Predictive Control of Three Phase AC/DC Converters

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2 CHAPTER 1. INTRODUCTION Vector Based Controllers Scalar Based Controllers VOC DPC DPC-SVM Predictive Control VFOC VF-DPC VF-DPC-SVM Figure 1.1: Predictive control implementation in conjunction with main control methods used for VSC Most popular control method is VOC [1], [2], [3], [4], [5], [8]. It gives high dynamic and static performance via internal current control loops. All equations are transformed into new, rotating synchronously with line voltage space vector coordinates, which allows to fully use advantages of linear PI controllers. To improve robustness on line voltage distortions, a Virtual Flux (VF) [9], [10] was introduced. Another method, which was adopted from induction motor controls is DPC (Direct Power Control) [1], [6], [9], [11]. This control does not use any coordinate transformations, because it operates directly on instantaneous active and reactive powers. High dynamic is guaranteed by hysteresis controllers and look-up table. However, high sampling frequency requirement and variable switching frequency are the main drawbacks of the look-up table based DPC method. Therefore, to overcome that disadvantages, a Space Vector Modulator (SVM) was introduced to DPC structure, giving new method called Direct Power Control with Space Vector Modulator [12], [13]. DPC-SVM joins important advantages of SVM [14] (e.g. constant switching frequency, unipolar voltage switchings, low current distortions) with DPC features (e.g. simple and robust structure, lack of internal current control loops, good dynamics, etc.). However, in spite of mentioned advantages DPC-SVM dynamic still depends on the quality of the applied PI controller design algorithms. Table 1.1 presents main features of described AC voltage sensorless control methods. Another group of VSC controls is predictive control. It is very wide class of controllers, that have been adopted for power electronics. The main characteristic of predictive control is use of model of the system for the prediction of the controlled variables. Next, predefined optimization criterion selects appropriate control set. The proposed classification for different control methods is shown in Fig. 1.2.
Based Trajectory Based Deadbeat Control Hysteresis Predictive Control (MPC) Model 3 Feature VOC DPC DPC-SVM VFOC VF-DPC VF-DPC-SVM Switching Constant Variable Constant frequency SVM blocks Yes No Yes Coord. trans. Yes (two) No Yes (one) Direct control of: Line currents Line powers Line powers Estimation of: Virtual Flux Virtual Flux Virtual Flux and Powers and Powers Current ripple Low High Low Sampling Low High Low frequency Line voltage Yes Yes Yes sensorless Table 1.1: Comparison of classical AC voltage sensorless control methods Predictive Control with control MPC finite Figure 1.2: Classification of predictive control methods used in power electronics set control with set continous MPC Hysteresis based predictive control tries to keep controlled variables between hysteresis bands. Using predictive current control, switching instants can be determined by error boundaries. When referenced vector touches the controller band then prediction and optimization of next switching state occurs [15]. The principle of trajectory based predictive control is to force the system’s variables onto precalculated trajectories. For example direct self control [16], direct mean torque control [17], direct torque control [18] may be included to this category. A well known type of predictive controller is the deadbeat controller. It uses the model of the system to calculate reference voltage vector, in order to set the controlled variable error to zero within one sampling time. Next, the referenced voltage vector is realized by modulator. It has been applied for current con-
Page 1: WARSAW UNIVERSITY OF TECHNOLOGY Fac
Page 5 and 6: Contents Contents i 1 Introduction
Page 7: CONTENTS iii List of Symbols and Ab
Page 11: Chapter 1 Introduction AC/DC Voltag
Page 15 and 16: 5 which properties are deteriorated
Page 17 and 18: Chapter 2 Voltage Source Converter
Page 19 and 20: (Sa=1, Sc=0) UP2 (Sa=1, UP1 Sb=1, S
Page 21 and 22: IL UL jωLIL UL jωLIL 2.2. MATHEMA
Page 23 and 24: ILα 1 sL+RSα - ULα 32IDC 1 sCUDC
Page 25: 2.3. SUMMARY 15 2.3 Summary In this
Page 28 and 29: Iqref Idref ILq ILd ILq φ uLab UDC
Page 30 and 31: UDC Filter 20 CHAPTER 3. CONTROL ST
Page 32 and 33: Qref dP dQ uLab UDC Sabc 22 CHAPTER
Page 34 and 35: 24 CHAPTER 3. CONTROL STRATEGIES FO
Page 36 and 37: Qref Pref uLab UDC Sabc 26 CHAPTER
Page 38 and 39: UDC Filter 28 CHAPTER 3. CONTROL ST
Page 40 and 41: ILq φ ωL 30 CHAPTER 3. CONTROL ST
Page 42 and 43: Lα 32 CHAPTER 3. CONTROL STRATEGIE
Page 51 and 52: Chapter 4 Predictive Direct Power C
Page 53 and 54: 4.3. VARIABLE SWITCHING FREQUENCY P
Page 55 and 56: UPdqUDC Qref UDCSabc uLab iLab 4.3.
Page 57 and 58: UPdqUDC UDCSabc uLab iLab 4.4. CURR
Page 59 and 60: UPdqUDC Qref Pref UDCSabc uLab iLab
Page 61 and 62: 4.6. CONSTANT SWITCHING FREQUENCY P
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PP1 fq1 fq2 PP4 PP5 PP6 PP3 fp3 fp3
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Sb Sc Sa Sb Sa Sc Sb Sa 4.6. CONSTA
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fqi fpi Qref Sabc 4.6. CONSTANT SWI
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4.7. VF BASED CSF - PREDICTIVE DIRE
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Qref fpi Sabc iLab 4.7. VF BASED CS
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4.8. SIMULATION RESULTS 63 200 150
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4.8. SIMULATION RESULTS 67 Mag (% o
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4.9. SUMMARY 75 Control Method t se
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Chapter 5 Investigations of Control
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5.1. ROBUSTNESS TO PARAMETERS MISMA
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Sabc UDC UPαβ UPαβ Lest Lest UP
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5.4. LINE VOLTAGE DISTURBANCES 83 (
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5.4. LINE VOLTAGE DISTURBANCES 85 (
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5.4. LINE VOLTAGE DISTURBANCES 87 C
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Chapter 6 Experimental Study Experi
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6.1. STEADY STATE OPERATION 91 (a)
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6.1. STEADY STATE OPERATION 93 Cont
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6.2. TRANSIENT OPERATION 95 (a) ST-
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6.3. OPERATION WITH LOW SWITCHING F
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6.4. SUMMARY 107 Control Method t s
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110 CHAPTER 7. SUMMARY AND FINAL CO
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112 BIBLIOGRAPHY [11] K. Hyosung an
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114 BIBLIOGRAPHY [38] A. Nasiri,
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116 BIBLIOGRAPHY [66] F. Morel, J.
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118 BIBLIOGRAPHY 13. A. Lopez de He
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Appendix A Coordinate transformatio
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q β A.2. ROTATING SYSTEM 123 A.2 R
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Appendix B Predictive Current Contr
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∆ILαβP6 ∆ILαβP5 Figure B.2:
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Figure B.4: Vector diagram of predi
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132 APPENDIX C. PREDICTIVE DIRECT P
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List of Symbols and Abbreviations S
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137 Symbols Description Definition
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List of Figures 1.1 Conjunction bet
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LIST OF FIGURES 141 5.3 Line curren
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LIST OF TABLES 143 B.2 An example o
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Predictive Control of Three Phase AC/DC Converters

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