Marine direct-current wind turbine generator simplified model construction and application method based on LLC resonant converter

Abstract

The invention provides a simplified model construction and application method of an offshore direct current wind turbine generator based on an LLC resonant converter. The simplified model construction and application method comprises the following steps: establishing a pneumatic mechanical model and a generator model of the offshore direct current wind turbine generator; the method comprises the following steps: establishing a simplified model of an offshore DC wind turbine generator converter, including a DC / DC converter simplified model which is composed of a controlled current source and a controlled voltage source and has electromechanical transient characteristics of 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 converter simplified model. According to the method, the LLC resonant converter-based offshore direct-current wind turbine generator simplified model considering the complexity and the accuracy can be established, and a reliable model basis is provided for planning design and stable calculation of a large-scale offshore direct-current wind power access power grid.

Description

Technical Field

[0001] The present invention belongs to the technical field of wind power generation, and in particular to a simplified model construction of an offshore DC wind turbine generator set based on an LLC resonant converter and an application method thereof. Background Art

[0002] As one of the most mature forms of renewable energy generation, wind power has experienced rapid development and widespread application worldwide in recent years. Currently, offshore wind turbines are becoming increasingly larger, with increasing blade size, increasing spacing between turbines, and increasing the length of cables in power transmission networks. Under traditional AC transmission, the capacitance of submarine cables to the ground leads to increasingly severe problems with reactive charging currents and overvoltages within wind farms. These issues can be addressed by establishing fully DC wind farms that utilize DC generation, DC transmission, and DC transmission for grid connection. Compared to AC transmission, DC transmission not only solves these problems but also offers significant advantages in terms of equipment size and weight, system losses, and construction costs, as it eliminates the need for bulky and heavy AC transformers.

[0003] The LLC resonant converter offers advantages such as fault current isolation, low switching losses, low cost, and compact size, making it a promising DC / DC converter topology for offshore DC wind turbines. Currently, there is a lack of research on offshore DC wind turbines based on LLC resonant converters, both domestically and internationally. Especially with the large-scale development of offshore DC wind power, there is an urgent need to develop a simplified model of offshore DC wind turbines that balances accuracy and computational efficiency to facilitate the planning, design, and stability analysis of large-scale offshore DC wind power grid integration. Summary of the Invention

[0004] The purpose of the present invention is to address the deficiencies of the above-mentioned prior art and provide a simplified model construction method for offshore DC wind turbines based on LLC resonant converters, so as to provide a model basis for the planning, design and stability analysis of large-scale offshore DC wind power access to the power grid.

[0005] The technical solution for achieving the purpose of the present invention is as follows: On the one hand, a method for constructing a simplified model of an offshore DC wind turbine based on an LLC resonant converter is provided, the method comprising:

[0006] Step 1: Establish an aerodynamic mechanical model and a generator model of an offshore DC wind turbine;

[0007] Step 2: Establish a simplified converter model of an offshore DC wind turbine, including a simplified DC / DC converter model; the simplified DC / DC converter model consists of a controlled current source and a controlled voltage source, and has the electromechanical transient characteristics of an LLC resonant converter;

[0008] Step 3: Establish an offshore DC wind turbine controller model;

[0009] The offshore DC wind turbine controller model transmits control signals to the offshore DC wind turbine aeromechanical model and the offshore DC wind turbine converter simplified model to form a simplified offshore DC wind turbine model, thereby controlling the offshore DC wind turbine to operate stably.

[0010] Furthermore, the aerodynamic mechanical model of the offshore DC wind turbine in step 1 includes a wind speed model, a wind turbine model, a transmission chain model and a pitch model; and the generator model adopts a permanent magnet synchronous motor.

[0011] Furthermore, the simplified converter model of the offshore DC wind turbine also includes a simplified AC / DC converter model, which is composed of a controlled current source and a controlled voltage source.

[0012] Furthermore, the offshore DC wind turbine controller model includes a pitch angle control model, an AC / DC converter control model and a DC / DC converter control model.

