Voltage source type offshore wind turbine generator control method and device and medium

Abstract

The invention discloses a voltage source type offshore wind turbine generator control method and device and a medium. The problem of black start of a multi-converter cabinet unit in an off-grid scene is solved, when an off-grid state is detected, black start is triggered, one converter is selected from a plurality of converters connected in parallel to serve as a starting converter, the rest converters are kept disconnected, power supply conflicts caused by simultaneous starting of the converters are avoided, and the networking efficiency of a single converter is focused. The problem of disordered starting in an off-network scene is solved; energy storage charges a grid-side direct-current bus of a starting converter, machine-side modulation builds a stable direct-current power supply, grid-side modulation generates preset parameter grid voltage, the problem of no external power supply support during off-grid is solved, charging impact and damage to equipment are avoided, and safe grid building is achieved; after the starting converter networking is stable, the other converters are started step by step; the voltage source control converter is responsible for voltage / frequency stabilization, and the grid-following control converter adjusts power according to unit states and loads to ensure power grid stability and power matching.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of wind turbines, in particular to a voltage source type offshore wind turbine control method, device and medium. BACKGROUND

[0002] The increase of new energy ratio leads to the decrease of grid inertia and strength, the voltage and frequency stability problem is highlighted, the offshore wind turbine extends to the deep sea and island, the weak grid and off-grid scene expands and faces the operation and maintenance and extreme weather challenges.

[0003] The existing technology mainly uses grid-connected control, relies on stable grid voltage and frequency, synchronizes through phase-locked loop, and indirectly adjusts power and voltage through control output current; the grid-connected control is a controlled current source, which cannot actively provide inertia and short-circuit capacity, and is easy to cause grid instability under weak grid, and is completely not suitable for off-grid scene.

[0004] For the weak grid / off-grid scene, mainly rely on voltage source technology to simulate synchronous unit characteristics, double-fed wind turbine single cabinet converter has realized off-grid starting, but off-grid black start and debugging rely on diesel generator system. The mainstream direct-drive wind turbine in the deep sea mainly uses double-cabinet / multi-cabinet parallel converter, and the existing control method is only suitable for double-fed unit single-cabinet converter, which has insufficient matching; the diesel generator system has slow response, poor controllability and pollutes the environment, and cannot meet the rapid power support demand; although energy storage has the advantages of flexible control and fast response, it has not been applied to voltage source type unit black start and island operation; double converters are directly connected in parallel in voltage source mode, which is easy to short circuit, and there is a lack of cooperative control scheme, which limits the operation of large-capacity units.

[0005] In summary, there is an urgent need for an offshore wind turbine control method to solve the black start problem of multi-converter cabinet unit in off-grid scene, which is a technical problem to be solved by personnel in the field. SUMMARY

[0006] The purpose of the present application is to provide a voltage source type offshore wind turbine control method, device and medium to solve the black start problem of multi-converter cabinet unit in off-grid scene.

[0007] To solve the above technical problems, the present application provides a voltage source type offshore wind turbine control method, which is applied to multiple parallel connected converters,

[0008] When the off-grid state is detected, the black start control mode is triggered, one of the multiple parallel connected converters is selected as the starting converter, and the remaining converters are kept in the disconnected state;

[0009] The energy storage system charges the grid-side DC bus of the starting converter, and after the bus voltage is stable, the starting converter machine-side starts to modulate to establish a stable DC power supply, and then the starting converter grid-side starts to modulate to generate a grid voltage that meets the preset voltage amplitude and frequency parameters, and completes the black start basic network building.

[0010] When the grid voltage generated by the starting converter meets the stability determination requirement, the remaining parallel converters are started step by step; wherein, the starting converter maintains the voltage source control mode, and the remaining parallel converters perform the grid following control mode;

[0011] Wherein, the converter in the voltage source control mode is responsible for maintaining the stability of the grid voltage and frequency, and the converter in the grid following control mode adjusts the output power according to the wind turbine operating state parameters and the load demand of the grid-connected point.

[0012] Optionally, in the above-mentioned voltage source type offshore wind turbine control method, when the off-grid state is detected, the black start control mode is triggered, and the above-mentioned method further comprises:

[0013] Collecting energy storage system state parameters, including energy storage charging and discharging time, initial SOC value, energy storage rated capacity, energy storage charging efficiency and energy storage charging and discharging current change function;

[0014] Determining the energy storage SOC according to the energy storage system state parameters and the first formula;

[0015] The first formula is:

[0016] ;

[0017] In the formula, SOC (t) represents the energy storage SOC at time t, t represents the energy storage charging and discharging time, SOC0 represents the initial SOC value, C n represents the rated capacity of the energy storage, η represents the energy storage charging efficiency, I τ represents the energy storage charging and discharging current change function, d τ represents the integral of time τ from 0 to t; when charging, η < 1, when discharging, η ≈ 1, when charging, I τ <0, when discharging, I τ > 0;

[0018] Correspondingly, before triggering the black start control mode, the above-mentioned method further comprises:

[0019] Determining whether the current energy storage SOC is greater than the discharging threshold value;

[0020] If yes, triggering the black start control mode;

[0021] If not, ending.

[0022] Optionally, in the above-mentioned voltage source type offshore wind turbine control method, further comprising: collecting wind turbine operating state parameters and grid-connected point electrical parameters; the wind turbine operating state parameters include real-time generator speed; the grid-connected point electrical parameters include grid-side three-phase voltage, grid-side three-phase current and each phase power factor;

[0023] determining the unit grid-side output power according to the grid-side three-phase voltage, the grid-side three-phase current, the power factor of each phase and a second formula;

[0024] The second formula is:

[0025] ;

[0026] In the formula, represents the unit grid-side output power, U a is the grid-side A-phase voltage, I a is the grid-side A-phase current, cosφ a is the grid-side A-phase power factor; U b is the grid-side B-phase voltage, I b is the grid-side B-phase current, cosφ b is the grid-side B-phase power factor; U c is the grid-side C-phase voltage, I c is the grid-side C-phase current, cosφ c is the grid-side C-phase power factor;

[0027] determining the torque limiting value according to the unit grid-side output power and a third formula;

[0028] The third formula is:

[0029] ;

[0030] In the formula, represents the torque limiting value, represents the real-time speed of the generator;

[0031] determining whether the unit speed is less than the intermediate speed;

[0032] If yes, determining that the maximum value of the given torque output value does not exceed the torque limiting value;

[0033] If no, determining that the maximum value of the given torque output value does not exceed the torque limiting value.

[0034] Optionally, in the voltage source type offshore wind turbine control method, the voltage source control mode comprises:

[0035] acquiring the active power set value, the reactive power set value, the rated speed, the internal electromotive force when the unit is in no-load operation, the unit grid-side output power, the actual value of the reactive power, the real-time speed of the generator, the damping coefficient and the virtual inertia, and obtaining the speed deviation according to a fourth formula;

[0036] The fourth formula is:

[0037] ;

[0038] wherein, represents virtual inertia, represents speed deviation, represents active power set value, represents rated speed, represents damping coefficient;

[0039] a current generator speed reference value is obtained according to the speed deviation and a fifth formula;

[0040] the fifth formula is:

[0041]

[0042] wherein, represents generator speed reference value;

[0043] a voltage phase angle is obtained by integrating the current generator speed reference value;

[0044] an output electromotive force amplitude and a terminal voltage reference value are obtained according to a sixth formula and a seventh formula;

[0045] the sixth formula is:

[0046] the seventh formula is:

[0047] wherein, represents electromotive force amplitude, represents terminal voltage reference value, represents internal electromotive force when in no-load operation, represents reactive-voltage droop regulation coefficient, represents reactive power set value, represents reactive power actual value;

[0048] the voltage phase angle and the electromotive force amplitude are input into outer loop voltage control to generate dq coordinate system voltage instruction, and after current inner loop decoupling control and PI regulation, three-phase voltage is output through PWM modulation.

