Masters Degrees (Electrical and Electronic Engineering)

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A comprehensive methodology for impact assessment studies of energy storage systems on low voltage distribution feeders
(Stellenbosch : Stellenbosch University, 2020-12) Rhoda, Courtney; Bekker, Bernard; Stellenbosch University. Faculty of Engineering. Dept. of Electrical and Electronic Engineering.
ENGLISH ABSTRACT: This research investigates the technical impacts of energy storage systems (ESSs) on low voltage (LV) residential feeders. A critical literature review on the existing impact assessment methodologies informs on the requirements of an efficient methodology that ensures the accurate and detailed assessment of feeder performance under ESS penetration. Based on the review’s findings, a comprehensive stochastic-probabilistic methodology is proposed that directly accounts for the unpredictability in customer behaviour and the subsequent impact on the diversity and variability in simulation inputs and outcomes of load flow analysis (something that most impact assessment methodologies do not adequately account for). The proposed methodology makes use of the Monte Carlo Simulation method as a stochastic simulator to simulate the uncertainty in the feeder placement of ESSs, and the Herman-Beta extended algorithm to solve the probabilistic load flow analysis. This proposed methodology can be used to assess the hosting capacity of radial LV distribution feeders to increasing penetrations of ESSs. The simulation results, from detailed and comprehensive input modelling, can provide helpful and more accurate and representative information to distribution network planners and policymakers, than simplified methodologies.
The Coordination and control of smart inverters utilizing Volt-VAr and Volt-Watt in low voltage networks, and opportunities for South Africa
(Stellenbosch : Stellenbosch University, 2022-04) Xavier, Ria; Bekker, Bernard; Stellenbosch University. Faculty of Engineering. Dept. of Electrical and Electronic Engineering.
ENGLISH ABSTRACT: Increasing photovoltaic (PV) penetration in the low-voltage (LV) distribution network leads to grid-interconnection issues for electric utilities. These issues include voltage violations, equipment overloading and frequency instability. To mitigate these problems, advanced smart inverter functionality is becoming increasingly popular in states and countries with high renewable energy penetration levels. Although smart inverters have a wide range of benefits for the utility, these benefits are limited to the local level due to autonomous inverter control. This research investigates the benefits of coordinated inverter control in mitigating voltage violations in LV feeders due to increasing PV penetrations. A critical literature review on the grid interconnection requirements and smart inverter functionality guidelines informs on the gaps that need to be addressed to allow for increased smart inverter deployment in South Africa. The literature review also explores the benefits of distributed energy resource management systems (DERMS) and virtual power plants (VPPs), and the requirements for each platform. Based on the literature review’s findings, a simulation has been conducted to investigate the benefits of coordinated smart inverter voltage regulation control, particularly Volt-VAr and Volt-Watt, to increase hosting capacity in LV networks. The proposed methodology considers the feeder-wide voltage conditions instead of local point of connection (PoC) conditions using sensor measurements, and the fairness of voltage regulation and active power curtailment among customers on a feeder. This proposed methodology can be used as an intermediate solution for coordinating smart inverters without the use of extensive communication infrastructure and advanced aggregating platforms. The simulation results show an improvement in voltage profiles using coordinated Volt-VAr and Volt Watt inverter control and feeder-wide awareness. The improved voltage profiles can accommodate higher levels of PV penetration and thus increase hosting capacities in LV feeders.
Incorporating short-term operational constraints into long-term generation planning: a Namibian case study
(Stellenbosch : Stellenbosch University, 2023-03) Mouton, Daniello; Bekker, Bernard; Stellenbosch University. Faculty of Engineering. Dept. of Electrical and Electronic Engineering.
