A. Zuccato

Digital adaptive hysteresis current control with clocked commutations and wide operating range

A new hysteresis current control technique for voltage source inverters is proposed, which uses digital calculation to predict the proper band amplitude in order to minimize the error and give a switching frequency synchronized with a clock. The technique is self-adapting to supply and load parameters, and is easily extended to three-phase systems using the decoupling approach already proposed by the same authors. The proposed technique exhibits both the advantages typical of the hysteresis methods, and those of the digital controls. The implementation of the control is done by means of a standard microcontroller and simple additional circuitry. Simulations and experimental tests confirmed the advantages and the excellent performance of the new modulation method. >

Electromagnetic compatibility issues in industrial equipment

The aspects covered by the EMC regulations, in particular European Directive 89/336/EEC, are numerous and often complex. In this article, the authors have tried to summarize the standards recalled by the Directive for industrial and residential equipment and to emphasize some relevant measurement and design problems. The picture is surely vague and incomplete, but one point should be evident: EMC is a real problem and finding solutions which are technically suitable and economically competitive is todays challenge for design engineers.

An AC power supply with sliding-mode control

A sliding-mode control in electronic AC power supplies is presented. This control technique makes it possible to satisfy the increasing demand for the high-level performance of these systems, which include uninterruptible power supplies, test supplies, and fuel cell, and solar cell supplies. The existence and hitting conditions are discussed, and criteria for the selection of the control parameters which define the sliding surface and determine the quality of response are described. Improvements of the method are introduced to accommodate for the time-varying voltage reference and in the presence of an insulation transformer. A three-level, constant-frequency, variable-band dead-beat modulation technique is associated with the sliding control, producing ultrasonic, low-ripple modulation. Tests performed on an experimental prototype confirm the outstanding performance of the adopted control.<<ETX>>

Performance optimization of quasi-direct converters

The paper describes a three-phase to three-phase quasi-direct power converter, i.e. a forced commutated AC/DC/AC power converter with small energy storage devices in the DC link. Since energy storage minimization calls for instantaneous input/output power balance, a proper control strategy is needed. In the paper, an effective digital control of the line current waveforms capable to work with unbalanced line and/or load voltages and providing also high power factor, is presented. After a discussion of the general properties of quasi-direct power converters, design criteria of both power and control sections are given, and experimental results of a 2 kVa prototype are reported.<<ETX>>

Optimum digital control of PWM rectifiers

The paper presents an optimum digital control technique suitable for three-phase PWM rectifiers with a capacitive filter in the DC link. The proposed technique is based on a predictive current control loop, which does not need line voltage sensing and results in minimum RMS current absorption and unity power factor in any operating condition. Moreover, a smooth transition from sinusoidal to square-wave operation is provided and calculation delays are compensated. The control algorithm has been implemented on a INTEL 80C196KC microcontroller and tested on a 2.5 kVA prototype. Some experimental results are reported together with a description of the implemented algorithms.<<ETX>>

Integrated optimum control of quasi-direct converters

This paper deals with control and design of quasi-direct converters, i.e. AC/AC converters including a forced-commutated rectifier, an inverter, and a small filter in the DC link. Converter performance can be optimized by means of a predictive digital control strategy, which ensures instantaneous input-output power balance, fast response, and high power factor. After a discussion of the control strategy, the paper gives design criteria of both power and control sections. Experimental results of a 2.5-kVA prototype are reported.

Analysis of conducted and radiated noise of soft-switched flyback DC-DC converter

This paper is aimed at the design of soft-switched flyback DC-DC converters taking into account conducted and radiated emission noise aspects. In fact, by a proper system design, the use of an active voltage clamp in flyback converters may result in reduced voltage stresses, soft switching of the main devices, and improved EMI. The paper discusses different design aspects and their impact on the generated noise. Theoretical results are confirmed by experimental measurements.