A Three-Phase Inverter with Reactive Power Control

A new type of self-commutated inverter for fixed or moderately variable frequency has been developed. The inverter is characterized by an extremely uncomplicated main circuit. In its basic form the inverter contains two converter circuits: a principal converter circuit and an auxiliary converter circuit. The principal converter circuit transfers power from the input dc side to the output ac side, and the auxiliary converter circuit generates an inductive current to balance the reactive current of a three-phase capacitor on the ac side. This capacitor has the combined function of a phase compensator, a filter capacitor, and is also the source of the commutating voltage. Both converter circuits are of the line commutated type, meaning that at power frequencies normal converter thyristors can be employed. This makes it possible to build high-power inverters without series or parallel connected thyristors. All filter reactors are smoothing reactors placed on the dc side of the converter circuits. Thus the inverter has a very good efficiency even at the higher frequencies. The ability of a converter circuit to generate a negative sequence current when unsymmetrically controlled makes the inverter insensitive to unbalanced loads. The transient behavior of the inverter is similar to that obtained from a conventional self-commutated inverter with an output filter.     

一种感应电机驱动器容错控制方法

感应电机闭环变频驱动系统中,转速传感器、电流传感器、电压传感器作为反馈单元在速度反馈和磁通估算中起到了重要作用,当其出现故障时会因驱动器故障保护功能造成系统停机.该文研究了感应电机驱动器的四种基本控制方法,针对变频器的传感器故障,提出了一种基于数据融合的容错控制方案.仿真研究证明了所提出的控制方法的有效性.     

Control System Design of a Current Inverter Induction Motor Drive

An analytical design is presented of the control system of a slip-controlled current inverter induction motor drive. First of all, the drive dynamics are modeled in a control-oriented perspective. Afterwards, the transfer function between the rectifier output voltage and the inverter current is thoroughly analyzed and the results used to design the current controller. Two function generators are then synthetized and incorporated in the speed loop so as to obtain constant rotor flux operation and satisfactory torque dynamics. Lastly, the speed controller is designed for a fast and accurate response. All the parameters of the control system are given in terms of performance specifications and drive data. A computer implementation of the drive system is carried out and performance tests are shown.     

负载不对称三相串联谐振逆变器电流平衡控制策略

为实现对三相无线电能传输系统功率传输的有效控制,对一次侧采用串联谐振逆变器的三相无线电能传输系统进行了详细的分析。基于PR控制器可有效实现对某一频率的正弦信号进行跟踪控制,针对负载不对称工作模式下三相电流不平衡导致功率传输控制困难问题,在??坐标系中采用PR控制器,对一次侧三相电流进行电流平衡控制。仿真和实验结果表明,PR控制器能够对三相串联谐振逆变器的负载电流进行追踪控制,较好地解决三相电流不平衡问题,为三相无线电能传输系统的功率传输控制研究奠定了基础。     

基于dSPACE平台的多相感应电机控制系统研究

介绍一种基于dSPACE半实物仿真技术的舰船电力推进多相感应电机控制系统.本系统在MATLAB/Simulink环境中建立数据采集、驱动、保护等硬件系统的仿真模型和矢量变换、dq轴电流PI调节等相关控制算法,利用dSPACE快速控制原型方法对多相感应电机及其逆变器进行控制,并通过ControlDesk模块开发后期管理和监控平台.15 kW样机试验研究表明,所建立的半实物仿真控制系统稳定、可靠,实时性好,且便于在线修改控制结构和相关参数,为舰船电力推进变频调速系统提供一种可行方案,同时也较好地解决了大型舰船综合电力推进系统的试验室闭环测试问题.     

Optimal Efficiency Drive of a Current Source Inverter Fed Induction Motor by Flux Control

When an induction motor is driven under light loads, the efficiency can be substantially improved by reducing the air-gap flux of the motor. The air-gap flux can be indirectly controlled by adjusting the stator current and slip frequency in the case of a current source inverter induction motor drive system. The relationship between the stator current and the slip frequency for an optimal efficiency control is derived, and the control loop is suggested. By this method, ten percent or more improvement in the efficiency is obtained at a quarter of the full load. Generally, the reduced air-gap flux may result in undesirable dynamic responses. The small signal analysis is used in order to estimate the transient characteristics. The experimental results indicate a stable operation and a good dynamic response.     