ENGLISH ABSTRACT: Namibia possesses an abundance of natural energy resources that have the potential to be used for electricity production. At present, Namibia does not have enough generation capacity to meet its electricity demand. The Namibian Ministry of Mines and Energy thus published the National Integrated Resource Plan in 2016 with a view to meet 100% of its peak load demand and at least 75% of its energy demand through internal or local sources. This study is motivated by three key issues identified in the Namibian generation expansion plan contained in the National Integrated Resource Plan, namely: (1) challenges presented by an increased amount of variable renewable energy present in Namibia’s power system; (2) the sole use of traditional reliability metrics such as Loss of Load Probability and Expected Unsupplied Energy; and (3) the absence of any flexibility assessment of the proposed power system. This study hypothesises that the sole use of conventional reliability metrics in long-term generation expansion planning does not guarantee adequate flexibility in power systems with high shares of variable renewable energy. The flexibility constraints of the power system are also considered with a view to test the hypothesis, which is necessary in the context of the three aforesaid key issues. To this end, this study makes use of emerging generation planning techniques, including Flexibility Assessment Methods, that are capable of ensuring better evaluation of operational reliability. By simulating the Namibian power system within the context of the recently published National Integrated Resource Plan, the hypothesis is proven, and this study concludes that the sole use of conventional reliability metrics in Namibia’s long-term generation expansion plan does not guarantee adequate flexibility in its power systems that has a high share of variable renewable energy.
Investigating probabilistic techniques for calculating the system capacity in the South African transmission network
(Stellenbosch : Stellenbosch University, 2024-03) De Bruyn, Johannes; Bekker, Bernard; Dalton, Amaris; Stellenbosch University. Faculty of Engineering. Dept. of Electrical and Electronic Engineering.
ENGLISH ABSTRACT: he large-scale introduction of variable renewable energy (VRE) generators to existing power systems, which were predominantly designed for centralised and dispatchable generation, comes with capacity and stability planning challenges. Academic literature suggests that these challenges are not sufficiently addressed using traditional power system analysis and modelling methods. Many research papers therefore call for the adoption of more statistically sophisticated methodologies that can more adequately describe the uncertainties inherent to variable renewable energy resources. Probabilistic load flow techniques especially have been found to provide a more nuanced representation of the capacity of a power system to host additional generation. This study sets out to prove the hypothesis that using a simplified probabilistic load flow methodology for calculating system capacity would more comprehensively clarify the constraints associated with hosting VRE in the South African transmission network. It does this by developing and applying such a methodology to the Northern Cape transmission network based on similar methodologies in literature. The probabilistic methodology is compared against results gained from a deterministic system capacity analysis also applied to the same portion of the transmission network. Two significant concerns regarding probabilistic analyses are the relatively long solution times and extensive data requirements. Literature suggests that simplifying network representations with equivalent circuits could reduce both while maintaining an acceptable level of accuracy. This study included a brief analysis of these claims by reducing the transmission network model to only the Northern Cape using Ward equivalents for the rest of the system and comparing the power flows in the full and simplified system under various conditions. The results showed that equivalent circuits can reduce solution times considerably without introducing significant errors when care is taken in setting up the internal and external networks. This study further showed that deterministic scenario analyses do not consistently, when seasonal variations are introduced, predict the extreme behaviour of power systems unless a large number of scenarios are considered. Probabilistic system capacity analyses on the other hand were consistent in providing the likely and extreme loading states of the Northern Cape. Recommendations for future studies are the expansion of the methodology presented to include calculating the hosting capacity of the South African system probabilistically to determine whether current deterministic methods are overly conservative in their estimations. Another study would be identifying edge-case scenarios for deterministic analyses in the current South African power system.
The potential of photovoltaics and battery energy storage to address declining electricity price margins within South African municipalities
(Stellenbosch : Stellenbosch University, 2024-03) Rhode, Aiden; Nicholls, Christo; Bekker, Bernard; Stellenbosch University. Faculty of Engineering. Dept. of Electrical and Electronic Engineering.
