Biomass Combined Heat and Power Generation for Anticosti Island: A Case Study

Combined heat and power (CHP) plants (co-generation plants) using biomass as fuel, can be an interesting alternative to the predominant electrical heating in Canada. The biomass-fueled boiler provides heat for the steam cycle which in turn generates electricity from the generator connected to the steam turbine. In addition, heat from the process is supplied to a district heating system. The heat can be extracted from the system in a number of ways, by using a back-pressure steam turbine, an extraction steam turbine or by extracting heat directly from the boiler. The objective of the paper is the design, modeling and simulation of such CHP plant. The plant should be sized for providing electric-ity and heat for the Anticosti Island community in Quebec.

Reciprocating Engine Step Load Response in Islanded Power Generation

The step load response of reciprocating engines is one of the key characteristics when considering its application in medium to large scale stationary power generation especially with islanded generation. This paper discusses the impacts of power frequency deviation on the generators and electrical equipment in the network and presents the relationship between step load capabilities and generator operating parameters. For a power plant consisting of a number of generators both step load and power output requirements must be satisfied. An analysis method is proposed to facilitate the development of an operation strategy which can meet both step load and power demand requirements in the full load range.? Typical reciprocating engine step load curves are used to demonstrate the analysis method and the results are further optimised for lower operational cost. This analysis method provides a general approach to operation strategy of large reciprocating engines used in islanded power generation.

Active splitting strategy searching approach based on MISOCP with consideration of power island stability

Active splitting control utilizes real-time decision and system-level splitting to prevent cascading blackouts and to maintain power supply under severe disturbances. Splitting strategy searching(SSS) is one of the most crucial issues in active splitting control for deciding‘‘where to split’’. SSS determines the splitting surface in real time to properly divide the asynchronous generators into isolated islands with an optimal control effect. In this paper, an SSS approach that focuses on island stability is presented. The proposed SSS approach is designed to ensure a rational stability margin and regulation ability on each island during and after the transient process of system splitting. This method includes the active/reactive power flow feasibility constraints and voltage/angle stability constraints in the steady state as well as the frequencyresponse capability constraints in the transient process. By considering the island stability constraints in the SSS, the proposed approach can avoid the splitting strategies with poor stability performance. Therefore, the major advantage of the proposed approach is that it can ensure better island static and transient stability during and after the splitting control. In addition, the entire model is formulated as a mixed-integer second-order cone programming(MISOCP)model. Thus, it can be rapidly solved by using commercial optimization solvers. Numerical simulations of a realistic provincial power system in central China demonstrate thevalidity of the proposed approach and the necessity of considering the island stability issues.

基于Matlab和Matpower的孤岛判别与处理

孤岛的判别与处理对电力系统可靠性评估具有重要意义,为了提高孤岛判别与处理的速度和精度,提出一种基于Matlab和Matpower的孤岛处理与判别方法,该方法根据孤岛的性质利用Matlab建立孤岛判别矩阵,并对Matpower中参数进行修改,使Matpower能够对孤岛系统直接进行直流潮流计算。相较于之前的人工计算,该方法不仅在速率上得到较大的提升,而且具有较高的准确性和可操作性。适用于电力系统的可靠性评估过程中的孤岛判别与处理。

Islanding Detection Method for Multi-Inverter Distributed Generation

Islanding detection is an essential function for safety and reliability in grid-connected distributed generation (DG) systems. Several methods for islanding detection are proposed, but most of them may fail under multi-source configurations, or they may produce important power quality degradation which gets worse with increasing DG penetration. This paper presents an active islanding detection algorithm for Voltage Source Inverter (VSI) based multi-source DG systems. The proposed method is based on the Voltage Positive Feedback (VPF) theory to generate a limited active power perturbation. Theoretical analyses were performed and simulations by MATLAB /Simulink /SimPowerSystems were used to evaluate the algorithm’s performance and its advantages concerning the time response and the effects on power quality, which turned out to be negligible. The algorithm performance was tested under critical conditions: load with unity power factor, load with high quality factor, and load matching DER’s powers.

