【作者】 方天治；

【导师】 阮新波；

【作者基本信息】 南京航空航天大学 ， 电力电子与电力传动， 2009， 博士

【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。更多还原

【Abstract】 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.更多还原