A protection method, device, storage medium and computer equipment for outgoing lines of a double-fed wind turbine system

Abstract

The present application discloses a protection method, device, storage medium and computer equipment for the outgoing line of a doubly-fed wind turbine system. The method comprises: in response to the doubly-fed wind turbine system being in a fault state, determining the positive-sequence equivalent impedance and the negative-sequence equivalent impedance of the doubly-fed wind turbine system according to the voltage data and current data at the distance relay corresponding to the doubly-fed wind turbine system; determining the system equivalent impedance of the doubly-fed wind turbine system according to the positive-sequence equivalent impedance and the negative-sequence equivalent impedance; determining the compensation impedance according to the positive-sequence equivalent impedance and the system equivalent impedance; and compensating the set impedance of the distance relay according to the compensation impedance to update the action characteristic equation of the distance relay. The present application corrects the set impedance through the compensation impedance to compensate for the influence of the unequal positive and negative-sequence impedances and the load conditions of the doubly-fed wind turbine system on the protection range of the distance relay, thereby improving the judgment accuracy of the distance relay, expanding the protection range, and reducing the risk of power grid operation.

Description

Technical Field

[0001] The present application relates to the technical field of power system protection, and in particular to a protection method, device, storage medium and computer equipment for outgoing lines of a doubly-fed wind turbine system. Background Art

[0002] As a new energy source, the capacity of wind power systems entering the power grid is increasing day by day. However, the fault properties of wind power systems are different from those of conventional power sources, and their impact on power grid protection systems is becoming increasingly prominent.

[0003] Compared with traditional power grids, wind power systems have obvious particularities. For example, after a fault occurs in the outgoing line of a double-fed induction generator (DFIG) system, the positive and negative sequence impedances are no longer equal, and the load conditions before the fault significantly affect the detection and positioning of the fault by the protection components, reducing the judgment accuracy of the power grid protection system, and may also lead to a reduction in the protection range, increasing the risk of power grid operation. Summary of the invention

[0004] In view of this, the present application provides a protection method, device, storage medium and computer equipment for the outgoing lines of a doubly-fed wind turbine system, which corrects the set impedance of the distance relay by compensating the impedance, compensates for the impact of the unequal positive and negative sequence impedances of the doubly-fed wind turbine system and the load conditions of the doubly-fed wind turbine system on the protection range of the distance relay, improves the judgment accuracy of the distance relay, expands the protection range, and reduces the risk of power grid operation.

[0005] According to one aspect of the present application, a protection method for outgoing lines of a doubly fed wind turbine system is provided, comprising: in response to a doubly fed wind turbine system being in a fault state, determining the positive-sequence equivalent impedance and the negative-sequence equivalent impedance of the doubly fed wind turbine system according to voltage data and current data at a distance relay corresponding to the doubly fed wind turbine system; determining the system equivalent impedance of the doubly fed wind turbine system according to the positive-sequence equivalent impedance and the negative-sequence equivalent impedance; determining a compensation impedance according to the positive-sequence equivalent impedance and the system equivalent impedance; and compensating the set impedance of the distance relay according to the compensation impedance to update the action characteristic equation of the distance relay.

[0006] According to another aspect of the present application, a protection device for outgoing lines of a doubly-fed wind turbine system is provided, comprising:

[0007] a determination module, configured to determine, in response to a doubly-fed wind turbine system being in a fault state, a positive-sequence equivalent impedance and a negative-sequence equivalent impedance of the doubly-fed wind turbine system according to voltage data and current data at a distance relay corresponding to the doubly-fed wind turbine system; and

[0008] Determining the system equivalent impedance of the doubly-fed wind turbine system according to the positive-sequence equivalent impedance and the negative-sequence equivalent impedance; and

[0009] Determining a compensation impedance according to the positive sequence equivalent impedance and the system equivalent impedance;

[0010] An updating module is used to perform compensation processing on the setting impedance of the distance relay according to the compensation impedance to update the action characteristic equation of the distance relay.

[0011] According to another aspect of the present application, a readable storage medium is provided, on which a program or instruction is stored. When the program or instruction is executed by a processor, the steps of the above-mentioned method for protecting the outgoing line of the doubly-fed wind turbine system are implemented.

[0012] According to another aspect of the present application, a computer device is provided, including a storage medium, a processor, and a computer program stored on the storage medium and executable on the processor, and when the processor executes the program, the steps of the above-mentioned method for protecting the outgoing line of the doubly-fed wind turbine system are implemented.

[0013] By means of the above technical scheme, the protection method, device, storage medium and computer equipment of the outgoing line of the doubly-fed wind turbine system described in the present application, in the case of a fault in the doubly-fed wind turbine system, determines the system equivalent impedance reduced due to the unequal positive and negative sequence equivalent impedances according to the positive sequence equivalent impedance and the negative sequence equivalent impedance of the doubly-fed wind turbine system, and then determines the compensation impedance according to the difference between the system equivalent impedance and the positive sequence equivalent impedance, so as to reflect the influence of the unequal positive and negative sequence equivalent impedances on the system impedance of the doubly-fed wind turbine system. Thus, the compensation impedance is used to correct the set impedance, and the set impedance value of the distance relay is increased by the compensation impedance value, so as to update the action characteristic equation according to the actual fault situation, compensate for the influence of the unequal positive and negative sequence equivalent impedances on the protection range, improve the accuracy of protection, expand the protection range, enhance the ability to resist transition resistance, reduce the risk of power grid operation, and contribute to the stable operation of the power grid.

[0014] The above description is only an overview of the technical solution of the present application. In order to more clearly understand the technical means of the present application, it can be implemented in accordance with the contents of the specification. In order to make the above and other purposes, features and advantages of the present application more obvious and easy to understand, the specific implementation methods of the present application are listed below. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] The drawings described herein are used to provide a further understanding of the present application and constitute a part of the present application. The illustrative embodiments of the present application and their descriptions are used to explain the present application and do not constitute an improper limitation on the present application. In the drawings:

[0016] Figure 1A schematic diagram of a flow chart of a protection method for outgoing lines of a doubly-fed wind turbine system provided in an embodiment of the present application is shown;

[0017] Figure 2 A structural block diagram of a protection device for outgoing lines of a doubly-fed wind turbine system provided in an embodiment of the present application is shown;

[0018] Figure 3 The positive sequence equivalent circuit diagram provided by the embodiment of the present application is shown;

[0019] Figure 4 The negative sequence equivalent circuit diagram provided by the embodiment of the present application is shown;

[0020] Figure 5 An equivalent circuit diagram when the BC two-phase short circuit is provided in an embodiment of the present application is shown;

[0021] Figure 6 An equivalent circuit diagram of a power system before a fault provided by an embodiment of the present application is shown;

[0022] Figure 7 The fault additional state equivalent circuit diagram provided by the embodiment of the present application is shown;

[0023] Figure 8 An equivalent circuit diagram of the doubly-fed wind turbine system provided in an embodiment of the present application when used as a power source requiring protection is shown;

[0024] Fig. 9 The operating characteristic diagram of the distance relay on the impedance complex plane provided by the embodiment of the present application is shown;

[0025] Fig.10 A graph showing the variation of the compensation voltage of a distance relay provided by an embodiment of the present application over time is shown;

[0026] Fig.11 A graph showing the variation of the compensation voltage of another distance relay provided by an embodiment of the present application over time is shown;

[0027] Fig.12 A graph showing the variation of the compensation voltage of another distance relay provided in an embodiment of the present application over time is shown;

[0028] Fig.13 A graph showing the variation of the compensation voltage of another distance relay provided in an embodiment of the present application over time is shown;

[0029] Fig.14 A graph showing the variation of the compensation voltage of another distance relay provided in an embodiment of the present application over time is shown;

[0030] Fig.15 A graph showing the variation of the compensation voltage of another distance relay provided in an embodiment of the present application over time is shown;

[0031] Fig.16 A graph showing the variation of the compensation voltage of another distance relay provided in an embodiment of the present application over time is shown;

[0032] Fig.17 A graph showing the variation of the compensation voltage of another distance relay provided in an embodiment of the present application over time is shown;

[0033] Fig.18 A graph showing the variation of the compensation voltage of another distance relay provided in an embodiment of the present application over time is shown;

[0034] Fig.19 A graph showing the variation of the compensation voltage of another distance relay provided in an embodiment of the present application over time is shown;

[0035] Fig. 20 A graph showing the variation of the compensation voltage of another distance relay provided in an embodiment of the present application over time is shown. DETAILED DESCRIPTION

[0036] The present application will be described in detail below with reference to the accompanying drawings and in combination with embodiments. It should be noted that the embodiments and features in the embodiments of the present application can be combined with each other without conflict.

