Three phase inverter of UPS control system for harmonic compensator and power factor correction using modified synchronous reference frame

This paper proposes modified synchronous reference frame (MSRF) to improve three phases Uninterruptible Power Supply (UPS) controller. The technique compensates harmonics and power factor correction of voltage distortions due to nonlinear load. The MSRF contains two stages. The first stage is utilization of synchronous reference frame dq with angular frequency and proportional integral (PI) controllers to ensure voltage and current regulation. In this stage, the voltage and current are decomposed into their symmetrical components, positive, negative and zero ones sequentially. The components are then transformed into dq that controlled by means of PI. The last one is converting PI controller output signal to manage the output inverter via a Sinusoidal Pulse Width Modulation (SPWM). Simulation results show the validity of the innovative control strategy.