CN109301884B - Low voltage ride through method of DFIG - Google Patents
Low voltage ride through method of DFIG Download PDFInfo
- Publication number
- CN109301884B CN109301884B CN201811340020.8A CN201811340020A CN109301884B CN 109301884 B CN109301884 B CN 109301884B CN 201811340020 A CN201811340020 A CN 201811340020A CN 109301884 B CN109301884 B CN 109301884B
- Authority
- CN
- China
- Prior art keywords
- current
- rotor
- resistor
- voltage
- resistance
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Active
Links
Images
Classifications
-
- 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
-
- 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
The application discloses a low voltage ride through method of a DFIG, which comprises the following steps: when a fault occurs, monitoring the current voltage of a grid-connected point, the current rotor current between a rotor and a rotor side converter and the current voltage of a direct current side of the rotor side converter; if the current rotor current exceeds a first preset current value, a bypass switch between the rotor and the rotor side converter is turned off, a brake resistor connected with the bypass switch in parallel is connected, and the resistance value of the brake resistor corresponds to the current grid-connected point voltage; and if the current direct-current side voltage exceeds a voltage threshold, the direct-current side of the rotor side current transformation is connected with an unloading circuit. The resistance value of the brake resistor can be flexibly selected under different fault degrees, so that the defect of a fixed resistor is overcome, the instant performance of a unit is improved, and the low-voltage ride-through effect is better. Because the crowbar protection is eliminated, the rotor side converter is still in a controllable state when the brake resistor is connected, the reactive power absorbed by the DFIG from the power grid is reduced, and the voltage of the power grid is recovered to be normal.
Description
Technical Field
The invention relates to the field of circuit design, in particular to a low-voltage ride through method of a DFIG.
Background
In recent years, with the rapid development of power electronic technology, wind power generation technology taking environmental protection and recycling as starting points is mature day by day, the proportion of a fan in a power grid is increased continuously, and the influence of the fan on the whole power grid is not negligible. The doubly-Fed Induction generator DFIG (double Fed Induction generator) is used as a main flow fan type, has the advantages of low cost, easiness in maintenance, capability of realizing active and reactive decoupling control, maximum power tracking and the like, but the special structure of the generator set causes the generator set to be sensitive to system disturbance and faults, and the transient characteristic is more complex. When the DFIG is seriously interfered, the DFIG can select to be off-line for protecting the DFIG, and the active shortage of the power grid is greatly increased by simultaneously off-line of a plurality of fans, so that the stability and the electric energy quality of the power grid are threatened, and the power grid can be broken down when the DFIG is serious. Therefore, the technical specification of accessing the wind power plant into the power system provides that the grid-connected fan needs to have certain low voltage ride through capability, that is, when the power grid fails, the fan should be capable of keeping running for a period of time without being disconnected from the power grid, and provide certain reactive power for the power grid to help the power grid to recover to normal.
At present, the low voltage ride through mode of the double-fed fan can be divided into two types of improving a control strategy and adding hardware equipment:
the first type mainly realizes low voltage ride through by accelerating the attenuation speed of some transient electric quantities and reducing the amplitude of the transient electric quantities through various control strategies, and the method is limited by the capacity of the converter and is suitable for the condition of light voltage drop.
The second category is generally suitable for situations where voltage sag is severe, where crowbar protection is widely used in practical engineering. The traditional crowbar protection has a good current limiting effect, but in the input process of the traditional crowbar protection, the connection between a rotor winding and a converter is disconnected, and the DFIG is in an asynchronous running state and absorbs reactive power from a power grid to excite. The crowbar protection is developed to date, the resistance value and switching time of the crowbar are optimized, and an improved method for dynamically adjusting the resistance of the crowbar to adapt to various voltage drop degrees is also provided.
In addition, the scholars provide a scheme for coordinately controlling a rotor side series resistor and a direct current side charging-discharging circuit, the series resistor has the obvious advantage of directly controlling the current, the current flowing to a direct current bus capacitor is effectively reduced, the direct current bus overvoltage is avoided, however, the flexibility of a series fixed resistor is not high, the low voltage ride through effect under different voltage drop degrees cannot be considered, the brake resistor is mostly set according to the most serious fault condition at present, and the rotor voltage and the electromagnetic torque oscillation amplitude are large due to the fact that a large resistor is added when the voltage drop is light, and the transient stability of a unit is easily influenced.
Therefore, how to provide a solution to the above technical problems is a problem to be solved by those skilled in the art.
