind of energy storage systems, comprising: controller, DC / AC conversion circuit, at least one battery unit and corresponding first transmission branch, and battery heating circuit, battery heating circuit is powered by DC bus, controller controls each first transmission branch and DC / AC conversion circuit work, so that each battery unit realizes the electric energy conversion and transmission between power grid and / or load, and when the temperature of at least one battery unit is lower than preset temperature value, the heating power of the corresponding battery heating circuit is adjusted, so that the battery heating circuit generates Joule heat, and the Joule heat is used to heat the corresponding battery unit. Since the battery heating circuit in the present application directly obtains the supply voltage from the DC bus, and the voltage of the DC bus can be provided by the battery unit, the battery heating circuit can obtain the supply voltage from the DC bus based on the battery unit while ensuring the normal start of the battery unit. The whole process is not affected by the alternating current power grid, so as to improve the user experience. 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 embodiment or prior art description. Obviously, the drawings in the following description are only embodiments of the present application, and those skilled in the art can obtain other drawings according to the disclosed drawings without creative labor.

[0051] Figure 1 The structure diagram of the energy storage system disclosed in the embodiment of the present application is shown in the figure.

[0052] Figure 2 The structure diagram of another energy storage system disclosed in the embodiment of the present application is shown in the figure.

[0053] Figure 3 A structural schematic diagram of another energy storage system disclosed in the embodiment of the present application;

[0054] Figure 4 A schematic diagram of a temperature corresponding relationship between a DC bus voltage and a battery unit disclosed in the embodiment of the present application;

[0055] Figure 5 A power scheduling diagram of a photovoltaic string and a battery unit disclosed in the embodiment of the present application;

[0056] Figure 6 A schematic diagram of a battery heating circuit disclosed in the embodiment of the present application;

[0057] Figure 7 A schematic diagram of another battery heating circuit disclosed in the embodiment of the present application;

[0058] Figure 8 A schematic diagram of another battery heating circuit disclosed in the embodiment of the present application;

[0059] Figure 9 A schematic diagram of a control cycle of a third total switch disclosed in the embodiment of the present application. DETAILED DESCRIPTION

[0060] The technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the 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 skilled in the art without creative efforts belong to the scope of protection of the present application.

[0061] The embodiment of the present application discloses an energy storage system, comprising a controller, a DC / AC conversion circuit, at least one battery unit and a corresponding first transmission branch, and a battery heating circuit, the battery heating circuit is powered by a DC bus, the controller controls the operation of each first transmission branch and the DC / AC conversion circuit, so that each battery unit realizes the conversion and transmission of electric energy between the power grid and / or the load, and when the temperature of at least one battery unit is lower than a preset temperature value, the heating power of the corresponding battery heating circuit is adjusted, so that the battery heating circuit generates Joule heat, and the Joule heat is used to heat the corresponding battery unit. Since the battery heating circuit in the present application directly obtains the supply voltage from the DC bus, and the voltage of the DC bus can be provided by the battery unit, the battery heating circuit can obtain the supply voltage from the DC bus based on the battery unit while heating the battery unit and ensuring the normal start of the battery unit, and the whole process is not affected by the alternating current power grid, thereby improving the user experience.

[0062] Referring to Figure 1 The energy storage system disclosed by the embodiment of the present application comprises a controller (not shown in the figure), a DC / AC conversion circuit 101, at least one battery unit 102 and a corresponding first transmission branch 103, and a battery heating circuit 104. Figure 1

[0063] Each battery unit 102 is connected to the DC bus of the DC / AC conversion circuit 101 through the corresponding first transmission branch 103, and each transmission branch 103 is used to realize the transmission of electric energy between the corresponding battery unit 102 and the DC bus. A bus capacitor is arranged between the positive and negative poles of the DC bus, and the bus capacitor comprises C1 (with a voltage of VbusP) and C2 (with a voltage of VbusN). The AC side of the DC / AC conversion circuit 101 is connected to the power grid and / or the load.

[0064] Each battery heating circuit 104 is arranged at a preset heating position of the corresponding battery unit 102 and is connected to the DC bus of the DC / AC conversion circuit 101.

[0065] The number of battery heating circuits 104 can be the same as or different from the number of battery units 102, which is determined according to actual needs, and is not limited in the present application.