[0037] The embodiments of the present application are described in detail below, and examples of the embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals throughout represent the same or similar elements or elements having the same or similar functions. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain the present application, and cannot be interpreted as limiting the present application.

[0038] Those skilled in the art will appreciate that, unless expressly stated, the singular forms "a", "an", "said" and "the" used herein may also include plural forms. It should be further understood that the term "comprising" used in the specification of the present application refers to the presence of the features, integers, steps, operations, elements and / or components, but does not exclude the presence or addition of one or more other features, integers, steps, operations, elements, components and / or groups thereof. It should be understood that when we refer to an element as being "connected" or "connected" to another element, it may be directly connected or connected to the other element, or there may be intermediate elements. In addition, the "connection" or "connection" used herein may include wireless connection or wireless fusion. The term "and / or" used herein includes all or any unit and all combinations of one or more associated listed items.

[0039] Now, exemplary embodiments according to the present application will be described in more detail with reference to the accompanying drawings. However, these exemplary embodiments can be implemented in a variety of different forms and should not be interpreted as being limited to the embodiments set forth herein. It should be understood that these embodiments are provided to make the disclosure of the present application thorough and complete, and to fully convey the concepts of these exemplary embodiments to those of ordinary skill in the art.

[0040] In this embodiment, a protection method for outgoing lines of a doubly-fed wind turbine system is provided. Figure 1 As shown, the method includes:

[0041] S101, in response to a doubly-fed wind turbine system being in a fault state, determining a positive-sequence equivalent impedance and a negative-sequence equivalent impedance of the doubly-fed wind turbine system according to voltage data and current data at a distance relay corresponding to the doubly-fed wind turbine system.

[0042] The voltage data includes positive-sequence voltage data and negative-sequence voltage data, and the current data includes positive-sequence current data and negative-sequence current data.

[0043] In this embodiment, when a fault occurs in the outgoing line of the doubly fed wind turbine system, based on the action principle of the power frequency sudden change distance protection, the positive sequence equivalent impedance Z of the doubly fed wind turbine system is determined according to the voltage data and current data at the distance relay corresponding to the doubly fed wind turbine system. w1 and negative sequence equivalent impedance Z w2 . Through the positive sequence equivalent impedance Z w1 and negative sequence equivalent impedance Z w2 The positive and negative sequence impedances in both transient and steady states are equivalent to accurately represent the actual impedance value of the doubly fed wind turbine system under fault conditions, thereby improving the accuracy of subsequent calculations.

[0044] Exemplarily, the distance relay corresponding to the doubly-fed wind turbine system is a distance relay within the outgoing line area of ​​the doubly-fed wind turbine system and close to the doubly-fed wind turbine system side.

[0045] It should be noted that since the doubly fed wind turbine system is a controlled time-varying power source, the doubly fed wind turbine system can be equivalent to a time-varying internal potential plus a constant internal impedance. The system impedance Z of the doubly fed wind turbine system identified by the system is w , which is essentially composed of the positive sequence impedance of the doubly fed wind turbine system, the changing internal potential introduced by transient control measures and the intervention of the crowbar circuit, and the additional impedance generated by the fault current. Under the fault state, the doubly fed wind turbine system fails to achieve its predetermined steady-state target and is in a continuous dynamic adjustment process. The internal potential continues to change until the fault reaches a stable state, resulting in significant instability in both the positive sequence impedance and the negative sequence impedance of the doubly fed wind turbine system, presenting both transient and steady-state states. Among them, the outgoing line of the doubly fed wind turbine system is the line connecting the doubly fed wind turbine system and the power grid system.

[0046] Further, as a refinement and expansion of the specific implementation methods of the above-mentioned embodiment, in order to fully illustrate the specific implementation process of this embodiment, step S101, that is, the step of determining the positive-sequence equivalent impedance and the negative-sequence equivalent impedance of the doubly fed wind turbine system according to the voltage data and current data at the distance relay corresponding to the doubly fed wind turbine system, specifically includes: determining the positive-sequence equivalent impedance according to the inverse of the quotient of the power frequency fault component of the positive-sequence voltage data and the power frequency fault component of the positive-sequence current data; determining the negative-sequence equivalent impedance according to the quotient of the power frequency fault component of the negative-sequence voltage data and the power frequency fault component of the negative-sequence current data.

[0047] Exemplarily, the positive sequence equivalent impedance is expressed as:

[0048]

[0049] The negative sequence equivalent impedance is expressed as:

[0050]

[0051] in, is the power frequency fault component of the positive sequence voltage data, is the power frequency fault component of the positive sequence current data, is the power frequency fault component of the negative sequence voltage data, Power frequency fault component of negative sequence current data.

[0052] In specific application scenarios, refer to Figure 3 and Figure 4 As shown in the figure, after the outgoing line of the doubly fed wind turbine system fails, the doubly fed wind turbine system detects rotor overcurrent and DC bus overvoltage, and the crowbar circuit starts. After the crowbar resistor is put into operation, the doubly fed wind turbine system loses control of the rotor-side converter and enters an asynchronous operation state, which is equivalent to a three-phase asynchronous motor with a large rotor series resistor.

[0053] For example, the positive sequence equivalent impedance Z of the doubly fed wind turbine system is w1 It can also be expressed as:

[0054]

[0055] Negative sequence equivalent impedance Z w2 It can also be expressed as:

[0056]

[0057] Among them, R s is the stator resistance of the doubly-fed wind turbine system, R r is the rotor resistance of the doubly-fed wind turbine system, X sσ is the stator leakage reactance of the doubly-fed wind turbine system, X rσis the rotor leakage reactance of the doubly-fed wind turbine system, X m is the excitation reactance, s is the slip rate of the doubly-fed wind turbine system, 0≤s≤1, R cr is the resistance of the crowbar circuit, and j is an imaginary number. Figure 3 As shown in is the stator side positive sequence voltage of the doubly fed wind turbine system, is the positive sequence current of the stator resistance of the doubly fed wind turbine system, is the positive sequence current of the rotor resistance of the doubly fed wind turbine system, is the positive sequence current of the magnetizing reactance. Figure 4 As shown in is the negative sequence voltage on the stator side of the doubly-fed wind turbine system, is the negative sequence current of the stator resistance of the doubly fed wind turbine system, is the negative sequence current of the rotor resistance of the doubly fed wind turbine system, It should be noted that, in this embodiment, all rotor side parameters are converted to the stator side.

[0058] It is worth mentioning that since 0≤s≤1, according to equations (3) and (4), under the fault condition, the negative sequence equivalent impedance Z w2 Less than the positive sequence equivalent impedance Z w1 , and the larger s is, the negative sequence equivalent impedance Z w2 The smaller.

[0059] S102: Determine the system equivalent impedance of the doubly-fed wind turbine system according to the positive-sequence equivalent impedance and the negative-sequence equivalent impedance.

[0060] In this embodiment, according to the positive sequence equivalent impedance Z of the doubly fed wind turbine system w1 Equivalent impedance to negative sequence Z w2 , redetermine the system equivalent impedance Z′ of the doubly fed wind turbine system in steady state after the fault w , in order to accurately represent the real system impedance of the doubly fed wind turbine system under fault conditions, thereby reflecting the impact of the outgoing line fault of the doubly fed wind turbine system on the doubly fed wind turbine system, which helps to improve the accuracy of fault detection and fault location.

