大量分布式光伏电源并网后的区域保护实现方法

研究了光伏电源并网的故障问题,分析了单个光伏电源并网与大量光伏电源并网的故障特性和保护动作特性。基于大量分布式光伏并网的运行特点及故障发生后的动作行为分析,提出了基于装置采集电量的主保护和基于网络通讯的区域后备保护方案。为尽量减少对现有系统的改动以及减少分布式光伏电源并网的投资,方案依托于新一代的分布式光伏并网接口装置来实现。该装置不仅能解决电网区域后备保护问题,还节约了投资,方便了现场设备安装和维护,为分布式光伏电源并网的大面积推广奠定基础。     

光伏电源对IEEE 34节点测试馈线过电流保护的影响

以IEEE 34节点测试馈线为研究对象,加入重合器和熔断器等过电流保护设备,在特定位置接入不同容量的光伏电源,利用PSCAD软件进行仿真,就短路电流和保护之间的协调性,研究光伏电源对过电流保护设备的影响.为此进行了多种故障仿真,以验证接入光伏电源后,电网的保护设备之间的协调性是否改变.仿真结果表明:并不是电网中的所有位置接入光伏电源,都会对保护产生影响,只有在特定位置接入光伏电源时,才会使某些保护失去选择性,导致其误动或拒动.     

分布式电源并网对电网运行和管理制度的影响及思考

结合苏州当前分布式电源接入电网项目的情况,总结了分布式电源发展的一些态势和规律,从继电保护、短路电流、谐波污染、无功平衡、经济运行等方面分析了光伏发电并网对电网的影响,分析了分布式电源并网运行后对原有电网管理制度带来的冲击,提出了在分布式电源并网利用中,电网公司作为重要的参与者和“补贴”方,应思考参与各方合作共赢的机制,确保分布式电源并网利用的高效安全以及可持续性.     

光伏并网对城市配电网保护影响及对策

介绍城市配电网保护现状,分析光伏电源在电网发生短路故障可能出现稳态的短路电流、并网不稳定以及孤岛效应,对配电网的准备性、灵敏度、选择性、快速性产生较大的影响,建议在把握原则的基础上,改进传统保护方案,应用"一主多从"的区域纵联保护方案,以实现对故障快速、准备、有选择性地定位与隔离,提高供电可靠性。     

利用串联制动电阻提高光伏并网系统故障穿越能力的研究

为了优化光伏并网系统的故障穿越能力,提出一种结构简单、设备经济的灵活串联制动电阻(flexibleseries braking resistors,FSBR)方法。在短路等引起的低电压故障中,FSBR能够以热能方式耗散掉短路冲击电流并且自身产生可观的压降,从而支撑并网公共点电压;在突然卸荷等引起的高电压故障中,FSBR能够以串联分压方式减轻过电压的冲击,从而保护直流母线侧电压恒定;在电压故障引起的频率跳变故障中,FSBR通过平衡光伏系统与电网两侧的功率供需间接提高频率跟踪性能。通过建立光伏并网模型,探讨FSBR制动电阻大小与运行时间、投切控制策略对故障穿越的影响。仿真结果表明所提FSBR方法在优化光伏并网系统故障穿越能力上具有可行性与优越性。     

计及光伏出力随机性的电网运行风险评估

针对光伏发电输出功率具有随机性、可能带来电网运行风险的问题,利用蒙特卡洛模拟法对太阳光辐照度分布区间进行模拟,建立了光伏随机输出模型,对整个系统的设备及光伏电源出力进行随机抽样;结合风险理论,对并网光伏系统随机出力情况下电网的运行风险指标进行了计算。以IEEE-RTS79系统为例,分析了不同光伏并网点和不同并网容量对电网运行风险的影响。结果表明,在负荷较重区域增设光伏并网,可以有效地降低电网运行风险。因此,选择适当的光伏并网点和容量可以降低电网运行风险。     

分布式光伏电源接入电网安全管理实践与研究

为研究分析分布式光伏电源接入电网后对电网控制、安全运行和配电网运维检修的影响,基于分布式光伏电源并网的原理和结构,通过实地调研和理论计算,分析了反送电的安全风险、对电网短路水平、继电保护、配电网自动化和系统稳定的影响,以及相关标准制度和反"孤岛"装置等的实践应用情况。最后,提出了加强安全管控的措施,建议严把并网设备安全关和作业安全措施关,这将在分布式光伏电源大力推广的同时,有效促进电网运行检修安全。     

限制过电压条件下的光伏发电并网设计

大规模发展分布式光伏发电有助于缓解能源危机,但随着分布式光伏发电的大规模接入,将对配电系统产生较大影响.阐述了光伏发电并网系统结构,结合分布式光伏发电特点和电网工程实际,设计出限制过电压条件下的光伏发电并网方案,提出光伏发电系统并网后直流与谐波分量的治理措施.实际运行表明,所设计的分布式光伏发电并网方案既能够保证接入点电压不越限,又能够有效减少占用线路走廊资源和电网调度、运行维护工作量.     

