Technical ReportPDF Available

Voltage Analysis of the LV Distribution Network in the Australian National Electricity Market Available at: https://prod-energycouncil.energy.slicedtech.com.au/lv-voltage-report

Authors:

Abstract and Figures

The Energy Security Board commissioned the Centre for Energy and Environmental Markets at the University of New South Wales to undertake analysis of voltage on the LV networks within the NEM, as well as distributed PV’s influence on that voltage. This work used a unique dataset of maximum and minimum voltage measurements over 12,000 sites in the LV network, provided by Solar Analytics, a company offering real-time performance monitoring for PV system owners.
Content may be subject to copyright.
A preview of the PDF is not available
... Example of curtailment resulting in lost self-consumption of DPV [1] DER curtailment therefore has financial impacts on energy users with DER, although prior work in [10] found that these costs remain small for the majority of cases with an average of $3 to $12 per year in impact based on 'worst case' conditions. It is important to note that this study used 2018 data with lower DER penetrations and only considered curtailment due to 'tripping' and therefore may underestimate current curtailment, however it is also critical to note that this previous study provided an upper limit on curtailment at the time, given that it only analysed clear sky days and was therefore likely to be a 'worst case scenario' under 2018 conditions [1]. ...
... Previous research has presented the voltage conditions across the low voltage networks in South Australia, as well as across other states in Australia [10]. This study particularly focuses on the sites within the metropolitan Adelaide region, with a smaller sample of sites; nevertheless, it is useful to observe and compare the voltage conditions in order to provide context to the over-voltage curtailment analysis that follows. ...
... Figure 10 presents the distribution of voltages from the AGL data-set across the 12 month period via the use of Box-Whiskers plot*. The voltages are lower during winter and higher during spring consistent with previous analysis [10]. On the other hand highest voltages are observed during summer instead of spring months. ...
Technical Report
Australia has world leading uptake of distributed PV (D-PV) and increasing installations of battery energy storage systems (BESS). Recent reports estimate one in four households own D-PV and installation rates are anticipated to grow in the years ahead. D-PV and BESS can provide various economic and environmental benefits to energy users, network companies and other industry stakeholders. However, integrating increasing levels of D-PV into electricity networks present a range of social, technical, and regulatory challenges. Voltage management in low voltage networks is one of the most imminent challenges posed by the integration of increasing levels of D-PV. Traditionally, in a network with uni-directional energy flow, distribution network service providers (DNSPs) set the LV voltages at the higher end of their allowed range to maintain reasonable voltages during periods of peak demand and hence voltage drop. However, as energy flows bi-directionally through the LV network with increasing levels of D-PV installations, D-PV exports can increase the local voltage range. To help DNSPs in managing network voltage effectively, it is increasingly required that D-PV and BESS inverters implement one or more of the following power quality response modes (PQRM): 1. Tripping (anti-islanding and limits for sustained operation) on excessive voltages 2. Volt-VAr (V-VAr) 3. Volt-Watt (V-Watt) The PQRMs can curtail power output which may limit opportunities and revenue that D-PV and BESS owners obtain from their investments. On the other hand, these modes can help with the management of voltage and therefore, support the integration of higher levels of D-PV. The Curtailment and Network Voltage Analysis Scoping Study (CANVAS) is a RACE for 2030 scoping study conducted by the Collaboration on Energy and Environmental Markets at UNSW, with industry partners AGL, SA Power Networks (SAPN) and Solar Analytics. As a five-month scoping study, CANVAS’s main motivation is to develop preliminary socio-technical insights to inform industry stakeholders and policy makers about the current state of D-PV and BESS curtailment due to PQRM requirements. CANVAS consists of two research streams, social science and technical, with both delivering evidence-based results that have important implications for Australia’s fast growing and ever-changing energy landscape, where previous evidence-based results and studies have been limited. The full and succinct public reports can be accessed via RACE for 2030 webpage, under Fast Track reports: https://www.racefor2030.com.au/publications/
Article
Full-text available
As distributed photovoltaics (PV) levels increase around the world, it is becoming apparent that the aggregate behavior of many small-scale PV systems during major power system disturbances may pose a significant system security threat if unmanaged. Alternatively, appropriate coordination of these systems might greatly assist in managing such disturbances. A key issue is PV behavior under extreme voltage events. PV connection standards typically specify aspects of inverter voltage behavior. However unresolved questions remain regarding compliance, ambiguity and transition between versions of these standards. In addition, how major voltage disturbances manifest in the low voltage network is complex, and analysis of operational system data could be particularly useful for establishing the behavior of distributed PV in the field. Our study utilizes 30 s operational PV generation data from 376 sites during two major voltage disturbances in Australia. Australia has one of the highest penetrations of distributed PV worldwide, and as such provides a useful case study. Results show that an aggregate ~30–40% reduction in distributed PV generation occurred during these events, but individual inverter behavior varied markedly. To the authors’ knowledge, this is the first time the aggregate response of distributed small-scale PV to voltage disturbances originating in the transmission system has been demonstrated. Four novel techniques for analyzing events are proposed. Results show a potential increase in system security service requirements as distributed PV penetrations grow. Our findings would seem to have major implications for development of composite load models used by power system operators and for contingency management.
Article
Full-text available
Photovoltaics (PVs) have been widely reported as causing power quality problems for electricity distribution networks. Much of this literature gives the impression that networks, particularly low voltage networks, were effectively and proficiently managed and operated before the rise of PVs and that this new technology is causing problems that did not previously exist and would not currently exist if there were no rooftop PV systems. The purpose of this paper is to examine measured data of power quality at the customer service point of four random households in four different distribution networks in Australia. This is the first report of power quality examination from the perspective of the end-user (solar households). The results show that the low voltage distribution networks reported in this study do not have networks that meet required power quality standards-and this cannot be attributed to the rooftop PV systems reported here. The paper proposes that power quality failures in these low voltage networks could be attributed to poor historical management, missed opportunities to embrace PVs as a means of better network management, lack of acknowledgement of the emergence of the prosumer and lack of total quality management and systems thinking.
