Swee Peng Ang

Modeling charging demands of various types of electric vehicles in an actual distribution system

Developing an elaborate load model for electric vehicles (EVs) charging is of great importance. First, analysis about the charging behaviors of five types of EVs is carried out based on survey results. Subsequently, a smart charging strategy which not only takes into account the user behaviors but also considers the real-time electricity price, is presented to regulate the charging behaviors of EVs by providing economic incentives. Considering the uncertainties of the charge price, the robust optimization model for smart charging is then developed and AMPL/CPLEX, a highly efficient commercial solver, is employed to obtain the optimal charging plan. Finally, a typical Hangzhou distribution system is employed to illustrate the efficiency of the proposed model. The results show that the existing distribution network can accommodate EVs more efficiently by employing the proposed decentralized smart charging strategy in comparison with the uncontrolled charging strategy.

Characterization of electric and magnetic fields near residential and industrial areas in brunei darussalam

Transmission lines near residential areas radiate electric and magnetic fields (EMF) which create cancer disease in the human health. Measurement of electric and magnetic fields are very important near high voltage transmission lines. EMF have been measured near residential and industrial areas using EMDEX II equipment. An empirical relationship between the electric field with the lateral distance and magnetic field with the lateral distance have been developed for both areas. The determination of coefficients for residential area in case of electric and magnetic fields are found to be 0.98 and 0.99 respectively.

Investigation of the role of void sizes for failure of high voltage bushing

This paper presents the investigation of the root causes of the high voltage bushing failure in a Power Station which occurred on July 12, 2015 in Brunei Darussalam. Upon physically examining the burning parts of the bushing, a computer simulation was carried out to analyze the contribution of void sizes towards the failure of bushing. COMSOL Multiphysics software was used for the analysis. For simulation, an actual diagram of the high voltage bushing was drawn using the Autodesk Inventor. Different scenarios with the presence of 1 mm and 1.5 mm diameter void sizes were considered in the XLPE insulation part of the high voltage bushing. Considering different depths of 1 mm, 5 mm and 11 mm, respectively, simulation results were obtained for void sizes with full, 50% less and without oil insulations. The simulation results showed that the bushing failure occurred due to oil leakage and different sizes of voids. It was also summarized that the physical inspection could help in predicting and preventing high voltage bushing failure in the future.

Transmission system planning considering integration of renewable energy resources

The penetration level of renewable energy generation has been increasing in some actual power systems, and hence introduces some new problems and even challenges for transmission system planning. In modern transmission system planning, it is necessary to consider the accommodation capability of renewable energy generation, in addition to the traditional requirement for power system reliability. Given this background, a bi-level transmission system planning model is presented for this purpose with transmission investment costs, load shedding costs, abandoned wind power costs as well as relevant operating constraints considered. In the upper level, the objective is to minimize the sum of annual investment cost and the expected value of annual economic loss of shedding load and wind energy abandoned for given scenarios. In the lower level, the objective is to minimize the sum of economic loss of shedding load energy and wind energy abandoned for each scenario. These two levels are implemented interactively and iteratively, and the optimal transmission system planning scheme will ultimately be attained. The upper level model is described as a mixed-integer optimization problem, and solved by the well- established particle swarm optimization algorithm; the lower level model is formulated as a linear programming problem, and solved by the linear programming solver ILOG CPLEX. Finally, the essential characteristics of the proposed models and adopted algorithms are demonstrated by a modified 18-bus sample power system.

A settlement method for inter-provincial electricity trading employing a modified transmission loss rate

In the current practice in China, electricity trading among various province is generally governed by relevant provincial governments, in the form of electricity contracts negotiated by two trading parties. The currently employed inter-provincial electricity trading mode and settlement method in China Southern Power Grid (CSG) are first introduced in this paper, and two main issues of the current settlement method are analyzed: 1) the issue of negative settled transmission loss rate when significant discrepancy occurs between actual electric quantity and dispatching plan; 2) the inapplicability for the increasing number of participants along with the promotion of direct power purchase by large consumers. To address these issues, a method based on a modified transmission loss rate for inter-provincial electricity trading settlement is proposed and compared with the currently employed one. Simulation results with actual trading data show the feasibility of the proposed method.

An energy acquisition model for an aggregator considering demand responses

An aggregator undertakes multiple tasks in smart distribution network such as energy trading, grouping and providing market access to demand response (DR) resources, coordinating EV charging, efficiently controlling smart appliances of consumers and communicating with the distribution system operator (DSO). In this context, a bi-level linear programming model is established for an aggregator of day-ahead energy acquisition in a smart distribution system with DR into consideration. The outer-level simulates the decision-making process of an aggregator who endeavors to maximize its profit by optimal energy acquisition and flexible energy consumption strategy. The decision-maker of the innerlevel is DSO, who takes the responsibility for the economic dispatch of the distribution system and determines load interruptions systematically. A highly efficient commercial solver CPLEX is utilized in the MATLAB environment to solve the developed model. Finally, a modified IEEE 33-bus distribution system is employed to demonstrate the essential features of the developed model and method.

A data-mining-based system design for cost management and control of power transmission and transformation project

Monitoring, managing and controlling the cost of a power transmission and transformation project (PTTP) plays an essential role in meeting the growing power demand and achieving the sustainable power project construction development. A model of cost management and control system for PTTP on the basis of the data mining theory is addressed. Seven tiers are designed to collect cost information, compile and store data, analyze the project costs and correct their deviations. These tiers specifically generate topology diagrams between all the factors giving rise to a fluctuation of the cost, analyze the correlation of factors, predict the cost, and raise several deviation-corrected proposals to users. A 110kV substation project is employed to demonstrate the proposed approach, in terms of the data deduction in three periods, including the budgetary estimation (BE), settlement and post evaluation. This system demonstration consists of price forecast by means of the well-established back-propagation neural network, price fluctuation tracking and cost analysis.

OPNET-based performance analysis of the communication network in a charging station of electric vehicles

Electric vehicles (EVs) will play an important role in the future smart grids. In order to implement the charging/discharging optimization and control for numerous electric vehicles, a large amount of data will be generated and transmitted. The communication of vast information imposes a significant challenge to the performance of the communication network in a charging station of EVs. Given this background, the characteristics of different types of data are analyzed first. Then, simulations of the communication network in a charging station of EVs are carried out by employing the optimized network engineering tool (OPNET). Simulation results demonstrate that giving a higher priority to the important data is helpful for maintaining the normal work of charging/discharging when the code rate of the video monitoring information is high. In some scenarios, establishing a dedicated network for transmitting video monitoring information is a better option.

Impacts of initial flux on transformer ferroresoance modes

A ferroresonace circuit consists of a voltage source, a capacitor and a nonlinear inductor connected in series. The initial flux in transformer core plays an important role on the onset of different types of ferroresonance modes. In this paper, the likelihood of the onset of sustained fundamental mode ferroresonance under the influence of the initial flux is investigated. The flux linkage, the voltages across the transformer and the voltage across the series capacitor are investigated by using Matlab toolbox. The initial results are presented and then verified with the simulation results obtained from ATP software. The results between them are found in good agreement.