Shunt Isolated Active Power Filter with Common DC Link in Urban Rail Transit System

In urban rail transit, there is a large quantity of harmonics brought by diode rectifiers, and shunt active power filters (APFs) are an effective method of harmonics rejection. Traditional shunt APFs work with a dedicated DC link, while those with a common DC bus but using non-isolated topologies bring serious problems of zero-sequence circulating current (ZSCC). This paper puts forward a novel isolated APF with a common DC link based on existing diode rectifiers in urban rail transit. To this end, harmonics brought by diode rectifiers are reduced while rejecting ZSCC. Finally, simulation and experiment using a 1-kW prototype converter verify the feasibility and validity.