태양광 시스템에서 불연속 전압 변조 방법 적용에 따른 단상 5-레벨 T-type NPC 인버터의 전력 반도체 소자의 전력손실 및 열 부하 분석

The pulse width modulation method has a significant effect on the power losses and thermal loadings of power devices of a single-phase five-level T-type NPC photovoltaic (PV) inverter. In this paper, the comparative analysis of the power losses and thermal loadings of a single-phase five-level T-type NPC inverter is performed under the different pulse width modulation methods. When the unipolar pulse width modulation method is applied, the power losses and thermal loadings of the power devices are evaluated, and the reliable critical power devices with the highest thermal loadings are identified. Subsequently, the power losses and thermal loadings of the power devices are analyzed by applying the discontinuous pulse width modulation methods such as one-pole clamping pulse width modulation method and equally distributed discontinuous pulse width modulation method. Their effects on the reliability of the inverter are evaluated. Additionally, the operation of a T-type NPC inverter with three PWM methods is verified through the experiment.