Minimum/maximum excitation limiter performance goals for smallgeneration

Small generators connected to the electric utility system often act as followers as they tend to follow power system bus voltage variations. For the lack of kVA capacity, small machines tend to be susceptible to becoming over or underexcited (excessive VArs in or VArs out of the generator) as the voltage regulator tries to maintain its setpoint with variations in system bus voltage. Minimum and maximum excitation limiters are utilized to limit the voltage regulator characteristic response to system bus voltage changes, that can otherwise result in machine overheating and/or pulling out of synchronization. This paper reviews the operating performance of minimum and maximum excitation limiters used on small machines, and provide the user typical performance expectations. The examples shown by the authors highlight both main field and exciter field applications     

Verification of limiter performance in modern excitation controlsystems

Modern excitation systems include devices for controlling or limiting machine terminal voltage (overvoltage limiters), volts per hertz ratio (V/Hz limiters), maximum machine field current (overexcitation limiters), and the reactive load absorbed by the machine (underexcitation limiters). Functional testing of these limiters before they are placed into commercial service is recommended. The Bureau of Reclamation (USA) routinely performs functional testing to determine the actual settings and operational characteristic of these limiters as part of excitation system commissioning tests on its hydroelectric generators. This paper discusses the purpose and practice of functionally testing these limiters     

An adaptive generator excitation controller based on linear optimalcontrol

An adaptive excitation controller for a synchronous generator based on the linear optimal control theory is proposed. The generator operating conditions are tracked by a model whose parameters are identified every sampling interval using the actual input and output of the generator. The control is computed by solving a third-order Riccati equation and the identified model parameters. Studies on a single-machine infinite-bus system and a three-machine infinite-bus system show that the proposed controller exhibits better performances than an automatic voltage regulator (AVR) with a conventional power system stabilizer (PSS)     

Robust controller design for generator excitation systems

This paper deals with the design and evaluation of a robust controller for generator excitation systems to improve the steady-state and transient stabilities. The unique approach used is to first treat the nonlinear characteristics of the system as model uncertainties, and then to take into account such uncertainties at the controller design stage using a robust control methodology. The performance of the controller has been evaluated extensively by nonlinear simulation. It is concluded that the robust controller provides better damping to the oscillatory modes of the system than the conventional PSS in all the cases studied     

Co-ordinated control of synchronous generator excitation and staticVAR compensator

The application of multivariable control to a synchronous generator excitation and static volt-ampere reactive (VAR) compensator system is described to design a coordinated excitation and firing angle discrete controller. It is based on a reduced-order linearized model, obtained by system identification, which represents the nonlinear dynamics around a specified operating point. The model structure was investigated by simulation studies indicating that a third-order representation was suitable. Direct comparisons of identified model responses with corresponding results from the nonlinear model show that accurate modeling can be achieved by this approach. Quantitative assessments also established that the models are satisfactory. The controller was evaluated by simulation of a nonlinear generator model, involving comparisons between the coordinated controller with several different controllers, over a wide range of operating conditions and disturbances. It is shown that the coordinated control arrangement can provide better stability, voltage control, and damping than the other schemes     

交流辅助发电机励磁调节器的设计

给出NJ1型交流传动内燃机车辅助发电机励磁调节器主电路及控制电路主要元器件的选择及确定.该调节器采用了新型电力半导体器件IPM.     

燃气轮发电机数字式励磁控制系统

本文介绍了用于燃气轮发电机的数字式励磁控制系统的原理及运行中出现问题的解决方法。     

Transient performance of an isolated induction generator underunbalanced excitation capacitors

This paper presents transient performance of a stand-alone self-excited induction generator (SEIG) under unbalanced excitation capacitors. An approach based on a three-phase induction machine model is employed to derive dynamic equations of an isolated SEIG under unbalanced conditions. The neutral points of both a Y-connected excitation capacitor bank and Y-connected stator windings of the SEIG is connected together through a neutral line. Experimental results obtained from a laboratory 1.1 kW induction machine driven by a DC motor are also performed to confirm the feasibility and effectiveness of the proposed method     

A novel stand-alone dual stator-winding induction generator with static excitation regulation

On the basis of the new idea of electric power integration, a novel stand-alone dual stator-winding induction generator (DWIG) system is built. In this generator, there are two sets of windings to be embedded in the stator slots. One, referred to as the 12-phase power winding, supplies power to the dc load via a 12-phase bridge rectifier, and the other, called the 3-phase excitation winding, is connected to a pulsewidth modulation (PWM) voltage source static excitation regulator (SER). A solid iron squirrel cage rotor is suitable for high speed generation. Experiments and simulations show the ac capacitors can reduce the inductance of rectifier loads and help to reduce the capacitance of the SER. A simple control methodology based on stator voltage orientation (SVO) is presented to regulate the output voltage of the 12-phase bridge rectifier in this paper. Moreover, the electric energy quality and the relative influence factors are studied by detailed experiments and analyses. The proposed system is especially suitable for self contained electrical systems, such as those found on electric vehicles, ships, and aircraft, where high performance and compact size are essential.     

