Parallel Active Power Filter with Predictive Structure for Reference Current Determination – Experimental System

U svrhu eksperimentalne provjere rezultata simulacije trofaznog aktivnog filtra s prediktivnim određivanjem referentne struje izrađena je njegova laboratorijska maketa. U radu je prikazan funkcionalan opis laboratorijske makete trofaznog aktivnog filtra. Energetski krug aktivnog filtra sastoji se od tri jednofazne prigušnice, trofaznog izmjenjivača s IGBT-ovima i dva simetrična kondenzatora na istosmjernoj strani. Regulacija struje realizirana je pomoću tri neovisna histerezna regulatora. Razrađen je algoritam filtarskog sustava s prediktivnom strukturom za određivanje referentne struje i implementiran na DSP. Prikazani su eksperimentalni rezultati ostvarenog trofaznog aktivnog filtra u stacionarnom i dinamičkom režimu rada. Dobiveni eksperimentalni rezultati potvrđuju učinkovitost aktivnog energetskog filtra pri slabljenju viših harmonika struje u mreži.For the purpose of simulation results testing, a laboratory prototype of three-phase active power filter with predictive structure for reference current determination has been developed. A functional description of the laboratory prototype is presented. Power stage of the proposed active filter has been realized using three serial inductance, three-phase IGBT based current control voltage inverter with two symmetrical capacitors on dc bus. Three independent hysteresis controllers on the base of reference currents were used to generate switching signals for inverter transistors. The algorithm for current reference determination as a combination of digital predictive filter and low pass filter was developed and implemented on DSP controller. The experimental results of three-phase active power filter for stationary and dynamic regimes are presented. Experimental results show that the active power filter gives satisfactory performance in power system harmonic attenuation

REDUCTION OF THE INRUSH CURRENT OF THREE-PHASE POWER TRANSFORMERS

Udarne struje koje se javljaju prilikom uklopa energetskog transformatora mogu doseći vrlo velike iznose te uzrokovati mnogobrojne probleme u elektroenergetskom sustavu. Za istraživanje ove pojave razvijen je matematički model transformatora s uračunatim efektima zasićenja, histereze i zaostalog magnetskog toka, a opisan je i algoritam za određivanje povoljnog trenutka uklopa s ciljem smanjenja udarnih struja. Za metodu mjerenja zaostalog magnetskog toka, predložena je integracija napona sekundara pri prethodnom isklopu. Realizirana je laboratorijska maketa sustava za upravljani uklop trofaznog transformatora na kojoj su mjerenjem potvrđeni rezultati simulacija.Inrush currents that occur during the energization of a three-phase power transformer can reach very high values and cause many problems in an electrical power system. A mathematical model of a transformer has been developed for the investigation of this problem, taking into account the effects of saturation, hysteresis and remanent magnetic flux. An algorithm has been described for the determination of the optimal instant of energization, with the goal of reducing inrush currents. As a method for measuring remanent magnetic flux, integration of the secondary voltage during the previous de-energization is proposed. A circuit model has been prepared of a system for the controlled energization of a three-phase transformer in which the simulation results are confirmed by measurement