On-line loss minimization by HVDC dispatch using OPF in EMS

In Alberta, two HVDC lines went in service in 2015. While enhancing the flexible control of power flow for system operations, they also introduced new operational challenges at the AESO. One of the challenges is to optimize the MW flow on the two HVDC lines to minimize the MW losses in Alberta power grid. A tool was developed at the AESO to provide HVDC power orders for loss minimization based on off-line studies. The tool calculates the HVDC set points using weighted summation of MW flow of selected AC lines. Different pre-calculated weight sets are selected under different real-time outage conditions. The limitation of this approach is that there is no security validation to ensure the change in HVDC MW flows won't cause additional violations in the Alberta power grid. To overcome the limitation, this paper proposed a new approach of using on-line Optimal Power Flow (OPF) in EMS to determine the HVDC power orders for MW loss minimization and ensure the system operates within security limits. A case study demonstrated the advantages of the proposed on-line OPF approach on loss minimization and mitigation of limit violations. The results from the existing tool are also provided for comparison purposes.