Analysis of PWM current source GTO inverter with PWM-controlledthyristor rectifier for induction motor drive

With the application of an energy rebound circuit for the pulsewidth modulation (PWM)-controlled rectifier, an improved current source gate turn-off thyristor (GTO) inverter system capable of producing sinusoidal inputs and outputs is presented. The energy rebound circuit in the inverter is used to turn off the thyristors in the rectifier for applying PWM control techniques and also to clamp the spike voltage produced in the inverter circuit. The principles and circuit operations of this system are described in detail, and requirements for PWM control of the rectifier are investigated. The conditions for satisfying the requirements of the energy rebound circuit are analyzed by experimental and theoretical methods. The PWM-controlled current source GTO inverter system is used to drive an eight-pole 400 Hz 5.5 kW induction motor. Analytical and experimental results, as well as the characteristics of the motor drives, are given     

A Current Source GTO Inverter with Sinusoidal Inputs and Outputs

With the application of gate turn-off thyristors (GTO's) and PWM control techniques, a current source inverter capable of producing sinusoidal input/output (I/O) voltages and currents has been developed. The sinusoidally modulated current is fed to the GTO's in the rectifier and inverter sections. The overvoltage-absorption capacitors connected to the ac input and output terminals function as a filter and, consequently, the waveforms of the input/output voltages and currents become sinusoidal. Because the PWM control utilizes the high-speed switching characteristics of the GTO's, the dc link current smoothing reactor and the overvoltage absorption capacitors are greatly reduced. The dc link voltage in the rectifier section is controlled to adjust the ac motor current. This is accomplished by using the firing angle shift method in conjunction with the method involving varying the width of the bypass gate pulses, which put the rectifier section into a bypass state. The current source GTO inverter is used to drive an 11-kW induction motor. As a result, excellent acceleration and deceleration characteristics are obtained, which verifies that the new current source inverter is quite suitable for driving an ac motor at variable speeds.     

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.     

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.     

Study of dead time of PWM rectifier of Voltage-source inverter without DC-link components and its operating characteristics of induction motor

A voltage-source inverter without dc-link components is an ac-to-ac converter having dual bridges of a pulsewidth-modulated (PWM) rectifier and a PWM inverter that can be controlled independently. While conventional matrix converters have disadvantages, such as a complicated commutation scheme and necessity of a large-sized clamp circuit, commutation, and protection of our inverter can be implemented easily. In order to control the PWM rectifier and the PWM inverter independently, snubber circuits for the PWM rectifier are required to assure the path of load current during dead time. In this paper, analytical method of a snubber circuit and operating characteristics of a snubber circuit are described when a 0.75-kW induction motor is driven by our inverter.     

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     

能馈式级联型高压变频器运行特性研究

基于传统级联型变频器驱动的高压异步电动机只能电动运行,为克服这一不足,提出了一种能馈式级联型高压变频器。用PWM整流器替代传统级联单元的不控整流桥,并对输入电流进行直接控制,在异步电动机处于再生制动状态时,输入电流自动反相,将再生能量回馈到电网,进而实现异步电动机的再生运行。所提出的新型高压变频器具有输入电流波形近似正弦,谐波污染小,自动实现能量双向流动,节能效果明显等优点。仿真和实验研究结果证明了该新型变频器的正确性和可行性。     

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     

A New Current Source GTO Inverter with Sinusoidal Output Voltage and Current

A new current source inverter with sinusoidal output voltage and current is presented. Gate turn-off thyristors (GTO's) and pulsewidth modulation (PWM) control techniques are used in the current source inverter to produce the sinusoidal output voltage and current. Three capacitors are connected to the ac output terminals to absorb overvoltages which occur when the GTO current is cut off and to provide a filter function for reducing harmonics in the output current. Voltage spikes, which have been a serious problem in the practical application of this inverter, are suppressed by adding gate pulses which force the inverter into a state of shoot-through. Moreover, this inverter permits the capacitance of an ac output terminal capacitor for absorbing overvoltages to be reduced to one-tenth or less of that of a commutating capacitor in a conventional thyristor type current source inverter. A 3.7-kW induction motor is driven by the inverter. The motor efficiency and noise level are measured and compared with those obtained when the motor is driven by a conventional voltage source PWM inverter. An operating efficiency five or six percent higher and noise level 10 dB lower are obtained for the former. Therefore, this current source GTO inverter is very suitable for ac motor variable speed drives.     

