A quantitative analysis method for DC side stability of grid-connected direct-drive wind turbines

Abstract

This invention discloses a quantitative analysis method for the DC-side stability of a grid-connected direct-drive wind turbine, belonging to the field of wind turbine power generation technology. The method includes: establishing a DC-side impedance model of the grid-connected direct-drive wind turbine corresponding to the turbine-side converter, grid-side converter, and DC capacitor; performing an equivalent transformation on the DC-side impedance model to establish a characteristic equation for measuring the DC-side stability of the grid-connected direct-drive wind turbine, thereby obtaining a quantitative index for measuring the DC-side stability of the grid-connected direct-drive wind turbine; and judging the DC-side stability of the grid-connected direct-drive wind turbine based on the comparison result of the proposed quantitative index ζ and a reference threshold. This method overcomes the problem that existing stability studies on grid-connected direct-drive wind turbines only focus on the interaction between the turbine and the grid, without considering the interaction between the turbine-side converter and the grid-side converter, resulting in inaccurate stability analysis results.

Description

Technical Field

[0001] The present invention belongs to the technical field of wind turbine generator set power generation, and more specifically, relates to a method for quantitatively analyzing the DC side stability of a grid-type direct-drive wind turbine set. Background Art

[0002] Building a new power system with new energy as the main body will make the "double high" characteristics of the power system, namely, a high proportion of new energy and a high proportion of power electronic equipment, more prominent. The abnormal interaction between new energy converters and the power grid will gradually increase, causing problems such as subsynchronous oscillations and harmonic oscillations, endangering the safe and stable operation of the power system.

[0003] Grid-forming control realizes autonomous grid synchronization by simulating the dynamics of synchronous generators, which belongs to the formative grid-connected control method. The converter of grid-forming control presents the voltage source external characteristics similar to synchronous generators, can operate in an autonomous network, and actively respond to load power fluctuations, which is suitable for new power systems with new energy as the dominant power source.

[0004] However, most of the existing stability analyses of grid-connected wind turbines only consider the interaction between the grid-connected wind turbines and the power grid. Relevant studies have shown that the output impedance of grid-connected wind turbines exhibits inductive characteristics, which often leads to erroneous stability analysis conclusions. Summary of the invention

[0005] In view of the above defects or improvement needs of the prior art, the present invention provides a method for quantitatively analyzing the DC side stability of a grid-type direct-drive wind turbine, which aims to solve the technical problem that the results determined by the existing stability analysis method of a grid-type wind turbine are not accurate enough.

[0006] To achieve the above object, according to one aspect of the present invention, a method for quantitatively analyzing the DC side stability of a grid-type direct-drive wind turbine is provided, comprising:

[0007] S1: Taking the DC capacitor as the dividing line, the DC side of the grid-type direct-drive wind turbine is divided into the grid-side converter part, the machine-side converter part and the DC capacitor part;

[0008] S2: Obtain the impedance Z of the grid-side converter on the DC side gsc , the impedance Z of the machine-side converter on the DC side msc and the impedance Z of the DC capacitor part on the DC side C ;

[0009] S3: The machine-side converter is equivalent to a controlled voltage source u msc Series DC impedance Z msc , the grid-side converter is equivalent to a controlled voltage source u gsc Series impedance Zgsc , and then the controlled voltage source u msc Series impedance Z msc The impedance Z of the DC capacitor part connected in parallel C , and then connect the DC impedance Z in series gsc and the controlled voltage source u gsc , obtain the DC side impedance model of the grid-type direct-drive wind turbine; then the machine-side converter part and the DC capacitor part in the DC side impedance model are equivalent to a controlled voltage source u eq Series equivalent impedance Z eq form;

[0010] S4: Using the equivalent impedance Z eq and the impedance Z of the grid-side converter on the DC side gsc Constructing a characteristic equation for measuring the DC side stability of a grid-type direct-drive wind turbine generator set, and using the characteristic value of the characteristic equation to calculate a quantitative index ζ for measuring the DC side stability of the grid-type direct-drive wind turbine generator set;

[0011] S5: Compare the quantitative index ζ with a reference threshold, and determine the stability of the grid-type direct-drive wind turbine generator set on the DC side according to the comparison result.

