C. Grantham

University of New South Wales, Kensington, New South Wales, Australia

Are you C. Grantham?

Claim your profile

Publications (110)43.02 Total impact

  • [Show abstract] [Hide abstract]
    ABSTRACT: High temperature superconducting (HTS) cable has now reached the stage where their application in power systems is in the process of being implemented. Liquid Nitrogen $(hbox{LN}_{2})$ and polyimide film have been used as a coolant and insulation in HTS cable systems. Partial discharge (PD) events may lead to material degradation and total breakdown. PD testing is an important quality check for the insulation of HTS cable. Thus it is necessary to consider PD for the insulation testing in $hbox{LN}_{2}$ which is generated in void defects of the insulation layers. The PD characterizations of polyimide film in different defects were investigated under 50 Hz AC voltages in $hbox{LN}_{2}$ and at room temperature (298 K). The results show that the number of discharges and the discharge quantity increase with the increasing of the applied voltage and the defect size. The PD inception voltage decreases when the void defect diameter enlarged and it is higher in $hbox{LN}_{2}$ than that at room temperature. The maximum field strength for HTS tape insulation increases with the defect close to the tape boundary and the addition of contaminant relative permittivity. Obtained results at cryogenic temperature provide necessary information for insulation design and pre-shipment inspections of HTS cable system.
    IEEE Transactions on Applied Superconductivity 10/2014; 24(5):1-5. · 1.20 Impact Factor
  • D. J. McKinnon, C. Grantham
    [Show abstract] [Hide abstract]
    ABSTRACT: The paper describes a novel technique for on line parameter identification of three-phase induction motors from a single, run up to speed test. Data is sampled during this test with the normal locked rotor and synchronous speed data captured on the way to reaching the motor's rated speed. Rotor parameter variations with frequency due to skin and proximity effects and other non linear imperfections such as heating and main flux path saturation are taken into account. This method is ideal for determining and/or verifying parameters used in high performance drives.
    Journal of international Conference on Electrical Machines and Systems. 01/2010; 1(2).
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: This paper presents a new method of online estimation of the stator and rotor resistance of the induction motor in the indirect vector-controlled drive, with artificial neural networks. The back propagation algorithm is used for training of the neural networks. The error between the rotor flux linkages based on a neural network model and a voltage model is back propagated to adjust the weights of the neural network model for the rotor resistance estimation. For the stator resistance estimation, the error between the measured stator current and the estimated stator current using neural network is back propagated to adjust the weights of the neural network. The performance of the stator and rotor resistance estimators and torque and flux responses of the drive, together with these estimators, is investigated with the help of simulations for variations in the stator and rotor resistance from their nominal values. Both types of resistance are estimated experimentally, using the proposed neural network in a vector-controlled induction motor drive. Data on tracking performances of these estimators are presented. With this approach, the rotor resistance estimation was found to be insensitive to the stator resistance variations both in simulation and experiment.
    Advances in Fuzzy Systems 01/2009; 2009.
  • C. Grantham, D.J. McKinnon
    [Show abstract] [Hide abstract]
    ABSTRACT: This paper describes two novel methods of full load testing for temperature rise and efficiency evaluation of three-phase induction motors. Synthetic loading techniques are used, without the need to connect a load to the machinepsilas drive shaft. These new methods use a digital signal processor controlled power electronic inverter to continually accelerate and decelerate the induction machine, while using a new real time data acquisition system to accurately determine and record the machinepsilas performance. The methods proposed reduce the testing time and floor space required for both load testing and efficiency evaluation of induction motors when compared with conventional methods of temperature rise and efficiency measurement.
    Electrical Machines and Systems, 2008. ICEMS 2008. International Conference on; 11/2008
  • B. Karanayil, M.F. Rahman, C. Grantham
    [Show abstract] [Hide abstract]
    ABSTRACT: This paper presents a new method of on-line estimation for the stator and rotor resistances of the induction motor in the indirect vector controlled drive, using artificial neural networks. The back propagation algorithm is used for training of the neural networks. The error between the rotor flux linkages based on a neural network model and a voltage model is back propagated to adjust the weights of the neural network model for the rotor resistance estimation. For the stator resistance estimation, the error between the measured stator current and the estimated stator current using neural network is back propagated to adjust the weights of the neural network. The performance of the stator and rotor resistance estimators and torque and flux responses of the drive, together with these estimators, are investigated with the help of simulations for variations in the stator and rotor resistances from their nominal values. Both resistances are estimated experimentally, using the proposed neural networks in a vector controlled induction motor drive. Data tracking performances of these estimators are presented. With this approach the rotor resistance estimation was found to be insensitive to the stator resistance variations both in simulation and experiment.
