Droop control method of micro-grid and related device

Abstract

The invention provides a droop control method of a micro-grid and a related device. The microgrid comprises an energy storage system, the energy storage system comprises a plurality of battery modules, and the droop control method comprises the following steps: acquiring the state of charge and temperature of each battery module; judging whether the range of the state of charge of the battery module in the energy storage system is smaller than a preset value or not; if yes, a first working mode is adopted, and the droop coefficient of the first working mode is related to the temperature of the battery module; if not, a second working mode is adopted, and the droop coefficient of the second working mode is related to the temperature and the charge state of the battery module; and controlling the output power of the battery module based on the first working mode or the second working mode. According to the technical scheme provided by the invention, the output power of the battery module can be controlled, so that power distribution among a plurality of battery modules is realized.

Description

Technical Field

[0001] This invention relates to the field of microgrid technology, and in particular to a droop control method and related apparatus for microgrids. Background Technology

[0002] With the continuous application and development of renewable energy, microgrids have emerged to meet the demands of large-scale development and improve power supply reliability and flexibility. Microgrids include DC microgrids and AC microgrids. AC microgrids connect the grid side, photovoltaic cell side, and energy storage system through a power conversion system (PCS). DC microgrids connect loads, photovoltaic cells, and energy storage system through a DC bus and interact with the AC grid through a bidirectional DC / AC converter.

[0003] Energy storage systems, as a crucial component of microgrids, consist of multiple battery modules connected in parallel. Ensuring the operational stability and lifespan of these systems requires addressing the critical technical challenge of power distribution among these battery modules. Summary of the Invention

[0004] This application provides a droop control method and related device for microgrids to control the output power of battery modules and improve the working stability and service life of energy storage systems.

[0005] In a first aspect, this application provides a droop control method for a microgrid, the microgrid including an energy storage system, the energy storage system including multiple battery modules, the method comprising: Obtain the state of charge and temperature of each battery module; Determine whether the range of the state of charge of the battery modules in the energy storage system is less than a preset value; If so, the first working mode is adopted, and the droop coefficient of the first working mode is related to the temperature of the battery module; If not, the second working mode is adopted, and the droop coefficient of the second working mode is related to the temperature and state of charge of the battery module. The output power of the battery module is controlled based on the first operating mode or the second operating mode.

[0006] In conjunction with the first aspect, in one possible implementation, the droop coefficient of the first operating mode satisfies the following relationship with the temperature of the battery module:

[0007] Among them, K r1K0 is the droop coefficient for the first working mode, and T is the initial droop coefficient. i T is the temperature of the i-th battery module. avg The average temperature of the battery module in the energy storage system.

[0008] In conjunction with the first aspect, in one possible implementation, the droop coefficient of the second operating mode, the temperature of the battery module, and the state of charge of the battery module satisfy the following relationship:

[0009] Among them, K r2 Here, K0 is the initial droop coefficient, m1 is the first weighting coefficient, m2 is the second weighting coefficient, and SOC is the droop coefficient for the second working mode. i For the i-th battery module, the State of Charge (SOC) avg T represents the average state of charge of the battery modules in the energy storage system. i T is the temperature of the i-th battery module. avg The average temperature of the battery module in the energy storage system.

[0010] In conjunction with the first aspect, in one possible implementation, the droop coefficient of the second operating mode is also related to the charge and discharge state of the battery module.

[0011] In conjunction with the first aspect, in one possible implementation, the droop coefficient of the second operating mode, the temperature of the battery module, the state of charge of the battery module, and the state of charge / discharge of the battery module satisfy the following relationship:

[0012] Among them, I o The output current of the battery module is denoted as , and sign() is the sign function.

[0013] In conjunction with the first aspect, in one possible implementation, when the battery module is in a charging state, I o When the battery module is in a discharging state, I is positive. o It is negative.

[0014] In conjunction with the first aspect, in one possible implementation, the preset value is 5%.

[0015] Secondly, this application provides a droop control device for a microgrid, which can be used to implement various modules of the method in the first aspect or possible implementations of the first aspect, each module being implemented in hardware and / or software.

[0016] For example, the device may include a processing module. The processing module is configured to acquire the state of charge and temperature of each battery module; the processing module is further configured to determine whether the range of the state of charge of the battery modules in the energy storage system is less than a preset value; if so, a first operating mode is adopted, the droop coefficient of the first operating mode being related to the temperature of the battery module; if not, a second operating mode is adopted, the droop coefficient of the second operating mode being related to the temperature and state of charge of the battery module; the processing module is further configured to control the output power of the battery modules based on the first operating mode or the second operating mode.

