基于标签 Petri 网的自动制造系统初始资源配置优化

自动制造系统初始资源配置优化问题是指在使用最少初始资源成本的前提下,完成预设生产任务。 针对该问题,提出 了一种基于标签 Petri 网和整数线性规划的计算方法。 首先,根据标签 Petri 网的结构化特性给出拟执行任务与初始资源的约 束关系,将初始资源配置优化问题抽象为整数线性规划问题;其次,利用 Lingo 等软件求解该整数线性规划问题;最后,通过实 例对提出方法进行验证。 实验结果表明,提出的方法简单高效,对实际自动制造系统的初始资源配置具有一定借鉴意义。     

机组组合问题的复合控制有色Petri网模型

文章针对有色Petri网对复杂控制系统建模的不便之处进行了改进:使各种控制条件直接作用于有色Petri网的可控变迁,将变迁分为时钟推进控制变迁、外部事件控制变迁、不可控变迁和计算用变迁四种,并提出了一种复合控制有色Petri网(CCCP)模型.在某些情况下,由于触发颜色的不同,同一变迁可属于不同的类型,各类变迁的区别主要在于触发条件不同.文章还利用定义的CCCP对考虑时间约束的发电机组组合问题进行了建模、分析,并通过举例进一步阐述了CCCP在对机组组合这类复杂控制问题进行建模时的作用.该模型为机组组合问题提供了一个新的建模思想和较好的解决方案.     

基于Petri网的消防机器人任务分配及路径规划方法

针对多类型消防机器人协同工作的任务分配及路径规划问题,建立了能够描述消防机器人运行状态的Petri网模型.以消防机器人总工作时间最小化为优化目标,结合Petri网结构特性提出了一种整数线性规划方法.首先,根据消防机器人的任务需求,将消防机器人的工作环境划分为不同类型的工作区域.其次,基于Petri网的结构特性构建整数线性规划模型.最后,利用一个消防机器人工作实例对提出的方法进行仿真.仿真结果表明,提出的方法能够快速、有效地获得消防机器人协同完成任务的路径.对消防机器人实现高效救援具有一定的指导意义.     

考虑柔性交流输电系统设备控制的校正型安全约束最优潮流

为提升安全约束最优潮流调度的经济性与安全性,提出一种基于直流潮流的考虑柔性交流输电系统(FACTS)设备控制的校正型安全约束最优潮流模型。在线路故障发生后,通过FACTS设备校正措施,将线路潮流控制在其容许范围内。由于所提模型为大规模的非凸、非线性优化问题,难以直接求解,因此先采用大M法,将原非线性优化模型转换为混合整数线性规化模型,并采用Benders分解算法将转换后的模型分解为基态最优潮流主问题与N-1故障校验子问题。通过固定整数变量的方法,将非凸的混合整数优化子问题转换为线性规划子问题,从而能向主问题返回对应的Benders割。6节点系统与IEEE RTS-79节点系统算例验证了所提模型与算法的有效性。结果表明,考虑FACTS设备校正控制的安全约束最优潮流能有效提升调度运行的经济性。     

Petri网在液压驱动机械手控制系统PLC程序设计中的应用

为有效解决具有并发、协调、竞争等复杂事件的PLC控制系统编程问题,探讨一种基于Pe试网模型的可编程序控制器（PLC）程序设计方法。通过赋予Petri网的位置和变迁控制属性,实现Pe伍网对典型控制系统的有效描述。根据Petri网的基本规则,可方便地实现Petri网模型到PLC梯形图的转换。将Petri网应用在液压驱动机械手控制系统中,实例表明,其具有易于理解和修改的优点,并能对控制系统的性能进行分析,以确保所设计程序的正确性。     

计及可控负荷的独立微网分布式电源容量优化

针对独立微网中分布式电源容量优化问题,建立了计及可控负荷的优化模型,其优化目标为电源年投资替换成本、运行维护费用和可控负荷的调度成本最小,约束条件包括机组出力约束、储能电池运行约束和可控负荷运行约束。根据可中断负荷和可平移负荷的现实调度要求,建立了相应的线性化模型。通过调用CPLEX求解器的混合整数线性规划法对所建立的混合整数模型进行求解,算例仿真验证了所建立的模型是正确有效的。多场景下最优方案的对比分析表明在电源规划阶段合理考虑可控负荷的影响,将不仅有利于降低系统运营总成本,而且有利于降低系统的弃风光率。     

基于混合整数线性规划的含ZIP负荷有源配电网重构方法

随着分布式电源并网和负荷类型的日益复杂,传统配电网重构模型尚未考虑复杂的综合负荷模型。提出了考虑ZIP综合负荷模型的有源配电网混合整数线性规划方法。在辐射状配电网二阶锥潮流模型的基础上,通过线性回归法将ZIP负荷模型等效为ZP负荷模型,建立基于混合整数二阶锥规划的有源配电网重构模型。通过多面体近似将二阶锥约束进行线性化,建立基于混合整数线性规划的有源配电网重构模型。在三个不同规模配电系统的仿真结果表明,基于混合整数线性规划的有源配电网重构模型精度与基于混合整数二阶锥规划的几乎相同,但优化效率提高了15%~30%,具有较高的优化精度和效率。     

