Smooth starting method and device for wind power plant of offshore wind power flexible direct current power transmission system

Abstract

The invention relates to the technical field of new energy, and discloses a smooth starting method and device for a wind power plant of an offshore wind power flexible direct current power transmission system. The method is applied to an offshore wind power flexible direct-current power transmission system and comprises the following steps: controlling an onshore converter station to establish direct-current voltage for a direct-current power transmission line; the offshore flexible direct current converter valve is controlled to charge a first wind turbine generator set in a mode of boosting from zero, and the first wind turbine generator set is any one of the at least one wind turbine generator set; and after charging of the first wind turbine generator is completed, the first wind turbine generator is started. According to the method, the offshore flexible direct current converter valve is used for boosting from zero to achieve simultaneous smooth starting of the multiple wind power units, the starting time of the wind power plant is shortened, the starting efficiency of the wind power plant is improved, meanwhile, the influence of boosting variable excitation inrush current of the wind power units caused by a traditional starting mode can be eliminated, and impact on key electrical equipment in the starting process is avoided.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of new energy, in particular to a wind farm smooth starting method and device for offshore wind power flexible DC transmission system. BACKGROUND

[0002] Currently, in actual engineering, only one wind turbine is started at the same time on one AC transmission sea cable when the offshore wind turbine is started, because when the wind turbine booster high-voltage side switch is closed, the excitation inrush current is generated, and the excitation inrush current is usually 6 to 7 times the rated current. If multiple wind turbines are started at the same time, the superimposed excitation inrush current will exceed the current carrying limit of the sea cable, resulting in damage to the sea cable. Therefore, the wind turbines connected to one sea cable can only be started one by one, which is low in efficiency, and even if it is single starting, it still faces the impact of excitation inrush current. In addition, the DC side capacitor voltage of the converter in the wind turbine is close to 0 at the starting moment. In order to avoid the damage of the wind turbine caused by the instantaneous overcurrent impact of the grid-connected breaker, in the related technology, soft starting equipment such as soft starting resistor and bypass switch is configured in each wind turbine. The soft starting equipment limits the impact current on the wind turbine at the initial starting stage, and after the DC capacitor voltage rises to a certain level, the soft starting resistor is taken out of operation through the bypass switch. The charging time of each wind turbine through the soft starting resistor is about 20 seconds. The number of wind turbines in the wind farm is large, and the soft starting of multiple wind turbines significantly increases the starting time. Even if the soft starting equipment is configured, the starting impact cannot be completely avoided. Specifically, after the DC capacitor charging is completed through the soft starting resistor, when the wind turbine booster low-voltage side switch is closed, a large instantaneous charging current is still generated, which increases the equipment failure rate. SUMMARY

[0003] Therefore, the present application provides a wind farm smooth starting method and device for offshore wind power flexible DC transmission system to solve the problem of reducing the starting cost of the wind farm.

[0004] In a first aspect, the present application provides a wind farm smooth starting method for offshore wind power flexible DC transmission system, which is applied to the offshore wind power flexible DC transmission system, and the system comprises: an onshore power grid, an onshore converter station, an offshore converter station and an offshore wind farm. The onshore power grid is connected with the onshore converter station. The onshore converter station is connected with the offshore converter station through a DC transmission line. The offshore converter station comprises an offshore flexible DC converter valve and an offshore AC bus. The offshore wind farm comprises at least one wind turbine. For each wind turbine, the wind turbine is connected with the offshore flexible DC converter valve through an AC transmission sea cable and the offshore AC bus. The method comprises: controlling the onshore converter station to establish a DC voltage for the DC transmission line; The offshore flexible converter is controlled to charge the first wind turbine in a zero-voltage-rising manner, wherein the first wind turbine is any one of at least one wind turbine; After the first wind turbine is charged, the first wind turbine is started.

[0005] By the method provided in the embodiment, in the first aspect, in the related art, when the high-voltage side switch of the wind turbine booster is closed, an excitation inrush current of 6 to 7 times the rated current or more is generated. If multiple wind turbines are started at the same time, the superimposed excitation inrush current will exceed the current carrying limit of the submarine cable, resulting in overheating and damage of the submarine cable. Therefore, only one wind turbine can be started at the same time on one AC power transmission submarine cable. For example, in the related art, 10 wind turbines are connected by one submarine cable, and each wind turbine needs to be started one by one, during which the wind farm can only generate part of the power, and a large amount of electric energy is wasted. In the embodiment of the present application, the offshore flexible converter charges the wind turbine in a zero-voltage-rising manner, and all wind turbines on one submarine cable can be boosted and excited at the same time, or even the wind turbines of the entire wind farm can be boosted and excited, without generating an excitation inrush current. For example, in the submarine cable loop of 10 wind turbines, the 10 wind turbines can be charged and started at the same time by using the method of the present application. In this way, the wind farm is started smoothly, the overall starting time of each wind turbine in the wind farm is shortened, the starting efficiency of the wind farm is improved, the "curtailed wind power" loss during the starting stage is greatly reduced, and the annual power generation and economic benefits of the wind farm are indirectly improved. In the second aspect, compared with the related art in which each wind turbine needs to be charged by soft-start resistors, bypass switches and other soft-start devices to charge the converter DC capacitor, each charging time is at least about 20 seconds. By using the method provided in the embodiment, the offshore flexible converter is controlled to charge the first wind turbine in a zero-voltage-rising manner, and during the black start process of the wind turbine, the soft-start device is not needed for charging, and the DC capacitor can be charged directly by the zero-voltage-rising of several hundred milliseconds. In this way, the charging time of each wind turbine and the entire wind farm is further shortened, while the operation is simple and the reliability is high. In the third aspect, in the related art, even if the soft-start device is configured, the starting impact cannot be completely avoided. Specifically, after the DC capacitor is charged by the soft-start resistor, a large instantaneous charging current is still generated at the moment when the low-voltage side switch of the wind turbine booster is closed, and the impact repeatedly acts on the components in the wind turbine converter, accelerates the insulation aging and mechanical wear of the components, and causes the equipment failure rate to increase. In the starting process of the present application, the voltage and current change smoothly during the zero-voltage-rising process of the offshore flexible converter, and gradually rises from 0 to the target value, so that the wind turbines in the wind farm are started smoothly, the damage of the impact load to the core components of the wind turbine is avoided, the service life of the equipment is significantly prolonged, the maintenance cost of the wind farm is reduced, and the long-term economic benefits of the wind farm are further improved.