[0012] In one embodiment, the impedance Z of the grid-side converter part on the DC side in S2 gsc The calculation process is: using the formula Z gsc = Δu dc / Δi dcg = U dc / [ U dc / (G g -P g0 / U dc )] Calculate the impedance Z of the grid-side converter on the DC side gsc ; Δu dc is the change in DC voltage; Δi dcg is the DC current variation of the grid-side converter; U dc is the steady-state value of the DC voltage of the grid-side converter, P g0 is the steady-state value of the active power output by the grid-side converter, G g The active power change ΔP output by the grid-side converter g The change of DC voltage Δu dc The transfer function of ΔP g =U dc Δi dcg +I dcg Δu dc , I dcgis the steady-state value of the DC current input to the grid-side converter part.

[0013] In one embodiment, the impedance Z of the machine-side converter part on the DC side in S2 is msc The calculation process is: using the formula Z msc = Δu dc / Δi dcm = U dc / [ U dc / (P m0 / U dc -G m )] Calculate the impedance Z of the machine-side converter on the DC side msc ; Δu dc is the change in DC voltage; Δi dcm is the DC current change of the input side converter output, U dc is the steady-state value of the DC voltage of the grid-side converter, P m0 is the steady-state value of the active power output by the machine-side converter, G m The active power change ΔP output by the grid-side converter m The change of DC voltage Δu dc The transfer function of ΔP m =U dc Δi dcm +I dcm Δu dc , I dcm is the steady-state value of the DC current input to the machine-side converter part.

[0014] In one embodiment, the equivalent impedance Z in S3 is eq The formula Z is used eq =Z msc Z C / (Z msc + Z C ) calculated.

[0015] In one embodiment, the S4 includes:

[0016] S41: Using the formula f(s)=Z eq +Z gsc The characteristic equation f(s) for measuring the DC side stability of the grid-type direct-drive wind turbine is expressed as follows; let the value of the characteristic equation f(s) be 0 to obtain the characteristic values ​​λ1, λ2, ..., λ m ;

[0017] S42: Using the eigenvalues ​​λ1, λ2, ..., λ mThe quantitative index ζ of the DC side stability of the grid-type direct-drive wind turbine generator system is calculated.

[0018] In one embodiment, the S42 includes:

[0019] Using the formula Calculate the quantitative index ζ, real() is a function for extracting the real part of a complex number, || means taking the absolute value, It means that h takes the minimum value in [] when it increases from 1 to m.

[0020] In one of the embodiments, S5 includes: if ζ is less than or equal to the reference threshold, it is determined that the DC side of the grid-type direct-drive wind turbine group is unstable; if ζ is greater than the reference threshold, it is determined that the DC side of the grid-type direct-drive wind turbine group is stable, and the larger the ζ value is, the stronger the DC side stability margin of the grid-type direct-drive wind turbine group is.

[0021] According to another aspect of the present invention, a DC side stability quantitative analysis device for a grid-type direct-drive wind turbine generator system is provided, comprising:

[0022] A division module is used to divide the DC side of the grid-type direct-drive wind turbine into a grid-side converter part, a machine-side converter part and a DC capacitor part, with the DC capacitor as a dividing line;

[0023] An acquisition module is used to obtain the impedance Z of the grid-side converter on the DC side. gsc , the impedance Z of the machine-side converter on the DC side msc and the impedance Z of the DC capacitor part on the DC side C ;

[0024] A building module is used to convert the machine-side converter part into a controlled voltage source u msc Series DC impedance Z msc , the grid-side converter is equivalent to a controlled voltage source u gsc Series impedance Z gsc , and then the controlled voltage source u msc Series impedance Z msc The impedance Z of the DC capacitor part connected in parallel C , and then connect the DC impedance Z in series gsc and the controlled voltage source u gsc , obtain the DC side impedance model of the grid-type direct-drive wind turbine; then the machine-side converter part and the DC capacitor part in the DC side impedance model are equivalent to a controlled voltage source u eq Series equivalent impedance Z eq form;

[0025] Calculation module for using the equivalent impedance Z eqand the impedance Z of the grid-side converter on the DC side gsc Constructing a characteristic equation for measuring the DC side stability of a grid-type direct-drive wind turbine generator set, and using the characteristic value of the characteristic equation to calculate a quantitative index ζ for measuring the DC side stability of the grid-type direct-drive wind turbine generator set;

[0026] The determination module is used to compare the quantitative index ζ with a reference threshold value, and determine the stability of the grid-type direct-drive wind turbine generator set on the DC side according to the comparison result.

