Study of Micro Grid Safety &Protection Strategies with Control System Infrastructures

Microgrids have been proposed in order to improve reliability and stability of electrical system and to ensure power quality of grid. Microgrid consists of low voltage distribution systems with distributed energy resources, such as wind turbine and photovoltaic power systems, together with storage devices. It is essential to protect a micro grid in both the grid-connected and the islanded mode of operation against all different types of faults. This paper describes micro grid protection and safety concept with central control and monitoring unit where multifunctional intelligent digital relay could be used. This central control & monitoring infrastructure is used for adaptive relay settings strategy for micro grid protection. Also operational safety design concept and fault mitigation technique is proposed to ensure confidence in protection system.

Energy Management for a Residential Microgrid Using Wavelet Transform and Fuzzy Control Including a Vehicle-to-Grid System

This paper presents the design and implementation of an energy management system （EMS） with wavelet transform and fuzzy control for a residential micro-grid. The hybrid system in this paper consists of a wind turbine generator, photovoltaic （PV） panels, an electric vehicle （EV）, and a super capacitor （SC）, which is able to connect or disconnect to the main grid. The control strategy is responsible for compensating the difference between the generated power by the wind and solar generators and the demanded power by the loads. Wavelet transform decomposes the power difference into a smoothed component and a fast fluctuated component. The command approach used for fuzzy logic rules considers the state of charging （SOC） of EV, renewable production, and the load demand as parameters. Furthermore, the command rules are developed in order to ensure a reliable grid when taking into account the EV battery protection to decide the output power of the EV. The model of the hybrid system is developed in detail under Matlab/Simulink software environment.

Micro-Grid Smooth Switchover Method Based on Controller State Following

Micro-grid smooth switchover between different operation modes is important for steady operation and reliable power supply of micro-grid. In order to reduce the transient fluctuation of voltage and frequency during switchover, this paper proposed a new switchover method based on controller state following. When transferring to island mode, the control method for inverter of storage device changed from PQ control to V/f control. Before switchover, the output of V/f controller is always following the output of PQ controller. So that the sudden change of output is avoided at the moment of switchover. A micro-grid model with photovoltaic and battery is built on DIgSILENT Power Factory simulation software, to simulate micro-grid switchover from grid-connected mode to island mode. Results show this method can effectively suppress the transient fluctuation of voltage and frequency, and reduce the influence of transient process on power grid. This conclusion has important practical significance on micro-grid smooth switchover from grid-con- nected mode to island mode.

Control System Development and Test for the Operation of a Micro-Grid System—PART I

This paper presents design, analysis and simulation performance of an active power controller for stable and reliable operation of a micro-grid system. Power balance between generation and consumer is a critical issue for stable and reliable operation of the micro-grid systems. This issue becomes more critical when a micro-grid system contains stochastic nature distributed generations such as wind and solar because their output power changes non-uniformly. In order to achieve accurate and fast power balance in such a micro-grid system, power in the system has to be regulated continuously. Such an objective can be achieved using droop based alternating current control technique. Because the droop characteristic employed into the developed controller initiates determining the power deviation in the system which is continuously regulated by controlling the current flow into dump power resistors. The designed controller is simulated for the operation of a micro-grid system in stand-alone mode under various operating conditions. The simulated results show the ability of the developed controller for stable and reliable operation of the micro-grid that contains renewable sources. The experimental development of the micro-grid system and the testing of the developed active power controller are presented in PART II of this paper.

Operation and Control of Microgrids Using IoT (Internet of Things)

The current microgrid power management system is undergoing a significant and drastic overhaul. The integration of existing electrical infrastructure with an information and communication network is an inherent and significant need for microgrid classification and operation in this case. Microgrid technology’s most important features: 1) Full duplex communication;2) Advanced metering infrastructure;3) Renewable and energy resource integration;4) Distribution automation and complete monitoring, as well as overall power system control. A microgrid’s communication infrastructure is made up of several hierarchical communication networks. Microgrid applications can frequently be found in numerous aspects of energy consumption. Because it provides a spontaneous communicational network, the Internet of Things plays a fundamental and crucial role in Microgrid infrastructure. This paper covers the deployment of a comprehensive energy management system for microgrid communication infrastructure based on the Internet of Things (IoT). This paper discusses microgrid operations and controls using the Internet of Things (IoT) architecture. Microgrids make use of IoT-enabled technologies, in conjunction with power grid equipment, which are enabling local networks to provide additional services on top of the essential supply of electricity to local networks that operate in parallel with or independently of the regional grid. Local balancing, internal blockage management, and request for support marketplace or grid operator activities are examples of auxiliary services provided by the microgrid that can add value to each end-user and other true stakeholders. Different technologies, architectures, and applications that use IoT as a key element with the main purpose of preserving and regulating innovative smart microgrids in accordance with modern optimization features and regulations are designed to update and improve efficiency, resiliency, and economics.

