High power, medium voltage, series resonant converter for DC wind turbines

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Abstract

A new modulation scheme is introduced for a single-phase series-resonant converter, which permits continuous regulation of power from nominal level to zero, in presence of variable input and output dc voltage levels. Rearranging the circuit to locate the resonant LC tank on the rectifier side of the high turns-ratio transformer combined with frequency control and phase-shifted inverter modulation keep transformer flux constant from nominal frequency down to DC, always in sub-resonant continuous or discontinuous conduction mode. This overcomes the principal deficit of series-resonant converters, and the resulting compact and efficient transformer, and soft-commutated inverter, present particular advantages in high-power, high-voltage applications, like DC offshore wind turbines. With transformer excitation frequency in hundreds of Hz range, line-frequency diodes can be employed in the high-voltage rectifier valve. Circuit operation and conduction modes, governing equations and sample waveforms are presented, together with experiments from a scaled demonstrator.
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A new modulation scheme is introduced for a single-phase series-resonant converter, which permits continuous regulation of power from nominal level to zero, in presence of variable input and output dc voltage levels. Rearranging the circuit to locate the resonant LC tank on the rectifier side of the high turns-ratio transformer combined with frequency control and phase-shifted inverter modulation keep transformer flux constant from nominal frequency down to DC, always in sub-resonant continuous or discontinuous conduction mode. This overcomes the principal deficit of series-resonant converters, and the resulting compact and efficient transformer, and soft-commutated inverter, present particular advantages in high-power, high-voltage applications, like DC offshore wind turbines. With transformer excitation frequency in hundreds of Hz range, line-frequency diodes can be employed in the high-voltage rectifier valve. Circuit operation and conduction modes, governing equations and sample waveforms are presented, together with experiments from a scaled demonstrator.
Original languageEnglish
JournalI E E E Transactions on Power Electronics
VolumePP
Issue number99
ISSN0885-8993
DOI
StateE-pub ahead of print - 2018
Publication categoryResearch
Peer-reviewedYes
ID: 264752959