[0006] In an alternative embodiment, each wind turbine generator includes a wind turbine converter; the offshore converter station further includes a linking transformer; the wind turbine converter is connected to the AC transmission cable through the corresponding wind turbine booster transformer low-voltage side switch, the wind turbine booster transformer high-voltage side switch, and the AC transmission cable is connected to the offshore AC bus through the AC transmission cable outlet switch; the offshore AC bus is connected to the offshore HVDC converter valve through the linking transformer grid side switch, the linking transformer, and the linking transformer valve side switch; Before controlling the offshore HVDC converter valve to charge the first wind turbine generator in a zero-voltage-rising manner, the method further includes: closing the corresponding wind turbine booster transformer low-voltage side switch, the wind turbine booster transformer high-voltage side switch, the AC transmission cable outlet switch, the linking transformer grid side switch, and the linking transformer valve side switch of the first wind turbine generator.

[0007] In an alternative embodiment, each wind turbine generator further includes a wind turbine booster transformer; Controlling the offshore HVDC converter valve to charge the first wind turbine generator in a zero-voltage-rising manner includes: controlling the offshore HVDC converter valve to charge the wind turbine converter in the first wind turbine generator in a zero-voltage-rising manner, simultaneously charging the AC transmission cable corresponding to the first wind turbine generator, and exciting the wind turbine booster transformer in the first wind turbine generator.

[0008] In an alternative embodiment, the wind turbine converter includes a machine-side converter, a grid-side converter, and a DC capacitor; Controlling the offshore HVDC converter valve to charge the wind turbine converter in a zero-voltage-rising manner includes: controlling the offshore HVDC converter valve to charge the DC capacitor in a zero-voltage-rising manner through AC voltage amplitude and frequency control (V / F control).

[0009] In an alternative embodiment, the method further includes: After the DC voltage of the DC capacitor reaches a preset DC voltage, determining that the charging of the wind turbine converter is complete.

[0010] In an alternative embodiment, the wind turbine converter includes a grid-side converter; after the charging of the first wind turbine generator is complete, starting the first wind turbine generator includes: after the charging of the wind turbine converter is complete, unlocking the grid-side converter; controlling the grid-side converter to establish a rated DC voltage corresponding to the first wind turbine generator to start the first wind turbine generator.

[0011] In a second aspect, the present application provides a wind farm smooth starting device for offshore wind power flexible DC power transmission system, which is applied to offshore wind power flexible DC power transmission system, and the system comprises: an onshore power grid, an onshore converter station, an offshore converter station and an offshore wind farm; the onshore power grid is connected with the onshore converter station; the onshore converter station is connected with the offshore converter station through a DC transmission line; the offshore converter station comprises an offshore flexible DC converter valve and an offshore AC bus; the offshore wind farm comprises at least one wind turbine, and for each wind turbine, the wind turbine is connected with the offshore flexible DC converter valve through an AC transmission cable and the offshore AC bus. The device comprises: a first control module configured to control the onshore converter station to establish a DC voltage for the DC transmission line; a second control module configured to control the offshore flexible DC converter valve to charge a first wind turbine in a zero-voltage step-up manner, wherein the first wind turbine is any one of the at least one wind turbine; a starting module configured to start the first wind turbine after the first wind turbine is charged.

[0012] The device provided by the embodiment, first, in the related art, when the closed fan booster is high-voltage side switch, a magnetic surge current of 6 to 7 times the rated current or more is generated, if multiple fans are started at the same time, the superimposed magnetic surge current will exceed the current carrying limit of the submarine cable, resulting in overheating and damage of the submarine cable. Therefore, only one fan can be started at the same time on one AC power transmission submarine cable. Taking a submarine cable connected to 10 fans as an example, in the related art, each fan needs to be started one by one, and during this period, the wind farm can only generate part of the power, wasting a large amount of electric energy. In the embodiment of the application, the offshore flexible HVDC valve charges the fan in a zero-voltage starting and boosting mode, and can boost the excitation of all fans on one submarine cable at the same time, or even support the excitation of all fans in the entire wind farm, without generating a magnetic surge current. Taking the submarine cable loop of 10 fans as an example, the method of the application can realize the simultaneous charging and synchronous starting of 10 fans. While starting the wind farm smoothly, the overall starting time of each wind farm in the wind farm is shortened, the starting efficiency of the wind farm is improved, the "curtailed wind" loss during the starting stage is greatly reduced, and the annual power generation and economic benefit of the wind farm are indirectly improved. Second, compared with the related art, each wind turbine generator needs to charge the converter DC capacitor through soft starting resistors, bypass switches and other soft starting devices, and each charging time is at least about 20 seconds. Through the method provided by the embodiment, the offshore flexible HVDC valve charges the first wind turbine generator in a zero-voltage starting and boosting mode, and does not need to charge through soft starting devices during the black start process of the wind turbine generator. The DC capacitor charging can be completed through zero-voltage starting and boosting of hundreds of milliseconds. While being simple to operate and highly reliable, the charging time of a single fan and the entire wind farm is further shortened. Third, in the related art, even if soft starting devices are configured, starting impact cannot be completely avoided. Specifically, after completing the DC capacitor charging through the soft starting resistor, a large instantaneous charging current is still generated at the moment of closing the fan booster low-voltage side switch, and the impact repeatedly acts on the components in the fan converter, accelerating the insulation aging and mechanical wear of the components, and causing the equipment failure rate to rise. In the starting process of the application, the voltage and current change smoothly during the zero-voltage starting and boosting process of the offshore flexible HVDC valve, gradually rising from 0 to the target value, realizing the smooth starting of each fan in the wind farm, avoiding the damage of the impact load to the core components of the fan, significantly prolonging the service life of the equipment, reducing the maintenance cost of the wind farm, and further improving the long-term economic benefit of the wind farm.

[0013] Third, the application provides a computer device, comprising a memory and a processor, the memory and the processor are in communication connection with each other, the memory stores computer instructions, and the processor executes the computer instructions to perform the offshore wind power flexible DC power transmission system wind farm smooth starting method of the first aspect or any of the corresponding embodiments thereof.

[0014] In a fourth aspect, the present application provides a computer readable storage medium, having stored thereon computer instructions for causing a computer to execute the offshore wind farm smooth starting method of the offshore wind farm flexible HVDC power transmission system according to the first aspect or any of the corresponding embodiments thereof.

