Method and device for enhancing power grid admittance adaptability of grid construction control of wind power grid-connected converter

Abstract

The invention discloses a power grid admittance adaptability method and device for enhancing grid construction control of a wind power grid-connected converter, and the method comprises the steps: dividing a wind power grid-connected converter system into a rotor-side converter and a grid-side converter for admittance modeling, and obtaining an RSC admittance model and a GSC admittance model; the grid-connected converter system comprises an RSC, a direct-current bus and a GSC, the RSC is used for converting alternating-current electric energy generated by wind power generation into direct-current electric energy, the GSC is used for converting the direct-current electric energy into grid-connected alternating-current electric energy, and the direct-current bus is connected with the RSC and the GSC; adjusting admittance phases of the RSC admittance model and the GSC admittance model by using a preset phase correction scheme; the preset phase correction scheme adjusts admittance phases of the RSC admittance model and the GSC admittance model based on a lead-lag correction transfer function. According to the invention, risks of alternating-current power oscillation and direct-current voltage oscillation can be reduced.

Description

Technical Field

[0001] The present invention relates to the technical field of power system stability analysis and control, and in particular to a method and a device for enhancing the adaptability of grid admittance of a wind power grid-connected converter network control. Background Art

[0002] This section is intended to provide a background or context to the embodiments of the invention recited in the claims. No admission is made that the description herein is prior art by inclusion in this section.

[0003] With the development of large-scale renewable energy, renewable energy, mainly wind power and photovoltaic power, will become the main energy source of the future power system. Grid-connected converters, as the interface between renewable energy and the power grid, are key equipment for power transmission. The existing grid control uses methods such as virtual synchronous generator control, droop control, and virtual oscillator control. However, due to the large-scale access of wind power and photovoltaic power, the inertia of the power grid will continue to decrease, causing the future power grid to be in a weak grid state. At this time, the wind power generation system or photovoltaic power generation system with the grid-connected converter as the interface has the risk of interacting with the power grid on the AC side, causing power oscillation on the AC side. In the wind power grid-connected converter system with a more complex structure, different power units inside it will also interact, causing DC voltage oscillation. Summary of the invention

[0004] The embodiment of the present invention provides a method for enhancing the grid admittance adaptability of the grid control of the wind power grid-connected converter, so as to effectively suppress the interaction between the grid-connected converter system and the grid on the AC side, and the interaction inside the grid-connected converter system on the DC side, and reduce the risks of AC power oscillation and DC voltage oscillation. The method includes:

[0005] The wind power grid-connected converter system is divided into a rotor side converter (RSC) and a grid side converter (GSC) for admittance modeling, and an RSC admittance model and a GSC admittance model are obtained; the grid-connected converter system connects a renewable energy power generation system such as a wind power and a photovoltaic power generation system and a public power grid, and the grid-connected converter system includes an RSC, a DC bus and a GSC, the RSC is used to convert the AC power generated by the renewable energy power generation system into DC power, the GSC is used to convert the DC power into AC power that can be connected to the grid, and the DC bus connects the RSC and the GSC;

[0006] The preset phase correction scheme is used to adjust the admittance phase of the RSC admittance model and the GSC admittance model; the preset phase correction scheme adjusts the admittance phase of the RSC admittance model and the GSC admittance model based on the lead-lag correction transfer function to eliminate the interaction between the GSC and the public power grid on the AC side, and the interaction between the RSC and the GSC on the DC side.

[0007] The embodiment of the present invention provides a grid admittance adaptability device for enhancing the grid control of a wind power grid-connected converter, which is used to effectively suppress the AC side interaction between the grid-connected converter system and the grid, and the DC side interaction within the grid-connected converter system, and reduce the risks of AC power oscillation and DC voltage oscillation. The device includes:

[0008] An admittance modeling module is used to divide the wind power grid-connected converter system into RSC and GSC for admittance modeling, and obtain an RSC admittance model and a GSC admittance model; the grid-connected converter system is connected to the renewable energy power generation system and the public power grid, and the grid-connected converter system includes an RSC, a DC bus and a GSC, the RSC is used to convert the electric energy generated by the renewable energy power generation system into DC electric energy, the GSC is used to convert the DC electric energy into AC electric energy, and the DC bus connects the RSC and the GSC;

[0009] The phase compensation control module is used to adjust the admittance phase of the RSC admittance model and the GSC admittance model by using a preset phase correction scheme; the preset phase correction scheme adjusts the admittance phase of the RSC admittance model and the GSC admittance model based on a lead-lag correction transfer function to eliminate the interaction between the GSC and the public power grid on the AC side and the interaction between the RSC and the GSC on the DC side.

[0010] An embodiment of the present invention also provides a computer device, including a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein when the processor executes the computer program, the above-mentioned method for enhancing the grid admittance adaptability of the grid-connected converter network control is implemented.

[0011] An embodiment of the present invention further provides a computer-readable storage medium storing a computer program, and when the computer program is executed by a processor, the method for enhancing the grid admittance adaptability of the grid-connected converter network control is implemented.

[0012] An embodiment of the present invention further provides a computer program product, which includes a computer program. When the computer program is executed by a processor, the method for enhancing the grid admittance adaptability of the grid-connected converter network control is implemented.

