Impact of hybrid FACTS devices on the stability of the Kenyan power system

Flexible alternating current transmission system (FACTS) devices are deployed for improving power system’s stability either singly or as a combination. This research investigates hybrid FACTS devices and studies their impact on voltage, small-signal and transient stability simultaneously under various system disturbances. The simulations were done using five FACTS devices-static var compensator (SVC), static synchronous compensator (STATCOM), static synchronous series compensators (SSSC), thyristor controlled series compensator (TCSC) and unified power flow controller (UPFC) in MATLAB’s power system analysis toolbox (PSAT). These five devices were grouped into ten pairs and tested on Kenya’s transmission network under specific contingencies: the loss of a major generating machine and/or transmission line. The UPFC-STATCOM pair performed the best in all the three aspects under study. The settling times were 3 seconds and 3.05 seconds respectively for voltage and rotor angle improvement on the loss of a major generator at normal operation. The same pair gave settling times of 2.11 seconds and 3.12 seconds for voltage and rotor angle stability improvement respectively on the loss of a major transmission line at 140% system loading. From the study, two novel techniques were developed: A performance-based ranking system and classification for FACTS devices

Fault clearance and transmission system stability enhancement using unified power flow controller

Abstract: Fault current introduces voltage and reactive power imbalances which are major problems in power systems. This study shows the ability of Unified Power Flow Controller (UPFC) to clear a single line to ground fault and improves transmission system stability. The device under review is one of the most advanced classes of Flexible Alternating Current Transmission System (FACTS) devices. A 30-bus transmission line system is modelled with MATLAB/Simulink software. Two cases were simulated to evaluate the performance of UPFC. In Case 1, the 30-bus network system is modelled and simulated without a compensating device whilst Case 2, the system is modelled with UPFC. The system models are designed to have a single line to ground fault with resistance 0.010Ω and ground resistance of 0.001Ω occurring at bus 1. The fault is expected to cause instability in the system and be cleared after 0.04s in both cases. The simulated results of the two cases were compared to determine the performance of UPFC in improving the voltage stability and power profile of the system. The results show that UPFC has the ability of stabilizing voltage and power profile of transmission system. The study has thus, increased insight on the use of the device in transmission system stability and control

Do energy-pollution-resource-transport taxes yield double dividend for Nordic economies?

With the policy performance of the Nordic countries especially from the aspects of energy security, energy equity, and environmental sustainability, this study provides more in-depth on the performance of the countries’ disaggregated environmental taxes. To examine the greenhouse gas emission and energy intensity effects of energy tax, pollution tax, resource tax, and transport tax alongside controlling for the role of employment rate and gross domestic product over the period 1995–2020, empirical tools such as the method of moments quantile regression, short- and long-run cointegration, and Granger causality approaches were utilized. Importantly, there are series of interesting results from this investigation. Firstly, the result posits the feasibility of Green growth in the panel of Nordic countries while a significant and negative nexus between GDP and energy intensity was also established. Secondly, also from the panel result, we found that only energy tax significantly mitigates both emissions and energy intensity across the quantiles while pollution tax and resource tax exacerbate emissions and energy intensity. Thus, for the panel case, only energy tax could validate the double dividend hypothesis. Thirdly, the result revealed that double dividend hypothesis and by large extent co-benefit is achievable with pollution and resource tax policies in Finland but in the short-run. Similarly, pollution, resource, and transport tax policies in Sweden are all desirable for achieving both environmental and economic benefits in the short-run. However, there is no valid evidence to support the validity of double dividend hypothesis in Denmark and Norway. Lastly, we found a one-way Granger causality from GDP, energy tax, resource tax, and transport tax to greenhouse gas emission while a one-way Granger causality also exists from GDP, energy tax, and transport tax to energy intensity. Overall, compelling policy dimensions are inferred from the investigation.© 2022 The Authors. Published by Elsevier Ltd. This is an open access article under the CC BY license (http://creativecommons.org/licenses/by/4.0/).fi=vertaisarvioitu|en=peerReviewed

Optimal dispatch for a microgrid incorporating renewables and demand response

Abstract: Please refer to full text to view abstrac

A novel approach for the identification of critical nodes and transmission lines for mitigating voltage instability in power networks

Abstract: Voltage collapse is a major issue combating the effectiveness and optimal operation of modern power systems in recent times. This has been a great threat to the security and the reliability of a modern power system and has been a growing concern to power system engineers, researchers and the utilities recently. A prompt identification of the sets of transmission lines whose outage could lead to a cascading failure and the sets of nodes where voltage collapse could erupt is therefore a vital issue for a reliable and secure power system operation. An alternative approach to solving these problems is therefore presented in this paper. The problem is viewed from the graph-theoretical perspective, considering the topological properties of the networks. Application of the fundamental circuit theory is employed and the Bus-to-Line matrix (BLM) is formulated. This matrix provides insights about the interconnections of the components within the network. This valuable information is captured and used for identifying the critical elements where a suitable location for reactive power support could be placed to avoid voltage collapse of the network. The effectiveness of the proposed approach is tested using a simple 10-bus power network. The results obtained are compared with that obtained from the existing approaches. The results obtained show a strong correlation and agreement and proved the efficiency of the proposed approach