[0015] In a fifth aspect, the present application provides a computer program product comprising computer instructions for causing a computer to execute the offshore wind farm smooth starting method of the offshore wind farm flexible HVDC power transmission system according to the first aspect or any of the corresponding embodiments thereof. BRIEF DESCRIPTION OF DRAWINGS

[0016] In order to more clearly illustrate the specific embodiments of the present application or the technical solutions in the prior art, the drawings required to be used in the specific embodiments or prior art description will be briefly introduced as follows. Obviously, the drawings in the following description are some embodiments of the present application, and other drawings can also be obtained by those skilled in the art without any creative effort on the basis of these drawings.

[0017] Figure 1 is a structural schematic diagram of an offshore wind farm flexible HVDC power transmission system according to an embodiment of the present application; Figure 2 is a schematic diagram of connection between a wind turbine generator and an offshore HVDC converter valve in an offshore wind farm according to an embodiment of the present application; Figure 3 is a flowchart of an offshore wind farm flexible HVDC power transmission system wind farm smooth starting method according to an embodiment of the present application; FIG. 4(a) is a schematic diagram of wind turbine generator terminal voltage when starting the wind farm by using a soft starting device according to an embodiment of the present application; FIG. 4(b) is a schematic diagram of wind turbine generator terminal voltage when starting the wind farm by using the starting method provided in the embodiments of the present application according to an embodiment of the present application; FIG. 5(a) is a schematic diagram of charging current when starting the wind farm by using a soft starting device according to an embodiment of the present application; FIG. 5(b) is a schematic diagram of charging current when starting the wind farm by using the starting method provided in the embodiments of the present application according to an embodiment of the present application; FIG. 6(a) is a schematic diagram of wind turbine generator converter DC voltage when starting the wind farm by using a soft starting device according to an embodiment of the present application; FIG. 6(b) is a schematic diagram of wind turbine generator converter DC voltage when starting the wind farm by using the starting method provided in the embodiments of the present application according to an embodiment of the present application; Figure 7 is a structural block diagram of an offshore wind farm flexible HVDC power transmission system wind farm smooth starting device according to an embodiment of the present application; Figure 8 This is a schematic diagram of the structure of a computer device according to an embodiment of the present invention. Detailed Implementation

[0018] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0019] Figure 1 This is a schematic diagram of a flexible DC transmission system for offshore wind power. Figure 1 As shown, the system includes: onshore power grid 1, onshore converter station 2, offshore converter station 3, and offshore wind farm 4.

[0020] Among them, the onshore power grid 1 is connected to the onshore converter station 2; the onshore converter station 2 (including the onshore flexible DC converter valve) is connected to the offshore converter station 3 through the DC transmission line; the offshore converter station 3 includes the offshore flexible DC converter valve 31 and the offshore AC bus 32.

[0021] The offshore wind farm 4 includes at least one wind turbine 41. For each wind turbine 41, the wind turbine 41 is connected to the offshore flexible DC converter valve 31 via an AC transmission submarine cable 42 and an offshore AC bus 32.

[0022] Figure 2 This is a schematic diagram showing the connection between a wind turbine in an offshore wind farm and an offshore flexible DC converter valve. Figure 2 As shown, the wind turbine generator set 41 includes a wind turbine converter 411 and a wind turbine step-up transformer 412. The offshore converter station 3 also includes a connecting transformer 33; the wind turbine converter 411 is connected to the AC transmission submarine cable through the low-voltage side switch 413 of the wind turbine step-up transformer 412 and the high-voltage side switch 414 of the wind turbine step-up transformer corresponding to the wind turbine generator set 41; the AC transmission submarine cable 42 is connected to the offshore AC busbar 32 through the AC transmission submarine cable 42 outgoing switch; the offshore AC busbar 32 is connected to the offshore flexible DC converter valve 31 through the connecting transformer side switch 34, the connecting transformer 33 and the connecting valve side switch 35.

[0023] Specifically, the wind turbine converter 411 is a power electronic device used to convert the electrical energy output from the generator into AC-DC-AC converters. The wind turbine converter 411 includes a machine-side converter (MSC), a grid-side converter (GSC), and a DC capacitor C. Figure 2In the middle, the machine side converter is connected with the grid side converter through the DC capacitor (C).

[0024] The fan booster transformer 412 is a device for raising low-voltage alternating current to high-voltage alternating current in the wind turbine 41. The fan converter 411 is connected with the wind turbine 41 through the corresponding fan booster low-voltage side switch 413, the fan booster transformer 412, the fan booster high-voltage side switch 414, and the AC power transmission submarine cable 42.

[0025] The machine side converter is the part of the fan converter 411 connected with the wind generator, usually a rectifier, which converts the variable-frequency alternating current output by the generator into direct current, achieving energy transmission and motor control.

[0026] The grid side converter is the part of the fan converter 411 connected with the fan booster transformer 412, usually an inverter, which converts the direct current side energy into alternating current of the same frequency and phase as the power grid, achieving grid control.

[0027] The DC capacitor is an energy storage element connecting the machine side converter and the grid side converter, usually an electrolytic capacitor or a film capacitor, which is used to stabilize the DC voltage, buffer energy fluctuations, and suppress voltage pulsation.

[0028] In the fan converter 411, the AC input end of the machine side converter is connected with the stator or rotor winding of the wind generator, the DC output end of the machine side converter is connected with the DC capacitor through a bus, the other end of the DC capacitor is connected with the DC input end of the grid side converter through a bus, and the AC output end of the grid side converter is connected with the fan booster low-voltage side switch 413 through a filter composed of an inductor (L C ) and a capacitor (C f ). Figure 2

[0029] Figure 2 For example, in the related art, first, the rated AC bus voltage is established through the offshore HVDC converter valve 31. Then, the AC power transmission submarine cable outlet switch 43 is closed to charge the AC power transmission submarine cable. Next, the fan booster high-voltage side switch 414 and the fan booster low-voltage side switch 413 connected with the fan booster transformer 412 are closed, and the AC voltage charges the DC capacitor through the anti-parallel diode of the grid side converter. To avoid overcurrent impact damage to the fan caused by the instantaneous closing of the fan booster high-voltage side switch 414, a soft start device (including a soft start resistor and a corresponding contactor) is connected in series with the DC capacitor to charge it when the fan starts. Finally, when the DC capacitor is charged to a certain preset DC voltage, the contactor connected in parallel with the soft start resistor in the soft start device is closed to bypass the branch with the soft start resistor, completing the start of the fan. Figure 2 ​​​

