Offshore direct-current wind turbine generator modeling method based on LLC resonant converter

Abstract

The invention discloses an offshore direct-current wind turbine generator modeling method based on an LLC resonant converter. The method comprises the following steps: establishing an offshore direct-current wind turbine generator pneumatic mechanical model; the method comprises the following steps: establishing an offshore direct current wind turbine generator converter model which comprises a DC / DC converter model which adopts an LLC resonant converter; establishing a seaborne direct current wind turbine generator controller model; and establishing an external DC power grid model. And the offshore direct-current wind turbine generator controller model transmits a control signal to the offshore direct-current wind turbine generator pneumatic mechanical model and the offshore direct-current wind turbine generator generator converter model. According to the method, the electromagnetic transient simulation model of the offshore direct-current wind turbine generator based on the LLC resonant converter, which reflects actual operation characteristics, can be established, and a reliable model basis is provided for simulation calculation of an offshore wind power access power grid.

Description

Technical Field

[0001] The invention belongs to the technical field of wind power generation, and in particular to a modeling method of an offshore direct current wind turbine set based on an LLC resonant converter. Background Art

[0002] With the proposal of the "carbon peak and carbon neutrality" goals, the low-carbon transformation of energy will be significantly accelerated. Among them, wind power, as one of the most mature forms of renewable energy generation, has been rapidly developed and widely used worldwide in recent years. At present, offshore wind turbines are developing in the direction of super-large-scale, the blades of wind turbines are constantly increasing, the intervals between wind turbines are constantly increasing, and the cable length of the power collection network is also increasing. Under the traditional AC collection method, the effect of the submarine cable on the ground capacitance has caused the reactive charging current and overvoltage problems in the wind farm network to become increasingly serious. The above problems can be solved by establishing a full DC wind farm that adopts DC collection and transmission grid connection. Compared with AC collection, the DC collection method not only solves the above problems, but also has obvious advantages in equipment volume and quality, system loss and construction cost because it does not require bulky and bulky industrial frequency AC transformers.

[0003] LLC resonant converter can be selected as the DC / DC converter topology of offshore DC wind turbines due to its advantages of isolating fault current, low switching loss, low cost and small size. At present, there is a lack of research on offshore DC wind turbines based on LLC resonant converters at home and abroad, so there is an urgent need for a model that can be used to study the characteristics of offshore DC wind turbines based on LLC resonant converters. Summary of the invention

[0004] The purpose of the present invention is to provide a modeling method for an offshore DC wind turbine model based on an LLC resonant converter to address the deficiencies of the above-mentioned prior art, and to complete the modeling of an offshore DC wind turbine aerodynamic mechanical model, an offshore DC wind turbine generator converter model, an offshore DC wind turbine controller model, and an external DC power grid model. The modeling method proposed in the present invention provides a model basis for studying the dynamic characteristics and effectiveness of the control strategy of a DC wind turbine based on an LLC resonant converter.

[0005] The technical solution to achieve the purpose of the present invention is: a modeling method for an offshore DC wind turbine based on an LLC resonant converter, the method comprising the following steps:

[0006] Step 1, establishing an aerodynamic mechanical model of an offshore DC wind turbine;

[0007] Step 2, establishing a generator converter model of an offshore direct current wind turbine, including a DC / DC converter model; the DC / DC converter model adopts an LLC resonant converter;

[0008] Step 3, establishing an offshore DC wind turbine controller model;

[0009] Step 4, establishing an external DC grid model;

[0010] The offshore DC wind turbine controller model transmits control signals to the offshore DC wind turbine aerodynamic mechanical model and the offshore DC wind turbine generator converter model.

[0011] Furthermore, in step 1, an aerodynamic mechanical model of an offshore DC wind turbine is established based on power system simulation software, and the aerodynamic mechanical model of an offshore DC wind turbine includes: a wind speed model, a wind turbine model, a transmission chain model and a pitch model.

[0012] Furthermore, in step 2, an offshore DC wind turbine generator converter model is established based on power system simulation software, and the offshore DC wind turbine generator converter model also includes: a generator model and an AC / DC converter model.

