The Reasearch For Three-phase System Frequence And Phase Track Based On DSP

The solar energy, because of cleanliness, high efficiency and continuable development, attracts more and more attention by many countries. Grid-connected photovoltaic (PV) system is the trend of photovoltaic system's development.This thesis mainly researches the PV grid-connected inverter, which is the most important device in Grid-connected PV system. It's function includes two sides: the first is that it makes the inverter work in Maximum power point state, the second is that it converts the DC generated by PV to AC ,it also makes it sure that the current which is the output of the Inverter is synchronous with grid voltage. The thesis firstly introduces the circuit structure of three-level inverter, compares two modulation arithmetic of the inverter, mainly analyses the principle and realization steps of Space Vector Pulse Width Modulation (SVPWM). Next, the thesis introduces the method of three-phase grid's Phase Lock based on instantaneous reactive power。Traditional PLL is not satisfactory in the unbalanced AC power system condition, For this reason, the thesis gives the improved method. Then, the thesis establishes the mathematical mode of Grid-connected PV system in three kinds of coordinate system, the voltage and current pairs of two closed-loops vector control strategy is importantly studied,uses the methods of typical control system designation and experimentation to solve the factors of PI controller.The thesis gives the inverter's soft system designation based on the DSP chip of TMS320F2812, also gives the flow chart of soft arithmetic. The simulation of SVPWM, SPLL,PV grid-connected control strategy is researched by MATLAB, and the rule of PI controller is also summarized. The result shows the exactness of PV grid-connected control strategy, the energy generated by PV can be feed back to AC power system with high power-factor.