25MW급 대용량 멀티레벨 인버터의 시뮬레이션 기반 손실해석과 출력특성 비교 분석

The multi-level inverters are highly efficient for high-power and medium-voltage AC driving applications, such as high-speed railway systems and renewable energy resources, because such inverters generate lower total harmonic distortion (THD) and electromagnetic interface (EMI). Lower switching stress occurs on switching devices compared with conventional two-level inverters. Depending on the multi-level inverter topology, the required components and number of switching devices are different, influencing the overall efficiency. Comparative studies of multi-level inverters based on loss analysis and output characteristic are necessary to apply multi-level inverters in high-power AC conversion systems. This paper proposes a theoretical loss analysis method based on piecewise linearization of characteristic curves of power semiconductor devices as well as loss analysis and output performance comparison of five-level neutral-point clamped, flying capacitor inverters, and high-level cascaded H-bridge multi-level inverters.