Monitoring frequency control in the Turkish power system

Frequency control is a key ancillary service for the secure and reliable operation of power systems, and especially in isolated power systems such as Turkey which is not yet synchronously connected to the UCTE European system. Frequency control has been defined in the Turkish power system as a mandatory remunerable ancillary service that is provided by generating units and managed by the system operator. This paper develops a centralized monitoring system of frequency that informs the System Operator if the generating units comply with the technical requirements of the Turkish Grid Code. The system consists of a reference model that validates the real operation of the primary and secondary regulation of the generating units comparing it with the desired behavior established by the technical requirements of the Turkish Grid Code. A number of quantitative measures, based on the deviation between the real and the desired response are proposed to evaluate the adequacy of each unit behavior. Application examples of the proposed monitoring system of frequency control are provided using real data of different Turkish power plants.     

基于斜坡渐变扰动的新型电力系统等效惯量评估

基于阶跃扰动的惯量评估方式依赖难以准确测量的初始频率变化率（RoCoF）与稀少的频率事件,而基于类噪声扰动的惯量评估方法无法评估电流源型虚拟惯量且对数据要求高。对此,提出基于可再生能源机组主动输出斜坡渐变扰动功率的惯量评估方法。建立含RoCoF与斜坡渐变扰动功率的等效惯量评估基础模型。考虑RoCoF噪声阶跃易导致等效惯量评估产生较大误差,推导双二阶广义积分锁相环中的q轴电压分量变化量与RoCoF的线性关系,并将其代入基础评估模型替代RoCoF。采用改进的非线性最小二乘拟合斜坡渐变扰动下q轴电压分量变化量与时间的非线性表达式,从拟合的表达式中提取系统等效惯量。在改进的EPRI-36中验证了所提评估方法相较于常规方法的优越性。     

基于模糊控制的电池储能系统辅助AGC调频方法

针对AGC控制中火电机组响应时滞长、机组爬坡速率低的问题,提出了一种基于模糊控制策略的电池储能系统(Battery Energy Storage System,BESS)辅助AGC调频方法。该方法以区域控制偏差(Area Control Error,ACE)及其变化率作为模糊控制器的输入量,BESS的参考功率变化量作为输出量,根据系统的运行状态调节BESS输出功率,辅助火电机组改善电网的动态调频性能。基于Matlab/Simulink平台的仿真结果表明,BESS能够迅速响应负荷扰动,减小了系统频率偏差和联络线功率偏差,降低了系统的超调作用,有助于提高电网AGC调频能力和增强系统的稳定性。     

高比例可再生能源电力系统的快速频率响应市场发展与建议

随着非同步电源渗透率增加,电网的惯性逐步降低,扰动后电网的频率变化率变大,频率调控面临着巨大挑战.近年来,快速频率响应(FFR)的概念已被提出,并应用于一次调频之前,为一次调频响应争取时间,使低惯性系统在一次调频响应前不至于到达系统低频减载的频率阈值.文中从典型FFR资源、辅助服务产品设计、市场交易和应用实例等几方面总结了国外FFR市场开展现状.结合中国电网应对未来低惯性系统的调频需求,阐述了FFR技术的研究趋势,并为中国FFR市场建设提出了建议和展望.     

基于转子动能的直驱式风电系统RoCoF下垂控制策略

大规模风电并网会引起系统的等效惯量阻尼下降,降低系统频率的稳定性。微电网系统以电力电子设备为主导,在受到外界扰动时,更易出现电网频率偏差和频率变化率（RoCoF）过大的问题。在分析直驱永磁同步发电机（D-PMSG）并网系统动态响应基础上,将其与低惯量微电网相连接,提出了一种基于有源低通滤波器（LPF）的RoCoF下垂控制策略,该策略在风机侧引入电网的RoCoF,在频率跌落RoCoF突变的瞬间释放转子能量,补偿系统不平衡功率。在Matlab/Simulink中建立仿真模型,验证控制策略的有效性及经济性。 结果表明,增加下垂系数Kd和降低截止频率ωc,可使系统惯量越高,系统对RoCoF的抑制效果越好。     