[0061] It should be noted that when the protection method for the outgoing line of the doubly-fed wind turbine system is applied to the doubly-fed wind turbine system, it is based on the setting that the positive sequence impedance and the negative sequence impedance are equal. When there is no fault in the outgoing line of the doubly-fed wind turbine system, the positive sequence impedance and the negative sequence impedance of the doubly-fed wind turbine system are equal. At this time, the system impedance Z of the doubly-fed wind turbine system identified by the system is w It is represented by positive sequence impedance. According to step S101, after a fault occurs, due to the intervention of the crowbar circuit, the positive sequence equivalent impedance Z of the doubly fed wind turbine system w1 Equivalent impedance to negative sequence Z w2are not equal, and the negative sequence equivalent impedance Z w2 Less than the positive sequence equivalent impedance Z w1 , so that the system impedance Z of the double-fed wind turbine system is identified w changes have occurred.

[0062] Further, as a refinement and extension of the specific implementation methods of the above-mentioned embodiment, in order to fully illustrate the specific implementation process of this embodiment, step S102, that is, the step of determining the system equivalent impedance of the doubly fed wind turbine system according to the positive-sequence equivalent impedance and the negative-sequence equivalent impedance, specifically includes: determining the first impedance according to the product of the preset positive-sequence current distribution coefficient and the positive-sequence equivalent impedance; determining the second impedance according to the product of the preset negative-sequence current distribution coefficient and the negative-sequence equivalent impedance; determining the target impedance according to the first impedance and the second impedance; determining the target distribution coefficient according to the preset positive-sequence current distribution coefficient and the preset negative-sequence current distribution coefficient; determining the system equivalent impedance according to the quotient of the target impedance and the target distribution coefficient.

[0063] For example, refer to Figure 5 As shown in the figure, when a phase-to-phase short circuit occurs in the outgoing line area of ​​the doubly fed wind turbine system, based on the power frequency mutation distance protection principle, the system equivalent impedance Z′ of the doubly fed wind turbine system is determined according to the following formula: w :

[0064]

[0065] in, It is the power frequency fault component of the voltage data at the installation location of the distance relay corresponding to the doubly fed wind turbine system when a short circuit occurs between the two phases BC; It is the power frequency fault component of the current data at the installation location of the distance relay corresponding to the doubly-fed wind turbine system when a short circuit occurs between the two phases BC; It is the power frequency fault component of the positive sequence current data at the installation location of the distance relay corresponding to the doubly fed wind turbine system when a short circuit occurs between the two phases BC; C is the power frequency fault component of the negative sequence current data at the installation location of the distance relay corresponding to the double-fed wind turbine system when a phase-to-phase short circuit occurs between the two phases BC; 1 is the preset positive sequence current distribution coefficient at the distance relay installation location corresponding to the double-fed wind turbine system, C 2 is the preset negative sequence current distribution coefficient at the distance relay installation location corresponding to the doubly fed wind turbine system, I w1 is the positive sequence current at the installation location of the distance relay corresponding to the doubly fed wind turbine system, I w2 It is the negative sequence current at the installation point of the distance relay corresponding to the doubly fed wind turbine system.

[0066] Furthermore, according to the fault additional network, the positive sequence current distribution coefficient C is preset by using the current shunt theorem. 1and preset negative sequence current distribution coefficient C 2 Can be expressed as:

[0067]

[0068] Among them, Z S1 is the positive sequence impedance on the power grid system side, Z S2 is the negative sequence impedance on the grid system side, Z k1 is the positive sequence impedance of the line from the doubly fed wind turbine system to the fault point, Z k2 is the negative sequence impedance of the line from the doubly fed wind turbine system to the fault, Z′ k1 is the positive sequence impedance of the line from the power grid system to the fault, Z′ k2 It is the negative sequence impedance of the line from the power grid system side to the fault point.

[0069] For example, under the fault condition, the positive sequence equivalent impedance Z of the doubly fed wind turbine system is w1 Equivalent impedance to negative sequence Z w2 inequality, set Z w2 =k 3 Z w1 , where Z 3 is the preset proportionality coefficient, so the system equivalent impedance Z′ is significantly affected by the inequality w It can also be expressed as:

[0070]

[0071] In actual application scenarios, many impedances under the above-mentioned fault conditions cannot be directly measured. The preset positive and negative current distribution coefficients can be reasonably set according to relevant parameters such as the fault condition and the structure of the doubly-fed wind turbine system, and this application does not make specific limitations.

[0072] Furthermore, as a refinement and expansion of the specific implementation methods of the above-mentioned embodiments, in order to fully illustrate the specific implementation process of this embodiment, the protection method for the outgoing lines of the doubly fed wind turbine system also includes: determining a preset positive-sequence current distribution coefficient according to the inverse of the positive-sequence equivalent impedance; determining a preset negative-sequence current distribution coefficient according to the inverse of the negative-sequence equivalent impedance.

[0073] Exemplarily, when the doubly-fed wind turbine system is in a no-load state before a fault occurs, when a two-phase phase-to-phase fault occurs in the outgoing line of the doubly-fed wind turbine set, there exists a relationship shown in equations (8) and (9), and equations (8) and (9) are as follows.

[0074] Z w1 >>Z S1 +Z k1 (8)

[0075] Z w2 >>Z S2 +Zk2 (9)

[0076] According to the above formula (6), the preset positive and negative current distribution coefficients are composed of the system impedance, line impedance and positive and negative sequence equivalent impedance of the double-fed wind turbine system side, and the positive and negative sequence equivalent impedance of the double-fed wind turbine system side is much larger than the system impedance of the grid system side. 1 Approximately equal to the positive sequence equivalent impedance Z of the doubly fed wind turbine system w1 The negative sequence current distribution coefficient C is preset 2 Approximately equal to the negative sequence equivalent impedance Z of the doubly fed wind turbine system w2 The reciprocal of but:

[0077] Therefore, according to formula (5), the system equivalent impedance Z′ of the double-fed wind turbine system under fault condition is determined: w for:

[0078]

[0079] S103, determining a compensation impedance according to the positive sequence equivalent impedance and the system equivalent impedance.

[0080] According to step S102, after a fault occurs in the outgoing line of the doubly-fed wind turbine system, the impedance of the doubly-fed wind turbine system identified by the distance relay corresponding to the doubly-fed wind turbine system changes from the system impedance Z w Becomes the system equivalent impedance Z′ w According to formula (11), when other conditions remain unchanged, as the negative sequence equivalent impedance Z w2 The introduction of the system equivalent impedance Z′ w Relative system impedance Z w The greater the difference between the positive and negative sequence equivalent impedances, the greater the system equivalent impedance Z′ w The smaller.

[0081] Further, as a refinement and extension of the specific implementation of the above embodiment, in order to fully illustrate the specific implementation process of this embodiment, step S103 specifically includes: determining the compensation impedance according to the difference between the positive sequence equivalent impedance and the system equivalent impedance, that is, the compensation impedance ΔZ w = Positive sequence equivalent impedance Z w1 -

[0082] System steady-state equivalent impedance Z′ w .

[0083] In this embodiment, by compensating the impedance ΔZ w Represents the system impedance change value of the doubly fed wind turbine system, so according to the compensation impedance ΔZ wIt reflects the impact of unequal positive and negative sequence impedances on the system impedance of the doubly fed wind turbine system.

[0084] S104, compensating the set impedance of the distance relay according to the compensation impedance to update the action characteristic equation of the distance relay.

[0085] Specifically, the operating principle of the power frequency sudden change distance protection is based on comparing the compensation voltage The magnitude of the power supply electromotive force under fault conditions The action characteristic equation of power frequency sudden change distance protection is expressed as:

[0086]

[0087] For example, refer to Figure 6 and Figure 7 As shown, E w is the power supply to be protected, E s is the power grid system, line MN is the power outgoing line, and k is the fault that occurred. The power supply electromotive force amplitude under the fault state Cannot be measured directly, use the voltage at the fault point before the fault Indicates the power supply electromotive force amplitude under fault conditions So the action characteristic equation is determined as:

[0088]

[0089] in, is the compensation voltage at the distance relay on the M side, is the power frequency fault component of the voltage data at the distance relay on the M side, is the power frequency fault component of the current data at the distance relay on the M side, Z set is the set impedance of the distance relay on the M side. When the power outgoing line fails, the full voltage measured by the distance relay installed on the M side and full current Respectively expressed as, They are the non-power frequency fault component voltage and non-power frequency fault component current before the fault.

