Design And Optimization Of Micro Grid Connected Photovoltaic Inverter

With the appearance of polluted environment and energy wasting, there is an growing demand for the renewable and clean energy. Especially in recent years, our country has strengthened environmental supervision and paid more attention to environmental treatment. The traditional energy sources such as thermal power are facing the the predicament of the increasing cost of original energy and environmental protection. In this situation, it has important realistic meanings that we can converse solar energy into electricity effectively, which is sustainable and environmentally friendly. The conversion efficiency and stability of photovoltaic inverter which is the core of photovoltaic conversion will directly affect the investment value.The thesis targets on the design and optimization of the micro grid photo-voltaic inverter which convert dc to 220V/50 Hz ac. By analyzing circuit structure, two level structure of energy transformation is adopted. Max power point tracking and remote control based on power line carrier are used in the design. Thesis also analyzes the phaselock technique and deduces the principle of dq phaselock.Main works are as follows:1. After analyzing the circuit, the flyback inverter structure is adopted for simple, well electrical isolation, high stability and easy multiplexing output. By adding some auxiliary circuits, leakage inductance energy is absorbed. The inverter has two outputs. This structure not only reduces the burden of circuit, but also guarantees the simpleness. By absorbing the leakage, switch tube is protected and energy utilization is improved.2. SPWM is used to control main switch tubes. By analyzing the resonance of power tube, the parameters of SPWM are modified by resonant period to reduce the switching loss. Switch tubes work in low power consumption, reducing the power loss of inverter.3. By building model of PV, control principle of max power point track is analyzed. The algorithm without current detection is derived in detail. After these, control method of MPPT based on fuzzy control is designed. This method not only needs less circuit, but also is efficiency.4. Communication circuit using MI200 E which is based on power line carrier is designed. PC codes are written by using MScomm or Cserialport. By remote monitor, the inverter is controlled efficiently.Finally, test circuit which uses MC56F8 XXX series digital signal controller from Freescale is made. All above functions are released.