Single-phase grid-connected inverters with simplified SPWM control

Abstract

The conventional grid-connected inverters require a sophisticated digital signal processor to generate the demanded reference signal as a feedforward signal for the sinusoidal pulse width modulation (SPWM) control. However, the reference signal needs to be re-calculated to maintain the demanded power control as the ac mains varies. It increases the computation burden of the controller and has become a major obstacle of the grid connected energy storage system with demanded power flow control. Therefore, a simplified approach to reduce the computation burden of the controller is proposed in this paper. With the proposed simplified equation for the power flow control, the usage of a low cost microcontroller unit becomes possible. In additional, no additional sensors or circuitries are needed. Meanwhile, the performance of desired power flow control by using the simplified control is almost unaffected. The proposed simplified algorithm is validated via mathematical calculations, computer simulation and experimental results. By using the proposed simplified control, 52.3% of the computational clock cycles can be reduced. Different operation scenarios were tested to validate the performance of the proposed simplified control via the MATLAB/Simulink simulations and the 1kVA prototype experiments.