Review on Power System Frequency Regulation with High Wind Power Permeability

In recent years, global wind power has developed rapidly to alleviate environmental pollution and energy crisis. Due to the potential of enhancing the stability of power system through the application of wind power participating in power grid frequency regulation, the large-scale integration of wind power has become a hot issue for academic research in recent years. This paper classifies the frequency control problems of wind power integration and summarizes the research of power system frequency regulation strategy with high wind power permeability. Energy storage system participating in frequency regulation of the power system with high wind permeability is reviewed and analyzed.

Coordinated Frequency Control for Isolated Power Systems with High Penetration of DFIG-Based Wind Power

This paper proposes a coordinated frequency control scheme for emergency frequency regulation of isolated power systems with a high penetration of wind power.The proposed frequency control strategy is based on the novel nonlinear regulator theory,which takes advantage of nonlinearity of doubly fed induction generators(DFIGs)and generators to regulate the frequency of the power system.Frequency deviations and power imbalances are used to design nonlinear feedback controllers that achieve the reserve power distribution between generators and DFIGs,in various wind speed scenarios.The effectiveness and dynamic performance of the proposed nonlinear coordinated frequency control method are validated through simulations in an actual isolated power grid.

Challenges of Power Delivery from Jiuquan Wind Power Base

The 10-GW-class Jiuquan Wind Power Base in Gansu Province is to get its Phase I Project completed soon, and will further expand and become the world largest wind power base in the future. Whether electricity from the wind power base can be delivered on such a large scale becomes the focus of attention of the world. This paper analyzes four challenges facing the wind power base, including transmission capability, peak regulation and frequency modulation, capacity balance and generation accommodation, as well as system stability.

Integrated Frequency-constrained Scheduling Considering Coordination of Frequency Regulation Capabilities from Multi-source Converters

As the proportion of renewable energy(RE)increases,the inertia and the primary frequency regulation(FR)capability of the power system decrease.Thus,ensuring frequency security in the scheduling model has become a new technical requirement in power systems with a high share of RE.Due to a shortage of conventional synchronous generators,the frequency support of multi-source converters has become an indispensable part of the system frequency resources,especially variable-speed wind turbine generation(WTG)and battery energy storage(BES).Quantitative expression of the FR capability of multi-source converters is necessary to construct frequency-constrained scheduling model.However,the frequency support performance of these converter-interfaced devices is related to their working states,operation modes,and parameters,and the complex coupling of these factors has not been fully exploited in existing models.In this study,we propose an integrated frequency-constrained scheduling model considering the coordination of FR capabilities from multi-source converters.Switchable FR control strategies and variable FR parameters for WTG with or without reserved power are modeled,and multi-target allocation of BES capacity between tracking dispatch instruction and emergency FR is analyzed.Then,the variable FR capabilities of WTG and BES are embedded into the integrated frequency-constrained scheduling model.The nonlinear constraints for frequency security are precisely linearized through an improved iteration-based strategy.The effectiveness of the proposed model is verified in a modified IEEE 24-bus standard system.The results suggest that the coordinated participation of BES and WTG in FR can effectively reduce the cost of the scheduling model while meeting frequency security constraints.

风电虚拟惯量延时的影响机理模型解析及替代性研究

风电机组采用虚拟惯量参与电网调频时,其本质是带延时的快速功率响应,但虚拟惯量延时对频率控制的非线性影响尚不清晰。同时,虚拟惯量存在测频精度要求高、延时大、频率微分环节放大量测误差等固有缺陷。为此,提出了风电机组虚拟惯量延时的影响机理模型解析及替代性研究的思路。首先,通过将风电机组虚拟惯量和下垂控制的延时特性近似等效为一阶惯性环节,建立风电调频使用虚拟惯量和下垂控制的系统频率响应模型;其次,基于劳斯近似法对高阶模型进行降阶解析,求得系统频率最低点的解析表达式;然后,解析求解风电调频仅使用下垂控制的系统频率响应模型,并在频率最低点指标下给出与虚拟惯量和下垂控制相同调频效果的下垂控制系数设定方法。进一步,在设定下垂控制参数下,对比两种控制方式下的最大频率变化率、稳态频率等关键指标关系,得出结论:适当改变下垂系数可替代带延时虚拟惯量,并能取得比虚拟惯量和下垂控制更佳的调频效果。最后,建立仿真模型,并从系统频率响应动态、调频能量需求、风电机组响应功率等方面验证了分析的正确性。

