MGWO-PI controller for enhanced power flow compensation using unified power quality conditioner in wind turbine squirrel cage induction generator

Power quality is considered to be the major challenging one in the realization of the smart grid. So as to compensate for the issues occurring in power quality, active power filter (APFs) is mainly chosen as they are capable of filtering fast and has some active compensation. Also, load current related power quality constraint can be solved, such as unbalanced power, huge (Total harmonic distortion) THD level, and reduced power factor. For correcting the inappropriate supply of voltage and load current, the unified power quality conditioner (UPQC) and an effective integration of wind turbine are employed. A UPQC is a group of both shunt and series APF in a continuous manner having a conventional DC link capacitor. The voltage control of the DC link capacitor is significant in attaining a preferred performance on UPQC. In this paper, the UPQC with a Modified Grey Wolf Optimization (MGWO) based PI controller integrated with renewable energy like Wind turbine squirrel cage induction generator (SCIG) was implemented for the elimination of voltage and current harmonics imperfection precisely. Likewise, the Modified Grey Wolf Optimization (MGWO) was also exploited in UPQC. The performance analysis was made with UPQC, without UPQC, and with MGWO & UPQC and the simulation, outcomes are estimated and compared for the parameters THD values, load voltage and current. Also, the performance analysis was implemented in hardware prototype set-up and the results attained are depicted.     

Finite‐time angular velocity observers for rigid‐body attitude tracking with bounded inputs

The attitude tracking of a rigid body without angular velocity measurements is addressed. A continuous angular velocity observer with fractional power functions is proposed to estimate the angular velocity via quaternion attitude information. The fractional power gains can be properly tuned according to a homogeneous method such that the estimation error system is uniformly almost globally finite‐time stable, irrespective of control inputs. To achieve output feedback attitude tracking control, a quaternion‐based nonlinear proportional‐derivative controller using full‐state feedback is designed first, yielding uniformly almost globally finite‐time stable of the attitude tracking system as well as bounded control torques a priori. It is then shown that the certainty equivalent combination of the observer and nonlinear proportional‐derivative controller ensures finite‐time convergence of the attitude tracking error for almost all initial conditions. The proposed methods not only avoid high‐gain injection, as opposed to the semi‐global results, but also overcome the unwinding problem associated with some quaternion‐based observers and/or controllers. Numerical simulations are presented to verify the effectiveness of the proposed methods. Copyright © 2016 John Wiley & Sons, Ltd.     

Observer‐based finite‐time output‐feedback controller for DC‐DC buck converters with unknown load variations

The output voltage regulation problem of a DC‐DC buck converter is investigated in this paper via an observer‐based finite‐time output‐feedback control approach. Considering the effects of unknown load variations and the case without current sensor, by using the technique of adding a power integrator and the idea of nonseparation principle, a finite‐time voltage regulation control algorithm via dynamic output feedback is designed. The main feature of the designed observer and controller does not need any load's information. Theoretically, it is proven that the output voltage can reach the desired voltage in a finite time under the proposed controller. The effectiveness of the proposed control method is illustrated by numerical simulations and experimental results.     

Delay‐ and Packet‐Disordering‐Dependent H∞ Output Tracking Control for Networked Control Systems

This paper is concerned with the problem of H_∞ output tracking control for networked control systems (NCSs) with network‐induced delay and packet disordering. Different from the results in existing literature, the controller design in this paper is both delay‐ and packet‐disordering‐dependent. Based on the different cases of consecutive predictions, the networked output tracking system is modeled into a switched system. Moreover, by the corresponding switching‐based Lyapunov functional approach, a linear matrix inequality (LMI)‐based procedure is proposed for designing state‐feedback controllers, which guarantees that the output of the closed‐loop NCSs tracks the output of a given reference model well in the H_∞ sense. In addition, the proposed method can be applied variously due to all kinds of prediction numbers of the consecutive disordering packet have been considered, and the designed controller is based on the prediction case in the last transmission interval, which brings about less conservatism. Finally numerical examples and simulations are used to illustrate the effectiveness and validity of the proposed switching‐based method and the delay‐ and packet‐disordering‐dependent H_∞ output tracking controller design.     

