CN101834446B

CN101834446B - Sub-synchronous oscillation suppression method based on controlled series compensation

Info

Publication number: CN101834446B
Application number: CN2010101308628A
Authority: CN
Inventors: 徐政; 郑翔; 张静
Original assignee: Zhejiang University ZJU
Current assignee: Zhejiang University ZJU
Priority date: 2010-03-23
Filing date: 2010-03-23
Publication date: 2012-06-27
Anticipated expiration: 2030-03-23
Also published as: CN101834446A

Abstract

The present invention is based on the concept of damping torque, adopts the design method of phase compensation, and generates an additional control signal to modulate the firing angle of the TCSC by appropriately amplifying and phase-shifting the generator speed signal Δω, thereby changing the equivalent reactance of the TCSC , enabling the TCSC to provide positive electrical damping throughout the subsynchronous frequency band, thereby completely eliminating the SSR problem caused by the series-compensated capacitor.

Description

A Subsynchronous Oscillation Suppression Method Based on Controllable Series Compensation

技术领域 technical field

本发明提出一种基于晶闸管控制的串联电容器(即可控串补)的次同步振荡抑制方法，属于电力系统控制的创新技术。The invention proposes a sub-synchronous oscillation suppression method based on a thyristor-controlled series capacitor (that is, a controllable series compensation), which belongs to an innovative technology of power system control.

背景技术 Background technique

输电线路加串联电容补偿能够提高输电能力，因此在世界范围内已得到了广泛的应用。但是高串补度的固定串联电容补偿可能会引起电力系统的次同步谐振，进而造成汽轮发电机的轴系损坏，严重影响电力系统的安全运行。The addition of series capacitance compensation to transmission lines can improve the transmission capacity, so it has been widely used in the world. However, fixed series capacitor compensation with high series compensation may cause subsynchronous resonance of the power system, and then cause damage to the shafting of the turbogenerator, seriously affecting the safe operation of the power system.

随着电力电子器件的发展，基于晶闸管控制的串联电容器(TCSC)因具有较高的系统响应速度，近年来在抑制次同步谐振方面越来越受到重视。TCSC的基本模块由一个串联的电容器C和一个晶闸管控制的电抗L并联组成，其结构如图1所示，图中T₁，T₂为两个反相并联的晶闸管。如以电容电压u_C由负变正过零时刻开始计算正向晶闸管的触发角，则对于给定参数的C和L，TCSC的稳态基波等效阻抗由触发角α决定。如式(1)所示：With the development of power electronic devices, Thyristor Controlled Series Capacitor (TCSC) has received more and more attention in suppressing subsynchronous resonance in recent years because of its high system response speed. The basic module of TCSC is composed of a capacitor C connected in series and a reactance L controlled by a _thyristor connected in _parallel . If the firing angle of the forward thyristor is calculated from the moment when the capacitor voltage u _C changes from negative to positive and crosses zero, then for the given parameters C and L, the steady-state fundamental equivalent impedance of the TCSC is determined by the firing angle α. As shown in formula (1):

${X x}_{TCSC TCSC} = = {X x}_{c c} - - \frac{{K K}^{22} {X x}_{c c}}{π π (({K K}^{22} - - 11))} [[22 \cdot &Center Dot; ((π π - - α α)) + + sin sin 22 ((π π - - α α))]] + +$

$\frac{44 {K K}^{22} {X x}_{c c} {cos cos}^{22} ((π π - - α α))}{π π (({K K}^{22} - - 11))} [[K K tan the tan K K ((π π - - α α)) - - tan the tan ((π π - - α α))]] - - - - - - ((11))$

$K K = = \sqrt{{X x}_{C C} / / {X x}_{L L}}$

式中，X_L为可变电抗器的基频电抗，X_C为基频下电容器的容抗值。K是TCSC主回路的特征参数，为避免TCSC出现多个谐振点，K的取值通常小于3.0。In the formula, X _L is the fundamental frequency reactance of the varactor, and X _C is the capacitive reactance value of the capacitor at the fundamental frequency. K is the characteristic parameter of the TCSC main circuit. In order to avoid multiple resonance points in the TCSC, the value of K is usually less than 3.0.

