Search

This paper describes an innovative scheme based on a pluralistic load frequency control (LFC) and aimed at performing cross-border power control, secondary frequency regulation, and internal congestion resolution. Such an LFC scheme applies to a pluralistic block of control areas, whose regulators can adjust the production of their generators with respect to the request of the coordinating area when the power flows through grid sections exceed their maximum admissible values. This paper introduces the theoretical aspects and functional design of such an advanced LFC scheme, capable of controlling at the same time the cross border exchanges of the pluralistic block and the power flows between network subareas defined as market zones. Simulations on the Italian power system show the performance, main advantages, and limits of the proposed control method. [ABSTRACT FROM AUTHOR]

This paper considers a profit-maximizing thermal producer that participates in a sequence of spot markets, namely, day-ahead, automatic generation control (AG C), and balancing markets. The producer behaves as a price-taker in both the day-ahead market and the AGC market but as a potential price-maker in the volatile balancing market. The paper provides a stochastic programming methodology to determine the optimal bidding strategies for the day-ahead market. Uncertainty sources include prices for the day-ahead and AGC markets and balancing market linear price variations with the production of the thermal producer. Results from a realistic case study are reported and analyzed. Conclusions are duly drawn. [ABSTRACT FROM AUTHOR]

This paper presents a systematic way of using linear analysis techniques to find and rank candidate locations for controlled shunt and series compensations for power system damping purposes. A two-stage approach based on frequency response computations is introduced using a 4780-bus system model of the Nordic power system for assessment of controlled shunt compensations. In the first stage, their controllability is determined by means of long-distance frequency responses. In the second stage, the frequency responses of the transfer functions from the bus shunt susceptance to the bus voltage magnitude are computed for buses that have shown high controllability. This paper shows that the interpretation of the frequency responses of these local transfer functions, for buses that have exhibited high controllability, is in most cases sufficient to predict the behavior of controlled shunt compensation at different locations in the system. The interpretation is based on the observation of amplitudes, phase angles, and the rate of change of the phase angles around the interarea resonance frequencies. An important finding was that controlled shunt compensation located in an area with high-power import over ac interconnections lowered the damping of at least one of the interarea oscillation modes if operating in normal voltage control. This finding was also verified with nonlinear simulations. The first stage of the proposed frequency response-based approach has also been introduced for assessment of controlled series compensations. The strength of the new methods is that they can be used with both linear and nonlinear system models. [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]

Tidal stream generation is a form of renewable energy that is predicable but variable in nature. The paper initially identifies the tidal resource around Ireland, utilizing the most appropriate and developed tidal energy technology, thus providing a potential magnitude and output profile. Methods of deployment and control, including the down rating of the generator relative to turbine size and operational output reduction, are suggested to reduce capital cost, increase the capacity factor and reduce the impact on the grid system. The combination of the potential resource and the application of control methods provide the basis to study the effect on the grid system in terms of ramp rate and the demand profile. The same inputs also provide the ability to analyze generator characteristics such as the capacity credit. [ABSTRACT FROM AUTHOR]

Within an optimal power flow market clearing framework, this paper provides expressions to compute the sensitivities of locational marginal prices with respect to power demands. Sensitivities with respect to other parameters can also be obtained. An example and a case study are used to illustrate the expressions derived. [ABSTRACT FROM AUTHOR]

Performance specifications place restrictions on the dynamic response of many systems, including power systems. Quantitative assessment of performance requires knowledge of the bounding conditions under which specifications are only just satisfied. In many cases, this limiting behavior can be related to grazing phenomena, where the system trajectory makes tangential contact with a performance constraint. Other limiting behavior can be related to time-driven event triggering. In all cases, pivotal limiting conditions can be formulated as boundary value problems. Numerical shooting methods provide efficient solution of such problems. Dynamic performance. assessment is illustrated in the paper using examples drawn from protection operation, transient voltage overshoot, and induction motor stalling. [ABSTRACT FROM AUTHOR]

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]