Offshore wind power generation system based on inductor motor and control method and system

Abstract

The invention discloses an offshore wind power generation system based on an inductor motor and a control method and system, and belongs to the technical field of new energy power generation equipment. Comprising blades, a gear box and a motor system which are connected in sequence, and the motor system comprises an inductor motor, a four-quadrant converter, an excitation converter and an excitation transformer; the four-quadrant converter is used for controlling the frequency of a stator rotating magnetic field of the inductor motor through the machine-side converter according to the actual wind speed, changing the synchronous speed of the inductor motor, keeping the frequency of the output voltage constant through the grid-side converter, and achieving variable-speed constant-frequency power generation operation. According to the offshore wind power generation system based on the inductor motor, the structural advantages of the rotor of the inductor motor can be brought into full play, the reliability of a unit is greatly improved, the maintenance frequency and cost of the motor are reduced, and the capacity of the unit is further improved.

Description

Technical Field

[0001] The present invention belongs to the technical field of renewable energy power generation equipment, and more specifically, relates to an offshore wind power generation system based on an induction motor and a control method and system. Background Art

[0002] To build a new power system with new energy as the main body, it is urgent to develop renewable energy represented by wind power and photovoltaics on a large scale. Offshore wind power resources are abundant and will be the main source of incremental installed capacity of new energy power generation in the future. According to the type of generator, the existing wind power generation system can be mainly divided into permanent magnet direct drive / semi-direct drive full-power wind power generation system, double-fed high-speed partial-power wind power generation system, asynchronous high-speed full-power wind power generation system, etc. Among them, the permanent magnet direct drive / semi-direct drive wind power generation system has become the mainstream technical route in offshore wind turbines due to its advantages of high reliability and high transmission efficiency. However, with the increasing depletion of rare earth resources, the cost of permanent magnet wind turbines continues to increase, and permanent magnet motors still face risks such as demagnetization, which is not conducive to the further increase and promotion of offshore wind turbine capacity. Summary of the invention

[0003] In view of the defects or improvement needs of the prior art, the purpose of the present invention is to provide an offshore wind power generation system with an induction motor, which improves the reliability of the motor by adopting the integral forging of the rotor solid alloy steel material, and avoids the long-term maintenance of the offshore unit. The motor has no slip ring brushes and no permanent magnet material. There are no windings or any additional parts on the rotor. By increasing the motor diameter, the advantage of the rotor being able to run at a higher edge line speed is further improved and utilized, which helps to continuously improve the capacity of the single unit of the wind turbine.

[0004] To achieve the above object, the present invention provides an offshore wind power generation system based on an induction motor, comprising blades, a gearbox and a motor system connected in sequence, wherein the motor system comprises an induction motor, a four-quadrant converter, an excitation converter and an excitation transformer;

[0005] The four-quadrant converter is connected to the stator armature winding of the induction motor, and is used to control the frequency of the stator rotating magnetic field of the induction motor through the machine-side converter according to the actual wind speed, change the synchronous speed of the induction motor, and keep the frequency of the output voltage constant through the grid-side converter to achieve variable speed constant frequency power generation operation;

[0006] The excitation converter is connected to the stator excitation winding of the induction motor and is used to convert the voltage of the three-phase AC excitation power supply into a DC excitation current to provide DC excitation for the induction motor;

[0007] The excitation transformer is connected to the excitation converter and is used to provide a three-phase AC excitation power supply for the excitation converter.

[0008] Furthermore, the induction motor includes a stator and a rotor, the stator includes a stator core, a stator armature winding, and a stator excitation winding, the stator armature winding is located on both sides of the stator core, and the stator excitation winding is located in the middle of the stator core; the rotor is a solid steel structure.

[0009] Furthermore, the rotor is a salient pole rotor, including a first rotor and a second rotor that are bilaterally symmetrical, and the salient pole axes of the first rotor and the second rotor are staggered by 180° electrical angle.

[0010] Furthermore, the gearbox is a three-stage or higher gearbox, which is coaxially connected to the rotor of the induction motor.

[0011] Furthermore, the induction motor adopts a magnetic suspension bearing.

