Wind generating set based on stepless adjustable resistor and grid connection method thereof

Abstract

The invention belongs to the technical field of wind power generation, and relates to a wind generating set based on a stepless adjustable resistor and a grid connection method thereof.The wind generating set based on the stepless adjustable resistor comprises a motor, an automatic voltage regulator, the stepless adjustable resistor and a control system, and the automatic voltage regulator and the stepless adjustable resistor are both connected with the motor; the control system is connected with the power grid, the motor, the automatic voltage regulator and the stepless adjustable resistor, and sends a first control instruction to the automatic voltage regulator to change the output current of the automatic voltage regulator by monitoring the power grid voltage, the power grid frequency, the motor voltage and the motor frequency in real time when the motor voltage is not equal to the power grid voltage; the motor voltage is changed; when the motor frequency is not equal to the power grid frequency, a second control instruction is sent to the stepless adjustable resistor to change the output power of the stepless adjustable resistor, so that the motor frequency is changed; and when the motor voltage is equal to the power grid voltage and the motor frequency is equal to the power grid frequency, controlling the motor to switch on and grid-connected.

Description

Technical Field

[0001] The present invention relates to the technical field of wind power generation, and in particular to a wind turbine generator set based on a continuously adjustable resistor and a grid connection method thereof. Background Art

[0002] The electric energy generated by a wind turbine generator set needs to be connected to the power grid through grid connection in order to deliver the electric energy to the user side to meet the user's electricity demand. Since the wind speed is the power source of wind power generation, but the wind speed is random and intermittent and difficult to accurately predict and control, this results in frequent and large fluctuations in the output power of the wind turbine generator set, making its grid connection process require complex control systems and control methods to achieve.

[0003] In the prior art, a soft switching-in method using a bidirectional thyristor is proposed. A bidirectional thyristor is connected between the motor and the control system. When the rotational speed of the motor driven by the wind turbine approaches the synchronous speed, the control angle of each bidirectional thyristor directly connected to the power grid gradually and synchronously opens between 180° and 0°, and the conduction angle of the bidirectional thyristor as a non-contact switch for each phase also gradually and synchronously increases between 0° and 180°. At the beginning of the conduction stage of the bidirectional thyristor, the motor operates as a motor. As the rotational speed increases, the slip rate gradually approaches zero. When the slip rate is zero, all the bidirectional thyristors are fully conducted, and the motor successfully completes grid connection. Since the grid connection current is limited by the conduction angle of the thyristor, the grid connection process is relatively stable and will not cause current impact on the power grid. However, the soft switching-in device must use bidirectional thyristors that can withstand high reverse voltage and large current, and the price is relatively expensive. Moreover, the conduction angle of the bidirectional thyristor must be accurately and appropriately opened according to the rotational speed of the motor, which requires complex debugging by comprehensively considering the characteristics of the motor and the parameters of the power grid, etc.

[0004] In summary, the existing wind turbine generator sets based on bidirectional thyristors have the problems of high price and complex debugging process during grid connection. Summary of the Invention

[0005] Therefore, the technical problem to be solved by the present invention is to overcome the problems of high price and complex debugging process during grid connection of the existing wind turbine generator sets based on bidirectional thyristors.

[0006] To solve the above technical problem, the present invention provides a wind turbine generator set based on a continuously adjustable resistor, including: A motor, connected to the control system; An automatic voltage regulator, connected to the motor and the control system; A continuously adjustable resistor, connected to the motor and the control system; A control system, connected to the power grid, is used to monitor the grid voltage, grid frequency, motor voltage and motor frequency in real time. When the motor voltage is not equal to the grid voltage, a first control instruction is sent to the automatic voltage regulator to change the output current of the automatic voltage regulator, thereby changing the motor voltage; when the motor frequency is not equal to the grid frequency, a second control instruction is sent to the continuously adjustable resistor to change the output power of the continuously adjustable resistor, thereby changing the motor frequency; when the motor voltage is equal to the grid voltage and the motor frequency is equal to the grid frequency, the motor is controlled to close and be connected to the grid.

