发电机定转子烧毁事故与对策

本介绍甘电厂因事故烧毁一台发电机定子与转子以及烧坏两台发电机转子的实况,分析了原因,提出了反事故技术措施。     

基于转子电流的双馈感应电机无速度传感器控制

提出一种基于转子电流的模型参考自适应系统(MRAS)的双馈感应电机(DFIM)无速度传感器控制方法.首先建立了基于定子磁链定向的DFIM矢量控制模型,实现了电机转速/转矩控制和有功/无功功率解耦控制,然后采用基于MRAS的转速辨识方法,将测量得到的转子电流作为参考模型,通过定子电压和电流估测得到的转子电流作为自适应模型,用PI闭环控制构造转子位置和转速信息.为验证理论分析的正确性,以50 kW的DFIM为例设计了一套控制系统.通过电动机运行工况下的空载变速实验和发电机运行工况下的功率控制实验,估测转子位置和转速在不同转速和功率工况下都能准确跟踪实际值.仿真和实验结果表明系统能实现对DFIM无速度传感器控制,证明了所提出的方案的可行性.     

ADTR-motor drive for electric vehicle

A new motor (ADTR-motor: Anti-Directional Twin Rotary Motor) for electric vehicle drive is proposed. A stator in a conventional motor is reformed to be movable, and the stator (outer rotor) and the rotor (inner rotor) rotate in anti-directions. The IM-type ADTR-motor and the SM-type ADTR-motor are considered, and in this paper a prototype of the IM-type ADTR-motor is constructed experimentally. When the ADTR-motor is used for an EV drive, the direction of one of the rotors should be reversed. Both rotors, when rotated in the same direction, propel the two wheels of EV. The torque of the wheels can be balanced without differential gear. The fundamental characteristics of ADTR-motor are clarified. The characteristics are the structure of ADTR-motor, the equivalent circuit parameters, the torque balance theory, the torque-speed characteristics, the rotor speed transient characteristics, and the transient response under the speed sensorless torque control.     

First and High Order Sliding Mode Control of a DFIG-Based Wind Turbine

Abstract

Wind energy has many advantages, because it does not pollute and is an inexhaustible source of energy. In this paper, we study the dynamical behavior of the Horizontal Axis Wind Turbine (HAWT) with MPPT (Maximum Power Point Tracking) algorithm and a pitch control, using a Doubly Fed Induction Generator (DFIG). The DFIG stator is directly linked to the grid; the rotor is connected via a back-to-back converter. To ensure a maximal power extraction, we use the MPPT algorithm combined with a PI controller to generate the maximum power and to force the system to work at the maximum operation point. The pitch control is used to protect the Wind Turbine (WT) against high wind speed. Field Oriented Control (FOC) based on a Sliding Mode (SM) first order and high order (super-twisting) are compared. These schemes control the stator active and reactive powers as well as the stator power factor and improve the power quality injected in the grid. Simulations illustrate the active and reactive power control of the HAWT by adjusting the rotor voltages of the DFIG. We choose the two rotor currents to define the sliding surfaces, in order to avoid the measurement of the electromagnetic torque and stator active and reactive powers. Adequate simulations results with Matlab-Simulink of the whole system including the MPPT algorithm, pitch control and SM controllers are presented and discussed.     

纵扭复合型超声波电机的力传递模型

复合型超声波电机是各种超声波电机中最典型的低速大力矩电机,其定转子接触方式是断续面接触,这与行波型电机连续的若干点接触不同,也是实现大力矩的根本原因,因此分析其定转子的力传递模型很重要。该文先简单叙述了以往采用等效电路描述具有的问题,其次,通过电机轴向冲量守恒建立了定转子接触角与电机预压力和摩擦材料物理参数的关系,随后利用振动周期内周向电机负载和驱动力所作的功相同的原理,给出电机负载与定子纵 扭振动和转子参数的关系,并据此确定电机转子参数和预压力,研制的复合型超声波电机(直径80mm)的堵转力矩为13.2 N穖的大力矩,空转转速为12.5 r/min。初步形成了电机转子设计的理论基础。     

