The direct starting of induction motors may cause various problems such as high inrush currents, voltage dips and harmonics. There have been numerous methods proposed to mitigate these stresses that are imposed on the power grid. This paper considers a starting method based on external rotor resistance control scheme that is used with wound-rotor induction machines. The so-called rotor-chopper-controlled topology is used to start an induction machine with maximum torque. The Automated state model generation (ASMG) algorithm is used to implement detailed switching model of the system in MATLAB/Simulink. Computer studies of a typical high power induction machine demonstrate that the machine start-up currents and the total energy consumption are significantly reduced while the induced electromagnetic torque is greatly increased with the rotor chopper controller applied.
Variable-voltage variable-frequency (VVVF) drives has been widely accepted by electrical and building services engineers. Electronic variable-frequency drives have been widely adopted in the area of heating, ventilation and air-conditioning (HVAC) applications and became the substantial energy consumption in both commercial and residential buildings. Since the speed of the single-phase compressor cannot be varied, it is either switched ldquoONrdquo, working at maximum capacity or switched ldquoOFFrdquo by a thermistor. The magnet-assisted reluctance motor driven compressor delivers an enhanced performance over conventional AC induction motor driven system, providing variable-speed operation as the temperature changes, while improving the overall energy efficiency. This paper aims to investigate the performance of both conventional single-phase induction motor and the most recent variable-frequency DC motor compressor drives for residential air-conditioning applications. Their cooling performance and harmonic distortions will be investigated and compared.
Estimating cost function of firms is very important in competitive electricity market. Complete information on the factors which can be used for estimating cost function is not definite and also is not accessible. The importance of cost function estimation is appeared when the independent system operator (ISO) decide to measure the market power which can be exerted by a market participant. In this paper a new method is applied for estimating cost function using observed bid information, weighted average prices and quantities in pay as bid auction in which each firm submit its prices and quantities. Wolakpsilas cost function estimation model which is in uniform pricing auction, is applied to Iranpsilas Electricity Market (IEM), where each genset submit its prices in ten increments which can be changed hourly, and quantities for producing in each load period. In this market, firmpsilas cost function is recovered by optimizing behavior for each firm. After defining the profit of the firm and using the first order conditions for expected profit maximization, the generalized method of moment (GMM) is used for estimating cost function. In estimation procedure, the firmpsilas cost function is obtained by using the weighted average prices, for computing the total revenue of each firm and the maximum accepted price, instead of market clearing price.
This paper presents a method to discriminate a temporary fault from a permanent one in an extra high voltage (EHV) transmission line so that improper reclosing of the line onto a fault is avoided. The fault identification prior to reclosing is based on optimized artificial neural network associated with standard Error Back-Propagation, Levenberg Marquardt Algorithm and Resilient Back-Propagation training algorithms together with Taguchi’s Method. The algorithms are developed using MATLAB software. A range of faults are simulated on EHV modeled transmission line using SimPowerSytems, and the spectra of the fault data are analyzed using fast Fourier transform to extract features of each type of fault. For both training and testing purposes, the neural network is fed with the normalized energies of the DC component, the fundamental and the first four harmonics of the faulted voltages. The developed algorithm is effectively trained, verified and validated with a set of training, dedicated testing and validation data respectively.
Single phase to three phase conversion is required to run the auxiliary machines of the AC locomotives of Indian railway. Both ARNO converter and static converters are used on Indian railway to convert single phase alternating supply to three phase alternating supply. This paper describes briefly the ARNO converter and static converter and their relative merits and demerits and then compares the Performance of ARNO converter and static converter provided on 25 KV, 50 Hz AC locomotive of Indian Railway. Annual saving and life cycle power saving by providing static converters is also calculated which prefers use of static converters on AC locomotives than ARNO converter.
This paper presents the industrial sector results of a study conducted for BC Hydro by a team of consultants led by Willis Energy Services Professionals. The study assessed the potential energy and peak demand savings over 20 years from existing technologies, emerging technologies, operations and maintenance and fuel switching. The study results guide strategic planning, program design and the DSM portion of BC Hydropsilas integrated electricity plan. They will also be used by stakeholder organizations in promoting conservation. The Conservation Potential Review (CPR) 2007 [1] estimates that there is enough economic savings potential in B.C. to flatten consumption. The conservation measures outlined in the CPR 2007 are estimated to require roughly half of the utility investment when compared to the investment required for new supply. The results of this study will help to ensure that British Columbiapsilas future energy needs will be met through cost effective and environmentally friendly conservation measures.
