EPE Journal Volume 05-3/4 
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EPE Journal Volume 05-3/4 - Editorial
EPE Journal Volume 05-3/4 - Papers



 EPE Journal Volume 05-3/4 - Editorial 

Power Electronics in Europe in 1996  [Details]
By B. Sneyers

The Editorial of the EPE Journal Volume 5 N°3/4, "Power Electronics in Europe in 1996", written by Ir. Brigitte Sneyers, the Editor of EPE Association


 EPE Journal Volume 05-3/4 - Papers 

Gate-Controlled dv/dt- and di/dt-Limitation in High power IGBT Converters  [Details]
By C. Gerster, P. Hofer

A central issue in reducing the size and cost of IGBT power converters is to control or limit dv/dt and di/dt during the switching process. Load side snubbers and clamp circuits are bulky and expensive. Increasing the gate resistors values is cheap and simple but switching times as well as power losses are increased.

In this article the authors suggest to use a gate-side control loop to limit the switching transients. No extra components are needed on the load side since the internal stray inductance of the power module is used to sense the current. The only extra component is a high voltage capacitor of some picofarads to sense the voltage transients. The overall losses are reduced compared to the traditional method, where the gate resistor value is increased to limit the switching speed. The proposed method can easily be integrated in an intelligent gate-drive circuit.

The AC-DC Stage: A Survey of Structures and Chopper Control Modes for Power Factor Correction  [Details]
By C. Andrieu; J.-P. Ferrieux; M. Rocher

Over the last few years, power factor correction has become an important field of research, due mainly to changing low frequency EMC standards. Our interest lies in AC/DC conversion from 230 V line voltage. Since July 1 1995 and for this type of line, European standard EN 61000-3-2 has replaced EN 60555-2, which entails great change for low and medium power converters.
Usually, the stage between the network and a DC/Dc converter is composed of an uncontrolled diode rectifier followed by a structure comprising at least an inductor and a capacitor. First, the capacitor sets the voltage variation in primary DC voltage and the inductor induces the input current waveform. However, these characteristics are not controlled by the typical rectifier and depend on network conditions or on load variations. This low-cost, robust system is analysed respecting EN 60555-2 and EN 61000-3-2 criteria. The relation between total harmonic distortion and the power factor is shown.
In order to improve the behavior of this stage, an active component has been added to the existing passive components when redesigning the chopper. This chopper is controlled in "Power Factor Correction" mode i.e. input current is triggered to a sinusoidal current from a loop. Depending on the choice of the chopper, one or several high frequency passive components are needed but a low frequency filter (capacitance on output) is still required.
The paper goes on to study the use of the boost chopper as a preregulator in association with another converter, and then the use of the insulated flyback converter to supply DC output voltage. For both, the different PFC control modes which enable a sinusoidal line current to be obtained are analysed and discussed for discontinuous and continuous conduction modes.

The Behaviour of Homogeneous NPT-IGBTs at Hard and Soft Switching  [Details]
By M. Cotorogea; T. Reimann; S. Bernet

At present, power converter systems with d.c.-link on the basis of hard switching dominate in the field of power electronics. However, higher switching frequencies are necesasry to reduce the noise as well as the size and weight of passive energy stores in a lot of applications. There are two ways to realize soft switching processes in principle: Zero-Current-Switching (ZCS) and Zero-Voltage-Switching (ZVS). The paper describes the behaviour of NPT-IGBTs at hard and soft switching (ZVS, ZCS).
The internal processes of the Non-Punch-Through (NPT)-structure are analysed on the basis of a new very accurate Pspice IGBT model.
Additional measurements show that NPT-IGBTs possess a very good behaviour under hard switching conditions. By contrary to that Punch-Through (PT)-IGBTs offer the best features at soft switching.

The Effect of Carrier Frequency Modulation of PWM Waveforms on Conducted EMC Problems in Switched Mode Power Supplies  [Details]
By D. Stone; B. Chambers

Electromagnetic compatibility (EMC) remains an issue which can present many problems to designers of high frequency power converter circuits. Usual techniques for alliviating the problems of interference generation by power converters involve the use of screening materials and filters, however, the effectiveness of such measures depends on the frequency of the interference and the power density at each frequency of interest. As pulse width modulation (PWM) generates high frequency harmonics at multiples of the switching frequency, modulation of the switching frequency may be used to spread the spectral power density present at these harmonic frequencies. This paper presents a technique of frequency-hopping spread-spectrum modulation which may be applied to switched-mode power converters (SMPC's) to reduce the spectral popwer density at harmonics of the switching frequency. The influence of the peak frequency deviation, the modulation sequence length and the type of modulation sequence on the resultant spectrum are discussed. These prediction have been broadly confirmed in practice, with measurements carried out with an EMC pre-compliance test system.