磁阻式旋转变压器极槽配合研究

磁阻式旋转变压器主要用于伺服控制系统中,针对极槽配合方式选择的问题,将信号绕组极对数引入到正弦绕组匝数计算中,推导出磁阻式旋转变压器定子齿数、信号绕组极对数和转子极对数之间的配合关系,并通过有限元仿真和样机试验验证了极槽配合方式的可行性。由极槽配合方法,信号绕组的极对等于转子极同一个定子可以与不同     

PMSG风力发电系统转速估计算法的研究

提出了一种无传感器直驱式永磁同步风力发电机控制系统的转子速度估算法。该算法可由简单的定子磁通方程推导,且只需检测定子电压和电流。定子磁通估算通过基于定子电压模型的可编程低通滤波器而设计,建立了基于递归最小二乘法的电机转速辨识模型,并将实时辨识的电机转速用于转子位置观测和转子磁场定向矢量控制。仿真结果表明,实现了最大功率跟踪控制,验证了控制算法的有效性和可行性。     

Broken Rotor Bar Detection in Line-Fed Induction Machines Using Complex Wavelet Analysis of Startup Transients

Fault detection of line-connected induction machines using complex vector wavelets to analyze the transient stator currents during startup is proposed in this paper. When a machine is connected to the line, the startup transient is characterized by large stator (and rotor) currents as well as by large slips (i.e., the rotor speed is significantly smaller than the excitation frequency). The stator current of machines with damaged rotors includes large rotor speed dependent components during the startup transient. Such components, however, fade away or coincide with components not containing fault-related information (e.g., saturation-induced components) once the machine reaches steady state. Because of this, the startup transient provides an opportunity for performing diagnostics on the machine. This paper shows that the information contained in the startup transient signal can be effectively separated and detected using a complex vector wavelet transform.     

并网双馈发电机电网电压定向励磁控制的研究

在分析并网双馈发电机传统矢量控制策略的基础上，提出了一种基于电网电压定向的励磁控制策略。该控制策略仅需要定子侧电流、电网电压和转子位置角信号，避免了矢量控制系统中对定、转子量测量精度、实时性和一致性的严格要求，使控制系统得到了简化。利用该文提出的控制策略对双馈发电机有功、无功和转速稳态调节特性及机端三相对地突然短路的过渡过程进行了仿真研究，结果表明该控制策略能实现双馈发电机有功、无功和转速的解耦控制及短路故障切除后其有功、无功和转速都能回到原来的设定值稳定运行。     

Compensation for parameter variation of induction motor improved torque control characteristics in low- and high-speed regions

In the vector control system using the slip frequency control method, the rotor resistance of an induction motor is used to calculate a slip frequency. Thus the change in temperature of the rotor resistance causes the deterioration of the torque control characteristic. This paper presents a new method of compensating for the rotor resistance change which is robust for the stator resistance change. A current control loop is composed of the λ-δ axes in which the λ axis is coincident to the stator current. In this method, the stator voltage error on the δ axis which is directly obtainable from this current control loop was used. The change in the stator voltage was able to be detected accurately, therefore the torque control accuracy was improved, particularly in the low-speed region. The experimental results of the current response and the compensation for the rotor resistance deviation also are shown. Moreover, although the mutual inductance has been treated as an invariable value, the value does change by a frequency and an exciting command. In this control method, an initial tuning of the equivalent mutual inductance was achieved by detecting the deviation component of the stator voltage on the δ axis at the no-load running condition. Furthermore, in the region with the constant power where the field weakening control was achieved, the excellent experimental results of the compensation for the deviation of the equivalent mutual inductance are shown.     

