A control method to realize sinusoidal input and output current waveforms for matrix converters based on PWM

A matrix converter (MC) is a three‐phase AC‐to‐AC direct converter without any energy storage requirement. It is expected to be a next‐generation converter by reason of possibilities of small size and high efficiency. At present, there are some problems preventing it from being used practically. One of the problems is the distortion in the input current. The control methods proposed so far have not realized sufficient reduction of the input current harmonics compared with conventional PWM rectifiers. As a solution to these problems, many approaches have been proposed. In the present paper, an improved PWM method that can achieve both sinusoidal input and output currents simultaneously is considered. In this method, the MC is treated as a controlled voltage source viewed from the load side. On the other hand, it is treated as a controlled current source viewed from the line side. The proposed control method is based on the mathematical expression of the function of the PWM operation of MC. To improve the input current waveform, two line‐to‐line voltages of the three‐phase line are used to control the output current. The output duty ratio of the two line‐to‐line voltages is utilized to improve the input current waveform without affecting the controllability of the output current. In addition, the compensation of the variations in the line voltage and the output current are introduced. In this way, the proposed method can realize the sinusoidal input and output currents. The effectiveness of the proposed control method is confirmed by some experimental results employing a laboratory prototype. © 2007 Wiley Periodicals, Inc. Electr Eng Jpn, 161(1): 66–76, 2007; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.20242     

空间矢量PWM多相变频调速系统非正弦供电技术

针对多相感应电机正弦供电时直流母线电压利用率低、输出转矩小的问题,建立了多相感应电机非正弦空间电压矢量PWM(NSVPWM)的数学模型,分析了NSVPWM与谐波注入PWM的内在联系,探讨了NSVPWM各个d-q平面参考电压矢量给定问题.以一台九相集中整距绕组感应电机为例,在保持齿、轭部磁密幅值分别相等、定子铜耗相同的前提下,将其分别在SPWM、正弦空间电压矢量PWM和NSVPWM调制策略下的输出转矩进行比较.试验结果证明,采用NSVPWM控制策略时,九相集中整距绕组感应电机输出转矩比采用SPWM时提高了大约6.42%,最后分析了其原因.     

Output voltage control method of PWM-controlled cycloconverters with space vectors

A new output voltage control method for PWM-controlled cycloconverters with space vectors is proposed in this paper. Results are as follows:. (1) The classification and the systematic behavior of the space vectors of PWM-controlled cycloconverters are clarified through the analysis. (2) A new output voltage control method that makes excellent output voltage waveforms is proposed using the results of this analysis. (3) Feasibility of the proposed output voltage control method is confirmed by simulation. (4) Output voltage waveforms of the PWM-controlled cycloconverters are compared with those of the PWM-controlled inverters, using the performance index of variance of time-integral of higher harmonic components. Therefore, the proposed control method may reduce both acoustic noise and torque ripple of induction motors.     

A family of single-phase direct-link uninterruptible power supply with unity power factor and sinusoidal input current

In this paper, a family of single-phase direct-link uninterruptible power supply (DLUPS) is proposed to achieve sinusoidal input current waveforms, unity power factors without current sensors and conduct single-stage voltage conversion in normal, backup and charging modes. The design considerations concerning the determination of the power circuit elements are also given for reference. Finally, some examples of simulated and experimental results are presented.     

A control method for improving ac input current waveform of current-type PWM rectifiers

Recently, PWM rectifiers which realize high-power factor and almost sinusoidal ac input current have been proposed and some of them have already been put into practice. In many cases the PWM rectifiers are of current type, that is, they have a smoothing reactor on the dc side. In such rectifiers, an LC filter has to be inserted on the ac side to reduce current harmonics due to the PWM operation. However, the LC filter may cause waveform distortion and transient oscillation of the ac side current. As a solution to this problem, a new control method is proposed introducing ac side current control by means of state feedback of the LC filter. In this case, both the dc output current and the ac input current controls should be achieved by the PWM operation of the rectifier. Furthermore, to obtain sufficient controllability regardless of the operating condition, the dc output and ac input current controls should be done independently. To meet these requirements, existing control methods for PWM rectifiers are not directly applicable. In this paper, a novel control circuit configuration and a method of generating a PWM pulse pattern suitable for the proposed control method are described in detail. From the viewpoint of stability, feedback coefficients and circuit parameters are investigated on the basis of root locus analysis. Some experimental results also are shown to confirm the effectiveness of the proposed control method and the validity of the analytical results. Improvement of the ac side current waveform and the stability of the transient response are demonstrated by these experimental results.     