Control System Development and Test for the Operation of a Micro-Grid System—PART II

This paper presents experimental development and performance testing of an active power controller for stable and reliable operation of a micro-grid system. In order to achieve accurate and fast power balance in a micro-grid system that contains renewable energy sources, power in the system has to be regulated continuously. Such an objective can be achieved using droop based alternating current control technique. Because the droop characteristic employed into the developed controller initiates to determine the power deviation in the system which is continuously regulated by controlling the current flow into dump power resistors. The designed controller is tested and validated using a micro-grid prototype in the laboratory environment for stand-alone mode of operation under various operating conditions. The key development in the micro-grid prototype is the development of a wind turbine simulator. A dSPACE ds1104 DSP board is used to implement and interface the designed controller with the micro-grid system. The experimental investigation of the developed controller presents the significant capability to achieve continuous power balance in the micro-grid system, while it maintains stable and reliable operation of the system. Finally, the power quality of the isolated micro-grid system is presented and discussed under the operation of the developed controller.

Micro-source Inverters With Capacitive Equivalent Output Impedance for Improving Micro-grid Voltages

将分布式电源逆变器等效输出阻抗设计成容性可使其体现对系统无功电压调整过程相逆的电源特性,这种特性使得分布式电源逆变器更容易参与公共连接点处的电压调整。对比等效输出阻抗成感性、阻性和容性的3类逆变器下垂控制特性,对容性等效输出阻抗逆变器电压电流控制环进行数学建模;针对容性等效输出阻抗逆变器设计具备下垂调节和克服电压偏离功能的鲁棒功率外环控制器。对比仿真和实验证明,容性输出阻抗分布式电源逆变器控制器能够快速抑制系统功率变化带来的电压波动,能有效地参与系统电压调整。

Trends and Overview Regarding the Involvement of Micro-Grids in Modern Power Systems

Customer satisfaction and participation in utility supply packages is the first and foremost factor in the success of any supplying agency whether wholesale or retail dealer. The paper presents the concept of major prospects of non- autonomous micro-grids installed in a certain locality. The article shows the basic background that is required for the installment of micro grid in a particular area and discusses the primary factors or pre-requisites that are required for the existence and operation of micro-grids. It elaborate the major profitable applications and benefits that developing and developed states get by using micro-grids in an area where utility grid is already functioning .It also explains the basic improvement in the quality of supply from micro grid after its installment. It also throws light on afterwards impact on society with this system, such impacts include reliability, tariff rates, economics etc. The article discusses micro-grids as the future of modern power systems. This paper shows significance of modernization by latest topologies in power systems and its effect that will come afterwards.

Managing of Smart Micro-Grid Connected Scheme Using Group Search Optimization

This article introduces a group search optimization (GSO) based tuning model for modelling and managing Smart Micro-Grids connected system. In existing systems, typically tuned PID controllers are engaged to point out the load frequency control (LFC) problems through different tuning techniques. Though, inappropriately tuned PID controller may reveal pitiable dynamical reply and also incorrect option of integral gain may even undermine the complete system. This research is used to explain about an optimized energy management system through Group Search Optimization (GSO) for building incorporation in smart micro-grids (MGs) with zero grid-impact. The essential for this technique is to develop the MG effectiveness, when the complete PI controller requires to be tuned. Consequently, we proposed that the proposed GSO based algorithm with appropriate explanation or member representation, derivation of fitness function, producer process, scrounger process, and ranger process. An entire and adaptable design of MATLAB/SIMULINK also proposed. The related solutions and practical test verifications are given. This paper verified that the proposed method was effective in Micro-Grid (MG) applications. The comparison results demonstrate the advantage of the proposed technique and confirm its potential to solve the problem.

