CN109301884A - A kind of low-voltage ride-through method of DFIG - Google Patents
A kind of low-voltage ride-through method of DFIG Download PDFInfo
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- CN109301884A CN109301884A CN201811340020.8A CN201811340020A CN109301884A CN 109301884 A CN109301884 A CN 109301884A CN 201811340020 A CN201811340020 A CN 201811340020A CN 109301884 A CN109301884 A CN 109301884A
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- braking resistor
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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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- 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
- H02J3/12—Circuit arrangements for ac mains or ac distribution networks for adjusting voltage in ac networks by changing a characteristic of the network load
Abstract
This application discloses the low-voltage ride-through methods of DFIG a kind of, comprising: in the event of a failure, monitors the current DC voltage of current rotor electric current between current grid entry point voltage, rotor and rotor-side converter, rotor-side converter；If current rotor electric current is more than the first pre-set current value, the by-pass switch between rotor and rotor-side converter is turned off, accesses the braking resistor in parallel with by-pass switch, the resistance value of braking resistor is corresponding with current grid entry point voltage；If current DC voltage is more than voltage threshold, discharging circuit is accessed in the DC side of rotor-side unsteady flow.Due in the present invention braking resistor resistance value under different fault degrees can flexible choice, the shortcomings that overcoming fixed resistance, improve the moment performance of unit, have better low voltage crossing effect.Due to getting rid of crow bar protection, when accessing braking resistor, rotor-side converter is still in controllable state, reduces the reactive power that DFIG is absorbed from power grid, facilitates network voltage and restores normal.
Description
Technical field
The present invention relates to circuit design field, in particular to a kind of low-voltage ride-through method of DFIG.
Background technique
In recent years, with the rapid development of power electronic technique, with environmental protection and the wind-force hair for starting point can be recycled
Power technology also reaches its maturity, and blower is continuously improved in power grid proportion, it influences neglect caused by entire power grid
Slightly.Double fed induction generators DFIG (Doubly Fed Induction Generator) be used as mainstream blower type, have at
The advantages that this is low, easy to maintain, is able to achieve active and reactive decoupling control and maximal power tracing, but its special structure leads to machine
Group is more sensitive to the disturbance of system and failure, and transient characterisitics are more complicated.DFIG may be in order to protect when heavily disturbed
Itself and select off-grid, and off-grid considerably increases the active vacancy of power grid to more Fans simultaneously, to the stability and electricity of power grid
Energy quality constitutes a threat to, and mains breakdown can be caused when serious.Therefore wind power plant access power system technology regulation, grid-connected blower need
When possessing certain low voltage ride-through capability, i.e. grid collapses, blower should be able to be kept not off-grid operation a period of time, and
And certain reactive power is provided to help it to restore normal to power grid.
The low voltage crossing mode of double-fed blower, which can be divided into, at present improves control strategy and adds two class of hardware device:
The first kind mainly by various control strategies accelerate certain transient state electrical quantity the rate of decay and reduce its amplitude come
Realize low voltage crossing, such method is limited to the amount of capacity of current transformer, the situation lighter suitable for Voltage Drop.
Second class is generally adapted Voltage Drop serious situation, and wherein crow bar (crowbar) protection is widely used in reality
In the engineering of border.Traditional crow bar protection has good metering function, but during its investment, the connection of rotor windings and current transformer
It is disconnected, DFIG is in asynchronous operation state, will absorb from power grid idle with excitation.Crow bar Protect and development so far, has to sled
Stick resistance value and the time-optimized research of switching have dynamic adjustment crow bar resistance also to adapt to the improvement side of various Voltage Drop degree
Method, although above-mentioned strategy can reduce the nothing of DFIG absorption by reducing investment number and the time of crow bar to a certain extent
Function, but eventually without solving the problems, such as that current transformer is out of control.
