Optimal control strategy of a DC micro grid

Microgrids include distributed energy resources, controllable loads, and storage devices, and they can be classified into AC and DC types, depending on the characteristics of the supply voltage. In this paper, an optimal control strategy for a DC microgrid is proposed, and the strategy is aimed at minimizing the daily total energy costs. The DC micro grid can include non-dispatchable generation units (such as photovoltaic power generation) and dispatchable generation units, energy storage systems (batteries), and controllable/not controllable loads. The control strategy is based on a two-step procedure, i.e., (1) the implementation of one day-ahead scheduling and (2) a very short-time predictive control. The day-ahead scheduling is formulated using integer linear programming methodology and is aimed at achieving the optimal scheduling of controllable loads. The very short-time predictive control is based on the solution of a non-linear, multi-period, optimization problem and is aimed at achieving the real-time optimal charging/discharging profile of storage powers and the real-time optimal profile of powers of dispatchable generators thereby minimizing the cost of total daily energy. For both procedures, optimization models were formulated and solved, including technical constraints that guaranteed an adequate lifetime of the storage system. Case studies relative to a DC microgrid obtained by a modification of the actual structure of the electrical power plant of an Italian industrial facility were investigated in order to show the feasibility and the effectiveness of the proposed approach.     

电网能源多层次优化调度模型设计及其Matlab仿真分析

为了提高电网能源多层次优化调度效率,对分层和总体架构展开设计,并建立优化调度模型。利用优化调度模型并结合遗传算法来构建求解模型,采用MATLAB仿真软件测试了分层优化方法对系统分布式设备的效果,优化结果表明:在区域边际成本比电价低的情况下,则对配网进行售电。区域3具有较低的发电成本,使其跟上级配电网大部分时间具有正的交换功率,区域3对配网实施售电获得利润3。区域3优化调度电能供需运行功率好交换功率,除了在10:00～14:00时间之外,微型燃气轮机都保持满发的状态。该区域在许多时段都是从配网中购入电量后再提供给用户,从而达到降低经济成本的目的。     

Optimal operation modes of photovoltaicbatteryenergy storage system basedpower plants considering typical scenarios

Emission of greenhouse gases and depletion of fossil fuel reserves are two key drivers, which are forcing the mankind to generate the future energy demand from the renewable energy resources. These resources are generally distributed in nature and are directly integrated at distribution levels. Increasing penetration of the distributed energy resources in distribution power networks creates additional operational and control issues. These are mostly regulatory, economical load dispatching, power quality and protection issues. Generally power distribution systems are protected with the help of dedicated over current based protection schemes. But increasing share of distributed energy resources penetration in electric utilities poses a serious threat to the existing protection coordination schemes of the distribution systems. Distributed energy resources connected distribution networks become interconnected in nature and protection coordination schemes, which are designed for unidirectional flow of fault currents become ineffective/non-functional. Therefore, new protection coordination schemes are required for providing the adequate protection coordination for distributed energy resources connected electric power networks. In the available literature, the protection coordination schemes for radial distribution systems and developments in the area of protection coordination are discussed in detail. A thorough review for all these protection coordination schemes for distribution systems with and without distributed energy resources is done in this review article. It includes the analytical and artificial intelligence based techniques application for coordination of protective relays in the distribution systems. The limitations and research gaps in the area of protection coordination schemes are also presented in this review article. The aim of this research paper is to bring all the available research in the area of relay coordination on one platform, so that it will help the emerging researcher to identify the future scope of relay coordination application for distributed energy resources connected distribution systems.     

未来电网初探

由于化石能源的日益枯竭和节能减排的迫切需求,人类逐渐认识到必须发展以可再生能源为主的清洁能源系统.由于可再生能源的主要利用方式是发电,且可再生能源资源及其发电方式与化石能源资源及发电方式具有很大的不同,因此,可再生能源的广泛应用将对电力生产、输配和消费模式等产生深刻的影响.有鉴于此,对未来电网的探索就显得非常重要.本文...     

