Network construction control method and device of offshore wind power DRU transmission system, terminal and medium

Abstract

This application discloses a grid-connection control method, device, terminal, and medium for an offshore wind power DRU transmission system. The solution provided in this application constructs the power relationship of the wind turbine and calculates the active power reference value and reactive power reference value, thereby generating the d-axis voltage reference value and phase reference value, and using these to control the grid-side converter. This enables the offshore wind power DRU transmission system to actively construct and support the voltage and frequency of the offshore AC network, reducing the dependence on external high-precision global clock signals, effectively improving the stability and reliability of the system under harsh sea conditions, and avoiding the risk of system instability caused by communication interruption or interference.

Description

Technical Field

[0001] This application relates to the field of offshore wind power technology, and in particular to a grid control method, device, terminal and medium for an offshore wind power DRU transmission system. Background Technology

[0002] Offshore wind power has become an important direction for wind power engineering construction in recent years. With increasing distance from shore, traditional AC transmission methods are no longer suitable due to issues with submarine cable charging current and losses, making high-voltage direct current (HVDC) transmission the mainstream technology choice. Currently, while flexible HVDC transmission technology based on modular multilevel converters using fully controllable devices (such as IGBTs) is maturely applied, its offshore converter stations suffer from significant drawbacks, including high cost, large size and weight, and complex construction and maintenance of offshore platforms, thus hindering the economic viability of offshore wind power development.

[0003] To reduce costs and complexity, the industry is exploring the use of diode-based uncontrolled rectifier units (DRUs) as offshore rectifier stations. DRUs offer inherent advantages such as simple structure, low cost, high reliability, and the elimination of complex control systems. However, a DRU is essentially an uncontrolled rectifier bridge; it cannot actively build or adjust the voltage amplitude and phase on its AC side. This makes the offshore AC network connected to the DRU a typical "passive network." To achieve synchronization of multiple wind turbines in a passive network, current control schemes heavily rely on high-precision global clock signals provided by global satellite navigation systems such as GPS and BeiDou, which are then sent to each turbine. This makes the stable operation of the entire wind farm completely dependent on the reliability of external communication links. Communication interruptions or interference in harsh sea conditions can directly lead to system instability, resulting in serious failure risks. Summary of the Invention

[0004] This application provides a grid control method, device, terminal, and medium for an offshore wind power DRU transmission system, which aims to improve system stability and reliability, reduce dependence on communication links, and lower the risk of instability.

[0005] To achieve the above-mentioned objectives, the first aspect of this application provides a grid control method for an offshore wind power DRU transmission system, comprising:

[0006] Obtain the topology information of the offshore wind power DRU transmission system;

[0007] Based on the topology information and the operating characteristics of diode uncontrolled rectification, a power relationship formula for the wind turbine is constructed to calculate the active power reference value and reactive power reference value of the wind turbine through the power relationship formula.

[0008] Based on the active power reference value, and combined with the active power-voltage outer loop control logic, the d-axis voltage reference value of the wind turbine grid connection point is calculated.

[0009] Based on the aforementioned reactive power reference value, and combined with the reactive-frequency outer loop control logic, the phase reference value of the wind turbine grid connection point is calculated.

[0010] Based on the d-axis voltage reference value and the preset q-axis voltage reference value, the first modulation voltage reference value in the dq coordinate system is obtained by sequentially processing through the voltage control inner loop and the current control inner loop.

[0011] Based on the phase reference value, the first modulation voltage reference value is transformed to obtain the second modulation voltage reference value in the abc coordinate system. Based on the second modulation voltage reference value and combined with the PWM modulation mode circuit, a three-phase drive signal is obtained to control the grid-side converter in the offshore wind power DRU transmission system.

[0012] Preferably, the calculation of the d-axis voltage reference value at the grid connection point of the wind turbine, based on the active power reference value and combined with the active power-voltage outer loop control logic, includes:

[0013] Based on the active power reference value, determine the active power deviation value between the active power reference value and the actual active power value;

[0014] Based on the active power deviation value and the reference value of the voltage amplitude at the PCC point of the offshore wind power DRU transmission system, combined with PI control logic, an active power-voltage outer loop control logic is constructed, and the d-axis voltage reference value at the grid connection point of the wind turbine is calculated through the active power-voltage outer loop control logic.

[0015] Preferably, based on the reactive power reference value and combined with the reactive-frequency outer loop control logic, the phase reference value of the wind turbine grid connection point is calculated as follows:

[0016] Based on the reactive power reference value, determine the reactive power deviation value between the reactive power reference value and the actual reactive power value;

[0017] Based on the reactive power deviation value, combined with PI control logic, the angular frequency deviation value of the offshore AC system is obtained. Then, the angular frequency deviation value is superimposed on the reference angular frequency of the offshore AC system to obtain the AC angular frequency reference value of the wind turbine grid connection point. The phase reference value of the wind turbine grid connection point is then calculated based on the AC angular frequency reference value.

[0018] Preferably, the formula for calculating the active power reference value is:

[0019]

[0020] In the formula, U is the active power reference value. r X is the effective value of the AC voltage at point PCC, T is the turns ratio of the converter transformer, and X is the effective value of the AC voltage at point PCC. t K is the leakage reactance of the converter transformer. r U represents the number of 6-pulse DRUs connected in series. dcr For the DC voltage of a single 6-pulse DRU, I dcr For the DC current of the series DRU valve, U const P is the steady-state approximation of the DC voltage of the DRU. r The active power transmitted by the DRU.

[0021] 5. The grid control method for an offshore wind power DRU transmission system according to claim 1, characterized in that the formula for calculating the reactive power reference value is:

[0022]

[0023] In the formula, Q is the reference value for reactive power. r The reactive power absorbed by the DRU, φ is the power factor angle of the DRU, ω is the angular frequency of the marine AC system, and U r U is the effective value of the AC voltage at point PCC, C is the equivalent capacitance of the AC filter, and U is the effective value of the AC voltage at point PCC. const P is the steady-state approximation of the DC voltage of the DRU. r Active power transmitted by DRU.

[0024] Preferably, the formula for calculating the d-axis voltage reference value is:

[0025]

[0026] In the formula, This is the reference value for the d-axis voltage. The active power reference value is... K represents the actual value of the active power. PP and K IP U represents the proportional and integral coefficients of the PI controller in the active-voltage outer loop, s is the Laplace operator, and U... d0 This is a reference value for the voltage amplitude at the PCC point.

