Case Study of a Multi-Infeed HVDC System

There are serious concerns relating to a multi-infeed HVDC system when feeding a weak AC network. Typical issues concerning multi-infeed configurations are: need for coordination of the recovery control, need for different DC modulation strategies to stabilize the system, possibility of voltage instability of the area receiving large amount of power from multiple HVDC links and the risk of mutual commutation failures. In contrast, if the area receiving electrical power from multiple HVDC transmission links is relatively strong due to the presence of large amount of generation units nearby there are still some questions that need to be investigated such as the issues underlining the operation of such a multi-infeed system, the proper design of the controls of the HVDC systems and the system dynamic performance under extreme contingencies. This paper investigates into an example of such a multi-infeed HVDC system. The authors have performed small signal analysis of the system to assess instability associated with the control modes. Electromechanical and voltage stability analysis were performed for harmful contingencies. Dynamic performance analysis was also carried out to analyze the interaction amongst various HVDC inverters during disturbances.