A converter control arrangement for regulating the output current of a dc source power converter adapted to connect an ac system to a multi-source dc power transmission system, the converter control arrangement comprising:- a current regulator for regulating the output current of the dc source power converter comprising: a comparator which compares an output current value (I out) of the dc source power converter with a target current value (I tgt) by subtracting the output current value (I out) from the target current value (I tgt); and a current controller which outputs a control signal based on the comparison, to control the operation of the dc source power converter to regulate the output current (I out) to be consistent with the target current value (I tgt); wherein: when an output voltage value (V out) of the dc source power converter is within a normal operating voltage range between minimum and maximum voltage values (V min, V max) defined with reference to a voltage reference value (V ref) of the dc source power converter, the converter control arrangement operates to control the target current value (I tgt) so that it is equal to a reference current value (I ref); and when the output voltage value (V out) is outside the normal operating voltage range, the converter control arrangement operates to modulate the reference current value (I ref) to provide a reduced target current value (I tgt) that is less than the reference current value (I ref); wherein the converter control arrangement includes a gain controller which operates to control the level of modulation applied to the reference current value (I ref) when the output voltage value (V out) exceeds the maximum voltage value (V max), to thereby provide the reduced target current value (I tgt) and a gain controller which operates to control the level of modulation applied to the reference current value (I ref) when the output voltage value (V out) is less than the minimum voltage value (V min), to thereby provide the reduced target current value (I tgt). a current regulator for regulating the output current of the dc source power converter comprising: a comparator which compares an output current value (I out) of the dc source power converter with a target current value (I tgt) by subtracting the output current value (I out) from the target current value (I tgt); and a current controller which outputs a control signal based on the comparison, to control the operation of the dc source power converter to regulate the output current (I out) to be consistent with the target current value (I tgt); a comparator which compares an output current value (I out) of the dc source power converter with a target current value (I tgt) by subtracting the output current value (I out) from the target current value (I tgt); and a current controller which outputs a control signal based on the comparison, to control the operation of the dc source power converter to regulate the output current (I out) to be consistent with the target current value (I tgt); wherein: when an output voltage value (V out) of the dc source power converter is within a normal operating voltage range between minimum and maximum voltage values (V min, V max) defined with reference to a voltage reference value (V ref) of the dc source power converter, the converter control arrangement operates to control the target current value (I tgt) so that it is equal to a reference current value (I ref); and when the output voltage value (V out) is outside the normal operating voltage range, the converter control arrangement operates to modulate the reference current value (I ref) to provide a reduced target current value (I tgt) that is less than the reference current value (I ref); when an output voltage value (V out) of the dc source power converter is within a normal operating voltage range between minimum and maximum voltage values (V min, V max) defined with reference to a voltage reference value (V ref) of the dc source power converter, the converter control arrangement operates to control the target current value (I tgt) so that it is equal to a reference current value (I ref); and when the output voltage value (V out) is outside the normal operating voltage range, the converter control arrangement operates to modulate the reference current value (I ref) to provide a reduced target current value (I tgt) that is less than the reference current value (I ref); wherein the converter control arrangement includes a gain controller which operates to control the level of modulation applied to the reference current value (I ref) when the output voltage value (V out) exceeds the maximum voltage value (V max), to thereby provide the reduced target current value (I tgt) and a gain controller which operates to control the level of modulation applied to the reference current value (I ref) when the output voltage value (V out) is less than the minimum voltage value (V min), to thereby provide the reduced target current value (I tgt).