In this paper, the price elasticity of electricity demand, representing the sensitivity of customer demand to the price of electricity, has been estimated for South Australia. We first undertake a review of the scholarly literature regarding electricity price elasticity for different regions and systems. Then we perform an empirical evaluation of the historic South Australian price elasticity, focussing on the relationship between price and demand quantiles at each half-hour of the day.This work attempts to determine whether there is any variation in price sensitivity with the time of day or quantile, and to estimate the form of any relationships that might exist in South Australia. (C) 2011 Elsevier Ltd. All rights reserved.

The paper proposes a novel method of forecasting short-term electricity price based on a two-stage hybrid network of self-organised map (SOM) and support-vector machine (SVM). In the first stage, a SOM network is applied to cluster the input-data set into several subsets in an unsupervised manner. Then, a group of SVMs is used to fit the training data of each subset in the second stage in a supervised way. With the trained network, one can predict straightforwardly the next-day hourly electricity prices. To confirm its effectiveness, the proposed model has been trained and tested on the data of historical energy prices from the New England electricity market.

This paper aims to develop a load forecasting method for short-term load forecasting, based on an adaptive two-stage hybrid network with self-organized map (SOM) and support vector machine (SVM). In the first stage, a SOM network is applied to cluster the input data set into several subsets in an unsupervised manner. Then, groups of 24 SVMs for the next day's load profile are used to fit the training data of each subset in the second stage in a supervised way. The proposed structure is robust with different data types and can deal well with the nonstationarity of load series. In particular, our method has the ability to adapt to different models automatically for the regular days and anomalous days at the same time. With the trained network, we can straightforwardly predict the next-day hourly electricity load. To confirm the effectiveness, the proposed model has been trained and tested on the data of the historical energy load from New York Independent System Operator.

This paper aims to study the short‐term peak load forecasting (PLF) by using Kohonen self‐organizing maps (SOM) and support vector regression (SVR). We first adopt a SOM network to cluster the input data set into several subsets in an unsupervised learning strategy. Then, several SVRs for the next day's peak load are used to fit the training data of each subset in the second stage. In the numerical experiments, data of electricity demand from the New York Independent System Operator (ISO) are used to verify the effectiveness of the prediction for the proposed method. The simulation results show that the proposed model can predict the next day's peak load with a considerably high accuracy compared with the ISO forecasts. © 2006 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.

Power electronic transformer (PET) is a new type of transformer, which realizes voltage transformation and power delivery in a power system through power electronic conversion. This paper aims to apply PET to power system and propose a new coordinated control strategy to improve the system stability by a generator-PET unit. We first develop a power system model with a generator-PET unit, and then propose a new optimal coordinated PET and synchronous generator excitation control strategy. Simulation results demonstrate that the proposed controller is superior to the conventional approaches in terms of dynamical performances for a variety of disturbances. Compared with the conventional generator-transformer unit equipped with AVR+PSS controller, the optimal coordinated controller can improve the system damping and voltage characteristics effectively.

This paper studies the design of the heat sinking in 6kV/2.5kW variable frequency drive system.Forced air cooling technology is applied in the drive system.Based on the calculation of power losses,the heat sinks are designed ac-cording to the relation between power losses and temperature rise.The scheme of air conduit is presented,which include:front air intake,sealed wind cavity and back air outtake.Each heat sink is joined into the close wind cavity separately.The experiment results show that the heat sinking is satisfied.

According to the power characteristics of PET(Power Electronic Transformer),an ap-proach to improving power system dynamic characteristics with PET is proposed. The secondary side of PET is connected with the transmission line and its primary side with an infinite-bus system,and it can be equivalent to a controllable voltage source. A mathematical model of the power system with generator excitation and PET is established,in which the power angle,angular velocity and terminal voltage are state variables and the excitation voltage of generator,amplitude and phase-angle of the controllable voltage source are control variables. An optimal coordinated control strategy for the generator excitation and PET is deduced. Simulation shows that,the rapid power exchange and bi-directional power flow between PET and system occur increases system damping and suppresses system oscillation under disturbances. This project is supported by Natural Science Foundation of Hubei Province(2001ABB026).