基于无模型算法和电动汽车辅助调节的新能源电力系统频率协调控制

为解决风电并网导致电力系统频率偏差过大的问题,设计了一种基于无模型负荷频率控制和电动汽车辅助调节的频率协调控制策略,能够在系统受到风电和负荷扰动时对其频率偏差进行快速调节。利用新能源电力系统的频率偏差设计了无模型自适应滑模负荷频率控制器,对传统机组进行二次频率调节。同时为充分利用电动汽车的快速响应能力,采用分频技术将区域控制高频偏差信号接入集群电动汽车控制中心作为调频参考指令,使得电动汽车参与辅助系统调频。最后通过Matlab/Simulink软件在不同的工况下进行对比分析,仿真结果验证了所提出策略的有效性。     

基于广域测量信息的直流调制新方法

提出了一种系统化的大规模交直流电力系统中基于广域测量信息的直流阻尼调制信号的筛选和集成方法。定义了一个新的概念“模式可观惯量中心”。对于多区域互联电网，当直流线路连接了2个区域电网时，区域电网“模式可观惯量中心”间的频率差可以作为直流调制信号。新信号考虑了大规模交直流电力系统的特点。与现有的调制信号相比，新信号可以更好地反映区间振荡。在南方电网的仿真研究表明，基于广域信息的直流调制新方案优于传统的直流调制方法。     

东北电网频率与联络线潮流的关系

介绍了东北电网的频率与联络线潮流控制方式,结合东北电网2002年几起大机组跳闸后频率及区域联络线潮流实时记录数据,分析了各区域联络线潮流的变化情况,计算了辽宁、黑龙江电网的自然频率特性系数,结果表明电网运行中自然频率特性系数随运行方式变化而不断变化.还分析了频率波动及区域电网频率特性系数对东北电网内各区域间联络线潮流的影响,证明了区域频率特性系数的设定应稍大于自然频率特性系数以利于调整频率及联络线功率偏差.     

异步互联方式下西南电网AGC方案优化及工程应用

异步联网方式下的中国西南电网通过多条高压直流线路将大功率能源送出至经济发达的负荷中心,其大规模功率送出和负荷较小的特性使得西南电网的频率稳定问题较为显著。结合中国西南电网的实际异步运行试验,分析了自动发电控制(AGC)策略和模式在频率调节过程中的问题。然后,提出在西南区域多调度管理机制下的AGC策略和模式改进方法,以解决日常负荷波动下频率超调问题和在大功率损失下非故障的省级电网反向调节问题。最后,基于电力系统全过程动态仿真程序(PSD-FDS)仿真和实际电网运行效果验证了改进策略和模式的有效性。     

Age-of-information-aware PI controller for load frequency control

Open communication system in modern power systems brings concern about information staleness which may cause power system frequency instability. The information staleness is often characterized by communication delay. However, communication delay is a packet-centered metric and cannot refect the requirement of information freshness for load frequency control (LFC). This paper introduces the age of information (AoI), which is more compre-hensive and informative than the conventional communication delay modeling method. An LFC controller and com-munication are integrated into the design for LFC performance improvement. An AoI-aware LFC model is formulated frst, and considering each allowable update period of the smart sensor, diferent AoI-aware PI controllers are then designed according to the exponential decay rate. The right AoI-aware controller and update period are selected according to the degree of frequency fuctuation of the power system. Case studies are carried out on one-area and two-area power systems. The results show the superior performance of the AoI-aware controllers in comparison to the delay-dependent controllers.     