出于造价的考虑，TCSC通常不单独用于串联补偿，会与固定串联电容配合使用。这样虽然能够降低成本，在一定程度上减缓次同步振荡，但往往不能彻底抑制次同步振荡的发生。For cost considerations, TCSCs are usually not used for series compensation alone, but are used in conjunction with fixed series capacitors. Although this can reduce costs and slow down subsynchronous oscillations to a certain extent, it often cannot completely suppress the occurrence of subsynchronous oscillations.

发明内容 Contents of the invention

本发明基于阻尼转矩的概念，采用相位补偿的设计方法，在TCSC开环控制器上设计了一个附加SSR阻尼控制器，能够在整个次同步频段内提供正的电气阻尼，从而彻底消除由串补电容引起的SSR问题。Based on the concept of damping torque, the present invention adopts the design method of phase compensation, and designs an additional SSR damping controller on the TCSC open-loop controller, which can provide positive electrical damping in the entire sub-synchronous frequency band, thereby completely eliminating the SSR problems caused by supplementary capacitors.

一种基于可控串补的抑制电力系统次同步振荡的方法，通过对发电机转速信号Δω进行适当的放大和移相处理，生成附加控制信号对TCSC触发角进行调制，从而改变TCSC的等效电抗X_eff，提高系统的电气阻尼。具体实施过程如图2所示，包括如下步骤：A controllable series compensation-based method for suppressing subsynchronous oscillations in power systems. By appropriately amplifying and phase-shifting the generator speed signal Δω, an additional control signal is generated to modulate the firing angle of the TCSC, thereby changing the equivalent of the TCSC The reactance X _eff increases the electrical damping of the system. The specific implementation process is shown in Figure 2, including the following steps:

(1)采集电力系统中发电机(本发明中若无特殊说明，所述的发电机均指需要通过本发明方法保护的那台发电机)的转速差信号Δω，转速差信号是指发电机的实际转速与额定转速的差；(1) Acquisition of the speed difference signal Δω of the generator in the power system (if there is no special instruction in the present invention, the generator refers to the generator that needs to be protected by the method of the present invention), the speed difference signal refers to the generator The difference between the actual speed and the rated speed;

(2)对转速差信号Δω进行滤波处理，滤除低频信号和高次谐波，得到次同步频段内的发电机扭振频率信号。所采用的带通滤波器，其通带频率为10Hz～55Hz。故滤波器截止频率为ω_c1＝55Hz、ω_c2＝10Hz，其传递函数可以表示为：(2) Filter the speed difference signal Δω, filter out the low-frequency signal and high-order harmonics, and obtain the generator torsional vibration frequency signal in the sub-synchronous frequency band. Adopted band-pass filter, its pass-band frequency is 10Hz- 55Hz. Therefore, the filter cutoff frequency is ω _c1 = 55Hz, ω _c2 = 10Hz, and its transfer function can be expressed as:

$H h ((s the s)) = = \frac{{ω ω}_{c c 11}^{44}}{{s the s}^{44} + + 2.613 2.613 {ω ω}_{c c 11} {s the s}^{33} + + 3.414 3.414 {ω ω}_{c c 11}^{22} {s the s}^{22} + + {2.613 2.613 ω ω}_{c c 11}^{33} s the s + + {ω ω}_{c c 11}^{44}}$

$\cdot \cdot \frac{{s the s}^{44}}{{s the s}^{44} + + 2.613 2.613 {ω ω}_{c c 22} {s the s}^{33} + + 3.414 3.414 {ω ω}_{c c 22}^{22} {s the s}^{22} + + 2.613 2.613 {ω ω}_{c c 22}^{33} s the s + + {ω ω}_{c c 22}^{44}} - - - - - - ((22))$

(3)对滤波得到的信号进行放大和相位补偿后，得到附加信号Δα叠加到TCSC的基准触发角α₀上。(3) After the filtered signal is amplified and phase compensated, an additional signal Δα is obtained and superimposed on the reference firing angle α ₀ of the TCSC.