    Electrical Machines and Systems, 2008. ICEMS 2008. International Conference on; 11/2008
  • Source
    C. Chao, C. Grantham
    [Show abstract] [Hide abstract]
    ABSTRACT: An iron-cored high-temperature superconductor (HTS) inductor has to be cooled for superconducting operation. By design, it can be either warm-cored or cold-cored. A warm cored HTS inductor has only the winding cooled in the cryostat, while a cold-cored one has both the winding and the iron-core cooled in the cryostat. Each design has its own advantages and disadvantages. By analysing the advantages and disadvantages, this paper provides some guidelines for those who are designing a practical HTS inductor for electric power applications.
    Physica C Superconductivity 09/2008; 468(15):2149-2151. · 0.72 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: This paper presents a new method of online estimation for the stator and rotor resistances of the induction motor for speed sensorless indirect vector controlled drives, using artificial neural networks. The error between the rotor flux linkages based on a neural network model and a voltage model is back propagated to adjust the weights of the neural network model for the rotor resistance estimation. For the stator resistance estimation, the error between the measured stator current and the estimated stator current using neural network is back propagated to adjust the weights of the neural network. The rotor speed is synthesized from the induction motor state equations. The performance of the stator and rotor resistance estimators and torque and flux responses of the drive, together with these estimators, are investigated with the help of simulations for variations in the stator and rotor resistances from their nominal values. Both resistances are estimated experimentally, using the proposed neural network in a vector controlled induction motor drive. Data on tracking performances of these estimators are presented. With this speed sensorless approach, the rotor resistance estimation was made insensitive to the stator resistance variations both in simulation and experiment. The accuracy of the estimated speed achieved experimentally, without the speed sensor clearly demonstrates the reliable and high-performance operation of the drive
    IEEE Transactions on Industrial Electronics 03/2007; · 6.50 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: The inevitable time delay of the digital controller can degrade the performance of a converter system. Further, this time delay may depend on both sampling and switching cycles of the converter. Therefore, with applications where the converter operates at low or medium switching frequency, the time delay can severely affect the system dynamics. Further, in controlling a current-source converter, this time delay can cause oscillation in the system. The paper proposes the use of an observer-predictor state feedback algorithm to compensate the time delay in a DSP based controller. Experimental result shows that the time delay in a DSP-based controller can have significant effect on the CSC performance. Simulation and experimental results also shows the proposed control approach can successfully compensate the time delay and provides fast dynamics to the CSC.
    01/2007;
  • Jun Zhang, M.F. Rahman, Colin Grantham
    [Show abstract] [Hide abstract]
    ABSTRACT: This paper presents a new direct torque control (DTC) scheme based on space vector modulation (SVM) for interior permanent magnet synchronous machine (IPMSM) drives. The new scheme provides a variable option for the improvement of DTC controlled IPMSM. Closed-loop control of both torque and flux is developed with two proportional-integral (PI) controllers. The stator voltage is generator through SVM unit. The torque and flux ripples are greatly reduced with fixed inverter switching frequency comparing with classical switching-table based DTC scheme. The analysis of the control principle provides a guide to design the controller parameters. Modeling results confirm the effectiveness of the proposed scheme
    Power Electronics and Motion Control Conference, 2006. IPEMC 2006. CES/IEEE 5th International; 09/2006
  • T. Manmek, C.P. Mudannayake, C. Grantham
    [Show abstract] [Hide abstract]
    ABSTRACT: This paper presents a fast voltage dip detection technique that is suitable for use in a distribution static synchronous compensator (D-STATCOM) in compensating balanced dip and unbalanced voltages in power systems. The proposed voltage dip detection method is based on an efficient least squares algorithm which offers structural simplicity and less computational complexity while maintaining dynamic performance and accuracy. It is also robust against distortions present in voltage waveforms. The proposed method extracts the active and reactive parts of the positive- and negative-sequence component for generating reference values of current that need to be injected into the point of connection D-STATCOM in order to compensate the voltage errors. The effectiveness of the voltage dip detection method in the D-STATCOM application has been verified by simulation results