Grid power quality enhancement using an ANFIS optimized PI controller for DG

Grid frequency variation causes phase angle deviation in current with respect to voltage. This is sensed at the phase-locked loop in the controller. In past studies the effect of grid frequency variation is neglected while designing the controller for power quality restoration. When modern grids are connected to large numbers of non-linear loads and various types of distributed generation (DG), it results in continuous variation in grid frequency. Thus it is necessary to consider the grid frequency variation for effective power quality restoration. However, tuning of conventional PI controller gains considering frequency variation is very difficult. Thus it is necessary to develop an adaptive intelligent nonlinear controller to tackle the effects of frequency variation, voltage distortion and non-linear load simultaneously. This paper presents the importance of considering the effects of the frequency variation, grid voltage distortion and non-linear load, while designing and deploying a controller for power quality restoration. The proposed controller supplies power to local load as well as transferring surplus power to the grid from DG along with the additional benefit of improving grid power quality. A DG with an ANFIS optimized PI current controller for power quality enhancement is proposed. The method is economical as it requires no additional hardware. Results are compared with PI, PI-RC and fuzzy current controllers to validate the effectiveness of the proposed controller.     

RoCoF下垂控制的直驱式风电系统惯量特性分析

直驱式风电机组大规模接入电网,导致传统电网的惯量减小,电网频率支撑能力相对减弱,在受到扰动时更容易引起电网频率偏移和频率变化率过大。针对此类问题,本文首先提出一种频率变化率(the rate of change of frequency, RoCoF)下垂控制策略,旨在提高直驱式风电系统的惯量作用,抑制频率偏移量和RoCoF。其次,类比传统同步机在机电时间尺度下的动态分析理论和方法,建立了风电系统在直流电压时间尺度(DC-Voltage Timescale, DVT)下的动态模型。基于所建立的DVT动态模型,采用经典的电气转矩分析法研究了风电系统的惯量效应,揭示了主要的控制环节对风电系统惯量特性的影响规律、主导因素与作用机制。最后,对传统的频率偏差下垂控制与本文提出的RoCoF下垂控制策略进行了详细的对比,并通过实验验证了所提出的控制方法和分析结论的正确性。     

直流调制对南方电网交直流混联输电系统暂态稳定裕度的影响

交直流混联输电系统中,直流系统的控制及调制措施对系统的暂态稳定具有重要影响。以南方电网2005年丰大运行方式下,贵广直流单极运行、天广直流双极运行为例,当北通道交流输电系统发生扰动时,研究了直流系统在一定的控制方式下,调制增益的变化对系统暂态稳定裕度及直流系统的影响;分别取北通道功率变化率及南通道功率变化率为调制信号对系统暂态稳定裕度及直流系统的影响;考察了直流系统运行在不同控制方式下时,大方式调制和双侧频率调制等措施对混联系统暂态稳定裕度、送端电网机组及直流系统的影响,研究结果对实际电网运行中直流调制措施的制定具有一定的参考价值。     

2004～2005年江苏电网分层分区运行分析

介绍了江苏电网概况 ,以及苏南苏北电网分区、宁镇常与无锡电网分区、无锡电网与苏州电网分区的分层分区初步设想。对江苏电网分层分区运行后 ,主网潮流分布、主要变电站短路容量、电网稳定性及地区电网建设原则进行了分析 ,指出江苏电网在 2 0 0 4～ 2 0 0 5年间已具备分区运行条件 ,可逐步实现分区运行 ,从而使整个江苏电网结构更加合理。     

配电网电能质量测试系统的设计与仿真

针对目前几种电能质量干扰发生装置的模型存在的不足之处,提出了一种基于电力电子技术的电能质量干扰源设计方案。采用DSP控制器、三相PWM有源可控整流和可控逆变控制技术,结合不对称与高谐波条件下的MRF补偿算法,以15 kVA 容量为例对加入干扰源的配电网动模系统进行了仿真分析。仿真结果表明,加入干扰源的动模系统可以模拟多种电能质量干扰环境,并且可用于大功率场合,运行经济,效益较好,较好地满足了对电能质量控制治理设备测试的有效性和实用性要求。     

