CN109474028A - Based on system stability optimal control method under power grid friendly DFIG control strategy - Google Patents
Based on system stability optimal control method under power grid friendly DFIG control strategy Download PDFInfo
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
- H02J3/00—Circuit arrangements for ac mains or ac distribution networks
- H02J3/38—Arrangements for parallely feeding a single network by two or more generators, converters or transformers
- H02J3/46—Controlling of the sharing of output between the generators, converters, or transformers
- H02J3/48—Controlling the sharing of the in-phase component
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
- H02J3/00—Circuit arrangements for ac mains or ac distribution networks
- H02J3/38—Arrangements for parallely feeding a single network by two or more generators, converters or transformers
- H02J3/46—Controlling of the sharing of output between the generators, converters, or transformers
- H02J3/50—Controlling the sharing of the out-of-phase component
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Abstract
It is influenced based on system stability optimal control method under power grid friendly DFIG control strategy, including for traditional power grid friendly DFIG control strategy interaction, determines optimizing control models；Using transient state real power control model is crossed over, DFIG active power output changes during analysis system short trouble；Using the idle correcting current Controlling model of additional constraint, the idle power output variation of DFIG during analysis system short trouble；Comprehensive assessment is carried out to the system stability improvement after optimal control.The method of the present invention considers control strategy reciprocal influence, from active clipping and restore the influence to virtual inertia control effect, various factors such as influence of the virtual inertia control to the idle control effect of transient state are analyzed, using DFIG power output variation during the idle correcting current control-Strategy analysis system short-circuit fault across transient state real power control strategy and additional constraint, overall merit finally is carried out to system stability improvement after optimal control.
Description
Technical field
The present invention relates to network optimization control fields, and in particular to one kind based on being under power grid friendly DFIG control strategy
System optimizing stability control method.
Background technique
Under the thinking of wind farm close friendization, in DFIG universal model, comprising can during short circuit with short circuit
It limits active given during active recovery, has to mitigate current transformer load pressure and reduce the active too fast transient state for restoring impact afterwards
Power control system；And idle injection can be improved during short circuit, reduce the idle control of transient state of DFIG off-grid risk.Except this it
The frequency stabilization of system when outside, to guarantee that big active vacancy (or surplus) scene occurs for system, virtual inertia control is in recent years
Also become research hotspot.Although the design starting point of the above three classes power grid friendly DFIG control strategy is different, due to DFIG
(active) control of revolving speed in control system is overlapped with idle control time scale with system electromechanics time scale, so working as system
When short trouble occurs, active/idle control of DFIG transient state can respond the variation of DFIG set end voltage, and virtual inertia control is then
Can response system frequency instantaneous offsets, and the transient state that rapidly changes DFIG is active with idle output characteristics, thus to system
Angle stability and Voltage Drop amplitude generate different influences.
Although the more adequately research existing to the influence that system is stable of the above three classes power grid friendly DFIG control strategy,
But the influence stable to system of single control strategy is usually only focused under study for action, and it is mutual between less consideration control strategy
It influences, so as to restrict power grid friendly DFIG control strategy mutually in practical applications, influences respective control effect.
If transient state is active with idle influence of the control for virtual inertia control effect, although virtual inertia control has improvement system function
The stable ability in angle, but this advantage under certain condition can and idle control active by transient state limitation.For another example virtual inertia control
The influence to the idle control effect of transient state is made, this influences whether that DFIG changes Voltage Drop level in failure under certain condition
Kind effect.
Summary of the invention
Stablized in order to solve the above technical problems, the present invention provides one kind based on system under power grid friendly DFIG control strategy
Property optimal control method, this method consider control strategy reciprocal influence, from active clipping and restore to virtual inertia control imitate
The influence of fruit, various factors such as the influence of virtual inertia control to the idle control effect of transient state are analyzed, using leap
DFIG goes out during transient state real power control strategy and the idle correcting current control-Strategy analysis system short-circuit fault of additional constraint
Power variation, finally carries out overall merit to system stability improvement after optimal control.
