Power losses in transmission systems are most of the time seen as a small amount (2-5%) from the total power carried over the network. However, transmission loss allocation may play a crucial role in the congestion management of balancing markets. Several loss allocation and loss cost allocation methods have been proposed and implemented in different markets. Most of these methods are intended to be used post market. This paper presents a novel near real-time loss allocation method suitable to be applied in real-time markets as envisioned in the smart grid context. The proposed method allocates the total system losses fairly to all the demand and generator buses, by taking into account the dynamical changes of the power network states, which are provided by an accurate state estimation. The power flows required to determine the allocated losses are executed after an economic dispatch procedure that ignores losses, making the choice of the slack bus an independent factor. The proposed method can be used as an accurate real-time pricing for network usage while the resolving of transmission congestion can be more reliable.

In contemporary power systems, conventional load shedding schemes are typically used. These load shedding schemes employ a preset step-level structure that identifies the amount of load to be shed. There are predefined candidate circuit breakers to be opened, based on the importance of loads, historical data for the load demand at each substation, and the operator's experience. Clearly, real conditions at the time of fault differ, resulting in the shedding of a larger or smaller amount of load and to a nonoptimal operation of the load shedding scheme. A second point to note is that adaptive load shedding schemes are usually only theoretically functional due to the large amount of real-time monitoring data required to perform satisfactorily. These data cannot be obtained on a large scale and in a cost effective manner. Last but not least, adaptive load shedding schemes do not always respond adequately against newly emerging or combinational events. In this paper, an adaptive load shedding scheme is proposed, based on a single measurement of the electric frequency of the power system. It approximates online the certain structure of the nonlinearities of the swing equation of the power system and adaptively bounds the load disturbances and the functional approximation errors of the nonlinearities. This way, a control law is extracted that "cancels" the nonlinearities and responds adequately to the load disturbances, achieving the frequency stability of the system effectively.Index Terms-Adaptive load shedding, frequency stability, smart grid, underfrequency load shedding. 1932-8184

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