Optimal operation planning of distribution systems considering security constraints

The paper concerns the development of new approaches to the optimal operation planning of radial distribution networks. In particular the model described attempts to configure the medium voltage networks radially for low losses, while meeting constraints on security (reliability), currents and voltages. The model appears to be a very useful tool for planning the normal operating configuration of the distribution system and for reconfiguring radial feeder systems during either emergency or planned outages.     

Cell-based fully integrated CMOS frequency synthesizers

A family of standard cells for phase-locked loop (PLL) applications is presented. The applications are processed using a 1.5 μm, n-well, double-polysilicon, double-layer metal CMOS process. Applications include frequency synthesis for computer clock generation, disk drives, and pixel clock generators for computer monitors, with maximum frequencies up to 80 MHz. The synthesizers require no external components since the loop filter and oscillator are on chip with the phase frequency detector and the charge pump. Special voltage and current reference cells are discussed. Analysis of noise sources in the PLL demonstrates the need for reducing the phase noise of the system. A low phase noise is achieved through supply rejection techniques and by placing the oscillator in a high-gain feedback loop to minimize its noise contributions. Laboratory measurements of completed silicon show synthesizers with exceptionally linear gain, as well as transient responses and phase noise similar to predicted results     

Reliability indices for electric-power wheeling

Transmission networks are being used more extensively to accommodate energy transactions that use the economic benefits of pooling. This paper evaluates the probabilistic wheeling capability of an interconnected power transmission system. Large electric power wheeling can degrade the reliability of the electric power network. This problem is also important for power system control and planning purposes. This paper discusses, from the viewpoint of power network reliability, the problem of power wheeling from Western Europe to Greece through the Yugoslav electric power system. The relative cost of the wheeling due to reliability indices is 2% of the production cost for the power wheeled. The calculation of reliability indices of wheeling enable more adequate estimation of the wheeling rate for power transactions between utilities. This paper describes an approach to calculate cost of the average energy not supplied and load curtailed due to wheeling. This cost can even be negative, which depends mostly on the amount of wheeling power and consumer loads. The reliability index EENS (expected energy not supplied) is more comprehensive than PI (performance index) for the contingency severity selection procedure     

Reliability analysis of capacity and voltage constrained, optimallyoperated, electric power systems

A method for reliability evaluation of capacity and voltage constrained bulk power systems is suggested based upon contingency analysis. For each contingency and consumer load demand situation assumed, the optimal operation of the power system is established that minimizes the total system consumer curtailment cost. Consumer demands at different nodes may be treated as synchronous or as mutually uncorrelated quantities, depending on the data available. The method uses a version of the decoupled power flow network model that makes its possible to determine optimal generation of both real and reactive powers for the system sequentially. This property makes the method superior to other available approaches for bulk power system reliability analysis. An illustrative example is included