New Publications are available for Nonlinear control systems
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New Publications are available now online for this publication.
Please follow the links to view the publication.A sensorless control using a sliding-mode observer for an electromagnetic valve actuator in automotive applications
http://dl-live.theiet.org/content/conferences/10.1049/cp.2012.0270
In this paper, based on a non-linear model, a particular sliding mode observer is presented. Considerations on constructive aspects concerning observability is made. Control strategy is presented and discussed as well. Both computer simulation and laboratory experimental of the controlled system are presented which demonstrate promising behavior. (6 pages)Decentralized coordinated robust controller design for multimachine power system based on multi-agent system
http://dl-live.theiet.org/content/conferences/10.1049/cp.2012.0084
A decentralized coordinated control is researched based on multi-agent structure for transient stability improvement of large-scale power system in this paper. First, a multi-agent system (MAS) model is structured based on the wide-area measurement system (WAMS), which consists of both upper and lower level agents. The upper level coordinated agents are mainly responsible for coordinating and controlling the lower level agents via sending coordinated control signals into local decentralized control loops in order to damp lower frequency oscillations between regions. And the main function of lower level agents is to continuously regulate generator unit through excitation controller to overcome small disturbances. Then, the focal task of this paper is to design a decentralized coordinated controller based on the MAS model. To eliminate the nonlinearities and interconnections of multimachine models, a direct feedback linearization (DFL) compensator is designed through the decentralized excitation control loop. Besides, taking consideration of the effects of uncertainty introduced by transient process, the H<sub xmlns="http://pub2web.metastore.ingenta.com/ns/">∞</sub> robust control method integrating with linear matrix inequality (LMI) technology is used to seek the solutions of the decentralized coordinated controller. Finally, simulation demonstrates that the MAS based decentralized coordinated robust controller has better transient stabilization performance than the conventional PSS. (6 pages)Frequency-Domain Control Design for High-Performance Systems
http://dl-live.theiet.org/content/books/ce/pbce078e
<p xmlns="http://pub2web.metastore.ingenta.com/ns/">This book serves as a practical guide for the control engineer, and attempts to bridge the gap between industrial and academic control theory. Frequency domain techniques rooted in classical control theory are presented with new approaches in nonlinear compensation that result in robust, high-performance closed-loop systems. Illustrative examples using data from actual control designs are included.</p>Modelling and power quality enhancement of induction motor with soft starter using synchronous reference frame theory
http://dl-live.theiet.org/content/conferences/10.1049/cp.2011.0333
An This paper presents a method for obtaining the desired reference current for Voltage Source Inverter (VSI) of Shunt Active Filter fed Induction motor using Synchronous Reference Frame (SRF) theory. The modeling is based on the a-b-c stationary frame to 0-d-q rotating frame transformation of the ac system variables. The cur rents injected by the active filter are controlled in the synchronous orthogonal 0-d-q frame using a decoupled nonlinear control strategy. The reference harmonic components are extracted from the sensed nonlinear load currents by applying the synchronous reference frame method, where an AC voltage controller fed three-phase Induction motor is taken as the nonlinear load. To improve the performance of the PI controller, the feedback path to the integral term is introduced to compensate the winding up phenomenon due to integrator. The Phase Locked Loop (PLL) with PI filter is used for Synchronization, with much emphasis on minimizing delays. The results confirm the performances considered theoretically for the shunt active filter topology and to comply with IEEE 519 recommended harmonic standards.Load frequency controller with PI controller considering non-linearities and boiler dynamics
http://dl-live.theiet.org/content/conferences/10.1049/cp.2011.0376
This paper describes the Load Frequency Control (LFC) of two area interconnected reheat thermal system using conventional Proportional Integral (PI) controller. The system is incorporated with governor dead band, generation rate constraint non-linearity and boiler dynamics. The conventional PID & P controllers do not yield adequate control performance with the consideration of nonlinearities and boiler dynamics. To overcome this drawback PI Controller has been employed in the system. The aim of PI is to restore the frequency and tie line power in very smooth way to its nominal value in the shortest possible time. Time domain simulations are used to study the performance of the power system. System performance is examined considering 1% step load perturbation in either area of the system.An innovated nonlinear voltage regulator for DC/DC converters: theoretical and experimental results on PV applications
http://dl-live.theiet.org/content/conferences/10.1049/cp.2011.0132
In this paper, a nonlinear dynamic controller is proposed for regulating the dc bus voltage of a DC/DC boost power converter in a stand-alone photovoltaic system. The controller is proven to achieve the desired voltage regulation independently from the PV source voltage, the converter parameters and the kind of the load. Extended mathematical analysis shows that the proposed control scheme guarantees damping characteristics (passivity) of the closed-loop system, which represents a fundamental property for achieving stability at the desired equilibrium. Simulation and experimental results verify the controller efficiency for a single resistance-inductance load case and for a nonlinear load consisted of a three-phase voltage source inverter and a three-phase resistance-inductance. (6 pages)Fuzzy generalized synchronization between non-smooth-air-gap and smooth-air-gap PMSM chaotic systems with channel delay
