Mechanism of Primary Frequency Regulation for Battery Hybridization in Hydropower Plant

Battery hybridization in hydropower plants is a hydropower flexibility enhancement technology innovation that can potentially expand hydropower’s contributions to the grid,but its fundamental characteristics and influencing mechanisms are still unclear.In this paper,primary frequency regulation(PFR)performance and the mechanism of this new technology are studied.A battery hybridized hydropower plant(BH-HPP)model,based on a field-measured-data-based hydropower plant(HPP)model and a verified battery simplified model,is established.Analysis of system stability and dynamics is undertaken for three different battery control strategies by root locus and participation factor methods.Compared to conventional HPPs,analysis results theoretically reveal BH-HPP can not only accelerate system regulation rapidity but also effectively enlarge HPP stability region during PFR process.Time domain simulation verifies the results and further shows synthetic control has better performance among introduced strategies.Besides,initial design ranges of control parameters considering battery capacity and a renewable energy source scenario case are also discussed.This work could provide theoretical support for flexibility enhancement solutions for hydropower systems.

Decentralized Primary Frequency Regulation for Hybrid Multi-terminal Direct Current Power Systems Considering Multi-source Enhancement

Hybrid multi-terminal direct current(MTDC)transmission technology has been a research focus,and primary frequency regulation(FR)improvement in the receiving-end system is one of the problems to be solved.This paper presents a decentralized primary FR scheme for hybrid MTDC power systems considering multi-source enhancement to help suppress frequency disturbance in the receiving-end systems.All the converters only need local frequency or DC voltage signal input to respond to system disturbance without communication or a control center,i.e.,a decentralized control scheme.The proposed scheme can activate appropriate power sources to assist in FR in various system disturbance severities with fine-designed thresholds,ensuring sufficient utilization of each power source.To better balance FR performance and FR resource participation,an evaluation index is proposed and the parameter optimization problem is further conducted.Finally,the validity of the proposed scheme is verified by simulations in MATLAB/Simulink.

Tuning method for governor control parameters of hydropower generator in isolated grid considering primary frequency performance and small-signal stability

This paper presents a method of tuning governor control parameters of an isolated hydropower generator considering the primary frequency performance and small-signal stability. First, generators that can be operated in isolated state are identified. Second, different schemes are proposed for generator mode switching from on-grid to off-grid state through comparison and mechanism analysis. Third, the time domain model and frequency domain model of the isolated generator governor are constructed to respectively estimate the primary frequency performance and small signal stability. Parameter sets that satisfy the primary frequency performance and small signal stability are acquired as optimal values of governor control parameters. Finally, the measurement-based parameters of the governor are identified and validated using simulations to demonstrate the feasibility and effectiveness of the method.

Frequency-constrained Unit Commitments with Linear Rules Extracted from Simulation Results Considering Regulations from Battery Storage

Heavy renewable penetrations and high-voltage cross-regional transmission systems reduce the inertia and critical frequency stability of power systems after disturbances.Therefore,the power system operators should ensure the frequency nadirs after possible disturbances are within the set restriction,e.g.,0.20 Hz.Traditional methods utilize linearized and simplified control models to quantify the frequency nadirs and achieve frequency-constrained unit commitments(FCUCs).However,the simplified models are hard to depict the frequency responses of practical units after disturbances.Also,they usually neglect the regulations from battery storage.This paper achieves FCUCs with linear rules extracted from massive simulation results.We simulate the frequency responses on typical thermal-hydro-storage systems under diverse unit online conditions.Then,we extract the rules of frequency nadirs after disturbances merely with linear support vector machine to evaluate the frequency stability of power systems.The algorithm holds a high accuracy in a wide range of frequency restrictions.Finally,we apply the rules to three typical cases to show the influences of frequency constraints on unit commitments.

Novel Optimal Load Control for Power System Frequency and Voltage Regulation

The sudden generation-consumption imbalance is becoming more frequent in modern power systems, causing voltage and frequency stability issues. One potential solution is load participation in primary control. We formulate a novel optimal load control(NOLC) problem that aims to minimize the disutility of controllable loads in providing primary regulation. In this paper, we show that the network dynamics, coupled with welldefined load control(obtained via optimality condition), can be seen as an optimization algorithm to solve the dual problem of NOLC. Unlike most existing load control frameworks that only consider frequency response, our load-side primary control focuses on frequency, voltage, and aggregate cost. Simulation results imply that the NOLC approach can ensure better frequency and voltage regulations. Moreover, the coordination between NOLC and other devices enabled in the system, the NOLC performance against the total size of controllable loads, and the NOLC effectiveness in a multi-machine power system are also verified in MATLAB/Simulink.

