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The output power fluctuation of such renewable energy power plants as a wind-turbine generator and a photovoltaic system results in frequency deviation and terminal voltage fluctuation. Furthermore, these power fluctuations also affect the turbine shafting of diesel generator and gas-turbine generators, which are the main power generation systems in isolated islands. This article presents a control strategy that achieves torsional torque suppression and power system stabilization. Since the measurement of torsional torque is difficult technically, and there is uncertainty in mechanical constants of the shaft torsional system, the torsional torque is estimated by using a linear quadratic regulator observer with a parameter identification system. The simulation results validate the effectiveness of the proposed control system. [ABSTRACT FROM AUTHOR]

Simulation has become the most important technique used today for evaluation of engineering solutions, and modeling plays a crucial part in the design of intelligent control paradigms for complex dynamic structures. For the analysis of a megawatt-class wind-energy conversion system (WECS), this research adopts the \cal H\infty control theory in designing an advanced control paradigm that accomplishes the dual purpose of energy capture optimization, as well as power train cyclic load alleviation by mitigating against wind-speed fluctuations. This work is presented in two parts: The first details the modeling of the subsystems of WECS and introduces the multiobjective \cal H\infty control concept, and the second deals with the implementation of the control paradigm. Presented herein is a modeling approach of individual subsystems as a basis for devising the unified control strategy for a 2-MW grid-connected pitch-regulated variable-speed WECS that incorporates a doubly fed induction generator. The credibility of the archetype, to establish the argument that the models produce sound insights and comparable results to data from the real system, is ascertained via validation. [ABSTRACT FROM AUTHOR]

The control of wind-energy conversion systems (WECSs) is still a challenging task for design engineers. Despite being ubiquitous in the wind industry, the performance of classical proportional–integral–derivative controllers is not ideal, and they require additional notch filters to handle turbine nonlinearity. This has triggered interest toward advanced control concepts that are multiobjective and multivariable. With optimality, feedback, and robustness being prerequisites in developing control policies that guarantee high-integrity and fault-tolerant control systems, \cal H\infty control theory has become a standard design method of choice over the past two decades and is gaining prominence in industrial (and WECS) control applications. Based on the linear matrix inequality approach, this paper presents a comprehensive and systematic way of applying the \cal H\infty control design algorithm for automatically gain-scheduling the linear-parameter-varying turbine plant along parameter trajectories. Control seeks to regulate both power and voltage via a synthesis of two controllers, namely, pitch and generator torque, respectively, for a megawatt-class WECS. Digital simulations executed in a MATLAB/Simulink environment ascertain that the control paradigm meets the objectives of optimizing power conversion throughout the operating envelope, as well as eliminating power oscillations through system damping. [ABSTRACT FROM AUTHOR]

Abstract: The output power fluctuations of renewable energy plants such as wind turbine generators and photovoltaic systems cause frequency deviations and terminal voltage fluctuations. Furthermore, these power fluctuations also affect the turbine shaft of diesel generator and gas-turbine generators which are usually the main electric power systems in isolated islands. This paper presents a control strategy that achieves torsional torque suppression and power system stabilization. Since the measurement of the torsional torque is technically difficult and there is uncertainty in mechanical constants of the shaft torsional system, the torsional torque is estimated by using a H ∞ observer. The simulation results validate the effectiveness of the proposed control system. [Copyright &y& Elsevier]

Electric utility deregulation enabled PPSs (Power Producers and Suppliers) to enter the electricity market. PPSs are supposed to achieve 30-minute balancing control for stable power supply of electric power. In addition, load rejection and instantaneous voltage drops greatly affect turbine shafting, that is, torsional torque oscillation. Therefore, PPSs must consider a reduction of torsional torque in order to prevent generator shaft damage. This paper proposes a control system which allows the achievement of both 30-minute balancing control and reduction of torsional torque by using an H∞ controller. The effectiveness of the proposed controller is validated by using MATLAB. © 2009 Wiley Periodicals, Inc. Electr Eng Jpn, 170(1): 16–25, 2010; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/eej.20868 [ABSTRACT FROM AUTHOR]

Abstract: This paper proposes a technique that determines the optimal windmill operation speed and the optimal rotor flux. Moreover, the position and speed sensor-less wind generation system using the electromotive voltage observer to estimate rotor position and full-order observer to estimate rotor speed and the windmill output torque are proposed. The position and speed sensor-less maximum power point of wind power generation system is controlled by using the above estimated values, optimized windmill operation speed for maximum output power and optimized rotor flux for minimum generator losses. The effectiveness of the position and speed sensor-less maximum power point tracking control for wind power generation system with squirrel cage induction generator is verified by simulations. The simulation results confirm that the proposed method can estimate the operation speed efficiently. [Copyright &y& Elsevier]

