可控串联电容补偿器的负阻尼特性研究

由于在暂稳控制器的设计中通常将可控串联电容补偿器(TCSC)处理为带限幅器的一阶惯性环节,而忽略了电力系统动态行为对TCSC脉冲触发过程影响以及装置动态响应特性的研究。文中建立了装有TCSC的电力系统的扩展PhillipsHeffron模型,通过分析TCSC对系统同步和阻尼转矩的贡献,给出了在开环定触发角控制下TCSC表现为负阻尼特性的解析解。基于NETOMAC的数字仿真结果验证了模型分析的正确性,同时指出通过合适的底层控制策略可以减弱和消除负阻尼,有效地改善TCSC的动态响应特性。     

TCSC采样-数据模型在次同步振荡分析中的适用性研究

由于电力系统次同步振荡(SSO)问题要分析的是既非工频又非低频的成分,故不能采用工频准稳态模型或认为工频电量上有低频调制来进行分析,使用的TCSC动态数学模型必须在整个次同步振荡范围内都有效,因此TCSC动态模型适用性验证的工作非常重要。提出通过对比含TCSC系统在整个次同步频域内的阻尼特性来验证TCSC动态模型的适用性。一方面,TCSC采用采样-数据模型,运用小扰动分析法建立系统的状态空间矩阵,并通过矩阵变换直接求取系统的电气阻尼特性;另一方面,在PSCAD中搭建系统时域仿真模型,TCSC模型精确到器件级,然后采用测试信号法获取系统的电气阻尼特性;最后,将两种方法获得的电气阻尼进行对比。结果表明：基于TCSC采样-数据模型较为精确,适用于次同步振荡问题的分析。     

TCSC对发电机组次同步谐振阻尼特性影响研究

采用基于时域仿真实现的复转矩系数法—测试信号法研究了含有可控串补(TCSC)的电力系统中的次同步谐振(SSR)阻尼特性。采用 IEEE SSR第一标准测试系统模型,将其中部分固定串补电容改造为 TCSC。TCSC采用3种闭环控制方式如恒电流、恒功率及阻尼功率振荡控制。通过频率扫描计算出发电机组在次同步频率范围内的电气阻尼特性曲线,分别研究了开环控制和3 种不同闭环控制方式下 TCSC导通角对电气阻尼特性的影响。结果表明,不论在何种控制方式下,相对于固定电容串补,TCSC都能大大减小谐振点附近的电气负阻尼;TCSC的导通角对阻尼特性有很大影响,TCSC运行在较大导通角时可有效减小谐振点附近的电气负阻尼。     

TCSC的稳态及暂态仿真

提出了含有TCSC装置的电力系统仿真的原理和方法。仿真研究表明，TCSC的等间隔触发控制策略［2］，能有效地提高系统的动态性能，过冲小且更快地趋于稳定。仿真研究还表明，采用电容电压过零时刻为基准的触发控制方式比以线路电流过零时刻为基准的控制方式具有更好的阻尼系统振荡的性能。这一点在以往许多研究文章中，由于采用电流源作为其分析TCSC动态特性的基础，而没有被揭示。     

TCSC对电力系统次同步谐振的影响

以IEEE次同步谐振第1标准模型为研究对象,采用扫频和时域仿真相结合的复转矩系数法,从系统阻尼特性的角度分析了系统发生SSR的危险性,并用时域仿真法验证了该方法的正确性.在系统中加入TCSC,通过对电气阻尼特性的深入研究,发现在一定的条件下,TCSC使系统的电气谐振点发生了偏移,从而破坏系统发生SSR的条件;但是TCSC运行在较小导通角时,可能引起系统负阻尼频带加宽的现象,从而引起系统的次同步振荡,并通过时域仿真验证了该现象的危险性.讨论了TCSC的参数设计原则,使TCSC能够最大限度地提高对SSR的抑制能力.     

