Characteristics of PM synchronous motor drives with a trapezoidal EMF

A permanent magnet synchronous motor (PMSM) with nonsinusoidal electromotive force (EMF) generates torque ripple even if the sinusoidal PWM inverter drives the PMSM. A new modified trapezoidal modulating signal for PWM inverter suitable for PMSM drive with nonsinusoidal EMF is proposed in this paper. A new modulating signal for the PMSM drive is determined by the condition of reducing torque ripple of the motor with various trapezoidal EMF. When the PWM inverter using modified trapezoidal modulating signal drives the PMSM having a nonsinusoidal EMF, the torque ripple of the motor can be reduced, the DC link voltage utilization is improved, and reduction of switching loss can be obtained. © 2007 Wiley Periodicals, Inc. Electr Eng Jpn, 159(1): 62–71, 2007; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.20441     

New GTO Current Source Inverter with Pulsewidth Modulation Control Techniques

A new GTO current source inverter in which two auxiliary GTO's are added to the basic inverter circuit, which consists of six GTO's and three capacitors, is presented. One of the auxiliary GTO's is connected between the positive line of the inverter and the neutral of three Y-connected capacitors; another is connected between the negative line and the neutral. In the proposed inverter, the charges of three capacitors are controlled at the same time by means of pulsewidth modulation (PWM) to main GTO's and auxiliary GTO's. This inverter can supply both the sinusoidal current and voltage to the motor. The PWM control technique, the operating principle, and the experimental results for 2.2-kW induction motor drives are described. The output current waveform of this inverter is closely sinusoidal, as opposed to trapezoidal in the basic inverter circuit. The steady-state characteristics of the GTO-CSI induction motor drive system are analyzed by the state-variable methods, and a close agreement between the analyzed and the experimental results is obtained. Smooth and noiseless drive of induction motor over a wide range of speed is observed.     

Waveform Distortion and Correction Circuit for PWM Inverters with Switching Lag-Times

The switching lag-time that prevents the phase shortage of inverter arms causes serious waveform distortions and fundamental voltage drops in pulsewidth-modulated inverter output. Distortions in the PWM inverter-fed induction motor system over the various frequencies of the carrier are investigated and a correction circuit with PWM potential feedback is proposed; the effectiveness of that circuit is shown by experiments.     

Quick regulation of sinusoidal output current in PWMconverter-inverter system

An induction motor drive system composed of a current output-type power converter and a current source inverter with sinusoidal input and output voltage/current is presented. Pulsewidth modulation (PWM) strategies with GTOs are applied to the converter and the inverter sections from the point of view of reduction of the current harmonics and suppression of the motor torque pulsations. A simple method for quick regulation of the AC output current amplitude is presented and applied to the PWM inverter section. To demonstrate the improvement in the current response of the inverter, a slip frequency/current regulation of an induction motor is considered. The experimental results of steady-state and dynamic operations of the motor are shown. The merits and demerits of this control method are discussed     

电压型逆变器供电三相异步电机瞬态过程仿真

本文分析了6阶梯波和脉宽调制两种电压型逆变器供电时异步电机的调速运行。异步电机采用相对定子静止的坐标系描述的数学模型。分别计算了电机带恒转矩负载和风机类负载时的运行状况。     

A New Quick-Response and High-Efficiency Control Strategy of an Induction Motor

New quick-response and high-efficiency control of an induction motor, which is quite different from that of the field-oriented control is proposed. The most obvious differences between the two are as follows. 1) The proposed scheme is based on limit cycle control of both flux and torque using optimum PWM output voltage; a switching table is employed for selecting the optimum inverter output voltage vectors so as to attain as fast a torque response, as low an inverter switching frequency, and as low harmonic losses as possible. 2) The efficiency optimization in the steady-state operation is also considered; it can be achieved by controlling the amplitude of the flux in accordance with the torque command. To verify the feasibility of this scheme, experimentation, simulation, and comparison with field-oriented control are carried out. The results prove the excellent characteristics for torque response and efficiency, which confirm the validity of this control scheme.     

