Improved Vsg Control Strategy Based on the Combined Power Generation System with Hydrogen Fuel Cells and Super Capacitors

Abstract

Hydrogen fuel cells (HFCs) occupy a dominant position in the development of renewable energy due to their environmental protection and high power generation efficiency. The control technology of their connection to the microgrid has become a research hotspot. However, the lack of power cannot be compensated immediately by HFCs when they encounter peak demand or transient events. In order to overcome this shortcoming, supercapacitors (SCs) are introduced as auxiliary power sources. The virtual synchronous generator (VSG) control strategy based on this combined power generation system is proposed to introduce virtual inertia to alleviate the impact of load disturbance on the microgrid in this paper. Through the small signal model, the influence of the control strategy parameters of VSG based on the HFCs and SCs combined power generation system on the system stability is studied. In addition, the parameters of the combined system are designed. In the VSG controller, the voltage and current double closed-loop is improved to suppress the negative sequence component in the output voltage under unbalanced conditions, thereby reducing the unbalance of the output voltage. Finally, simulation results in MATLAB/Simulink environment verify that dynamic changes of the load can be quickly tracked by the proposed control strategy and sufficient power is provided. Compared with the droop control, the rate of the change of frequency and voltage is greatly reduced. This could be explained by the virtual inertia of frequency and voltage responses. At the same time, the three-phase voltage of the microgrid under the improved VSG control strategy in different operating conditions can maintain balanced outputs. Compared with the traditional VSG control, it has better dynamic characteristics of the output voltage and higher steady-state accuracy.