实际应用中，通过采用多个超前滞后环节对经过放大的信号进行相位补偿，实现较大角度的相位补偿。In practical applications, the phase compensation of the amplified signal is performed by using multiple lead-lag links to achieve phase compensation of a larger angle.

所述的超前滞后环节的传递函数可以表示为

的形式，其中：The transfer function of the lead-lag link can be expressed as

in the form of:

T_a、T_b为超前滞后环节的时间常数，T _a and T _b are the time constants of the lead-lag link,

n＝T_b/T_a＝(1-sinφ)/(1+sinφ)n=T _b /T _a ＝(1-sinφ)/(1+sinφ)

${T T}_{a a} = = 11 / / (({ω ω}_{x x} \sqrt{n no}))$

T_b＝nT_a T _b = nT _a

ω_x为所选择的相位补偿频率；φ为ω_x所对应的需要补偿的滞后相角。ω _x is the selected phase compensation frequency; φ is the lagging phase angle corresponding to ω _x that needs to be compensated.

在确定需要补偿的滞后相角φ时，参见式(3)When determining the lag phase angle φ that needs to be compensated, refer to formula (3)

${D D.}_{e e} = = Re Re ((\frac{Δ Δ {T T}_{e e}}{Δω Δω})) - - - - - - ((33))$

式(3)中ΔT_e为发电机的转矩偏差、Δω为发电机的转速差信号、D_e为电力系统的电气阻尼；In formula (3), ΔT _e is the torque deviation of the generator, Δω is the speed difference signal of the generator, and D _e is the electrical damping of the power system;

由式(3)可以得出，当ΔT_e和Δω之间的相角差在-90°到+90°时，电力系统的电气阻尼D_e将为正。当ΔT_e和Δω同相时，系统能够提供最大的电气阻尼。需要使ΔT_e与Δω尽量同相，从而为抑制SSR提供最大的电气阻尼。From formula (3), it can be concluded that when the phase angle difference between ΔT _e and Δω is between -90° and +90°, the electrical damping _De of the power system will be positive. When ΔT _e and Δω are in phase, the system can provide maximum electrical damping. It is necessary to make ΔT _e and Δω as in-phase as possible to provide maximum electrical damping for SSR suppression.

为了得到确定的需要补偿的滞后相角φ，可以利用时域频率扫描法求得TCSC附加控制信号Δα到发电机附加电磁转矩ΔT_e间传递函数G(s)的相位特性，在使得发电机转速增量Δω到发电机电磁转矩增量ΔT_e间相位特性在±90°之内的原则下确定需要补偿的滞后相角φ，使得TCSC能够在整个次同步频段内都能够正的电气阻尼。In order to obtain the determined lag phase angle φ that needs to be compensated, the phase characteristics of the transfer function G(s) between the TCSC additional control signal Δα and the generator additional electromagnetic torque ΔT _e can be obtained by using the time-domain frequency scanning method, so that the generator The lag phase angle φ that needs to be compensated is determined under the principle that the phase characteristics between the rotational speed increment Δω and the generator electromagnetic torque increment ΔT _e are within ±90°, so that the TCSC can have positive electrical damping in the entire subsynchronous frequency band .

具体步骤为：The specific steps are:

(a)在基准触发角α₀上施加一串包含10Hz～55Hz，频率间隔为0.2Hz次同步频率的扫频信号。(a) Apply a series of frequency sweeping signals including 10 Hz to 55 Hz and a frequency interval of 0.2 Hz sub-synchronous frequency on the reference trigger angle α ₀ .

(b)施加扫频信号后，一直到电力系统再次进入稳态，截取一个公共周期上的发电机电磁转矩T_e和施加扫频信号后的TCSC触发角α_m。(b) After the frequency sweep signal is applied, until the power system enters the steady state again, intercept the generator electromagnetic torque T _e on a common period and the TCSC firing angle α _m after applying the frequency sweep signal.