变频器供电异步电动机绝缘系统概述

变频器供电异步电动机通常指变频调速电动机（以下简称电动机）。大多变频器输出PWM脉宽调制波形,含有大量谐波,将增加附加损耗。变频器输出电压的峰值较高,对电动机的绝缘造成严重的威胁,产生的高次谐波会导致电动机绝缘被击穿。由于变频电源的特殊性,以及系统对高速或低速运转、转速动态响应的需求,对作为动力主体的电动机,提出苛刻的要求,尤其是电动机绝缘系统。为更好地消除因变频器供电对电动机绝缘系统产生的不利影响,对电磁线槽绝缘、相间绝缘、浸渍漆、浸漆工艺予以概述。     

Optimal pulse patterns of a nine-phase voltage source PWM inverter for use with a triple three-phase wound ac motor

The authors have already described the nine-phase inverter driving system providing both the triple three-phase voltage source inverter with 180-deg conducting period and the ac motor windings with triple three-phase construction. The nine-pulse inverter driving system used three small-capacity three-phase coupling reactors having special windings for current balance and reduction of higher harmonics. In addition, for voltage control, current balance, and waveform improvement, optimal PWM pulse patterns were applied to the six-phase inverter driving system using a three-phase coupling reactor to provide double three-phase construction. In the system based on the mode in the title, the PWM control was applied to the nine-phase inverter driving system described in the foregoing. The coupling reactors in the system balance the fundamental currents of three sets of three-phase inverters and also absorb higher harmonic voltages other than 18p±1 (p = 1, 2, …) orders. The optimal pulse patterns found by the approach to make the performance index minimum using the Lagrange multiplier method can be applied to the PWM to reduce the higher harmonic currents greater than those calculated by the modulation method comparing the sinusoidal signal wave with triangular carrier signal. This system can have a larger capacity than the six-phase PWM inverter driving system in which coupling reactors absorb higher harmonic voltages other than the 12p±1 orders and also improve output current waveforms. In addition, the system includes the capacity of coupling reactors slightly larger than the six-phase PWM inverter driving system but enables operation with smaller torque ripples and electromagnetic noises in low- to high-frequency ranges.     

Direct Flux and Torque Regulation in a PWM Inverter-Induction Motor Drive

A dc motor drive is controlled by varying the armature current and field current. The field is a measure of flux, and the armature current times field current is a measure of torque. Various approximate means of estimating the flux and torque levels in an induction motor exist. Most of these methods are sensitive to motor parameter value changes and do not work well near zero speed. Also, the harmonics in the motor voltage and current due to the nonsinusoidal inverter waveform cause errors in the estimated torque. A practical method has been developed to measure the flux level in an induction motor in the actual operating environment. Using the flux signals and stator current, the actual electromagnetic torque can be obtained. This torque signal responds correctly to motor saturation and inverter voltage waveform harmonics. The motor can be designed to operate without the customarily required flux margin, since the flux level is accurately controlled. The control strategy for use with these feedback signals does not require the use of a tachometer.     

基于多电平逆变器的感应加热双频率输出设计

为了提高双频率感应加热设备的电源利用率,对基于多电平技术的双频感应加热的电压输出问题进行了研究。采用阶梯波近似模拟所需双频信号的合成波形,依据近似波形构造逆变器的输出电压波形。利用输出波形的傅里叶展开式,建立以逆变器触发延迟角为自变量的频率信号幅值方程。基于方程的求解结果,对所构造的输出电压信号和相同电平数的常规多电平信号进行基波调制系数及3次谐波调节范围的对比分析、所构造的输出电压信号具有更大的谐波调节范围。采用二极管钳位H桥逆变器拓扑,设计了实现所构造电压信号的逆变器触发方式,并兼顾考虑了逆变器分压电容的电压均衡问题。逆变器的仿真与实验结果验证了所提逆变器触发方式的有效性及对所构造信号计算分析的正确性。     