三电平PWM整流器双环控制技术及中点电压平衡控制技术的研究

该文在建立了三电平PWM整流器系统数学模型的基础上,比较了三电平PWM整流器模型与直流电机模型的相似性,基于对控制对象的状态反馈解耦,提出把直流电机的双闭环控制应用于三电平PWM整流器中,使三电平PWM整流器具有良好的动态性能和稳态性能,并且保证输入电流波形正弦性好,实现了单位功率因数。同时,针对三电平PWM整流器所固有的直流侧电容中点电压平衡问题,提出根据每相输入电流方向和中点电压波动方向来优化选取冗余的正小矢量和负小矢量,实现中点电压平衡控制的方法。最后通过实验验证了双环控制器和控制中点电压方法的可行性和有效性。     

PWM-CSI induction motor drive with phase angle control

The authors describe a pulse-width-modulated current-source inverter drive system using an induction motor. Its dominant feature is that it provides adequate control of either torque or speed over a wide range without requiring a shaft position or speed sensor. The capacitor-loaded current-source invertor system has the advantages of simplicity, low switching frequency, four-quadrant operation, overcurrent protection, and low harmonic content in the motor current and voltage. The choice of maximum value for the capacitor depends on the degree of nonlinearity that can be tolerated in the torque-stator current relation, whereas its minimum value depends on the need for a low impedance path for inverter current harmonics. The control strategy is based on the concept of controlling the stator phase angle of the induction motor. The stator voltage is sensed, and the current-source inverter is used to inject current into the motor with the desired phase angle     

双馈电机基于双三电平空间矢量控制方法研究

采用AC/DC/AC拓扑结构,利用三电平PWM整流、逆变原理,构建了双馈电机控制变频器.采用简化的三电平SVPWM算法,外加中点电位控制,对整流和逆变进行仿真,仿真结果表明控制效果良好.同时,给出了双馈电机试验平台的整体硬件设计框图,实验证明了该方法对双馈电机控制的可行性.     

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     

High performance current regulator for a field-oriented controlledinduction motor drive

In this paper, a novel strategy of current regulation of a field-orientation induction motor drive using the GTO inverter is proposed, which is based on a multivariable state feedback control with an integrator. The controller is designed by pole placement technique of multivariable system regulation theory. In addition, feedforward control is included in the control laws to improve transient responses. For the linear state feedback control, the rotor flux is separated as a disturbance and is estimated with a reduced-order state observer. A good steady-state performance is obtained by means of an integral compensation and symmetrical space voltage vector PWM, and fast transient response is also feasible since the required voltage is directly calculated from the feedforward control. Also, it is demonstrated that an instantaneous current control without the calculation time delay can be implemented. The excellence of the proposed current regulation scheme is verified by experiments for the GTO inverter-fed induction motor drive system controlled by a DSP-TMS320C30     

PWM电机驱动系统中共模电压和轴电压的抑制

为了抑制PWM驱动电机系统中的高频共模电压和轴电压.提出一种无源滤波器拓扑结构.通过对传导干扰传播途径的分析,设计滤波器拓扑结构及其参数.该滤波器包括了一个共模滤波器和一个差模滤波器,连接在PWM逆变器的输出侧及整流器的输入侧,共模滤波器分别消除逆变器输出侧与电机之间的共模电压及整流器交流侧的共模电压,差模滤波器消除三相线和线之间的高频差模电压及衰减电机终端出现的过电压.实验结果表明本文提出的方法有效地抑制了共模电压和轴电压,并且使系统的传导干扰发射在整个频段内均不超标,验证了所提出无源滤波器拓扑结构的正确性及参数选择的有效性.     