Design of low-torque-ripple synchronous reluctance motors

A design approach oriented to the minimization of torque ripple is presented for synchronous reluctance motors of the transverse-laminated type. First, the possible types of rotors are classified and the more suited rotor structure is evidenced, to be matched to a given stator. Then, the inner rotor design is described, pointing out the low-ripple measures. Lastly, experimental results are given from three different rotors; they confirm the validity of the proposed approach     

Modelling and simulation of a double‐star induction machine vector control using copper‐losses minimization and parameters estimation

This paper shows that it is possible to extend the principle of field‐oriented control (FOC) approach to a double‐star induction motor (DSIM). In the first stage, a robust variable structure current controller based on space phasor voltages PWM scheme is established. In this current controller design, only the stator currents and rotor speed sensors are used. In the second stage, the FOC method developed for DSIM is motivated by the minimization of the copper losses. The developed approach uses a loss model controller (LMC) and an adaptive rotor flux observer to compute the adequate rotor flux value minimizing the copper losses. The control variables are the stator currents or the machine input power. Compared to the constant rotor flux approach, it is proved that higher performances are achieved. However, the sensitivity of the FOC to parameter error of the machine still remains a problem. To guarantee the performance of the vector control, the stator and rotor resistances are adapted on‐line, based on the Lyapunov theory. An appropriate choice of the reference model allows building a Lyapunov function by means of which the updating law can be found. The simulation results show the satisfactory behaviour of the proposed identification algorithm. Copyright © 2002 John Wiley & Sons, Ltd.     

A flexible power control strategy for rotor-side converter of DFIG under unbalanced grid voltage sags

Doubly fed induction generator (DFIG) is widely applied in variable-speed wind energy conversion system. The disconnection of a substantial amount of DFIG may arouse the instability problem of power system, thus wind power generators have to remain connected during short-time grid faults. As a result, the voltage sag will lead to overcurrent and overvoltage in the rotor winding of a DFIG, moreover the unbalanced voltage sags will also cause serious fluctuations in its electromagnetic torque and output power. This paper studies the relationship of the stator instantaneous powers with the three-phase stator voltage and rotor current of a DFIG under unbalanced grid voltages. A generalized formula of current reference for the rotor-side converter of DFIG is constructed by introducing continuous adjustment coefficients. Meanwhile, the analytical equations of rotor peak current, stator active and reactive power fluctuations are derived to characterize the operating performance of DFIG. The impacts of adjustment coefficients on DFIG control performance and the feasible region of coefficients restrained by the rotor current constraint are discussed. In consideration of the rotor current limit, the flexible power control strategy for DFIG in unity power factor mode (UPFM) and reactive power supporting mode (RPSM) is presented. The correctness of proposed method is verified by simulation and experiment tests of single-DFIG and multi-DFIG systems.     

感应电机无速度传感器矢量控制系统的定子电阻在线辨识

该文针对利用磁通观测器推算转子磁通的感应电机无速度传感器矢量控制系统，提出了定子电阻在线辨识法。在利用q轴磁通推算转速的基础上，该系统利用d轴磁通误差实现定子电阻在线辨识，该方案的优点是系统简单，解决了低速运行时电压模型的定子电阻变化对系统稳定性和速度控制精度的影响问题。数字仿真和实验结果验证了定子电阻在线辨识的必要性和该方案的有效性。     

Speed sensorless vector control of induction motor using extendedKalman filter

A vector control of an induction motor by an estimated speed using an extended Kalman filter is proposed. With this method, the states are composed of stator current and rotor flux. The rotor speed is regarded as a parameter, and the composite states consist of the original states and the rotor speed. The extended Kalman filter is employed to identify the speed of an induction motor and rotor flux based on the measured quantities such as stator currents and DC link voltage. The estimated speed is used for vector control and overall speed control. Since the current control is performed at a synchronous rotating reference frame, the estimated speed information is also used for the reference frame transformation of the current controller. Computer simulations and experiments of the speed control have been carried out to test the usefulness of the speed estimation algorithm. The experimental results show that the performance of the speed estimation is very good     

Determining electrical efficiency of permanent magnet synchronous machines with different control methods

An algorithm to calculate the electrical efficiency of permanent magnet synchronous machines with four different control methods is presented. The direct- and quadrature-axis stator current components are optimized to find the control method producing the maximum electrical efficiency. The developed computation algorithm was tested with three different permanent magnet synchronous machine applications, i.e., a low-speed high-torque direct-driven wind power generator with rotor surface magnets, a hybrid drive for an energy recovery system and a geared wind power generator with rotor buried magnets. The performance of the developed computation algorithm was verified by comparing the calculated electrical efficiencies with the measurements in the case of the hybrid drive machine.     

