Patent ID: 8203856

Claim:
A method to reverse a power flow between a first and a second converter station which are coupled to each other via a direct current link, where each converter station comprises a first or second line commutated converter, respectively, the method comprising: operating the first converter as a rectifier before power reversal and as an inverter after power reversal, operating the second converter as an inverter before power reversal and as a rectifier after power reversal, controlling in the first station a direct current, controlling in the second station an extinction angle of the second converter or controlling a direct voltage, carrying out during power reversal a change in the first station from control of the direct current to control of the extinction angle of the first converter or to control of the direct voltage, which is performed in synchronization with a change in the second station from control of the extinction angle of the second converter or from control of the direct voltage to control of the direct current.