定制化求解机组组合混合整数线性规划模型的固定—推断法

为了突破机组组合算法的自主可控问题,基于开源混合整数线性规划求解器CBC,提出一种快速获取机组组合问题可行解的固定—推断法。首先将机组组合模型转换为推断标准模型,然后按重要性对所有整数变量进行排序。并利用约束违反函数依次确定整数变量的值,实现整数变量的固定,利用约束关系推断出与其相关的整数变量值。最后经过多轮的固定—推断可以实现所有整数变量的取值,从而求解一个线性规划问题即可得到各机组的出力。仿真结果表明,所述算法能有效求解大规模机组组合问题,可在更短时间内获取质量较好的可行解。与CBC求解器结合,能显著提升CBC求解器对于机组组合问题的求解效率。此外,所述算法还具备在其他求解器上进行定制的潜力。     

一种混和Petri网结构分析方法

混和Petri网可很好地描述由连续动态和离散动态相互混和、相互作用而形成的混和系统.其特点是,将位置和变迁区分为连续和离散两种类型,以表征连续变量过程和离散事件过程.Petri网是离散系统建模和分析的一种有效的图形和数学工具.在文中,基于图论提出一种分析Petri网结构特性的方法,然后介绍转换矩阵和Petri网的对应关系.其次,应用转换矩阵的特征多项式和方程分析Petri网的结构特性;最后,应用例子来说明该方法的应用.     

Petri网在模块化制造系统PLC程序设计中的应用

在对模块化制造系统(MPS)进行设计时,运用Petri网建立其状态转换模型,从逻辑控制的角度出发,给出了用Petri网控制器工具设计PLC程序的一般方法。并从实例出发介绍了基于Petri网控制器的MPS单站PLC程序的设计,说明了Petri网方法是MPS系统PLC建模和程序设计的切实可行的方法。     

Deadlock Avoidance Controller Design for Timed Petri Nets Using Stretching

The recently introduced method, which was called ldquostretching,rdquo is extended to timed Petri nets which may have both controllable and uncontrollable transitions. Using this method, a new Petri net, called ldquostretched Petri net,rdquo which has only unit firing durations, is obtained to represent a timed-transition Petri net. Using this net, the state of the original timed Petri net can be represented easily. This representation also makes it easy to design a supervisory controller for a timed Petri net for any purpose. In this paper, supervisory controller design to avoid deadlock is considered in particular. Using this method, a controller is first designed for the stretched Petri net. Then, using this controller, a controller for the original timed Petri net is obtained. Algorithms to construct the reachability sets of the stretched and original timed Petri nets, as well as algorithms to obtain the controller for the original timed Petri net are presented. These algorithms are implemented using Matlab. Examples are also presented to illustrate the introduced approach.     

基于UML和Petri网的电力系统恢复模型

为了描述电力系统恢复过程,提出了基于UML的电力系统恢复过程建模方法,使用类图表示参与电力系统恢复的主要元件的静态特性,使用状态图表示各元件的动态特性。对所建模型进行了仿真和验证,提出了将UML模型转化为赋时Petri网的方法,将UML模型的操作转化为Petri网中的变迁,将UML模型中操作的输入、输出及约束表示为Petri网的库所。以IEEE RTS-96系统验证了所提方法的可行性,该方法易于对电力系统恢复过程进行模型化分析和软件实现。     

Modeling by petri net with place invariants for sequential control systems

It is more difficult to model a discrete system than a continuous system. Recently, a great number of applications of Petri nets to the design and the analysis of discrete systems has been reported. However, a common problem in its applications is that the required computer memories and the computation times increase explosively in accordance with the increase in the number of systems components. Some methods to divide or to reduce Petri nets have been proposed to solve this problem. Although the liveness and boundedness of Petri nets are held in the divided or reduced Petri nets, the reachability problem cannot be solved by these methods. This paper proposes another method to model discrete systems by Petri nets with place invariants. A sequential control system will be described as a typical kind of discrete system, and its structural characteristics will be used in modeling. Each component of a sequential control system will be modeled by a sub-Petri net with place invariants. There are many components in one sequential control system, but not each one is necessarily complicated. Most sub-Petri nets do not have so many places or transitions. It is also well known that a Petri net with place invariants is bounded and can be live by placing sufficient tokens into its initial marking. Besides, the reachability problem is not so difficult to solve in a small sub-Petri net. Further, an activating relation to combine two or more sub-Petri nets is defined, and some rules to reduce conflicts among enabled transitions will be described for simulations.     

