CN102570950B - Subsynchronous damping control system and subsynchronous damping control method for generator terminals - Google Patents

Abstract

The invention discloses a design method of the subsynchronous damping control of a generator terminal. The subsynchronous damping control of the generator terminal is designed according to an upper controller, a lower controller and a primary device, wherein the upper controller implements the control strategy and information monitoring of subsynchronous resonance, the lower controller implements the large-current output of a control instruction through driving a power electronic power component, and the primary device contains the power electronic power component and a transformer for controlling a current to be compensated to the generator terminal; the upper controller carries out sampling, demodulating and filtering processing as well as independent proportional phase shift processing on a rotating-speed pulse signal so as to obtain a rotor-side modal controlled quantity, then, the modal controlled quantity is converted into a three-phase control current instruction according to an obtained electrical angle coordinate of the system, and the lower controller controls the power electronic power component to output a three-phase power current according to the received control current instruction; and the three-phase power current is injected into the generator terminal by a step-up transformer. By using the design method disclosed by the invention, a current is outputted at the generator terminal so as to carry out compensation according to an identified torsional vibration modal signal of a generator set, thereby improving the modal damping of the generator set.

Description

A kind of Generator end hyposynchronous damped control system and subsynchronous damping control method

Technical field

The invention belongs to power system stability and control technology field, be specifically related to a kind of method for designing of Generator end Subsynchronous Damping Controller, for resolution system sub-synchronous oscillation provides a kind of new solution.

Background technology

Along with the increase in demand of long-distance and large-capacity power transmission, particularly large moulded coal electricity base is due to away from load center, mostly adopt remote factory to net Transmission Mode, in order to improve transmission capacity and the stability of a system, adopt more and more fixed series capacitor compensation (FSC), high voltage direct current transmission (HVDC) and some high-speed control devices based on power electronic technology.But these devices may cause subsynchronous resonance (SSR) or vibration (SSO) problem under certain condition.Slight SSR/SSO can reduce the turbonator shafting life-span, and serious SSR/SSO can cause turbonator shafting fracture, threatens the safe and stable operation of unit and electric power system.

Investigation shows, some large moulded coal electricity bases of China, and as the Tuoketuo Power Plant of North China Power Telecommunication Network, Shang Dou power plant, Jin Jie power plant, the Yi Min power plant of Northeast China Power Grid etc., generally the at a distance large capacity of employing factory is to net string benefit Transmission Mode.Analysis shows, the large capacity factory of this remote (200 kilometers and more than), middle high series compensatnig degree (30% and more than) is to net transmission system, there is SSR risk in various degree, and often occur the subsynchronous frequency mode of unstable or underdamping (being multi-modal SSR/SSO) of more than one under certain condition; Also may there is potential SSO problem in the large thermal power plant (as Guo Hua Suizhong Power "Promplast-14" Co., Ltd) being connected with HVDC system on the other hand; SSR/SSO problem becomes the realistic problem in the urgent need to address that electric power netting safe running faces, and must take the necessary measures and effectively dissolve risk, guarantees machine network operation safety.

Solving in SSR/SSO problem, there is at present multiple solution, mainly comprise: the SVC solution based on thyristor power electronic device; Supplementary excitation damping control solution based on excitation system and block filter carry out the solution of filtering etc., and all have at home the case of use.Some limitation when these solutions control technology feature has separately determined each comfortable practical application: traditional thyristor control of the employing of (1) SVC, technology is relatively backward, harmonic characterisitic is poor, and floor space is larger simultaneously, and cost is higher.(2) supplementary excitation damping control is the best a kind of solution of current cost performance, and it is to adopt secondary device on field regulator, to suppress SSR problem by being attached to.But this method transmitting-receiving motor excitation holds quantitative limitation, and the inhibition providing is limited in one's ability.(3) adopt the scheme cost of block filter the highest, and filtering characteristic is subject to the impact of components and parts (inductance, electric capacity) very large, and inductance, electric capacity are subject to the such environmental effects such as temperature larger, so the maintenance cost of equipment is very high after operation.

The subsynchronous damping control method of Generator end that the present invention is designed, adopts advanced control device, control strategy advanced person, and valency is higher frequently, and harmonic characterisitic is relatively good, and capacity extension is very convenient, meets the requirement that large capacity engineering is used.

Summary of the invention

The method for designing that the object of this invention is to provide a kind of Generator end hyposynchronous damped control system suppresses phylogenetic SSR/SSO problem, for solving the multi-modal subsynchronous resonance of electric power system and oscillation problem, provides a kind of brand-new solution.

