This paper proposes a new technique to identify sets of branches that form heavily loaded and potentially vulnerable flowgates within power grids. To this end, a directed acyclic graph is used to model the instantaneous state of power grids. One of the advantages of directed acyclic graphs is they allow the identification of where power flows are coherent e.g where power flows in a uniform direction along a set of branches that partition the network into two islands. This paper uses topological sorts to identify many sets of branches having this property. Definitions are provided for two new concepts, termed coherent cut-sets and coherent crack-sets, which are particular sets of branches extracted from a specific topological sort. Notably, there are numerous possible topological sorts for a directed acyclic graph and calculating distinctive topological sorts is challenging. In this paper a novel optimization algorithm is proposed to find multiple, diverse topological sorts each of which implies many cut-sets. The effectiveness of the proposed methods for enhancing grid observability and situational awareness is demonstrated using two standard test networks.

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Distributed Series Reactances are devices that dynamically increase the impedance of a line to reduce the power flow it carries. This work explores whether widely deploying these devices enhances a power system's robustness against line overload cascading failures. The presence of Distributed Series Reactances may make it less likely that equipped lines would become overloaded by contingencies elsewhere, and so their presence may arrest the propagation of line overloads through a system. However, the efficacy of these devices in this role has not been widely investigated. Likewise, there are few extant methodologies for siting dynamic reactances within the grid to mitigate the propagation of cascades. In this paper, the ability of these devices to arrest the propagation of cascading failures within power grids is investigated. First, a novel power flow is formulated, which models dynamic line impedances. A novel methodology is proposed for siting the devices on lines spread throughout the network. With these innovations in hand, the devices' effects on cascade propagation are simulated using a sizeable database consisting of multiple load & generation snapshots across eight test networks. No major beneficial effect is found, even when 25% of lines are equipped.

In this paper, a novel method is presented to optimize distributed generation (DG) in distribution networks. The suggested method shows how DGs should change their sizes and places, if it is necessary, to improve the voltage profile and total power loss of distribution networks. For this purpose, game theory is applied to model the optimization problem. At the first step, an appropriate game based on the Nash equilibrium is suggested. Using the specific features of game theory, the procedure of decision making in the operator centers of distribution grids is considered. Then, the optimization problem is solved by finding Nash equilibrium point. To solve the Nash equilibrium, a specific kind of genetic algorithm (GA) called Nash GA is applied.

Abstract--This paper aims to find the optimal place and size of an energy storage system in a microgrid, considering the gridconnected mode and autonomous mode simultaneously. Energy storage systems are one of the most effective components in today's power grids to improve the power quality of power grids, therefore attracting more attention in this field. Specially, in microgirds which use various kinds of distributed generations, using energy storage systems is necessary to improve their power quality. Finding the optimal place and size of energy storage systems is a common action in microgrids. However, it should be noted that most microgrids can be operated in both of their operation modes and finding optimal place and size of an energy storage system for one of these operation modes doesn't mean that they are optimal for the other mode. This paper presents a new method to find the optimal place and size of an energy storage system for microgrids during daily operation, considering both grid-connected mode and autonomous mode simultaneously. The presented method is based on applying the AC-optimal power flow to find the optimal place and size of the energy storage system.