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MINISTRY OF EDUCATION & TRAINING - MINISTRY OF TRANSPORT HO CHI MINH CITY UNIVERSITY OF TRANSPORT PHAM THUY NGOC ADAPTIVE CONTROL FOR SIX PHASE INDUCTION MOTOR DRIVES Major: Automation and Control Engineering Code: 9520216 Ph.D THESIS SUMMARY TP Ho Chi Minh- 2019 The Thesis was completed at Ho Chi Minh City University of Transport Science instructor 1: Assoc.Prof Nguyen Huu Khuong Science instructor 2: PhD Tran Thanh Vu Reviewer 1: Reviewer 2: Reviewer 3: INTRODUCTION Introduction Automatic control for the three phase induction motor drives has always been one of the great interested areas from scientists in order to improve the quality and performance of the electric drives Especially, in the conditions the hardware devices supporting for control system are increasingly advanced such as memory capacity, processing speed, I/O ports number, etc These also make increase the requirements when designing the optimized control systems In recent decades, to meet the increasing requirements for the electric drives using AC motors such as: improving control quality and energy save efficiency, safe operation, increasing fault tolerance of the system, Scientists have studied to control AC motor from many different approaches In particular, there are two main approaches that are most focused on research: The first approach is the improvement of hardware such as semiconductor components, inverter structure (multi-level inverter) and increase in the phase number of machine (multi-phase motor) The second approach involves the development of control techniques With the rapid development of microprocessor technology and DSP digital control, These improved devices have the high computing speed, these are one of the important contributions to enable scientists to develop complex control algorithms but providing better control quality, more reliable for the AC motor drives In the first approach, multi-phase motors have been focused on research and development in recent decades due to outstanding advantages, higher reliability in the whole system than the traditional three-phase motor Among the multi-phase motors that have been focused on research, the six-phase induction motor (SPIM) is one of the most common types of multi-phase induction motors The second approach when researching and developing SPIM drive control techniques, there are some problems: The first problem is related to the unbalanced current between the three phase windings (This problem of asymmetry between the stator three-phase windings has been discussed and addressed also quite effectively in [28]) The second problem related to common mode voltage: Some practical solutions such as using the common mode current filter connected in series with the inverter or using hardware circuits in order to compensate the common mode voltage However, they are expensive [32-33] Therefore, simpler solutions using PWM techniques to reduce common mode voltage and low level stator current harmonic components are increasingly being studied The third issue relates to the field of precise speed control of SPIM drives, the control quality and performance of SPIM drives are highly dependent on the accurate information of motor parameters and nonlinear coupling of the machine, so it is difficult to provide satisfactory control quality for high quality SPIM drive systems Especially when operating in the low frequency area, the parameter sensitivity issues and nonlinear coupling are more pronounced and these make the control quality of the drives cannot be met Nonlinear and intelligent control techniques have been researched and developed recently to overcome these issue On the other hand, in SPIM drives that require high control quality, limiting and reducing the number of the sensors have received great attention from scientists around the world in the past few decades [54-62] Reviewing and updating of the publications in this area shows a huge concentration of research, an increase in both the number and quality of published works in the field of speed sensorless control shows the efficiency and inevitable replacement trend as well as the sustainable development for speed sensorless vector control of AC induction motor drives With the desire to provide the effective solutions to improve the quality of the automatic control system for sensorless vector control of SPIM drives in low speed operating range - limited area of control and speed estimation_ to enhance the practical application of the six-phase drives in practice The stability control issues, improving the quality