Permanent magnet direct drive fan modeling method considering mechanical system and related equipment

Abstract

The invention relates to the technical field of permanent magnet direct-drive fans, and discloses a permanent magnet direct-drive fan modeling method considering a mechanical system and related equipment. A mechanical system transfer function and a complete electrical system transfer function including a permanent magnet synchronous generator stator loop, a machine side converter, a grid side inverter and the like are established; a permanent magnet direct drive fan small signal admittance model is constructed, the defect that a previous model neglects a mechanical system or part of an electrical system is made up, the model can accurately reflect the influence of mechanical shafting dynamic characteristics on harmonic transmission of an electrical subsystem through electromagnetic torque disturbance, and the accuracy of the fan broadband admittance model is improved. A reliable basis is provided for broadband oscillation analysis of an offshore wind power plant grid-connected system, the new energy delivery capacity is improved, and safe and stable operation of a novel electric power system is guaranteed.

Description

Technical Field

[0001] This invention belongs to the field of permanent magnet direct-drive fan technology, specifically a modeling method and related equipment for permanent magnet direct-drive fans that considers the mechanical system. Background Technology

[0002] Currently, we are vigorously developing new energy sources and building a new power system with new energy sources as the main body. However, as new energy sources are connected to the grid on a large scale, when the grid strength is weak, the fast control characteristics of new energy grid-connected equipment may interact with the grid, which may cause broadband oscillation problems. Broadband oscillation problems restrict the transmission capacity of new energy sources and affect the safe and stable operation of the power system.

[0003] Offshore wind power, due to its advantages such as stable resources, stable turbine operation, high energy output, and minimal environmental impact, has become an important strategic direction for my country's energy development in recent years. The stability of offshore wind farm grid-connected systems has also increasingly become a key research focus. Impedance analysis is frequently used in studies of broadband oscillation problems. When studying the stability of offshore wind farm grid-connected systems, the impedance models of the wind turbines and the power grid in the system must first be established separately. Then, the Nyquist stability criterion based on impedance ratio is applied to determine the system's stability. Impedance modeling is a crucial step in applying impedance analysis; the accuracy of the impedance model directly affects the accuracy of the stability assessment.

[0004] Offshore wind farms mostly use permanent magnet direct-drive wind turbines; therefore, the focus of this invention is to establish an accurate broadband admittance model for permanent magnet direct-drive wind turbines. The power generation principle of a wind turbine is to use the kinetic energy in the flowing air to drive the turbine blades to rotate, converting kinetic energy into mechanical energy, which is then converted into electrical energy by the power generation equipment inside the turbine. Therefore, it mainly consists of two parts: a mechanical system and an electrical system. The electrical system includes a grid-side converter, a turbine-side converter, and a permanent magnet synchronous generator. Previous admittance models for permanent magnet direct-drive wind turbines often neglected the influence of the turbine-side converter, synchronous generator, and mechanical system, only considering the small-signal admittance model of the grid-side inverter, using the grid-side inverter's admittance to represent the turbine's admittance. This approach is clearly inaccurate. Current research has made improvements by considering the influence of the turbine-side inverter and permanent magnet synchronous generator. However, these studies rarely include the mechanical system in their considerations. Yet, the dynamic characteristics of the mechanical shaft system can affect the harmonic transmission of the electrical subsystem through electromagnetic torque disturbances, thereby changing the turbine's output impedance characteristics. The wind turbine impedance model that does not consider the mechanical system cannot accurately reflect this dynamic characteristic, leading to erroneous conclusions in the broadband oscillation analysis based on the impedance analysis method. Summary of the Invention

[0005] This invention provides a modeling method and related equipment for permanent magnet direct-drive fans that considers the mechanical system, solving the problem that the impedance model of the fan that does not consider the mechanical system cannot accurately reflect this dynamic characteristic, leading to erroneous conclusions in the broadband oscillation analysis obtained based on the impedance analysis method.

[0006] To achieve the above objectives, the present invention provides the following technical solution: A modeling method for permanent magnet direct-drive fans considering mechanical systems includes: Establish the transfer function of the mechanical system; Establish the transfer function of the electrical system, which includes the transfer function of the permanent magnet synchronous generator stator circuit, the transfer function of the generator-side converter, the transfer function of the grid-side inverter, and the transfer function of the AC / DC connection between the generator side and the grid side; A small-signal admittance model for a permanent magnet direct-drive fan is established based on the transfer functions of the mechanical and electrical systems.