Separately there is scholar to propose that the scheme of rotor-side series resistance and DC side-discharging circuit coordinated control, series resistance have
The remarkable advantage for directly controlling size of current effectively reduces the electric current for flowing to DC bus capacitance, to avoid DC bus
Overvoltage, but often flexibility is not high for fixed resistance of connecting, and cannot be considered in terms of the low voltage crossing that different voltages are fallen under degree and imitates
Fruit, braking resistor is to adjust by the fault condition of most serious, and big resistance is put into when Voltage Drop is lighter mostly at present
It will cause rotor voltage and electromagnetic torque oscillation amplitude be big, be easy to influence the transient stability of unit.
Therefore, how to provide a kind of scheme of solution above-mentioned technical problem is that current those skilled in the art need to solve
Problem.
Summary of the invention
In view of this, the purpose of the present invention is to provide the low-voltage ride-through methods of DFIG a kind of, so as to reduce
The reactive power that DFIG is absorbed from power grid neatly copes with various faults environment, reaches preferable protecting effect.Its concrete scheme
It is as follows:
A kind of low-voltage ride-through method of DFIG, comprising:
In the event of a failure, monitor current rotor electric current between current grid entry point voltage, rotor and rotor-side converter,
The current DC voltage of the rotor-side converter；
If current rotor electric current is more than the first pre-set current value, turn off between the rotor and the rotor-side converter
By-pass switch accesses the braking resistor in parallel with the by-pass switch, the resistance value of the braking resistor and current grid entry point voltage
It is corresponding；
If current DC voltage is more than voltage threshold, discharging circuit is accessed in the DC side of the rotor-side converter.
Preferably, if the current rotor electric current is more than the first pre-set current value, the rotor and the rotor-side are turned off
By-pass switch between current transformer accesses after the braking resistor in parallel with the by-pass switch, further includes:
If current rotor electric current continues to rise, increase the resistance value of the braking resistor.
Preferably, if the current rotor electric current is more than the first pre-set current value, the rotor and the rotor-side are turned off
By-pass switch between current transformer, accesses the braking resistor in parallel with the by-pass switch, the resistance value of the braking resistor with work as
The corresponding process of preceding grid entry point voltage, specifically includes:
If current rotor electric current is more than the first pre-set current value, turn off between the rotor and the rotor-side converter
By-pass switch accesses the braking resistor in parallel with the by-pass switch, the resistance value of the braking resistor and current grid entry point voltage
Current voltage to fall rank corresponding；
If then the current rotor electric current continues to rise, increases the process of the resistance value of the braking resistor, specifically includes:
If current rotor electric current continues to rise, increase the resistance value of the braking resistor to the current grid entry point voltage of correspondence
Next Voltage Drop rank.
Preferably, the resistance value that every voltage order one falls the corresponding braking resistor of rank is obtained by following tuning process:
The minimum resistance and maximum resistance that current voltage falls rank are obtained according to setting principle；
The minimum resistance and maximum resistance for falling rank according to current voltage obtain the adjusting electricity that current voltage falls rank
The resistance value of the corresponding braking resistor of resistance；
Wherein, the setting principle includes:
The peak value of current rotor electric current after accessing the braking resistor is less than the second pre-set current value；
The current exchange side voltage of the rotor-side converter is less than the voltage threshold.
Preferably, the tuning process of the Voltage Drop rank less than or equal to 50% specifically includes:
The minimum resistance and maximum resistance that current voltage falls rank are obtained according to setting principle；
According to the first tuning formulae RSDR=RSDR.min+(RSDR.max-RSDR.min) × 30% obtains current voltage and falls rank
Set resistor RSDR, wherein RSDR.minAnd RSDR.maxThe respectively current voltage minimum resistance and maximum resistance of falling rank；
Wherein, current voltage falls in the setting principle of rank, the specified electricity that second pre-set current value is 1.7 times
Stream.