[0012] The present invention also provides a control method for the above-mentioned offshore wind power generation system based on an induction motor, comprising the following steps:

[0013] When the wind speed changes, the current of the excitation converter is adjusted to ensure the constant voltage at the induction motor terminal, and the frequency of the output voltage is kept constant by controlling the modulation frequency of the four-quadrant converter, thereby achieving variable speed, constant frequency and constant voltage power generation of the unit at different wind speeds.

[0014] The present invention also provides a control system for an offshore wind power generation system based on an induction motor, comprising: a computer-readable storage medium and a processor;

[0015] The computer-readable storage medium is used to store executable instructions;

[0016] The processor is used to read the executable instructions stored in the computer-readable storage medium to execute the above control method.

[0017] Compared with the prior art, the above technical solutions conceived by the present invention can achieve the following

[0018] Beneficial effects:

[0019] (1) Compared with existing double-fed units and permanent magnet units, the offshore wind power generation system based on the induction motor provided by the present invention has no slip ring brushes, no permanent magnet materials, no windings on the rotor and any additional parts, which can give full play to the structural advantages of the induction motor, greatly improve the reliability of the unit, reduce the frequency and cost of motor maintenance, and help to further increase the unit capacity and cope with the large-scale development of offshore wind power resources;

[0020] (2) The offshore wind power generation system based on the induction motor provided by the present invention can give full play to the structural advantages of the induction motor rotor, increase the rotor running edge linear speed, and further increase the motor volume to increase the motor single unit capacity. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 A topological schematic diagram of an offshore wind power generation system based on an induction motor provided in an embodiment of the present invention. DETAILED DESCRIPTION

[0022] In order to make the purpose, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention. In addition, the technical features involved in the various embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0023] The present invention provides an offshore wind power generation system based on an induction motor, comprising: an induction motor, a gearbox, blades, a four-quadrant converter, an excitation converter, an excitation transformer, etc. Among them, the gearbox can flexibly select three-stage or multi-stage transmission according to the unit capacity and the motor speed.

[0024] The induction motor includes: a stator structure and a rotor structure, wherein the stator structure includes: an iron core, a stator armature winding, and a stator annular excitation winding, wherein the stator iron core can be divided into two left and right parts, each of which is embedded with the stator armature winding, and the annular excitation winding is placed between the two stator iron cores; the rotor structure includes: a salient pole rotor, which is usually composed of a whole section of solid steel and is divided into two left and right parts with the same structure, and the salient pole axes of the left and right rotors are staggered by 180° electrical angle.

[0025] The gearbox can be a high-speed ratio gearbox with three or more stages, which is coaxially connected to the motor rotor to increase the speed of the fan blades to a higher rotation speed, which is conducive to taking advantage of the induction motor rotor being able to run at a higher edge linear speed, thereby improving the power density of the motor and increasing the capacity of a single machine.

[0026] The four-quadrant converter is connected to the stator armature winding of the induction motor, and is used to control the frequency of the stator rotating magnetic field through the machine-side converter according to the actual wind speed, change the synchronous speed of the motor, and maintain the frequency of the output voltage constant through the grid-side converter to achieve variable speed constant frequency power generation operation.

[0027] The excitation converter is connected to the stator excitation winding of the induction motor through a rectifier circuit to achieve DC excitation, thereby adjusting the reactive power of the motor to meet the grid's demand for the motor's output reactive power, which helps to keep the motor terminal voltage basically constant.

