Dynamic damping with power electronics: industrial cases

Due to non-linear loads or non-linear behavior of some elements, harmonics currents are injected in the network generating a voltage distortion. To improve the voltage quality, some passive filtering are used to trap these harmonic currents. However a simple passive filter modifies significantly the characteristics of the network by generating a parallel resonance and can create some problems of oscillations and instability when associated with power electronics converters as large rectifiers or static var compensator. To avoid these problems, passive damping with parallel resistors is generally introduced. However this technique generates some losses in the whole filter and alters the efficiency of the filtering. This paper shows that dynamic damping with voltage source converter can contribute to improve the damping without altering the filter efficiency and to optimize the whole losses of the hybrid filter. Two industrial cases are presented: dynamic damping in the case of power supply and dynamic damping in the case of shunt compensation. Extension of this principle in a hybrid filter is presented in this paper with regards on losses and sizing. This article shows the strategic interest of small converters in AC filtering to make it evolute in new techniques associating passive and active elements to form hybrid dynamic damped filter