[0013] Furthermore, the generator model adopts a permanent magnet synchronous motor, and the AC / DC converter model adopts a three-phase controlled rectifier circuit.

[0014] Furthermore, in step 3, an offshore DC wind turbine controller model is established based on power system simulation software, and the offshore DC wind turbine controller model includes: a pitch angle controller model, an AC / DC converter controller model and a DC / DC converter controller model.

[0015] Furthermore, in step 4, an external DC power grid model is established based on power system simulation software, and the external DC power grid model is represented in the form of a DC voltage source connected in series with a resistor.

[0016] Furthermore, the offshore DC wind turbine controller model transmits control signals to the offshore DC wind turbine aerodynamic mechanical model and the offshore DC wind turbine generator converter model, specifically including:

[0017] Acquire the rotation speed of the permanent magnet synchronous generator and generate a first control signal;

[0018] Controlling the wind turbine pitch angle according to the first control signal, thereby controlling the speed of the permanent magnet synchronous generator;

[0019] Acquire the speed, stator current and stator voltage of the permanent magnet synchronous generator and generate a second control signal;

[0020] Controlling the AC / DC converter according to the second control signal, thereby controlling the output power of the permanent magnet synchronous generator;

[0021] Acquire the input side voltage and input side current of the DC / DC converter and generate a third control signal;

[0022] Controlling the DC / DC converter according to the third control signal, thereby controlling the input side voltage of the DC / DC converter;

[0023] The stable operation of the offshore DC wind turbine is ensured by controlling the pitch angle, output power and input voltage of the DC / DC converter.

[0024] Furthermore, the obtaining of the rotation speed of the permanent magnet synchronous generator and generating the first control signal specifically includes:

[0025] The rotation speed of the permanent magnet synchronous motor is obtained, and the difference between the maximum allowable rotation speed of the permanent magnet synchronous motor and the rotation speed is sent to the PI regulator to obtain a first control signal.

[0026] Further, the obtaining of the rotation speed, stator current and stator voltage of the permanent magnet synchronous generator and generating the second control signal specifically includes:

[0027] Obtain the speed of the permanent magnet synchronous motor and calculate the electromagnetic power reference value through the maximum wind energy tracking algorithm;

[0028] Obtain the stator current of the permanent magnet synchronous motor, and obtain the d-axis current and q-axis current through Clark-Park transformation;

[0029] Obtain the stator voltage of the permanent magnet synchronous motor, and obtain the d-axis voltage and q-axis voltage through Clark-Park transformation;

[0030] Dividing the electromagnetic power reference value by the rotation speed to obtain an electromagnetic torque reference value;

[0031] Sending the electromagnetic torque reference value to a conversion link to obtain a q-axis current reference value;

[0032] The q-axis current reference value is subtracted from the q-axis current and then sent to the current loop PI regulator to obtain the q-axis voltage reference value before compensation of the permanent magnet synchronous motor;

[0033] The d-axis current reference value is subtracted from the d-axis current and then sent to the current loop PI regulator to obtain the d-axis voltage reference value before compensation of the permanent magnet synchronous motor;

[0034] The q-axis voltage reference value before compensation is added to the q-axis voltage compensation value to obtain the q-axis reference voltage;

[0035] The d-axis voltage reference value before compensation is added to the d-axis voltage compensation value to obtain the d-axis reference voltage;

[0036] The d-axis voltage reference value and the q-axis voltage reference value are transformed by inverse Park transformation and SVPWM algorithm to obtain a second control signal.

[0037] Further, the obtaining of the input side voltage and input side current of the DC / DC converter and generating the third control signal specifically includes:

[0038] Obtain the input voltage of the DC / DC converter, make a difference between the set DC voltage reference value and the input voltage, and send it to the PI regulator to obtain the input current reference value;

[0039] The input current of the DC / DC converter is obtained, and the difference between the input current reference value and the input current is sent to the PI regulator to obtain the switching frequency compensation value of the DC / DC converter;

[0040] Subtracting the switching frequency reference value from the switching frequency compensation value to obtain a switching frequency reference value of the DC / DC converter;

[0041] The switching frequency reference value is processed by a PWM algorithm to obtain a third control signal.

