The Use of the Hybrid Active Power Filter in LCC-HVDC Considering the Delay-Dependent Stability

The line commutated converter (LCC) based HVDC projects generally use passive AC filters for harmonic cancellation, which has disadvantages of large footprint, poor filtering effect due to the offset of the resonance point, etc. This paper introduces a high-power LC hybrid active power filter (HAPF), which can meet the requirements of filtering and dynamic reactive power compensation. First, the passive part of the HAPF adopts two parallel single-tuned LC filters, which has low impedance at 12
^th
and 24
^th
. Second, considering the effects of the time delay of the high-voltage sensors, current controller and valve controllers, the possible negative impedance of the HAPF may bring a great risk of resonance and thus endanger the stability of the system. Third, an impedance model of the HAPF is established and the impact of the time delay on system stability is analyzed. Further, an adaptive resonance damping strategy based on least mean square (LMS) algorithm is proposed. Finally, the overall performances of the HAPF are verified by simulations on PSCAD/EMTDC.