A Common-Mode Voltage Elimination Approach Based on Modulation Signal Decomposition for the Three-Level Back-to-Back Converter

Three-level back-to-back neutral-point clamped (3L-BTB-NPC) converters find extensive application in four-quadrant AC-DC-AC frequency conversion occasions. However, the issue of common-mode voltage (CMV) in such converters poses challenges to the system's safety and stability. To address this problem, this paper proposes a CMV elimination approach based on decomposing the modulation signal. The method involves the division of each original reference modulation signals into two virtual reference signals. Subsequently, the real PWM signals for each phase are derived by calculating the difference between two virtual output voltages, which are generated through comparison of the virtual reference signals with a triangular carrier. Then, the CMV is eliminated to zero using this modulation method. Experimental validations are conducted to confirm the efficacy of the proposed CMV elimination approach.