科研之友
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摘要
Parallel three-level inverters are widely used in highpower applications for increasing the power capacity of the system. However, when multiple three-level T-type inverters are connected to a single dc bus, the zero sequence circulating current (ZSCC) will be generated. For the operation of paralleled inverters, another requirement is to reduce the common mode voltage (CMV) associated with pulsewidth modulation (PWM) method. As these two issues are mutually coupled, the conventional space vector modulation (SVM) and active control methods reported so far cannot address them properly simultaneously. To overcome this limitation, a modified SVM technique is proposed to reduce the CMV, suppress ZSCC, and balance neutral point (NP) voltage. The generating mechanism of the ZSCC with respect to modulation scheme is analyzed. Based on the analysis, the large, medium, small, zero vector modulation method is proposed for reducing ZSCC and balancing the NP voltage with reduced CMV as the same in large, medium, zero vector modulation. Furthermore, the effectiveness of the proposed method is verified by comparing its results with those of the convectional PWM. The results are obtained from simulation and experiments.