Disclosure of Invention
In view of the above, an object of the present invention is to provide a low voltage ride through method for a DFIG, so as to reduce reactive power absorbed by the DFIG from a power grid, flexibly cope with various fault environments, and achieve a better protection effect. The specific scheme is as follows:
a low voltage ride through method of a DFIG, comprising:
when a fault occurs, monitoring the current voltage of a grid-connected point, the current rotor current between a rotor and a rotor side converter and the current voltage of a direct current side of the rotor side converter;
if the current rotor current exceeds a first preset current value, a bypass switch between the rotor and the rotor side converter is turned off, a brake resistor connected with the bypass switch in parallel is connected, and the resistance value of the brake resistor corresponds to the current grid-connected point voltage;
and if the current direct-current side voltage exceeds a voltage threshold value, an unloading circuit is connected to the direct-current side of the rotor-side converter.
Preferably, if the current rotor current exceeds a first preset current value, the method further includes the steps of turning off a bypass switch between the rotor and the rotor-side converter, and switching in a brake resistor connected in parallel with the bypass switch:
and if the current rotor current continues to rise, increasing the resistance value of the brake resistor.
Preferably, if the current rotor current exceeds a first preset current value, the method turns off a bypass switch between the rotor and the rotor-side converter, and switches in a brake resistor connected in parallel with the bypass switch, and a process in which a resistance value of the brake resistor corresponds to the current grid-connected point voltage specifically includes:
if the current rotor current exceeds a first preset current value, a bypass switch between the rotor and the rotor side converter is turned off, a brake resistor connected with the bypass switch in parallel is connected, and the resistance value of the brake resistor corresponds to the current voltage drop level of the current grid-connected point voltage;
if the current rotor current continues to rise, the process of increasing the resistance value of the brake resistor specifically includes:
and if the current rotor current continues to rise, increasing the resistance value of the brake resistor to the next voltage drop level corresponding to the current grid-connected point voltage.
Preferably, the resistance value of the brake resistor corresponding to each voltage drop level is obtained by the following setting process:
obtaining the minimum resistance and the maximum resistance of the current voltage drop level according to a setting principle;
obtaining the resistance value of the setting resistor of the current voltage drop level corresponding to the brake resistor according to the minimum resistor and the maximum resistor of the current voltage drop level;
wherein the setting principle comprises:
the peak value of the current rotor current after the brake resistor is connected is smaller than a second preset current value;
the current alternating-current side voltage of the rotor-side converter is smaller than the voltage threshold value.
Preferably, the setting process of the voltage sag level less than or equal to 50% specifically includes:
obtaining the minimum resistance and the maximum resistance of the current voltage drop level according to a setting principle;
according to a first setting formula RSDR＝RSDR.min+(RSDR.max-RSDR.min) Obtaining the setting resistance R of the current voltage drop grade by multiplying by 30 percentSDRWherein R isSDR.minAnd RSDR.maxRespectively the minimum resistance and the maximum resistance of the current voltage drop level;
in the current voltage drop level setting principle, the second preset current value is 1.7 times of rated current.
Preferably, the setting process of the voltage drop level greater than 50% specifically includes:
obtaining the minimum resistance and the maximum resistance of the current voltage drop level according to a setting principle;
according to a second setting formula RSDR＝RSDR.min+(RSDR.max-RSDR.min) Obtaining the setting resistance R of the current voltage drop grade by multiplying by 70 percentSDRWherein R isSDR.minAnd RSDR.maxRespectively the minimum resistance and the maximum resistance of the current voltage drop level;
in the current voltage drop level setting principle, the second preset current value is 1.9 times of rated current.
Preferably, if the current grid-connected point voltage is 0, the resistance value of the connected brake resistor is the maximum resistor of the current voltage drop level.
Preferably, the switching in of the braking resistor connected in parallel with the bypass switch, and the process of the resistance value of the braking resistor corresponding to the current voltage of the grid-connected point specifically include:
and respectively controlling the on-off of the control switch group of each of the first resistor and the second resistor, so that the equivalent resistance values of the first resistor and the second resistor correspond to the current grid-connected point voltage.
Preferably, the control switch of the first resistor is connected in series with the first resistor to obtain a first series circuit, the control switch of the second resistor is connected in series with the second resistor to obtain a second series circuit, and both the first series circuit and the second series circuit are connected in parallel with the bypass switch.
Preferably, the control switch of the first resistor is connected in parallel with the first resistor to obtain a first parallel circuit, the control switch of the second resistor is connected in parallel with the second resistor to obtain a second parallel circuit, and the first parallel circuit and the second parallel circuit are connected in series and then connected in parallel with the bypass switch.
