隨著電力電子技術的飛速發展，電能轉換器已經應用于市電並網、不間斷供電系統、馬達驅動等很多領域。随着新能源发电的发展和电力传输要求的提高，关于高功率转换器的研究受到越来越多的重视。針對於高壓設備，電能轉換器中的開關需要可以承受相當高的電壓。多階層轉換器為高壓設備提供了重要的解決方案。
本研究製作一部基於分切合整數位控制的多階層模組化雙向轉換器。多階層模組化轉換器廣泛應用於靜態同步補償器、高壓直流輸電、可再生能源發電及電池儲能系統。本電路架構採用分切合整數位控制進行電流追蹤和直流側穩壓及模組電容穩壓。此控制法考量電感值變化和市電諧波的影響，可以實現快速電流追蹤和有效降低輸出電流失真。基於能量守恆定律，決定每相電路中的直流電流和交流電流。採用電荷守恆和分切合整控制技術，達到電路中直流側電容穩壓和平衡及模組電容電壓的穩壓。為了降低輸出電流之連波，本論文對於模組電容穩壓調節因子進行討論。在本論文中，首先介紹多階層模組化雙向轉換器之電路架構，接下來推導電流追蹤和直流側電容穩壓及模組電容穩壓之控製法則。然後是討論轉換器中電路設計和程式流程圖設計。最後，論文將呈現54kw之模擬結果和20kw之實作結果以驗證轉換器之工作原理和控制方法。
關鍵詞：分切合整數位控制、多階層模組化轉換器、電容穩壓。

This paper presents a division-summation (D-Σ) digital control based modular multilevel converter. Modular multilevel converters (MMC) have been applied to static synchronous compensators, high-voltage direct-current transmission, wind/solar power generation and battery storage systems. The D-Σ digital control is adopted to track current reference, balance dc-bus capacitor voltage and regulate cell capacitor voltage. The adopted D-Σ digital control can accommodate wide filter inductance variation and take care of source voltage harmonics to achieve fast tracking response and low-distortion output current for the applications of active and reactive power injection and rectification with power factor correction. Simulated and experimental results obtained from the MMC have verified the analysis and discussion.

TABLE OF CONTENTS

ABSTRACT I
ACKNOWLEDGEMENTS III
NOMENCLATURES IV
LIST OF FIGURES VII
LIST OF TABLES XI
Chapter 1 Introduction 1
1.1 Background 1
1.2 Objectives 2
1.3 Thesis Outline 3
Chapter 2 Configuration and Operational Principle of MMC 4
2.1 Module Configuration and Operation 4
2.2 7-level Modular Multilevel Converter 6
2.3 Operational Principle 7
Chapter 3 Control Strategy for MMC 12
3.1 Modulation Techniques 13
3.2 DC-Bus Capacitor Voltage Regulation 18
3.3 DC-Bus Capacitor Voltage Balancing 20
3.4 Cell-Capacitor Voltage Regulation 23
Chapter 4 Circuit Design of MMC 26
4.1 Cell-Module Circuit 26
4.1.1 Auxiliary Power Supply 26
4.1.2 Voltage Scaling-down Circuit 27
4.1.3 Switching Interlock Circuit 29
4.2 Signal Connection Board 30
4.2.1 Differential Voltage Step-down Circuit 30
4.2.2 Control Circuit of Relay 31
4.3 Control Stage Circuit 33
4.3.1 Grid voltage Feedback Circuit 33
4.3.2 DC-bus Voltage Feedback Circuit 34
4.3.3 Arm Current Feedback Circuit 35
4.3.3 Overvoltage & Overcurrent Protection Circuit 36
Chapter 5 Software Outline for MMC 38
5.1 Structure of Software 38
5.2 Introduction to RX63T 39
5.3 Flowchart of Control Program 40
5.3.1 System Main Program 40
5.3.2 A/D Interrupt Subroutine 41
5.3.3. DC-Bus Capacitor Voltage Balancing Subroutine 42
5.3.4. Cell-capacitor Voltage Regulation Subroutine 43
5.3.5. Circuit Protection Subroutine 45
Chapter 6 Simulated and Experimental Results 46
6.1 Specifications 46
6.2 Simulated Results 47
6.2.1 Pre-charging circuit simulation 47
6.2.2 Control Strategy Simulation 49
6.3 Experimental Results 57
6.3.1 Single-phase MMC 57
6.3.2 Three-phase MMC 59
Chapter 7 Conclusions and Future Work 64
7.1 Conclusions 64
7.2 Future Work 65
References 66
Appendices A Circuit photographs 69