[0042] Compared with the prior art, the present invention has the following significant advantages:

[0043] 1) The established offshore DC wind turbine model based on LLC resonant converter can be used for load, power curve, power quality, power control, grid adaptability and low voltage ride-through performance analysis and evaluation, which provides an important technical means for the stability analysis of offshore DC wind turbines connected to the grid based on LLC resonant converter.

[0044] 2) It is versatile and can be easily extended to various power generation systems that interface with the power grid through power electronic devices, as well as new power electronic interface new energy power generation systems that are rapidly developing and emerging, and has broad application prospects.

[0045] The present invention is further described in detail below in conjunction with the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0046] Figure 1 It is a schematic diagram of the overall structure of the grid access analysis model of an offshore DC wind turbine generator set based on LLC resonant converter according to the present invention.

[0047] Figure 2 It is a schematic diagram of the structure of a generator converter model in an embodiment.

[0048] Figure 3 Schematic diagram of a pitch angle controller model in an embodiment.

[0049] Figure 4 FIG. 4 is a schematic diagram of an AC / DC converter controller model in an embodiment.

[0050] Figure 5 FIG. 4 is a schematic diagram of a DC / DC converter controller model in an embodiment.

[0051] Figure 6 The present invention is a curve diagram of various variables of an offshore DC wind turbine under wind speed fluctuation in an embodiment, wherein Figures (a) to (h) are simulation curve diagrams of wind speed, generator mechanical angular velocity, generator stator current, generator electromagnetic power, DC / DC converter input voltage, DC / DC converter output voltage, DC / DC converter output current and DC / DC converter output power, respectively.

[0052] Figure 7 The present invention is a curve diagram of various variables of an offshore DC wind turbine under the condition of DC grid voltage fluctuation in an embodiment, wherein Figures (a) to (g) are simulation curve diagrams of generator mechanical angular velocity, generator stator current, generator electromagnetic power, DC / DC converter input voltage, DC / DC converter output voltage, DC / DC converter output current and DC / DC converter output power, respectively.

[0053] Figure 8 The present invention is a curve diagram of various variables of an offshore DC wind turbine in the case of a collection line short circuit fault in an embodiment, wherein Figures (a) to (h) are simulation curve diagrams of the generator mechanical angular velocity, the generator stator current, the generator electromagnetic power, the DC / DC converter input voltage, the DC / DC converter output voltage, the DC / DC converter output current and the DC / DC converter output power, respectively. DETAILED DESCRIPTION

[0054] In order to make the purpose, technical solution and advantages of the present application more clearly understood, the present application is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present application and are not used to limit the present application.

[0055] It should be noted that if there are descriptions involving "first", "second", etc. in the embodiments of the present invention, the descriptions of "first", "second", etc. are only used for descriptive purposes and cannot be understood as indicating or implying their relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined as "first" and "second" may explicitly or implicitly include at least one of the features. In addition, the technical solutions between the various embodiments can be combined with each other, but they must be based on the ability of ordinary technicians in the field to implement them. When the combination of technical solutions is contradictory or cannot be implemented, it should be deemed that such a combination of technical solutions does not exist and is not within the scope of protection required by the present invention.

[0056] In one embodiment, in combination Figure 1 , provides a modeling method for an offshore DC wind turbine based on an LLC resonant converter, the method comprising the following steps:

[0057] Step 1, establishing an aerodynamic mechanical model of an offshore DC wind turbine;

[0058] Step 2, establishing a generator converter model of an offshore direct current wind turbine, including a DC / DC converter model; the DC / DC converter model adopts an LLC resonant converter;

[0059] Step 3, establishing an offshore DC wind turbine controller model;

[0060] Step 4, establishing an external DC grid model;

[0061] The offshore DC wind turbine controller model transmits control signals to the offshore DC wind turbine aerodynamic mechanical model and the offshore DC wind turbine generator converter model.

