A Novel DC-Link Voltage Control for Small-Scale Grid-Connected Wind Energy Conversion System

This paper proposed a novel DC-link voltage control method for small-scale grid-connected three-phase power converters in variable-speed wind energy conversion systems to minimize the fluctuation in the DC-link voltage caused by wind power variations. In a typical three-phase PWM converter, DC-link capacitors are normally used as an energy buffer to balance the power difference between the input and output, but the voltage across the capacitors varies significantly under rapidly changing working conditions. Hence, a proper DC-link voltage control is essential to perform fast DC-link voltage regulation to minimize these fluctuations. The proposed DC-link voltage control method estimates the input power of the converter using a state observer and integrates with a conventional PI controller, combining the advantages of the robustness of a PI controller and the fast-transient response and disturbance rejection capability offered by the observer-based feed-forward compensation but without additional measurement components. The comparison between the proposed control algorithm and a conventional PI controller is presented in both simulations and experiments in this paper to verify the effectiveness and the advantages of the proposed observer-based DC-link control algorithm.