The Faculty of Electrical Engineering was founded in 1953 as one of three faculties of the Railway College in Prague, and was re-established during restructuralization changes in 1992. At present the process of faculty development still continues and some new branches of educational, research and technological development complete the traditional educational orientations, namely: information technologies, power electronic systems and modern methods of electric networks control. The interdisciplinary branches as for example mechatronics, telecommunication management and biomedicine are also in progress.

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Faculty of Electrical Engineering

Modern controlled electric drives are exclusively based on three-phase motors that are fed from three-phase pulse width modulated (PWM) inverters. Most of modern controlled electric drive applications, such as lifts, cranes and tooling machines are characterized by high ratio of the peak to average power, and high demand for braking at the rated power. In ordinary drives, the braking energy, which represents 30-50% of the consumed energy, is dissipated on a braking resistor. Apart from the “energetic” issue, the mains interruption and degradation, the input current quality and the load fluctuation are additional issues to be addressed and solved.The ultra-capacitor dedicated for power conversion applications has been discussed. In comparison to electrochemical batteries, the ultra-capacitors have higher power density and efficiency, longer life time and greater cycling capability. This makes the ultra-capacitor an excellent candidate for power conversion applications.A new electric drive converter equipped with the ultra-capacitor is presented in the dissertation. The ultra-capacitor with an inter-connection dc-dc converter is used to store and recover the drive braking energy. Moreover, the dc-dc converter controls the rectifier current and the dc bus voltage. The drive input current THD is reduced to 30%. The dc bus voltage is boosted and controlled constant and ripple free regardless on the load and the mains voltage variation. Moreover, the drive input peak power can be smoothed. The presented solution is theoretically analysed and verified by set of simulations and experiments. The results are presented and discussed

Ultra-capacitor based regenerative energy storage and power factor correction device for controlled electric drives

This study presents a novel algorithm for the induction motor torque control in field-weakening region. The proposed method insures maximum DC bus utilisation and extends the torque–speed curve up to the system limits. Controller is based on the stator voltage angle control. It provides full DC-link disturbance rejection and offers the torque response time sufficient for most applications. The algorithm is simple, without neither the outer flux loop nor the inner current loop. Dynamic response is preserved over wide speed range by means of gain-scheduling. Simulations and experiments prove an ease of implementation and the robustness of the proposed solution. This study comprises analytical considerations, simulation results, a detailed description of implementation steps and extensive experimental results.

Voltage angle direct torque control of induction machine in field-weakening regime

In this paper, the problem of the ripple torque experienced with permanent magnet synchronous motors (PMSM) is discussed and solved by adopting advanced simulation tools The two pulsating torque components are identified: the cogging (detent) torque and the slot harmonics caused ripple Simulated results are verified by using finite element method (FEM), taking into account the nonlinearity of magnetic material and secondary effects The results are than proved on the experimental setup Simplified model for the torque disturbance is proposed, suitable for designing active and passive compensating measures

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Torque Ripple Verification in PM Machines

The paper presents the implementation of a rapid prototyping system that includes a floating-point digital signal processor, a field programmable gate array (FPGA)-based pulse width modulation (PWM) signal generator and a multiport A/D converter. The PWM generator is implemented using XILINX SPARTAN II FPGA and the Verilog hardware description language. The system is a 4-channel PWM generator prototype designed for development needs.

A DSP-controlled PWM generator using field programmable gate array

1. Introduction. General characteristics of model of electric drive and control systems. General remarks on control by means of microprocessors. 2. Signal Processing. Sampling of continuous signals. Analogue and digital filters. Quantization of signals. A/D and D/A converters. The systems for connecting microcomputers with peripheral equipment. 3. Digital Control Algorithms. General problems. Digital algorithms of the PID class. Controller with definite setting time. Other algorithms of digital control. 4. Computer-aided Design of the Digital Control of Electric Drives. General principles. Principles of the simulation of digitally controlled electric drive systems. Principles of parametric computer optimization. Computer methods of designing digital filters. Discrete frequency computer methods. 5. The Many-sided Problems of Electric Drive Controls. Multimachine electric drive systems. Systems, large-scale systems and complex systems. A complex mathematical model of a rolling mill. Types of hierarchical structures. The organization of a multiprocessor system. Complex automatic systems. References. Index.

Ludger M. Szklarski

Papers

Digital control of electric drives