[0027] Preferably, the formula for calculating the phase reference value is:

[0028]

[0029] In the formula, The phase reference value is... K is the reference value for the AC angular frequency. PQ and KIQ The proportional and integral coefficients of the PI controller in the reactive-frequency outer loop are given, where ω0 is the actual value of the frequency of the marine AC system, and ω base Let be the reference value for the angular frequency of the marine communication system, and s be the Laplace operator. The reactive power reference value is... This is the actual value of the reactive power.

[0030] The second aspect of this application provides a grid-connected control device for an offshore wind power DRU transmission system, comprising:

[0031] The system topology acquisition unit is used to acquire the topology information of the offshore wind power DRU transmission system;

[0032] The power reference value determination unit is used to construct the power relationship of the wind turbine based on the topology information and the operating characteristics of the diode uncontrolled rectification, so as to calculate the active power reference value and reactive power reference value of the wind turbine through the power relationship.

[0033] The active voltage outer loop control unit is used to calculate the d-axis voltage reference value of the wind turbine grid connection point based on the active power reference value and in combination with the active-voltage outer loop control logic.

[0034] The reactive power frequency outer loop control unit is used to calculate the phase reference value of the wind turbine grid connection point based on the reactive power reference value and in combination with the reactive power frequency outer loop control logic.

[0035] The modulation voltage reference value conversion unit is used to obtain the first modulation voltage reference value in the dq coordinate system by sequentially processing the voltage control inner loop and the current control inner loop based on the d-axis voltage reference value and the preset q-axis voltage reference value.

[0036] The converter drive signal conversion unit is used to perform coordinate transformation on the first modulation voltage reference value according to the phase reference value to obtain the second modulation voltage reference value in the abc coordinate system, so as to obtain the three-phase drive signal for controlling the grid-side converter according to the second modulation voltage reference value and in combination with the PWM modulation mode circuit.

[0037] A third aspect of this application provides a grid control terminal for an offshore wind power DRU transmission system, comprising: a memory and a processor;

[0038] The memory is used to store program code, which corresponds to the grid control method for the offshore wind power DRU transmission system provided in the first aspect of this application.

[0039] The processor is used to read and execute the program code to implement the grid control method of the offshore wind power DRU transmission system.

[0040] The fourth aspect of this application provides a computer-readable storage medium storing program code, which is read and executed by a processor to implement the grid control method for the offshore wind power DRU transmission system provided in the first aspect of this application.

[0041] As can be seen from the above technical solutions, this application has the following advantages:

[0042] The solution provided in this application constructs the power relationship of wind turbine units and calculates active power reference values ​​and reactive power reference values, thereby generating d-axis voltage reference values ​​and phase reference values, and using these to control the grid-side converter. This enables the offshore wind power DRU transmission system to actively construct and support the voltage and frequency of the offshore AC network, reducing the dependence on external high-precision global clock signals, effectively improving the stability and reliability of the system under harsh sea conditions, and avoiding the risk of system instability caused by communication interruption or interference. Attached Figure Description

[0043] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0044] Figure 1 This is a flowchart illustrating an embodiment of a grid control method for an offshore wind power DRU transmission system provided in this application.

[0045] Figure 2 This is a block diagram of the grid-type control of wind turbine generators based on the grid-type control method of the offshore wind power DRU transmission system provided in this application.

[0046] Figure 3 This is a schematic diagram of the architecture of an embodiment of a grid control device for an offshore wind power DRU transmission system provided in this application.

[0047] Figure 4 This is a schematic diagram of the architecture of an embodiment of the grid control system for an offshore wind power DRU transmission system provided in this application. Detailed Implementation

[0048] This application provides a network control method, device, terminal, and medium for an offshore wind power DRU transmission system, which aims to improve system stability and reliability, reduce dependence on communication links, and lower the risk of instability.

[0049] To make the inventive objectives, features, and advantages of this application more apparent and understandable, the technical solutions in the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the embodiments described below are only some embodiments of this application, and not all embodiments. Based on the embodiments in this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0050] First, a detailed description of an embodiment of a grid control method for an offshore wind power DRU transmission system provided in this application is as follows:

[0051] Please see Figure 1 and Figure 2 This application provides an embodiment of a grid control method for an offshore wind power DRU transmission system, the steps of which include:

[0052] Step 101: Obtain the topology information of the offshore wind power DRU transmission system;

[0053] Step 102: Based on the topology information and the operating characteristics of diode uncontrolled rectification, construct the power relationship formula of the wind turbine, and calculate the active power reference value and reactive power reference value of the wind turbine through the power relationship formula.

[0054] Step 103: Based on the active power reference value and combined with the active power-voltage outer loop control logic, calculate the d-axis voltage reference value at the grid connection point of the wind turbine.

[0055] Step 104: Based on the reactive power reference value and combined with the reactive-frequency outer loop control logic, calculate the phase reference value of the wind turbine grid connection point;

[0056] Step 105: Based on the d-axis voltage reference value and the preset q-axis voltage reference value, the first modulation voltage reference value in the dq coordinate system is obtained by sequentially processing through the voltage control inner loop and the current control inner loop.

[0057] Step 106: Based on the phase reference value, perform coordinate transformation on the first modulation voltage reference value to obtain the second modulation voltage reference value in the abc coordinate system. Based on the second modulation voltage reference value and combined with the PWM modulation mode circuit, obtain the three-phase drive signal to control the grid-side converter in the offshore wind power DRU transmission system.

[0058] It should be noted that, for ease of understanding of this embodiment, some key terms involved are explained below:

[0059] Offshore wind power DRU transmission system refers to a power system that rectifies the electrical energy generated by offshore wind turbine generators through diode uncontrolled rectifier units (DRUs) and transmits it to the onshore power grid via direct current (DC) transmission. This system typically includes wind turbine generators, DRUs, DC transmission lines, and grid-side converters as its main components.

[0060] A diode uncontrolled rectifier (DRU) is a rectifier bridge composed solely of diodes. It is characterized by its simple structure, low cost, and high reliability. Since a DRU cannot actively construct or regulate the voltage amplitude and phase on its AC side, the marine AC network to which it is connected is typically considered a passive network.

[0061] Topology information refers to the connections, electrical parameters, and physical layout of various devices in an offshore wind power DRU (Device Root Unit) transmission system. This information forms the basis for constructing the system's mathematical model and formulating control strategies.

[0062] The power relationship formula is a mathematical expression established based on the operating characteristics and system topology of the wind turbine generator set (DRU) to describe the relationship between the active and reactive power of the wind turbine generator set and system parameters such as voltage, current, and impedance. This formula is used to calculate the power reference value of the wind turbine generator set.