[0090] In this embodiment, the doubly-fed wind turbine system is used as the power source to be protected. Since the doubly-fed wind turbine system is a nonlinear system, its internal potential will continue to change with its internal control after a fault, and it is impossible to decompose the power frequency fault component data from the state at the time of the fault. It is related to the operating state of the doubly fed wind turbine system before the fault. If the doubly fed wind turbine system is in an unloaded state before the fault, then If the doubly-fed wind turbine system is in a loaded state before the fault occurs, The greater the load, Less than The more values ​​​​are.

[0091] For example, refer to Figure 8 As shown in the figure, when a positive fault occurs in the outgoing line of the doubly fed wind turbine system, if the doubly fed wind turbine system is in a no-load state before the fault, the voltage at the fault point can be regarded as equal to the voltage of the bus at the distance relay corresponding to the doubly fed wind turbine system, that is,

[0092] Where c is the current distribution coefficient at the distance relay on the M side during a forward fault. is the power frequency fault component of the current data at the distance relay on the N side, R g is the transition resistance at the fault, Z m is the measured impedance during forward fault, Z m =Z k +cR g , Z k is the line impedance from the doubly-fed wind turbine system to the fault point. Figure 8 The Z shown in k ' is the line impedance from the power grid system to the fault point, Z s is the system impedance of the power grid system.

[0093] If the double-fed wind turbine system is in a loaded state before the fault, according to the voltage U N and the preset reliability coefficient k rel , determine the voltage at the fault before the fault Right now

[0094] According to equations (14) and (15), the voltage at the fault point before the fault is determined under different load conditions of no-load state and loaded state. As shown in formula (16).

[0095]

[0096] Where p is the preset load factor, When the doubly-fed wind turbine system is in an unloaded state before the fault, the preset load factor p is 1; when the doubly-fed wind turbine system is in a loaded state before the fault, the preset load factor p is greater than 1.

[0097] In actual application scenarios, the value of the preset load factor p is related to the power supply electromotive force amplitude under fault conditions. is closely related to the magnitude of the power supply electromotive force under fault conditions. It reflects the voltage at the fault location before the fault, which is closely related to the load of the doubly-fed wind turbine system before the fault. Therefore, the preset load factor p can be specifically set according to the load of the doubly-fed wind turbine system before the fault, and this application does not make specific restrictions. For example, the loaded state of the doubly-fed wind turbine system is divided into two conditions, light load and heavy load, and the value of the preset load factor is set according to parameters such as the specific load of the doubly-fed wind turbine system.

[0098] Specifically, according to the inequality of positive and negative sequence equal-value impedances, the action characteristic equation can be updated in impedance form and further refined as follows:

[0099] |Z w ′+Z set |≥p|Z w ′+Z m |. (17)

[0100] It should be noted that, refer to Fig. 9 As shown, Fig. 9 is the action characteristic diagram of the distance relay on the impedance complex plane obtained according to formula (17). If a two-phase short circuit occurs, the protection range of the protection method of the outgoing line of the double-fed wind turbine system is -Z′ w The end is the center of the circle, with Z′ w +Z set A circle with a radius of . When the action characteristics fall within this circle, the fault can be effectively identified.

[0101] It is worth mentioning that, referring to Fig. 9 As shown, with the system equivalent impedance Z′ w The decrease in impedance will lead to a decrease in the protection range of the protection method for the outgoing line of the doubly fed wind turbine system, and the smaller the area covered by the protection range on the impedance plane, the smaller the protection's ability to resist transition resistance.

[0102] In this embodiment, according to formula (17), under the fault condition, the protection method of the outgoing line of the doubly fed wind turbine system is subject to the system equivalent impedance Z′ w In addition to the influence of set impact.

[0103] Furthermore, as a refinement and expansion of the specific implementation methods of the above-mentioned embodiment, in order to fully illustrate the specific implementation process of this embodiment, before the step of compensating the set impedance of the distance relay according to the compensation impedance, the protection method for the outgoing line of the doubly fed wind turbine system also includes: determining the first correction impedance according to the product of the inverse of the preset load factor and the set impedance of the distance relay; determining the second correction impedance according to the product of the preset load factor and the steady-state equivalent impedance of the system; and updating the set impedance according to the sum of the first correction impedance and the second correction impedance.

[0104] Exemplarily, according to equations (17), (18) and (19), the set impedance value of the distance relay corresponding to the double-fed wind turbine system under the fault state is updated to determine the current set impedance Z set ', as shown in formula (20), to express the impact of the fault on the distance relay parameters.

[0105]

[0106] |Z′ w +Z s ' et |≥|Z′ w +Z m |. (19)

[0107]

[0108] According to formula (20), the load condition of the double-fed wind turbine system before the fault and the system equivalent impedance Z′ w Due to the influence of the load factor p, when a two-phase short circuit occurs in the positive direction of the outgoing line of the doubly fed wind turbine system, the setting impedance involved in the action characteristic equation is no longer a constant. And because the preset load factor p is greater than 1, With the system equivalent impedance Z′ w The current setting impedance Z set ' value decreases accordingly. And the greater the load of the double-fed wind turbine system before the fault, the greater the preset load factor p value, making the current setting impedance Z set 'The value decreases further.

[0109] In this embodiment, according to the preset load factor p and the system equivalent impedance Z′ w Update the set impedance value and determine the current set impedance Z′ of the distance relay set , in order to accurately reflect the load of the doubly fed wind turbine system before the fault and the impact of unequal positive and negative sequence impedances on the distance relay, improve the sensitivity of the distance relay, so that the distance relay can make accurate judgments on the actual situation of the outgoing line fault of the doubly fed wind turbine system and improve reliability.

[0110] Specifically, according to the load of the doubly fed wind turbine system before the fault and the inequality of the positive and negative sequence equivalent impedances, the action characteristic equation can be further refined as follows:

[0111] |Z w ′+Z set ′|≥p|Z w ′+Z m |. (21)

[0112] Furthermore, according to formula (21), when the double-fed wind turbine system is loaded before the fault, the protection range of the distance relay is -Z′w The end is the center of the circle, with Z′ w +Z′ set A circle with a radius of -Z' relative to the no-load condition w The end is the center of the circle, with Z′ w +Z set The circle with radius Z is significantly reduced. And after the outgoing line of the double-fed wind turbine system fails, the protection range of the distance relay is increased from Z to w +Z set The circle with radius Z′ w +Z s ' et The circle with radius Z′ is represented by the reduced protection range: w +Z s ' et )-(Z w +Z set )=(Z′ w -Z w )+(Z s ' et -Z set ). Among them, (Z′ w -Z w ) is caused by the unequal impedance of positive and negative sequences, (Z′ set -Z set ) is caused by the load condition of the doubly-fed wind turbine system before the fault.

[0113] Furthermore, as a refinement and extension of the specific implementation method of the above-mentioned embodiment, in order to fully illustrate the specific implementation process of this embodiment, the step of compensating the set impedance of the distance relay according to the compensation impedance specifically includes: calculating the sum of the compensation impedance and the current set impedance as the corrected set impedance.

[0114] Among them, the corrected set impedance is expressed as: Z setx =Z′ set +ΔZ w .(twenty two)

[0115] Specifically, the updated action characteristic equation is expressed as: |Z′ w +Z setx |≥|Z′ w +Z m |. (23)

[0116] In this embodiment, the setting impedance of the distance relay is updated according to the load of the double-fed wind turbine system before the fault, and the compensation impedance ΔZ is used. wThe set impedance is compensated, and the set impedance value of the distance relay is increased by compensating the impedance value to compensate for the impact of the unequal impedance of the positive and negative sequences on the protection range, thereby expanding the protection range. w and the corrected set impedance Z setx The action characteristic equation is updated, and the action characteristics of the protection method of the outgoing line of the doubly fed wind turbine system are improved according to the actual situation of the doubly fed wind turbine system under fault conditions, so as to improve the reliability, applicability and flexibility of the protection and increase the anti-transition resistance capability.