[0066] The preset heating position can be the bottom of the battery unit 102, the side of the battery unit 102, or the surrounding of the battery unit 102, which is determined according to the specific application environment and is within the protection scope of the present application.

[0067] The battery unit 102 in the embodiment can refer to a battery cluster or a battery pack. The energy storage system can be applied to a photovoltaic power generation system, and at this time, in order to match the voltage of the photovoltaic string in the photovoltaic power generation system, the battery unit 102 is preferably a battery cluster. The specific application environment is determined, which is within the protection scope of the present application.

[0068] The controller is used to control the operation of each first transmission branch 103 and the DC / AC conversion circuit 101, so that each battery unit 102 realizes the conversion and transmission of electric energy between the power grid and / or the load; for example, the controller controls each battery unit 102 to output electric energy, which is sequentially transmitted through the corresponding transmission branch 103 and the DC / AC conversion circuit 101 to supply power to the power grid and / or the load; or the controller controls each battery unit 102 to sequentially pass through the corresponding transmission branch 103 and the DC / AC conversion circuit 101 to receive electric energy from the power grid for charging.

[0069] ​In addition, the controller is configured to adjust the heating power of the battery heating circuit 104 when the temperature of at least one of the battery units 102 is lower than a preset temperature value, so as to heat the corresponding battery unit 102. This is because the battery heating circuit has a certain internal resistance, and thus, by adjusting the heating power of the battery heating circuit 104, the Joule heat can be generated on the battery heating circuit 104, and the Joule heat can be used to heat the corresponding battery unit 102.

[0070] In the embodiment, the preset temperature value refers to the normal minimum temperature of the battery unit 102, i.e., the maximum temperature limit of the battery unit 102. When the temperature of the battery unit 102 is lower than the preset temperature value, the battery unit 102 is heated. When the temperature of the battery unit 102 is heated to the preset temperature value, the heating of the battery unit 102 can be stopped.

[0071] It should be noted that the lower the temperature, the more likely the battery unit 102 will be overcharged (exceeding the maximum value Vmax) or undercharged (lower than the minimum value Vmin) due to charging or discharging. Therefore, in actual applications, the temperature (e.g., Temp1 in FIG. 6) and the voltage (e.g., Vrack1 in FIG. 6) of each battery unit 102 can be sampled. Figure 1 Figure 1 In order to prevent the battery unit 102 from being abnormal, the temperature of the battery unit 102 can be monitored in real time when the controller heats the corresponding battery unit 102. If the temperature of the battery unit 102 is lower than the preset temperature value, the heating power of the corresponding battery heating circuit 104 can be adjusted to heat the corresponding battery unit 102.

[0072] The process of heating the corresponding battery unit 102 by the controller can be performed before the normal operation of the energy storage system, or can be performed simultaneously with the normal operation of the energy storage system. The specific application environment can be determined, and the application is within the protection scope.

[0073] ​In conclusion, the application discloses a kind of energy storage system, comprising: controller, DC / AC conversion circuit 101, at least one battery unit 102 and corresponding first transmission branch 103, and battery heating circuit 104, battery heating circuit 104 is powered by DC bus, controller controls each first transmission branch 103 and DC / AC conversion circuit 101 work, so that each battery unit 102 realizes the electric energy conversion and transmission between power grid and / or load, and when the temperature of at least one battery unit 102 is lower than the preset temperature value, the heating power of corresponding battery heating circuit 104 is adjusted, so that battery heating circuit 104 generates Joule heat, and the Joule heat is used to heat corresponding battery unit 102. Since the battery heating circuit 104 in the application directly obtains the supply voltage from the DC bus, and the voltage of the DC bus can be provided by the battery unit 102, the battery heating circuit 104 can obtain the supply voltage from the DC bus based on the battery unit 102 while heating the battery unit 102 and ensuring the normal start of the battery unit 102, and the whole process is not affected by the alternating current power grid, thereby improving the user experience.

[0074] It should be noted that, in order to realize the basic functions of each battery unit 102, each DC / DC conversion circuit in the application is a bidirectional DC / DC conversion circuit.

[0075] When the energy storage system is applied to a photovoltaic power generation system, each battery unit 102 can share the DC / AC conversion circuit 101 with each photovoltaic string, that is, at least one photovoltaic string can also be connected to the DC bus.

[0076] Therefore, in order to further optimize the above embodiment, referring to Figure 2 The application discloses another structure diagram of the energy storage system, which is based on Figure 1 The energy storage system can further include at least one photovoltaic string 105 and corresponding second transmission branch 106.