[0063] The active power-voltage outer loop control logic refers to a control strategy used to adjust the d-axis voltage reference value at the grid connection point of a wind turbine. This logic generates the d-axis voltage reference value by comparing the active power reference value with the actual value and combining it with the voltage amplitude reference value at the PCC point, thereby achieving coordinated control of the system's active power and voltage.

[0064] The reactive power-frequency outer loop control logic refers to a control strategy used to adjust the phase reference value at the grid connection point of a wind turbine. This logic generates an AC angular frequency deviation value by comparing the reactive power reference value with the actual value, and then obtains the phase reference value to achieve coordinated control of the system's reactive power and frequency.

[0065] The dq coordinate system is a synchronous rotating coordinate system commonly used in vector control of AC motors and power system analysis. In this coordinate system, three-phase AC quantities are decomposed into DC components along the d-axis (direct axis) and q-axis (quadrature axis), facilitating control and analysis.

[0066] The ABC coordinate system refers to a static three-phase coordinate system that directly corresponds to the three-phase AC voltage and current in a power system.

[0067] A grid-side converter is a power electronic device that connects the offshore AC system to the onshore power grid. Its function is to convert the DC power rectified by the DRU into AC power and send it to the onshore power grid. At the same time, it provides grid construction function to support the voltage and frequency of the offshore AC network.

[0068] Specifically, the network control method in this embodiment includes the following steps:

[0069] First, the topology information of the offshore wind power DRU transmission system is obtained. This topology information can be manually entered, for example, by operators manually configuring the device connection relationships and line parameters in the system. As an optional implementation method, this topology information can also be obtained automatically by the system scanning or reading pre-stored configuration files.

[0070] Secondly, based on the acquired topology information and the operating characteristics of diode uncontrolled rectifiers (DRUs), a power relationship formula for the wind turbine is constructed. This power relationship formula can be derived from circuit theory and power electronics principles by analyzing the equivalent circuit model of the DRU, thus deriving a mathematical model describing the relationship between its AC-side power and DC-side parameters. For example, a simplified equivalent circuit can be established, and the relationship can be derived using Kirchhoff's laws and the power balance principle. Therefore, the active power reference value and reactive power reference value of the wind turbine can be calculated using this power relationship formula. These reference values ​​can be determined according to system operating requirements or preset dispatch instructions.

[0071] Furthermore, based on the calculated active power reference value and combined with the active power-voltage outer loop control logic, the d-axis voltage reference value at the wind turbine grid connection point is calculated. This active power-voltage outer loop control logic can take various forms. For example, it can be a mapping relationship based on a lookup table or a preset curve, directly mapping the active power reference value to the d-axis voltage reference value. Alternatively, it can be a simple proportional controller that adjusts the d-axis voltage reference value proportionally according to the magnitude of the active power reference value.

[0072] Simultaneously, based on the calculated reactive power reference value and combined with the reactive power-frequency outer loop control logic, the phase reference value at the wind turbine grid connection point is calculated. This reactive power-frequency outer loop control logic can also take various forms. For example, it could be a mapping relationship based on a preset function or empirical model, converting the reactive power reference value into a frequency deviation, and then integrating to obtain the phase reference value. Alternatively, it could be a simple integral controller that continuously accumulates the phase reference value based on the reactive power reference value.

[0073] Subsequently, based on the calculated d-axis voltage reference value and the preset q-axis voltage reference value, the first modulated voltage reference value in the dq coordinate system is obtained through sequential processing via voltage control inner loop and current control inner loop. The q-axis voltage reference value is typically preset to zero to achieve decoupled control. The voltage control inner loop can be a simple proportional controller used to adjust the output voltage to track the reference value. The current control inner loop can be a current regulator based on a proportional-integral controller used to control the current flowing through the converter.

[0074] Finally, based on the calculated phase reference value, the first modulation voltage reference value is transformed to obtain the second modulation voltage reference value in the abc coordinate system. This coordinate transformation can be achieved through the inverse Park transform. Therefore, based on this second modulation voltage reference value and combined with the PWM modulation circuit, a three-phase drive signal is obtained. This three-phase drive signal is used to control the grid-side converter in the offshore wind power DRU transmission system, thereby providing voltage and frequency support for the offshore AC network.

[0075] The grid-based control method proposed in this embodiment constructs the power relationship of wind turbine units and calculates active and reactive power reference values, thereby generating d-axis voltage and phase reference values, and using these to control the grid-side converter. This method enables the offshore wind power DRU transmission system to actively construct and support the voltage and frequency of the offshore AC network, reducing dependence on external high-precision global clock signals, effectively improving the stability and reliability of the system under harsh sea conditions, and avoiding the risk of system instability due to communication interruptions or interference.

[0076] In some of the embodiments described above in this application, a method is proposed to calculate the d-axis voltage reference value of the wind turbine grid connection point based on the active power reference value combined with the active power-voltage outer loop control logic.

[0077] Based on this, this application further proposes the following steps for calculating the d-axis voltage reference value of the wind turbine grid connection point based on the active power reference value and combined with the active power-voltage outer loop control logic: determining the active power deviation value between the active power reference value and the actual active power value based on the active power reference value; constructing the active power-voltage outer loop control logic based on the active power deviation value and the PCC point voltage amplitude reference value of the offshore wind power DRU transmission system, combined with PI control logic; and calculating the d-axis voltage reference value of the wind turbine grid connection point through the active power-voltage outer loop control logic.

[0078] Specifically, such as Figure 2 As shown, firstly, based on the active power reference value (i.e. Figure 2 P in ref The active power deviation value is determined by comparing the reference active power value with the actual active power value. This step aims to quantify the difference between the actual active power output of the wind turbine and the preset active power reference value by monitoring the actual active power output in real time. This active power deviation value serves as an error signal for the control system and forms the basis for subsequent adjustments, reflecting the degree of deviation between the current active power output and the target value. The actual active power value can be calculated from the voltage and current measurements at the grid connection point.

[0079] Secondly, based on the active power deviation value and the reference value of the PCC point voltage amplitude of the offshore wind power DRU transmission system, an active power-voltage outer loop control logic is constructed in conjunction with PI control logic. This logic is then used to calculate the d-axis voltage reference value at the wind turbine grid connection point. Specifically, the PI control logic receives the active power deviation value as input, responds instantly to the current deviation through a proportional (P) stage, and eliminates long-standing steady-state errors through an integral (I) stage, ensuring that the active power can ultimately accurately track the reference value. Simultaneously, this control logic also incorporates the reference value of the PCC point voltage amplitude of the offshore wind power DRU transmission system, ensuring that the generation of the d-axis voltage reference value considers not only the adjustment requirements of active power but also the stability of the grid connection point voltage amplitude. By combining the output of the PI controller with the PCC point voltage amplitude reference value, the d-axis voltage reference value at the wind turbine grid connection point is jointly determined, thereby achieving precise control of the wind turbine's active power and effective support for the grid voltage.

