变频器对电机性能的影响及其对策

目前广泛使用的变频器都会产生不同程度的高次谐波和dv/dt问题。为此 ,本文着重分析了高次谐波和dv/dt对异步电动机性能的影响 ,同时给出了一些解决问题的方法     

Inertia-lowering control of induction motor

There are many requests for selecting freely the moment of inertia, even though the moment of inertia is determined by the materials, structure, shape, and size of the motors. From the standpoint of control, reducing the moment of inertia will make it possible to construct well-controlled drive systems and expand the applications in which a motor may be used to replace another nonelectric machine. An “inertia-lowering control” system has been developed that uses disturbance observer to reduce inertia. To realize this control system with vector-controlled induction motors, the equations and machine constants needed for designing the systems have been clarified. A digital signal processor and a microprocessor were adopted for induction motor control, and good results were obtained through the experiments.     

A study of the electromagnetic vibration of a capacitor induction motor caused by time-harmonic voltages

In recent years, power source voltage waveform distortion has become noticeable, as electrical appliances with rectifier circuits have become widely used. Connecting capacitor inductor motor (CRM) to such distorted supply, or controlling CRM by simple controller with a switching device (such as triacs), harmonic voltage is supplied to CRM. In that case, CRM produces electromagnetic vibrations caused by not only the fundamental voltage but also time-harmonic voltages in the distorted voltage. In addition, CRM produces electromagnetic vibration due to backward magnetic fields. Thus, it is difficult to clarify a relationship between electromagnetic vibration of CRM and harmonic voltages. In this paper, the causes of the electromagnetic vibration of CRM operating under distorted wave supply voltage are discussed. First, a general equation of dominant electromagnetic force waves is shown considering not only forward magnetic fields but also backward magnetic fields. Using a general equation, causes of dominant electromagnetic vibration can be clarified. Next, by discussing in detail some examples of the dominant vibration, the relationship between the vibration and harmonic voltages becomes evident. Furthermore, the relationship between the vibration and backward magnetic field is clarified.     

A low‐loss snubber for reducing motor terminal surge voltage

The development of an advanced Insulated Gate Bipolar Transistor (IGBT) has enabled high‐frequency switching operation and has improved the performance of PWM inverters for motor drive. However, the IGBT's high rate of dv/dt has adverse effects on motor insulation stress. In many motor drive applications, the inverter and motor are separated, requiring long motor feeds. The long cable contributes high‐frequency ringing at the motor terminal and results in high surge voltage which stresses the motor insulation. The inverter output filter and RDC snubber are the conventional method for reducing the surge voltage. In this paper, we propose a new low‐loss snubber to reduce the motor terminal surge voltage. The snubber consists of the series connection of chraging/discharging capacitor and the voltage‐clamped capacitor. At IGBT turn‐off, the snubber starts to operate when the IGBT voltage reaches the voltage‐clamped level. Since dv/dt is decreased by snubber operating, the peak level of the surge voltage can be reduced. Also the snubber operates at the IGBT voltage above the voltage‐clamped level, and the snubber loss is largely reduced compared with the RDC snubber. The proposed snubber enables reduction of the motor terminal surge voltage with low loss. © 2005 Wiley Periodicals, Inc. Electr Eng Jpn, 150(4): 64–72, 2005; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.10378     

计及电动机动态的电压稳定问题仿真分析

对一个三相系统模型进行仿真,分析了感应电机动态负荷特性对系统电压稳定性的影响,并给出改善电机节点电压性能的措施。     

一种基于静态特性的直线感应电机参数辨识方法

直线感应电机(LIM)具有机械间隙大、定转子漏感差别明显、边缘效应影响等特点,准确测量电机参数难度较大.通常的电机空载试验参数测量方法在直线轨道上难于实施,特别是用于地铁和磁浮列车牵引的直线电机,由于运动位置重复性差,在线辨识实现困难.本文提出一种新的基于变频器驱动的直线感应电机等效电路参数辨识方法,利用不同频率时的电机推力、变频器输出电压和电流等静态堵转特性,结合最小二乘法推算出适合控制用的直线感应电机等效电路中的初级电阻、漏感、次级等效电阻和漏感参数.测量设备即为实际驱动电机的变频器.对一台基于直线感应电机牵引系统的测试结果表明了该方法的有效性.     