Preferably, the tuning process of the Voltage Drop rank greater than 50% specifically includes:
The minimum resistance and maximum resistance that current voltage falls rank are obtained according to setting principle；
According to the second tuning formulae RSDR=RSDR.min+(RSDR.max-RSDR.min) × 70% obtains current voltage and falls rank
Set resistor RSDR, wherein RSDR.minAnd RSDR.maxThe respectively current voltage minimum resistance and maximum resistance of falling rank；
Wherein, current voltage falls in the setting principle of rank, the specified electricity that second pre-set current value is 1.9 times
Stream.
Preferably, if current grid entry point voltage is 0, the resistance value of the braking resistor accessed is that current voltage falls grade
Other maximum resistance.
Preferably, the access braking resistor in parallel with the by-pass switch, the resistance value of the braking resistor with currently
The corresponding process of grid entry point voltage, specifically includes:
The on-off for controlling first resistor and the respective control switch group of second resistance respectively, makes the first resistor and described
The equivalent resistance of second resistance is corresponding with current grid entry point voltage.
Preferably, the control switch of the first resistor connects to obtain the first series circuit with the first resistor, described
The control switch of second resistance connects to obtain the second series circuit, first series circuit and described with the second resistance
Two series circuits are in parallel with the by-pass switch.
Preferably, the control switch of the first resistor is in parallel with the first resistor obtains the first parallel circuit, described
The control switch of second resistance is in parallel with the second resistance to obtain the second parallel circuit, first parallel circuit and described
It is in parallel with the by-pass switch after two parallel circuit in series.
The invention discloses the low-voltage ride-through methods of DFIG a kind of, comprising: in the event of a failure, monitors current grid entry point
The current DC voltage of current rotor electric current, the rotor-side converter between voltage, rotor and rotor-side converter；If
Current rotor electric current is more than the first pre-set current value, turns off the by-pass switch between the rotor and the rotor-side converter,
The braking resistor in parallel with the by-pass switch is accessed, the resistance value of the braking resistor is corresponding with current grid entry point voltage；If working as
Preceding DC voltage is more than voltage threshold, accesses discharging circuit in the DC side of the rotor-side converter.Due in the present invention
Braking resistor resistance value do not fix, therefore under different fault degrees, conjunction corresponding with current grid entry point voltage may be selected
Suitable resistance, improves the moment performance of unit, has better low voltage crossing effect the shortcomings that overcoming fixed resistance.
And due to getting rid of crow bar protection, when accessing braking resistor, rotor-side converter is still in controllable state, reduces DFIG
The reactive power absorbed from power grid facilitates network voltage and restores normal.
Detailed description of the invention
In order to more clearly explain the embodiment of the invention or the technical proposal in the existing technology, to embodiment or will show below
There is attached drawing needed in technical description to be briefly described, it should be apparent that, the accompanying drawings in the following description is only this
The embodiment of invention for those of ordinary skill in the art without creative efforts, can also basis
The attached drawing of offer obtains other attached drawings.
Fig. 1 is a kind of step flow chart of the low-voltage ride-through method of DFIG in the embodiment of the present invention；
Fig. 2 is a kind of topology diagram of rotor-side protection circuit in the embodiment of the present invention；
Fig. 3 is a kind of structural topology figure of specific rotor-side protection circuit in the embodiment of the present invention；
Fig. 4 is the structural topology figure that another specific rotor-side protects circuit in the embodiment of the present invention.
Specific embodiment
Following will be combined with the drawings in the embodiments of the present invention, and technical solution in the embodiment of the present invention carries out clear, complete
Site preparation description, it is clear that described embodiments are only a part of the embodiments of the present invention, instead of all the embodiments.It is based on
Embodiment in the present invention, it is obtained by those of ordinary skill in the art without making creative efforts every other
Embodiment shall fall within the protection scope of the present invention.
