State-Space-Based Three-Phase Inverter Modeling under Nonlinear Load

Harmonic current distortion happens due to the three-phase inverter with a nonlinear load. Accurate mathematical modeling of the three-phase inverter is challenging. This paper proposes an approach based on the state-space average to build a three-phase inverter model with a nonlinear load. Firstly, the small-signal state equation of three-phase inverter under linear load is established via coordinate transformation and state-space average, and its average variable is separated from the perturbation. Secondly, the state-space average model of three-phase inverter under nonlinear load is obtained by linearization approximation and Laplace transformation. Thirdly, the state-space model of the system is simulated using MATLAB software under both linear and nonlinear load conditions. The simulation results are accurate, the steady-state error is small, and the simulation time is short. Finally, the experimental platform of three-phase inverter system is set up to further verify the feasibility and effectiveness of the proposed method.