[0049] Optionally, in the above-mentioned voltage source type offshore wind turbine control method, the energy storage system is used to charge the grid-side DC bus of the starting converter, after the bus voltage is stabilized, the starting converter is controlled to start modulation on the machine side to establish a stable DC power supply, and then the starting converter is controlled to start modulation on the grid side to generate a power grid voltage meeting preset voltage amplitude and frequency parameters, thereby completing black start basic network building, including:

[0050] the energy storage system is used to charge the grid-side DC bus of the starting converter;

[0051] ​​​Issue the opening instruction to the variable pitch system to open the blades of the unit, and increase the generator speed;

[0052] Determine in real time whether the grid-connected speed, voltage phase sequence, and voltage amplitude meet preset conditions;

[0053] If yes, establish a stable DC power supply through machine-side modulation;

[0054] Start the grid-side converter modulation to establish a grid voltage with a fixed frequency and amplitude;

[0055] When the unit grid-side output power is greater than the auxiliary power circuit load power, the energy storage system gradually reduces the discharge current until it completely exits the black start control mode.

[0056] Optionally, in the above-mentioned voltage source type offshore wind turbine control method, when the grid voltage generated by the starting converter meets the stability determination requirement, the remaining parallel converters are gradually started; wherein, the starting converter remains in the voltage source control mode, and the remaining parallel converters execute the grid-following control mode, including:

[0057] Determine the unit grid-side output power according to the second formula;

[0058] Determine the given torque output value of the starting converter according to the current unit grid-side output power, to control the starting converter;

[0059] Determine the active range of the parallel converter executing the grid-following control mode according to the eighth formula;

[0060] The eighth formula is: ;

[0061] In the formula, Pn represents the rated active power of the unit, Kopt represents the optimal gain of the unit, Pd represents the active range;

[0062] Determine the torque output value of the parallel converter executing the grid-following control mode according to the active range and the ninth formula, to control the parallel converter;

[0063] The ninth formula is: ;

[0064] In the formula, T represents the torque output value of the parallel converter executing the grid-following control mode.

[0065] Optionally, in the above-mentioned voltage source type offshore wind turbine control method, when it is detected that the current state is grid-connected and no converter is in the voltage source control mode, the method further includes:

[0066] Determine whether the current energy storage SOC is less than the maximum energy storage threshold;

[0067] If yes, control the energy storage system to charge until the energy storage SOC is 100% and stop charging.

[0068] To solve the above technical problems, the application further provides a voltage source type offshore wind turbine control device, which is applied to multiple parallel converters and comprises:

[0069] The black start triggering module is configured to trigger a black start control mode when detecting an off-grid state, select one of the multiple parallel converters as a starting converter, and control the remaining converters to remain in an open state.

[0070] The black start network building module is configured to charge the grid-side DC bus of the starting converter through the energy storage system, control the machine-side of the starting converter to open modulation to build a stable DC power supply after the bus voltage is stable, and then control the grid-side of the starting converter to start modulation to generate a grid voltage meeting preset voltage amplitude and frequency parameters, thereby completing black start basic network building.

[0071] The voltage source control module is configured to gradually start the remaining parallel converters when the grid voltage generated by the starting converter meets stable determination requirements; wherein the starting converter remains in a voltage source control mode, and the remaining parallel converters execute a grid-following control mode.

[0072] The converter in the voltage source control mode is responsible for maintaining grid voltage and frequency stability, and the converter in the grid-following control mode adjusts output power according to wind turbine operating state parameters and grid-connected point load requirements.

[0073] To solve the above technical problems, the application further provides a voltage source type offshore wind turbine control device, which comprises:

[0074] The memory is configured to store a computer program.

[0075] The processor is configured to execute the computer program to implement the steps of the above-mentioned voltage source type offshore wind turbine control method.

[0076] To solve the above technical problems, the application further provides a computer readable storage medium, which has a computer program stored thereon, and the computer program is executed by a processor to implement the steps of the above-mentioned voltage source type offshore wind turbine control method.

[0077] The voltage source type offshore wind turbine control method provided in the application is applied to multiple parallel converters, triggers black start after detecting an off-grid state, selects one from the multiple parallel converters as a start converter, and keeps the rest disconnected, avoids power supply conflicts caused by simultaneous start of multiple converters, focuses on the network building efficiency of a single converter, and solves the start disorder problem in the off-grid scenario; the energy storage charges the grid-side DC bus of the start converter, the machine-side modulation builds a stable DC power supply, and the grid-side modulation generates a preset parameter grid voltage, replacing the traditional diesel generator system, solving the problem of no external power support when off-grid, avoiding damage to equipment caused by charging impact, and realizing safe network building; after the start converter builds a stable network, the remaining converters are gradually started, and the division of labor between the start converter voltage source control and the remaining converter grid-connected control is clear, solving the multiple converter parallel short circuit risk in voltage source mode; the voltage source control converter is responsible for voltage / frequency stability, and the grid-connected control converter adjusts power according to the unit state and load to ensure grid stability and power matching.

[0078] In addition, the application also provides a device and a medium corresponding to the above-mentioned voltage source type offshore wind turbine control method, and the effects are the same as above. BRIEF DESCRIPTION OF DRAWINGS

[0079] In order to more clearly illustrate the embodiments of the present application, the drawings needed in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present application, and other drawings can be obtained by those skilled in the art without creative labor on the basis of these drawings.

[0080] Figure 1 A flow chart of a voltage source type offshore wind turbine control method provided by an embodiment of the present application;

[0081] Figure 2 A direct-drive wind turbine-energy storage system principle topology diagram provided by an embodiment of the present application;

[0082] Figure 3 A unit speed-torque characteristic curve diagram provided by an embodiment of the present application;

[0083] Figure 4 A torque given control diagram provided by an embodiment of the present application;

[0084] Figure 5 A voltage source type direct-drive wind turbine control topology diagram provided by an embodiment of the present application;

[0085] Figure 6 A structure diagram of a voltage source type offshore wind turbine control device provided by an embodiment of the present application;

[0086] Figure 7Another structural diagram of a voltage source type offshore wind turbine control device provided by the embodiment of the present application. DETAILED DESCRIPTION

[0087] The technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all the embodiments of the present application. Based on the embodiments in the present application, all other embodiments obtained by a person of ordinary skill in the art without creative work fall within the protection scope of the present application.

[0088] The core of the present application is to provide a voltage source type offshore wind turbine control method, device and medium.

[0089] In order for the person in the technical field to better understand the present application scheme, the present application will be further described in detail below with reference to the drawings and specific embodiments.

[0090] The embodiment of the present application provides a voltage source type offshore wind turbine control method, which is applied to multiple parallel connected converters, such as Figure 1 As shown in the figure, the method comprises the following steps.