[0013] Furthermore, the offshore DC wind turbine controller model transmits control signals to the offshore DC wind turbine aeromechanical model and the offshore DC wind turbine converter simplified model to form a simplified offshore DC wind turbine model, and controls the offshore DC wind turbine to operate stably, specifically including:

[0014] Acquire the rotation speed of the permanent magnet synchronous motor and generate a first control signal;

[0015] controlling the pitch angle of the wind turbine according to the first control signal, thereby controlling the speed of the permanent magnet synchronous motor;

[0016] Obtaining the speed, stator current, and stator voltage of the permanent magnet synchronous motor and generating a second control signal;

[0017] Acquire the electromagnetic power of the permanent magnet synchronous motor and the output side voltage of the AC / DC converter and generate a third control signal;

[0018] controlling the AC / DC converter according to the second control signal and the third control signal, thereby controlling the output power of the permanent magnet synchronous motor;

[0019] Acquire the input side voltage of the DC / DC converter and generate a fourth control signal;

[0020] Acquire the input side voltage and output power of the DC / DC converter and generate a fifth control signal;

[0021] Controlling the DC / DC converter according to the fourth control signal and the fifth control signal, thereby controlling the input side voltage of the DC / DC converter;

[0022] By controlling the pitch angle, output power and input voltage of the DC / DC converter of the offshore DC wind turbine, the stable operation of the offshore DC wind turbine is ensured.

[0023] Furthermore, the obtaining of the rotational speed of the permanent magnet synchronous motor and generating the first control signal specifically includes:

[0024] The speed of the permanent magnet synchronous motor is obtained, and the difference between the maximum allowable speed of the permanent magnet synchronous motor and the actual speed measurement value is sent to the PI regulator to obtain a first control signal.

[0025] Furthermore, the obtaining of the speed, stator current, and stator voltage of the permanent magnet synchronous motor and generating the second control signal specifically includes:

[0026] Obtain the speed of the permanent magnet synchronous motor and calculate the electromagnetic power reference value through the maximum wind energy tracking algorithm;

[0027] Obtain the stator current of the permanent magnet synchronous motor and obtain the d-axis current and q-axis current through Clark-Park transformation;

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

[0029] Dividing the electromagnetic power reference value by the rotational speed to obtain an electromagnetic torque reference value;

[0030] Sending the electromagnetic torque reference value to a conversion link to obtain a q-axis current reference value;

[0031] The difference between the q-axis current reference value and the q-axis current measured value is sent to the current loop PI regulator to obtain the q-axis voltage reference value before compensation of the permanent magnet synchronous motor;

[0032] The difference between the d-axis current reference value and the d-axis current measured value is sent to the current loop PI regulator to obtain the d-axis voltage reference value before compensation of the permanent magnet synchronous motor;

[0033] The q-axis voltage reference value before compensation is added to the q-axis voltage compensation value to obtain the q-axis voltage reference value;

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

[0035] The d-axis voltage reference value and the q-axis voltage reference value are subjected to inverse Park transformation to obtain a second control signal.

[0036] Furthermore, the acquiring of the electromagnetic power of the permanent magnet synchronous motor and the output voltage of the AC / DC converter and generating the third control signal specifically includes:

[0037] Acquire the electromagnetic power of the permanent magnet synchronous motor and the output side voltage of the AC / DC converter, and divide the electromagnetic power of the permanent magnet synchronous motor by the output side voltage of the AC / DC converter to obtain a third control signal;

[0038] The step of acquiring the input side voltage of the DC / DC converter and generating a fourth control signal specifically includes:

[0039] The input voltage of the DC / DC converter is obtained, and the difference between the set DC voltage reference value and the input voltage measured value is sent to the PI regulator to obtain a fourth control signal.

[0040] Furthermore, the obtaining of the input side voltage and output power of the DC / DC converter and generating the fifth control signal specifically includes:

[0041] The input side voltage and output power of the DC / DC converter are obtained, and the output power is divided by the input side voltage to obtain a fifth control signal.