An optimal coordinated control strategy between generator and VSC HVDC system is proposed in this paper. In the studied system, a generator is connected with infinite bus through parallel AC lines and VSC HVDC. The simulation results show that both the generator and the VSC HVDC system can be recovered rapidly from minor or severe disturbance, and the control strategy is robust to the parameter variety of power system. Simulation are also conducted when the generator and VSC HVDC system are controlled independently. The simulation results also show that the system has much better dynamic responses with the proposed coordinated control strategy than that with the independent control

The operation principle of electronic power transformer is analyzed in this paper. Then the control scheme is proposed to achieve application of electronic power transformer in the distribution systems. The results of the simulation show: on the one hand, the effectiveness of the control scheme is validated. And the other hand, electronic power transformer can not only realize the conventional power transformer's functions of transformation, isolation and energy transmission, but also prevent from sags, swells, flickers, harmonics and unbalance infecting the voltage of the load, and avoid load chocking infecting the primary system.

IGCT单独使用时可以不用缓冲电路.但是6 kV及以上高压变频器需要将IGCT串联使用以获得更高的耐压水平.此时,IGCT需要并联缓冲电路才能安全工作.为设计6 kV高压变频器串联吸收电路,通过对IGCT特性进行分析,给出了设计IGCT缓冲电路的具体方法,通过试验验证吸收电路的工作效果.

A three-phase four-wire distribution system electronic power transformer(EPT) implemented with the input stage,isolation stage and output stage was presented and its load characteristics were analyzed.A simple and appropriate control was developed to obtain good characteristics based on analyzing the demand of the primary system and the loads.In this control scheme the dual-loop decouple control in synchronous rotating d-q frame was adopted in the input stage and the dual-loop control based on voltage instantaneous value was introduced in the output stage.The load characteristics of the electronic power transformer were investigated in detail by simulations under Matlab/Simulink.The results show that the EPT has good performances with the proposed control scheme under balance and imbalance loads,which makes the input current sinusoidal and keeps the load voltage in normal value.

Power Electronic Transformer (PET) is a new type of transformer, which realizes voltage transformation and power delivery in the power system through power electronic conversion. The authors research the coordinated control of Generator-PET unit in power system. Firstly a mathematical model of power system constituted by generator-PET units is built, on this basis a new optimal coordinated control strategy for generator-PET unit is proposed by use of optimal control theory, where the control variables are defined as the generator excitation voltage, the modulation index and phase angle of pulse width modulation of the voltage source converter (VSC) in primary and secondary sides of PET while the feedback variables are power angle, angle velocity, voltage at generator terminals and DC bus voltage of PET. Simulation results show that compared with the power system constituted by traditional generator-transformer units equipped with auto voltage regulator (AVR) and power system stabilizer (PSS) controller, the proposed coordinated controller can effectively improve the system damping and voltage characteristics under disturbances.

SummaryA real-time optimal excitation controller (RTOEC) is proposed in this paper. The identifier in the RTOEC can properly identify the system parameters by the nonlinear least squares method. Thus a new optimal feedback matrix can be calculated in real-time from the identification results and the disturbances in the system. So the RTOEC can track quickly the operating status of the generator and always provide optimal control. Simulation studies carried out on the Three Gorges 700MW hydropower generator show that the RTOEC can provide good performance over a wide range of operating conditions and improve the static and transient stability of power system effectively. Additional informationNotes on contributorsFan ShuFan ShuFan Shu received his B.S. and M.S. degrees in Department of Electrical Engineer, from Huazhong University of Science and Technology (HUST), in 1995 and 2000 respectively. Presently he is working for his Ph.D. degree in HUST. His research interests are power system operation and intelligent control system.Mao ChengxiongMao ChengxiongMao Chengxiong received his B.S., M.S. and Ph.D. degrees in electrical engineering, from HUST, Hubei China, in 1984, 1987 and 1991 respectively. He was appointed as visiting scholar at University of Calgary, Canada from 1989 to 1990, at Queen’s University Belfast from 1994 to 1996 and at Technische University Berlin from 1996 to 1997. Presently, he is a professor of HUST. His fields of interest are power system operation and control, the excitation control of synchronous generator and applications of high power electronic technology to power systems.Lu JimingLu JimingLu Jiming received his B.S. degree from Shanghai Jiaotong University, and received his M.S. degree from HUST. His research is focused on the excitation control based on microcomputer.O.P. MalikO.P. MalikO. P. Malik received the National Diploma in electrical engineering from Delhi Polytechnic, Delhi, India, the M.E. degree in electrical machine design from Roorkee University, Roorkee, India, the Ph.D. degree in electrical engineering from the University of London, London, U.K., and the D.I.C. degree from Imperial College, London, U.K., in 1952, 1962, and 1965, respectively.In 1974, he became a Professor in the Department of Electrical and Computer Engineering, University of Calgary, Calgary, AB, Canada, and is presently a Professor Emeritus there. He has performed research in collaboration with teams from Russia, Ukraine, China, and India. In addition to his research and teaching, he has served in many additional capacities at the University of Calgary including Associate Dean Academic/Student Affairs and Acting Dean of the Faculty of Engineering.