[0013] In an embodiment of the present invention, firstly, the wind power grid-connected converter system is divided into two parts, RSC and GSC, for admittance modeling, and the corresponding admittance model is obtained. Secondly, the GSC AC side admittance is analyzed through the admittance model to affect the GSC DC side coupling admittance, and the phase-lead-lag correction is used to adjust the GSC AC side admittance and the RSC DC side coupling admittance phase respectively, so as to eliminate the AC side interaction between the GSC and the public power grid, and ensure that the RSC and GSC inside the grid-connected converter system do not interact on the DC side. The embodiment of the present invention can effectively suppress the AC side interaction between the grid-connected converter system and the power grid, reduce the AC power oscillation, and effectively suppress the DC side interaction between the RSC and GSC inside the grid-connected converter system, reducing the risk of DC voltage oscillation. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the prior art descriptions. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work. In the drawings:

[0015] Figure 1 It is a flow chart of a method for enhancing the grid admittance adaptability of a wind power grid-connected converter network control in an embodiment of the present invention;

[0016] Figure 2 Schematic diagram of the main circuit of the wind power generation system in an embodiment of the present invention;

[0017] Figure 3 A control schematic diagram of a rotor-side converter RSC in a grid-connected converter system in an embodiment of the present invention;

[0018] Figure 4 A control schematic diagram of a grid-side converter GSC in a grid-connected converter system in an embodiment of the present invention;

[0019] Figure 5 Schematic diagram of the amplitude-phase curve of the lead-lag link in the embodiment of the present invention;

[0020] Figure 6 A schematic diagram of lead-lag compensation correction in an embodiment of the present invention;

[0021] Figure 7 The Bode diagram of the interaction between the GSC AC admittance and the grid admittance before and after the lead-lag correction is added to the GSC AC side in the example of the present invention;

[0022] Figure 8Bode diagrams of the interaction between the AC and DC coupling admittances of the RSC and the AC and DC coupling admittances of the GSC before and after the lead-lag correction is added to the GSC only, and before and after the lead-lag correction is added to both the GSC and the RSC in the example of the present invention;

[0023] Fig. 9 The Bode diagram of the interaction between the GSC DC admittance and the RSC DC admittance before and after the lead-lag correction is added to the GSC only and before and after the lead-lag correction is added to both the GSC and the RSC in the example of the present invention;

[0024] Fig.10 The waveforms of the GSC output voltage, current, power and DC voltage before and after the lead-lag correction is added to the GSC AC side only in the example of the present invention are compared;

[0025] Fig.11 The waveforms of the AC output voltage, current, power and DC voltage of the GSC before and after adding the lead-lag correction to the GSC and RSC in the example of the present invention are compared;

[0026] Fig.12 It is a schematic diagram of a grid admittance adaptability device for enhancing grid control of a wind power grid-connected converter in an embodiment of the present invention. DETAILED DESCRIPTION

[0027] To make the purpose, technical solution and advantages of the embodiments of the present invention more clear, the embodiments of the present invention are further described in detail below in conjunction with the accompanying drawings. Here, the exemplary embodiments of the present invention and their descriptions are used to explain the present invention, but are not intended to limit the present invention.

[0028] In view of the problems existing in the prior art, the embodiment of the present invention takes the grid-connected converter system as the research object, and proposes to use lead-lag phase correction to adjust the GSC AC side admittance phase and the RSC DC side coupling admittance phase in the grid-connected converter system, so as to eliminate the AC side interaction between the GSC and the power grid, and the DC side interaction between the RSC and the GSC, and suppress the oscillation of AC power and DC voltage. In addition, this method can be easily extended to multiple interaction occasions with multiple oscillation frequencies.

[0029] Figure 1 FIG. 1 is a flow chart of a method for enhancing grid admittance adaptability of wind power grid-connected converter network control in an embodiment of the present invention. Figure 1 As shown, the method includes:

[0030] Step 101, dividing the wind power grid-connected converter system into RSC and GSC for admittance modeling, and obtaining an RSC admittance model and a GSC admittance model; the grid-connected converter system is connected to the renewable energy power generation system and the public power grid, the grid-connected converter system includes an RSC, a DC bus and a GSC, the RSC is used to convert the electric energy generated by the renewable energy power generation system into DC electric energy, the GSC is used to convert the DC electric energy into AC electric energy, and the DC bus connects the RSC and the GSC;

[0031] Step 102: Use a preset phase correction scheme to adjust the admittance phase of the RSC admittance model and the GSC admittance model; the preset phase correction scheme adjusts the admittance phase of the RSC admittance model and the GSC admittance model based on a lead-lag correction transfer function to eliminate the interaction between the GSC and the public power grid on the AC side and the interaction between the RSC and the GSC on the DC side.

[0032] The grid admittance adaptability method in the embodiment of the present invention is explained in detail below.

[0033] The renewable energy power generation system in the embodiment of the present invention can be photovoltaic power generation, wind power generation, etc. Taking wind power generation as an example, refer to Figure 2 , Figure 2 FIG. 1 is a schematic diagram of the main circuit of a wind power generation system according to an embodiment of the present invention. Figure 2 As shown in the main circuit of the wind power generation system, the leftmost part is the wind turbine, PMSG represents the permanent magnet synchronous generator, θr represents the PMSG rotor angle, the middle part includes RSC, DC bus and GSC, and the rightmost part represents the access to the public grid, u dc is the DC bus voltage, C dc is the DC bus capacitance, i dc is the DC bus current, L c and R c is the inductance and resistance of the output filter, L g and R g are the line inductance and line resistance of the grid, Indicates the output voltage of the GSC module, Indicates the grid connection point voltage, Indicates the grid-connected current, i.e., the GSC output current. is the dq component of the modulation coefficient, d abc It is the duty cycle of the three-phase modulation wave of A, B, and C, and Sabc is the IGBT switching signal.