新能源场站快速频率支撑能力评估研究现状与技术展望

随着以风电、光伏为代表的新能源发电逐步取代同步机组,系统调频资源不足、抗扰动能力下降,频率安全问题凸显,新能源场站提供快速频率支撑成为构建新型电力系统的必然要求。新能源场站快速频率支撑是其内部多设备、多环节综合作用的结果,受风光资源、控制策略、电网条件等多因素的影响和制约。量化评估新能源场站的快速频率支撑能力是指导场站调频优化控制、分析新型电力系统频率响应特性、实现场站调频资源与电网交互的基础和前提。文中对新能源场站快速频率支撑能力评估问题进行了全面综述。首先,分析场站快速频率支撑的特征,并给出了场站快速频率支撑能力的定义;然后,从状态属性、控制特性、调频效果3个维度梳理了场站快速频率支撑能力的评估指标体系,并对各类评估指标的常用计算方法进行分析评述;最后,提出了值得关注和进一步研究的关键技术问题。

基于频率响应特性的储能辅助电网调频方法

新能源渗透率的提高增加了电网频率控制的复杂度,储能辅助电网调频能在一定程度上缓解该问题,但受储能运行的安全性与经济性约束,要求调频措施更具针对性。文中对此展开研究,提出一种基于频率响应特性的储能辅助电网一次调频方法。首先,在储能辅助电网调频模型基础上,选择惯性加下垂的储能辅助电网调频综合控制方法,通过电网频率变化率(rate of change of frequency,RoCoF)、频率偏差与调频需求的关联性分析,设计基于频率响应特性的调频需求分区规则;然后,根据不同调频需求对应的分区判断,对储能有功输出方式进行动态调整,以响应调频需求的不确定性,并在此基础上,针对调频需求与储能出力需求、储能出力强弱与其循环使用寿命间的矛盾关系,通过多目标优化问题的设计与求解来予以平衡;最后,仿真结果验证了所提方法能够在保证电网调频效果的基础上,有效降低储能充放电深度。

电力电子变压器参与配电网调压调频的应用研究

为提升配电网的稳定性,该文提出利用配电网电力电子变压器对配电网的电压和频率进行调节。通过电力电子变压器输入级进行配电网无功功率调节,利用母线电压下垂特性提出无功调节方法,并引入无功电流反馈以提高配电网电压质量和稳定性;同时,通过电力电子变压器输出级控制负载电压以调节配网有功功率,作为一次调频储备负载,从而在频率暂态期间减小频率偏差。通过对基于配电网电力电子变压器的调压调频控制方法进行实验验证,所提控制策略能改善配电网电压和频率质量,有效提升配电网的稳定性。

PV-VSG光伏电站一次调频试验及性能评估方法研究与应用

光伏发电的随机性导致了不同光伏电站出现一次调频性能不足、接入电网频率失稳等问题。而光伏场站的一次调频能力是维持电网稳定性的关键,因此对光伏电站的一次调频能力进行测试与评估具有重要意义。以石城子某光伏电站机组为例,详细介绍了PV-VSG光伏电站实施一次调频的意义、原理及措施,并提出了适用于该光伏电站的一次调频试验技术方案和试验方法。通过频率阶跃及模拟实际电网频率扰动、防扰动性能及自动发电控制(Automatic generation control,AGC)协调的合格率对光伏电站的安全性及稳定性进行评估,具有实际应用价值和推广意义。

