An Optimized Switching Strategy for Quick Dynamic Torque Control in DTC-Hysteresis-Based Induction Machines

Abstract

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 DTChysteresis-based method.

An Improved FPGA Implementation of Direct Torque Control for Induction Machines

“…If the band is set to be too small, the overshoot of the torque beyond the hysteresis band could cause a reverse active voltage vector selection, instead of a zero voltage vector selection. The selection of the reverse voltage vector causes the torque to decrease rapidly and as a result the torque ripple increases [8,18,[21][22][23][24]. This situation is illustrated in Fig.…”

“…Thus, the sampling period to execute the overall DTC algorithms can be minimized to the output torque ripple [16][17][18]. However, the combination of controllers increases the cost and complexity of the interfacing circuit, and is not a practical solution for commercialization purposes.…”

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“…Only eight space vector voltage can be chosen lead to the ripple of stator flux and torque in this control. Thus, application of PMSM in high-precision occasion is limited [1].…”

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“…Some applications for these new converters include industrial drives [5], flexible ac transmission systems (FACTS) [6]- [8], and vehicle propulsions [9], [10]. One area where multilevel inverters are particularly suitable is that of renewable photovoltaic energy where efficiency and power quality are of great concern to researchers [11].…”