[0042] In another aspect, a method for applying a simplified model of an offshore DC wind turbine is provided, the method comprising:

[0043] Establish an external DC grid model;

[0044] The external DC grid model is connected to a simplified model of an offshore DC wind turbine, thereby carrying out planning, design and stability analysis of large-scale offshore DC wind power grid access, including analysis of the electromechanical transient timescale stability of the power system.

[0045] Compared with the prior art, the present invention has the following significant advantages:

[0046] 1) The simplified model of offshore DC wind turbines based on LLC resonant converters can accurately reflect the electromechanical transient time scale characteristics of the model while reducing the complexity of the model, providing an important model basis for the planning, design and stability analysis of large-scale offshore DC wind power grid access.

[0047] 2) The proposed model simplification method is universal and can be easily extended to various power generation systems that interface with the power grid through power electronic devices, as well as the rapidly developing and emerging new energy power generation systems with power electronic interfaces. It has broad application prospects.

[0048] The present invention is further described in detail below with reference to the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0049] Figure 1 It is a schematic diagram of the overall structure of the grid access analysis model of the offshore DC wind turbine based on the LLC resonant converter of the present invention.

[0050] Figure 2It is a schematic diagram of a simplified converter model structure in an embodiment.

[0051] Figure 3 FIG. 1 is a schematic diagram of a pitch angle control model in an embodiment.

[0052] Figure 4 FIG. 1 is a schematic diagram of an AC / DC converter control model in an embodiment.

[0053] Figure 5 FIG. 1 is a schematic diagram of a DC / DC converter control model in an embodiment.

[0054] Figure 6 The figure is a graph of various variables of a simplified model and a detailed model of an offshore DC wind turbine under wind speed fluctuations in an embodiment, wherein Figures (a) to (f) are simulation graphs of wind speed, generator speed, DC / DC converter output voltage, DC / DC converter input voltage, DC / DC converter output current, and DC / DC converter output power, respectively.

[0055] Figure 7 The present invention is a graph of various variables of a simplified model and a detailed model of an offshore DC wind turbine under DC grid voltage fluctuations in an embodiment, wherein Figures (a) to (d) are simulation graphs of the DC / DC converter input voltage, DC / DC converter output current, DC / DC converter output voltage, and DC / DC converter output power, respectively. DETAILED DESCRIPTION

[0056] In order to make the purpose, technical solutions and advantages of this application more clear, the following further describes this application in detail with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain this application and are not intended to limit this application.

[0057] 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 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 such 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 this 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.

[0058] In one embodiment, combined Figure 1 , provides a simplified model construction method for an offshore DC wind turbine generator system based on an LLC resonant converter, the method comprising:

[0059] Step 1: Establish an aerodynamic mechanical model and a generator model of an offshore DC wind turbine;

[0060] Step 2: Establish a simplified converter model of an offshore DC wind turbine, including a simplified DC / DC converter model; the simplified DC / DC converter model consists of a controlled current source and a controlled voltage source, and has the electromechanical transient characteristics of an LLC resonant converter;

[0061] Step 3: Establish an offshore DC wind turbine controller model;

[0062] The offshore DC wind turbine controller model transmits control signals to the offshore DC wind turbine aeromechanical model and the offshore DC wind turbine converter simplified model to form a simplified offshore DC wind turbine model, thereby controlling the offshore DC wind turbine to operate stably.

[0063] Furthermore, in one embodiment, in step 1, an offshore DC wind turbine aerodynamic mechanical model and a generator model are established based on power system simulation software, and the offshore DC wind turbine aerodynamic mechanical model includes a wind speed model, a wind turbine model, a transmission chain model, and a pitch model.

[0064] Here, in some embodiments, the wind speed model may adopt random wind or measured data, the wind turbine model adopts a wind turbine model based on Betz theory, the transmission chain adopts a single mass block model, and the pitch model adopts a first-order inertia link representation.

[0065] The wind turbine model can be obtained by formula (1):

[0066]

[0067] 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.