[0091] S11: When the off-grid state is detected, a black start control mode is triggered, one of the multiple parallel connected converters is selected as a starting converter, and the remaining converters are controlled to remain in a disconnected state;

[0092] S12: The energy storage system is used to charge the grid side DC bus of the starting converter, and after the bus voltage is stabilized, the machine side of the starting converter is controlled to start modulation to establish a stable DC power supply, and then the grid side of the starting converter is controlled to start modulation to generate a grid voltage meeting preset voltage amplitude and frequency parameters, thereby completing black start basic network building;

[0093] S13: When the grid voltage generated by the starting converter meets the stable determination requirement, the remaining parallel connected converters are gradually started; wherein, the starting converter remains in a voltage source control mode, and the remaining parallel connected converters execute a grid following control mode;

[0094] Among them, the converter in the voltage source control mode is responsible for maintaining the stability of the grid voltage and frequency, and the converter in the grid following control mode adjusts the output power according to the wind turbine operation state parameters and the grid point load demand.

[0095] The multiple parallel connected converters refer to two or more full power converters (1#, 2#, 3#) connected in an electrical parallel mode to adapt to the demand of large capacity offshore direct drive wind turbines. The core role is to jointly undertake the tasks of unit power conversion and power output. Generally speaking, the common configuration is double cabinet parallel connected converters (i.e. 2 converters in parallel), but the embodiment does not make strict restrictions. Figure 2A direct-drive wind turbine-energy storage system principle topology provided by the embodiment of the application is shown in FIG. 1. The direct-drive wind turbine is composed of double-cabinet full-power converters, and the energy storage system is connected to the AC side. The black start control of the direct-drive wind turbine is mainly to replace the power grid with the energy storage system to provide power, so that the unit control system and auxiliary variable system can normally standby. At the same time, the DC bus of the unit converter is slowly charged, and a stable DC power supply is established through machine side modulation. Then, the grid side converter starts to modulate to establish a grid voltage with a fixed frequency and amplitude, thereby realizing the black start of the wind turbine. Figure 2

[0096] The off-grid state is a state in which the electrical connection between the unit and the land grid or regional distribution network is interrupted. The detection basis includes a grid connection point voltage interruption signal and a grid fault alarm signal. In the embodiment, the three-phase voltage at the grid connection point is monitored in real time by a voltage sensor. For example, when the effective value of the voltage is less than 10% of the rated voltage for 300 ms, it is determined that the off-grid state is reached.

[0097] The selection of a starting converter is based on the optimal logic of the operating state of the converter. In the embodiment, the converter with the least number of historical faults and the shortest connection distance to the energy storage system is selected as the starting converter. At the same time, the 2# and 3# converters are kept in a disconnected state by controlling the switching devices, so as to avoid electrical conflicts during the starting process.

[0098] Detecting the off-grid state is a prerequisite for triggering the black start, which can avoid equipment damage caused by false start in non-off-grid scenarios. Secondly, the optimal starting converter can improve the success rate of black start and reduce energy loss during the starting process. Disconnecting the remaining converters can avoid the short circuit risk caused by the direct parallel connection of multiple voltage sources and lay a safe foundation for subsequent step-by-step network building.

[0099] The energy storage system is an energy storage device (lithium battery energy storage system in the embodiment) with charging and discharging functions. Its core function is to replace the traditional diesel generator system to provide starting power. The grid side DC bus charging refers to the output of current from the energy storage system to the grid side DC bus of the starting converter through a DC / DC converter.

[0100] The determination standard of the bus voltage stability is not an absolute fixed value. In the embodiment, it is set to a bus voltage fluctuation range ≤ ± 2% of the rated bus voltage and a duration of a preset time. The machine side opening modulation refers to the generation of a stable DC voltage by the machine side converter of the starting converter through pulse width modulation (PWM modulation).

[0101] The grid side starting modulation refers to the conversion of the DC power supply into an AC voltage by the grid side converter of the converter. The preset voltage amplitude and frequency parameters generally need to match the rated operating parameters of the unit, and the generated grid voltage is the internal grid reference for the subsequent operation of the unit.

[0102] ​The energy storage system supplies power to the start-up converter, solves the core problem of no external power support in off-grid scenarios, and compared with the diesel generator system, the energy storage has faster response speed and stronger controllability; the step-by-step charging and modulation logic is to gradually establish a stable electrical environment and avoid voltage mutation causing damage to the converter or generator, and finally complete the network construction without network through network-side modulation, providing a power grid foundation for subsequent multi-converter collaborative operation.

[0103] The stability determination requirement is that the internal power grid generated by the start-up converter meets the preset stability index, ensuring that the power grid has sufficient support capability when subsequent converters are connected.

[0104] Step-by-step start-up does not mean continuous start-up without interval, for example, in the embodiment, the interval between the start-up of adjacent converters is set to 800ms, the power grid parameter is monitored for 300ms after the start-up of the 2# converter, and then the 3# converter is started, to avoid power grid fluctuation caused by simultaneous connection of multiple converters.

[0105] The voltage source control mode is a control mode in which the converter actively maintains the stability of the power grid voltage and frequency, the core of which is to simulate the characteristics of a synchronous generator; the grid-following control mode is that the converter adjusts its output according to the existing power grid parameters (voltage, frequency, phase), without actively participating in the construction of the power grid, in the embodiment, the 1# converter maintains voltage source control, and the 2# and 3# converters perform grid-following control.

[0106] The step-by-step start-up strategy balances the start-up efficiency and the stability of the power grid, avoiding the electrical impact caused by the simultaneous connection of multiple converters; the differentiated allocation of control modes solves the risk of multiple converter parallel short-circuit in the voltage source mode from the root, and through functional division, multiple converters are coordinated, which not only ensures the stability of the power grid, but also improves the total output power of the unit.

[0107] In the voltage source control mode, the stability of the power grid voltage and frequency is maintained, specifically, the 1# converter monitors the electrical parameters of the grid connection point in real time, when the frequency increases by 0.3Hz due to load change, the output active power is adjusted to reduce the frequency, when the voltage decreases by 5%, the output reactive power is adjusted to raise the voltage, to ensure that the power grid parameters are always within the allowable range. The wind turbine operating state parameters include real-time generator speed, blade angle, wind speed, etc., and the grid connection point load demand is the total power demand of the user or electrical equipment in the island scenario (in the embodiment, the load power is 8MW), the 2# and 3# grid-following converters adjust the output power according to the speed and wind speed, so that the total output power of the three converters matches the 8MW load demand.

[0108] The core role of the voltage source control mode is to give the wind turbine the ability to actively support the power grid, changing the limitations of the traditional grid-following control that passively follows the power grid, so that the internal power grid has the ability to resist disturbances; the grid-following control mode realizes precise matching of power by adapting the operating state of the unit and the load demand, avoiding operating abnormalities caused by power excess or deficiency.