[0062] Furthermore, in one of the embodiments, in step 1, an aerodynamic mechanical model of an offshore DC wind turbine is established based on power system simulation software, and the aerodynamic mechanical model of an offshore DC wind turbine includes: a wind speed model, a wind turbine model, a transmission chain model and a variable pitch model.

[0063] Here, in some embodiments, the wind speed model may use random wind or measured data, the wind turbine model may use a wind turbine model based on Betz theory, the transmission chain model may use a single mass block model, and the variable pitch model may use a first-order inertia link as a replacement.

[0064] The wind turbine model uses formula (1) to obtain:

[0065]

[0066] Where: P m is the mechanical power captured by the wind turbine, ρ is the air density, R is the rotor radius, v is the wind speed, C p is the wind energy utilization coefficient, β is the pitch angle, λ is the tip speed ratio, ω r is the angular velocity of the wind turbine.

[0067] The transmission chain model is obtained by formula (2):

[0068]

[0069] Where, J is the total moment of inertia of the wind turbine rotor and generator, P e is the electromagnetic power of the generator.

[0070] The variable pitch model is obtained by formula (3):

[0071]

[0072] In the formula, β * is the pitch angle reference value, T ris the inertia time constant of the pitch model.

[0073] Furthermore, in one of the embodiments, in step 2, an offshore DC wind turbine generator converter model is established based on power system simulation software, and the offshore DC wind turbine generator converter model also includes: a generator model and an AC / DC converter model.

[0074] Here, in some embodiments, Figure 2 As shown, the generator model adopts a permanent magnet synchronous machine (PMSG), and the AC / DC converter model adopts a three-phase controlled rectifier circuit.

[0075] Furthermore, in one of the embodiments, in step 3, an offshore DC wind turbine controller model is established based on power system simulation software, and the offshore DC wind turbine controller model includes: a pitch angle controller model, an AC / DC converter controller model and a DC / DC converter controller model.

[0076] Furthermore, in one of the embodiments, in step 4, an external DC grid model is established based on power system simulation software, and the external DC grid model is represented in the form of a DC voltage source connected in series with a resistor.

[0077] Further, in one of the embodiments, the offshore DC wind turbine controller model transmits control signals to the offshore DC wind turbine aeromechanical model and the offshore DC wind turbine generator converter model, specifically including:

[0078] Acquire the rotation speed of the permanent magnet synchronous generator and generate a first control signal;

[0079] Controlling the wind turbine pitch angle according to the first control signal, thereby controlling the speed of the permanent magnet synchronous generator;

[0080] Acquire the speed, stator current and stator voltage of the permanent magnet synchronous generator and generate a second control signal;

[0081] Controlling the AC / DC converter according to the second control signal, thereby controlling the output power of the permanent magnet synchronous generator;

[0082] Acquire the input side voltage and input side current of the DC / DC converter and generate a third control signal;

[0083] Controlling the DC / DC converter according to the third control signal, thereby controlling the input side voltage of the DC / DC converter;

[0084] The stable operation of the offshore DC wind turbine is ensured by controlling the pitch angle, output power and input voltage of the DC / DC converter.

[0085] Here, in some embodiments, the pitch angle controller is as follows: Figure 3 As shown, the pitch angle controller generates a first control signal by acquiring the speed of the permanent magnet synchronous motor, specifically including:

[0086] Set the maximum allowable speed of the permanent magnet synchronous motor ω rmax .

[0087] Get the speed ω of the permanent magnet synchronous motor r , the speed ω r and the maximum permissible speed ω rmax After the difference is taken, it is sent to the PI regulator, and the output of the PI regulator is the first control signal.

[0088] Here, in some embodiments, the AC / DC converter controller is as follows: Figure 4 As shown, the AC / DC converter controller obtains the speed, stator current and stator voltage of the permanent magnet synchronous motor and generates a second control signal, which specifically includes:

[0089] Get the speed ω of the permanent magnet synchronous motor r , the electromagnetic power reference value P is calculated by the Maximum Power Point Tracking (MPPT) algorithm ref .

[0090] The speed ω r Multiply by the number of pole pairs n of the permanent magnet synchronous motor p Get the electrical angular velocity ω e

[0091] Obtain the stator current of the permanent magnet synchronous motor and obtain the d-axis current i through Clark-Park transformation sd and q-axis current i sq .

