Research On 230W Two-staged Grid-connected Photovoltaic Inverter

Photovoltaic (PV) power generation has become a very important part of future renewable energy in China. For the advangtage of high reliability, easy modularization, and whithout the components nonmatching and hot spot issues, the AC-module (A low power photovoltaic module with an integral grid-connected dc to ac inverter) structure is one of the development trends of photovoltaic systems. However, the relatively high losses and system cost are in the way of its widespread application. According to the design purpose of high efficiency, low cost and small size, a 230W two-staged Grid-connected inverter prototype is produced, in which Piccolo28035 is used for the control chip and the main circuit topology is a two-satged structure with a push-pull forward converter plus a full-bridge inverter.The thesis analyzes the working mechanism of photovoltaic cells and their output characteristics, illustrates the principle of maximum power point tracking (MPPT), gives an introduction of general MPPT methods, and makes algorithm design and simulation anaysis to a widely applied MPPT method of perturb and observe (P&O), describes the generation and damage of island effects, explains the importance of islanding detection, and respectively introduces the active and passive detection method on the island effects.The thesis importantly makes complete detail principle analysis and design for front-end dc/dc converter and latter-end dc/ac inverter, including the selection of main circuit topology, the establishment of control strategy, the selection of SPWM for full-bridge inverter, and the analysis and design of the main power circuit and control circuit.Besides, the paper presents the soft design of the grid-connected PV system, including the introduction of control chip system structure, allocation of the control resource, and the design of program flow. Finally, hardware debugging as well as some experiments is completed on the prototype, and the system simulation results and experimental waveforms are given.