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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
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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
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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
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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
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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.
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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
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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; · 2.27 Impact Factor
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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
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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
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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
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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
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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
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ABSTRACT: This paper presents an investigation into the effects of timer jitter on the accuracy of measured results when using a digital signal processor card in a PC based measurement system. These results are particularly applicable for drive system engineers. Jitter is the error between the ideal sampling period and the actual sampling period. Timer jitter has different effects on the accuracy of the measured output depending upon the type of signal to be measured. Current sampling frequencies (10-20 kHz) of typical DSP systems are too low for the measurement of PWM waveforms in power applications. Timer error means that pulses that are small in width may be missed when sampled, even if the measurement system is synchronized with the PWM generation. The resulting sampled data misrepresents the actual waveform. However, the error as a result of timer jitter in the measured data is negligible when sampling sinusoidal or slow changing waveforms. Experimental results are presented to show the effect of timer error. Timer jitter was measured and found to be as high as +/-10% for a stated sampling period of 50 /spl mu/s for the DSP card being used. Timer jitter had a negligible effect on the sampled data when the signal was a near sinusoidal waveform. Spectral analysis was also undertaken to highlight the results. Computer simulated results confirmed the errors produced by timer jitter.
Power Electronics and Motion Control Conference, 2004. IPEMC 2004. The 4th International; 09/2004
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ABSTRACT: This work presents a control strategy for a current-source active power filter in which a minimum number of current sensors is used. The derivation of a simplified model for the active power filter and the selection of compensators for its controller are also presented. Simulation results show that the proposed active filter system can compensate effectively both harmonic currents and reactive power of nonlinear load. Furthermore, its performance is still maintained under unbalanced and/or distorted condition of the mains.
Power Electronics and Motion Control Conference, 2004. IPEMC 2004. The 4th International; 09/2004
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ABSTRACT: A novel and efficient linear least squares algorithm for a real time measurement technique that can track the harmonics in power system waveforms is presented. The proposed algorithm does not require matrix inversion. The technique produces accurate real time measurements of the amplitude and phase of the harmonics present in a power system. To verify the theoretical analysis, computer simulation has been used and tested with a hypothetical signal. The results obtained confirm that the method is computationally efficient and suitable for real time applications. The simulation has shown that the computational requirement has been reduced significantly and that the identification of harmonics buried in a noisy signal is accurate.
Power Electronics and Motion Control Conference, 2004. IPEMC 2004. The 4th International; 09/2004
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ABSTRACT: This paper investigates a programmable cascaded low pass filter for the estimation of rotor flux of an induction motor, with a view to estimate the rotor time constant of an indirect field orientation controlled induction motor drive. Programmable cascaded low pass filters have been traditionally used in stator flux oriented vector control of the induction motor. This paper extends the use of this filter to estimate the rotor flux for the indirect field orientation control by generating rotor flux estimates from stator flux estimates. This is achieved by using a three-stage programmable cascaded low pass filter. The three-stage programmable cascaded low-pass filter investigated in this paper has resulted in excellent estimation of rotor flux in the steady-state and transient operation of an indirect field oriented drive. The estimated rotor flux data have also been used for the on-line rotor resistance identification with artificial neural network. Modeling and experiment results presented in this paper demonstrate this method of estimating rotor flux clearly.
IEEE Transactions on Power Electronics 04/2004; · 4.65 Impact Factor
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ABSTRACT: This paper presents a new method of on-line estimation for the rotor and stator resistances of the induction motor in the indirect vector controlled drive, using artificial neural networks and a simple PI compensator. The back propagation algorithm is used for the training of the neural networks for rotor resistance identification. The error between the desired state variable of an induction motor and the actual state variable of a neural model is back propagated to adjust the weights of the neural model, so that the actual state variable tracks the desired value. A PI compensator is used to estimate and update the stator resistance used in the rotor resistance estimation in order to eliminate the error in rotor resistance estimation. The performance of the induction motor drive with the above rotor and stator resistance estimators is investigated in detail for torque and flux responses, to analyze the effects of stator resistance observer on rotor resistance identification, for variations in the stator and rotor resistances from their nominal values, conducting both simulations and experiments.
Power Electronics and Drive Systems, 2003. PEDS 2003. The Fifth International Conference on; 12/2003
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ABSTRACT: This paper proposes a controller implemented in a current-source active power filter (CS-APF) which can adjust adaptively the reactive power generated by the APF. With this controller, the line current distortion level can be kept within a certain limit whilst the system power factor can be maintained at a highest available level. In an APF with DSP-based controller, the proposed algorithm can be implemented with some modification in the controller software only. Performance of a CS-APF with and without this adaptive controller are simulated and compared to show the validity of the proposed approach.
Power Electronics and Drive Systems, 2003. PEDS 2003. The Fifth International Conference on; 12/2003
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ABSTRACT: Pure integrators pose a problem in the flux estimation of induction motors. The performance of the induction machine control mainly depends on the accuracy of the estimated flux. Error in the flux estimation system comprises of a drift produced by the integrator as a consequence of initial conditions and a drift produced by an offset error present in the back electromotive force (emf) due to terminal voltage and/or phase current sensor measurement offset error. The method proposed in this paper provides a simple and effective solution to these problems. The method compensates the error produced by the inherent problem in the pure integrator and measurement error. It can easily be applied in a DSP based induction machine control system for flux estimation. The computation burden is light and as such execution time remains low.
Industrial Electronics Society, 2003. IECON '03. The 29th Annual Conference of the IEEE; 12/2003
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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 backpropagation algorithm is used for training of the neural networks. The error between the desired state variable of an induction motor and the actual state variable of a neural model is back propagated to adjust the weights of the neural model, so that the actual state variable tracks the desired value. The performance of the neural estimator and torque and flux responses of the drive, together with this estimator, are investigated with the help of simulations for variations in the stator and rotor resistance from their nominal values. Both these resistances are estimated experimentally, in a vector controlled induction motor drive and found to give accurate estimates. The rotor resistance estimation was found to be insensitive to the stator resistance variations both in simulation and experiment.
Industrial Electronics Society, 2003. IECON '03. The 29th Annual Conference of the IEEE; 12/2003
