Research On Single-phase Photovoltaic Grid-Connected Inverter And Islanding Detection Method

Solar energy is recognized as one of the ideal alternative energy in the future as to it is renewable and non-polluting. In recent years, the photovoltaic power generation, as a direct use of solar energy, has been attracting much attention, and photovoltaic grid-connected inverter technology has become a hot research.This paper focuses on single-phase photovoltaic grid-connected inverter, on the basis of studying its topology, modulation method and grid-connected control strategy, the islanding detection technology of photovoltaic grid-connected power generation system was analyzed and researched in-depth. The main work is as follows:1. Through analysing the characteristics and working principle of the photovoltaic grid-connected inverter with different structures, the main circuit topology of inverter was established in this paper; As for the main circuit topology, the paper focuses on the basic principles of the sinusoidal pulse width modulation technique as well as the phase locked loop technique, furthmore, software realization methods are given based on DSP; By comparatively analysing several classic current control strategy, a design method based on the output current instantaneous value of the grid voltage feedforward control was derived;2. The principle of islanding detection was analyzed in detail and several common islanding detection methods were introduced, then their strengths and weaknesses and the scope of application were pointed out. The effectiveness evaluation system for the inverter’s internal active detection and passive detection was analyzed and dicussed deeply, and the non-decetion zone in various coordinate systems was described quantitatively;3. The principle of active frequency drift islanding detection method was analyzed deeply, the effectiveness of the active frequency drift with positive feedback was evaluated and simulated in terms of the non-decetion zone and power quality, as the parameter selection of the traditional active frequency drift with positive feedback islanding detection algorithm’s non-decetion zone and output power quality can not take into account at the same time, a fuzzy adaptive frequency drift algorithm was proposed in this paper and simulated. The results show that this method has a fast detection, no non-decetion zone, low distortion and so on;4. The experimental prototype of photovoltaic grid-connected inverter was builded based on TMS320F2808, the design of the hardware and software was described in detail. At last, some system and related experiments of islanding detection of grid-connected have done, and the experimental results were analyzed.