The invention discloses a low voltage ride through method of a DFIG, which comprises the following steps: when a fault occurs, monitoring the current voltage of a grid-connected point, the current rotor current between a rotor and a rotor side converter and the current voltage of a direct current side of the rotor side converter; if the current rotor current exceeds a first preset current value, a bypass switch between the rotor and the rotor side converter is turned off, a brake resistor connected with the bypass switch in parallel is connected, and the resistance value of the brake resistor corresponds to the current grid-connected point voltage; and if the current direct-current side voltage exceeds a voltage threshold value, an unloading circuit is connected to the direct-current side of the rotor-side converter. Because the resistance value of the brake resistor is not fixed, under different fault degrees, the appropriate resistor corresponding to the current grid-connected point voltage can be selected, the defect of the fixed resistor is overcome, the instant performance of the unit is improved, and the low-voltage ride-through effect is better. And because the crowbar protection is got rid of, rotor side converter still is in controllable state when switching in braking resistance, reduces DFIG from the reactive power that absorbs in the electric wire netting, helps the electric wire netting voltage to resume normal.
Drawings
In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly described below, it is obvious that the drawings in the following description are only embodiments of the present invention, and for those skilled in the art, other drawings can be obtained according to the provided drawings without creative efforts.
FIG. 1 is a flowchart illustrating steps of a DFIG low voltage ride through method according to an embodiment of the present invention;
fig. 2 is a topology structure diagram of a rotor-side protection circuit according to an embodiment of the present invention;
FIG. 3 is a structural topology diagram of a specific rotor-side protection circuit according to an embodiment of the present invention;
fig. 4 is a structural topology diagram of another specific rotor-side protection circuit according to an embodiment of the present invention.
Detailed Description
The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
The embodiment of the invention discloses a low voltage ride through method of DFIG, which is shown in figure 1 and comprises the following steps:
s1: when a fault occurs, monitoring the current voltage of a grid-connected point, the current rotor current between a rotor and a rotor side converter and the current voltage of a direct current side of the rotor side converter;
s2: if the current rotor current exceeds a first preset current value, a bypass switch between the rotor and the rotor side converter is turned off, a brake resistor connected with the bypass switch in parallel is connected, and the resistance value of the brake resistor corresponds to the current grid-connected point voltage;
the first preset current value can generally take a value of 1.6 times of the rated current.
S3: and if the current direct-current side voltage exceeds a voltage threshold value, an unloading circuit is connected to the direct-current side of the rotor-side converter.
Referring to the topology of the rotor-side protection circuit shown in fig. 2, wherein the rotor of the DFIG is connected to the rotor-side converter through the bypass switch S0, because the rotor current is ac, the bypass switch may include two switching tubes with opposite directions to achieve the purpose of turning on or off; the access of the brake resistor R0 connected in parallel with the bypass switch also utilizes the brake resistor switch connected with the bypass switch, and the brake resistor switch has similar function with the bypass switch and can realize the on-off function by two switch tubes in opposite directions; an unloading circuit is connected between the rotor-side converter and the grid-side converter, and the voltage and the current of the unloading circuit are direct currents, so that the unloading circuit can be connected or disconnected by using one switching tube.
It can be understood that, in this embodiment, if a fault occurs, the operation parameters of each key part are monitored; if the rotor current is found to exceed a first preset current value in the monitoring process, a brake resistor is connected, the equivalent resistance of the rotor is increased after the brake resistor is put into use, the attenuation time of the direct current component is effectively shortened, the initial value of the attenuation alternating current component and the amplitude of the steady-state alternating current component are reduced, the transient rotor current peak value is reduced, and the rotor-side converter is still continuously controllable;
further, in step S2, if the current rotor current exceeds a first preset current value, the method further includes the steps of turning off a bypass switch between the rotor and the rotor-side converter, and switching on a brake resistor connected in parallel with the bypass switch:
and if the current rotor current continues to rise, increasing the resistance value of the brake resistor.
It can be understood that the original resistance value of the brake resistor corresponds to the current voltage of the grid-connected point, but the rotor current still continues to rise after the brake resistor with the resistance value is applied, which means that the control effect of the brake resistor is poor, the resistance value of the brake resistor needs to be further increased, the current limiting capability of the rotor equivalent resistor is improved, the rising trend of the rotor current is inhibited, and the rotor-side converter is in a controllable state.
In step S3, if it is detected that the current dc-side voltage exceeds the voltage threshold, an unloading circuit is connected, and the unloading circuit can consume excess energy in the circuit to maintain safe operation of the converter.
