| With the global energy crisis and environmental pollution draw more and more people’s attention, PV and other renewable energy generation technology has risen rapidly, and it has become the inevitable trend of the development of sustainable energy strategies in the world. Because of the influence which high penetration of PV brings to protection, study on the improved protection has a very important significance for safe and reliable operation of the distribution network.Different from rotary type synchronous generator, PV system applies a large number of power electronic devices, which result to the difference of fault current characteristics. In this paper, according to the research on analysis and simulation of PV’s fault current characteristics, influence on protection has been discussed. Then improved protection methods or schemes were proposed. The main work done as follows:1) According to the introduction of PV’s main components and control strategy, the grid-connected PV system has been built and simulated. With the analysis of two control mode, short-circuit faults under different types have been analysised and simulated.2) Based on the 110 k V substation and 10 k V feeders in Baoding region, the influences including transformer zero sequence voltage protection, zero-sequence current protection and feeders current protection were detailly simulated and analysed. The aspects analysed include power supply reliability, protection malfunction and refuse to operate, changes of protection sensitivity, etc.3) Based on the simulation and analysis mentioned above, new schemes to the substation and feeders were proposed. The main contents are improved inverse current protection and new current differential protection scheme. The operation with CT saturation was analyzed in this paper. The current differential protection scheme is simple, reliable, and economical, and it has a better practical value. Lastly, the reclosing mode selection and time setting were discussed. |
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