[0109] The voltage source type offshore wind turbine control method provided in the application is applied to multiple parallel converters, and when an off-grid state is detected, black start is triggered, one of the multiple parallel converters is selected as a starting converter, and the remaining converters are kept disconnected, so as to avoid power supply conflicts caused by simultaneous starting of multiple converters, focus on the network building efficiency of a single converter, and solve the problem of disordered starting in an off-grid scenario; the energy storage charges the grid-side DC bus of the starting converter, the machine side modulates to build a stable DC power supply, and the grid side modulation generates a preset parameter grid voltage, thereby replacing the traditional diesel generator system, solving the problem of no external power support in an off-grid state, avoiding damage to equipment caused by charging impact, and realizing safe network building; after the starting converter builds a stable network, the remaining converters are gradually started, and the division of labor between the voltage source control of the starting converter and the grid-following control of the remaining converters is clear, so as to solve the risk of parallel short circuit of multiple converters in the voltage source mode; the voltage source control converter is responsible for voltage / frequency stability, and the grid-following control converter adjusts power according to the operating state of the unit and the load, so as to ensure grid stability and power matching.

[0110] Specifically, when the off-grid state is detected, the black start control mode is triggered, and the previous method further includes the following steps:

[0111] The state parameters of the energy storage system are collected, including the energy storage charging and discharging time, the initial state of charge (SOC) value, the rated capacity of the energy storage, the energy storage charging efficiency, and the energy storage charging and discharging current change function;

[0112] The SOC of the energy storage is determined according to the state parameters of the energy storage system and the first formula;

[0113] The first formula is:

[0114] ;

[0115] In the formula, SOC(t) represents the SOC of the energy storage at time t, t represents the energy storage charging and discharging time, SOC0 represents the initial SOC value, C n represents the rated capacity of the energy storage, η represents the energy storage charging efficiency, I τ represents the energy storage charging and discharging current change function, d τ represents the integral of time τ from 0 to t; when charging, η < 1, and when discharging, η ≈ 1; when charging, I τ <0, and when discharging, I τ > 0;

[0116] Correspondingly, before triggering the black start control mode, the method further comprises:

[0117] determining whether the current energy storage SOC is greater than a discharge threshold value;

[0118] if yes, triggering the black start control mode;

[0119] if no, ending.

[0120] The energy storage system state parameters are core parameters for characterizing the energy storage operation state. In the embodiment, the energy storage management system (EMS) is used to collect the energy storage charge and discharge time, the initial SOC value, the energy storage rated capacity, the energy storage charging efficiency, and the energy storage charge and discharge current variation function in real time. It should be noted that the parameter collection is not completed at one time, but is collected in real time after the off-grid state detection and before the black start triggering, to ensure the data timeliness. Meanwhile, the charge and discharge current variation function is not a fixed value, but dynamically changes with the energy storage operation state. In the embodiment, the current sensor is used to monitor and record the variation curve in real time.

[0121] The energy storage SOC calculation (based on the first formula) is to calculate the remaining energy of the energy storage through integral operation.

[0122] The discharge threshold value is the minimum energy storage capacity required for the entire black start process (energy storage power supply, converter network building, and unit speed-up). Based on the calculation result, if the current energy storage SOC is greater than the discharge threshold value, the threshold value requirement is met, and thus the black start control mode is triggered. If not, it is determined that the energy is insufficient, the black start process is ended, and the energy storage is prevented from being damaged due to over-discharge or power failure during the start.

[0123] In addition, the discharge threshold value is not fixed and unchangeable. Generally, it needs to be dynamically adjusted according to the unit capacity, the converter startup power consumption, and the energy storage type. In the embodiment, no strict limitation is made, and the individualized needs of different units are adapted.

[0124] The new step is located between the off-grid state detection and the black start triggering. The off-grid state is a prerequisite for triggering the black start, and the SOC meeting the threshold value is a prerequisite for triggering the black start in terms of energy. Both are indispensable, and the invalid start due to the scenario meeting but the energy being insufficient is avoided.

[0125] In a specific embodiment, the method further comprises collecting wind turbine operation state parameters and grid connection point electrical parameters. The wind turbine operation state parameters include the real-time speed of the generator. The grid connection point electrical parameters include the grid-side three-phase voltage, the grid-side three-phase current, and the power factor of each phase.

[0126] The unit grid-side output power is determined according to the grid-side three-phase voltage, the grid-side three-phase current, the power factor of each phase, and the second formula.

[0127] The second formula is:

[0128] ;

[0129] In the formula, represents the unit set side output power, U a is the grid side A phase voltage, I a is the grid side A phase current, cosφ a is the grid side A phase power factor; U b is the grid side B phase voltage, I b is the grid side B phase current, cosφ b is the grid side B phase power factor; U c is the grid side C phase voltage, I c is the grid side C phase current, cosφ c is the grid side C phase power factor;

[0130] According to the unit set side output power, the third formula determines the torque limiting value;

[0131] The third formula is:

[0132] ;

[0133] In the formula, represents the torque limiting value, represents the real-time speed of the generator;

[0134] Determine whether the unit speed is less than the intermediate speed;

[0135] If it is less than, determine that the maximum value of the given torque output value does not exceed the torque limiting value;

[0136] If it is not less than, determine that the maximum value of the given torque output value does not exceed the torque limiting value.

[0137] The wind turbine operating state parameter focuses on the real-time speed of the generator. In this embodiment, the speed sensor is used to collect the real-time speed to ensure the real-time and accuracy of the speed data. The grid-connected point electrical parameters include three-phase voltage, three-phase current and power factor of each phase. The voltage sensor, current sensor and power factor monitoring module of the grid-connected point are used to collect the data synchronously. The sampling frequency can be set as required.

[0138] It should be noted that the parameter collection is throughout the whole process of black start network building and multi-converter cooperative operation, and is not only collected at a certain node, but also dynamically updated to provide real-time data support for subsequent power and torque calculation. At the same time, the collection of each parameter needs to be time-synchronized to avoid distortion of the calculation results due to time sequence deviation.

[0139] The calculation of the generator's grid-side output power (based on the second formula) uses a quantitative model of the generator's actual output power obtained by superimposing three-phase electrical parameters onto a computer. Its core function is to reflect the effective power transferred by the generator to the grid. It should also be noted that this formula is applicable to power calculations for three-phase AC systems. Whether the generator is in the black-start grid construction phase or the normal load operation phase, the actual output power can be accurately obtained using this formula, and it is not limited to a specific operating scenario.

[0140] The torque limit calculation (based on the third formula) is a torque calculation model derived from the physical relationship between power and speed. The core of this model is to convert the unit's output power into a torque constraint index.

[0141] The generator's real-time speed is dynamically adjusted according to wind speed. When the wind speed increases, causing the speed to increase, if... remain unchanged. The torque limit will decrease accordingly; conversely, it will increase, therefore the torque limit value... It is not a fixed value, but is dynamically updated according to the operating conditions to ensure the real-time performance and adaptability of the constraints.

[0142] Intermediate speed is the critical speed set based on the unit's speed-torque characteristic curve. It lies between the grid-connected speed and the rated speed and is the dividing point of the torque constraint logic. Figure 3 This is a schematic diagram of a unit speed-torque characteristic curve provided in an embodiment of this application, as shown below. Figure 3 As shown, when the unit reaches its grid-connected speed, the wind turbine begins generating electricity, and the torque instantly jumps from point A to point B. As wind speed increases, both the speed and torque rise, as shown in segment BD. When the generator speed reaches its rated speed, if the wind speed continues to increase, it enters segment DE for constant speed operation, where the unit increases power output by increasing torque. Upon reaching point E, the wind speed is at its rated speed, and the wind turbine output power is at its rated power, representing full-capacity output.