http://dl-live.theiet.org/content/conferences/10.1049/cp.2010.0785
The generalized synchronization problem between non-smooth-air-gap and smooth-air-gap PMSM chaotic systems is studied in this paper. In addition, the channel delay is considered in the realization of the chaotic synchronization. Firstly, the nonsmooth-air-gap PMSM chaotic system and the smooth-air-gap PMSM chaotic system are represented by the T-S fuzzy models without any modeling error. Then, a simple fuzzy state feedback controller is designed based on the parallel distributed compensation technique. By virtue of the definition of lag synchronization and fuzzy control idea, the asymptotical synchronization is realized by choosing appropriate controller gain matrices. Finally, an illustrative example is presented to demonstrate the effectiveness of the proposed fuzzy synchronization method.Design and realization of a sliding mode control scheme for a pneumatic cylinder X-Y axles position servo system
http://dl-live.theiet.org/content/conferences/10.1049/cp.2010.0598
Due to the pneumatic air provided a large effective power, the pneumatic system are adopted in many automation industries. However, the pneumatic air is compressible, and pneumatic system has many nonlinear characteristics, such as the mass flow rate parameters variable and the servo valve dead zone problems. In this paper, a sliding mode control for a pneumatic cylinder position servo control system was proposed to realize position regulating and tracking control. The key feature of this control scheme is the using of extra adjustable free parameters to the design of sliding surface and switching variable boundary layer for the pneumatic servo system to improve the control performances. The validity of the proposed control scheme is verified through practical testing on an experimental pneumatic cylinder X-Y axle servo system device. In the cases of step, multi-steps, and sinusoidal level position command inputs, the test results show that the proposed control scheme is capable of improving the tracking precision.A new nonlinear dynamic output voltage controller for power dc/dc boost converters
http://dl-live.theiet.org/content/conferences/10.1049/cp.2010.0880
A new nonlinear control scheme suitable for dc/dc power boost converters is presented. As shown in the paper, the proposed controller is capable of regulating the converter output at the desired level independently from the kind of the load. It is proven that in both cases, i.e. of a pure resistance load and a resistance-inductance load, the controller preserves the passivity property which is a fundamental property of the open-loop system guaranteeing a satisfactory response. This is the main advantage of the proposed controller against other advanced standard techniques, such as the IDAPBC design which may fail in cases where resistance-inductance load appears. Simulation results that include comparisons with the IDA-PBC controller performance, demonstrate the superiority of the proposed approach. (5 pages)Conception of robust neural networks for hybrid control of asynchronuous motor drives
http://dl-live.theiet.org/content/conferences/10.1049/cp.2010.0069
It is well known that the combination between Neural networks and fuzzy controllers are considered as the most efficient approximators of different functions and also proves their capability of controlling nonlinear dynamical systems So, in this paper, the authors introduce a novel technique of control called" hybrid control" which is Based on Feedback Linearization and Field Oriented Control of an Induction Motor, in order to replace the sliding mode controllers (speed and flux ones). In fact, the objectives required by the introduction of neural networks (RANNCs) is to perform the control which is shown by simulation results. (7 pages)On a variation of the Gershgorin circle theorem with applications to stability theory
http://dl-live.theiet.org/content/conferences/10.1049/cp.2009.1687
The conclusions of the Gershgorin circle theorem are significantly extended for the special case of real matrices. The extended result is applied to the problem of the absolute stability of both continuous- and discrete-time Lur'e systems containing sector nonlinearities. Specifically necessary conditions for the existence of common unic Lyapunov functions are presented in the form of constraints upon the root locus of the linear, time-invariant component. (5 pages)Research on adaptive niche differential evolution algorithm for reactive power optimization
http://dl-live.theiet.org/content/conferences/10.1049/cp.2009.1803
Reactive power optimization which is the foundation for optimal control of voltage and reactive power is a very complex non-linear mixed integer programming problem. To deal with this optimization problem, an Adaptive Niche Differential Evolution algorithm (ANDE) is presented to avoid the premature phenomenon in DE. To maintain the population diversity, niche-sharing mechanism is adopted. To improve the rate of convergence, penalty function is used by niche-eliminating mechanism to deal with some low fitness individuals. To improve searching capability of algorithm, niching radius can also be adjusted adaptively on the basis of the relative distance between individuals which reflect the aggregation of population. Using the above method, the global searching ability of this algorithm could be improved. The proposed algorithm has been tested on IEEE-6, IEEE-30 and IEEE-118 bus systems and the calculation proves the effectiveness and practicability of the above algorithm. (6 pages)Environment modelling in mobile robotics through Takagi-Sugeno fuzzy model
