Modulation of a trapezoidal signal: improving signal quality and reducing costs in power inverters

Abstract

Power inverters applied in industries have seen a growth in modulation techniques over recent years. The aim of modulation techniques is to improve the quality of the inverter output signal and to reduce inverter losses. To improve an output signal, the amplitude of the fundamental frequency should be increased and the harmonics should be reduced. If a modulation technique can achieve these two objectives, a much smaller output filter is required to reduce hardware cost and filter losses. In this study, a technique is proposed where the obtained modulated signal can be directly used without the need of filtering. The resulting frequency profile fulfils the EN50160 standard, which sets the limits for harmonic components to ensure the quality in public low-voltage and medium-voltage power supplies. In addition, the proposed scheme requires a low computational algorithm allowing the use of low-cost microprocessors or Digital Signal Processor (DSPs). The proposed algorithm is based on a simple vector seed, making it possible to obtain all the patterns of Pulse Width Modulation (PWM).