[0143] In combination with the above Figure 3 In the wind turbine control system, torque T m As a limit value for the given torque, when the speed is less than the intermediate speed ω2, the given torque output value T t The maximum value does not exceed T m Value; when the rotational speed is greater than or equal to the intermediate rotational speed ω2, the given torque output value T t The maximum value is not less than T m value.

[0144] Figure 4 A torque setpoint control diagram provided for embodiments of this application, such as Figure 4 As shown, ω m To measure the rotational speed, ω set To set the rotational speed, T t-1is the torque given value of the last time, and is the torque increment value calculated by a proportional-integral (PI) controller through the speed deviation.

[0145] Generally speaking, the setting of the intermediate speed needs to be combined with the mechanical characteristics and operation requirements of the specific unit. The present embodiment does not make strict restrictions, and different models can be flexibly adjusted according to their speed-torque curves. The core is to realize the smooth transition and safety constraint of torque output.

[0146] The wind turbine operating state parameters (real-time speed of the generator) and grid-connected point electrical parameters (three-phase voltage, current, power factor) collected in this step are consistent with the parameter collection logic of the SOC determination step of the energy storage described above, and are realized through the unit sensor and the monitoring module to form a unified parameter collection system, ensuring the consistency and reliability of the data source. At the same time, the parameter collection in this step provides a basis for subsequent torque calculation and is a prerequisite for torque limiting control.

[0147] In the black start network building phase, during the step-by-step network building process of the starting converter, this step synchronously calculates the torque limiting value to constrain the torque output of the starting converter, avoiding abnormal modulation of the converter due to excessive torque during network building. When the network building is completed, the remaining converters are gradually started, and this step provides independent torque constraints for each converter to ensure torque balance during multi-converter collaborative operation.

[0148] The converter in the voltage source control mode needs to dynamically adjust the output power to maintain the stability of the power grid. This step provides torque constraint boundaries for power adjustment by calculating the torque limiting value in real time. The converter in the grid-connected control mode also needs to follow the torque limiting value under the corresponding working condition to avoid the influence of single converter torque overrun on the overall grid stability.

[0149] In a specific embodiment, the voltage source control mode includes:

[0150] The active power set value, the reactive power set value, the rated speed, the internal electromotive force when the unit is running at no load, the unit grid-side output power, the actual value of the reactive power, the real-time speed of the generator, the damping coefficient and the virtual inertia are obtained, and the speed deviation is obtained according to the fourth formula.

[0151] The fourth formula is:

[0152] ;

[0153] In the formula, represents the virtual inertia, represents the speed deviation, represents the active power set value, represents the rated speed, represents the damping coefficient;

[0154] According to the rotational speed deviation, a fifth formula obtains a current generator rotational speed reference value;

[0155] The fifth formula is:

[0156]

[0157] In the formula, represents the generator rotational speed reference value;

[0158] According to the current generator rotational speed reference value, an integral operation is performed to obtain a voltage phase angle;

[0159] According to a sixth formula and a seventh formula, an output electromotive force amplitude and a terminal voltage reference value are obtained;

[0160] The sixth formula is:

[0161] The seventh formula is:

[0162] In the formula, represents the electromotive force amplitude, represents the terminal voltage reference value, represents an internal electromotive force when the unit is in no-load operation, represents a reactive-voltage droop adjustment coefficient, represents a reactive power set value, represents a reactive power actual value;

[0163] The voltage phase angle and the electromotive force amplitude are input into outer loop voltage control to generate dq coordinate system voltage instructions, and after current inner loop decoupling control and PI adjustment, three-phase voltages are output through PWM modulation.

[0164] The set values include an active power set value, a reactive power set value, a rated rotational speed, an internal electromotive force when the unit is in no-load operation, a damping coefficient, a virtual inertia, and a reactive-voltage droop adjustment coefficient; and the measured values include a unit grid-side output power (calculated in the foregoing), a reactive power actual value, and a real-time generator rotational speed.

[0165] It should be noted that the set values can be dynamically adjusted according to grid requirements (for example, the reactive-voltage droop adjustment coefficient can be increased to improve voltage support capability in a weak grid scenario), the measured values are collected in real time through unit sensors and monitoring modules, the sampling frequency and torque limiting control are consistent (100 Hz), and the parameter synchronism is ensured; the virtual inertia and the damping coefficient are core parameters for simulating the characteristics of a synchronous generator, and are not actual mechanical inertia and damping, but are virtually introduced through a control algorithm, and are used for adjusting the grid frequency response speed.

[0166] ​​​Speed deviation calculation (based on the fourth formula): the frequency regulation model is derived based on the synchronous generator rotor motion equation, the core is to adjust the speed change rate through the active power deviation and the speed deviation, to realize the frequency stability.

[0167] Generator speed reference value calculation (based on the fifth formula): the speed reference value is obtained by integrating the speed change rate, the core is to generate the reference value of the grid frequency.

[0168] The voltage phase angle is obtained by integrating the current speed reference value; the phase angle determines the phase reference of the output voltage, ensuring the symmetry of the three-phase voltage phase.

[0169] The electromotive force amplitude and the terminal voltage reference value are calculated by the sixth and seventh formulas, generally speaking, the outer ring voltage control is responsible for the accurate control of the voltage amplitude and phase, the current inner ring is responsible for quickly tracking the current command and suppressing harmonics, the proportional coefficient and integral coefficient of PI regulation can be optimized according to the system response characteristics, to ensure the rapidity and stability of voltage regulation.

[0170] Figure 5 A voltage source direct-drive wind turbine control topology provided by the embodiment of the application is shown in FIG. 1. Figure 5 The amplitude and angle of the voltage are obtained by the virtual synchronous control method, the voltage loop and current loop control are performed, the modulated three-phase voltage is output, and the voltage source control target based on the virtual synchronous technology is realized.

[0171] In a specific embodiment, the energy storage system is used to charge the grid-side DC bus of the starting converter, after the bus voltage is stabilized, the starting converter machine side is controlled to start modulation to establish a stable DC power source, and then the starting converter grid side is controlled to start modulation to generate a grid voltage meeting the preset voltage amplitude and frequency parameters, to complete the black start basic network building, including:

[0172] The energy storage system is used to charge the grid-side DC bus of the starting converter;

[0173] The pitch system is instructed to open the blades, so that the generator speed rises;

[0174] It is judged in real time whether the grid-connected speed, voltage phase sequence and voltage amplitude meet the preset conditions;

[0175] If yes, a stable DC power source is established through machine side modulation;

[0176] The grid side converter modulation is started to establish a grid voltage with a constant frequency and amplitude;

[0177] When the grid side output power of the unit is greater than the auxiliary circuit load power, the energy storage system gradually reduces the discharge current until it completely exits the black start control mode.

[0178] The starting converter grid-side DC bus is the core electrical circuit connecting the converter grid-side converter with the energy storage system and the power grid. To avoid current impact damage to the bus capacitor, the charging uses a constant current limiting mode, and the bus voltage is monitored in real time during the charging process.

[0179] It should be noted that the charging current is not a fixed value and can be dynamically adjusted according to the energy storage SOC. If the SOC is close to the discharge threshold (such as 20%), the charging current can be appropriately reduced to extend the energy storage discharge time and avoid depletion of the power during the start-up. Conversely, the charging current can be increased to shorten the charging time.