[0077] Each photovoltaic string 105 is connected to the DC bus of the DC / AC conversion circuit 101 through the corresponding second transmission branch 106;

[0078] The controller is used to control each second transmission branch 106 and the DC / AC conversion circuit 101 to work, so that each photovoltaic string 105 realizes the electric energy conversion and transmission between the power grid and / or the load.

[0079] Therefore, in this embodiment, the DC bus voltage can be provided by the battery unit 102 and / or the photovoltaic string 105.

[0080] In this embodiment, the voltage of the photovoltaic string 105 can be monitored in real time, and the voltage of the DC bus can be adjusted based on the voltage of the photovoltaic string 105.Figure 2 The voltage provided by the photovoltaic module string 105 to the DC bus is determined according to the voltage of the DC bus.

[0081] In practical applications, the DC / AC conversion circuit 101 can be a circuit structure inside the energy storage system or a circuit structure in the photovoltaic power generation system inverter; it is determined according to the specific application environment, and it is within the protection scope of the present application.

[0082] As can be seen, the battery heating circuit 104 in the present application directly obtains the power supply voltage from the DC bus, and the voltage of the DC bus can be provided by the battery unit 102 and / or the photovoltaic module string 105, and the battery unit 102 and the photovoltaic module string 105 are not affected by the AC power grid, so the present application realizes the normal start of the battery unit 102 while ensuring that the battery heating circuit 104 heats the battery unit 102, thereby improving the user experience.

[0083] In practical applications, the controller can adjust the heating power of the battery heating circuit 104 from two aspects of voltage and impedance.

[0084] (I) Adjusting the heating power of the battery heating circuit 104 from the voltage aspect

[0085] The controller is used to adjust the heating power of the corresponding battery heating circuit 104, and is used to heat the corresponding battery unit 102, and is specifically used for:

[0086] Dynamically controlling the voltage of the DC bus to adjust the heating power of the battery heating circuit 104 to heat the corresponding battery unit 102.

[0087] Specifically, referring to Figure 3 , another embodiment of the present application discloses a structure diagram of an energy storage system, in the embodiment, the first transmission branch 103 includes: a first DC / DC conversion circuit;

[0088] When the energy storage system only contains the first transmission branch 103 and does not contain the photovoltaic module string 105 and the corresponding second transmission branch 106, the controller is used to dynamically control the voltage of the DC bus of the DC / AC conversion circuit 101, and is specifically used for:

[0089] Controlling the corresponding first DC / DC conversion circuit to perform reverse rectification to control the voltage of the DC bus.

[0090] In another embodiment, when the energy storage system contains the first transmission branch 103 and the second transmission branch 106 at the same time, as shown in Figure 3 , the first transmission branch 103 includes: a first DC / DC conversion circuit (see Figure 3The second transmission branch 106 includes a second DC / DC conversion circuit (see details in Figure 3 The second DC / DC conversion circuit.

[0091] The controller is used to dynamically control the voltage of the DC bus of the DC / AC conversion circuit 101, and is specifically used to:

[0092] (1) When the electrical energy of the photovoltaic string is higher than a first energy threshold, the corresponding second DC / DC conversion circuit is preferentially controlled to dynamically control the voltage of the DC bus;

[0093] (2) When the electrical energy of the photovoltaic string is lower than a second energy threshold, the corresponding first DC / DC conversion circuit is preferentially controlled to perform reverse rectification to dynamically control the voltage of the DC bus;

[0094] (3) When the electrical energy of the photovoltaic string is higher than the second energy threshold and lower than the first energy threshold, the corresponding first DC / DC conversion circuit and the second DC / DC conversion circuit are simultaneously controlled to dynamically control the voltage of the DC bus.

[0095] Wherein, the first energy threshold is greater than the second energy threshold, and the value of the first energy threshold greater than the second energy threshold is determined according to actual needs, which is not limited in the present application.

[0096] As can be seen from the above, in the present embodiment, (1) when the electrical energy of the photovoltaic string is higher than the first energy threshold, it indicates that the electrical energy of the photovoltaic string is sufficient, at this time, the energy of photovoltaic power generation is used as much as possible to adjust the voltage of the DC bus to provide energy for the battery unit 102 heating.

