THE DESIGN AND ANALYSIS OF EXPERIMENTS. By Oscar Kempthorne. New York, John Wiley and Sons, Inc., 1952. 631 pp. $8.50. This book by a teacher of statistics (as well as a consultant for \"experimenters\") is a comprehensive study of the philosophical background for the statistical design of experiment. It is necessary to have some facility with algebraic notation and manipulation to be able to use the volume intelligently. The problems are presented from the theoretical point of view, without such practical examples as would be helpful for those not acquainted with mathematics. The mathematical justification for the techniques is given. As a somewhat advanced treatment of the design and analysis of experiments, this volume will be interesting and helpful for many who approach statistics theoretically as well as practically. With emphasis on the \"why,\" and with description given broadly, the author relates the subject matter to the general theory of statistics and to the general problem of experimental inference. MARGARET J. ROBERTSON

The Design and Analysis of Experiments

Fractional Differential Equations

Due to the stochastic nature of wind, electric power generated by wind turbines is highly erratic and may affect both the power quality and the planning of power systems. Energy Storage Systems (ESSs) may play an important role in wind power applications by controlling wind power plant output and providing ancillary services to the power system and therefore, enabling an increased penetration of wind power in the system. This article deals with the review of several energy storage technologies for wind power applications. The main objectives of the article are the introduction of the operating principles, as well as the presentation of the main characteristics of energy storage technologies suitable for stationary applications, and the definition and discussion of potential ESS applications in wind power, according to an extensive literature review.

A review of energy storage technologies for wind power applications

Energy storage systems (ESSs) are enabling technologies for well-established and new applications such as power peak shaving, electric vehicles, integration of renewable energies, etc. This paper presents a review of ESSs for transport and grid applications, covering several aspects as the storage technology, the main applications, and the power converters used to operate some of the energy storage technologies. Special attention is given to the different applications, providing a deep description of the system and addressing the most suitable storage technology. The main objective of this paper is to introduce the subject and to give an updated reference to nonspecialist, academic, and engineers in the field of power electronics.

Energy Storage Systems for Transport and Grid Applications

Superconducting magnetic energy storage (SMES) is known to be a very good energy storage device. This article provides an overview and potential applications of the SMES technology in electrical power and energy systems. SMES is categorized into three main groups depending on its power conditioning system, namely, the thyristor-based SMES, voltage-source- converter-based SMES, and current-source-converter-based SMES. An extensive bibliography is presented on the applications of these three types of SMES. Also, a comparison is made among these three types of SMES. This study provides a basic guideline to investigate further technological development and new applications of SMES, and thus benefits the readers, researchers, engineers, and academicians who deal with the research works in the area of SMES.

/pdf/an-overview-of-smes-applications-in-power-and-energy-systems-168707qbsk.pdf

An Overview of SMES Applications in Power and Energy Systems

Injection of the wind power into an electric grid affects the power quality. The performance of the wind turbine and thereby power quality are determined on the basis of measurements and the norms followed according to the guideline specified in International Electro-technical Commission standard, IEC-61400. The influence of the wind turbine in the grid system concerning the power quality measurements are-the active power, reactive power, variation of voltage, flicker, harmonics, and electrical behavior of switching operation and these are measured according to national/international guidelines. The paper study demonstrates the power quality problem due to installation of wind turbine with the grid. In this proposed scheme STATic COMpensator (STATCOM) is connected at a point of common coupling with a battery energy storage system (BESS) to mitigate the power quality issues. The battery energy storage is integrated to sustain the real power source under fluctuating wind power. The STATCOM control scheme for the grid connected wind energy generation system for power quality improvement is simulated using MATLAB/SIMULINK in power system block set. The effectiveness of the proposed scheme relives the main supply source from the reactive power demand of the load and the induction generator. The development of the grid co-ordination rule and the scheme for improvement in power quality norms as per IEC-standard on the grid has been presented.