http://dl-live.theiet.org/content/conferences/10.1049/cp.2009.1701
The modelling of uncertain and dynamic environments is an important and challenging problem in mobile robotics. Nonlinear dynamic systems can be represented as Takagi-Sugeno (T-S) fuzzy models, with linear or affine consequence. This paper proposes a novel method of object tracking in cluttered environments for mobile robots using T-S fuzzy models. The model has been tested on a Patrolbot which tracks a ball using a camera and avoids obstacles using six sonars. (6 pages)Research on trajectory tracking control of nonholonomic wheeled mobile service robots
http://dl-live.theiet.org/content/conferences/10.1049/cp.2009.1523
Nonholonomic wheeled mobile service robot's posture error model denoted by Cartesian coordinates in local coordinates is established. A novel nonlinear state feedback trajectory tracking control law is proposedL which causes closed-loop system state space equation of robot to have isolated euqilibrium state at origin.Through analysing the local uniform asymptotical stability at origin and the instability of isolated boundary equilibrium state at non-origin under the proposed trajectory tracking control lawL the scale of control parameters is confirmed. By Lyapunov candidate function methodL this paper concludes that the elosed-loop system is globally uniformly asymptotically stable at origin. Simulation results show the effectiveness of the proposed control law. (5 pages)Control of a highly non-linear multi-variable thermal processing furnace
http://dl-live.theiet.org/content/conferences/10.1049/cp_20080642
Tuning a controller's parameters can sometimes be a very complex and challenging task. Many methods have been used through the years to try and overcome this difficult challenge. In this paper we investigate the linear quadratic regulator (LQR) as a method for giving robust control for the non-linear multiple input multiple output system discussed in this paper. The system is a thermal processing furnace used to anneal 150 mm wafer batches in the 250°C to 450°C range in high vacuum. A plant model was developed which is a hybrid of a physical-law heat-transfer model and measurement data based model of the system. Numerical optimization was used to minimize the difference between measured data and model predicted outputs. Then, multiple linearized models were obtained. LQR was applied to one such model. It achieved the required specifications over the specified temperature range. The important specifications in this application are rise time, steady state accuracy and overshoot which are critical to the process.Wide-area measurement based nonlinear global optimal control for power system stability enhancement
http://dl-live.theiet.org/content/conferences/10.1049/cp_20080070
Centralized control using the wide-area information has been suggested to enhance the dynamic performance of large interconnected power systems. According to the inverse system method and LQR optimal control theory, this paper presents a nonlinear hierarchical global controller based on the wide-area information including the on-line measured center of rotor angle and total unbalanced power. Moreover, it has been verified that the optimal control in the sense of linear quadratic state regulator principle for the linearized system is equivalent to an optimal control in the sense of extended quadratic output regulator performance index for the primitive nonlinear system. So, the designed controller is an optimal controller for the nonlinear system digital simulation demonstrates that the multi-machine power system under the nonlinear global control has less settling time, swing times, oscillatory peak value and more critical clearing time and better voltage stability performance than that under PID control and nonlinear decentralized control.ANFIS gain scheduled CSTR with genetic algorithm based PID minimizing integral square error
http://dl-live.theiet.org/content/conferences/10.1049/ic_20070587
In this paper, a new control scheme, the artificial neuro fuzzy inference system (ANFIS) gain scheduled genetic algorithm (GA) based PID is proposed for continuous stirred tank reactor (CSTR). CSTR is a highly nonlinear process that exhibits stability in certain region and instability in some regions. The proposed control scheme implements the characteristics of the genetic algorithm's (GA) global optimization to optimize the PID's three control parameters: k<sub xmlns="http://pub2web.metastore.ingenta.com/ns/">p</sub>, k<sub xmlns="http://pub2web.metastore.ingenta.com/ns/">i</sub>, k<sub xmlns="http://pub2web.metastore.ingenta.com/ns/">d</sub>, to obtain the best control effect by minimizing integral square error online. The GA tuned PID controller parameters are gain scheduled using ANFIS. ANFIS gain- scheduling is a special form of neuro-fuzzy control that uses linguistic rules and fuzzy reasoning to determine the controller parameter transition policy for the dynamic plant subject to large changes in its operating state. Simulation result shows the feasibility of using the proposed controller for the control of the dynamical nonlinear CSTR.Fuzzy gain scheduled pole placement based state feedback control of CSTR
http://dl-live.theiet.org/content/conferences/10.1049/ic_20070588
