2010

School of Electrical Engineering &

Telecomm

unications

UNSW ENGINEERING @

UNSW

10 Author: Simon Lewis Supervisor: Iain MacGill Industry Supervisor: Kevin Nuner (Integral Energy) Assessor: Jayashri Ravishankar

Analysis and Management of the Impacts of Photovoltaics in a Distribution Network

AbstractThe prevalence of grid connected Photovoltaics (PV) throughout the electricity network is increasing due to initiatives such as generous feed in tariffs and the Blacktown solar cities program. In fact in the Integral Energy area approximately 150 new applications for solar panels occur every day. It is the aim of this thesis to get a practical idea of the impacts that these numerous PV systems are currently having on the network, investigate the effect the predicted increased penetration will have via modelling and to provide recommendations to network service providers (NSP) on how to best tackle this issue. Results indicate that current impacts are minimal but future penetrations could cause problems

PV System Performance ChallengesA surprising result is the actual generated output from the PV systems. The generation data analysed suggests that the average generation is approximately 64% of the rated value. This limited output was also examined by taking field surveys of streets with high PV penetrations. This result highlights the challenges faced by installing a large number of PV systems in a real scenario, such as orientation and shading issues.

Implications for Network Service

ProvidersThe data analysis uncovered that the current penetration of PV systems were impacting the power factor of the systems, as shown above, as well as the current harmonic distortion. The impact wasn’t significant enough to mean supply standards are not being met but are possibly introducing losses into the network via harmonic and power factor issues impacting the efficiency of equipment like transformers. Surprisingly voltage problems weren’t visible at current penetrations but have been seen in special cases (such as high impedance rural lines). Simulation results indicate that with increased penetration comes significant load voltage increases. Additionally in the event of all PV systems shutting off due to protection, current swings of up to 100A will eventuate, creating current surge problems on the network. Overvoltage is one possible trigger for this.

BackgroundThere is growing international concern over the impacts of the increasing number ofPV systems. In Australia much of the researchhas used modelling not practical data. Thusamongst NSP’s knowledge about the practical integration a large number of these systems is unknown. Integration issues tend to occur because PV power production times in residential systems is at the times of lowest load. This mismatch provides the challenge of greater load variability in the network.Current research suggests that this can cause the following major integration issues: impacts on voltage levels, power factor, harmonic distortion and protection [1,2,3]. Furthermore it is suggested that the major concern for NSP’s are the impacts on voltage levels being why customer supply standards will not be met with increased penetration.

Research Methodology

Conclusions And RecommendationsFor areas analysed the current penetration levels coupled with non ideal photovoltaic outputs meant that there are issues currently occurring on the network but supply standards are not being exceeded.This work has highlighted the value of for NSP’s to considering the following management options in order to circumvent future problems:• Implement a data centre and monitoring program• Consider policy to limit penetration on LV feeders• Look into storage options such as batteries to shift the PV production to peak times

AcknowledgementsI would like to acknowledge the assistance of Integral Energy in their guidance and provision of the data behind this thesis.References1. Intelligent Energy Europe PV Upscale. (2006). Publications review on the impacts of PV Distributed Generation and Electricity networks. Intelligent Energy Europe.2. Srinivasan, D. (2008). Field Experiences with Utility Scale PV System Grid Interconnection. AIRE Workshop.3. CSIRO. (2009). Intelligent Grid A Value Proposition for Distributed Energy in Australia. Sydney: CSIRO.

Case Study Area Identification• Identify areas with high PV penetration• Charictersise these areas (site surveys, geographically, etc)

Data Collection and Cleanup• Collect PV system performance data and data for relevant network

parameters• Cleanup data via data logic check, filtering of incorrect data, etc.

PV System Performance Analysis• Gather information on numerous PV systems of different sizes• Use statisical analysis to appraise average PV system performance

Analysis of Current Integration Issues • Compile network data on voltage, current , harmonics and power levels• Use statistical tools to show the effect of PV systems on these network

parameters.

Analysis of Future Integration Issues• Creation of scenario prediction tools to see the potential shape of PV

integration in the future• Creation of simulations to model future of increased PV penetrations