[0092] Obtain the stator voltage of the permanent magnet synchronous motor and obtain the d-axis voltage u through Clark-Park transformation sd and q-axis voltage u sq .

[0093] The electromagnetic power reference value P ref Divide by the speed ω r , get the electromagnetic torque reference value T ref .

[0094] The electromagnetic torque reference value T ref Send it to the conversion link to get the q-axis current reference value

[0095] The conversion link is represented as where ψ f is the permanent magnet flux strength of permanent magnet synchronous motor.

[0096] Set the q-axis current reference value and q-axis current i sq After the difference is made, it is sent to the current loop PI regulator to obtain the q-axis voltage reference value before compensation of the permanent magnet synchronous motor

[0097] The q-axis voltage reference value before compensation and q-axis voltage compensation value Δu sq After summing, we get the q-axis voltage reference value

[0098] Among them, Δu sq =R s i sq +ω e (L d i sd +ψ f ).

[0099] Set the d-axis current reference value Set to zero, that is

[0100] Set the d-axis current reference value and d-axis current i sd After the difference is made, it is sent to the current loop PI regulator to obtain the d-axis voltage reference value before compensation of the permanent magnet synchronous motor

[0101] The d-axis voltage reference value before compensation and q-axis voltage compensation value Δu sd After summing, we get the d-axis voltage reference value

[0102] Where Δu sd =R s i sd -ω e L q i sq .

[0103] The d-axis voltage reference value and q-axis voltage reference value The second control signal is obtained through inverse Park transformation and SVPWM algorithm.

[0104] Specifically, the d-axis voltage reference value and q-axis voltage reference value After performing inverse Park transformation to obtain the voltage reference value in the αβ coordinate system, the second control signal is obtained through the Space Vector Pulse Width Modulation (SVPWM) algorithm.

[0105] Here, in some embodiments, the DC / DC converter controller is as follows: Figure 5 As shown, the DC / DC converter controller obtains the input voltage and input current of the DC / DC converter and generates a third control signal, specifically including:

[0106] Get the input voltage V of the DC / DC converter dc , set the DC voltage reference value V dcref With input voltage V dc After the difference is made, it is sent to the PI regulator to obtain the input current reference value

[0107] Get the input current i of the DC / DC converter in , the input current reference value With input current i in After taking the difference, it is sent to the PI regulator to obtain the switching frequency compensation value Δf of the DC / DC converter.

[0108] Set the switching frequency reference value f * After subtracting the switching frequency compensation value Δf, the switching frequency reference value f of the DC / DC converter is obtained. s .

[0109] Set the switching frequency reference value f s The third control signal is obtained through a PWM algorithm.

[0110] In one embodiment, a modeling system for an offshore DC wind turbine based on an LLC resonant converter is provided, the system comprising:

[0111] The first module is used to establish an aerodynamic mechanical model of an offshore DC wind turbine;

[0112] The second module is used to establish a generator converter model of an offshore DC wind turbine, including a DC / DC converter model; the DC / DC converter model adopts an LLC resonant converter;

[0113] The third module is used to establish the controller model of the offshore DC wind turbine;

[0114] The fourth module is used to establish an external DC grid model;

[0115] The offshore DC wind turbine controller model transmits control signals to the offshore DC wind turbine aerodynamic mechanical model and the offshore DC wind turbine generator converter model.

[0116] For the specific limitations of the offshore DC wind turbine modeling system based on LLC resonant converter, please refer to the limitations of the offshore DC wind turbine modeling method based on LLC resonant converter mentioned above, which will not be repeated here. Each module in the above-mentioned offshore DC wind turbine modeling system based on LLC resonant converter can be implemented in whole or in part through software, hardware and a combination thereof. The above-mentioned modules can be embedded in or independent of the processor in the computer device in the form of hardware, or can be stored in the memory of the computer device in the form of software, so that the processor can call and execute the operations corresponding to the above modules.