TCSC在次同步谐振中的借阻尼现象

采用了基于时域仿真的复转矩系数法研究电力系统的电气阻尼特性.在IEEE次同步谐振第一标准模型的基础上,分别将其25%,50%,100%容量的固定串补替换为TCSC后进行仿真分析.分析结果表明,在串补度相同的情况下,系统总阻尼近似守恒,TCSC基本不提供正阻尼,但TCSC由于其高度非线性,使系统不同频率问发生了能量交互,从而增加了某些频率的阻尼,同时也降低了另外一些频率处的阻尼,出现了借阻尼现象.讨论了借阻尼现象对SSR的正反两方面影响,并利用仿真实验验证了TCSC抑制和引起SSR的可能性.该现象的发现对TCSC的实际运行具有一定的参考价值.     

PSS和TCSC联合抑制互联电网低频振荡

分析推导了含有PSS和TCSC阻尼控制器且适用于小扰动稳定分析的多机电力系统线性化模型,提出了利用改进遗传算法对电力系统中的PSS和TCSC阻尼控制器进行鲁棒分散协调控制,以所有弱阻尼运行方式下的系统机电振荡模式特征值阻尼比之和为目标函数,对阻尼控制器进行了参数优化.仿真结果表明,通过协调控制系统中分散的阻尼控制器,不仅显著 提高了系统的阻尼比,而且对严重故障下产生的持续振荡具有很好的抑制作用.     

TCSC抑制电力系统次同步振荡的研究

常规的固定串联电容补偿(FSC)在补偿度较高时,就会诱发系统发生次同步振荡(Subsynchronous Oscillation,SSO),在这种情况下,为了克服固定串补的不足和抑制电力系统的次同步振荡,可控串联电容补偿(TCSC)就应运而生了.文章分析了TCSC的基频阻抗特性和次频阻抗特性,提出了确定最优的TCSC的主电路特征参数K值的方法,利用测试信号法和时域仿真法研究了TCSC在容抗调节模式下不同触发角时的电气阻尼特性和轴系扭振的变化情况.仿真结果表明了TCSC具有一定的抑制次同步振荡的能力,得出了TCSC在容抗调节模式下次频正电阻能削弱和缓解SSO,但不能完全消除SSO,呈容性的次频电抗在一定触发角范围内仍能有效抑制SSO的结论.     

PSS和TCSC联合抑制互联电网低频振荡

分析推导了含有PSS和TCSC阻尼控制器且适用于小扰动稳定分析的多机电力系统线性化模型,提出了利用改进遗传算法对电力系统中的PSS和TCSC阻尼控制器进行鲁棒分散协调控制,以所有弱阻尼运行方式下的系统机电振荡模式特征值阻尼比之和为目标函数,对阻尼控制器进行了参数优化。仿真结果表明,通过协调控制系统中分散的阻尼控制器,不仅显著提高了系统的阻尼比,而且对严重故障下产生的持续振荡具有很好的抑制作用。     

多机电力系统强迫功率振荡稳态响应特性分析

采用复模态叠加方法推导了多机电力系统强迫功率振荡的稳态响应,分析了多机电力系统强迫功率振荡发生共振的条件及其振荡大小的主要影响因素.通过讨论多机弱阻尼系统共振情况下强迫功率振荡稳态响应与传统的负阻尼低频振荡响应的相似和不同之处,阐述了对多机系统强迫功率振荡稳态响应特性的一些基本认识,有助于更好地理解强迫功率振荡理论及其振荡分布特性.分别通过2区4机系统和新英格兰10机39节点系统的仿真分析对这些特性进行了验证.     

