A new self-excitation scheme for three-phase synchronous generators

A new self-excitation scheme has been developed for three-phase synchronous generators. The generator that uses this scheme behaves as a flat-compound machine without automatic voltage regulators. The stator of the generator is provided with an armature winding that generates the fundamental and 2nd-harmonic mmfs. The rotor is equipped with a field winding and a harmonic winding. The harmonic winding is magnetically coupled to the 2nd-harmonic mmf produced by the armature winding. The current flows in the stator armature winding by way of a three-phase set of capacitors connected across its three-phase terminals and the ac voltage is induced in the rotor harmonic winding due to the armature 2nd-harmonic mmf. By connecting the harmonic winding to the field winding through a rectifier circuit, self-excitation of the generator is obtained. This excitation scheme is both self-excited and brushless, and no exciter is required. Additionally, voltage regulation due to load variation can be improved by connecting suitable capacitors. In this paper the operating principle and circuit configuration of the generator are explained and the experimental results using a 1-kVA prototype machine are shown. The generator characteristics are theoretically clarified by approximate analysis, and appropriateness of the theory and the usefulness of the proposed scheme are experimentally confirmed.     

Brushless self-excited three-phase synchronous generator without exciter

This paper describes principles together with analytic and experimental studies of an exciterless, brushless, and self-excited three-phase synchronous generator which was devised by authors. Since traditional brushless and dc self-excited three-phase synchronous generators without exciter did not have the self-exciting function by series characteristic component proportional to the load current inside the generator, they need auto-voltage regulating equipment or a transformer with three windings and condensers to obtain constant voltage characteristics. It also has the following problem in the case of two-pole traditional generator: oscillatory tension is generated at the shaft of the rotor caused by the magnetic force between magnetic poles of stator and rotor windings, and it causes mechanical vibration and noise. This paper proposes a new brushless and self-excited three-phase generator solving the aforementioned problems: the ratio of poles of the windings for providing power to load (armature and field windings) to the windings for supplying exciting power (stator and rotor exciting windings) is 1 to 5. Then oscillatory tension does not generate theoretically. Furthermore, a self-exciting three-phase generator using the 5th-harmonic component of armature reaction which makes series characteristic component proportional to the load current, currently is available. In this paper, the winding construction, the electric circuit, and the principle of the aforementioned generator are described, and the experimental results of the trial-produced generator show that the three-phase terminal voltage waveforms are almost sinusoidal and also balanced, and the voltage can be kept almost constant for the change of load. This generator has high reliability because of its simple construction.     

Fundamental characteristics of a brushless and self-excited sinusoidal-wave single-phase synchronous generator having a two-phase field winding excited by a half-wave rectified current

It is desired from the viewpoints of maintenance and construction to make single-phase synchronous generators of brushless and self-excited types. A novel brushless and self-excited single-phase synchronous generator was devised by one of the authors. The stator exciting current is made to flow simultaneously with the load current in the armature winding. Thus, the iron core for the magnetic circuit can be both for the synchronous generator itself and for the exciter. Experimental studies of the brushless and self-excited single-phase synchronous generator of which the rotor winding is used as a rotor exciting winding and a field winding are described in this paper. In the proposed generator, the rotor is provided with a balanced two-phase field winding to improve the voltage wave distortion. The terminal voltage of this generator can be kept constant in spite of the load variation. Therefore, the proposed synchronous generator can be expected to be used widely.     

新型混合励磁发电系统用无刷励磁机电磁性能分析

本文提出了新型混合励磁发电系统,它由混合励磁发电机、无刷励磁机和旋转整流器构成,其中混合励磁发电机转子由结构上独立的两部分——永磁体和电励磁组成,定子铁心沿轴向分为三段:永磁部分定子铁心、电励磁部分定子铁心以及中间部分定子铁心,其中中间部分定子铁心采用非导磁材料。新型混合励磁系统具有永磁电机高效、高功率密度的优点。本文仅针对新型混合励磁发电系统中的无刷励磁机进行分析,无刷励磁机结构与绕线式异步电机结构相似,定、转子均采用三相绕组,无刷励磁机的转子与混合励磁发电机转子同轴,转子绕组经固定在同发电机转轴上的二极管整流将交流变为直流,供给混合励磁发电机励磁。同时本文采用电磁场有限元法对无刷励磁运行机理和电磁性能进行分析,其中包括供电电源类型、定子电流特性和转矩特性等。本研究成果对掌握无刷励磁机运行特性具有重要作用。     

一种新型混合励磁同步发电机的两级式无刷励磁方法

针对切向/径向混合励磁同步发电机(tangential/radialhybrid excitation synchronous generators,T/R-HESG),提出了一种两级式无刷化自励方法。根据切向/径向混合励磁同步发电机的结构特点和磁路特性设计了两级式无刷化方法,实现了完全自励。同时,完成了励磁机的设计,通过对空载特性以及旋转整流器换相重叠角的研究,结合有限元仿真,优化了其结构,以保证励磁机与主发电机的匹配。对两级式无刷系统进行建模,通过整体仿真验证了该种方案的正确性。加工了一台基于T/R-HESG的两级式无刷励磁样机,测试了励磁机的电流放大特性、两级式无刷励磁系统的静态特性和动态特性,结果表明该两级式无刷发电机具有良好的工作性能。在航空航天、风力发电等领域有广阔的应用前景。     