[0034] Figure 3 FIG. 1 is a control schematic diagram of a rotor-side converter RSC in a grid-connected converter system according to an embodiment of the present invention. Figure 3 As shown, RSC control mainly includes: current loop and DC voltage control. Figure 3middle, represents the d-axis current reference value of RSC, Represents the d-axis current sampling value of RSC, Represents the q-axis current sampling value of RSC, Indicates the q-axis current reference value of RSC, H cc represents the current control transfer function, Indicates the steady-state value of the grid angular frequency, L p represents the stator inductance of PMSG, represents the d-axis component of the RSC input voltage, represents the q-axis component of the RSC input voltage, , represents the d-axis component and q-axis component of the RSC modulation coefficient, u dc.ref Indicates the DC bus voltage reference value, Indicates the DC bus voltage sampling value, G dc represents the DC bus control transfer function.

[0035] according to Figure 3 The expressions of AC voltage and DC current of RSC can be deduced as:

[0036] (1)

[0037] (2)

[0038] In the formula, Represents the small signal change of the dq component of the RSC input voltage, Represents the small signal change of the PMSG output voltage dq component, Δi dc Indicates the small signal change of DC bus current, Represents the small signal change of the dq component of the RSC modulation coefficient, Δu dc Indicates the small signal change of DC bus voltage, They represent the steady-state value of DC bus voltage, the steady-state value of RSC modulation coefficient dq component, the steady-state value of PMSG output voltage dq component, the steady-state value of RSC input current dq component, and the steady-state value of DC bus current. Represents the small signal change of the dq component of the RSC input current, Represents the small signal change of the PMSG output voltage dq component.

[0039] according to Figure 3 The small signal model of the modulation coefficient of RSC can also be deduced as:

[0040] (3)

[0041] Substituting formula (3) into formula (1) yields:

[0042] (4)

[0043] By deriving formula (4), we can get the RSC and The expression is:

[0044] (5)

[0045] in, ,and and It can be expressed as:

[0046] (6)

[0047] in, , substituting formula (5) into formula (2), we can get RSC and The expression is:

[0048] (7)

[0049] in, and It can be expressed as:

[0050] (8)

[0051] Therefore, by modeling the main circuit and control process of the grid-connected converter system RSC, performing theoretical deduction, and combining Ohm's law, the RSC admittance model can be obtained. The specific steps are: first, the main circuit of the RSC is modeled and analyzed to obtain formulas (1) and (2), then the control strategy is modeled to obtain formula (3), and formula (3) is substituted into formula (1) to obtain formula (4). Formula (4) is deduced to obtain formulas (5) and (6), and then formula (5) is substituted into formula (2) to obtain formulas (7) and (8), where formulas (6) and (8) are RSC admittance models. The admittance model of RSC can be respectively expressed as It is represented by, which is composed of DC admittance, AC admittance, DC coupling admittance and AC coupling admittance. That is, the RSC admittance model is expressed as shown in equations (6) and (8).

[0052] Figure 4 FIG. 1 is a control schematic diagram of a grid-side converter GSC in a grid-connected converter system according to an embodiment of the present invention. Figure 4 As shown, GSC control mainly includes: speed regulator, active power loop, reactive power loop, voltage and current loop. Figure 4 , Figure 3The same characters represent the same physical parameters, and the repeated parts will not be described again. Figure 4 In, ω g , ω0, ω represent the instantaneous value of grid angular frequency, the steady-state value of grid angular frequency, and the instantaneous value of grid-connected converter angular frequency, respectively. pv Represents the primary frequency modulation coefficient, P e , P ref They are respectively represented as the grid-connected converter electromagnetic power sampling value and electromagnetic power reference value, D p represents the virtual damping coefficient, J s represents the virtual inertia coefficient, s represents the differential operator, θ represents the GSC power angle, Q e , Q ref They are respectively represented as the reactive power sampling value and reactive power reference value of the grid-connected converter, k q represents the reactive power droop coefficient, , , , They represent the d-axis component and q-axis component of the GSC output voltage, the d-axis component and q-axis component of the GSC output voltage reference value, respectively. vc , G cc , G f They represent the voltage control transfer function matrix, the current control transfer function matrix, and the feedforward link transfer function matrix respectively. , They represent the q-axis component and d-axis component of the modulation coefficient in the GSC control coordinate system, respectively. c represents the output filter inductance, , , , They respectively represent the GSC current reference value d-axis component, the GSC current reference value q-axis component, the GSC current sampling d-axis component, and the GSC current sampling q-axis component.

[0053] GSC adopts virtual synchronous generator control method, according to Figure 4 The AC voltage and DC current expressions of GSC can be deduced as:

[0054] (9)

[0055] (10)

[0056] (11)

[0057] Among them, Z f is the filter impedance of the GSC, represents the steady-state value of the dependent variable, represents the dq-axis component of the output voltage in the GSC control coordinate system, Rc represents the output filter resistance, Respectively represent the small signal changes of the d-axis and q-axis components of the GSC output current, , They represent the small signal changes of the dq axis components of the output voltage in the GSC control coordinate system, u dc0 Indicates the steady-state value of the DC bus voltage, Indicates the steady-state value of the dq-axis component of the GSC modulation coefficient, Δu dc Indicates the small signal change of DC bus voltage, Δi dc Indicates the small signal change of DC bus current.

[0058] according to Figure 4 The small signal model of the modulation coefficient of GSC can be deduced as:

[0059] (12)

[0060] in, represents the modulation coefficient dq component in the GSC control coordinate system, It represents the dq component of the output current reference value in the GSC control coordinate system, Z del represents the coupling impedance, Represents the dq component of the output current sampling value in the GSC control coordinate system, Represents the dq components of the output voltage sampling value in the GSC control coordinate system.

