Alternate ASDs: evaluation of the converter topologies suited for integrated motor drives

This article investigates alternative three-phase ASD topologies for integrated motor drives by discussing the hardware requirements and comparing their performance, size of magnetics, and efficiency, which in this case is important in order to determine their cooling requirements. It presents possible converter topologies for the next generation of integrated motor drives, which are arranged in three groups. The grid side performance is analyzed by simulations and their losses estimated. Three recommendations are made, while, for a general application ASD with sinusoidal input current, the choice is given by the price of four diodes against a RB-IGBT.     

三相电压源逆变器内部IGBT模块温度的求解及评估

三相电压源逆变器的工作性能、使用寿命等方面均与其内部绝缘栅双极晶体管(IGBT)模块温度直接相关,故求解及评估该逆变器中IGBT模块的温度对于确保逆变器系统的安全可靠运行具有重要意义。针对现有模型及方法难以求解IGBT模块温度的问题,本文借鉴直接法的思想,提出了一种新的简单实用的IGBT模块温度求解算法。基于拟合及插值算法,推导并建立了IGBT模块功率损耗模型;基于电热比拟理论,探讨并建立了集中参数的IGBT模块等效Cauer传热网络模型,并将传热微分方程差分化;最终,在同一电路仿真器中构建出IGBT模块温度的求解算法。在三相电压源逆变器的算例中,通过与英飞凌IPOSIM的温度计算结果对比,表明本文算法最大误差为3.01%,且温度变化趋势与IPOSIM基本一致,最后利用该算法评估了逆变器在不同负载工况下的IGBT模块温度,所得结果可为合理地进行三相电压源逆变器的散热设计、长期可靠性评估等服务。     

单相有源电力滤波器拓扑结构的分析研究

有源电力滤波器（APF）是现今治理谐波效果最好的补偿装置之一,但由于成本高,难于得到广泛应用。本文在对常规拓扑结构的有源电力滤波器的分析基础上,提出了两种新的拓扑结构———单桥臂带直流电容与不带直流电容拓扑结构,同时提出简单的控制策略。MATLAB仿真研究表明,单桥臂带直流电容拓扑结构的有源滤波器综合效果优于其他两种有源滤波器,该滤波器结构简单、成本低、易于推广使用。     

一种电压型串联谐振逆变电路的仿真分析

为了深入了解且更好地使用电压型逆变电路,对两种电压型逆变电路进行了简要的描述,利用PSPICE软件对两种电路进行了基于实际负载的仿真分析.重点分析传统串联谐振逆变电路与用于负载匹配的串联谐振逆变电路的工作过程,比较它们的优缺点,并给出仿真结果.仿真结果在证明电路能够进行负载匹配的同时也为进一步研究此问题提供了依据.     

A study of a single-phase thyristor inverter

The results of studying the switching processes in a single-phase thyristor inverter operating at a low-voltage controlled thyristor rectifier with constant output current are given. Depending on the angle of rectifier voltage regulating, three switching modes are identified and considered. The maximum values of currents and voltages are defined for each of the modes. The waveforms of currents and voltages are given. It is shown that the nature and duration of the inverter switching processes depend strongly on the angle of rectifier regulating, which is especially to be considered when the inverter operates at higher frequencies.     

Simplified models of a single-phase power electronic inverter for railway power system stability analysis—Development and evaluation

Use of power electronic equipment has increased and introduced new dynamical phenomena in power systems. For example, new electric rail vehicles (locomotives) equipped with modern power electronic traction chains have caused situations of low-frequency power oscillations and instability in single-phase railway power supply systems. This paper presents the development and implementation of an instantaneous value model and simplified fundamental frequency (RMS) models of such an advanced electric rail vehicle in order to investigate their representation of low-frequency dynamics. The dynamical behaviour is studied by use of both time-domain simulations and linear analysis (eigenvalues) and the degree of simplifications regarding controller dynamics and power system dynamics are presented and discussed. An enhanced RMS model is tested in order to account for the impact of fast current dynamics on the low-frequency behaviour. The results show that this enhanced model is corresponding more closely to the instantaneous value model than what can be obtained by the traditional RMS simplifications and indicate that current dynamics should be included in stability studies involving power electronic inverters.     

An algorithm for controlling a multilevel voltage inverter

A vector algorithm for the control of a multilevel voltage inverter is presented. The algorithm is characterized by high efficiency and does not depend on the number of levels in the inverter; it is of methodical importance for understanding the principles based on which multilevel inverters operate.     

Development of a high-efficiency inverter without audible noise

The proposed inverter combines two methods which can significantly decrease the on-state and switching losses. The first method, using a current transformer and a single transistor, makes possible the reduction of the on-state loss to less than one-third of the usual Darlington transistor. The second method, using an auxiliary commutation IGBT in parallel with the transistor, makes possible zero-voltage switching, resulting in no switching loss. To realize higher inverter efficiency, a snubber and its loss recovery circuit are employed. Three-phase inverters were fabricated experimentally to evaluate our idea. Device volume and weight can be decreased to one-third those of a conventional three-phase inverter, and an efficiency of 98.0% from 5 kW to 20 kW is obtained at a switching frequency of 16 kHz. © 1997 Scripta Technica, Inc. Electr Eng Jpn, 120(1): 62–69, 1997     

