Active DC filter for harmonics suppression and regulating load of passive filters on the DC-side of Gezhouba converter station

Since the beginning of operation of China´s ±500 kV Gezhouba-Nanqiao (GZB-NQ) HVDC link, the smoothing reactor and the capacitors of its DC filters have faulted many times due to reasons of design, construction and others. In order to solve these problems, a method of harmonics suppression and passive filter regulation is presented using an active DC filter on the DC-side of the GZB power converter substation. The active DC filter is connected at the bottom of one existing passive DC filter at the GZB converter station. The construction and control strategies of the active DC filter, as well as the principle of regulating passive filter load are presented. Digital simulation results show that the practical feasibility of the control technique and load regulation scheme for passive filters proposed in this paper