Analysis And Comprehensive Evaluation Based On Positive And Negative Impacts For Grid-connected Photovoltaic Power Station On The Distribution Network

This thesis was supported by Natural Science Foundation of Chongqing(CSTC2009BB6190) and independent research project of State Key Laboratory of PowerTransmission Equipment&System Security and New Technology(2007DA10512709208).Photovoltaic power generation, with the advantage of renewable energy andconvenient installation, has been widely used in distributed generation in distributionnetwork as the technology gradually developed. Grid-connected photovoltaic powergeneration station not only changes the structure single terminal power supplydistribution network, affect the operation of distribution network due to its fluctuant andintermittent characteristics. As grid-connected photovoltaic power station adopts powerelectronic converter for the connection to distribution network, the harmonic voltageand current as well as the DC components are inevitable. Therefore, the impact analysisand the comprehensive evaluation of grid-connected photovoltaic power station arestudied. The main contents are as follows:①Study the classification, power generation methods and connection methods ofgrid-connected photovoltaic power generation system. There are five differenttopologies for power generation, including centralized structure, group of stringstructure, multiple groups of string structure, string component and group coordinationcontrol structure. Based on the filed measured data of the photovoltaic power station, asystematical analysis of impact photovoltaic power station on distribution network isconducted through the different aspects such as voltage, frequency and harmonics. Atdifferent penetration power, the frequency variation of distribution network caused bythe power fluctuation of photovoltaic power station, as well as the additionalphotovoltaic inverter harmonic current during the asymmetric distribution network faultare studied.②Based on the multiple CPUs embedded measurement and evaluation systemdesigned for the grid-connected photovoltaic power generation station, a positive andnegative effect index is proposed for its comprehensive evaluation. With FFT as basicpower measurement algorithm and adopted DSP computing unit, data manage unit andanalysis unit, a real-time calculation of positive and negative effect index is realized.③Common weights of the index are determined by DS/AHP method with incomplete information, and then the weight synthesizing of positive and negative effectindex are conducted through penalty-incentive balance functions respectively. Thecomprehensive evaluation results are generated by the method of grey relation analysis.