A neural network optimal excitation controller based on system identification (NNOEC) for multi-machine power system is proposed in this paper. In this NNOEC, a neural network is used to adjust the optimal feedback gains according to the state variables of the generator in real-time. So the controller can be adapted to the changed operating conditions of the power system and the optimal control is always given. To simplify the design of the controller in multi-machine system, a non-linear least square identification method is proposed to identify the parameters of the system. Thus the training samples for the neural network can be calculated from the identification results and the disturbances in the system. The simulation results in a three-machine power system are show that the designed NNOEC can provide good control performance under various operating points and different disturbances.

分析了电流互感器10%误差特性曲线测试原理、数据处理方法和基于最小二乘法曲线拟合技术绘制误差特性曲线的相关算法.根据测得的数据,求出最优拟合模型,再绘制该特性曲线,并通过微型打印机打印该曲线.采用多项式拟合曲线,可以发挥其便于计算和分析的优点,能够更好地反映电流互感器10%误差特性,使用方便.

Power electronic transformer (PET) is a new type power transmission device, which realizes voltage transformation and power delivery through power electronic conversion. In this paper, a new PET control strategy based on single-generator infinite system is presented. Simulations based on MATLAB/Simulink are carried out, and the results show that the proposed controller can improve the system stability effectively under different disturbance. 

EPT (Electronic Power Transformer) is a new type of transformer,which realizes voltage trans-formation and power delivery in power system through power electronic conversion. The main principle of EPT is described and simulation of a new EPT scheme is carried out,in which its steadystate characteristic and dynamic characteristic in four conditions are involved. Simulative results show that EPT guarantees good voltage and current waveforms in both primary and secondary sides and has good control performance. It can be used as a new regulating device of power quality for its regulating function.

分析和讨论了电力电子变压器(PET)的基本理论和实现方案,并提出了两种新的拓扑结构.仿真研究表明,PET可保证原副方良好的电压、电流波形,并具备良好的控制特性.

The simplified circuit models of both common mode current loop an d leakage current loop for the output cable of PWM(Pulse Width Modulation)volt age source inverter have been in-troduced.Its principle of voltage reflection and its capacitance effect on the motor are analyzed in detail.For effectively eliminating the bad impact of the output cable,a topological structure of LRC filter is presented and its principle of parameter selection is given.Based on a topological structure of6kV/2250kW motor fed by24-pulse rectifier thr ee-level inverter,the simulative study is done for the presented topology of t he filter and the long cable of various lengths,using Matlab’s simulation tool s.The relevant simulation waveforms are presented.

An optimal coordinated excitation and SMES (Superconducting Magnetic Energy Storage) controller is proposed in this paper. In the analysis, the voltage source SMES system is considered as a controllable voltage source whose magnitude and phase can be changed rapidly, and the system model for the design of the optimal coordinated controller is established. Then optimal coordinated control for generator excitation and SMES is deduced. In the proposed controller, the control variables are the excitation voltage, the magnitude and phase angle of the controllable voltage source. Simulation results show that the proposed controller can provide good control performance under different disturbances, improve the system transient stability effectively.