[0028] The induction motor has a special rotor structure, which is generally made of solid alloy steel forging. The rotor has high strength and reliability, and is suitable for high linear speed rotation. In particular, the induction motor does not require slip rings or brushes, and its rotor has no windings or any additional parts, no permanent magnet materials, and is relatively simple to manufacture. It can meet the extremely high reliability and maintenance-free requirements of offshore wind turbines for motors, and can adapt to the development trend of the continuous increase in the capacity of a single unit of the unit. Based on this, an embodiment of the present invention provides an offshore wind power generation system based on an induction motor, such as Figure 1 As shown, it includes: an induction motor, a gear box, blades, a four-quadrant converter, an excitation converter, an excitation transformer, etc. The induction motor comprises: a stator structure and a rotor structure, wherein the stator structure comprises: an iron core, a stator armature winding, and a stator annular excitation winding, wherein the stator iron core can be divided into two left and right parts, each of which is embedded with the stator armature winding, and an annular excitation winding is placed between the two stator iron cores; the rotor structure comprises: a salient pole rotor, which is usually composed of a whole section of solid steel and is divided into two left and right parts with the same structure, and the axes of the salient poles of the left and right rotors are staggered by 180° electrical angle; the four-quadrant converter is connected to the stator armature winding of the induction motor, and is used to control the frequency of the stator rotating magnetic field through the machine-side converter according to the actual wind speed, change the synchronous speed of the motor, and keep the frequency of the output voltage constant through the grid-side converter to realize variable speed constant frequency power generation operation; the excitation converter is connected to the stator excitation winding of the induction motor through a rectifier circuit to realize DC excitation, thereby adjusting the reactive power of the motor to meet the grid's demand for the output reactive power of the motor, and helps to keep the motor terminal voltage basically constant. When the wind speed changes, the fan blades drive the gearbox and other transmission systems, and finally transfer mechanical energy to the induction motor. The rotor speed of the induction motor changes with the fan impeller. At this time, adjusting the current of the excitation converter can ensure that the motor terminal voltage is basically constant, and the frequency of the output voltage is kept constant by controlling the modulation frequency of the four-quadrant converter, thereby realizing variable speed, constant frequency and constant voltage power generation of the unit at different wind speeds.

[0029] It will be easily understood by those skilled in the art that the above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. An offshore wind power generation system based on an induction motor, It is characterized in that It includes blades, a gearbox and a motor system connected in sequence, wherein the motor system includes an induction motor, a four-quadrant converter, an excitation converter and an excitation transformer; The four-quadrant converter is connected to the stator armature winding of the induction motor, and is used to control the frequency of the stator rotating magnetic field of the induction motor through the machine-side converter according to the actual wind speed, change the synchronous speed of the induction motor, and keep the frequency of the output voltage constant through the grid-side converter to achieve variable speed constant frequency power generation operation; The excitation transformer is connected to the excitation converter and is used to provide a three-phase AC excitation power supply for the excitation converter; The excitation converter is connected to the stator excitation winding of the induction motor and is used to convert the voltage of the three-phase AC excitation power supply into a DC excitation current to provide DC excitation for the induction motor.

2. The offshore wind power generation system based on the induction motor according to claim 1, It is characterized in that The induction motor comprises a stator and a rotor, wherein the stator comprises a stator core, a stator armature winding and a stator excitation winding, wherein the stator armature winding is located at both sides of the stator core and the stator excitation winding is located in the middle of the stator core; and the rotor is a solid steel structure.

3. The offshore wind power generation system based on the induction motor according to claim 2, It is characterized in that The rotor is a salient pole rotor, including a first rotor and a second rotor that are bilaterally symmetrical, wherein the salient pole axes of the first rotor and the second rotor are staggered by an electrical angle of 180°.

4. The offshore wind power generation system based on the induction motor according to claim 2, It is characterized in that The gearbox is a three-stage or higher gearbox, and is coaxially connected to the rotor of the induction motor.

5. The offshore wind power generation system based on the induction motor according to claim 2, It is characterized in that The induction motor adopts a magnetic suspension bearing.

6. A control method for an offshore wind power generation system based on an induction motor according to any one of claims 1 to 5, It is characterized in that The following steps are involved: When the wind speed changes, the current of the excitation converter is adjusted to ensure the constant voltage at the induction motor terminal, and the frequency of the output voltage is kept constant by controlling the modulation frequency of the four-quadrant converter, thereby achieving variable speed, constant frequency and constant voltage power generation of the unit at different wind speeds.

7. A control system for an offshore wind power generation system based on an induction motor, It is characterized in that include: A computer readable storage medium and a processor; The computer-readable storage medium is used to store executable instructions; The processor is used to read the executable instructions stored in the computer-readable storage medium to execute the control method described in claim 6.

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