Transient stability analysis method and device for voltage source type doubly-fed fan, and electronic equipment

Abstract

The invention discloses a transient stability analysis method and device for a voltage source type doubly-fed fan, and electronic equipment, and the method comprises the steps: constructing a priority current limiter expression, employing a stator voltage and stator current expression of the voltage source type doubly-fed fan of a priority current limiter, and enabling the voltage source type doubly-fed fan to be connected to a far-end AC power grid through a power grid inductor; according to the priority current limiter expression, two power angle sets enabling the system to enter a fault current limiting state and recover a normal operation state are calculated respectively; according to the priority current limiter expression and the stator voltage and stator current expression of the voltage source type doubly-fed fan, calculating the output active power of the voltage source type doubly-fed fan in the fault current limiting state; and determining the influence of different saturation current angles on the transient stability of the voltage source type doubly-fed fan according to the two power angle sets and the output active power.

Description

Technical Field

[0001] The present application relates to the technical field of grid-connected control of doubly-fed wind turbines, and in particular to a method and device for analyzing transient stability of a voltage source doubly-fed wind turbine, and electronic equipment. Background Art

[0002] As the penetration rate of new energy sources gradually increases, the global wind power installed capacity has increased significantly, which requires wind turbines to adopt voltage source control strategies to support grid voltage and frequency.

[0003] Since the voltage source doubly fed wind turbine exhibits voltage source characteristics, it is very important to select a suitable overcurrent protection strategy to protect the rotor-side converter under large disturbances. Considering that the current controller of the voltage source type device can often achieve fast command tracking, the application of a current limiter can effectively limit the rotor overcurrent of the voltage source doubly fed wind turbine. Among the many current limiters, the priority current limiter has the advantage of flexibly adjusting the dq axis current ratio during a fault, and has therefore been widely used.

[0004] Since the priority current limiter is always triggered during the grid fault, it is worth further analyzing whether the system can restore normal operation and ensure transient stability after the grid fault is cleared. To this end, relevant scholars have conducted the following research: ① The literature [Huang L, Xin H, Wang Z, Zhang L, Wu K and Hu J, Transient Stability Analysis and Control Design of Droop-Controlled Voltage Source Converters Considering Current Limitation [J]. IEEE Transactions on Smart Grid, 2019, 10 (1): 578-591.] reveals the transient instability mechanism of the voltage source converter with d-axis priority current limiter after the grid fault is cleared. ② The literature [Rokrok E, Qoria T, Bruyere A, Francois B and Guillaud X, Transient Stability Assessment and Enhancement of Grid-Forming Converters Embedding Current Reference Saturation as Current Limiting Strategy [J]. IEEE Transactions on Power Systems, 2022, 37 (2): 1519-1531.] designed the optimal saturation current angle to increase the critical fault clearing time of the voltage source converter. ③ The literature [Fan B and Wang X, Fault Recovery Analysis of Grid-Forming Inverters with Priority-Based Current Limiters [J]. IEEE Transactions on Power Systems, 2023, 38 (6): 5102-5112.] explains the influence of short-circuit ratio and current limiter parameters on the fault recovery process of voltage source converter. It can be seen that the above research is mainly carried out on voltage source converters, and the characteristics of the power controller are mainly considered when establishing the system transient model.

[0005] However, when the research object is a voltage source doubly fed wind turbine, due to the existence of an asynchronous motor as an intermediate link between the control target (stator side voltage source function) and the implementation means (rotor converter outputs rotor voltage), the dynamic response of its voltage controller needs to be considered during the transient stability analysis. This characteristic is completely different from that of a voltage source converter, so directly applying existing research on voltage source converters to voltage source doubly fed wind turbines will lead to problems such as inaccurate transient stability analysis and failure to reflect the actual operating conditions of the unit. Summary of the invention

[0006] In view of this, the embodiments of the present application provide a method and device for analyzing transient stability of a voltage source doubly-fed wind turbine, and an electronic device.

