Turn‐off scheme of thyristor switches for network reconfiguration in FRIENDS

The authors have proposed FRIENDS as a concept of the future electric power system. In order to realize FRIENDS, it is necessary to design the concrete interior structure and control scheme of the Quality Control Center (QCC) which is to be installed between distribution substation and customers. Hybrid‐type transfer switches are assumed to be installed on the high‐voltage side of the QCC to realize network reconfiguration. Some devices for handling power quality are also assumed to be installed on the low‐voltage side to realize customized power quality. In this paper, a novel control scheme for shutoff of the thyristor switches by the power quality handling devices is proposed and the effectiveness of the proposed scheme is investigated through momentary analysis using PSCAD/EMTDC. © 2002 Wiley Periodicals, Inc. Electr Eng Jpn, 142(1): 32–41, 2003; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.10077     

Energy-efficient operation of indirect adiabatic data center cooling systems via Newton-like phasor extremum seeking control

This paper considers the problem of optimizing the operation of Indirect Adiabatic Cooling (IAC) systems with application to data centers. Optimal operation is achieved when the required cooling demand is satisfied at the minimum energy cost. For this purpose, we design a supervisory control system, where the higher layer determines the optimal set-points for the local controllers by employing an Extremum Seeking Control (ESC) scheme. In particular, we consider a Newton-like phasor ESC, which augments the derivative estimator underlying the phasor approach to capture also the Hessian of the plant index and then it uses these estimates to steer the system along a Newton-like direction. The effectiveness of the considered approach is tested in simulation by exploiting a Matlab-based simulation environment including an IAC system and a computer room.     

Compensation of performance degradation caused by fault based on GIMC structure: Application to a redundant sensor fault of flexible arm

In recent years, control system reliability has received much attention with an increase of situations where computer‐controlled systems such as robot control systems are used. In order to improve reliability, control systems need to have abilities to detect a fault (fault detection) and maintain the stability and the control performance (fault tolerance). This paper deals with the strain gauge sensor fault of a flexible arm robot. In order to achieve a fault‐tolerant control system, the effect of the fault is identified as dual Youla parameter by regarding the estimation error of the faulty sensor signal as the faulty plant output. Moreover, Youla parameter is designed so as to suppress the effect of dual Youla parameter. Youla parameter is implemented in GIMC (Generalized Internal Model Control) structure proposed by Zhou. Since GIMC structure includes a conditional feedback, it is suitable for achieving a fault‐tolerant control system. The effectiveness of the proposed fault‐tolerant control system is confirmed by experiments. © 2009 Wiley Periodicals, Inc. Electr Eng Jpn, 168(3): 48–58, 2009; Published online in Wiley InterScience ( www. interscience.wiley.com ). DOI 10.1002/eej.20830     

Adaptive Internal Model Control with fractional order parameter

In this paper we have introduced as a model in the adaptive Internal Model Control (IMC) structure a fractional order system to obtain a fractional adaptive IMC scheme. We have shown that this adaptive control scheme always provides theoretical guarantees of stability when a stable fractional order transfer function is used as an IMC parameter and that the use of this fractional IMC parameter can improve the performances of the control system along with its robustness against noises. A comparative simulation example is given to illustrate the efficiency of the proposed fractional order adaptive control scheme. Copyright © 2010 John Wiley & Sons, Ltd.     

Online trained support vector machines‐based generalized predictive control of non‐linear systems

In this work, an online support vector machines (SVM) training method (Neural Comput. 2003; 15 : 2683–2703), referred to as the accurate online support vector regression (AOSVR) algorithm, is embedded in the previously proposed support vector machines‐based generalized predictive control (SVM‐Based GPC) architecture (Support vector machines based generalized predictive control, under review), thereby obtaining a powerful scheme for controlling non‐linear systems adaptively. Starting with an initially empty SVM model of the unknown plant, the proposed online SVM‐based GPC method performs the modelling and control tasks simultaneously. At each iteration, if the SVM model is not accurate enough to represent the plant dynamics at the current operating point, it is updated with the training data formed by persistently exciting random input signal applied to the plant, otherwise, if the model is accepted as accurate, a generalized predictive control signal based on the obtained SVM model is applied to the plant. After a short transient time, the model can satisfactorily reflect the behaviour of the plant in the whole phase space or operation region. The incremental algorithm of AOSVR enables the SVM model to learn the new training data pair, while the decremental algorithm allows the SVM model to forget the oldest training point. Thus, the SVM model can adapt the changes in the plant and also in the operating conditions. The simulation results on non‐linear systems have revealed that the proposed method provides an excellent control quality. Furthermore, it maintains its performance when a measurement noise is added to the output of the underlying system. Copyright © 2006 John Wiley & Sons, Ltd.     