[0030] In related technologies, such as Figure 2 As shown, to avoid damage to equipment from instantaneous overcurrent surges when closing the grid-connected circuit breaker, a set of soft-start equipment, including soft-start resistors, bypass switches, and their controls, is configured. Each wind turbine takes approximately 20 seconds to charge through the soft-start resistor. With a large number of wind turbines in a wind farm, the soft-starting of multiple turbines significantly increases the startup time. Furthermore, even with the soft-start equipment, startup shocks cannot be completely avoided. Specifically, after charging the DC capacitor through the soft-start resistor, a large instantaneous charging current is still generated when closing the low-voltage side switch of the turbine's step-up transformer, leading to an increased equipment failure rate. Therefore, how to achieve a smooth startup of the wind farm during the black start phase without using soft-start equipment is a current focus.

[0031] In view of this, this application provides a method for smooth startup of a wind farm in an offshore wind power flexible DC transmission system. The method includes: first, controlling the onshore converter station 2 to establish DC voltage for the DC transmission line; then, controlling the offshore flexible DC converter valve 31 to charge a first wind turbine in a zero-start voltage boost manner, wherein the first wind turbine is any one of at least one wind turbine 41; finally, after the first wind turbine has been charged, starting the first wind turbine.

[0032] By the method provided in the embodiment, in the first aspect, in the related art, when the booster of the closed fan is high-voltage side switch, an excitation inrush current of 6 to 7 times the rated current or more will be generated, if multiple fans are started at the same time, the superimposed excitation inrush current will exceed the current carrying limit of the submarine cable, resulting in overheating and damage of the submarine cable. Therefore, only one fan can be started at the same time on one AC power transmission submarine cable. Taking a submarine cable connected to 10 fans as an example, in the related art, each fan needs to be started one by one, and during this period, the wind farm can only generate part of the power, wasting a large amount of electric energy, while in the embodiment of the application, the offshore HVDC valve charges the fan in a zero-voltage boosting manner, and the excitation inrush current is generated when the voltage of the fan is boosted on the same submarine cable, or even the excitation inrush current is generated when the voltage of the fan is boosted in the entire wind farm. The same example of a submarine cable loop of 10 fans is taken, and the method of the application can realize the charging and synchronous starting of 10 fans at the same time. While starting the wind farm smoothly, the overall starting time of each wind farm in the wind farm is shortened, the starting efficiency of the wind farm is improved, the "curtailed wind" loss in the starting stage is greatly reduced, and the annual power generation and economic benefit of the wind farm are indirectly improved. In the second aspect, compared with the related art, each wind turbine generator needs to charge the converter DC capacitor through soft start resistance, bypass switch and other soft start devices, and the charging time of each fan is at least about 20 seconds. Through the method provided in the embodiment, the offshore HVDC valve charges the first wind turbine generator in a zero-voltage boosting manner, and the soft start device is not needed during the black start process of the wind turbine generator, and the DC capacitor charging can be completed directly through the zero-voltage boosting of hundreds of milliseconds. While the operation is simple and reliable, the charging time of a single fan and the entire wind farm is further shortened. In the third aspect, in the related art, even if the soft start device is configured, the starting impact cannot be completely avoided. Specifically, after the DC capacitor is charged through the soft start resistance, a large instantaneous charging current will be generated at the moment when the low-voltage side switch of the fan booster is closed, and the impact will repeatedly act on the components in the fan converter, accelerating the insulation aging and mechanical wear of the components, and causing the equipment failure rate to rise. In the starting process of the application, the voltage and current change smoothly during the zero-voltage boosting process of the offshore HVDC valve, gradually rising from 0 to the target value, realizing the smooth starting of each fan in the wind farm, avoiding the damage of the impact load to the core components of the fan, significantly prolonging the service life of the equipment, reducing the maintenance cost of the wind farm, and further improving the long-term economic benefit of the wind farm.

[0033] It should be noted that the execution subject of the offshore wind power flexible DC power transmission system wind farm smooth starting method provided by the embodiment of the present application can be an offshore wind power flexible DC power transmission system wind farm smooth starting device, and the offshore wind power flexible DC power transmission system wind farm smooth starting device can be realized by software, hardware or a combination of software and hardware to become part or all of an electronic device, wherein the electronic device can be a server or a terminal, wherein the server in the embodiment of the present application can be a server, or a server cluster composed of multiple servers, and the terminal in the embodiment of the present application can be a smart phone, a personal computer, a tablet computer, a wearable device, a smart robot and other smart hardware devices. In the following method embodiment, the execution subject is taken as an example to be an electronic device.

[0034] According to the embodiment of the present application, an offshore wind power flexible DC power transmission system wind farm smooth starting method embodiment is provided. It should be noted that the steps shown in the flowchart of the accompanying drawings can be executed in a computer system such as a set of computer executable instructions, and although the logical order is shown in the flowchart, in some cases, the steps shown or described can be executed in an order different from here.

[0035] In the present embodiment, an offshore wind power flexible DC power transmission system wind farm smooth starting method is provided, which can be used for the above-mentioned electronic device, such as a server, etc. Figure 3 The flowchart of the offshore wind power flexible DC power transmission system wind farm smooth starting method according to the embodiment of the present application is shown as Figure 3 The flowchart includes the following steps: S101, controlling the onshore converter station to establish a DC voltage for the DC power transmission line.

[0036] The offshore wind power flexible DC power transmission system wind farm smooth starting method provided by the embodiment of the present application will be described exemplarily below. Figure 1 Figure 2 In the case where the onshore converter station 2 includes an onshore flexible DC converter valve, the trigger angle of the insulated gate bipolar transistor (IGBT) in the onshore flexible DC converter valve is controlled to gradually increase the DC voltage output by the onshore flexible DC converter valve. In the process of voltage step-up, the DC voltage of the DC power transmission line is collected in real time and compared with the target DC voltage, and the trigger angle is adjusted according to the deviation until the collected DC voltage stabilizes at the target DC voltage.

[0037] S102, controlling the offshore flexible DC converter valve to charge the first wind turbine in a zero-voltage step-up manner.

