Design Of The Intelligent Photovoltaic Grid_Connected Inverter Based On DSP

With the gradual reform of China energy structure and national policies, distributed small-scale photovoltaic(PV) power has gradually opened up to the entity and individuals. It also has become the research hotspot owning to its advantage. As we all known, PV grid-connected inverter is the key link in the network and power system, so the design of intelligent, efficient, and reliable small-scale photovoltaic grid-connected inverter and promotion of the popularization and application of distributed photovoltaic power generation has very important practical significance. In this thesis,2KW and two levels photovoltaic grid-connected inverter without transformer had been designed, which controlled by DSP.Firstly, the design parameters were decided based on the results of analyzing the development status and key technology of photovoltaic grid-connected inverter. According to the design parameters, the full design scheme was achieved which includes the hardware part and the algorithm part. Hardware part:the main circuit topology structure and the type of main chip were chosen. Software part:Maximum Power Point Tracking (MPPT) control algorithm, Grid inverter control strategy, PLL synchronous phase lock algorithm, SPWM generate and control mode, PIDcontrol algorithm.Secondly, modular design of the inverter hardware circuit was designed, which included hardware overall structure, DC/DC boost circuit parameters, DC/AC full-bridge inverter circuit parameters, DSP core board, DSP control plate board, IGBT driver board and auxiliary switching power supply board, and then given the specific design process of the circuit parameters and given the circuit schematic.Thirdly, the MPPT control algorithm, the double-loop control strategy and the sampled phase-locked (SPLL) inverter control algorithms were discussed. Combing the improved perturbation and observation method (P&Q) with the character of the DC/DC Boost, the MPPT control algorithm of variable step size duty cycle perturbation was realized. With the generation of SPWM based on symmetric regular sampling method and incremental PI algorithm, the double-loop inverter control strategy based on SPWM was achieved in DC/AC full-bridge inverter circuit. At last, with the help of the DSP CAP capture unit, frequency tracking and phase synchronization, the SPLL control algorithm of net voltage was realized.Finally, software program was designed, including DSP programming steps, DSP program optimization method, DSP resource allocation, Overall Program Design, main program design, subprograms design, ARM GUI design and given a specific software implementation process and program flow. And then, building the experimental platform and testing the hardware of the inverter were completed, the experimental results were gived, and the results were analyzed.The test result indicated that the design of the inverter reached the expected goal.