It is shown in Figure 1 the embodiment of the invention discloses the low-voltage ride-through method of DFIG a kind of, comprising:
S1: in the event of a failure, the current rotor electricity between current grid entry point voltage, rotor and rotor-side converter is monitored
The current DC voltage of stream, the rotor-side converter；
S2: if current rotor electric current is more than the first pre-set current value, turn off the rotor and the rotor-side converter it
Between by-pass switch, access the braking resistor in parallel with the by-pass switch, the resistance value of the braking resistor and current grid entry point
Voltage is corresponding；
Wherein, the first pre-set current value generally can value be 1.6 times of rated current.
S3: it if current DC voltage is more than voltage threshold, is unloaded in the DC side access of the rotor-side converter charged
Road.
Rotor-side shown in Figure 2 protects circuit topological structure, and wherein the rotor of DFIG by by-pass switch S0 and turns
Sub- side current transformer is connected, because rotor current is exchange, by-pass switch may include the opposite switching tube of both direction, with reality
The purpose being now switched on or off；The access of the braking resistor R0 in parallel with by-pass switch is also with the braking resistor being attached thereto
Switch, braking resistor switch is similar with by-pass switch function, can also be realized by the opposite switching tube of both direction open or
Turn-off function；Discharging circuit is connected between rotor-side converter and grid-side converter, voltage, the electric current of discharging circuit are direct current,
Therefore discharging circuit is switched in or out using a switching tube.
It is understood that if a failure occurs, starting the operating parameter for monitoring each key position in the present embodiment；Such as
It finds that rotor current is more than the first pre-set current value in fruit monitoring process, then accesses braking resistor, rotor after braking resistor investment
Equivalent resistance increases, and effectively shortens die-away time of DC component, reduces the initial value and metastability exchange point of damped alternating current component
The amplitude of amount, to reduce transient state rotor current peak value, rotor-side converter still continues controllably at this time；
Further, if the current rotor electric current described in step S2 is more than the first pre-set current value, turn off the rotor with
By-pass switch between the rotor-side converter accesses after the braking resistor in parallel with the by-pass switch, further includes:
If current rotor electric current continues to rise, increase the resistance value of the braking resistor.
It is understood that the resistance value of script braking resistor is corresponding with current grid entry point voltage, but put into the resistance value
Rotor current still continues to rise after braking resistor, it is meant that the control effect of braking resistor is bad, needs to further increase system
The resistance value of dynamic resistance, improves the current limiting capacity of rotor equivalent resistance, inhibits the ascendant trend of rotor current, make rotor-side converter
In controllable state.
Wherein, if it is also mentioned that also monitoring that current DC voltage more than voltage threshold, accesses off-load in step S3
Circuit, discharging circuit can consume the excess energy in circuit, maintain the safe operation of current transformer.
When rotor current, DC voltage are restored to rated value, braking resistor and discharging circuit are cut off, bypass is connected and opens
It closes, circuit is made to return to original operating status.
The invention discloses the low-voltage ride-through methods of DFIG a kind of, comprising: in the event of a failure, monitors current grid entry point
The current DC voltage of current rotor electric current, the rotor-side converter between voltage, rotor and rotor-side converter；If
Current rotor electric current is more than the first pre-set current value, turns off the by-pass switch between the rotor and the rotor-side converter,
The braking resistor in parallel with the by-pass switch is accessed, the resistance value of the braking resistor is corresponding with current grid entry point voltage；If working as
Preceding DC voltage is more than voltage threshold, accesses discharging circuit in the DC side of the rotor-side converter.Due in the present invention
Braking resistor resistance value do not fix, therefore under different fault degrees, conjunction corresponding with current grid entry point voltage may be selected
Suitable resistance, improves the moment performance of unit, has better low voltage crossing effect the shortcomings that overcoming fixed resistance.
And due to getting rid of crow bar protection, when accessing braking resistor, rotor-side converter is still in controllable state, reduces DFIG
The reactive power absorbed from power grid facilitates network voltage and restores normal.
The embodiment of the invention discloses the low-voltage ride-through methods of specific DFIG a kind of, relative to a upper embodiment, originally
Embodiment has made further instruction and optimization to technical solution.