Avoiding singularities in recurrent neural control for induction motors

In this paper, a master–slave synchronization scheme based on parameter identification is proposed to overcome the controller singularity problem that appears when linearization‐like techniques are applied in indirect adaptive neural control, like Neural Block Control (NBC). Such a synchronization strategy requires an identifier‐like recurrent neural network and an adaptive law to update the neural weights. The proposed adaptive law prevents both, specific adaptive weights zero‐crossing and the ‘parameter drift’ phenomenon. NBC consists of two tasks; synchronizing an identifier‐like recurrent neural network (slave) with the plant (master) and controlling the system based on the slave model. The effectiveness of the synchronization law is tested using NBC for controlling the angular speed and magnetic flux magnitude of an induction motor. Usingit a priori knowledge about the real plant, a high‐order recurrent neural network is proposed as the slave system. Based on the slave neural model, a discontinuous control law is derived, which combines Block Control and Sliding Modes. NBC with the proposed synchronization strategy is tested via simulations, comparing results with a standard parameters adaptive law. Copyright © 2011 John Wiley & Sons, Ltd.     

Position and speed sensorless control for IPMSM based on estimation of position error

In most variable‐speed drives of PMSM, some type of shaft sensor such as an optical encoder or resolver is connected to the rotor shaft. However, such sensor presents several disadvantages such as drive cost, machine size, reliability, and noise immunity. Therefore, the sensorless control of PMSM is desired and various sensorless control strategies have been investigated. This paper presents a novel sensorless control strategy for an interior permanent magnet synchronous motor (IPMSM). A new model of IPMSM using an extended electromotive force (EMF) in the rotating reference frame is utilized in order to estimate both position and speed. The extended EMF is estimated by the least‐order observer, and the estimation position error is directly obtained. The proposed scheme corrects the estimated position and speed so that the estimation position error becomes zero. The proposed system is very simple and the design of the controller is easy. Several drive tests are carried out and the experimental results show the effectiveness of the proposed sensorless control system. © 2003 Wiley Periodicals, Inc. Electr Eng Jpn, 144(2): 43–52, 2003; Published online in Wiley InterScience ( www. interscience.wiley.com ). DOI 10.1002/eej.10180     

Transient performance improvement in indirect model reference adaptive control using perturbation‐based extremum seeking identifier

One of the main drawbacks of model reference adaptive control (MRAC) is the weakness of its transient performance. The key reason of this imperfection is parameter's estimation error convergence. For many cases in the closed‐loop control, the plant input signal cannot satisfy the persistence of excitation (PE) condition which yields poor parameters estimation error convergence. In this paper, we use a fast perturbation‐based extremum seeking (PES) scheme without steady‐state oscillation as the parameter identifier in indirect MRAC. The estimated parameters through the PES identifier contain the additive sinusoidal signals with distinct frequencies in the transient, which satisfy the PE condition of the plant input. Therefore, convergence of the parameters estimation error to zero will be guaranteed that results in improvement of transient performance for indirect MRAC. Also, the contrary effects on the steady‐state behaviour is eliminated since the sinusoidal excitation signals amplitude exponentially converge to zero and reinitiate with every change in the unknown parameters. Simulation results for a second order example have been presented to illustrate the effectiveness of the proposed scheme.     

A practical design of multiloop robust PID control systems

In this paper, a new design scheme of multiloop predictive self‐tuning PID controllers is proposed for multivariable systems. The proposed scheme first uses a static precompensator as an approximately decoupling device in order to roughly reduce the interaction terms of the controlled object. The static matrix precompensator is adjusted by an on‐line estimator. Furthermore, by regarding the approximately decoupled system as a series of single‐input single‐output subsystems, a single‐input single‐output PID controller is designed for each subsystem. The PID parameters are calculated on‐line based on the relationship between the PID control and the generalized predictive control laws. The proposed scheme is numerically evaluated on a simulation example. © 2004 Wiley Periodicals, Inc. Electr Eng Jpn, 147(3): 63–71, 2004; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.10284     

MIMO multi‐periodic repetitive control system: universal adaptive control schemes

This paper presents a simple adaptive multi‐periodic repetitive control scheme when the MIMO LTI plant is not necessarily positive real (PR), however it is strictly minimum‐phase, the spectrum of high‐frequency gain matrix CB is symmetric and lies in the open right/left half complex plane(sign/spectrum definite). The non‐identifier‐based direct adaptive control technique, which does not need plant parameter information, is used to construct adaptive schemes and the system stability is analysed by Lyapunov second method. The extension to plant under certain non‐linear perturbations and an exponential stability scheme are also discussed. Finally, an adaptive proportional plus multi‐periodic repetitive control scheme is proposed. The theoretical findings are supported with simulations. Copyright © 2006 John Wiley & Sons, Ltd.     