[0007] Preferably, the continuously adjustable resistor is connected to the user-side electrical equipment and is used to consume the electric energy generated by the wind turbine when the electricity consumption of the user-side electrical equipment is less than the power generation of the wind turbine.

[0008] Preferably, it further includes an off-grid operation module, which is connected to the motor and the control system.

[0009] Preferably, the control system is further used to send a third control instruction to the off-grid operation module when the power grid is powered off, so that the off-grid operation module adjusts the motor speed and output power, thereby enabling the motor to enter the island operation mode.

[0010] Preferably, when the grid voltage monitored by the control system is lower than the preset voltage threshold within a preset time period, it is determined that the power grid is powered off; or When the deviation value between the grid frequency monitored by the control system and the standard frequency of the power system is greater than the preset frequency deviation threshold, it is determined that the power grid is powered off.

[0011] Preferably, it further includes a reverse current prevention device, one end of which is connected to the user-side electrical equipment and the other end is connected to the power grid, and is used to prevent the electric energy from being transmitted from the user-side electrical equipment to the power grid.

[0012] Preferably, the reverse current prevention device is a reverse diode or a reverse power protection device.

[0013] Preferably, the continuously adjustable resistor is a full-power resistor.

[0014] The present invention also provides a grid connection method for a wind turbine based on a continuously adjustable resistor. The method is applied to the above-mentioned wind turbine based on a continuously adjustable resistor and includes: The control system monitors the grid voltage, grid frequency, motor voltage and motor frequency in real time; When the motor voltage is not equal to the grid voltage, the control system sends a first control instruction to the automatic voltage regulator to change the current of the automatic voltage regulator, thereby changing the motor voltage; When the motor frequency is not equal to the grid frequency, the control system sends a second control instruction to the continuously adjustable resistor to change the power of the continuously adjustable resistor, thereby changing the motor frequency; When the motor voltage is equal to the grid voltage and the motor frequency is equal to the grid frequency, the control system controls the motor to switch on and connect to the grid.

[0015] Preferably, it further includes: when the power grid is powered off, the control system sends a third control instruction to the off-grid operation module, so that the off-grid operation module adjusts the motor speed and output power, so that the motor enters the island operation mode.

[0016] The wind power generation set based on the continuously adjustable resistor provided by the present application includes a motor, an automatic voltage regulator, a continuously adjustable resistor, and a control system; wherein, the control system is connected to the power grid, the motor, the automatic voltage regulation, and the continuously adjustable resistor, and both the automatic voltage regulator and the continuously adjustable resistor are connected to the motor. The control system monitors the grid voltage, grid frequency, motor voltage, and motor frequency in real time. When the grid voltage is inconsistent with the motor voltage, by sending a first control instruction to the automatic voltage regulator, the current of the automatic voltage regulator is changed to change the motor voltage, so that the motor voltage is consistent with the grid voltage; when the grid frequency is inconsistent with the motor frequency, by sending a second control instruction to the continuously adjustable resistor, the power of the continuously adjustable resistor is changed to change the motor frequency, so that the motor frequency is consistent with the grid frequency. When the motor voltage is consistent with the grid voltage and the motor frequency is consistent with the grid frequency, it indicates that the speed of the motor has reached the synchronous speed corresponding to the grid frequency and meets the grid connection conditions. By controlling the motor to switch on, the stable grid connection of the wind power generation set and the power grid can be realized. By changing the system structure of the wind power generation set, the present application uses the automatic voltage regulator to regulate the motor voltage and the continuously adjustable resistor to adjust the motor frequency, so as to find the grid connection point, without using expensive and high-complexity bidirectional thyristors for soft grid connection, which not only reduces the grid connection cost of the wind power generation set, but also simplifies the grid connection complexity. Description of the Drawings