CSTR plays a vital role in almost all the chemical industries. Continuous stirred tank reactor (CSTR) is a highly nonlinear process exhibiting stable and unstable steady state at different regions. Control of CSTR in the complete range is a mind boggling problem. In this paper, a fuzzy scheduled pole placement based state feedback control of CSTR is investigated. The entire region is divided into three regions; low, middle and the high region. The low and the high region have stable steady state and the middle region have unstable steady state. Initially, the gain matrix of the state feedback controller is computed for each region using pole placement technique. Then using fuzzy gain scheduler, the complete controller is formed. The result shows the feasibility of using the proposed controller for the control of CSTR. In this chapter optimal control of CSTR is investigated for the tracking and regulatory problems.Control design and performance evaluation of energy source interfaced DSTATCOM
http://dl-live.theiet.org/content/conferences/10.1049/ic_20070666
The widespread application of DSTATCOM for filtering load harmonics is expected to occur in the near future. Although the requirement of DSTATCOM is universally accepted, equipment cost can still be an impediment for its wide usage. The use of DSTATCOM can be very well justified by incorporating multiple control functions on the same equipment. In this paper, the performance evaluation of a Single DSTATCOM which can perform the three major functions namely the elimination of harmonics, load balancing and reactive power compensation is investigated. The study is performed on a representative system and the transient simulation is carried out by the detailed nonlinear model of DSTATCOM using MATLAB-SIMULINK.Novel topologies for identification and control of PMSM using artificial neural network
http://dl-live.theiet.org/content/conferences/10.1049/ic_20070590
Rotor speed and performance of permanent magnet synchronous motor (PMSM) suffers from accuracy due to variation of motor parameters such as stator resistance, stator inductance or torque constant. The conventional linear estimators are not adaptive. Neural networks (ANN) have shown better results when estimating or controlling nonlinear systems. In this paper an artificial neural network based high performance speed control system for a PMSM with different topologies and their performance comparison is presented. The main purpose is to achieve accurate trajectory control of the speed, when the motor and load parameters are unknown. The PMSM motor was identified using three different topologies (speed, voltage and current). The unknown nonlinear dynamics of the motor and the load are captured by the ANN. The performance of the identification and control algorithm are evaluated by simulating them on a typical PMSM motor model.Dynamic analysis of multi-output push-pull ZCS-quasi resonant converter
http://dl-live.theiet.org/content/conferences/10.1049/ic_20070616
High frequency dc-dc converters are now-a- days widely used in power electronic applications. High operating frequencies entail a reduction in size of the passive components such as inductor, capacitor and power transformers. By operating the converter at higher switching frequencies with conventional hard switching topologies the transistor switching losses increases at both turn on and turn off. In order to achieve a high frequency operation with moderate switching losses a number of soft switching topologies have been studied. So modeling and analysis of soft switching converter is preferable. In this paper modeling and analysis of a multi-output push-pull ZCS quasi-resonant converter is carried out using state-space averaging technique. State space averaging technique allows a switched system to be approximated as a continuous non-linear system and linearization allows the resulting non-linear system to be approximated as a linear system. The advantages of state space design are especially apparent when the system to be controlled has more then one control input and more than one sensed output and also it shows the internal behaviour of the system.Closed loop stability analysis for the particle swarm optimization dynamics
http://dl-live.theiet.org/content/conferences/10.1049/ic_20070589
The paper presents an alternative formulation of the PSO dynamics by a closed loop control system, and analyzes the stability behavior of the system by using Jury's test and root locus technique. Previous stability analysis of the PSO dynamics was restricted because of no explicit modeling of the non-linear element in the feedback path. In the present analysis, the model of the nonlinear element is considered for closed loop stability analysis. Unlike the previous works on stability analysis, where the acceleration coefficients have been combined into a single term, we in this paper consider their separate existence to determine their suitable range to ensure stability of the dynamics. The range of parameters of the PSO dynamics, obtained by Jury's test and root locus technique are also confirmed by computer simulation of the PSO algorithm.Bumpless transfer for wireless cellular networks
http://dl-live.theiet.org/content/conferences/10.1049/cp_20070770
This paper presents a nonlinear control method known as bumpless transfer that addresses the question of seamless controller switching during handoff for a roaming user in a wireless cellular network. The work explicitly considers the uncertain effects of multiple access interference, path loss, multi- path fading, shadowing and round trip delay in a system theoretic context, as well as the costs that are imposed through the implementation in hardware of output transmission power control.Predictive control tool kit
http://dl-live.theiet.org/content/conferences/10.1049/ic_20060266
The talk presents a graphical framework for designing and configuring model predictive control applications. This predictive control toolkit developed for LabVIEW contains linear as well as nonlinear predictive control methods. The toolkit is tightly integrated with LabVIEW system identification, control design toolkits and the simulation module for design verification and deployment. The control solutions can be easily imported to a real time platform for industrial applications. Linear and nonlinear predictive control strategies are presented in details and the performances are illustrated in various case studies.A new fuzzy sliding-mode control for MW variable speed-variable pitch wind turbine
