摘要
标准化模块的串并联组合系统是电力电子系统集成的一个重要研究内容,其优点是可以降低系统的开发难度、简化系统热设计、提高系统可靠性、降低开发成本、缩短研发周期。根据联结方式的不同,串并联组合系统可以分为以下四类:输入并联输出并联(IPOP)、输入并联输出串联(IPOS)、输入串联输出并联(ISOP)、输入串联输出串联(ISOS)。按照能量变换形式,标准化模块可分为DC/DC变换器、DC/AC逆变器、AC/DC整流器和AC/AC变频器四大类。本文主要研究以DC/AC逆变器为基本模块的IPOP和ISOS逆变器组合系统,其中前者适用于UPS以及航空静止变流器等系统中,后者适用于输入电压和输出电压均较高的场合。
本文针对串并联逆变器组合系统提出了一种通用控制策略,根据输入输出端功率都需达到均衡的原则,将控制策略分为输出端的控制策略和复合式的控制策略。对于输入并联型逆变器组合系统,可以考虑采用输出端的控制策略以及复合式的控制策略,前者更加简单。而对于输入串联型逆变器组合系统而言,采用输出端的控制策略不能保证系统的稳定运行,故需采用复合式的控制策略,即在控制输入均流/均压的同时,控制输出电流/电压的幅值或相位相同。
对于IPOP逆变器组合系统,原有的一种平均电流分布式并联控制方案通过对电压基准求同步和电流给定取平均实现了输出均流控制,由于系统中各模块采用分布式结构,所以易实现热插拔和冗余控制。然而,该方案存在输出外特性较差的缺陷,本文针对这一点提出引入负载电流前馈的方案,并将负载电流前馈点置于电流给定平均点之前时,作平均的将仍是原方案中的电感电流给定信号。这种方案在保留原方案的输出限流功能和均流效果不变的同时,可大大改善模块及系统的输出外特性。进一步的,本文从输出外特性与输出环流两个方面对原方案和改进方案进行详细对比分析,并从理论分析及相量的角度指出两种方案中影响环流的两个主要因素:逆变器之间电流放大倍数KI和输出滤波电容Cf的差异。前者的差异同时引起有功环流和无功环流,而后者的差异只引起无功环流。当各模块的KI和Cf均相互匹配时,便可实现系统输出均流。仿真及实验结果均验证了以上理论分析的正确性,研制的样机亦同时实现了改进方案下IPOP系统的热插拔及冗余控制。
对于ISOS逆变器组合系统,其控制目标是要实现系统的输入均压和输出均压。本文首先揭示输入均压与输出均压的关系,即:如果控制各模块输出均压,则可实现各模块输入均压,但不能保证系统稳定工作;如果控制各模块输入均压,则只能保证各模块输出有功功率的均衡,而无功功率未必均衡,也就不能保证输出均压;如果在控制系统输入均压的基础上,同时控制各模块输出电压的幅值或相位相同,则可实现各模块输出均压,这就是复合式控制策略。进一步的,本文就复合式控制策略提出一种具体实现方案,即输入均压结合输出同角度的控制策略,其控制环路包含输入均压环、输出电压环、各模块的电流内环。由于电流内环采用电容电流反馈,实现了输出电压相位相同,从而又在输入均压控制的配合下保证了输出均压。本文还讨论了一种电感电流反馈的三环控制策略,它虽也能实现系统的稳定工作和输入均压,但要在输出滤波电容匹配时才能实现输出均压,这与输入均压结合输出同角度控制策略的无条件实现输出均压相比较佐证了后者的优越性。本文还进一步分析了系统在采用输入均压结合输出同角度控制策略时输入均压环与输出电压闭环之间的解耦关系,并对两者分别进行了环路的参数设计。
Series-parallel power conversion systems, in which multiple standardized converter modules are connected in series or parallel at the output and input sides, can be classified into four possible architectures on the basis of the connection forms, namely, input-parallel-output-parallel (IPOP), input-parallel-output-series (IPOS), input-series-output-parallel (ISOP), and input-series-output-series (ISOS). The advantages of systems constructed from connecting multiple converter modules include ease of thermal design, increased overall system reliability, shortened design process and lowered cost for the system; improved system reliability, and ease of expansion of power system capability. The standardized converter modules include four possible kinds, i.e., dc/dc converter, dc/ac inverter, ac/dc rectifier, and ac/ac cycloconverter. This dissertation focuses on the control of IPOP and ISOS dc/ac inverter systems. IPOP inverter system is suitable for the high output current applications such as UPS and aviation static inverter, while ISOS inverter system is suitable for high input voltage and high output voltage applications.