A robust energy and reserve dispatch model for prosumer microgrids incorporating demand response aggregators

Abstract: The uncertainty introduced by intermittent renewable energy generation and prosumer energy imports makes operational planning of renewable energy‐assisted prosumer microgrids challenging. This is due to the difficulty in obtaining accurate forecasts of energy expected from these renewable energy sources and prosumers. Operators of such microgrids therefore require additional grid‐balancing tools to maintain power supply and demand balance during grid operation. In this paper, the impact of demand response aggregators (DRA’s) in a prosumer microgrid is investigated. This is achieved by developing and solving a deterministic mathematical formulation for the operational planning of the grid. Also, taking a cue from CAISO’s proposed tariff revision which allows the state‐of‐charge of non‐generator resources (like storage units) to be submitted as a bid parameter in the day‐ahead market and permits scheduling coordinators of these resources to self‐manage their energy limits and state‐of‐charge, the proposed formulation permits prosumers to submit battery energy content as a bid parameter and self‐manage their battery energy limits. Furthermore, a robust counterpart of the model is developed. Both formulations are constrained mixed integer optimization problems which are solved using the CPLEX solver in Advanced Interactive Multidimensional Modelling System (AIMMS) environment. Results obtained from tests carried out on a hypothetical prosumer microgrid show that the operating cost of the microgrid reduces in the presence of DRA’s. In addition, the storage facility owner may benefit from self‐managing its energy limits, but this may cut the amount of grid‐balancing resource available to the microgrid operator, thereby increasing the operating cost of the microgrid

A mathematical formulation of the joint economic and emission dispatch problem of a renewable energy-assisted prosumer microgrid

Abstract: Operational planning of prosumer microgrids with solar and wind energy sources is quite a complex task considering the intermittency of these sources and energy import/export from prosumers. Reserve capacities which can be reliably provided by dispatchable sources like conventional generators (CGs) may be needed to ensure reliability of the grid. However, these sources produce emissions which have adverse effects on the environment. Hence, emission curtailment should be incorporated in the operational planning of microgrids with these generators. In this paper, a mathematical formulation for the joint economic and emission dispatch of a renewable energy-assisted prosumer microgrid is presented and solved using the CPLEX Solver in Advanced Interactive Multidimensional Modelling System (AIMMS). A modified microgrid test system is used as a case study in this work. Results show that incorporating an emission function in the objective of the operational dispatch formulation not only reduces emissions, but could be of advantage to customers as larger capacities of their behind-the–meter resources get the chance to provide grid ancillary services; however, it also puts a restriction on the profit that could be made from selling energy to the main grid during periods when energy prices are high

IoT-based smart water network management challenges and future trend

Abstract: In recent years, internet of things (IoT)-based tech- nology has been deployed to different areas of water supply system. This is in line with the Smart Water Network Manage- ment (SWNM) initiative, that aims to propose a methodology to improve operational performance and monitoring of water supply systems. In the smart water network management applications, IoT-based technology is facing quite a few challenges. In this paper, we present IoT’s applications for monitoring the water supply network with emphasis on its application to water quality and leakage monitoring. In these applications, the technical challenges of IoT-based technology are also discussed. Finally, future research directions in this domain are also highlighted, which may be useful for further studies

Exploring the driving factor on prepaid electricity meter rejecting the largest township of South Africa

Abstract: Technology rejection phenomenon manifests itself differently across different societies. Over the past two decades, low income households in Soweto have persistently rejected prepaid electricity meters. Until now, the basis of the rejection in the region remains scientifically underexplored. We therefore conduct an exploratory study of pertaining prepaid meter rejection in Soweto. Through triangulation research and survey approach, 88 households based in Orlando East and Diepkloof were interviewed by means of a questionnaire. Our findings show that three aspects contributing to this phenomenon, namely: lack of quality consultation and education, the high levels of electricity consumption, and unattainable politically motivated promises are the main reasons that currently fuel prepaid meter rejection. We emphasise that the current state of the Free Basic Electricity (FBE) (2003) policy also fuels rejection, as it remains socio-economically inadequate and irrelevant for indigent households. We therefore note the need for an FBE policy review and update as well as the establishment of a policy monitoring committee to ensure implementation and enforcement

Temporal analysis of electricity consumption for prepaid metered low and high income households in Soweto, South Africa

Abstract : This study explores the temporal trend in electricity consumption since the introduction of prepaid meters in low income households of Soweto, and compares the findings with high income households. Monthly electricity consumption data (over 96 months: 2007-2014) on 4427 households in Soweto, for both low and high income households, was collected from Eskom. Using a simple linear model to analyse consumption trends in low income households, we ascertain that electricity consumption has decreased by 48% since the inception of prepaid meters. Nonetheless, it is noted that 60% of household incomes are spent on electricity bills, which is way above the threshold set for energy poverty. Comparatively, high income households consume lower electricity than low income households do. Overall, the prepaid meter programme is producing expected results for Eskom but remains a challenge for low income households, which are still entrenched in energy poverty. We call for an energy policy that is tailored for each income groups and the formulation of laws and policies to protect the energy vulnerable households