A power factor correction with two‐input current mode using voltage doubler rectifier

For rectifier circuits with a small capacity, such as those for consumer electronics and appliances, capacitor input‐type rectifier circuits are generally used. Consequently, various harmonics generated within the power system become a serious problem. Various studies of this effect have been reported. However, most of these employ switching devices, such as FETs and the like. The absence of switching devices makes systems more tolerant to overload, and brings low radio noise benefits. We propose a power factor correction scheme using a voltage doubler rectifier without switching devices. In this method, the input current is divided into two periods, where one period charges the small input capacitor and the other charges the large output capacitor. By dividing the input current into two different modes, the current conduction period can be widened and harmonics can largely be canceled between the two modes. Hence, the harmonic characteristics can be significantly improved, whereby the lower‐order harmonics, such as the fifth and seventh orders, are much reduced. The results are confirmed by theoretical and experimental implementations. © 2001 Scripta Technica, Electr Eng Jpn, 137(3): 52–58, 2001     

AC voltage and current sensorless control method for three‐phase PWM converter

We present a three‐phase PWM converter without AC voltage and AC current sensors. The phase angle used in the control system is adjusted by using a PLL controller without sensing AC voltage. To prevent overcurrent at startup, the initial phase angle of the source voltage is estimated from the shunt current using a novel strategy. Furthermore, the phase currents can be reconstructed from the shunt current without any modification of the PWM pattern. To reduce the effect of current ripple, the shunt current is sampled twice for every phase in one PWM period and the sample timings are carefully adjusted. All of the proposed control schemes can be implanted using a single chip microprocessor (SH7046, Renesas Tech.). Simulation and experimental results with a 5‐kW prototype confirmed that the schemes worked well. © 2010 Wiley Periodicals, Inc. Electr Eng Jpn, 172(4): 48–57, 2010; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.20983     

A three‐phase voltage‐source PWM inverter system characterized by sinusoidal output voltage with neither common‐mode voltage nor normal‐mode voltage

This paper deals with an inverter system integrating a small‐rated passive EMI filter with a three‐phase voltage‐source PWM inverter. The purpose of the EMI filter is to eliminate both common‐mode and normal‐mode voltages from the output voltage of the inverter. The motivation of this research is based on the well‐known fact that the higher the carrier or switching frequency, the smaller and the more effective the EMI filter. An experimental system consisting of a 5‐kVA inverter, a 3.7‐kW induction motor, and a specially designed passive EMI filter was constructed to verify the viability and effectiveness of the EMI filter. As a result, it is shown experimentally that both three‐phase line‐to‐line and line‐to‐neutral output voltages look purely sinusoidal as if the inverter system were an ideal variable‐voltage, variable‐frequency power supply when viewed from the motor terminals. This results in complete solution of serious issues related to common‐mode and normal‐mode voltages produced by the inverter. © 2003 Wiley Periodicals, Inc. Electr Eng Jpn, 145(4): 88–96, 2003; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.10206     

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     

A new control strategy for voltage-type PWM rectifiers to realizezero steady-state control error in input current

In this paper, a new simple control strategy for AC input current of voltage-type pulsewidth modulation (PWM) rectifiers which can eliminate the steady-state control error completely is proposed. This control method requires neither the instantaneous value of the supply voltage nor any accurate circuit parameters on the AC side of the rectifier. Thus, a robust operation against the variation of the circuit parameters can be achieved. In the proposed control system, a digital resonant element implemented by a digital signal processor (DSP) is introduced as a feedback controller. The digital resonant element exhibits a function similar to an integrator for the fundamental frequency components. Thus, it can eliminate the steady-state control error of the input current completely, The principle of the proposed control method is discussed, and its effectiveness is shown theoretically. The detailed method of the implementation of the lossless digital resonant element is explained. The effects of the harmonics in the supply voltage on the AC input current waveform are clarified. To confirm the effectiveness of the proposed control method, some experimental results from two laboratory test systems are shown     

Improved current control technique of VSI PWM inverters withconstant modulation frequency and extended voltage range