H∞ switching fuzzy control of solar power generation systems with asymmetric input constraint

This paper aims at presenting a maximum power point tracking (MPPT) controller for photovoltaic (PV) systems subject to asymmetric input constraint. Indeed, the output voltage of the DC‐DC converter used for adjusting the photovoltaic output power can be controlled by means of variation of duty ratio limited between 1 and 0. The control design goal is to improve the efficiency of PV systems under asymmetric saturation of duty ratio. To achieve this goal, first, a Takagi‐Sugeno (T‐S) fuzzy model is used to represent the nonlinear behavior of the PV system. A T–S reference model is employed to give the ideal state direction which must be followed. To achieve a good steady state tracking, the integral of the state tracking error is used to define an extended system state vector. Second, the input characteristic is partitioned into several regions. In each region, the asymmetric saturation function can be considered as a symmetric saturation function. Furthermore, H∞ stabilization conditions for the resulting switching fuzzy control of the PV system under actuator saturation are formulated in term of linear matrix inequalities (LMI) using the Lyapunov approach. Simulation results are exhibited to demonstrate the effectiveness of the proposed design method.     

Design of intelligent power controller for DC–DC converters using CMAC neural network

DC–DC converters are the devices which can convert a certain electrical voltage to another level of electrical voltage. They are very popularly used because of the high efficiency and small size. This paper proposes an intelligent power controller for the DC–DC converters via cerebella model articulation controller (CMAC) neural network approach. The proposed intelligent power controller is composed of a CMAC neural controller and a robust controller. The CMAC neural controller uses a CMAC neural network to online mimic an ideal controller, and the robust controller is designed to achieve L ₂ tracking performance with desired attenuation level. Finally, a comparison among a PI control, adaptive neural control and the proposed intelligent power control is made. The experimental results are provided to demonstrate the proposed intelligent power controller can cope with the input voltage and load resistance variations to ensure the stability while providing fast transient response and simple computation.     

An active‐matrix organic light‐emitting‐diode pixel circuit for the compensation of I × R voltage drop in power line

Abstract— A new voltage‐driving active‐matrix organic light‐emitting diode (AMOLED) pixel circuit is proposed to improve the display image‐quality of AMOLED displays. Because OLEDs are current‐driven devices, the I × R voltage drop in the power lines is evitable. Accordingly, the I × R voltage‐drop compensation scheme should be included in the pixel‐driving method when a voltage‐compensation method is used. The proposed pixel was designed for the compensation of an I × R voltage drop in the power lines as well as for the compensation of the threshold‐voltage non‐uniformity of low‐temperature polycrystalline‐silicon thin‐film transistors (LTPS TFTs). In order to verify the compensation ability of the proposed pixel, SPICE simulation was performed and compared with those of other conventional pixels. When the Vss voltage varies from 0 to 1 V, the drain current of the proposed pixel decreased by under 1% while that of conventional Vth compensation methods without Vss compensation decreased by over 60%. 2.2‐in. QCIF⁺ full‐color AMOLED displays, which employ the proposed pixel, have been also developed. It was verified by comparison of the display image quality with a conventional panel that our proposed panel successfully overcame the voltage‐drop problems in the power lines.     

三相四线APF直流侧的T-S模糊均压控制

电容分裂中点式三相四线有源电力滤波器（APF）是解决三相四线电力系统谐波治理的有效方法,由于直流侧两组电容电压需要单独控制,增加了均压控制难度并直接影响补偿的效果。分析了该APF的电路拓扑,采用T-S模糊控制的方法对电容分裂中点式三相四线APF的直流侧均压控制进行建模,将直流侧两组电容电压分别作为输入前件变量,对电源电流实施反馈控制。设计的T-S模糊反馈控制器使APF直流侧两组电容电压实现自动均压,满足了APF对负载谐波的补偿控制要求。仿真及实验结果验证了所建立T-S模糊均压控制模型的有效性,APF直流侧两组电容的电压保持均衡,具有较高的稳态精度和良好的动态性能。     

Robust Stabilization and Tracking Control for a Class of Switched Nonlinear Systems

This paper addresses the problem of robust stabilization and tracking control for a class of switched nonlinear systems via the multiple Lyapunov functions (MLFs) approach. First, a state feedback controller and a state dependent switching law are designed to globally asymptotically stabilize the switched system via linear matrix inequalities (LMIs). The main objective of this paper is to develop a tracking control approach that assures global asymptotic output and state tracking with zero tracking error in the steady state. Then, the tracking control is formulated such that the robust H_∞ tracking performance is achieved. Finally, a simulation example is provided to demonstrate the effectiveness of the main method.     

