Quaternion Control of Four-Leg Inverter for Distribution System with Harmonic-Producing Load

Nowadays, three-phase four-wire power distribution systems with pulse width modulation electronic converters and multiple generating sources are operating under conditions of load unbalance and voltage waveform distortions. In this context, the main challenge for these applications is to provide balanced sinusoidal voltages for arbitrary single-/three-phase loads. The paper presents a new concept for instantaneous compensation of the distorting effects that occur due to load disturbances. The proposed control strategy a four-leg full-bridge inverter is based on a separation of three-phase voltages into balanced sinusoidal and unbalanced multi-harmonic components in the quaternion domain. The simulation results have demonstrated the effectiveness, robustness and fast-response of the quaternion approach under unbalanced and distorted waveform conditions.