[0007] According to a first aspect of an embodiment of the present application, a method for analyzing transient stability of a voltage source doubly-fed wind turbine is provided, comprising: Constructing a priority current limiter expression, and stator voltage and stator current expressions of a voltage source doubly fed wind turbine using the priority current limiter, wherein the voltage source doubly fed wind turbine is connected to a remote AC power grid through a grid inductor; According to the priority current limiter expression, two power angle sets are calculated to respectively make the system enter a fault current limiting state and restore a normal operating state; According to the priority current limiter expression and the stator voltage and stator current expressions of the voltage source double-fed wind turbine, the output active power of the voltage source double-fed wind turbine under the fault current limiting state is calculated; According to the two power angle sets and the output active power, the influence of different saturation current angles on the transient stability of the voltage source doubly fed wind turbine is determined.

[0008] According to a second aspect of an embodiment of the present application, a voltage source doubly-fed wind turbine transient stability analysis device is provided, comprising: A construction module, used to construct a priority current limiter expression, and a stator voltage and stator current expression of a voltage source type doubly fed wind turbine using the priority current limiter, wherein the voltage source type doubly fed wind turbine is connected to a remote AC power grid through a grid inductor; A first calculation module is used to calculate two power angle sets for causing the system to enter a fault current limiting state and restore a normal operation state according to the priority current limiter expression; A second calculation module is used to calculate the output active power of the voltage source double-fed wind turbine under the fault current limiting state according to the priority current limiter expression and the stator voltage and stator current expressions of the voltage source double-fed wind turbine; The analysis module is used to determine the influence of different saturation current angles on the transient stability of the voltage source doubly fed wind turbine according to the two power angle sets and the output active power.

[0009] According to a third aspect of an embodiment of the present application, there is provided an electronic device, including: one or more processors; A memory for storing one or more programs; When the one or more programs are executed by the one or more processors, the one or more processors implement the method as described in the first aspect.

[0010] According to a third aspect of an embodiment of the present application, a computer-readable storage medium is provided, on which computer instructions are stored. When the instructions are executed by a processor, the steps of the method described in the first aspect are implemented.

[0011] The technical solution provided by the embodiments of the present application may have the following beneficial effects: This application calculates two sets considering the dynamic coupling of the voltage controller and the priority current limiter, overcoming the lack of research on the transient stability of voltage source doubly fed wind turbines in related technologies, which leads to the problem of being unable to provide guidance for the design of key control parameters, and thus achieves the effect of quantitatively analyzing the impact of different saturation current angles on the transient stability of voltage source doubly fed wind turbines, guiding the selection of current limiting parameters to improve system robustness.

[0012] It should be understood that the foregoing general description and the following detailed description are exemplary and explanatory only and are not restrictive of the present application. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments consistent with the present application and, together with the description, serve to explain the principles of the present application.

[0014] Figure 1 The present invention is a flow chart of a method for analyzing transient stability of a voltage source doubly-fed wind turbine according to an exemplary embodiment.

[0015] Figure 2 The topology structure of a voltage source doubly-fed wind turbine is shown according to an exemplary embodiment.

[0016] Figure 3 The transient stability analysis result of the system under different saturation current angle selections is shown according to an exemplary embodiment.

[0017] Figure 4 is a simulation waveform shown according to an exemplary embodiment.

[0018] Figure 5 It is a block diagram of a voltage source doubly-fed wind turbine transient stability analysis device according to an exemplary embodiment. DETAILED DESCRIPTION

[0019] Exemplary embodiments will be described in detail herein, examples of which are shown in the accompanying drawings. When the following description refers to the drawings, the same numbers in different drawings represent the same or similar elements unless otherwise indicated. The implementations described in the following exemplary embodiments do not represent all implementations consistent with the present application. Instead, they are merely examples of devices and methods consistent with some aspects of the present application as detailed in the appended claims.

[0020] The terms used in this application are for the purpose of describing specific embodiments only and are not intended to limit this application. The singular forms of "a", "said" and "the" used in this application and the appended claims are also intended to include plural forms unless the context clearly indicates other meanings. It should also be understood that the term "and / or" used herein refers to and includes any or all possible combinations of one or more associated listed items.

