Research On The Influence Of Distributed Photovoltaic Access To Distribution Network On Electric Energy Metering

With the rapid development of distributed photovoltaic in our country,its influence on the power measurement of distribution network is increasing day by day.Many stations even have abnormal line loss after connecting to distributed photovoltaic,which makes the influence of distributed photovoltaic connecting to distribution network on electric energy metering become a research topic that can not be ignored.This paper focuses on two main factors of the influence of distributed photovoltaic grid connection on electric energy metering: harmonic and voltage fluctuation.The main research contents are as follows:The distributed photovoltaic grid-connected system,the classification and working principle of the inverter,and the working principle of the triangular wave multiplier are briefly introduced.The mathematical model of typical photovoltaic cells,the circuit structure of MPPT inverter based on disturbance observation method,and the physical model of triangle wave beat multiplier are explained in detail,and a20 kW photovoltaic grid-connected system and a triangle wave beat multiplier simulation model are established.The harmonic characteristics and voltage fluctuation caused by distributed photovoltaic grid connected to the power grid are analyzed.According to the Fourier expansion of the voltage signal output from the inverter in theory and simulation,the harmonic characteristics of distributed photovoltaic injected into the distribution network are extracted;This paper expounds the mechanism of voltage fluctuation caused by the change of photovoltaic output power,and summarizes the mathematical expression of voltage fluctuation.This paper analyzes the principle of the increase of power metering error under the condition of harmonic and voltage fluctuation,and the law and trend of the change of power metering error with the change of harmonic and voltage fluctuation characteristics.The power measurement method based on wavelet packet transform is used to reduce the power measurement error under the condition of voltage fluctuation,and the validity of the method is verified by the power simulation measurement of the voltage fluctuation signal under the single frequency amplitude modulation wave;A strategy based on harmonic instantaneous power correction is proposed to reduce the power metering error under harmonic background,and the effectiveness of the strategy is verified by the simulation of fundamental wave superimposed with single frequency harmonic.