New Islanding Detection Method with Better Performance in Presence of Non-resistive Load

Islanding detection is a mandatory component in grid-connected photovoltaic （PV） inverters. It is also a key issue in the photovoltaic agriculture. In this work, an overview on the islanding effect in grid-connected PV power systems was provided. Various islanding detection methods were introduced and their strength and weakness were dicussed. An improved islanding detection method was proposed based on active frequency drift （AFD）. The new method tolerated capacitive and inductive loads, because its perturbation signal was not offset by the non-resistive load. The new method through simulation in MATLAB/Simulink was evaluated and the advantages of the new method were demonstrated.

Performance Assessment of Islanding Detection for Mul-ti-inverter Grid-connected Photovoltaic Systems

Islanding detection is an essential function for safety and reliability in grid-connected Distributed Generation Systems (DGS). Passive and active islanding detection methods have been analyzed in literature considering DGS with only one inverter connected to the utility. With the big scale application of photovoltaic (PV) power systems, islanding detection technology of multi-inverter DGS has been paid more attention. This paper analyzes the performance of diverse islanding detection methods in multiple inverters grid-connected PV systems. Non-Detection Zones (NDZ) of multi-inverter systems in a load parameter space are used as analytical tool. The paper provides guidance for the islanding detection design in multiple grid-connected inverters.

Impact of Reactive Power in Power Evacuation from Wind Turbines

Application of Distributed Generation (DG) to supply the demands of a diverse customer base plays a vital role in the renewable energy environment. Various DG technologies are being integrated into power systems to provide alterna-tives to energy sources and to improve reliability of the system. Power Evacuation from these remotely located DG’s remains a major concern for the power utilities these days. The main cause of concern regarding evacuation is con-sumption of reactive power for excitation by Induction Generators (IG) used in wind power production which affects the power system in variety of ways. This paper deals with the issues related to reactive power consumption by Induc-tion generators during power evacuation. Induction generator based wind turbine model using MATLAB/SIMULINK is simulated and its impact on the grid is observed. The simulated results are analyzed and validated with the real time results for the system considered. A wind farm is also modeled and simulations are carried out to study the various im-pacts it has on the grid &nearby wind turbines during Islanding and system event especially on 3-Phase to ground fault.

基于电阻变化率和有功功率的混合孤岛检测方法

为解决传统检测方法阈值设置困难、对电能质量影响大的问题,提出一种基于电阻变化率和有功功率扰动相结合的混合孤岛检测方法。电阻变化率作为被动方法,该特征量在孤岛后可快速响应,有功功率扰动模块仅在被动方法怀疑孤岛时开启,自适应注入能使公共耦合点电压越限的最小有功功率。仿真结果表明,该方法可快速正确地检测出孤岛,即便在非孤岛情况下也不会发生误判。

“印太战略”框架下美国对太平洋岛国的嵌入式援助

嵌入式援助是指一国在对外援助的过程中,利用本国的政治力量、社会力量和市场力量优势把本国的治理理念、规范制度、治理模式嵌入到受援国的治理架构中,重构受援国治理体系和治理能力,以深度影响受援国治理议程和政策偏好为目标的援助形态。近年来,出于制衡中国崛起、利用太平洋岛国的独特地缘战略价值、护持太平洋霸权和扩展软实力影响的战略需要,美国将太平洋岛国纳入其“印太战略”框架,着力实施嵌入式援助,推动太平洋岛国与美国实现战略耦合,呈现出多主体参与、全政府协同、注重治理经验输出、依赖联盟网络、采用项目外包和嵌入领域广泛的特点。美国的嵌入式援助在本质上就是以柔性、隐蔽和伪善的方式,试图在大国竞争中以治理软实力塑造太平洋岛国的美国认知、治理结构与对外关系,维护其在太平洋岛国的话语影响力和战略控制力,稳定由其主导的“印太秩序”。由于受到自身霸权相对衰落、部分太平洋岛国与美国存在利益冲突以及太平洋岛国的自主性增强等多重因素限制,未来美国对太平洋岛国的嵌入式援助成效将充满不确定性。