(c)将步骤(b)得到的T_e和α_m进行Fourier分解，求得TCSC触发角增量Δα_m到发电机电磁转矩增量ΔT_e间传递函数G(s)的相位特性。(c) Perform Fourier decomposition of T _e and α _m obtained in step (b), and obtain the phase characteristics of the transfer function G(s) between the TCSC firing angle increment Δα _m and the generator electromagnetic torque increment ΔT _e .

(d)然后确定需要补偿的滞后相角φ，使得在整个10Hz～55Hz次同步频段内发电机转速增量Δω到发电机电磁转矩增量ΔT_e间相位特性在±90°之内。(d) Then determine the lag phase angle φ that needs to be compensated, so that the phase characteristics between the generator speed increment Δω and the generator electromagnetic torque increment ΔT _e within the entire 10Hz-55Hz sub-synchronous frequency band are within ±90°.

本发明方法通过TCSC触发角的附加控制，使TCSC能够在整个次同步频率范围提供正的电气阻尼，从而达到消除SSR的目的，在实际工程应用中具有重大参考价值。The method of the invention enables the TCSC to provide positive electrical damping in the entire sub-synchronous frequency range through the additional control of the TCSC firing angle, thereby achieving the purpose of eliminating SSR, and has great reference value in practical engineering applications.

附图说明 Description of drawings

图1TCSC基本结构示意图；Figure 1 Schematic diagram of the basic structure of TCSC;

图2采用本发明方法的TCSC控制系统框图；Fig. 2 adopts the TCSC control system block diagram of the inventive method;

图3实施例中测试系统接线图；Test system wiring diagram in the embodiment of Fig. 3;

图4补偿前和补偿后G(s)相频特性；Figure 4 G(s) phase-frequency characteristics before and after compensation;

图5采用本发明方法后系统电气阻尼；System electrical damping after Fig. 5 adopts the inventive method;

图6原测试系统发电机各轴段上的扭矩；Figure 6 The torque on each shaft section of the generator in the original test system;

图7采用本发明方法后发电机各轴段上的扭矩。Fig. 7 is the torque on each shaft section of the generator after adopting the method of the present invention.

具体实施方式 Detailed ways

以下结合附图和实施例详细描述本发明的具体实施方式，但本发明不受所述具体实施例所限。The specific implementation of the present invention will be described in detail below in conjunction with the drawings and examples, but the present invention is not limited by the specific examples.

采用的测试系统基于IEEE SSR第一标准测试系统，如图3所示。将原系统中的部分固定串联补偿电容用可控串补代替，线路总串补度取45％，其中TCSC的电抗X_TCSC占总串补电抗的20％，其电抗标么值见图3。TCSC采用开环恒阻抗控制，取TCSC的主电路特征参数

TCSC的基准触发角α₀为158.8°。选择发电机的运行方式为P_G＝0.9pu，功率因数为0.9(滞后)。发电机的轴系由高压缸(HP)、中压缸(IP)、低压缸A(LPA)、低压缸B(LPB)以及发电机(GEN)和励磁机(EXC)六个集中质量块组成。一般情况下，具有n个质量块的轴系有n-1个扭振模式。本例中的轴系有六个质量块，故对应有5个扭振模式，分别为：15.7、20.2、25.6、32.3和47.5Hz。由于扭振模式5(47.5Hz)的模态阻尼非常大，一般不会发生机网扭振相互作用，在相位补偿时将不考虑模式5的影响。The test system used is based on the IEEE SSR first standard test system, as shown in Figure 3. Part of the fixed series compensation capacitors in the original system are replaced by controllable series compensation. The total series compensation degree of the line is 45%, and the reactance X _TCSC of TCSC accounts for 20% of the total series compensation reactance. The standard unit value of the reactance is shown in Figure 3. TCSC adopts open-loop constant impedance control, and the characteristic parameters of the main circuit of TCSC are taken

The reference firing angle α ₀ of TCSC is 158.8°. Select the operating mode of the generator as _PG = 0.9pu, and the power factor is 0.9 (lag). The shafting of the generator consists of six concentrated masses of high pressure cylinder (HP), medium pressure cylinder (IP), low pressure cylinder A (LPA), low pressure cylinder B (LPB), generator (GEN) and exciter (EXC) . In general, a shafting with n masses has n-1 torsional vibration modes. The shaft system in this example has six mass blocks, so there are five corresponding torsional vibration modes: 15.7, 20.2, 25.6, 32.3 and 47.5Hz. Since the modal damping of the torsional vibration mode 5 (47.5 Hz) is very large, the torsional vibration interaction of the machine-network generally does not occur, and the influence of the mode 5 will not be considered in the phase compensation.