Five-level GTO inverters for large induction motor drives

The development of large induction motor drives with low torque ripple and fast dynamic response for new or retrofit applications has been limited by the device ratings and problems of series connections. This paper investigates the use of a five-level GTO voltage-sourced inverter for large induction motor drives. The advantages of such a drive are that single GTO thyristors may be used at each level, thereby avoiding the need for series connection of the thyristors. The thyristors are well protected from overvoltages by the clamping action of the DC supply capacitors. The disadvantages are that each DC level requires a separate supply, four in the case of the five-level inverter, and that the devices are not equally loaded. This paper reviews the basic operation of the five-level inverter and possible PWM voltage/frequency control techniques for the specific application of induction motor drives. The simulation results clearly show the unequal loading of the devices and the need for independent voltage supplies for the five levels. It is shown that a combination of several PWM techniques offers the best solution for the drives application. The conclusions indicate that large induction motors with ratings up to 22 MVA, 7.46 kV may be supplied by the five-level inverter using available 4.5 kV, 3.0 kA GTO thyristors. The recommended supply for such an inverter with full regenerative operation over the complete speed range is four, four-quadrant converters in a quasi-24-pulse configuration     

New Approach to a High-Power GTO PWM Inverter for AC Motor Drives

A control method for GTO PWM inverter parallel-set operation and a new protection system for prevention of short-circuit faults caused by turn-off failure, both to realize a high-power drive system are described. Timing control of GTO gate pulse command provided by a feedback loop, and a reactor at the output of the inverter can minimize the cross current flowing between inverters and can balance the output current of each inverter in inverter parallel-set operation. This method eliminates the necessity of selecting GTO's of equal characteristics, and can apply to parallel-set operation of three or more inverters. The new protection system judges the on and off states of the GTO from the GTO gate-cathode voltage and detects turn-off failure of the GTO. This method positively stops the inverter system safely and reliably upon turn-off failure of the GTO. Experiments are carried out on a 30-kVA inverter and two sets of 450-kVA GTO inverters.     

Induction motor drive behavior during unbalanced faults

The ability of an induction motor drive to ‘ride through’ short-term power system faults or voltage dips of several cycles is of interest in processing plants where shutdowns are expensive. In this paper, the rectifier/inverter induction motor drive is modeled to include the effects of an unbalanced supply circuit, such as that caused by a fault in the supply. A three-phase diode bridge rectifier is used to simulate the effects of the overlap angle caused by the unbalanced source reactance and associated harmonics. The filter circuit between the rectifier and inverter is included. A detailed switching function model is chosen for the inverter so that generated harmonics are included in the motor voltage. Experimental results are included.     

Modeling and simulation of ac–dc buck-boost converter fed dc motor with uniform PWM technique

PWM controlled rectifiers can efficiently and economically be employed in low and medium power applications of dc drives and in front-end converters of rectifier–inverter systems while maintaining the advantages of design simplicity and operation reliability of naturally commutated schemes. Due to the high dc voltage that is produced which is greater than the peak voltage of the utility supply, the ac–dc buck-boost converter is especially suited as a front-end power source in variable-speed drive systems to convert the utility supply voltage into a variable dc link voltage where a single-phase or a three-phase utilities power supply is available. In this paper, the dynamic model and steady state equivalent circuit of a single-phase ac–dc buck-boost converter fed dc motor with uniform PWM control is presented. The waveforms of voltage and current, the input and output characteristics of the converter are discussed and verified. Measured, computed and simulated results are shown to be very close and the model is proved to be efficient and accurate.     

复合型电流质量调节装置的研究

提出了一种级联型复合电流质量调节装置主电路拓扑,与传统拓扑相对比,采用了双PWM变换技术.PWM整流器为装置提供了稳定的直流电压,实现输入功率因数近似为1,同时实现了直流电压与输出电流的解耦控制.逆变侧采用谐波与无功统一补偿的控制策略,并采用输出电流直接PI闭环反馈控制,保证良好的电流跟踪效果.最后设计了一套基于DSP+FPGA控制的低压实验原理样机,验证了所提出的主电路拓扑及控制策略的可行性和有效性.