光伏发电功率短期预测方法研究

煤炭、石油、天然气等不可再生能源的使用,严重降低了空气质量,光伏并网由于可再生、无污染以及资源丰富的特点受到了社会各界人士的喜爱,但是光伏并网发电系统会从许多的不同层面影响电网的电能质量。本文重点分析了分布式光伏发电并网系统,对低压配电网的数学模型进行推导,并且从电路基本理论角度分析光伏配电电源对配电网电能质量产生的作用,发现配电网电压波动与光伏电源容量和短路容量密切相关。     

风电、光伏并网保护配置差异化分析

分析了风电、光伏发电单线并网线路近区电网保护配置的差异。根据两种新能源短路电流的特点,对风电、光伏发电保护及安全自动配置差异形成的原因进行了解释,尤其对防孤岛安稳装置的配置差异进行剖析。最后结合风光电网近区故障的典型案例,对故障时风光保护及安全自动装置的动作行为进行了分析。     

并网光伏发电系统动态特性的对比分析

大量光伏电站的并网,相应地带来并网稳定性、自身抗扰动性等相关问题。由于单级型光伏并网系统和双级型光伏并网系统的拓扑结构不同,其并网运行的动态特性也不尽相同。文章基于PSCAD/EMTDC电磁暂态仿真软件,分别搭建单级型和双级型光伏并网系统模型,并对比仿真了光照扰动与电网电压跌落扰动下两种光伏并网系统的动态特性,单级型光伏并网系统更适合于大中型光伏电站。     

光伏发电并网大电网面临的问题与对策

妥善解决光伏发电系统接入大电网后2部分都能安全、高效运行是光伏发电技术大规模工业化应用的关键之一。分析了光伏发电系统及其并网的技术特点,简要阐述了光伏发电并网问题的研究现状。指出光伏发电大规模并网使大电网在研究与实验验证手段、对光伏发电系统影响大电网机理的认识、新型配电系统的规划、电网运行控制、电网监测保护与控制装备、技术标准与规范等方面面临新的问题,并提出了应对这些问题的策略。     

Bidirectional energy storage photovoltaic grid-connected inverter application system

A novel topology of the bidirectional energy storage photovoltaic grid-connected inverter was proposed to reduce the negative impact of the photovoltaic grid-connected system on the grid caused by environmental instability. Using the proposed Inverter as a UPS power supply in case of a grid failure, storage electrical energy and regulating the energy delivered to the grid for reducing the pressure on the grid. A new artificial fish-swarm algorithm and variable step voltage perturbation method were presented to track the maximum power point of the solar panels. Analysis was done to reduce the output ripple of the inverter and sinusoidal pulse width modulation (SPWM) was selected to control the inverter. Model simulation was performed using PSpice software to obtain the volt-ampere characteristic curve of the solar panel output. The solar array simulator was used to verify the effect of maximum power point tracking at different light intensities. The study concludes that the maximum power point tracking (MPPT) efficiency of the bidirectional energy storage photovoltaic grid-connected inverter designed was as high as 99.9%. The distortion rate of the grid-connected current waveform was within 2% and the DC current component was less than 0.5%. The output voltage and power were in full compliance with the grid connection standard.     

