【作者】 张尧；

【导师】 何湘宁； 马皓；

【作者基本信息】 浙江大学 ， 电气工程， 2010， 博士

【摘要】 如何将通讯技术更好的应用到电力电子的控制系统,成为一个越来越重要的研究领域。本文在总结现有电力电子的通讯应用与研究的基础上,对电力电子系统网络控制进行了深入研究。网络信道不仅仅是一般电力电子信息传递的媒介,更能成为电力电子控制系统的重要参与者。电力电子系统网络控制通过让网络配合控制环运行,利用网络的调度合理分配电力电子信息数据流的运动并提高电力电子系统的性能。本文在对基于功率下垂控制的逆变器并联以及电力电子系统网络控制进行研究的基础上,提出了基于网络控制和功率下垂控制的逆变器并联技术,提高并联系统的性能和可靠性。在此基础上,本文探讨了影响电力电子系统网络控制性能的主要因素,对基于逆变器并联系统网络控制中的网络时延与数据包丢失等影响做了详细分析,提出了系统的设计方法和解决方案。首先,基于逆变器无互联信号线并联系统,本文提出了用于提高稳态与动态性能的改进型功率下垂控制算法。由于功率下垂控制算法的逆变器系统的均流效果依赖于逆变器的输出阻抗与连线阻抗,本文在传统的功率下垂方程中加入系数调整环节,根据输出功率大小的不同而改变下垂系数,最终使并联稳态下输出功率差值减小而达到较好的均流度,实验表明即使在逆变器输出阻抗与连线阻抗不均衡的情况下也能取得良好性能。为了抑制并联系统的直流环流,本文提出了一种直流环流抑制器,通过闭环控制使稳态下的输出电压直流分量渐进接近参考0,实现了直流环流的抑制。本文提出了一种改进功率下垂控制并联系统动态性能的方法,在系数调整控制方程中加入积分与微分环节,仿真和实验研究表明下垂系数与积分、微分系数如果选取得当,能较好的改善动态性能。其次,本文对电力电子系统的网络控制进行了深入研究,将网络控制应用于逆变器并联系统中,提出了基于网络控制和功率下垂控制的逆变器并联技术,实现了并联系统性能的提高。介绍了电力电子系统网络控制的概念、应用前景和设计思路,并提出了一些电力电子系统的网络控制设计方法。本文将网络控制用于逆变器并联系统,通过网络传输让逆变器模块间获取对方的功率信息,在功率下垂控制方法的基础上得到新的网络控制均流策略。在分析了该系统的控制数据类型与网络环境之后,使用了实时性数据一次性丢弃的数据链路控制辅助技术——TOD(Try-Once-Discarded)动态存取方式。本文对采用新方法与传统功率下垂法进行了实验对比研究,验证了采用新的控制策略的逆变器并联输出电流稳态不均流度更小,性能得到了优化。本文在分析电力电子系统网络控制的主要影响因素的基础上,重点研究了网络时延与数据包丢失等因素对基于功率下垂策略的逆变器并联网络控制系统的影响,提出了稳定性分析方法及相关设计技术。本文给出了一种基于网络联合调度方法的网络时延分析方法,对基于平均功率下垂控制法的并联网络控制系统建立了以时延为变量的数学模型,以TOD动态存取算法为对象,通过线性控制理论估算出最大允许传输区间,作为网络时延的先期预估,通过观察不同时延下并联的输出电流动态结果实验验证了估算的有效性。本文还给出了一种网络时延小于一个控制周期的时延的情况下系统的稳定性分析方法,根据网络传输信号与传输速率的不同,实现了逆变器并联的网络控制策略,然后以不同网络时延为变量建立离散时间系统模型,通过时延符号矩阵是否为Schur稳定矩阵判断系统的稳定情况,实验与理论结果大致相符。本文接着给出了一种固定事件发生概率的数据包丢失的分析方法,在构建两种非线性方程的基础上利用线性系统理论得出使系统稳定的固定丢包率的计算结果。本文还分析了数据错序匹配对系统控制的影响,对其进行了实验研究。最后,为了有利于系统在时延、数据包丢失等因素影响时,仍能稳定可靠运行,本文提出了两种解决方案:一是从网络控制的算法角度提出了新的数据调度方式,使逆变器并联系统在网络通讯正常时能获得较好动静态性能,在网络通讯异常时仍能稳定可靠运行;二是根据随机性时延等网络状况设计新的反馈控制,并从并联的输出电流均流度、同等时延条件的输出对比等角度论述了采用这两种方案的有效性。更多还原