[0061] In formula (13), L, P, and Q can be expressed as:

[0062] (13)

[0063] (14)

[0064] (15)

[0065] Substituting formula (12) into formula (9), we can obtain:

[0066] (16)

[0067] Therefore, we can find the GSC and It can be expressed as:

[0068] (17)

[0069] in and It can be expressed as:

[0070] (18)

[0071] in, , and can launch GSC and It can be expressed as:

[0072] (19)

[0073] in and It can be expressed as:

[0074] (20)

[0075] Therefore, by modeling the main circuit and control process of the grid-connected converter system GSC, performing theoretical deduction and combining Ohm's law, the GSC admittance model can be obtained. The specific steps are: first, the main circuit of the GSC is modeled and analyzed to obtain formulas (9), (10), and (11), and then the control strategy is modeled to obtain formula (12). Formula (12) is substituted into formula (9) to obtain formula (16). Formula (16) is deduced to obtain formulas (17) and (18). Formulas (16) and (17) are substituted into formula (11) to obtain formulas (19) and (20), where formulas (18) and (20) are RSC admittance models. The admittance model of GSC is given by That is, the GSC admittance model is expressed as formula (18) (20).

[0076] in, ;

[0077] ;

[0078] ;

[0079] Where θ0 represents the steady-state value of the GSC power angle, H cc represents the current control transfer function, G vc represents the voltage control transfer function, k q represents the reactive droop coefficient, s represents the differential operator, , It represents the d-axis component and q-axis component of the GSC output voltage, Z del represents the coupling impedance, represents the steady-state value of the GSC modulation coefficient dq, represents the steady-state value of the output current dq component in the control coordinate system, represents the steady-state value of the GSC output voltage dq in the control coordinate system, G v1 , G i1 , Gm1 Represents the matrix expression of output voltage, output current and modulation coefficient in the system coordinate system, represents the parameter matrix composed of the GSC output voltage and output current, k pv represents the primary frequency modulation coefficient, , represents the parameter matrix, C dc is the DC bus capacitance, represents the steady-state value of the dq component of the GSC output voltage, represents the steady-state value of the q-axis component of the GSC output current, H f represents the feedforward control transfer function, D p represents the virtual damping coefficient, ω0 represents the steady-state value of the grid angular frequency, represents the steady-state value of the dq component of the GSC output current, represents the DC voltage control proportional coefficient, represents the DC voltage control integral coefficient, Represents the GSC modulation coefficient dq steady-state value vector form.

[0080] After the wind power grid-connected converter system is divided into a rotor-side converter RSC and a grid-side converter GSC for admittance modeling, and the RSC admittance model and the GSC admittance model are obtained, the admittance phase of the RSC admittance model and the GSC admittance model is adjusted using a preset phase correction scheme; the preset phase correction scheme adjusts the admittance phase of the RSC admittance model and the GSC admittance model based on a lead-lag correction transfer function to eliminate the interaction between the GSC and the public power grid on the AC side, and the interaction between the RSC and the GSC on the DC side. The grid-connected converter system is used to convert the electric energy generated by renewable energy into AC power that meets the grid standard.

[0081] In the embodiment of the present invention, the GSC adopts virtual synchronous generator (VSG) control for network control. According to the admittance modeling analysis of the GSC, the interaction between the weak grid and the GSC will cause the AC side power oscillation of the grid-connected converter system. The general mainstream control method changes the output impedance of the GSC to eliminate the interaction between the AC side and the grid and reduce the AC power oscillation, but this will affect the power generation efficiency, and the excessive output impedance will cause system instability. Similarly, it can be seen from the GSC admittance modeling process that the change of the GSC AC side admittance will affect its DC side coupling admittance, and there is also a risk of causing the DC side voltage to oscillate due to the DC side interaction, and when there are multiple interaction points in the system, the entire system may oscillate at multiple frequencies.

[0082] The embodiment of the present invention presets a phase correction scheme, which uses a lead-lag phase correction strategy including a lead-lag correction transfer function to adjust the AC admittance phase of the GSC and the RSC DC side coupling admittance phase in the grid-connected converter system, eliminate the AC power oscillation caused by the AC side interaction between the GSC and the power grid in the grid-connected converter system, and also eliminate the DC voltage oscillation problem caused by the interaction between the RSC and the GSC on the DC side.

[0083] Figure 5 Schematic diagram of the amplitude-phase curve of the lead-lag link in the embodiment of the present invention, Figure 5 The red curve above is the lead-lag correction amplitude-frequency characteristic curve, and the red curve below is the lead-lag link phase-frequency characteristic curve. The vertical coordinates L (s), Respectively represent the amplitude and phase, the horizontal axis ω com Indicates frequency, through Figure 5 The middle curve reflects that the lead-lag correction can perform lead correction and lag correction on the system phase in different angular frequency bands. If it is applied to the admittance phase correction, the purpose of eliminating the interaction can be achieved by correcting the admittance phase of GSC and RSC. The specific lead-lag correction transfer function can be expressed as:

[0084] (twenty one)

[0085] In the formula, G c (s) represents the lead-lag correction transfer function, α and β are parameters, s represents the differential operator, and T1 and T2 represent the corresponding time constants respectively.

[0086] If there are multiple interaction points between the grid-connected converter system and the power grid, the lead-lag link can be expressed as:

[0087] (twenty two)

[0088] Among them, α j , β i 、T i 、T j They are represented by different parameters and time parameters respectively, and j represents the number of specific correction links.

[0089] The essence of the lead-lag phase correction in the preset phase correction scheme of the embodiment of the present invention is to improve the system characteristics by using the phase enhancement characteristics of the lead link and the phase attenuation characteristics of the lag link, which is mainly reflected in the stability error e ss , cut-off frequency ω c0 , phase margin γ0 and other indicators.

[0090] In one embodiment, a preset phase correction scheme is used to adjust the admittance phase of the RSC admittance model and the GSC admittance model, including the following steps (1) to (3).

[0091] (1) According to the steady-state error e ss Determine the system open-loop gain k. Among them, the steady-state error e ss It can be obtained by subtracting the output current reference value from the output current sampling value. The open-loop gain k can be obtained by k=1 / e ss get.