Calculation of damping torque of power systems compensated with TCSC

The thyristor‐controlled series capacitor (TCSC) is being developed to improve the transmission capability of power systems. The TCSC is thought to compensate transmission line reactance without causing subsynchronous resonance (SSR). However, in order to evaluate its effect quantitatively, we must calculate the frequency response of the generator damping torque. Simulations need a long computing time, and it is hard to choose the frequency freely. In this paper, we propose a method of analytically calculating the damping torque. First, when a generator rotor oscillates at some frequency, two voltage components appear. We analytically calculate the damping torque from small current variations due to the voltage components. The damping characteristic changes depending on the method of firing thyristors. The best characteristic is obtained when triggering with reference to the fundamental wave of TCSC voltage or current is used. By choosing an appropriate firing angle, we can drastically reduce negative damping by the TCSC. The damping characteristic is closely related to the system impedance. The fact that the TCSC has large resistance in the 0 to 60 Hz range helps significantly in improving the characteristic. Lastly, numerical simulations of SSR are used to examine the validity of our investigation. © 2003 Wiley Periodicals, Inc. Electr Eng Jpn, 143(1): 39–49, 2003; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.10068     

相控电容器式可控串补特性分析

揭示了相控电抗器式可控串补与相控电容器式可控串补的对偶特征。用对偶原理阐述了相控电容器式可控串补的性能及相控特点。分析说明了串补电容器、GTO网的电流电压峰值与串补线路电流峰值、串补电容器的工频容抗值之间的关系，这对于理论上确认相控电容器式可控串补的优越性非常重要。阐述了相控电容器式可控串补具有阻尼次同步谐振和抑制低频功率振荡的能力；相控电抗器式可控串补装置的动态性能是一个其时间常数不大于工频0．25周期的一阶惯性环节。     

Subsynchronous resonance analysis using a discrete time model of thyristor controlled series compensator

The characteristic of a thyristor controlled series compensator (TCSC) is nonlinear in nature. Usually the TCSC control systems employs a conventional type controller to obtain the reactance order, which in turn, is converted into the corresponding firing angle of the TCR through a look-up table. The main drawback of this approach is the absence of a closed-loop model through which the stability of the system can be analyzed. To alleviate this problem a linear, discrete-time state space model of a TCSC compensated transmission line in the d–q domain is proposed (Srivastava et al., Model-based control design of a TCSC compensated power system, to appear in Electrical Power and Energy Systems). This model is further utilized in this paper for damping torsional oscillations arising due to subsynchronous resonance (SSR). The model is interfaced with synchronous generator and turbine-shaft models to obtain a closed form homogeneous state space representation that is suitable for eigenvalue analysis. Through eigenvalue analysis it is shown that proper choice of control gains can effectively damp out SSR. The eigenvalue analysis results are subsequently validated through PSCAD/EMTDC simulation studies.     

伊敏-冯屯可控串补控制策略的RTDS实验研究

采用RTDS实时仿真工具验证了我国东北电网伊敏－冯屯500 kV交流输电架空线路可控串联补偿控制器的各项控制性能,检验了可控串联补偿装置的稳态运行特性,研究了可控串联补偿装置的阻抗阶跃特性和运行模式转换特性,最后通过三相故障的工况验证了可控串联补偿装置提高系统暂态稳定性尤其是阻尼低频功率振荡的作用。     

A study of thyristor controlled series capacitor models for power system stability analysis

The thyristor‐controlled series capacitor (TCSC) is promising as a powerful device to increase power transfer capability and transient stability. The basic configuration of the TCSC consists of a series of capacitors connected antiparallel with thyristor‐controlled reactors, so that firing angle control of the thyristors makes the TCSC capable of achieving impedance control in a wide range with quick response. It is important to clarify the relationship between the fundamental reactance of the TCSC and the firing angle of the thyristors, thus leading to practical applications of the TCSC for enhancement of power transfer capability and transient stability in transmission lines. Two relationship equations for the TCSC's fundamental reactance have already been proposed. One is the relationship equation derived from a TCSC circuit whose source is a voltage. The other is the relationship equation derived from a TCSC circuit whose source is a current. For TCSC installed in a transmission line, it is clear which equation is more adequate for analyzing power system stability. In this paper, the authors determine whether either of the equations is valid for analyzing a power system stability.