[0097] (2) When the electrical energy of the photovoltaic string is lower than the second energy threshold, it indicates that the electrical energy of the photovoltaic string is insufficient, at this time, the energy of the power grid is preferentially used to adjust the voltage of the DC bus to provide energy for the battery unit 102 heating.

[0098] (3) When the electrical energy of the photovoltaic string is higher than the second energy threshold and lower than the first energy threshold, (1) and (2) work simultaneously to adjust the voltage of the DC bus to provide energy for the battery unit 102 heating.

[0099] From Figure 2 and Figure 3The battery heating circuit 104 obtains a supply voltage through a DC bus, and the voltage of the DC bus can be provided by the battery cell 102 and / or the photovoltaic string 105. However, the customer configuration of the battery cell 102 and the photovoltaic string 105 is very large in the voltage value range, which makes it difficult to select the battery heating circuit 104. For example, the configuration voltage of the photovoltaic string 105 can be 200 V or 1000 V. When the resistance in the battery heating circuit 104 is 2000 Ω, if the configuration voltage of the photovoltaic string 105 is 200 V, the heating power of the battery heating circuit 104 is only 20 W. At this time, the heating power of the battery heating circuit 104 is too low, which leads to insufficient heating of the battery cell 102. If the configuration voltage of the photovoltaic string 105 is 1000 V, the heating power of the battery heating circuit 104 is as high as 500 W. At this time, the heating power of the battery heating circuit 104 is too high, which leads to excessive heating of the battery cell 102, thereby affecting the service life of the battery cell 102.

[0100] Therefore, the controller is used to dynamically control the voltage of the DC bus, and is specifically used to:

[0101] When the temperature of at least one battery cell 102 is higher than a preset minimum temperature limit value and lower than a preset temperature value, the voltage of the DC bus is controlled to be not lower than a voltage preset value.

[0102] The preset minimum temperature limit value is less than the preset temperature value. When the temperature of the battery cell 102 is between the preset minimum temperature limit value and the preset temperature value, it indicates that the temperature of the battery cell 102 is not very low, but still needs to be heated.

[0103] The voltage preset value Vset is determined according to actual needs, such as 700 V. The present application does not limit this. It needs to be particularly pointed out that when the temperature of the battery cell 102 is particularly low and needs to be quickly heated, the value of the voltage preset value Vset can be increased.

[0104] In the embodiment, when the voltage of the DC bus is lower than the voltage preset value, the DC / DCm or the DC / DC1 is controlled to work in the step-up mode, so as to avoid the difficulty in selecting the battery heating circuit 104.

[0105] To further optimize the above embodiment, the controller is used to dynamically control the voltage of the DC bus, and is specifically used to:

[0106] When the temperature of at least one battery cell 102 is lower than a preset minimum temperature limit value, the voltage of the DC bus is controlled to be increased, and the heating power of the corresponding battery heating circuit 104 is increased, so as to quickly heat the corresponding battery cell 102. The preset minimum temperature limit value is less than the preset temperature value.

[0107] When the temperature of the corresponding battery unit 102 rises from below the preset minimum temperature limit to a first temperature value and below the preset temperature value, the voltage of the direct current bus is controlled to be reduced, the heating power of the corresponding battery heating circuit 104 is reduced, and the corresponding battery unit 102 is slowly heated.

[0108] In the embodiment, when the temperature of the battery unit 102 is below the preset minimum temperature limit, it indicates that the temperature of the battery unit 102 is particularly low, at this time, the direct current bus voltage can be particularly high, and the heating power of the battery heating circuit 104 can be increased to accelerate the heating of the battery unit 102; when the temperature of the battery unit 102 rises but still needs to be heated, the direct current bus voltage can be appropriately reduced, the heating power of the battery heating circuit 104 can be reduced, and the battery unit 102 can continue to be heated. Although the temperature rising speed of the battery unit 102 is slightly slow, the rapid heating of the battery unit 102 can still be realized.

[0109] The application realizes the rapid heating of the battery unit 102 by dynamically adjusting the high and low of the voltage of the direct current bus. The corresponding relationship between the direct current bus voltage and the temperature of the battery unit 102 can be seen from the power scheduling diagram of the photovoltaic module string and the battery unit shown in Figure 4 .