[0038] The first wind turbine is any one of the at least one wind turbine 41.​

[0039] Specifically, the zero-voltage boosting refers to gradually and smoothly increasing the voltage from an initial state of zero voltage until reaching the preset DC voltage.

[0040] For example, the offshore flexible HVDC valve 31 gradually increases the AC output voltage according to the preset boosting rate, and the AC output voltage is transmitted to the first wind turbine through the offshore AC bus 32 and the AC transmission cable 42.

[0041] S103, after the first wind turbine is charged, starting the first wind turbine.

[0042] For example, after the first wind turbine is charged, the process of starting the first wind turbine includes: first, controlling the pitch system to gradually pitch the blades from the standby angle (such as 90°, at which the blades are almost not windward) to the optimal windward angle (such as 30°). Then, as the wind speed drives the blades to rotate, the generator speed gradually increases, and when the speed reaches the grid-connected speed (such as 1500r / min, corresponding to 50Hz AC power), the grid-connected switch is closed to connect the first wind turbine to the offshore AC bus 32. After grid connection, the blade angle and the generator excitation current are adjusted according to the wind speed to gradually increase the output power of the first wind turbine to the rated power.

[0043] For example, during the boosting process, the DC voltage of the DC capacitor in the first wind turbine is detected in real time until the DC voltage of the DC capacitor reaches the preset DC voltage, at which point it is determined that the first wind turbine is charged and the first wind turbine is started.

[0044] In some embodiments, before controlling the offshore flexible HVDC valve 31 to charge the first wind turbine in a zero-voltage boosting manner, the method provided by the embodiments of the present application further includes the following contents: Close the wind turbine boosting low-voltage side switch 413, the wind turbine boosting high-voltage side switch 414, the AC transmission cable outlet switch 43, the coupling variable grid side switch 34, and the coupling variable valve side switch 35 corresponding to the first wind turbine.

[0045] The closing sequence of the switches is not limited in the embodiments of the present application. For example, the coupling transformer-side switch 35, the coupling transformer-network-side switch 34, the AC transmission cable outlet switch 43, the fan booster transformer high-voltage-side switch 414, and the fan booster transformer low-voltage-side switch 413 are closed in sequence. After each switch is closed, whether the switch is closed to the position can be detected by the auxiliary contact or the sensor installed at the switch. In this way, by closing the switches in sequence, a complete charging circuit from the offshore HVDC converter 31 to the wind turbine generator 41 is established, so that the current generated by the subsequent zero-voltage rise can smoothly reach the wind turbine generator 41 for charging. The charging failure caused by the failure of closing a switch is avoided, and the reliability of the starting process is improved. In addition, the closing operation of all switches is completed before the zero-voltage rise, so that the operation impact caused by the switching operation during the charging process is avoided, the smoothness of the subsequent zero-voltage rise process is ensured, and the wind turbine generator equipment is further protected.

[0046] In an alternative embodiment, in S102, the offshore HVDC converter 31 is controlled to charge the first wind turbine generator in a zero-voltage rise manner, which specifically includes the following contents: The offshore HVDC converter 31 is controlled to charge the fan converter 411 in the first wind turbine generator in a zero-voltage rise manner, simultaneously charge the AC transmission cable 42 corresponding to the first wind turbine generator, and excite the fan booster transformer 412 in the first wind turbine generator.

[0047] Specifically, for example, the path for charging the fan converter 411 in the first wind turbine generator is offshore HVDC converter 31 → coupling transformer-side switch 35 → coupling transformer 33 → coupling transformer-network-side switch 34 → offshore AC bus 32 → AC transmission cable outlet switch 43 → AC transmission cable 42 → fan booster transformer high-voltage-side switch 414 → fan booster transformer 412 → fan booster transformer low-voltage-side switch 413 → fan converter 411 DC capacitor. Figure 2

[0048] In the process of charging the fan converter 411, the charging of the AC transmission cable and the excitation of the booster transformer are also included. The charging of the AC transmission cable is that as the output voltage of the converter rises, the distributed capacitance of the cable is gradually charged, and the voltage gradually rises from 0 to the preset DC voltage. The excitation of the booster transformer refers to when the voltage rises to the voltage required for the excitation of the transformer (such as 5% of the rated voltage), the magnetic field of the transformer core begins to be established, and the excitation current gradually stabilizes at the rated excitation current (such as 0.5 A).

[0049] ​Exemplarily, in the process of charging the first wind turbine generator, the DC side voltage of the wind turbine converter 411 can be detected in real time, such as by a sensor provided in the converter, and when the voltage reaches 95% of the preset DC voltage (such as 1045V), the boost rate is reduced. At the same time, the charging current of the AC power transmission cable (through the current transformer at the inlet end of the cable) is monitored to ensure that it does not exceed the limit, and the excitation current of the wind turbine boost transformer (through the current transformer at the neutral point of the transformer) is monitored to prevent excitation inrush current.

[0050] In the related art, an excitation inrush current of 6-7 times the rated current is still generated when the transformer switch is closed, and long-term impact can cause deformation of the transformer winding and aging of the insulation; the starting method provided in the embodiments of the present application achieves smooth excitation of the transformer by zero boost, no inrush current is generated, simultaneous starting of multiple wind turbine generators on the entire cable is achieved, the starting efficiency is greatly improved, the wind farm starting time is greatly shortened, and the power generation time is increased. At the same time, the voltage rise rate is controlled by zero boost, so that the cable charging current changes smoothly, and the risk of cable failure is reduced. Moreover, compared with at least 30 seconds required for charging a wind turbine generator in the related art, the charging of a wind turbine generator is completed by the zero boost process in the embodiments of the present application, only 500 milliseconds are required, and the charging time of a single wind turbine and the entire wind farm is shortened. In addition, the voltage and current change smoothly in the zero boost process of the offshore HVDC converter valve, gradually rising from 0 to the target value, which reduces the closing impact current and voltage during the charging phase while achieving black start of the wind turbine generator without the need for soft start equipment.

[0051] In a possible implementation, the offshore HVDC converter valve 31 is controlled to charge the wind turbine converter 411 in a zero boost manner by AC voltage amplitude and frequency control (V / F control).

[0052] The parameters in the AC voltage amplitude and frequency control include but are not limited to boost time, frequency change range, maximum charging current limit, etc. The parameters in the AC voltage amplitude and frequency control are not specifically limited in the present application, and can be set according to actual conditions.