[0080] Through the above technical solutions, this application can effectively solve the problems of insufficient active power control accuracy and poor grid connection stability. By clearly calculating the deviation between the active power reference value and the actual value, and using PI control logic for closed-loop regulation, the system can achieve accurate tracking and rapid response of the active power output of the wind turbine, effectively eliminating steady-state errors. Simultaneously, by integrating the PCC point voltage amplitude reference value into the active-voltage outer loop control logic, the generation of the d-axis voltage reference value not only serves the regulation of active power but also actively participates in the stable support of the grid connection point voltage. This improves the performance of the wind turbine as a grid-connected power source in the offshore wind power DRU transmission system, ensuring that the system can maintain stable active power output and grid connection voltage even during grid fluctuations or load changes, thereby enhancing the operational reliability and grid adaptability of the entire offshore wind power DRU transmission system.

[0081] In the aforementioned grid control method for offshore wind power DRU transmission systems, it is necessary to calculate the phase reference value at the wind turbine grid connection point based on the reactive power reference value and combined with the reactive power-frequency outer loop control logic. However, in practical applications, how to accurately and stably control the system frequency and thus determine the phase reference value using the reactive power reference value to ensure that the wind turbine provides stable frequency support at the grid connection point is a key aspect that requires further refinement and optimization.

[0082] In response, this application further proposes a step for calculating the phase reference value of the wind turbine grid connection point based on the reactive power reference value and combined with the reactive power-frequency outer loop control logic. The steps include: determining the reactive power deviation value between the reactive power reference value and the actual reactive power value based on the reactive power reference value; obtaining the angular frequency deviation value of the offshore AC system based on the reactive power deviation value and combined with PI control logic; and then superimposing the angular frequency deviation value on the reference angular frequency of the offshore AC system to obtain the AC angular frequency reference value of the wind turbine grid connection point, so as to convert the phase reference value of the wind turbine grid connection point according to the AC angular frequency reference value.

[0083] Specifically, firstly, based on the reactive power reference value (i.e. Figure 2 Q in ref The reactive power deviation is determined by comparing the reactive power reference value with the actual reactive power value. This step aims to quantify the difference between the current reactive power and the expected reactive power of the system. The reactive power reference value is a target value calculated by the system based on topology information and DRU operating characteristics, representing the reactive power that the wind turbine should provide to the grid. The actual reactive power value is the reactive power output of the wind turbine to the grid at the current moment, calculated by real-time measurement of parameters such as voltage and current at the wind turbine's grid connection point. By comparing these two values, the reactive power deviation value can be obtained. This deviation value reflects the system's reactive power adjustment needs and serves as the basis for subsequent frequency regulation in the control system.

[0084] Secondly, based on the reactive power deviation value and combined with PI control logic, the angular frequency deviation value of the marine AC system is obtained. PI (Proportional-Integral) control logic is a feedback control algorithm widely used in industrial control. It responds to the current deviation through a proportional term and eliminates steady-state error through an integral term.

[0085] Furthermore, by superimposing the angular frequency deviation value onto the reference angular frequency of the offshore AC system, a reference AC angular frequency value for the wind turbine grid connection point is obtained. The reference angular frequency of the offshore AC system is the nominal frequency during normal system operation, such as the angular frequency corresponding to 50Hz or 60Hz. By superimposing the angular frequency deviation value output by the PI controller onto this reference angular frequency, the required AC angular frequency reference value for the wind turbine grid connection point can be obtained. This reference value comprehensively considers the system's reactive power adjustment requirements and the system's inherent frequency, and is the basis for generating the voltage phase at the wind turbine grid connection point. Through this superposition, it is ensured that when the reactive power deviation is zero, the system frequency can be stabilized at the reference frequency, while the frequency can be adjusted accordingly when a deviation exists.

[0086] Finally, the phase reference value of the wind turbine grid connection point is calculated based on the AC angular frequency reference value. The phase reference value is a key parameter for controlling the output voltage of the grid-side converter. The AC angular frequency reference value is the instantaneous value of the frequency, while the phase is the integral of the frequency over time. Therefore, by integrating the AC angular frequency reference value, the phase reference value of the wind turbine grid connection point can be obtained in real time. This phase reference value will be directly used for subsequent coordinate transformation and PWM modulation to generate the three-phase drive signal for controlling the grid-side converter, thereby precisely controlling the voltage phase and frequency of the wind turbine grid connection point and realizing the grid control function.

[0087] Through the aforementioned technical solution, this application achieves precise frequency regulation of the offshore AC system by calculating a clear reactive power deviation value and combining it with PI control logic. By superimposing this angular frequency deviation value with a reference angular frequency, a stable and responsive AC angular frequency reference value is ensured at the wind turbine grid connection point. Finally, by converting this AC angular frequency reference value, a phase reference value for the wind turbine grid connection point can be accurately generated, thereby providing precise control commands to the grid-side converter. This solves the problems of insufficient frequency control accuracy or lag in traditional methods, improves the support capability and stability of the offshore wind power DRU transmission system for grid frequency in grid-connected operation mode, enables wind turbines to participate more effectively in grid frequency regulation, and enhances the grid adaptability of the entire system.

[0088] In the grid control method of offshore wind power DRU transmission systems, it is necessary to construct the power relationship of wind turbines based on system topology information and the operating characteristics of diode uncontrolled rectification in order to calculate the active power reference value of the wind turbines. However, if the calculation model for the active power reference value is not accurately established, the subsequent active-voltage outer loop control logic may be unable to accurately calculate the d-axis voltage reference value at the grid connection point of the wind turbines, thereby affecting the stability and accuracy of the entire grid control.

