| Recently, with the rapid development and promotion of photovoltaic grid connected power generation technology, the permeability of photovoltaic power generation in the distribution network gradually increased. Grid connected photovoltaic power generation unit is interfaced to grid by the grid connected inverter. on the one hand, grid connected inverter has the ability of converting PV array’s DC power to AC power; on the other hand, basing on the present characteristics of grid connected photovoltaic power generation, the grid connected inverter’s control system applies the PQ control pattern, which has integrated abnormal voltage and over-current protection.The main contents of this paper are as follows:1) Due to the relationship of photovoltaic power system’s fault response between control mode and protection of grid connected inverter, the photovoltaic inverter PQ control mode and method was analyzed to obtain the output characteristics of photovoltaic power supply when the power grid at fault conditions;2) The influence on grid’s short circuit capacity was also concerned in this papers. A new calculation method with the equivalent current source of photovoltaic power was proposed as well. When the power grid was in a fault, PV system would provide short-circuit capacity, which is relatively close to its capacity and disagreed with other rotary distributed power.3) concerned of 10~35k V protection in distribution network and the photovoltaic power characteristics, the influence of the distributed PV power on the short-circuit capacity of the power distribution network is analyzed based on the MATLAB/Simulink, and the correctness of the theoretical calculation and analysis is verified also.Finally, the work of this paper is summarized in three aspects. And according to the existing problems of PV system and future development of the power grid, three suggestions were put forward for the further research work. |
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