Multi-agent system for energy resource scheduling of integrated microgrids in a distributed system

This paper proposes a multi-agent system for energy resource scheduling of an islanded power system with distributed resources, which consists of integrated microgrids and lumped loads. Distributed intelligent multi-agent technology is applied to make the power system more reliable, efficient and capable of exploiting and integrating alternative sources of energy. The algorithm behind the proposed energy resource scheduling has three stages. The first stage is to schedule each microgrid individually to satisfy its internal demand. The next stage involves finding the best possible bids for exporting power to the network and compete in a whole sale energy market. The final stage is to reschedule each microgrid individually to satisfy the total demand, which is the addition of internal demand and the demand from the results of the whole sale energy market simulation. The simulation results of a power system with distributed resources comprising three microgrids and five lumped loads show that the proposed multi-agent system allows efficient management of micro-sources with minimum operational cost. The case studies demonstrate that the system is successfully monitored, controlled and operated by means of the developed multi-agent system.     

基于短路容量量化评估的大规模新能源直流送端电网运行方式优化方法

直流送端电网中需保证一定数量的常规机组提供短路容量以平抑电压波动,而开机容量过大将挤占新能源消纳空间,为电网运行方式优化带来了难题.对此,基于支路潮流法揭示了暂态过电压与直流母线短路容量的关系,推导出保证一定暂态过电压水平的最小母线短路容量的量化算法,提出了利用常规机组短路电流权重指数作为考虑短路容量约束的机组优化组合权重因子,给出了常规机组开机方式与各条直流短路容量需求之间的量化关联关系.基于该方法建立了考虑直流近区短路容量约束的机组组合优化模型,采用机组组合优化算法统筹考虑各种约束,优化机组开机方式,在保证安全稳定运行的基础上实现了新能源最大消纳.最后以西北某省级电网为例验证了所提方法的有效性及优越性.     

基于能源托管的电网企业节能服务运作模式研究

以南方电网开展基于能源托管的节能服务项目为例,阐述了能源托管模式的优势,实际运作流程和难点,以及如何加速推广能源托管模式的建议。     

The value of the grid and the role of the utility in managing it

Distributed energy resources and electrification are countervailing trends in the electricity business. DER challenges the traditional electric utility business model, while electrification presents new opportunities for the economy, for the environment, and for utilities. Both of these new developments highlight the importance of the electric grid, and the critical need for utilities to manage this integrated grid of the future.     

计及循环寿命和运营策略的风电汇集区域储能电站优化配置

风电汇集区域建设储能电站可在保证整个区域一次调频能力的同时提高经济性。针对风电汇集区域建设储能电站提出一种基于运营策略的储能容量配置方法。储能电站采用独立运营机制,在保证区域一次调频容量的前提下参与电力市场交易,实现储能利用率、效益最大化。提出储能电站运营配置协同优化双层模型,外层以全生命周期投资回报率最大为目标进行储能配置,内层计及储能循环寿命以日运行期望利润最大为目标优化运营策略,内外层联合优化达到综合最优,从而得出储能配置结果。提出一种改进麻雀搜索算法提高收敛速度,对双层配置模型进行求解。通过算例验证了所提方法能够在确保区域具备一次调频能力的同时提高储能的经济性。     

配网分布式电源并网对电网潮流的影响

基于极坐标系下的牛顿法的配电网潮流计算,对单种不同分布式电源以及多种分布式电源并网对潮流的影响作了对比分析,结果表明牛顿法对不同的分布式发电电源类型以及并网控制策略,其潮流计算结果均能较好地收敛,且仿真结果显示,分布式发电电源的接入能有效抬升系统各节点电压水平。     