of SPIM control by keeping non-linear components to control precisely, following the given targets with minimum errors is a requirement For this purpose, the author has chosen and researched the subject: "Adaptive control for the six-phase induction motor drives" The sensorless vector control of six-phase induction motor drives and the problems In the last few decades, The attention for the multi-phase induction motor drives has increased dramatically In order to improve the quality of vector control for SPIM drives, the PID control was gradually replaced by nonlinear control techniques However, due to SPIM's non-linear coupling structure, as well as machine parameter uncertainty and external load disturbances, the application of independent non-linear control methods has not fully overcome the limitations of the non-linear drives Therefore, the need for a robust, stable control system and always maintaining the desired control effect are still a challenge and the same time, it is also a motivation for scientists to continue researching, improving the solutions to further optimize the controllers for the SPIM drives In addition to improving and optimizing control techniques, we also realize that the robustness, reliability, quality and of the SPIM vector control system are in part dependent on the machine parametric identifiers and rotor speed observer In the last few decades the control of SPIM drives without the use of speed sensors mounted on motor shafts has been focused on research and development These strategies are quite successful in the high and medium speed range However, maintaining the accurate speed estimation at low speeds and zero speeds are still a major challenge, so studies to improve the quality of speed observers especially at zero and low speed regions has received great attention and been focusing on recent developments PHD thesis objectives Building adaptive control system for sensorless vector control of the SPIM drives based on adaptive control, nonlinear control and intelligent control techniques to improve control quality and practical applicability of the SPIM drives The common mode voltage reduction algorithms for SPIM drives has also been developed to further improve the quality and performance of the SPIM drive system Specific objectives: To achieve objectives of the thesis, specific objectives are set as follows: - Building an adaptive speed observer using intelligent control (neural networks) and sliding mode control for sensorless vector control of SPIM drives to improve the control quality of the SPIM drives, especially at zero and low speed regions - Building a novel non-linear control structure to enhance the control quality of SPIM drives - Building the common mode voltage reduction algorithms for six-phase voltage source inverters SPVSI - Building the simulation models and conducting the surveys for SPIM drive using the proposed schemes on Matlab-Simulink software - Assessing the quality and effectiveness of SPIM drive using the proposed control and observation schemes Scope of the thesis - Researching the mathematical model of SPIM and SPIM drives - Researching the IFOC control techniques for SPIM drives - Researching the sensorless techniques based on stator current reference model - Research and applying the adaptive control, intelligent control, sliding model into the controllers, parameter identifiers, speed observers of the sensorless vector control of SPIM drives Structure of the thesis The thesis structure includes chapters Chapter presents the mathematical model of SPIM and SPIM drives, the sensorless vector control of SPIM drives and the problems The common mode voltage reduction algorithms for SPVSI are described in Chapter Chapter introduces the novel BS_PCH control structure for the vector control of SPIM drives Chapter presents an adaptive speed observer based on stator current reference model using NN and SM In Chapter 5, the application of SPIM drive using the proposed control and observation schemes, the common mode voltage reduction algorithm in the field of transportation (electric propulsion system in Electric Vehicle) CHAPTER 1: THE MATHEMATICAL MODEL OF SPIM DRIVES AND SENSORLESS VECTOR CONTROL OF SPIM DRIVE 1.1 The mathematical model of SPIM drives 1.1.1 The mathematical model of SPIM The system includes the six phase induction motor fed by a six-phase Voltage Source Inverter (SPVSI) and a DC link A diagram of the SPIMD is illustrated as in Fig.1 In this part, the Vector Space Decomposition (VSD) technique also has applied, the original six-dimensional space of the machine is transformed