The present invention is specifically by the following technical solutions:

A kind of Generator end hyposynchronous damped control system, comprises side controller, lower side controller, electric and electronic power unit, damped control system step-up transformer; It is characterized in that:

Described upper side controller gathers the rotational speed pulse signal of generator, from rotational speed pulse signal, extract after torsional vibration signals, by mode filtering, obtain each subsynchronous mode torsional vibration signals, and mode torsional vibration signals ratio is amplified and phase shift processing, obtain the mode controlled quentity controlled variable of generator amature side;

Described upper side controller gathers three-phase voltage, the three-phase current electric parameters of Generator end, obtains the current magnetic field rotating angle of generator, converts the mode controlled quentity controlled variable of generator amature side the instruction of to three-phase target current;

Described upper side controller and lower side controller are by optical fiber connecting communication, and described upper side controller is handed down to lower side controller by the instruction of described three-phase target current;

The output of described lower side controller connects electric and electronic power unit input, and according to the three-phase target current instruction that receives control electric power electron power element IGBT conducting, turn-off angle, convert three-phase target current to three-phase alternating current output;

The output of described electric and electronic power unit is connected to the input of damped control system step-up transformer, by damped control system step-up transformer, the described three-phase alternating current output of electric and electronic power unit is converted to the offset current of the same voltage levvl grade of Generator end and injects Generator end.

Based on above-mentioned Generator end hyposynchronous damped control system, disclosed herein as well is a kind of subsynchronous damping control method, described method can realize the damping of the subsynchronous model frequency that increases generating set, reach the control target that suppresses unit subsynchronous resonance, it is characterized in that, the method comprises the following steps:

(1) upper side controller gathers rotational speed pulse signal, Generator end three-phase voltage, the three-phase current signal of generator, by cable, electric and electronic power unit is exported to side controller in three-phase voltage, the access of output three-phase current and monitor, upper strata controller and lower floor's controller are by optical fiber connecting communication;

(2) described upper side controller carries out demodulation and obtains the torsional vibration signals d ω of unit to rotational speed pulse signal, the torsional vibration signals d ω of unit is carried out to filtering processing simultaneously and obtains the each subsynchronous mode torsional vibration signals d ω (k) after modal separation;

(3) the mode controlled quentity controlled variable d ω ' that described upper side controller obtains rotor-side to the described mode torsional vibration signals d ω (k) processing after filtering through the processing of ratio amplification, phase shift and amplitude limit link (k);

(4) upper side controller carries out phase-locked closed-loop processing to the Generator end three-phase voltage collecting, and obtains the electric angle θ of generator system;

(5) the mode controlled quentity controlled variable d ω ' of rotor-side, (k) by comprising system electrical angle θ and the dq coordinate transform of the angle θ ' that can adjust, is transformed into the controlled quentity controlled variable of stator side, i.e. the final three-phase target current instruction i controlling _a, i _b, i _c, three-phase target current instruction i _a, i _b, i _ccomprise two frequency component: ω ₀+ d ω ' (k) and ω ₀-d ω ' (k), wherein, ω ₀for power system frequency, the angle of can adjusting θ ' adjusts by the mode of field test;

(6) lower side controller receives the three-phase target current instruction i that upper side controller issues _a, i _b, i _c, by voltage balance control, generate the departure of target current instruction, this departure and three-phase target current instruction i simultaneously _a, i _b, i _ccomprehensive summation, generates final tracking export target instruction i _a', i _b', i _c';

(7) described lower side controller is according to final tracking export target instruction i _a', i _b', i _c' control IGBT conducting, shutoff angle in the each link of electric and electronic power unit, finally generate the three phase power electric current output i of low-voltage-grade _a", i _b", i _c";

(8) described three phase power electric current output i _a", i _b", i _c" again through the final three-phase offset current i that compensates to Generator end that generates of damped control system step-up transformer _a" ', i _b" ', i _c" '.

The present invention proposes a kind of by carry out the machine end hyposynchronous damped control system of subsynchronous current compensation and the control method based on this control system at Generator end, by control system of the present invention and control method, can realize the target of carrying out subsynchronous resonance inhibition at machine end, the volume controlled of the method is well arranged simultaneously, capacity extension is convenient, can adapt to solve the demand of different actual field problems.