考虑可再生能源消纳的CCHP微能源网优化配置模型

微能源网中电、气、热等多种能源相互耦合,其容量与运行协调优化是促进可再生能源消纳和提高能源利用率的关键。针对含冷热电联供系统(CCHP)的微能源网优化配置问题,首先分析了含电、气输入和电、热输出耦合的微能源网系统构架和能量流,提出考虑促进可再生能源消纳和提高能源利用率的运行策略,建立基于能量流的供热可靠性指标,然后建立考虑投资费用、一次能源消耗、CO2排放、供能可靠性的综合评价指标的含CCHP的微能源网系统容量和运行策略的优化配置模型。算例仿真结果表明,所建立的模型在保证系统供能可靠性下能够促进可再生能源的消纳并提高系统的经济性。     

基于主从博弈的含碳捕集与热电联产综合能源系统优化运行

为了合理的分配综合能源系统中各主体之间的利益,促进能源低碳化,文中基于主从博弈框架建立了含碳捕集系统的综合能源系统优化调度模型,降低了热电联产机组的碳排放量和系统的运营成本。首先,构建碳捕集、电转气和热电联产的联合运行模型,在考虑综合需求响应的基础上,建立综合能源系统各主体的收益模型;其次,构建一主多从的Stackelberg博弈模型,并证明了该博弈纳什均衡的存在;由于构建的优化模型具有大规模、非线性、非凸的特点,难以求解,提出一种新型的天牛郊狼算法结合二次规划的分布式算法求解模型;最后以北方某工业园区为算例进行验证,分析结果表明文中提出的模型及改进算法与传统模型相比,有效的降低了综合能源系统的运行成本和碳排放量,且提高了可再生能源的消纳能力。     

大容量调相机对省级电网的影响分析

随着交直流混联电网的发展,越来越多地采用大容量调相机为系统提供无功支撑,提高电网运行的安全稳定性。对大容量调相机在特高压直流受端电网的应用进行研究,将调相机与电网中其他无功设备协调优化。通过对电压-无功的稳态和动态相关性分析,确定调相机的周边机组和相应的局部电网。构建含大容量调相机的非线性无功优化模型,优化局部电网的无功裕度。依据优化变量的不同特性,对连续变量和离散变量交替计算。以河南电网为算例,考虑不同负荷水平和电网结构的典型运行方式,模拟省调AVC的运行性能,进行计算分析,说明所述算法的可行性和实用性。     

面向灵活爬坡服务的高比例新能源电力系统可调节资源优化调度模型

随着高比例新能源接入电网,新能源出力和负荷的波动性及不确定性对系统的灵活爬坡能力提出更高的要求。提出了一种面向灵活爬坡服务的针对高比例新能源电力系统中常规发电机组、储能、柔性负荷等可调节资源的优化调度模型。首先,提出一种考虑日前预测净负荷不确定性的灵活爬坡需求估计方法,根据爬坡起始和结束时刻净负荷及其安全裕度,量化估计电力系统灵活爬坡需求。其次,基于生成的净负荷不确定性场景,提出了考虑系统灵活爬坡需求的基于两阶段混合整数线性规划的可调节资源优化调度模型,从日前-实时两个阶段实现可调节资源的优化调度。最后,基于IEEE-RTS-24节点系统,在4种典型方案场景下对比验证所提优化调度模型。结果表明所提模型能有效提升系统灵活性,降低系统运行成本。     

柔性直流电网潮流转移特性及安全运行影响分析

直流电网潮流大范围转移可能导致换流站运行于安全边界之外,进而引发直流系统连锁故障.为厘清不同情况下直流系统潮流分布转移特性及其对安全运行的影响,首先在主从控制、下垂控制方式下分别对故障线路切除和换流站注入功率改变后潮流转移特性进行了理论分析,并得出了不同运行方式下潮流转移定量计算方法.然后基于PQ功率域分析了复杂直流电...     