http://dl-live.theiet.org/content/conferences/10.1049/cp_20062102
Recently, an increasing number of larger wind turbines (1 MW and up) are being developed with a variable speed-variable pitch control mechanism. The main objective of using a variable speed-variable pitch control strategy is to improve the fast response speed and get maximum energy. But the power generated by wind turbine changes rapidly because of the continuous fluctuation of wind speed and direction. At the same time, wind energy conversion systems are of strong nonlinear characteristics because of many uncertain factors. Based on combined nonlinear sliding-mode control and fuzzy set theory, this paper presents a new kind of state controller to eliminate the steady state error, compensate the nonlinearity and have excellent robustness. (5 pages)Realization of close coupling plane double inverted pendulum based on digital motion technology
http://dl-live.theiet.org/content/conferences/10.1049/cp_20061098
Inverted pendulum system is a typical close coupling, nonlinear system with high-rank, multi-variable and serious instability. Aiming at the control problem of Inverted pendulum, the conventional operators have PID operator, pole disposition operator and optimal control operator and so on, most of which are aimed at the single linear or single plane inverted pendulum. Taking into account the control law of the car's displacement, speed, angle, angular-rate and angular acceleration of rod 1 and rod 2 under the input electric voltage, these traditional operators such as LQR (linear quadratic regulator) have an effect of better stability, but sacrifice the robust and transient performance. In view of uncertain factors in pendulum systems, authors design an intelligent controller, i.e. the robust LQR controller for plane two rods inverted pendulum based on the robust optimal control with self-adaptive performance in order to improve the transient state and robustness of the system, then simulate the pendulum system by Matlab. Thus we can get the contrasted response curves of the angle of two rods and car situation according to the two designed methods to compare their advantages and disadvantages. Finally BC 3.1 is adopted to write the digital motion control program and realize the real time control and material object control of the plane two rods inverted pendulum.Nonlinear control of interconnected power systems based on multi-agent technology
http://dl-live.theiet.org/content/conferences/10.1049/cp_20062100
Combining the multi-agent technology and nonlinear control knowledge, this paper presents an intelligent nonlinear control structure of the power system based on the multi-agent technology. It is a multi-agent system (MAS), which is composed by corresponding layer and implementing layer. The corresponding layer determines the optimum location scheme of the nonlinear control using the "dynamic residue" method. The implementing layer controls the switch between the nonlinear control and the general control. Applying results on ten-generation system indicate that it can eliminate the zero dynamic characteristic and improve the transient stability of the multi-generation power system. (8 pages)Nonlinear integrated control with objective holographic feedbacks for the generator set
http://dl-live.theiet.org/content/conferences/10.1049/cp_20061998
This paper proposes the nonlinear control design method with objective holographic feedbacks (NCOHF) for the multiple inputs multiple outputs (MIMO) nonlinear control system. The NCOHF technique can transform all control objectives of the nonlinear control system into the linear space, and punish them by the quadratic performance index. According to the design principal of NCOHF, the control law derived can contain the feedback informations of all control objectives, and the control system needn't have the same inputs and outputs. Applying NCOHF into a condensed steam generator set, a nonlinear integrated control law with objective holographic feedbacks (NICOHF) is deduced. The NICOHF contains the feedback informations of all interested variables of the generator set. Simulation results indicate that these interested variables of the generator set have good dynamic and static performances. Thus, NICOHF improves the output characteristics of the generator. (6 pages)Damping controller for DG unit with synchronous generator
http://dl-live.theiet.org/content/conferences/10.1049/cp_20060066
The paper develops power system stabiliser (PSS) for a synchronous generator equipped with static excitation system such that the PSS produces damping torque component only. The simplicity of the design methodology makes it especially useful for the design of small distributed generators. Good dynamic properties of the plant equipped with the proposed PSS are confirmed by simulation using non-linear, multi-machine model of a power system.On the closed-loop control of an argon plasma process
http://dl-live.theiet.org/content/conferences/10.1049/cp_20060476
Closed-loop control of a plasma process for etching applications is discussed in this study. Plasma processes are highly nonlinear systems that typically feature complex chemical and physical reactions. A laboratory-based plasma reactor is presented in this work, and issues concerning its closed-loop control are discussed. A PID controller for the experimental plasma process is developed and its performance is analyzed. The need for a more advance control methodology is studied and some appropriate control structures are proposed. Finally, a description of the practical implementation of real-time multivariable closed-loop control for the studied plasma reactor is presented.An overview on transient stability control in modern power systems
http://dl-live.theiet.org/content/conferences/10.1049/cp_20062213
