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A Compound Repetitive Control Strategy of H14 Three-level Inverter for Bearing Current Suppression in Wind Power System

In this paper, H14 three-level inverter is proposed to reduce the bearing current in doubly-fed induction wind generator system (DFIG). The topology of H14 three-level inverter is presented and analysed under different switching patterns, and the corresponding CMV under each operation states is investigated. The control method of H14 inverter is presented by following a feasible minimal CMV output within the switching patterns. Furthermore, the compound controller is designed for the control system of the generator-side converter, which consists of the traditional PI control and the repetitive control. The repetitive controller based on the bandwidth coefficient (BRC) is used in the inner loop control and the traditional PI controller is used in the outer loop control. Through the stability analysis, the compensation term of BRC is determined. The simulation results fully verify that under the compound control, the H14 topology can effectively suppress the bearing current of the DFIG, and the harmonic characteristics of the DFIG maintains well.