Search

This paper presents sizing approaches to improve output torque performance in PM motor when partial stator body is removed. As the output torque performance is directly proportional to the electric loading, Q, modification on stator geometry affects the output torque performance and special procedures have to be taken to restore the desired output torque capability. Influences of split ratio, tooth body width, airgap and magnet thickness of magnet in PM motor with asymmetry stator design are carried out and the performance verification are referred to the back-emf, average output torque, torque ripple as well as cogging torque. From the investigation using 2D-Finite Element Analysis, optimum size of tooth body width and optimum number of coil turns result better output torque while other sizing approaches result no significant change as quick saturation took place. [ABSTRACT FROM AUTHOR]

This paper presents a novel direct torque control (DTC) approach for induction machines, based on an improved torque and stator flux estimator and its implementation using field-programmable gate arrays (FPGA). The DTC performance is significantly improved by the use of FPGA, which can execute the DTC algorithm at higher sampling frequency. This leads to the reduction of the torque ripple and improved flux and torque estimations. The main achievements are: 1) calculating a discrete integration operation of stator flux using backward Euler approach; 2) modifying a so called nonrestoring method in calculating the complicated square root operation in stator flux estimator; 3) introducing a new flux sector determination method; 4) increasing the sampling frequency to 200 kHz such that the digital computation will perform similar to that of the analog operation; and 5) using two's complement fixed-point format approach to minimize calculation errors and the hardware resource usage in all operations. The design was achieved in VHDL, based on a Matlab/Simulink simulation model. The Hardware-in-the-Loop method is used to verify the functionality of the FPGA estimator. The simulation results are validated experimentally. Thus, it is demonstrated that FPGA implementation of DTC drives can achieve excellent performance at high sampling frequency. [ABSTRACT FROM PUBLISHER]

This paper presents a simple dynamic overmodulation method to obtain a fast dynamic torque response in direct torque control (DTC) of induction machines with constant-switching-frequency controller. A fast dynamic torque response can be obtained by switching only the most optimized voltage vector during torque dynamic condition. The optimized voltage vector can be identified by comparing the rate of change of torque produced between applications of two possible active voltage vectors, according to the flux position. The selection of the optimized voltage vector can be simply implemented by modifying the flux error status before it is being fed to the lookup table. It will be shown that the proposed switching strategy facilitates the DTC to perform under six-step mode to achieve the fastest dynamic torque response. The effectiveness of the proposed dynamic overmodulation to obtain the fast torque response is verified with some experimental results. [ABSTRACT FROM AUTHOR]

A dynamic overmodulation strategy for fast dynamic torque control in direct torque control (DTC)-hysteresis-based induction machine is proposed. The fastest dynamic torque response with a six-step mode can be achieved in the proposed method by switching only the most optimized voltage vector that produces the largest tangential component to the circular flux locus. This paper also discusses the performance of dynamic torque control in basic DTC in order to justify on how the proposed selected voltage vector results in excellent dynamic torque performance. The main benefit of the proposed method is its simplicity, since it only requires a minor modification to the conventional DTC-hysteresis-based structure and does not require a space vector modulator. To verify the feasibility of the proposed dynamic overmodulation strategy, simulation and experimentation, as well as comparison with the conventional DTC scheme, are carried out. Results showed a significant improvement in the dynamic torque response when compared to the conventional DTC-hysteresis-based method. [ABSTRACT FROM PUBLISHER]

This paper presents a new design of the torque and stator flux estimators for Direct Torque control (DTC) for Field Programmable Gate Array (FPGA) implementation, which permit very fast calculations. An alternative variable word-size approach in two's complement fixed-point format is used for the implementation, in order to minimize calculation errors and the hardware resource usage. The simulation results of DTC model in Matlab, which performed double-precision calculations, are used as references to digital computations executed in FPGA implementation. The Hardware-in-the-loop (HIL) method is used to verify the minimal error between Matlab simulation and the experimental results, and thus the well-functionality of the implemented estimators. [ABSTRACT FROM AUTHOR]