[0089] In response, this application further proposes a reference value for active power. The calculation formula is as follows:

[0090]

[0091] In the formula, The active power reference value represents the expected active power that a wind turbine should output or absorb under specific operating conditions, and its accuracy directly affects the performance of the entire grid control system; U rX is the effective value of the AC voltage at the PCC point, which is the actual effective value of the AC voltage at the grid connection point of the wind farm. It serves as a fundamental parameter for power calculation and is typically obtained in real-time through voltage sensors. T represents the turns ratio of the converter transformer, indicating the ratio of the primary and secondary voltages or turns. It determines the voltage level conversion relationship and directly affects the voltage and current values ​​along the power transmission path. t The leakage reactance of the converter transformer is an inherent reactance component within the transformer. It causes voltage drops and reactive power losses during power transmission and is a crucial parameter affecting the system's power transmission capacity; K r This refers to the number of 6-pulse DRUs connected in series. Since DRUs are typically modular in design, connecting multiple DRUs in series can increase the DC voltage rating and power capacity; U dcr The DC voltage of a single 6-pulse DRU refers to the DC-side voltage of each independent 6-pulse DRU unit after rectification, and is a key indicator of the DRU's operating status; I dcr The DC current for the series-connected DRU valve refers to the current flowing through the DC side of the series-connected DRU unit. It, along with the DC voltage, determines the DC power transmitted by the DRU; U const P is the steady-state approximation of the DC voltage of the DRU, which is an estimated or designed value of the DC voltage of the DRU under stable operating conditions. It can be used to simplify control algorithms or as a reference benchmark. r The active power transmitted by the DRU refers to the actual active power transmitted by the DRU, and is an important component of system power balance.

[0092] By introducing the specific calculation formula for the aforementioned active power reference value, this application can accurately quantify the active power output demand of wind turbine generators in the DRU transmission system. This formula comprehensively considers key parameters such as the effective value of the AC voltage Ur at the PCC point, the turns ratio T and leakage reactance Xt of the converter transformer, the number of series-connected 6-pulse DRUs Kr, the DC voltage Udcr of a single 6-pulse DRU, the DC current Idcr of the series-connected DRU valve, the steady-state approximation value Uconst of the DRU DC voltage, and the active power Pr transmitted by the DRU. This ensures that the calculated active power reference value highly matches the actual operating characteristics of the DRU transmission system. This accurate reference value calculation provides a reliable input for the subsequent active-voltage outer loop control logic, enabling more accurate calculation of the d-axis voltage reference value at the wind turbine grid connection point. This, in turn, improves the stability and response speed of the entire offshore wind power DRU transmission system's grid control, avoiding control deviations caused by inaccurate active power reference values.

[0093] In the grid control method of offshore wind power DRU transmission systems, it is necessary to calculate the reactive power reference value of the wind turbine generators as the input of the subsequent reactive power-frequency outer loop control logic. However, if the calculation of the reactive power reference value is not accurate enough or the operating characteristics of the DRU transmission system are not fully considered, it may lead to inaccurate reactive power control, which in turn affects the stability of the grid connection point voltage and the overall grid performance of the system.

[0094] In this regard, this application further proposes the following formula for calculating the reactive power reference value:

[0095]

[0096] Specifically, reactive power reference value This is the target value of reactive power that the wind turbine should provide or absorb at the grid connection point. In grid control, an accurate reactive power reference value is fundamental to achieving grid connection point voltage stability and system reactive power balance. Its calculation requires comprehensive consideration of the DRU's operating characteristics, system parameters, and expected reactive power output. r The reactive power absorbed by the DRU refers to the reactive power absorbed by the diode uncontrolled rectifier (DRU) from the AC system during operation. Due to its uncontrolled characteristics, the DRU typically absorbs a certain amount of reactive power, which needs to be accurately quantified for compensation or management at the system level. φ is the power factor angle of the DRU, reflecting the degree of reactive power absorbed by the DRU. The larger the power factor angle, the more reactive power the DRU absorbs. This angle is usually related to the operating state of the DRU and the phase relationship between the AC side voltage and current. ω is the angular frequency of the offshore AC system, referring to the angular frequency of the offshore wind farm's AC grid, usually the angular frequency corresponding to the rated frequency (such as 50Hz or 60Hz). It is a fundamental parameter of AC system operation and affects the calculation of reactive power. Ur is the effective value of the AC voltage at the PCC point, referring to the effective value of the AC voltage at the point of common coupling (PCC) of the wind turbine. The PCC point voltage is a key indicator for measuring system voltage quality and stability, and its effective value directly affects the transmission and calculation of reactive power. C represents the equivalent capacitance of the AC filter. In DRU output systems, AC filters are typically configured to suppress harmonics and provide partial reactive power compensation. This capacitance value represents the equivalent capacitance of the AC filter at the fundamental frequency, and the reactive power it provides needs to be included in the total reactive power calculation.

[0097] The above technical solution clarifies the specific calculation formula for the reactive power reference value in the offshore wind power DRU transmission system. This formula comprehensively considers the reactive power Q absorbed by the DRU. r The power factor angle φ of the DRU, the angular frequency ω of the marine AC system, and the effective value of the AC voltage U at the PCC point. rThe equivalent capacitance C of the AC filter and the steady-state approximation U of the DC voltage of the DRU. const This includes key parameters such as the active power Pr transmitted by the DRU. This precise calculation method, based on system operating characteristics and the inherent properties of the DRU, ensures that the obtained reactive power reference value accurately reflects the system's current reactive power demand and the DRU's reactive power absorption. Therefore, when this precise reactive power reference value is input into the reactive-frequency outer loop control logic, the grid-side converter can more accurately adjust the reactive power output, effectively compensate for the reactive power absorbed by the DRU, and maintain the stability of the grid connection point voltage. This improves the reactive power control accuracy and voltage support capability of the offshore wind power DRU transmission system in grid-connected operation mode, thereby enhancing the overall system stability and power quality.

[0098] Furthermore, this application also proposes a formula for calculating the d-axis voltage reference value, the specific expression of which is as follows:

[0099]

