Dynamic analysis of DC-DC converter internal to an offshore wind farm

Abstract

This paper investigates the dynamic performance of an active rectifier integrated into a wind park. The small changes in the DC current and the DC voltage are examined. The small variations are caused by the miniature power flow unbalance between the offshore wind park and the grid land. Internal DC collector is considered into the wind park, which provides an internal DC medium voltage bus. The AC output signal from the wind generator to the internal DC collector or DC bus is regulated through active rectifier. An active rectifier is a cascade connection of an uncontrolled full bridge diode rectifier and a controlled DC-DC boost converter. The small changes in the DC current and DC voltage due to power flow unbalance are analysed across the boost converter. The way in which these small variations affect the internal medium DC voltage is determined. The results are presented in the form of small signal transfer functions and are evaluated with MATLAB software.

Analysis of a DC Collector-based Power Converter Topology for an Offshore Wind Farm

“…Detailed derivations method of the open-loop and closed-loop transfer functions of the DC-DC converter can be found in [13]. The two switches of the interleaved boost converter have (18)- (21) and the closed-loop functions in Eqs.…”

“…Boost inductors L b1 and L b2 are sized using Eqs. (12) and (13). The DC-link voltage, which is the output voltage of the interleaved DC/DC converter, is given as v d0 (t) = 6kV; note that i d0 (t) = P 0 /v d0 (t).…”

“…However, gate signals to the interleaved phases are generated in such a man-ner as to allow equal current sharing among the phases and also ensure ripple cancellation. The dynamic model and oper-ating principle of a single DC-DC boost converter is derived in [13]. The advantage of using the proposed topology com-pared to the conventional full-bridge VSC topology are that the switching losses that cause power losses are reduced due to the lower switching frequency or lower duty ratio.…”