• 1. In the steady state, the TCSC fundamental reactance is analyzed and compared with the two equations and EMTP. It is clear that the TCSC reactance based on current source is adequate.
• 2. The swing angle of a generator when the firing angle is stepped up is analyzed with EMTP and an analytical model using the TCSC model based on current source. It is shown that the proposed model is effective for power system stability analysis. © 1999 Scripta Technica, Electr Eng Jpn, 129(1): 20–28, 1999

     

Nonlinear controller design of thyristor controlled series compensation for damping inter-area power oscillation

A design method of nonlinear controllers of thyristor controlled series compensation (TCSC) for damping inter-area power oscillation based on direct feedback linearization (DFL) is presented in this paper. To damp inter-area power oscillation of power systems, the power modulation action of the TCSC is illustrated firstly. Then the nonlinear model of a two-area power system with the TCSC control is constructed, and is linearized by the DFL. Finally, the design of the nonlinear optimal controller of the TCSC has been completed using the criterion of integration for time and absolute error (ITAE). The digital simulation results using NETOMAC program and detail models show that the presented controller of the TCSC can efficiently improve inter-area power oscillation damping of power systems.     

Fuzzy based damping controller for TCSC using local measurements to enhance transient stability of power systems

This paper proposes a local fuzzy based damping controller (LFDC) for thyristor controlled series capacitor (TCSC) to improve transient stability of power systems. In order to implement the proposed scheme, detailed model of TCSC, based on actual behavior of thyristor valves, is adopted. The LFDC uses the frequency at the TCSC bus as a local feedback signal, to control the firing angle. The parameters of fuzzy controller are tuned using an off-line method through chaotic optimization algorithm (COA). To verify the proposed LFDC, numerical simulations are carried out in Matlab/Simpower toolbox for the following case studies: two-area two-machine (TATM), WSCC three-machine nine-bus and Kundur’s two-area four-machine (TAFM) systems under various faults types. In this regard, to more evaluate the effectiveness of the proposed method, the simulation results are compared with the wide-area fuzzy based damping controller (WFDC). Moreover, the transient behavior of the detailed and phasor models of the TCSC is discussed in the TATM power system. The simulation results confirm that the proposed LFDC is an efficient tool for transient stability improvement since it utilizes only local signals, which are easily available.     

Analytical modeling of thyristor-controlled series capacitors forSSR studies

Thyristor-controlled series capacitors (TCSC) have dynamic characteristics that differ drastically from conventional series capacitors especially at frequencies outside the operating frequency range. Therefore suitable models are needed to properly study the applications of TCSC on a utility power system. An accurate analytical model of the TCSC which is valid in the frequency range from 0 Hz to twice the operating frequency is presented. The model incorporates the thyristor triggering logic, the synchronization system, and higher level control loops such as power oscillation damping loop. This model is suited for linearized analyses of a power system using frequency domain methods such as eigenvalues. It is particularly valuable in studying subsynchronous resonance (SSR) enables the utility industry to better evaluate interactions between TCSC and other devices     

考虑阻抗双解现象的可控串补模式切换控制方法

可控串联补偿(thyristor controlled series capacitor,TCSC)的模式切换对电力系统的稳定控制具有重要意义。TCSC阻抗双解现象的存在对其模式切换提出了更高的要求,单一改变触发角的方法无法实现模式切换。在考虑阻抗双解现象影响的基础上,提出了一套相应的TCSC模式切换控制方法。通过强制晶闸管支路电流与线路电流同步,实现由容性区到Bypass模式的切换;在由容性区到感性微调模式切换的过程中提出了晶闸管条件触发的方法,即当线路电流和电容电压满足同向条件时晶闸管才触发导通。同时为及时向切换控制提供线路电流同步信号,提出了一种预测电流过零的新方法。数字仿真及动模实验结果表明,提出的切换方法能使切换过程平稳迅速,且动态特性良好。