[0017] Thirdly, this application provides a droop control device for a microgrid, including a processor coupled to a memory for executing instructions in the memory to implement the method in the first aspect or any possible implementation thereof. Optionally, the device further includes a memory. Optionally, the device further includes a communication interface, to which the processor is coupled.

[0018] Fourthly, this application provides a microgrid including the droop control device as described in the second aspect or any possible implementation of the second aspect or the third aspect.

[0019] Fifthly, this application provides a computer-readable medium storing program code for execution by a device, the program code including methods for performing the methods described in the first aspect or any possible implementation thereof.

[0020] Sixthly, this application provides a computer program product containing instructions that, when run on a computer, cause the computer to perform the method as described in the first aspect or any possible implementation thereof.

[0021] This application provides a droop control method and related apparatus for microgrids. The technical solution provided in this application utilizes a current-voltage (IV) type droop control method to quickly respond to load changes and adjusts the output power of each battery module based on parameters such as the state of charge (SOC) and temperature of the battery modules. This ensures that the SOC and temperature of the battery modules are within the same range, thereby improving the operational stability and lifespan of the energy storage system. The technical solution provided in this application can be used to solve the power distribution problem of parallel-connected battery modules in energy storage systems. The technical solution provided in this application can be applied to both AC and DC microgrids. Attached Figure Description

[0022] Figure 1 This is a schematic system structure diagram of an AC microgrid; Figure 2This is a schematic system structure diagram of a DC microgrid; Figure 3 A schematic flowchart illustrating a droop control method for a microgrid provided in this application; Figure 4 This application provides a schematic control structure diagram of a battery module in a DC microgrid; Figure 5 A current-voltage linear relationship diagram for a type IV droop control method provided in this application; Figure 6 This application provides a schematic structural block diagram of a droop control method. Detailed Implementation

[0023] The technical solution of the present invention will now be clearly and completely described with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. 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.

[0024] First, combine Figure 1 and Figure 2 This application explains the technical problem it aims to solve.

[0025] With the continuous application and development of renewable energy, microgrids have emerged to meet the needs of their large-scale development and improve power supply reliability and flexibility. Microgrids include DC microgrids and AC microgrids.

[0026] Figure 1 A schematic system architecture diagram of an AC microgrid is shown. Figure 1 As shown, in an AC microgrid, a power conversion system (PCS) connects the grid side, the photovoltaic (PV) cell side, and the energy storage system. The grid side supplies power to the loads. The energy storage system comprises multiple battery modules connected in parallel. The PCS is connected to each battery module in the PV and energy storage systems via direct current / direct current (DC / DC) converters.

[0027] Figure 2 A schematic system architecture diagram of a DC microgrid is shown. (For example...) Figure 2As shown, in a DC microgrid, loads, photovoltaic (PV) systems, energy storage systems, and the grid side are connected via a DC bus. The energy storage system comprises multiple battery modules connected in parallel. Each battery module in the load, PV, and energy storage systems is connected to the DC bus via a DC / DC converter. The DC bus interacts with the AC grid via a DC / AC converter, enabling centralized management and distribution of DC-side power.

[0028] For AC microgrids, when the load changes during power supply to the external system, causing variations in the power output of the power consumption circuit (PCS), the energy storage system needs to dynamically allocate the power of each battery module to ensure its operational stability and lifespan. Similarly, for DC microgrids, when the load changes during power supply to the external system, causing variations in the output power of the DC bus, the energy storage system also needs to dynamically allocate the power of each battery module to ensure its operational stability and lifespan. Therefore, how to achieve power allocation among the battery modules in an energy storage system becomes a technical problem that needs to be solved.

[0029] In view of this, this application provides a droop control method and related apparatus for microgrids. The technical solution provided in this application utilizes a current-voltage (IV) type droop control method to quickly respond to load changes and adjusts the output power of each battery module according to parameters such as the state of charge (SOC) and temperature of the battery modules, ensuring that the SOC and temperature of the battery modules are within the same range, thereby improving the operational stability and lifespan of the energy storage system. In this application, the battery module can be replaced with a battery cluster or battery cell. The technical solution provided in this application can be used to solve the power distribution problem of parallel-connected battery modules in energy storage systems. The technical solution provided in this application can be applied to both AC and DC microgrids.