[0007] Preferably, the small-signal admittance model of the permanent magnet direct-drive fan is:

[0008]

[0009]

[0010]

[0011]

[0012]

[0013] in, This is a small-signal admittance model for a permanent magnet direct-drive fan. Here is the filter output impedance matrix in the dq coordinate system. DC side voltage Let be the transfer function between the modulation signal and the AC current of the grid-side inverter in the system coordinate system. Let be the transfer function between the modulation signal and the DC-side voltage in the system coordinate system. Let be the transfer function between the AC side voltage and the DC side voltage of the grid-side inverter in the system coordinate system. Let be the transfer function between the AC side current and DC side voltage of the grid-side inverter in the system coordinate system. It is the identity matrix. Let be the transfer function between the modulation signal and the AC side voltage of the grid-side inverter in the system coordinate system. This is the transfer function between the modulation signal of the generator-side converter and the AC current measurement. The transfer function for the decoupling stage of the generator-side converter control. The transfer function for the inner loop controller of the generator-side converter current. For the transfer function of the turbine-side converter speed loop controller, Let be the transfer function between the rotor electrical angle and the mechanical angular velocity. For mechanical system transfer function, For the Laplace operator, Synchronization and flux transfer functions, This is the transfer function between the AC current and DC voltage of the machine-side converter. This is the stator impedance matrix of the synchronous machine. The transfer function between rotor electrical angle and AC current measured by the machine-side converter. The transfer function between the DC-side voltage and the AC voltage measured at the machine-side converter. This is the transfer function between the DC-side current and the DC-side voltage. This is the transfer function between the AC current and the DC current of the machine-side converter. This is the transfer function between the modulation signal of the machine-side converter and the DC-side current. This is the transfer function between the AC current and the DC current of the grid-side inverter. This is the transfer function between the grid-side inverter modulation signal and the DC-side current. This is the transfer function for the grid-side inverter current inner loop controller. For the transfer function of the outer loop controller of the grid-side inverter voltage, Let be the transfer function between the grid-side inverter modulation signal and the DC-side voltage in the system coordinate system. The transfer function for the decoupling stage of the grid-side inverter controller. Let be the transfer function between the difference between the current in the grid-side inverter system coordinate system and the current in the controller coordinate system, and the voltage in the system coordinate system. It is the transfer function between the difference between the modulation signal in the grid-side inverter system coordinate system and the modulation signal in the controller coordinate system, and the voltage in the system coordinate system.

[0014] Preferably, the transfer function of the mechanical system is:

[0015] in, The number of pole pairs of the synchronous machine rotor. For rotor flux linkage, For the Laplace operator, This represents the relationship between the rotor's mechanical angular velocity and electromagnetic torque.

[0016] Preferably, the transfer function of the stator circuit of the permanent magnet synchronous generator is:

[0017]

[0018]

[0019] in, R s For the stator resistance of the synchronous machine, L d For the stator of the synchronous machine d Shaft inductor, L q For the stator of the synchronous machine q Shaft inductor, I Gd For the stator of the synchronous machine d Steady-state value of shaft current I Gq For the stator of the synchronous machine q Steady-state value of shaft current Synchronization and flux transfer functions, For the Laplace operator, For rotor flux linkage, The transfer function between rotor electrical angle and AC current measured by the machine-side converter. This is the stator impedance matrix of the synchronous machine.

[0020] Preferably, the transfer function of the machine-side converter is:

[0021] in, For the transfer function of the machine-side converter, For machine-side converter d Steady-state value of the axis modulation signal For machine-side converter q Steady-state value of the axis modulation signal.

[0022] Preferably, the establishment of the grid-side inverter transfer function specifically involves establishing the filter electrical loop transfer function, the grid-side inverter transfer function in the controller dq coordinate system and the system dq coordinate system, the voltage outer loop controller transfer function, and the current inner loop controller transfer function in sequence.

[0023] A modeling system for permanent magnet direct-drive fans considering mechanical systems, comprising: Mechanical system creation module: used to create the transfer function of the mechanical system; Electrical system establishment module: used to establish the transfer functions of the electrical system, which include the transfer functions of the permanent magnet synchronous generator stator circuit, the generator-side converter, the grid-side inverter, and the transfer functions of the AC / DC connection between the generator side and the grid side; Wind turbine model building module: used to build a small-signal admittance model of a permanent magnet direct-drive wind turbine based on the mechanical system transfer function and the electrical system transfer function.

[0024] A computer device includes a memory, a processor, and a computer program stored in the memory, the processor executing the computer program to implement the steps of a modeling method for a permanent magnet direct-drive fan considering a mechanical system.

[0025] A computer-readable storage medium having a computer program stored thereon, which, when executed by a processor, implements the steps of a modeling method for a permanent magnet direct-drive fan considering a mechanical system.