【Abstract】 How to use the communication technique fully in power electronics has been a more and more important research field. After the summary of current application and research in power electronics communication, the concept and idea of networked control is furthered in this dissertation. Network channel can be not only the medium of power electronic data transmission, but also the key participation of power electronic control system. Networked control for power electronic system is to make network cooperate with control loop in operation, allocate the power electronic data flow rationally by means of network scheduling and enhance the performance of power electronic system.Based on the research on inverter parallel with power droop control and networked control for power electronic system, inverter parallel technique with networked control and power droop control is proposed in this dissertation. Moreover, the main factors influencing power electronic system features are introduced. Among them, the influence of the network time-delay and data dropout in power electronic system with networked control are analyzed in detail. The design method and problem-solving strategy of networked control for power electronic system is proposed.Firstly, to enhace the stable and dynamic performance, modified power droop control algorithms towards inverter parallel system without control interconnection are proposed in this dissertation. Because the current-sharing feature of inverter parallel system with power droop algorithm depends upon the output and link impedance of inverter, the parameter adjustment is added in traditional power droop equation. By changing droop parameter varied with output power, the difference of output power in steady-state can be decreased and the ideal current equation degree can be achieved finally. Experiment demonstrates that the ideal performance can be attained even in unbalance of inverter output and link impedance. Moreover a novel attenuator to decrease DC current circulating is presented in this dissertation. By controlling DC component of output voltage to zero through close-loop, the DC circulating restriction is realized. A novel power droop method for improving dynamic performance of parallel system is presented. Integration and differential is added in antecedent parameter adjustment equation. The simulation and experiment shows that dynamic performance can be enhanced if droop, integration and differential coefficient are in proper design.Then, networked control of power electronics system is furthered in this dissertation. By adopting networked control in inverter parallel system, inverter parallel technique based on networked control and power droop control is proposed in order to improve the system performance. The concept, application foreground and design method of networked control in power electronics system are introduced, as well as some networked control design methods. Networked control is employed in inverter parallel system in this dissertation. The individual power information of inverter modules can be achieved by each other through network transmission. The novel networked control strategy is proposed based on power droop control in this dissertation. After the analysis of control data type and network environment of this system, the dynamic access mode of Try-Once-Discarded, one-time abandonment MAC for real-time data is employed. In experimental analysis, the comparison between novel method and traditional method is carried on. It proves that degree of current equation error of parallel output current of inverter is even less and performance is optimized after using new control strategy.Furthermore, based on the main influence factors of networked control for power electronics, the effect of time-delay and data drop-out over networked control system of inverters is emphasized. Stablility analysis and related design techniques is presented. One analysis method based on network combined allocating is proposed. The mathematical model with variable of time-delay for networked control based on average power droop method is constructed. As the predictive estimation of network time-delay. Maximum Allowable Transfer Interval based on TOD dynamic access algorithm can be calculated with linear control theory. The experiment results verify the validity of estimation by watching output current in dynamic state with different time-delay. Moreover, one analysis method of system stability with time-delay within one control period is presented in this dissertation. Then each discrete-time system model with variable of different time-delay is built by each strategy. The judgment of system stability depends on time-delay symbolic matrix whether is Schur stable, and the experiment results is in accord with theoretical results approximately. Following, one analysis method of constant occurrence rate for data dropout is proposed in this dissertation. On the basic of the construction of two non-linear functions using linear control system theory, the calculation method of stable data dropout rata to guarantee system stable is presented. The effect of data misfit over system control is analyzed and described by experiment.Finally, to guarantee system stable under the influenece of time-delay and data dropout, two problem-solving strategies are proposed in this dissertation: On the one hand, new data dispatching mode is given from the point of view of networked control algorithm, which ideal dynamic and static performance can be achieved in normal communication condition and reliable operation will maintain even in abnormal network condition. On the other hand, new feedback control design is presented based on network condition with random time-delay. The validity of these two strategies is verified by experiment in the way of parallel output current-sharing error and output comparison with the same time-delay condition.更多还原