This paper presents the fundamentals and the algorithm of a new methodology for the design of robust power system damping controllers. The methodology provides controllers capable of fulfilling various practical requirements of this problem, which could not be simultaneously satisfied by the majority of the proposed robust control approaches until now. The design procedure is based on a special formulation of the dynamic output feedback control problem, in which the design problem can be expressed directly in the form of linear matrix inequalities. The formulation also allows the incorporation of decentralization constraints on the controller matrices, one of the practical requirements for power system damping controllers. Other practical requirement is satisfied with the use of the polytopic model (to ensure the robustness of the closed-loop system with respect to the variation of operating conditions). Moreover, the inclusion of a regional pole placement criterion allows the specification of a minimum damping factor for all modes of the controlled system. The results show the controller is able to provide adequate damping for the system oscillation modes.

A robust multivariable controller with the objective of enhancing the low-voltage ride-through (LVRT) capability of wind farms with fixed-speed induction generators is presented in this paper. The nonlinear dynamics of the wind generator is represented as a linear system and a norm-bounded nonlinear uncertain term, derived from the Cauchy remainder of the Taylor series. The designed robust controller provides acceptable post-fault performance for both small and large perturbations. Large disturbance simulations demonstrate that the designed controller enhances voltage stability as well as transient stability of the system during lowvoltage ride-through transients and thus enhances the LVRT capability of fixed-speed wind generators.

The complexity of power systems has increased in recent years due to the operation of existing transmission lines closer to their limits, using flexible AC transmission system devices (FACTS), and also due to the increased penetration of new types of generators that have more intermittent characteristics and lower inertial response, such as wind generators. This changing nature of a power system has considerable effect on its dynamic behaviours resulting in power swings, dynamic interactions between different power system devices and less synchronized coupling. This paper presents some analyses of this changing nature of power systems and their dynamic behaviours to identify critical issues that limit the large-scale integration of wind generators and FACTS devices. In addition, this paper addresses some general concerns towards high compensations in different grid topologies. The studies in this paper are conducted on the New England and New York power system model under both small and large disturbances. From the analyses, it can be concluded that high compensation can reduce the security limits under certain operating conditions, and the modes related to operating slip and shaft stiffness are critical as they may limit the large-scale integration of wind generation.

This paper describes the two test systems for voltage stability studies set up by the IEEE PES Task Force on "Test Systems for Voltage Stability Analysis and Security Assessment" under the auspices of the Power System Stability Subcommittee of the Power System Dynamic Performance Committee. These systems are based on previous test systems, making them more representative of voltage stability constraints. A set of representative results are provided for both systems, with emphasis on dynamic simulation. They illustrate various aspects such as longterm dynamics, voltage security assessment, real-time detection, and corrective control of instabilities. The value for educators, researchers and practitioners are emphasized.

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This paper presents a novel modelling and excitation control design to enhance large-disturbance voltage stability in power systems with significant induction motor (IM) loads. The excitation controller is designed using minimax linear quadratic Gaussian (LQG) controller synthesis method. The nonlinear power system model is reformulated with a linear and a nonlinear term. The nonlinear term is the Cauchy remainder in the Taylor series expansion and its bound is used, in this paper, in a robust control design. An advantage of this approach over the existing linearisation scheme is the treatment of the nonlinear dynamic load model in a rigorous framework for excitation control design. The performance of the designed controller is demonstrated by large disturbance simulations on a benchmark power system for various types of loads.