SOC Balancing Control Based on Multi-Agent for Multiple Energy Storage Units in MMC High Power Energy Storage System

Since high power energy transmission is required for a grid-level energy storage system, a high-power energy storage system based on modular multilevel converter (MMC) is very promising at present. However, in order to produce desired high power, an MMC-based energy storage system needs to be constructed by cascading a large number of energy storage units, which will make it difficult to balance state of charge (SOC) of these units. To solve SOC unbalancing of these units, special modeling and control methods are employed and an SOC balancing controller is designed. First, a high-power energy storage system is modeled as a multi-agent model. Then, an event-trigger control method is used to control information transmission and operation period of the energy storage agent, which further reduces the amount of communication and computation. Moreover, observers are designed to estimate battery current, which can reduce in half the amount of status information that needs to be collected. Finally, the simulation platform of the MMC-based storage system is established with MATLAB, the proposed SOC balancing control method is simulated and its validity is verified.