Research on DC Component Disturbance Suppression Strategy of Islanded T-Type Three-Level Inverter Based on Improved Backstepping Control Theory

Aiming at the problem that the DC component in the output voltage of the T-type three-level inverter in the island mode is obvious, due to its hardware differences, a nonlinear control strategy combining the backstepping method, sliding mode theory, and the principle of the second-order generalized integrator (SOGI) is proposed. Firstly, the DC component in the output voltage of the inverter is regarded as a disturbance, and the mathematical model of the inverter with DC component disturbance is established. Secondly, the detected neutral point potential deviation of the DC side of the inverter is compensated to the modulation signal by proportional-integral (PI) control, to maintain the normal operating state of the three-level inverter. Then, the backstepping-sliding mode controller is constructed to improve the robustness T-type three-level inverter. And the SOGI is utilized to overcome the shortcomings of backstepping control which is easy to amplify the measurement noise and cause differential explosion. Meanwhile, the stability of the designed controller is analyzed by using the Lyapunov stability principle. Finally, the effectiveness of the proposed control strategy is verified by 10 kW prototype. The experimental results show that the proposed control strategy can not only effectively suppress the DC component of the inverter output voltage and improve the robustness of the system, but also has fast dynamic characteristics.