Research On The Photovoltaic Off - Grid Inverter

In order to solve the basic need of families which in remote areas without electricity, designed an off-grid PV inverter with rated output power of 500 W.First, according to the system requirements to design the overall framework and the hardware circuit; by investigating the demand of electricity of the families in the region without electricity to select the appropriate storage batteries and solar cells. The system mainly consists of solar input, battery charging, DC / AC conversion, filtering and boost output, DSP and its auxiliary circuit, the auxiliary circuit of DSP consists of the sampling circuit, driver circuit, auxiliary power supply and protection circuit. The hardware main circuit topology consists of a DC buck circuit, full-bridge inverter circuit, the frequency step-up transformer and LC filter circuit,and calculate the relevant parameters of the circuit.Second, the software is designed for this paper. The system uses two TMS320F28023 DSP to control battery charging and DC / AC conversion. Through the study of the battery works and the charging method of battery, according to the need of the system, this paper designed a method to charge the battery; through the study of SPWM modulation, determine use unipolar frequency doubling modulation to achieve the control of the inverter circuit. Design DSP1, DSP2 main program flow, interrupts flow chart, the battery charge with MPPT flowchart, PWM generation flowchart.Finally, simulation and experiment are achieved. The models of full-bridge inverter circuit and MPPT are established on matlab/Simulink, full-bridge inverter circuit is verified whether the output waveform quality meet the requirements by the control of SPWM, the MPPT control method can be achieved or not. Then, making an output power of 500 W prototype to verify that system design requirements can be achieved or not. Through the analysis of the experimental results, the system designed rationally, output can meet the requirements.