Jiri Skramlik

An Analytical Modelling of Three-Phase Four-Switch PWM Rectifier Under Unbalanced Supply Conditions

A new description of the three-phase four-switch converter aimed at compensating reactive power in the general case of unbalanced source voltages is proposed. A mixed p-z approach based on integral transformations (the Laplace and modified Z-transform) is suggested for obtaining solution in a closed form. The analytical procedure is verified by experimental results to confirm the effectiveness of the proposed control scheme.

High frequency models of transistor voltage inverter-fed induction motor drives

The paper deals with equivalent multiblock circuits of the induction motor suitable for the analysis of parasitic high-frequency currents in the common and differential modes. Theoretical considerations are supplemented by several illustrative examples aimed at computational and experimental determination of a number of different quantities such as time responses of currents in both modes in a system consisting of the PWM inverter, long cable and induction motor. Discussed are also possibilities of evaluation of interferences in parallel telecommunication and signal lines produced by current pulses in the power feeding cable.

Three-Phase Four-Switch PFC and Its Analytical Model

This paper presents a three-phase four-switch converter aimed at compensating reactive power in case of distorted and unbalanced source voltages. A space-vector PWM scheme is adopted to reduce the switching state of power switches. In the proposed control scheme, proper voltage vectors are generated on the ac terminal for drawing nearly sinusoidal line currents with unity power factor. An original closed-form solution of line currents, based on the mixed p-z approach is presented. The analytical and experimental results are provided to verify the effectiveness of the proposed control scheme.

Current control techniques for mains connected converters under unbalanced conditions

Electric equipments connected to the mains usually consist of a converter, a DC intermediate circuit and an inverter. The power from the mains should be consumed with unity power factor, the mains current should be harmonic, the power flow bidirectional, and also the equipment should be functional under distorted mains conditions. The dual-current control of the converter has been recently developed to meet the mentioned requirements. An overview and comparison of several different control methods are presented in the paper.

Coupled feedback and feedforward control of hybrid power filter

A coupled feedback and feedforward control strategy of the parallel hybrid power filter (HPF) is presented in the paper. It features a small sensitivity against a disturbed supply voltage system and enables us to set grid phase currents in the phase with respective voltages. The experimental data agree with theoretical expectations.

Software phase lock loops for pulse width modulated rectifiers

Simulation and experimental results of the use of three SPLL (Software PLL) that differ by the method of the detection of symmetrical grid voltage sequences (positive and negative ones) in case of an unsymmetrical grid voltage system with harmonics and under usual disturbances and parameter changes of the grid are presented. The function of the DSC (Delayed Signal Cancellation) based SPLL with was experimentally verified under different grid voltage disturbances with satisfactory results. S 1600 Hz = f

Closed-form analytical model of three phase four-switch PWM rectifier under unbalanced voltage system

The mathematical model and description of the three-phase four-switch converter aimed at compensating reactive power is proposed. A mixed p-z approach based on integral transformations (the Laplace and Modified Z-transform) is used for obtaining solution in a closed-form. The analytical procedure is verified by experimental results to confirm the effectiveness of the proposed control scheme.

Control strategy of hybrid power filter under disturbed voltage system conditions

In the paper a combined feedback and feedforward control strategy of the parallel hybrid power filter (HPF) is presented, which features a small sensitivity against a disturbed supply voltage system and enables us to set grid phase currents in the phase with respective voltages. The experimental data show that the modified control strategy yields better results than those obtained by using the control system reported previously, especially in case of an unsymmetrical and non-sinusoidal voltage system and the demand of zero reactive power withdrawn from the grid.