-This paper presents a method for voltage stability monitoring based on the maximum power transfer to the load. The only required information is the system topology, the data from PMUs and the operational status of synchronous generators. With this information, the Thevenin impedance seen from a load bus can be estimated and by using the Thevenin theorem for maximum power transfer an impedance based stability index can be established. Since the Thevenin impedance is influenced by the operational conditions of the synchronous generators, it is consequently not a constant value and differs from the short circuit impedance of the bus. It is emphasized that the method requires only the information of the considered subsystem. Therefore, since the computation requirement is insignificant, the algorithm can be used for online monitoring. The validation of the approach is achieved by simulating a simple transmission system.
Abstract-This paper presents a topology-based scheme for adaptive underfrequency load shedding (UFLS). By tracking changes of power system topology and information about power flow, the proposed method is able to identify islanded conditions, the number of islands and their deficits of active power, which are fundamental parameters for the adaptive UFLS scheme. The algorithm is also applicable to interconnected power systems, where islanding of the power grid can go beyond country borders and create new asynchronous areas that can comprise several national transmission systems. In this case, the proposed method can properly estimate the power deficit of each area and coordinate the load shedding of several affected power systems in the underfrequency area. The main idea of the proposed method is demonstrated by simulations of the IEEE reliability test system in PSS/E and real time coordination of the adaptive UFLS schemes in Labview.
This paper presents the performance evaluation of an empirical method for online detection of power and voltage oscillations electric grids and is used as a monitoring system to evaluate the grid performance. Additionally, the method is applied to a multiterminal HVDC grid. Finally, the performance is evaluated based on a database from the simulation results.
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