[0021] It should be understood that although the terms first, second, third, etc. may be used in the present application to describe various information, these information should not be limited to these terms. These terms are only used to distinguish the same type of information from each other. For example, without departing from the scope of the present application, the first information may also be referred to as the second information, and similarly, the second information may also be referred to as the first information. Depending on the context, the word "if" as used herein may be interpreted as "at the time of" or "when" or "in response to determining".

[0022] Figure 1 FIG. 1 is a flow chart showing a method for analyzing transient stability of a voltage source doubly-fed wind turbine according to an exemplary embodiment. Figure 1 As shown, the method may include the following steps: S1: constructing a priority current limiter expression, and stator voltage and stator current expressions of a voltage source doubly fed wind turbine using the priority current limiter, wherein the voltage source doubly fed wind turbine is connected to a remote AC grid through a grid inductor; Specifically, the priority current limiter can flexibly adjust the ratio of the dq axis rotor current of the voltage source doubly fed wind turbine during a fault, and has the advantage of supporting the grid voltage / frequency. The expression is as follows: ; in: Output reference current phasor for voltage controller, Output reference current phasor for priority current limiter, I max is the maximum allowable current amplitude on the rotor side of the doubly fed wind turbine, is the saturation current angle of the priority current limiter, j is a unit imaginary number.

[0023] The stator voltage equation and grid impedance voltage drop expression of the voltage source doubly fed wind turbine are as follows: ; in: u sdq is the stator voltage of the doubly-fed wind turbine, j is a unit imaginary number, ω 1 is the rated angular frequency, L s is the stator inductance of the doubly-fed wind turbine, i sdq is the stator current of the doubly-fed wind turbine, L m is the excitation inductance of the doubly-fed wind turbine, i rdq is the doubly-fed wind turbine rotor current, V g is the grid voltage amplitude, δ is the power angle, L g is the grid inductance.

[0024] According to the above expressions, the stator voltage and stator current expressions of the voltage source doubly fed wind turbine can be obtained as follows: ; in: u sdq is the stator voltage of the doubly-fed wind turbine, L s is the stator inductance of the doubly-fed wind turbine, V g is the grid voltage amplitude, δ is the power angle, j is a unit imaginary number, ω 1 is the rated angular frequency, L g is the grid inductance, L m is the excitation inductance of the doubly-fed wind turbine, i rdq is the doubly-fed wind turbine rotor current, i sdq is the stator current of the doubly fed wind turbine.

[0025] The expressions of the stator voltage and stator current of the doubly-fed wind turbine are functions of the rotor current and will be used many times in the following analysis and calculation.

[0026] S2: According to the priority current limiter expression, two power angle sets are calculated to respectively make the system enter a fault current limiting state and restore a normal operating state; Specifically, since the voltage source doubly fed wind turbine realizes the stator side voltage source function through the rotor side converter, it is necessary to consider the dynamic characteristics of its voltage controller to reflect the control effect of the rotor current on the stator voltage. Figure 2 As shown in the figure, the voltage controller expression of the voltage source doubly fed wind turbine is:

[0027] in: Output reference current phasor for voltage controller, E is the internal voltage phasor, ω 1 is the rated angular frequency, j is a unit imaginary number, Z v = R v + jω 1 L v is the virtual impedance, R v and L v are virtual resistance and virtual inductance respectively, i sdq is the stator current of the doubly-fed wind turbine, k pv is the proportional coefficient of the voltage controller of the doubly fed wind turbine, u sdq is the stator voltage of the doubly-fed wind turbine, L s is the stator inductance of the doubly-fed wind turbine, L m is the excitation inductance of the doubly-fed wind turbine.

[0028] When the system is in normal operation, the stator voltage and stator current expressions of the voltage source doubly fed wind turbine are substituted into the voltage controller expression to obtain the power angle set that causes the voltage source doubly fed wind turbine to enter the fault current limiting state as follows:

[0029] in: δ is the power angle, Ω1 represents the power angle set for switching from the normal operation state to the fault current limiting state, and the set S represents the unit circle, δ́ is the power angle within the unit circle, ω 1 is the rated angular frequency, L g is the grid inductance, L s is the stator inductance of the doubly-fed wind turbine, E is the internal voltage phasor, j is a unit imaginary number, Z v =R v + jω 1 L v is the virtual impedance, R v and L v are virtual resistance and virtual inductance respectively, V g is the grid voltage amplitude, L m is the excitation inductance of the doubly-fed wind turbine, I max It is the maximum allowable current amplitude on the rotor side of the doubly fed wind turbine.

