IMPROVEMENTS IN OR RELATING TO POWER DISSIPATING CONVERTERS

In the field of high voltage direct current (HVDC) power transmission, there is a need for an improved power dissipating converter (30). A power dissipating converter (30) for use with a power converter (10) configured to convert between AC power and DC power, comprises first and second DC terminals (12, 14) for connection to a DC network (20). The power dissipating converter (30) also includes a converter limb (32) that extends between the first and second DC terminals (12, 14) and which includes first and second limb portions (34, 36) that are separated by a ground terminal (38) for connection to ground (40). Each limb portion (34, 36) includes a chain- link converter (44) which is connected in series with a power dissipating resistor (46). Each chain-link converter (44) includes a plurality of series-connected chain-link modules (48), and each chain-link module (48) includes a plurality of switching elements (50) that are connected in parallel with an energy storage device (52) whereby each chain-link module (48) is selectively operable to provide a voltage source and the corresponding chain-link converter (44) is selectively operable to provide a stepped variable voltage source. The power dissipating converter (30) further includes a controller (70) which is programmed to operate the power dissipating converter (30) in first and second modes, the first mode being an inactive mode in which the power dissipating converter (30) is prevented from exchanging current with a DC network (20) connected in-use to the first and second DC terminals (12, 14) and no power from the DC network (20) is dissipated by either power dissipating resistor (46), and the second mode being an active mode in which the power dissipating converter (30) exchanges a discharge current with the DC network (20) and power from the DC network (20) is dissipated by each power dissipating resistor (46). The controller (70), when operating the power dissipating converter (30) in the first inactive mode, is programmed to prevent an exchange of current with the in-use connected DC network (20) by controlling the chain-link modules (48) in each chain-link converter (44) to store an individual energy amount whereby the cumulative voltage source provided by the sum of all of the individual energy amounts in a respective chain-link converter (44) is equal to the DC voltage presented at the corresponding DC terminal (12, 14). Dans le domaine de la transmission de puissance à courant continu haute