A Microcomputer-Based Control Signal Generator for a Three-Phase Switching Power Inverter

A three-phase electronic switching inverter has been firmly established as a power source for ac motors in variable-speed applications. In generating control signals for such an inverter, microcomputers are playing an increasingly important role. A micro- computer-based system (using 8051 from Intel) for the generation of pulsewidth modulated (PWM) control signals for a transistorized voltage controlled three-phase inverter is described. The computational algorithm is based on modification of the triangular modulation strategy. The polarity of the triangular timing wave is made the same as the polarity of the reference wave. This eliminates the potential hazard of a "shoot-through" at each zero crossing of the control signal. The widths of the pulses, their positions along the time axis, and the number of pulses per period of the output signal are computed in real time.     

基于级联型逆变器的感应电机无速度传感器矢量控制

针对采用级联型逆变器的感应电机矢量控制系统,提出了基于反电动势的转速辨识方法。该方法以反电动势作为系统模型输出来构造模型参考自适应系统(MRAS)。MRAS采用参考模型和可调模型并联型结构实现转速辨识,消除了纯积分环节带来的问题。将所提方法应用于感应电机矢量控制系统并通过仿真和试验得以实现。仿真和试验结果表明,该方法易于实现,能够准确估计电机的转速。     

A New Control of PWM Inverter Waveform for Minimum Loss Operation of an Induction Motor Drive

A simplified method to calculate harmonic currents of an induction motor and optimum PWM switching patterns to minimize the harmonic loss are presented. Neglecting the harmonic iron loss, the harmonic loss of the motor is proportional to the square of the rms current. The waveform of the harmonic current is approximately equal to that of the leakage reactance applied to the same PWM voltage. Its approximation error is very small under normal operating condition. The main results obtained using these approximation are as follows: 1) the optimum PWM patterns of the pulsenumber from seven to 41; 2) how to choose the optimum pattern and calculate it by using a computer; 3) the effect of a resistance of the windings and skin effect of the secondary conductor; and 4) microcomputer PWM optimum voltage control schemes. Comparison with other controls is shown by using experimental and calculating results and confirms the effectiveness of this control scheme.     

Analysis of Field Orientation Control of Current Source Inverter Drive Induction Motor Systems

The field orientation control of current source inverter (CSI) drive induction motor (IM) systems has been known to give an induction motor dc motorlike characteristics. As a result of an analysis, the characteristic of these systems does not necessarily coincide with that of dc motor systems, especially with light loads. The result of the analysis is verified by experiments.     

无线电能传输系统三相相移控制逆变器研发

设计一种为无线电能传输系统提供高频交流电的三相相移控制逆变器。该逆变器由三相D类半桥逆变桥组成,其开关管运行于固定的切换频率下,通过调整各相半桥的驱动相位差来调节输出电压,从而实现无线电能传输系统功率的调节。对三相相移逆变器的主要性能,包括相移角与输出电压的关系、相电流、各相零电压切换状态等进行分析,并推导无线电能传输系统在使用相移控制和频率控制下的效率。开发三相的相移逆变器原型机并应用于无线电能传输系统,在两个外边长为90cm、70cm的平面矩形螺旋线圈间传输能量。实验表明当相移角从0°到120°之间调节时,在接收端10Ω电阻负载上接收到的功率从5.2kW到0变化。同时在最大输出功率时测得逆变器直流输入到接收端直流负载的DC-DC最大效率为94%。     

Thermal Behavior of a Three-Phase Induction Motor Fed by a Fault-Tolerant Voltage Source Inverter

This paper presents the results of an investigation regarding the thermal behavior of a three-phase induction motor when supplied by a reconfigured three-phase voltage source inverter with fault-tolerant capabilities. For this purpose, a fault-tolerant operating strategy based on the connection of the faulty inverter leg to the dc link middle point was considered. The experimentally obtained results show that, as far as the motor thermal characteristics are concerned, it is not necessary to reinforce the motor insulation properties since it is already prepared for such an operation     

Performance Analysis of a Three-Phase Induction Machine With Inclined Static Eccentricity

Fault diagnosis is gaining more attention for electric machines running critical loads, whose sudden breakdown can result in unpredictable revenue losses. Consequently, the motor drive systems with fault diagnostic and prediction features are of great concern and are becoming almost indispensable. Among all kinds of common faults, quite a few have relationship with unequal air gap. So far, work on detection of eccentricity-related faults in induction and synchronous machines has been well documented. However, a few are reported on faults resulting from axial nonuniform air gap. This paper investigates the performance of a three-phase induction machine with nonuniform static eccentricity (SE) along axial direction or inclined SE. A variant of modified winding function approach is applied to study this fault. The relationship between the number of rotor bars and poles, and the existence of fault-related current harmonics is discussed. It is shown that inclined eccentricity also demonstrates similar characteristics such as circumferential nonuniform air gap (SE). More importantly, it has been proved conclusively that inclined eccentricity symmetric to the midpoint of the machine shaft cannot be recognized from the current spectrum and would therefore require some other form of detection. Finite-element results to verify the inductance values used in simulation are also presented. The analysis is supplemented by the stator current spectra obtained from simulated results for different load and fault conditions. Finally, a four-pole 45-rotor-bar 2-kW induction motor is used to validate the theoretical and simulation results experimentally. Both current as well as vibration spectra are presented     