A general control strategy is proposed for the series-parallel connected inverters system in this dissertation. In light of the power balance of both the input and the output sides, the general control strategy can be divided into two kinds: the strategy of controlling the output and the compound strategy. For the input-parallel inverters system, the strategy of controlling the output and the compound strategy can both be considered and the former is simpler. However, for the input-series inverters system, the stable operation of the system can not be ensured if the strategy of controlling the output is employed. So the compound method should be adopted. That is, controlling ICS or IVS as well as controlling the magnitude or phase of output current or output voltage to be equal.
In the case of the IPOP inverters system, a distributed control strategy based on average current control has been proposed to obtain output current sharing by synchronizing the voltage reference and averaging the current reference. In this method the instantaneous current sharing is acquired with simple circuit, and hot swap and redundancy are easy to achieve. While the inductor-current feedback control is employed in this method, the output characteristics are poor. In this dissertation, the load current feed-forward control is introduced into the above average current control method and it is located before the point of averaging current reference. As a result, the output characteristics of each module and the whole system are improved, and meanwhile, the functions of output current limiting and the effect of current sharing are kept as the original method. Then, the output characteristics and circulating current between the original and improved methods are compared, and what’s more, by theoretical and phasor means, the dissertation points out two key factors, namely the difference of KI and the difference of Cf of the inverter modules operating in parallel, determine the circulating current under both the two strategies. The difference of KI causes real and reactive circulating current, and the difference of Cf only results in the reactive circulating current. The output current sharing will be implemented only when KI and Cf of all the modules are both matched. Finally, the simulation and experimental results are presented to verify the effectiveness of the improved method, and the prototype is also achieve hot swap and redundancy.
The control objective of the ISOS inverter system is to achieve input voltage sharing (IVS) and output voltage sharing (OVS) of the constituent modules. This dissertation firstly reveals the relationship of IVS and OVS. If OVS is achieved, so is IVS, but the controlling the output voltage of the modules to achieve OVS is not stable. If IVS is achieved, OVS is not ensured, it is because only the output real powers of the modules are balanced, but the output reactive powers of the modules are not always balanced. OVS can be achieved by controlling the magnitude or phase of output voltage to be equal based on controlling IVS. Moreover, this dissertation proposed a practical implementation of the compound strategy, i.e., the method of IVS combined with the same output voltage angle. The compound strategy includes IVS loop, system output voltage loop, and current loop of each module. In the above strategy, the capacitor-current feedback control is introduced to accomplish the same phase of output voltage of all modules. And then combined with controlling IVS, OVS is achieved. Furthermore, this dissertation also proposes another three-loop strategy based on the inductor-current feedback control which can realize IVS but can reach OVS only when the output filter capacitors of all the modules are matched. The defect of this method demonstrates the superiority of aforementioned three-loop strategy based on the capacitor-current feedback control which can obtain OVS unconditionally. Finally, the decoupling relationship between IVS loop and output voltage loop is analyzed and the design of two control loops is also presented.
引文
[1]丁道宏.电力电子技术.北京:航空工业出版社, 1992.
[2] Lee F C, Peng D. Power electronics building block and system integration. Proc. IEEE IPEMC, 2000: 1-8.
[3] Blaabjerg F, Consoli A, Ferreira J A, and et al. The future of electronic power processing and conversion. IEEE Trans. on Industry Applications, 2005, 41(1): 3-8.
[4] Ohashi H. Power electronics innovation with next generation advanced power devices. Proc. IEEE INTELEC, 2003: 9-13.
[5] Van Wyk J D, Lee F C. Power electronics technology at the dawn of the new millennium-status and future. Proc. IEEE PESC, 1999: 3-12.
[6] Van Wyk J D, Lee F C, Boroyevich D. Power electronics technology: present trends and future developments. in Scanning the Issue, Proceedings of the IEEE, 2001, 89(6): 799-802.
[7] Dai H, Xing K, Lee F C. Inverstigation of soft-switching techniques for power electronics building blocks (PEBB). Proc. IEEE APEC, 1998: 633-639.
[8] Xing K. Modeling, analysis, and design of distributed power electronics system based on building block concept. Ph. D. Dissertation. Center for Power Electronics Systems, 1999.
[9] Lee F C, Boroyevich D, Xing K, et al. PEBBs and system integration at Virginia Power Electronics Center, Integrated power electronics module-a building block concept for system integration. Proc. CPES, 2000: 1-4.