超级电容参与风电调频的动态响应优化策略

随着风电渗透率的不断提高,电力系统逐步呈现低惯量的特征。低惯量系统在故障时的频率变化率(RoCoF)和最大频率偏差显著增大,传统频率控制方法效果减弱,频率的安全、稳定面临挑战。针对上述问题,先于一次调频动作的快速频率响应(FFR)已成为解决低惯量系统频率稳定问题的重要手段。首先,建立风-火-储电力系统频率响应模型,分析FFR调频资源对低惯量系统频率响应的影响;其次,基于模糊逻辑推理,提出了一种超级电容参与风电调频的储能动态响应优化策略以控制储能,使其能够动态响应系统频率变化,在频率跌落期遏制频率跌落,在频率恢复期调控储能恢复功率以维持荷电状态稳定;最后,对提出的控制策略进行仿真验证。仿真结果表明,所提策略能够利用超级电容快速动态响应系统频率变化,从而为低惯量系统提供功率支撑,弥补风电调频的不足,相较传统的风电机组虚拟惯量控制策略,在减小最大RoCoF及抑制最大频率偏差效果上均有大幅提升。

电网故障下含直驱风电机组的电力系统频率动态响应分析

电网受扰后基于模型解析的频率响应分析对电力系统安全评估与紧急控制具有重要意义。电网发生故障时,直驱风电机组(DDWT)并网点电压幅值跌落引发控制器暂态响应,同时电压相位突变引发锁相暂态响应,锁相暂态响应又通过变流器控制传导产生功率控制误差,可能导致现有以负荷突变场景为对象的频率特性分析产生较大偏差。为此,提出了电网故障下DDWT锁相偏差的量化方法;解析了锁相偏差经DDWT变流器控制的传导路径,提出了锁相暂态响应导致DDWT功率控制误差的机理及其计算方法;建立了电网故障下含DDWT的电力系统频率响应模型,提出了锁相暂态响应影响下系统频率变化率和最大频率偏差的计算方法,解析了电网故障下考虑DDWT功率控制误差的电力系统频率动态响应特性,并通过算例分析验证了所提方法的有效性。

避免频率二次跌落的风储联合调频控制策略

风电高渗透电力系统中,风机释放转子动能参与频率响应改善系统频率稳定性,但存在欠响应支撑效果不足或过响应导致系统频率二次跌落现象。储能响应不受时空因素影响,通过整定储能响应参数,可提升风电频率响应的有效性。该文首先基于统一结构模型分析系统频率二次跌落与风机控制策略之间的作用机理。其次,整定充分利用风机频率响应能力及避免系统频率二次跌落的风电机组频率响应系数。然后,引入频率稳定裕度概念,并基于关系矩阵整定的储能最小出力,等效扩展系统频率稳定裕度。基于以上分析,综合考虑时空因素对系统频率响应影响,提出一种多时间尺度下避免频率二次跌落的风储联合调频控制策略。最后,基于DIgSILENT搭建风电高渗透4机4区系统进行仿真验证。结果表明,所提控制策略在不同风速下兼顾风机频率响应能力,同时避免频率二次跌落,提高全网频率安全稳定裕度。

风力发电参与调频市场的机制优化及收益研究

随着风力发电并网容量日益增加,传统能源提供的调频容量已无法满足系统调频需求,目前政策允许风电参与系统调频,但现有调频辅助服务机制无法有效衡量风电参与调频的真实容量,对系统安全稳定运行带来了严峻挑战。在现有调频辅助服务机制基础上,引入风电调频可信度指标及综合调频性能指标对调频市场主体报价进行调整以衡量风电参与调频的真实容量,同时优化现有调频辅助服务机制的补偿细则。针对上述优化部分,建立风电参与调频市场的出清模型。算例结果表明,优化后的机制能够有效衡量风电提供的真实调频容量,促使优质的调频资源优先出清,同时风电可提高调频可信度指标及综合调频性能指标以获得较高的调频收益。

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。

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.

Coordinated Operation of Concentrating Solar Power Plant and Wind Farm for Frequency Regulation

As a dispatchable renewable energy technology, the fast ramping capability of concentrating solar power (CSP) can be exploited to provide regulation services. However, frequent adjustments in real-time power output of CSP, which stems out of strategies offered by ill-designed market, may affect the durability and the profitability of the CSP plant, especially when it provides fast regulation services in a real-time operation. We propose the coordinated operation of a CSP plant and wind farm by exploiting their complementarity in accuracy and durability for providing frequency regulation. The coordinated operation can respond to regulation signals effectively and achieve a better performance than conventional thermal generators. We further propose an optimal bidding strategy for both energy and frequency regulations for the coordinated operation of CSP plant and wind farm in day-ahead market (DAM). The validity of the coordinated operation model and the proposed bidding strategy is verified by a case study including a base case and sensitivity analyses on several impacting factors in electricity markets.