Accompanying drawing explanation

Fig. 1 machine end hyposynchronous damped control system structure chart;

The subsynchronous damping control method flow chart of Fig. 2 machine end;

Fig. 3 tach signal modal separation process;

The implementation procedure of Fig. 4 coordinate transform

The control flow of side controller under Fig. 5;

The structure chart of Fig. 6 power electronic element;

The data analysis of Fig. 7 dynamic simulation test.

Embodiment

Below in conjunction with Figure of description, the concrete enforcement of technical scheme of the present invention is described in further detail.

Method for designing of the present invention comprises primary equipment and secondary device, crucial control algolithm is applied in the embedded environment of secondary device, this example is introduced the concrete upper and lower sides controller control flow of application the method realization and the primary equipment access procedure of high-power electric current output access Generator end, to realize 10MVA capacity as example.

Be illustrated in figure 1 machine end hyposynchronous damped control system structure chart disclosed by the invention.Rotational speed pulse signal accesses upper side controller by transducer through cable, three-phase voltage, the three-phase current of Generator end access upper side controller by the instrument transformer of Generator end through cable, and the three-phase current that electric and electronic power unit sends accesses upper side controller by the instrument transformer of Generator end through cable.Three-phase voltage, the three-phase current of Generator end access lower side controller by the instrument transformer of Generator end through cable, the three-phase current that electric and electronic power unit sends is by instrument transformer side controller under cable access of Generator end, and the low-pressure side voltage of damped control system step-up transformer is by instrument transformer side controller under cable access.

The data of upper side controller collection have: the three-phase current that rotational speed pulse signal, Generator end three-phase voltage, three-phase current and the electric and electronic power unit of generator sends.Upper side controller carries out demodulation to rotational speed pulse signal, extracts after torsional vibration signals, by mode filtering, obtains each subsynchronous mode signal, and mode torsional vibration signals ratio is amplified and phase shift processing, obtains the mode controlled quentity controlled variable of generator amature side; Upper side controller through based on the phase-locked coordinate transform of obtaining system electrical angle of machine end three-phase voltage, generates rotor-side mode controlled quentity controlled variable the mode controlled quentity controlled variable of stator side, and under the mode with optical-fibre communications, passes to lower side controller.

The output of lower side controller connects electric and electronic power unit input, and according to the upper side controller three-phase target current order that receives control electric power electron power element IGBT conducting, turn-off angle, three-phase target current instruction transformation is become to three-phase alternating current output, what power electronic element adopted chain type opens up benefit structure, every by multiple power unit cascades, often in this implementation by 11 units in series, formed, realize powerful output, opening up of electric and electronic power unit mended structure as shown in Figure 5.The output of electric and electronic power unit is connected to the input of step-up transformer, by step-up transformer, the described three-phase alternating current output of electric and electronic power unit is converted to the offset current of the same voltage levvl grade of Generator end and injects Generator end.

Be the subsynchronous damping control method based on hyposynchronous damped control system disclosed by the invention as shown in Figure 2, said method comprising the steps of.

Step 1: the building of control system, upside and downside control gather Generator end signal

The signal of upper side controller collection mainly contains: the rotational speed pulse signal of (1) generator amature, tach signal is transformed into by transducer the upper side controller of rotational speed pulse signal access that upper side controller adapts to, the signal frequency of tacho-pulse, at 0～10K, common are 3K, 6.7K etc.; (2) three-phase voltage of Generator end, three-phase current electric parameters are by electric parameters access controller, for monitoring and phase-locked function; (3) output current of electric and electronic power unit passes through cable access controller on the spot.The signal that lower side controller mainly gathers has: three-phase voltage, the three-phase current electric parameters of (1) Generator end are passed through electric parameters access controller; (2) direct voltage of each link is by transducer access controller; (3) output current of electric and electronic power unit passes through cable access controller on the spot.Upper side controller is connected by optical fiber with lower side controller.

Step 2: demodulation filtering mode signal separates

Rotational speed pulse signal is carried out to demodulation process, tacho-pulse is according to the number of teeth of concrete on-the-spot actual speed fluted disc configuration, frequency is between 3K～10K, what domestic use was many is the fluted disc of 134 teeth, be that the frequency of corresponding tacho-pulse is at 6.7K, when having torsional vibration signals, the frequency of tacho-pulse changes near 6.7K.From rotational speed pulse signal, extract after torsional vibration signals, need to carry out the real-time separation of each model frequency signal so that carry out independently multi-modal control.Take domestic 600MW turbo generator set main flow unit as example, the subsynchronous model frequency of shaft system of unit has three, respectively near 16Hz, 27Hz and 30Hz.Modal filter group by design separates this model frequency signal, obtains each real-time mode signal, and the bank of filters of modal separation forms as shown in Figure 3.At this, realize in example, filter is that 1KHz designs according to sample frequency.