[10] Lee F C, Van Wyk J D, Liang Z X, et al. An integrated power electronics modular approach: concept and implementation. Proc. IEEE IPEMC, 2004: 1-13.
[11]陈文洁,杨旭,杨拴科,等.分立元件构成的电力电子集成功率模块的设计.中国电机工程学报, 2003, 23(12): 104-110.
[12]王兆安,杨旭,王晓宝.电力电子集成技术的现状及发展方向.电力电子技术, 2003, 37(5): 90-94.
[13]陈桥梁,杨旭,王兆安,等.基于电力电子集成技术的开关电源模块研究.电力电子技术, 2004, 38(2): 51-53.
[14]顾亦磊,汤建新,吕征宇,等.电力电子系统集成技术发展的若干新思路.电力电子技术, 2005, 39(6): 141-144.
[15]王兆安,陈桥梁.集成化是电力电子技术发展的趋势.变流技术与电力牵引, 2006, 1(1): 2-6.
[16]钱照明,张军明,谢小高,等.电力电子系统集成研究进展与现状.电工技术学报, 2006, 21(3): 1-14.
[17]张军明.中功率DC/DC变流器模块标准化若干关键问题研究, [博士学位论文],杭州:浙江大学, 2004.
[18] Zhang J, Xie X, Jiao D, et al. Stability problems and input impedance improvement for cascaded power electronic systems. Proc. IEEE APEC, 2004: 1018-1024.
[19] Zhang J, Xie X, Wu X, et al. Comparison study of phase-shifted full bridge ZVS converters. Proc. IEEE PESC, 2004: 533-539.
[20] Chen Q, Wang R, Yang X. Research on Hybrid IPEMs for Front-end Converter in Distributed Power system. Proc. IEEE PESC, 2005: 1756-1760.
[21] Zhang J, Xie X, Wu X, et al. A novel zero-current-transition full bridge dc/dc converter. IEEE Trans. on Power Electronics, 2006, 21(2): 354-360.
[22]王建冈,阮新波,吴伟,等.倒装芯片集成电力电子模块.中国电机工程学报, 2005, 25(17): 32-36.
[23] Ayyanar R, Giri R, Mohan N. Active input-voltage and load-current sharing in input-series and output-parallel connected modular dc-dc converters using dynamic input-voltage reference scheme. IEEE Trans. on Power Electronics, 2004, 19(6): 1462-1473.
[24] Chen W, Ruan X. Modularization structure for series-parallel connected converters. Proc. IEEE APEC, 2008: 1531-1535.
[25] Tuladhar A. Advanced control techniques for parallel inverter operation without control interconnections. Ph. D. Dissertation. The University of British Columbia, 2000.
[26] Lin X, Feng F, Duan S, et al. The droop characteristic decoupling control of parallel connected UPS with no control interconnection. Proc. IEEE IEMDC, 2003: 1777-1780.
[27] De Brabandere K, Bolsens B, Van den Keybus J, et al. A Voltage and Frequency Droop Control Method for Parallel Inverters. IEEE Trans. on Power Electronics, 2007, 22(4): 1107-1115.
[28] Yao W, Chen M, Chen J, et al. An improved multiple-loop controller for parallel operation of single-phase inverters with no control interconnections. Proc. IEEE PESC, 2007: 448-452.
[29] Ju H, Ding M, Su J, et al. Communicationless parallel inverters based on inductor current feedback control. Proc. IEEE APEC, 2007: 1385-1389.
[30] Yao W, Chen M, Gao M, et al. A wireless load sharing controller to improve the performance of parallel-connected inverters. Proc. IEEE APEC, 2008: 1628-1631.
[31] Guerrero J M, Berbel N, De Vicuna L G, et al. Droop control method for the parallel operation of online uninterruptible power systems using resistive output impedance. Proc. IEEE APEC, 2006:1716-1722.
[32] Chiang S J, Chang J M. Parallel control of the UPS inverters with frequency-dependent droop scheme. Proc. IEEE PESC, 2001: 957-961.
[33] Guerrero J M, De Vicuna L G, Matas J, et al. Output impedance design of parallel-connected UPS inverters with wireless load-sharing control. IEEE Trans. on Industrial Electronics, 2005, 52(4): 1126-1135.
[34] Guerrero J M, Berbel N, Matas J, et al. Droop control method with virtual output impedance for parallel operation of uninterruptible power supply systems in a microgrid. Proc. IEEE APEC, 2007: 1126-1132.
