Research On Serial-Parallel Combined Inverter And Grid-tied Control Strategy Based On DSP Control

The developments of new, renewable energy and distributed generation system have been attracted more and more attentions because of the lack of energy, pollution and shortage of concentrative power generation. The inverter is an important part of distributed generation system. But the grid voltage is different in many countries, so the research of an inverter, which can be used in many countries, will become a trend. A grid-connected inverter in grid-tied and off-grid modes has many advantages such as peak shaving to reduce the overall cost of power by generating during peak load hours in grid-tied mode, and standby generation to provide power during system outages until service can be restored in off-grid mode. The researches on the grid-connected inverter are a hot spot now.A serial and parallel combined inverter based on digital signal processing (DSP) control is proposed. The proposed inverter can output many countries'grid voltage. The operation principle, stability and current ripple of the output filter inductor between serial and parallel modes are analyzed. A 1000 VA serial and parallel combined dual buck half-bridge inverter (DBHBI) has been implemented to verify the analysis.In order to eliminate the influence of the output filter capacitor current on the grid current, a novel control strategy for the grid-connected inverter in grid-tied and off-grid modes is proposed. The control strategy can also realize seamless transfer between grid-tied and off-gird modes. The grid-connected inverter can supply power to the critical load when the grid is off. A 500 W grid-connected DBHBI is designed based on DSP control to verify the analysis.Software and hardware of the DSP are also analyzed and designed.