核电站大型无刷励磁发电机转子温度测量方法分析

主要介绍了核电站百万千瓦级,不同无刷励磁方式下汽轮发电机组转子温度的测量方法。大亚湾核电站、岭澳一期核电站采用三机旋转励磁,通过在励磁机定子的磁极之间装设探测线圈,在励磁机转子轴上安装测量滑环,测量转子电压、电流得到转子温度。在正在建设的岭澳二期项目中,采用机端励磁变压器构成两机励磁系统,通过工厂实验数据和一定算法测量转子实时温度的新方法。该方法实现简单,无需额外装置,测量可靠性高,提高了发电机的安全运行水平,在我国积极发展核电的今天,具有一定的参考意义。     

新型无刷自励恒压输出三相同步发电机的研究

介绍一种新型无刷自励三相同步发电机。发电机的励磁电流是由电枢反应磁场的空间二次谐波所产生,无刷结构、自励磁,并且无需自动电压调节器,能在负荷变动情况下保持恒压输出。同时给出了1kW同步发电机的实验特性。     

转子绕组匝间短路故障谐波传递特征仿真

发电机转子绕组匝间短路时,其故障特征可以传递到励磁机励磁绕组上去。应用Matlab软件,对故障谐波传播效率受转子绕组感应电动势的幅值和频率的影响进行了仿真分析。     

Excitation scheme of brushless self-excited-type three-phasesynchronous machine

AC excitation schemes of a brushless self-excited-type three-phase synchronous machine are presented. The rotor field windings of the machine are short circuited with the diodes, and an exciter or other exciting equipment is not required in this machine. On the positive-phase-sequence rotating field of the stator, the plural rotating fields with different speeds from it are superimposed by using a machine-side voltage source PWM inverter/converter, and the field MMF is obtained by half rectifying AC voltages induced in the rotor field windings. Two excitation schemes are proposed that have the advantage of the reduction of the torque pulsation as compared with the scheme that superimposes the singular rotating field with a different speed from the positive-phase-sequence field. This is confirmed by simulation, and experimental results are given     

同步风力发电机无刷励磁系统设计

提出了无刷励磁同步风力发电机励磁系统设计方案,采用可控硅静止励磁装置向交流励磁机定子励磁绕组提供直流电,励磁机发出交流电经过旋转整流器供给风力发电机励磁。只需跟随风速变化,控制励磁机的励磁从而可以控制同步发电机的励磁,使得输出电压恒定。在额定风速以下,获得最大风能利用系数,额定风速以上,保证输出功率恒定。并提出了基于单神经元自适应PID控制算法的控制器设计,该系统具有可靠性高、抗干扰能力强、硬件简单和系统可扩展性强的特点。     

Use of multifield induction machine to determine the characteristics of self-excited generator systems at variable speed,constant voltage and constant frequency

This paper considers a generator system using variable energy such as wind power. The variable energy influences the voltage and frequency of a generator system. However, the load requires constant voltage and frequency. Therefore, this paper proposed that a generator system have the following good points:

• (1) This generator is a brushless system which makes use of the multifield induction machine;
• (2) Frequency converter of small capacity which is used for constant voltage and frequency in load at variable speed;
• (3) The PWM inverter can supply reactive power to the self-excited generator; and
• (4) Voltage wave of load is sine wave by LC filter of the frequency converter.

The multifield induction machines of this generator system have 4 poles and 8 poles similar to stator winding. The rotor of the multifield machine is especially cage type. This rotor can transform among the 4-pole field and 8-pole field on the stator. In this paper, an experimental study of the brushless, self-excited, constant voltage, constant frequency, variable speed and sine wave generator system by multifield induction machine is described. The component of this generator system, operation of multifield induction machine, characteristics of generator system, and the effect of LC filter in frequency converter are described.     

Electrical characteristics of a fully superconducting brushless generator equipped with a magnetic flux pump

The study of efficient excitation systems is important in order to enhance the potential of superconducting ac generators. We have fabricated a model machine for generating electricity with a brushless exciter system, which consists of a superconducting dynamo or “magnetic flux pump.” A fully superconducting generator in which both armature and field windings are made of superconductors has also been studied. The paper presents power output tests and calculated results on transients as well as the static electrical characteristics of a model machine equipped with a magnetic flux pump when operated as a fully superconducting brushless generator in persistent current mode. © 1997 Scripta Technica, Inc. Electr Eng Jpn, 120 (3): 64–72, 1997     

核电站大型无刷励磁发电机转子温度测量方法综述

核电站百万千瓦级无刷励磁方式下 ,汽轮发电机组转子温度测量可以有不同方法。其中有在三机旋转励磁时 ,通过在励磁机定子的磁极之间装设探测线圈 ,在励磁机转子轴上安装测量滑环 ,测量转子电压、电流得到转子温度的方法 ,以及对于机端励磁变压器构成的两机励磁系统 ,采取通过工厂实验数据和一定算法测量转子实时温度的新方法。     