[0027] According to another aspect of the present invention, a wind farm control system is provided, comprising a memory and a processor, wherein the memory stores a computer program, and the processor implements the steps of the above method when executing the computer program.

[0028] According to another aspect of the present invention, a computer-readable storage medium is provided, on which a computer program is stored, and when the computer program is executed by a processor, the steps of the above method are implemented.

[0029] In general, the above technical solutions conceived by the present invention can achieve the following beneficial effects compared with the prior art:

[0030] (1) The present invention provides a method for quantitatively analyzing the DC side stability of a grid-type direct-drive wind turbine, establishes a DC side impedance model of the grid-type direct-drive wind turbine corresponding to a machine-side converter part, a grid-side converter part and a DC capacitor part, performs equivalent transformation on the DC side impedance model to establish a characteristic equation for measuring the DC side stability of the grid-type direct-drive wind turbine, and further obtains a quantitative index ζ for measuring the DC side stability of the grid-type direct-drive wind turbine; the DC side stability of the grid-type direct-drive wind turbine is judged based on a comparison result between the proposed quantitative index ζ and a reference threshold, thereby overcoming the problem that the existing research on the stability of the grid-type direct-drive wind turbine only focuses on the interaction between the turbine and the power grid, but does not consider the interaction between the machine-side converter part and the grid-side converter part, resulting in inaccurate stability analysis results.

[0031] (2) This scheme uses formula Z gsc = Δu dc / Δi dcg = U dc / [ U dc / (G g -P g0 / U dc )] Calculate the impedance Z of the grid-side converter on the DC side gsc ; Δu dc is the change of DC voltage; the control characteristics of the grid-side converter are taken into consideration, and the analytical calculation of the DC side impedance of the grid-side converter is realized.

[0032] (3) This scheme uses formula Z msc = Δu dc / Δi dcm = U dc / [ U dc / (P m0 / U dc -G m )] Calculate the impedance Z of the machine-side converter on the DC side msc ; The control characteristics of the machine-side converter are taken into consideration, and the analytical calculation of the DC side impedance of the machine-side converter is realized.

[0033] (4) Equivalent impedance Z in this scheme eq The formula Z is used eq =Z msc Z C / (Z msc + Z C ) is calculated, taking into account the influence of the machine-side converter and DC capacitor, and realizing the equivalent modeling of the machine-side converter and DC capacitor.

[0034] (5) This scheme uses the formula f(s)=Z eq +Z gsc The characteristic equation f(s) for measuring the DC side stability of the grid-type direct-drive wind turbine is expressed as follows; let the value of the characteristic equation f(s) be 0 to obtain the characteristic values ​​λ1, λ2, ..., λ m ; The influence of the machine-side converter, grid-side converter and DC capacitor is taken into consideration, and the eigenvalue is solved.

[0035] (6) This scheme uses the formula The quantitative index ζ is calculated; the influence of all eigenvalues ​​is taken into account, and the quantification of the DC side stability of the grid-type direct-drive wind turbine is achieved.

[0036] (7) In this scheme, if ζ is greater than the reference threshold, the DC side of the grid-connected direct-drive wind turbine is determined to be stable, and the larger the ζ value is, the stronger the DC side stability margin of the grid-connected direct-drive wind turbine is. The interaction between the machine-side converter and the grid-side converter is taken into account, and the DC side stability of the grid-connected direct-drive wind turbine is determined. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] Figure 1 This is a flow chart of a method for quantitatively analyzing the DC side stability of a grid-type direct-drive wind turbine provided in Example 1 of the present invention.

[0038] Figure 2 This is a schematic diagram of the DC side impedance of a grid-type direct-drive wind turbine provided in Example 1 of the present invention.

[0039] Figure 3 This is a schematic diagram of the DC side model of the grid-type direct-drive wind turbine provided in Example 1 of the present invention.

[0040] Figure 4 Schematic diagram of the DC side equivalent model of the grid-type direct-drive wind turbine provided in Example 1 of the present invention.