The technical scheme adopted by the invention is as follows:
Based on system stability optimal control method under power grid friendly DFIG control strategy, comprising the following steps:
Step 1: being influenced for traditional power grid friendly DFIG control strategy interaction, determine optimizing control models；
Step 2: using the optimizing control models, DFIG power output variation during analysis system short trouble；
Step 2 includes:
Step 2.1: using transient state real power control model is crossed over, DFIG active power output becomes during analysis system short trouble
Change；
Step 2.2: using the idle correcting current Controlling model of additional constraint, during analysis system short trouble DFIG without
Function power output variation；
Step 3: comprehensive assessment is carried out to the system stability improvement after optimal control.
It is of the invention a kind of based on system stability optimal control method under power grid friendly DFIG control strategy, beneficial effect
It is as follows:
1) it, from wind farm close friendization angle, has fully considered the interaction between control strategy, has improved and only close
Infuse the insufficient status of the single control strategy influence stable to system.
2), the opposite idle power output for improving DFIG, reduces DFIG off-grid risk.
3) stability of system head pendulum and anti-wobble, can be improved.
4), from more fully angle, sending angle stability is improved, while reducing Voltage Drop depth during failure
Degree.
Detailed description of the invention
Present invention will be further explained below with reference to the attached drawings and examples.
Fig. 1 is rotor-side converter control logic schematic diagram.
Fig. 2 be failure during with given figure active after failure.
Fig. 3 is to improve transient current to give control figure.
Fig. 4 is to improve real power control principle analysis figure.
Fig. 5 (a) is time-domain-simulation system rack schematic diagram；
Fig. 5 (b) is the active curve graph of DFIG；
Fig. 5 (c) is system power-angle curve figure；
Fig. 5 (d) is the idle curve graph of DFIG；
Fig. 5 (e) is that boosting becomes idle curve graph；
Fig. 5 (f) is set end voltage curve graph.
Specific embodiment
Based on system stability optimal control method under power grid friendly DFIG control strategy, comprising the following steps:
Step 1: being influenced for traditional power grid friendly DFIG control strategy interaction, determine optimizing control models；
Step 2: using the optimizing control models, DFIG power output variation during analysis system short trouble；
Step 2 includes:
Step 2.1: using transient state real power control model is crossed over, DFIG active power output becomes during analysis system short trouble
Change；
Step 2.2: using the idle correcting current Controlling model of additional constraint, during analysis system short trouble DFIG without
Function power output variation；
Step 3: comprehensive assessment is carried out to the system stability improvement after optimal control.
In the step 1, traditional power grid friendly DFIG control strategy include: transient state real power control, transient state is idle control,
Virtual inertia control；
Transient state real power control model includes amplitude limitation ird_max,
UmeasFor the end DFIG voltage；
Transient state is idle, and Controlling model includes the idle control output quantity Δ i of transient stateQ:
ΔiQ=Kv*(1-Umeas),Umeas≤0.9pu,Kv≥2 (2)
KvFor the idle gain of DFIG transient state.
After DFIG set end voltage breaks through controlling dead error, transient state is idle control output quantity Δ iQIt can be described with formula (2).
In general, amplitude limits module can be by active preferential switching to guarantee to give full play to DFIG reactive power support ability during short trouble
It is extremely idle preferential, therefore i during transient staterd_ref1It will also coordinate with the idle control output of transient state.
The active clipping i determined is controlled by transient state is idlep_maxCalculating formula is as follows:
imaxElectric current, i can be born for current transformer maximump_maxMaximum capable of emitting watt current, i when being idle preferentialQ0It is steady
State reactive current, irq_refFor q axis meritorious reference current, Δ iQFor the idle control output quantity of transient state.
During short trouble when the idle control action of transient state, stable state is idle, and control integrator is blocked, iQ0It remains unchanged.