[0117] It should be noted that two-phase short circuit is asymmetrical compared with other fault types occurring in the outgoing line of the doubly fed wind turbine system, and the inequality of the positive and negative sequence equivalent impedances of the doubly fed wind turbine system must be considered. When a symmetrical fault such as a three-phase short circuit occurs in the outgoing line of the doubly fed wind turbine system, only the opposite number of the positive sequence equivalent impedance of the doubly fed wind turbine system needs to be considered. At this time, the protection range is calculated by -Z w1 The end is the center of the circle, with Z w1 +Z set Represented by a circle with a radius of . Compared with a three-phase short circuit, the action characteristics of the protection during a two-phase short circuit are more affected by the inequality of the positive and negative sequence equal impedances, the protection range becomes smaller, and in actual application scenarios, the fault situation of a two-phase short circuit is more complicated. On this basis, the positive direction fault includes a larger fault range, more fault types, and is more representative than the negative direction fault. Therefore, the present application adopts the fault example of a two-phase short circuit in the positive direction to apply to all fault types on the outgoing line of the doubly fed wind turbine system, thereby improving the comprehensiveness of the protection method for the outgoing line of the doubly fed wind turbine system, improving the reliability, sensitivity and anti-interference ability of fault identification, and increasing the accuracy of fault detection and positioning. Among them, the positive direction fault is a fault that occurs in the outgoing line area of ​​the doubly fed wind turbine system.

[0118] In response to the doubly-fed wind turbine system being in a fault state, the application provides a positive sequence equivalent impedance Z of the doubly-fed wind turbine system. w1 and negative sequence equivalent impedance Z w2 , determine the system equivalent impedance Z′ that is reduced due to the unequal positive and negative sequence equivalent impedances w , and then according to the system equivalent impedance Z′ w Equivalent impedance Z w1 The difference between the compensation impedance ΔZ is determined w According to the load condition of the double-fed wind turbine system before the fault, the current setting impedance Z of the distance relay is determined. s ' et , in order to improve the accuracy and sensitivity of distance relay protection. w For setting impedance Z setCorrection is made by increasing the set impedance value of the distance relay through the compensation impedance value, so as to update the action characteristic equation according to the actual fault situation, compensate for the impact of unequal impedance of positive and negative sequence on the protection range, improve the accuracy of protection, expand the protection range, enhance the ability to resist transition resistance, reduce the risk of power grid operation, and contribute to the stable operation of the power grid.

[0119] For example, this embodiment establishes a double-fed wind turbine system simulation model in PSCAD. In the double-fed wind turbine system simulation model, the outgoing line of the double-fed wind turbine system is a transmission line with a voltage level of 35kV and a length of 80km. The unit positive sequence line impedance and inductance are respectively: R ll1 =0.04Ω / km, X l1 =0.4Ω / km. The left side (N side) of the doubly fed wind turbine system simulation model is a traditional system power supply, and the right side (M side) is a doubly fed wind turbine with a capacity of 10MW. The main components of the doubly fed wind turbine system include wind turbines, gearboxes, asynchronous motors, and key power electronic components - rotor-side converters and grid-side converters. In addition, crowbar circuits and unloading resistors are embedded in the doubly fed wind turbine system, which are respectively configured in the bypass of the rotor winding and the DC bus. These configurations meet the low voltage ride-through conditions of the doubly fed wind turbine required in the past. The rotor-side control system of the doubly fed wind turbine system simulation model is based on stator flux orientation and adopts PQ decoupling control mode, and the grid-side control system is based on grid voltage orientation. On this basis, for the implementation of the protection method of the doubly fed wind turbine system outgoing line, the setting impedance Z of the distance relay on both sides of the outgoing line MN of the doubly fed wind turbine system is set The setting is based on 85% of the total resistance of the outgoing line of the double-fed wind turbine system, that is, Z set =27.4∠84.3°Ω,Z w1 =21.7∠115.2°Ω, Z′ w =6.3∠-4.4°Ω, ΔZ w =25.4∠-53°Ω, the protection range is 68km, and the reliability coefficient k rel Set to 1.2.

[0120] For example, in this embodiment, a phase-to-phase short circuit fault occurs in the outgoing line of the doubly fed wind turbine system. When a BC phase-to-phase short circuit fault occurs in the outgoing line of the doubly fed wind turbine system, the transient maximum amplitude of the positive sequence equivalent impedance is 217.1Ω, the minimum amplitude is 11Ω, the transient process lasts for about 0.166 seconds, and its steady-state amplitude is stable at 24Ω. In contrast, the transient maximum amplitude of the negative sequence equivalent impedance is 47.5Ω, the minimum amplitude is 8.7Ω, which is the same as the positive sequence equivalent impedance. The transient process also lasts for 0.166 seconds, and the steady-state amplitude of the negative sequence equivalent impedance is also 8.7Ω. The amplitudes and phase angles of the positive and negative sequence equivalent impedances of the doubly fed wind turbine system are significantly different, and the positive sequence impedance fluctuates more. After the fault stabilizes, the positive sequence equivalent impedance is much larger than the negative sequence equivalent impedance.

[0121] For example, in this embodiment, at 3 seconds, a BC interphase metallic short circuit fault is set at 5km, 10km, 25km and 50km away from the distance relay on the M side, and the double-fed wind turbine system is in an unloaded state before the fault. This embodiment is based on formula (13) to determine whether the distance relay is activated during the fault. Among them, Fig.10 The middle curve 101 is the compensation voltage variation curve when a fault occurs at a position 25 km away from the M-side distance relay and the double-fed wind turbine system is in a no-load state before the fault; the dotted line 102 is the voltage amplitude of the bus where the M-side distance relay is located before the fault occurs corresponding to the curve 101. Fig.11 The middle curve 111 is the compensation voltage variation curve when a fault occurs at a location 50 km away from the M-side distance relay and the double-fed wind turbine system is in an unloaded state before the fault; the dotted line 112 is the voltage amplitude of the busbar where the M-side distance relay is located before the fault occurs corresponding to the curve 111. Furthermore, at 3 seconds, a BC interphase metallic short circuit fault is set at a location 50 km away from the N-side distance relay. The distance protection action based on formula (13) is as follows: Fig.12 shown. Fig.12 The middle curve 121 is the compensation voltage variation curve at the N side distance relay when a BC phase-to-phase metallic short circuit fault occurs 50 km away from the N side distance relay, and the dotted line 122 is the voltage amplitude of the bus where the N side distance relay is located before the fault corresponding to curve 121 occurs.

[0122] In this embodiment, as the fault time goes by, the compensation voltage changes significantly in the fault state. When the fault occurs in the positive area 5km and 10km away from the M-side distance relay, the M-side distance relay can accurately identify the fault. Fig.10 and Fig.11When the fault occurs in the forward area 25km away from the M-side distance relay, the M-side distance relay can just identify the fault. However, since the compensation voltage is not longer than the voltage at the installation point of the M-side distance relay, the protection may not be able to operate accurately. However, if the fault occurs in the forward area 50km away from the M-side distance relay, when the fault occurs, the compensation voltage is less than the voltage at the installation point of the M-side distance relay, and the M-side distance relay will definitely not operate correctly. Fig.12 , in the protection on the power supply side of the traditional system, even if the fault occurs in the positive area 50km away from the N-side distance relay, when the fault occurs, the compensation voltage can still be greater than the voltage at the installation point of the M-side distance relay, and the N-side distance relay can still correctly identify and respond to the fault. This difference highlights the impact of the inequality of the positive and negative sequence equivalent impedances of the doubly fed wind turbine system on the protection method of the outgoing lines of the doubly fed wind turbine system. Compared with the traditional system power supply, the protection range of the doubly fed wind turbine system is significantly reduced. Considering that the compensation voltage is greater than the voltage at the installation point of the distance relay for more than 10ms, it can only cover 25% of the total length of the line, that is, the protection range is 20km, which is consistent with the setting of the set impedance Z set Compared with the corresponding protection range, the protection range was reduced by 70.59%.