[0180] The opening paddle instruction is an angle adjustment instruction issued by the unit main control system to the variable pitch system. For example, in this embodiment, the paddle opening rate is set to 1° / s, and the target opening paddle angle is 30° (adapted to the low wind speed scenario in the start-up phase).

[0181] After receiving the instruction, the variable pitch system drives the paddle to gradually open from the shutdown angle (90°, the propeller state), the wind wheel captures wind energy to drive the generator rotor to rotate, and the speed gradually rises. It should be noted that the opening paddle rate and the target angle need to be adjusted in combination with the real-time wind speed: when the wind speed is high (such as 8 m / s), the opening paddle rate can be reduced (0.5° / s) to avoid the speed rising too fast; when the wind speed is low (such as 4 m / s), the target opening paddle angle can be increased (such as 35°) to improve the wind energy capture efficiency and ensure that the speed meets the grid connection requirements.

[0182] Real-time judgment is made on whether the grid connection speed, voltage phase sequence, and voltage amplitude meet the preset conditions, i.e., the corresponding threshold values. After all the preset conditions are met, the subsequent machine-side modulation step is triggered. If one condition is not met (such as the speed is only 8 rpm), the opening paddle state is maintained until all conditions meet the standards to avoid equipment damage caused by forced start-up.

[0183] Machine-side modulation is the core function of starting the converter machine-side converter, which converts the variable frequency and voltage alternating current output by the generator into stable direct current through PWM modulation. Grid-side modulation is the process of converting stable direct current into three-phase alternating current grid voltage by the grid-side converter. After receiving the stable direct current power provided by the machine side, the grid-side converter starts PWM modulation to generate a positive sequence symmetrical three-phase alternating voltage. During the modulation process, the phase symmetry of the three-phase voltage is ensured through phase-locked loop synchronization technology.

[0184] The core determination condition for the energy storage to exit is that the unit grid-side output power > auxiliary electrical circuit load power, and in this embodiment, the auxiliary electrical circuit load power includes the power consumption of the main control system, the variable pitch system, the cooling system, and other electrical equipment.

[0185] After the grid-side modulation is completed, the unit starts to supply power to the auxiliary power circuit, the output power gradually increases, and the energy storage discharge current gradually decreases, thereby avoiding current mutation to cause grid voltage fluctuation. After the energy storage completely exits, the auxiliary power circuit is independently powered by the unit, the black start control mode automatically exits, it is determined that the black start basic network construction is completed, and the unit enters a stable off-grid operation state or a grid-connected preparation state.

[0186] In a specific embodiment, when the grid voltage generated by the starting converter meets the stability determination requirement, the remaining parallel converters are gradually started; wherein the starting converter maintains the voltage source control mode, and the remaining parallel converters execute the grid-following control mode, including:

[0187] determining the unit grid-side output power according to the second formula;

[0188] determining the given torque output value of the starting converter according to the current unit grid-side output power, to control the starting converter;

[0189] determining the active range of the parallel converter executing the grid-following control mode according to the eighth formula;

[0190] The eighth formula is: ;

[0191] In the formula, Pgrid represents the unit rated active power, Kopt represents the unit optimal gain, Pgrid represents the active range;

[0192] determining the torque output value of the parallel converter executing the grid-following control mode according to the active range and the ninth formula, to control the parallel converter;

[0193] The ninth formula is: ;

[0194] In the formula, Tgrid represents the torque output value of the parallel converter executing the grid-following control mode.

[0195] Here, the second formula is continued, which is used to obtain the actual output power of the unit after the starting converter is stable, to provide a data basis for subsequent torque control and power distribution.

[0196] In this embodiment, the grid-connected point parameters are collected after the network is stable, and the unit grid-side output power is calculated by substituting the parameters into the formula. The value reflects the output capacity of the current unit single converter (starting converter).

[0197] The starting converter maintains the voltage source control mode, and the given torque output value is determined based on the current unit grid-side output power and the real-time speed of the generator, to ensure that the torque output and power output of the starting converter are matched, and at the same time, do not exceed the mechanical safety threshold.

[0198] In this embodiment, the real-time speed of the generator is used as the given torque output value of the starting converter to maintain its stable operation in the voltage source control mode and ensure that the grid voltage and frequency are not affected by the subsequent grid-connected converter.

[0199] The active range determination of the grid-connected converter is based on the grid-connected converter active power constraint model derived from the principle of maximizing wind energy utilization. The core is to limit the maximum active output of a single grid-connected converter to avoid overload and ensure that the total power of the unit does not exceed the rated value.

[0200] The torque output value calculation of the grid-connected converter (based on the ninth formula) is a model that converts the active range of the grid-connected converter into a torque control instruction. The core is to match the torque output and active output of the grid-connected converter, while following the grid parameters constructed by the starting converter for stable operation. This value is used as the torque output value of the 2# and 3# grid-connected converters to control their power output in the grid-connected mode. The grid-connected converter adjusts its torque output by tracking the grid voltage, frequency, and phase parameters.

[0201] The remaining parallel converters are started gradually. For example, the 2# converter is started first, and the 3# converter is started after the 2# converter is stable. The interval between the start of adjacent converters is set to 800ms. When each grid-connected converter is started, it first synchronizes with the grid parameters (voltage amplitude, frequency, and phase) constructed by the starting converter through a phase-locked loop, and then adjusts the output according to the calculated torque output value. After being connected, the power fluctuation at the grid connection point is monitored in real time. If the fluctuation is ≤±2% within 300ms, it is determined that the start is stable, and the next one is started.

[0202] The interval between the start of adjacent converters and the stability determination link avoids the grid parameter fluctuation caused by the simultaneous connection of multiple grid-connected converters, ensures that the grid constructed by the starting converter is always in a stable state, and improves the reliability of the coordinated operation of multiple converters.

[0203] In a specific embodiment, when it is detected that the current is in a grid-connected state and no converter is in a voltage source control mode, it further includes:

[0204] determining whether the current energy storage SOC is less than the maximum energy storage threshold;

[0205] If yes, control the energy storage system to charge until the energy storage SOC is 100% and stop charging.

[0206] When the unit is in a stable grid-connected operation state and all parallel converters are executing grid-connected control mode (no voltage source control converter), the grid support demand is low, and the redundant power of the unit can be used to charge the energy storage. The maximum energy storage threshold is the SOC corresponding to the full energy state of the energy storage (generally 100%), which is monitored in real time by the first formula in the previous section.

[0207] Execution flow: if the current energy storage SOC < 100%, control the grid-connected converter to shunt part of the active power (without affecting the power balance of the grid), to charge the energy storage system; when the current energy storage SOC rises to 100%, immediately stop charging to avoid damage to the energy storage due to overcharging.

[0208] Maintain the full charge state of the energy storage to ensure that the energy storage has sufficient power to support black start in subsequent off-grid scenarios, thereby improving the emergency response capability of the unit. It does not affect the grid-connected control of the converter and the stability of the grid. The energy storage is charged through power shunting, taking into account both operational stability and energy storage needs.

[0209] In the above embodiment, the control method of the voltage source type offshore wind turbine is described in detail, and the application also provides an embodiment of a voltage source type offshore wind turbine control device. It should be noted that the embodiments of the device part are described from two angles, one based on functional modules and the other based on hardware.