[0117] In one embodiment, a computer device is provided, 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 following is achieved:

[0118] Step 1, establishing an aerodynamic mechanical model of an offshore DC wind turbine;

[0119] Step 2, establishing a generator converter model of an offshore direct current wind turbine, including a DC / DC converter model; the DC / DC converter model adopts an LLC resonant converter;

[0120] Step 3, establishing an offshore DC wind turbine controller model;

[0121] Step 4, establishing an external DC grid model;

[0122] The offshore DC wind turbine controller model transmits control signals to the offshore DC wind turbine aerodynamic mechanical model and the offshore DC wind turbine generator converter model.

[0123] For the specific limitations of each step, please refer to the limitations of the modeling method of offshore DC wind turbines based on LLC resonant converters mentioned above, which will not be repeated here.

[0124] In one embodiment, a computer-readable storage medium is provided, on which a computer program is stored, and when the computer program is executed by a processor, the computer program implements:

[0125] Step 1, establishing an aerodynamic mechanical model of an offshore DC wind turbine;

[0126] Step 2, establishing a generator converter model of an offshore direct current wind turbine, including a DC / DC converter model; the DC / DC converter model adopts an LLC resonant converter;

[0127] Step 3, establishing an offshore DC wind turbine controller model;

[0128] Step 4, establishing an external DC grid model;

[0129] The offshore DC wind turbine controller model transmits control signals to the offshore DC wind turbine aerodynamic mechanical model and the offshore DC wind turbine generator converter model.

[0130] For the specific limitations of each step, please refer to the limitations of the modeling method of offshore DC wind turbines based on LLC resonant converters mentioned above, which will not be repeated here.

[0131] As a specific example, in one of the embodiments, the present invention is further verified and explained.

[0132] The offshore DC wind turbine model based on LLC resonant converter established by the method of the present invention is verified under the conditions of wind speed fluctuation and DC voltage fluctuation. Figure 6 It can be seen that when the wind speed increases, the fan adjusts the speed to achieve maximum power tracking, the fan output power increases, and the DC bus voltage is well controlled and always maintained near the rated value; Figure 7 It can be seen that when the DC collection network voltage fluctuates slightly, the offshore DC wind turbine model proposed in the present invention can operate stably, thereby proving the effectiveness and practicality of the modeling method proposed in the present invention.

[0133] The above shows and describes the basic principles, main features and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited by the above embodiments, and the above embodiments and descriptions are only for explaining the principles of the present invention. Without departing from the spirit and scope of the present invention, any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. A modeling method for an offshore DC wind turbine based on LLC resonant converter, characterized in that: The method comprises the following steps: Step 1, establishing an aerodynamic mechanical model of an offshore DC wind turbine; Step 2, establishing a generator converter model of an offshore direct current wind turbine, including a DC / DC converter model; the DC / DC converter model adopts an LLC resonant converter; Step 3, establishing an offshore DC wind turbine controller model; Step 4, establishing an external DC grid model; The offshore DC wind turbine controller model transmits control signals to the offshore DC wind turbine aerodynamic mechanical model and the offshore DC wind turbine generator converter model.

2. The modeling method of an offshore DC wind turbine based on LLC resonant converter according to claim 1 is characterized in that: In step 1, an aerodynamic mechanical model of an offshore DC wind turbine is established based on power system simulation software, wherein the aerodynamic mechanical model of an offshore DC wind turbine includes: a wind speed model, a wind turbine model, a transmission chain model and a pitch model.

3. The modeling method of an offshore DC wind turbine based on LLC resonant converter according to claim 1 is characterized in that: In step 2, a generator converter model of an offshore DC wind turbine is established based on power system simulation software, wherein the generator converter model of an offshore DC wind turbine also includes a generator model and an AC / DC converter model.

4. The modeling method of an offshore DC wind turbine based on LLC resonant converter according to claim 1 is characterized in that: The generator model adopts a permanent magnet synchronous motor, and the AC / DC converter model adopts a three-phase controllable rectifier circuit.

5. The modeling method of an offshore DC wind turbine based on LLC resonant converter according to claim 1, characterized in that: In step 3, an offshore DC wind turbine controller model is established based on power system simulation software, and the offshore DC wind turbine controller model includes: a pitch angle controller model, an AC / DC converter controller model and a DC / DC converter controller model.