[0123] For example, in this embodiment, two conditions of light load and heavy load of the double-fed wind turbine system before the fault are simulated, and a BC phase short circuit fault is set at 10km and 25km away from the M side distance relay at 3 seconds. This embodiment is based on the setting impedance Z in formula (17) set and the current setting impedance Z in equation (21) s ' et , determine whether the distance relay is activated, in order to explore the fault response characteristics of the double-fed wind turbine system under load. Fig.13 The middle curve 131 is the double-fed wind turbine system under light load before the fault. When the fault occurs at a position 25 km away from the M side distance relay, according to Z set The compensation voltage change curve when making judgments; the dotted line 132 is the voltage amplitude of the busbar where the M-side distance relay is located before the fault occurs in curve 131; curve 133 is the voltage amplitude of the busbar where the M-side distance relay is located when the double-fed wind turbine system is lightly loaded before the fault occurs, according to Z set 'Compensation voltage change curve when making judgment. Fig.14 The middle curve 141 is the case of a double-fed wind turbine system under heavy load before the fault. When the fault occurs at a position 25 km away from the M side distance relay, according to Z set The compensation voltage change curve when making judgments; the dotted line 142 is the voltage amplitude of the busbar where the M-side distance relay is located before the fault occurs in curve 141; curve 143 is the voltage amplitude of the busbar where the M-side distance relay is located when the double-fed wind turbine system is overloaded before the fault occurs, according to Z set'Compensation voltage change curve when making judgment.

[0124] In this embodiment, under light load and heavy load conditions, when the fault occurs in the positive area 10 km away from the M side distance relay, if according to Z set When the protection is judged, the compensation voltage is greater than the voltage at the installation point of the M-side distance relay during the fault, and the M-side distance relay can correctly identify the fault. Fig.13 and Fig.14 , under light load and heavy load conditions, when the fault occurs in the positive area 25km away from the M side distance relay, if according to Z set When making protection judgments, the compensation voltage is lower than the voltage at the installation location of the distance relay on the M side during the fault, and the distance relay on the M side fails to correctly identify and respond to the fault, resulting in a reduction in the protection range compared to the double-fed wind turbine system under no-load conditions. Considering that the compensation voltage is greater than the voltage at the installation location of the distance relay on the M side for more than 10ms, based on the Z set The calculated protection range is 16 km for light load and 13 km for heavy load, which is significantly reduced from the expected protection range of 85%, and further reduced by 20% and 35% respectively compared to the no-load state. Fig.13 and Fig.14 As shown in the figure, when the fault occurs in the positive area 25km away from the M side distance relay, if according to Z s ' et The protection judgment is carried out. When the fault occurs, the compensation voltage is greater than the voltage at the installation location of the distance relay on the M side. The distance relay on the M side can correctly identify the fault. Considering that the compensation voltage is greater than the voltage at the installation location of the distance relay on the M side for more than 10ms, based on Z s ' et The calculated protection range is 24km under light load and 20km under heavy load. It can be seen that under load, the greater the load, the smaller the protection range.

[0125] For example, in this embodiment, a simulation analysis is performed under load conditions, and the corrected setting impedance Z is determined according to equations (20) and (22). setx =41.44∠-69.47°Ω, and further simulate the protection characteristics of BC phase short circuit fault at 20km, 50km, 55km and 60km from the M side distance relay at 3 seconds according to formula (23). Among them, Fig.15 The middle curve 151 is the double-fed wind turbine system under light load before the fault. When the fault occurs at a position 60 km away from the M side distance relay, according to Z setThe compensation voltage change curve when making judgments; the dotted line 152 is the voltage amplitude of the busbar where the M-side distance relay is located before the fault occurs in curve 151; curve 153 is the voltage amplitude of the busbar where the M-side distance relay is located when the double-fed wind turbine system is under light load before the fault occurs, when the fault occurs at a position 60km away from the M-side distance relay, according to Z set 'Compensation voltage change curve when making judgment; Curve 154 is the double-fed wind turbine system under light load before the fault, when the fault is 60km away from the M side relay, according to Z setx Compensate for the voltage change curve when making a judgment. Fig.16 The middle curve 161 is the case of a double-fed wind turbine system under heavy load before the fault. When the fault occurs at a position 60 km away from the M side distance relay, according to Z set The compensation voltage change curve when making judgments; the dotted line 162 is the voltage amplitude of the busbar where the M-side distance relay is located before the fault occurs in curve 161; curve 163 is the voltage amplitude of the busbar where the M-side distance relay is located when the double-fed wind turbine system is overloaded before the fault occurs, according to Z set 'Compensation voltage change curve when making judgment; Curve 164 is the double-fed wind turbine system under heavy load before the fault, when the fault is 60km away from the M side relay, according to Z setx Compensate for the voltage change curve when making a judgment.

[0126] In this embodiment, no matter whether the double-fed wind turbine system is light-loaded or heavy-loaded before the fault, when the fault occurs in the positive area 20 km away from the M side distance relay, if according to Z set It is judged that the compensation voltage is lower than the voltage at the installation point of the distance relay on the M side during the fault, and the distance relay on the M side cannot identify the fault. set 'The fault can be identified, but the protection may not be able to operate accurately because the compensation voltage is not greater than the voltage at the M side distance relay installation point for a long enough time. setx When making a judgment, the compensation voltage at the time of fault is much larger than the voltage at the distance relay on the M side and lasts for a period of time. The distance relay on the M side can accurately identify the fault.

[0127] Furthermore, when the fault occurs in the forward area 50km and 55km away from the M-side distance relay, no matter whether the double-fed wind turbine system is light-loaded or heavy-loaded before the fault, if the fault is based on Z set or Z set 'When judging, the compensation voltage at the time of fault was lower than the voltage at the installation point of the distance relay on the M side, and the distance relay on the M side failed to identify the fault. setx When making a judgment, the compensation voltage is greater than the voltage at the distance relay on the M side during a fault, and the distance relay on the M side can identify the fault.

[0128] contrast Fig.15 and Fig.16 , when the corrected setting impedance Z is used setx When the short circuit occurs at a location 60 km away from the M-side distance relay installation location, it can be identified regardless of whether it is light load or heavy load. However, since the compensation voltage is not longer than the voltage at the M-side distance relay installation location, the protection may not be able to operate accurately. Considering that the compensation voltage is greater than the voltage at the M-side distance relay installation location for more than 10ms, based on Z setx The calculated protection range is 57 km under light load conditions, which is still lower than the setting range of 68 km, but is much better than using the uncorrected Z set As the set impedance of the protection, the protection range has been increased by 256%; and the protection range in the heavy load case is 55km, which is 256% higher than that of the uncorrected Z set As the set impedance of the protection, the protection range has achieved a 323% increase. Therefore, the greater the load, the more obvious the effect of this application is, which verifies the effectiveness of this application in improving the adaptability and accuracy of the sudden change distance protection in the double-fed wind turbine system, especially when the double-fed wind turbine system is in a loaded state before the fault. By correcting the set impedance, the protection method of the outgoing line of the double-fed wind turbine system has significantly enhanced its ability to identify and respond to BC phase-to-phase faults.