[0068] The transmission chain model can be expressed by formula (2):

[0069]

[0070] Where, J is the total moment of inertia of the wind turbine rotor and generator, P e is the electromagnetic power of the generator.

[0071] The pitch model is expressed by formula (3):

[0072]

[0073] Where, β * is the pitch angle reference value, T r is the inertia time constant of the pitch model.

[0074] Furthermore, in one embodiment, the simplified converter model of the offshore DC wind turbine also includes a simplified AC / DC converter model.

[0075] Here, in some embodiments, as Figure 2 As shown, the generator model adopts a permanent magnet synchronous machine (PMSG). The simplified AC / DC converter model is a combination of a controlled current source and a controlled voltage source.

[0076] Furthermore, in one embodiment, the offshore DC wind turbine controller model includes a pitch angle control model, an AC / DC converter control model and a DC / DC converter control model.

[0077] Furthermore, in one embodiment, the offshore DC wind turbine controller model transmits control signals to the offshore DC wind turbine aeromechanical model and the offshore DC wind turbine converter simplified model to form a simplified offshore DC wind turbine model, and controls the offshore DC wind turbine to operate stably, specifically including:

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

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

[0080] Obtaining the speed, stator current, and stator voltage of the permanent magnet synchronous motor and generating a second control signal;

[0081] Acquire the electromagnetic power of the permanent magnet synchronous motor and the output side voltage of the AC / DC converter and generate a third control signal;

[0082] controlling the AC / DC converter according to the second control signal and the third control signal, thereby controlling the output power of the permanent magnet synchronous motor;

[0083] Acquire the input side voltage of the DC / DC converter and generate a fourth control signal;

[0084] Acquire the input side voltage and output power of the DC / DC converter and generate a fifth control signal;

[0085] Controlling the DC / DC converter according to the fourth control signal and the fifth control signal, thereby controlling the input side voltage of the DC / DC converter;

[0086] By controlling the pitch angle, output power and input voltage of the DC / DC converter of the offshore DC wind turbine, the stable operation of the offshore DC wind turbine is ensured.

[0087] 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:

[0088] Set the rated speed of the permanent magnet synchronous motor ω N ;

[0089] Get the speed ω of the permanent magnet synchronous motor r , the speed ω r With rated speed ω N After the difference is taken, it is sent to the PI regulator, and the output of the PI regulator is the first control signal.

[0090] 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, specifically including:

[0091] Get the speed ω of the permanent magnet synchronous motor r , the electromagnetic power reference value P is calculated by the Maximum Power Tracking (MPPT) algorithm ref ;

[0092] 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 ;

[0093] 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 ;

[0094] 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 ;

[0095] The electromagnetic power reference value P ref Divide by the speed ω r , get the electromagnetic torque reference value T ref ;

[0096] The electromagnetic torque reference value T ref Send it to the conversion link to get the q-axis current reference value

[0097] The conversion link is represented as where ψ f is the flux linkage strength of the permanent magnet synchronous motor.

[0098] Set the q-axis current reference value and q-axis current i sq The measured value is subtracted and sent to the current loop PI regulator to obtain the q-axis voltage reference value before compensation of the permanent magnet synchronous motor.

[0099] The front q-axis voltage reference value will be compensated and q-axis voltage compensation value Δu sq After summing, we get the q-axis voltage reference value

[0100] Where Δu sq =R s i sq +ω e (L d i sd +ψ f ).

[0101] Set the d-axis current reference value Set to zero, that is

[0102] Set the d-axis current reference value and d-axis current i sd The measured value is subtracted and sent to the current loop PI regulator to obtain the D-axis voltage reference value before compensation of the permanent magnet synchronous motor.

[0103] The front d-axis voltage reference value will be compensated and q-axis voltage compensation value Δu sd The d-axis voltage reference value is obtained after summing

[0104] Where Δu sd =R s i sd -ω e L q i sq .

[0105] Set the d-axis voltage reference value and q-axis voltage reference value The second control signal is obtained by inverse Park transformation.

