High penetration of PV systems in low voltage distribution networks: investigation of power quality challenges and mitigation

Abstract

World electricity demand is continuously increasing and fossil fuel supplies are not sustainable. Solar Photovoltaic (PV) energy is one of the emerging resources around the world, which produces emission free electricity. Nowadays, the advancements in rooftop solar PV technology, government subsidies, decreasing capital cost and feed-in-tariffs have promoted installation in residential and commercial applications. The exponential uptake in widespread integration of PV systems in existing low voltage (LV) distribution networks is raising additional new challenges in terms of power quality, stability and protection. In LV distribution networks, poor power quality (PQ) is the most serious concern.Characteristically, LV distribution networks are not designed for significant back-feed of power generation to the main grid. Also, these networks are unbalanced in nature due to asymmetry in system impedances and single-phase loads. This together with a large number of small-scale PV system integrations in LV networks can cause poor PQ challenges in terms of voltage quality and harmonics. PV systems can themselves generate harmonics, due to the usage of power electronic inverters. In addition, the augmentation of power electronics based Furthermore, this research has suggested a novel solution to overcome the above PQ issues.The concept of adopting the PV inverter as a virtual DSTATCOM named as Solar-DSTATCOM has been proposed. Also, a new control strategy for the PV inverter has been developed to provide independent phase voltage regulation and load reactive power and harmonic compensation, which could eliminate issues in the unbalanced distribution network.Initially, the Solar-DSTATCOM controller has been verified in a PSCAD simulation environment. Further, different case studies have been performed on the IEEE-13 bus network for PQ issues compensation. In addition, the proposed Solar-DSTATCOM control system has been tested and verified in controller hardware-in-the-loop simulation environment, which combines the real-time digital simulator and dSPACE DS1103 hardware board. Detailed investigations are carried out for various different case studies, which include daytime, nighttime operations, the impact of dynamic load profiles and finally harmonic analysis. The analysis has revealed that Solar-DSTATCOM exceptional performance in the hardware environment has enhanced the grid PQ by providing voltage regulation, reactive power compensation and power factor correction. The harmonic emissions are well within the limits.iii Declaration by authorThis thesis is composed of my original work, and contains no material previously published or written by another person except where due reference has been made in the text. I have clearly stated the contribution by others to jointly-authored works that I have included in my thesis.

Impact of service and feeder cable upgrade on hosting capacity for single phase connected photovoltaics

“…Grid reinforcement by service cable upgrade has been proposed in many studies to solve the feeder overloading [2]. Other studies have stated the benefit of bigger cable size of not only increasing the ampacity but also improving the voltage level [18], [21], [22].…”

Evaluation of the Impact of Rooftop Solar Power on the Power Quality of Vietnam Urban Distribution Networks according to Relevant Vietnamese and IEEE and IEC Standards

“…The integration of PV sources may make this problem more severe [16]. The installation of PV sources in the power grid is mainly based on customer needs, so the location and capacity of these sources are highly random and depend on the customer's wishes [17]. Furthermore, harmonics generated during the operation of the inverter affect power quality because of harmonic pollution.…”

Analysis of Some Power Quality Parameters at the Points of Common Coupling of Photovoltaic Plants Based on Data Measured by Inverters

“…Therefore, one of the main challenges that need to be overcome to speed up the deployment of this type of renewable sources is their correct integration in energy networks, needed to ensure that distributed PV's growth is sustainable. As a result, there are numerous studies in the literature that review the potential impacts of distributed PV on the LV distribution grids [9,11,12,26] and they propose a variety of methods to mitigate the effects that might be produced on them, such as coordinated control strategies [7,27,28], distributed energy storage systems [8,13], geographical dispersion of distributed resources [13], active power curtailment [13], production forecasting [29], reactive power management [29,30] or improving electricity infrastructure [31].…”