Power electronic loads inject harmonic currents into the utility causing overheating of power transformers and neutral wires, the power system, unpredictable performance of protection systems etc. In addition, electric resonances in such loads can also cause other undesirable phenomena like voltage fluctuations, ratio frequency interference (RFI) etc. To mitigate these undesirable effects, a new class of power electronics equipment (Active Filters) is being considered. A review of present-day solutions in the area of active filters is conducted in this paper. Finally, this paper discusses the trends in the design of active filters and the factors influencing them.