基于自抗扰控制的并网逆变器环流抑制策略

谐波交互是影响微网正常运行的主要扰动之一,为此带来的谐波谐振和谐波环流等问题备受关注。环流抑制是确保微网系统可靠工作的关键技术,为应对双闭环PI控制受扰动情况下抑制环流效果不佳,提出了一种基于自抗扰控制的多逆变器并联环流抑制策略,由线性扩张状态观测器对扰动进行估计并进行反馈补偿,配合独有的带宽法调参改善多逆变器并联均流控制效果。文章的主要内容是:建立了逆变器拓扑结构,进行环流的数学物理机理分析,通过两台逆变器并联在并网情况下的MATLAB仿真,证明了并联系统在扰动存在的条件下,自抗扰控制对环流有较好的抑制能力,使系统有很好的动态响应性能和均流效果,提高了并联系统的抗扰能力和可靠性。

Autonomous Multi-Factor Energy Flows Controller (AmEFC): Enhancing Renewable Energy Management with Intelligent Control Systems Integration

The transition to sustainable energy systems is one of the defining challenges of our time, necessitating innovations in how we generate, distribute, and manage electrical power. Micro-grids, as localized energy hubs, have emerged as a promising solution to integrate renewable energy sources, ensure energy security, and improve system resilience. The Autonomous multi-factor Energy Flow Controller (AmEFC) introduced in this paper addresses this need by offering a scalable, adaptable, and resilient framework for energy management within an on-grid micro-grid context. The urgency for such a system is predicated on the increasing volatility and unpredictability in energy landscapes, including fluctuating renewable outputs and changing load demands. To tackle these challenges, the AmEFC prototype incorporates a novel hierarchical control structure that leverages Renewable Energy Sources (RES), such as photovoltaic systems, wind turbines, and hydro pumps, alongside a sophisticated Battery Management System (BMS). Its prime objective is to maintain an uninterrupted power supply to critical loads, efficiently balance energy surplus through hydraulic storage, and ensure robust interaction with the main grid. A comprehensive Simulink model is developed to validate the functionality of the AmEFC, simulating real-world conditions and dynamic interactions among the components. The model assesses the system’s reliability in consistently powering critical loads and its efficacy in managing surplus energy. The inclusion of advanced predictive algorithms enables the AmEFC to anticipate energy production and consumption trends, integrating weather forecasting and inter-controller communication to optimize energy flow within and across micro-grids. This study’s significance lies in its potential to facilitate the seamless incorporation of RES into existing power systems, thus propelling the energy sector towards a more sustainable, autonomous, and resilient future. The results underscore the potential of such a system to revolutionize energy management practices and highlight the importance of smart controller systems in the era of smart grids.

基于改进下垂的多逆变器并联控制策略

针对微电网孤岛运行时,传统解耦式下垂控制策略由于未能考虑线路阻抗的影响,多逆变器并联运行时存在无功功率分配不均、环流等问题,论文提出一种基于自适应电压补偿的改进下垂控制策略。文中首先针对因线路阻抗不同所带来的电压跌落问题,增加了线路压降补偿环节,在此基础上,考虑逆变器出口处电压与母线电压的一致性,改进了下垂控制式,并利用低带宽通信技术获取各逆变器输出功率信息,引入自适应电压补偿环节,提高了逆变器间无功功率的均分精度。最后,基于Matlab平台搭建文章所提控制策略的仿真模型,仿真结果验证了所提控制策略的正确性与有效性。

基于预期动态方程的含高比例可再生能源孤岛运行微电网负荷频率控制

针对高比例可再生能源并入微电网带来的负荷频率控制问题,提出基于预期动态方程的比例-积分-微分(PID)控制策略.在分析微电网负荷频率控制模型和控制难点的基础上,设计基于预期动态方程的PID控制策略,采用单一变量法分析控制器参数对控制效果的影响,总结了简单、实用的参数整定流程,并在微电网负荷频率控制系统中应用.在不同工况下与多种控制器进行仿真对比,结果表明:所提控制策略能够在保证鲁棒性的前提下取得最佳控制效果,展现出很高的工程应用价值.

面向直流微电网的混合级联多电平逆变器阶梯波控制策略研究

级联多电平变换器将数个全桥逆变模块以级联方式进行连接并予以控制,适用于中压大功率输出场景下的直流微电网,广泛应用于能量路由器、智能电能网关、固态变压器等电力电子装置中.传统级联多电平变换器所级联的每一路逆变模块的电压相同,限制了多电平输出电压的电平数量.为解决上述问题,将传统的母线电压相等的三路级联7电平逆变器改造成母线电压为2的倍数关系(20∶21∶22)的三路混合级联15电平逆变器,通过采用阶梯波控制方法,并针对最近电平逼近法进行了改良以产生开关器件的触发信号,可有效降低开关器件的开关频率和开关损耗,并将输出电压由7电平增加到15电平,有效降低谐波.从混合级联15电平逆变器工作原理、阶梯波调制方法、输出电压谐波等角度开展了理论分析与计算,最终搭建样机进行实验,有效验证了所提出的分析和研究.