Sliding‐mode control of a three‐degrees‐of‐freedom nanopositioner

This paper presents the sliding‐mode control of a three‐degrees‐of‐freedom nanopositioner (Z, θ_x, θ_y). This nanopositioner is actuated by piezoelectric actuators. Capacitive gap sensors are used for position feedback. In order to design the feedback controller, the open‐loop characteristics of this nanopositioner are investigated. Based on the results of the investigation, each pair of piezoelectric actuators and corresponding gap sensors is treated as an independent system and modeled as a first‐order linear model coupled with hysteresis. When the model is identified and the hysteresis nonlinearity is linearized, a linear system model with uncertainty is used to design the controller. When designing the controller, the sliding‐mode disturbance (uncertainty) estimation and compensation scheme is used. The structure of the proposed controller is similar to that of a proportional integral derivative controller. Thus, it can be easily implemented. Experimental results show that 3‐nm tracking resolution can be obtained. Copyright © 2008 John Wiley and Sons Asia Pte Ltd and Chinese Automatic Control Society     

Eso‐Based Adaptive Robust Control of Dual Motor Driving Servo System

Based on extended state observer (ESO), we propose an adaptive robust control (ARC) for a dual motor driving servo system, in which there exist nonlinearities affecting control performance. To apply ESO and estimate the lumped uncertainty online, backlash and friction are analyzed and the nonlinear model of the plant is derived. We achieve several control objectives. First, the bias torque is considered in order to eliminate the effect of backlash. Second, the speed feedback is used to maintain the speed synchronization of motors. Then, to achieve feedforward control, finite‐time ESO is designed to estimate the unknown nonlinearities online. Furthermore, the ESO‐based adaptive robust controller is designed to guarantee L_∞ of tracking error by an initialization method, maintaining the transient performance of tracking behavior. Finally, extensive experimental results on a practical test rig validate the effectiveness of our proposed method.     

H ∞ output tracking control for discrete‐time switched systems via output feedback

This paper studies the problem of H _∞ output tracking control for a class of discrete‐time switched systems. Neither the measurability of the system state nor the solvability of the output tracking control problem for each individual subsystem is required. We design controllers for subsystems and a switching law to solve the H _∞ output tracking problem for the switched system. The designed controllers use only the measured output feedback, and the switching law is based on the measured output tracking error. In addition, the quadratic function corresponding to each subsystem is not required to be positive definite. A numerical example is provided to demonstrate the feasibility and validity of the proposed design method. Copyright © 2013 John Wiley & Sons, Ltd.     

Finite‐time geometric control for underactuated aerial manipulators with unknown disturbances

In this article, the finite‐time geometric control for underactuated aerial manipulators is investigated. The dynamics of the aerial manipulator with unknown disturbances is analyzed first. The dynamics of the system is decomposed into the locked subsystem and shape subsystem. The finite‐time controller for the aerial manipulator is then designed based on the analyzed dynamics. In the controller, the attitude tracking error of the aircraft base is expressed from the rotation matrix, which makes the controller continuous and almost globally stable on SO(3). A continuous adaptive term is added in the controller to compensate for the unknown disturbances. Finite‐time filters are designed to ensure the smoothness of the commands on each loop. The convergence of the entire controlled system is strictly proved using Lyapunov theory and the definition of finite‐time stability. The results show that the tracking error and the disturbance bound estimation error of the entire system are finite‐time bounded near origin. Finally, comparative simulation results are presented to show the performance of the proposed controller.     

Output‐feedback stabilization for planar output‐constrained switched nonlinear systems

In this paper, globally asymptotical stabilization problem for a class of planar switched nonlinear systems with an output constraint via smooth output feedback is investigated. To prevent output constraint violation, a common tangent‐type barrier Lyapunov function (tan‐BLF) is developed. Adding a power integrator approach (APIA) is revamped to systematically design state‐feedback stabilizing control laws incorporating the common tan‐BLF. Then, based on the designed state‐feedback controllers and a constructed common nonlinear observer, smooth output‐feedback controllers, which can make the system output meet the predefined constraint during operation, are proposed to deal with the globally asymptotical stabilization problem of planar switched nonlinear systems under arbitrary switchings. A numerical example is employed to verify the proposed method.     

H∞Fuzzy State‐Feedback Control Plus State‐Derivative‐Feedback Control Synthesis for Photovoltaic Systems

This paper addresses the problem of designing an H_∞fuzzy state‐ feedback (SF) plus state‐derivative‐feedback (SDF) control system for photovoltaic (PV) systems based on a linear matrix inequality (LMI) approach. The TS fuzzy controller is designed on the basis of the Takagi‐Sugeno (TS) fuzzy model. The sufficient condition is found such that the system with the fuzzy controller is asymptotically stable and an H_∞performance is satisfied. First, a dc/dc buck converter is considered to regulate the power output by controlling state and state‐derivative variables of PV systems. The dynamic model of PV systems is approximated by the TS fuzzy model in the form of nonlinear systems. Then, based on a well‐known Lyapunov functional approach, the synthetic is formulated of an H_∞fuzzy SF plus SDF control law, which guarantees the L₂‐gain from an exogenous input to the regulated output to be less than or equal to some prescribed value. Finally, to show effectiveness, the simulation of the PV systems with the proposed control is assessed by the computer programme. The proposed control method shows good performance for power output and high stability for the PV system.     