A hysteresis control method for three-phase, current-controlled, VSI PWM (pulse width modulation) inverters characterized by constant switching frequency is presented. The method is based on substantial improvement of the principle of minimization of interference among modulations of the various phases, which does not require any knowledge of load parameters or EMF, provided the load is symmetric. Interference minimization allows PLL (phase-locked loop) control of switching frequency. The inherent benefits of the proposed technique are full exploitation of inverter voltage capabilities and a definite reduction ion commutation losses. The method minimizes commutation losses and current ripple while allowing maximum output AC voltage to be obtained from the inverter. The method exhibits all the favorable characteristics of hysteresis controls: fast response, good accuracy, and robustness. Experimental tests confirmed theoretical forecasts, showing excellent performance of the control     

三相PWM整流器电压定向控制算法研究

详细分析了三相PWM整流器电压定向控制方法的基本原理,给出了其数学模型及控制系统的结构图,说明了各个部分的作用。利用Matlab/Simulink工具箱,建立了仿真模型进行了研究。仿真结果表明,该方法效果优异,系统能够很好地实现控制目标。     

Design aspects of synchronous PWM rectifier-inverter systems underunbalanced input voltage conditions

A complete analysis of a synchronous front-end PWM rectifier-inverter system under unbalanced input voltage conditions is presented. The analysis includes the harmonic assessment of input/output current and voltage waveforms. It is shown both theoretically and experimentally that input voltage unbalance generates uncharacteristic low-frequency harmonic components in the input and output currents. Special emphasis is given to the generation of a DC component in the inverter output voltage in the case in which the output frequency is twice the input frequency. System design curves for different degrees of unbalance for all major system components are reported. Key predicted results are confirmed experimentally     

三相电压型PWM整流器的二自由度I-PD电压控制

伺服电机为负载的三相PWM整流器系统中,传统PI级联控制结构不能兼顾定点跟踪和抗负载扰动.结合二自由度控制理论和整流器运行特点,提出基于I-PD电压控制器的二自由度控制策略.根据整流器dq坐标系下的数学模型,推导出控制器参数选取的步骤和原则.对控制器抗负载扰动性能,以及网侧电压波动对系统的影响进行分析,得出不同参数下的系统稳定界限.给出系统静动态的仿真和实验结果,并与传统控制结构进行静动态性能的对比分析.仿真和实验结果验证理论分析的正确性,表明该控制策略能够有效抑制初始母线电压超调和电流浪涌,加快电流对负载扰动的动态响应速度,提高系统的稳定性,尤其适合在低压大功率的伺服系统中应用.     

A voltage source PWM rectifier-inverter with feedforward control of instantaneous power

In general, diode rectifiers with electrolytic capacitors on the dc side have been used as dc power supplies for voltage source inverters. This type of rectifiers, however, causes many problems such as poor power factor and harmonics. Recently, voltage source PWM rectifier-inverters have been studied to provide the following advantages; (1) harmonic-free on both ac sides; (2) unity power factor on the input ac side; (3) power flow of either direction or power regeneration; (4) reduction of the dc capacitor. It is, however, difficult for a conventional one to regulate the capacitor voltage on transient states because of having only a voltage feed-back loop. This paper describes a voltage source PWM rectifier-inverter with feed-forward control of instantaneous power. Based on the pq theory, the instantaneous power which is calculated in the control circuit of the inverter is fed forward to the control circuit of the rectifier. The feed-forward control of instantaneous power makes a great contribution to sufficiently suppress voltage fluctuation of the dc capacitor on transient states. Transient characteristics are discussed and some interesting experimental results of a laboratory model are shown.     

Real-time estimation of the electric parameters of an inductionmachine using sinusoidal PWM voltage waveforms

This paper studies the parameter estimation of induction machines. The problems associated with the parameter estimation of induction machines are analyzed through sensitivity functions. Then, models and a procedure to estimate a set of four basic parameters (r_s, σl_s, l_s, and τ_r) are proposed. The discrete-time parameter estimation models are written in the δ operator specifically because it provides good numerical properties at high sampling rates, where the discrete-time model approaches its continuous-time equivalent. This feature permits the direct estimation of the continuous-time parameters. The main feature of the proposed procedure is the possibility to estimate the parameters by using sinusoidal signals, and without the measurement of the machine speed. The experimental results obtained with the proposed estimation procedure are presented and demonstrate that it is possible to map the parameters in terms of the operating conditions of the induction machine