Research On Single Phase Grid-Connected Inverter And Islanding Detection Strategy

This paper focuses on the research of the single-phase grid-connected inverter and the anti-islanding strategy. The power energy is transmitted by grid-connected inverters in distributed generation systems. The research on the grid-connected inverters has become one of the intensive activities. This paper briefly introduces the background and significance of new power energy generation. This thesis focuses on three aspects summarized as follows:Part 1 of this thesis presents the structure of PLL, gives a PLL strategy used in single phase grid-connected systems, this strategy is based on d-q transformation. Specially, expatiates with the transformation method of SOGI, analyses and solves the existed problem of the DC component of the new strategy. Simulations and experiments have proved the effectiveness of the new phase-locked loop, it can quickly and accurately track the fundamental component of grid voltage.Part 2 of this thesis analyses the causes and the damages of the islanding, introduces the islanding detection strategies and the effectiveness of islanding detection algorithms, explains the failure reasons of the anti-islanding detection method based on Active Frequency Drift (AFD), describes Non Detection Zone (NDZ) by using the phase criterion, Uses the NDZ to improve the algorithm by introducing the positive feedback to the AFD method.Part 3 of this thesis focuses on the design of the hardware platform of the inverter system. First selects the power switch, SSR, after analyses the output filter, designs the LCL type filter which has a better performance on high-frequency attenuation.This thesis gives a more detailed description and analysis on the three core parts of the grid-connected inverter system, and lists not only the system simulation and prototype verification, but also the simulation and experimental results. Ultimately, the thesis achieves the requirements of the project through a series of improvement action.