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This paper addresses the design and implementation of a novel control scheme for a doubly fed induction generator (DFIG), of the type employed with wind turbines, to provide support to power system operation. It is shown that this controller provides a DFIG-based wind farm with operational and control compatibility with conventional power stations, the ability to contribute to voltage support and recovery following network faults, the ability to provide a power system stabilizer capability that improves overall system damping, and the capability of contributing short-term frequency support following loss of network generation. A simple but realistic test network that combines synchronous and wind farm generation has been modeled and used to assess dynamic performance. Simulation results are presented and discussed that demonstrate the capabilities and contributions of the new DFIG controller to network support. [ABSTRACT FROM AUTHOR]

This paper proposes a novel technique for representing system security constraints that properly include voltage stability limits in the operation of competitive electricity markets. The market-clearing algorithm is modeled as a voltage stability constrained optimal power flow (OPF) problem, while the distance to the closest critical power flow solution is represented by means of a loading parameter and evaluated using a continuation power flow (CPF) technique. Sensitivities obtained at the OPF step are used to estimate power directions for the CPF method, while the CPF analysis provides the loading parameter to be used in the OPF problem based on an N - 1 contingency criterion. The OPF and the CPF steps are repeated until the maximum loading parameter is found, thus providing optimal solutions considering both proper market conditions and security margins. Two benchmark systems with both supply and demand bidding are used to illustrate and test the proposed technique. [ABSTRACT FROM AUTHOR]

We show that the system loss function in a power network is bounded below by any number of supporting hyper-planes in the space of generalized injections. A supporting hyper-plane is defined by the linear Taylor series expansion of the system loss function around a given operating point. The supporting hyperplane property is valid provided that the expansion point is sufficiently near the flat-voltage profile. We have assessed experimentally the range of validity of this assumption, called the range of hyper-plane support (RHS), showing that for typical networks, the RHS is broad, particularly when the bus voltages are controlled near 1 per unit. The supporting hyper-plane model was also tested as part of an economic dispatch with transmission losses to demonstrate that this linear model provides the same results as when the losses are treated as a nonlinear function. [ABSTRACT FROM AUTHOR]

A novel multirate method of simulating power-electronic-based systems containing a wide range of time scales is presented. In this method, any suitable integration algorithm, with fixed or variable time-step, can be applied to the fast and/or slow subsystems. The subsystems exchange coupling variables at a communication interval that can be fixed or varied dynamically depending upon the state of the system variables. The proposed multirate method is applied to two example power systems that include power-electronic subsystems. Increases in simulation speed of 183-281% over established single-rate integration algorithms are demonstrated. [ABSTRACT FROM AUTHOR]