In this article, a mathematical model of ultrasonic motors for speed control, which includes the non-linearity and approximation of the dead-zone in control input, is presented. The intrinsic properties of ultrasonic motors (high torque for low speed, high static torque, compact in size, etc.) offer great advantages for industrial applications. However, the speed property of ultrasonic motors has a strong non-linear property as well as the dead-zone effect in control input associated with load torque. These properties present serious problems for accurate speed control. This article presents a mathematical model represented by a sinusoidal function, which includes these properties. The model is simple and has good approximation of the non-linearity and time varying properties. The proposed speed model has been validated by experimental results. [ABSTRACT FROM AUTHOR]

Abstract: Probabilistic paradigms for wind turbine controller design have been gaining attention. Motivation derives from the need to replace outdated empirical-based designs with more physically relevant models. This paper proposes an adaptive controller in the form of a linear quadratic Gaussian (LQG) for control of a stall-regulated, variable speed wind turbine generator (WTG). In the control scheme, the strategy is twofold: maximization of energy captured from the wind and minimization of the damage caused by mechanical fatigue due to variation of torque peaks generated by wind gusts. Estimated aerodynamic torque and rotational speed are used to determine the most favorable control strategy to stabilize the plant at all operating points (OPs). The performance of the proposed controller is compared with the classical proportional-integral-derivative (PID) controller. The LQG is seen to be significantly more efficient especially in the alleviation of high aerodynamic torque variations and hence mechanical stresses on the plant drive train. Simulation results validate the effectiveness of the proposed method. [Copyright &y& Elsevier]

The ultrasonic motor has nonlinearity characteristics, which varies with driving conditions associated with the variations of temperature and applied load torque of ultrasonic motor. The nonlinearity characteristics for actuators are problems in accurate position control. To improve the control performance of the ultrasonic motor, we apply two-control inputs H∞ controller for position control of the ultrasonic motor. Applying an H∞ methodology we derive a stabilizing controller to meet design objectives and robust stability and performance against such variations. The validity of the proposed method is confirmed by experimental results. [ABSTRACT FROM AUTHOR]

The ultrasonic motor has nonlinear characteristics, which vary with driving conditions and possess variable dead-zone in the control input that is associated with the applied load torque. The dead-zone has a problem in accurate positioning actuator. To improve the control performance of the ultrasonic motor, the dead-zone nonlinearity should be eliminated. This article proposes a new position control scheme for the ultrasonic motors that eliminates the problem due to dead-zone by employing fuzzy neural network (FNN). To achieve the accurate position control when drive conditions vary, FNN can adjust the membership function for the antecedent part. The training of FNN is achieved using online backpropagation algorithm. The dead-zone is compensated by FNN, and PI controller performs the accurate positioning of the drive system. The validity of the proposed method is confirmed by experimental results. [ABSTRACT FROM AUTHOR]

Motor parameters are necessary to achieve several surface-mounted permanent magnet synchronous motor (SPMSM) drive strategies, such as model-based high efficiency control and direct torque control. This article presents a new parameter measurement strategy for vector controlled SPMSM. Iron loss resistance associated with stator iron loss as well as conventional electrical parameters, i.e., electromotive-force (emf) coefficient and stator inductance, are measured on a vector control system. Stator iron loss is measured separately from mechanical and stray losses. As a result, the accuracy on the measurement of iron loss resistance is improved. The validity of the proposed method is confirmed by the comparison between calculated and measured torques. [ABSTRACT FROM AUTHOR]

The ultrasonic motor has comparatively high nonlinearity which varies with driving conditions, and possesses a variable dead zone in control input associated with the applied load torque. The dead zone is a problem for industrial applications and it is important to eliminate the dead zone in order to improve control performance. This paper proposes a new position control scheme for ultrasonic motors to overcome the dead zone. The dead zone is compensated by fuzzy inference, and backstepping control performs accurate position control. Compared with model reference adaptive control, which uses an augmented error, backstepping control can analyze a transient response. Mathematical models are formulated and experimental results show the effectiveness of the proposed position control scheme. © 2004 Wiley Periodicals, Inc. Electr Eng Jpn, 149(1): 69–77, 2004; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/eej.20016 [ABSTRACT FROM AUTHOR]

In recent years, gas turbines have been attracting a lot of attention in the field of dispersed generations and co-generation systems. The gas turbine generation system always has the problem of the shaft torsional oscillation, and their counter measures that can apply especially for the in-house generating plants at 10 MW scale are required. For technical and financial reasons, the number of sensors has to be reduced to an acceptable minimum, and generally it is not possible to measure the torsional oscillations at all critical shaft locations. Thus the torsional oscillations on the crucial components should be estimated by using the measured rotating speed at turbine shaft end. This paper presents the shaft torque observer and coordinated controllers for the in-house generating plants. In this study the turbine model with 7-mass has been used, and the rate of the in-house generating shaft is 5 MVA. Linear quadratic regulat or theory (LQR) is used to design the observer gain, which provides acceptable estimated values. The estimation accuracy of this observer is within 10%, and the influence by the measurement error of the shaft parameter is also a little. [Copyright &y& Elsevier]