[1] L.Medina, “Design and control of single-phase Modular Multilevel Converter,” Master Thesis, Oviedo, Spain, 2013.
[2] A.Timofejevs, D. Gamboa, “Control of MMC in HVDC applications,” Master Thesis, Aalborg, Denmark, 2013.
[3] J.-S. Lai and F. Z. Peng, "Multilevel converters - A new breed of power converters", IEEE Transactions on Industry Applications, Vol. 32, No. 3, May/June 1996, pp. 509-517.
[4] E. Behrouzian, M. Bongiorno, and H. Z. De La Parra, “An overview of multilevel converter topologies for grid connected applications,” in Proc. 15th EPE Appl. Conf., 2013, pp. 1-10.
[5] S. Kouro, M. Malinowski, et al., “Recent advances and industrial applications of multilevel converters,” IEEE Trans. Ind. Electron., Vol. 57, no. 8, Aug. 2010, pp. 2553-2580.
[6] P. Ladoux, N. Serbia, L. Rubino, and P. Marino, “Comparative study of variant topologies for MMC,” in Proc. Int. Symp. Power Electron., Elect. Drives, Autom. Motion (SPEEDAM), Ischia, Italy, Jun. 2014, pp. 659-664.
[7] M.Carpaneto, M. Marchesoni, and L. Vaccaro, “A new cascaded multilevel converter based on NPC cells,” in Proc. IEEE ISIE, Jun. 2007, pp. 1033-1038.
[8] A. Nabae, I. Takahashi, and H. Akagi, “A new neutral-point-clamped PWM inverter,” IEEE Trans. Ind. Appl., Vol 17, no. 5, September, 1981, pp. 518-523.
[9] J. Rodrigues, S. Bernet, J. O. Pontt and, S. Kouro, "Multilevel voltage sources converter topology for industrial medium voltage drives," IEEE Trans. Industrial Electronics, Vol.54, No. 6, Dec. 2007, pp. 2930-2945.
[10] H. Shaojun, L. Mathe, and R. Teodorescu, "A new method to implement resampled uniform PWM suitable for distributed control of modular multilevel converters," in proc. of IECON 2013 - 39th Annual Conference of the IEEE, 2013, pp. 228-233.
[11] V. Najmi, M. N. Nazir, and R. Burgos, "A new modeling approach for modular multilevel converter (MMC) in D-Q frame" in Proc. of IEEE Applied Power Electronics Conference and Exposition, 2015, pp. 2710-2717.
[12] M. Hagiwara, R. Maeda, and H. Akagi, “Control and analysis of the modular multilevel cascade converter based on double-star chopper-cells (MMCC-DSCC),” IEEE Trans. Power Electronics, Vol. 26, no. 6, Jun. 2011, pp. 1649-1658.
[13] J. Wang, R. Burgos, and D. Boroyevich."Model-predictive control to realize the switching-cycle capacitor voltage control for the modular multilevel converters." in proc. of APEC, 2015, pp. 1512-1519.
[14] T.-F. Wu, C.-H. Chang, L.-C. Lin, Y.-C. Chang and Y.-R. Chang, “Two-phase modulated digital control for three-phase bi-directional inverter with wide inductance variation,” IEEE Trans. on Power Electron., Vol. 28, April 2013, pp. 1598–1607.
[15] T.-F. Wu, C.-H. Chang, L.-C. Lin, G.-R. Yu and Y.-R. Chang, “A D-Σ digital control for three-phase inverter to achieve active and reactive power injection,” IEEE Trans. on Power Electron., Vol. 61, no. 8, Aug. 2014, pp. 3879-3890.
[16] K. Shi, F. Shen, D. Lv, P. Lin, M. Chen, and D. Xu, “A novel start-up scheme for modular multilevel converter,” in Proc. Conf. IEEE Energy Convers. Congr, Expo, 2012, pp. 4180–4187.
[17] Wang, R. Burgos, D. Boroyevic, and B. Wen, “Power-cell switching cycle capacitor voltage control for the modular multilevel converters,” in Proc. IEEE Int. Power Electron. Conf., May 2014, pp. 944–950.
[18] M. Hagiwara, R. Maeda, and H. Akagi, “Control and analysis of the modular multilevel cascade converter based on double-star chopper-cells (MMCC-DSCC),” IEEE Trans. Power Electron., vol. 26, no. 6, pp. 1649– 1658, Jun. 2011.
[19] G. S. Konstantinou and V. G. Agelidis, “Performance evaluation of halfbridge cascaded multilevel converters operated with multicarrier sinusoidal PWM techniques,” in Proc. 4th IEEE ICIEA, 2009, pp. 3399–3404.
[20] L. G. Franquelo, J. Rodriguez, J. I. Leon, S. Kouro, R. Portillo and M. M. Prats, “The age of multilevel converters arrives,” IEEE Trans. Ind. Electron. Magazine, vol. 2, no. 2, pp. 28–39, June 2008.
[21] A. Tsunoda, Y. Hinago, and H. Koizumi, “Level and phase shifted PWM for seven-level switched-capacitor inverter using series/parallel conversion,” IEEE Trans. Ind. Electron., vol. 61, no. 8, pp. 4011–4021, Aug. 2014.
[22] Panagiotis.Asimakopoulos, “Design and control of modular multilevel converter in an active front end application,” Master Thesis, Göteborg, Sweden, 2013.
[23] UC3843 datasheet, Fairchild, 2002.
[24] LOC110 datasheet, IXYS, 2016.
[25] OJE-SS-112HMF datasheet, TE, 2011.
[26] RX63T Group datasheet Rev. 2.00, Renesas, 2013.