Hybrid Space Vector Modulation Scheme to Reduce Common-Mode Voltage Magnitude and Frequency in Three-Level Quasi-Z-Source Inverter

Abstract

The three-level quasi-Z-source inverter (TLQZSI) is an attractive topology that is suitable for voltage buck and boost operation. This article further presents a hybrid space vector modulation (HSVM) scheme to reduce the common-mode voltage (CMV) magnitude and frequency simultaneously. At first, the selection of basic vectors is optimized. Six medium vectors, six small vectors that have low CMV magnitudes, one zero vector, and three shoot-through vectors are utilized to produce the ac output voltage. The shoot-through state is properly inserted within the zero vector without affecting the normal ac output voltage. The effective small vector is selected according to the neutral-point voltage (NPV). Duty cycles of the adopted vectors are updated accordingly, and the restriction of the duty cycle of effective small vector is also derived. When comparing with the conventional SVM method, the CMV magnitude for the proposed scheme is suppressed by half. Furthermore, the CMV frequency is reduced by comparison to the conventional CMV reduction method. The feasibility of the proposed scheme has been tested by using the Simulink platform and a hardware-based test rig.