This paper proposes a novel tracking state estimator to process both fast-rate synchronized phasor and slowrate SCADA measurements. The former are assumed to be in limited number. The latter are exploited as and when they arrive to the control center. In order to restore observability, after each execution of the tracking state estimator, forecasted SCADA measurements are used as pseudo-measurements in the next estimation. An event detection analysis allows assessing if the system is in quasi steady-state. If so, an innovation analysis is performed to identify and eliminate erroneous SCADA measurements. The system state is computed by Hachtel's augmented matrix method. The option of exploiting time-tagged SCADA measurements is also considered. The method is illustrated through detailed dynamic simulations of a test system evolving towards voltage collapse, with and without emergency control.

No abstract

Abstract-This paper proposes a new tracking state estimator aimed at following some of the dynamics of the network state (bus voltage phasors) by a hybrid processing of SCADA and synchronized phasor measurements. The latter are assumed to be available in limited number. To avoid time skew effects, only the SCADA measurements received since the last execution of the estimator are processed. To ensure observability, estimated SCADA measurements are used as pseudo-measurements. The procedure includes a prediction, an innovation analysis and a correction step. The latter consists of solving a constrained least-squares optimization. The simulation results refer to a test system undergoing large disturbances, evolving to longterm voltage instability or stabilized by emergency control. The proposed method appears to satisfactorily track the overall network evolution, even during those severe conditions.

No abstract

This paper puts forward a new practical voltage source converter (VSC) based AC-DC converter model suitable for conducting power flow assessment of multi-terminal VSCbased high-voltage direct current (VSC-MTDC) systems. The model uses an advanced method to handle the operational limits and control modes of VSCs into the power flow formulation. The new model is incorporated into a unified framework encompassing AC and DC power grids and is solved by using the Newton-Raphson method to enable quadratically convergent iterative solutions. The use of complementarity constraints, together with the Fischer-Burmeister function, is proposed to enable the seamless incorporation of operational control modes of VSC and automatic enforcement of any converter' s operational limits that become violated during the iterative solution process. Thus, a dedicated process for checking limits is no longer required. Furthermore, all existing relationships between the VSC control laws and their operational limits are considered directly during the solution of the power flow problem. The applicability of the new model is demonstrated with numerical examples using various multi-terminal AC-DC transmission networks, one of which is a utility-sized power system.