Accurate day-ahead electricity price forecasting (DEPF) has significant meanings in deregulated electrical power market due to its profitable function for all the participants to make reasonable decisions during the market business activities. However, the DEPF with satisfactory precision is difficult to be gained because of the violent volatility of electricity price caused by many factors. In this study, a multilayer perceptron artificial neural networks model is constructed for the DEPF in spot market of Nord Pool which is one of the most successful electrical power markets in the world. The major influencing factors are chosen by statistical methods called auto correlation function (ACF) and cross correlation function (CCF), and the standard error back-propagation algorithm is improved by using self-adaptive learning rate and self-adaptive momentum coefficient algorithm to make the training process more efficient both in global optimization and time saving. The most suitable structure of the network is determined by a trial-and-error experiment minimizing MAPE and MSRE of the network and several commonly used error indicators are employed to evaluate the goodness of fit performance of the model. The case study indicates that the DEPF of the proposed model is more reasonable and accurate, comparing with that of traditional ARIMA model.
This paper presents an innovative hybrid PWM technology, its corresponding structures and characteristics suitable for high voltage direct current transmission system based on voltage source converter (VSC-HVDC). The features of optimized PWM (OPWM) are presented and a new algorithm based on the theory of power sums for solving non-linear transcendental equations is introduced. The properties of 3rd harmonic injection SPWM are also presented. The working mechanism and configuration of the hybrid PWM are discussed in detail. The features of mode detector (the key building block) are also presented. A two terminals VSC-HVDC transmission system is simulated by the simulation software PSCAD/EMTDC linked to Matlab/Simulink, demonstrating the good performances of this new hybrid PWM technology. The theory analyses and simulation results show that this new hybrid PWM technology has great potentiality in the application of VSC-HVDC projects in future.
A parallel AC/DC power system with long distance and heavy capacity will be formed till 2010 in southern China power grid. In simulation program BPA, machine-electric transient model of HVDC is used, which is not proper for unsymmetrical fault. To verify its distortion under unsymmetrical fault and its validity under' symmetrical fault, quasi steady state model and electromagnetic transient model of Yun-Guang UHVDC are respectively established, and dynamic characteristic such as DC power,DC current and voltage of converter bus are simulated and analyzed under unsymmetrical and symmetrical disturbance, which provides reference for the operation and simulation for Yun-Guang UHVDC-AC hybrid system.
This paper describes a major research initiative by British Columbia Institute of Technology for the construction of an Intelligent Micro Grid on its campus in Burnaby, BC, Canada.
Demand Side management (DSM) is considered a strategic solution in the new power system. DSM is now divided in to demand response and energy efficiency. Home electrical appliances are a good target for energy efficiency projects. One of the most important factors in these kinds of projects is the high participation factor which is gained through guiding the ordinary customers to select the efficient appliance or optimal appliance. This optimality should be defined and must consider both the electric utilities and customerpsilas considerations, and in the same time it must be easy to understand for the ordinary customers, so a new index to measure these hybrid characteristics should be designed. In this paper an easy to understand but precis index is proposed which considers all the technical aspects of an appliance energy standard and the important considerations of electricity utility and customer in the same time. In the end the index is calculated for some home electrical appliances in Iran.
This paper presents a calculation method of customer outage costs using customer damage functions. In this study, two large power substations of the Provincial Electricity Authority (PEA) of Thailand that supply a number of industrial customers are selected. Nhong-Pling (NPL) substation located in Siam Industrial Land (SIL) industrial real estate that supplies 6 distribution feeders, and Navanakorn III (NVC) substation located in Navanakorn Industrial real estate that supplies 8 feeders in the central region of Thailand are surveyed for the outage cost study. Subsequently, the customer damage functions are derived from survey data via on-site interview during years 2006-2007. They are piecewise linear functions, and each interval contains two parameters that represent outage cost per momentary interruption, and outage cost per duration. Therefore, such functions can be used for outage cost assessment of industrial customers, when power interruption records are available. As a result, the distribution feeders of the case study can be prioritized for maintenance planning and reliability improvement.
St. Clair curve provides a simple means for estimating power transfer capabilities of transmission lines. It concerns three limiting factors: thermal limit, voltage quality (or drop) limit, and angular stability limit. This paper illustrates the influence of voltage stability limit and presents an extended loadability curve. Moreover, the impacts of line resistance and shunt compensation on line loadability are investigated.