[0100] in, The d-axis voltage reference value, in the dq coordinate system, is the target value of the d-axis component used to control the output voltage of the grid-side converter. In the synchronous rotating coordinate system, the d-axis is usually aligned with the voltage vector direction; therefore, the d-axis voltage reference value directly affects the amplitude and stability of the grid-connected voltage. Its accurate calculation is crucial for realizing the grid connection function of wind turbine units, as it directly determines the amplitude control of the converter output voltage. This is the active power reference value, which is the target value of active power output expected by the wind turbines. This reference value is usually given by the upper-level dispatch or system operation strategy, reflecting the real-time active power demand that the wind turbines should provide to the grid. This is the actual active power value, measured in real time at the wind turbine's grid connection point. It is compared with the active power reference value. By comparing these values, the active power deviation can be obtained and used as part of the PI controller input. PP and K IP Here are the proportional and integral coefficients of the PI controller in the active-voltage outer loop, where K... PP The proportional gain, K, is the active-voltage outer loop PI controller. IP These are the integral coefficients. These two parameters together determine the dynamic response characteristics of the PI controller, including response speed, overshoot, and steady-state error. By properly tuning K... PP and K IP This ensures that active power deviations can be eliminated quickly and stably, thereby ensuring that the actual active power... Tracking active power reference value This ultimately affects the generation of the d-axis voltage reference value. s is the Laplace operator, used in control theory to represent differentiation and integration operations, typically in frequency domain analysis and controller design. In this formula, 1 / s represents the integral element, reflecting the integral role in the PI controller, used to eliminate steady-state error. U d0 This is a reference value for the voltage amplitude at the PCC point, which is the baseline or expected value for the voltage amplitude at the PCC point, the grid connection point of the offshore wind power DRU. In grid control, the stability of the voltage amplitude at the PCC point is crucial for the normal operation of the system. d0 As a reference for the d-axis voltage, it ensures that when the active power deviation is zero, the d-axis voltage reference value can be stabilized near the expected PCC point voltage amplitude, thereby maintaining the stability of the grid connection point voltage.

[0101] The above technical solution clarifies the specific calculation formula for the d-axis voltage reference value. This value is processed by an active power-voltage outer loop PI controller and, combined with the PCC point voltage amplitude reference value Ud0, directly generates the d-axis voltage reference value at the wind turbine grid connection point. This explicit mathematical expression makes the implementation of the active power-voltage outer loop control logic more precise and controllable.

[0102] Furthermore, this application also proposes a formula for calculating the phase reference value, the specific expression of which is as follows:

[0103]

[0104] Specifically As a phase reference value, K is the reference value for AC angular frequency. PQ and K IQ The proportional and integral coefficients of the PI controller in the reactive power-frequency outer loop are key parameters used to adjust the performance of the reactive power-frequency outer loop controller. This PI controller uses a reactive power reference value... Compared with the actual value of reactive power The deviation between the two values ​​is taken as input, and the output is a frequency deviation quantity, which is related to the reference value ω of the angular frequency of the marine AC system. base The superposition forms an AC angular frequency reference value. ;K PQ This determines the instantaneous response strength of the controller to reactive power deviation, while K IQ This is used to eliminate reactive power deviation in the system under steady state, ensuring that reactive power can accurately track the reference value. This is achieved by appropriately tuning K... PQ and K IQThis can optimize the controller's dynamic response speed, reduce overshoot, and improve system stability, enabling it to quickly and smoothly adjust the frequency in the face of reactive power fluctuations. ω0 is the actual value of the frequency of the offshore AC system, which is usually measured or estimated in real time from the grid connection point voltage or current through frequency detection units such as phase-locked loops (PLLs). As a feedback signal, ω0 provides the controller with information on the current frequency status of the system, allowing the controller to adjust according to the actual situation to maintain the system's frequency stability; ω base Let be the reference value for the angular frequency of the marine communication system, and s be the Laplace operator. This is a reference value for reactive power. This represents the actual value of reactive power.

[0105] The above technical solution clarifies the specific calculation formula for the phase reference value, particularly by integrating the AC angular frequency reference value to obtain the phase, and defines in detail the proportional and integral coefficients K of the reactive-frequency outer loop PI controller. PQ and K IQ This explicit mathematical formulation allows controller designers to precisely tune control parameters, thereby optimizing the dynamic response and steady-state performance of the reactive-frequency outer loop.

[0106] The above is a detailed description of an embodiment of a grid control method for an offshore wind power DRU transmission system provided in this application. The following is a detailed description of an embodiment of a grid control device for an offshore wind power DRU transmission system provided in this application.

[0107] Please see Figure 3 The second aspect of this application provides a grid control device for an offshore wind power DRU transmission system, comprising:

[0108] System topology acquisition unit 201 is used to acquire topology information of the offshore wind power DRU transmission system;

[0109] The power reference value determination unit 202 is used to construct the power relationship of the wind turbine based on the topology information and the operating characteristics of the diode uncontrolled rectifier, so as to calculate the active power reference value and reactive power reference value of the wind turbine through the power relationship.

[0110] The active voltage outer loop control unit 203 is used to calculate the d-axis voltage reference value of the wind turbine grid connection point based on the active power reference value and combined with the active-voltage outer loop control logic.

[0111] The reactive power frequency outer loop control unit 204 is used to calculate the phase reference value of the wind turbine grid connection point based on the reactive power reference value and combined with the reactive power frequency outer loop control logic.

[0112] The modulation voltage reference value conversion unit 205 is used to obtain the first modulation voltage reference value in the dq coordinate system by sequentially processing the voltage control inner loop and the current control inner loop based on the d-axis voltage reference value and the preset q-axis voltage reference value.

[0113] The converter drive signal conversion unit 206 is used to perform coordinate transformation on the first modulation voltage reference value according to the phase reference value to obtain the second modulation voltage reference value in the abc coordinate system, so as to obtain the three-phase drive signal for controlling the grid-side converter according to the second modulation voltage reference value and in combination with the PWM modulation mode circuit.

[0114] Specifically, the offshore wind power DRU transmission system consists of wind turbine generators, diode uncontrolled rectifier units, DC transmission lines, and grid-side converters. The diode uncontrolled rectifier units, composed only of diodes, cannot actively adjust the AC voltage amplitude and phase, resulting in a passive characteristic of the offshore AC network. The system topology acquisition unit establishes a system model by collecting data from acquisition devices. The power reference value determination unit derives the power relationship based on the equivalent circuit of the DRU, enabling localized calculation of active and reactive power reference values. The active voltage outer loop control unit generates a d-axis voltage reference value by comparing the active power deviation with the PCC point voltage amplitude reference value to coordinate active power and voltage control. The reactive frequency outer loop control unit calculates the angular frequency deviation value based on the reactive power deviation, integrates it to obtain the phase reference value, and coordinates reactive power and frequency control. The modulation voltage reference value conversion unit uses a dual inner loop structure of voltage and current to process the reference value. The converter drive signal conversion unit performs coordinate transformation and PWM modulation, ultimately outputting a three-phase drive signal to control the switching action of the grid-side converter.

[0115] Through the above technical solution, the device achieves autonomous network control based on system topology and DRU operating characteristics, generating voltage and phase reference values ​​without relying on external high-precision global clock signals. This enables the offshore wind power DRU transmission system to actively build and maintain the voltage and frequency stability of the offshore AC network, maintaining reliable operation even in the event of communication interruption. It significantly improves system robustness under harsh sea conditions, effectively solves the problem of passive network synchronization, and provides an economical and feasible technical path for offshore wind power development.