[0053] Exemplarily, in the process of charging the DC capacitor in a zero boost manner, the charging current, the ratio of AC voltage to frequency, the temperature of the grid-side converter (to avoid overheating), the insulation state, and the DC voltage of the DC capacitor are monitored to ensure smooth starting of the wind turbine. Specifically, the charging current is monitored in real time, such as by a DC side current sensor, and if it exceeds the preset charging current, the boost is paused. The ratio of AC voltage to frequency is monitored to ensure that it strictly conforms to the preset V / F curve.

[0054] In this way, the charging current is always controlled in a safe range, the temperature rise of the capacitor does not exceed the preset temperature difference, and the service life of the capacitor is prolonged. In the embodiment of the application, the AC voltage amplitude and frequency control does not need complex phase synchronization or current closed-loop control, and smooth charging can be realized, and the control algorithm is simple and reliable.

[0055] In the embodiment of the application, after the DC voltage of the DC capacitor reaches the preset DC voltage, it is determined that the fan converter charging is completed.

[0056] The preset DC voltage can be set according to the rated power of the first wind turbine, the design parameters of the converter (such as the rated voltage of the capacitor, the withstand voltage value of the switching device), and the like, which is not specifically limited in the embodiment of the application.

[0057] For example, a voltage sensor (such as a Hall voltage sensor) is connected in parallel across the positive and negative electrodes of the DC capacitor to collect the voltage value of the DC capacitor in real time.

[0058] In some embodiments, in S103 above, after the first wind turbine charging is completed, the first wind turbine is started, specifically including the following steps: First, after the fan converter charging is completed, the grid-side converter is unlocked.

[0059] Specifically, unlocking the grid-side converter means unlocking the standby lock state of the grid-side converter, so that the grid-side converter is switched from the non-working mode to the operable mode to perform conversion, voltage regulation and the like. Before unlocking, the power switching device (such as IGBT) of the grid-side converter is in an off state and cannot realize power conversion; after unlocking, the device can normally turn on and off and enter the working state.

[0060] Then, the grid-side converter is controlled to establish the rated DC voltage corresponding to the first wind turbine to start the first wind turbine.

[0061] Specifically, the rated DC voltage refers to the standard working voltage that the fan converter 411 DC side (mainly the two ends of the DC capacitor) should maintain when the first wind turbine is designed, which is the core voltage parameter for the normal operation of the fan and needs to be matched with the power level of the converter, the withstand voltage value of the IGBT device and the power generation of the fan.

[0062] Fig. 4(a), Fig. 5(a), Fig. 6(a) are respectively schematic diagrams of the wind turbine terminal voltage, the charging current and the wind turbine converter DC voltage when the soft start device is used to start the wind farm. Fig. 4(b), Fig. 5(b), Fig. 6(b) are respectively schematic diagrams of the wind turbine terminal voltage, the charging current and the wind turbine converter DC voltage when the starting method provided in the embodiment of the present application is used to start the wind farm. It can be compared from the above figures that after the soft start device charges the DC capacitor, a large instantaneous wind turbine terminal voltage, charging current and wind turbine converter DC voltage will still be generated at the moment when the wind turbine booster low-voltage side switch is closed. When the starting method provided in the embodiment of the present application is used to start the wind farm, the wind turbine terminal voltage, the charging current and the wind turbine converter DC voltage all change smoothly and are maintained within the preset range, avoiding the damage of the impact load to the core components of the wind turbine. Therefore, it can be concluded that the starting method provided in the embodiment of the present application is far superior to the starting mode using the soft start device in the related art, which can start multiple wind turbines in parallel through a simple and reliable control strategy while smoothly starting the wind farm, shorten the overall starting time of the wind farm, improve the starting efficiency and reduce the cost of the wind farm.

[0063] The above describes the scheme provided in the embodiment of the present application mainly from the perspective of the method.

[0064] In the embodiment of the present application, a wind farm smooth starting device of an offshore wind power flexible DC power transmission system is also provided, which is used to implement the above embodiments and preferred embodiments, and will not be described herein. As used below, the term "module" can be a combination of software and / or hardware that implements a predetermined function. Although the device described in the following embodiments is preferably implemented in software, hardware or a combination of software and hardware is also possible and contemplated.

[0065] The embodiment provides a wind farm smooth starting device of an offshore wind power flexible DC power transmission system, which is applied to an offshore wind power flexible DC power transmission system. The system comprises a land power grid, a land converter station, an offshore converter station and an offshore wind farm. The land power grid is connected with the land converter station. The land converter station is connected with the offshore converter station through a DC transmission line. The offshore converter station comprises an offshore flexible DC converter valve and an offshore AC bus. The offshore wind farm comprises at least one wind turbine. For each wind turbine, the wind turbine is connected with the offshore flexible DC converter valve through an AC transmission cable and the offshore AC bus.

[0066] As shown in Fig. 7, the device comprises: Figure 7 A first control module 701 is configured to control the land converter station to establish a DC voltage for the DC transmission line. ​The second control module 702 is configured to control the offshore HVDC valve to charge the first wind turbine in a zero-voltage boosting manner, wherein the first wind turbine is any one of the at least one wind turbine. The starting module 703 is configured to start the first wind turbine after the charging of the first wind turbine is completed.