When the rotor current and the DC side voltage are recovered to the rated values, the brake resistor and the unloading circuit are cut off, and the bypass switch is switched on, so that the circuit returns to the original running state.
The invention discloses a low voltage ride through method of a DFIG, which comprises the following steps: when a fault occurs, monitoring the current voltage of a grid-connected point, the current rotor current between a rotor and a rotor side converter and the current voltage of a direct current side of the rotor side converter; if the current rotor current exceeds a first preset current value, a bypass switch between the rotor and the rotor side converter is turned off, a brake resistor connected with the bypass switch in parallel is connected, and the resistance value of the brake resistor corresponds to the current grid-connected point voltage; and if the current direct-current side voltage exceeds a voltage threshold value, an unloading circuit is connected to the direct-current side of the rotor-side converter. Because the resistance value of the brake resistor is not fixed, under different fault degrees, the appropriate resistor corresponding to the current grid-connected point voltage can be selected, the defect of the fixed resistor is overcome, the instant performance of the unit is improved, and the low-voltage ride-through effect is better. And because the crowbar protection is got rid of, rotor side converter still is in controllable state when switching in braking resistance, reduces DFIG from the reactive power that absorbs in the electric wire netting, helps the electric wire netting voltage to resume normal.
The embodiment of the invention discloses a specific low voltage ride through method for DFIG, and compared with the previous embodiment, the embodiment further explains and optimizes the technical scheme.
Specifically, in step S2, if the current rotor current exceeds a first preset current value, the step of turning off a bypass switch between the rotor and the rotor-side converter, and switching in a brake resistor connected in parallel with the bypass switch, where a resistance of the brake resistor corresponds to the current grid-connected point voltage specifically includes:
if the current rotor current exceeds a first preset current value, a bypass switch between the rotor and the rotor side converter is turned off, a brake resistor connected with the bypass switch in parallel is connected, and the resistance value of the brake resistor corresponds to the current voltage drop level of the current grid-connected point voltage;
if the current rotor current continues to rise, the process of increasing the resistance value of the brake resistor specifically includes:
and if the current rotor current continues to rise, increasing the resistance value of the brake resistor to the next voltage drop level corresponding to the current grid-connected point voltage.
It can be understood that the voltage of the grid-connected point is an analog value, and a corresponding relation between the voltage of the grid-connected point and the resistance value of the brake resistor can be designed, but before the brake resistor is connected to the system each time, the resistance value of the brake resistor needs to be calculated according to the corresponding relation and accurately adjusted, and when a fault occurs, a quick response is required, and the time cost of calculation and adjustment affects the response speed, and the excessively accurate regulation and control is not necessary. Therefore, in order to reduce workload, the grid-connected point voltage can be divided into a plurality of determined voltage steps according to the voltage drop level, each voltage step only corresponds to one determined resistance value, the corresponding relation between the voltage drop level and the resistance value of the brake resistor can be calculated and stored in a strategy table in advance, once a fault occurs and the current rotor current exceeds a first preset current value, a proper resistance value is searched and selected in the strategy table and connected to the brake resistor, the resistance value of the brake resistor is determined to omit a redundant calculation process, the adjustment of the brake resistor is not stepless smooth adjustment any more, but a plurality of determined gears are adopted, and therefore the reaction speed is obviously improved.
Specifically, the voltage sag level is a voltage sag level, which is a reference, and a voltage sag depth of 10% or 5% or other values is set as a voltage step. The voltage drop degree is specifically the percentage of the difference between the rated voltage and the current grid-connected point voltage and the rated voltage, and the voltage drop depth is the difference between the maximum voltage drop degree and the minimum voltage drop degree in each voltage drop level. It can be understood that the voltage drop degree is directly related to the current grid-connected point voltage, and a voltage step can be directly set according to the size of the grid-connected point voltage, only the voltage drop level converts a simple numerical value of the current grid-connected point voltage into a change percentage of the grid-connected point voltage from the rated voltage, and the drop degree of the grid-connected point voltage and the severity of a fault can be more remarkably expressed.
Specifically, a 10% voltage drop depth is set as a policy table for voltage steps, which is shown in table 1 below, where the setting drop depth is a left-open and right-closed interval, and as the voltage drop degree increases, the resistance value of the setting resistor also increases.
TABLE 1 policy Table
| Voltage sag level | Voltage sag depth | Setting resistance of access (p.u.) |
| 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 of the brake resistor corresponding to each voltage drop level is obtained through the following setting process:
obtaining the minimum resistance and the maximum resistance of the current voltage drop level according to a setting principle;
obtaining the resistance value of the setting resistor of the current voltage drop level corresponding to the brake resistor according to the minimum resistor and the maximum resistor of the current voltage drop level;
wherein the setting principle comprises:
the peak value of the current rotor current after the brake resistor is connected is smaller than a second preset current value;
the current alternating-current side voltage of the rotor-side converter is smaller than the voltage threshold value.
