A Novel Vdc Voltage Monitoring and Control Method for Three-Phase Grid-Connected Inverter

Space vector PWM (SVPWM) three-phase voltage source inverters (VSI) are an important interface between the grid and distributed generation systems. However, traditional SVPWM brings drawbacks to current controller, because it cannot deal with the grid voltage harmonic disturbance and nonlinearity of the system. PI controller, predictive algorithms and real-time sampling techniques have become basic methods to solve these problems. Most of these methods depend on the measure voltage and current accuracy. If DC voltage (Vdc) sensor, one of the most important sensors, sends out an incorrect signal, not only could the output current quality be below the requirements of some standards, but also the inverter can be damaged in some serious situations. In this paper, PI and predictive methods are simultaneously utilized to control a three- phase grid-connected inverter. PI controller is given a new function: monitoring and controlling Vdc. In this new control structure, the output current of the inverter has high quality, and more importantly, Vdc can be double checked to guarantee the inverter reliability and safety. If a Vdc sensor fails or cannot send out the accurate signal, the PI controller will become a Vdc protection controller to ensure the inverter normal operation.