ANN based pattern classification of synchronous generator stabilityand loss of excitation

The paper presents a novel artificial intelligence-based neural network (ANN) pattern classification and online detection scheme for a single machine infinite bus system. The proposed online relay and dynamic pattern classifier utilizes specific frequency spectra of the hyperplane discriminant vector of machine rotor angle, speed, accelerating power, instantaneous power, voltage, and current using either a perceptron single layer detection scheme or a two layer feedforward ANN for online classification and detection of fault condition causing first swing transient stability or loss of excitation. Other relay binary outputs include fault type and allowable clearing time identification. The detection accuracy is improved by utilizing the cross spectra of discriminant vector input variables correlations. The proposed pattern classification technique can be extended to interconnected multimachine power systems by using relative rotor angles, frequency deviations, tie-line powers, and their cross spectra variables     

石泉水电厂3号发电机组励磁系统改造

对石泉水电厂3号发电机组励磁系统由原来的直流励磁机励磁改造为广州电器科学研究所的FJL型静止式励磁装置励磁的改造过程、经验进行了总结,并对新励磁系统的构造、性能和功能进行了主要介绍。     

A fault warning for inter-turn short circuit of excitation winding of synchronous generator based on GRU-CNN

Synchronous generators are important components of power systems and are necessary to maintain its normal and stable operation.To perform the fault diagnosis of mild inter-turn short circuit in the excitation winding of a synchronous generator,a gate recurrent unit-convolutional neural network (GRU-CNN) model whose structural parameters were determined by improved particle swarm optimization (IPSO) is proposed.The outputs of the model are the excitation current and reactive power.The total offse...     

A novel excitation scheme for a stand-alone three-phase induction generator supplying single-phase loads

This paper presents the operating principle and steady-state analysis of a novel excitation scheme for a stand-alone three-phase induction generator that supplies single-phase loads. The phase windings and excitation capacitances are arranged in the form of the Smith connection and the excitation scheme is referred to as the SMSEIG. In addition to providing the reactive power for self-excitation, the capacitances also act as phase balancers. With this novel excitation scheme, isolated single-phase loads can be supplied with good phase balance in the induction machine, resulting in high efficiency, large power output, and quiet machine operation. Performance analysis is based on the method of symmetrical components, from which the input impedance of the generator can be determined. Numerical solution of a simplified equivalent circuit for the machine variables, namely the excitation frequency and magnetizing reactance, enables the generator performance to be evaluated for any load and speed. With the aid of a phasor diagram, the conditions for achieving perfect phase balance are deduced and a method to compute the capacitances required is developed. Experimental investigations on a 2.2-kW induction machine confirm the feasibility of the SMSEIG.     

Design of a thermoelectric generator with fast transient response

Thermoelectric modules are currently used both in Peltier cooling and in Seebeck mode for electricity generation. The developments experienced in both cases depend essentially on two factors: the thermoelectric properties of the materials that form these elements (mainly semiconductors), and the external structure of the semiconductors. Figure of Merit Z is currently the best way of measuring the efficiency of semiconductors, as it relates to the intrinsic parameters of the semiconductor: Seebeck coefficient, thermal resistance, and thermal conductivity. When it comes to evaluating the complete structure, the Coefficient of Performance (COP) is used, relating the electrical power to the thermal power of the module. This paper develops a Thermoelectric Generator (TEG) structure which allows minimising the response time of the thermoelectric device, obtaining short working cycles and, therefore, a higher working frequency.     

Damping of torsional oscillations using excitation control ofsynchronous generator: the IEEE Second Benchmark Modelinvestigation

A simple lead-lag excitation controller using generator shaft speed deviation (Δω) as a feedback signal to damp all of the IEEE Second Benchmark Model, system-1 torsional oscillations is presented. In order to stabilize all the torsional modes, modal control theory is used to determine the parameters of the dynamic output feedback controller. Various degrees of series compensation, different loading conditions, and torsional mode shapes for a torsional oscillations study are also investigated. In addition, time-domain simulation using a nonlinear system model are examined to demonstrate the effectiveness of the proposed countermeasure under torque disturbance conditions     

贴在墙上的发电机

目前，石油价格节节上升，使得像美国、日本、中国等石油进口大国经济受到一定的影响。因此，寻找替代品成了这些国家的一项国策。在美国，太阳能发电、潮汐发电、垃圾发电、甚至利用火鸡的废料发电等一一上马，并且取得了一定的成就。其后，五花八门的新能源研究齐头并进，光伏发电就是很受人们推崇的清洁能源。那么，“发电机”是怎么贴到墙上的呢？     

基于风电机组无功响应速度的风电场闪变研究

针对风电机组无功响应速度对风电场并网点电压闪变的影响,从风力发电机组特性出发,基于DIg SILENT建立了含风电机组的电网仿真模型,研究风速波动时风机无功响应速度对风电场并网点电压波动与闪变的影响。算例结果表明:风电机组无功响应速度对并网点电压闪变的影响程度与系统短路容量密切相关,加快风电机组无功响应速度能有效抑制风电场并网点的电压闪变。     

基于垂直轴风力机的盘式永磁电机的试验研究

随着永磁材料的发展,盘式永磁发电机的技术突破,基于盘式发电机的小型垂直轴风力发电机重新得到重视。设计出双外转子中间定子的盘式永磁发电机,安装在Φ型风力机下端,利用风洞实验室进行不同风速下的试验研究,试验得到无负载与蓄电池负载下的2组数据。数据表明,盘式发电机应用在Φ型垂直轴风力机中,启动性能不理想,但在风力机启动后功率可以很快达到额定功率,故在启动性能好组合式垂直轴风力发电机具有良好适用性。     

Comparison of the response of doubly fed and fixed-speed induction generator wind turbines to changes in network frequency

Synchronous and fixed-speed induction generators release the kinetic energy of their rotating mass when the power system frequency is reduced. In the case of doubly fed induction generator (DFIG)-based wind turbines, their control system operates to apply a restraining torque to the rotor according to a predetermined curve with respect to the rotor speed. This control system is not based on the power system frequency and there is negligible contribution to the inertia of the power system. A DFIG control system was modified to introduce inertia response to the DFIG wind turbine. Simulations were used to show that with the proposed control system, the DFIG wind turbine can supply considerably greater kinetic energy than a fixed-speed wind turbine.