Analysis on the control principle of the active DC filter in the Lindome converter station of the Konti-Skan HVDC link

The control principle of a hybrid passive-active DC filter installed in the Lindome HVDC converter station is analyzed in this paper. The controller of the active filter includes two basic functions: an integrator and a compensator. The main advantage of the Lindome controller is its simple structure for implementation in a digital signal processor (DSP). The drawbacks of this controller are its long response time, low stability margin and the filtering of an unnecessary number of frequencies. An alternative control strategy using a number of notch filters has been investigated. The notch filters can be tuned to those frequencies that need to be damped. This controller gives a much shorter system response time and improved stability margin.