Energy storage system and self-heating method thereof

Abstract

The application provides an energy storage system and a self-heating method thereof. When the temperature of a battery of the energy storage system is lower than a preset allowable working temperature, the energy conversion device is controlled to operate in a reactive working mode. Since the coolant of the energy storage system can conduct heat with the energy conversion device and the battery pack, the heat brought by the operation of the energy conversion device can replace the heating device in the prior art to heat the coolant. Then, the coolant flows to heat the battery pack. When the temperature of the battery reaches the preset allowable working temperature, the energy conversion device is controlled to operate in a normal working mode. Therefore, the application can omit the heating device in the prior art, save costs, reduce heating time, and improve efficiency.

Description

Technical Field

[0001] This application relates to the field of power electronics technology, and in particular to an energy storage system and its self-heating method. Background Technology

[0002] With the rapid development of energy storage, its application scenarios and environments are also increasing, which puts forward more requirements for the stable operation of energy storage systems. Especially in low-temperature environments below zero degrees Celsius, due to the temperature sensitivity of batteries, the battery pack needs to be heated to the allowable operating temperature in order to enter the normal operating mode.

[0003] Currently, the main solution to the battery pack heating problem is to add a heating device to the liquid cooling system to heat the coolant, and then the flow of the coolant heats the battery pack. However, this heating method is time-consuming, inefficient, and costly. Summary of the Invention

[0004] In view of this, this application provides an energy storage system and a self-heating method thereof to reduce heating time, improve efficiency, and reduce costs.

[0005] To achieve the above objectives, this application provides the following technical solution:

[0006] The first aspect of this application provides a self-heating method for an energy storage system, comprising:

[0007] Determine whether the battery temperature of the energy storage system is lower than the preset allowable operating temperature;

[0008] If the battery temperature is lower than the preset allowable operating temperature, the power conversion device in the energy storage system is controlled to operate in a reactive working mode to heat the coolant in the energy storage system that conducts heat with the power conversion device and the battery pack.

[0009] Once the battery temperature reaches the preset allowable operating temperature, the power conversion device is controlled to operate in normal working mode.

[0010] Optionally, the number of power conversion devices in the energy storage system is greater than 1, and the sum of the reactive power of each power conversion device when operating in reactive power mode is zero.

[0011] Optionally, the number of power conversion devices in the energy storage system is even, and they have the same rated power;

[0012] When each of the aforementioned power conversion devices operates in reactive power mode, half of the power conversion devices operate at full power with positive reactive power, while the other half operate at full power with negative reactive power.

[0013] Optionally, after determining whether the battery temperature is lower than the preset allowable operating temperature, the method further includes:

[0014] If the battery temperature is not lower than the preset allowable operating temperature, the power conversion device is controlled to operate in normal working mode.

[0015] Optionally, before controlling the operation of the power conversion device, the method further includes:

[0016] Control the power conversion device to precharge the bus.

[0017] Optionally, controlling the power conversion device to perform bus pre-charging includes:

[0018] Read the remaining SOC of the battery pack connected to the power conversion device;

[0019] According to the SOC, the power conversion device is pre-charged on the bus using source-side power or battery-side power.

[0020] Optionally, based on the SOC, the power conversion device is pre-charged on the bus using source-side power or battery-side power, including:

[0021] Determine whether the SOC is greater than a preset lower limit value;

[0022] If the SOC is less than or equal to the preset lower limit of SOC, then the power conversion device is pre-charged by the source-side power.

[0023] If the SOC is greater than the preset lower limit of SOC, the power conversion device is pre-charged by the battery-side power.

[0024] Optionally, controlling the power conversion device to perform bus pre-charging includes:

[0025] The power conversion device is pre-charged on the bus using either source-side or battery-side power.

[0026] A second aspect of this application provides an energy storage system, comprising: a controller, a cooling system, and at least one energy storage unit; wherein,

[0027] The energy storage unit includes: a power conversion device and at least one battery cluster;

[0028] In the energy storage unit, the battery side of the power conversion device is connected to the battery cluster through a corresponding first pre-charging module; the power conversion device is connected in parallel with a second pre-charging module.

[0029] The coolant in the cooling system is used to conduct heat with the power conversion device and the battery pack in the battery cluster, thereby regulating the battery temperature.

[0030] The power conversion device, the first pre-charging module, and the second pre-charging module are controlled by the controller.