[0017] In order to make the content of the present invention easier to be clearly understood, the following further describes the present invention in detail according to the specific embodiments of the present invention and in combination with the drawings, wherein: Figure 1 is a schematic structural diagram of the wind power generation set based on the continuously adjustable resistor provided by the present application; Figure 2 is a flowchart of the grid connection method of the wind power generation set based on the continuously adjustable resistor provided by the present application; Description of the drawings: 1. Wind power generation set; 11. Motor; 12. Automatic voltage regulator; 13. Continuously adjustable resistor; 14. Control system; 15. Wind turbine; 16. Speed increaser; 17. Off-grid operation module; 18. Anti-backflow device; 2. Power grid; 3. User-side electrical equipment. Detailed Embodiments

[0018] The present invention will be further described below in conjunction with the accompanying drawings and specific embodiments, so that those skilled in the art can better understand the present invention and be able to implement it, but the embodiments cited are not intended to limit the present invention.

[0019] Please refer to Figure 1 , Figure 1 which shows a schematic structural diagram of a wind power generation unit based on a continuously adjustable resistor provided by the present application. The wind power generation unit 1 based on the continuously adjustable resistor is connected to the power grid 2 and the user-side electrical equipment 3. The generated electric energy is connected to the power grid 2 through grid connection, so as to transmit the electric energy to the user-side electrical equipment 3 to meet the user's electricity demand.

[0020] The wind power generation unit 1 based on the continuously adjustable resistor includes a motor 11, an automatic voltage regulator 12, a continuously adjustable resistor 13, and a control system 14.

[0021] The motor 11 is connected to the control system 14. When the rotational speed of the motor 11 approaches the synchronous speed, the control system 14 controls the motor 11 to switch on and connect to the grid.

[0022] Specifically, as shown in Figure 1 , the wind turbine 15 is connected to the motor 11 through a speed increaser 16. The wind turbine 15 consists of multiple blades and is the core component of the wind power generation unit for capturing wind energy. When the wind turbine rotates, it can transfer the obtained mechanical energy to the main shaft of the motor 11, driving the transmission system and the motor 11 to operate, thereby providing a power source for power generation. Since the rotational speed of the wind turbine 15 under natural wind speed is relatively low, in order to achieve the best power generation efficiency, the low rotational speed of the wind turbine 15 is increased to the high rotational speed required by the motor 11 through the speed increaser 16.

[0023] The automatic voltage regulator 12 is connected to the motor 11 and the control system 14. The control system 14 can change the voltage of the motor 11 by adjusting the current of the automatic voltage regulator 12.

[0024] The continuously adjustable resistor 13 is connected to the motor 11 and the control system 14. The control system 14 can change the frequency of the motor 11 by adjusting the power of the continuously adjustable resistor 13.

[0025] The control system 14 is connected to the motor 11, the automatic voltage regulator 12, the continuously adjustable resistor 13, and the power grid 2, and monitors the motor voltage, motor frequency, grid voltage, and grid frequency in real time. When the motor voltage is not equal to the grid voltage, a first control instruction is sent to the automatic voltage regulator 12, thereby changing the current of the automatic voltage regulator 12, and further changing the motor voltage; when the motor frequency is not equal to the grid frequency, a second control instruction is sent to the continuously adjustable resistor 13, thereby changing the power of the continuously adjustable resistor 13, and further changing the motor frequency; when the motor voltage is equal to the grid voltage and the motor frequency is equal to the grid frequency, the control system 14 controls the motor 11 to switch on and connect to the grid.