[0067] By the device provided in the embodiment, in the first aspect, in the related art, when the high-voltage side switch of the wind turbine booster is closed, a magnetic inrush current of 6 to 7 times the rated current or more is generated. If multiple wind turbines are started at the same time, the superimposed magnetic inrush current will exceed the current carrying limit of the submarine cable, resulting in overheating and damage of the submarine cable. Therefore, only one wind turbine can be started at the same time on one AC power transmission submarine cable. For example, in the related art, 10 wind turbines are connected by one submarine cable, and each wind turbine needs to be started one by one. During this period, the wind farm can only generate part of the power, and a large amount of electric energy is wasted. In the embodiment of the present application, the offshore HVDC valve charges the wind turbine in a zero-voltage boosting manner, and all wind turbines on one submarine cable can be boosted and magnetized at the same time, or even the wind turbines of the entire wind farm can be boosted and magnetized without generating a magnetic inrush current. For example, in the submarine cable loop of 10 wind turbines, the 10 wind turbines can be charged and started at the same time by using the method of the present application. In this way, the wind farm is started smoothly, the overall starting time of each wind turbine in the wind farm is shortened, the starting efficiency of the wind farm is improved, the loss of "abandoned wind" during the starting stage is greatly reduced, and the annual power generation and economic benefits of the wind farm are indirectly improved. In the second aspect, compared with the related art, each wind turbine needs to be charged by a soft start resistor, a bypass switch, and other soft start devices to charge the converter DC capacitor. Each charging time is at least about 20 seconds. By using the method provided in the embodiment, the offshore HVDC valve is controlled to charge the first wind turbine in a zero-voltage boosting manner. During the black start process of the wind turbine, the soft start device is not needed for charging, and the DC capacitor charging can be completed directly through the zero-voltage boosting of hundreds of milliseconds. In this way, the charging time of a single wind turbine and the entire wind farm is further shortened, and the operation is simple and reliable. In the third aspect, in the related art, even if the soft start device is configured, the starting impact cannot be completely avoided. Specifically, after the DC capacitor is charged by the soft start resistor, a large instantaneous charging current is still generated at the moment when the low-voltage side switch of the wind turbine booster is closed. The impact repeatedly acts on the components in the wind turbine converter, accelerates the insulation aging and mechanical wear of the components, and causes the equipment failure rate to increase. In the starting process of the present application, the voltage and current change smoothly during the zero-voltage boosting process of the offshore HVDC valve, and gradually increases from 0 to the target value. In this way, the wind turbines in the wind farm are started smoothly, the damage of the impact load to the core components of the wind turbine is avoided, the service life of the equipment is significantly prolonged, the maintenance cost of the wind farm is reduced, and the long-term economic benefits of the wind farm are further improved.

[0068] In a possible implementation, each wind turbine generator includes a wind turbine converter; the offshore converter station further includes a coupling transformer; the wind turbine converter is connected with the corresponding wind turbine booster transformer low-voltage side switch, wind turbine booster transformer high-voltage side switch and AC transmission sea cable, and the AC transmission sea cable is connected with the offshore AC bus through the AC transmission sea cable outlet switch; the offshore AC bus is connected with the offshore HVDC converter valve through the coupling transformer side switch, the coupling transformer and the coupling transformer valve side switch. The second control module 702 is specifically configured to close the wind turbine booster transformer low-voltage side switch, the wind turbine booster transformer high-voltage side switch, the AC transmission sea cable outlet switch, the coupling transformer side switch and the coupling transformer valve side switch corresponding to the first wind turbine generator.

[0069] In a possible implementation, each wind turbine generator further includes a wind turbine booster transformer; the second control module 702 is specifically configured to control the offshore HVDC converter valve to charge the wind turbine converter in the first wind turbine generator in a zero-voltage-rising manner, charge the AC transmission sea cable corresponding to the first wind turbine generator, and excite the wind turbine booster transformer in the first wind turbine generator.

[0070] In a possible implementation, the wind turbine converter includes a machine-side converter, a grid-side converter and a DC capacitor; the second control module 702 is specifically configured to control the offshore HVDC converter valve to charge the DC capacitor in a zero-voltage-rising manner through AC voltage amplitude and frequency control (V / F control).

[0071] In a possible implementation, the starting module 703 is further configured to determine that the charging of the wind turbine converter is completed when the DC voltage of the DC capacitor reaches a preset DC voltage.

[0072] In a possible implementation, the wind turbine converter includes a grid-side converter; the starting module 703 is further configured to unlock the grid-side converter after the charging of the wind turbine converter is completed. The grid-side converter is controlled to establish a rated DC voltage corresponding to the first wind turbine generator, so as to start the first wind turbine generator.

[0073] Further function descriptions of the above-mentioned modules and units are the same as those of the above-mentioned corresponding embodiments, and will not be described here again.

[0074] The offshore wind power flexible HVDC transmission system wind farm smooth starting device in the embodiment is presented in the form of a functional unit. The unit herein refers to an ASIC (Application Specific Integrated Circuit, Application Specific Integrated Circuit) circuit, a processor and a memory executing one or more software or fixed programs, and / or other devices that can provide the above-mentioned functions.

[0075] The embodiment of the present application further provides a computer device having the above-mentionedFigure 7 The offshore wind power flexible DC transmission system wind farm smooth starting device is shown.

[0076] Referring to Figure 8 Figure 8 is a structural schematic diagram of a computer device provided by an optional embodiment of the present application, as Figure 8 shown, the computer device includes one or more processors 10, a memory 20, and interfaces for connecting various components, including high-speed interfaces and low-speed interfaces. Various components are communicatively connected by different buses, and can be installed on a common mainboard or in other ways as needed. The processor can process instructions executed within the computer device, including instructions stored in the memory or on the memory to display graphical information of a GUI on an external input / output device, such as a display device coupled to the interface. In some optional embodiments, multiple processors and / or multiple buses can be used with multiple memories, if needed. Also, multiple computer devices can be connected, each providing part of the necessary operations (e.g., as a server array, a group of blade servers, or a multi-processor system). Figure 8 The processor 10 is taken as an example in the figure.

[0077] The processor 10 can be a central processor, a network processor, or a combination thereof. The processor 10 can further include a hardware chip. The hardware chip can be an application specific integrated circuit, a programmable logic device, or a combination thereof. The programmable logic device can be a complex programmable logic device, a field programmable logic gate array, a generic array logic, or any combination thereof.

[0078] The memory 20 stores instructions executable by the at least one processor 10, so that the at least one processor 10 executes the method shown in the above embodiments.

[0079] The memory 20 can include a program storage area and a data storage area. The program storage area can store an operating system and application programs required by at least one function; the data storage area can store data created according to the use of the computer device, etc. In addition, the memory 20 can include a high-speed random access memory, and can also include a non-transitory memory, such as at least one magnetic disk storage device, a flash memory device, or other non-transitory solid-state memory device. In some optional embodiments, the memory 20 can optionally include a memory remotely arranged with respect to the processor 10, and these remote memories can be connected to the computer device through a network. Examples of the network include but are not limited to the Internet, an intranet, a local area network, a mobile communication network, and a combination thereof.

[0080] ​The memory 20 can include a volatile memory, such as a random access memory, and / or a non-volatile memory, such as a flash memory, a hard disk, or a solid state disk. The memory 20 can also include a combination of the above-mentioned types of memories.

[0081] The computer device also includes a communication interface 30 for the computer device to communicate with other devices or communication networks.