[0026] A computer program product includes a computer program that, when executed by a processor, implements the steps of a modeling method for a permanent magnet direct-drive fan that takes into account a mechanical system.

[0027] Compared with existing technologies, the present invention has the following beneficial effects: The present invention provides a modeling method for permanent magnet direct-drive wind turbines that considers the mechanical system. By establishing the transfer function of the mechanical system and the complete electrical system transfer function including the stator circuit of the permanent magnet synchronous generator, the turbine-side converter, the grid-side inverter, etc., a small-signal admittance model of the permanent magnet direct-drive wind turbine is constructed. This makes up for the shortcomings of previous models that ignore the mechanical system or part of the electrical system. The model can accurately reflect the influence of the dynamic characteristics of the mechanical shaft system on the harmonic transmission of the electrical subsystem through electromagnetic torque disturbance, improve the accuracy of the broadband admittance model of the wind turbine, provide a reliable basis for broadband oscillation analysis of offshore wind farm grid-connected systems, help improve the new energy transmission capacity, and ensure the safe and stable operation of the new power system. Attached Figure Description

[0028] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of the present invention and should not be regarded as a limitation on the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.

[0029] Figure 1 This invention provides a modeling method for a permanent magnet direct-drive fan that considers a mechanical system. Figure 2 The topology of existing permanent magnet direct drive wind turbine units; Figure 3 This is a control block diagram of the generator-side converter of an existing permanent magnet direct-drive wind turbine unit; Figure 4 The control block diagram of the grid-side inverter for an existing permanent magnet direct-drive wind turbine; Figure 5The system dq coordinate system and the controller dq coordinate system are shown in the embodiments of the present invention. Figure 6 This is the final small-signal admittance model of the direct-drive fan established in this embodiment of the invention; Figure 7 This is a comparison between the calculated and measured impedance values ​​of the direct-drive fan in an embodiment of the present invention. Figure 8 This is a block diagram of a permanent magnet direct-drive fan modeling system considering a mechanical system, according to an embodiment of the present invention. Detailed Implementation

[0030] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. The components of the embodiments of the present invention described and shown in the accompanying drawings can generally be arranged and designed in various different configurations.

[0031] Therefore, the following detailed description of the embodiments of the invention provided in the accompanying drawings is not intended to limit the scope of the claimed invention, but merely to illustrate selected embodiments of the invention. All other embodiments obtained by those skilled in the art based on the embodiments of the invention without inventive effort are within the scope of protection of the invention.

[0032] It should be noted that similar labels and letters in the following figures indicate similar items. Therefore, once an item is defined in one figure, it does not need to be further defined and explained in subsequent figures.

[0033] To enable those skilled in the art to better understand the technical solution of the present invention, the present invention will be further described in detail below with reference to the accompanying drawings.

[0034] like Figure 1 As shown, this invention provides a modeling method for permanent magnet direct-drive fans considering mechanical systems, including: S1: Establish the transfer function of the mechanical system; S2: Establish the transfer function of the electrical system, which includes the transfer function of the permanent magnet synchronous generator stator circuit, the transfer function of the generator-side converter, the transfer function of the grid-side inverter, and the transfer function of the AC / DC connection between the generator side and the grid side; S3: Establish a small-signal admittance model for the permanent magnet direct-drive fan based on the transfer functions of the mechanical system and the electrical system.

[0035] By establishing the transfer function of the mechanical system and the complete electrical system transfer function including the stator circuit of the permanent magnet synchronous generator, the turbine-side converter, and the grid-side inverter, a small-signal admittance model for permanent magnet direct-drive wind turbines is constructed. This model overcomes the shortcomings of previous models that neglected the mechanical system or part of the electrical system. The model can accurately reflect the impact of the dynamic characteristics of the mechanical shaft system on the harmonic transmission of the electrical subsystem through electromagnetic torque disturbance, improve the accuracy of the broadband admittance model of wind turbines, provide a reliable basis for broadband oscillation analysis of offshore wind farm grid-connected systems, help improve the capacity for transmitting new energy, and ensure the safe and stable operation of new power systems.

[0036] The detailed steps are as follows: The admittance of a permanent magnet direct-drive wind turbine is the ratio of the current to the voltage at the node connected to the AC grid. The topology of a permanent magnet direct-drive wind turbine and the control block diagram of the turbine-side converter and grid-side inverter are shown below. Figure 2 , 3 As shown in Figure 4.