[0041] Figure 5 This is a characteristic root locus curve diagram of a grid-type direct-drive wind turbine generator system considering DC side interaction provided in Example 1 of the present invention.

[0042] Figure 6 This is a stability quantification index curve diagram of a grid-type direct-drive wind turbine generator system considering DC side interaction according to an embodiment of the present invention.

[0043] Figure 7 This is a simulation waveform diagram of a grid-connected direct-drive wind turbine generator system when increasing the grid-connected active power in a simulation embodiment of the present invention. DETAILED DESCRIPTION

[0044] In order to make the purpose, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention. In addition, the technical features involved in the various embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0045] Example 1

[0046] like Figure 1 As shown, this embodiment provides a method for quantitatively analyzing the DC side stability of a grid-type direct-drive wind turbine, including steps S1-S5. S1: Using the DC capacitor as a dividing line, the DC side of the grid-type direct-drive wind turbine is divided into a grid-side converter part, a machine-side converter part, and a DC capacitor part; S2: Obtaining the impedance Z of the grid-side converter part on the DC side gsc , the impedance Z of the machine-side converter on the DC side msc And the impedance Z of the DC capacitor on the DC side C ; S3: Equivalent the machine-side converter part to a controlled voltage source u msc Series DC impedance Z msc , the grid-side converter is equivalent to a controlled voltage source u gsc Series impedance Z gsc , and then the controlled voltage source u msc Series impedance Z msc The impedance Z of the DC capacitor connected in parallel C , and then connect the DC impedance Z in series gsc and the controlled voltage source u gsc, the DC side impedance model of the grid-type direct-drive wind turbine is obtained; then the machine-side converter part and the DC capacitor part in the DC side impedance model are equivalent to the controlled voltage source u eq Series equivalent impedance Z eq In the form of; S4: using equivalent impedance Z eq and the impedance Z of the grid-side converter on the DC side gsc A characteristic equation for measuring the DC side stability of the grid-type direct-drive wind turbine is constructed, and the eigenvalue of the characteristic equation is used to calculate the quantitative index ζ for measuring the DC side stability of the grid-type direct-drive wind turbine; S5: the quantitative index ζ is compared with a reference threshold, and the stability of the grid-type direct-drive wind turbine on the DC side is determined according to the comparison result.

[0047] It should be understood that although Figure 1 The steps in the flowchart are shown in sequence as indicated by the arrows, but these steps are not necessarily executed in the order indicated by the arrows. Unless otherwise specified in this document, there is no strict order restriction for the execution of these steps, and these steps can be executed in other orders. Moreover, Figure 1 At least part of the steps may include multiple sub-steps or multiple stages. These sub-steps or stages are not necessarily executed at the same time, but can be executed at different times. The execution order of these sub-steps or stages is not necessarily sequential, but can be executed in turn or alternately with other steps or at least part of the sub-steps or stages of other steps.

[0048] Among them, Figure 2 As shown, step S1: taking the DC capacitor part as the dividing line, the DC side of the grid-type direct-drive wind turbine generator set is divided into a grid-side converter part, a machine-side converter part and a DC capacitor part.

[0049] Among them, Figure 3 As shown, step S2: respectively calculate the impedance Z of the grid-side converter part on the DC side gsc , the impedance Z of the machine-side converter on the DC side msc And the impedance Z of the DC capacitor on the DC side C .

[0050] Furthermore, the impedance Z of the grid-side converter on the DC side is gsc It is calculated as follows.

[0051] Calculate the active power P of the grid-side converter connected to the grid g as follows:

[0052] P g =u dc i dcg (1)

[0053] where u dc is the DC voltage of the grid-side converter, i dcg is the DC current of the grid-side converter; the active power P of the grid-side converter connected to the grid at the steady-state operating point g Linearization can be obtained:

[0054] ΔP g =U dc Δi dcg +I dcg Δu dc (2)

[0055] Among them, U dc is the DC voltage steady-state value of the grid-side converter, I dcg is the steady-state value of the DC current of the input grid-side converter, Δu dc is the change in DC voltage, Δi dcg is the DC current change of the input grid-side converter, ΔP g is the change in active power output by the grid-side converter; the impedance Z of the grid-side converter on the DC side gsc The calculation formula is:

[0056] Z gsc = Δu dc / Δi dcg = U dc / [ U dc / (G g -P g0 / U dc )](3)

[0057] Where P g0 is the steady-state value of the active power output by the grid-side converter, G g The active power change ΔP output by the grid-side converter g The change of DC voltage Δu dc The transfer function of G g Obtained based on the small signal control loop of the grid-side converter part.

