Dual Sequence Controller with Delayed Signal Cancellation in the
Rotating Reference Frame
Abstract
Manuscript submitted to the Twenty-second IEEE Workshop on Control and
Modeling for Power Electronics (COMPEL 2021).
Abstract: Dual-sequence current controllers of voltage source converters
(VSCs) feature two separate rotating reference frames (RRFs), commonly
named dq frames, and rely on techniques that isolate the positive and
negative sequences of three-phase measurements. One of these techniques
is the delayed signal cancellation (DSC). It is performed in the
stationary reference frame (SRF), also known as αβ frame. The DSC
combines old values of one axis with new values of the other axis of the
SRF. The results are, then, transformed into the RRFs for use in the
current controller. This filtering process introduces an extra layer of
complexity for dual-sequence current controllers, which could otherwise
operate solely in the RRFs. This paper introduces a frequency adaptive
DSC method that operates directly in the RRF. Moreover, an averaging of
two of the proposed DSC filters with contiguous integer delays is
employed for reducing discretization errors caused by grid frequency
excursions. A formal proof of the equivalence between the αβ and dq DSC
methods is presented. Furthermore, computer simulations of a case study
support the interpretation of the results.