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.     

Characteristics of a self-excited induction generator at constant voltage and constant frequency under speed change

A self-excited wound-type induction generator, excited by capacitor, which changes its speed as a wind generator and can be used as a separate small power source, is described. The voltage and frequency of this generator change in accordance with the capacitance C of capacitor, generator speed and loads, and the like. The constant-voltage generator with constant C is achieved by returning the secondary power of the induction generator to the primary source through a converter, an inverter, and a transformer, and controlling the inverter control angle. But the frequency changes slightly. In order to eliminate frequency variation under constant C, a constant-frequency source such as synchronous generator or a constant-frequency generator is connected to the primary or secondary side of the transformer and operated in parallel. Constant voltage and constant frequency are achieved in spite of the change of generator speed and load. The characteristics resulting from these various measures are compared. The constant-frequency generator is better than the synchronous generator in terms of life, maintenance, and the like. In parallel operation with the constant-frequency generator connected to the primary or the secondary side of the transformer, various characteristics at constant voltage and commercial frequency are compared and analyzed. © 1997 Scripta Technica, Inc. Electr Eng Jpn 119(1): 90–100, 1997     

Basic characteristics of a self-excited induction generator under secondary excitation at constant voltage

A self-excited wound-rotor induction generator excited with a capacitor can be used as an independent source for small-capacity wind power generator. With constant excitation capacitance, the secondary-circuit power of the induction generator is returned to the primary circuit through a converter, an inverter and a transformer; the power is controlled at the inverter so that the generator voltage is always maintained constant in spite of the changes of generator speed and load. The basic characteristics of the generator under the above conditions are analyzed. The fundamental waves of both the main circuit and the feedback circuit are determined. Using these results, the equations for various portions of the generator are derived, the performance characteristics of the generator are then analyzed and compared with experimental results.     

双PWM变频器励磁的变速恒频风电系统

采用双PWM变频器作为双馈感应发电机(DFIG)变速恒频风力发电系统的励磁电源,分析了发电机的数学模型及系统的控制策略.网侧变换器采用电网电压定向控制策略,以保持直流电压稳定和网侧单位功率因数运行,实现能量的双向流动.转子侧变换器采用定子磁链定向控制策略,以实现最大风能捕获和定子无功功率的调节.在Matlab/Simu...     

Double-fed induction generator control for variable speed wind power generation

Vector control of a doubly fed induction generator drive for variable speed wind power generation is described. A wound rotor induction machine with back-to-back three phase power converter bridges between its rotor and the grid forms the electrical system. The control scheme uses stator flux-oriented control for the rotor side converter bridge control and grid voltage vector control for the grid side converter bridge. A complete simulation model is developed for the control of the active and reactive powers of the doubly fed generator under variable speed operation. Several studies are performed to test its operation under different wind conditions. A laboratory test setup consisting of a wound rotor induction machine driven by a variable speed dc motor is used to validate the software simulations.     

兆瓦级变速恒频风力发电机组控制系统

基于定子磁链定向的双馈电机控制理论，采用双PWM变换器结构，完成了兆瓦级变速恒频双馈风力发电机组的控制系统。其网侧变换器采用电压电流双闭环控制策略，转子侧变换器并网前采用转子电流开环控制策略，并网后采用有功、无功电流闭环解耦控制策略。该系统完成了亚同步、超同步运行时的系统满载实验以及模拟风速变化情况时系统有功、无功功率解耦控制的实验。实验结果验证了控制系统的可行性。     

无刷双馈风力发电机空载试验问题探讨

针对无刷双馈变速恒频风力发电系统空载特性试验中出现的电机转速突增、突减甚至快速停机,以及与双馈发电机控制绕组相联的变频器滤波电容奇异击穿甚至爆炸等一些在普通电机中非常少见的特殊现象和问题,从交流电机的基本理论出发,阐述了无刷双馈风力发电机的变速恒频原理、空载特性试验的测量方法,分析了此类问题与现象存在的根源,给出了若干建议和注意事项。     

Self-regulated self-excited brushless three-phase synchronous generator

For lightweight and compact implementation of a generation set, many attempts have been made by some researchers to develop a brushless self-excited synchronous generator without an ac exciter. A previous paper proposed a novel self-excitation scheme by which the second-space harmonic component of armature mmf is used for exciting the rotor field system. In this excitation scheme the effect of the series excitation characteristic, as well as a self-excited and brushless implementation without an ac exciter is automatically obtained. However, in the case of system configuration of the generator already reported, voltage regulation in the inductive load condition was very large. To remove this problem, this paper presents a new system configuration of the generator with a self-regulating feature that can compensate voltage regulation automatically. The new generator consists of a stator installing two three-phase windings, externally connected to a load and a capacitor bank, respectively, and a rotor with field and harmonic windings. In this paper the system configuration and theoretical concepts of the presented generator are described and detailed experimental investigations with a laboratory machine are also shown.     

开绕组无刷双馈风力发电机直接功率控制容错策略

针对无刷双馈发电机提出了一种控制绕组采用开绕组拓扑(OW-BDFG)的馈电方案,将三相控制绕组两端打开分别连接变流器构成双两电平变流器(D-TLCs)馈电拓扑,对机侧变流器功率器件IGBT因故障切除后的容错控制策略进行深入分析,提出了功率偏差比较直接功率控制(PEC-DPC)的D-TLCs电压空间矢量优化方案。对比分析了8/4极25 kW样机的仿真及实验结果,表明：当机侧变流器1个或2个IGBT被切除后,所提OW-BDFG的PEC-DPC仍可实现变速恒频、最大功率点跟踪及单位功率因数控制,进一步提高了该发电机系统的可靠性和鲁棒性。     

无刷级联双馈感应发电机稳压控制策略

针对级联双馈感应电机作为无刷变速恒频发电机带负载独立运行控制问题，设计了一种新型稳压控制策略。基于级联双馈感应电机作为无刷变速恒频发电机运行的数学模型，设计了一种易于实施的间接磁场定向矢量控制，可在转速和负载单独变化或一起变化时，稳定发电机的输出电压幅值和频率。同时，电压控制器设计避免了前馈补偿及其所需额外电流传感器的应用，即通过合理设计抑制了耦合效应带来的扰动。利用所搭建的级联双馈感应电机测试平台开展了实验研究，测试结果验证了电压控制器的稳压性能。     

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.     