[0058] Furthermore, the impedance Z of the machine-side converter on the DC side is msc It is calculated as follows.

[0059] Active power P output by the converter on the computer side m as follows:

[0060] P g =u dc i dcm (4)

[0061] where i dcm is the DC current output by the machine-side converter; is the active power P output by the machine-side converter at the steady-state operating point m Linearization is performed, and we get:

[0062] ΔP m =U dc Δi dcm +I dcm Δu dc (5)

[0063] Among them, I dcm is the DC current steady-state value output by the machine-side converter, Δi dcm is the DC current change of the machine-side converter output, ΔP m is the change in active power output by the machine-side converter; the impedance Z of the machine-side converter on the DC side msc for:

[0064] Z msc = U dc / [ U dc / (P m0 / U dc -G m )](6)

[0065] Among them, P m0 is the steady-state value of the active power output by the machine-side converter, G m The active power change ΔP output by the machine-side converter m The change of DC voltage Δu dc The transfer function of G m Obtained based on the small signal control loop of the machine-side converter part.

[0066] Furthermore, the impedance Z of the DC capacitor on the DC side is C Calculate as follows:

[0067] Z C =1 / (sC) (7)

[0068] Among them, s is the Laplace operator, and C is the capacitance of the DC capacitor part.

[0069] Step S3: The impedance Z of the grid-side converter part on the DC side determined in step S2 gsc , the impedance Z of the machine-side converter on the DC side msc And the impedance Z of the DC capacitor on the DC side C Construct the DC side impedance model of the grid-connected direct-drive wind turbine; specifically, Figure 3 As shown, the machine-side converter is equivalent to a controlled voltage source u mscSeries DC impedance Z msc , the grid-side converter is equivalent to a controlled voltage source u gsc Series DC impedance Z gsc ; controlled voltage source u msc Series DC impedance Z msc After that, the impedance Z of the parallel DC capacitor part C , and then connect the DC impedance Z in series gsc and the controlled voltage source u gsc .like Figure 4 As shown in the figure, according to the DC side impedance model of the grid-connected direct-drive wind turbine, the machine-side converter part and the DC capacitor part are equivalent to a controlled voltage source u eq Series equivalent impedance Z eq The equivalent impedance Z eq Calculate as follows:

[0070] Z eq =Z msc Z C / (Z msc + Z C )(8).

[0071] Step S4: Based on the determined equivalent impedance Z eq and the impedance Z of the grid-side converter part on the DC side determined in step S2 gsc Calculate the quantitative index ζ to measure the DC side stability of grid-connected direct-drive wind turbines.

[0072] Furthermore, the quantitative index ζ for measuring the DC side stability of the grid-type direct-drive wind turbine is calculated as follows; the characteristic equation f(s) for measuring the DC side stability of the grid-type direct-drive wind turbine is calculated as follows:

[0073] f(s)=Z eq +Z gsc (9)

[0074] Let the characteristic equation f(s) be zero and find the characteristic values ​​λ1, λ2, ..., λ m ; For example, the one with the smallest real part in the eigenvalue can be selected, and the ratio of its real part to the absolute value can be used as the quantitative index ζ; Preferably, the quantitative index ζ for measuring the DC side stability of the grid-type direct-drive wind turbine is:

[0075] (10).

[0076] Furthermore, the stability of the DC side of the grid-type direct-drive wind turbine is determined according to the quantitative index ζ: if ζ is less than or equal to zero, the DC side of the grid-type direct-drive wind turbine is unstable; if ζ is greater than zero, the DC side of the grid-type direct-drive wind turbine is stable, and the larger the ζ value is, the stronger the stability margin of the DC side of the grid-type direct-drive wind turbine is.