基于MPPT控制的两级式直流孤岛检测方法研究

针对主动式孤岛检测方法存在扰动同步注入、影响电网供电质量等问题,提出了一种基于最大功率点跟踪(MPPT)控制的两级式直流孤岛检测方法。该方法通过检测并网变换器直流侧电流来判断疑似孤岛,然后利用疑似孤岛信号触发电压扰动的注入使得孤岛后的公共耦合点(PCC)电压出现特定频率的波动。由于扰动信号的注入受疑似孤岛信号控制,减少了正常状态下扰动的注入时长,有效降低对系统电能质量的影响。此外建立小信号模型分析了耦合点电压对扰动分量的频域特性,选取扰动信号的最优频率。最后通过仿真与实验验证了所提方法在单机与多机工况下的有效性。

交流微电网谐波功率分布式共享控制策略

交流母线电压的电能质量是微电网分布式控制的关键问题之一,该文将含逆变器接口的分布式发电机连接到微电网母线上,重点研究了含非线性负荷的微电网谐波功率共享问题。为了解决非线性负荷引起的电压畸变,设计了谐波下垂控制器和模型预测电压控制器,替代传统的电压电流双闭环控制。在此基础上,提出了一种基于有限集模型预测控制的分布式协同一致协议,使每个分布式发电单元的谐波功率在公共耦合点均匀分布。该方法可以提高微电网系统的可靠性和灵活性,防止电网扰动和馈线阻抗失配,使谐波功率在分布式发电机组之间精确地按比例分配。仿真结果表明,该控制策略在实现谐波功率共享和改善公共耦合点电压谐波失真方面具有良好的效果。

基于多目标协调的混合储能功率自适应分配方法

混合储能具有良好的功率可控特性,在孤岛微网中常被用作功率缓冲器,补偿分布式电源和负荷多变的功率潮流.围绕储能的功率响应问题,本文设计了混合储能的功率控制方案,并提出了一种基于多目标协调的子单元功率自适应分配方法.首先基于对母线功率供求平衡关系的分析,设计了主从并联型储能功率控制方案.其次利用积分器的“时空调零”特性,实现了子单元的功率自主分配;基于此,考虑了不同荷电状态(SOC)下储能最大充放电功率的差异,设计了子单元的SOC分层管理和多目标功率协调策略.仿真结果表明,所提策略实现的功率分配效果满足子单元的功率响应特性;随着超级电容SOCscn偏移加深,所提策略对SOCscn的优化能力越强,初始SOCscn为97%时能提高10.10%的优化性能,这保障了超级电容作为电压源的功率输出能力;所提策略降低了超级电容常态下的蓄电池的输出深度,蓄电池的最大功率深度降低了46.70%,这提高了蓄电池的使用寿命.

时滞孤岛微电网负荷频率控制系统在采样控制下的指数稳定

孤岛微电网配有开放式通讯网络。通讯信息不可避免存在的延迟,会对系统的稳定造成显著影响。针对变时滞影响下的孤岛微电网负荷频率控制系统的稳定性问题进行了研究。首先,建立了考虑时滞的孤岛微电网负荷频率控制系统模型,并据此推导出含时滞项的系统状态方程。然后,在基于采样的事件触发非周期间歇控制策略下,通过数学推导证明了系统在变时滞的影响下能够实现指数稳定。最后,通过仿真分析,验证了所提控制策略的有效性,并将其与最近提出的基于状态控制宽度的事件触发非周期间歇控制策略进行了对比。结果显示,相较于后者,提出的控制策略在系统稳定性方面表现更为高效,且所需的控制次数更少。

基于改进模拟退火遗传算法的配电网动态故障恢复策略

计及分布式电源出力波动性对故障恢复效果带来的不利影响,提出1种利用光伏出力预测的配电网动态故障恢复方案。故障发生后,首先对动态变化的光伏系统输出功率进行预测,并研究了负荷动态特性;其次,以配电网恢复重要负荷总量最大、故障恢复成本最小和故障停电损失最少为目标函数,构建基于动态树背包模型的最优故障恢复模型,该模型可快速适应配电网拓扑变化情况。采用改进模拟退火遗传算法求解最优故障恢复方案,提高了算法的收敛速度与稳定性。最后,在IEEE69节点系统进行仿真,结果表明所提算法可适应复杂配电网的故障恢复,提高配电网供电可靠性,并降低配电网故障带来的恢复成本与停电损失。

