Security Analysis of Embedded HVDC in Transmission Grids

Security-constrained optimal power flow is widely used by grid operators during their short-term operations. Possible contingencies (e.g. outages of lines, generators) analyzed during this phase may be very critical for the stability of the power system. Thus, a simplified or reduced approach might not be desired. Moreover, the presence of embedded high-voltage direct current (HVDC) links (i.e. the DC link is done between two or more synchronous AC nodes) increases the degrees of freedom of the physical problem and thus an economically better working point for the system can be reached. To do this, a coordinated control between the AC and DC systems is required using one single stage of optimal power flow including the security assessment. In this work the SC-OPF (Security-Constrained Optimal Power Flow) approach is used to analyse the effects of contingency cases within the DC system.