Fault‐tolerant load frequency control for one‐area power systems with time‐varying delays and actuator failures

This article aims to address the reliable quantized sampled‐data load frequency control (LFC) synthesis problem for semi‐Markov jump interconnected multi‐area power systems (IMAPSs) suffering from incomplete transition rates (TRs) and actuator failures. Primarily, the semi‐Markov process configurated with incomplete TRs is utilized to model the structural and coefficient switchings of IMAPSs, which enables a more precise representation of reality and a wider range of application. Subsequently, in order to reduce the control cost and facilitate data processing, an aperiodic quantization sampling mechanism is introduced. Furthermore, a mode‐dependent and comprehensive actuator faulty model is scheduled to portray various stochastically occurring actuator failures, which is more in line with practical application. Then, by fully utilizing the state information of sampled intervals, a two‐sided looped functional with some matrices that are not required to be strictly positive is constructed to enhance the flexibility. In what follows, on the basis of stochastic analysis technique and looped functional, sufficient conditions with two scenarios are established in the form of linear matrix inequalities (LMIs) to guarantee the stochastic stability with an performance of the resultant semi‐Markov jump IMAPSs. Finally, the effectiveness of the proposed control synthesis methodology is validated through a numerical simulation.

Load frequency control (LFC) is crucial for the economic operation and safety of power systems. Therefore this paper addresses the LFC problem for uncertain multi-area power systems with actuator failures. Specifically, actuator failures, uncertainties and communication bandwidth constraints appearing in multi-area power systems are taken into account simultaneously, and novel reliable event-triggered LFC schemes are proposed to cope with these troubles. The proposed schemes can ensure the asymptotical stability of the closed-loop system when only matched uncertainty exists. For the case of coexisting matched and mismatched uncertainties, the state trajectories of the closed-loop system can be controlled within a bounded set, where the size of the bounded set is only related to the mismatched uncertainty. To illustrate the theoretical results, a numerical example of three-area interconnected power system is presented. <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">Note to Practitioners</i> —Load frequency directly affects the quality of electric energy and is one of the main observation states of power systems, hence LFC has been widely investigated in the literature. For multi-area power systems, the system model to be controlled may be subjected to multiple unfavorable factors in practical situations, such as limited bandwidths, model uncertainties and actuator failures. To cope with these unfavorable factors, this paper is devoted to developing a unified control framework to guarantee the stability of the frequency deviation based on the event-triggered mechanism. Considering both matched and unmatched system uncertainties may exist as well as the bound of system uncertainties can be unknown, event-triggered control schemes including static event-triggered LFC and adaptive event-triggered LFC are accordingly designed to deal with aforementioned situations such that the closed-loop system is asymptotically or boundedly stable. The research outcome of this paper provides simple but effective LFC approaches that can be used to maintain the reliable and stable operation of multi-area power systems.

In power systems, load frequency control (LFC) matters significantly to achieve stability. Dealing with the fluctuations in the frequency of a multi-area power system becomes more challenging by incorporating additional energy resources. In this research, a multi-area power system is built by integrating thermal power systems with photovoltaic (PV) cells, wind turbines, and electric vehicles (EV). The addition of an electric vehicle “to a thermal power system which is integrated with a renewable energy source (RES)” increases the system productivity but also increases the system complexity, making it more problematic for LFC. Looking at the stability criteria for LFC, frequencies in two areas (Area-1 & Area-2) and tie-line power are considered for measurements. For the tuning of the proposed cascaded (1+PI)-PID controller, a new approach Bald Eagle Sparrow Search Optimization (BESSO) algorithm is implemented which is strongly inspired by nature. BESSO is a combination of bald eagle and sparrow searching techniques and performs comparatively better for fast convergence due to their strong food-seeking natural behavior to find the best solution for controller gains. Controller effects on multi-area systems are compared with the addition of PV, wind, and EV and resulting measurements meet the stability criteria with high accuracy even with the complexity of the system and also undertake a stability analysis to prove the performance by minimizing undershoot, overshoot, steady-state error and settling time for system frequencies and tie-line power. Simulation results are examined at different load-changing conditions. In contrast with similar combinations of PID controller with proposed cascaded (1+PI)-PID controller, it is claimed that the effect of the proposed controller is much finer and more reliable, even with electric vehicles to avoid system blackout caused by frequency fluctuations in interconnected power system.

This paper investigates the design of the reliable guaranteed cost control problem for continuous-time systems with actuator failures. The actuator failure model is formulated. Based on this model, the problem is to design a reliable guaranteed cost state feedback control law which can tolerate actuator failure, such that the cost function of the closed-loop system is guaranteed to be no more than a certain upper bound. A sufficient condition for the existence of reliable guaranteed cost controllers is derived via the linear matrix inequality (LMI) method, and by using Matlab, this controller is easy to implement. Furthermore, a convex optimization problem with LMI constraints is formulated to design the optimal reliable guaranteed cost controller which minimizes the upper bound of the closed-loop system cost. Finally, a numerical example is given to illustrate the effectiveness of the proposed design method.

