CN-122001046-A - SOC rapid equalization power distribution method applied to multi-energy-storage module cascade energy storage system

Abstract

The invention discloses a power distribution method applied to SOC rapid equalization of a multi-energy storage module cascade energy storage system, which is characterized in that the minimum voltage V min and the maximum voltage V max of the output voltage of a submodule are determined according to the duty ratio range D min ~D max of a switching tube of a converter in an energy storage submodule, the rated voltage V SMN of the converter and the load power P L , the range of the output voltage is finally determined, the weight factor omega i of each submodule is calculated according to the SOC of a battery pack in each energy storage submodule, the output voltage u SMiref of each submodule is further calculated, the voltage out-of-limit judgment is carried out on u SMiref , whether each u SMiref exceeds the output voltage range is determined, if so, the omega i of the corresponding submodule is regulated, and u SMiref of each submodule is recalculated until all u SMiref output voltage instructions are output after the output voltage range, and under the condition of stabilizing the DC bus voltage, the SOC equalization of the multi-energy storage module cascade system can be realized, and the SOC equalization speed is accelerated.

Inventors

• ZHANG XIAOTONG
• ZHAO YUANZHE
• ZHAO HANQING
• Gao Guangle
• TONG XIANGQIAN
• MA WENTAO
• DING TAO

Assignees

• 西安理工大学

Dates

Publication Date

20260508

Application Date

20260211

Claims (9)

1. 1. The power distribution method for SOC rapid equalization applied to the multi-energy storage module cascade energy storage system is characterized by comprising the following steps: Firstly, determining a rated voltage V bN of a battery pack in an energy storage sub-module, a discharge cut-off voltage V bmin of the battery pack, a full charge voltage V bmax of the battery pack, a switching tube duty ratio range D min ~D max of an inverter, a rated voltage V SMN of the inverter, a system load power P L , an SOC i of an ith battery pack and a rated power P SMN of the energy storage module, and calculating an SOC ave of an SOC average value of each battery pack and a maximum difference value delta SOC max of each battery pack according to the SOC i of the battery pack; According to the rated voltage V bN of the battery pack in the energy storage submodule, the discharge cut-off voltage V bmin of the battery pack, the full charge voltage V bmax of the battery pack, the duty ratio range D min ~D max of a switching tube of the converter, the rated voltage V SMN of the converter and the system load power P L , the minimum voltage V min and the maximum voltage V max of the output voltage of the submodule are determined, and finally the range V min ~V max of the output voltage is determined; Calculating each sub-module weight factor omega i according to the SOC i of the ith battery pack, the SOC ave of the average value of the battery packs and the maximum difference value delta SOC max of the battery packs; Calculating the output voltage u SMiref of each sub-module; when the obtained output voltage u SMiref of the ith sub-module exceeds the maximum voltage V max of the output voltage, the omega i of the sub-module is correspondingly reduced, and when the obtained output voltage u SMiref of the ith sub-module is lower than the minimum voltage V min of the output voltage, the omega i of the sub-module is correspondingly increased, the calculation is readjusted until the output voltages u SMiref of all the sub-modules are within the range of the output voltage, and then a u SMiref instruction is sent to a module level control loop; When the module level control loop obtains a u SMiref instruction, the module level control loop controls the DC-DC converter in the energy storage module to output a given output voltage u SMiref , and the sum of the output voltages of all the submodules is the voltage of the direct current bus.
2. 2. The power distribution method for SOC rapid equalization applied to a multi-energy storage module cascade energy storage system of claim 1, wherein SOC ave of each battery pack SOC average value and each battery pack SOC maximum difference value Δsoc max : ; ; the SOC i is the SOC of the ith battery pack, the SOC max and the SOC min are the maximum SOC value and the minimum SOC value in each battery pack, and n is the number of energy storage modules.
3. 3. The power distribution method for SOC rapid equalization applied to a multi-energy storage module cascade energy storage system of claim 1, wherein the minimum voltage V min and the maximum voltage V max of the sub-module output voltage are specifically: Where V Dmax and V Dmin are maximum and minimum voltages considering only the sub-module switching tube duty cycle and the rated output voltage, and V Pmax and V Pmin are maximum and minimum voltages considering only the rated output power limit.
4. 4. The power distribution method applied to SOC rapid equalization of a multi-energy storage module cascade energy storage system of claim 3, wherein considering only the maximum voltage V Dmax and the minimum voltage V Dmin when the sub-module switching tube duty cycle and the rated output voltage are: Wherein, D max and D min are the maximum value and the minimum value of the duty ratio of the switching tube of the submodule respectively, V SMN is the rated output voltage of the submodule, V bN is the rated output voltage of the battery pack, V bmin is the discharge cut-off voltage of the battery pack, and V bmax is the full charge voltage of the battery pack.
5. 5. The power distribution method for SOC rapid equalization applied to a multi-energy storage module cascade energy storage system of claim 3, wherein the maximum voltage V Pmax and minimum voltage V Pmin considering only rated output power limit are specifically: Wherein P SMN is the rated output power of the submodule, P L is the load power of the energy storage system, u dcref is the direct current bus voltage of the energy storage system, and n is the number of the energy storage modules.
6. 6. The power distribution method applied to SOC rapid equalization of a multi-energy storage module cascade energy storage system of claim 1, wherein each sub-module weight factor ω i is specifically: ; Wherein a is ln (V Dmax /V Dmin ), β is 0.001, SOC ave is the average value of the battery packs, delta SOC max is the maximum difference value of the battery packs, sgn (i dc ) is the charge and discharge state coefficient of the energy storage system, i dc is the output current of the energy storage system when the energy storage system is discharged, sgn (i dc ) is 1, and sgn (i dc ) is-1 when the energy storage system is charged.
7. 7. The power distribution method applied to SOC rapid equalization of a multi-energy storage module cascade energy storage system according to claim 1, wherein the output voltage u SMiref of each sub-module is specifically: ; wherein u dcref is the voltage of the direct current bus of the energy storage system, and n is the number of energy storage modules.
8. 8. The method for rapidly equalizing the power distribution of the SOC of the cascade energy storage system with multiple energy storage modules according to claim 1, wherein in step S5, when the output voltage u SMiref of the ith sub-module obtained in step S4 is greater than the maximum voltage V max of the output voltages of the sub-modules, the weight factor ω i of the ith sub-module is reduced, the calculation is returned to step S4, and when the output voltage u SMiref of the ith sub-module obtained in step S4 is less than the minimum voltage V min of the output voltages of the sub-modules, the weight factor ω i of the ith sub-module is increased, and the calculation is returned to step S4.
9. 9. The power distribution method for SOC rapid equalization applied to a multi-energy storage module cascade energy storage system of claim 1, wherein the sum of all sub-modules is a dc bus voltage specifically: ; wherein u dcref is the voltage of the direct current bus of the energy storage system, and n is the number of energy storage modules.