Iterative Voltage and Current High Frequency Line Conditioner  [Details]
By F. Yeves; J. Carpio; S. Martínez; V. Feliu

This paper describes the theory and some practical results of a voltage and current line conditioner based on high frequency active IGBT filters. This conditioner has been developed for a power range of 50 kVA to 1000 kVA under a P.I.E. project led by the utility company IBERDROLA in colaboration with SAFT-NIFE Ibérica and ASINEL.
The power topology consists on a parallel current active filter aimed to cancel current harmonics and reactive current from non ideal loads which in time feeds a series voltage active filter which reduces the line voltage distortion, steps, flicker and slow voltage changes. In the case of a short interruption, the current filter will act as a voltage inverter, feeding a practical part of the load during 500 ms. The power circuit has also the possibility of working as a universal conditioner.
The control circuit is based on two independent DSP's. This fact allows the current filter to work as a separate equipment. A very great effort is being done on optimizing the control algorithms in order to reduce response time and the noise immunity. The converters control actuates on both the duty cycle and the polarity of the modulation. First practical results have been presented at PQA '94.

The 3-Phase Stepping Motor System, Background, Functions  [Details]
By W. Siefert

Stepping motors are known as cost-effective, robust drives. They are used in a whole range of machines and devices and perform all kinds of tasks from simple point-to-point positioning in handling and automation systems, fast, short-term movements in the textile industry to high precision synchronized movements in printing applications. Stepping motors excel with a simple, sturdy construction (usually without feedback systems), they can be installed quickly and easily without requiring the user to set up complex control parameters. And they are, to a considerable degree, independent of the load and the inert mass.
2-phase stepping motors are usually employed for simple applications, while the 5-phase stepping motor has become the reliable solution for more demanding tasks. The advantages of the 5-phase stepping motor include the high natural resolution of 500 or 1.000 steps per revolution, its low noise and low resonance operation. Its low detent torque makes it ideal for micro-step operation. On the other hand, the considerable wiring and switching technology required for the 5-phase stepping motor can adversely affects the system costs.
The increasing demands on a state-of-the-art stepping motor system primarily focus on reduced noise development and increased power of the drive. At the same time, the cost factor plays an important role. As it becomes possible to develop circuits with ever higher degrees of of integration, BERGER LAHR decided to face the challenge and break new ground in the area of stepping motor technology. By means of using a 3-phase sine control, it is possible to reduce the number of phase windings. The number of steps per revolution is only determioned by the number of pole pairs of the motor and by the electronic system. For decades, the 3-phase technology has been used as a cost-effective system for generating rotating fields in the area of electronic power engineering. The advantages are self-evident. Therefore, the development of a 3-phase stepping motor system is a natural consequence. In addition to the new features, the system was supposed to meet all requirements known from the 5-phase stepping motor system at significantly reduced costs. This involved considerable development efforts, both in terms of the motor itself and in terms of the electronic system.

Voltage Source Converters and Drives Simulation at System Level for Control Design Applications  [Details]
By M. Carpita

The paper describes the simulation of power converters at system level, with reference to the Matlab-Simulink program. The characteristics of Matlab-Simulink as a simulation tool for power electronics system are decribed, especially as far as the analysis of the control system is concerned. Some examples are presented, relative to both power converters and motor models. An example related to the simulation of an induction motor drive with power and control aspects is described too.

A Space Vector Induction Motor Model for the PSpice Circuit Simulator  [Details]
By J. Salo; J. Pyrhönen; M. Niemelä

The article introduces a linear space vector induction motor model for the PSpice circuit simulator. Circuit simulator software programs are widely used in the area of electronics, but these programs can be used to simulate power electronic devices and drives as well. Commercially available circuit simulators are usually missing motor models. Induction motor model in the circuit simulator should behave like a real machine, providing same response to the input as a real motor. The simulated current waveforms drawn by the motor model must be similar to the real ones with acceptable accuracy. That helps in selecting suitable switches for the drive. The space vector model developed here is designed for the SPICE family circuit simulators.
The properties of the linear space vector induction motor model introduced here are verified with experimental tests in sinusoidal conditions and also with a square-wave inverter supply.