The development of the modern power system has led to an increasing complexity in the study of power systems, and also presents new challenges to power system stability, and in particular, to the aspects of transient stability (TS) and small- signal stability (SS). Transient stability control plays a significant role in ensuring the stable operation of power systems in the event of large disturbances and faults, and is thus a significant area of research. In this paper, the applications of nonlinear control theories in power system stability control are presented together with a brief description of the various control objectives in power systems. Issues regarding coordination of controls and new technologies are also discussed, and the implications of such issues on further research are also provided. (7 pages)Nonlinear coordination control strategy of DC power modulation in multi-infeed HVDC power systems
http://dl-live.theiet.org/content/conferences/10.1049/cp_20062076
A novel nonlinear DC power modulation control strategy is proposed in multi-infeed HVDC power systems. The essential design idea is to drive the center of inertias (COI) of individual areas linked by AC/DC lines to a stable equilibrium point, so that the inter-area oscillations of multi-infeed HVDC systems can be damped out. COI signals are assumed to be available from the wide area measurement system (WAMS). Based on a three-area AC/DC system model derives in COI coordinate, the back-stepping method is applied to work out the nonlinear robust adaptive control law, which is adaptive to the unknown parameters and is robust to model error, disturbances and equilibrium point change. Computer simulation results of a six-generator-three-area test AC/DC system show that the proposed controller is superior to conventional DC power modulation controllers and can well coordinate to each other to damp interarea oscillations. Besides, the controller performance is not sensitive to the system structure and operation point changes. (7 pages)Quantitative feedback design for a benchmark quadruple-tank process
http://dl-live.theiet.org/content/conferences/10.1049/cp_20060470
In this paper level control for a quadruple-tank process with variable nonlinear zero dynamics is considered. This provides a nice benchmark problem that illustrates some of the challenges posed by complex interconnected systems for linear design paradigms. A quantitative feedback theory (QFT) methodology is used to provide robust control of the water level in the lower two tanks. The linear design is validated on the nonlinear system model.The gain-scheduled control of a non-linear laboratory heating and ventilation process
http://dl-live.theiet.org/content/conferences/10.1049/cp_20050285
This paper details the control of a pilot scale laboratory heating and ventilation system (VVS-400 product, Instrutek Ltd., Norway). The system is represented in 2×2 multi-input, multi-output (MIMO) form. A process reaction curve identification technique was used to model (in first order lag plus delay - FOLPD - form) the flow process and temperature process portions of the system, over a range of operating conditions. Tests revealed that both processes were continuously non-linear. A gain scheduler with static decoupling was designed, using look-up tables, to continuously interpolate for the most suitable PI/PID controller settings and decoupler gains. The contribution of this paper is the careful application, using well-known techniques, of a complete controller design cycle for a laboratory scale system.Optimal guaranteed cost control for a class of nonlinear uncertain system
http://dl-live.theiet.org/content/conferences/10.1049/cp_20050335
In this paper, the guaranteed cost control problem for a class of nonlinear uncertain systems is studied. The problem is to design a memoryless state feedback controller such that the closed-loop system is asymptotically stable and the closed-loop cost function value is less than a specified upper bound for all admissible uncertainties. A sufficient condition for the existence of such controllers is presented in terms of the solvability to a certain system of LMIs, and a parametrized representation of a set of guaranteed cost controllers is provided by the feasible solutions to the system of LMIs. Furthermore, a procedure is given to select an optimal guaranteed cost control law in the sense of minimizing the upper bound of the cost function. At last, a numerical example is given to illustrate the design procedures and their effectiveness. The results show that there is distinct improvement in the aspect of conservation.Control Theory
http://dl-live.theiet.org/content/books/ce/pbce064e
<p xmlns="http://pub2web.metastore.ingenta.com/ns/">This fully revised and updated edition of Control Theory: a guided tour addresses recent developments in the field. It discusses how the rise of Hoo and similar approaches has allowed a combination of practicality, rigour and user interaction to be brought to bear on complex control problems and has helped bridge the gap between control theory and practice. The book also examines the effects of the rise of artificial intelligence techniques and the increasing availability of comprehensive software packages.</p>Internet-based monitoring and control of protective relays and disturbance recorders
http://dl-live.theiet.org/content/conferences/10.1049/cp_20040209
This paper describes automatic data transfer from digital relays and disturbance recorders to the "protective relay monitoring centre". In addition, the Internet is used to access relay and disturbance recorders data as well as data in the event database. When an event occurs in the power system the developed software logs the event in the database and sends an SMS note to the protection engineer who is on duty. This way the information regarding the event in the power system is provided immediately. Consequently, a higher availability of the entire power system is achieved since devices can be monitored and accessed wherever the Internet is available.Simulation studies of OLTC transformer AVC relays operating in series using a RTDS, real time digital simulator