[0031] The controller is used to execute the self-heating method of the energy storage system as described in any of the first aspects above.

[0032] Optionally, the number of energy storage units is greater than 1, and the source side of each of the power conversion devices is connected in parallel.

[0033] Optionally, the first pre-charge module and the second pre-charge module include: a switch and a resistor;

[0034] The switch and the resistor are connected in series.

[0035] Optionally, the first pre-charge module is connected in parallel with the DC switch in the power transmission circuit on the battery side of the power conversion device.

[0036] Optionally, the cooling system includes: coolant transmission pipelines, a water pump, and valves;

[0037] The coolant flows through the coolant transmission pipeline, passing through the water pump and the valve;

[0038] The coolant transmission pipeline passes through the power conversion device and the battery pack.

[0039] Optionally, the power conversion device is a power storage converter (PCS).

[0040] The self-heating method for an energy storage system provided in this application controls the power conversion device to operate in a reactive power mode when the battery temperature of the energy storage system is lower than a preset allowable operating temperature. Since the coolant in the energy storage system can conduct heat with the power conversion device and the battery pack, the heat generated by the operation of the power conversion device can replace the heating device in the prior art to heat the coolant. The flow of the coolant then further heats the battery pack. Once the battery temperature reaches the preset allowable operating temperature, the power conversion device can be controlled to operate in normal operating mode. Therefore, this application eliminates the need for the heating device in the prior art, saving costs and reducing heating time, thus improving efficiency. Attached Figure Description

[0041] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on the provided drawings without creative effort.

[0042] Figure 1 This is a schematic diagram of the cooling system of the energy storage system provided in the embodiments of this application;

[0043] Figure 2 A flowchart of a self-heating method for an energy storage system provided in an embodiment of this application;

[0044] Figure 3 Another flowchart of the self-heating method of the energy storage system provided in the embodiments of this application;

[0045] Figure 4 Another flowchart of the self-heating method of the energy storage system provided in the embodiments of this application;

[0046] Figure 5 A partial flowchart of the self-heating method for an energy storage system provided in this application embodiment;

[0047] Figure 6 This is a schematic diagram of the energy storage system provided in an embodiment of this application. Detailed Implementation

[0048] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0049] In this application, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitation, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes that element.

[0050] This application provides a self-heating method for an energy storage system to reduce heating time, improve efficiency, and lower costs.

[0051] Cooling systems in energy storage systems, such as Figure 1 As shown, its coolant transmission pipeline passes through the power conversion device and the battery pack. When the number of power conversion devices and / or battery packs in the energy storage system is greater than 1, the coolant transmission pipeline is also set to pass through each power conversion device and each battery pack, thereby realizing heat conduction for all power conversion devices and battery packs.

[0052] See Figure 2 The self-heating method of the energy storage system includes:

[0053] S101. Determine whether the battery temperature of the energy storage system is lower than the preset allowable operating temperature.

[0054] The battery temperature refers to a parameter that reflects the temperature of the battery pack in the energy storage system. It can be the average internal temperature of each battery pack, or it can be the common ambient temperature of each battery pack, depending on the specific application environment. All of these are within the scope of protection of this application.

[0055] If the battery temperature is lower than the preset allowable operating temperature, then execute S102.

[0056] S102. Control the power conversion device in the energy storage system to operate in reactive mode, and heat the coolant in the energy storage system that conducts heat with the power conversion device and battery pack.

[0057] When the power conversion device is running, the operation of its internal power devices will generate a certain amount of heat. This heat can be conducted between the device and the coolant to heat the coolant, replacing the heating device in the existing technology.

[0058] Moreover, the power conversion device operates in reactive mode, which can avoid consuming energy from the energy storage system.

[0059] S103 will be executed only after the battery temperature reaches the preset allowable operating temperature.

[0060] S103, Control the power conversion device to operate in normal working mode.

[0061] That is, before the power conversion device enters normal operating mode, such as upon receiving an operating command, S101 is executed first; if the battery temperature is low, the battery pack is first heated via S102. After a period of reactive operation, once the preset allowable operating temperature is met, the device can switch to normal operating mode for charging and discharging. Furthermore, after S101, if the battery temperature is not lower than the preset allowable operating temperature, S103 can be executed directly.