[0210] Based on the functional module angle, Figure 6 The structural diagram of a voltage source type offshore wind turbine control device provided by the embodiments of the application is shown in Figure 6 As shown in the structural diagram of a voltage source type offshore wind turbine control device, applied to multiple parallel-connected converters, comprising:

[0211] The black start triggering module 11 is used to trigger the black start control mode when the off-grid state is detected, and select one of the multiple parallel-connected converters as the starting converter, and control the remaining converters to remain in the disconnected state;

[0212] The black start network building module 12 is used to charge the grid-side DC bus of the starting converter through the energy storage system, and after the bus voltage is stabilized, control the starting converter to start modulation on the machine side to establish a stable DC power supply, and then control the starting converter to start modulation on the grid side to generate a grid voltage that meets the preset voltage amplitude and frequency parameters, and complete the black start basic network building;

[0213] The voltage source control module 13 is used to gradually start the remaining parallel-connected converters when the grid voltage generated by the starting converter meets the stability determination requirements; wherein the starting converter remains in the voltage source control mode, and the remaining parallel-connected converters execute the grid-connected control mode.

[0214] Among them, the converter in the voltage source control mode is responsible for maintaining the stability of the grid voltage and frequency, and the converter in the grid-connected control mode adjusts the output power according to the wind turbine operating state parameters and the grid-connected point load demand.

[0215] Since the embodiments of the device part correspond to the embodiments of the method part, the embodiments of the device part are described in the description of the embodiments of the method part, which will not be described here.

[0216] Figure 7 Another structure diagram of the voltage source type offshore wind turbine control device provided by the embodiment of the present application is shown in FIG. 2. The voltage source type offshore wind turbine control device includes a memory 20 for storing a computer program. Figure 7

[0217] The processor 21 is configured to implement the steps of the method for obtaining the user operation habit information according to the above embodiment (voltage source type offshore wind turbine control method) when executing the computer program.

[0218] The voltage source type offshore wind turbine control device provided by the embodiment of the present application can include but is not limited to a mobile terminal, a personal computer, a workstation, etc.

[0219] The processor 21 can include one or more processing cores, such as a 4-core processor, an 8-core processor, etc. The processor 21 can be implemented in at least one of a hardware form of a Digital Signal Processor (DSP), a Field-Programmable Gate Array (FPGA), a Programmable Logic Array (PLA). The processor 21 can also include a main processor and a coprocessor. The main processor is a processor for processing data in an awake state, also known as a Central Processing Unit (CPU). The coprocessor is a low-power processor for processing data in a standby state. In some embodiments, the processor 21 can be integrated with a Graphics Processing Unit (GPU). The GPU is responsible for rendering and drawing the content required to be displayed on the display screen. In some embodiments, the processor 21 can also include an Artificial Intelligence (AI) processor for processing machine learning related computing operations.

[0220] ​The memory 20 can include one or more computer-readable storage media that can be non-transitory. The memory 20 can also include high-speed random access memory and nonvolatile, computer-readable storage media such as one or more magnetic disk storage devices, flash memory devices. In this embodiment, the memory 20 is at least used to store the following computer program 201, wherein the computer program is loaded and executed by the processor 21, and can realize the related steps of the voltage source type offshore wind turbine control method disclosed in any of the foregoing embodiments. In addition, the resources stored by the memory 20 can also include an operating system 202 and data 203, etc., and the storage mode can be temporary storage or permanent storage. The operating system 202 can include Windows, Unix, Linux, etc. The data 203 can include but is not limited to data related to the implementation of the voltage source type offshore wind turbine control method, etc.

[0221] In some embodiments, the voltage source type offshore wind turbine control device can further include a display screen 22, an input / output interface 23, a communication interface 24, a power supply 25, and a communication bus 26.

[0222] Those skilled in the art can understand that the structure shown in the above-mentioned embodiments does not constitute a limitation on the voltage source type offshore wind turbine control device, and can include more or fewer components than those shown in the drawings. Figure 7

[0223] The voltage source type offshore wind turbine control device provided by the embodiments of the present application includes a memory and a processor, and the processor can realize the following method when executing the program stored in the memory: the voltage source type offshore wind turbine control method.

[0224] Finally, the present application also provides an embodiment of a computer-readable storage medium. The computer-readable storage medium stores a computer program, and the computer program is executed by the processor to realize the steps recorded in the above-mentioned voltage source type offshore wind turbine control method embodiments.

[0225] It can be understood that if the method in the above-mentioned embodiments is realized in the form of a software function unit and sold or used as an independent product, it can be stored in a computer-readable storage medium. Based on such understanding, the technical solutions of the present application essentially or the part that contributes to the prior art or the whole or part of the technical solutions can be embodied in the form of a software product. The computer software product is stored in a storage medium, and executes all or part of the steps of the methods of the embodiments of the present application. The foregoing storage medium includes: a U disk, a mobile hard disk, a read-only memory (Read-Only Memory, ROM), a random access memory (Random Access Memory, RAM), a magnetic disk or an optical disk, and various media that can store program codes.​

[0226] The computer readable storage medium provided by the embodiment stores a computer program, and when a processor executes the program, the following method can be realized: a voltage source type offshore wind turbine control method.

[0227] The voltage source type offshore wind turbine control method, device and medium provided by the present application are described in detail above. The embodiments in the specification are described in a progressive manner, and each embodiment mainly describes the difference from other embodiments. The same or similar parts of each embodiment can be understood by referring to each other. For the device disclosed in the embodiments, since it corresponds to the method disclosed in the embodiments, the description is relatively simple, and the related parts can be understood by referring to the method part. It should be pointed out that for ordinary skilled in the art, without departing from the principles of the present application, the present application can be improved and modified, and these improvements and modifications also fall within the protection scope of the claims of the present application.

[0228] It should also be noted that in the present specification, relationship terms such as first and second are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between the entities or operations. Moreover, the terms "include", "contain" or any other variants thereof are intended to cover non-exclusive inclusion, so that the process, method, article or device including a series of elements not only includes those elements, but also includes other elements not explicitly listed or inherent to such process, method, article or device. Without more limitations, the element defined by the statement "including a" does not exclude the presence of other identical elements in the process, method, article or device including the element.

Claims

1. A control method for a voltage source type offshore wind turbine, applied to multiple parallel converters, characterized in that: When an off-grid status is detected, the black start control mode is triggered, and one of the multiple parallel converters is selected as the starting converter, while the other converters are kept disconnected. The grid-side DC bus of the starter converter is charged by the energy storage system. After the bus voltage stabilizes, the starter converter is controlled to start modulation on the machine side to establish a stable DC power supply. Then, the grid-side modulation of the starter converter is controlled to generate a grid voltage that meets the preset voltage amplitude and frequency parameters, thus completing the basic grid construction for black start. When the grid voltage generated by the starting converter meets the stability judgment requirements, the remaining parallel converters are started gradually; among them, the starting converter maintains the voltage source control mode, while the remaining parallel converters execute the grid-following control mode; In the voltage source control mode, the converter is responsible for maintaining the stability of the grid voltage and frequency, while in the grid-connected control mode, the converter adjusts the output power according to the wind turbine's operating status parameters and the load demand at the grid connection point.