Virtual inertia control changes meritorious reference current ird_ref0Action principle are as follows: change revolution speed control system generate
Dtc signal Tref, warp and Lmψs/LsWatt current is obtained after being divided by with reference to ird_ref0, wherein Lm, ψs, LsRespectively motor mutual inductance,
Stator magnetic linkage and stator self inductance；
The control strategy interaction includes:
(1), influence of two kinds of clipping effect size relations to the active clipping of transient state under different condition,
(2), the influence of active clipping and recovery to virtual inertia control effect,
(3), virtual inertia controls the influence to the idle control effect of transient state；
Specific control strategy interaction analytic process is as follows,
1) i, is analyzedrd_maxWith ip_maxThe size relation of two kinds of clipping effects at different conditions:
Assuming that DFIG uses unity power factor control, i.e. i when steady-state operationQ0=0, then during failure, when 0.868pu≤
UmeasWhen≤0.9pu, have:
Work as ird_max≥ip_maxWhen, there is Kv(1-Umeas) >=0.2, constructed fuction f1(Umeas(the 1-U of)=0.2/meas), work as Kv≥
When 2, the f on [0.868,0.9] section1(Umeas) codomain be [1.52,2], have Kv≥f1(Umeas) perseverance establishment, i.e. KvWhen >=2
ird_max≥ip_maxPerseverance set up, so when the active clipping of transient state by ip_maxIt determines.
Similarly, as 0.116pu≤UmeasWhen≤0.868pu, have
Work as ird_max≥ip_maxWhen, have
Inequality right-hand vector is configured to function f2(Umeas), on section [0.116,0.868] its codomain be [- 0.968,
1.0987], it is seen that work as Kv>=2 up-to-date styles (6) are permanent to be set up, i.e. ird_max≥ip_maxPerseverance is set up, and the active clipping of transient state is by ip_maxIt determines.
Work as UmeasWhen≤0.116pu, i at this timerd_maxIt is 0, i.e., active clipping is 0, to sum up, due to general in grid-connected directive/guide
It is required that Kv>=2, therefore practical active clipping i during transient statep_limAre as follows:
Therefore, in UmeasWhen >=0.116pu, the active maximum value of transient state is actually determined by the idle control of transient state.
2) it, analyzes active clipping and restores the influence to virtual inertia control effect:
When DFIG sensory perceptual system frequency instantaneous offsets in short trouble, so that virtual inertia control output TVIGreater than 0, so that
(Tref-TVI) reduce, (Tref-TVI) reference of corresponding watt current and ip_maxBetween size relation will determine transient state during
Meritorious reference current gives ird_ref2.Work as UmeasWhen >=0.116pu, if virtual inertia control parameter KdSmaller or frequency shift (FS) compared with
Small, active reference will be by i during short circuitp_maxIt determines；If virtual inertia control parameter KdLarger or frequency shift (FS) is larger, the short-circuit phase
Between given will be controlled by virtual inertia of watt current determine.Work as UmeasIt is active during short trouble to be referenced as when≤0.116pu
0, active power output is 0 constant during short circuit.
After short trouble is removed, DFIG enters active Restoration stage, and the starting point and short trouble restored remove the moment
The given correlation of watt current, it is contemplated that system generator rotor angle causes system frequency to fluctuate still in swing phase after short trouble, at this time
Virtual inertia control can still act.
Therefore the active clipping of DFIG transient state controls the virtual inertia control effect during will affect short circuit, active recovery control
It will affect the effect that virtually inertia controls after short trouble, be allowed to be unable to fully response system frequency shift (FS).
3) influence of the virtual inertia control to the idle control effect of transient state, is analyzed:
Active when further decreasing during DFIG virtual inertia control causes short circuit, control that transient state is idle, which exports, can also subtract
It is small, and output apparent energy of the DFIG during short circuit is finally made to be less than specified apparent energy, cause DFIG unsteady flow during short circuit
The waste of the controllable capacity of device, supporting role of the DFIG for the stabilization of power grids during decrease short circuit.