[0030] When the system is in a fault current limiting state, the expression of the priority current limiter triggering period is substituted into the voltage controller expression of the voltage source double-fed wind turbine, and the power angle set for restoring the voltage source double-fed wind turbine to a normal operating state is obtained as follows:

[0031]

[0032] in: δ is the power angle, Ω2 represents the power angle set for switching from the fault current limiting state to the normal operating state, and the set S represents the unit circle, δ́ is the power angle within the unit circle, E is the internal voltage phasor, k pv is the proportional coefficient of the voltage controller of the doubly fed wind turbine, L s is the stator inductance of the doubly-fed wind turbine, V g is the grid voltage amplitude, j is a unit imaginary number, ω 1 is the rated angular frequency, L g is the grid inductance, L m is the excitation inductance of the doubly-fed wind turbine, I max is the maximum allowable current amplitude on the rotor side of the doubly fed wind turbine, is the saturation current angle of the priority current limiter, Z v = R v + jω 1 L v is the virtual impedance, R v and L vThey are virtual resistance and virtual inductance respectively. Figure 3 The yellow area represents δ Ω2 and δ Ω1 is established, and the pink area represents δ Ω2 and δ Ω1 holds.

[0033] S3: Calculate the output active power of the voltage source doubly fed wind turbine in a fault current limiting state according to the priority current limiter expression and the stator voltage and stator current expressions of the voltage source doubly fed wind turbine; Specifically, according to the stator voltage and stator current expressions of the voltage source doubly fed wind turbine, the output active power of the voltage source doubly fed wind turbine is calculated as follows:

[0034] in: P Output active power for voltage source doubly fed wind turbine, L m is the excitation inductance of the doubly-fed wind turbine, V g is the grid voltage amplitude, i rdq is the doubly-fed wind turbine rotor current, δ is the power angle, L g is the grid inductance, L s is the stator inductance of the doubly-fed wind turbine.

[0035] According to the priority current limiter expression, the output active power of the voltage source doubly fed wind turbine in the fault current limiting state is calculated as follows:

[0036] in: P limit is the output active power of the voltage source doubly fed wind turbine under fault current limiting state, L m is the excitation inductance of the doubly-fed wind turbine, V g is the grid voltage amplitude, I max is the maximum allowable current amplitude on the rotor side of the doubly fed wind turbine, is the saturation current angle of the priority current limiter, δ is the power angle, L g is the grid inductance, L s is the stator inductance of the doubly-fed wind turbine.

[0037] According to the output active power expression of the voltage source doubly fed wind turbine under the fault current limiting state, the stable equilibrium point and unstable equilibrium point of the system under different saturation current angle selection can be obtained, as shown in Figure 3 Shown as red and blue lines in (a).

[0038] S4: determining the influence of different saturation current angles on the transient stability of the voltage source doubly fed wind turbine according to the two power angle sets and the output active power of the voltage source doubly fed wind turbine under the fault current limiting state; Specifically, Figure 3 In (a), the purple star-shaped vertical axis represents the saturation current angle of the selected priority current limiter, and the horizontal axis represents the position of the corresponding power angle at the moment of grid fault clearance. The green solid line with an arrow represents the moving direction of the power angle after the fault is cleared.

[0039] like Figure 3 As shown in Case 1, when the grid fault is cleared, δ Ω2 and δ Ω1 is established, the system exits the fault current limiting state, corresponding to Figure 4 (a) shows the simulation results; like Figure 3 As shown in Case 2, when the grid fault is cleared, δ Ω2 and δ Ω1 is established, the system will experience high-frequency oscillation, corresponding to Figure 4 (b) shows the simulation results; like Figure 3 As shown in Case 3, when the grid fault is cleared, δ When the system reaches the stable equilibrium point under the fault current limiting state, the system is locked in the fault current limiting state, corresponding to Figure 4 The simulation results are shown in (c).

