Study on a novel control strategy of three-phase inverter under unbalanced load

This paper proposes a control strategy which is combined with a novel decoupling control and negative sequence correction strategies. Firstly, based on superimpose theory, the coupled relationship between three-phase output voltage and three-phase sinusoidal pulse width modulation (SPWM)control wave is deduced. Secondly, according to symmetrical component decomposing theorem, mathematical expressions of positive and negative sequence components under the dq coordinate are presented. Amplitude and phase of negative sequence component delegate degree of unbalanced situation. Detailed design method about proposed controller is discussed. Via Matlab/Simulink softwave tool, simulation works were implemented to testify its effectiveness. Simulation results show that the proposed scheme can suppress unbalance degree under about 0.2% when inverter operated under serious unbalanced load. Compared with other current methods, the performance of proposed method in this paper is much better.