Energy Storage Sub-Module Switching for SOC Balance
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Solution Overview
Problem
The energy storage system in VSC-HVDC systems faces challenges in maximizing utilization rate due to state of charge (SOC) imbalance among energy storage sub-modules, which affects the available capacity and reliability of the system.
Innovation Solution
A control method that acquires and controls the SOC and charge-discharge limiting current of each energy storage sub-module to determine their switched-on or switched-off states, ensuring SOC balance and optimizing the number of sub-modules participating in charging or discharging based on their SOC and charge-discharge limiting currents.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If energy storage sub-modules are connected in series to form ultra-high voltage for energy storage, then the energy storage capability is improved, but SOC imbalance among sub-modules occurs leading to reduced available capacity
Solution Approach 1:
The patent dynamically adjusts the working states (switched-on or switched-off) of individual energy storage sub-modules based on their SOC levels and charge-discharge limiting currents. By changing the operational parameters of each sub-module according to its specific state, the system maintains SOC balance while preserving overall energy storage capability.
Solution Approach 2:
The control method implements dynamic switching of sub-module states based on real-time SOC and current measurements. The system continuously adapts the configuration of working sub-modules to maintain optimal performance, transforming from a static series connection to a dynamically reconfigurable system that responds to varying operational conditions.
2Device complexity
If a fixed number of energy storage sub-modules are used for charging and discharging, then the system structure is simplified, but the utilization rate of the energy storage system decreases due to SOC imbalance
Solution Approach 1:
The patent divides the energy storage system into multiple independently controllable sub-modules, each with its own SOC and current characteristics. This segmentation allows selective activation of sub-modules based on their individual states, enabling flexible resource allocation that improves utilization rate while maintaining manageable system complexity through modular architecture.
Solution Approach 2:
The control strategy applies different operational requirements to different sub-modules based on their local characteristics (SOC level and charge-discharge limiting current). Each sub-module is evaluated and controlled according to its specific state rather than applying a uniform control approach, which optimizes the utilization rate while keeping the overall control logic relatively simple.
3Quantity of substance
If all energy storage sub-modules operate simultaneously, then the available capacity is maximized, but SOC imbalance causes the system to lose available capacity
Solution Approach 1:
The patent implements a feedback control mechanism that continuously monitors the SOC and charge-discharge limiting current of each sub-module. Based on this feedback information, the system dynamically adjusts which sub-modules are switched on or off, creating a closed-loop control system that maintains SOC balance while maximizing the utilization of available capacity.
Data Source
AI summary
Provided are a control method for an energy storage system and the energy storage system. The energy storage system includes N energy storage sub-modules, where N is a positive integer greater than 1. The control method for the energy storage system includes: acquiring an SOC and a charge-discharge limiting current of each of the N energy storage sub-modules; and controlling working states of the N energy storage sub-modules according to the SOC and the charge-discharge limiting current of each of the energy storage sub-modules, where the working states include a switched-on state and a switched-off state. According to the technical solution provided by embodiments of this application, the problem of SOC imbalance among the energy storage sub-modules can be solved, so that the utilization rate of the energy storage system is improved.