虚拟同步耦合下储能的频率支撑与功率振荡多目标协调控制

准确评估系统惯量、阻尼和一次调频需求,弱化虚拟同步机阻尼支撑和一次调频间的耦合性,是实现储能并网发电系统多目标协调控制的关键。基于同步机的功率响应方程,建立虚拟调速器系统,弱化虚拟同步机单位调节功率和阻尼的耦合性。根据同调发电系统的频率稳定约束,量化评估储能的单位调节功率和惯量需求,以保障系统频率安全。根据阻尼比约束设计储能阻尼,以保障同调发电系统的振荡抑制能力,并结合频率安全需求提出含虚拟调速系统的虚拟同步多目标协调主动支撑控制策略,充分发挥储能的惯量、一次调频及阻尼支撑潜力。搭建风储高渗透率并网仿真系统,验证所提控制策略可显著改善储能支撑系统频率稳定和抑制功率振荡的能力。

Scenario-based Unit Commitment Optimization for Power System with Large-scale Wind Power Participating in Primary Frequency Regulation

Continuous increase of wind power penetration brings high randomness to power system,and also leads to serious shortage of primary frequency regulation(PFR)reserve for power system whose reserve capacity is typically provided by conventional units.Considering large-scale wind power participating in PFR,this paper proposes a unit commitment optimization model with respect to coordination of steady state and transient state.In addition to traditional operation costs,losses of wind farm de-loaded operation,environmental benefits and transient frequency safety costs in high-risk stochastic scenarios are also considered in the model.Besides,the model makes full use of interruptible loads on demand side as one of the PFR reserve sources.A selection method for high-risk scenarios is also proposed to improve the calculation efficiency.Finally,this paper proposes an inner-outer iterative optimization method for the model solution.The method is validated by the New England 10-machine system,and the results show that the optimization model can guarantee both the safety of transient frequency and the economy of system operation.

风机与储能参与电网调频协调控制技术综述

风机自身的调频能力有限,已无法满足电网调频需求。储能的柔性控制、吞吐容量大以及响应速度快等特点可以弥补风机的不足,适合形成风储联合系统参与电网的调频控制。通过对储能与风机参与电力系统调频的原理和控制策略进行的详细梳理,介绍了储能参与调频的原理、特点以及储能的调频模型与控制策略,对不同类型以及混合储能系统的调频特点与效果进行分析;接着对风机的调频原理及不同控制策略进行阐述,以风机分别以变桨控制、转子动能控制和联合控制方式进行分类。最后对本领域的现状和未来发展进行了总结与展望。

基于逐次变分模态分解的飞轮-火电一次调频控制策略

随着新型电力系统的大力建设与推广,火电机组面临的调频压力增大,提出一种逐次变分模态分解的飞轮-火电一次调频控制策略。首先,以飞轮储能和火电机组为研究对象,建立考虑新能源占比的飞轮-火电一次调频模型;其次,将一次调频功率指令利用逐次变分模态方法分解,由火电机组响应分解后的低频功率指令,同时设计飞轮储能下垂优化控制方法,实现飞轮储能与火电机组响应频率变化的协同控制;最后在不同工况下仿真验证,结果表明所提策略可有效避免火电机组一次调频时的频繁出力,减小火电机组响应频率变化时的调控要求,同时可最大限度地利用飞轮储能调频容量并保证飞轮储能调频期间的运行安全,进一步提升了系统的频率响应能力。

适用于一次调频能力在线监测的锅炉蓄热系数计算方法

锅炉蓄热系数是衡量火电机组一次调频能力的重要参数,实际运行中随着机组工况变化,但目前仿真中多忽略变工况下的蓄热系数变化对调频能力的影响。为准确掌握机组运行中真实的一次调频能力,需要在线确定蓄热系数。基于IEEE标准模型的框架,提出适用于一次调频能力在线监测的锅炉蓄热系数计算方法。建立考虑工质流动与传热过程的锅炉热力系统动态模型。以某1000 MW超临界机组为算例,结果表明所提出的变工况锅炉蓄热系数算法能更准确地描述一次调频过程中热力参数的动态变化。一次调频60 s内积分电量相较于IEEE标准模型减小62.4%。且低负荷下蓄热系数大,蓄热释放速率慢。该方法能根据现场实时数据确定当前工况下的蓄热系数,可应用于一次调频能力在线监测。