[0129] For example, in this embodiment, based on the simulation analysis under load conditions, the BC phase short circuit fault at 30 km from the M side relay at 3 seconds is analyzed according to formula (23), and the transition resistances are 2Ω, 10Ω and 20Ω respectively. Fig.17 The middle curve 171 is the double-fed wind turbine system under light load before the fault, when the transition resistance is 10Ω, and the fault is at a position 30km away from the M side relay. set The compensation voltage change curve when making judgments; the dotted line 172 is the voltage amplitude of the busbar where the distance relay on the M side is located before the fault occurs in curve 171; curve 173 is the voltage amplitude of the busbar where the double-fed wind turbine system is located before the fault occurs, when the transition resistance is 10Ω, and the fault occurs at a position 30km away from the distance relay on the M side, according to Z set 'Compensation voltage change curve when making judgment; Curve 174 is the double-fed wind turbine system under light load before the fault, when the transition resistance is 10Ω, when the fault is 30km away from the M side relay, according to Z setx Compensate for the voltage change curve when making a judgment. Fig.18 The middle curve 181 is the case of a double-fed wind turbine system under heavy load before the fault. When the transition resistance is 10Ω, the fault occurs at a location 30km away from the relay on the M side. According to Z setThe compensation voltage change curve when making judgments; the dotted line 182 is the voltage amplitude of the busbar where the M-side distance relay is located before the fault occurs in curve 181; curve 183 is the voltage amplitude of the busbar where the double-fed wind turbine system is located before the fault occurs, when the transition resistance is 10Ω, and the fault occurs at a position 30km away from the M-side distance relay according to Z set 'Compensation voltage change curve when making judgment; Curve 184 is the double-fed wind turbine system under heavy load before the fault, when the transition resistance is 10Ω, when the fault is 30km away from the M side relay, according to Z setx Compensate for the voltage change curve when making a judgment. Fig.19 The middle curve 191 is the double-fed wind turbine system under light load before the fault, when the transition resistance is 20Ω, and the fault occurs at a location 30km away from the relay on the M side. set The compensation voltage change curve when making judgments; the dotted line 192 is the voltage amplitude of the busbar where the M-side distance relay is located before the fault occurs corresponding to curve 191; curve 193 is the voltage amplitude of the busbar where the double-fed wind turbine system is located before the fault occurs, when the transition resistance is 20Ω, and the fault occurs at a position 30km away from the M-side distance relay according to Z set 'Compensation voltage change curve when making judgment; Curve 194 is the double-fed wind turbine system under light load before the fault, when the transition resistance is 20Ω, when the fault is 30km away from the M side relay, according to Z setx Compensate for the voltage change curve when making a judgment. Fig. 20 The middle curve 201 is the case of a double-fed wind turbine system under heavy load before the fault. When the transition resistance is 20Ω, the fault occurs at a location 30km away from the relay on the M side. set The compensation voltage change curve when making judgments; the dotted line 202 is the voltage amplitude of the busbar where the M-side distance relay is located before the fault occurs corresponding to curve 201; curve 203 is the voltage amplitude of the busbar where the double-fed wind turbine system is located before the fault occurs, when the transition resistance is 20Ω, and the fault occurs at a position 30km away from the M-side distance relay according to Z set 'Compensation voltage change curve when making judgment; Curve 204 is the double-fed wind turbine system under heavy load before the fault, when the transition resistance is 20Ω, when the fault is 30km away from the M side relay, according to Z setx Compensate for the voltage change curve when making a judgment.

[0130] In this embodiment, when the fault occurs in the forward area 30 km away from the M side distance relay and the transition resistance is 2Ω, if the corrected setting impedance Z is used setx Regardless of whether the double-fed wind turbine system is light-loaded or heavy-loaded before the fault, the compensation voltage is greater than the voltage at the M-side distance relay installation point and lasts for a period of time. The M-side distance relay can accurately identify the fault. On the contrary, regardless of whether the double-fed wind turbine system is light-loaded or heavy-loaded before the fault, when the transition resistance is 2Ω, if according to Z set or Zset 'It was determined that the compensation voltage was lower than the voltage at the installation location of the distance relay on the M side during the fault, and the distance relay on the M side failed to identify the fault.

[0131] contrast Figures 17 to 20 , when the corrected setting impedance Z is used setx When the load is light or heavy, if a fault with a transition resistance of 20Ω occurs at a location 30km away from the M-side distance relay installation, the M-side distance relay can identify the fault. However, since the compensation voltage is not long enough to exceed the voltage at the M-side distance relay installation location, the protection may not be able to operate accurately. When a fault with a transition resistance of 10Ω occurs at a location 30km away from the M-side distance relay installation location, the protection can fully identify the fault accurately and operate reliably. However, compared with the uncorrected setting impedance Z set When a fault with a transition resistance of 2Ω occurs at a position 30km away from the M side where the relay is installed, the fault can be identified under light load conditions, but it cannot operate correctly. Under heavy load conditions, the fault cannot be accurately identified. Therefore, the present application can improve the ability of the protection method for the outgoing lines of the doubly fed wind turbine system to resist transition resistance.

[0132] It should be noted that the size of the serial numbers of the steps in the above embodiments does not mean the order of execution. The execution order of each process should be determined by its function and internal logic, and should not constitute any limitation on the implementation process of the embodiments of the present application.

[0133] Furthermore, if Figure 2 As shown, as a specific implementation of the above-mentioned protection method for the outgoing line of the doubly-fed wind turbine system, an embodiment of the present application provides a protection device 1800 for the outgoing line of the doubly-fed wind turbine system, and the protection device 1800 for the outgoing line of the doubly-fed wind turbine system includes: a determination module 1801 and an update module 1802.

[0134] Wherein, the determination module 1801 is used for determining the positive-sequence equivalent impedance and the negative-sequence equivalent impedance of the doubly-fed wind turbine system according to the voltage data and the current data at the distance relay corresponding to the doubly-fed wind turbine system in response to the doubly-fed wind turbine system being in a fault state; and, determining the system equivalent impedance of the doubly-fed wind turbine system according to the positive-sequence equivalent impedance and the negative-sequence equivalent impedance; and, determining the compensation impedance according to the positive-sequence equivalent impedance and the system equivalent impedance;

[0135] The updating module 1802 is used to perform compensation processing on the setting impedance of the distance relay according to the compensation impedance to update the action characteristic equation of the distance relay.

[0136] Optionally, the protection device for the outgoing line of the doubly-fed wind turbine system further includes:

[0137] The first calculation module is used to determine the compensation impedance according to the difference between the positive sequence equivalent impedance and the system equivalent impedance.

[0138] Optionally, the protection device for the outgoing line of the doubly-fed wind turbine system further includes:

[0139] The second calculation module is used to determine the first correction impedance according to the product of the inverse of the preset load factor and the set impedance of the distance relay; determine the second correction impedance according to the product of the preset load factor and the system equivalent impedance; and update the set impedance according to the sum of the first correction impedance and the second correction impedance.

[0140] Optionally, the protection device for the outgoing line of the doubly-fed wind turbine system further includes:

[0141] The third calculation module is used to determine the preset positive-sequence current distribution coefficient according to the inverse of the positive-sequence equivalent impedance; and to determine the preset negative-sequence current distribution coefficient according to the inverse of the negative-sequence equivalent impedance.

[0142] Optionally, the determination module is specifically used to determine the positive-sequence equivalent impedance according to the inverse of the quotient of the power frequency fault component of the positive-sequence voltage data and the power frequency fault component of the positive-sequence current data; and determine the negative-sequence equivalent impedance according to the quotient of the power frequency fault component of the negative-sequence voltage data and the power frequency fault component of the negative-sequence current data. The positive-sequence equivalent impedance is greater than the negative-sequence equivalent impedance.

[0143] Optionally, the determination module is specifically used to determine the first impedance according to the product of a preset positive-sequence current distribution coefficient and the positive-sequence equivalent impedance; determine the second impedance according to the product of a preset negative-sequence current distribution coefficient and the negative-sequence equivalent impedance; determine the target impedance according to the sum of the first target impedance and the second impedance; determine the target distribution coefficient according to the preset positive-sequence current distribution coefficient and the preset negative-sequence current distribution coefficient; and determine the system equivalent impedance according to the quotient of the target impedance and the target distribution coefficient.

[0144] Optionally, the updating module is specifically configured to calculate the sum of the compensation impedance and the current setting impedance as the corrected setting impedance.