[0092] (2) Using the system open-loop gain k, calculate the open-loop transfer function L0(s) before phase correction and the cutoff frequency ω c0 , the phase margin is γ0. The leading link is used to correct the frequency band where the phase needs to be corrected, and the lagging link is used to adjust the system phase margin at the attenuation cutoff frequency.

[0093] (3) Lead-lag compensation correction. The details are as follows:

[0094] 3-1) The GSC and RSC in the grid-connected converter are used as the corrected system. By determining the cutoff frequency ω of the corrected system cut , and calculate ω cut The maximum lead angle required The specific correction function is achieved by connecting the lead-lag link in series with the RSC or GSC control structure.

[0095] 3-2) Reference Figure 6 , Figure 6 Schematic diagram of lead-lag compensation correction in an embodiment of the present invention, where L0(s) is the open-loop transfer function before system correction, G c (s) is the lead-lag transfer function, L * (s) is the open-loop transfer function after correction, at the cutoff frequency ω cut Draw a vertical line at point a, intersecting the open-loop transfer function L0 (s) of the GSC or RSC before compensation at point a, and draw the mirror image point b of a about 0dB. Draw a straight line with a speed of 20dB / dec with point b as the center, respectively and Intersect at points c and d.

[0096] 3-3) Determine point e on the horizontal line passing through point d, and then make a straight line of -20dB / dec through point e and intersect 0dB at point f, then the lead-lag correction transfer function can be obtained as:

[0097] (twenty three)

[0098] Among them, G c(s) represents the lead-lag correction transfer function, s represents the differential operator, ω d represents the angular frequency at point d, ω c represents the angular frequency at point c, ω f represents the angular frequency at point f, ω e Represents the angular frequency of point e. Equation (21) and Equation (38) are two expressions of lead-lag correction. Equation (38) is the lead-lag correction transfer function derived from the perspective of control theory, and Equation (21) is the lead-lag correction transfer function derived from the perspective of specific engineering design. The two are equivalent.

[0099] Figure 7 In order to compare the Bode diagrams of the interaction between the GSC AC admittance and the grid admittance before and after the lead-lag correction is added to the GSC AC side only, Figure 7 It can be seen that after the lead-lag correction is added to the GSC AC side, the phase of the frequency interaction point corresponding to the interaction between the GSC AC admittance and the grid admittance decreases from 223° to 164° and 106°. Although an interaction point is added, the phase margin remains in the stable range of [-90°-- +90°], indicating that the method proposed in the embodiment of the present invention can eliminate the interaction on the AC side.

[0100] Figure 8 To compare the Bode diagrams of the interaction between the AC and DC coupling admittance of GSC and the AC and DC admittance of RSC before and after the lead-lag correction is added to GSC only and both GSC and RSC, as shown in Figure 2. Figure 8 As shown in the figure, after adding phase correction to the GSC AC side, it will affect its DC side admittance phase, causing the DC side interaction between the RSC and GSC at around 260Hz, causing DC voltage oscillation. After adding lead-lag correction to the RSC DC side, it can be seen that the DC side interaction is eliminated and the DC voltage oscillation is suppressed.

[0101] Fig. 9 To compare the Bode diagrams of the interaction between the GSC DC admittance and the RSC DC admittance before and after the lead-lag correction is added to the GSC only and the GSC and RSC, as shown in Figure 2. Fig. 9 As shown in the figure, the change of GSC AC side admittance affects GSC DC admittance and The influence of is not significant, but it will affect the GSC DC coupling admittance. The DC voltage oscillation is mainly caused by the GSC and RSC coupling admittance. and Therefore, the DC voltage oscillation has little to do with the DC admittance, but has a greater impact on the DC coupling admittance.

[0102] Fig.10To compare the GSC output voltage, current, power and DC voltage waveforms after adding lead-lag correction only on the GSC AC side, Fig.10 The specific operating condition is the GSC AC output and DC voltage waveforms with lead-lag correction added only on the GSC AC side when the grid is weak (SCR=1.1). (a) is the GSC output voltage, (b) is the GSC output current, (c) is the GSC output active power, (d) is the GSC output active power amplified waveform, (e) is the DC voltage, and (f) is the DC voltage amplified waveform. Fig. 9 It can be seen that after adding lead-lag phase correction on the AC side of the GSC, the output voltage waveform on the AC side of the GSC is significantly improved, the output power oscillation is significantly reduced, and the output current is significantly improved. However, due to the influence on the coupling admittance on the DC side, the DC voltage oscillates.

[0103] Fig.11 To compare the GSC and RSC AC side output voltage, current, power and DC voltage waveforms before and after adding lead-lag correction, Fig.11 The specific operating condition is when the power grid is weak (SCR=1.1), and the GSC AC output and DC voltage waveforms are added with lead-lag correction on both the GSC AC side and the RSC DC side. (a) is the GSC output voltage, (b) is the GSC output current, (c) is the GSC output active power, (d) is the GSC output active power amplified waveform, (e) is the DC voltage, and (f) is the DC voltage amplified waveform. Fig.10 It can be seen that after adding phase lead-lag correction to both the GSC AC side and the RSC DC side. First, the voltage quality of the GSC AC side is significantly improved, while the output power oscillation is significantly reduced, and the output current is significantly improved. Moreover, the DC voltage quickly returns to stability after a short overshoot. This shows that the lead-lag phase correction proposed by the present invention can not only eliminate the interaction on the AC side, but also effectively suppress the interaction on the DC side.