[35] Chen J F, Chu C L. Combination voltage-controlled and current-controlled PWM inverter for UPS parallel operation. IEEE Trans. on Power Electronics, 1995, 10(5): 547-558.
[36] Van Der Broeck H, Boeke U. A simple method for parallel operation of inverters. Proc. IEEE INTELEC, 1998: 143-150.
[37] Lee W C, Lee T K, Lee S H, et al. A master and slave control strategy for parallel operation of three-phase UPS systems with different ratings. Proc. IEEE APEC, 2004: 456-462.
[38] Chiang S J, Lin C H, Yen C Y. Current limitation control technique for parallel operation of UPS inverters. Proc. IEEE PESC, 2004: 1922-1926.
[39] Perez-Ladron G, Cardenas V, Espinosa G. Analysis and implementation of a master-slave control based on a passivity approach for parallel inverters operation. Proc. IEEE International Power Electronics Congress, 2006: 1-5.
[40] Zhang C, Chen G, Guo Z, et al. An alternating-master-slave parallel control research for single phase paralleled inverters based on CAN bus. Proc. IEEE IPEMC, 2006: 1-5.
[41] Oshima H, Miyazawa Y, Hirata A. Parallel redundant UPS with instantaneous PWM control. Proc. IEEE INTELEC, 1991: 436-442.
[42] Lin X, Chen X, Kang Y, et al. Parallel three-phase UPS inverters with a new control technique. Proc. IEEE PESC, 2002: 905-908.
[43] Tan J, Lin H, Zhang J, et al. A novel load sharing control technique for paralleled inverters. Proc. IEEE PESC, 2003: 1432-1437.
[44] Chen L, Xiao L, Gong C, et al. Circulating current’s characteristics analysis and the control strategy of parallel system based on double close-loop controlled VSI. Proc. IEEE PESC, 2004: 4791-4797.
[45] Yu W, Xu D, Zhou C. Parallel control of the UPS inverters. Proc. IEEE APEC, 2008: 939-944.
[46]邢岩,严仰光.一种实现瞬时均流的UPS冗余并联新方法.清华大学学报(自然科学版), 2003,43(3): 333-336.
[47] Sun X, Lee Y S, Xu D. Modeling, analysis, and implementation of parallel multi-inverter systems with instantaneous average-current-sharing scheme. IEEE Trans. on Power Electronics, 2003, 18(3): 844-856.
[48] Xing Y, Huang L, Sun S, et al. Novel control for redundant parallel UPSs with instantaneous current sharing. Proc. IEEE PCC, 2002: 959-963.
[49] Xing Y, Huang L, Yan Y. A decoupling control method for inverters in parallel operation. Proc. IEEE POWERCON, 2002: 1025-1028.
[50] Xing Y, Huang L, Yan Y. Redundant parallel control for current regulated inverters with instantaneous current sharing. Proc. IEEE PESC, 2003: 1438-1442.
[51] He Z, Xing Y, Hu Y. Low cost compound current sharing control for inverters in parallel operation. Proc. IEEE PESC, 2004: 222-227.
[52] Ruan X, Cheng L, Zhang T. Control strategy for input-series output-parallel converter. Proc. IEEE PESC, 2006: 238-245.
[53]程璐璐,阮新波,章涛.输入串联输出并联的直流变换器控制策略研究.中国电机工程学报, 2006, 26(22): 67-73.
[54] Bhinge A, Mohan N, Giri R, et al. Series-parallel connection of DC-DC converter modules with active sharing of input voltage and load current. Proc. IEEE APEC, 2002: 648-653.
[55]章涛,阮新波.输入串联输出并联全桥变换器的均压均流的一种方法.中国电机工程学报, 2005, 25(24): 47-50.
[56] Ma X, Niu J, Kang Y. Two full-bridge input-series-output-parallel integrated-magnetic converter for high input voltage. Proc. ICEMS, 2005: 1356-1360.
[57] Kim J W, You J S, Cho B H. Input series-output parallel connected converter configuration for high voltage power conversion applications. Proc. ICPE, 1998: 201-205.
[58] Kim J W, You J S, Cho B H. Modeling, control, and design of input-series-output-parallel- -connected converter for high-speed-train power system. IEEE Trans. on Industrial Electronics, 2001, 48(3): 536-544.
[59] Giri R, Ayyanar R, Ledezma E. Input-series and output-series connected modular dc-dc converters with active input voltage and output voltage sharing. Proc. IEEE APEC, 2004: 1751-1756.
[60] Zhuang K, Ruan X. Control strategy to achieve input voltage sharing and output current sharing for input-series-output-parallel inverter. Proc. IEEE PESC, 2008: 3655-3658.