[0110] It should be noted that the direct current bus voltage is not necessarily constant, and can be combined with high and low to avoid the temperature of the battery heating circuit 105 being always very high, and to achieve the purpose of cooling the battery heating circuit 105 by controlling the high and low of the direct current bus voltage. The power scheduling diagram of the photovoltaic module string and the battery unit shown in Figure 5 . The direct current bus voltage in the power scheduling diagram Figure 5 is only schematic, and is determined according to actual needs.

[0111] (II) Adjusting the heating power of the battery heating circuit 104 from the impedance angle

[0112] In order to further optimize the above embodiment, the controller is used to adjust the heating power of the corresponding battery heating circuit 104 to heat the corresponding battery unit 102, and is specifically used to:

[0113] The heating impedance of the corresponding battery heating circuit 104 is controlled to adjust the heating power of the battery heating circuit 104 to heat the corresponding battery unit 102.

[0114] Specifically, referring to the schematic diagram of the battery heating circuit disclosed in the embodiment of the application, the battery heating circuit comprises: a first heating impedance R1, a first circuit total switch S1, and at least one first battery heating branch. Each first battery heating branch comprises: a second heating impedance (see Figure 6 . Figure 6Rc1, Rc2, ……RcN, N≥1) and a controllable switch (see Figure 6 K1, K2, ……K N , N≥1);

[0115] The first heating impedance R1 and each of the first battery heating branches are connected in parallel, and a total circuit composed of the first heating impedance R1 and each of the first battery heating branches is connected in series with the first circuit total switch S1.

[0116] In the embodiment, each controllable switch can be an IGBT (Insulated Gate Bipolar Transistor), an MOSFET (Metal-Oxide-Semiconductor Field-Effect Transistor), a relay, or the like, or a device capable of automatic switching such as a PTC resistor, and the specific type is determined according to actual needs, which is not limited in the present application.

[0117] The controller controls the heating impedance of the corresponding battery heating circuit 104, and is specifically used for:

[0118] When the voltage across the first heating impedance R1 is higher than a first voltage threshold, or the temperature of at least one battery unit 102 is higher than a highest temperature limit, the controller controls each controllable switch in each of the first battery heating branches to be turned off, so that the impedance of the battery heating circuit 104 is equal to the first heating impedance R1, and the heating power of the corresponding battery heating circuit 104 is reduced.

[0119] The values of the first voltage threshold and the highest temperature limit are determined according to actual needs, which are not limited in the present application.

[0120] Specifically, when the voltage across the first heating impedance R1 is too high or the temperature of at least one battery unit 102 is too high, the controllable switch in each first battery heating branch can be controlled to be turned off, so that only the first heating impedance R1 is connected in the entire battery heating circuit 104. Since the first heating impedance R1 and each second heating impedance are connected in parallel, when all the second heating impedances are working, the total impedance of the entire battery heating circuit 104 is the smallest. In the embodiment, the controllable switch connected in series with each second heating impedance is turned off, so that only the first heating impedance R1 is used for heating in the entire battery heating circuit 104, which can increase the total impedance of the battery heating circuit 104, thereby reducing the voltage across the first heating impedance R1 and the heating power of the battery heating circuit 104, and facilitating the selection of the battery heating circuit 104.

[0121] When the controllable switch in the first battery heating branch is a PTC resistor, the temperature is too high, the impedance becomes large, and the second heating impedance is switched automatically.

[0122] The controller controls the heating impedance size of the corresponding battery heating circuit, and is specifically used for:

[0123] When the temperature of at least one battery cell 102 is lower than the minimum temperature limit, the controller controls each controllable switch in each first battery heating branch to be turned on, so that the impedance of the battery heating circuit 104 is equal to the parallel total impedance of the first heating impedance R1 and each second heating impedance, and the heating power of the corresponding battery heating circuit 104 is increased.

[0124] The value of the minimum temperature limit is determined according to actual needs, which is not limited in the present application.

[0125] In actual application, the temperature of the battery cell 102 and the voltage across the first heating impedance R1 are monitored in real time. When the temperature of at least one battery cell 102 is too low, each controllable switch in each first battery heating branch is controlled to be turned on, so that the first heating impedance R1 and the second heating impedance in the battery heating circuit 104 are heated, the total impedance of the battery heating circuit 104 is the parallel total impedance of the first heating impedance R1 and each second heating impedance, and the total impedance of the battery heating circuit 104 is reduced, and accordingly, the heating power of the battery heating circuit 104 is increased, so that the temperature of the battery cell 102 can be quickly increased.