[0037] direct drive fan dq The admittance model can be established in two parts: the mechanical system and the electrical system. The electrical system model includes the small-signal admittance model of the permanent magnet synchronous generator stator circuit, the generator-side inverter model, the grid-side controller model, and the AC / DC interconnection model.

[0038] Establish the transfer function of the mechanical system: The mechanical system consists of: The input power of a wind turbine is equal to the kinetic energy of the air in the plane where the wind turbine is located, which can be expressed as: (1) in E As for aerodynamic energy, m For air quality, v This refers to wind speed.

[0039] Air quality can be expressed as: (2) in S Let ρ be the cross-sectional area of ​​the wind turbine through which the wind passes, and ρ be the air density. Substituting equation (2) into equation (1), we can obtain the expression for the wind turbine's captured power as follows: (3) Since wind energy cannot be completely captured in practice, a wind energy utilization factor is needed. C p This represents the efficiency with which the wind turbine captures wind energy, ultimately yielding the mechanical power output of the wind turbine. P m The expression is: (4) In the formula Affected by parameters such as propeller pitch angle, rotational speed, and wind speed, The expression is: (5) In the formula: =0.5176, =116, =0.4, =5, =21, =0.0068; For the tip speed ratio, The pitch angle is the propeller angle. The radius of the wind turbine blades; This refers to the mechanical speed of the fan.

[0040] Small-signal admittance model of mechanical system (1) Relationship between mechanical torque and mechanical angular velocity The mechanical torque of a wind turbine is related to its mechanical angular velocity and blade pitch angle as follows: (6) in, T m For mechanical rotation speed, R f The radius of the wind turbine blades. v f For wind speed, ω m This represents the mechanical angular velocity of the synchronous machine rotor. (Constant coefficient) c 1 = 0.5176, c 2 = 116 c 3 = 0.4 c 4 = 5 c 5 = 21 c 6 = 0.0068 λ For the tip speed ratio, β Let be the propeller pitch angle. Based on the four formulas above, calculate... T m right ω m The derivative of this derivative yields the transfer function between the small signal quantities of mechanical torque and mechanical angular velocity: (7) in (8) The relationship between electromagnetic torque and mechanical angular velocity: The equation of motion for the synchronous machine rotor is: (9) Therefore, the relationship between the mechanical torque and the small-signal quantity of the electromagnetic torque of the synchronous machine can be obtained as follows: (10) in (11) (3) The relationship between electromagnetic torque and stator current: For a salient-pole engine, the relationship between electromagnetic torque and stator current is as follows: (12) (4) Relationship between rotor electrical angle and stator current: Rotor electrical angle With mechanical angular velocity The relationship between them is: (13) in p This represents the number of pole pairs in the synchronous machine.

[0041] Combining (10), (12) and (13) yields (14) Where the transfer function T is (15) in, The number of pole pairs of the synchronous machine rotor. For rotor flux linkage, For the Laplace operator, This represents the relationship between the rotor's mechanical angular velocity and electromagnetic torque.

[0042] Equation (15) establishes the relationship between the mechanical system and the electrical circuit.

[0043] Establish the transfer function of the electrical system, which includes the transfer function of the permanent magnet synchronous generator stator circuit, the transfer function of the generator-side converter, the transfer function of the grid-side inverter, and the transfer function of the AC / DC connection between the generator side and the grid side; Stator circuit of permanent magnet synchronous generator: The conventional stator voltage equation for a generator in the frequency domain is: (16) in V Gd For stator d shaft voltage, V Gq For stator q shaft voltage, I Gd For stator d shaft current, IGq For stator q shaft current, R s This represents the stator resistance of the synchronous generator. L d For stator d Shaft inductor, L q For stator q Shaft inductor, For synchronous electromechanical angular velocity, For permanent magnet flux linkage. Defined in the rotor of a synchronous machine. dq A small-signal admittance model is established in coordinate system (g). A small-signal quantity is added to equation (16), and after linearization, the following is obtained: (17) in, For stator current small signal quantity, Stator voltage small signal quantity This represents the small signal quantity of the rotor electrical angle. The expressions for each transfer function are: (18) (19) (20) in, R s For the stator resistance of the synchronous machine, L d For the stator of the synchronous machine d Shaft inductor, L q For the stator of the synchronous machine q Shaft inductor, I Gd For the stator of the synchronous machine d Steady-state value of shaft current I Gq For the stator of the synchronous machine q Steady-state value of shaft current Synchronization and flux transfer functions, For the Laplace operator, For rotor flux linkage, The transfer function between rotor electrical angle and AC current measured by the machine-side converter. This is the stator impedance matrix of the synchronous machine.