事件触发改进一致性算法的孤岛混合微电网并联互联变流器分布式协调控制策略

在交直流混合微电网中,并联互联变流器(parallel bidirectional power converters,BPCs)可以实现大容量的功率传输,以满足新型电力系统在空间上的供需匹配。如何在占用更少资源的同时协调控制BPCs实现功率的比例共享,是交直流混合微电网中BPCs控制的研究难点。因此,该文设计了一种针对BPCs的事件触发改进一致性协调控制策略。以归一化下垂控制为基础,提出了改进的比例功率一致性算法,实现BPCs间高精度比例功率共享。在此之上,基于BPCs比例功率误差建立事件触发改进一致性算法,并预设触发函数的预判阈值,从而降低系统在稳定状态下的通信次数。最后进行仿真对比分析,结果表明该文提出的方法相比基本一致性算法通信量减少98.35%;同时,与现有控制策略相比,该文提出的方法有着更好的控制性能。

Kenics型静态混合器中幂律流体与颗粒混合过程分析

针对Kenics型静态混合器内固体颗粒在幂律流体中的孤岛现象的产生机理进行研究。运用Fluent数值模拟固相颗粒与CMC水溶液在Kenics静态混合器中的混合过程,并利用浓度变异系数(COV)对颗粒分布特性进行量化分析。研究表明:提高流体表观黏度和流体入口速度,颗粒停留时间缩短,COV值降低,混合效果提高。在第4~8个扭旋叶片中间截面上均形成了两对对称的无粒子孤岛,降低流体表观黏度和提高流体入口速度,孤岛边界更清晰。扭旋叶片诱导的内流涡旋和近壁面涡旋有较高的涡量,涡旋中心局域形成无粒子孤岛,相邻叶片交错区域,随着涡旋耗散孤岛消失。

适用于多逆变器小波变换被动式孤岛检测法

该文针对多逆变器并网情况下孤岛检测方法进行了研究,提出一种基于小波变换的被动式孤岛检测方法。通过检测公共点电压和频率,以无功功率作为参考,计算熵值作为附加判定条件,来进行孤岛检测。同时建立了光伏并网仿真模型,在不同情况下验证了该检测方法的可行性。仿真结果表明,小波变换优化了繁琐的特征分层和检测范围,确定了过程复杂度的缺点,缩短了检测时间。与应用于多台逆变器的主动孤岛检测方法相比,该方法不存在稀释效应和对电能质量的干扰问题。与其他类似原理的检测方法相比,该方法也能有效地识别虚假孤岛。

离网式风光氢醇一体化系统容量配置运行调度优化及经济性分析

为解决可再生能源消纳及氢能源存储、运输难题,提出一种离网式风光氢醇一体化系统。该系统离网运行,利用风力和光伏发电提供电能;通过蓄电池和储氢罐作为储能和储氢设备,以削峰填谷的方式稳定供应电能和氢能,确保电解槽和甲醇生成设备的稳定连续生产甲醇。以系统总收益最大化为目标构建了风光储氢醇的数学模型,并通过混合整数线性规划算法,结合风光真实数据分析,确定系统最佳设备容量与运行调度。以典型日分析其运行策略及系统能量,最后对所制绿色甲醇经济性分析。结果表明:系统能够根据外界条件的变化,合理切换工作状态,实现系统能量平衡;在满足各项约束条件下,提高了可再生能源利用率,降低了系统制甲醇的平准化成本。此研究为新能源消纳与氢能源利用提出了一条可行技术路线,并可为相关示范项目建设提供指导。

爱尔兰岛高比例新能源电力系统运行经验与启示

随着全球能源转型步伐的加快,世界各国电力系统均大力发展以风电和光伏发电为主的新能源。爱尔兰岛电力系统为岛屿独立同步电网,具有新能源渗透率高、与外部电网交互功率小等特点。经过长期摸索与发展,爱尔兰岛高比例新能源电力系统运行水平处于世界前列,其先进经验对我国新型电力系统建设具有重要借鉴意义。介绍了爱尔兰岛电力工业的概况,分析了爱尔兰岛电力系统的运行情况,探究了爱尔兰岛电力公司为保证高比例新能源电力系统安全高效运行采取的措施,最后总结其对我国新型电力系统建设的经验与启示。