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。

构网型和跟网型电力电子装备混联系统惯量响应的匹配问题综述

构网型和跟网型电力电子装备具有异质化调频特性,导致2类装备交直流混联系统惯量响应阶段的动态交互作用机理复杂,传统的惯量参数匹配原则难以优化系统频率响应的问题。阐述了电力电子装备系统的惯量响应匹配问题,并对现有电压源型变流器的调频控制方法进行了概述。从功频响应分析方法、调频功率分配原则和频率响应特性3个方面对电力电子装备系统惯量配置问题的研究现状展开梳理。对电力电子装备混联系统的统一建模及惯量响应匹配问题提出了研究思路,旨在通过惯量支撑功率的匹配控制提升低惯量电力系统的频率稳定性,从系统层面为高比例电力电子装备友好并网提供基础理论和关键技术支撑。

Participation of large-scale wind power generation in power system frequency regulation

The initiative participation of wind power generators in power system frequency regulation is an inevitable demand to ensure power system safe operation with large-scale wind power integration.However,it is principally difficult for conventional wind turbines to participate in power system frequency regulation.For this reason,solution to this problem is becoming a hot topic in the current studies.This paper systematically reviews the relevant research progresses in the control strategies and the capability assessment of using wind power generators in the power system frequency regulation,including the comparing among the emulating inertia control,the droop control,the rotor speed control,the pitch angle control and the coordinated control.Also,future research in this area is pointed out in the paper.

面向电网频率快速支撑的风电场自适应分布式协调控制

随着风电渗透率升高,系统惯量降低,许多国家在其电网导则中要求风电场需具备主动频率支撑能力。然而,风电场受到地理位置分布、风速风向、尾流效应等影响,风电场内风速分布不均,风机运行状态各异,所具备的调频能力不尽相同,且存在转子动能限制,风电场提供频率支撑过程中存在风机功率不合理的分配问题。因此,该文提出了一种适应于风电场的自适应分布式快速频率支撑协调控制,在兼顾安全性的同时充分利用风电场调频能力,提升频率调节效果。该控制主要包括以下3部分:首先,提出考虑风机状态的一致性分布式协调控制,实现频率支撑功率的合理分配;在此基础上,加入考虑风电场状态和频率事件严重程度的自适应控制,保证风电场运行稳定性;随后,在风电场提供频率支撑后的转速恢复阶段采用了预设恢复控制,缓解二次频率跌落问题。最后,通过含风电的四机两区域系统验证所提自适应分布式控制策略相对于集中式控制及固定系数的分布式控制均有更好的调频表现。

基于双层网络频率控制的分布式风电并网研究

为研究含通信控制层的双层电网中分布式风电入网位置的选择,电网层采用二阶类Kuramoto模型进行建模,通信控制层收集发电机及其邻居节点信息形成控制信号并调整发电机的频率。根据负荷到原电网发电机节点的平均距离定义了3种并网方式,研究比较了含功率波动的分布式风电并网时最佳的入网位置。研究表明,加入双层网络频率控制可有效提高电网的同步性能和抗扰能力;分布式风电选择离原电网发电机节点平均距离小的负荷并网可提高电网稳定性。

预防双馈风机调频期间失速的功率轨迹预设策略

为解决双馈风机阶跃惯性控制过程中易导致频率二次跌落和分机失速的问题,在斜坡形阶跃惯性控制方法基础上考虑风机有效旋转动能,建立转速减速阶段增发功率、加速阶段降低功率与线性下降阶段时间的数学关系,计算风机有功功率线性下降阶段不引起风机失速的最大持续时间,对功率轨迹线性下降阶段时间加以约束,使风机具有与斜坡形阶跃惯性控制相同频率支撑效果,同时防止风机失速、减少二次频率跌落。利用EMTP-RV平台对不同扰动大小、渗透率、风速情形进行仿真,验证了所提方法的有效性。

基于随机预测理论的双馈风电机组参与电网调频控制策略

随着电力系统中的风电渗透率不断提高,系统中风电功率的随机波动给电网频率稳定性带来巨大挑战。针对上述问题,该文提出基于机会约束随机模型预测控制的附加功率调频控制策略。首先,综合考虑系统中风速及负荷的实时随机波动问题,建立风电并网系统频率响应模型;其次,以系统频率变化及风电输出功率波动最小为控制目标建立期望目标函数,并将机会约束纳入随机最优化模型中;最后,根据随机扰动的分布信息或坎泰利不等式,结合状态反馈控制律求解随机最优化模型,得到当前时刻的最优控制律。利用MATLAB/Simulink搭建风电并网系统进行仿真验证,结果表明,所提策略能够有效抑制风电功率波动及系统频率变化,提高了电网的频率稳定性。

双馈风电机组利用转子动能进行一次调频能力动态估计

通过释放转子动能参与一次调频的风电机组,其一次调频能力随外界工况特别是风速的波动而变化,需要动态估计一次调频能力,从而为电力系统运行规划、控制策略制定等提供依据。基于风电机组参与一次调频的功率转换动态过程分析,提出了计及风电机组转子转速动态变化的一次调频简化解析模型,借助其一次调频能力的解析解,可快速分析风速波动对风电机组一次调频能力的影响;提出双馈风电机组一次调频能力的概率解析描述,利用点估计与Gram-Charlier级数展开,获得了风电机组一次调频能力随风速波动的概率分布特征。仿真验证了所提动态解析模型的准确性和一次调频能力概率估计方法的可行性与有效性。