An AC and DC Inertia Enhancement Strategy for Bidirectional Grid-Connected Converter in DC Microgrid

The virtual synchronous generator (VSG) strategy has good application prospects as an effective measure to improve the grid inertia level. However, VSG strategy cannot stabilize DC voltage and may even affect the stability of DC voltage. To address this issue, this paper proposes an AC and DC inertia enhancement strategy for a bidirectional grid-connected converter (BGC) in a DC microgrid, which is simple and easy to implement, and highly similar to the traditional VSG strategy in terms of control structure. When the load fluctuates, the strategy can better improve DC voltage stability, slow down AC frequency variations, and adjust the active power of the BGC more smoothly. Firstly, the integration of the virtual inertia equations on both sides of the AC and DC is achieved without using the differentiator. Secondly, the proportional relationship between DC voltage and frequency is utilized to simplify the AC virtual inertia equation and improve the control dynamic response speed. Finally, simulation and experimental results validate the effectiveness of the proposed strategy.