两种不同笼型转子结构无刷双馈电机的稳态运行性能对比

无刷双馈电机(BDFM)在变频调速及风能发电领域具有良好的应用前景。目前,转子磁场调制效果差、运行效率偏低的问题仍然制约着笼型转子BDFM的发展。首先从理论上分析了带公共笼条和公共端环的笼型转子产生的空间谐波磁动势及其影响因素,充分考虑了不同笼型转子结构的特点以及转子各短路环在电磁耦合中的作用。在此基础上,提出了一种混联式笼型转子结构,并通过有限元法对两种不同笼型转子结构BDFM样机的运行性能进行了数值计算与对比分析。最后,成功研制了混联式笼型转子样机,并对两种不同转子结构样机的稳态运行性能进行了对比实验研究。结果表明,混联式笼型转子样机定子绕组空载电流较低,运行效率及功率因数均明显提高,为笼型转子BDFM的发展拓宽了研究思路。     

Mathematical simulation of a high-speed single-phase machine with alternating current direction

A new design of a single-phase flux reversal machine (FRM) and a procedure of mathematical simulation of the FRM are described in this article. Technical features of the FRM (such as efficiency, specific power, and specific torque) that are close to those of synchronous motors with magnets on the rotor have greater reliability for high speed applications. The main advantages of an FRM involve the absence of permanent magnets or electric conductors on a rotating rotor and their being positioned on a stator. The new design of a single-phase FRM consists of a rotor with four teeth and a stator with four teeth and a magnetic system. The magnetic system on the stator teeth surface has two magnets on each stator tooth and generates two magnetic poles on each one. The adjacent poles on the adjacent teeth of stator are similar. The total angular size of new design is slightly less than the perimeter of the circle. Therefore, the stator surface is much better used (unlike the prototype), which results in an increase in the specific power and power efficiency, as well as a decrease in the cost of the FRM. A method for mathematical simulation of an FRM that is based upon solving magnetostatic problems with common geometry is proposed. Different positions of the rotor are simulated by joining boundary conditions. The method allows one to determine the electric losses in steel and magnets in postprocessing.     

Induction motor drive based on the stator flux vector control

This paper presents a new torque control algorithm for induction motors, based on the stator flux vector control. For each sampling period, the value of the stator voltage is calculated to keep the stator flux equal to the reference vector, while the stator flux reference vector is calculated to keep the rotor flux amplitude constant at all operating conditions. An improved stator and rotor flux estimation algorithm is proposed, enabling robust and stable operation of the drive, even at low speeds. The induction motor torque is manipulated by variations of the flux angular velocity, enabling drive operation with fixed switching frequency and ripple-free torque in the steady state. The performance of the proposed algorithm is tested through various experimental runs, proving good behavior of the drive in both transient and steady-state operating conditions.     

不平衡电压下双馈感应发电机转子侧变流器的灵活功率控制

针对不平衡电压下双馈感应发电机(DFIG)转子侧变流器的控制,分析定子瞬时有功和无功功率与三相定子电压、转子电流的关系,通过引入连续调节系数得到转子三相电流指令值的通用计算式。进一步地,求得指令电流调节系数、转子电流峰值及DFIG定子有功和无功波动的表达式,分析DFIG控制特性随调节系数、电压不平衡度的变化规律;分析不平衡电压跌落下DFIG的可控性,给出电压跌落后定子电压的临界值和转子侧变流器可控的判断条件;以功率波动设定值为目标,计及转子电流峰值限制,建立DFIG单位功率因数和无功功率支持2种模式下的灵活功率控制策略,通过仿真验证所提方法的可行性。