[0116] Furthermore, this application also proposes an embodiment of a grid-connected control terminal for an offshore wind power DRU transmission system. As the physical carrier for implementing the aforementioned grid-connected control method, it integrates the necessary hardware resources and software environment, aiming to provide a stable and efficient platform for executing complex control algorithms, processing real-time data, and generating control commands. This control terminal typically possesses industrial-grade reliability and anti-interference capabilities to adapt to the harsh operating environment of offshore wind farms, ensuring the stable and reliable operation of the control method.

[0117] like Figure 4 As shown, the control terminal includes a memory 33 and a processor 31, which are connected via a communication bus 34. The memory 33 is used to persistently store program code, as well as intermediate data and results generated during program execution. It can be a combination of various forms such as read-only memory (ROM), random access memory (RAM), flash memory, or hard disk. The memory 33 ensures that the instruction set and configuration parameters required by the control method can be stably saved and quickly accessed by the processor during system startup or operation, providing a data foundation for the smooth execution of the control method. The processor 31 is the core computing unit of the control terminal, responsible for reading and executing the program code in the memory, performing various arithmetic and logical operations and control operations. The processor can be a microcontroller (MCU), digital signal processor (DSP), field-programmable gate array (FPGA), or a more advanced central processing unit (CPU), the choice depending on the complexity of the control algorithm and real-time requirements. By executing the program code, the processor 31 transforms the abstract control method into specific electrical signals and control instructions, thereby achieving precise control of the grid-side converter of the offshore wind power DRU transmission system. The program code stored in the memory corresponds to the grid-connected control method of the offshore wind power DRU transmission system. This program code is a set of instructions written according to this method. The processor reads and executes the operation strictly according to the logical order and calculation rules of this program code, thereby transforming the theoretical control method into a practically operable control process, and finally realizing the grid-connected control function of the grid-side converter of the offshore wind power DRU transmission system.

[0118] Furthermore, this application also proposes an embodiment of a computer-readable storage medium. This computer-readable storage medium refers to any medium capable of storing digital data and readable by a computer or similar device. It can be a transient medium, such as electrical signals, optical signals, or electromagnetic waves, or a non-transient medium, such as read-only memory (ROM), random access memory (RAM), electrically erasable programmable read-only memory (EEPROM), flash memory, disk storage (such as hard disks and floppy disks), optical disk storage (such as CD-ROMs and DVD-ROMs), etc. In this application, this medium is mainly used for persistent storage of the instruction set for implementing the network control method. The computer-readable storage medium stores program code, which refers to a series of computer-executable instructions or statements organized to complete specific tasks or functions. In this application, the program code specifically includes all the logic and calculation steps for implementing the network control method of the offshore wind power DRU transmission system, such as topology information acquisition, power relationship construction, calculation of active power reference values ​​and reactive power reference values, determination of d-axis voltage reference values ​​and phase reference values, conversion of modulation voltage reference values, and generation of three-phase drive signals, etc. Program code is read and executed by a processor. The processor is the core component of a computer system, responsible for interpreting and executing the instructions contained in the program code. A processor can be one or more central processing units (CPUs), graphics processing units (GPUs), digital signal processors (DSPs), microcontrollers (MCUs), or other programmable logic devices. By reading program code stored in a computer-readable storage medium, the processor can execute grid control methods according to a predetermined logical sequence, thereby achieving precise control of the grid-side converter in the offshore wind power DRU transmission system.

[0119] Those skilled in the art will clearly understand that, for the sake of convenience and brevity, the specific working processes of the terminals, devices, and units described above can be referred to the corresponding processes in the foregoing method embodiments, and will not be repeated here.

[0120] In the several embodiments provided in this application, it should be understood that the disclosed terminals, devices, and methods can be implemented in other ways. For example, the device embodiments described above are merely illustrative; for instance, the division of units is only a logical functional division, and in actual implementation, there may be other division methods. For example, multiple units or components may be combined or integrated into another system, or some features may be ignored or not executed. Furthermore, the coupling or direct coupling or communication connection shown or discussed may be an indirect coupling or communication connection between devices or units through some interfaces, and may be electrical, mechanical, or other forms.

[0121] The terms “first,” “second,” “third,” “fourth,” etc. (if present) in the specification and accompanying drawings of this application are used to distinguish similar objects and are not necessarily used to describe a particular order or sequence. It should be understood that such data can be interchanged where appropriate so that embodiments of the application described herein can be implemented, for example, in orders other than those illustrated or described herein. Furthermore, the terms “comprising” and “having,” and any variations thereof, are intended to cover a non-exclusive inclusion; for example, a process, method, system, product, or apparatus that comprises a series of steps or units is not necessarily limited to those steps or units explicitly listed, but may include other steps or units not explicitly listed or inherent to such processes, methods, products, or apparatus.

[0122] It should be understood that in this application, "at least one (item)" means one or more, and "more than" means two or more. "And / or" is used to describe the relationship between related objects, indicating that three relationships can exist. For example, "A and / or B" can represent three cases: only A exists, only B exists, and both A and B exist simultaneously, where A and B can be singular or plural. The character " / " generally indicates that the preceding and following related objects are in an "or" relationship. "At least one (item) of the following" or similar expressions refer to any combination of these items, including any combination of single or plural items. For example, at least one (item) of a, b, or c can represent: a, b, c, "a and b", "a and c", "b and c", or "a and b and c", where a, b, and c can be single or multiple.

[0123] The units described as separate components may or may not be physically separate. The components shown as units may or may not be physical units; that is, they may be located in one place or distributed across multiple network units. Some or all of the units can be selected to achieve the purpose of this embodiment according to actual needs.

[0124] Furthermore, the functional units in the various embodiments of the present invention can be integrated into one processing unit, or each unit can exist physically separately, or two or more units can be integrated into one unit. The integrated unit can be implemented in hardware or as a software functional unit.

[0125] If the integrated unit is implemented as a software functional unit and sold or used as an independent product, it can be stored in a computer-readable storage medium. Based on this understanding, the technical solution of the present invention, in essence, or the part that contributes to the prior art, or all or part of the technical solution, can be embodied in the form of a software product. This computer software product is stored in a storage medium and includes several instructions to cause a computer device (which may be a personal computer, server, or network device, etc.) to execute all or part of the steps of the methods described in the various embodiments of the present invention. The aforementioned storage medium includes various media capable of storing program code, such as USB flash drives, portable hard drives, read-only memory (ROM), random access memory (RAM), magnetic disks, or optical disks.

