Tracing And Analysis Of Harmonic Contributions Of Multiple Distributed Generations In Active Distribution Network

With an increasing number of distributed generations?DGs?being integrated into active distribution systems,power quality problems have been caused in distribution systems,thus more attention has been paid to power quality analysis and management.Since a large number of DGs start and stop irregularly and frequently,their power generations are fluctuating,and they can't coordinate with power loads perfectly.The voltage in the distribution system will be impacted and the voltage fluctuation will be generated.Besides,as DGs incorporate power conditioning units,which can make voltage and current waveform distortion and can generate harmonic.This paper focuses on the harmonic in power quality,quantifies the influence of voltage quality and harmonic on distribution systems caused by the fluctuation of power generations of DGs.The main work of the paper is as follows:This paper creates harmonic tracing models for DGs,including affine output model and affine impedance model for DGs.Considering that when primary energy change randomly,power generations of DG are fluctuating,the paper proposes uncertain models of wind turbine and photovoltaic based on affine arithmetic.On this basis,considering the U_dc of impedance model is fluctuating,the paper creates an affine impedance model for DG inverters.With the recording characteristics of affine mathematics,the paper presents a new index to quantify harmonic contributions of DGs.Combining with three-phase harmonic power flow the paper proposes a method to trace harmonic contributions of individual DGs and calculate indices of DGs.The method is tested via a typical test system of distribution network.Some influence factors like location and fluctuation of DG are evaluated.Conclusions show that the proposed method can quantitatively evaluate harmonic contributions of individual DGs in distribution systems.