三相感应电机电流模式定向控制与新逆变驱动

提出了三相感应电机新的逆变驱动策略与电流模式定向控制(Current Mode Oriented Control,简称CMOC)的方法.在新逆变驱动策略的控制下,三相感应电机具有平滑的控制输入和更高的控制精度.完整的控制系统由内部控制环与外部控制环组成,内环实现感应电机速度调节和电流控制,而外环实现电机驱动.由于新逆变驱动策略具有LC滤波,因此感应电机的控制输入平滑.逆变器开关驱动由滑模控制实现.由于逆变器开关律由滑模控制直接驱动,因此不存在PWM驱动方式下的死因时间问题.实验结果验证了该方案的有效性.     

不平衡工况下基于虚拟阻抗法的并联三相四桥臂逆变器的桥臂控制

不平衡工况下,三相四桥臂逆变器并联系统不仅可以输出平衡的三相电压波形,而且还可以拓展系统的容量。与传统的三桥臂逆变器并联系统相比,三相四桥臂逆变器并联系统需要对正序、负序和零序电流进行控制,因此三相四桥臂逆变器的并联控制系统更为复杂。该文对三相四桥臂逆变器并联运行时,各序电流的分配进行了分析。为了使逆变器输出的正序、负序和零序电流能够按并联逆变器的容量分配,提出了正序电流使用下垂控制、负序电流与第四桥臂电流使用虚拟阻抗法分别控制正序、负序和零序电流的分配,并且对三相四桥臂逆变器的前三桥臂与第四桥臂分别进行控制,最终在不平衡工况下使并联三相四桥臂逆变器系统输出电压平衡且输出电流和输出功率按并联逆变器的容量分配,减小系统的环流。仿真和实验验证了该方法的有效性。     

基于三电平逆变器的异步电动机直接转矩控制

构建了基于二极管中点钳位型三电平逆变电路的异步电动机直接转矩控制系统。在对控制系统进行深入理论分析的基础上,提出了一种简单的开关矢量选择方案,有效地实现了矢量选择与中点电压平衡,并通过仿真分析验证了所提出算法的有效性。该方案适合应用于大容量传动场合。     

Control Algorithm for the Inverter Fed Induction Motor Drive with DC Current Feedback Loop Based on Principles of the Vector Control

ABSTRACT

This paper brings out a control algorithm for VSI fed induction motor drives based on the converter DC link current feedback. It is shown that the speed and flux can be controlled over the wide speed and load range quite satisfactorily for simpler drives. The base commands of both the inverter voltage and frequency are proportional to the reference speed, but each of them is further modified by the signals derived from the DC current sensor. The algorithm is based on the equations well known from the vector control theory, and is aimed to obtain the constant rotor flux and proportionality between the electrical torque, the slip frequency and the active component of the stator current. In this way, the problems of slip compensation, Ri compensation and correction of U/f characteristics are solved in the same time. Analytical considerations and computer simulations of the proposed control structure are in close agreement with the experimental results measured on a prototype drive.     

电流源型逆变器供电的感应电动机最佳效率运行的研究

本文提出了一个电流源型逆变器供电的感应电动机在轻载下以最佳效率运行的方法,通过调节定子电路和转差频率,减少轻载时电动机的气隙磁通,提高运行效率,试验表明,四分之一额定负载下,效率可以提高百分之十以上。     

Triac Speed Control of Three-Phase Induction Motor with Phase-Locked Loop Regulation

The speed control of a three-phase squirrel cage induction motor by employing triacs in the lines which operate in the normal phase control mode is described. The inherent limitation of low circuit commutated (dv/dt), which makes the triac circuit somewhat unreliable, has been overcome by suitably designing the snubber circuit. The closed-loop speed regulation of the system is then investigated by employing digital phase-locked loop scheme. Compared to the conventional method with antiparallel SCR's and analog servo, the present scheme is somewhat simpler, more economical, and extreme precision in speed control is possible. A complete model of the speed control system has been designed and experimentally evaluated in the laboratory.     

变频液压型注塑机生产成品质量控制

因系统变频改造所受到的影响,注塑机射胶速度动态性能下降,变频液压型注塑机生产率以及成品率下降。通过自学习思想和前馈控制算法在变频液压注塑机系统中的运用,很好地改进了原系统性能,应用前景广阔。