考虑中点电压不平衡的中点箝位型三电平逆变器空间矢量调制方法

论述了中点电压偏移时,中点箝位型(neutral point clamped, NPC)三电平逆变器的空间矢量调制方法(space vector pulse-width modulation,SVPWM)。当中点电压偏移时,电压矢量本身的变化和平衡算法所带来的冗余矢量作用时间所引起的合成误差。经计算得到不同调制度时的合成误差曲线。将中点电压的不平衡因子引入矢量的选择和作用时间的计算中,利用不平衡因子调整矢量作用时间。比较了当逆变器带有异步电机负载时,传统矢量调制方法和改进的调制方法在电机启动过程系统的响应特性。表明改进的算法不仅能使三电平逆变器的输出电压谐波含量大幅减少,并且中点电压不平衡、电机转矩脉动、电流畸变也大幅度减小。     

开关线性复合式VVVF功率变换器研究

基于开关线性复合(SLH)技术,提出一种新型VVVF功率变换器拓扑结构,目的在于将开关线性复合技术用于异步电动机变频调速领域,从而获得开关线性复合技术固有的优波特性及负载鲁棒性。系统仿真及实验结果表明,该系统在克服电机低速转矩脉动、抗负载扰动特性、抑制PWM高频脉冲对电机的损害方面与传统变频调速系统相比具有明显的优势。     

Analysis of PWM GTO Current Source Inverter-Fed Induction Motor Drive System

A GTO current source inverter which consists of six main GTO's, two auxiliary GTO's, and three capacitors is presented. This inverter can supply both the sinusoidal voltage and current to the motor by pulsewidth modulation (PWM) techniques. The normal PWM pattern produced by two control signals with the carrier and the modulating waves and the optimal PWM pattern determined by the harmonic analysis are described. The experimental waveforms for 2.2-kW induction motor drives are given and the circuit operation of this inverter in the PWM technique is clearly shown. In addition, the steady-state characteristics of this inverter-induction motor drive system are analyzed by the state-variable methods, and a close agreement between the analyzed and the experimental waveforms is obtained. It is shown that the harmonic components are eliminated or reduced by using the optimal PWM pattern, and the new inverter with sinusoidal current and voltage is very excellent for ac motor drive.     

一种模块化48脉冲大功率PWM逆变器

多脉冲逆变器通过移相变压器原副边移相角度的精确设计,可以在工频开关方式下,实现交流侧阶梯波输出,经过滤波得到高质量的正弦波形,但工频开关方式使其输出调压困难,而且随着脉冲数的提高,逆变器连接的变压器结构复杂,多个绕组之间的匝比难以兼顾,因此实际应用中多脉冲逆变器的通道数多在4以下。提出一种只有两个规格移相变压器结构的模块化48脉冲大功率PWM逆变器,该逆变器具有8个通道的三相逆变器和对应移相变压器组成,且每个三相逆变器采用低频PWM调制策略,实现输出电压调节。构建了一台8通道48脉冲的PWM逆变器样机,在各种运行状态下的输出波形以及相关测试数据验证了所提出的模块化多脉冲逆变器在输出波形、开关频率以及输出调节特性等方面的优势。     

Current regulated PWM-CSI induction motor drive system without aspeed sensor

This paper deals with a current source inverter-induction motor drive system without a speed sensor, and the speed estimation with only sense of the motor voltage is investigated. The input DC link current which is kept constant by a pulsewidth modulated (PWM) converter with sinusoidal input current is supplied to the PWM inverter. The inverter output current with sinusoidal wave is directly regulated by employing the modulation index control of the PWM strategy. The motor is driven by a slip frequency/current regulation control. The motor speed is estimated by using the measured voltage and current, or using the measured voltage and the estimated current. The filter capacitor which is installed in the inverter circuit is taken into consideration for the current estimation. A digital signal processor is employed for calculation. As the PWM pulse of the inverter is calculated by an online real-time system, the quick regulation of the sinusoidal output current is achieved. The experiments show that the high performance steady state behavior and the acceleration/deceleration characteristics with smooth drives and low noise of the motor is obtained     

