Research On Control Technology Of Double-Mode Inverter With Grid-Connected Mode And Stand-Alone Mode

The control technology of grid-connected inverter, as the key technology inrenewable energy generation system, have attracted more and more attentions. ThePWM inverter which has grid-connected/stand-alone function can realize interactiveutility with grid;maintain a continuous, uninterrupted, flexible AC power supply.The characteristics of grid-connected inverter, and classic control methods wereresearched and compared in this paper. According to the bi-level hysteresistechnology and double-frequency PWM technology, a novel tri-level hysteresistechnology with double-frequency function were designed. Based on the analysis ofoperation principle of tri-level hysteresis technology and the comparison betweenbi-level and tri-level hysteresis in different aspects, the relation between frequencyand hysteresis band was induced. The corresponding PSPICE simulation model and 1kVA prototype were designed;related simulations and experiments were done. Theresults illustrated that the grid-connected inverter with tri-level double-frequencyhysteresis controller had the advantages of faster dynamical responsibility, lowercurrent ripple and higher efficiency than that with bi-level hysteresis controller.The essential condition and rules of transition between grid-connected andstand-alone were analyzed;a corresponding transition strategy was designed. So theinverter can only be operated in grid-connected mode or stand-alone mode, but alsotransition seamlessly between two modes. So the inverter-grid interactive system canbe utilized, the reliability of power supply was strengthened.Finally, the simulation and experiment results were analyzed in detail. Andseveral assumptions and schemes were given in this paper.