Stability analysis of sensorless speed control of IPMSM

In the speed control of an interior permanent magnet synchronous motor (IPMSM), for stability reasons, the closed‐loop pole positions should be on the left‐hand side of the S‐plane, and for fast response requirements these poles should have a small time constant. Unfortunately, the motor poles have a very long time constant, which makes the system response very slow. To solve this problem, the zeros of PI controllers are used to compensate the motor poles. As the motor operates, the temperature increases, which changes the parameters of the motor and, accordingly, the motor poles change their position so the PI controller cannot compensate these poles. To solve this problem, many parameter estimation algorithms have been used to detect new parameter values and adapt the PI controller gains so that to compensate the motor poles continually. These parameter estimation algorithms complicate and add cost to the system. This paper demonstrates that, for a temperature up to 70 °C, the system is capable of giving fast response and stable operation by using a good design of the PI controller regardless of the parameter changes.     

A new PID load frequency controller design method in frequency domain through direct synthesis approach

In this paper a new PID controller design method based on the direct synthesis (DS) approach of controller design in frequency domain is presented. The parameters of the PID controller are obtained through frequency response matching with the DS controller. The method yields linear algebraic equations, solution of which gives the controller parameters. The design method has been developed for single-area as well as multi-area power systems. Non-linearity like the generation rate constraint (GRC) has been considered. Several examples are taken from the literature to demonstrate the effectiveness of the proposed method in comparison with some prevalent design methods.     

永磁同步电机调速系统的快速幂次趋近律控制

针对在采用PI控制器的永磁同步电动机(permanent magnet synchronous motor,PMSM)调速系统中,PI控制器无法满足高精度控制要求,且易出现积分饱和的问题,提出一种基于快速幂次趋近律的滑模变结构控制器。该趋近律是在幂次趋近律的基础上,加入指数项以及系统状态变量。其中,指数项具有较快的收敛速度,可以解决幂次趋近律在远离滑模面时趋近速度慢的问题,系统状态变量可抑制由于引入指数项带来的抖振。基于该改进趋近律设计永磁同步电动机滑模速度调节器,并采用李雅普诺夫函数对其进行稳定性分析。经过与PI速度控制器进行仿真实验比较,结果表明采用该控制器的系统可实现速度无超调跟踪,并具有稳定性高、抗负载扰动强的优点。     

Design of a robust PWM power amplifier using approximate two‐degree‐of‐freedom integral‐type control

A method is proposed for designing a robust controller for PWM power amplifiers, which are widely used as amplifiers and power supplies. The main technical requirements imposed on PWM power amplifiers are linearity in a wide frequency range and a well‐damped fast dynamic response in the presence of extensive load and DC power supply variations. Therefore, in order to satisfy the design specifications, namely, linearity in a wide frequency range and no overshoots during transients, an approximate two‐degree‐of‐freedom integral control structure is proposed and a design procedure for the robust controller is discussed. It is shown by some simulations and experiments that the designed controller shows especially good dynamic performance and effective disturbance rejection in the presence of external disturbances, that is, load and power‐supply variations. © 2003 Wiley Periodicals, Inc. Electr Eng Jpn, 144(1): 68–77, 2003; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.10102     

高渗透率水电接入的变电站备自投逻辑优化研究

首先分析了含高渗透率水电区域电网的孤网运行频率特性,指出水电残压造成变电站备自投动作时间长、正确动作率低的问题,提出了含高渗透率水电区域电网的快速同期并网功能的方案,并指出了增加频率变化率作为快速同期并网判据以及水电机组高频保护判据的必要性。提出了基于扩展卡尔曼滤波的快速频率及频率变化率计算方法,给出了电网基波频率快速跟踪算法流程。在此基础上,根据小水电孤网初期频率不能突变的特征,提出了改进的备自投及水电机组高频保护逻辑。通过PSCAD仿真验证了对含高渗透率水电区域电网的孤网运行频率特性分析的正确性,并在自主研发的备自投装置中实现并验证了所提算法。通过实际工程验证了所提备自投方案的有效性。所提备自投方案可显著降低含高渗透率水电区域电网的备自投时间,提升电网的供电可靠性。