[0104] The embodiment of the present invention also provides a device for enhancing the adaptability of grid admittance of grid-connected converter network control, as described in the following embodiment. Since the principle of solving the problem by the device is similar to the method for enhancing the adaptability of grid admittance of grid-connected converter network control, the implementation of the device can refer to the implementation of the method for enhancing the adaptability of grid admittance of grid-connected converter network control, and the repeated parts will not be repeated.

[0105] Fig.12 FIG. 1 is a schematic diagram of a grid admittance adaptability device for enhancing grid control of a wind power grid-connected converter according to an embodiment of the present invention. Fig.12 As shown, the device 1200 includes:

[0106] The admittance modeling module 1201 is used to divide the wind power grid-connected converter system into RSC and GSC for admittance modeling, and obtain the RSC admittance model and the GSC admittance model; the grid-connected converter system is connected to the renewable energy power generation system and the public power grid, and the grid-connected converter system includes RSC, a DC bus and GSC, the RSC is used to convert the electric energy generated by the renewable energy power generation system into DC electric energy, the GSC is used to convert the DC electric energy into AC electric energy, and the DC bus connects the RSC and the GSC;

[0107] The phase compensation control module 1202 is used to adjust the admittance phase of the RSC admittance model and the GSC admittance model by using a preset phase correction scheme; the preset phase correction scheme adjusts the admittance phase of the RSC admittance model and the GSC admittance model based on the lead-lag correction transfer function to eliminate the interaction between the GSC and the public power grid on the AC side and the interaction between the RSC and the GSC on the DC side.

[0108] In one embodiment, the RSC admittance model is expressed as follows:

[0109] ;

[0110] ;

[0111] In the formula, They represent RSC AC admittance, RSC DC admittance, RSC DC coupling admittance, and RSC AC coupling admittance respectively. represents the parameter matrix, u dc0 Represents the steady-state value of the DC bus voltage, G dc represents the DC voltage control transfer function, m dq0 represents the steady-state value of the RSC modulation coefficient dq, Represents the steady-state value of the RSC input voltage dq, Represents the steady-state value of the RSC input current dq, i dc0 Indicates the steady-state value of the DC bus current.

[0112] In one embodiment, the GSC admittance model is expressed as follows:

[0113] ;

[0114] ;

[0115] In the formula, They represent GSC AC admittance, GSC DC admittance, GSC DC coupling admittance, and GSC AC coupling admittance, respectively. dc0 Represents the steady-state value of the DC bus voltage, Z f represents the RSC output filter impedance, represents the steady-state value of the GSC modulation coefficient dq, represents the steady-state value of the GSC output voltage dq, represents the steady-state value of the GSC output current dq, i dc0 represents the steady-state value of the DC bus current; L, P, Q represent the parameter matrix, specifically:

[0116] ;

[0117] ;

[0118] ;

[0119] ;

[0120] Where θ0 represents the steady-state value of the GSC power angle, H cc represents the current control transfer function, G vc represents the voltage control transfer function, k q represents the reactive droop coefficient, s represents the differential operator, , It represents the d-axis component and q-axis component of the GSC output voltage, Z del represents the coupling impedance, represents the steady-state value of the GSC modulation coefficient dq, represents the steady-state value of the output current dq component in the control coordinate system, represents the steady-state value of the GSC output voltage dq in the control coordinate system, G v1 , G i1 , G m1 Represents the matrix expression of output voltage, output current and modulation coefficient in the system coordinate system, represents the parameter matrix composed of the GSC output voltage and output current, k pv represents the primary frequency modulation coefficient, , represents the parameter matrix, C dc is the DC bus capacitance, represents the steady-state value of the dq component of the GSC output voltage, represents the steady-state value of the q-axis component of the GSC output current, H f represents the feedforward control transfer function, D p represents the virtual damping coefficient, ω0 represents the steady-state value of the grid angular frequency, represents the steady-state value of the dq component of the GSC output current, represents the DC voltage control proportional coefficient, represents the DC voltage control integral coefficient, Represents the GSC modulation coefficient dq steady-state value vector form.

[0121] In one embodiment, the lead-lag correction transfer function is expressed as follows:

[0122] ;

[0123] In the formula, G c (s) represents the lead-lag correction transfer function, s represents the differential operator, ω d represents the angular frequency at point d, ω c represents the angular frequency at point c, ω f represents the angular frequency at point f, ω e It represents the angular frequency of point e. Points d, c, f and e are determined as follows:

[0124] On the graph where the open-loop transfer function before correction, the lead-lag transfer function, and the open-loop transfer function after correction coexist, draw a vertical line at the cutoff frequency, intersecting the open-loop transfer function before correction at point a, draw the mirror image point b of point a about 0dB, and draw a straight line of 20dB / dec with the mirror image point b as the center, respectively. and It intersects at points c and d, ω represents the angular frequency, α is the parameter, point e is determined on the horizontal line passing through point d, and then a straight line of -20dB / dec is made through point e and intersects with 0dB at point f.

[0125] An embodiment of the present invention also provides a computer device, including a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein when the processor executes the computer program, the above-mentioned method for enhancing the grid admittance adaptability of the grid-connected converter network control is implemented.

[0126] An embodiment of the present invention further provides a computer-readable storage medium storing a computer program, and when the computer program is executed by a processor, the method for enhancing the grid admittance adaptability of the grid-connected converter network control is implemented.

[0127] An embodiment of the present invention further provides a computer program product, which includes a computer program. When the computer program is executed by a processor, the method for enhancing the grid admittance adaptability of the grid-connected converter network control is implemented.