[0030] Figure 3 This is a schematic flowchart illustrating a droop control method for a microgrid provided in this application. Figure 3 As shown, the method may include S310, S320 and S330.

[0031] As an example, the method can be executed by a control unit in a microgrid, which can be a software and / or hardware module, and this application does not limit this.

[0032] S310 acquires the state of charge and temperature of each battery module.

[0033] In this application, the state of charge (SOC) and temperature of each battery module in the energy storage system can be obtained. For example, when the energy storage system includes n battery modules, the SOC of each battery module can be expressed as: SOC = [SOC1, SOC2, ..., SOC2]. nThe temperature of each battery module can be expressed as: T = [T1, T2, ..., T]. n [n] is a positive integer. This application does not limit the specific implementation method for obtaining the state of charge and temperature of each battery module in the energy storage system. Optionally, the control unit can communicate with each battery module to obtain the state of charge and temperature.

[0034] Optionally, after obtaining the state of charge (SOC) and temperature of each battery module, the following can be further determined for the battery modules in the energy storage system: the average SOC, the average temperature, and the SOC range. It should be noted that the SOC range is the difference between the maximum and minimum SOC values ​​of the battery modules in the energy storage system.

[0035] S320 determines whether the range of the state of charge of the battery module in the energy storage system is less than a preset value.

[0036] After determining the range of the state of charge, it can be further determined whether the range of the state of charge is less than a preset value. It should be noted that the preset value can be set according to actual needs, and this application does not impose any restrictions on it. In some embodiments, the preset value can be 5%.

[0037] In this application, if the range of the state of charge is less than a preset value, the first operating mode can be adopted.

[0038] Optionally, the droop factor of the first operating mode is related to the temperature of the battery modules. It should be noted that energy storage systems are highly sensitive to temperature. Significant temperature differences between battery modules in different locations can lead to varying degrees of aging, affecting their lifespan and consequently the stability and lifespan of the energy storage system. Therefore, when the difference in the state of charge (SOC) of battery modules in different locations is small, the droop factor of the first operating mode can be determined solely based on temperature to adjust the output power of the battery modules, ensuring that the temperature of each battery module in the energy storage system is within a uniform range. This can improve the stability and lifespan of the energy storage system.

[0039] Optionally, the droop coefficient of the first operating mode can satisfy the following relationship with the temperature of the battery module:

[0040] Among them, K r1 K0 is the droop coefficient for the first working mode, and T is the initial droop coefficient. i Let T be the temperature of the i-th battery module in the energy storage system. avg This represents the average temperature of the battery modules in the energy storage system.

[0041] In this application, if the range of state-of-charge (SOC) values ​​is not less than a preset value, or if the range of SOC values ​​is greater than or equal to a preset value, a second operating mode can be adopted. The droop coefficient of the second operating mode is related to the temperature and SOC of the battery modules. It should be noted that a large difference in SOC among the battery modules increases the difficulty of adjusting the bus voltage, thus affecting the total output power of the energy storage system. Therefore, when the SOC difference among the battery modules is large, the droop coefficient of the second operating mode can be determined based on temperature and SOC to adjust the output power of the battery modules, ensuring that the temperature and SOC of each battery module are within the same range, thereby improving the stability and lifespan of the energy storage system. For example, when the temperature of each battery module is consistent, the output current of the battery modules can be reduced based on the droop coefficient of the second operating mode to ensure that the SOC of the battery modules are within the same range. However, this will also reduce the output power of the energy storage system. Therefore, to ensure the maximum output power of the energy storage system, the solution provided in this application only adjusts the output power of the battery modules based on SOC when the SOC difference among the battery modules is large.

[0042] Optionally, the droop coefficient, battery module temperature, and battery module state of charge in the second operating mode can satisfy the following relationship:

[0043] Among them, K r2 Here, K0 is the initial droop coefficient, m1 is the first weighting coefficient, m2 is the second weighting coefficient, and SOC is the droop coefficient for the second working mode. i For the i-th battery module in the energy storage system, SOC (State of Charge) avg T represents the average state of charge of the battery modules in the energy storage system. i Let T be the temperature of the i-th battery module in the energy storage system. avg This represents the average temperature of the battery module in the energy storage system. It should be noted that m1 and m2 can be set according to actual needs, and this application does not impose any restrictions on them.

