A discrete-time model of thyristor controlled series compensators

The current trend in power systems is to use power electronic devices to enhance both system stability and power transfer limits. A recent point of interest is the use of thyristor control devices in series compensation of AC transmission lines. In this paper a linearized, discrete-time model of a thyristor controlled series compensated line is presented. The samples for these discrete models are obtained at the peaks of the capacitor voltage of the series compensator. Since these peaks are broad rather than sharp spikes they are quite good indicators of variations in the fundamental component. During transients this will result in variation from uniform sampling. However, the system degenerates to a uniform sampled system in the steady state and thus all the standard tools for the analysis of the standard discrete-time model can be applied. The model developed is validated through digital computer simulation studies.     

可控相间功率控制器(TCIPC)运行特性分析

研究了相间功率控制器IPC(Interphase Power Controller)基本结构和数学模型,通过晶闸管触发控制电感支路构成可控相间功率控制器(TCIPC),并将其应用于交流弱联系的互联电网中,推导了晶闸管触发延迟角与TCIPC参数以及两侧电网戴维南等值参数之间的关系,分析了计及两侧电网等值参数影响下的TCIPC运行特性.以东北-华北电网经带TCIPC的联络线交流弱联系为例,说明TCIPC对互联电网具有动态连续潮流控制能力.     

可控串联补偿阻抗控制策略研究

提出触发角修正反馈阻抗控制策略,与常规阻抗误差反馈修正命令阻抗的方式相比,避免了每次修正后都需查表求触发角,提高了底层响应速度.可控串联补偿(TCSC)采用非线性控制方法进行阻抗闭环控制效果最佳,但所需数据量大,实现困难.设计触发角修正变结构PID阻抗控制器:在测量阻抗第1次到达或接近命令阻抗之前,积分环节参数为0,即为PD控制器;之后则投入积分环节,恢复为PID控制器.当TCSC从不同的阻抗值阶跃到同一阻抗值时,误差累加器的值接近,从而可以得到非常接近的控制效果.数字仿真和动模实验结果表明该控制策略超调小、响应速度快,并能快速消除偏差,具有良好的动态和静态性能,且结构简单,易于工程实现.     

Frequency response of the thyristor controlled series capacitor

This paper introduces the application of a new method based on Fourier series expansion, to derive the frequency response of a thyristor controlled series capacitor (TCSC). The theory and the numerical approach are presented and the results are reported. Although this method is solely applied to the TCSC device in this context, it is completely general and may well be applied to any type of switched power device. The analysis shows the behavior of a TCSC at frequencies other than fundamental frequency. Such information is very important for sub-synchronous resonance (SSR) as well as other harmonic related studies     

可控相间功率控制器(TCIPC)运行特性分析

研究了相间功率控制器IPC(Interphase Power Controller)基本结构和数学模型,通过晶闸管触发控制电感支路构成可控相间功率控制器(TC IPC),并将其应用于交流弱联系的互联电网中,推导了晶闸管触发延迟角与TC IPC参数以及两侧电网戴维南等值参数之间的关系,分析了计及两侧电网等值参数影响下的TC IPC运行特性。以东北-华北电网经带TC IPC的联络线交流弱联系为例,说明TC IPC对互联电网具有动态连续潮流控制能力。     

Improvement of power system transient stability by a thyristor controlled thermoelectric converter

An application of a thyristor controlled thermoelectric converter (TCTEC) to a power system is proposed. The purpose of using a TCTEC is basically for electric power generation in the normal operating phase; however, such a device will also improve transient stability. Owing to the EMF caused by the Seebeck effect acting to enhance power dissipation in the thermoelectric semiconductor resistance, a TCTEC can act as a power compensator during upswings and downswings with the help of feedback control. The performance of a TCTEC is superior to that of the conventional braking resistor in absorbing power during the voltage drop on the machine terminal bus. The effectiveness of a TCTEC was tested on a two-machine infinite-bus system with a digital computer. The simulation results show that a TCTEC with a rotor relative angular velocity feedback channel improves not only the first-swing stability, but also plays a very important role in providing damping and assuring stability throughout subsequent swings.     

Analysis of start-up regimes of an induction motor controlled by a thyristor regulator

The start-up regimes of an induction motor controlled by a thyristor voltage regulator are considered. The cases of the fixed stator voltage and different types of loads are analyzed.     

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.     

一种晶闸管全控整流式三相交流调压电路

提出了一种用晶闸管三相全控整流电路用作三相Y接对称性电阻性负载进行的三相交流调压电路,此调压电路由晶闸管三相全控整流电路改造而成,并分析了工作原理,给出了实验结果。结果表明,对Y接的三相对称性电阻性负载采用此调压电路实现三相交流调压,方法可行。     

Differential energy based relaying for thyristor controlled series compensated line

The paper presents a differential energy based protection scheme for transmission line including Thyristor Controlled Series Compensator (TCSC) using time–frequency transform such as S-transform. Initially the current at sending and receiving ends are retrieved and processed through the time–frequency transform such as S-transform to generate the time–frequency patterns (frequency contours). Spectral energy content of the frequency contours of both current signals are calculated and differential energy is computed to register the fault patterns in the transmission line. The tripping signal can be issued based on a set threshold, within two cycles from the fault inception, meeting the speed criteria of the digital relay. The results indicate that the differential energy based protection scheme can reliably detect the fault patterns in TCSC line including wide variations in operating conditions of the faulted power network.     

