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Earlier studies have pointed out the limitations of conventional inverters, especially in high-voltage and high-power applications. In recent years, multilevel inverters are becoming increasingly popular for high-power applications due to their improved harmonic profile and increased power ratings. Several studies have been reported in the literature on multilevel inverters topologies, control techniques,...
Classical direct torque control (DTC) has advantage in absence of coordinate transform and voltage modulator block. However, it may have disadvantage in controlling electromagnetic torque. DTC produces high ripple in electromagnetic torque as it is not directly controlled. High torque ripple causes vibrations to the motor which may lead to component lose, bearing failure or resonance. Thus, Fuzzy...
In the traditional direct torque control (DTC) of induction motor, the low order harmonic component of stator current is very large when the motor is running at low speed. It leads to high torque ripple of motor in low speed. To solve this problem, a new control method has been proposed in this paper. Base on the traditional DTC method, electromagnetic torque and flux models have been analyzed. To...
This paper presents a fuzzy logic controller (FLC) based direct torque control (DTC) scheme for speed control of IM drive over a wide speed range. The FLC is used to adjust the bandwidth of torque hysteresis controller in order to reduce the torque ripple of developed torque and hence to improve motor dynamic response. The effects of torque hysteresis band amplitude on the torque ripple of IM are...
In this paper, we present a wireless instantaneous torque measurement system based on MEMS accelerometers and high frequency RF transmitter. We develop this system for instantaneous torque and speed measurement on machine rotary shafts. Real time data are transmitted to the DSP board that is used to implement traditional vector control of an induction motor. It can be applied to any rotating system...
A sliding mode controller for induction motor (IM) is investigated in this paper. It features in very low flux and torque ripple. In order to guarantee electromagnetic torque and stator flux to track its reference signal strictly, the electromagnetic torque sliding mode variable and stator flux sliding mode variable were selected separately. Furthermore, a robust stator flux observer is designed for...
Normal direct torque control have the problem of big electricity and torque ripple in low speed, a new control method was presented in this paper in order to solve this problem. We use discrete duty ratio control technology in high region while intelligent direct torque control is used for the low speed region control. Simulation and experiment result show that new method is more effective than traditional...
A novel direct torque control strategy, using genetic algorithm on-line to optimize the fuzzy PI controller, is proposed. In this approach, according to speed error and its first time derivative, the proportional coefficient Kp and integral coefficient Ki can be on-line adjusted by fuzzy adaptive PI speed regulation, and the fuzzy logic adapter parameters are optimized by genetic algorithm to improve...
A new energy-saving scheme of voltage-regulation control for induction motors at periodically varying loads with almost constant speed is presented in this paper. The energy-saving principle, control strategies, triggering mode of SCRs are studied. Based on the analysis of the current oscillation in the voltage-regulation by 3-phase thyristors with the synchronous voltage signal, the solution to current...
A novel method of stator resistance identification based on wavelet network is presented and the determination of wavelet network structure is discussed in order to improve the low-speed dynamic performance of induction motor in direct torque control. The current error and the change in the current error is the inputs of the wavelet network and the stator resistance error is the output of the wavelet...
In this paper, an approach to DTC control scheme for induction machine is developed which makes DTC more applicable while it has lower torque ripple, lower flux ripple and almost fixed switching frequency rather than other DTC methods. Comparisons between simulation and practical results confirm that not any noticeable advantage of other developed DTCs is lost while it becomes more applicable. The...
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