چكيده به لاتين
Phase, frequency, and amplitude of the grid voltage are three important factors in the grid-connected photovoltaic systems. The true and fast estimation of these parameters under grid variations and disturbances have great significance for the proper performance and stability of the system. In this thesis, three new phase locked loop structures are proposed. These PLLs have fast dynamic response in the phase, frequency and amplitude estimation of the grid voltage. In the first proposed PLL, the phase variations related to frequency change have been compensated in PLLs based on frequency locked loops. existance of DC variations at the input of PLL results in errors in estimation. In the second and third proposed PLLs, the error in estimation due to DC offset have been solved by utilizing an offset rejection loop. Also, fuzzy controller has been used in the third structure. Eventually, in this thesis the proposed PLLs are used to synchronize the injected current of a 250watt grid connected photovoltaic micro-inverter. The implementation results of the PLLs (using ARM micro-controller) are also presented to evaluate the practical performance.
Keywords: photovoltaic, micro-inverter, phase estimation, frequency estimation, fast dynamic response, DC offset, synchronization, fuzzy controller.