时间约束的改进分层模糊Petri网的配电网故障诊断方法

配电网发生故障后,迅速利用大量的告警信息判别出故障元件,能为调度中心的工作人员提供重要的决策支持。针对现有Petri网的故障诊断方法未应用在配电网中的问题,提出了一种时间约束的改进分层模糊Petri网的配电网故障诊断方法。对配电网中的可疑故障元件建立改进的分层模糊Petri网模型,能够适应网络拓扑结构的变换,利用获得的报警信息通过反向和正向时序推理对保护和断路器进行时序检查,对不满足时间约束的库所进行置信度修正。给出了改进分层模糊Petri网模型的推理流程及矩阵推理算法,在矩阵推理过程中引入高斯函数修正概率,使概率始终保持在0～1,最终得到故障元件的置信概率及其时间点约束。通过对配电网系统算例的比较、分析,验证了所提方法的正确性和合理性,能够有效地诊断出配电网的故障元件。     

A high‐speed‐execution method for a program written in factory‐automation‐cell control language

A new programming method called Cell Control Language (CCL) for factory‐automation systems has been developed. In CCL programming, an action sequence of each functional unit in each operation mode is first described as a net module. This net module is a subclass of Petri nets, and this subclass is equivalent to a state‐transition diagram (a conventional design method). Several net modules are merged and translated into an internal code program, which is executed in a cell controller. To improve the ability of the controller to respond to state changes, we developed two new methods based on CCL. One is that for efficiently describing a CCL program, which needs a quick response to state changes, and the other is that for executing the program in a short cycle. The execution method was applied to an actual cell controller, which confirmed that it can improve the ability to respond to state changes without reducing the total control performance. © 2003 Wiley Periodicals, Inc. Electr Eng Jpn, 144(2): 34–42, 2003; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.10167     

Optimization-based scheduling of hydrothermal power systems withpumped-storage units

This paper presents an optimization-based method for scheduling hydrothermal systems based on the Lagrangian relaxation technique. After system-wide constraints are relaxed by Lagrange multipliers, the problem is converted into the scheduling of individual units. This paper concentrates on the solution methodology for pumped-storage units. There are, many constraints limiting the operation of a pumped-storage unit, such as pond level dynamics and constraints, and discontinuous generation and pumping regions. The most challenging issue in solving pumped-storage subproblems within the Lagrangian relaxation framework is the integrated consideration of these constraints. The basic idea of the method is to relax the pond level dynamics and constraints by using another set of multipliers. The subproblem is then converted into the optimization of generation or pumping; levels for each operating state at individual hours, and the optimization of operating states across hours. The optimal generation or pumping level for a particular operating state at each hour can be obtained by optimizing a single variable function without discretizing pond levels. Dynamic programming is then used to optimize operating states across hours with only a few number of states and transitions. A subgradient algorithm is used to update the pond level Lagrangian multipliers. This method provides an efficient way to solve a class of subproblems involving continuous dynamics and constraints, discontinuous operating regions, and discrete operating states     

满足静态电压稳定增强要求的发电机最佳调整方法

为增强电力系统的静态电压稳定性,同时最大限度地减小运行人员的操作工作量,提出了一种综合经济性和静态电压稳定性的发电机最佳调整模型。该模型以发电机参与调整台数最少和发电成本最小为目标,约束条件包括系统负荷裕度满足设定提升要求和电力系统安全运行要求。该问题的数学本质是一个多目标非线性混合整数规划问题。为实现上述问题的求解,首先以线性灵敏度方法快速估算所需调整出力的发电机,求解控制数量最少的整数规划问题。然后以发电成本最小为目标,利用线性规划法求解各台发电机的调整出力值。最后在IEEE39节点算例和IEEE118节点算例进行仿真验证,结果表明所提模型与求解方法能很好地解决系统的静态电压稳定性增强控制问题。     

基于改进遗传算法与原对偶内点法的无功优化混合算法

基于改进遗传算法和原对偶内点法提出一种求解无功优化问题的混合算法。首先通过改进遗传算法求解无功优化问题中的离散变量,然后采用原对偶内点法求解与已获得离散变量最匹配的连续变量。在改进遗传算法中采用交叉、变异算子并基于可行域规则处理离散约束,有效提高了混合优化算法的整体寻优效率。在IEEE 118节点系统中的仿真计算结果验证了本文方法的有效性。该方法已应用于福建电网自动电压控制系统中。     

基于机会约束的微电网混合整数规划优化调度

为解决微电网短期及超短期优化调度问题,考虑微电网运行过程中不确定因素的影响。以最小化微电网运行成本为目标,综合考虑功率平衡、机会约束等约束条件,提出了一种基于机会约束的微电网混合整数规划优化调度模型。针对模型中机会约束确定性转化问题,采用基于采样的机会约束条件确定性转化方法,将机会约束变为混合整数线性约束。同时,为了提高计算速度,将目标函数中的非线性函数进行分段线性化。算例结果表明,基于机会约束的微电网混合整数规划优化调度模型具有较好的可行性和有效性。