If turning off the rotor and institute specifically, current rotor electric current described in step S2 is more than the first pre-set current value
The by-pass switch between rotor-side converter is stated, the braking resistor in parallel with the by-pass switch is accessed, the braking resistor
Resistance value process corresponding with current grid entry point voltage, specifically includes:
If current rotor electric current is more than the first pre-set current value, turn off between the rotor and the rotor-side converter
By-pass switch accesses the braking resistor in parallel with the by-pass switch, the resistance value of the braking resistor and current grid entry point voltage
Current voltage to fall rank corresponding；
If then the current rotor electric current continues to rise, increases the process of the resistance value of the braking resistor, specifically includes:
If current rotor electric current continues to rise, increase the resistance value of the braking resistor to the current grid entry point voltage of correspondence
Next Voltage Drop rank.
It is understood that grid entry point voltage is the analogue value, can design grid entry point voltage and braking resistor resistance value it
Between corresponding relationship formula, but every time access braking resistor before need according to the corresponding relationship formula calculate braking resistor resistance value simultaneously
The accurate adjustment of resistance value is carried out, and requires fast reaction when failure generation, this time cost for calculating, adjusting will affect reaction
Speed, and excessively accurately regulation is not necessarily to.It therefore, can be by grid entry point voltage according to electricity in order to reduce workload
Pressure falls the voltage ladder that rank is divided into multiple determinations, and each voltage ladder only corresponds to a determining resistance value, Voltage Drop grade
It is pre-stored in Policy Table after can not calculated with the corresponding relationship of the resistance value of braking resistor, once failure occurs, is current
Rotor current is more than the first pre-set current value, searches in Policy Table and chooses suitable resistance value and access braking resistor, this
When braking resistor resistance value determines and is omitted extra calculating process, the adjustment of braking resistor is also no longer no dead smooth adjustment,
But multiple determining gears, therefore it has been obviously improved reaction speed.
Specifically, Voltage Drop rank is setting 10% or 5% or other numerical value using Voltage Drop degree as reference quantity
Voltage Drop depth as a voltage ladder.The Voltage Drop degree is specially voltage rating and current grid entry point voltage
The percentage of difference and voltage rating, Voltage Drop depth be then in each Voltage Drop rank maximum voltage fall degree with most
Small voltage falls the difference of degree.It is understood that Voltage Drop degree is directly related with current grid entry point voltage, directly press
Can also be with according to the size setting voltage ladder of grid entry point voltage, only Voltage Drop rank is by simple currently grid entry point voltage
Numerical value conversion is the variation percentage of grid entry point voltage distances voltage rating, and more can significantly show grid entry point voltage falls degree
With the severity of failure.
Specifically, the Policy Table when Voltage Drop depth of setting 10% is as voltage ladder is referring to shown in the following table 1, wherein
Adjusting drop depth is that the right section closed is opened on a left side, and with the increase of Voltage Drop degree, the resistance value of set resistor also increases.
1 Policy Table of table
| Voltage Drop rank | Voltage Drop depth | The set resistor (p.u.) of access |
| 1 | 10%~20% | R1 |
| 2 | 20%~30% | R2 |
| 3 | 30%~40% | R3 |
| 4 | 40%~50% | R4 |
| 5 | 50%~60% | R5 |
| 6 | 60%~70% | R6 |
| 7 | 70%~80% | R7 |
| 8 | 80%~90% | R8 |
| 9 | 90%~100% | R9 |
Specifically, the resistance value that every voltage order one falls the corresponding braking resistor of rank is obtained by following tuning process:
The minimum resistance and maximum resistance that current voltage falls rank are obtained according to setting principle；
The minimum resistance and maximum resistance for falling rank according to current voltage obtain the adjusting electricity that current voltage falls rank
The resistance value of the corresponding braking resistor of resistance；
Wherein, the setting principle includes:
The peak value of current rotor electric current after accessing the braking resistor is less than the second pre-set current value；
The current exchange side voltage of the rotor-side converter is less than the voltage threshold.