[0106] Specifically, the d-axis voltage reference value and q-axis voltage reference value Perform an inverse Park transform to obtain a voltage reference value in the abc coordinate system as the second control signal.

[0107] The AC / DC converter controller calculates and generates a third control signal by acquiring the electromagnetic power of the permanent magnet synchronous generator and the voltage at the output side of the AC / DC converter, specifically including:

[0108] Get the electromagnetic power P of the permanent magnet synchronous motor e and the AC / DC converter output voltage V dc ;

[0109] The electromagnetic power P e Divide by the AC / DC converter output voltage V dc A third control signal is obtained.

[0110] Here, in some embodiments, the DC / DC converter controller is as follows: Figure 5 As shown, the DC / DC converter controller obtains the input side voltage of the DC / DC converter and generates a fourth control signal, specifically including:

[0111] Get the input side voltage V of the DC / DC converter dc , set the DC voltage reference value V dcref The measured value of the input voltage V dc After taking the difference, it is sent to the PI regulator to obtain the fourth control signal.

[0112] The DC / DC converter controller obtains the input side voltage and output power of the DC / DC converter and generates a fifth control signal, specifically including:

[0113] Get the input side voltage V of the DC / DC converter dc and output power P wt ;

[0114] The output power P wt Divide by the input voltage V dc A fifth control signal is obtained.

[0115] In one embodiment, a method for applying a simplified model of an offshore DC wind turbine is provided, the method comprising:

[0116] Establish an external DC grid model;

[0117] The external DC grid model is connected to a simplified model of an offshore DC wind turbine, thereby conducting planning, design, and stability analysis for large-scale offshore DC wind power grid access, including analysis of the electromechanical transient time-scale stability of the power system (conducting electromechanical transient simulation calculations of the power system to achieve improved computational efficiency while ensuring accuracy).

[0118] Here, in some embodiments, 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.

[0119] In one embodiment, a simplified model construction system for an offshore DC wind turbine generator system based on an LLC resonant converter is provided, the system comprising:

[0120] The first module is used to establish the aerodynamic mechanical model and generator model of the offshore DC wind turbine;

[0121] The second module is used to establish a simplified converter model for an offshore DC wind turbine, including a simplified DC / DC converter model; the simplified DC / DC converter model consists of a controlled current source and a controlled voltage source, and has the electromechanical transient characteristics of an LLC resonant converter;

[0122] The third module is used to establish the controller model of the offshore DC wind turbine;

[0123] The offshore DC wind turbine controller model transmits control signals to the offshore DC wind turbine aeromechanical model and the offshore DC wind turbine converter simplified model to form a simplified offshore DC wind turbine model, thereby controlling the offshore DC wind turbine to operate stably.

[0124] Regarding the specific limitations of the simplified model construction system for offshore DC wind turbines based on LLC resonant converters, please refer to the limitations of the simplified model construction method for offshore DC wind turbines based on LLC resonant converters above, which will not be repeated here. Each module in the simplified model construction system for offshore DC wind turbines based on LLC resonant converters can be implemented in whole or in part through software, hardware, and a combination thereof. Each of the above modules can be embedded in or independent of the processor in the computer device in hardware form, or can be stored in the memory of the computer device in software form, so that the processor can call and execute the operations corresponding to each of the above modules.

[0125] In one embodiment, a computer device is provided, comprising 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:

[0126] Step 1: Establish an aerodynamic mechanical model and a generator model of an offshore DC wind turbine;

[0127] Step 2: Establish a simplified converter model of an offshore DC wind turbine, including a simplified DC / DC converter model; the simplified DC / DC converter model consists of a controlled current source and a controlled voltage source, and has the electromechanical transient characteristics of an LLC resonant converter;

[0128] Step 3: Establish an offshore DC wind turbine controller 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 converter simplified model to form a simplified offshore DC wind turbine model, thereby controlling the offshore DC wind turbine to operate stably.