基于双谐波绕组的混合励磁发电机励磁控制系统

为了解决不同运行工况下混合励磁同步发电机端电压恒定的问题,设计了一种基于全桥变换器拓扑的励磁控制系统。励磁系统采用以电枢绕组电压为外环、定子谐波励磁绕组电流为内环的双闭环控制策略,以谐波无刷混合励磁同步发电机端电压为反馈信号,通过调节定子谐波励磁绕组电流,以维持发电机端电压恒定。阐述了双谐波绕组的混合励磁发电机的基本结构和工作原理,设计了励磁控制系统的软硬件,并测试了励磁控制系统的性能。实验结果表明：调节定子谐波励磁绕组电流,可以很好的调节发电机的端电压;通过励磁控制系统的自动调节功能,实现了发电机在不同负载情况下的输出电压恒定。     

A new variable speed constant voltage controller for self-excited induction generator

A new variable speed, constant voltage controller for self-excited induction generator (SEIG) is presented in this paper. The proposed PWM controller regulates the induction generator (IG) terminal voltage against varying rotor speed and changing load conditions. This scheme does not require any real time computations and information regarding rotor speed for calculating the excitation current, thereby minimizing the electronic hardware and the cost of the controller. A simple, over-current protection is incorporated to protect the inverter switches. Computer simulation and experimental results show satisfactory operation of an induction generator with the proposed control scheme.     

2500kW高压无刷三相同步发电机

介绍了同步发电机的几种励磁方式和2500kW高压无刷三相同步发电机的无刷励磁系统。着重叙述了该发电机（包括主机，交流励磁机，旋转整流器，副绕组和恒压装置）的结构特点以及试验结果。     

基于免疫算法的无刷励磁发电机旋转整流器故障诊断

在大型发电机的无刷励磁系统中,旋转整流器承受着强大的离心力和电磁作用,故障发生率相对较高。采用旋转整流器故障时交流励磁机旋转电枢产生的谐波磁场在其定子励磁线圈中感应谐波电势的电磁特性,从中提取旋转整流器故障信号波形。运用傅里叶分解故障信号波形,对故障信号波形的特征值进行编码处理,并用免疫算法中的反向选择算法对傅里叶分解后的故障特征值进行计算,完成旋转整流器的故障诊断。利用人工免疫的反向选择算法,对一台15 kW无刷励磁同步发电机旋转整流器的短路与开路故障进行仿真诊断。仿真结果表明,基于免疫系统反向选择机制的人工免疫算法,与傅里叶分解算法相结合,进一步提高了无刷励磁同步发电机旋转整流器故障诊断的准确率,可达95%以上。     

同步风力发电机无刷励磁系统设计

分析了基于可旋转变换器的无刷励磁原理,提出了基于可旋转变换器的同步风力发电机无刷励磁系统的设计方案。旋转变换器的输入为直流电,经过全桥逆变电路和旋转变压器以后,将电能传递到旋转部分,再经过整流以后给同步风力发电机励磁绕组提供直流电。根据风速变化,控制励磁机的励磁从而可以控制同步发电机的励磁,使得输出电压恒定;在额定风速...     

改进的乒乓式转子接地保护在无刷励磁发电机中的应用

无刷励磁发电机通常采用单端注入式原理构成转子一点接地保护,针对该保护无法计算接地故障位置的问题,提出采用自动举刷方式改变转子绕组的引出方式(由固定负端引出变更为正负两端均引出),进而采用双端注入直流电压的乒乓式原理构成转子一点接地保护.给出了改进的乒乓式接地保护原理、接地电阻计算方法和保护动作判据,并采用Matlab/Simulink软件构建转子一点接地故障仿真模型.仿真试验结果表明,改进的乒乓式转子特地保护能够满足无刷励磁发电机实际运行需要的精度和灵敏度.     

Robust control of an isolated hybrid wind-diesel power system using Linear Quadratic Gaussian approach

This paper presents the application of the Linear Quadratic Gaussian (LQG) controller for voltage and frequency regulation of an isolated hybrid wind-diesel scheme. The scheme essentially consists of a vertical axis wind turbine driving a self-excited induction generator connected via an asynchronous (AC-DC-AC) link to a synchronous generator driven by a diesel engine. The synchronous generator is equipped with a voltage regulator and a static exciter. The wind generator and the synchronous generator together cater for the local load and power requirement. However, the load bus voltage and frequency are governed by the synchronous generator. The control objective aims to regulate the load voltage and frequency. This is accomplished via controlling the field voltage and rotational speed of the synchronous generator. The complete nonlinear dynamic model of the system has been described and linearized around an operating point. The standard Kalman filter technique has been employed to estimate the full states of the system. The computational burden has been minimized to a great extent by computing the optimal state feedback gains and the Kalman state space model off-line. The proposed controller has the advantages of robustness, fast response and good performance. The hybrid wind diesel energy scheme with the proposed controller has been tested through a step change in both wind speed and load impedance. Simulation results show that accurate tracking performance of the proposed hybrid wind diesel energy system has been achieved.