Fuzzy logic switching of thyristor controlled braking resistorconsidering coordination with SVC

This paper presents a new switching control scheme for braking resistors (BR) using fuzzy logic to enhance overall stability of electric power systems. In addition, the coordination with an SVC is also considered to achieve a wider stable region. The braking resistor is set on one of the generator busbars, where the real power output from the generator is measured to determine the firing-angle of the thyristor switch. The switching control scheme is simple so as not to require heavy computation on the microcomputer based switching controller. An SVC is set on one of the busbars in the system. The switching of the SVC uses a similar fuzzy logic control scheme to the one for the BR. Simulation results show the effectiveness of the proposed fuzzy logic switching control scheme     

晶闸管控制串联电容换级特性研究

研究了晶闸管控制的分级串联电容换级时的暂态过程。采用编程仿真的方式,对单级电路和多级电路分析后,提出了晶闸管开关最佳接入时刻为被短接电容电压为零时;分析了阻尼电阻、电感对暂态过程的影响以及它们之间的参数配合;采用电容分级式可控串补策略可大大降低可调电感容量及成本。高压输电线路分级电容可控串补的应用可提高系统的稳定性。     

新型混合型磁控电抗器的特性研究

针对传统磁控电抗器功率损耗大,谐波电流含量高的特点,设计了一种新型混合型磁控电抗器,该混合型磁控电抗器采用磁阀式可控电抗器与不饱和铁芯电抗器线圈串联技术,中间柱不饱和铁芯上流过的交流磁通为两个边柱铁芯交流磁通之和,磁阀式可控电抗器的直流磁通不流过中间柱铁芯.该结构可以大大减小磁阀式电抗器的线圈匝数,从而减小磁控电抗器的...     

A method for harmonic reduction on the source side of a parallel-connected thyristor converter having an interphase reactor

A parallel-connected twelve-pulse thyristor converter consisting of two six-pulse groups with an interphase reactor has been used for low-voltage high-current dc power supplies because of its high efficiency compared with a series one. It seems to be the most suitable converter for superconducting magnetic energy storage systems (SMES), which are expected to be used in actual power systems in the near future as a power system stabilizer. Harmonic reduction on the source side is required for such large-capacity thyristor converters. A number of methods have been proposed. These methods, however, require additional devices. Thus, a simple parallel-connected converter without any additional device remains to be constructed to reduce harmonic currents on the source side. This paper attempts to construct a simple 12-pulse thyristor converter by proposing a novel design concept of the interphase reactor. This method proposed here requires no additional devices and only reducing the inductance of the interphase reactor. The source current of the 12-pulse thyristor converter with the reduced inductance interphase reactor approaches sinusoidal waveforms, which are approximately equivalent to those of the 36-pulse thyristor converter. Simulation results show that decreasing the inductance of the interphase reactor contributes to reducing harmonic currents on the source side. In addition to the simulation results, experimental results verify the validity and practicability of the proposed novel design concept of the interphase reactor. © 1997 Scripta Technica, Inc. Electr Eng Jpn, 121(1): 82–90, 1997     

An adaptive stabilizer for thyristor controlled static VARcompensators for power systems

The authors present the analytical development of a controller scheme for a static VAr system and present detailed simulation results to highlight its effectiveness in comparison with a discrete PI (proportional-integral) stabilizer under a variety of operating conditions for power transmission systems. The adaptive stabilizer is suitable for microprocessor digital implementation as the numerical steps involved are minimal. The adaptive stabilizer uses a stochastic variant simplified parameter estimator routine, thus providing a faster sampling rate and identification of a larger number of parameters in real time. The implementation of this stabilizer is simple as it involves additions, multiplications without matrix inversion, etc     

基于参数协调的可控相间功率控制器调节特性研究

研究了可控相间功率控制器(TCIPC)的基本结构和数学模型,通过控制晶闸管触发角等效调节相间功率控制器的基本参数,从而协调输出功率,其中,通过控制晶闸管触发延迟角等效地改变电感支路的电抗参数,通过晶闸管控制投切不同组数的电容器等效地改变电容支路的电容参数.基于简化模型绘制出TCIPC功率P-Q运行曲线图,对参数协调下的TCIPC调节特性进行研究.以实例验证了由带TCIPC联络线进行交流弱联系的两侧电网在相位相对滑移时,可以通过协调TCIPC的等效参数控制联络线传输的功率,避免有功功率大幅波动,并保证端口的电压质量,有效地缓解了常规IPC可能出现的过电压问题.     

晶闸管控制三相电容器投切过程分析及仿真研究

针对三相供电系统中晶闸管投切电容器（TSC）的无功补偿问题,重点分析了TSC工作原理和投切过程,借助Matlab/Simulink平台对电容器的三角形外接法进行建模、动态仿真分析和研究,提出了无功补偿电容器合理投切方式和投切时刻控制方案,有效减小了投切过程中的冲击电流。