[0062] The self-heating method for the energy storage system provided in this embodiment controls the power conversion device to operate in a reactive mode when the battery temperature of the energy storage system is lower than the preset allowable operating temperature. The heat generated by the operation of the power conversion device replaces the heating device in the prior art to heat the coolant. The flow of the coolant then heats the battery pack. Once the battery temperature reaches the preset allowable operating temperature, the power conversion device can be controlled to operate in normal operating mode. Therefore, the heating device in the prior art can be omitted, saving costs and reducing heating time, thus improving efficiency.

[0063] Based on the previous embodiment, preferably, the self-heating method provided in this embodiment sets the number of power conversion devices in the energy storage system to be greater than 1, and the sum of the reactive power of each power conversion device when it is operating in reactive power mode is zero, thereby avoiding the impact on the external power supply of the energy storage system.

[0064] For example, when the power conversion device is a PCS (Power Conversion System), the AC side of each PCS is usually connected to the power grid through a corresponding transformer. In this case, if the sum of the reactive power of each PCS is zero, the coolant can be heated by the heat generated by the PCS without affecting the power grid.

[0065] Specifically, when the number of power conversion devices in the energy storage system is even and their rated power is the same, it can be set that when each power conversion device operates in reactive power mode, half of the power conversion devices operate at full power with positive reactive power, and the other half operate at full power with negative reactive power. In this way, not only can the impact on the external power supply of the energy storage system be avoided, but also the large heat generation of each power conversion device can achieve rapid heating.

[0066] In practical applications, if the number of power conversion devices in the energy storage system is odd, or if the rated power of each power conversion device is different, the sum of reactive power can be made zero, or as close to zero as possible, by allocating the power of each power conversion device to avoid affecting the external power supply of the energy storage system. The specific allocation method can be determined according to the actual situation, and will not be elaborated here.

[0067] Based on the above embodiments, the self-heating method provided in this embodiment further includes, before controlling the operation of the power conversion device, such as before executing S102 at low temperatures, or before directly executing S103 at normal temperatures, the following additional steps: Figure 3 As shown:

[0068] S201, Control the power conversion device to precharge the bus.

[0069] In practical applications, the power device is connected to the battery side of the corresponding battery cluster, such as the DC side of the PCS, and can be equipped with a corresponding pre-charging module; moreover, the power device is connected to the source side of the power supply, such as the AC side of the PCS, and can also be connected to its battery side through a corresponding pre-charging module; therefore, S201 can specifically use source-side power to pre-charge the power conversion device on the bus, or it can use battery-side power to pre-charge the power conversion device on the bus, depending on the specific application environment, and both are within the protection scope of this application.

[0070] In other words, the startup method of this energy storage system during actual reactive power operation can be either slow pre-charging from the battery side and then grid-connected to generate reactive power, or bus pre-charging from the source side and then grid-connected to generate reactive power.

[0071] It should be noted that this self-heating method utilizes reactive power characteristics, theoretically enabling heating of the battery pack without consuming energy. However, in practical applications, such as when generating full reactive power, the power conversion device will experience some DC losses. For example, a single 200kW PCS unit will have a DC loss of approximately 1kW during operation. Therefore, in low-temperature environments, factors such as the battery pack's SOC (state of charge, also known as remaining charge) need to be fully considered when selecting an appropriate start-up method. For instance, if the power conversion device still starts and connects to the grid to generate reactive power from the battery side when the SOC is at its lower limit, the DC loss will be drawn from the battery side, further lowering the SOC and causing significant damage to the battery.

[0072] Therefore, in the preferred embodiment of the self-heating method, step S201, controlling the power conversion device to pre-charge the bus, specifically includes... Figure 4 As shown:

[0073] S301. Read the SOC of the battery cluster connected to the power conversion device.

[0074] S302. Based on the SOC, the power conversion device is pre-charged on the bus using source-side power or battery-side power.

[0075] Moreover, the S302 may specifically include Figure 5 As shown:

[0076] S401. Determine whether the SOC is greater than the preset lower limit of SOC.

[0077] If the SOC is less than or equal to the preset lower limit of SOC, then execute S402. If the SOC is greater than the preset lower limit of SOC, then execute S403.

[0078] S402. The power conversion device is pre-charged on the bus using source-side electrical energy.

[0079] S403, The power conversion device is pre-charged on the bus using battery-side electrical energy.