Robust speed estimation and control of an induction motor drive based on artificial neural networks

In this paper, a speed estimation and control scheme of an induction motor drive based on an indirect field‐oriented control is presented. On one hand, a rotor speed estimator based on an artificial neural network is proposed, and on the other hand, a control strategy based on the sliding‐mode controller type is proposed. The stability analysis of the presented control scheme under parameter uncertainties and load disturbances is provided using the Lyapunov stability theory. Finally, simulated results show that the presented controller with the proposed observer provides high‐performance dynamic characteristics and that this scheme is robust with respect to plant parameter variations and external load disturbances. Copyright © 2007 John Wiley & Sons, Ltd.     

Design of a robust PWM power amplifier using approximate two‐degree‐of‐freedom integral‐type control

A method is proposed for designing a robust controller for PWM power amplifiers, which are widely used as amplifiers and power supplies. The main technical requirements imposed on PWM power amplifiers are linearity in a wide frequency range and a well‐damped fast dynamic response in the presence of extensive load and DC power supply variations. Therefore, in order to satisfy the design specifications, namely, linearity in a wide frequency range and no overshoots during transients, an approximate two‐degree‐of‐freedom integral control structure is proposed and a design procedure for the robust controller is discussed. It is shown by some simulations and experiments that the designed controller shows especially good dynamic performance and effective disturbance rejection in the presence of external disturbances, that is, load and power‐supply variations. © 2003 Wiley Periodicals, Inc. Electr Eng Jpn, 144(1): 68–77, 2003; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.10102     

A design of multivariable,self‐tuning PID controllers with an internal model structure

Self‐tuning control schemes (STC) are useful for systems with unknown or slowly time‐varying parameters. Some single‐input/single‐output PID control schemes based on STCs have been proposed for such systems. However, there are a lot of multivariable systems in real process industries. And these systems often have relatively large time delays. In this paper, a design scheme of self‐tuning PID control system is proposed for multivariable systems with unknown parameters and time delays. The controlled object is equipped with an internal model in order to compensate the time delay and also unstable zeros. Subsequently, a multivariable PID controller is designed for the augmented or compensated system. The PID parameters are calculated recursively based on the relationship between the minimum variance control law and the PID control law. A simulation example is presented to demonstrate the effectiveness of the proposed scheme. © 2004 Wiley Periodicals, Inc. Electr Eng Jpn, 146(4): 58–64, 2004; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.10241     

Interior structure of a quality control center at the low‐voltage side considering power conditioning by SMES

The authors have proposed FRIENDS—Flexible, Reliable and Intelligent Electrical eNergy Delivery System—as a future electric power distribution system. The most important idea of FRIENDS is to install new facilities called Quality Control Centers (QCCs) between the distribution substation and customers. By controlling QCCs appropriately, various purposes of FRIENDS can be achieved. It is indispensable to design the concrete interior structure of QCC in order to realize FRIENDS. This paper proposes the interior structure and control methods of QCC from the viewpoint of power conditioning functions by energy storage system in QCC. In this paper, it is assumed that SMES is used as the energy storage system in QCC. The proposed interior structure is based on the concept of UPS (Uninterruptable Power Supply). In this paper, SMES is installed in the DC side of UPS. Further, this paper proposes control methods of SMES and PWM converters. The proposed control methods are used to satisfy various purposes, such as load fluctuation compensation, load leveling, and cooperation with dispersed‐type generator. Finally, the validity of these control methods is confirmed through transient analysis PSCAD/EMTDC. © 2003 Wiley Periodicals, Inc. Electr Eng Jpn, 143(3): 20–28, 2003; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.10056     

Dynamic behavior of a combined cycle power plant in the presence of a frequency drop

A combined cycle power plant which combines a gas turbine and a steam turbine can achieve high energy efficiency. Many combined cycle plants have been installed worldwide. However, a large‐scale blackout due to combined cycle chain trip‐out occurred in Malaysia in 1996. The cause of this chain trip was considered to be a large drop of system frequency. Thus, there is a need to investigate the stability of the combined cycle power plant for the frequency drop. Several dynamic models of a combined cycle plant have been proposed. In our analysis, we use some of them and build a model for a single‐shaft combined cycle plant. We execute numerical simulations to see how the combined cycle plant behaves when the system frequency drops. The cause and the countermeasure of the combined cycle plant trip‐out are explained. © 2003 Wiley Periodicals, Inc. Electr Eng Jpn, 143(3): 9–19, 2003; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.10117     