into three two-dimensional orthogonal subspaces in the stationary reference frame (α-β), ( x - y) and (zl -z2) This transformation is obtained by means of x transformation matrix: T6 =  1      1 3  0  1  0 2 - 2 2 - 2 2  0   -1   0   -1  0   (1.1) The math equations of SPIM be written in the stationary reference frame as  Vsα   R s +pLs V    sβ  =     pL m       -ωr L m R s +pLs ωr L m pL m pL m R r +pL r -ωr L m  isα  pL m   iβ  ωr L r  i rα    R r +pL r  i rβ  (1.2) For control purposes, a transformation matrix must be used to represent the stationary reference coordinates (α-β) in the dynamic (dq) rotating reference coordinates This matrix is given:  cos  δ r  sin  δ r   T2 =   -sin  δ r  cos  δ r   (1.3) 1.1.2 The mathematical model of SPIM drives The detailed diagram of SPIM drive is shown in Figure 1.1 According to the rotor flux orientation, that is ψrq =0; ψr =ψrd , The electromagnetic torque can be expressed in a dq rotating reference frame: Lm Lr Te = P ψrdisq (1.4) the mathematical model of SPIM in dq rotating coordinate system can be expressed as follows:  di sd  Ls dt = -ai sd + Ls ωei sq + bR r ψ rd + cu sd   L di sq = -ai + L ω i +b ω ψ + cu s sq s e sd r e rd sq  dt    dω r = P δσLs (ψ rd i sq ) - TL - Bω r  dt J J  dψ L  rd = m i sd ψ rd τr τr   dt (1.5) Vd/2 DC Link Vd O a b A B c C Vd/2 + + VAs Vas _ + Vbs _ Vcs _ + + + VBs _ _ VCs _ N1 N2 Fig 1: Diagram of SPIM drives 1.2 the problems and the proposed solutions for sensorless vector control of SPIM drives As as analyzed above, the effectiveness of the traditional FOC strategy using PID controllers is diminished due to SPIM parameter uncertainty and load noise Nonlinear control techniques have been researched, developed and applied in new FOC strategies to replace traditional PID control Sensorless control techniques for SPIM drives have been extensively researched and developed over the past two decades However, the speed estimating performance at zero and low speed regions remains a major challenge Many scientists have researched to improve the efficiency of speed observers for sensorless control at this area In addition, traditional PWM methods for six-phase voltage source inverters used in SPIM drives often cause high common mode voltage Therefore, the development of common mode voltage reduction solutions is a feasible research direction and it has attracted much attention of scientists in recent times 1.3 Conclusion In this chapter, SPIM drive's mathematical model is built on vector space decomposition to match the proposed and developed control techniques in the thesis Details in the vector control techniques and the remaining issues are also presented in this chapter CHAPTER 2: COMMON MODE VOLTAGE REDUCTION TECHNIQUES FOR SIX PHASE VOLTGE SOURCE INVERTER 2.1 Introdution This chapter proposes the novel carrier pulse modulation techniques that reduces common mode voltage (RCMV) for sixphase voltage source inverter (SPVSI) Reducing common mode voltage has been done easily by the carrier PWM techniques The results of the research presented in this chapter are published in the articles [6], [7], [15] belong the list of publications 2.2 Kỹ thuật điều khiển PWM giảm CMV cho BNL pha Vref Vrefa e-jπ/6 VrefA sa sb sc CBPWM GENERATOR I Vrefb Vrefc VrefB VrefC sA sB sC CBPWM GENERATOR II Fig 1: CBPWM technique for SPIM drives Fig 2.1 describes the principle of implementing CBPWM for 6P_VSI The configuration of 6P_VSI is not symmetrical with two neutral points of two 3P_VSI I and II isolation VcomI, VcomI for 6P_VSI is determined: va0 + v b0 + vc0 Vd   vcomI =  vA0 + vB0 + vC0 Vd v =  comII Common mode voltage of SPVSI is determined as in [136]: v + vcomII va0 + vb0 + vc0 + vA0 + vB0 + vC0 Vd vcom = comI = (2.1) (2.2) 2.3 RCMV 4S-CBPWM techniques for SPVSI 2.3.1 RCMV 4S-CBPWM technique with average common mode voltage VcomMid All common mode function values are set up individually and they allow reducing Vcom The common mode function for two VSI I and II performs to reduce common mode voltage by the formula: V vcomI = vcomMidI = MidI d V vcomII = vcomMidII = MidII d (2.3) Average value of common mode voltage of 6P_VSI: V vcom = vcomMid =  MidI+MidII  d (2.4) 2.3.2 RCMV 4S-CBPWM technique with the minimum common mode voltage Vcomopt We can choose the optimal and minimum common mode voltage in the equation (22) as follows: VcomOpt=Min(Vcom) SPVSI using 4S-RCMV PWM technique with the minimum common mode voltage VcomOpt reaches the minimum average common mode voltage value Find the common mode function for VSI I and II when the function VcomOpt = can be implemented by giving the parameter k, 0