Specifically, the second pre-set current value be the rated current based on rotor current value, the voltage threshold with above
The voltage threshold of middle access discharging circuit is identical.
During failure, current transformer continuous service after braking resistor is accessed, rotor current peak value can be write as:
Wherein,For rotor current before failure；Us、UsfFor the grid entry point voltage before and after failure；τr=σ Lr/(Rr+
RSDR) it is equivalent rotor time constant after access resistance；RSDRFor set resistor, Rs、RrRespectively stator and rotor resistance parameters；Lr、LsPoint
It Wei not stator, inductor rotor；LmFor magnetizing inductance；For leakage inductance coefficient；S is revolutional slip；ωs、ωrRespectively
For synchronous angular velocity and rotor velocity；ω=ωs-ωrFor slip angular velocity；To convert the rotor voltage width for arriving stator side
Value.
The maximum amplitude of rotor voltageAre as follows:
Stator side is converted to obtain:
Wherein, k is the concatenated turn ratio of the every phase winding of stator and rotor.
In conjunction with setting principle and formula (1) (2) (3), corresponding minimum resistance and maximum resistance can be calculated.
When the weight difference of Voltage Drop degree, setting principle is different with the coefficient magnitude of set resistor is determined.
It should be noted that rotor accesses braking resistor suddenly and also belongs to a kind of disturbance from the perspective of DFIG operation,
The case where slightly falling for voltage, small resistance is accessed under the premise of ensuring current transformer safety can effectively reduce protection circuit
Negative effect to several groups, therefore it is less than or equal to 50% Voltage Drop rank (Usf>=0.5p.u.) the tuning process
It specifically includes:
The minimum resistance and maximum resistance that current voltage falls rank are obtained according to setting principle；
According to the first tuning formulae RSDR=RSDR.min+(RSDR.max-RSDR.min) × 30% obtains current voltage and falls rank
Set resistor RSDR, wherein RSDR.minAnd RSDR.maxThe respectively current voltage minimum resistance and maximum resistance of falling rank；
Wherein, current voltage falls in the setting principle of rank, the specified electricity that second pre-set current value is 1.7 times
Stream；Simultaneously because the required precision of set resistor is not high, calculated to simplify, utilize current rotor electric current 1.7IrNMaximum face
Dividing value calculates the current exchange side voltage of rotor-side converter, namely setting principle at this time is
Wherein, IrNFor rated current, UdcmaxFor voltage threshold.
Similar, in order to ensure braking resistor can inhibit rotor current in the range of current transformer can be born, electricity of calming
Resistance value is bigger than normal, therefore is greater than 50% Voltage Drop rank Usf< 0.5p.u.RSDR.maxThe tuning process specifically include:
The minimum resistance and maximum resistance that current voltage falls rank are obtained according to setting principle；
According to the second tuning formulae RSDR=RSDR.min+(RSDR.max-RSDR.min) × 70%Usf< 0.5p.u.RSDR.maxIt obtains
Current voltage falls the set resistor R of rankSDR, wherein RSDR.minAnd RSDR.maxRespectively current voltage falls the minimum electric of rank
Resistance and maximum resistance；
Wherein, current voltage falls in the setting principle of rank, the specified electricity that second pre-set current value is 1.9 times
Stream；Similarly, it since the required precision of set resistor is not high, is calculated to simplify, utilizes the maximum critical value of current rotor electric current
The current exchange side voltage of rotor-side converter is calculated, namely setting principle at this time is
In addition, when three-phase ground short circuit occurs for grid entry point, namely current grid entry point voltage is 0 (Usf=0), short circuit currentIt can be write as:
The case where meter and failure most serious, should choose braking resistor is maximum valueNamely access
The resistance value of braking resistor be that current voltage falls the maximum resistance of rank.