Harmonic experiences with a large load-commutated inverter drive

This paper illustrates the use of a high-pass filter for reducing troublesome harmonic distortion caused by a large load-commutated inverter drive at a large petrochemical plant. Actual field measurement data of the 12.47 kV distribution system of the plant is given to show the harmonic distortion that was causing operational problems. The harmonic system impedance derived from these measurements was used in the development of an accurate harmonic analysis computer model. This harmonic model was then used to evaluate the application of a high-pass filter to reduce harmonic distortion. Actual field measurements were then made after the installation of the high-pass filter to verify the results of the simulations. The tools used for this paper included a harmonic analyzer, an oscilloscope, a harmonic simulation program, and an electromagnetic transient simulation program. The results of this investigation lead to proposed improvements to IEEE Std 519     

A novel approach for a sinusoidal output inverter

Minimization of the total harmonic distortion (THD) at the output of an inverter is essential to reach the ideal case, i.e. a pure sinusoidal. So far, very intensive studies about this topic have been carried out. In this study, a fully rectified version of a sinusoidal voltage waveform at an utility amplitude and frequency obtained from a well-known buck–boost regulator has been converted to a sinusoidal AC voltage waveform with a simple inverter operation. The purpose of this innovative circuit is to generate an approximate sinusoidal voltage waveform with a quite low THD at the inverter output without invoking the harmonic elimination techniques. Since distortions in the AC link voltage in this circuit fully depend on how well the capacitor current is regulated to its reference, the value of the load current is a critical component in this regulation.     

The comparative evaluation of excellence for student awards

A recurring problem in the award of academic honors is the comparison of the highest grade achieved by students from different groups with different traditions, practices, and evaluation scales. Group averages are not useful because it is the position of the top student that is of interest, not the average; also, the normal distribution cannot be assumed for the upper tail of the distribution, which must be obtained from the data. We find that the upper grades of each group can be modeled very well, permitting the statistical theory of extremes to be used. From the model which we fit to each group separately, we obtain the probability for a top grade at least as high as the one observed, and from this, we obtain the return period which is the expected interval before the return of a similarly high grade. This return period is a common measure which enables top grades from several disparate groups to be compared on the basis of how rare or exceptional they are as members of their own group. The precision of the return period is estimated from the correlation coefficient of the regression model and used to indicate the effectiveness of the decision in a particular case. The method is applied to data from different disciplines at the University of Waterloo, including comparisons among Engineering Departments     

新型PWM逆变器输出无源滤波器的研究

研究了变频器在长线传输时产生的过电压问题，理论分析表明，电动机端过电压与PWM变频器采用的开关器件上升时间和PWM变频器与电动机之间的电缆长度密切相关：上升时间越短，电缆长度越长，电压反射现象越显著，过电压也越高。为消除PWM变频器长线传输时在电动机端产生的过电压等负面效应，提出了一种逆变器输出无源滤波器。实验研究验证了该滤波器能够将变频器输出的PWM电压滤成近似正弦波，从而有效地抑制电动机端的过电压。这种滤波器还可以有效降低共模电压。文中分析了这种滤波器的共模结构及其可以降低共模电压的原因，实验验证了设计思想的正确性。同一种结构的滤波器能够同时消除差模dv／dt和共模电压，减小了滤波器的体积和成本，结构简单，是一种消除逆变器输出负面效应的有效手段。     

Sensorless control of SRM based on a simple expression of magnetization characteristics

Switched reluctance motors (SRM) have a simpler and more rugged construction than conventional ac motors, and hence are suitable for low‐cost variable‐speed drives in many industrial applications. However, the need to use a traditional position sensor for their control is one of the disadvantages of SRM from the standpoints of cost, size, and reliability. For practical use, there is a need for sensorless drive of SRM. This paper describes position‐sensorless control of SRM based on a simple expression of their nonlinear magnetization characteristics. Successful experiments using a 1.5‐kW, 5400‐rpm SRM with a 6/4 pole configuration have verified the practicability of the proposed sensorless control scheme. © 2001 Scripta Technica, Electr Eng Jpn, 137(2): 52–60, 2001     

一种新型太阳能逆变器辅助电源设计

详细分析了反激控制器边界工作模式原理,设计了一种具有5路独立输出的3 kW太阳能逆变器辅助电源,无需复杂的光耦反馈稳压控制回路,具有结构简单、成本低、效率高和工作可靠等特点.论文给出了多输出太阳能逆变器辅助电源的原理图和反激式高频变压器的具体设计,并对太阳能逆变器辅助电源设计中的EMI抑制措施进行了详细介绍.所设计的电源已经应用于太阳能逆变器中,实验结果表明,电源工作稳定,输出纹波小,变压器无发热现象,满足太阳能逆变器的设计要求.     

A single-phase inverter with a deadbeat regulator of a pulse-wide modulator

The structure of a control system for a pulse-wide modulator (PWM) of a single-phase voltage inverter is proposed; this control system comprises a deadbeat regulator for inducing transient processes with a finite duration in the near vicinity of an equilibrium position. A method for synthesizing the parameters of the regulator for an inverter that includes an active-inductive load with an output voltage feedback is described. Results of modeling the processes, which show a higher efficiency of the deadbeat regulator, are presented.     

Shaping of the load characteristic of a welding inverter

A computer model is used to assess the influence of the transmission coefficient and time constant of the control system on the load characteristic of a high-frequency AC welding inverter.