An offshore wind power generation system based on an induction sub-motor and a control method and system thereof

Abstract

The application discloses a kind of offshore wind power generation systems and control method, system based on induction sub motor, belong to new energy power generation equipment technical field. Including: the blade, gear box and motor system connected in turn, motor system includes induction sub motor, four quadrant converter, excitation converter and excitation transformer;Four quadrant converter is used to according to actual wind speed, through machine side converter control induction sub motor's stator rotating magnetic field's frequency, change induction sub motor's synchronous speed, and through grid side converter keep the frequency of output voltage constant, realize variable-speed constant-frequency power generation operation.The offshore wind power generation system based on induction sub motor provided in the application can fully exert the structural advantages of the rotor of the induction sub motor, greatly improve the reliability of the unit, reduce the maintenance frequency and cost of the motor, and help to further improve the unit capacity.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of new energy power generation equipment, and more particularly to an offshore wind power generation system based on an induction sub-motor and a control method and system. BACKGROUND

[0002] A new power system mainly based on new energy needs to be developed on a large scale to develop renewable energy represented by wind power and photovoltaic power. Offshore wind power resources are abundant and are the main incremental source 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 / half 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 and the like. Among them, the permanent magnet direct drive / half direct drive wind power generation system has become the mainstream technical route in offshore wind turbine units due to its advantages of high reliability and high transmission efficiency. However, with the decreasing of rare earth resources, the cost of permanent magnet wind power generator is increasing, and the permanent magnet motor still faces the risk of demagnetization, which is not conducive to the further improvement and promotion of offshore wind turbine capacity. SUMMARY

[0003] In view of the defects or improvement needs of the prior art, the purpose of the present application is to provide an offshore wind power generation system based on an induction sub-motor, which improves the reliability of the motor by using a rotor solid alloy steel material for overall forging, and avoids long-term maintenance of offshore units. The motor has no slip ring brush and no permanent magnet material. There is no winding and no any additional parts on the rotor. By increasing the diameter of the motor, the advantages of higher edge line speed operation of the rotor are further improved, which helps to continuously improve the single machine capacity of the wind turbine unit.

[0004] To achieve the above-mentioned purpose, the present application provides an offshore wind power generation system based on an induction sub-motor, comprising blades, a gear box and a motor system connected in sequence, wherein the motor system comprises an induction sub-motor, a four-quadrant converter, an excitation converter and an excitation transformer.

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

[0006] The excitation converter is connected with the stator excitation winding of the induction sub-motor, and is used to convert the voltage of the three-phase alternating current excitation power supply into direct current excitation current to provide direct current excitation for the induction sub-motor.

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

[0008] Further, the inductor motor comprises a stator and a rotor, the stator comprises 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] Further, the rotor is a salient pole rotor, comprising a left-right symmetrical first rotor and a second rotor, and the axial lines of the salient poles of the first rotor and the second rotor are staggered by 180 degrees of electric angle.

[0010] Further, the gear box is a three-stage or more gear box and is coaxially connected with the rotor of the inductor motor.

[0011] Further, the inductor motor adopts a magnetic suspension bearing.

[0012] The application further provides a control method of the offshore wind power generation system based on the inductor motor.

[0013] When the wind speed changes, the current size of the excitation current is adjusted to ensure that the terminal voltage of the inductor motor is constant, and the frequency of the output voltage is kept constant by controlling the modulation frequency of the four-quadrant converter, so that the unit realizes variable-speed constant-frequency constant-voltage power generation under different wind speeds.

[0014] The application further provides a control system of the offshore wind power generation system based on the inductor motor, comprising: a computer readable storage medium and a processor.

[0015] The computer readable storage medium is used for storing executable instructions.

[0016] The processor is used for reading the executable instructions stored in the computer readable storage medium and executing the control method.

[0017] Through the above technical scheme conceived by the application, the following advantages can be achieved compared with the prior art

[0018] Advantages:

[0019] (1) The offshore wind power generation system based on the inductor motor provided by the application has no slip ring brush and no permanent magnet material, and there is no winding and any additional parts on the rotor, so that the structural advantages of the inductor motor can be fully utilized, the reliability of the unit is greatly improved, the maintenance frequency and cost of the motor are reduced, the unit capacity is further improved, and the large-scale development of offshore wind power resources is responded to.

[0020] (2) The offshore wind power generation system based on induction motor provided by the present invention can give full play to the structural advantages of the rotor of induction motor, increase the linear velocity of the rotor running edge, and further increase the motor volume to increase the single-unit capacity of the motor. Attached Figure Description

[0021] Figure 1 This is a schematic diagram of the topology of an offshore wind power generation system based on an induction sub-motor, provided for an embodiment of the present invention. Detailed Implementation

[0022] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention. Furthermore, the technical features involved in the various embodiments of this invention described below can be combined with each other as long as they do not conflict with each other.

[0023] This 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, and an excitation transformer. The gearbox can be flexibly configured with three or more transmission stages depending on the turbine capacity and motor speed.

