A single wind turbine can no longer meet the increasing installed capacity and reliability requirements. Therefore, the power level and stability requirements of the wind power generation system can be improved through the parallel connection of three-level back-to-back converters. However, the zero-sequence circulating current (ZSCC) will distort the three-phase current, increase the power loss and reduce the system efficiency. Therefore, this paper establishes the ZSCC equivalent model of the back-to-back parallel converter, and analyzes the generation principle of the zero-sequence circulating current. In order to reduce the switching loss of the system and increase the system efficiency, a novel DPWM modulation strategy is proposed. At the same time, in order to control the zero-sequence circulating current of the parallel system, a hybrid switching modulation strategy using DPWM1 and DPWM3 based on hysteresis control is proposed. The simulation and experimental results verify the effectiveness of the zero-sequence circulation suppression strategy for the parallel system.
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