Step 3: each mode signal carries out independent ratio and amplifies phase control

In this example, it is the fixed time interval of 1ms that data processing is interrupted, 3 mode signal d ω after treatment (1), d ω (2) and d ω (3) are carried out respectively to independent gain phase-amplitude control, and the control change of gain phase-amplitude is:

${\mathrm{d\&omega;}}^{\&prime;}\left(1\right)=\mathrm{limit}(\mathrm{d\&omega;}\left(1\right)*k_1*{\left[\frac{1-T_1\mathrm{<figure-callout\; id="1"\; label="s"\; filenames="HDA0000131930170000022.png,HDA0000131930170000031.png"\; state="\{\{state\}\}">s</figure-callout>}}{1+T_{1}s}\right]}^2)$

${\mathrm{d\&omega;}}^{\&prime;}\left(2\right)=\mathrm{limit}(\mathrm{d\&omega;}\left(2\right)*k_2*{\left[\frac{1-T_2\mathrm{<figure-callout\; id="1"\; label="s"\; filenames="HDA0000131930170000022.png,HDA0000131930170000031.png"\; state="\{\{state\}\}">s</figure-callout>}}{1+T_{2}s}\right]}^2)$

${\mathrm{d\&omega;}}^{\&prime;}\left(3\right)=\mathrm{limit}(\mathrm{d\&omega;}\left(3\right)*{\mathrm{<figure-callout\; id="3"\; label="k"\; filenames="HDA0000131930170000031.png"\; state="\{\{state\}\}">k</figure-callout>}}_3*{\left[\frac{1-T_3\mathrm{<figure-callout\; id="1"\; label="s"\; filenames="HDA0000131930170000022.png,HDA0000131930170000031.png"\; state="\{\{state\}\}">s</figure-callout>}}{1+T_{3}s}\right]}^2)$

Wherein T1, T2, T3 are the phase shift time constants of 3 mode, and k1, k2, k3 are the proportionality coefficients of the controlling unit of 3 mode, and limit represents that the real time data after ratio phase shift is carried out amplitude limit to 3 mode.When computer realization, s territory expression formula is carried out to discrete transform under the sample rate of 1K, generate discrete domain expression formula.

Step 4: the obtaining of system electrical angle

By step 1,2, obtained the mode controlled quentity controlled variable of rotor-side, will be this control-action compensation to stator side, need to know the electric angle of system, by the real-time tracking of Generator end three-phase voltage is carried out, in sample rate take sample rate as 1K, side controller gathers three-phase phase voltage, take the q axle component of three-phase voltage as 0 as controlling target, calculate in real time the q axle component of three-phase voltage, component using q axle carries out negative feedback control as departure, the target that finally realizes q axle component trend 0, system electrical angle is now the electric angle of real system.

Step 5: the coordinate transform of controlled quentity controlled variable

Because final controlled quentity controlled variable is the stator side that is added in generator, compensate control, and control inputs amount is the shafting torsional oscillation signal of generator amature, the controlled quentity controlled variable of 3 mode need to be carried out to coordinate transform, is transformed into stator controlled quentity controlled variable and controls.

$\left[\begin{array}{c}{{\mathrm{d\&omega;}}^{\&prime;}}_{1a}\\ {{\mathrm{d\&omega;}}^{\&prime;}}_{1b}\\ {{\mathrm{d\&omega;}}^{\&prime;}}_{1c}\end{array}\right]={\mathrm{<figure-callout\; id="1"\; label="T"\; filenames="HDA0000131930170000022.png,HDA0000131930170000031.png"\; state="\{\{state\}\}">T</figure-callout>}}_{1\mathrm{dq}-\mathrm{abc}}\left[\begin{array}{c}{\mathrm{d\&omega;}}^{\&prime;}\left(1\right)\\ 0\\ 0\end{array}\right]$

$\left[\begin{array}{c}{{\mathrm{d\&omega;}}^{\&prime;}}_{2a}\\ {{\mathrm{d\&omega;}}^{\&prime;}}_{2b}\\ {{\mathrm{d\&omega;}}^{\&prime;}}_{2c}\end{array}\right]={\mathrm{<figure-callout\; id="2"\; label="T"\; filenames="HDA0000131930170000031.png"\; state="\{\{state\}\}">T</figure-callout>}}_{2\mathrm{dq}-\mathrm{abc}}\left[\begin{array}{c}{\mathrm{d\&omega;}}^{\&prime;}\left(2\right)\\ 0\\ 0\end{array}\right]$

