Natural disasters can cause large blackouts. Research into natural disaster impacts on electric power systems is emerging to understand the causes of the blackouts, explore ways to prepare and harden the grid, and increase the resilience of the power grid under such events. At the same time, new technologies such as smart grid, micro grid, and wide area monitoring applications could increase situational awareness as well as enable faster restoration of the system. This paper aims to consolidate and review the progress of the research field towards methods and tools of forecasting natural disaster related power system disturbances, hardening and pre-storm operations, and restoration models. Challenges and future research opportunities are also presented in the paper.

Research on Resilience of Power Systems Under Natural Disasters—A Review

The loss minimum reconfiguration problem in the open loop radial distribution system is basically one of complex combinatorial optimization, since the normal open sectionalizing switches must be determined appropriately. The genetic algorithm was successfully applied to the loss minimum reconfiguration problem. In the proposed algorithm, strings consist of sectionalizing switch status or radial configurations, and the fitness function consists of the total system losses and penalty value of voltage drop and current capacity violations. The loss minimum reconfiguration problem is formulated as a mixed integer programming problem. The essential components of the genetic algorithm are briefly described. A detailed solution methodology by the use of genetic algorithm is outlined. Numerical examples demonstrate the validity and effectiveness of the proposed methodology. >

Implementation of genetic algorithm for distribution systems loss minimum re-configuration

Microgrids with distributed generation (DG) provide a resilient solution in the case of major faults in a distribution system due to natural disasters. This paper proposes a novel distribution system operational approach by forming multiple microgrids energized by DG from the radial distribution system in real-time operations to restore critical loads from the power outage. Specifically, a mixed-integer linear program is formulated to maximize the critical loads to be picked up while satisfying the self-adequacy and operation constraints for the microgrids formation problem by controlling the ON/OFF status of the remotely controlled switch devices and DG. A distributed multiagent coordination scheme is designed via local communications for the global information discovery as inputs of the optimization, which is suitable for autonomous communication requirements after the disastrous event. The formed microgrids can be further utilized for power quality control and can be connected to a larger microgrid before the restoration of the main grids is complete. Numerical results based on modified IEEE distribution test systems validate the effectiveness of our proposed scheme.

Resilient Distribution System by Microgrids Formation After Natural Disasters

This paper presents an algorithm for network reconfiguration based on the heuristic rules and fuzzy multiobjective approach. Multiple objectives are considered for load balancing among the feeders and also to minimize the real power loss, deviation of nodes voltage, and branch current constraint violation, while subject to a radial network structure in which all loads must be energized. These four objectives are modeled with fuzzy sets to evaluate their imprecise nature and one can provide his or her anticipated value of each objective. Heuristic rules are also incorporated in the algorithm for minimizing the number of tie-switch operations. The effectiveness of the proposed method is demonstrated through an example.

A fuzzy multiobjective approach for network reconfiguration of distribution systems

Microgrids can act as emergency sources to serve critical loads when utility power is unavailable. This paper proposes a resiliency-based methodology that uses microgrids to restore critical loads on distribution feeders after a major disaster. Due to limited capacity of distributed generators (DGs) within microgrids, dynamic performance of the DGs during the restoration process becomes essential. In this paper, the stability of microgrids, limits on frequency deviation, and limits on transient voltage and current of DGs are incorporated as constraints of the critical load restoration problem. The limits on the amount of generation resources within microgrids are also considered. By introducing the concepts of restoration tree and load group, restoration of critical loads is transformed into a maximum coverage problem, which is a linear integer program (LIP). The restoration paths and actions are determined for critical loads by solving the LIP. A 4-feeder, 1069-bus unbalanced test system with four microgrids is utilized to demonstrate the effectiveness of the proposed method. The method is applied to the distribution system in Pullman, WA, resulting in a strategy that uses generators on the Washington State University campus to restore service to the Hospital and City Hall in Pullman.

Microgrids for Service Restoration to Critical Load in a Resilient Distribution System

An application of expert system techniques to the restoration of distribution systems is reported. Primary feeders are typically radial in structure. To increase system reliability, neighboring feeders are connected through a normally open tie switch. When load zones on a feeder interrupted due to a fault, system operators need to identify neighboring feeders and try to restore customers through the tie switches. To restore the maximum number of zones, several steps are followed: group restoration, zone restoration and, if necessary, load transfer. Based on the methodology, an expert system is developed which can be utilized as an online aid to system operators in a distribution SCADA (supervisory control and data acquisition) environmental. The proposed expert system is implemented in Prolog. Knowledge representation, portability of the system, and computational efficiency are discussed. Several examples illustrate the capabilities of the system. >

An expert system operational aid for restoration and loss reduction of distribution systems

An Extended Expert System for Service Restoration of Distribution Feeders

The service restoration planning in distribution systems deals with the determination of necessary switching actions to restore the service of customers affected by an outage. In practice, it has been performed by system dispatchers based on experience. In this paper, an expert system which has the following capabilities is presented: two-phase service restoration considering zone priority and supervised switches, maintenance switching and user-specified zone priority ordering. The proposed expert system ERP (Enhanced Restoration Planner) is implemented in PROLOG and is able to come up with appropriate switching actions within a few seconds. The proposed expert system can be a powerful tool in aiding the distribution system dispatchers in emergency situations.

S.S. Venkata

Papers

An expert system operational aid for restoration and loss reduction of distribution systems

An Extended Expert System for Service Restoration of Distribution Feeders

An extended expert system for service restoration of distribution feeders