[0126] Referring to Figure 7 , another schematic diagram of a battery heating circuit disclosed by the embodiment of the present application is provided, which includes a third heating impedance R3, a second circuit total switch S2, and at least one second battery heating branch. Each second battery heating branch includes a fourth heating impedance (see Figure 7 Rc1, Rc2, …, Rc M M≥1) and a controllable switch (see Figure 6 K1, K2, …, K M M≥1) connected in series with the fourth heating impedance.

[0127] The third heating impedance R3 is connected in series with the second circuit total switch S2 through each second battery heating branch connected in series.

[0128] In this embodiment, each controllable switch can be an IGBT (Insulated Gate Bipolar Transistor), a MOSFET (Metal-Oxide-Semiconductor Field-Effect Transistor), a relay, or any other device capable of automatic switching, such as a PTC resistor, and the specific choice depends on actual needs, which is not limited in the present application.

[0129] The controller controls the heating impedance of the corresponding battery heating circuit, and is specifically used for:

[0130] When the voltage across the third heating impedance R3 is higher than a first voltage threshold, or the temperature of at least one battery unit is higher than the maximum temperature limit, the controller controls each controllable switch in each second battery heating branch to be turned off, so that the impedance of the battery heating circuit 104 is equal to the total impedance of the series connection of the third heating impedance R3 and each fourth heating impedance, and the heating power of the corresponding battery heating circuit 104 is reduced.

[0131] The values of the first voltage threshold and the maximum temperature limit depend on actual needs, which are not limited in the present application.

[0132] Specifically, when the voltage across the third heating impedance R3 is too high or the temperature of at least one battery unit 102 is too high, the controllable switch in each second battery heating branch can be controlled to be turned off, so that the first heating impedance R1 and each fourth heating impedance in the entire battery heating circuit 104 are heated, the total impedance of the entire battery heating circuit 104 is increased, and thus the voltage across the third heating impedance R3 and the heating power of the battery heating circuit 104 are reduced, facilitating the selection of the battery heating circuit 104.

[0133] When the controllable switch in the second battery heating branch is a PTC resistor, its impedance increases when the temperature is too high, and the fourth heating impedance is automatically connected, so that the heating power of the entire battery heating circuit 104 is reduced.

[0134] The controller controls the heating impedance of the corresponding battery heating circuit, and is specifically used for:

[0135] When the temperature of at least one battery unit 102 is lower than a minimum temperature limit, the controller controls each controllable switch in each second battery heating branch to be turned on, so that the impedance of the battery heating circuit is equal to the third heating impedance R3, and the heating power of the corresponding battery heating circuit 104 is increased.

[0136] Or, when the voltage of the direct current bus is greater than a preset value, the controller controls the controllable switches in each of the second battery heating branches to be turned off, so that the impedance of the battery heating circuit is equal to the total impedance of the third heating impedance R3 and the series connection of the fourth heating impedances, and the heating power of the corresponding battery heating circuit 104 is reduced.

[0137] The minimum temperature limit is determined according to actual needs, and the present application does not limit it.

[0138] In actual application, the temperature of the battery unit 102 and the voltage of the direct current bus are monitored in real time. When the temperature of at least one battery unit 102 is too low, the controllable switches in each second battery heating branch are turned on, so that only the third heating impedance R3 in the battery heating circuit 104 heats the battery unit 102. Since the impedance of the entire heating circuit 104 is smaller, the heating power of the corresponding battery heating circuit 104 is increased, and the heating rate of the battery unit 102 is improved.

[0139] When the voltage of the direct current bus is too high and greater than a preset value, the controllable switches in each second battery heating branch can be dynamically turned off, so that the fourth heating impedance in each second battery heating branch is put into use.

[0140] Referring to Figure 8 , another schematic diagram of a battery heating circuit is disclosed in the embodiment of the present application. The battery heating circuit comprises a fifth heating impedance R5 and a third circuit total switch S3.

[0141] The fifth heating impedance R5 and the third circuit total switch S3 are connected in series.

[0142] The controller controls the heating impedance of the corresponding battery heating circuit, and is specifically used for:

[0143] The third circuit total switch S3 is controlled to be turned on and turned off according to a preset on-off period, so as to control the impedance of the battery heating circuit.

