Nonlinear control of standalone inverter with unbalanced, nonlinear load

In this paper, a nonlinear backstepping controller is proposed for the control of a 3-phase 3-level diode clamped inverter with an output LC filter under different loads including balanced, unbalanced, linear and nonlinear loads. Also, the seamless transition of the inverter from standalone to grid-tie is investigated while the inverter is under the control of the proposed scheme. Lyapunov stability analysis and simulation results validate the effectiveness of the proposed control solution in terms of tracking objective and in meeting the Total Harmonic Distortion (THD) requirements of IEEE 519 and EN 50160 standards for US and European power systems, respectively.