[0040] It can be seen from the above embodiments that the present application achieves the effect of quantitatively analyzing the impact of different saturation current angles on the transient stability of the voltage source doubly fed wind turbine by calculating two sets that consider the dynamic coupling of the voltage controller and the priority current limiter, thereby guiding the selection of current limiting parameters to improve the system robustness.

[0041] Corresponding to the aforementioned embodiment of the method for analyzing transient stability of a voltage source doubly-fed wind turbine, the present application also provides an embodiment of a device for analyzing transient stability of a voltage source doubly-fed wind turbine.

[0042] Figure 5 1 is a block diagram of a voltage source doubly-fed wind turbine transient stability analysis device according to an exemplary embodiment. Figure 5 , the device comprises: A construction module 1 is used to construct a priority current limiter expression, and a stator voltage and stator current expression of a voltage source doubly fed wind turbine using the priority current limiter, wherein the voltage source doubly fed wind turbine is connected to a remote AC power grid through a grid inductor; A first calculation module 2, used for respectively calculating two power angle sets for causing the system to enter a fault current limiting state and restore a normal operation state according to the priority current limiter expression; The second calculation module 3 is used to calculate the output active power of the voltage source double-fed wind turbine under the fault current limiting state according to the priority current limiter expression and the stator voltage and stator current expressions of the voltage source double-fed wind turbine; The analysis module 4 is used to determine the influence of different saturation current angles on the transient stability of the voltage source doubly fed wind turbine according to the two power angle sets and the output active power.

[0043] Regarding the device in the above embodiment, the specific manner in which each module performs operations has been described in detail in the embodiment of the method, and will not be elaborated here.

[0044] For the device embodiment, since it basically corresponds to the method embodiment, the relevant parts can refer to the partial description of the method embodiment. The device embodiment described above is only schematic, wherein the units described as separate components may or may not be physically separated, and the components displayed as units may or may not be physical units, that is, they may be located in one place, or they may be distributed on multiple network units. Some or all of the modules may be selected according to actual needs to achieve the purpose of the present application scheme. A person of ordinary skill in the art can understand and implement it without paying any creative work.

[0045] Correspondingly, the present application also provides an electronic device, comprising: one or more processors; a memory for storing one or more programs; when the one or more programs are executed by the one or more processors, the one or more processors implement the transient stability analysis method of the voltage source doubly fed wind turbine as described above.

[0046] Correspondingly, the present application also provides a computer-readable storage medium on which computer instructions are stored, and when the instructions are executed by a processor, the transient stability analysis method of a voltage source doubly-fed wind turbine as described above is implemented.

[0047] Those skilled in the art will readily appreciate other embodiments of the present application after considering the description and practicing the contents disclosed herein. The present application is intended to cover any modification, use or adaptation of the present application, which follows the general principles of the present application and includes common knowledge or customary techniques in the art that are not disclosed in the present application. The description and examples are intended to be exemplary only, and the true scope and spirit of the present application are indicated by the claims.

[0048] It should be understood that the present application is not limited to the precise structures that have been described above and shown in the drawings, and that various modifications and changes may be made without departing from the scope thereof. The scope of the present application is limited only by the appended claims.

Claims

1. A transient stability analysis method for a voltage source doubly-fed wind turbine, characterized in that: include: Constructing a priority current limiter expression, and stator voltage and stator current expressions of a voltage source doubly fed wind turbine using the priority current limiter, wherein the voltage source doubly fed wind turbine is connected to a remote AC power grid through a grid inductor; According to the priority current limiter expression, two power angle sets are calculated to respectively make the system enter a fault current limiting state and restore a normal operating state; According to the priority current limiter expression and the stator voltage and stator current expressions of the voltage source double-fed wind turbine, the output active power of the voltage source double-fed wind turbine under the fault current limiting state is calculated; According to the two power angle sets and the output active power, the influence of different saturation current angles on the transient stability of the voltage source doubly fed wind turbine is determined.

2. The method according to claim 1, characterized in that The priority limiter expression is as follows: ； in: Output reference current phasor for voltage controller, Output reference current phasor for priority current limiter, I max is the maximum allowable current amplitude on the rotor side of the doubly fed wind turbine, is the saturation current angle of the priority current limiter, j is a unit imaginary number.

