SUMMARYThis paper presents a new method to determine the locations and sizes of Distributed Generations (DGs) for loss reduction and voltage profile enhancement in distribution systems. The strategic placement of DG can help reduce power losses and improve feeder voltage profile. Fuzzy Goal Programming (FGP) is adopted to handle the multiobjective DG placement problem incorporating the voltage characteristics of each individual load component. The original objective functions and constraints are transformed into the multiobjective function with fuzzy sets by FGP. The transformed multiobjective function with fuzzy sets represents the imprecise natures for criterion of loss reduction and voltage profile enhancement, and the number and total capacities of DGs. The solution of the transformed multiobjective function with fuzzy sets is searched by Genetic Algorithm (GA). The proposed method is tested on the IEEE 34-bus system to demonstrate its effectiveness.

SUMMARYRecent large-scale blackouts in North America, Europe, and other countries raised great concerns over the reliability of our electric energy infrastructure and the economic impacts of blackouts. These blackouts were caused by a cascading sequence of events involving line outages, overloading of other lines, malfunctions of protection systems, power oscillations and voltage problems, and system separation and collapse. In this paper, common characteristics of blackouts are identified by analyzing the cascaded events of the blackouts. It is important to take appropriate control actions to alleviate overload and emergency conditions in a power system in order to avoid catastrophic power outages. This paper discusses available control procedures and emergency control systems needed to help prevent catastrophic outages. Economic losses from these blackouts in the U.S., Europe, and other countries were significant. An evaluation of the economic costs of blackouts can be used to estimate the benefits of emergency control systems that can be installed to prevent blackouts. This paper provides an overview of the assessment methods and procedures for evaluation of the economic costs of blackouts. This paper also describes the generic procedure of an event study to measure the economic impact of blackouts on the values of the firms in financial markets.

In a power grid, the distributed generations (DGs) are not generally controlled by the system operator. Fault current levels in the power grid may change because of unpredictable changes in the status of noncontrollable DGs. These changes in the fault current can have an impact on the relay coordination. In this paper, the uncertainty associated with the connection status of DGs is reflected in the relay coordination. Superconducting fault current limiter (SFCL) placement can be effective for reducing the fault current while eliminating misoperation of the relays caused by DGs. However, an SFCL may also have a negative impact on the operation of the relays. An effective SFCL placement method is needed because of the high cost of the SFCL and the impact on the power system protection. In this paper, an SFCL placement method based on the minimax regret criterion is proposed for power system protection considering the uncertainty of the DGs.

No abstract

No abstract