http://dl-live.theiet.org/content/conferences/10.1049/cp_20040200
The most effective method for demonstrating the performance of protection relay schemes is to test them using a power supply network. If this is not possible, the operation of real protection relays can be demonstrated using a specialist real time power system simulator. This paper describes a series of tests conducted to demonstrate the operation of new tap changer control strategies using a commercial real time digital simulator (RTDS) and commercially available automatic voltage control (AVC) relays. The demonstration tests used AVC relays operating at different voltage levels in the network. Each relay was provided with the required voltage and current outputs from the RTDS as derived from the appropriate locations on the power system network. Different scenarios were then simulated and the performance of the different AVC voltage regulation strategies was investigated. Since the relays were effectively connected in series, the operation of any one of the relays influenced the other AVC relays in the network. The response of the AVC relays with a selection of control strategies to different power system scenarios was demonstrated. The use of the RTDS enabled the real time adaptive features of the different control strategies to be investigated. This was achieved by interfacing the relay inputs and outputs through the RTDS system with control logic developed in PSCAD. These techniques and the results of the tests are described in this paper.Intelligent control schemes for a static compensator connected to a power network
http://dl-live.theiet.org/content/conferences/10.1049/cp_20040355
Two intelligent controllers are designed for a static compensator (STATCOM) connected to a single machine infinite bus power system (SMIB): a novel nonlinear adaptive controller using artificial neural networks based on the indirect adaptive control technique and a Takagi-Sugeno type fuzzy controller. Both schemes provide nonlinear adaptive control with better performance compared to the conventional PI controllers. Simulation results are presented to compare the performances of these controllers with that of the conventional PI controllers. (6 pages)Optimal design of UPFC nonlinear control system
http://dl-live.theiet.org/content/conferences/10.1049/cp_20030622
In order to improve the control capabilities of power flow and system stability, unified power flow controller (UPFC) is widely studied. A nonlinear control system is designed in line with direct feedback linearization (DFL) theory and the excitation control system is taken into account. On the basis of the designed control system, a number of simulation researches are implemented which show that the nonlinear controller has much better performance than the linear.Capability assessment of high-performance control schemes for PWM voltage-source rectifiers fed from weak power systems
http://dl-live.theiet.org/content/conferences/10.1049/cp_20020093
It is a known fact that waning power systems worldwide are being supported using distributed power generation. This type of generation however adversely affects the end-users' power quality by increasing voltage and frequency disturbances. This paper presents a capability assessment of high-performance control schemes for PWM voltage source rectifiers operating under these conditions. The strategies considered are: a cascaded current/voltage scheme with PI controllers and a decoupling feedforward term, a cascaded nonlinear control scheme, and a paralleled current/voltage nonlinear control scheme. The analysis employs α-β stationary frame modeling and sequence decomposition theory. The strategies were implemented and experimentally tested using a TMS320C32 DSP based system. The evaluation considered industry standard disturbances, namely sags, swells, and frequency fluctuations. Results obtained showed that the paralleled nonlinear scheme presents the best performance.Optimised torque control of marine transverse-flux propulsion machines
http://dl-live.theiet.org/content/conferences/10.1049/cp_20020080
This paper focuses on describing a generalised approach to torque control that utilises the motor's magnetic flux characteristic that ensures that maximum torque is produced for minimal input power. The method is generalised for any separately excited synchronous, permanent magnet or reluctance machine, including axial flux machine (AFM) and transverse flux machine (TFM). A TFM motor is used to illustrate the performance of this control algorithm, chosen because of its nonlinear nature.Analytical investigation of large-scale use of static VAr compensation to aid damping of inter-area oscillations
http://dl-live.theiet.org/content/conferences/10.1049/cp_20010540
This paper presents the results of analytical studies undertaken to assess the effectiveness of multiple static VAr compensation (SVC) in aiding the damping of interarea oscillations in the Mexican interconnected power system. A frequency-domain methodology is adopted to coordinate controllers as well as to minimise the potential for adverse interaction between control loops. The effectiveness of SVC voltage support for damping inter-area oscillations is verified by nonlinear time domain simulation studies.Analysis of a robust DC-bus voltage control system for a VSC transmission scheme
http://dl-live.theiet.org/content/conferences/10.1049/cp_20010529
This paper proposes a high dynamic digital control scheme for IGBT based VSC HVDC power transmission, i.e. VSC-HVDC system, based on equivalent continuous-time state-space models for the rectifier/inverter actuators, using a nonlinear approach. In this paper, both tracking and regulation problems are presented in order to perform a robust DC-bus voltage control. Results illustrate the good behaviour of the system variables in response to positive and negative active power steps.Improved voltage quality through advances in voltage control techniques