Specifically, the second preset current value is a current value based on the rated current of the rotor, and the voltage threshold is the same as the voltage threshold of the access unloading circuit in the foregoing.
During the fault, the converter is continuously operated after the brake resistor is connected, and the peak value of the rotor current can be written as follows:
wherein the content of the first and second substances,
is the pre-fault rotor current; u shapes、UsfThe grid-connected point voltage before and after the fault; tau isr＝σLr/(Rr+RSDR) Is the equivalent rotor time constant after the resistance is connected; rSDRTo set the resistance, Rs、RrRespectively a stator resistor and a rotor resistor; l isr、LsRespectively stator and rotor inductors; l ismIs an excitation inductor;
is a leakage inductance coefficient; s is slip; omegas、ωrSynchronous angular velocity and rotor angular velocity, respectively; omega-omegas-ωrIs the slip angular velocity;
to translate the rotor voltage amplitude to the stator side.
Maximum amplitude of rotor voltage
Comprises the following steps:
converting to the stator side to obtain:
and k is the turn ratio of each phase of windings of the stator and the rotor in series connection.
And (3) combining the setting principle and the expressions (1), (2) and (3), and calculating to obtain the corresponding minimum resistance and the maximum resistance.
When the voltage drop degree is different, the setting principle and the coefficient determining the setting resistance are different in size.
It should be noted that, from the view point of DFIG operation, the sudden connection of the rotor to the braking resistor also belongs to a disturbance, and in case of a slight voltage drop, the connection of a small resistor under the premise of ensuring the safety of the converter can effectively reduce the negative effects of the protection circuit on several groups, so that the voltage drop level (U) is less than or equal to 50%sfNot less than 0.5p.u.) the setting process specifically comprises:
obtaining the minimum resistance and the maximum resistance of the current voltage drop level according to a setting principle;
according to a first setting formula RSDR＝RSDR.min+(RSDR.max-RSDR.min) Obtaining the setting resistance R of the current voltage drop grade by multiplying by 30 percentSDRWherein R isSDR.minAnd RSDR.maxRespectively the minimum resistance and the maximum resistance of the current voltage drop level;
in the current voltage drop level setting principle, the second preset current value is 1.7 times of rated current; meanwhile, because the precision requirement of the setting resistor is not high, in order to simplify the calculation, the current rotor current of 1.7I is utilizedrNThe maximum critical value of the current AC side voltage of the rotor side converter is calculated, namely the setting principle at the moment is
Wherein, IrNFor rated current, UdcmaxIs a voltage threshold.
Similarly, in order to ensure that the braking resistor can restrain the rotor current within the range that the converter can bear, the value of the stabilizing resistor is larger, so that the voltage drop level U is more than 50 percentsf＜0.5p.u.RSDR.maxThe setting process specifically comprises:
obtaining the minimum resistance and the maximum resistance of the current voltage drop level according to a setting principle;
according to a second setting formula RSDR＝RSDR.min+(RSDR.max-RSDR.min)×70％Usf＜0.5p.u.RSDR.maxObtaining the setting resistance R of the current voltage drop levelSDRWherein R isSDR.minAnd RSDR.maxRespectively the minimum resistance and the maximum resistance of the current voltage drop level;
in the current voltage drop level setting principle, the second preset current value is 1.9 times of rated current; similarly, because the requirement on the precision of the setting resistor is not high, in order to simplify the calculation, the current alternating-current side voltage of the rotor-side converter is calculated by using the maximum critical value of the current rotor current, namely the setting principle at the moment is
In addition, when the grid-connected point generates a three-phase grounding short circuit, namely the voltage of the current grid-connected point is 0 (U)sf0), short-circuit current
Can be written as:
considering the most serious fault condition, the brake resistor should be selected as the maximum resistance value
That is, the resistance value of the connected brake resistor is the highest value of the current voltage drop levelA large resistance.
The embodiment of the invention discloses a specific low voltage ride through method for DFIG, and compared with the previous embodiment, the embodiment further explains and optimizes the technical scheme. Specifically, the variable resistance value of the brake resistor in this embodiment is obtained by matching and equating duty ratios of the control switch sets of the first resistor and the second resistor.