[0145] The specific definition of the protection device for the outgoing line of the doubly-fed wind turbine system can be found in the definition of the protection method for the outgoing line of the doubly-fed wind turbine system mentioned above, which will not be repeated here. Each module in the above-mentioned protection device for the outgoing line of the doubly-fed wind turbine system can be implemented in whole or in part by software, hardware and a combination thereof. The above-mentioned modules can be embedded in or independent of the processor in the computer device in the form of hardware, or can be stored in the memory of the computer device in the form of software, so that the processor can call and execute the operations corresponding to the above modules.

[0146] Based on the above Figure 1 The method shown, accordingly, an embodiment of the present application also provides a readable storage medium, on which a computer program is stored, and when the program is executed by a processor, it implements the protection method for the outgoing line of the double-fed wind turbine system shown in the figure.

[0147] Based on this understanding, the technical solution of the present application can be embodied in the form of a software product, which can be stored in a non-volatile storage medium (which can be a CD-ROM, a USB flash drive, a mobile hard disk, etc.), and includes a number of instructions for enabling a computer device (which can be a personal computer, a server, or a network device, etc.) to execute the methods described in each implementation scenario of the present application.

[0148] Based on the above Figure 1 The method shown, and Figure 2 In order to achieve the above-mentioned purpose, the embodiment of the present application further provides a computer device, which can be a personal computer, a server, a network device, etc. The computer device includes a storage medium and a processor; the storage medium is used to store a computer program; the processor is used to execute the computer program to achieve the above-mentioned Figures 1 to 3 The protection method for the outgoing lines of the doubly-fed wind turbine system is shown.

[0149] Optionally, the computer device may further include a user interface, a network interface, a camera, a radio frequency (RF) circuit, a sensor, an audio circuit, a WI-FI module, etc. The user interface may include a display, an input unit such as a keyboard, etc., and the optional user interface may also include a USB interface, a card reader interface, etc. The network interface may optionally include a standard wired interface, a wireless interface (such as a Bluetooth interface, a WI-FI interface), etc.

[0150] Those skilled in the art will appreciate that the computer device structure provided in this embodiment does not limit the computer device, and may include more or fewer components, or a combination of certain components, or different component arrangements.

[0151] The storage medium may also include an operating system and a network communication module. The operating system is a program that manages and saves the hardware and software resources of the computer device, and supports the operation of information processing programs and other software and / or programs. The network communication module is used to realize communication between the components inside the storage medium, and communication with other hardware and software in the physical device.

[0152] Through the description of the above implementation methods, those skilled in the art can clearly understand that the present application can be implemented by means of software plus necessary general hardware platforms, or by hardware.

[0153] Those skilled in the art will appreciate that the accompanying drawings are only schematic diagrams of a preferred implementation scenario, and the modules or processes in the accompanying drawings are not necessarily necessary for implementing the present application. Those skilled in the art will appreciate that the modules in the devices in the implementation scenario can be distributed in the devices of the implementation scenario according to the description of the implementation scenario, or can be changed accordingly and located in one or more devices different from the present implementation scenario. The modules of the above-mentioned implementation scenario can be combined into one module, or can be further split into multiple submodules.

[0154] The above serial numbers of this application are only for description and do not represent the advantages and disadvantages of the implementation scenarios. The above disclosure is only a few specific implementation scenarios of this application, but this application is not limited to them, and any changes that can be thought of by technicians in this field should fall within the scope of protection of this application.

Claims

1. A protection method for outgoing lines of a doubly-fed wind turbine system, characterized in that: The method comprises: In response to a doubly-fed wind turbine system being in a fault state, determining a positive-sequence equivalent impedance and a negative-sequence equivalent impedance of the doubly-fed wind turbine system according to voltage data and current data at a distance relay corresponding to the doubly-fed wind turbine system; Determining the system equivalent impedance of the doubly-fed wind turbine system according to the positive-sequence equivalent impedance and the negative-sequence equivalent impedance; Determining a compensation impedance according to the positive sequence equivalent impedance and the system equivalent impedance; The set impedance of the distance relay is compensated according to the compensation impedance to update the action characteristic equation of the distance relay.

2. The protection method for outgoing lines of a doubly-fed wind turbine system according to claim 1, characterized in that: The method further comprises: The compensation impedance is determined according to a difference between the positive sequence equivalent impedance and the system equivalent impedance.

3. The protection method for outgoing lines of a doubly-fed wind turbine system according to claim 1, wherein the compensation processing of the set impedance of the distance relay according to the compensation impedance specifically comprises: The sum of the compensation impedance and the current setting impedance is calculated as the corrected setting impedance.

4. The protection method for outgoing lines of a doubly-fed wind turbine system according to claim 1, characterized in that: Before compensating the set impedance of the distance relay according to the compensation impedance, the method further includes: Determining a first correction impedance according to the product of the inverse of a preset load factor and a setting impedance of the distance relay; Determining a second modified impedance according to the product of the preset load factor and the system equivalent impedance; The set impedance is updated according to the sum of the first corrected impedance and the second corrected impedance.

5. The protection method for outgoing lines of a doubly-fed wind turbine system according to claim 1, characterized in that: The voltage data includes positive-sequence voltage data and negative-sequence voltage data, the current data includes positive-sequence current data and negative-sequence current data, and the positive-sequence equivalent impedance and negative-sequence equivalent impedance of the doubly-fed wind turbine system are determined according to the voltage data and current data at the distance relay corresponding to the doubly-fed wind turbine system, specifically including: Determining the positive-sequence equivalent impedance according to the inverse of the quotient of the power frequency fault component of the positive-sequence voltage data and the power frequency fault component of the positive-sequence current data; Determining the negative-sequence equivalent impedance according to the quotient of the power frequency fault component of the negative-sequence voltage data and the power frequency fault component of the negative-sequence current data; Wherein, the positive-sequence equivalent impedance is greater than the negative-sequence equivalent impedance.

6. The protection method for outgoing lines of a doubly-fed wind turbine system according to claim 1, characterized in that: Determining the system equivalent impedance of the doubly-fed wind turbine system according to the positive-sequence equivalent impedance and the negative-sequence equivalent impedance specifically includes: Determining a first impedance according to a product of a preset positive-sequence current distribution coefficient and the positive-sequence equivalent impedance; Determining a second impedance according to a product of a preset negative-sequence current distribution coefficient and the negative-sequence equivalent impedance; determining a target impedance according to the first impedance and the second impedance; Determining a target distribution coefficient according to the preset positive-sequence current distribution coefficient and the preset negative-sequence current distribution coefficient; The system equivalent impedance is determined according to a quotient of the target impedance and the target distribution coefficient.

7. The protection method for outgoing lines of a doubly-fed wind turbine system according to claim 6, characterized in that: The method further comprises: Determining the preset positive-sequence current distribution coefficient according to the inverse of the positive-sequence equivalent impedance; The preset negative-sequence current distribution coefficient is determined according to the inverse of the negative-sequence equivalent impedance.

8. A protection device for outgoing lines of a doubly-fed wind turbine system, characterized in that: The device comprises: a determination module, configured to determine, in response to a doubly-fed wind turbine system being in a fault state, a positive-sequence equivalent impedance and a negative-sequence equivalent impedance of the doubly-fed wind turbine system according to voltage data and current data at a distance relay corresponding to the doubly-fed wind turbine system; and Determining the system equivalent impedance of the doubly-fed wind turbine system according to the positive-sequence equivalent impedance and the negative-sequence equivalent impedance; and Determining a compensation impedance according to the positive sequence equivalent impedance and the system equivalent impedance; An updating module is used to perform compensation processing on the setting impedance of the distance relay according to the compensation impedance to update the action characteristic equation of the distance relay.

9. A readable storage medium having a program or instruction stored thereon, characterized in that: When the program or instruction is executed by the processor, the steps of the method for protecting the outgoing line of the doubly-fed wind turbine system as described in any one of claims 1 to 7 are implemented.

10. A computer device comprising a storage medium, a processor, and a computer program stored in the storage medium and executable on the processor, characterized in that: When the processor executes the program, the protection method for outgoing lines of a doubly-fed wind turbine system according to any one of claims 1 to 7 is implemented.

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