[0077] See also Figure 5 This embodiment provides a characteristic root locus curve of a direct-drive wind turbine generator set with DC side interaction, wherein the grid short-circuit ratio is 2, and the machine-side converter part of the grid-type wind turbine generator set adopts vector control based on rotor flux orientation. The control targets of the machine-side converter part are DC voltage and reactive power, and the grid-side converter part controls the active power and reactive power of the grid. Figure 5 It can be seen that there are four characteristic roots. As the active power P of the wind turbine connected to the grid increases g As it gradually increases to the rated value, the characteristic root trajectories of No. 1 and No. 2 change little, while the characteristic root trajectories of No. 3 and No. 4 move from the left half plane to the right half plane, indicating that when the output active power increases, it is easy to cause abnormal interaction on the DC side of the grid-type direct-drive wind turbines, resulting in oscillation instability.

[0078] See also Figure 6 This embodiment provides a stability quantification index curve of a direct-drive wind turbine generator system with consideration of DC side interaction, wherein the grid short-circuit ratio is 2, the machine-side converter part of the grid-type wind turbine generator system adopts vector control based on rotor flux orientation, the control target of the machine-side converter part is DC voltage and reactive power, and the grid-side converter part controls the active power and reactive power of the grid. Figure 6 It can be seen that as the active power P of the wind turbine connected to the grid increases g It gradually increases to the rated value, and the stability quantitative index ζ considering the DC side interaction gradually decreases from a positive value to a negative value, and the corresponding grid-type wind turbine unit becomes unstable.

[0079] See also Figure 7 This embodiment provides a simulation waveform of a grid-connected direct-drive wind turbine when increasing the grid-connected active power, wherein the grid short-circuit ratio is 2, the machine-side converter part of the grid-connected wind turbine adopts vector control based on rotor flux orientation, the control target of the machine-side converter part is DC voltage and reactive power, and the grid-side converter part controls the active power and reactive power of the grid. Figure 7 It can be seen that as the active power output of the grid-side converter of the grid-type direct-drive wind turbine gradually increases to 0.6 pu, the active power and DC voltage gradually oscillate and diverge, and the wind turbine becomes unstable. Figure 7 The grid-connected active power value corresponding to the critical instability of medium-grid wind turbines and Figure 6The results are consistent with the theoretical analysis values ​​shown in the figure, which verifies the correctness of the proposed quantitative analysis method for the DC side stability of grid-connected direct-drive wind turbines.

[0080] In summary, the present invention provides a quantitative analysis method for the DC side stability of a grid-type direct-drive wind turbine set, establishes an impedance model of the machine-side converter part, the grid-side converter part and the DC capacitor part on the DC side, performs an equivalent transformation of the DC side of the grid-type direct-drive wind turbine set, establishes a characteristic equation for measuring the DC side stability of the grid-type direct-drive wind turbine set, and proposes a quantitative index ζ for measuring the DC side stability of the grid-type direct-drive wind turbine set; the DC side stability of the grid-type direct-drive wind turbine set can be judged according to the value of the proposed quantitative index ζ, which overcomes the limitation that the existing research on the stability of the grid-type direct-drive wind turbine set only focuses on the interaction between the unit and the power grid, but does not consider the interaction between the machine-side converter part and the grid-side converter part.

[0081] Example 2

[0082] This embodiment provides a DC side stability quantitative analysis device for a grid-type direct-drive wind turbine, including: a division module, an acquisition module, a construction module, a calculation module, and a determination module. The division module is used to divide the DC side of the grid-type direct-drive wind turbine into a grid-side converter part, a machine-side converter part, and a DC capacitor part based on the DC capacitor as a dividing line; the acquisition module is used to obtain the impedance Z of the grid-side converter part on the DC side. gsc , the impedance Z of the machine-side converter on the DC side msc And the impedance Z of the DC capacitor on the DC side C ; Building module, used to convert the machine-side converter part into a controlled voltage source u msc Series DC impedance Z msc , the grid-side converter is equivalent to a controlled voltage source u gsc Series impedance Z gsc , and then the controlled voltage source u msc Series impedance Z msc The impedance Z of the DC capacitor connected in parallel C , and then connect the DC impedance Z in series gsc and the controlled voltage source u gsc , the DC side impedance model of the grid-type direct-drive wind turbine is obtained; then the machine-side converter part and the DC capacitor part in the DC side impedance model are equivalent to the controlled voltage source u eq Series equivalent impedance Z eq The calculation module is used to use the equivalent impedance Z eq and the impedance Z of the grid-side converter on the DC side gscA characteristic equation for measuring the DC side stability of a grid-type direct-drive wind turbine is constructed, and the eigenvalue of the characteristic equation is used to calculate a quantitative index ζ for measuring the DC side stability of the grid-type direct-drive wind turbine. A judgment module is used to compare the quantitative index ζ with a reference threshold, and judge the DC side stability of the grid-type direct-drive wind turbine according to the comparison result.