[0128] In the embodiment of the present invention, firstly, the wind power grid-connected converter system is divided into two parts, RSC and GSC, for admittance modeling, and the corresponding admittance model is obtained. Secondly, the admittance model is used to analyze that the AC side admittance of the GSC will also affect its DC side coupling admittance, and the phase lead-lag correction is used to adjust the GSC AC side admittance phase and the RSC DC side coupling admittance phase respectively, so as to eliminate the AC side interaction between the GSC and the public power grid, and ensure that the RSC and GSC inside the grid-connected converter system do not interact on the DC side. The embodiment of the present invention can effectively suppress the interaction between the renewable energy power generation system and the power grid, reduce the AC power oscillation, effectively suppress the DC side interaction inside the grid-connected converter system, and reduce the risk of DC voltage oscillation.

[0129] It will be appreciated by those skilled in the art that embodiments of the present invention may be provided as methods, systems, or computer program products. Therefore, the present invention may take the form of a complete hardware embodiment, a complete software embodiment, or an embodiment combining software and hardware. Furthermore, the present invention may take the form of a computer program product implemented on one or more computer-usable storage media (including but not limited to disk storage, CD-ROM, optical storage, etc.) containing computer-usable program code.

[0130] The present invention is described with reference to flowcharts and / or block diagrams of methods, devices (systems), and computer program products according to embodiments of the present invention. It should be understood that each process and / or block in the flowchart and / or block diagram, as well as the combination of processes and / or blocks in the flowchart and / or block diagram, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, a special-purpose computer, an embedded processor, or other programmable data processing device to generate a machine, so that the instructions executed by the processor of the computer or other programmable data processing device generate instructions for implementing the processes in the flowchart and / or block diagram. Figure 1 A process or multiple processes and / or boxes Figure 1 A device that provides the functions specified in a block or multiple blocks.

[0131] These computer program instructions may also be stored in a computer-readable memory capable of directing a computer or other programmable data processing device to operate in a specific manner, so that the instructions stored in the computer-readable memory produce an article of manufacture comprising an instruction device, which implements the process Figure 1 A process or multiple processes and / or boxes Figure 1 A function specified in one or more boxes.

[0132] These computer program instructions can also be loaded onto a computer or other programmable data processing device so that a series of operating steps are executed on the computer or other programmable device to produce a computer-implemented process, thereby providing instructions for implementing the process. Figure 1 A process or multiple processes and / or boxes Figure 1 A step that specifies a function in one or more boxes.

[0133] The specific embodiments described above further illustrate the objectives, technical solutions and beneficial effects of the present invention in detail. It should be understood that the above description is only a specific embodiment of the present invention and is not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A method for enhancing the grid admittance adaptability of wind power grid-connected converter network control, characterized in that: include: The wind power grid-connected converter system is divided into a rotor-side converter RSC and a grid-side converter GSC for admittance modeling, and an RSC admittance model and a GSC admittance model are obtained; the grid-connected converter system is connected to a renewable energy power generation system and a public power grid, and the grid-connected converter system includes an RSC, a DC bus and a GSC, the RSC is used to convert the electric energy generated by the renewable energy power generation system into DC electric energy, the GSC is used to convert the DC electric energy into AC electric energy, and the DC bus connects the RSC and the GSC; The preset phase correction scheme is used to adjust the admittance phase of the RSC admittance model and the GSC admittance model; the preset phase correction scheme adjusts the admittance phase of the RSC admittance model and the GSC admittance model based on the lead-lag correction transfer function to eliminate the interaction between the GSC and the public power grid on the AC side and the interaction between the RSC and the GSC on the DC side.

2. The method according to claim 1, characterized in that The RSC admittance model is expressed as follows: ； ； ； In the formula, They represent RSC AC admittance, RSC DC admittance, RSC DC coupling admittance, and RSC AC coupling admittance respectively; represents the parameter matrix, H cc represents the current control transfer function, Indicates the steady-state value of the grid angular frequency, L p represents the stator inductance of PMSG; u dc0 Represents the steady-state value of the DC bus voltage, G dc represents the DC voltage control transfer function, m dq0 represents the dq steady-state value of the RSC modulation coefficient, represents the dq steady-state value of the RSC input voltage, represents the dq steady-state value of the RSC input current, i dc0 Indicates the steady-state value of the DC bus current.

3. The method according to claim 1, characterized in that The GSC admittance model is expressed as follows: ； ； In the formula, They represent GSC AC admittance, GSC DC admittance, GSC DC coupling admittance, and GSC AC coupling admittance, respectively. dc0 Represents the steady-state value of the DC bus voltage, Z f represents the RSC output filter impedance, represents the steady-state value of the GSC modulation coefficient dq, represents the steady-state value of the GSC output voltage dq, represents the steady-state value of the GSC output current dq, i dc0 represents the steady-state value of the DC bus current; L, P, Q represent the parameter matrix, specifically: ； ； ； ； Where θ0 represents the steady-state value of the GSC power angle, H cc represents the current control transfer function, G vc represents the voltage control transfer function, k q represents the reactive droop coefficient, s represents the differential operator, , It represents the d-axis component and q-axis component of the GSC output voltage, Z del represents the coupling impedance, represents the steady-state value of the GSC modulation coefficient dq, represents the steady-state value of the output current dq component in the control coordinate system, represents the steady-state value of the GSC output voltage dq in the control coordinate system, G v1 , G i1 , G m1 Represents the matrix expression of output voltage, output current and modulation coefficient in the system coordinate system, represents the parameter matrix composed of the GSC output voltage and output current, k pv represents the primary frequency modulation coefficient, , represents the parameter matrix, C dc is the DC bus capacitance, represents the steady-state value of the dq component of the GSC output voltage, represents the steady-state value of the q-axis component of the GSC output current, H f represents the feedforward control transfer function, D p represents the virtual damping coefficient, ω0 represents the steady-state value of the grid angular frequency, represents the steady-state value of the dq component of the GSC output current, represents the DC voltage control proportional coefficient, represents the DC voltage control integral coefficient, Represents the GSC modulation coefficient dq steady-state value vector form.

