Novel Nonlinear DC-Link Voltage Control for Small-Scale Grid-Connected Wind Power Converters

A novel nonlinear observer-based DC-link voltage control algorithm is proposed in this paper for small-scale grid-connected variable-speed wind power converters to minimize the voltage fluctuation across DC-link capacitors caused by wind power variations. The DC-link capacitors, in wind power converters, are normally used to buffer the difference between the input and output power. However, the DC-link voltage varies significantly under rapidly changing working conditions. Hence, a proper DC-link voltage controller is essential to regulate the DC-link voltage in order to minimize these fluctuations. The proposed algorithm estimates the power fed into the converter system using a nonlinear observer integrated with a PI controller, combining the advantages of fast dynamic response capability offered by the proposed observer and control robustness from the PI controller without any additional measurement components. The effectiveness of the proposed control algorithm is verified by both simulation and experimental results.