In the step 2.1, the leap transient state real power control model includes:
Virtual inertia controls output quantity TVIThe watt current directly affected refers to ird_ref0It needs by clipping and climbing
Limitation becomes ird_ref2It just refers to as final watt current, using transient state real power control strategy is crossed over, enables afterwards
The active clipping of transient state is got around during short circuit between active convalescence and slope limitation controls, so as to sufficiently respond to system frequency
Offset, when meeting condition Pmeas<P(Tref) when, DFIG can reduce more active power outputs during short circuit, keep DFIG true
Real response system frequency, by changing itself active power output, the neighbouring synchronous motor generator rotor angle of reduction is deviated, rather than merely with a certain
Rate or curve carry out active recovery.
In the step 2.2, the idle correcting current Controlling model of the additional constraint includes idle correction amount iq_add。
iq_addValue consider two kinds of situations, as condition Pmeas<P(Tref) and UmeasWhen < 0.9pu is set up simultaneously its value by
Formula (9) is given, and otherwise its value is 0,
iq_add=imax-|ird_ref2|-|irq_ref| (9)
ird_ref2With irq_refIt is referred to for finally given active and reactive current, imaxFor i in maximum current formula (9)maxWith
|irq_ref| difference, that is, active clipping ip_max, DFIG active power output (the corresponding controllable electric during making short circuit across transient state real power control
Stream | ird_ref2|) when further decreasing, iq_addIt will increase, so that the idle power output of DFIG be made to change.
In the step 3, assessment content includes: the power-angle stability after optimization, the Voltage Drop degree after optimization.
1) power-angle stability after, optimizing:
Compared to system head pendulum under Traditional control strategy and anti-wobble generator rotor angle, using additional first across system after transient state real power control
It puts and reduces with the generator rotor angle of anti-wobble, DFIG is enable to sufficiently respond to when neighbouring synchronous motor generator rotor angle is swung caused by bring generator terminal
The offset of system frequency, therefore system power-angle stability is available is effectively improved.
2) the Voltage Drop degree after, optimizing:
It is additional across transient state real power control on the basis of additional constraint the control of idle correcting current after, DFIG is in short circuit
Idle level is significantly improved before comparing optimal control during failure, and makes DFIG set end voltage is opposite to improve, while can increase
Strong DFIG low voltage ride-through capability.
Embodiment:
Using two regions, four machine system, Fig. 5 (a) is seen, each parameter is as follows:
1. network parameter:
It is much larger than outside typical China three northern areas of China wind-powered electricity generation of sending end synchronous motor inertia for simulation receiving end synchronous motor inertia
System is sent, synchronous motor G3 inertia is set as 50 times of G1 inertia, and other parameters are identical as original system.G1 is set as PV node,
G3 is balance nodes.Synchronous motor G2 and G4 and its boosting, which become, in former two district systems is removed.Line parameter circuit value and bus electricity
Press grade identical as original system.
It is included that boosting becomes DFIG_2.5MW model in T1 parameter and DIgSIENT/PowerFactory Templates module
Boosting change Trf 0.69/20kV parameter is consistent, and boosting becomes T2 forward-sequence reactance as 0.15pu.
2. double-fed asynchronous generator:
Double-fed blower model is derived from DFIG_2.5MW model in DIgSIENT/PowerFactory Templates module,
But correlation module is improved according to the control program of design, other modules do not change.Double-fed blower goes out when stable state
Power is 300MW/0Mvar, using 150 double-fed fan parallel-connection forms, every power output 2MW/0Mvar.
3. load and reactive power compensator parameter:
Load L1 is 150MW/100Mvar；Load L2 is 650MW/100Mvar；Reactive power compensator C1 is exported
200Mvar；Reactive power compensator C2 output is 150Mvar.
