Three-phase Resonant DC-link Converter

Research output: PhD thesis

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The purpose of the project is to develop a three-phase resonant converter suitable for standard speed drives. The motivation for working with resonant converters is found in the problem of the standard converter type used today.
In standard converter type Pulse Width Modulated-Voltage Source Inverter, PWM-VSI, the switches are subject to high current and voltage stress during switching, which causes losses. The fast switching of modern switches reduces switching losses. Unfortunately this procedure increased dv/dt and the size of the input/output filters of the PWM-SVI must be increased. The high speed of the switches cannot be fully utilizied.
By using a parallel resonant converter the switching happens at low or zero voltage which reduses switch losses. The dv/dt is controlled by the resonant circuit, and it is therefore reduced significantly. The perspective using a resonant converter is high switching frequency combined with a high converter efficiency and low dv/dt.
In the first report several resonant converters are investigated to find a resonant converter that can complete with the standard PWM-VSI converter. Four converters were selected for the theoretical analysis, and the converters are simulated. An evaluation of the resonant converters is made, and one converter is selected for the realization.
In the second report the realization of the selected resonant converter is described. This includes analysis, design and test of the converter.
A new control principle, using no additional power electric components is eliminating the high voltage peaks associated with the resonant circuit. The resonant link voltage peaks are limited below 2.1 times the DC link voltages.
A new principle eliminating former resonant converter stability problems are proposed, implemented and tested. A resonant converter efficiency of 97 [%] was measured. The low dv/dt of the converter makes it possible to drive long cables without filtering. A successful test with a 300 [m] long cable and an induction machine load was carried out.
It is concluded that a stable, high efficiency and high switching frequency three phase parallel resonant converter is realized.
Original languageEnglish
Place of PublicationAalborg
Print ISBNs87-89179-16-1
Publication statusPublished - 1997

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