电压稳定分析中异步电动机动态负荷建模探讨

探讨电压稳定分析中异步电动机(IM)负荷的建模问题。分析一般的动态负荷模型(GDLM)不能捕捉IM动态行为的机理。分别以IM的滑差模型和滑差磁链模型为基础，严格地导出了适用于电压稳定分析的简化一阶(SIM)和详细三阶(DIM)动态负荷模型，同时还说明了SIM和DIM模型实质上是对GDLM模型进行了不同程度的改进。对SIM和DIM模型在暂态电压稳定分析和静态电压稳定分析中的适用性进行分析比较，仿真结果表明：SIM和DIM分别以不同的准确度适用于不同场合的电压稳定分析。     

感应电动机变频运行的方式及特性

在感应电动机等效电路的基础上，分析了当电源频率发生改变时，等值电路中主要参数的变化规律。给出了变频调速状态下感应电动机恒电压频率比、恒磁通、恒电流和恒功率调速情况下的运行特性。     

电流控制电压源逆变器驱动的感应电机逆解耦控制

在转子磁链坐标系下,以电流控制电压源逆变器供电驱动电机运行.通过在电流内环采用高增益控制器,感应电机模型中的2个定子电流分量可近似为定子参考电流,从而可忽略定子电流动态特性的影响,将以定子电压为控制量的感应电机四阶模型降阶成以定子电流为控制量的二阶模型.采用状态反馈线性化方法求得感应电机的逆系统,将多变量、非线性、强耦合的感应电机动态解耦成转速与转子磁链2个一阶子系统.在此基础上,设计一种积分比例(IP)控制器对解耦子系统进行闭环控制.电流内环采用滞环比较器,直接获得PWM信号,控制逆变器实现电流跟踪,从而使调速系统具有快速的动态响应性能.仿真结果验证所提控制方案的有效性和优越性.     

复合型超声电动机无负载转速的数值计算

无负载转速是电动机设计过程中的一个重要参数。本文利用等效电路，给出一种复合型超声电动机无负载转速的数值计算方法，为该型电动机的设计、分析提供了理论依据。     

考虑带泵类负载感应电动机影响的静态电压稳定性分析

为了更准确计及泵类负载机械特性对配电网静态电压稳定的影响,建立了一种将感应电动机T型等效电路与泵类负载机械特性相结合的感应电动机负荷模型。将其用于配电网潮流计算,采用前推回代法求解。进而将其用于连续潮流计算,建立了带泵类负载多台相同感应电动机的等效负荷模型,分析负荷连续增长对配电网静态电压稳定的影响。采用IEEE33节点算例对提出的模型与方法进行仿真验证,并与负荷按恒功率因数增加模型的连续潮流进行了对比。仿真计算验证了所提方法的合理性和有效性,表明采用该模型所得的静态电压稳定裕度要小于采用恒功率因数负荷计算结果,更接近工程实际情况。     

用神经网络实现对感应电机转速估计

根据数学模型．提出了一种利用神经网络进行感应电机转速估计的新方法。方法是采用一个3层神经网络作为速度估计器来估计转速。仿真结果表明，这种基于人工神经网络的转速估计模型可以准确地跟踪感应电机转速的变化，具有良好的动态跟随性能。     

Characteristics of short primary linear induction motor with a partially adopted wound secondary member

This paper describes single‐sided linear induction motors (LIMs) with a short primary member. In these machines a solid‐plate conductor is usually used for the secondary. We here propose the partial adoption of wound secondary members in LIMs. The characteristics of such machines are summarized as follows. 1. Basic characteristics: The wound secondary shortens the magnetic clearance and makes the characteristics of the machine superior to those of the solid‐plate conductor version. In addition, we can improve the thrust and efficiency characteristics by applying the proportional shifting method. 2. Primary and secondary winding scheme: Parallel connection is appropriate for the primary and independently shorted‐circuit scheme in order to obtain stable performance. 3. Transient phenomena at the boundary between the wound secondary and the solid‐plate secondary: Undesirable phenomena develop at the boundary, especially at the end of the solid‐plate conductor. Thus, we propose a novel boundary structure that yields stable transient performance. © 2001 Scripta Technica, Electr Eng Jpn, 135(3): 48–55, 2001     