Robust discrete‐time output feedback model reference control design with state and unknown input estimation

For MIMO discrete‐time linear systems with unknown input in which the matching condition does not hold, the use of estimation method in an output feedback controller is proposed in this paper. Provided that the variation of unknown input in the two consecutive sampling instances is not changed significantly, both the system state and unknown input can be simultaneously estimated by our proposed observer algorithm with the estimation error being constrained in a small bounded region of the order of O(T). Then, a method utilizing command generator tracker is designed to generate the reference model. Concurrently with the estimations of the system state and unknown input are used in the controller where it can cause the tracking error to be bounded in a small region with the guaranteed system stability. Finally, the feasibility of our algorithm can be proved to be valid through the demonstration of a simulation‐based example. Copyright © 2008 John Wiley & Sons, Ltd.     

Output feedback finite‐time stabilization of a class of nonlinear time‐delay systems in the p‐normal form

This article investigates the finite‐time output feedback stabilization problem for a class of nonlinear time‐varying delay systems in the p‐normal form. First, a reduced‐order state observer is designed to estimate the unmeasurable state. Then, an output feedback controller is constructed, with the help of the finite‐time Lyapunov stability theorem, it is proved that the state of the resulting closed‐loop system converges to the origin in finite time. Two simulation examples are given to verify the effectiveness of the proposed scheme.     

Separation principle for quasi‐one‐sided Lipschitz nonlinear systems with time delay

In this article, we address the problem of output stabilization for a class of nonlinear time‐delay systems. First, an observer is designed for estimating the state of nonlinear time‐delay systems by means of quasi‐one‐sided Lipschitz condition, which is less conservative than the one‐sided Lipschitz condition. Then, a state feedback controller is designed to stabilize the nonlinear systems in terms of weak quasi‐one‐sided Lipschitz condition. Furthermore, it is shown that the separation principle holds for stabilization of the systems based on the observer‐based controller. Under the quasi‐one‐sided Lipschitz condition, state observer and feedback controller can be designed separately even though the parameter (A,C) of nonlinear time‐delay systems is not detectable and parameter (A,B) is not stabilizable. Finally, a numerical example is provided to verify the efficiency of the main results.     

Output feedback transient stabilization and voltage regulation of synchronous generators

In this brief note, we consider the transient stabilization and voltage regulation problem for a synchronous generator connected to an infinite bus. We show how a much simpler output feedback controller, compared with previous results, can be obtained if a different stability analysis is carried out: a suitable change of coordinates is performed so that advantageous triangularity properties of the regulation error dynamics are highlighted. A novel first order estimator for the uncertain mechanical input power is designed: it is the only adaptation scheme used by the controller. The innovative crucial step in the presented control design relies on relaxing the constraint imposed by the typically (previously) adopted back‐stepping techniques and constituted by the required availability of the regulation/tracking error variables: the converging estimate of the mechanical input power directly becomes the reference value for the electrical power and allows for the straightforward computation of the uncertain power angle constant value guaranteeing voltage regulation at steady state. Copyright © 2011 John Wiley & Sons, Ltd.     

Time‐varying input delay compensation for nonlinear systems with additive disturbance: An output feedback approach

This paper addresses the output feedback tracking control of a class of multiple‐input and multiple‐output nonlinear systems subject to time‐varying input delay and additive bounded disturbances. Based on the backstepping design approach, an output feedback robust controller is proposed by integrating an extended state observer and a novel robust controller, which uses a desired trajectory‐based feedforward term to achieve an improved model compensation and a robust delay compensation feedback term based on the finite integral of the past control values to compensate for the time‐varying input delay. The extended state observer can simultaneously estimate the unmeasurable system states and the additive disturbances only with the output measurement and delayed control input. The proposed controller theoretically guarantees prescribed transient performance and steady‐state tracking accuracy in spite of the presence of time‐varying input delay and additive bounded disturbances based on Lyapunov stability analysis by using a Lyapunov‐Krasovskii functional. A specific study on a 2‐link robot manipulator is performed; based on the system model and the proposed design procedure, a suitable controller is developed, and comparative simulation results are obtained to demonstrate the effectiveness of the developed control scheme.