Control circuit

A control circuit comprising first and second primary terminals for connection to a DC network, the first primary terminal and the second primary terminal each having a plurality of modules and a plurality of primary energy conversion elements connected in series therebetween to define a current transmission path, each module including at least one energy storage device, each energy storage device being selectively removable from the current transmission path;

• the control circuit further including a secondary terminal connected in series between the first primary terminal and the second primary terminal, the plurality of modules including at least one first module and at least one second module, the or each first module being connected in series with at least one primary energy conversion element between the first primary terminal and the secondary terminal to define a first current transmission path portion, the or each second module being connected in series with at least one other primary energy conversion element between the second primary terminal and the secondary terminal to define a second current transmission path portion;
• the control circuit further including an auxiliary resistor and an auxiliary terminal, the auxiliary resistor being connected in series between the secondary and auxiliary terminals, the auxiliary resistor having at least as much resistance as the at least one primary energy conversion element between the first primary terminal and the secondary terminal, the auxiliary resistor having at least as much resistance as the at least one other primary energy conversion element between the second primary terminal and the secondary terminal, the auxiliary terminal being for connection to ground.