计及频率特性的感应电动机参数变化对负荷特性的影响

对于网架结构比较薄弱的省网系统或者系统解列后形成的孤岛,发生故障时会引起比较大的频率波动。感应电动机作为电力系统动态负荷的主要成分,进行建模时考虑其频率特性尤为重要。基于感应电动机数学模型,考虑恒机械转矩、恒机械功率和变机械转矩等不同负载特性,在计及频率特性的情况下,通过解析法得到感应电动机转子滑差、有功功率和无功功率的表达式。当感应电动机的定子电感、转子电感、励磁电感和转子电阻变化幅度分别为±30%时,分析负荷特性参数变化对不同频率下的感应电动机吸收有功功率和无功功率的影响。利用Matlab建立感应电动机五阶电磁暂态仿真模型,仿真分析感应电动机参数变化对负荷特性的影响。将理论计算与仿真实验的结果进行对比,验证了所提方法的正确性。     

基于PWM逆变器的直线感应电机参数辨识方法

针对直线感应电机初级漏感和次级漏感不相等的特性,提出了一种基于PWM逆变器的直线感应电机参数辨识方法,将堵转试验的等效电路改进后得到方程组计算电机的参数。将此方法应用于一额定电压30V的直线感应电机参数辨识中,试验结果与传统方法得到的试验结果比较,证明了所提出的方法提高了辨识精度。     

考虑频率特性的感应电动机负荷模型的对比研究

以往主要研究负荷的电压特性,很少研究频率特性。而在小电网或者薄弱电网频率可能有明显变化,所以需要研究电力负荷的频率特性。给出考虑频率特性的五阶电动机负荷模型和新三阶实用电动机负荷模型,提出两种负荷模型的参数辨识方法,通过蚁群算法辨识其中的重点参数。结合仿真算例,分别对比考虑和不考虑频率变化时的五阶电动机负荷模型、新三阶实用电动机负荷模型,还对比了两种负荷模型。根据新疆电网的实际扰动数据,对考虑频率特性的必要性进行了校验,结果表明,考虑频率特性所得参数辨识结果更精确、拟合效果更好,考虑频率特性时五阶电动机负荷模型效果更好。     

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     

Carrier-based unbalanced phase voltage space vector PWM strategy for asymmetrical parameter type two-phase induction motor drives

This paper proposes a space vector pulse width modulation (SVPWM) method based on a carrier providing unbalanced phase voltages for asymmetrical parameter type two-phase induction motor drives using a three-leg voltage source inverter (VSI). The principle is fully described. The proposed space vector equivalent phase leg reference voltages are derived from conventional ones. With the proposed SVPWM method, the output voltages are displaced at 90° with controllable amplitudes. The validity of the proposed method is verified by both calculated and experimental results.     

基于无源性的鼠笼式感应电机转速控制系统

以鼠笼式感应电机为研究对象,在分析电机数学模型的基础上,建立了鼠笼式感应电机的Eulerlagrange方程,结合转子磁链定向原理,将无源性控制应用在感应电机转速控制系统中,并对系统的无源性进行了理论证明。在Matlab的Simulink中建立仿真模型,实现了对电机转速的精确控制。     

A new method of characteristic analysis for three‐phase induction motors

Generally speaking, the characteristics of induction motors (IM) are analyzed by means of the equivalent circuit with d–q transformation. Although this method is simple, the magnetic flux distributions in the stator and rotor are defined as sinusoidal waves. Therefore, the equivalent circuits become relatively complex for the high‐frequency components and transient states. For detailed analysis, the finite element method (FEM) is used. The FEM can take account of the influence of skewed rotor bars and slots, and of the skin coefficient. However, the calculation time is very long for high‐frequency components and transient analysis. We therefore propose a new method of characteristic analysis for IM. The proposed method analyzes the magnetic flux simply based on the construction of the IM. It can analyze transient and steady states and high‐frequency components regardless of the type of source. The influence of skewed rotor bars and slots can also be treated simply. This paper describes the method of analysis, presents the results of the proposed method and compares them with experimental results, and describes the d–q transition. © 2001 Scripta Technica, Electr Eng Jpn, 135(4): 64–75, 2001