Establish simulation model finally by DIgSILENT, carry out the correctness of time-domain-simulation verifying Influencing Mechanism analysis with
Improve the validity of control.
When short trouble occurs for Fig. 1 system, the end DFIG voltage UmeasWith phaselocked loop measurement frequency fmeasIt can change,
Wherein fmeasIt will affect the virtual inertia control output T of DFIGVI, UmeasIt is active with idle control that transient state will be influenced simultaneously.
(t~t during Fig. 2 failure1)UmeasWhen >=0.116pu, if ip_maxFor numerical value B, then as (Tref-TVI) corresponding have
When function reference current is numerical value A, practical watt current is given as numerical value B during failure, i.e., virtual inertia control parameter KdIt is smaller
Or frequency shift (FS) it is smaller when, (Tref-TVI) corresponding meritorious reference current A will be greater than ip_max(numerical value B), so having during failure
Function is referred to by ip_maxIt determines.Similarly, as virtual inertia control parameter KdLarger or frequency shift (FS) is larger, makes (T during failureref-
TVI) corresponding meritorious reference current is when reaching numerical value C, the watt current during failure is given to be determined by the control of virtual inertia.When
UmeasActive during failure to be referenced as 0 when≤0.116pu, active power output is 0 constant during failure.After fault clearance, DFIG into
Enter active Restoration stage, the starting point restored is given related to the watt current at fault clearance moment, is carved with when the failure clears
It when function given value of current is respectively B, C, 0, is limited after failure by fixed regeneration rate or fixed recovery curve, watt current ginseng
Examining will be given by curve 1,2,3 respectively.In view of post-fault system generator rotor angle is still in swing phase, system frequency is caused to fluctuate,
Virtual inertia control can still act at this time, but TVIStill with TrefSuperposition, if gained superposition numerical value is higher than the corresponding number of curve 1~3
When value or DFIG are restored by fixed curve, virtual inertia control will not affect that DFIG active power output during active recovery.
Short trouble occurs for Fig. 3-4, if not added improvement real power control, virtual inertia controls signal T during failureVI
Will directly with active torque reference TrefIt is overlapped, reflection is (t~t during reducing failure since X point into Fig. 41) have
Function electric current is to numerical value A.If the corresponding watt current of practical active clipping is numerical value C during failure, at this time DFIG actually it is active go out
Power is given by C value, and virtual inertia, which controls determined numerical value A, will not generate practical function.Active Restoration stage after failure,
DFIG will be restored since C value by given pace or curve, such as curve 1, although virtual inertia controls response system frequency at this time
Offset, but it is from E point and F point and TrefCorresponding watt current is overlapped, and institute's value is greater than the number that curve 1 gives
Value, so the practical power output of DFIG is determined by curve 1, virtual inertia control will not influence DFIG active power output.And after improving control,
When meeting Pmeas<P(Tref) when, i.e., when DFIG active power output is below steady-state value, the control of virtual inertia will directly numerical value C with
Be overlapped on curve 1 (such as Y, E ', F ' point), this will make DFIG reduce more active power outputs during failure (becomes from numerical value C
A '), and enable the true response system frequency of DFIG by being superimposed with curve 1 during active recovery, it is active to change itself
Power output reduces neighbouring synchronous motor generator rotor angle and deviates, rather than carries out active recovery merely with a certain rate or curve.