首先在TCSC基准触发角α₀上施加一串包含10Hz～55Hz，频率间隔为0.2Hz次同步频率的扫频信号。施加扫频信号后，一直到电力系统再次进入稳态，截取一个公共周期上的发电机电磁转矩T_e和施加扫频信号后的TCSC触发角α_m，对得到的T_e和α_m进行Fourier分解，然后求得TCSC触发角增量Δα_m到发电机电磁转矩增量ΔT_e间传递函数G(s)的相位特性，如图4所示。Firstly, apply a series of frequency sweeping signals including 10 Hz to 55 Hz and a frequency interval of 0.2 Hz sub-synchronous frequency on the TCSC reference trigger angle α ₀ . After the frequency sweep signal is applied, until the power system enters the steady state again, intercept the electromagnetic torque T _e of the generator on a common period and the TCSC firing angle α _m after applying the frequency sweep signal, and perform a calculation on the obtained T _e and α _m Fourier decomposes, and then obtains the phase characteristics of the transfer function G(s) between the TCSC firing angle increment Δα _m and the generator electromagnetic torque increment ΔT _e , as shown in Figure 4.

设计次同步振荡阻尼控制器所采用的带通滤波器，其通带频率为10Hz～55Hz。采用4阶巴特沃兹滤波器，其传递函数可以表示为：The band-pass filter adopted by the subsynchronous oscillation damping controller is designed, and its pass-band frequency is 10Hz-55Hz. Using a 4th-order Butterworth filter, its transfer function can be expressed as:

$\cdot &Center Dot; \frac{{s the s}^{44}}{{s the s}^{44} + + 2.613 2.613 {ω ω}_{c c 22} {s the s}^{33} + + 3.414 3.414 {ω ω}_{c c 22}^{22} {s the s}^{22} + + 2.613 2.613 {ω ω}_{c c 22}^{33} s the s + + {ω ω}_{c c 22}^{44}} - - - - - - ((44))$

然后确定需要补偿的滞后相角φ，使得在整个10Hz～55Hz次同步频段内发电机转速增量Δω到发电机电磁转矩增量ΔT_e间相位特性在±90°之内，式(4)中s为拉普拉斯算子。Then determine the lag phase angle φ that needs to be compensated, so that the phase characteristics between the generator speed increment Δω and the generator electromagnetic torque increment ΔT _e in the entire 10Hz-55Hz sub-synchronous frequency band are within ±90°, formula (4) Among them, s is the Laplacian operator.

再利用形如

的超前滞后环节来补偿G(s)的相位滞后，使得发电机转速增量Δω到发电机电磁转矩增量ΔT_e间相位特性在±90°之内。采用如下公式确定补偿环节的时间常数。Reuse as

The phase lag of G(s) is compensated by the advanced lag link, so that the phase characteristics between the generator speed increment Δω and the generator electromagnetic torque increment ΔT _e are within ±90°. Use the following formula to determine the time constant of the compensation link.

$a a = = \frac{11 - - sin sin φ φ}{11 + + sin sin φ φ}$

${T T}_{a a} = = 11 / / ((22 π π {f f}_{x x} \sqrt{a a})) - - - - - - ((55))$

T_b＝aT_a T _b = aT _a

式中，f_x为进行相位补偿的频率点，φ为f_x所对应的需要补偿的滞后相角，T_a和T_b为补偿环节的时间常数；s为拉普拉斯算子。考虑带通滤波器的相位滞后特性后，用4个滞后环节在15Hz处各补偿-50°，在60Hz用3个超前环节各补偿40°。各补偿环节的时间常数列于表1。In the formula, f _x is the frequency point for phase compensation, φ is the lag phase angle corresponding to f _x that needs to be compensated, T _a and T _b are the time constants of the compensation link; s is the Laplace operator. After considering the phase lag characteristics of the band-pass filter, use 4 lag links to compensate -50° at 15Hz, and use 3 lead links to compensate 40° at 60Hz. The time constants of each compensation link are listed in Table 1.