This article investigates the problem of robust dissipative fault‐tolerant control for discrete‐time systems with actuator failures. Based on the Lyapunov technique and linear matrix inequality (LMI) approach, a set of delay‐dependent sufficient conditions is developed for achieving the required result. A design scheme for the state‐feedback reliable dissipative controller is established in terms LMIs which can guarantee the asymptotic stability and dissipativity of the resulting closed‐loop system with actuator failures. In addition, the proposed controller not only stabilize the fault‐free system but also to guarantee an acceptable performance of the faulty system. Also as special cases, robust H∞ control, passivity control, and mixed H∞ and passivity control with the prescribed performances under given constraints can be obtained for the considered systems. Finally, two numerical examples are provided to illustrate the effectiveness of the proposed fault‐tolerant control technique. © 2016 Wiley Periodicals, Inc. Complexity 21: 579–592, 2016

The non-fragile reliable controller design problem for a dynamic interval system against actuator failures in the input channels and a given quadratic cost function is discussed. A sufficient condition is established such that the closed-loop system stability and cost function is guaranteed to be no more than a certain upper bound with all admissible uncertainties as well as actuator failures. A modified interval system described by matrix factorization will lead to less conservative conclusions. An effective linear matrix inequality (LMI) approach is developed to solve the addressed problem. Furthermore, a convex optimization problem is formulated to design the optimal non-fragile reliable guaranteed cost controller which minimizes the upper bound of the closed-loop system cost. The effectiveness of this approach has been verified on an aircraft angle control system design. Simulation results on a test example are presented to validate the proposed design approach.

T For the networked control system (NCS), the considered system has actuator and sensor failures. In considering the impact of the network delay on system performance, establish a new class of uncertain NCS fault model Then use Lyapunov stability theory, fault-tolerant control theory and the static state feedback, the sufficient conditions for closed-loop NCS possessing robust asymptotically stable against actuator and sensor failure are given . And the robust H-inf fault-tolerant controller design method under the sensor and actuator failures is deduced in terms of linear matrix inequalities (LMI). An numerical simulation is provided to show the effectiveness of the proposed conclusion.

This paper studies the problem of event-triggered robust $$H_\infty $$ control for a class of networked flight control systems (NFCSs), in which parameter uncertainties and actuator failures are jointly involved. Firstly, under networked environments, we design an adaptive event-triggered mechanism (AETM) in order to reduce the data transmissions, whose triggering thresholds can be dynamically adjusted to real-time variations of NFCSs. Secondly, based on AETM and state feedback controller, a closed-loop model can be obtained and an augmented Lyapunov–Krasovskii functional can be further constructed. Thirdly, by means of two effective inequalities, some sufficient conditions on designing the AETM and controller are expressed via linear matrix inequalities, which can ensure the NFCSs to achieve control target and lead to less conservatism. Finally, a numerical example is presented to illustrate the proposed results.

The problem of robust Hinfin reliable control is investigated for time-varying delayed uncertain systems against actuator failures. In the considered system, the parameter uncertainty satisfies a generalized matching condition, and the time-varying delay is bounded and its derivative is unbounded. All the outputs of the actuator failures are assumed to be zero. Based on Lyapunov-Razumkhin stability theory, a sufficient condition of the existence of robust reliable controller which enables the closed-loop system to possess Hinfin performance index is given. At the same time, a designing approach of memoryless state-feedback controller is presented. The sufficient condition is represented by linear matrix inequalities (LMIs) and has relevance to time delay. The resultant control systems retain asymptotic stability and disturbance attenuation with Hinfin -norm bounds irrespective of any outages within a prespecified subset of actuators. A numerical example shows the validity of the proposed design method.

This article addresses the reliable problem for networked control systems with actuator failure. By combining the Lyapunov stability theory, the linear matrix inequality (LMI) optimization technique, and structural constraints, an optimal reliable feedback controller is established to guarantee asymptotically stable even though some control component (actuator) failures occur. Finally, an illustrative example is provided to demonstrate the effectiveness of the results developed in this paper.

In this paper, an observer‐based fault estimation and fault‐tolerant control scheme for intermittently sampled singular systems subject to simultaneous actuator and sensor failures, time‐varying interval delays, and external disturbances is investigated. A new observer, the extended sampled‐data proportional–integral observer (SPIO), is designed. Compared with the conventional PIO, better estimation performance can be obtained by using the designed observer. In addition, the impulsive nature of the closed‐loop system can be eliminated by adding state estimation derivatives, which improves the design scheme of the FTC for singular system. All feasible conditions are given in the linear matrix inequality (LMI) framework. Finally, the superiority and practicality of the scheme are verified through simulation and comparison with existing literatures.

This paper deals with the problem of robust fault-tolerant dynamic output feedback controllers design for time-delay systems. The system under consideration involves parameter uncertainties and time-delay. The purpose is to design the dynamic output feedback controller such that, for all admissible uncertainties as well as actuator failures, the system remains stable. The sufficient condition is given in the form of linear matrix inequalities (LMIs) to maintain the stability of the closed-loop system for the time-delay system against actuator failures, and the design of the dynamic output feedback controller is proposed. Finally, an illustrative example and simulation results are given to demonstrate the effectiveness of the proposed method.

Event triggered control for fault tolerant control system with actuator failure and randomly occurring parameter uncertainty

Robust fault-tolerant control for power systems against mixed actuator failures

The problem of guaranteed cost fault-tolerant control for networked control systems (NCSs) is discussed in this paper. Based on Lyapunov stability theory and linear matrix inequality (LMI), the sufficient conditions which can meet a cost function for closed-loop networked control systems possessing robust integrity against actuator failures are given by adopting memory state feedback control law, and the robust fault-tolerant controller is designed via solving several linear matrix inequalities. Finally, the numerical example is given to demonstrate the effectiveness and feasibility of the proposed approach..