This paper proposes a methodology to benchmark lighting energy consumption for new building design or new lighting systems in existing buildings. The influences of electric lighting, daylighting and the lighting control system are evaluated for every building zone. This methodology uses the installed lighting power density, the area of the daylit and non-daylit sections and the effective operational times during daytime and night-time for each building zone.The calculations (based on the German standard DIN 18599 and the North-American standard ASHRAE-IESNA 90.1) allow a trade-off of the energy consumption between different technical areas such as lighting, heating and cooling. The energy consumption of these different technical areas can be compared enabling the user to monitor the influence of different choices (e.g. installing a different technical system). This methodology forms the basis for the lighting trade-off compliance path of the Canadian Model National Energy Code for Buildings (MNECB).
This paper presents a stochastic model for optimal generating unitspsila restoration planning. Restoration plans will be performed based on different objectives i.e. total system risk, total served energy in the period of restoration, and total restoration time. The proposed model is a multi objective stochastic program in which generating unitspsila restoration plan is assumed to optimize different kinds of objective function. The proposed approach to the optimal restoration of generating units can be used by vertically integrated utilities as well as the ISOs in electricity markets. The approach coordinates the optimal start up of generating units within the restoration period. Physical constraints of generating units and power system restoration constraints are taken into account. The proposed approach highlights a trade-off between different objectives of power system restoration. A simple system is used for detailed analyses and simulation results exhibit the effectiveness of the proposed restoration approach.
BC Hydro has conducted an adaptive lighting pilot project in an office building in Burnaby, British Columbia, Canada. Adaptive lighting refers to an intelligent lighting system equipped with integral sensors and actuators that allow the system to dynamically adapt to the needs of individual occupants. This project aimed at quantifying the achievable energy savings. The installation on multiple floors of the BC Hydro Power Smart offices included long-term monitoring of the lighting systempsilas performance and evaluation of the occupantspsila satisfaction with the lighting system and their work environment. The intent of this pilot project was to evaluate the potential of deploying the system to the utilitypsilas other office facilities and to demonstrate energy efficient technologies to the utilitypsilas customers. This paper discusses the project findings that resulted in significant energy savings compared to conventional, statically controlled lighting systems commonly used in an office environment.
Nowadays in deregulated electricity markets, forecasting becomes more and more important. Accurate estimating price is the most essential task and the basis for any decision making and developing biding strategies. In this paper Artificial Neural Network (ANN) is applied to forecast electricity price. ANNs have been used successfully in many forecasting applications recently. Historical data of weighted average prices in electricity market that cleared with pay as bid settlement rule and also forecasted electricity demand are used to train neural networks (NN) model. The data for historical electricity prices are considered by two criterion of temperature and load in order to improve training. Data are categorized in to two seasonal parts of warm and cold days and also they are categorized by three loads level of low, normal and peak. To support better accuracy of estimating prices six different NN architectures are modeled for combination of the criterions, the NN also selected electricity prices of similar days in previous year. In the end, the results of forecasting prices of ANNs are compared with the results obtained from regression model. There is confirmed that, AANs have better performance comparing to traditional method in forecasting electricity prices.
Different power generation schemes have been developed all over the world to cater the hotel load requirements of the train. Indian railway uses end-on generation (EOG) scheme for meeting the hotel load requirements of superfast Shatabdi Express Trains. This paper describes briefly EOG scheme and its drawbacks. A novel approach of head end power (HEP) for feeding the hotel load requirements is also presented, which utilizes power of overhead catenary through a traction transformer. A static converter of 500 KVA is recommended to be provided in generator car (by removing one DG set) converting single phase to three phase supply. Life cycle power saving and pay back period of static converter is also calculated which prefers to implement HEP scheme than EOG scheme on Shatabdi Express Trains.
This paper presents the measured impedance by a distance relay in the presence of Thyristor Controlled Series Compensator (TCSC), one of the series connected FACTS devices, on a transmission line, considering its Metal Oxide Varistor (MOV) operation, in the case of inter, phase to phase and three phase, faults. The measured impedance at the relaying point is affected by the power system structural conditions, pre-fault loading, and the fault resistance, as well as the presence of TCSC. In addition to TCSC compensation degree and MOV operational mode, TCSC installation location also affects the measured impedance. The variation of the ideal tripping characteristic due to TCSC compensation degree, MOV operational mode, and its installation location would be investigated.
