Grid-Connected SRG Interfaced With Bidirectional DC-DC Converter in WECS

Abstract

This paper presents an interfaced wind energy conversion system (WECS) using the switched reluctance generator (SRG). A bidirectional DC-DC converter is adopted as an interface stage to achieve optimal excitation voltage at the SRG side, while a voltage source converter regulates the DC-bus voltage. The SRG works with superior performance, which is characterized by a compromise between efficiency and torque ripple, using the optimal excitation parameters. In addition, the interface stage adds a filtering behavior, mitigating the voltage ripple produced by the SRG, thus improving the power quality reflected in the grid current. A comparison of optimized SRG systems, with direct connection and with interfaced connection, is conducted. Experimental results show that the interface converter improves the performance of the SRG in WECS. Although the extra converter efficiency is approximately 88%, the overall system efficiency is only reduced by up to 2.5% due to the SRG optimal parameters. Nonetheless, as advantages of the method, the torque oscillations are reduced by up to 9.5% in high speeds. Moreover, due to the converter filtering behavior, the grid current harmonic content is reduced by up to 6% in the comparison. Therefore, this research indicates that the proposed approach is a viable option for SRG in WECS, especially for scenarios where the DC-DC converter is already necessary, such as in a microgrid application.