[0044] Machine-side converter: (1) Rotational speed outer ring Depend on Figure 3 The outer loop PI controller for the speed of the machine-side converter (twenty one) in This is a small-signal quantity that serves as a reference value for the stator dq-axis current. For the outer loop speed controller, its expression is: (twenty two) This refers to the proportional element coefficient of the outer loop controller for the rotational speed. It is the coefficient of its integral element.

[0045] (2) Current inner loop Depend on Figure 1 The current inner loop controller of the machine-side converter is as follows: (twenty three) in This refers to the small signal quantity used to modulate the signal for the machine-side converter. It is a current inner-loop PI controller. The expressions for the controller decoupling terms are as follows: (twenty four) (25) (3) Relationship between converter modulation signal and AC / DC side voltage The converter modulation signal mGdq, stator voltage VGdq, and DC-side voltage Vdc have the following relationship: (26) Adding a small semaphore to equation (26) and linearizing it yields... (27) in , For small-signal DC-side voltage, the transfer function The expression for is shown in equation (28), where , This represents the steady-state value of the modulation signal.

[0046] (28) in, For the transfer function of the machine-side converter, For machine-side converter d Steady-state value of the axis modulation signal For machine-side converter q Steady-state value of the axis modulation signal.

[0047] Grid-side inverter: (1) Filter electrical circuit for Figure 1 The filter loop in the circuit can be obtained from Kirchhoff's voltage law: (29) Equation (29) can be transformed into the state equation in the dq coordinate system after the abc-dq coordinate system transformation, as shown below. (30) in (31) By adding small signal quantities to each voltage and current in the dq coordinate system in equation (A2) and linearizing them, we can obtain: (32) In equation (32), each transfer function is: (33) (34) (35) (36) Where M d M q The modulated signal m d m q The steady-state values ​​are given by Id and Iq, which are the steady-state values ​​of the grid-side inverter output currents id and iq, respectively.

[0048] Phase-locked loop: Due to the presence of the phase-locked loop (PLL), the grid-side inverter has two dq coordinate systems: one is the system dq coordinate system (s) defined by the grid voltage, and the other is the controller dq coordinate system (c) defined by the PLL, as follows: Figure 5 As shown. In steady state, the two coordinate systems are aligned, but when a small signal disturbance is introduced into the grid voltage, the system... dq The position of the coordinate systems has changed, and the two coordinate systems are no longer aligned, with an angle of Δθ between them, as shown in Figure A3. This can be determined using matrix T. Δθ Rotate the voltage and current vectors in the system's dq coordinate system to the controller. dq Feedback control is performed in the coordinate system. Then, it is controlled by matrix T. Δθ The inverse of the feedback control will rotate the duty cycle command generated by the feedback control to the system. dq The power semiconductor is controlled in a coordinate system. This process has been derived in detail in previous studies, and the conclusions are as follows.

[0049] Small-signal disturbances in the system voltage propagate to the PLL output angle in the controller's dq coordinate system, and then to the current and duty cycle vectors. The transfer function expression for this process is: (37) The expressions for each transfer function are as follows: (38) (39) (40) In the above matrix, G PLL The expression is (41) in (42) (3) Voltage outer loop controller Depend on Figure 1 Voltage outer loop controller (43) in For the voltage outer loop PI controller, its expression is shown in equation (44). This is the coefficient for the proportional element. The coefficients of the integral element.

[0050] (44) (4) Current inner loop controller Depend on Figure 1 The grid-side inverter current loop control shown is (45) in This refers to the small signal quantity used to modulate the signal for the machine-side converter. It is a current inner-loop PI controller. The expressions for the controller decoupling terms are as follows: (46) (47) DC connection section: (1) DC side voltage and current relationship The relationship between DC voltage and current in the time domain is as follows: (48) Perform a Laplace transform, add a small signal, and linearize to obtain (49) The transfer function expression is shown in equation (50). C This is the capacitance value of the DC side capacitor.

[0051] (50) (2) Relationship between DC side current and AC side current of the two converters From KCL and coordinate system transformation, we get (51) Adding a small semaphore to equation (51) and linearizing it yields... (52) The expressions for each transfer function are as follows: (53) (54) (55) (56) Equation (52) establishes the relationship between the physical quantities of the two converters on the machine side and grid side and the physical quantities on the DC side.