[0026] Specifically, if the motor voltage is higher or lower than the grid voltage, at the moment when the wind turbine is connected to the grid, due to the voltage difference, a large circulating current will be generated, which will damage the motor and the grid; similarly, if the motor frequency is higher or lower than the grid frequency, at the moment when the wind turbine is connected to the grid, it will cause power oscillation between the motor and the grid and cannot work in coordination with other power sources in the grid. Since there is a strict corresponding relationship between the rotational speed and frequency of an asynchronous motor, that is , where represents the rotational speed of the asynchronous motor, represents the frequency of the asynchronous motor, represents the number of pole pairs of the asynchronous motor. It can be seen from the formula that when the frequency of the asynchronous motor is equal to the grid frequency, the rotational speed of the asynchronous motor reaches the synchronous speed corresponding to the grid frequency, meeting the grid connection conditions of the motor, and thus enabling the stable grid connection of the wind turbine and the grid. Therefore, this application directly changes the system structure of the wind turbine, uses an automatic voltage regulator to control the motor voltage, and uses a stepless adjustable resistor to adjust the motor frequency, thereby finding the grid connection point, without using expensive and complex-to-commission bidirectional thyristors for soft grid connection, which not only reduces the grid connection cost of the wind turbine but also simplifies the grid connection complexity.

[0027] Furthermore, when the power generation of the wind turbine 1 is higher than the power consumption of the user-side electrical equipment 3, if a storage device is used to store the excess power, it may bring relatively high device and control costs. This is because the prices of common electrical energy storage devices such as lithium battery packs, flow batteries, and lead-acid batteries are relatively expensive. Large-scale energy storage devices also need to be equipped with battery management devices to ensure the safe operation of the batteries. At the same time, the energy storage device needs to adjust the charge and discharge current and voltage in real time according to multiple parameters such as the state of charge, temperature, and voltage of the battery to prevent overcharging, over-discharging, and thermal runaway problems, thus bringing relatively high device costs and control costs.

[0028] For the above reasons, as shown in Figure 1 , in some embodiments of this application, the stepless adjustable resistor 13 is also connected to the user-side electrical equipment 3. When the power consumption of the user-side electrical equipment 3 is less than the power generation of the wind turbine 1, it consumes the excess electrical energy generated by the wind turbine 1.

[0029] Furthermore, in some embodiments of this application, the wind turbine 1 further includes an off-grid operation module 17, which is connected to the motor 11 and the control system 14.

[0030] When the power grid 2 is in a power outage state, the control system 14 sends a third control instruction to the off-grid operation module 17, and the off-grid operation module 17 adjusts the rotational speed and output power of the motor 11, so that the motor enters the island operation mode, ensuring that the wind turbine generator 1 maintains a relatively stable working state, reducing the start-stop times of the wind turbine generator 1, and thus protecting the performance of the wind turbine generator 1.

[0031] Specifically, when the power grid 2 is operating normally, its voltage will fluctuate within a relatively stable range. When the power grid voltage value continuously drops below a certain proportion of the lower limit of the normal voltage range, it can be determined that the power grid 2 is in a power outage state. Similarly, the frequency of the power grid 2 will also remain at a stable value during normal operation, and its allowable deviation range is usually between ±0.2Hz and ±0.5Hz. When the deviation between the power grid frequency and the standard frequency is greater than the preset threshold, or the frequency suddenly disappears after large fluctuations, it can also be determined that the power grid 2 is out of power.

[0032] Therefore, in some embodiments of the present application, when the power grid voltage monitored by the control system 14 is lower than the preset voltage threshold within the preset time period, it is determined that the power grid 2 is out of power; or when the deviation value between the power grid frequency monitored by the control system 14 and the standard frequency of the power system is greater than the preset frequency deviation threshold, it is determined that the power grid 2 is out of power.

[0033] Furthermore, in some wind power generation scenarios of self-consumption, the electric energy generated by the wind turbine generator 1 can only be consumed by the electrical equipment 3 on the user side and is not allowed to feed power back to the power grid 2. Therefore, in some embodiments of the present application, the wind turbine generator 1 further includes a reverse power flow prevention device 18, one end of which is connected to the electrical equipment 3 on the user side and the other end is connected to the power grid 2, for preventing the electric energy from being transmitted from the electrical equipment 3 on the user side to the power grid 2.

[0034] Optionally, the reverse power flow prevention device 18 can be an anti-reverse diode, a reverse power protection device, etc.