[0130] Step 4: Establish an external DC grid model;

[0131] The external DC grid model is connected to a simplified model of an offshore DC wind turbine, thereby carrying out planning, design and stability analysis of large-scale offshore DC wind power access to the grid, including analysis of the electromechanical transient time-scale stability of the power system.

[0132] For the specific limitations of each step, please refer to the limitations of the simplified model construction method for offshore DC wind turbines based on LLC resonant converters above, which will not be repeated here.

[0133] 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:

[0134] Step 1: Establish an aerodynamic mechanical model and a generator model of an offshore DC wind turbine;

[0135] Step 2: Establish a simplified converter model of an offshore DC wind turbine, including a simplified DC / DC converter model; the simplified DC / DC converter model consists of a controlled current source and a controlled voltage source, and has the electromechanical transient characteristics of an LLC resonant converter;

[0136] Step 3: Establish an offshore DC wind turbine controller model;

[0137] 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 converter simplified model to form a simplified offshore DC wind turbine model, thereby controlling the offshore DC wind turbine to operate stably.

[0138] Step 4: Establish an external DC grid model;

[0139] The external DC grid model is connected to a simplified model of an offshore DC wind turbine, thereby carrying out planning, design and stability analysis of large-scale offshore DC wind power access to the grid, including analysis of the electromechanical transient time-scale stability of the power system.

[0140] For the specific limitations of each step, please refer to the limitations of the simplified model construction method for offshore DC wind turbines based on LLC resonant converters above, which will not be repeated here.

[0141] As a specific example, the present invention is further verified and explained in one of the embodiments.

[0142] The simplified model of offshore DC wind turbine generator system based on LLC resonant converter established by the method of the present invention is compared with the detailed model to verify the model effect under the conditions of wind speed fluctuation and DC voltage fluctuation. Figure 6 It can be seen that when the wind speed increases, the wind turbine adjusts the speed to achieve maximum power tracking, the output power of the wind turbine increases, and the DC bus voltage is well controlled and always maintained near the rated value. The dynamics of each variable in the simplified model is basically consistent with the detailed model; Figure 7 It can be seen that when the DC network voltage fluctuates slightly, the simplified model of the offshore DC wind turbine proposed in this invention can operate stably, and the dynamics of the various variables in the simplified model are basically consistent with those in the detailed model. This demonstrates the effectiveness and practicality of the modeling method proposed in this invention.

[0143] 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 to the above embodiments. The above embodiments and descriptions are only illustrative of the principles of the present invention. Without departing from the spirit and scope of the present invention, any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention shall be included in the scope of protection of the present invention.

Claims

1. A simplified model construction method for an offshore DC wind turbine generator system based on an LLC resonant converter, characterized in that: The method comprises: Step 1: Establish an aerodynamic mechanical model and a generator model of an offshore DC wind turbine; Step 2: Establish a simplified converter model of an offshore DC wind turbine, including a simplified DC / DC converter model; the simplified DC / DC converter model consists of a controlled current source and a controlled voltage source, and has the electromechanical transient characteristics of an LLC resonant converter; Step 3: Establish an offshore DC wind turbine controller model; The offshore DC wind turbine controller model transmits control signals to the offshore DC wind turbine aeromechanical model and the offshore DC wind turbine converter simplified model to form a simplified offshore DC wind turbine model, thereby controlling the offshore DC wind turbine to operate stably.

2. The simplified model construction method of an offshore DC wind turbine generator system based on an LLC resonant converter according to claim 1, characterized in that: In step 1, the aerodynamic mechanical model of the offshore DC wind turbine includes a wind speed model, a wind turbine model, a transmission chain model, and a pitch model; the generator model adopts a permanent magnet synchronous motor.

3. The simplified model construction method of an offshore DC wind turbine generator system based on an LLC resonant converter according to claim 2, characterized in that: The simplified converter model of the offshore DC wind turbine also includes a simplified AC / DC converter model, which is composed of a controlled current source and a controlled voltage source.

4. The simplified model construction method of an offshore DC wind turbine generator system based on an LLC resonant converter according to claim 3, characterized in that: The offshore DC wind turbine controller model includes a pitch angle control model, an AC / DC converter control model and a DC / DC converter control model.