[0052] Based on the transfer functions of the mechanical and electrical systems, a small-signal admittance model of the permanent magnet direct-drive fan is established. From the relationships between the various physical quantities derived above, we can obtain... Figure 6 The transfer function block diagram shown is used to obtain the wind turbine's DQ admittance, from which the small-signal admittance model of the wind turbine can be calculated: (57) (58) (59) (60) (61) (62) in, This is a small-signal admittance model for a permanent magnet direct-drive fan. Here is the filter output impedance matrix in the dq coordinate system. DC side voltage Let be the transfer function between the modulation signal and the AC current of the grid-side inverter in the system coordinate system. Let be the transfer function between the modulation signal and the DC-side voltage in the system coordinate system. Let be the transfer function between the AC side voltage and the DC side voltage of the grid-side inverter in the system coordinate system. Let be the transfer function between the AC side current and DC side voltage of the grid-side inverter in the system coordinate system. It is the identity matrix. Let be the transfer function between the modulation signal and the AC side voltage of the grid-side inverter in the system coordinate system. This is the transfer function between the modulation signal of the generator-side converter and the AC current measurement. The transfer function for the decoupling stage of the generator-side converter control. The transfer function for the inner loop controller of the generator-side converter current. For the transfer function of the turbine-side converter speed loop controller, Let be the transfer function between the rotor electrical angle and the mechanical angular velocity. For mechanical system transfer function, For the Laplace operator, Synchronization and flux transfer functions, This is the transfer function between the AC current and DC voltage of the machine-side converter. This is the stator impedance matrix of the synchronous machine. The transfer function between rotor electrical angle and AC current measured by the machine-side converter. The transfer function between the DC-side voltage and the AC voltage measured at the machine-side converter. This is the transfer function between the DC-side current and the DC-side voltage. This is the transfer function between the AC current and the DC current of the machine-side converter. This is the transfer function between the modulation signal of the machine-side converter and the DC-side current. This is the transfer function between the AC current and the DC current of the grid-side inverter. This is the transfer function between the grid-side inverter modulation signal and the DC-side current. This is the transfer function for the grid-side inverter current inner loop controller. For the transfer function of the outer loop controller of the grid-side inverter voltage, Let be the transfer function between the grid-side inverter modulation signal and the DC-side voltage in the system coordinate system. The transfer function for the decoupling stage of the grid-side inverter controller. Let be the transfer function between the difference between the current in the grid-side inverter system coordinate system and the current in the controller coordinate system, and the voltage in the system coordinate system. It is the transfer function between the difference between the modulation signal in the grid-side inverter system coordinate system and the modulation signal in the controller coordinate system, and the voltage in the system coordinate system.

[0053] Building on the Siumlink platform Figure 1 The simulation model of the direct-drive fan is shown in Table 1.

[0054] Table 1 Fan Parameters

[0055] The calculation results of the direct-drive fan impedance model derived in this invention are compared with the Siumlink frequency sweep measurement results, for example... Figure 7 As shown. To verify whether the impact of the mechanical system on the accuracy of the calculation results was considered during the modeling process, Figure 7 The calculation results of the fan impedance without considering the mechanical system are listed side by side with the calculation results of the fan impedance considering the mechanical system.

[0056] Because direct-drive fans operate at unity power factor, their dq-axis impedance coupling is weak, resulting in extremely small dq-coupling impedance. Therefore, the calculation and measurement errors are negligible. Figure 7 It can be seen that the calculated and measured values ​​of the admittance model of the direct-drive fan considering the mechanical system established in this invention are consistent, which demonstrates the accuracy of the model established in this invention. Furthermore, the admittance model of the direct-drive fan considering the mechanical system proposed in this invention corrects the problem of inaccurate d-axis impedance in the low-frequency range of the admittance model of the direct-drive fan not considering the mechanical system. When applying impedance analysis for stability assessment, the admittance model proposed in this invention will be more accurate.

[0057] This invention proposes a modeling method for permanent magnet direct-drive wind turbines that considers the mechanical system. Compared to traditional admittance models for direct-drive wind turbines that do not consider the mechanical system, the proposed AC / DC hybrid admittance model simultaneously considers the influence of the synchronous generator, mechanical system, machine-side inverter, grid-side controller, and AC / DC interconnection in the permanent magnet direct-drive wind turbine. This model can more accurately reflect the dynamic characteristics of the system and improve the reliability of stability assessment for grid-connected direct-drive wind turbine systems.

[0058] like Figure 8 As shown, this embodiment of the invention provides a modeling system for permanent magnet direct-drive fans that considers mechanical systems, including: Mechanical system creation module: used to create the transfer function of the mechanical system; Electrical system establishment module: used to establish the transfer functions of the electrical system, which include the transfer functions of the permanent magnet synchronous generator stator circuit, the generator-side converter, the grid-side inverter, and the transfer functions of the AC / DC connection between the generator side and the grid side; Wind turbine model building module: used to build a small-signal admittance model of a permanent magnet direct-drive wind turbine based on the mechanical system transfer function and the electrical system transfer function.

