Deadbeat Control Strategy for Circulating Current Suppression in Multiparalleled Three-Level Inverters

This paper proposes a zero-sequence circulating current (ZSCC) control scheme for the multiparalleled three-level T-type inverters (3LT2Is). Based on the analysis with the proposed generalized model of multiparalleled 3LT2Is, it is seen that the ZSCC is influenced by the circuit parameters, duty cycles, and the circulating currents of the l th and first 3LT2I. To mitigate the circulating currents, a deadbeat control strategy for n-paralleled (n≥3) inverters is proposed, which is realized by adjusting the duty cycle of the small vectors in each PWM sampling period. Compared with the conventional PI control method, the ZSCC spike is mitigated with the proposed scheme, thus improving the quality of the output currents. Also, the reliability of the 3LT2Is system is improved because such a scheme only needs the information about the ZSCC and zero-sequence duty ratio in the l th and the first inverter. The proposed method can also be applied to the neutral-point-clamped converters. Simulation and experimental results verify the effectiveness of the theoretical analysis and the proposed method.