Renuga Verayiah

Bio: Renuga Verayiah is an academic researcher from Universiti Tenaga Nasional. The author has contributed to research in topics: Electric power system & AC power. The author has an hindex of 7, co-authored 30 publications receiving 179 citations. Previous affiliations of Renuga Verayiah include National University of Malaysia.

The Potential and Status of Renewable Energy Development in Malaysia

Abstract: The Malaysian Government has set an ambitious target to achieve a higher penetration of Renewable Energy (RE) in the Malaysian energy mix. To date, Malaysia has approximately 2% of its energy coming from RE generation sources compared to the total generation mix and targets achieving 20% penetration by 2025. The current energy mix for Malaysia power generation is mainly provided by natural gas and coal. The discussion will cover the traditional sources of generation including natural gas, coal and big hydro stations. In addition, the paper will cover in depth the potential of RE in the country, challenges, and opportunities in this sector. This study can give an initial evaluation of the Malaysian energy industry, especially for RE and can initiate further research and development in this area in order to support the Government target to achieve RE target of 20% by 2025.

A simplified approach in estimating technical losses in distribution network based on load profile and feeder characteristics

Abstract: This paper presents an approach to estimate technical losses of a large utility distribution network based on feeder load factor and feeder characteristics, such as feeder length, peak demand to installed capacity ratio, and load distribution profile along feeder. In this approach, feeders with different load distribution profile are modeled and simulated to establish generic peak power loss functions in three dimensions. A weighted average based on energy distribution along each feeder or network component (e.g distribution transformer) is then used to calculate the percentage technical losses for the whole network. The main advantages of this approach is it requires minimum set of input data which are commonly available in most utility distribution offices, while giving reasonably accurate results. The approach implemented with a spread sheet format is suitable for a quick energy auditing of existing distribution network technical losses as well as assessing sensitivity of distribution network efficiency to change in different network and load parameters.

A Three-Level Universal Electric Vehicle Charger Based on Voltage-Oriented Control and Pulse-Width Modulation

Abstract: Electric vehicles (EVs) could be used to address the issues of environmental pollution and the depletion of non-renewable energy resources. EVs, which are energized by a battery storage system, are becoming attractive because they keep the environment clean. Furthermore, the cost of EVs is becoming cheaper. Thus, EVs will become a significant load on utility distribution system in the future. EV chargers play a significant role in the expansion of EVs. The input current of an EV charger with a high total harmonic distortion (THD) and a high ripple distortion of the output voltage can impact battery life and battery charging time. Furthermore, the high cost and large size of the chargers are considered other issues in EV development. This work presents the complete design process of a universal EV charger with a special focus on its control algorithms. In this regard, a novel control algorithm based on the integration of voltage-oriented control (VOC) and the sinusoidal pulse-width modulation (SPWM) technique is proposed to ensure effective Levels 1, 2, and 3 battery charging. A simulation of the universal EV charger was conducted and assessed in MATLAB–Simulink. Moreover, a laboratory prototype was constructed with a TMS320F28335 digital signal processor (DSP) programmed as the controller to validate its operation and performance. The findings show that the proposed charger is able to provide a controllable and constant charging voltage for a variety of EVs, with an input current of low total harmonic distortion (THD) and an almost unity power factor.

Review of Under-voltage Load Shedding Schemes in Power System Operation

Abstract: A voltage collapse event is complex and localized in nature, but its effect is extensive. A vital effect of voltage collapse is total system collapse or blackouts, which will result in a significant loss to utility companies. Online monitoring of power system stability has thus become an important factor for electric power utilities. The final resort prevent the occurrence of a voltage collapse incident is the implementation of an under- voltage load shedding (UVLS) scheme. This paper focuses on the introduction of the UVLS scheme and presents an overview of the principles of the UVLS that are crucial to the design of such a protection scheme. This paper also presents the existing industrial practices and other research methods available to date. Streszczenie. W artykule opisano algorytm UVLS (Under Voltage Shedding Schemes) zastosowany do monitorowania stabilności systemu energetycznego I zapobiegania jego zapaściom. Artykul jest przeglądem metod stosowanych w praktyce oraz prac badawczych w tej dziedzinie. (Metody UVLS w zastosowaniu do monitorowania stabilności systemu energetycznego I zapobiegania jego zapaściom)

Fast-charging station deployment for battery electric bus systems considering electricity demand charges

Abstract: Battery electric buses (BEBs) are considered a promising alternative for bus fleets to alleviate the growing environmental problems in urban areas, and fast-charging technology has been introduced to BEB systems to help electric buses provide uninterrupted service without the need to carry a large onboard battery. The general consensus is that fast-charging may lead to high electricity demand charges, thus compromising the competitiveness of electric bus systems. However, a majority of current electric bus fast-charging station deployment models ignore these charges. The present study addresses this gap by explicitly considering the electricity demand charges in the optimal deployment problem of fast-charging stations for battery electric bus systems. The problem is formulated as a mixed integer linear programming model with the objective of minimizing the total cost of vehicle batteries, fast-charging stations, energy storage systems, and electricity demand charges. Numerical studies based on a real-world bus network in Salt Lake City, Utah, are conducted to demonstrate the effectiveness of the proposed model. The results show that the proposed model can effectively determine the deployment of fast-charging stations, the design of vehicle battery sizes, as well as the installation of energy storage systems. This study demonstrates that energy storage systems are a potential remedy for high demand charges from fast-charging.

Development and Application of a New Voltage Stability Index for On-Line Monitoring and Shedding

Abstract: Continuous assessment of voltage stability is vital to ensure a secure operation of the power system. Several voltage stability indicators have been developed in an attempt to quantify proximity to voltage collapse. Some of them are computationally expensive, whereas others are reported not to perform as expected under all conditions. This study proposes a new normalized voltage stability indicator called the P-index that is robust and based on solid theoretical foundations. The index was tested on the IEEE 14-, 57-, and 118-bus systems and compared to the well-established L-index node-based indicator. It was also shown how the P-index can be used to estimate distance to collapse and the amount of load to be shed. A comparison of distance to collapse was made with the coupled single-port circuit and tangent vector methods. Application of the P-index to a dynamic platform simulating stability monitoring with PMU measurements was performed on the Kundur 10-bus system and the appropriate load shedding using the P-index was calculated. The results show that the P-index gives a better indication of proximity to voltage collapse compared to the L-indices and tangent vectors and is more conservative than the coupled single-port circuit method. Results also indicate its potential for dynamic voltage stability assessment and load shedding purposes.

Optimization of electric bus scheduling considering stochastic volatilities in trip travel time and energy consumption

Abstract: This paper develops a vehicle scheduling method for the electric bus (EB) route considering stochastic volatilities in trip travel time and energy consumption. First, a model for estimating the trip energy consumption is proposed based on field-collected data, and the probability distribution function of trip energy consumption considering the stochastic volatility is determined. Second, we propose the charging strategy to recharge buses during their idle times. The impacts of stochastic volatilities on the departure time, the idle time, the battery state of charge, and the energy consumption of each trip are analyzed. Third, an optimization model is built with the objectives of minimizing the expectation of delays in trip departure times, the summation of energy consumption expectations, and bus procurement costs. Finally, a real bus route is taken as an example to validate the proposed method. Results show that reasonable idle times can be generated by optimizing the scheduling plan, and it is helpful to stop the accumulation of stochastic volatilities. Collaboratively optimizing vehicle scheduling and charging plans can reduce the EB fleet and delay times while meeting the route operation needs.