Hybrid Phase Opposite Disposition PWM With Improved Output Quality and Reduced Common-Mode Voltage for Coupled Ten-Switch Three-Phase Three-Level Inverter

Abstract

Due to the cost-effectiveness and high power density, the coupled ten-switch three-phase three-level inverter (TP-TLI) has been an attractive candidate in industry. However, it has high common-mode voltage (CMV) and low output quality when using the phase disposition pulsewidth modulation (PDPWM) for the coupled ten-switch TP-TLI. To address these issues, this article proposes a hybrid phase opposite disposition PWM (HPODPWM) based on hybrid-level modulation (HLM). First, the characteristics of PODPWM in traditional TP-TLIs are analyzed. A case that does not generate the undesired switching states, which cannot be generated by the ten-switch TP-TLI, is explored. This helps to improve the output quality. Second, the HLM concept, which generates positive, zero, and negative levels within one switching cycle, is proposed based on modulation wave decomposition. In the HPODPWM, the middle phase utilizes HLM, and the other phases adopt three-level modulation (3LM). The CMV of HPODPWM is naturally reduced by 33.3% compared with PDPWM for the ten-switch TP-TLI. Third, a neutral-point voltage (NPV) control method based on zero-sequence voltage (ZSV) injection is also proposed. It could balance the NPV under different modulation indexes and power factors (PFs) since the NP current is considered. Experimental results are carried out to validate the effectiveness of the proposed HPODPWM.