[61] Silva C, Oliveira D, Bascope R. A DC-AC converter with high frequency isolation. Proc. IEEE ISIE, 2007: 953-958.
[62] Xue Y, Chang L, Bordonau J, et al. Topologies of single-phase inverters for small distributed power generators: an overview. IEEE Trans. on Power Electronics, 2004, 19(5): 1305-1314.
[63] Kjaer S B, Pedersen J K, Blaabjerg F. A review of single-phase grid-connected inverters for photovoltaic modules. IEEE Trans. on Industry Applications, 2005, 41(5): 1292-1306.
[64]徐永红,高压直流航空电源系统中静止变流器DC/DC级研制, [硕士学位论文],南京:南京航空航天大学, 2006.
[65]阮新波,严仰光.脉宽调制DC/DC全桥变换器的软开关技术.北京:科学出版社, 1999.
[66]阮新波,严仰光.直流开关电源的软开关技术.北京:科学出版社, 2000.
[67] Redl R, Sokal N, Balogh L. A novel soft-switching full-bridge dc/dc converter: analysis, design considerations, at 1.5 kW, 100 kHz. IEEE Trans. on Power Electronics, 1991, 6(3): 408-418.
[68] Redl R, Balogh L, Edwards D. Optimal zvs full-Bridge dc/dc converter with pwm phase-shift control: analysis, design considerations, and experimental results. Proc. IEEE APEC, 1994: 159-165.
[69]陈敏. 9kVA组合式三相逆变器的研制, [硕士学位论文],南京:南京航空航天大学, 2002.
[70]陈东华.瞬时值控制逆变器技术研究, [硕士学位论文],南京:南京航空航天大学, 2003.
[71]邢岩.逆变器并联运行系统的研究, [博士学位论文],南京:南京航空航天大学, 1999.
[72]陈良亮.无输出隔离变压器的逆变器并联系统研究, [博士学位论文],南京:南京航空航天大学, 2004.
[73]肖岚,陈良亮,李睿,等.基于有功和无功环流控制的DC-AC逆变器并联系统分析与实现.电工技术学报, 2005, 20(10): 7-12.
[74]邢岩,严仰光.电流型调节逆变器的冗余并联控制方法.中国电机工程学报, 2004, 24(11): 199-202
[75] http://pdf.dzsc.net.cn/7-M/MAX507-MAX508_1146610.pdf
[76]胡寿松.自动控制原理(第四版).北京:科学出版社, 2001.
[77] Erickson R W and Maksimovic D, Fundamentals of Power Electronics(2nd Edition), USA, Kluwer Academic Publishers, 2001.
[78]蔡宣三,龚绍文.高频功率电子学,北京:科学出版社, 1993.
[79]陈伯时.电力拖动自动控制系统.北京:机械工业出版社, 1992.
[80] Venkataramanan G, Divan D M, Malesani L, et al. Control strategies for synchronized resonant link inverters. Proc. IEEE IPEC, 1990: 338-345.
[81] Venkataramanan G, Divan D M, Jahns T M. Discrete pulse modulation strategies for high-frequency inverter systems. IEEE Trans. on Power Electronics, 1993, 8(3): 279-287.
[82] Venkataramanan G, Divan D M. Pulse width modulation with resonant dc link converters. IEEETrans. on Industry Applications, 1993, 9(1): 113-120.
[83]李爱文,张承慧.现代逆变技术及其应用.北京:科学出版社, 2000.
[84]朱成花.直流分布式电源系统子系统相互作用分析, [博士学位论文],南京:南京航空航天大学, 2005.
[85]程璐璐.输入串联输出并联组合变换器控制策略的研究, [硕士学位论文],南京:南京航空航天大学, 2007.
[86]徐德鸿.电力电子系统建模及控制.北京:机械工业出版社, 2006.
[87] http://www.ncd.com.cn/
[88] http://www.bj798.com.cn/
[89] Unitrode, BiCMOS advanced phase-shift PWM controller UCC1895/2895/3895, 1999.
[90]李启明.正激直流环节单相和三相软开关静止变流器的研究, [博士学位论文],南京:南京航空航天大学, 2001.
[91] http://www.zxdkj.com.
[92]梅烨,石健将,何湘宁. 6kVA逆变器滞环调制与单极性SPWM倍频调制的比较.电源技术应用, 2005, 8(3): 24-27.
[93] http://www.analog.com/UploadedFiles/Data_Sheets/AD633.pdf