Control strategy for fluctuating voltage generation in cascaded H bridge converters

This paper presents a novel fluctuating rms value feedback control (FRFC) for the cascaded H-bridge (CHB) converter, which uses the output voltage sliding window rms value as the feedback variable and the fluctuating signal sliding window rms value as the reference for voltage control. The proposed strategy can easily set the controller parameter, has high accuracy in the output voltage fluctuation and frequency, and is suitable for high voltage and power applications in real industry. Modeling and analysis of the FRFC is elaborated in this paper. A parameter design method is proposed as well. Finally, the field experimental results on the 35 kV- 6 MW wind turbine testing prototype sufficiently verify the feasibility and effectiveness of the proposed FRFC. According to the experimental results, the relative error of the fluctuating output voltage is less than 2% by utilizing the proposed FRFC.