含电转热氢装置的综合能源系统经济运行

为解决富余电力对电网的冲击问题,需要为分布式电源配置储能装置,以提高综合能源系统运行经济性。将富余电力转化为氢气已经被证明是有效的处理方法,然而传统的电氢转换效率通常低于70%,且忽略了转换过程中的热损失问题。基于此,首先,介绍了一种考虑热回收的电转氢技术,即电转热氢技术。其次,将电转热氢技术应用于电解槽中,提出了一种含电转热氢装置的综合能源系统模型。同时,以购电成本、购气成本以及富余电力惩罚成本最小为目标,协同考虑电转热氢装置的温度特性,设计了三种不同的工作场景。最后,使用改进粒子群优化算法求解可知,引入电转热氢装置后,系统交易成本降低了1.48万元。算例结果表明,电转热氢装置的加入能够有效提高综合能源系统的经济性,验证了所提模型的有效性。     

Optimal integration of DGs into radialdistribution network in the presence ofplug-in electric vehicles to minimize dailyactive power losses and to improve thevoltage profile of the system using bioinspiredoptimization algorithms

Purpose: The increase in plug-in electric vehicles (PEVs) is likely to see a noteworthy impact on the distribution system due to high electric power consumption during charging and uncertainty in charging behavior. To address this problem, the present work mainly focuses on optimal integration of distributed generators (DG) into radial distribution systems in the presence of PEV loads with their charging behavior under daily load pattern including load models by considering the daily (24 h) power loss and voltage improvement of the system as objectives for better system performance. Design/methodology/approach: To achieve the desired outcomes, an efficient weighted factor multi-objective function is modeled. Particle Swarm Optimization (PSO) and Butterfly Optimization (BO) algorithms are selected and implemented to minimize the objectives of the system. A repetitive backward-forward sweep-based load flow has been introduced to calculate the daily power loss and bus voltages of the radial distribution system. The simulations are carried out using MATLAB software. Findings: The simulation outcomes reveal that the proposed approach definitely improved the system performance in all aspects. Among PSO and BO, BO is comparatively successful in achieving the desired objectives. Originality/value: The main contribution of this paper is the formulation of the multi-objective function that can address daily active power loss and voltage deviation under 24-h load pattern including grouping of residential, industrial and commercial loads. Introduction of repetitive backward-forward sweep-based load flow and the modeling of PEV load with two different charging scenarios.     

基于串级PI-(1+PD)算法的含飞轮储能互联电网AGC控制器设计

针对传统控制器存在的响应速度较慢、超调较大及鲁棒性较差等问题,提出一种基于串级PI-(1+PD)算法的含飞轮储能互联电网AGC控制器设计方法。首先,建立含飞轮储能的两区域互联电网AGC系统模型,模拟飞轮储能联合火电机组参与AGC的过程。然后,设计一种基于串级PI-(1+PD)算法的AGC控制器。外环采用PI控制,内环采用带滤波系数的(1+PD)控制。在保证系统稳态性能的前提下,提高动态响应速度和抗扰能力,并通过粒子群算法的迭代寻优获得最优的控制器参数。最后,基于Matlab/Simulink进行算例仿真分析。结果表明：与传统PID控制和PI-PD控制相比,所提方法不仅具有更快的响应速度与更小的超调量,而且增强了系统抵御内部参数摄动的鲁棒性。     

混沌正余弦算法在含风能电力系统经济排放调度中的应用

由于风能的随机性,含风能的经济排放调度问题变得更加复杂。因此,为了解决含风能的经济排放调度问题,将该问题描述为一个机会约束问题来处理风力发电的随机特性。基于此,提出了一种混沌正余弦算法来提供最优发电计划,以同时最小化发电成本和碳排放量。该算法利用混沌序列替代正余弦算法的随机数,避免了局部最优点的早熟收敛,提高了解的精度。然后,对比实数编码化学反应优化算法和基于二次逼近的混合人工协同搜索算法,通过2个10-unit案例仿真,验证了所提方法的有效性和准确性。最后研究了约束条件阀值水平σ对优化结果的影响,当σ增加时,风电渗透率增加,从而导致总生产成本和排放值的降低。