6. The modeling method of an offshore DC wind turbine based on LLC resonant converter according to claim 1, characterized in that: In step 4, an external DC power grid model is established based on power system simulation software, and the external DC power grid model is represented in the form of a DC voltage source connected in series with a resistor.

7. The offshore DC wind turbine modeling method based on LLC resonant converter according to any one of claims 1 to 6, characterized in that: The offshore DC wind turbine controller model transmits control signals to the offshore DC wind turbine aerodynamic mechanical model and the offshore DC wind turbine generator converter model, specifically including: Acquire the rotation speed of the permanent magnet synchronous generator and generate a first control signal; Controlling the wind turbine pitch angle according to the first control signal, thereby controlling the speed of the permanent magnet synchronous generator; Acquire the speed, stator current and stator voltage of the permanent magnet synchronous generator and generate a second control signal; Controlling the AC / DC converter according to the second control signal, thereby controlling the output power of the permanent magnet synchronous generator; Acquire the input side voltage and input side current of the DC / DC converter and generate a third control signal; Controlling the DC / DC converter according to the third control signal, thereby controlling the input side voltage of the DC / DC converter; The stable operation of the offshore DC wind turbine is ensured by controlling the pitch angle, output power and input voltage of the DC / DC converter.

8. The modeling method of an offshore DC wind turbine based on LLC resonant converter according to claim 7 is characterized in that: The obtaining of the rotation speed of the permanent magnet synchronous generator and generating a first control signal specifically includes: The rotation speed of the permanent magnet synchronous motor is obtained, and the difference between the maximum allowable rotation speed of the permanent magnet synchronous motor and the rotation speed is sent to the PI regulator to obtain a first control signal.

9. The modeling method of an offshore DC wind turbine based on LLC resonant converter according to claim 7, characterized in that: The obtaining of the rotation speed, stator current and stator voltage of the permanent magnet synchronous generator and generating the second control signal specifically includes: Obtain the speed of the permanent magnet synchronous motor and calculate the electromagnetic power reference value through the maximum wind energy tracking algorithm; Obtain the stator current of the permanent magnet synchronous motor, and obtain the d-axis current and q-axis current through Clark-Park transformation; Obtain the stator voltage of the permanent magnet synchronous motor, and obtain the d-axis voltage and q-axis voltage through Clark-Park transformation; Dividing the electromagnetic power reference value by the rotation speed to obtain an electromagnetic torque reference value; Sending the electromagnetic torque reference value to a conversion link to obtain a q-axis current reference value; The q-axis current reference value is subtracted from the q-axis current and then sent to the current loop PI regulator to obtain the q-axis voltage reference value before compensation of the permanent magnet synchronous motor; The d-axis current reference value is subtracted from the d-axis current and then sent to the current loop PI regulator to obtain the d-axis voltage reference value before compensation of the permanent magnet synchronous motor; The q-axis voltage reference value before compensation is added to the q-axis voltage compensation value to obtain the q-axis reference voltage; The d-axis voltage reference value before compensation is added to the d-axis voltage compensation value to obtain the d-axis reference voltage; The d-axis voltage reference value and the q-axis voltage reference value are transformed by inverse Park transformation and SVPWM algorithm to obtain a second control signal.

10. The modeling method of an offshore DC wind turbine based on LLC resonant converter according to claim 7, characterized in that: The step of obtaining the input side voltage and the input side current of the DC / DC converter and generating a third control signal specifically includes: Obtain the input voltage of the DC / DC converter, make a difference between the set DC voltage reference value and the input voltage, and send it to the PI regulator to obtain the input current reference value; The input current of the DC / DC converter is obtained, and the difference between the input current reference value and the input current is sent to the PI regulator to obtain the switching frequency compensation value of the DC / DC converter; Subtracting the switching frequency reference value from the switching frequency compensation value to obtain a switching frequency reference value of the DC / DC converter; The switching frequency reference value is processed by a PWM algorithm to obtain a third control signal.

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