计及风力发电机转速安全约束的DFIG一次调频模型预测控制策略

针对传统方法控制双馈感应发电机(DFIG)的调频效果过于依赖参数整定的问题,该文提出了一种基于模型预测控制(MPC),计及转速安全约束的风力发电机参与一次调频控制策略。该方法结合风力发电机动力学模型与频率响应模型建立预测模型,通过线性回归方法变参考值将风力发电机转速的稳定性纳入考虑。相较于虚拟惯性控制等方法将系统频率偏差与转子动能直接关联,该文方法通过建立全新的预测模型,实时统筹考虑整个系统的状态信息,无需反复调整参数,在考虑转速安全性的同时兼顾全局性能。最后,通过实际算例分析验证了该文调频策略的有效性以及相对现有方法的优越性。

异步联网下水电站一次调频功能设计与优化

异步联网下机组一次调频功能的合理设计关系到电网频率稳定和电网安全稳定运行。根据国家电网和南方电网对一次调频相关技术要求,阐述了开度模式下和功率模式下水电机组一次调频功能的设计,探讨了水电站一次调频与AGC协调控制策略。研究结果可供复杂电网环境水电站一次调频功能设计参考。

面向电网最大频率偏差的风电机组短时频率支撑最优策略与机理

当电网出现有功缺额并导致频率跌落时,风电机组可以通过释放自身轴系动能为电网提供短时频率支撑(short-term frequency support,STFS)。如何利用有限的风电机组轴系动能最大限度地支撑电网频率,是当前研究的热点问题。针对风电机组可释放动能和电网频率变化率约束下的电网最大频率偏差最小化问题,该文提出一种基于有功功率互补控制(active-power complementation control,ACC)的风电机组STFS策略,揭示STFS过程中风电机组的最小动能释放机理,并证明采用ACC释放全部轴系动能的STFS策略为上述问题的最优解。最后,基于含风电的电网动模实验平台的实验结果验证该文提出STFS策略的可行性与频率支撑效果。

考虑荷电状态一致性的分布式储能电站一次调频控制策略

随着可再生能源比例增加,电网新建储能电站成为提升系统频率稳定性的重要手段。针对电网中分布式储能电站(distributedenergystoragestations,DESS)参与一次调频面临的荷电状态均衡问题,提出了一种考虑荷电状态(state of charge,SOC)一致性的DESS协同控制策略。首先,构建了含分布式储能电站的区域电网调频模型,分析了传统调频控制方法的特点,并讨论了储能在高渗透率新能源电网中的调频及一致性控制需求;其次,分析了电网调频需求与DESS的SOC一致性调整需求之间的耦合关系,设计了基于一致性原理的SOC分布式控制策略,进而构建了兼顾两种需求的DESS一次调频协同控制方法,详细分析了关键控制参数的设计原则与取值方法。最后,搭建典型区域电网模型,结合不同频率波动工况进行了仿真验证,结果表明:所提控制策略可以有效改善电网频率质量,在不增加系统调频负担的前提下实现多个储能电站的SOC一致性调节,减小了DESS集群的SOC越限风险,增强了其聚合控制效果。

新型电力系统下燃煤火电机组一次调频面临的挑战与展望

频率稳定是未来新型电力系统运行的最关键要求之一。中国的能源禀赋决定了燃煤火电机组是最核心、最可靠的一次调频资源。然而,燃煤火电已开始出现一次调频能力不足的趋势。为了满足当前和长远发展的需要,文中综述了燃煤火电在一次调频领域所面临的挑战、研究现状和关键科学问题。首先,总结了新型电力系统发展背景下火电一次调频的4个重要趋势,分析了下一步调频在电网和火电厂运行中的不足,提炼出提高一次调频能力和快速准确模拟调频的关键挑战。其次,从电网和火电厂运行的双向视角,综述了调频能力提升和调频动态仿真的研究现状和存在的问题。最后,结合上述挑战和瓶颈,展望了未来新型电力系统火电一次调频的关键技术问题。

计及灵活经济环保运行的火电-飞轮储能系统容量配置与调频参数协同优化

提出了一种计及灵活经济环保运行的火储系统容量配置与调频参数协同优化方法。首先,设计了一种基于低通滤波自动分配火储功率和考虑储能荷电状态自恢复的火储联合一次调频协调控制策略;综合考虑系统调频性能、投入运行成本、污染物排放等,建立了火储容量配置与调频参数协同优化模型,并给出了基于粒子群算法的求解方法。最后,以某火储系统为例进行仿真验证。结果表明:协调控制策略和协同优化方法具有有效性。