Damping Wind Farm Resonances with Current Based Model Predictive Pulse Pattern Control

TL;DR

This paper introduces a high-bandwidth model predictive pulse pattern control method that enhances damping of grid resonances in medium-voltage wind power systems, overcoming limitations of traditional current controllers at low switching frequencies.

Contribution

It proposes a novel pulse pattern control approach that directly manages instantaneous currents, providing improved damping across a wider frequency range at low switching frequencies.

Findings

Achieves high damping gain at low switching frequencies.

Extends damping effectiveness over a broader frequency range.

Demonstrates benefits through numerical studies on wind power systems.

Abstract

It is well-established that a proportional current control gain emulates a resistor in the converter output impedance. Even though this resistance can provide additional damping to grid resonances, its effect for traditional linear current controllers is known to be rather limited. Moreover, for medium-voltage systems, high switching frequencies are not an option due to the high switching losses. To meet the harmonic standards, it is expedient to use optimized pulse patterns. This further exacerbates the problems with the resistance of classical controllers, since an additional filtering would be required so that the current controller acts only on the fundamental component (and not on the ripple component). Such a design limits the damping effect not only in its amplitude but also in the frequency range where it is active. This paper shows that a high-bandwidth current-based model predictive pulse pattern controller can alleviate these limitations. The pulse pattern control approach can achieve a high gain even at low switching frequencies, while controlling directly the instantaneous currents (i.e., the fundamental component and the ripple together). With a fast implementation cycle, the frequency range where this damping effect is active can be further extended. Numerical studies showcase these benefits for a multi-phase medium-voltage wind power conversion system.