A STATCOM-Control Scheme for Grid Connected Wind Energy System for Power Quality Improvement

This paper presents an improved direct torque control (DTC) method for an asymmetrical six-phase induction motor using a two-level six-phase inverter. As is well known, a simple extension of three-phase DTC technique to an asymmetrical six-phase motor, using large vectors only, introduces significant current harmonics of the order 6 n ±1 ( n = 1, 3, 5,…), which are mapped into the nonflux/torque producing ( xy ) plane. These harmonics cause only losses in the motor winding as they do not take part in torque production. Hence, a number of different improved DTC techniques have been developed in the past for multiphase motor drives. The paper takes one such DTC method as the starting point and improves it further by using the concept of virtual voltage vectors. Developed vector selection algorithm, based on two virtual voltage vectors, requires the information on position of the flux in the auxiliary ( xy ) subspace and provides stator current quality commensurate with the currently available best DTC algorithm for six-phase drives. However, use of two virtual voltage vectors enables a substantial reduction of the torque ripple, which is achieved by means of a five-level torque comparator. Extensive experimentation is performed and it is shown that the reduction of the current harmonics is in essence almost the same as in another recently developed DTC scheme, based on the use of a single virtual voltage vector. However, the achieved torque ripple reduction, which is verified experimentally, makes the scheme superior when compared to the existing approaches. At the same time, developed scheme retains qualities of conventional DTC schemes, such as simple structure and fast response. Its additional beneficial feature is the easiness of implementation.

/pdf/direct-torque-control-scheme-for-a-six-phase-induction-motor-3n08ysq0bu.pdf

Direct Torque Control Scheme for a Six-Phase Induction Motor With Reduced Torque Ripple

In the micro-grid network, it is especially difficult to support the critical load without uninterrupted power supply. The proposed micro-wind energy conversion system with battery energy storage is used to exchange the controllable real and reactive power in the grid and to maintain the power quality norms as per International Electro-Technical Commission IEC-61400-21 at the point of common coupling. The generated micro-wind power can be extracted under varying wind speed and can be stored in the batteries at low power demand hours. In this scheme, inverter control is executed with hysteresis current control mode to achieve the faster dynamic switchover for the support of critical load. The combination of battery storage with micro-wind energy generation system (μ WEGS), which will synthesize the output waveform by injecting or absorbing reactive power and enable the real power flow required by the load. The system reduces the burden on the conventional source and utilizes μ WEGS and battery storage power under critical load constraints. The system provides rapid response to support the critical loads. The scheme can also be operated as a stand-alone system in case of grid failure like a uninterrupted power supply. The system is simulated in MATLAB/SIMULINK and results are presented.

Micro Wind Power Generator With Battery Energy Storage for Critical Load

In a switching-table-based direct torque control method (ST-DTC), the torque ripple reduces with increasing number of levels of the torque comparator. The number of levels is decided by the availability of the number of voltage vectors according to the topology of the inverter. This paper proposes the seven-level torque comparator to reduce the torque ripple in the DTC-controlled five-phase induction motor fed by the three-level five-phase inverter. In the five-phase induction motor, an elimination of x − y stator flux is inevitable otherwise the stator phase current will be distorted. In order to eliminate the x − y stator flux, the virtual voltage vectors are formed. Experimental results are presented to validate the proposed DTC method.

Torque Ripple and Harmonic Current Reduction in a Three-Level Inverter-Fed Direct-Torque-Controlled Five-Phase Induction Motor

The aim of this paper is to employ fractional order proportional integral derivative &#x0028 FO-PID &#x0029 controller and integer order PID controller to control the position of the levitated object in a magnetic levitation system &#x0028 MLS &#x0029, which is inherently nonlinear and unstable system. The proposal is to deploy discrete optimal pole-zero approximation method for realization of digital fractional order controller. An approach of phase shaping by slope cancellation of asymptotic phase plots for zeros and poles within given bandwidth is explored. The controller parameters are tuned using dynamic particle swarm optimization &#x0028 dPSO &#x0029 technique. Effectiveness of the proposed control scheme is verified by simulation and experimental results. The performance of realized digital FO-PID controller has been compared with that of the integer order PID controllers. It is observed that effort required in fractional order control is smaller as compared with its integer counterpart for obtaining the same system performance.

Mohan V. Aware

Papers

A STATCOM-Control Scheme for Grid Connected Wind Energy System for Power Quality Improvement

Direct Torque Control Scheme for a Six-Phase Induction Motor With Reduced Torque Ripple

Micro Wind Power Generator With Battery Energy Storage for Critical Load

Torque Ripple and Harmonic Current Reduction in a Three-Level Inverter-Fed Direct-Torque-Controlled Five-Phase Induction Motor

Design and implementation of digital fractional order PID controller using optimal pole-zero approximation method for magnetic levitation system