That is, the process of switching in the brake resistor connected in parallel with the bypass switch, where the resistance value of the brake resistor corresponds to the current grid-connected point voltage specifically includes:
and respectively controlling the on-off of the control switch group of each of the first resistor and the second resistor, so that the equivalent resistance values of the first resistor and the second resistor correspond to the current grid-connected point voltage.
Referring to fig. 3, the control switch IGBT1 of the first resistor R1 is connected in series with the first resistor R1 to form a first series circuit, the control switch IGBT2 of the second resistor R2 is connected in series with the second resistor R2 to form a second series circuit, and the first series circuit and the second series circuit are both connected in parallel with the bypass switch.
The equivalent resistance values of the first resistor R1 and the second resistor R2 can be changed by controlling the duty ratio of the control switch IGBT1 of the first resistor and the control switch IGBT2 of the second resistor, and the input equivalent resistance values are as follows:
wherein D1、D2The duty ratios of the on pulse widths of the IGBT1 and the IGBT2, respectively.
In addition to the form of parallel connection of two resistors shown in fig. 3, the form of series connection of two resistors may also be designed, as shown in fig. 4, the control switch IGBT1 of the first resistor R1 is connected in parallel with the first resistor R1 to form a first parallel circuit, the control switch IBGT2 of the second resistor R2 is connected in parallel with the second resistor R2 to form a second parallel circuit, and the first parallel circuit and the second parallel circuit are connected in series and then connected in parallel with the bypass switch. The adjustment is similar to that of fig. 3, and is not described herein again.
Besides the various methods for adjusting the resistance value of the brake resistor mentioned in this embodiment, a circuit for implementing the function of the brake resistor may be provided in other manners, which is not limited herein.
Finally, it should also be noted that, herein, relational terms such as first and second, and the like may be used solely to distinguish one entity or action from another entity or action without necessarily requiring or implying any actual such relationship or order between such entities or actions. Also, the terms "comprises," "comprising," or any other variation thereof, are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements does not include only those elements but may include other elements not expressly listed or inherent to such process, method, article, or apparatus. Without further limitation, an element defined by the phrase "comprising an … …" does not exclude the presence of other identical elements in a process, method, article, or apparatus that comprises the element.
The low voltage ride through method of the DFIG provided by the present invention is described in detail above, and the principle and the implementation of the present invention are explained herein by applying specific examples, and the description of the above examples is only used to help understanding the method of the present invention and the core idea thereof; meanwhile, for a person skilled in the art, according to the idea of the present invention, there may be variations in the specific embodiments and the application scope, and in summary, the content of the present specification should not be construed as a limitation to the present invention.
Claims (5)
1. A low voltage ride through method for a DFIG, comprising:
when a fault occurs, monitoring the current voltage of a grid-connected point, the current rotor current between a rotor and a rotor side converter and the current voltage of a direct current side of the rotor side converter;
if the current rotor current exceeds a first preset current value, a bypass switch between the rotor and the rotor side converter is turned off, a brake resistor connected with the bypass switch in parallel is connected, and the resistance value of the brake resistor corresponds to the current grid-connected point voltage;
if the current direct-current side voltage exceeds a voltage threshold value, an unloading circuit is connected to the direct-current side of the rotor-side converter;
if the current rotor current exceeds a first preset current value, a bypass switch between the rotor and the rotor side converter is switched off, and after a brake resistor connected with the bypass switch in parallel is switched on, the method further comprises the following steps:
if the current rotor current continues to rise, increasing the resistance value of the brake resistor;
if the current rotor current exceeds a first preset current value, a bypass switch between the rotor and the rotor side converter is turned off, and the process of accessing a brake resistor connected with the bypass switch in parallel comprises the following steps:
if the current rotor current exceeds a first preset current value, a bypass switch between the rotor and the rotor side converter is turned off, a brake resistor connected with the bypass switch in parallel is connected, and the resistance value of the brake resistor corresponds to the current voltage drop level of the current grid-connected point voltage;
if the current rotor current continues to rise, the process of increasing the resistance value of the brake resistor specifically includes:
if the current rotor current continues to rise, increasing the resistance value of the brake resistor to the next voltage drop level corresponding to the current grid-connected point voltage;
the resistance value of the brake resistor corresponding to each voltage drop level is obtained through the following setting process:
obtaining the minimum resistance and the maximum resistance of the current voltage drop level according to a setting principle;
obtaining the resistance value of the setting resistor of the current voltage drop level corresponding to the brake resistor according to the minimum resistor and the maximum resistor of the current voltage drop level;
wherein the setting principle comprises:
the peak value of the current rotor current after the brake resistor is connected is smaller than a second preset current value;
the current alternating-current side voltage of the rotor-side converter is smaller than the voltage threshold value;
the setting process of the voltage sag level less than or equal to 50% specifically includes:
obtaining the minimum resistance and the maximum resistance of the current voltage drop level according to the setting principle;
according to a first setting formula RSDR＝RSDR.min+(RSDR.max-RSDR.min) Obtaining the setting resistance R of the current voltage drop grade by multiplying by 30 percentSDRWherein R isSDR.minAnd RSDR.maxRespectively the minimum resistance and the maximum resistance of the current voltage drop level;
in the current voltage drop level setting principle, the second preset current value is 1.7 times of rated current;
the setting process of the voltage drop level greater than 50% specifically includes:
obtaining the minimum resistance and the maximum resistance of the current voltage drop level according to the setting principle;
according to a second setting formula RSDR＝RSDR.min+(RSDR.max-RSDR.min) Obtaining the setting resistance R of the current voltage drop grade by multiplying by 70 percentSDRWherein R isSDR.minAnd RSDR.maxRespectively the minimum resistance and the maximum resistance of the current voltage drop level;
in the current voltage drop level setting principle, the second preset current value is 1.9 times of rated current.
