Research On The Photovoltaic Grid-connected Power Generation System Based On The PSM Cascaded Inverter

With the world's energy sources drying up day by day, the development and application of the reproducible energy sources get much world attention. Solar energy became the focus of human development and utilization new energy sources for its renewable and pollution-free. Now, solar energy is tending towards substitute sources from complementary sources, so photovoltaic grid-connected power generation system is the inevitable trend of using solar energy. As its hard core, inverter more and more arrests academe's and industry's attention. At present, voltage scale of solar cell isn't high enough, so it must add some middle taches such as transformer and DC/DC convertor etc in the PV grid-connected system. It makes the system's structure complicated and its reliability lower. Cascaded inverter can directly connect PV cell and high grid-connected. The structure of system was simplified and its reliability was heightened. However, now the structure of Cascaded inverter is complex and its modulation method is inconvenience.The pulse step modulation (PSM) technology is the combination of the pulse width modulation (PWM) and the step modulation (SM). It is an important technology which is used high-voltage, high-power switching power supply system. If the PSM technology can be used in cascaded inverter, the above problem will be resolved.This paper's main tasks are operating the PSM technology to cascaded inverter and making the PSM cascaded inverter applied to PV grid-connected system. The main works as follows: Firstly, the principle and the control method of the PSM cascaded inverter are expatiated and analyzed. Secondly, the control policy of the PV grid-connected system based on PSM cascaded inverter is researched and the simulation circuit of the system is designed under MATALEB/SIMULINK circumstance. At last, the advantages of the PSM cascaded inverter and the new system is verified on the result of simulation.