The embodiment of the invention discloses the low-voltage ride-through methods of specific DFIG a kind of, relative to a upper embodiment, originally
Embodiment has made further instruction and optimization to technical solution.The resistance value changeable terminals of braking resistor in specific the present embodiment by
The adjustment duty ratio cooperation of the control switch group of first resistor and second resistance is equivalent to be obtained.
That is, the access braking resistor in parallel with the by-pass switch, the resistance value of the braking resistor with currently simultaneously
The corresponding process of site voltage, specifically includes:
The on-off for controlling first resistor and the respective control switch group of second resistance respectively, makes the first resistor and described
The equivalent resistance of second resistance is corresponding with current grid entry point voltage.
Shown in Figure 3, the control switch IGBT1 of the first resistor R1 connects to obtain first with the first resistor R1
Series circuit, the control switch IGBT2 of the second resistance R2 connect to obtain the second series circuit, institute with the second resistance R2
It states the first series circuit and second series circuit is in parallel with the by-pass switch.
Duty ratio by controlling the control switch IGBT1 of first resistor and the control switch IGBT2 of second resistance can
To change the equivalent resistance of first resistor R1 and second resistance R2, the equivalent resistance of investment are as follows:
Wherein D1、D2The respectively duty ratio of IGBT1, IGBT2 conducting pulsewidth.
Other than the form of this two resistor coupled in parallel of Fig. 3, two concatenated forms of resistance are also designed to, referring to
Shown in Fig. 4, the control switch IGBT1 of the first resistor R1 is in parallel with the first resistor R1 to obtain the first parallel circuit, institute
State second resistance R2 control switch IBGT2 it is in parallel with the second resistance R2 obtain the second parallel circuit, described first is in parallel
It is in parallel with the by-pass switch after circuit and second parallel circuit in series.Its adjustment mode is similar with Fig. 3, no longer superfluous herein
It states.
It, can also be by other means other than the method for the resistance value for all kinds of adjustment braking resistors mentioned in the present embodiment
The circuit for realizing braking resistor function is set, here with no restriction.
Finally, it is to be noted that, herein, relational terms such as first and second and the like be used merely to by
One entity or operation are distinguished with another entity or operation, without necessarily requiring or implying these entities or operation
Between there are any actual relationship or orders.Moreover, the terms "include", "comprise" or its any other variant meaning
Covering non-exclusive inclusion, so that the process, method, article or equipment for including a series of elements not only includes that
A little elements, but also including other elements that are not explicitly listed, or further include for this process, method, article or
The intrinsic element of equipment.In the absence of more restrictions, the element limited by sentence "including a ...", is not arranged
Except there is also other identical elements in the process, method, article or apparatus that includes the element.
A kind of low-voltage ride-through method of DFIG provided by the present invention is described in detail above, it is used herein
A specific example illustrates the principle and implementation of the invention, and the above embodiments are only used to help understand
Method and its core concept of the invention；At the same time, for those skilled in the art is having according to the thought of the present invention
There will be changes in body embodiment and application range, in conclusion the content of the present specification should not be construed as to the present invention
Limitation.
Claims (10)
1. a kind of low-voltage ride-through method of DFIG characterized by comprising
In the event of a failure, current rotor electric current between current grid entry point voltage, rotor and rotor-side converter, described is monitored
The current DC voltage of rotor-side converter；
If current rotor electric current is more than the first pre-set current value, the bypass between the rotor and the rotor-side converter is turned off
Switch, accesses the braking resistor in parallel with the by-pass switch, and the resistance value of the braking resistor is corresponding with current grid entry point voltage；
If current DC voltage is more than voltage threshold, discharging circuit is accessed in the DC side of the rotor-side converter.
2. low-voltage ride-through method according to claim 1, which is characterized in that if the current rotor electric current is more than first pre-
If current value, the by-pass switch between the rotor and the rotor-side converter is turned off, is accessed in parallel with the by-pass switch
Braking resistor after, further includes:
If current rotor electric current continues to rise, increase the resistance value of the braking resistor.