[0035] Furthermore, the continuously adjustable resistor 13 is an electronic component that can continuously adjust the resistance value. When allowing surplus power to be fed into the grid or full power to be fed into the grid, the continuously adjustable resistor 13 can be replaced by a full-power resistor for the pneumatic brake. This is because when allowing surplus power to be fed into the grid or full power to be fed into the grid, the wind turbine generator 1 needs to transmit all the generated electric energy to the power grid 2 as efficiently as possible. The full-power resistor can withstand a large current and power, and can effectively adjust all the power output by the motor 11 under different wind speeds and power generation conditions, ensuring the stable operation of the motor 11 in various situations; at the same time, the full-power resistor can achieve continuous and smooth resistance adjustment, and can quickly and accurately adjust the operating parameters of the motor 11 according to the power grid frequency, so that the motor frequency remains within the range matching the power grid frequency, ensuring the smooth connection of the electric energy to the power grid 2.

[0036] Based on the wind turbine generator set with continuously adjustable resistors provided in the above embodiments, the embodiments of the present application also provide a grid connection method for a wind turbine generator set with continuously adjustable resistors. As Figure 2 shown, this method specifically includes: S10: The control system monitors the grid voltage, grid frequency, motor voltage, and motor frequency in real time.

[0037] S20: When the motor voltage is not equal to the grid voltage, the control system sends a first control instruction to the automatic voltage regulator to change the current of the automatic voltage regulator, thereby changing the motor voltage.

[0038] S30: When the motor frequency is not equal to the grid frequency, the control system sends a second control quality to the continuously adjustable resistor to change the power of the continuously adjustable resistor, thereby changing the motor frequency.

[0039] S40: When the motor voltage is equal to the grid voltage and the motor frequency is equal to the grid frequency, the control system controls the motor to switch on and connect to the grid.

[0040] Furthermore, in order to ensure that the wind turbine generator set can still operate stably when the grid power fails and reduce the number of starts and stops, the grid connection method for the wind turbine generator set with continuously adjustable resistors further includes that when the grid power fails, the control system sends a third control instruction to the off-grid operation module so that the off-grid operation module adjusts the motor speed and output power, thereby enabling the motor to enter the island operation mode.

[0041] Those skilled in the art should understand that the embodiments of the present application can be provided as a method, a system, or a computer program product. Therefore, the present application can take the form of a complete hardware embodiment, a complete software embodiment, or an embodiment combining software and hardware aspects. Moreover, the present application can take the form of a computer program product implemented on one or more computer-usable storage media (including but not limited to disk storage, CD-ROM, optical storage, etc.) that contain computer-usable program code.

[0042] The present application is described with reference to the flowcharts and / or block diagrams of methods, devices (systems), and computer program products according to the embodiments of the present application. It should be understood that each process and / or block in the flowchart and / or block diagram, and the combination of processes and / or blocks in the flowchart and / or block diagram, can be implemented by computer program instructions. These computer program instructions can be provided to the processor of a general-purpose computer, a special-purpose computer, an embedded processor, or other programmable data processing devices to generate a machine, so that the instructions executed by the processor of the computer or other programmable data processing devices generate means for implementing the functions specified in Figure 1 this process or multiple processes and / or blocks Figure 1 this block or multiple blocks.

[0043] These computer program instructions can also be stored in a computer-readable memory that can direct a computer or other programmable data processing apparatus to work in a particular manner, such that the instructions stored in the computer-readable memory produce a manufacture including an instruction device that implements the functions specified in one or more of the processes Figure 1 or sub-processes and / or boxes Figure 1 or sub-boxes or multiple boxes.

[0044] These computer program instructions can also be loaded onto a computer or other programmable data processing apparatus, such that a series of operational steps are performed on the computer or other programmable apparatus to produce a computer-implemented process, whereby the instructions executed on the computer or other programmable apparatus provide steps for implementing the functions specified in one or more of the processes Figure 1 or sub-processes and / or boxes Figure 1 or sub-boxes or multiple boxes.

