Output ripple performance evaluation and comparison of 2L-VSI and 3L-VSI considering the spectral characteristics

In this paper, two-level and three-level voltage source inverters (2/3L-VSIs) with popular pulse width modulation (PWM) methods are investigated in terms of their output (ac-side) voltage and current ripple spectral characteristics and waveform quality properties such as peak-to-peak ripple, rms ripple, and weighted total harmonic distortion. As the switching frequency and the filter size influence the output waveform quality, the inverter efficiency (loss) constraint on the switching frequency, and the size constraint on the filter are also taken into consideration. The waveform quality properties and power converter losses are characterized in normalized form for all possible VSI topology and PWM method pairs and the utilization of characterization results are illustrated through 20 kVA and 100kVA grid connected photovoltaic inverter application examples. The performance results are evaluated and comparisons provided. The performance advantage of advanced topologies and PWM methods and their matched pairs is shown. The study aids understanding the 2/3L-VSI output waveform quality attributes and establishes analytical and algorithmic design guidelines for inverter design.