梯形波相电流驱动下六相感应电机转矩研究

针对多相电机控制模式复杂性的特点,本文提出一种新颖的控制方式:六相感应电机梯形波相电流控制.该梯形波相电流由励磁电流和转矩电流组成,在该梯形波相电流驱动下六相定子绕组可以分为励磁绕组和转矩绕组,模拟直流电机实现励磁磁场和转矩的直接控制而不需要复杂的派克变换.本文主要通过理论分析计算、有限元分析和实验测量数据来研究梯形波相电流驱动下六相感应电机输出转矩性能,并对磁势解耦时的参数k进行了理论分析和计算.输出转矩的理论分析、有限元分析和实验结果是一致的,表明了分析模型的正确性以及该控制策略可以从真正意义上模拟直流电机的转矩输出性能.     

Optimum PWM Waveform Synthesis?A Filtering Approach

A fundamentally different approach is proposed for the synthesis of optimum pulsewidth modulated (PWM) waveforms for high-power inverter applications. Conventional optimum PWM waveform synthesis techniques which seek to control harmonic levels in the inverter output directly are seen to be equivalent to a filtering operation. Digital filter structures capable of processing PWM waveforms are examined and waveform synthesis strategies are proposed and verified experimentally. Finally, the design of a high-performance PWM waveform generator is detailed.     

异步电机低开关损耗的模型预测直接转矩控制

提出一种新颖的异步电机低开关损耗的模型预测直接转矩控制方法。通过建立异步电机离散时间预测模型,对不同开关矢量作用下的系统输出矢量进行轨迹外推,形成长预测范围的输出轨迹。同时分析三电平逆变器在开关切换时产生的开关损耗,以逆变器的平均开关损耗为价值函数,对不同开关矢量作用的输出轨迹进行在线评估,得到最优的开关矢量并将其作用于逆变器,从而有效降低了逆变器的开关损耗。仿真结果表明,基于该方法的驱动系统逆变器的开关损耗低,电机转矩和磁链动静态性能良好。     

基于Buck变换器的无刷直流电机转矩控制仿真

无刷直流电动机（BLDCM）存在转矩脉动的突出缺点，提出了一种基于直流环节电压控制和模糊PID控制器的新型混合控制策略，以抑制无刷直流电机的转矩脉。电路拓扑包含功率因数校正降压转换器和逆变器。降压转换器通过控制直流电路电压来降低换向转矩脉动，使用模糊PID控制器和脉冲宽度调制（PWM）技术的逆变器在导通区域提供适当的电流。 Buck变换器降低了通过控制直流环节电压换向转矩脉动，逆变器使用模糊PID和PWM技术提供导通区域的电流。该方法能够消除传导区转矩脉动,削弱换相区转矩脉动，仿真结果表明，该策略具有功率因数校正功能，可有效抑制转矩脉动，提升电机运行的鲁棒性。     

PAM inverter system with power-factor-corrected converter

In most cases, PWM power-factor-corrected (PFC) converters are constructed from a diode rectifier and an active power circuit such as a boost or buck-boost chopper. Besides the PFC operation, the active power circuit can control the dc output voltage. The output voltage of the PAM inverters is controlled by varying the level of the dc input voltage. The PAM method reduces the voltage and current stresses of the inverter and motors. This paper proposes a new PAM inverter system with high power factor converter to obtain a sinusoidal input current. The proposed PAM method to reduce the torque ripple in the induction motor can reduce switching losses by providing a pausing interval where the switching operation stops during part of one period. © 1998 Scripta Technica, Electr Eng Jpn, 124(2): 43–52, 1998