Development of a large‐current high‐precision pulse power supply

JAEA and KEK are jointly constructing a high‐intensity proton accelerator project J‐PARC. Its main accelerator is a 3‐GeV synchrotron. Its injection bump magnets, especially horizontal paint bump magnets, are excited by large pulse currents. Their rated currents are over 10 kA and pulse widths are about 1 ms. Tracking errors are required to be less than 1%. Multiple connected two‐quadrant IGBT choppers are adopted for their power supplies. Their output currents are controlled by feedback control with minor loop voltage control (m‐AVR). When output current of a chopper intermits at small current, its output voltage rises and current control becomes difficult. In this paper, response of m‐AVR and output voltage characteristics at current intermittent region are studied and an improved control scheme is proposed. The performance is confirmed by a test. © 2008 Wiley Periodicals, Inc. Electr Eng Jpn, 166(3): 62– 72, 2009; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.20783     

提高电机位置伺服系统鲁棒性能的最优模糊模型跟踪控制

提出一种应用在位置伺服系统上的最优模糊模型跟踪控制方案 ,并且将其与最优模糊控制进行了比较。研究结果表明 ,该方案即使在大的参数变化与负载扰动情况下 ,仍能保持系统输出最优或近似最优 ,具有很好的鲁棒性     

Voltage stability preventive and emergency‐preventive control using VIPI sensitivity

Recently, power systems have become larger and more complicated, and the rate of occurrence of constant power loads has increased. Under a situation like this, concerns about voltage instability phenomena have been raised. Therefore, in addition to the conventional local voltage control, the necessity of a global on‐line voltage control scheme has risen. In this paper, we propose a method of on‐line voltage stability control including preventive and emergency‐preventive controls to retain voltage stability even if a severe fault occurs. According to the result of contingency analysis for severe faults, we consider operation of control equipment as preventive control. And in the case that the fault seems severe still after preventive control, we consider load curtailment as emergency‐preventive control. When we select the control equipment and loads to curtail, we use voltage stability index VIPI sensitivity. And we determine the amount of control and load curtailment using Optimal Power Flow calculation. The effectiveness of the proposed method is verified by simulations using a 28‐bus system. © 2003 Wiley Periodicals, Inc. Electr Eng Jpn, 143(4): 22–30, 2003; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.10128     

A new method of damping harmonic resonance at the DC link in a large‐capacity rectifier‐inverter system

This paper proposes a new method of damping harmonic resonance in the DC link of a large‐capacity rectifier‐inverter system, such as in rapid‐transit railways. A voltage‐source PWM converter is connected in series to the DC capacitor of the rectifier through a matching transformer, acting as a damping resistor to the DC capacitor current. No filters are needed to extract harmonic components from the DC capacitor current. This results in a quick response and highly stable damping. The relationship between the control gain of the PWM converter and the required rating is theoretically discussed. We show that the required rating is less than one‐thousandth of that previously proposed. In particular, regenerating the power consumed by the PWM converter is very important because of the large power in practical systems. Normally, an additional PWM inverter is connected to the DC bus of the PWM converter to regenerate the consumed power. The additional inverter regenerates the DC power to the AC source through a transformer. This method, however, makes the damping circuit complex, thus the proposed method for the DC‐link harmonic resonance is less practicable. In this paper, a simple and novel scheme that utilizes the DC‐link voltage of the rectifier as a DC source for the PWM converter is proposed. The excellent practicability of the proposed damping method with the novel regenerating scheme is confirmed using digital computer simulation. © 2003 Wiley Periodicals, Inc. Electr Eng Jpn, 144(2): 53–62, 2003; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.10172     

An adaptive control scheme using multiple reference models

This paper develops an extended model reference adaptive control scheme to expand the capacity of state feedback state tracking adaptive control to handle the plant‐model matching uncertainties for single‐input LTI systems. The extended scheme is developed, using multiple reference model systems (only one of which is required to be able to match the controlled plant), and multiple controllers (which are updated from adaptive laws generated from multiple reference model systems based estimation errors), as two key features of such design to relax a plant‐model matching condition. A switching mechanism is constructed using those multiple estimation errors, capable of selecting the suitable control input from the multiple control signals, to achieve the desired system performance. An aircraft flight control example is presented to show the capacity of such design in relaxing a practical design condition. Copyright © 2013 John Wiley & Sons, Ltd.