An active filter connectable in parallel to a rectifier circuit between a set of AC input lines and a pair of DC buses (LH, LL) between which a load is connected, said rectifier circuit rectifying AC voltages (Vr, Vs, Vt) input from said set of AC input lines and outputting a DC voltage (Vdc) to said pair of DC buses, and said active filter comprises: a first capacitor comprising a first terminal and a second terminal; a first and a second current limiting elements (D1, D2, R2), each comprising a respective first and second terminal, and wherein the first terminal of the first current limiting element is connected to the first terminal of the first capacitor and the first terminal of the second current limiting element is connected to the second terminal of the first capacitor, and wherein the second terminal of the first current limiting element is connectable to one of the pair of DC buses and the second terminal of the second current limiting element is connectable to the other one of the pair of DC buses, such that the polarity of the voltage across the first capacitor matches with the polarity of the voltage across the DC buses, and at least one of the first and second current limiting elements is a diode connected with its cathode to the first terminal of the first capacitor with a highest voltage potential of the first capacitor or with its anode to the second terminal of the first capacitor with a lowest voltage potential of the first capacitor; and an inverter including: a set of AC-side terminals (51, 52, 53) connectable to said set of AC input lines; a plurality of diodes; a pair of DC-side terminals (54, 55), one of which is connected to the first terminal of the first capacitor and the other of which is connected to the second terminal of the first capacitor; and a plurality of switching elements, each of which connects respective one of the AC-side terminals (51, 52, 53) to the one of said pair of DC-side terminals or connects respective one of the AC-side terminals (51, 52, 53) to the other of said pair of DC-side terminals (54, 55), each of said plurality of diodes being connected in anti-parallel to respective said switching elements, characterized in that the active filter is arranged to perform an active filter compensation on harmonic input currents of the rectifier circuit, such that a current that flows from the AC power supply via the rectifier circuit to the load is superimposed by a current that flows from the AC power supply via interconnection reactors to the active filter for harmonic current compensation of a current flowing out of the AC power supply. a first capacitor comprising a first terminal and a second terminal; a first and a second current limiting elements (D1, D2, R2), each comprising a respective first and second terminal, and wherein the first terminal of the first current limiting element is connected to the first terminal of the first capacitor and the first terminal of the second current limiting element is connected to the second terminal of the first capacitor, and wherein the second terminal of the first current limiting element is connectable to one of the pair of DC buses and the second terminal of the second current limiting element is connectable to the other one of the pair of DC buses, such that the polarity of the voltage across the first capacitor matches with the polarity of the voltage across the DC buses, and at least one of the first and second current limiting elements is a diode connected with its cathode to the first terminal of the first capacitor with a highest voltage potential of the first capacitor or with its anode to the second terminal of the first capacitor with a lowest voltage potential of the first capacitor; and an inverter including: a set of AC-side terminals (51, 52, 53) connectable to said set of AC input lines; a plurality of diodes; a pair of DC-side terminals (54, 55), one of which is connected to the first terminal of the first capacitor and the other of which is connected to the second terminal of the first capacitor; and a plurality of switching elements, each of which connects respective one of the AC-side terminals (51, 52, 53) to the one of said pair of DC-side terminals or connects respective one of the AC-side terminals (51, 52, 53) to the other of said pair of DC-side terminals (54, 55), each of said plurality of diodes being connected in anti-parallel to respective said switching elements, a set of AC-side terminals (51, 52, 53) connectable to said set of AC input lines; a plurality of diodes; a pair of DC-side terminals (54, 55), one of which is connected to the first terminal of the first capacitor and the other of which is connected to the second terminal of the first capacitor; and a plurality of switching elements, each of which connects respective one of the AC-side terminals (51, 52, 53) to the one of said pair of DC-side terminals or connects respective one of the AC-side terminals (51, 52, 53) to the other of said pair of DC-side terminals (54, 55), each of said plurality of diodes being connected in anti-parallel to respective said switching elements, characterized in that the active filter is arranged to perform an active filter compensation on harmonic input currents of the rectifier circuit, such that a current that flows from the AC power supply via the rectifier circuit to the load is superimposed by a current that flows from the AC power supply via interconnection reactors to the active filter for harmonic current compensation of a current flowing out of the AC power supply.