表1相位补偿环节的时间常数Table 1 Time constant of phase compensation link

f_x f _x 15Hz 15Hz 60Hz 60Hz φ φ -50° -50° 40° 40° T_a T _a 3.862e-3 3.862e-3 5.688e-3 5.688e-3 T_b T _b 2.915e-2 2.915e-2 1.237e-3 1.237e-3 n n 4 4 3 3

补偿后的系统相位滞后特性如图4中C(s)G(s)曲线所示。The phase lag characteristics of the system after compensation are shown in the C(s)G(s) curve in Figure 4.

确定好TCSC附加控制器的参数后，采集本测试系统中发电机的转速差信号Δω，利用带通滤波器对转速差信号Δω进行滤波处理，再进行放大和相位补偿后，得到附加控制信号。附加控制信号与TCSC基准触发角叠加后，对TCSC进行触发控制，为电力系统提供正的电气阻尼以抑制次同步振荡。After determining the parameters of the TCSC additional controller, collect the speed difference signal Δω of the generator in this test system, filter the speed difference signal Δω with a band-pass filter, and then perform amplification and phase compensation to obtain the additional control signal. After the additional control signal is superimposed with the TCSC reference firing angle, the TCSC is triggered and controlled to provide positive electrical damping for the power system to suppress subsynchronous oscillation.

进行效果评价时，可利用时域频率扫描法测量系统的电气阻尼，验证本发明方法的有效性，当所得的电气阻尼在发电机各扭振频率处都为正值时，则说明本发明方法能够抑制电力系统发生次同步振荡。When carrying out effect evaluation, can utilize the electrical damping of time-domain frequency scanning method to measure system, verify the validity of the inventive method, when the electrical damping of gained is all positive value at each torsional vibration frequency place of generator, then illustrate the inventive method It can suppress the occurrence of subsynchronous oscillation in the power system.

测量系统电气阻尼的具体步骤包括：Specific steps for measuring system electrical damping include:

(1)对确定的运行工作点，待系统进入稳态运行后，在发电机的转子上施加一串频率成整数倍的小值脉动转矩：(1) For the determined operating point, after the system enters steady-state operation, a series of small-value pulsating torques whose frequency is an integer multiple are applied to the rotor of the generator:

式中，λ为常数且小于1，T_λ、

分别是频率为λω₀的脉动转矩的幅值和初相位。要求T_λ较小，以使ΔT_m的值不至于破坏系统可线性化的假设条件。In the formula, λ is a constant and less than 1, T _λ ,

are the amplitude and initial phase of the ripple torque with frequency λω ₀ , respectively. T _λ is required to be small so that the value of ΔT _m will not destroy the assumption that the system can be linearized.

(2)施加脉动转矩后，一直到系统再次进入稳态，截取一个公共周期上的发电机电磁转矩T_e和发电机角频率ω。(2) After the pulsating torque is applied, until the system enters the steady state again, intercept the generator electromagnetic torque T _e and the generator angular frequency ω on a common period.

(3)将发电机电磁转矩T_e和发电机角频率ω进行Fourier分解，得出不同频率下的ΔT_e和Δω。(3) Perform Fourier decomposition on generator electromagnetic torque _Te and generator angular frequency ω to obtain ΔT _e and Δω at different frequencies.

(4)根据求出电气阻尼转矩系数D_e。(4) According to Calculate the electrical damping torque coefficient D _e .