Conference Paper
Full-text available
Increasing penetrations of utility-scale PV introduce more operational uncertainty to power systems, as it firstly creates more short-term imbalance between demand and supply due to the variable and only partially predictable behaviour of PV over short time frames, and secondly displaces conventional generation which traditionally assists in managing system imbalance and provides inertia to resist short-term frequency deviations. In the Australian electricity market, frequency control ancillary services (FCAS) are used to purchase regulation services to correct short-term uncertainty within the 5-minute dispatch period, and contingency services to correct manage sudden unexpected changes in demand or supply. However, it is unclear if and how these arrangements might need to change with more PV. One risk is that penetrations of PV might be unnecessarily unlimited given the present uncertainties of its impacts. This paper seeks to address some of these questions by analysing the short-term operational characteristics of utility-scale PV in the Australian National Electricity Market, at the timescale of seconds. Several studies have been carried out to understand the short-term characteristics of PV output, including the magnitude and frequency of output fluctuations and ramp rates over different timescales in different regions. However, the limited availability of high resolution data for utility-scale PV has hampered such work. Our study analyses four second-resolution output from four utility-scale PV plants (20 MW-100 MW) that are registered generators in the Australian National Electricity Market (NEM). The statistical analysis examines the significance of PV output fluctuations at this 4-second timescale. The results show that the variability over a four second time interval is insignificant, but that extreme events, with ramp rates of the size of the entire utility PV plant, potentially sufficient to trigger frequency regulation and contingency services, do occur albeit infrequently. These events are much more likely to be caused by operation issues rather than cloud transients, a challenge shared by conventional generation which is also subject to sudden unexpected forced outages. Although the current level of PV penetration in the NEM is low such that the impacts are barely visible, the variability of combined PV plants suggests that there is more frequency occurrence of large magnitude change in aggregated PV power output. This study represents the first stage of work assessing the scale of the variability challenge imposed by utility PV, and hence appropriate management options.
Conference Paper
Full-text available
Consumers in Australia have made substantial investment into Distributed Energy Resources (DERs) and in particular, rooftop solar PV. However, there remains limited visibility of the technical conditions experienced by these technologies in the LV network. An improved understanding of these technical conditions has the potential to support more transparent, technically and economically appropriate investment and operational decision making by both consumers and network utilities. In this study, a suitably anonymised data set of voltage measurements at 2,010 sites across Australia with distributed PV provided by Solar Analytics is analysed. Our assessment highlights that, generally, voltage conditions on the low voltage networks at sites with distributed PV are high; the great majority of measurements are greater than the nominal voltage for each network region with some potential for non-compliance. Voltage conditions were also found to vary significantly over the course of the day for different regions and seasons, in accordance with varying net demand and, presumably, network voltage control actions. Importantly, a wide range of voltages are observed during solar generation periods as well as times of lowest load, with low voltage conditions seen at peak load periods in some jurisdictions. These variations have implications for the performance of distributed PV including questions of voltage 'headroom' for PV generation, the challenges of managing low voltage excursions at times of peak demand, as well as for network voltage management more generally. The study highlights the benefits of improved visibility regarding power quality conditions on the low voltage network.
Conference Paper
Full-text available
High penetration of photovoltaic (PV) inverters in low voltage (LV) distribution network challenges the voltage stability due to interaction between multiple inverters and grid. As the main objective is to provide more power injection from VSC-based PV inverters, grid stability, reliability and power quality must be maintained or improved by adding cooperative control features to the grid-connected inverters. This paper first gives an overview of bilateral impacts between multiple distributed generations (DG) and grid. Regarding of these impacts, recent advances in static grid voltage support functionalities to increase penetration level are compared considering voltage rise limitation. Steady-state simulation study is realized in PSCAD/EMTDC and the results are discussed in terms of total generation efficiency.
Article
Distributed generation is being deployed at increasing levels of penetration on electricity grids worldwide. It can have positive impacts on the network, but also negative impacts if integration is not properly managed. This is especially true of photovoltaics, in part because it's output fluctuates significantly and in part because it is being rapidly deployed in many countries. Potential positive impacts on grid operation can include reduced network flows and hence reduced losses and voltage drops. Potential negative impacts at high penetrations include voltage fluctuations, voltage rise and reverse power flow, power fluctuations, power factor changes, frequency regulation and harmonics, unintentional islanding, fault currents and grounding issues. This paper firstly reviews each of these impacts in detail, along with the current technical approaches available to address them. The second section of this paper discusses key non-technical factors, such as appropriate policies and institutional frameworks, which are essential to effectively coordinate the development and deployment of the different technical solutions most appropriate for particular jurisdictions. These frameworks will be different for different jurisdictions, and so no single approach will be appropriate worldwide.
Integrated System Plan
AEMO, "Integrated System Plan," 2018.
Influence of the supply voltage on the performance of household appliances
  • J Descheemaeker
  • M V Lumig
  • J Desmet
J. DESCHEEMAEKER, M. V. LUMIG and J. DESMET, "Influence of the supply voltage on the performance of household appliances," in CIRED 23rd International Conference on Electricity Distribution, Lyon, France, 2015.
Grid connection of energy systems via inverters
Australian Standards. AS/NZS 4777.2:2015 Grid connection of energy systems via inverters. Part 2: Inverter requirements2015.