ENGLISH ABSTRACT: This thesis explores the impact of Photovoltaic (PV) and Battery Energy Storage Systems (BESS) interventions in both municipal and private entity contexts on the municipal Electricity Price Margin (EPM). The research journey begins with a comprehensive literature review that provides various NERSA regulated tariff-setting methodologies such as benchmarking, for ensuring the sustainability of regulated municipal electricity businesses. It also investigates the challenges faced by municipalities, particularly concerning their electricity margins. By establishing the extent of the electricity price margin problem, the study highlights the potential applications of Distributed Energy Resources (DERs). To ensure a holistic investigation, a case-study design was adopted to investigate the potential of PV and BESS to address declining electricity price margins. This consisted of utilising PV and BESS interventions to reduce municipal cost of supply by means of implementing energy arbitrage and demand reduction strategies. The use of Homer in conjunction with Excel allowed for the sizing, simulation, and financial analyses of PV and BESS intervention in a municipal and private context. Two case studies were designed for municipal PV and BESS design and analyses to establish the impact the respective technologies could have on the municipal EPM. A third case study was introduced for designing and analysing the impact private BESS could have on private operations and the municipal EPM. The results of the simulations done in the case studies highlight the following: PV and BESS interventions can improve municipal EPM. However, given the base case EPMs of 36.17% and 43.76%, the interventions investigated within the case studies were unsuccessful in improving municipal EPM to the desired NERSA EPM benchmark. Even though the PV and BESS interventions improved municipal EPM to similar degrees, the analyses highlighted the importance of investigating the financial feasibility of the various interventions. A noteworthy result was that private ownership of BESS marginally improved municipal EPM but contrastingly reduced municipal electricity sales revenue. System sizing and ownership of the interventions as well as the tariff structure are critical factors to the improvement of EPM. Future research should explore the technical analysis of applicable intervention integration into distribution networks, the influence of different funding models, and the effectiveness of addressing additional NERSA performance indicators.
A probabilistic estimation of the capacity of solar PV SSEGs installed on a LV feeder network
(Stellenbosch : Stellenbosch University, 2020-03) Waswa, Lewis; Bekker, Bernard; Chihota, Justice; Stellenbosch University. Faculty of Engineering. Dept. of Electrical and Electronic Engineering.
ENGLISH ABSTRACT: Increased solar photovoltaic (PV) installation on to the grid has led to increased technical challenges in electricity network operations. These challenges mainly stem from the design structure of the grid, which only allows unidirectional power flow. This results in several challenges including violation of voltage limits, tripping of network protection systems and distribution line overloads among other issues. These challenges are mainly restricted to the distribution networks, as most solar PV small-scale embedded generators (PV SSEGs) are connected to the distribution networks, whose conditions are, in most cases, not remotely monitored. This results in increased challenges experienced by the networks in terms of network planning, distribution network operations, maintenance, regulation and grid control. To manage these challenges, the distribution operator needs to estimate the total capacity of solar PV installed on the distribution network, in addition to how much of that capacity is embedded in the network’s net demand, which is important in determining the condition of the network at any particular time. Several methods have been used to estimate the capacity of solar PV SSEGs installed in an area. Most studies apply remote sensing and computer vision algorithms to count the number of solar PV panels found in an area. Analysis of these studies indicate that the results obtained cannot be used in determining the condition of the network as they only determine the capacity of solar PV in an area. Secondly, disaggregation studies have largely been used to quantify the installed solar PV capacity embedded in the net demand of a feeder or network. These methods assume a multi-variable approach which requires multiple inputs that are not readily available. This study introduces a novel probabilistic method that applies Monte Carlo methods to quantify the solar PV SSEGs embedded in the net demand of a low voltage feeder. Historical demand, net demand and the solar PV output is used to determine the solar PV capacity embedded in the net demand of a feeder. The accuracy of the method is tested using simulated net demand and actual measured net demand metered from households connected on carefully selected feeders. Results demonstrate that the method performs well where the historical demand and the net metered demand are obtained from similar customer classes. Therefore, it is concluded that it is possible to estimate the capacity of solar PV SSEGs embedded in the net demand obtained from a feeder by analysing and comparing the net demand of that feeder and the historical demand of a similar customer class feeder.
Valuation of pumped storage in capacity expansion planning – a South African case study
(Stellenbosch : Stellenbosch University, 2022-04) Van Dongen, Caroline; Bekker, Bernard; Stellenbosch University. Faculty of Engineering. Dept. of Electrical and Electronic Engineering.
ENGLISH ABSTRACT: On the South African grid, pump storage schemes offer a range of benefits which can assist in the integration of increased variable renewable energy generation. The Integrated Resource Plan for South Africa currently proposes adding gas turbines and batteries to the future grid for peaking capacity and increased flexibility, with no added pump storage schemes. This thesis investigates the value of the services and contributions pumped storage provides the grid, the capital costs and history of this technology in order to determine its potential future role. The research aims to address the possible misconception of limited pump storage scheme site availability by providing an overview of site feasibility studies, including estimated cost projections and utilises these values in an energy optimisation model to investigate the economic case for pump storage.

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Browsing Masters Degrees (Electrical and Electronic Engineering) by browse.metadata.advisor "Bekker, Bernard"

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