[0045] Obviously, the above-described embodiments are merely examples for clear illustration and are not limitations on the implementation. For those of ordinary skill in the art, other different forms of changes or modifications can be made based on the above description. It is not necessary and impossible to list all the implementation manners here. And the obvious changes or modifications derived therefrom are still within the scope of protection of the present invention.

Claims

1. A wind turbine generator set based on stepless adjustable resistance, characterized in that: include: The motor is connected to the control system; an automatic voltage regulator, connected to the motor and control system; Stepless adjustable resistor, connected to the motor and control system; The control system is connected to the power grid and is used to monitor the power grid voltage, power grid frequency, motor voltage and motor frequency in real time. When the motor voltage is not equal to the power grid voltage, a first control instruction is sent to the automatic voltage regulator to change the output current of the automatic voltage regulator, thereby changing the motor voltage; when the motor frequency is not equal to the power grid frequency, a second control instruction is sent to the stepless adjustable resistor to change the output power of the stepless adjustable resistor, thereby changing the motor frequency; when the motor voltage is equal to the power grid voltage and the motor frequency is equal to the power grid frequency, the motor is controlled to close and connect to the grid.

2. The wind turbine generator set based on stepless adjustable resistance according to claim 1 is characterized in that: The stepless adjustable resistor is connected to the user-side electrical equipment and is used to consume the electrical energy generated by the wind turbine when the electrical energy consumption of the user-side electrical equipment is less than the power generation of the wind turbine.

3. The wind turbine generator set based on stepless adjustable resistance according to claim 1, characterized in that: It also includes an off-grid operation module, which is connected to the motor and control system.

4. The wind turbine generator set based on stepless adjustable resistance according to claim 3 is characterized in that: The control system is also used to send a third control instruction to the off-grid operation module when the power grid is out of power, so that the off-grid operation module adjusts the motor speed and output power, thereby allowing the motor to enter the island operation mode.

5. The wind turbine generator set based on stepless adjustable resistance according to claim 4 is characterized in that: When the grid voltage monitored by the control system is lower than a preset voltage threshold within a preset period of time, it is determined that the grid is out of power; or When the deviation between the grid frequency monitored by the control system and the standard frequency of the power system is greater than a preset frequency deviation threshold, it is determined that the grid is out of power.

6. The wind turbine generator set based on stepless adjustable resistance according to claim 1, characterized in that: It also includes a backflow prevention device, one end of which is connected to the user-side electrical equipment and the other end is connected to the power grid, for preventing electrical energy from being transmitted from the user-side electrical equipment to the power grid.

7. The wind turbine generator set based on stepless adjustable resistance according to claim 6, characterized in that: The anti-reverse current device is an anti-reverse diode or a reverse power protection device.

8. The wind turbine generator set based on stepless adjustable resistance according to claim 1, characterized in that: The non-protruding resistor is a full-power resistor.

9. A method for connecting a wind turbine generator set to the grid based on a stepless adjustable resistor, characterized in that: The method is applied to the wind turbine generator set based on the stepless adjustable resistor according to any one of claims 1 to 8, comprising: The control system monitors the grid voltage, grid frequency, motor voltage and motor frequency in real time; When the motor voltage is not equal to the grid voltage, the control system sends a first control instruction to the automatic voltage regulator to change the current of the automatic voltage regulator, thereby changing the motor voltage; When the motor frequency is not equal to the grid frequency, the control system sends the second control quality to the stepless adjustable resistor to change the power of the stepless adjustable resistor, thereby changing the motor frequency; When the motor voltage is equal to the grid voltage and the motor frequency is equal to the grid frequency, the control system controls the motor to close and connect to the grid.

10. The method for connecting a wind turbine generator set to the grid based on a stepless adjustable resistor according to claim 9, characterized in that: Also includes: When the power grid fails, the control system sends a third control instruction to the off-grid operation module so that the off-grid operation module adjusts the motor speed and output power, thereby making the motor enter the island operation mode.

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