高频震实台在消失模铸造生产线上的应用

介绍消失模铸造工艺对震实台的要求,高性能的震实台在消失模铸造中的重要性,并介绍美国GK公司的HDCT型重型高频震实台基本组成、性能特点以及在消失模铸造生产线的应用情况.     

Microgrid dynamic security consideringhigh penetration of renewable energy

This paper presents a coordination strategy of Load Frequency Control (LFC) and digital frequency protection for an islanded microgrid (MG) considering high penetration of Renewable Energy Sources (RESs). In such MGs, the reduction in system inertia due to integration of large amount of RESs causes undesirable influence on MG frequency stability, leading to weakening of the MG. Furthermore, sudden load events, and short circuits caused large frequency fluctuations, which threaten the system security and could lead to complete blackouts as well as damages to the system equipment. Therefore, maintaining the dynamic security in MGs is one of the important challenges, which considered in this paper using a specific design and various data conversion stages of a digital over/under frequency relay (OUFR). The proposed relay will cover both under and over frequency conditions in coordination with LFC operation to protect the MG against high frequency variations. To prove the response of the proposed coordination strategy, a small MG was investigated for the simulation. The proposed coordination method has been tested considering load change, high integration of RESs. Moreover, the sensitivity analysis of the presented technique was examined by varying the penetration level of RESs and reducing the system inertia. The results reveal the effectiveness of the proposed coordination to maintain the power system frequency stability and security. In addition, the superiority of the OUFR has been approved in terms of accuracy and speed response during high disturbances.     

Distributed Model Predictive Load Frequency Control of Multi-area Power System with DFIGs

Reliable load frequency control (LFC) is crucial to the operation and design of modern electric power systems. Considering the LFC problem of a four-area interconnected power system with wind turbines, this paper presents a distributed model predictive control (DMPC) based on coordination scheme. The proposed algorithm solves a series of local optimization problems to minimize a performance objective for each control area. The generation rate constraints (GRCs), load disturbance changes, and the wind speed constraints are considered. Furthermore, the DMPC algorithm may reduce the impact of the randomness and intermittence of wind turbine effectively. A performance comparison between the proposed controller with and without the participation of the wind turbines is carried out. Analysis and simulation results show possible improvements on closed-loop performance, and computational burden with the physical constraints.      

简单模式的一种匹配方法

模式匹配是包括LFC在内的大多数函数式语言都具有的特点。文章在LFC语言现有的模式匹配实现方法的基础上,结合常用的模式匹配树的构造思想,设计了一种模式匹配方法。这种模式匹配方法通过计算给定模式集合的扩展集合来构造模式匹配树。虽然在最坏情况下,该方法与LFC现有实现的空间复杂度一样,但当函数定义是部分构造式,而定义中的非项模式覆盖了较多项时,这种模式匹配方法可以避免LFC语言现有实现中较大的编码空间。这个方法略作修改即可用于复杂的嵌套模式,是一种通用的模式匹配方法。     

美国低阶煤提质技术发展概述

回顾了美国低阶煤提质技术的发展历程;重点介绍了LFC技术和ACCP技术的工艺流程、技术特点、开发历程和商业化示范装置运行概况;综合分析认为,LFC技术和ACCP技术已具备商业化应用的技术基础,建议我国可适时引进美国低阶煤提质技术,以提升我国低阶煤加工技术的进步。     

减少区域间扰动的LFC模糊监督控制器设计

在LFC控制中最典型的问题就是由于联络线上的功率流动无限制,电能的流向总是从频率高的区域流向频率低的区域,这就加重了频率高的区域的控制负担;再加上各区域控制动作的不协调,使扰动在不同的时间、不同幅值发生时,引起系统的调节过程的急剧恶化,甚至导致整个系统的不稳定。根据研究对象的特性以及调节对象的特点,文章提出一种基于模糊MAMDANI推理算法的模糊监督控制器,采用各个区域的频率偏差作为控制器的输人,考虑监督控制器作为一种前馈补偿,设计输出为一个ACE的倍数,用以加大或者减小控制器的动作量,来控制主汽门的开度,以求在有联络线相互干扰的条件下,系统能尽快的结束调节过程,进入稳定状态。经过实验仿真数据对比发现,提出的监督控制器能有效的提高系统的稳定性。     

负荷频率系统的LFC模糊监控器设计

应用在LFC控制中常规的模糊调整增益PI控制器和I控制器,只针对单一区域的负荷频率进行控制,并不考虑实际模型中的互相扰动.其中最突出的问题是由于不限制联络线上的功率流动,电能总是从频率高区域流向频率低区域,加剧了频率高区域的控制负担,再加上各区域控制动作的不协调,使得当扰动在不同的时间和幅值时引起系统调节过程的急剧恶化,导致整个系统不稳定.提出一种基于模糊MAMDANI推理算法的模糊监督控制器,采用各个区域的频率偏差作为控制器的输入,监督控制器作为一种前馈补偿,设计输出为一个ACE的倍数,加快调节过程,到达稳态.经过实验仿真数据对比,说明提出的监督控制器能有效提高系统的稳定性.     

消失模铸造涂料性能测试新方法

针对消失模铸造涂料性能测试方法上存在的问题,提出了用同一装置和试样连续测试多项性能的新方法,开发研究出了消失模铸造涂料多性能综合测定装置。运用该装置初步研究表明,这种方法便于综合分析涂料的性能,具有较高的可靠性和灵敏度。     

铝合金消失模铸造涂料行为的研究

研究了铝合金消失模铸造过程中的涂料行为。实验结果表明,保温涂料可以提高消失模铸造铝液的充型速度,但会降低铝件密度,而激冷涂料的作用与之相反。为提高消失模铸造铝液的充型速度,并减少其针孔,应采用低透气性的保温涂料,且涂层厚度不能太大,以０．２～０．３ ｍ ｍ 为佳。     

A Novel Modified Robust Load Frequency Control for Mass-Less Inertia Photovoltaics Penetrations via Hybrid PSO-WOA Approach

Abstract

The high penetrations of distributed energy resources (DERs) leads to severe problems such as reducing system inertia and increasing the frequency deviations from the nominal value. The main target of this study is to enable modern photovoltaics (PVs) with large penetration amounts to participate effectively in the load frequency control in the interconnected power systems, in which frequency and tie-line power sharing deviations exist. In this research, a model for the solar PV is developed to help study the heavy penetration of the solar PVs within interconnected power systems. Secondly, a time domain objective function based on the norm of the area control error is formulated. Thirdly, in order to tune the PI controllers, a combined meta-heuristic algorithm based on particle swarm optimization and whale optimization algorithm (PSO-WOA) is developed and compared with the individual PSO and WOA controllers. From the studied scenarios, the developed combined scheme outperforms the other algorithms in terms of system performance indices. Therefore, the developed PSO-WOA approach is plausible and straightforward to solve many engineering problems as it benefits from the exploitation characteristics of the conventional PSO and the exploration features of the WOA.