    Power Electronics and Motion Control Conference, 2006. IPEMC 2006. CES/IEEE 5th International; 09/2006
  • C Chao, H P To, C Grantham, M F Rahman
    [Show abstract] [Hide abstract]
    ABSTRACT: An active power filter improves the electric power quality through the compensation of harmonics in the power network. A current-source active power filter using a conventional copper inductor for its energy storage has a significant power loss. The loss in the copper inductor can be substantially reduced by using a high-temperature superconducting (HTS) inductor instead. Experiments have been conducted on a prototype current-source active power filter for studying the power loss reduction effect and harmonics compensation performance of the active power filter using a HTS inductor. Experimental results are analysed and discussed in this paper.
    Journal of Physics Conference Series 07/2006; 43(1):913.
  • Chen Chao, C. Grantham
    [Show abstract] [Hide abstract]
    ABSTRACT: Installing active power filters (sometimes called active harmonic filters or line conditioners) in an electric power network can improve the quality of electricity supply. A shunt active power filter, with a current-source PWM inverter and a conventional copper inductor as its energy storage, has a significant power loss. The power loss in this copper inductor can be substantially reduced by replacing the inductor with a high-temperature superconducting (HTS) magnet. Several solenoid design alternatives using silver-sheathed BSCCO-2223 tape have been made for the HTS magnet that has an inductance of 0.5 H for this application. A liquid-nitrogen-cooled HTS magnet has been built and tested for use in an active power filter. The loss-reduction effect of using the HTS magnet with the current-source active power filter has been investigated experimentally, and the results are compared with those when using a conventional copper inductor. Practical issues such as air-core design versus iron-core design and using liquid-nitrogen cooling or a cryocooling are analyzed and discussed
    IEEE Transactions on Applied Superconductivity 07/2006; · 1.20 Impact Factor
  • T. Manmek, C. Grantham, Toan Phung
    [Show abstract] [Hide abstract]
    ABSTRACT: The paper presents a real time measurement technique for tracking rms quantities of fundamental and harmonic components under nonsinusoidal conditions in a three-phase system based on the efficient least squares method. The proposed technique allows real time accurate measurements of the rms values and phase angles of the fundamental and harmonics present in distorted unbalanced three-phase waveforms. The effectiveness of the proposed measurement method is demonstrated by computer real time simulation and practical implementation in the laboratory establishes thee potential of this method. It is demonstrated that the proposed method can provide an accurate measurement of fundamental and harmonic rms quantities in a pollution measured waveform. Due to the fast response and accurate measurement, the proposed method makes it suitable for use in real time applications. Consequently, this technique can be used for control applications, protection applications, and power quality monitoring of power systems.
    Power Electronics and Drives Systems, 2005. PEDS 2005. International Conference on; 02/2006
  • Source
    B. Karanayil, M.F. Rahman, C. Grantham
    [Show abstract] [Hide abstract]
    ABSTRACT: This paper presents a new observer for the rotor resistance of an indirect vector controlled induction motor drive using artificial neural networks supplemented by a fuzzy logic based stator resistance observer. The error between the rotor flux linkages based on a neural network model and a voltage model is back propagated to adjust the weights of the neural network model for the rotor resistance estimation. The error between the measured stator current and its corresponding estimated value is mapped to a change in stator resistance with a proposed fuzzy logic. The stator resistance observed with this approach is used to correct the rotor resistance observer using neural networks. The performance of these observers and torque and flux responses of the drive, together with these estimators, are investigated with the help of simulations. Both modeling and experimental data on tracking performances of these observers are presented. With this approach accurate rotor resistance estimation was achieved and was made insensitive to stator resistance variations both in modeling and experiment.
    IEEE Transactions on Energy Conversion 01/2006; · 3.35 Impact Factor
  • Huu-Phuc To, M. F. Rahman, C. Grantham
    [Show abstract] [Hide abstract]
    ABSTRACT: This paper presents an algorithm to convert the PWM gating signals for a voltage-source converter (VSC) to the signals suitable for gating a current-source converter (CSC). The proposed algorithm requires only the VSC-PWM output signals, therefore, it is easy to be implemented. The proposed algorithm is validated by experimental results using this algorithm to convert different VSC-PWM schemes to CSC-PWM gating signals. The applicability of the algorithm is also confirmed by applying it in a controller for a prototype CSC active power filter
    01/2006;
  • Huu-Phuc To, F. Rahman, C. Grantham
    [Show abstract] [Hide abstract]
