The targeted and current development of wind energy in various countries around the world reveals that wind power is the fastest growing power generation technology. Among the several wind generation technologies, variable speed wind turbines utilizing doubly fed induction generators (DFIGs) are gaining momentum in the power industry. With the increase in penetration of these wind turbines, the power system dominated by synchronous machines will experience a change in dynamics and operational characteristics. Given this assertion, the present paper develops an approach to analyze the impact of increased penetration of DFIG-based wind turbines on transient and small signal stability of a large power system. The primary basis of the method is to convert the DFIG machines into equivalent conventional round rotor synchronous machines and then evaluate the sensitivity of the eigenvalues with respect to inertia. In this regard, modes that are both detrimentally and beneficially affected by the change in inertia are identified. These modes are then excited by appropriate disturbances and the impact of reduced inertia on transient stability performance is also examined. The proposed technique is tested on a large test system representing the Midwestern portion of the U.S. interconnection. The results obtained indicate that the proposed method effectively identifies both detrimental and beneficial impacts of increased DFIG penetration both for transient stability and small signal stability related performance.

Impact of Increased Penetration of DFIG-Based Wind Turbine Generators on Transient and Small Signal Stability of Power Systems

Techniques are presented for the evaluation and interpretation of eigenvalue sensitivities, in the context of the analysis and control of oscillatory stability in multimachine power systems These techniques combine the numeric power of model analysis of state-space modals with the insight that can be obtained from transfer-function descriptions Relationships with tools from selective model analysis (namely, participations) are stressed Examples of applications to a detailed multimachine power system model are given >

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On sensitivities, residues and participations: applications to oscillatory stability analysis and control

This paper presents techniques for the evaluation and interpretation of eigenvalue sensitivities, in the context of the analysis and control of oscillatory stability in multimachine power systems. These techniques combine the numeric power of modal analysis of state-space models with the insight that can be obtained from transfer function descriptions. Relationships with tools from Selective Modal Analysis (namely, participations) are stressed. Examples of applications to a detailed multimachine power system model are given.

On sensitivities, residues and participations

The targeted and current development of wind energy in various countries around the world reveals that wind power is the fastest growing power generation technology. Among the several wind generation technologies, variable speed wind turbines utilizing doubly fed induction generators (DFIGs) are gaining momentum in the power industry. With the increase in penetration of these wind turbines, the power system dominated by synchronous machines will experience a change in dynamics and operational characteristics. Given this assertion, the present paper develops an approach to analyze the impact of increased penetration of DFIG based wind turbines on transient and small signal stability of a large power system. The primary basis of the method is to convert the DFIG machines into equivalent conventional round rotor synchronous machines and then evaluate the sensitivity of the eigenvalues with respect to inertia. In this regard, modes that are both detrimentally and beneficially affected by the change in inertia are identified. These modes are then excited by appropriate disturbances and the impact of reduced inertia on transient stability performance is also examined. The proposed technique is tested on a large test system representing the Midwestern portion of the U.S. interconnection. The results obtained indicate that the proposed method effectively identifies both detrimental and beneficial impacts of increased DFIG penetration both for transient stability and small signal stability related performance.

Impact of increased penetration of DFIG based wind turbine generators on transient and small signal stability of power systems

This paper presents a novel approach based on eigenvalue and eigenvalue sensitivity analyses to predict both minimum and maximum values of capacitance required for the self-excitation of a three-phase induction generator. Numerous numerical methods based on steady-state equivalent circuit models have been proposed to find the minimum capacitance of self-excited induction generators by solving simultaneous nonlinear equations. Steady-state and sensitivity analyses of different capacitance values with respect to various system parameters are performed. Transient analyses of the studied induction generator under different loading conditions are also carried out. Experimental results obtained on a 1.1 kW induction machine confirm the feasibility and effectiveness of the proposed approach.

A novel analysis on the performance of an isolated self-excited induction generator

A practical digital computer method for obtaining eigenvalue sensitivities of interconnected power systems is presented. The method is especially suited to the analysis of detailed modelled synchronous machine systems where shaft and stator-network dynamic effects are significant. A unified structure in the construction of the state space equations permits the inclusion of a wide variety of control equipment and varying degrees of modelling complexity. Sample results are given for typical cases illustrating the significance of eigenvalue sensitivities. Specifically results are presented for a 4 generator hydroelectric system and for a 2 generator system exibiting subsynchronous torsional resonance.

Eigenvalue sensitivities of power systems including network and shaft dynamics

The application of state feedback decoupling is proposed for the minimization of transients following small changes in real and reactive power levels in a turbo-alternator connected to an infinite bus through u transmission line. For an example. a ninth-order linearized system model is decoupled into two third-order single-input-single-output systems. The poles of these systems are optimally placed to satisfy n variety of design specifications. From the computational point of view, t his approach is far more attractive than that using state-variable or output feedback without decoupling. It also provides better insight into the problem.

R. T. H. Alden

Papers

Eigenvalue sensitivities of power systems including network and shaft dynamics

Optimization of turbo-alternator dynamic response using state feedback decoupling