School of
Information Technology and Electrical Engineering

Investigation of Power Quality Issues in Low Voltage Distribution Network with High Penetrations of Rooftop PV Systems

Ms. Annapoorna ChiduralaMon, 16/12/2013 - 10:00
Prof Tapan Saha

 Due to rapid rising electricity demand and lack of fossil fuels, many nations worldwide are looking forward to integrate renewable energy for power generation. Recent years, distributed renewable energy resources have been gaining momentum significantly for energy generation in order to reduce carbon footprint and to meet the 2020 target. Amongst numerous resources, Solar Photovoltaic (PV) systems are one of the fast growing resources in worldwide due to decreasing capital cost. Current developments in the compact rooftop solar PV technology and feed-in-tariff have heightened the installations in residential, commercial and industrial applications. Australia is the ideal location for solar power production because of high insolation level. However, the high penetration of solar PV systems in existing electricity distribution network is imposing several Power quality, Stability and Protection challenges. With wide spread PV installations in low voltage distribution networks, power quality is the major area of concern.

 Typically, LV distribution networks have low X/R ratio and high impedance, which are not designed for significant back-feed of power generation to main grid. Also, these networks are unbalanced in nature due to asymmetry in system impedances and single phase loads possessing uneven voltage levels in each phase. Together with, the higher number of PV systems integrations in the form of rooftop installation can deteriorate the situation leading to poor power quality. The most frequent power quality issues are voltage quality issues such as over voltage, voltage unbalance, voltage fluctuations, unbalanced dips and swells. Among them overvoltage is the most prevalent limiting issue due to high penetrations of rooftop PV units. In addition, the augmentation of power electronics based appliances; the loads are becoming voltage sensitive and nonlinear in nature. The proliferations of widespread PV penetrations and with multitude of nonlinear characteristics from load have stringent impact on the harmonic distortion levels of the LV grid. The main objective of this research is to investigate impacts of massive PV penetrations on power quality of the distribution grid and aiming to alleviate them.

As the initial of part of the project, this research has focussed on the impact of solar PV inverter on the power quality of the distribution networks and proposed a new control method to address these issues. In present era, the solar PV inverters are intentionally designed to produce only active power during daytime. However, PV inverters can have versatile functionalities same as DSTATCOM by modifying some control capabilities to it. So that the inverters can provide reactive power support to grid during daytime and night-time in addition to real power generation.  Therefore, to utilize the PV inverter as a virtual DSTATCOM, denoting as Solar-DSTATCOM with a new control topology is proposed to enhance PQ in unbalanced network. This new control topology facilitates independent phase voltage regulation, harmonic and reactive power compensation for each phase independently during whole day. In this study, an IEEE-13 bus test system has been considered and complete system is modelled in PSCAD software. To verify the performance of the proposed Solar-DSTATCOM, simulations have been performed for different scenarios such as voltage variations, faults and harmonics and a comparative analysis has been presented. Preliminary results show that the proposed Solar-DSTATCOM with novel control strategy improved the power quality of the network.

 In future work, different power quality issues with more rooftop PV units in case of balanced and unbalanced networks will be investigated. Moreover, further studies will identify the issues in different PV inverter technologies and their impacts on distribution grid with random penetrations. After that, the analysis will be further expanded to study the effect of stochastic variation of solar insolation on voltage flicker and sag/swell, harmonics. In parallel, the investigation will be carried on applications of energy storage and compensation devices for power quality enhancement with scattered PV systems integrations. This research will be concentrated on developing new control techniques and algorithms for the utilities. Subsequently, the proposed control methods could be potentially verified in RTDS to evaluate the practicality in real power system. Finally, a penetration index will be developed in view of various power quality parameters. 


Annapoorna Chidurala received the B.Tech degree in Electrical and Electronics Engineering and M.Tech degree in Electrical Power Engineering, both from Jawaharlal Nehru Technological University (JNTU) Hyderabad, India, in 2009 and 2011 respectively. Currently, she is working towards the Ph.D. degree in PES research division of the School of ITEE, The University of Queensland, Australia. Her research interests include integration of solar energy in power systems, power quality, design and control of power converters and electrical energy storage technology. 

Seminar Type: 

PhD Confirmation Seminar