Fig. 5 (a)-(f) be arranged the position of fault 50% between node 9 and 10 at, trouble duration 0.2s, fault type
For the short circuit of three-phase metallic earthing, DFIG transient state is idle gain KvIt is 3.Four kinds of DFIG operating statuses, operating condition 1 are provided with when emulation
For virtual factor of inertia KdIt is 0, regeneration rate Tramp=0.5pu/s；Operating condition 2 is Kd=25 and Tramp=0.5pu/s；Operating condition 3
For KdThe active improvement control of=25, Tramp=0.5pu/s but only additional transient；Operating condition 4 is Kd=25, Tramp=0.5pu/s and
The active and idle improvement control of additional transient；Fig. 5 (b) active curve, comparison operating condition 2 and operating condition 1 are observed it is found that empty during failure
After quasi- inertia control reduces DFIG active power output, limited during active recovery by climbing after failure, operating condition 2 is with lower
Active horizontal and 1 same rate of operating condition restores, that is, numerical value C and 2 scene of curve in Fig. 2 occurs, and added improvement transient state is active given
After control, it is equivalent to virtual inertia control output and the active curve combining of operating condition 1, so active power output is less during transient state, and
It is not limited by climbing during active recovery, is able to respond system frequency dynamic.Fig. 5 (d) is observed it can be found that during failure
The transient state of each operating condition is idle control coefrficient KvIt is identical, but idle power output is different during failure.Comparison operating condition 3 and work in Fig. 5 (e)
Condition 1 it is found that during failure, operating condition 3DFIG boost low pressure side and high-pressure side it is idle difference it is smaller, i.e. operating condition 3DFIG boosts
It is idle smaller to become absorption, by front it is found that this is as caused by DFIG during failure active reduction.This phenomenon is further led
It causes DFIG to send the idle horizontal transience of route outside to improve, DFIG set end voltage improves (such as Fig. 5 (f)), and finally makes DFIG transient state
Idle output drop.
As shown in Fig. 5 (c), it is found that after added improvement real power control, system generator rotor angle head pendulum with second pendulum pivot angle into
One step reduces, and compares operating condition 2, and system head pendulum pivot angle is reduced by about 1.4 ° under the conditions of operating condition 3,4, and the second pendulum pivot angle is reduced by about 6.6 °,
Head pendulum is improved with the second pendulum stability.Shown in its reason such as Fig. 5 (b), operating condition 2 is compared, during failure (15s~
15.2s) DFIG active power output under the conditions of operating condition 3,4 is smaller, and second pendulum during (15.5s~16.4s) active power output more
Greatly, this active characteristic is conducive to system head pendulum and the second pendulum stability, and the root for generating this characteristic is that improvement has
Power control system enables DFIG to sufficiently respond to caused system frequency excursion when neighbouring synchronous motor generator rotor angle is swung.
As shown in Fig. 5 (f), operating condition 1 is compared, DFIG set end voltage during failure is higher under the conditions of operating condition 3, this is because
Under the conditions of operating condition 3 during failure DFIG issue it is active less, cause to send outside boosting become absorb it is idle tail off, cause to send route outside
Idle horizontal the phenomenon that being promoted in short-term and then DFIG set end voltage is caused to improve.It is added on the basis of added improvement real power control
After improving idle control, comparison operating condition 4 is with operating condition 3 it is found that DFIG idle level during failure obtains in Fig. 5 (d) and 5 (f)
It further increases, and further increases DFIG set end voltage, enhance DFIG low voltage ride-through capability.
Claims (5)
1. based on system stability optimal control method under power grid friendly DFIG control strategy, it is characterised in that including following step
It is rapid:
Step 1: being influenced for traditional power grid friendly DFIG control strategy interaction, determine optimizing control models；
Step 2: using the optimizing control models, DFIG power output variation during analysis system short trouble；
Step 2 includes:
Step 2.1: using transient state real power control model is crossed over, DFIG active power output changes during analysis system short trouble；
Step 2.2: using the idle correcting current Controlling model of additional constraint, DFIG is idle out during analysis system short trouble
Power variation；
Step 3: comprehensive assessment is carried out to the system stability improvement after optimal control.