[0083] The division of each module in the DC side stability analysis and quantification device of the above-mentioned grid-type direct-drive wind turbine group is only for illustration. In other embodiments, the DC side stability analysis and quantification device of the grid-type direct-drive wind turbine group can be divided into different modules as needed to complete all or part of the functions of the DC side stability analysis and quantification device of the above-mentioned grid-type direct-drive wind turbine group.

[0084] For the specific definition of the DC side stability analysis and quantification device of the grid-type direct-drive wind turbine group, please refer to the definition of the DC side stability analysis and quantification method of the grid-type direct-drive wind turbine group mentioned above, which will not be repeated here. Each module in the above-mentioned DC side stability analysis and quantification device of the grid-type direct-drive wind turbine group can be fully or partially implemented by software, hardware and their combination. 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.

[0085] Example 3

[0086] This embodiment provides a wind farm control system, including a memory and a processor, wherein the memory stores a computer program, and the processor implements the steps of the above method when executing the computer program.

[0087] Example 4

[0088] This embodiment provides a computer-readable storage medium on which a computer program is stored. When the computer program is executed by a processor, the steps of the above method are implemented.

[0089] It will be easily understood by those skilled in the art that the above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A quantitative analysis method for DC side stability of a grid-type direct-drive wind turbine generator system, characterized in that: include: S1: Taking the DC capacitor as the dividing line, the DC side of the grid-type direct-drive wind turbine is divided into the grid-side converter part, the machine-side converter part and the DC capacitor part; S2: Obtain the impedance Z of the grid-side converter on the DC side gsc , the impedance Z of the machine-side converter on the DC side msc and the impedance Z of the DC capacitor part on the DC side C ; S3: The machine-side converter is equivalent to a controlled voltage source u msc Series DC impedance Z msc , the grid-side converter is equivalent to a controlled voltage source u gsc Series impedance Z gsc , and then the controlled voltage source u msc Series impedance Z msc The impedance Z of the DC capacitor part connected in parallel C , and then connect the DC impedance Z in series gsc and the controlled voltage source u gsc , obtain the DC side impedance model of the grid-type direct-drive wind turbine; the machine-side converter part and the DC capacitor part in the DC side impedance model are equivalent to a controlled voltage source u eq Series equivalent impedance Z eq form; S4: Using the equivalent impedance Z eq and the impedance Z of the grid-side converter on the DC side gsc Constructing a characteristic equation for measuring the DC side stability of a grid-type direct-drive wind turbine generator set, and using the characteristic value of the characteristic equation to calculate a quantitative index ζ for measuring the DC side stability of the grid-type direct-drive wind turbine generator set; S5: Compare the quantitative index ζ with a reference threshold, and determine the stability of the grid-type direct-drive wind turbine generator set on the DC side according to the comparison result.

2. The DC side stability quantitative analysis method of a grid-type direct-drive wind turbine generator system according to claim 1, characterized in that: The impedance Z of the grid-side converter part on the DC side in S2 gsc The calculation process is: Using the formula Z gsc = Δu dc / Δi dcg = U dc / [ U dc / (G g -P g0 / U dc )] Calculate the impedance Z of the grid-side converter on the DC side gsc ; Δu dc is the change in DC voltage; Δi dcg The DC current variation of the grid-side converter part is input; U dc is the steady-state value of the DC voltage of the grid-side converter, P g0 is the steady-state value of the active power output by the grid-side converter, G g The active power change ΔP output by the grid-side converter g The change of DC voltage Δu dc The transfer function of ΔP g =U dc Δi dcg +I dcg Δu dc , I dcg is the steady-state value of the DC current input to the grid-side converter part.