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.     

无刷双馈电机在独立电源系统中应用的仿真研究

分析了无刷双馈电源系统变速恒频的运行原理,结合独立电源系统的特点,建立了系统在空载和带负载状态下的数学模型;对系统空载至负载、转速突变、负载突变等情况进行了仿真研究,分析了系统动态特性;通过仿真验证,可以实现变速恒频发电,而且通过电压的标量控制可以实现系统输出电压的恒定。     

无刷双馈风力发电系统的转速自抗扰控制

针对变速、恒频风力发电系统具有非线性、强耦合的特点,结合无刷双馈电机的结构特点及基本理论,导出其在发电状态下的转子速由轴电压、电流方程式,并以此为基础构建了无刷双馈发电机（brushlessdoubly—fedgenerator,BDFG）在双同步坐标系下的数学模型。对控制绕组子系统对应的转子磁链进行观测,引入自抗扰控制（active—disturbancerejectioncontrol,ADRC）策略实现转速解耦控制,使发电机转速跟踪风速变化,获得最佳叶尖速比;调节控制绕组频率,在低风速下可达到最大风能跟踪控制和变速恒频发电的目的。仿真结果表明：磁链观测器能较准确估计控制绕组子系统对应的转子磁链,ADRC受系统参数变化的影响较小,具有较强的鲁棒性和适应性,改善了系统的控制品质,验证了控制策略的可行性。     

双馈异步风力发电机建模与仿真研究

阐述了双馈异步风力发电机的工作原理,并建立了双馈异步发电机的数学模型;分析研究了双馈异步发电机并网前定子电压控制与并网发电后的有功无功控制原理;在STAR-90仿真支撑平台上建立仿真模型,并进行了仿真和实验,验证了双馈异步发电机模型和控制模型的正确性和有效性。     

电子变换器调压的无刷直流发电机PWM控制模式及其对电压脉动的影响

介绍了一种由同步电机和全波升压式C－dump变换器构成的新型无刷直流发电机的工作原理,详细分析了发电机的PWM调压模式及其对电压脉动的影响,在此基础上提出了可改善输出电压脉动的PWM控制方案。数字仿真与系统实验验证了理论分析的正确性。     

A Photovoltaic-based Improved Excitation Control Strategy of Three-phase Self-excited Induction Generator Suitable for Wind Power Generation

Abstract—Self-excited induction generators are extensively used for wind power generation in remote and grid-isolated areas. It is challenging to maintain constant voltage and frequency under variable loads and variable wind speed conditions for such kinds of generators. This article proposes a hybrid reactive power control technique for induction generators through a fixed capacitor bank connected at the stator terminals and a strategically switched inverter source. The inverter's DC bus is connected to a photovoltaic panel and a storage battery. This scheme provides stable voltage output with changing loads and widely varying wind speeds. The capacitor provides the bulk excitation current for the induction generator, while the inverter provides the additional reactive current desired to regulate the generator output voltage under variable wind speeds and variable loads. Suitable simulations and experiments validate the proposed concept.     

自激异步发电机电压和频率控制方法的改进

三相自激异步发电机在可再生能源,如风能、水能等方面起到重要作用。但其主要缺点是在不同的负载和速度下,电压和频率不易调节。介绍了一种新的用于三相异步发电机电压和频率控制的方法。该方法采用无直流电容电压调节的恒压恒频脉宽调制器。电容电压随负载和交流侧电压的调节(通过控制调节指数)而改变。此方法减少了一个直流侧辅助开关,降低了成本,同时也减少了流经直流电容器的高频电流分量,延长了使用寿命,最后给出了仿真和实验结果。     

Self-excited induction generator controlled by a VS-PWMbidirectional converter for rural applications

This paper concerns an application of a three-phase cage induction machine (IM) as a self-excited generator connected to the AC side of a voltage-source PWM bidirectional inverter. The generator is supposed to be driven by a low-head unregulated shaft hydraulic turbine. The proposed system is intended to be applied in rural plants as a low-cost source of high-quality AC sinusoidal regulated voltage with constant frequency. Simulation results are obtained based on the αβγ stationary reference frame model of the IM. The experimental results demonstrated that the system presents satisfactory behavior when feeding AC loads and during the startup of induction motors     

POWER CONTROLLER FOR A WIND-TURBINE-DRIVEN TANDEM INDUCTION GENERATOR

ABSTRACT

A controller for delivering either constant power or maximum power from a wind-turbine-driven grid connected induction generator with double stator windings, one fixed and the other able to be physically rotated, and a squirrel-cage rotor common to both stators is described. The load torque of the generator is controlled by varying the angular displacement between the two stators. The generator can feed power to the grid at variable speed and constant frequency and is termed a Tandem Induction Generator.

Dynamic models for the wind energy conversion system are proposed for both controlled and uncontrolled operation to predict changes in shaft speed to shifts in wind speed using data pertaining to a commercial wind turbine. Results based on laboratory tests on a 1hp tandem machine driven by a dc motor demonstrating the feasibility of both controllers are presented. A steady state model of the tandem generator is also proposed and compared to measurements made on the test machine.