2. The control method for voltage source type offshore wind turbines according to claim 1, characterized in that: When an offline status is detected, the black boot control mode is triggered, which previously included: Collect energy storage system status parameters, including energy storage charging and discharging time, initial SOC value, rated energy storage capacity, energy storage charging efficiency, and energy storage charging and discharging current variation function; The energy storage SOC is determined based on the energy storage system state parameters and the first formula. The first formula is: ； In the formula, Let SOC represent the state of energy storage at time t, where t represents the time of energy storage charging and discharging, and SOC0 represents the initial SOC value. n Indicates the rated capacity of the energy storage, η represents the energy storage charging efficiency, and I τ d represents the function of energy storage charging and discharging current variation. τ This represents the integral of time τ from 0 to t; during charging, η<1, during discharging, η≈1, and during charging, I... τ <0, during discharge, I τ >0; Correspondingly, the process before triggering the black boot control mode also includes: Determine if the current energy storage SOC is greater than the discharge threshold; If so, then trigger the black start control mode; If not, then the process ends.

3. The control method for voltage source type offshore wind turbines according to claim 2, characterized in that: It also includes: collecting wind turbine operating status parameters and grid connection point electrical parameters; the wind turbine operating status parameters include the real-time generator speed; the grid connection point electrical parameters include grid-side three-phase voltage, grid-side three-phase current and power factor of each phase; The grid-side output power of the unit is determined based on the grid-side three-phase voltage, grid-side three-phase current, power factor of each phase, and the second formula. The second formula is: ； In the formula, U represents the grid-side output power of the generator unit. a It is the grid-side A-phase voltage, I a It is the grid-side A-phase current, cosφ a It is the power factor of phase A on the grid side; U b It is the grid-side B-phase voltage, I b It is the grid-side B-phase current, cosφ b It is the grid-side B-phase power factor; U c It is the grid-side C-phase voltage, I c It is the grid-side C-phase current, cosφ c It is the C-phase power factor on the grid side; The torque limit value is determined based on the unit's grid-side output power and the third formula. The third formula is as follows: ； In the formula, Indicates the torque limiting value. Indicates the real-time speed of the generator; Determine if the unit speed is lower than the intermediate speed; If it is less than, then the maximum value of the given torque output value is determined to be no more than the torque limit value; If it is not less than, then the maximum value of the given torque output value is determined to be no less than the torque limit value.

4. The control method for voltage source type offshore wind turbines according to claim 3, characterized in that: The voltage source control modes include: Obtain the active power setpoint, reactive power setpoint, rated speed, internal electromotive force during no-load operation, grid-side output power of the generator unit, actual reactive power, real-time generator speed, damping coefficient, and virtual inertia, and obtain the speed deviation according to the fourth formula; The fourth formula is: ； In the formula, Represents virtual inertia. Indicates the speed deviation. This indicates the active power setpoint. Indicates the rated speed. Indicates the damping coefficient; The current generator speed reference value is obtained based on the speed deviation and the fifth formula. The fifth formula is: ； In the formula, This indicates the reference value for generator speed; The voltage phase angle is obtained by integrating the current generator speed reference value. The output electromotive force amplitude and terminal voltage reference value are obtained according to the sixth and seventh formulas. The sixth formula is: ; The seventh formula is: ; In the formula, Indicates the amplitude of electromotive force. This indicates the reference value of the terminal voltage. This represents the internal potential during no-load operation. This represents the reactive power-voltage droop adjustment coefficient. This indicates the reactive power setpoint. This represents the actual value of reactive power. The voltage phase angle and the electromotive force amplitude are input into the outer loop voltage control to generate a dq coordinate system voltage command. After decoupling control of the current inner loop and PI regulation, the three-phase voltage is output through PWM modulation.

5. The control method for voltage source type offshore wind turbines according to claim 1, characterized in that: The grid-side DC bus of the starting converter is charged through an energy storage system. After the bus voltage stabilizes, the starting converter's machine side is controlled to start modulation to establish a stable DC power supply. Then, the grid-side modulation of the starting converter is controlled to generate a grid voltage that meets the preset voltage amplitude and frequency parameters, thus completing the basic grid construction for black start, including: The grid-side DC bus of the start-up converter is charged through an energy storage system; The pitch control system sends a pitch command to the turbine blades to open, causing the generator speed to increase. Real-time assessment of whether grid-connected speed, voltage phase sequence, and voltage amplitude meet preset conditions; If so, a stable DC power supply is established through machine-side modulation; Start the grid-side converter modulation to establish a grid voltage with a set frequency and amplitude; When the grid-side output power of the generator unit exceeds the load power of the auxiliary power circuit, the energy storage system gradually reduces the discharge current until it completely exits the black start control mode.

6. The control method for voltage source type offshore wind turbines according to claim 3, characterized in that: When the grid voltage generated by the starting converter meets the stability criteria, the remaining parallel converters are gradually started. The starting converter maintains voltage source control mode, while the remaining parallel converters execute grid-following control mode, including: The grid-side output power of the generator set is determined according to the second formula; The given torque output value of the starting converter is determined based on the current grid-side output power of the unit, so as to control the starting converter; The active power range of the parallel converter executing the grid-connected control mode is determined according to the eighth formula. The eighth formula is: ; In the formula, This indicates the rated active power of the generator unit. Indicates the optimal gain of the generator set. Indicates the active power range; Based on the active power range and the ninth formula, the torque output value of the parallel converter executing the grid-connected control mode is obtained to control the parallel converter. The ninth formula is: ; In the formula, This indicates the torque output value of the parallel converter executing grid-connected control mode.

7. The control method for voltage source type offshore wind turbines according to claim 3, characterized in that: If it is detected that the current state is grid-connected and no converter is in the voltage source control mode, then the method further includes: Determine if the current energy storage SOC is less than the maximum energy storage threshold; If so, the energy storage system will be charged until the energy storage SOC reaches 100%, at which point charging will stop.

8. A voltage source type offshore wind turbine control device, characterized in that, For use with multiple converters connected in parallel, including: The black start trigger module is used to trigger the black start control mode when an off-grid status is detected, select one of the multiple parallel converters as the starting converter, and control the other converters to remain disconnected. The black start grid connection module is used to charge the grid-side DC bus of the starter converter through the energy storage system. After the bus voltage stabilizes, it controls the starter converter to start modulation on the machine side to establish a stable DC power supply. Then, it controls the starter converter to start modulation on the grid side to generate a grid voltage that meets the preset voltage amplitude and frequency parameters, thus completing the black start basic grid connection. The voltage source control module is used to gradually start the remaining parallel converters when the grid voltage generated by the starting converter meets the stability judgment requirements; wherein, the starting converter maintains the voltage source control mode, and the remaining parallel converters execute the grid-following control mode; In the voltage source control mode, the converter is responsible for maintaining the stability of the grid voltage and frequency, while in the grid-connected control mode, the converter adjusts the output power according to the wind turbine's operating status parameters and the load demand at the grid connection point.

9. A voltage source type offshore wind turbine control device, characterized in that, include: Memory, used to store computer programs; A processor, configured to execute the computer program to implement the steps of the voltage source type offshore wind turbine control method as described in any one of claims 1 to 7.

10. A computer-readable storage medium, characterized in that, The computer-readable storage medium stores a computer program that, when executed by a processor, implements the steps of the voltage source type offshore wind turbine control method as described in any one of claims 1 to 7.

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