By Topic

Electric Power Applications, IET

Issue 2 • Date March 2008

Filter Results

Displaying Results 1 - 6 of 6
  • Investigation of a new stator interior permanent magnet machine

    Page(s): 77 - 87
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (642 KB)  

    A new stator interior permanent magnet (PM) machine which is developed from the doubly salient PM machine is proposed. The novelty of this machine lies in the split stator pole and full-pitched windings, where tooth-shoe is adopted and the PM is inserted into the stator pole. This configuration can offer higher power density and lower cogging torque ripple than the doubly salient machine. In order to achieve high power density, the smaller thickness of PM may be more favourable. In this case, an analytical method is used to examine the demagnetisation of PM under short-circuit current. A prototype machine for wind power application is designed, built and tested. The experimental results validate the theoretical analysis and the effectiveness of the proposed stator interior PM machine. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Sensorless permanent-magnet synchronous motor drive using a reduced-order rotor flux observer

    Page(s): 88 - 98
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (812 KB)  

    A sensorless permanent-magnet synchronous motor (PMSM) drive is developed. A second-order Luenberger observer is used to estimate the position of the rotor flux and hence the rotor speed. The observer is computationally efficient as it has a simple structure and does not involve mechanical parameters. An integral-feedback method is adopted for the estimation of the rotor speed. The inner current loop is realised using a decoupling and diagonal internal model control algorithm. Details of the sensorless control system are given and the feasibility of the proposed method is verified through simulation and experiments. Satisfactory estimation accuracy is obtained even when the drive operates at very low speeds and also during rotor speed reversals. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Three-phase transformer modelling for unbalanced conditions, Part 1: core modelling and introductory examples

    Page(s): 99 - 112
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (608 KB)  

    A simple and systematic two-winding, three-phase transformer modelling for steady-state unbalanced conditions is proposed. The model is valid for three-legged, five-legged and triplex (transformer bank) core designs. It is derived from the primitive (or unconnected winding) equations of the transformer and uses two parameters only: the short-circuit and the zero-sequence magnetising impedances. Both phase and sequence nodal equations are systematically obtained for all possible phase shifts and all winding connections, including the isolated wyes and the impedance-grounded wyes on one or both transformer sides. The proposed model can be considered as a generalisation of the usual model in the literature (which is only valid for the transformer bank; moreover, only specific phase shifts have been developed and the impedance-grounded wyes are not usually considered). Furthermore, the zero-sequence scheme is analysed in depth, from which the following conclusions are highlighted: (1) the voltage of the neutral point in the isolated wye cases also depends on the connection of the other winding; (2) the zero-sequence admittances for all connections can be obtained from the zero-sequence admittances of the Yz-Yz connection by taking limits as ztildenp or ztildens tends to infinity or to zero. The study is divided into two parts. Part I is devoted to core modelling and to four detailed examples. Part II summarises the general procedure for all possible phase shifts, all winding connections and all core designs and also includes the numerical application examples. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Sensorless speed estimation in induction motor drives by using the space vector angular fluctuation signal

    Page(s): 113 - 120
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (225 KB)  

    A sensorless speed estimation method for real-time application in induction motor drives under steady-state condition is proposed. Speed harmonic component in the space vector angular fluctuation (SVAF) signal, which is caused by both dynamic and static eccentricity, is used for speed estimation. The SVAF signal is obtained from the stator currents of the induction motor. The extraction of speed information using digital signal processing techniques is considered. Experimental results are given to demonstrate the validity of the speed estimation method on an induction motor driven by an inverter. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Fault-tolerant control in variable speed drives: a survey

    Page(s): 121 - 134
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (558 KB)  

    A survey on fault-tolerant control is presented for variable speed drives (VSD), mainly addressing DC and induction motors. Thus, fault diagnosis, accommodation and hardware reconfiguration are reviewed with application to VSD. First, the most common fault scenarios in these electrical machines are described. These conditions are analysed, and their implications and mathematical modelling are discussed. Next, the fault diagnosis strategies based on signal processing, model-based techniques and artificial intelligence are reviewed. Moreover, the diverse hardware reconfiguration schemes of power actuators with semiconductor failures are detailed. A key piece in any VSD is the control algorithm, which can be severely affected in a fault condition. Finally, the fault accommodation schemes suggested so far in the literature are illustrated. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Protective relaying for power transformers using field programmable gate array

    Page(s): 135 - 143
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (598 KB)  

    A wavelet-based digital directional relay for power transformer protection, implemented using field programmable gate array. The general purpose SPARTAN3E FPGA kit was employed for developing the prototype relay, with all the coding done using the hardware description language VHDL. The relay logic consists of two parts: disturbance detection based on first-level high-frequency details of the voltage signals and fault discrimination using a power-based directional signal derived from the first-level high-frequency details of both voltage and current signals. The real-time windows target Toolbox of MATLAB was used to apply the current and voltage input signals to the prototype relay in real-time. The logic is deterministic, computationally efficient, fast, secure and highly reliable. The operating time is 6 ms, about one-third of power frequency cycle (20 ms). The scheme uses only the sign of the directional signals, rather than the difference in their magnitudes, hence it can work reliably in the presence of fault resistance and current transformer saturation. The validity of the proposed logic was exhaustively tested by simulating various types of internal and external faults, energisation conditions and load variations on a 132 kV system modelled in EMTP/ATP with a 31.5 MVA, 132/33 kV, Y-Delta transformer. The relay was able to correctly discriminate between internal faults, external faults and non-fault disturbances for the entire 880 test cases. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.

Aims & Scope

IET Electric Power Applications publishes papers of a high technical standard with a suitable balance of practice and theory.

Full Aims & Scope

Meet Our Editors

Publisher
IET Research Journals
iet_epa@theiet.org