基于模糊下垂补偿的直流微源并联改进控制

由于线路阻抗不可忽略,传统应用于直流微电网的DC/DC变换器的下垂控制会造成直流母线电压存在偏差,分布式单元输出电流/功率不均衡。因此,为了减小母线电压偏差并提高各单元输出电流/功率的均分程度,提出一种基于电压电流双补偿的改进下垂控制策略:利用模糊算法对电压偏差进行补偿,提升电压控制精度;同时通过相邻单元间的输出电流信息交互,精确分配各变换器的输出电流/功率。为了验证所提控制策略的可行性,分别搭建了基于双向有源桥(dual active bridge,DAB)结构的直流微电网模型,同时搭建了2台DAB并联的直流微网实物平台。仿真和实验结果证明了所提控制策略对于提升电压/电流控制精度的有效性和正确性。

碳足迹强制约束下的混合储能微电网分布式协调控制算法

为保证混合储能微电网在碳足迹强制约束下,实现碳排放量最小、混合储能系统功率优化分配,提出碳足迹强制约束下的混合储能微电网分布式协调控制算法。基于混合能源的全生命碳足迹,构建碳排放量最小化、混合能源最佳定容的混合储能微电网分布式协调控制目标函数,并确定约束条件;在此基础上,结合混合储能微电网的不确定特性改写目标函数,形成min-max两阶段分布鲁棒优化协调控制模型;采用列与约束生成算法求解该模型,获取目标函数的最优解。测试结果显示:该方法应用后,碳足迹系数的结果均低于9.0,超级电容的功率分配结果为4.8 MW左右,网损电量和最大电压偏差的最高值分别0.42 MW⋅h和0.067 V,间接和直接两种碳排放量显著下降,有效提升了混合储能系统的荷电状态。

不同工况下光储氢微网系统协调控制策略

针对光储氢微网系统运行时系统内部功率协调分配、切换平滑度以及电压稳定性等问题,提出一种考虑系统不同需求指令的功率分层协调运行策略。以提升系统稳定性、光氢系统结合度以及平滑运行为目的,搭建光储氢微网系统仿真模型,一方面,通过分层控制实现系统指令层与被控层之间的协调运行,并以上网电价为判断指标,保障系统经济性运行;另一方面,基于系统运行模式将系统运行工况分为8种,并通过多功率协调控制策略使得光储氢微网系统能够稳定运行、工况切换平滑以及母线电压稳定。最后通过仿真验证所建模型与控制策略的正确性与有效性。

基于自适应SMPC的风-光-储混合微电网实时优化调度研究

针对风力发电、光伏发电的随机性、波动性,研究了风-光-储混合微电网系统中新能源消纳、储能分时电价、联络线阻塞等问题,构筑了风能-光能-储能多能源互补下的微电网实时优化调度模型。首先,探究了风-光-储混合微电网模型,引入了一种自适应随机模型预测方法,将混合整数非线性优化问题转化为二次规划问题,使风电、光电具有一定的可调度性。其次,以经济性和稳定性最优为目标建立了混合系统的实时优化调度模型。最后,通过IEEE-30节点6机组系统仿真分析,验证了所提调度策略及模型算法的经济性与可行性。

计及控制策略的并网型微电网可靠性评估

当上层配电网故障或电能质量不满足要求时,微电网可通过控制策略切换等调度各微电源的出力,实现微电网孤岛运行。孤岛运行时,不同控制策略直接影响微电网的供电可靠性。通过对微电网最常见的两种控制策略(主从型和对等型)的分析,建立了计及控制策略的并网型微电网功率模型;通过对上层配电网进行最小路等值,建立微电网不同控制策略下的故障影响矩阵,提出了基于时序蒙特卡洛的并网型微电网可靠性评估方法。以此方法对改进的IEEE-RBTS系统进行可靠性评估,分析了两种控制策略对配电网可靠性指标的影响。算例表明:微电网加入配电网后可改善系统可靠性性能;对等型微电网比主从型微电网的可靠性要高。

基于太阳能锂电池及柴油发电机组的多能源(光柴储)船舶微网能量控制系统研发

在多能源船舶综合电力推进系统中,船舶微网的可靠性将直接影响船舶航行的安全。构建一类基于太阳能电池、柴油发电机组以及锂电池的多能源(光柴储)船舶微网系统,提出相应的控制策略,研发基于P LC及总线控制技术的控制系统和系统集成技术。实船应用结果表明,研发的控制策略实现了各个能量源的有效管理,船舶多能源微网控制系统运行稳定,提高了新能源的利用率和船舶的续航力。