Suppression measures of commutation failure in MIDC transmission systems

With the increasing of direct current (DC) transmission capacity, high-voltage DC (HVDC) location has become more and more intensive, and commutation failure has become increasingly prominent in multi-infeed DC (MIDC） transmission systems. To reduce the probability of commutation failure in MIDC systems, this study first analyses the fundamental causes of simultaneous or successive commutation failure, and puts forward the coordinated control strategy of voltage compensation variable slope voltage dependent current order limit, which takes the advantage of the DC current characteristics while fault occurs, and then proposes the influence factors and determination method of compensation coefficient K. Meanwhile add the switch function of K to compensate voltage according to the severity of the fault. Finally, built the actual system using PSCAD/EMTDC, simulation results show that the control strategy can effectively reduce the probability of commutation failure in MIDC transmission systems, and makes all DC systems recovery orderly after fault, meanwhile ensure the good recovery performance which can greatly improve the safety and reliability in MIDC transmission systems