一种基于三端口能量路由的单级式光储并网系统及其高压穿越技术

该文提出一种具有高压穿越能力的基于三端口能量路由的单级式光储并网系统（PV-ESS）。光伏最大功率跟踪始终由三相变换器控制完成。多端口能量路由器可根据不同运行工况使储能灵活接入,平抑光伏输出,使得系统具有更高的效率。在电网高压故障下,通过储能装置抬升直流母线电压,从而使系统具有高压穿越的能力,可在电网高压状态下不脱网连续运行,直至故障恢复。     

分布式光伏电站接入电网电能质量评估计算

光伏电站接入配电网后,在改变电网原有拓扑结构和潮流方向的同时,其电能输出特性直接影响到电网的电能质量。为保障现有电网的安全稳定,更好利用太阳能,在光伏电站接入系统前的设计阶段需对光伏发电接入系统进行电能质量评估。结合实际工程案例,以某MW级分布式光伏电站为研究对象,根据分布式光伏电站接入电网时的电能质量要求,基于Matlab/Simulink仿真平台进行建模,对并网电能质量进行评估计算,并进行相应的分析。计算结果表明：该分布式光伏电站接入点符合电能质量要求,允许接入系统。     

Distributed generation hybrid AC/DC microgrid protection: A critical review on issues,strategies, and future directions

The integration of distributed energy resources (DERs) with conventional systems emerges as an intelligent solution for providing uninterrupted and secure power even at times of high load demand. Better load management with a mature fault handling mechanism makes AC a viable option which has an efficiency of 78.24%. In contrast with less power loss and slightly better efficiency of 84.6%, DC microgrid is a reliable option in a low power environment. In order to accommodate all operating conditions and load types, a hybrid system can be designed with a theoretical efficiency of more than 90%. Bidirectional power flows, low inertia, the transition between different modes of operations are the challenges for the protection of alternating current (AC) and direct current (DC) microgrid systems. Power balance fluctuation, absence of zero-crossing currents, selection of suitable grounding, and coordination between different rating devices restrict the hybrid system to achieve the said efficiency constantly. This paper reviews in detail of existing protection along with grid-connected algorithms for both modes of operation. Finally, the limitation, major hurdles, and future course of action for a reliable, efficient, and secure hybrid grid system are figured out.     

Modeling and simulation of a grid-connected PV generation system for electromagnetic transient analysis

This paper addresses modeling and simulation of a grid-connected photovoltaic system (GCPS) to analyze its grid interface behavior and control performance in the system design. A simple circuit model of the solar array is used to easily simulate its inherent characteristics with the basic specification data. Detailed power and protection control of the GCPS as well as its electrical circuits have been represented by user-defined and built-in components to take into account transients in normal and fault conditions, which are dominated by its power electronic controller. The model has been described with the reference to and implemented in PSCAD/EMTDC, a power system transient software package. Extensive simulation results are presented and analyzed to validate that the proposed simulation model is effective for control and protection performance evaluation of the GCPS in terms of electromagnetic transient analysis.     

Techno-economic analysis of hydrogen energy for renewable energy power smoothing

With the increasing proportion of renewable energy (mainly wind power and photovoltaic) connected to the grid, the fluctuation of renewable energy power brings great challenges to the safe and reliable operation of power grid. As a clean, low-carbon secondary energy, hydrogen energy is applied in renewable energy (mainly wind power and photovoltaic) grid-connected power smoothing, which opens up a new way of coupling hydrogen storage energy with renewable energy. This paper focuses on the optimization of capacity of electrolyzers and fuel cells and the analysis of system economy in the process of power output smoothing of wind/photovoltaic coupled hydrogen energy grid-connected system. Based on the complementary characteristics of particle swarm optimization (PSO) and chemical reaction optimization algorithm (CROA), a particle swarm optimization-chemical reaction optimization algorithm (PSO-CROA) are proposed. Aiming at maximizing system profit, the capacity of electrolyzers and fuel cells are constrained by wind power fluctuation, and considering environmental benefits, government subsidies and time value of funds, the objective function and its constraints are established. According to the simulation analysis, by comparing the calculated results with PSO and CROA, it shows that PSO-CROA effectively evaluates the economy of the system, and optimizes the optimal capacity of the electrolyzers and fuel cells. The conclusion of this paper is of great significance for the application of hydrogen energy storage in the evaluation of power smoothness and economy of renewable energy grid connection and the calculation of economic allocation of hydrogen energy storage capacity.     

一起机端断路器非全相合闸案例的分析与思考

本文介绍了一起带机端断路器(GCB)机组非全相合闸并网的实例,分析了并网前后的零序电压接地保护动作情况,对故障时GCB两侧电压特征量进行了理论分析,并结合实际录波数据进行了验证.通过分析与研究,提出了增设机端断路器非全相保护的必要性与可行性,给同类型接线方式的发变组运行维护提供参考,提升发电机安全运行水平.