[0144] The control process of the third circuit total switch S3 according to the preset on-off period can be referred to the control period schematic diagram shown in Figure 9 The fifth heating impedance R5 and the battery unit 102 can be prevented from overheating by controlling the third circuit total switch S3 according to the control period schematic diagram shown in Figure 9

[0145] ​Finally, it should be noted that the terms "first", "second", and the like, herein do not denote any order, quantity, combination, or importance, but rather are used to distinguish one element from another, and are not intended to denote the presence of any such actual relationship or order. Moreover, the terms "comprises", "comprising", or any other variations thereof, are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements does not include only those elements but can also include other elements not expressly listed or inherent to such process, method, article, or apparatus. An element proceeded by "comprises... a" does not, without more constraints, exclude the presence of additional identical elements in the process, method, article, or apparatus that comprises the element.

[0146] The various embodiments in the specification are described with progression in this order of description. Embodiments having the same or similar descriptions are referenced by the same reference numerals.

[0147] The above description of disclosed embodiments provides enabling disclosure sufficient for one of ordinary skill in the art to practice the invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and generic principles defined herein can be applied to other embodiments without departing from the spirit or scope of the invention. Thus, the present invention is not to be limited to the embodiments shown herein but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. An energy storage system, characterized in that, include: The controller, DC / AC conversion circuit, at least one battery cell and corresponding first transmission branch, and battery heating circuit; Each of the battery cells is connected to the DC bus of the DC / AC conversion circuit through a corresponding first transmission branch; the voltage of the DC bus is provided by the battery cells and / or photovoltaic strings, and the voltage provided by the photovoltaic strings to the DC bus is determined by monitoring the voltage of the photovoltaic strings. Each of the battery heating circuits is respectively set at a preset heating position of the corresponding battery cell and connected to the DC bus; The AC side of the DC / AC conversion circuit is connected to the power grid and / or the load; The controller is used to control the operation of each of the first transmission branches and the DC / AC conversion circuit, so that each of the battery cells can realize the conversion and transmission of electrical energy between the power grid and / or the load; the controller is also used to adjust the heating power of the corresponding battery heating circuit by controlling the voltage of the DC bus or the heating impedance of the battery heating circuit when the temperature of at least one of the battery cells is lower than a preset temperature value, so as to heat the corresponding battery cell.

2. The energy storage system according to claim 1, characterized in that, It also includes: at least one photovoltaic string and its corresponding second transmission branch; Each of the photovoltaic strings is connected to the DC bus through a corresponding second transmission branch; The controller is used to control the operation of each of the second transmission branches and the DC / AC conversion circuit, so that each of the photovoltaic strings can realize the conversion and transmission of electrical energy between the grid and / or the load.

3. The energy storage system according to claim 2, characterized in that, The controller is used to adjust the heating power of the corresponding battery heating circuit to heat the corresponding battery cell, specifically for: The voltage of the DC bus is dynamically controlled to adjust the heating power of the battery heating circuit, thereby heating the corresponding battery cell.

4. The energy storage system according to claim 3, characterized in that, The first transmission branch includes: a first DC / DC converter circuit; The controller is used to dynamically control the voltage level of the DC bus, specifically for: The first DC / DC converter circuit is controlled to perform reverse rectification in order to control the voltage level of the DC bus.

5. The energy storage system according to claim 3, characterized in that, When the energy storage system includes both the first transmission branch and the second transmission branch, the first transmission branch includes a first DC / DC conversion circuit, and the second transmission branch includes a second DC / DC conversion circuit. The controller is used to dynamically control the voltage level of the DC bus, specifically for: When the electrical energy of the photovoltaic string is higher than the first energy threshold, the corresponding second DC / DC conversion circuit is preferentially controlled to dynamically control the voltage of the DC bus. When the electrical energy of the photovoltaic string is lower than the second energy threshold, the corresponding first DC / DC conversion circuit is preferentially controlled to perform reverse rectification to dynamically control the voltage level of the DC bus. When the electrical energy of the photovoltaic string is higher than the second energy threshold and lower than the first energy threshold, the corresponding first DC / DC conversion circuit and second DC / DC conversion circuit are controlled simultaneously to dynamically control the voltage level of the DC bus. Wherein, the first energy threshold is greater than the second energy threshold.

6. The energy storage system according to claim 3, characterized in that, The controller is used to dynamically control the voltage level of the DC bus, specifically for: When the temperature of at least one of the battery cells is higher than a preset minimum temperature limit but lower than the preset temperature value, the voltage of the DC bus is controlled to be no lower than a preset voltage value.