[0024] The induction motor includes a stator structure and a rotor structure. The stator structure includes an iron core, a stator armature winding, and a stator annular excitation winding. The stator iron core can be divided into left and right parts, which are respectively embedded in the stator armature winding. The annular excitation winding is placed between the two stator iron core sections. The rotor structure includes a salient pole rotor, which is usually made of a solid piece of steel and is divided into left and right parts with the same structure. The salient pole axes of the left and right rotor parts are offset by 180° electrical angle from each other.

[0025] The gearbox can be a three-stage or higher high-ratio gearbox, coaxially connected to the motor rotor, which increases the speed of the fan blades to a higher rotational speed. This helps to take advantage of the induction motor rotor's ability to operate at a higher edge linear speed, thereby increasing the power density of the motor and increasing the single-unit capacity.

[0026] The four-quadrant converter is connected to the stator armature winding of the induction motor. It is used to control the frequency of the stator rotating magnetic field according to the actual wind speed through the machine-side converter, change the synchronous speed of the motor, and maintain the frequency of the output voltage constant through the grid-side converter, so as to realize 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 regulating the reactive power of the motor to meet the grid's demand for the motor's output reactive power and helping to maintain the motor's terminal voltage at a basically constant level.

[0028] The induction motor rotor has a unique structure, typically forged from solid alloy steel. This results in high rotor strength and reliability, making it suitable for high linear speed rotation. Crucially, the induction motor eliminates the need for slip rings and brushes; its rotor has no windings or additional components, and no permanent magnets. This simplifies manufacturing and allows it to meet the extremely high reliability and maintenance-free requirements of offshore wind turbines. It also adapts to the increasing capacity of individual units. Based on this, this invention provides an offshore wind power generation system based on an induction motor. Figure 1 As shown, it includes: induction motor, gearbox, blades, four-quadrant converter, excitation converter, excitation transformer, etc. The induction motor includes a stator structure and a rotor structure. The stator structure includes an iron core, a stator armature winding, and a stator annular excitation winding. The stator iron core can be divided into left and right parts, each embedded with a stator armature winding, with the annular excitation winding placed between the two stator iron core sections. The rotor structure includes a salient pole rotor, typically constructed from a single piece of solid steel, divided into left and right parts with identical structures. The salient pole axes of the left and right rotor parts are offset by 180° electrical angles. A four-quadrant converter is connected to the stator armature winding of the induction motor. It is used to control the frequency of the stator rotating magnetic field according to the actual wind speed via a machine-side converter, thereby changing the synchronous speed of the motor. It also maintains a constant frequency of the output voltage via a grid-side converter, achieving variable-speed constant-frequency power generation. The excitation converter is connected to the stator excitation winding of the induction motor through a rectifier circuit to achieve DC excitation, thereby regulating the reactive power of the motor to meet the grid's demand for the motor's reactive power output and helping to maintain a basically constant voltage at the motor terminals. When the wind speed changes, the wind turbine 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 wind turbine impeller. At this time, adjusting the current of the excitation converter can ensure that the voltage at the motor terminals is basically constant, and by controlling the modulation frequency of the four-quadrant converter, the frequency of the output voltage is kept constant, thereby realizing variable speed constant frequency constant voltage power generation of the unit under different wind speeds.

[0029] Those skilled in the art will readily understand that the above description is merely 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 within the scope of protection of the present invention.

Claims

1. An offshore wind power generation system based on an induction generator, characterized in that, It includes blades, a gearbox, and a motor system connected in sequence, wherein the motor system includes an induction sub-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. It is used to control the frequency of the stator rotating magnetic field of the induction motor according to the actual wind speed via a machine-side converter, thereby changing the synchronous speed of the induction motor. It also maintains a constant output voltage frequency via a grid-side converter, achieving variable-speed constant-frequency power generation. 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. By controlling the modulation frequency of the four-quadrant converter to maintain a constant output voltage frequency, the unit achieves variable-speed constant-frequency constant-voltage power generation under different wind speeds. The excitation transformer is connected to the excitation converter and is used to provide three-phase AC excitation power to 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 DC excitation current to provide DC excitation for the induction motor; the voltage at the induction motor terminals is kept constant by adjusting the current of the excitation converter.

2. The offshore wind power generation system based on an induction generator according to claim 1, characterized in that, The rotor is a salient pole rotor, including a first rotor and a second rotor that are symmetrical from left to right, and the salient pole axes of the first rotor and the second rotor are offset from each other by 180° electrical angle.

3. The offshore wind power generation system based on an induction generator according to claim 1, characterized in that, The gearbox is a three-stage or higher gearbox and is coaxially connected to the rotor of the induction motor.

4. The offshore wind power generation system based on an induction sub-motor according to claim 1, characterized in that, The induction sub-motor uses a magnetic levitation bearing.

5. A control method for an offshore wind power generation system based on an induction generator as described in any one of claims 1 to 4, characterized in that, Includes the following steps: When the wind speed changes, the current of the excitation converter is adjusted to ensure that the voltage at the induction motor terminals remains 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 constant voltage power generation of the unit under different wind speeds.

6. A control system for an offshore wind power generation system based on an induction generator, characterized in that, include: Computer-readable storage media and processors; The computer-readable storage medium is used to store executable instructions; The processor is used to read executable instructions stored in the computer-readable storage medium and execute the control method of claim 5.

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