Description

SOC rapid equalization power distribution method applied to multi-energy-storage module cascade energy storage system Technical Field The invention belongs to the technical field of energy storage system control, and particularly relates to a power distribution method for SOC rapid equalization of a multi-energy storage module cascade energy storage system. Background With the increase of the share of renewable energy sources in the power system, the randomness and intermittence of renewable energy sources such as wind power generation, photovoltaic power generation and the like can cause the problems of electric energy fluctuation and electric energy quality reduction in the power system. The acceptance of renewable energy sources through micro-grids and the incorporation of battery energy storage systems for them are considered as important ways to meet the requirements of high quality and reliable supply of electrical energy. The battery energy storage system can be used for stabilizing intermittent electric energy fluctuation and improving electric energy quality and power supply reliability of the micro-grid. Therefore, the wide application of the battery energy storage system can improve the permeability of renewable energy sources in an electric power system. Compared with an alternating-current micro-grid, the direct-current micro-grid has no problems of frequency, phase and the like, and has low control complexity, so that people are interested in the energy storage system in the direct-current micro-grid. In the dc micro-grid, if the energy storage system does not control the State of Charge (SOC), the SOC of the battery packs will have a significant difference, and frequent load changes will further enlarge the SOC difference between the battery packs. The large SOC difference may cause overcharging or overdischarging of the single or multiple battery packs, which in turn may lead to reduced capacity utilization of the energy storage system and battery life. Therefore, the realization of the SOC balance of the energy storage system through the reasonable distribution of the power among the battery packs becomes one of the main targets of the control strategy of the energy storage system. In order to achieve higher voltages and power for energy storage systems, battery packs have been connected directly in series-parallel to a power conversion system. However, in the energy storage system with the structure of the series-parallel battery packs, SOC balance is difficult to realize among the battery packs, and the capacity utilization rate of the energy storage system is finally reduced. The modularized cascading DC-DC energy storage system has the advantages of easiness in configuration, capacity expansion in installation, unified design of module parameters, high reliability and the like in a bidirectional power supply system in a modularized mode. On the basis, the modularized cascading structure is beneficial to reducing the voltage stress of devices in the submodules, and the submodules can be independently controlled to realize SOC balance among the battery packs while meeting the load power. Therefore, in the direct current micro-grid, the modular cascade DC-DC energy storage system is selected to be matched with the SOC balance control strategy, so that the aim of improving the capacity utilization rate and the load capacity of the high-voltage and high-power energy storage system can be better achieved. The traditional droop control strategy or the SOC balance control strategy added with the self-adaptive coefficient is widely applied to the SOC balance of the multi-energy storage module of the modularized cascading DC-DC energy storage system. However, these methods have problems of low SOC equalization speed and unaccounted for the output voltage range of the sub-module, and thus the time required for SOC equalization of the entire energy storage system is prolonged, and even the capacity utilization of the energy storage system is reduced. Therefore, it is necessary to develop a charge-discharge power optimal distribution method for rapidly realizing SOC equalization for a modular cascading DC-DC energy storage system. Disclosure of Invention Based on the above, it is necessary to provide a power distribution method for SOC rapid equalization applied to a cascade energy storage system of multiple energy storage modules, that is, a SOC equalization control strategy based on weight factor optimization, to reasonably distribute output voltages according to an output voltage range and weight factors of the energy storage modules in the energy storage system, so as to solve the technical problem of long equalization time of the SOC equalization control strategy added with adaptive coefficients, and improve the speed of SOC equalization in the multiple energy storage modules. . The invention adopts the following technical scheme: the SOC rapid equalization power distribution method applied to