A power electronic converter (30)is for use in high voltage direct current power transmission and reactive power compensation, the power electronic converter (30) including three phase elements (32) defining a star connection (36) and a converter unit (34) including first and second DC terminals (50,52) for connection in use to a DC network (56) and three AC terminals (54), the converter unit (34) including a plurality of switching elements (70,74) controllable in use to facilitate power conversion between the AC and DC networks (44,56), the power electronic converter (30) further including a third DC terminal (78) connected between the first and second DC terminals (50,52), the third DC terminal (78) being connected to a common junction (40) of the star connection (36) to define an auxiliary connection (82), the auxiliary connection (82) including at least one dump resistor (84) connected between the common junction (40) and the third DC terminal (78), wherein the switching elements (70,74) of the converter unit (34) are controllable in use to modify a phase voltage at each AC terminal (54) to include a triplen harmonic voltage component so as to dissipate real power in the or each dump resistor (84) at a triplen harmonic frequency.