当所得的电气阻尼转矩系数D_e(即电气阻尼)在各扭振频率处都为正值时，所设计的控制器能够抑制系统发生次同步振荡。本例的计算结果如图5所示，可以发现，在采用本发明方法后，TCSC可以在整个次同步频带内提供正的电气阻尼，从根本上消除了SSR的危险。When the obtained electrical damping torque coefficient _De (namely electrical damping) is positive at each torsional vibration frequency, the designed controller can suppress the subsynchronous oscillation of the system. The calculation result of this example is shown in Fig. 5. It can be found that after adopting the method of the present invention, the TCSC can provide positive electrical damping in the entire sub-synchronous frequency band, fundamentally eliminating the danger of SSR.

为进一步验证本发明方法对抑制SSR的有效性，使用详细模型进行暂态时域仿真。图3系统进入稳态后，t＝15s时在F点加三相接地故障，并在0.05秒后切除。图6，7分别为原测试系统和采用本发明方法后发电机各轴段上的扭矩。可见在没有使用本发明方法时，发电机组各轴段上的扭矩是发散的，系统SSR不稳定。而使用本发明方法后，发电机各轴段上的扭矩是逐渐衰减的，系统是SSR稳定的，这与图5中的结果是吻合的。In order to further verify the effectiveness of the method of the present invention for suppressing SSR, a detailed model is used for transient time domain simulation. After the system in Fig. 3 enters the steady state, a three-phase grounding fault is added at point F at t=15s, and it is cut off after 0.05 seconds. Figures 6 and 7 are respectively the torque on each shaft section of the generator in the original test system and after adopting the method of the present invention. It can be seen that when the method of the present invention is not used, the torque on each shaft section of the generator set is divergent, and the system SSR is unstable. After using the method of the present invention, the torque on each shaft section of the generator is gradually attenuated, and the system is SSR stable, which is consistent with the result in Fig. 5 .

Claims

1. method based on the inhibition subsynchronous oscillation of electrical power system of controlled series compensation; It is characterized in that; Handle through generator speed difference signal Δ ω being amplified, generate additional control signal the trigger angle of controlled series compensation is modulated with phase shift, thus the equivalent reactance X of change controlled series compensation _Eff, the electrical damping of raising system, the additional control signal of described generation comprises the steps:

(1) gathers the speed discrepancy signal delta ω of generators in power systems, actual speed that described speed discrepancy signal is a generator and rated speed poor;

(2) speed discrepancy signal delta ω being carried out Filtering Processing, is band pass filter filters low signal and the high order harmonic component of 10～55Hz by passband, obtains the generator torsion frequency signal in the subsynchronous frequency range; The transfer function of the band pass filter that is adopted is expressed as:

H (s) = \frac{ω_{c 1}^{4}}{s^{4} + 2.613 ω_{c 1} s^{3} + 3.414 ω_{c 1}^{2} s^{2} + 2.613 ω_{c 1}^{3} s + ω_{c 1}^{4}}

\cdot \frac{s^{4}}{s^{4} + 2.613 ω_{c 2} s^{3} + 3.414 ω_{c 2}^{2} s^{2} + 2.613 ω_{c 2}^{3} s + ω_{c 2}^{4}}

In the formula, filter cutoff frequency is taken as ω _C1=55Hz, ω _C2=10Hz, s are Laplacian;

(3) signal that filtering is obtained amplify with phase compensation after, obtain additional control signal Δ α;

Wherein the signal that filtering obtains is carried out phase compensation, the transfer function of lead-lag link is

through a plurality of lead-lag links wherein:

T _a, T _bBe the time constant of lead-lag link,

n＝T _b/T _a＝(1-sinφ)/(1+sinφ)；

T_{a} = 1 / (ω_{x} \sqrt{n});

T _b＝nT _a；

ω _xFrequency for the needs compensation;

φ is ω _xThe pairing lagging phase angle that needs compensation;

Wherein utilize the time domain frequency sweep method to try to achieve the additional control signal Δ α of controlled series compensation to generator additional electromagnetic torque Δ T _eBetween the phase characteristic of transfer function, making generator speed increment Delta ω to generator electromagnetic torque increment Delta T _eBetween phase characteristic under the principle within ± 90 °, confirm to need the lagging phase angle φ of compensation.