$\left[\begin{array}{c}{{\mathrm{d\&omega;}}^{\&prime;}}_{3a}\\ {{\mathrm{d\&omega;}}^{\&prime;}}_{3b}\\ {{\mathrm{d\&omega;}}^{\&prime;}}_{3c}\end{array}\right]={\mathrm{<figure-callout\; id="3"\; label="T"\; filenames="HDA0000131930170000031.png"\; state="\{\{state\}\}">T</figure-callout>}}_{3\mathrm{dq}-\mathrm{abc}}\left[\begin{array}{c}{\mathrm{d\&omega;}}^{\&prime;}\left(3\right)\\ 0\\ 0\end{array}\right]$

Wherein:

System electrical angle θ obtains by the real-time tracking to system voltage, the angle of can adjusting

by on-the-spot parameter tuning, test to obtain, coordinate transform as shown in Figure 4.

Conversion process relates to the tracking problem of coordinate transform angle, consider the consideration of the real-time computational accuracy of computer and computing capability, according to fixing differential seat angle, set up sine and cosine table, adopt the mode of tabling look-up can very simply obtain sine and cosine value at any angle.

Final control output variable:

i _a＝dω′ _1a+dω′ _2a+dω′ _3a

i _b＝dω′ _1b+dω′ _2b+dω′ _3b

i _c＝dω′ _1c+dω′ _2c+dω′ _3c

Step 6: tracking and the DC voltage control of lower side controller to control command

As shown in Figure 5, lower floor's controller receives the target current instruction i that upper strata controller issues to the control flow of lower side controller _a, i _b, i _c, simultaneously by the departure of voltage balance control module generation target current instruction, this departure and target current instruction i _a, i _b, i _ccomprehensive summation, generates final tracking export target instruction i _a', i _b', i _c'.This process excessively in, voltage balance control guarantees that in direct voltage and AC system reciprocal process, fluctuation, in controlled scope, can not cause because of the fluctuation of output current the unstability of current transformer DC side.

Step 7: tracking and the electric current of lower side controller to control command exported in real time

Target instruction target word i _a', i _b', i _c' by electric current beat control, producing control command to go to control IGBT conducting, turn-off pulse, pulse distribution chains to 11 of every phases, finally generates the three-phase High-current output i of low-voltage-grade _a", i _b", i _c", i _a", i _b", i _c"; Again through the final three-phase offset current i that compensates to machine end that generates of damped control system step-up transformer _a" ', i _b" ', i _c" '; Lower side controller, the offset current of reality output is carried out to real-time monitoring, if there is the problems such as overcurrent, will carry out a series of safeguard measures fast, guarantee reliability and the fail safe of output.What power electronic element adopted chain type opens up benefit structure, every by multiple power unit cascades, realizes powerful output, and opening up of electric and electronic power unit mended structure as shown in Figure 6.

Step 8: the injection of boosting of offset current

The offset current electric pressure that electric and electronic power unit sends is also lower, can't reach the requirement of injecting Generator end, so need to offset current be finally transformed into by damped control system step-up transformer to the current i of set end voltage grade _a" ', i _b" ', i _c" ' compensate to machine end.The final connection realizing physically.

According to the control device that the design of 8 steps realizes above, the test of carrying out at the scene, result contrasts as shown in Figure 7, and light color is not for throwing the torsional oscillation vibration situation of generator end Subsynchronous Damping Controller, and dark color is the torsional oscillation vibration situation that drops into generator end Subsynchronous Damping Controller.By contrast, can see that this generator end Subsynchronous Damping Controller can be good at the positive damping of the subsynchronous resonance that unit is provided, guarantee that unit still can safe and stable operation in disturbance situation.

Claims (6)

1. a Generator end hyposynchronous damped control system, comprises side controller, lower side controller, electric and electronic power unit, damped control system step-up transformer; It is characterized in that:

Described upper side controller gathers the rotational speed pulse signal of generator, from rotational speed pulse signal, extract after torsional vibration signals, by mode filtering, obtain each subsynchronous mode torsional vibration signals, and mode torsional vibration signals ratio is amplified and phase shift processing, obtain the mode controlled quentity controlled variable of generator amature side;

Described upper side controller gathers three-phase voltage, the three-phase current electric parameters of Generator end, obtains the current magnetic field rotating angle of generator, converts the mode controlled quentity controlled variable of generator amature side the instruction of to three-phase target current;

Described upper side controller and lower side controller are by optical fiber connecting communication, and described upper side controller is handed down to lower side controller by the instruction of described three-phase target current;

The output of described lower side controller connects electric and electronic power unit input, and according to the three-phase target current instruction that receives control electric power electron power element IGBT conducting, turn-off angle, convert three-phase target current to three-phase alternating current output;

The output of described electric and electronic power unit is connected to the input of damped control system step-up transformer, by damped control system step-up transformer, the described three-phase alternating current output of electric and electronic power unit is converted to the offset current of the same voltage levvl grade of Generator end and injects Generator end.