[0080] Specifically, the current SOC of the battery cluster is first recorded as SOCt, and the preset lower limit of SOC is recorded as SOCth. Then, SOCt and SOCth are compared. If SOCt ≤ SOCth, the bus is charged using the source-side pre-charging method without consuming battery-side energy, and then the bus is connected to the grid for reactive power operation to increase the coolant temperature. If SOCt > SOCth, the bus is charged directly using the battery-side pre-charging method, and then the bus is connected to the grid for reactive power operation to increase the coolant temperature and avoid consuming source-side electrical energy.

[0081] In other words, this embodiment selects the start-up operation mode based on the SOC state of the battery cluster at low temperatures, avoiding the risk of the energy storage system still drawing power from the battery side in self-heating mode when the SOC is too low, thus further reducing the battery SOC.

[0082] Another embodiment of this application also provides an energy storage system, such as Figure 6 As shown, it includes: a controller (shown in the figure), a cooling system, and at least one energy storage unit 10; wherein:

[0083] The energy storage unit 10 includes: a power conversion device (PCS as shown in the figure) and at least one battery cluster (RACK as shown in the figure). In practical applications, when the number of battery clusters connected to the battery side of the power conversion device is greater than one, the battery clusters can be connected in parallel. The figure only shows an example of the power conversion device connected to one battery cluster. Multiple battery packs can exist within the battery cluster, and these battery packs are connected in series.

[0084] Furthermore, in the energy storage unit 10, the battery side of its power conversion device, that is, the DC side of the PCS, is connected to the corresponding battery cluster through the corresponding first pre-charge module 101; and the power conversion device is connected in parallel with the second pre-charge module 102.

[0085] In practical applications, both the first pre-charging module 101 and the second pre-charging module 102 may include a switch and a resistor connected in series. During bus pre-charging, the switch in the corresponding charging module is in a closed state.

[0086] When the power conversion device is precharged on the bus using source-side power, the power on both sides of the power conversion device cannot pass through the power conversion device, but instead passes through the second pre-charging module 102.

[0087] Moreover, the first pre-charging module 101 is connected in parallel with the DC switch in the power transmission circuit on the battery side of the power conversion device; therefore, when the power conversion device is pre-charged by the battery side power, the DC switch is in the open state, while the switch in the first pre-charging module 101 is in the closed state.

[0088] In addition, such as Figure 6 As shown, when the number of energy storage units 10 is greater than 1, the source side of each power conversion device, that is, the AC side of the PCS, is connected in parallel; and after the AC side of each PCS is connected in parallel, it can be connected to the power grid through the corresponding transformer. Figure 6 The thin lines in the diagram represent the power path of the energy storage system, while the thick lines represent the heat exchange path.

[0089] The coolant in this cooling system is used for heat conduction with the power conversion device and battery pack, regulating battery temperature; moreover, see... Figure 6 The cooling system may specifically include: a coolant transmission pipeline (as shown by the thick line in the figure), a water pump 201, and a valve 202; wherein, the coolant flows through the coolant transmission pipeline, passing through the water pump 201 and the valve 202; and the coolant transmission pipeline passes through the power conversion device and the battery pack.

[0090] The power conversion device, the first pre-charge module 101, and the second pre-charge module 102 are controlled by a controller; the controller is used to execute the self-heating method of the energy storage system as described in any of the above embodiments. The specific process and principle of the self-heating method can be found in the above embodiments, and will not be repeated here.

[0091] Through this self-heating method, the energy storage system can heat the coolant by generating reactive power through the power conversion device at low temperatures, thereby increasing the ambient temperature of the battery and achieving the purpose of low-temperature grid-connected charging and discharging.

[0092] Similar or identical parts between the various embodiments in this specification can be referred to mutually. Each embodiment focuses on describing the differences from other embodiments. In particular, for system or system embodiments, since they are basically similar to method embodiments, the description is relatively simple, and relevant parts can be referred to the description of the method embodiments. The systems and system embodiments described above are merely illustrative. The units described as separate components may or may not be physically separate. The components shown as units may or may not be physical units, that is, they may be located in one place or distributed across multiple network units. Some or all of the modules can be selected to achieve the purpose of this embodiment solution according to actual needs. Those skilled in the art can understand and implement this without creative effort.

[0093] Those skilled in the art will further recognize that the units and algorithm steps of the various examples described in conjunction with the embodiments disclosed herein can be implemented in electronic hardware, computer software, or a combination of both. To clearly illustrate the interchangeability of hardware and software, the components and steps of the various examples have been generally described in terms of functionality in the foregoing description. Whether these functions are implemented in hardware or software depends on the specific application and design constraints of the technical solution. Those skilled in the art can use different methods to implement the described functions for each specific application, but such implementations should not be considered beyond the scope of this invention.