2. it is based on system stability optimal control method under power grid friendly DFIG control strategy according to claim 1,
Be characterized in that: in the step 1, traditional power grid friendly DFIG control strategy includes: transient state real power control, transient state without power control
System, the control of virtual inertia；
Transient state real power control model includes amplitude limitation ird_max,
UmeasFor the end DFIG voltage；
Transient state is idle, and Controlling model includes the idle control output quantity Δ i of transient stateQ:
ΔiQ=Kv*(1-Umeas),Umeas≤0.9pu,Kv≥2 (2)
KvFor the idle gain of DFIG transient state；
After DFIG set end voltage breaks through controlling dead error, transient state is idle control output quantity Δ iQIt can be described with formula (2)；In general,
To guarantee to give full play to DFIG reactive power support ability during short trouble, amplitude limitation module can by it is active preferentially switch to it is idle
Preferentially, i therefore during transient staterd_ref1It will also coordinate with the idle control output of transient state；
The active clipping i determined is controlled by transient state is idlep_maxCalculating formula is as follows:
imaxElectric current, i can be born for current transformer maximump_maxMaximum capable of emitting watt current, i when being idle preferentialQ0It is idle for stable state
Electric current, irq_refFor q axis meritorious reference current, Δ iQFor the idle control output quantity of transient state；
During short trouble when the idle control action of transient state, stable state is idle, and control integrator is blocked, iQ0It remains unchanged；
Virtual inertia control changes meritorious reference current ird_ref0Action principle are as follows: change revolution speed control system generate torque
Signal Tref, warp and Lmψs/LsWatt current is obtained after being divided by with reference to ird_ref0, wherein Lm, ψs, LsRespectively motor mutual inductance, stator
Magnetic linkage and stator self inductance；
The control strategy interaction includes:
(1), influence of two kinds of clipping effect size relations to the active clipping of transient state under different condition,
(2), the influence of active clipping and recovery to virtual inertia control effect,
(3), virtual inertia controls the influence to the idle control effect of transient state；
Specific control strategy interaction analytic process is as follows,
1) i, is analyzedrd_maxWith ip_maxThe size relation of two kinds of clipping effects at different conditions:
Assuming that DFIG uses unity power factor control, i.e. i when steady-state operationQ0=0, then during failure, as 0.868pu≤Umeas
When≤0.9pu, have:
Work as ird_max≥ip_maxWhen, there is Kv(1-Umeas) >=0.2, constructed fuction f1(Umeas(the 1-U of)=0.2/meas), work as KvWhen >=2,
The f on the section [0.868,0.9]1(Umeas) codomain be [1.52,2], have Kv≥f1(Umeas) perseverance establishment, i.e. KvI when >=2rd_max≥
ip_maxPerseverance set up, so when the active clipping of transient state by ip_maxIt determines；
Similarly, as 0.116pu≤UmeasWhen≤0.868pu, have
Work as ird_max≥ip_maxWhen, have
Inequality right-hand vector is configured to function f2(Umeas), on section [0.116,0.868] its codomain be [- 0.968,
1.0987], it is seen that work as Kv>=2 up-to-date styles (6) are permanent to be set up, i.e. ird_max≥ip_maxPerseverance is set up, and the active clipping of transient state is by ip_maxIt determines；
Work as UmeasWhen≤0.116pu, i at this timerd_maxIt is 0, i.e., active clipping is 0, to sum up, due to generally requiring K in grid-connected directive/guidev
>=2, therefore practical active clipping i during transient statep_limAre as follows:
Therefore, in UmeasWhen >=0.116pu, the active maximum value of transient state is actually determined by the idle control of transient state；
2) it, analyzes active clipping and restores the influence to virtual inertia control effect:
When DFIG sensory perceptual system frequency instantaneous offsets in short trouble, so that virtual inertia control output TVIGreater than 0, so that
(Tref-TVI) reduce, (Tref-TVI) reference of corresponding watt current and ip_maxBetween size relation will determine transient state during
Meritorious reference current gives ird_ref2；Work as UmeasWhen >=0.116pu, if virtual inertia control parameter KdSmaller or frequency shift (FS) compared with
Small, active reference will be by i during short circuitp_maxIt determines；If virtual inertia control parameter KdLarger or frequency shift (FS) is larger, the short-circuit phase
Between given will be controlled by virtual inertia of watt current determine；Work as UmeasIt is active during short trouble to be referenced as when≤0.116pu
