There is restricted nature of AC filters installed in LCC HVDC, like voltage fluctuations when it’s switched, slow switching speed when HVDC blocks, large occupation and so on. As there are more and more renewable energy sources and power electronic loads in the net, these defects of AC filters restricted the development of LCC HVDC. The need to replace traditional AC filters is urgent.  Active filter is a new technology to replace traditional AC passive filters, develop the performance of HVDC and coordinate the AC and DC system.

In the work we developed Hybrid Active Filter technology, which is constituted by the passive AC filter and IGBT valves, designed the primary equipment and secondary control strategy, and compared the performance of active filter and traditional filters. The primary parameters of AC filter equipment depends on the reactive capability the net can tolerate and the harmonic spectrum of LCC. The whole active filter acts as a fortified passive filter the impedance of which  is extremely low at some harmonic order. We employed the HARMONIC CALCULATION PROGRESS of BDCC to calculate the harmonics of LCC and the PSCAD to verify the filter performance and dynamic performance. We calculated the harmonic voltage of LCC AC field and the cost and area of active filter also.

We find that the active filter can substantially increase the filter performance of AC filters, and one active filter can replace about 10 traditional AC filters in LCC HVDC. The number of switching of AC filters for harmonics is greatly decreased. The area of AC field is decreased. But the cost of active filter is obviously more than passive filters.

The performance of active filter is substantially better than passive filter, and it can restrict the harmonic interaction of two system. Nowadays in the net with massive power electronic  devices, the need to install active filter is urgent.

LCC-HVDC,harmonic,active filter,resonance