3. The DC side stability quantitative analysis method of a grid-type direct-drive wind turbine generator system according to claim 1, characterized in that: The impedance Z of the machine-side converter part on the DC side in S2 msc The calculation process is: Using the formula Z msc = Δu dc / Δi dcm = U dc / [ U dc / (P m0 / U dc -G m )] Calculate the impedance Z of the machine-side converter on the DC side msc ; Δu dc is the change in DC voltage; Δi dcm is the DC current change of the input side converter output, U dc is the steady-state value of the DC voltage of the grid-side converter, P m0 is the steady-state value of the active power output by the machine-side converter, G m The active power change ΔP output by the grid-side converter m The change of DC voltage Δu dc The transfer function of ΔP m =U dc Δi dcm +I dcm Δu dc , I dcm is the steady-state value of the DC current input to the machine-side converter part.

4. The DC side stability quantitative analysis method of a grid-type direct-drive wind turbine generator system according to claim 1, characterized in that: The equivalent impedance Z of S3 eq The formula Z is used eq =Z msc Z C / (Z msc + Z C ) calculated.

5. The DC side stability quantitative analysis method of a grid-type direct-drive wind turbine generator system according to claim 1, characterized in that: The S4 includes: S41: Using the formula f(s) = Z eq +Z gsc The characteristic equation f(s) for measuring the DC side stability of the grid-type direct-drive wind turbine is expressed as follows; let the value of the characteristic equation f(s) be 0 to obtain the characteristic values ​​λ1, λ2, ..., λ m ; S42: Using the eigenvalues ​​λ1, λ2, ..., λ m Calculate the quantitative index ζ of the DC side stability of the grid-type direct-drive wind turbine generator system.

6. The DC side stability quantitative analysis method of a grid-type direct-drive wind turbine generator system according to claim 5, characterized in that: The S42 includes: Using the formula Calculate the quantitative index ζ, real() is a function for extracting the real part of a complex number, || means taking the absolute value, It means that h takes the minimum value in [] when it increases from 1 to m.

7. The DC side stability quantitative analysis method of a grid-type direct-drive wind turbine generator system according to claim 5, characterized in that: The S5 includes: if ζ is less than or equal to the reference threshold, it is determined that the DC side of the grid-type direct-drive wind turbine group is unstable; if ζ is greater than the reference threshold, it is determined that the DC side of the grid-type direct-drive wind turbine group is stable, and the larger the ζ value is, the stronger the DC side stability margin of the grid-type direct-drive wind turbine group is.

8. A DC side stability quantitative analysis device for a grid-type direct-drive wind turbine generator set, characterized in that: include: A division module is used to divide the DC side of the grid-type direct-drive wind turbine into a grid-side converter part, a machine-side converter part and a DC capacitor part, with the DC capacitor as a dividing line; An acquisition module is used to obtain the impedance Z of the grid-side converter on the DC side. gsc , the impedance Z of the machine-side converter on the DC side msc and the impedance Z of the DC capacitor part on the DC side C ; A building module is used to convert the machine-side converter part into a controlled voltage source u msc Series DC impedance Z msc , the grid-side converter is equivalent to a controlled voltage source u gsc Series impedance Z gsc , and then the controlled voltage source u msc Series impedance Z msc The impedance Z of the DC capacitor part connected in parallel C , and then connect the DC impedance Z in series gsc and the controlled voltage source u gsc , obtain the DC side impedance model of the grid-type direct-drive wind turbine; then the machine-side converter part and the DC capacitor part in the DC side impedance model are equivalent to a controlled voltage source u eq Series equivalent impedance Z eq form; Calculation module for using the equivalent impedance Z eq and the impedance Z of the grid-side converter on the DC side gsc Constructing a characteristic equation for measuring the DC side stability of a grid-type direct-drive wind turbine generator set, and using the characteristic value of the characteristic equation to calculate a quantitative index ζ for measuring the DC side stability of the grid-type direct-drive wind turbine generator set; The determination module is used to compare the quantitative index ζ with a reference threshold value, and determine the stability of the grid-type direct-drive wind turbine generator set on the DC side according to the comparison result.

9. A wind farm control system, comprising a memory and a processor, wherein the memory stores a computer program, characterized in that: When the processor executes the computer program, the steps of the method according to any one of claims 1 to 7 are implemented.

10. A computer-readable storage medium having a computer program stored thereon, characterized in that: When the computer program 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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