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Various control methods which utilize online optimization have been developed. A quadratic programming (QP) problem is typically solved online in such methods. In this paper, we derive a regional sector condition for a QP problem. Then, based on the regional sector condition, we derive a condition to analyze regional l2‐performance of a feedback system with QP. The analysis condition is expressed as a set of linear matrix inequalities. Then, we show methods for applying the analysis condition to a model predictive control system and a feedback system with a control allocator. A numerical example is provided to show effectiveness of the result. © 2021 Institute of Electrical Engineers of Japan. Published by Wiley Periodicals LLC. [ABSTRACT FROM AUTHOR]

The stability of a power system has always been of concern. Now, wide‐area measurement systems are used widely. In this paper, we focus on supplementary turbine/governor control to enhance the stability of a power system with wide‐area measurement information. An H∞ supplementary turbine/governor controller based on the multi‐agent method is introduced to enhance power system stability. First, the synchronous generator is modeled as a second‐order agent. The information of communication topology and power network topology are used to build the system model and the controller design. Then, a linear output feedback controller is adopted. With a suitable Lyapunov function and by solving the linear matrix inequality, the parameters of the controller are tuned by the H∞ synthesis method. Finally, numerical simulations are presented on a Western Systems Coordinating Council three‐generator nine‐bus power system, validating the proposed design. © 2019 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc. [ABSTRACT FROM AUTHOR]

In this paper, the transient stability enhancement and voltage regulation of a multimachine power system are investigated taking into account the generator parameter uncertainties. An interval type‐2 Takagi–Sugeno (IT2 T‐S) fuzzy model is proposed to represent the nonlinear plant subject to parameter uncertainties. New basic concepts of the IT2 T‐S fuzzy model are proposed to reduce considerably the number of models adopted. A Lyapunov‐based approach is employed to analyze the stability and the pole placement of the IT2 fuzzy closed‐loop system formed by the IT‐2 T‐S fuzzy model and the IT‐2 fuzzy controller. This approach presents a simple closed mathematical form that provides the possibility to regulate the system under uncertain model parameters with closed‐loop design specifications as linear matrix inequality (LMI)‐based optimization problems without any assumptions about the membership functions. A simulation example is given to illustrate the effectiveness of the proposed IT‐2 fuzzy model‐based control approach. © 2019 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc. [ABSTRACT FROM AUTHOR]

This paper is concerned with the design of a robust, state-feedback, delay-dependent H∞ controller for an active vibration control of seismic-excited structural systems having actuator delay, norm bounded uncertainties, and L2 disturbances. The norm bounded uncertainties are assumed to exist in variations of structural stiffness and damping coefficients. Based on the selection of Lyapunov-Krasovskii functional, first a bounded real lemma (BRL) is obtained in terms of linear matrix inequalities (LMI5) such that the nominal, time-delay system is guaranteed to be globally asymptotically stable with minimum allowable disturbance attenuation level. Extending BRL, sufficient delay-dependent crite,ia are developed for a stabilizing H∞ controller synthesis involving a matrix inequality for which a nonlinear optimization algorithm with LMIs is proposed to get feasible solution to the problem. Moreover, for the case of existence of norm-bounded uncertainties, both the BRL and H∞ stabilization criteria are easily extended by employing a wellknown bounding technique. Then, a cone complementary algorithm is also utilized to solve the nonconvex optimization problem. By use of the proposed method, a suboptimal controller with maximum allowable delay bound, uncertainty bound and minimum allowable disturbance attenuation level can be easily obtained by solving the proposed convex optimization technique. A four-degree-of-freedom uncertain structural system subject to seismic excitations is used to illustrate the effectiveness of the approach through simulations. Simulation results, obtained by using real time-history data of Kobe and Kocaeli earthquakes show that the proposed controller is very effective in reducing vibration amplitudes of storeys and guarantees stability at maximum actuator delay and parametric uncertainty bound. [ABSTRACT FROM AUTHOR]