http://dl-live.theiet.org/content/conferences/10.1049/cp_20010173
It is incumbent upon power utilities to maintain customers' supplies within specified parameters under varying conditions of load. In the vast majority of cases, the last point at which the power utility can influence the voltage is the on-load tap-changer (OLTC). A number of factors influence the optimum tap change operating point: the power system voltage level; loading; power factor; and, for parallel transformers, the magnitude of any inter-transformer circulating current. As power systems have developed and become more complex, the potential efficiency savings of comprehensive voltage control system cannot be realised by the majority of existing automatic voltage control (AVC) relays. Indeed their complexity has often resulted in voltage control not being implemented. This paper describes a simple solution to remove the unneeded complexity, based upon the fundamental requirements of the power system. It then shows how AVC relays can be used to collect data to for power quality analysis. Since AVC relays exist throughout the electricity network, this leads to new possibilities for improving network power quality.Non-linear Predictive Control: theory and practice
http://dl-live.theiet.org/content/books/ce/pbce061e
<p xmlns="http://pub2web.metastore.ingenta.com/ns/">This book collates the important results which have emerged in the field of non-linear model based predictive control. Feedback linearisation, differential flatness, control Lyapunov functions, output feedback and neural networks are all discussed.</p>Genetic learning for direct inverse neural network control
http://dl-live.theiet.org/content/conferences/10.1049/ic_20000347
The application of neural nets (NN) as a direct inverse controller for general nonlinear systems is considered. Since little knowledge of the nonlinear plant is normally available, it is difficult to obtain an analytical expression for its Jacobian. Thus, an emulator is required as a channel to compute the derivative of the output with respect to the input for NN training. Neural net training using genetic algorithms (GA) offers several advantages. No understanding of the plant model is required. Since no derivative computations are involved, it is less likely for these algorithms to get trapped in local minima. The scheme generates individual controllers with the best fitness values. A hybrid coding method and several appropriate modifications of the classical genetic algorithms for NN control purposes are discussed. To overcome the difficulties of saturation and fluctuation in the controller output, the output of the NN controller is obtained as the sum of several small sigmoidal functions. This effectively increases the linear range of operation of controller output without affecting the nonlinear feature of a sigmoidal function. It is noted in this case that, better control is achieved. Fuzzy logic with dynamic features is used to provide an optimal direction for genetic search. It, thus, speeds up the process of convergence by bringing the chromosomes near to the problem space and bringing more exploration amongst the most desirable ones. The method is demonstrated with the control of a single-link flexible manipulator. (4 pages)Neural-learning control of nonlinear dynamical systems
http://dl-live.theiet.org/content/conferences/10.1049/ic_20000346
This paper is concerned with neural-learning control of nonlinear dynamical systems. Two control schemes using neural-learning techniques are introduced. One is adaptive neural control and the other is predictive neural control. An application of neural-learning control to an industrial combustion system is also included. (7 pages)Nonlinear iterative learning by an adaptive Lyapunov technique
http://dl-live.theiet.org/content/conferences/10.1049/ic_20000350
Summary form only given. The iterative learning problem is considered from an adaptive control viewpoint. We consider a wide variety of systems (e.g. linear, matched, strict feedback, output feedback) and show that by simple modifications to wide classes of adaptive designs, we can utilize the adaptive designs to solve the ILC problems. The main difference between these adaptive ILC designs and their conventional ILC counterparts is that the 'learning' is achieved during the passes, as opposed to the standard designs which only allow learning computations to occur at the end of each pass. The most obvious advantage is that the designs are robust to global parameter variations. In contrast to many other nonlinear ILC designs, we have no need to make restrictive global Lipschitz assumptions, nor do we restrict attention to systems with matched uncertainty. (2 pages)On-line implementation of a neural network model predictive controller
http://dl-live.theiet.org/content/conferences/10.1049/ic_20000119
Applications of neural networks in chemical process modelling and model predictive control (MPC) have been investigated for SISO systems. A multivariable, neural network modelling and MPC technique is investigated in this paper for application to a laboratory-scale chemical reactor. The reactor exhibits characteristics typical of many industrial processes, due to its nonlinearity, coupling effects among the controlled variables (temperature, pH and dissolved oxygen) and a long time-delay in the heat exchanger. Three neural models are developed for the three MISO subsystems of the process used in simulation to initially determine the control parameters and subsequently used online for the MPC of the process. Online control results are presented to illustrate the closed-loop performance of the MPC scheme. (4 pages)