7. The energy storage system according to claim 3, characterized in that, The controller is used to dynamically control the voltage level of the DC bus, specifically for: When the temperature of at least one of the battery cells is lower than a preset minimum temperature limit, the voltage of the DC bus is increased to increase the heating power of the corresponding battery heating circuit, so that the corresponding battery cell heats up quickly. The preset minimum temperature limit is less than the preset temperature value. When the temperature of the corresponding battery cell rises from below the preset minimum temperature limit to a first temperature value and below the preset temperature value, the voltage of the DC bus is reduced to decrease the heating power of the corresponding battery heating circuit, so that the corresponding battery cell heats up slowly.

8. The energy storage system according to claim 1 or 2, characterized in that, The controller is used to adjust the heating power of the corresponding battery heating circuit to heat the corresponding battery cell, specifically for: The heating power of the battery heating circuit is adjusted by controlling the heating impedance of the corresponding battery heating circuit, so as to heat the corresponding battery cell.

9. The energy storage system according to claim 8, characterized in that, The battery heating circuit includes: a first heating impedance, a first circuit main switch, and at least one first battery heating branch. Each first battery heating branch includes: a second heating impedance and a controllable switch connected in series with the second heating impedance. The first heating impedance and each of the first battery heating branches are connected in parallel, and the total circuit formed by the first heating impedance and each of the first battery heating branches is connected in series with the first circuit master switch.

10. The energy storage system according to claim 9, characterized in that, The controller controls the heating impedance of the corresponding battery heating circuit, specifically for: When the voltage across the first heating impedance is higher than the first voltage threshold, or the temperature of at least one of the battery cells is higher than the maximum temperature limit, the controllable switches in each of the first battery heating branches are turned off, so that the impedance of the battery heating circuit is equal to the first heating impedance, thereby reducing the heating power of the corresponding battery heating circuit.

11. The energy storage system according to claim 9, characterized in that, The controller controls the heating impedance of the corresponding battery heating circuit, specifically for: When the temperature of at least one of the battery cells is lower than the minimum temperature limit, the controllable switches in each of the first battery heating branches are turned on, so that the impedance of the battery heating circuit is equal to the parallel total impedance of the first heating impedance and each of the second heating impedances, thereby increasing the heating power of the corresponding battery heating circuit.

12. The energy storage system according to claim 8, characterized in that, The battery heating circuit includes: a third heating impedance, a second circuit main switch, and at least one second battery heating branch. Each second battery heating branch includes: a fourth heating impedance and a controllable switch connected in series with the fourth heating impedance. The third heating impedance is connected in series with the second circuit master switch through each of the second battery heating branches connected in series.

13. The energy storage system according to claim 12, characterized in that, The controller controls the heating impedance of the corresponding battery heating circuit, specifically for: When the voltage across the third heating impedance is higher than the first voltage threshold, or the temperature of at least one of the battery cells is higher than the maximum temperature limit, the controllable switches in each of the second battery heating branches are turned off, so that the impedance of the battery heating circuit is equal to the total series impedance of the third heating impedance and each of the fourth heating impedances, thereby reducing the heating power of the corresponding battery heating circuit.

14. The energy storage system according to claim 12, characterized in that, The controller controls the heating impedance of the corresponding battery heating circuit, specifically for: When the temperature of at least one of the battery cells is lower than the minimum temperature limit, the controllable switches in each of the second battery heating branches are turned on, so that the impedance of the battery heating circuit is equal to the third heating impedance, thereby increasing the heating power of the corresponding battery heating circuit. Alternatively, when the voltage of the DC bus is greater than a preset value, the controllable switches in each of the second battery heating branches are turned off, so that the impedance of the battery heating circuit is equal to the total series impedance of the third heating impedance and each of the fourth heating impedances, thereby reducing the heating power of the corresponding battery heating circuit.

15. The energy storage system according to claim 8, characterized in that, The battery heating circuit includes: a fifth heating impedance and a third circuit master switch; The fifth heating impedance and the third circuit master switch are connected in series; The controller controls the heating impedance of the corresponding battery heating circuit, specifically for: The main switch of the third circuit is controlled to turn on and off according to a preset on / off cycle, so as to control the impedance of the battery heating circuit.

Images