4. The method according to claim 1, characterized in that The lead-lag correction transfer function is expressed as follows: ； In the formula, G c (s) represents the lead-lag correction transfer function, s represents the differential operator, ω d represents the angular frequency at point d, ω c represents the angular frequency at point c, ω f represents the angular frequency at point f, ω e It represents the angular frequency of point e. Points d, c, f and e are determined as follows: On the graph where the open-loop transfer function before correction, the lead-lag transfer function, and the open-loop transfer function after correction coexist, draw a vertical line at the cutoff frequency, intersecting the open-loop transfer function before correction at point a, draw the mirror image point b of point a about 0dB, and draw a straight line of 20dB / dec with the mirror image point b as the center, respectively. and It intersects at points c and d, ω represents the angular frequency, α is the parameter, point e is determined on the horizontal line passing through point d, and then a straight line of -20dB / dec is made through point e and intersects with 0dB at point f.

5. A grid admittance adaptability device for enhancing the grid control of wind power grid-connected converter, characterized in that: include: An admittance modeling module is used to divide the wind power grid-connected converter system into RSC and GSC for admittance modeling, and obtain an RSC admittance model and a GSC admittance model; the grid-connected converter system is connected to the renewable energy power generation system and the public power grid, and the grid-connected converter system includes an RSC, a DC bus and a GSC, the RSC is used to convert the electric energy generated by the renewable energy power generation system into DC electric energy, the GSC is used to convert the DC electric energy into AC electric energy, and the DC bus connects the RSC and the GSC; The phase compensation control module is used to adjust the admittance phase of the RSC admittance model and the GSC admittance model by using a preset phase correction scheme; the preset phase correction scheme adjusts the admittance phase of the RSC admittance model and the GSC admittance model based on a lead-lag correction transfer function to eliminate the interaction between the GSC and the public power grid on the AC side and the interaction between the RSC and the GSC on the DC side.

6. The device according to claim 5, characterized in that The RSC admittance model is expressed as follows: ； ； In the formula, They represent RSC AC admittance, RSC DC admittance, RSC DC coupling admittance, and RSC AC coupling admittance respectively. represents the parameter matrix, u dc0 Represents the steady-state value of the DC bus voltage, G dc represents the DC voltage control transfer function, m dq0 represents the steady-state value of the RSC modulation coefficient dq, Represents the steady-state value of the RSC input voltage dq, Represents the steady-state value of the RSC input current dq, i dc0 Indicates the steady-state value of the DC bus current.

7. The device according to claim 5, characterized in that The GSC admittance model is expressed as follows: ； ； In the formula, They represent GSC AC admittance, GSC DC admittance, GSC DC coupling admittance, and GSC AC coupling admittance, respectively. dc0 Represents the steady-state value of the DC bus voltage, Z f represents the RSC output filter impedance, represents the steady-state value of the GSC modulation coefficient dq, represents the steady-state value of the GSC output voltage dq, represents the steady-state value of the GSC output current dq, i dc0 represents the steady-state value of the DC bus current; L, P, Q represent the parameter matrix, specifically: ； ； ； ； Where θ0 represents the steady-state value of the GSC power angle, H cc represents the current control transfer function, G vc represents the voltage control transfer function, k q represents the reactive droop coefficient, s represents the differential operator, , It represents the d-axis component and q-axis component of the GSC output voltage, Z del represents the coupling impedance, represents the steady-state value of the GSC modulation coefficient dq, represents the steady-state value of the output current dq component in the control coordinate system, represents the steady-state value of the GSC output voltage dq in the control coordinate system, G v1 , G i1 , G m1 Represents the matrix expression of output voltage, output current and modulation coefficient in the system coordinate system, represents the parameter matrix composed of the GSC output voltage and output current, k pv represents the primary frequency modulation coefficient, , represents the parameter matrix, C dc is the DC bus capacitance, represents the steady-state value of the dq component of the GSC output voltage, represents the steady-state value of the q-axis component of the GSC output current, H f represents the feedforward control transfer function, D p represents the virtual damping coefficient, ω0 represents the steady-state value of the grid angular frequency, represents the steady-state value of the dq component of the GSC output current, represents the DC voltage control proportional coefficient, represents the DC voltage control integral coefficient, Represents the GSC modulation coefficient dq steady-state value vector form.

8. The device according to claim 5, characterized in that The lead-lag correction transfer function is expressed as follows: ； In the formula, G c (s) represents the lead-lag correction transfer function, s represents the differential operator, ω d represents the angular frequency at point d, ω c represents the angular frequency at point c, ω f represents the angular frequency at point f, ω e It represents the angular frequency of point e. Points d, c, f and e are determined as follows: On the graph where the open-loop transfer function before correction, the lead-lag transfer function, and the open-loop transfer function after correction coexist, draw a vertical line at the cutoff frequency, intersecting the open-loop transfer function before correction at point a, draw the mirror image point b of point a about 0dB, and draw a straight line of 20dB / dec with the mirror image point b as the center, respectively. and It intersects at points c and d, ω represents the angular frequency, α is the parameter, point e is determined on the horizontal line passing through point d, and then a straight line of -20dB / dec is made through point e and intersects with 0dB at point f.

9. A computer device comprising a memory, a processor and a computer program stored in the memory and executable on the processor, characterized in that: When the processor executes the computer program, the method according to any one of claims 1 to 4 is implemented.

10. A computer-readable storage medium, characterized in that: The computer-readable storage medium stores a computer program, and when the computer program is executed by a processor, the method according to any one of claims 1 to 4 is implemented.

11. A computer program product, characterized in that The computer program product comprises a computer program, and when the computer program is executed by a processor, the method according to any one of claims 1 to 4 is implemented.

Images