[0059] A computer device is provided according to an embodiment of the present invention. This computer device includes a processor, a memory, and a computer program stored in the memory and executable on the processor. When the processor executes the computer program, it implements the steps in the various method embodiments described above. Alternatively, when the processor executes the computer program, it implements the functions of each module / unit in the various device embodiments described above.

[0060] The computer program can be divided into one or more modules / units, which are stored in the memory and executed by the processor to complete the present invention.

[0061] The computer device may be a desktop computer, laptop, handheld computer, or cloud server, etc. The computer device may include, but is not limited to, a processor and memory.

[0062] The processor may be a central processing unit (CPU), or other general-purpose processors, digital signal processors (DSPs), application-specific integrated circuits (ASICs), field-programmable gate arrays (FPGAs), or other programmable logic devices, discrete gate or transistor logic devices, discrete hardware components, etc.

[0063] The memory can be used to store the computer program and / or module, and the processor implements various functions of the computer device by running or executing the computer program and / or module stored in the memory, and by calling the data stored in the memory.

[0064] If the modules / units integrated into the computer device are implemented as software functional units and sold or used as independent products, they can be stored in a computer-readable storage medium. Based on this understanding, all or part of the processes in the methods of the above embodiments can also be implemented by a computer program instructing related hardware. The computer program can be stored in a computer-readable storage medium, and when executed by a processor, it can implement the steps of the various method embodiments described above. The computer program includes computer program code, which can be in the form of source code, object code, executable files, or certain intermediate forms. The computer-readable medium can include: any entity or device capable of carrying the computer program code, recording media, USB flash drives, portable hard drives, magnetic disks, optical disks, computer memory, read-only memory, random access memory, electrical carrier signals, telecommunication signals, and software distribution media, etc. It should be noted that the content included in the computer-readable medium can be appropriately added or removed according to the requirements of legislation and patent practice in the jurisdiction. For example, in some jurisdictions, according to legislation and patent practice, computer-readable media do not include electrical carrier signals and telecommunication signals.

[0065] The foregoing has shown and described the basic principles, main features, and advantages of the present invention. It will be apparent to those skilled in the art that the invention is not limited to the details of the exemplary embodiments described above, and that the invention can be implemented in other specific forms without departing from its spirit or essential characteristics. Therefore, the embodiments should be considered illustrative and non-limiting in all respects, and the scope of the invention is defined by the appended claims rather than the foregoing description. Thus, all variations falling within the meaning and scope of equivalents of the claims are intended to be included within the scope of the invention. No reference numerals in the claims should be construed as limiting the scope of the claims.

[0066] Furthermore, it should be understood that although this specification describes embodiments, not every embodiment contains only one independent technical solution. This narrative style is merely for clarity. Those skilled in the art should consider the specification as a whole, and the technical solutions in each embodiment can be appropriately combined to form other embodiments that can be understood by those skilled in the art. The above content is only for illustrating the technical concept of the present invention and should not be construed as limiting the scope of protection of the present invention. Any modifications made based on the technical concept proposed in this invention shall fall within the scope of protection of the claims of this invention.

Claims

1. A modeling method for a permanent magnet direct-drive fan considering a mechanical system, characterized in that, include: Establish the transfer function of the mechanical system; Establish the transfer function of the electrical system, which includes the transfer function of the permanent magnet synchronous generator stator circuit, the transfer function of the generator-side converter, the transfer function of the grid-side inverter, and the transfer function of the AC / DC connection between the generator side and the grid side; A small-signal admittance model for a permanent magnet direct-drive fan is established based on the transfer functions of the mechanical and electrical systems.

