Torque Ripple Reduction and Flux-droop Minimization of DTC with Improved Interleaving CSFTC of IM fed by Three-level NPC Inverter
- 주제(키워드) Constant switching frequency torque controller , direct torque control , induction motor , three-level neutral-point clamped inverter
- 발행기관 아주대학교
- 지도교수 Prof. Kyo-Beum Lee
- 발행년도 2020
- 학위수여년월 2020. 8
- 학위명 석사
- 학과 및 전공 일반대학원 전자공학과
- 실제URI http://www.dcollection.net/handler/ajou/000000030136
- 본문언어 영어
- 저작권 아주대학교 논문은 저작권에 의해 보호받습니다.
초록/요약
Among advanced AC motor control techniques is direct torque control (DTC), which is known for its fast decoupled control of both torque and flux. This great feature owning to its basic control structure that needs only three main components; torque and flux hysteresis, switching table and torque and flux calculation block. Therefore, unlike field oriented control (FOC), it does not require any modulation function or reference frame transformation. However, when the DTC technique is used to drive an induction motor (IM), there is a number of drawbacks including large torque and flux ripples, variable switching frequency for the inverter, and drop of the stator flux especially when the IM operates in the low-speed region. These problems are associated with the usage of the torque hysteresis controller (THC). To reduce the torque and flux ripples, the basic two-level inverter needs to be replaced by high level inverter and among these multilevel inverter is the well know three-level neutral-point clamped (NPC) inverter. In the case of having low and variable switching frequency for the inverter will create high torque and flux ripples. In addition, the issue related with unregulated stator flux coming about because of running the IM in the low-speed region creates high stator current distortion that thus debases the heartiness of the traditional DTC. To consider a solution for these issues, interleaving constant switching frequency torque controller based DTC (CSFTC-DTC) was executed. The interleaving CSFTC-DTC was intended to build the duration of the applied dynamic voltage vector and shorten the length of the applied zero vectors to improve the operation of the IM drives particularly in the low-speed region. Despite the fact that the conventional interleaving CSFTC-DTC takes care of the issue of the unregulated stator flux decreases the total harmonics distortion (THD) of the stator current, it delivers enormous torque and flux ripples—the primary drawback of traditional DTC. In this thesis, modified 5-level interleaving CSFTC-DTC is proposed to shorten the duration of the applied vectors of the three-level NPC inverter to restrain the impact of the enormous duration of the applied vectors on stator flux and torque ripples. The simulation and implementation results introduced approve the adequacy of the proposed method over the conventional interleaving CSFTC-DTC.
more목차
CHAPTER I. INTRODUCTION 1
CHAPTER II. SYSTEM MODELLING 4
2.1 INDUCTION MOTOR MODEL 4
2.2 THREE-LEVEL NPC INVERTER 4
2.3 DTC FOR THREE-LEVEL NPC INVERTER 6
2.3.1 TORQUE AND FLUX CALCULATION 7
2.3.2 TORQUE HYSTERESIS CONTROLLER 8
CHAPTER III. CSFTC FOR THREE-LEVEL NPC INVERTER 10
3.1 CONVENTIONAL INTERLEAVING CSFTC 11
3.2 PROPOSED INTERLEAVING CSFTC 13
CHAPTER IV. RESULTS 15
4.1 SIMULATION RESULTS 15
4.1.1 LOW-SPEED OPERATION 16
4.1.2 MEDIUM AND HIGH-SPEED OPERATION 17
4.2 EXPERIMENTAL VALIDATION 19
4.2.1 STEADY-STATE OPERATION 20
4.2.2 TRANSIENT-STATE OPERATION 22
4.3 SUMMARY OF RESULTS 24
CHAPTER V. CONCLUSION 26
REFERENCES 27
