The Impact of Large-scale Photovoltaic Penetration on Voltage in Distribution Systems

Large-scale distributed PV access changes the distribution of currents in the distribution grid, and the random volatility of its output is the main cause of voltage fluctuation. In order to comprehensively reveal the impact of large-scale distributed photovoltaic penetration on voltage in distribution network, this paper analyzes the theoretical mechanism of PV access to the distribution network on voltage deviation and voltage fluctuation, building a simulation model of the distribution network and PV based on Matlab/simulink, and analyzing the impact of various factors such as grid-connected location, access mode, PV output correlation, and weather conditions on voltage. In addition, for the voltage fluctuations under different weather conditions, the envelopes of the instantaneous values of nodal voltages are extracted by finding the wave crests and cubic spline interpolation, using the Hilbert-Huang transform (HHT) method, and the envelope signals are processed by empirical mode decomposition (EMD) and the Hilbert transform, to realize a detailed analysis of the modulation signals of the voltage fluctuations. The results show that large-scale distributed PV access significantly increases the voltage level of distribution network, and PV using single-phase grid-connected access will cause a large effect on the node voltage three-phase unbalance. The magnitude of voltage fluctuations increases with increasing PV output correlation. Distribution network node voltage with PV output changes occur random fluctuations, node voltage amplitude modulation effect by multiple low-frequency signals, the more drastic the change in illumination radiance, the greater the change in the amplitude of the modulating wave, the larger the voltage fluctuation.