5. The simplified model construction method of an offshore DC wind turbine generator system based on an LLC resonant converter according to claim 4, 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 converter simplified model to form a simplified offshore DC wind turbine model, and controls the offshore DC wind turbine to operate stably, specifically including: Acquire the rotation speed of the permanent magnet synchronous motor and generate a first control signal; controlling the pitch angle of the wind turbine according to the first control signal, thereby controlling the speed of the permanent magnet synchronous motor; Obtaining the speed, stator current, and stator voltage of the permanent magnet synchronous motor and generating a second control signal; Acquire the electromagnetic power of the permanent magnet synchronous motor and the output side voltage of the AC / DC converter and generate a third control signal; controlling the AC / DC converter according to the second control signal and the third control signal, thereby controlling the output power of the permanent magnet synchronous motor; Acquire the input side voltage of the DC / DC converter and generate a fourth control signal; Acquire the input side voltage and output power of the DC / DC converter and generate a fifth control signal; Controlling the DC / DC converter according to the fourth control signal and the fifth control signal, thereby controlling the input side voltage of the DC / DC converter; By controlling the pitch angle, output power and input voltage of the DC / DC converter of the offshore DC wind turbine, the stable operation of the offshore DC wind turbine is ensured.

6. The simplified model construction method of an offshore DC wind turbine generator system based on an LLC resonant converter according to claim 5, characterized in that: The obtaining of the rotational speed of the permanent magnet synchronous motor and generating the first control signal specifically includes: The speed of the permanent magnet synchronous motor is obtained, and the difference between the maximum allowable speed of the permanent magnet synchronous motor and the actual speed measurement value is sent to the PI regulator to obtain a first control signal.

7. The simplified model construction method of an offshore DC wind turbine generator system based on an LLC resonant converter according to claim 5, characterized in that: The obtaining of the speed, stator current, and stator voltage of the permanent magnet synchronous motor 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 rotational 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 difference between the q-axis current reference value and the q-axis current measured value is sent to the current loop PI regulator to obtain the q-axis voltage reference value before compensation of the permanent magnet synchronous motor; The difference between the d-axis current reference value and the d-axis current measured value is 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 voltage reference value; The d-axis voltage reference value before compensation is added to the d-axis voltage compensation value to obtain the d-axis voltage reference value; The d-axis voltage reference value and the q-axis voltage reference value are subjected to inverse Park transformation to obtain a second control signal.

8. The simplified model construction method of an offshore DC wind turbine generator system based on an LLC resonant converter according to claim 5, characterized in that: The obtaining of the electromagnetic power of the permanent magnet synchronous motor and the output side voltage of the AC / DC converter and generating the third control signal specifically includes: Acquire the electromagnetic power of the permanent magnet synchronous motor and the output side voltage of the AC / DC converter, and divide the electromagnetic power of the permanent magnet synchronous motor by the output side voltage of the AC / DC converter to obtain a third control signal; The step of acquiring the input side voltage of the DC / DC converter and generating a fourth control signal specifically includes: The input voltage of the DC / DC converter is obtained, and the difference between the set DC voltage reference value and the input voltage measured value is sent to the PI regulator to obtain a fourth control signal.

9. The simplified model construction method of an offshore DC wind turbine generator system based on an LLC resonant converter according to claim 5, characterized in that: The obtaining of the input side voltage and output power of the DC / DC converter and generating the fifth control signal specifically includes: The input side voltage and output power of the DC / DC converter are obtained, and the output power is divided by the input side voltage to obtain a fifth control signal.

10. The application method of the simplified model of the offshore DC wind turbine generator system according to any one of claims 1 to 9 is characterized in that: The application method comprises: Establish an external DC grid model; The external DC grid model is connected to a simplified model of an offshore DC wind turbine, thereby carrying out planning, design and stability analysis of large-scale offshore DC wind power grid access, including analysis of the electromechanical transient timescale stability of the power system.

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