On control strategy of cascaded H-bridge multilevel converter with fluctuating output voltage

A large sum of papers published focus on the steady-state and transient performance of the sinusoidal voltage-source single-phase inverter. However, few papers have discussed about a particular circumstance that the RMS value of the inverter output voltage fluctuates with certain frequency and amplitude. This paper presents the application of this special-outputting cascaded H-bridge (CHB) multilevel converter, grid-connected wind turbine converter testing. By comparing with the control scheme presented in former papers, such as deadbeat, repetitive, sliding mode and multiloop control, a fluctuating RMS value feedback control strategy is proposed which is simple and effective. Furthermore, modeling and analysis of this particular RMS value feedback control is elaborated. The validity of this control strategy is verified experimentally in the 35 kV–6 mW wind turbine converter testing equipment. In addition, a brief introduction of this equipment is also given in this paper.