    ABSTRACT: The inevitable time delay in a digital signal processing (DSP) based controller can significantly degrade the performance of an active power filter. With a current-source active power filter (CS-APF) the problem can be more severe as this time delay can excite the filter resonance and cause oscillations in the compensation current. The paper derives the state space model for the CS-APF where the time delay is modeled properly into the state equations of the system. This makes the system dynamic model more accurate and the time delay can be compensated when a controller is designed for the system. State space control strategy is selected for the CS-APF controller. Experimental results from our prototype CS-APF system are presented to show the effect of the time delay on the CS-APF response and the validity of the proposed approach.
    Industry Applications Conference, 2005. Fourtieth IAS Annual Meeting. Conference Record of the 2005; 11/2005
  • D.J. McKinnon, C. Grantham
    [Show abstract] [Hide abstract]
    ABSTRACT: The results in this paper demonstrate that the synthetic loading methods described are able to be used to evaluate the efficiency of three-phase induction machines. Synthetic loading causes the machine, as it is rotating, to periodically accelerate and decelerate. This causes the machine to draw, on average, rated current, at rated voltage at or near rated speed, thus producing rated losses. The total losses for efficiency evaluation are identified by taking the average of the measured input power over each synthetic loading cycle. The measured results give excellent agreement with the conventional full-load efficiency test method. The synthetic loading test methods are portable with no loss of accuracy, so they are suitable for either on-site or laboratory use. The test is easy to set up, requiring only that the motor be decoupled from the load and electrically connected to an inverter controlled from a PC that also displays the results in real time. The efficiency evaluation method proposed is accurate, easy to use and considerably reduces the testing time compared with conventional methods, hence reducing testing costs.
    Industry Applications Conference, 2005. Fourtieth IAS Annual Meeting. Conference Record of the 2005; 11/2005
  • T. Manmek, C. Grantham, T. Phung
    [Show abstract] [Hide abstract]
    ABSTRACT: This paper presents an alternative approach for real time measurement of all electrical quantities in a power system signal based on a new least squares algorithm. The advantage of this approach is that the least squares algorithm is an easy to understand, fast and cheap method that can be applied to track changes in power system quantities rapidly. The technique can be used to accurately evaluate the rms voltage and rms current magnitudes and phase angle of each harmonic component directly from single measurements of the voltage and current. Once these values have been evaluated all other quantities such as average power and power factor can be readily calculated. Computer simulation is used to evaluate the algorithm's accuracy. The results confirm the structural robustness of the proposed algorithm with respect to noise and distortions in the waveforms being measured.
    Industrial Electronics Society, 2004. IECON 2004. 30th Annual Conference of IEEE; 12/2004
  • H.-P. To, F. Rahman, C. Grantham
    [Show abstract] [Hide abstract]
    ABSTRACT: This paper presents the use of sliding mode control with a current-source active power filter. From the analysis of the system model, a suitable sliding control function is proposed and its implementation on a DSP-based controller is discussed. A new switching control strategy for the active filter converter with sliding mode control is also proposed. In addition, the effect of control delay on the system response is discussed and a simple measure to compensate this delay is presented. Simulation results show the validity the proposed approach.
    Industrial Electronics Society, 2004. IECON 2004. 30th Annual Conference of IEEE; 12/2004
  • H.-P. To, F. Rahman, C. Grantham
    [Show abstract] [Hide abstract]
    ABSTRACT: Shunt active power filters (APFs) can be used to compensate both harmonics and reactive powers from nonlinear loads. However, due to the limitation of the APF output current, the harmonics cannot be compensated successfully if the required compensating current is higher than a certain level. To overcome this problem, the paper proposed an adaptive algorithm for controlling reactive power generated by the APF. This control algorithm will permit the APF to fully compensate both harmonic and reactive currents if the total compensation demand is within the APF capacity. When a high level of compensation current is required, the reactive power generation will be reduced to save the APF capacity for the harmonic compensation task. The implementation of the adaptive algorithm with different types of APF controller is also discussed. Performances of APFs with and without the adaptive algorithm are simulated and compared to show the validity of the proposed approach.
    Industry Applications Conference, 2004. 39th IAS Annual Meeting. Conference Record of the 2004 IEEE; 11/2004

Publication Stats

598 Citations
43.02 Total Impact Points

Institutions

  • 1989–2009
    • University of New South Wales
      • • School of Electrical Engineering and Telecommunications
      • • School of Computer Science and Engineering
      Kensington, New South Wales, Australia
  • 1997–2008
    • University of Sydney
      Sydney, New South Wales, Australia
  • 1995–1999
    • University of Wollongong
      • Institute for Superconducting and Electronic Materials
      Wollongong, New South Wales, Australia
  • 1
    • University of South Wales
      Понтиприте, Wales, United Kingdom