3. The method according to claim 1, characterized in that The stator voltage and stator current expressions of the voltage source double-fed wind turbine are as follows: ； in: u sdq is the stator voltage of the doubly-fed wind turbine, L s is the stator inductance of the doubly-fed wind turbine, V g is the grid voltage amplitude, δ is the power angle, ω 1 is the rated angular frequency, L g is the grid inductance, L m is the excitation inductance of the doubly-fed wind turbine, i rdq is the doubly-fed wind turbine rotor current, i sdq is the stator current of the doubly-fed wind turbine, j is a unit imaginary number.

4. The method according to claim 2, characterized in that: The power angle set that causes the voltage source doubly fed wind turbine to enter the fault current limiting state is as follows: ； in: δ is the power angle, Ω1 represents the power angle set for switching from the normal operation state to the fault current limiting state, and the set S represents the unit circle, δ́ is the power angle within the unit circle, ω 1 is the rated angular frequency, L g is the grid inductance, L s is the stator inductance of the doubly-fed wind turbine, E is the internal voltage phasor, j is a unit imaginary number, Z v = R v + jω 1 L v is the virtual impedance, R v and L v are virtual resistance and virtual inductance respectively, V g is the grid voltage amplitude, L m is the excitation inductance of the doubly-fed wind turbine.

5. The method according to claim 4, characterized in that The power angle set that enables the voltage source doubly fed wind turbine to resume normal operation is as follows: ； ； in: δ is the power angle, Ω2 represents the power angle set for switching from the fault current limiting state to the normal operating state, and the set S represents the unit circle, δ́ is the power angle within the unit circle, E is the internal voltage phasor, k pv is the proportional coefficient of the voltage controller of the doubly fed wind turbine, L s is the stator inductance of the doubly-fed wind turbine, V g is the grid voltage amplitude, j is a unit imaginary number, ω 1 is the rated angular frequency, L g is the grid inductance, L m is the excitation inductance of the doubly-fed wind turbine, I max is the maximum allowable current amplitude on the rotor side of the doubly fed wind turbine, is the saturation current angle of the priority current limiter, Z v = R v + jω 1 L v is the virtual impedance, R v and L v They are virtual resistance and virtual inductance respectively.

6. The method according to claim 5, characterized in that The output active power is as follows: ； in: P limit It is the output active power of voltage source doubly fed wind turbine under fault current limiting state.

7. The method according to claim 6, characterized in that According to the two power angle sets and the output active power, the influence of different saturation current angles on the transient stability of the voltage source doubly fed wind turbine is determined, including: When the grid fault is cleared, δ Ω2 and δ If Ω1 holds, the system exits the fault current limiting state; When the grid fault is cleared, δ Ω2 and δ If Ω1 holds, the system will experience high-frequency oscillation; When the grid fault is cleared, δ When the system runs to the stable equilibrium point under the fault current limiting state, the system is locked in the fault current limiting state.

8. A voltage source doubly-fed wind turbine transient stability analysis device, characterized in that: include: A construction module, used to construct a priority current limiter expression, and a stator voltage and stator current expression of a voltage source type doubly fed wind turbine using the priority current limiter, wherein the voltage source type doubly fed wind turbine is connected to a remote AC power grid through a grid inductor; A first calculation module is used to calculate two power angle sets for causing the system to enter a fault current limiting state and restore a normal operation state according to the priority current limiter expression; A second calculation module is used to calculate the output active power of the voltage source double-fed wind turbine under the fault current limiting state according to the priority current limiter expression and the stator voltage and stator current expressions of the voltage source double-fed wind turbine; The analysis module is used to determine the influence of different saturation current angles on the transient stability of the voltage source doubly fed wind turbine according to the two power angle sets and the output active power.

9. An electronic device, characterized in that: include: one or more processors; A memory for storing one or more programs; When the one or more programs are executed by the one or more processors, the one or more processors implement the method according to any one of claims 1 to 7.

10. A computer-readable storage medium having computer instructions stored thereon, characterized in that: When the instruction is executed by a processor, the steps of the method according to any one of claims 1 to 7 are implemented.

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