2. The method according to claim 1, wherein if the current grid-connected point voltage is 0, the resistance value of the brake resistor is the maximum resistor of the current voltage drop level.
3. The low voltage ride through method according to any one of claims 1 to 2, wherein the switching in of the brake resistor connected in parallel with the bypass switch, and the process that the resistance value of the brake resistor corresponds to the current grid-connected point voltage specifically include:
and respectively controlling the on-off of the control switch group of each of the first resistor and the second resistor, so that the equivalent resistance values of the first resistor and the second resistor correspond to the current grid-connected point voltage.
4. The low voltage ride through method of claim 3, wherein the control switch of the first resistor is connected in series with the first resistor to form a first series circuit, the control switch of the second resistor is connected in series with the second resistor to form a second series circuit, and the first series circuit and the second series circuit are both connected in parallel with the bypass switch.
5. The low voltage ride through method of claim 3, wherein the control switch of the first resistor is connected in parallel with the first resistor to form a first parallel circuit, the control switch of the second resistor is connected in parallel with the second resistor to form a second parallel circuit, and the first parallel circuit and the second parallel circuit are connected in series and then connected in parallel with the bypass switch.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN201811340020.8A CN109301884B (en) | 2018-11-12 | 2018-11-12 | Low voltage ride through method of DFIG |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN201811340020.8A CN109301884B (en) | 2018-11-12 | 2018-11-12 | Low voltage ride through method of DFIG |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| CN109301884A CN109301884A (en) | 2019-02-01 |
| CN109301884B true CN109301884B (en) | 2022-04-19 |
Family
ID=65146237
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CN201811340020.8A Active CN109301884B (en) | 2018-11-12 | 2018-11-12 | Low voltage ride through method of DFIG |
Country Status (1)
| Country | Link |
|---|---|
| CN (1) | CN109301884B (en) |
Citations (6)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| KR101605268B1 (en) * | 2014-11-11 | 2016-03-21 | 현대중공업 주식회사 | Resistance measuring apparatus |
| CN105790296A (en) * | 2014-12-22 | 2016-07-20 | 国家电网公司 | Double-feed wind generator high voltage ride through method |
| CN107196338A (en) * | 2017-06-30 | 2017-09-22 | 天津大学 | A kind of double-fed blower fan low-voltage ride-through method of dynamic adjustment rotor crow bar resistance |
| CN107681698A (en) * | 2017-11-16 | 2018-02-09 | 宝鸡文理学院 | Double-fed fan motor rotor string resistance low voltage traversing control method based on power optimization |
| CN108471140A (en) * | 2018-04-26 | 2018-08-31 | 广东电网有限责任公司 | Double-fed wind turbine low voltage traversing control method and device |
| CN108493993A (en) * | 2018-03-27 | 2018-09-04 | 上海电力学院 | Adaptive double-fed fan motor low voltage crossing scheme based on rotor inline dynamic electric resistor |
Family Cites Families (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US7514907B2 (en) * | 2005-05-24 | 2009-04-07 | Satcon Technology Corporation | Device, system, and method for providing a low-voltage fault ride-through for a wind generator farm |
| JP4834691B2 (en) * | 2008-05-09 | 2011-12-14 | 株式会社日立製作所 | Wind power generation system |
| US9425726B2 (en) * | 2013-06-25 | 2016-08-23 | Masdar Institute Of Science And Technology | Fault-tolerant wind energy conversion system |
-
2018
- 2018-11-12 CN CN201811340020.8A patent/CN109301884B/en active Active
Patent Citations (6)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| KR101605268B1 (en) * | 2014-11-11 | 2016-03-21 | 현대중공업 주식회사 | Resistance measuring apparatus |
| CN105790296A (en) * | 2014-12-22 | 2016-07-20 | 国家电网公司 | Double-feed wind generator high voltage ride through method |
