Research on Control Strategy of an Isolated Two-Stage Battery Storage Converter

With the fossil fuels depletion, renewable energy resources have become an alternative choice in many different areas. However, it has many limitations for its volatility and instability. The integration of energy storage system can be a promising solution to overcome these limitations. In many energy storage systems, battery storage systems are widely used due to its high specific energy, less cost, easy installment and slow self-discharge rate. However, the extension of battery's lifespan and security problems do not be considered in many cases. In this paper, an isolated two-stage battery storage converter is presented, which is designed using Dual active bridge (DAB) converter with a high-frequency transformer and a neutral point clamped (NPC) three-level inverter. What's more, a seamless transfer by controller's desaturating from constant-current charging mode to constant-voltage charging mode is realized and a constant-current discharging control strategy is also presented in this article. In the end, the effectiveness and validation of the control strategy are verified by simulation and experiment. In this way, the safety of battery storage converter can be guaranteed and lifespan of battery is improved which is of great significance in the applications.