Voltage and current hybrid controlled PWM inverters using variable structure control

In this paper, the voltage and current hybrid PWM inverters using the variable structure control technique is proposed for parallel operation. The voltage-controlled PWM inverter (VCPI) unit is developed to provide a specific sinusoidal output voltage and the current-controlled PWM inverter (CCPI) units are employed to track the distributive current. Each of the VCPI and CCPI units can be operated independently. By using the variable structure control scheme, the parallel inverters can provide excellent performance without the phase-lock-loop (PLL) circuit for synchronization. The proposed scheme can result in fast dynamic response and robustness to parameter variations. Finally, simulation results are performed to verify the proposed control scheme.