2. The modeling method for a permanent magnet direct-drive fan considering a mechanical system according to claim 1, characterized in that, The small-signal admittance model of the permanent magnet direct-drive fan is as follows: in, This is a small-signal admittance model for a permanent magnet direct-drive fan. Let be the filter output impedance matrix in the dq coordinate system. DC side voltage Let be the transfer function between the modulation signal and the AC current of the grid-side inverter in the system coordinate system. Let be the transfer function between the modulation signal and the DC-side voltage in the system coordinate system. Let be the transfer function between the AC side voltage and the DC side voltage of the grid-side inverter in the system coordinate system. Let be the transfer function between the AC side current and DC side voltage of the grid-side inverter in the system coordinate system. It is the identity matrix. Let be the transfer function between the modulation signal and the AC side voltage of the grid-side inverter in the system coordinate system. This is the transfer function between the modulation signal of the generator-side converter and the AC current measurement. The transfer function for the decoupling stage of the generator-side converter control. The transfer function for the inner loop controller of the generator-side converter current. For the transfer function of the turbine-side converter speed loop controller, Let be the transfer function between the rotor electrical angle and the mechanical angular velocity. For mechanical system transfer function, For the Laplace operator, Synchronization and flux transfer functions, This is the transfer function between the AC current and DC voltage of the machine-side converter. This is the stator impedance matrix of the synchronous machine. The transfer function between rotor electrical angle and AC current measured by the machine-side converter. The transfer function between the DC-side voltage and the AC voltage measured at the machine-side converter. This is the transfer function between the DC-side current and the DC-side voltage. This is the transfer function between the AC current and the DC current of the machine-side converter. This is the transfer function between the modulation signal of the machine-side converter and the DC-side current. This is the transfer function between the AC current and the DC current of the grid-side inverter. This is the transfer function between the grid-side inverter modulation signal and the DC-side current. This is the transfer function for the grid-side inverter current inner loop controller. For the transfer function of the outer loop controller of the grid-side inverter voltage, Let be the transfer function between the grid-side inverter modulation signal and the DC-side voltage in the system coordinate system. The transfer function for the decoupling stage of the grid-side inverter controller. Let be the transfer function between the difference between the current in the grid-side inverter system coordinate system and the current in the controller coordinate system, and the voltage in the system coordinate system. It is the transfer function between the difference between the modulation signal in the grid-side inverter system coordinate system and the modulation signal in the controller coordinate system, and the voltage in the system coordinate system.

3. The modeling method for a permanent magnet direct-drive fan considering a mechanical system according to claim 1, characterized in that, The transfer function of the mechanical system is: in, The number of pole pairs of the synchronous machine rotor. For rotor flux linkage, For the Laplace operator, This represents the relationship between the rotor's mechanical angular velocity and electromagnetic torque.

4. The modeling method for a permanent magnet direct-drive fan considering a mechanical system according to claim 1, characterized in that, The transfer function of the stator circuit of the permanent magnet synchronous generator is: in, R s For the stator resistance of the synchronous machine, L d For the stator of the synchronous machine d Shaft inductor, L q For the stator of the synchronous machine q Shaft inductor, I Gd For the stator of the synchronous machine d Steady-state value of shaft current I Gq For the stator of the synchronous machine q Steady-state value of shaft current Synchronization and flux transfer functions, For the Laplace operator, For rotor flux linkage, The transfer function between rotor electrical angle and AC current measured by the machine-side converter. This is the stator impedance matrix of the synchronous machine.

5. The modeling method for a permanent magnet direct-drive fan considering a mechanical system according to claim 1, characterized in that, The transfer function of the machine-side converter is: in, For the transfer function of the machine-side converter, For machine-side converter d Steady-state value of the axis modulation signal For machine-side converter q Steady-state value of the axis modulation signal.

6. The modeling method for a permanent magnet direct-drive fan considering a mechanical system according to claim 1, characterized in that, The establishment of the grid-side inverter transfer function involves sequentially establishing the filter electrical loop transfer function, the grid-side inverter transfer function in the controller dq coordinate system and the system dq coordinate system, the voltage outer loop controller transfer function, and the current inner loop controller transfer function.

7. A modeling system for permanent magnet direct-drive fans considering mechanical systems, characterized in that, include: Mechanical system creation module: used to create the transfer function of the mechanical system; Electrical system establishment module: used to establish the transfer functions of the electrical system, which include the transfer functions of the permanent magnet synchronous generator stator circuit, the generator-side converter, the grid-side inverter, and the transfer functions of the AC / DC connection between the generator side and the grid side; Wind turbine model building module: used to build a small-signal admittance model of a permanent magnet direct-drive wind turbine based on the mechanical system transfer function and the electrical system transfer function.

8. A computer device, comprising a memory, a processor, and a computer program stored in the memory, characterized in that, The processor executes the computer program to implement the steps of the modeling method for a permanent magnet direct-drive fan considering a mechanical system as described in any one of claims 1-6.

9. A computer-readable storage medium having a computer program stored thereon, characterized in that, When executed by a processor, the computer program implements the steps of the modeling method for a permanent magnet direct-drive fan considering a mechanical system as described in any one of claims 1-6.

10. A computer program product, comprising a computer program, characterized in that, When executed by a processor, the computer program implements the steps of the modeling method for a permanent magnet direct-drive fan considering a mechanical system as described in any one of claims 1-6.

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