0, active power output is 0 constant during short circuit；
After short trouble is removed, DFIG enters active Restoration stage, and the starting point restored removes the active of moment with short trouble
Given value of current is related, it is contemplated that system generator rotor angle causes system frequency to fluctuate still in swing phase after short trouble, at this time virtually
Inertia control can still act；
Therefore the active clipping of DFIG transient state controls the virtual inertia control effect during will affect short circuit, active recovery is controlled shadow
The effect that virtually inertia controls after short trouble is rung, is allowed to be unable to fully response system frequency shift (FS)；
3) influence of the virtual inertia control to the idle control effect of transient state, is analyzed:
It is active during DFIG virtual inertia control causes short circuit that control that transient state is idle, which exports, can also reduce when further decreasing,
And output apparent energy of the DFIG during short circuit is finally made to be less than specified apparent energy, cause during short circuit that DFIG current transformer can
The waste of capacity is controlled, supporting role of the DFIG for the stabilization of power grids during decrease short circuit.
3. it is based on system stability optimal control method under power grid friendly DFIG control strategy according to claim 1,
Be characterized in that: in the step 2.1, the leap transient state real power control model includes:
Virtual inertia controls output quantity TVIThe watt current directly affected refers to ird_ref0It needs to limit by clipping and climbing
Become ird_ref2It just refers to as final watt current, using transient state real power control strategy is crossed over, enables in short circuit afterwards
The active clipping of transient state is got around between period and active convalescence and slope limitation controls, it is inclined so as to sufficiently respond to system frequency
It moves, when meeting condition Pmeas<P(Tref) when, DFIG can reduce more active power outputs during short circuit, keep DFIG true
Response system frequency, by changing itself active power output, the neighbouring synchronous motor generator rotor angle of reduction is deviated, rather than merely with a certain speed
Rate or curve carry out active recovery.
4. it is based on system stability optimal control method under power grid friendly DFIG control strategy according to claim 1,
Be characterized in that: in the step 2.2, the idle correcting current Controlling model of the additional constraint includes idle correction amount
iq_add；iq_addValue consider two kinds of situations, as condition Pmeas<P(Tref) and UmeasIts value is by formula when < 0.9pu is set up simultaneously
(9) it gives, otherwise its value is 0,
iq_add=imax-|ird_ref2|-|irq_ref| (9)
ird_ref2With irq_refIt is referred to for finally given active and reactive current, imaxFor maximum current
I in formula (9)maxWith | irq_ref| difference, that is, active clipping ip_max, DFIG has during making short circuit across transient state real power control
Function power output (corresponding controllable current | ird_ref2|) when further decreasing, iq_addIt will increase, so that the idle power output of DFIG be made to change.
5. it is based on system stability optimal control method under power grid friendly DFIG control strategy according to claim 1,
Be characterized in that: in the step 3, assessment content includes: the power-angle stability after optimization, the Voltage Drop degree after optimization；
1) power-angle stability after, optimizing:
Compared to system head pendulum under Traditional control strategy and anti-wobble generator rotor angle, using it is additional across system head pendulum after transient state real power control with
The generator rotor angle of anti-wobble reduces, and DFIG is enable to sufficiently respond to system caused by bring generator terminal when neighbouring synchronous motor generator rotor angle is swung
The offset of frequency, therefore system power-angle stability is available is effectively improved；
2) the Voltage Drop degree after, optimizing:
It is additional across transient state real power control on the basis of additional constraint the control of idle correcting current after, DFIG is in short trouble
Level that period is idle is significantly improved before comparing optimal control, and makes DFIG set end voltage is opposite to improve, and can be enhanced simultaneously
DFIG low voltage ride-through capability.
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