[0094] The features described above regarding the disclosed embodiments can be substituted for or combined with each other to enable those skilled in the art to implement or use the invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein can be implemented in other embodiments without departing from the spirit or scope of the invention. Therefore, the 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. A self-heating method for an energy storage system, characterized in that, include: Determine whether the battery temperature of the energy storage system is lower than the preset allowable operating temperature; If the battery temperature is lower than the preset allowable operating temperature, the power conversion device in the energy storage system is controlled to operate in a reactive working mode to heat the coolant in the energy storage system that conducts heat with the power conversion device and the battery pack. Once the battery temperature reaches the preset allowable operating temperature, the power conversion device is controlled to operate in normal working mode. In the energy storage system, the number of power conversion devices is greater than 1, and the sum of the reactive power of each power conversion device when it is operating in reactive power mode is zero. If the number of power conversion devices in the energy storage system is even and they have the same rated power, then When each of the aforementioned power conversion devices operates in reactive power mode, half of the power conversion devices operate at full power with positive reactive power, while the other half operate at full power with negative reactive power. If the number of power conversion devices in the energy storage system is odd, or if the rated power of each power conversion device is different, then by allocating the power of each power conversion device, the sum of reactive power can be made zero.

2. The self-heating method for an energy storage system according to claim 1, characterized in that, After determining whether the battery temperature is lower than the preset allowable operating temperature, the method further includes: If the battery temperature is not lower than the preset allowable operating temperature, the power conversion device is controlled to operate in normal working mode.

3. The self-heating method for an energy storage system according to any one of claims 1 to 2, characterized in that, Before controlling the operation of the power conversion device, the following is also included: Control the power conversion device to precharge the bus.

4. The self-heating method for an energy storage system according to claim 3, characterized in that, Controlling the power conversion device to perform bus pre-charging includes: Read the remaining SOC of the battery pack connected to the power conversion device; According to the SOC, the power conversion device is pre-charged on the bus using source-side power or battery-side power.

5. The self-heating method for an energy storage system according to claim 4, characterized in that, According to the SOC, the power conversion device is pre-charged on the bus using source-side power or battery-side power, including: Determine whether the SOC is greater than a preset lower limit value; If the SOC is less than or equal to the preset lower limit of SOC, then the power conversion device is pre-charged by the source-side power. If the SOC is greater than the preset lower limit of SOC, the power conversion device is pre-charged by the battery-side power.

6. The self-heating method for an energy storage system according to claim 3, characterized in that, Controlling the power conversion device to perform bus pre-charging includes: The power conversion device is pre-charged on the bus using either source-side or battery-side power.

7. An energy storage system, characterized in that, include: The system comprises a controller, a cooling system, and at least one energy storage unit; wherein, The energy storage unit includes: a power conversion device and at least one battery cluster; In the energy storage unit, the battery side of the power conversion device is connected to the battery cluster through a corresponding first pre-charging module; the power conversion device is connected in parallel with a second pre-charging module. The coolant in the cooling system is used to conduct heat with the power conversion device and the battery pack in the battery cluster, thereby regulating the battery temperature. The power conversion device, the first pre-charging module, and the second pre-charging module are controlled by the controller. The controller is used to execute the self-heating method of the energy storage system as described in any one of claims 1 to 6.

8. The energy storage system according to claim 7, characterized in that, The number of energy storage units is greater than 1, and the source sides of each of the power conversion devices are connected in parallel.

9. The energy storage system according to claim 7, characterized in that, The first pre-charge module and the second pre-charge module each include: a switch and a resistor; The switch and the resistor are connected in series.

10. The energy storage system according to claim 7, characterized in that, The first pre-charging module is connected in parallel with the DC switch in the power transmission circuit on the battery side of the power conversion device.

11. The energy storage system according to any one of claims 7 to 10, characterized in that, The cooling system includes: coolant transmission pipelines, a water pump, and valves; The coolant flows through the coolant transmission pipeline, passing through the water pump and the valve; The coolant transmission pipeline passes through the power conversion device and the battery pack.

12. The energy storage system according to any one of claims 7 to 10, characterized in that, The power conversion device is a power storage converter (PCS).

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