[0044] In some implementations, the droop coefficient of the second operating mode can also be related to the charge and discharge state of the battery module.

[0045] For example, the droop coefficient, battery module temperature, battery module state of charge, and battery module charge / discharge state in the second operating mode can satisfy the following relationship:

[0046] Among them, I o The output current of the battery module is denoted by , and sign() is the sign function.

[0047] Optionally, when the battery module is in a charging state, Io It can be positive, that is, sign(I) o Take the positive sign; when the battery module is in a discharging state, I o It can be negative, that is, sign(I) o Take the negative sign.

[0048] S330 controls the output power of the battery module based on either the first or second operating mode.

[0049] In this application, the output power of the battery module can be controlled based on a defined droop control operating mode. For example, the output current of the battery module can be adjusted based on the droop control method, thereby adjusting the output power of the battery module.

[0050] The technical solution provided in this application determines the operating mode of the droop control method by using the maximum state of charge value of the battery module in the energy storage system, thereby achieving control of the output power of the battery module in the energy storage system. In this application, determining the specific operating mode based on the actual operating state of the energy storage system can improve the accuracy of battery module output power control.

[0051] The following is combined with Figures 4 to 6 The method for controlling drooping in type IV of this application is described.

[0052] Figure 4 This application provides a schematic control structure diagram of a battery module in a DC microgrid. Figure 4 In the DC microgrid shown, each battery module in the energy storage system is connected to the DC bus via a DC / DC converter, and power is distributed to the battery modules through Type IV droop control.

[0053] like Figure 4 As shown, the inputs to Type IV droop control include: bus voltage U o The reference voltage U of the droop control output ref The battery module's state of charge (SOC) and temperature (T) are considered. The control unit can determine the droop factor K based on the battery module's SOC and temperature (T). r and based on bus voltage U o Reference voltage U ref and droop coefficient K r Determine the reference current I for the droop control output. ref The method for determining the droop coefficient can be found by referring to... Figure 3 The relevant descriptions in the document will not be repeated here.

[0054] Figure 5 A current-voltage linear relationship diagram for a type IV droop control method provided in this application. Figure 5In the middle, K r U is the droop coefficient. ref U is the reference voltage for the droop control output. min i is the minimum voltage for droop control output. max This is the maximum allowable current value for the droop control output.

[0055] according to Figure 5 It can be seen that the reference current of the droop control output and the droop coefficient can satisfy the following relationship:

[0056] Among them, I ref It is the reference current for the droop control output, U o It is the bus voltage.

[0057] like Figure 4 As shown, the reference current I can be... ref and the output current I of the battery module o The comparison is then fed into a proportional-integral (PI) controller to measure the reference current I. ref and output current I o The data is adjusted, and then pulse width modulation (PWM) is applied to generate a duty cycle. This duty cycle can be used to adjust the operating state of the DC / DC converter connected to the battery module, thereby controlling the output current of the battery module and thus regulating its output power. It can be seen that this application can achieve output power regulation for each battery module.

[0058] This application uses only a single PI controller, which improves the convergence and response bandwidth of droop control, thereby increasing the response speed to load changes and adapting to more frequent load variations, ultimately improving the performance of the energy storage system. However, using only a single PI controller can lead to excessive system overshoot. Therefore, feedforward compensation can be added to the droop control method to address the problem of excessive system overshoot, such as... Figure 6 As shown. The input to this compensator is the reference current I. ref and output current I o The difference, such as (I ref -I o The output of this compensator is: k p (I ref -I o ). k p This is a dynamic early-stage increment used to compensate for the input.

[0059] This application also provides a droop control device, which may include a processing module. The processing module is configured to acquire the state of charge and temperature of each battery module; the processing module is further configured to determine whether the range of the state of charge of the battery modules in the energy storage system is less than a preset value; if so, a first operating mode is adopted, the droop coefficient of the first operating mode being related to the temperature of the battery module; if not, a second operating mode is adopted, the droop coefficient of the second operating mode being related to the temperature and state of charge of the battery module; the processing module is further configured to control the output power of the battery modules based on the first operating mode or the second operating mode.

[0060] Optionally, the processing module can be implemented in hardware and / or software.