[0126] The above-described embodiments are only used to illustrate the technical solutions of this application, and are not intended to limit them. Although this application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of this application.

Claims

1. A method of meshing control for an offshore wind power DRU send-out system, characterized by, include: Obtain the topology information of the offshore wind power DRU transmission system; Based on the topology information and the operating characteristics of diode uncontrolled rectification, a power relationship formula for the wind turbine is constructed to calculate the active power reference value and reactive power reference value of the wind turbine through the power relationship formula. Based on the active power reference value, and combined with the active power-voltage outer loop control logic, the d-axis voltage reference value of the wind turbine grid connection point is calculated. Based on the aforementioned reactive power reference value, and combined with the reactive-frequency outer loop control logic, the phase reference value of the wind turbine grid connection point is calculated. Based on the d-axis voltage reference value and the preset q-axis voltage reference value, the first modulation voltage reference value in the dq coordinate system is obtained by sequentially processing through the voltage control inner loop and the current control inner loop. Based on the phase reference value, the first modulation voltage reference value is transformed to obtain the second modulation voltage reference value in the abc coordinate system. Based on the second modulation voltage reference value and combined with the PWM modulation mode circuit, a three-phase drive signal is obtained to control the grid-side converter in the offshore wind power DRU transmission system.

2. The grid control method for an offshore wind power DRU transmission system according to claim 1, characterized in that, The d-axis voltage reference value of the wind turbine grid connection point, calculated based on the active power reference value and combined with the active power-voltage outer loop control logic, includes: Based on the active power reference value, determine the active power deviation value between the active power reference value and the actual active power value; Based on the active power deviation value and the reference value of the voltage amplitude at the PCC point of the offshore wind power DRU transmission system, combined with PI control logic, an active power-voltage outer loop control logic is constructed, and the d-axis voltage reference value at the grid connection point of the wind turbine is calculated through the active power-voltage outer loop control logic.

3. The grid control method for an offshore wind power DRU transmission system according to claim 1, characterized in that, Based on the aforementioned reactive power reference value, and combined with the reactive-frequency outer loop control logic, the phase reference value at the grid connection point of the wind turbine is calculated as follows: Based on the reactive power reference value, determine the reactive power deviation value between the reactive power reference value and the actual reactive power value; Based on the reactive power deviation value, combined with PI control logic, the angular frequency deviation value of the offshore AC system is obtained. Then, the angular frequency deviation value is superimposed on the reference angular frequency of the offshore AC system to obtain the AC angular frequency reference value of the wind turbine grid connection point. The phase reference value of the wind turbine grid connection point is then calculated based on the AC angular frequency reference value.

4. The grid control method for an offshore wind power DRU transmission system according to claim 1, characterized in that, The formula for calculating the active power reference value is as follows: In the formula, U is the active power reference value. r X is the effective value of the AC voltage at point PCC, T is the turns ratio of the converter transformer, and X is the effective value of the AC voltage at point PCC. t K is the leakage reactance of the converter transformer. r U represents the number of 6-pulse DRUs connected in series. dcr For the DC voltage of a single 6-pulse DRU, I dcr For the DC current of the series DRU valve, U const P is the steady-state approximation of the DC voltage of the DRU. r Active power transmitted by DRU.

5. The grid control method for an offshore wind power DRU transmission system according to claim 1, characterized in that, The formula for calculating the reactive power reference value is as follows: In the formula, Q is the reference value for reactive power. r The reactive power absorbed by the DRU, φ is the power factor angle of the DRU, ω is the angular frequency of the marine AC system, and U r U is the effective value of the AC voltage at point PCC, C is the equivalent capacitance of the AC filter, and U is the effective value of the AC voltage at point PCC. const P is the steady-state approximation of the DC voltage of the DRU. r Active power transmitted by DRU.

6. The grid control method for an offshore wind power DRU transmission system according to claim 2, characterized in that, The formula for calculating the d-axis voltage reference value is as follows: In the formula, This is the reference value for the d-axis voltage. The active power reference value is... K represents the actual value of the active power. PP and K IP U represents the proportional and integral coefficients of the PI controller in the active-voltage outer loop, s is the Laplace operator, and U... d0 This is a reference value for the voltage amplitude at the PCC point.

7. The grid control method for an offshore wind power DRU transmission system according to claim 3, characterized in that, The formula for calculating the phase reference value is as follows: In the formula, The phase reference value is... K is the reference value for the AC angular frequency. PQ and K IQ The proportional and integral coefficients of the PI controller in the reactive-frequency outer loop are given, where ω0 is the actual value of the frequency of the marine AC system, and ω base Let be the reference value for the angular frequency of the marine communication system, and s be the Laplace operator. The reactive power reference value is... This is the actual value of the reactive power.

8. A grid-connected control device for an offshore wind power DRU transmission system, characterized in that, include: The system topology acquisition unit is used to acquire the topology information of the offshore wind power DRU transmission system; The power reference value determination unit is used to construct the power relationship of the wind turbine based on the topology information and the operating characteristics of the diode uncontrolled rectification, so as to calculate the active power reference value and reactive power reference value of the wind turbine through the power relationship. The active voltage outer loop control unit is used to calculate the d-axis voltage reference value of the wind turbine grid connection point based on the active power reference value and in combination with the active-voltage outer loop control logic. The reactive power frequency outer loop control unit is used to calculate the phase reference value of the wind turbine grid connection point based on the reactive power reference value and in combination with the reactive power frequency outer loop control logic. The modulation voltage reference value conversion unit is used to obtain the first modulation voltage reference value in the dq coordinate system by sequentially processing the voltage control inner loop and the current control inner loop based on the d-axis voltage reference value and the preset q-axis voltage reference value. The converter drive signal conversion unit is used to perform coordinate transformation on the first modulation voltage reference value according to the phase reference value to obtain the second modulation voltage reference value in the abc coordinate system, so as to obtain the three-phase drive signal for controlling the grid-side converter according to the second modulation voltage reference value and in combination with the PWM modulation mode circuit.

9. A grid control terminal for an offshore wind power DRU transmission system, characterized in that, include: Memory and processor; The memory is used to store program code, which corresponds to the grid control method of the offshore wind power DRU transmission system as described in any one of claims 1 to 7; The processor is used to read and execute the program code to implement the grid control method of the offshore wind power DRU transmission system.

10. A computer-readable storage medium, characterized in that, The computer-readable storage medium contains program code that is read and executed by a processor to implement the grid control method for the offshore wind power DRU transmission system as described in any one of claims 1 to 7.

Images