2. Generator end hyposynchronous damped control system according to claim 1, is characterized in that:

Described lower side controller also gathers the direct voltage of each link in described electric and electronic power unit, realizes the closed-loop control to electric and electronic power unit direct voltage.

3. Generator end hyposynchronous damped control system according to claim 1 and 2, is characterized in that:

Described electric and electronic power unit adopts chain inverter to open up benefit structure, and each of described electric and electronic power unit is linked and is comprised of multiple power unit cascades.

4. the subsynchronous damping control method of the Generator end hyposynchronous damped control system based on described in any one claim in claim 1-3, described method can realize the damping of the subsynchronous model frequency that increases generating set, reach the control target that suppresses unit subsynchronous resonance, it is characterized in that, the method comprises the following steps:

(1) upper side controller gathers rotational speed pulse signal, Generator end three-phase voltage, the three-phase current signal of generator, by cable, electric and electronic power unit is exported to side controller in three-phase voltage, the access of output three-phase current and monitor, upper strata controller and lower floor's controller are by optical fiber connecting communication;

(2) described upper side controller carries out demodulation and obtains the torsional vibration signals d ω of unit to rotational speed pulse signal, the torsional vibration signals d ω of unit is carried out to filtering processing simultaneously and obtains the each subsynchronous mode torsional vibration signals d ω (k) after modal separation;

(3) the mode controlled quentity controlled variable d ω ' that described upper side controller obtains rotor-side to the described mode torsional vibration signals d ω (k) processing after filtering through the processing of ratio amplification, phase shift and amplitude limit link (k);

(4) upper side controller carries out phase-locked closed-loop processing to the Generator end three-phase voltage collecting, and obtains the electric angle θ of generator system;

(5) the mode controlled quentity controlled variable d ω ' of rotor-side, (k) by comprising system electrical angle θ and the dq coordinate transform of the angle θ ' that can adjust, is transformed into the controlled quentity controlled variable of stator side, i.e. the final three-phase target current instruction i controlling _a, i _b, i _c, three-phase target current instruction i _a, i _b, i _ccomprise two frequency component: ω ₀+ d ω ' (k) and ω ₀-d ω ' (k), wherein, ω ₀for power system frequency, the angle of can adjusting θ ' adjusts by the mode of field test;

(6) lower side controller receives the three-phase target current instruction i that upper side controller issues _a, i _b, i _c, by voltage balance control, generate the departure of target current instruction, this departure and three-phase target current instruction i simultaneously _a, i _b, i _ccomprehensive summation, generates final tracking export target instruction i _a', i _b', i _c';

(7) described lower side controller is according to final tracking export target instruction i _a', i _b', i _c' control IGBT conducting, shutoff angle in the each link of electric and electronic power unit, finally generate the three phase power electric current output i of low-voltage-grade _a' ', i _b' ', i _c' ';

(8) described three phase power electric current output i _a' ', i _b' ', i _c' ' again through the final three-phase offset current i that compensates to Generator end that generates of damped control system step-up transformer _a' ' ', i _b' ' ', i _c' ' '.

5. subsynchronous damping control method according to claim 4, is characterized in that:

In described step (2), adopt the IIR bandpass digital filter based on elliptic filter prototype to carry out filtering processing to torsional vibration signals d ω, passband frequency range meets the fluctuation of generator unit shaft system model frequency.

6. subsynchronous damping control method according to claim 4, is characterized in that:

In described step (5), the mode controlled quentity controlled variable d ω ' of rotor-side, (k) through the dq coordinate transform by comprising electric power system electric angle θ and can adjusting angle θ ', obtains the final target current instruction i controlling _a, i _b, i _c, the angle of can adjusting θ ' is by testing ω ₀+ d ω ' (k) and ω ₀-d ω ' (k) two frequency signals adjusts in epitrochanterian phase-shift characterisitc measurement.

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