[0061] This application also provides a droop control device, including a processor coupled to a memory for executing instructions in the memory to implement the method shown in the foregoing embodiments. Optionally, the device may further include a memory. Optionally, the device may also include a communication interface, to which the processor is coupled.

[0062] This application also provides a microgrid for implementing the method shown in the foregoing embodiments.

[0063] This application also provides a computer-readable medium storing program code for execution by a device, the program code including methods for performing the methods shown in the foregoing embodiments.

[0064] This application provides a computer program product containing instructions that, when run on a computer, cause the computer to perform the methods shown in the foregoing embodiments.

[0065] The term "multiple" in this document refers to two or more. The character " / " generally indicates an "or" relationship between related objects; in formulas, " / " indicates a "division" relationship between related objects. Furthermore, it should be understood that in the description of this application, terms such as "first" and "second" are used only for descriptive purposes and should not be construed as indicating or implying relative importance or order.

[0066] It is understood that, in the embodiments of this application, the order of the above-mentioned process numbers does not imply the order of execution. The execution order of each process should be determined by its function and internal logic, and should not constitute any limitation on the implementation process of the embodiments of this application.

[0067] It should be emphasized that the above are merely preferred embodiments of the present invention and are not intended to limit the present invention in any way. Any simple modifications, equivalent changes and alterations made to the above embodiments based on the technical essence of the present invention shall still fall within the scope of the technical solution of the present invention.

Claims

1. A droop control method for a microgrid, characterized in that, The microgrid includes an energy storage system, the energy storage system includes multiple battery modules, and the method includes: Obtain the state of charge and temperature of each battery module; Determine whether the range of the state of charge of the battery modules in the energy storage system is less than a preset value; If so, the first working mode is adopted, and the droop coefficient of the first working mode is related to the temperature of the battery module; If not, the second working mode is adopted, and the droop coefficient of the second working mode is related to the temperature and state of charge of the battery module. The output power of the battery module is controlled based on the first operating mode or the second operating mode.

2. The sag control method according to claim 1, characterized in that, The droop coefficient of the first operating mode satisfies the following relationship with the temperature of the battery module: Among them, K r1 K0 is the droop coefficient for the first working mode, and T is the initial droop coefficient. i T is the temperature of the i-th battery module. avg The average temperature of the battery module in the energy storage system.

3. The sag control method according to claim 1, characterized in that, The droop coefficient of the second operating mode, the temperature of the battery module, and the state of charge of the battery module satisfy the following relationship: Among them, K r2 The droop coefficient for the second working mode is given by K0, the initial droop coefficient is given by m1, the first weighting coefficient is given by m2, and the second weighting coefficient is given by SOC. i For the i-th battery module, the State of Charge (SOC) avg T represents the average state of charge of the battery modules in the energy storage system. i T is the temperature of the i-th battery module. avg The average temperature of the battery module in the energy storage system.

4. The sag control method according to claim 3, characterized in that, The droop coefficient of the second operating mode is also related to the charge and discharge state of the battery module.

5. The sag control method according to claim 4, characterized in that, The droop coefficient of the second operating mode, the temperature of the battery module, the state of charge of the battery module, and the state of charge / discharge of the battery module satisfy the following relationship: Among them, I o The output current of the battery module is denoted as , and sign() is the sign function.

6. The sag control method according to claim 5, characterized in that, When the battery module is in a charging state, I o When the battery module is in a discharging state, I is positive. o It is negative.

7. The sag control method according to any one of claims 1 to 6, characterized in that, The preset value is 5%.

8. A droop control device for a microgrid, characterized in that, The microgrid includes an energy storage system, the energy storage system includes multiple battery modules, and the device includes a processing module; The processing module is used to obtain the state of charge and temperature of each battery module; The processing module is further configured to determine whether the range of the state of charge of the battery module in the energy storage system is less than a preset value; if so, a first working mode is adopted, wherein the droop coefficient of the first working mode is related to the temperature of the battery module; if not, a second working mode is adopted, wherein the droop coefficient of the second working mode is related to the temperature and state of charge of the battery module. The processing module is also used to control the output power of the battery module based on the first working mode or the second working mode.

9. A computer-readable medium, characterized in that, The computer-readable medium stores program code for computer execution, the program code including instructions for performing the method as described in any one of claims 1 to 7.

10. A computer program product, characterized in that, It includes computer program code that, when run on a computer, causes the computer to perform the method as described in any one of claims 1 to 7.

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