3. low-voltage ride-through method according to claim 2, which is characterized in that if the current rotor electric current is more than first pre-
If current value, the by-pass switch between the rotor and the rotor-side converter is turned off, is accessed in parallel with the by-pass switch
Braking resistor, the resistance value of braking resistor process corresponding with current grid entry point voltage specifically includes:
If current rotor electric current is more than the first pre-set current value, the bypass between the rotor and the rotor-side converter is turned off
Switch, accesses the braking resistor in parallel with the by-pass switch, and the resistance value of the braking resistor is worked as with current grid entry point voltage
Preceding Voltage Drop rank is corresponding；
If then the current rotor electric current continues to rise, increases the process of the resistance value of the braking resistor, specifically includes:
If current rotor electric current continues to rise, it is next to the current grid entry point voltage of correspondence to increase the resistance value of the braking resistor
Voltage Drop rank.
4. low-voltage ride-through method according to claim 3, which is characterized in that it is corresponding described that every voltage order one falls rank
The resistance value of braking resistor is obtained by following tuning process:
The minimum resistance and maximum resistance that current voltage falls rank are obtained according to setting principle；
The minimum resistance and maximum resistance for falling rank according to current voltage obtain the set resistor pair that current voltage falls rank
Answer the resistance value of the braking resistor；
Wherein, the setting principle includes:
The peak value of current rotor electric current after accessing the braking resistor is less than the second pre-set current value；
The current exchange side voltage of the rotor-side converter is less than the voltage threshold.
5. low-voltage ride-through method according to claim 4, which is characterized in that the Voltage Drop rank less than or equal to 50%
The tuning process specifically include:
The minimum resistance and maximum resistance that current voltage falls rank are obtained according to the setting principle；
According to the first tuning formulae RSDR=RSDR.min+(RSDR.max-RSDR.min) × 30% obtains current voltage and falls the whole of rank
Determine resistance RSDR, wherein RSDR.minAnd RSDR.maxThe respectively current voltage minimum resistance and maximum resistance of falling rank；
Wherein, current voltage falls in the setting principle of rank, the rated current that second pre-set current value is 1.7 times.
6. low-voltage ride-through method according to claim 5, which is characterized in that described in the Voltage Drop rank greater than 50%
Tuning process specifically includes:
The minimum resistance and maximum resistance that current voltage falls rank are obtained according to the setting principle；
According to the second tuning formulae RSDR=RSDR.min+(RSDR.max-RSDR.min) × 70% obtains current voltage and falls the whole of rank
Determine resistance RSDR, wherein RSDR.minAnd RSDR.maxThe respectively current voltage minimum resistance and maximum resistance of falling rank；
Wherein, current voltage falls in the setting principle of rank, the rated current that second pre-set current value is 1.9 times.
7. low-voltage ride-through method according to claim 6, which is characterized in that if current grid entry point voltage is 0, access
The resistance value of the braking resistor is the maximum resistance that current voltage falls rank.
8. according to claim 1 to any one of 7 low-voltage ride-through methods, which is characterized in that the access and the bypass
The braking resistor of switch in parallel, the resistance value of braking resistor process corresponding with current grid entry point voltage, specifically includes:
The on-off for controlling first resistor and the respective control switch group of second resistance respectively, makes the first resistor and described second
The equivalent resistance of resistance is corresponding with current grid entry point voltage.
9. low-voltage ride-through method according to claim 8, which is characterized in that the control switch of the first resistor with it is described
First resistor connects to obtain the first series circuit, and the control switch of the second resistance connects to obtain second with the second resistance
Series circuit, first series circuit and second series circuit are in parallel with the by-pass switch.
10. low-voltage ride-through method according to claim 8, which is characterized in that the control switch of the first resistor and institute
It states first resistor parallel connection and obtains the first parallel circuit, the control switch of the second resistance is in parallel with the second resistance to obtain
It is in parallel with the by-pass switch after two parallel circuits, first parallel circuit and second parallel circuit in series.
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