Voltage And Harmonics Influence On A Solar Photovoltaic Integrated Distribution Network

In recent years,a global focus toward renewable energy due to factor such as environmental concern and depletion of the available fossil fuels observed.Solar energy is amongst the easiest to harness.However,as the power output of the photovoltaic system depends on solar irradiance and weather conditions,hence the sudden change in irradiance results in a considerable fluctuation of the output power of the photovoltaic system which leads to voltage and current variation at the point of common coupling and produces total harmonic distortion during the cloudy conditions.In addition to the voltage fluctuation,power electronics used in photovoltaic systems are the major sources of harmonic distortion.This research is aimed to study the voltage response and harmonics impact on active distribution network due to the penetration of PV generation.It analyzed the impact PV power fluctuation on voltage characteristics of active distribution network considering a single point of integration and multi-point integration to the distribution network of photovoltaic generation.In this study,four PV generating units' harmonic models were built according to different research purposes because of the characteristics of the simulation research of distribution network.The characteristics of high-order harmonic and low-order harmonic in ADN were examined,and problems of access point voltage distortion and harmonic distortion when multiple PV generating units are connected into the ADN were investigated.Finally to enhance the power quality and to deal with aforementioned issues an adaptive virtual impedance is proposed for harmonics mitigation and reactive power control which is associate with voltage fluctuation.The filter capacitor voltage and virtual impedance loop are regulate by the voltage-current double loop in the primary control level.The secondary control level performs necessary measurement and send data to the primary control level of local control units for virtual impedance regulation and mitigation of altered voltage at sensitive load buses.The suggested virtual impedance have been designed based on proportional integral resonant(PIR)controller and the values of virtual resistance and inductance are calculated based grid voltage at load bus which make the algorithm an adaptive virtual impedance.The novelty of this study is the design of an adaptive virtual impedance which varies with gird voltage and line feeder impedance to offer and effective harmonic mitigation and voltage compensation despite fluctuation of PV output power and other aforementioned challenging operating conditions of the grid-connected PV system.