| CN107196338A (en) * | 2017-06-30 | 2017-09-22 | 天津大学 | A kind of double-fed blower fan low-voltage ride-through method of dynamic adjustment rotor crow bar resistance |
| CN107681698A (en) * | 2017-11-16 | 2018-02-09 | 宝鸡文理学院 | Double-fed fan motor rotor string resistance low voltage traversing control method based on power optimization |
| CN108493993A (en) * | 2018-03-27 | 2018-09-04 | 上海电力学院 | Adaptive double-fed fan motor low voltage crossing scheme based on rotor inline dynamic electric resistor |
| CN108471140A (en) * | 2018-04-26 | 2018-08-31 | 广东电网有限责任公司 | Double-fed wind turbine low voltage traversing control method and device |
Non-Patent Citations (1)
| Title |
|---|
| 基于转子串联电阻的双馈风力发电机低电压穿越;张文娟，马浩淼等;《电力自动化设备》;20151231;第35卷(第12期);28-33页 * |
Also Published As
| Publication number | Publication date |
|---|---|
| CN109301884A (en) | 2019-02-01 |
Similar Documents
| Publication | Publication Date | Title |
|---|---|---|
| Foster et al. | Coordinated reactive power control for facilitating fault ride through of doubly fed induction generator-and fixed speed induction generator-based wind farms | |
| EP2528184A1 (en) | Method and apparatus for controlling a DC-transmission link | |
| CN103441504B (en) | There is series compensation low voltage ride through device and the control method of self-charging function | |
| El Moursi et al. | Application of series voltage boosting schemes for enhanced fault ridethrough performance of fixed speed wind turbines | |
| CN111431206B (en) | Collaborative fault ride-through method for large-scale doubly-fed wind farm through flexible direct current delivery | |
| Moghadasi et al. | Enhancing LVRT capability of FSIG wind turbine using current source UPQC based on resistive SFCL | |
| CN217306019U (en) | Semi-physical simulation device for double-fed wind turbine generator | |
| CN106849175B (en) | Doubly-fed wind turbine generator crowbar resistance value setting method | |
| Justo et al. | Low voltage ride through enhancement for wind turbines equipped with DFIG under symmetrical grid faults | |
| Vajpayee et al. | Crowbar protection of grid connected double fed induction generator with variable speed wind turbine | |
| CN109301884B (en) | Low voltage ride through method of DFIG | |
| CN104362643B (en) | Method for calculating reactive compensation configured capacity for wind farm | |
| Makolo et al. | Fault ride through technique for dfig-based wind turbines under grid three-phase faults | |
| Zolfi et al. | Enhancement of LVRT capability of DFIG-based wind turbines by superconducting fault current limiter | |
| CN108471140B (en) | Double-fed fan low-voltage ride-through control method and device | |
| CN110544955B (en) | Operation control method and system of wind turbine generator in power grid voltage out-of-limit interval | |
| Divya | Combination of super capacitor-switch type fault current limiter for LVRT enhancement of DFIG wind turbines | |
| Abdellatif et al. | Fault-ride through capability enhancement of DFIG-based wind turbines by SFCL | |
| Saleh et al. | Enhancing the LVRT capability of grid connected wind energy conversion system using Unified Power Quality Controller | |
| Zhang et al. | Reactive power control of doubly fed induction generator during grid voltage dips | |
| CN213637482U (en) | Filter circuit of converter, converter and wind power plant power generation system | |
| Zhao et al. | A new site selection method applied to Synchronous condenser’s suppressing transient over-voltage at the sending end of new energy resources | |
| Bouaziz et al. | Using an FCL for the Improvement of the DFIG_WT LVRT Capability | |
| Wang et al. | The strategy of doubly-fed induction generator low-voltage ride-through based an integrated protection circuit | |
| Shabbir et al. | An Adaptive Droop Coefficient Based Voltage Control Approach for Wind Power Plants through Enhanced Reactive Power Support |
Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| PB01 | Publication | ||
| PB01 | Publication | ||
| SE01 | Entry into force of request for substantive examination | ||
| SE01 | Entry into force of request for substantive examination | ||
| GR01 | Patent grant | ||
| GR01 | Patent grant |