[0082] The embodiments of the present application also provide a computer readable storage medium, and the method according to the embodiments of the present application can be implemented in hardware, firmware, or recorded in a storage medium, or stored in a remote storage medium or a non-transitory machine readable storage medium and downloaded to a local storage medium through network, so that the method described herein can be processed by such software on a storage medium using a general purpose computer, a special purpose processor, or programmable or special purpose hardware. The storage medium can be a disk, an optical disk, a read-only memory, a random access memory, a flash memory, a hard disk, or a solid state disk, etc. Further, the storage medium can also include a combination of the above-mentioned types of memories. It can be understood that the computer, the processor, the microprocessor controller, or the programmable hardware includes a storage component that can store or receive software or computer code, when the software or computer code is accessed and executed by the computer, the processor, or the hardware, the method shown in the above embodiments is implemented.

[0083] Part of the present application can be applied as a computer program product, for example, computer program instructions, when executed by a computer, through the operation of the computer, the method and / or technical solutions according to the present application can be invoked or provided. Those skilled in the art should understand that the form of computer program instructions in a computer readable medium includes but is not limited to source files, executable files, installation package files, etc. Correspondingly, the way of computer program instructions executed by computer includes but is not limited to: the computer directly executes the instructions, or the computer compiles the instructions and then executes the corresponding compiled program, or the computer reads and executes the instructions, or the computer reads and installs the instructions and then executes the corresponding installed program. Here, the computer readable medium can be any available computer readable storage medium or communication medium accessible to the computer.

[0084] Although the embodiments of the present application are described in conjunction with the accompanying drawings, various modifications and changes can be made by those skilled in the art without departing from the spirit and scope of the present application, and such modifications and changes fall within the scope defined by the appended claims.

Claims

1. A method for smoothing start of offshore wind farm flexible HVDC power transmission system, characterized in that, The application is applied to a flexible HVDC transmission system of offshore wind power, and the system comprises a land power grid, a land converter station, an offshore converter station and an offshore wind farm. The land power grid is connected with the land converter station. The land converter station is connected with the offshore converter station through a DC transmission line. The offshore converter station comprises an offshore HVDC converter valve and an offshore AC bus. The offshore wind farm comprises at least one wind turbine. For each wind turbine, the wind turbine is connected with the offshore HVDC converter valve through an AC transmission cable and the offshore AC bus. The method comprises: controlling the land converter station to establish a DC voltage for the DC transmission line; controlling the offshore HVDC converter valve to charge a first wind turbine in a zero-voltage-rising manner, wherein the first wind turbine is any one of the at least one wind turbine; after the charging of the first wind turbine is completed, starting the first wind turbine.

2. The method of claim 1, wherein, Each wind turbine comprises a wind turbine converter. The offshore converter station further comprises a coupling transformer. The wind turbine converter is connected with the AC transmission cable through wind turbine booster low-voltage side switches, wind turbine booster high-voltage side switches corresponding to the wind turbine, and the AC transmission cable is connected with the offshore AC bus through an AC transmission cable outlet switch. The offshore AC bus is connected with the offshore HVDC converter valve through a coupling transformer grid side switch, the coupling transformer and a coupling transformer valve side switch. Before the step of controlling the offshore HVDC converter valve to charge the first wind turbine in a zero-voltage-rising manner, the method further comprises: closing the wind turbine booster low-voltage side switches, the wind turbine booster high-voltage side switches corresponding to the first wind turbine, the AC transmission cable outlet switch, the coupling transformer grid side switch and the coupling transformer valve side switch.

3. The method of claim 2, wherein, Each wind turbine further comprises a wind turbine booster transformer. The step of controlling the offshore HVDC converter valve to charge the first wind turbine in a zero-voltage-rising manner comprises: controlling the offshore HVDC converter valve to charge the wind turbine converter in the first wind turbine in a zero-voltage-rising manner, simultaneously charging the AC transmission cable corresponding to the first wind turbine, and exciting the wind turbine booster transformer in the first wind turbine.

4. The method of claim 3, wherein, The wind turbine converter comprises a machine side converter, a grid side converter and a DC capacitor. The step of controlling the offshore HVDC converter valve to charge the wind turbine converter in a zero-voltage-rising manner comprises: controlling the offshore HVDC converter valve to charge the DC capacitor in a zero-voltage-rising manner through AC voltage amplitude and frequency control.

5. The method of claim 4, wherein, The method further comprises: after the DC voltage of the DC capacitor reaches a preset DC voltage, determining that the charging of the wind turbine converter is completed.

6. The method according to any one of claims 2-5, characterized in that, The wind turbine converter comprises a grid side converter. The step of starting the first wind turbine after the charging of the first wind turbine is completed comprises: after the charging of the wind turbine converter is completed, unlocking the grid side converter; controlling the grid side converter to establish a rated DC voltage corresponding to the first wind turbine to start the first wind turbine.

7. A wind farm smoothing starting device for offshore wind power flexible direct current transmission system, characterized in that, The application is applied to a flexible DC power transmission system of offshore wind power, and the system comprises a land power grid, a land converter station, an offshore converter station and an offshore wind farm. The land power grid is connected with the land converter station. The land converter station is connected with the offshore converter station through a DC power transmission line. The offshore converter station comprises an offshore flexible DC converter valve and an offshore AC bus. The offshore wind farm comprises at least one wind turbine. For each wind turbine, the wind turbine is connected with the offshore flexible DC converter valve through an AC power transmission cable and the offshore AC bus. The device comprises: a first control module configured to control the land converter station to establish a DC voltage for the DC power transmission line; a second control module configured to control the offshore flexible DC converter valve to charge a first wind turbine in a zero-voltage-rising manner, wherein the first wind turbine is any one of the at least one wind turbine; a starting module configured to start the first wind turbine after the first wind turbine is charged.

8. A computer device, comprising: comprise: a memory and a processor, which are in communication connection with each other, and the memory stores computer instructions. The processor executes the computer instructions to perform the offshore wind power flexible DC power transmission system wind farm smooth starting method according to any one of claims 1 to 6.

9. A computer-readable storage medium, characterized in that, The computer readable storage medium stores computer instructions, and the computer instructions are used to make the computer execute the offshore wind power flexible DC power transmission system wind farm smooth starting method according to any one of claims 1 to 6.

10. A computer program product, characterised in that, The computer instructions are used to make the computer execute the offshore wind power flexible DC power transmission system wind farm smooth starting method according to any one of claims 1 to 6.

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