TRANSACTIONS ON ELECTRICAL ENGINEERING

ISSN 1805-3386

September 23, 2017






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2014 No.1

An Accurate Auto-Tuning Procedure for Encoderless AC Motor Drives in Industrial Environments

Weber, A. R., Weissbacher, J., Steiner, G., Horn, M.

Modern ac motor drives are based on field oriented vector control with feedback and feedforward control units. The feedback control unit for position and speed consists of two cascaded standard PI-controllers. These controllers require information of the position and the derivative of the position, respectively. Typically a shaft encoder provides this information but more often a position observer is used instead. The feedforward control unit uses the set position trajectory in combination with mechanical parameters and essentially imposes the overall dynamics. This work presents a new method for self-commissioning of speed controller, position controller and feedforward control unit for drives without a shaft encoder. Performance and feasibility of the proposed method are demonstrated by experimental results.

 

Keywords: self-commissioning, feedforward control, encoderless, sensorless, flux observer, field oriented vector control, ac motor drives, frequency response measurement, maximum peak criteria

 

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The Effect of Fault States of the Twelve-pulse Rectifier During the Recuperation

Mlynařík, L., Doleček, R.

The paper deals with analysis of states from the viewpoint of the rectifier DC side . In the case of diode breakdown the interphase short-circuit occurs and the transformer is disconnected from the primary side by a high-speed switch. After disconnecting the DC current of a recuperative traction vehicle influences the circuit. The fault states of the twelve-pulse rectifier in a substation of 3 kV DC traction system used at railways in the Czech Republic are analyzed. The situation at the rectifier diode breakdown and at the same time recuperative vehicles in power supply section is examined. The vehicle with recuperation can increase strain of elements in power supply system under certain conditions during fault states of the rectifier. The simulation computer model was created for analysis of current waveforms in trolley line at this situation. All simulations were created by the program PSpice. The main goal is to analyze the endanger of power supply system elements and to present the recommendation for increasing the reliability of this mentioned power supply system.

 

Keywords: component; twelve-pulse rectifier; diode breakdown; recuperation; traction substation; transformer

 

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Simulation of Magnetodynamic Forces Acting on the Eccentric Rotor of the Generator

Bachorec, T., Král, P.

The paper presents results of coupled electromechanical simulations for the generator transition to nominal and special operating conditions. Furthermore, results are given for calculations of the magnetodynamic forces and their spectral components acting on the rotor of the generator depending on its considered eccentricity. The simulations were performed on the electromechanical finite element model of a four-pole generator 130 kVA, 400V, 50Hz, 1500 rev./min in the ANSYS/Maxwell program.

 

Keywords: Simulation, generator, rotor, eccentricity, magnetodynamic, short-circuit, no-load

 

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Application of Resilient Power Pilot Project

Benes, I., Valasek, J.

The presented pilot project increases the resilience of power distribution against a national transmission grid blackout through adaptive distribution grid islanding. This function should be a basic function of smart grids. In 2011 the project team implemented the pilot project on a local micro-grid. The project demonstrates the possibility of crisis demand side management that enables necessary electricity for residents and critical infrastructure to be provided through adaptive distribution grid islanding.

 

Keywords: blackout, critical infrastructure resiliency, smart grids, island operation, black start, population protection

 

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Field-Circuit Modelling of Self-Excited Induction Generators

Miksiewicz, R.

In the paper computational models of an induction self-excited generator are presented. Circuit models taking into consideration nonlinearity of the magnetic circuit enable calculations of the generator static characteristic at an autonomic operation. The field-circuit model using Maxwell 2D software allows determination of time curves of any electrical variable in different conditions of the generator operation. There are presented basic determined static characteristics using both models and time curves of currents, voltages, torque during self excitation and under symmetrical load and one-phase short circuit, in cooperation with a rectifier system and during connection of the excited generator to network.

 

Keywords: induction generator, squirrel cage motor, cuircuit-field modelling

 

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