CN102545501A - Axial dual-stator brushless double-fed motor - Google Patents

Abstract

The invention discloses an axial double-stator brushless doubly-fed motor, which comprises a bidirectional rectification inverter, an end cover, a rotating shaft, a rotor arranged on the rotating shaft, a left stator and a right stator arranged symmetrically on both axial sides of the rotor , the rotating shaft and the end cover are connected by bearings, and there is an air gap between the two stators and the rotor. The axial double-stator brushless doubly-fed motor of the present invention has excellent adaptability, and can be designed as a variable-speed constant-frequency generator or a constant-frequency speed-regulating motor. The motor has a simple and compact structure and high power density. There is no brush slip ring, so the reliability is high, and the operation and maintenance costs are low.

Description

An axial double-stator brushless doubly-fed motor

technical field

The invention belongs to the technical field of motors and their control, and relates to a double-fed variable-speed constant-frequency generator/motor.

Background technique

As the whole society continues to pay attention to energy and environmental issues, the development and utilization of renewable energy is showing a trend of accelerated development. Wind energy exists widely on the earth and is currently one of the most mature renewable energy sources in our hands. A wind turbine is a device that converts mechanical energy into electrical energy in a wind power generation system, and its performance directly affects the quality and conversion efficiency of the output electrical energy.

At present, the generators used in the world's popular high-power wind power generation systems mainly include the following types:

1. Double-fed asynchronous wind turbine

In the doubly-fed asynchronous wind power generation system, a gearbox is used to convert the lower fan speed to a higher generator speed, which can be continuously variable speed and has a high wind energy conversion rate. The power converter is a partial power converter (about one-third of the total power), so the cost of the converter is relatively low. The disadvantage is that the motor has brushes and slip rings, which reduces reliability and increases manufacturing and maintenance costs. In addition, the existence of the gearbox increases the volume of the system and further reduces the reliability of the system.

2. Direct drive synchronous generator

The direct-drive synchronous generator is directly driven by the fan, so it does not need a gearbox, which improves the reliability of the entire system to a certain extent. Direct drive synchronous generators include electromagnetic and permanent magnet. Direct drive electrically excited synchronous generators are powered by an external field source and therefore still have brushes and slip rings. The direct-drive permanent magnet synchronous generator is excited by permanent magnet steel, eliminating the need for brushes and slip rings. Both motors run at a lower speed, which increases the number of poles and increases the volume of the motor. At the same time, all direct-drive synchronous power generation systems use full-power converters, so the cost of the converters is relatively high. In addition, the possible demagnetization of permanent magnets is also a problem faced by direct drive permanent magnet synchronous generators.

3. Brushless double-fed motor

There are two sets of independent windings with different pole pairs on the stator side of the brushless doubly-fed motor. The rotor adopts a self-closing loop structure. The two sets of stator windings are completely decoupled on the circuit and magnetic circuit, and the brushes and slip rings are eliminated. improve. Using part of the power converter, the cost of the converter is lower. Brushless double-fed motors can be divided into axial cascade type and shared stator core type according to whether they share the stator core. The axial cascaded brushless doubly-fed motor is composed of two asynchronous motors cascaded axially, one is a power machine and the other is a control machine. Due to the existence of the winding ends, the two axially cascaded stators There must be a certain distance between them, the utilization rate of the common rotor is low, the system occupies a large space, and the power density is low. Shared stator core type brushless doubly-fed motor has only one stator core on which two sets of windings with different numbers of pole pairs are placed, one set is power winding and the other set is control winding. There is a direct magnetic coupling between the sets of windings. At the same time, the squirrel cage rotor used has a special structure and needs to be specially designed.

Contents of the invention

Technical problem: The object of the present invention is to provide an axial double-stator brushless double-fed motor that can improve system reliability and space utilization.

Technical solution: The axial double-stator brushless doubly-fed motor of the present invention includes a bidirectional rectifier inverter, an end cover, a rotating shaft, a rotor arranged on the rotating shaft, and a left stator and a right stator arranged symmetrically on both axial sides of the rotor , the rotating shaft and the end cover are connected by bearings, and there is an air gap between the two stators and the rotor;

The left stator includes a left stator core and a left stator winding with 2p poles on the left stator core, and the right stator includes a right stator core and a right stator winding with 2q poles on the right stator core, where p and q are respectively positive Integer, and p and q are not equal; the three-phase lead-out line of the left stator winding is connected to the grid or main power supply; the three-phase lead-out line of the right stator winding is connected to the bidirectional rectifier inverter;

The rotor includes a disc-shaped mechanical support perpendicular to the axial direction of the rotating shaft. The two sides of the mechanical support are symmetrically arranged with circular left iron cores and right iron cores. The inner rings of the left iron core and the right iron core are respectively provided with left iron core end rings and The right iron core end ring, the rings of the left iron core and the right iron core are respectively provided with radial left iron core guide bars and right iron core guide bars uniformly arranged in the circumferential direction, one end of the left iron core guide bar is connected with the left iron core end ring, and the right iron core One end of the guide bar is connected with the right iron core end ring, and the left iron core guide bar is connected with the right iron core guide bar at the outer ring side of the left iron core and the right iron core.

In the present invention, both the left stator winding and the right stator winding are multi-phase symmetrical stator windings.

The electromagnetic structure of the present invention can be composed of a plurality of basic units, and the basic units are cascaded along the axial direction.

Beneficial effect: compared with the prior art, the present invention has the following advantages:

The brushless doubly-fed motor retains the advantages of direct-drive synchronous generators and doubly-fed asynchronous wind power generators, cancels brushes and slip rings, improves system reliability, and reduces maintenance costs. The electric power flowing through the power converter is the power of the control winding. Similar to the common doubly-fed asynchronous generator, the capacity of the power converter is small, about 1/3 of the total power of the motor, so the cost of the power converter is low.

When the traditional cascaded brushless doubly-fed motor adopts the axial magnetic flux structure, there are four winding ends along the radial direction, while the axial double-stator brushless doubly-fed motor with the axial magnetic flux structure of the present invention can combine the two The two stators are coaxially arranged on both sides of the rotor, and there are only two winding ends along the radial direction, which reduces the ineffective length, so the space utilization rate is high. Under the same power level, the axial length of the motor is shortened and the structure is more compact. In addition, a plurality of motor basic units can be arranged in the axial direction to increase the capacity of the motor and have greater flexibility.

Compared with the brushless double-fed double-stator motor with radial structure, its control winding is not limited by the limited space of the inner stator in the radial structure, and its capacity can be designed to be the same as that of the power winding. Therefore, the adjustable speed range of the motor can be obviously increase.

Compared with the shared stator core type brushless doubly-fed motor, the two stators are separated by a disc rotor, and the two layers of squirrel cages are connected with corresponding guide bars at one end, so that there is only a circuit connection between the two layers of squirrel cages. The magnetic field generated by the power winding and the magnetic field generated by the control winding are only indirectly coupled through the rotor, which eliminates the possible direct coupling between the two stator magnetic fields when the stator core is shared, and is easy to control. At the same time, the rotor uses a squirrel-cage structure similar to that of an ordinary induction motor, with mature technology and simple manufacturing, while the squirrel-cage winding of the shared-stator core-type brushless doubly-fed motor needs a special design to meet the requirements of electromagnetic performance.

Description of drawings

Fig. 1 is the schematic diagram of the axial dual-stator brushless doubly-fed wind power generator system of the present invention;

Fig. 2 is a schematic diagram of a full sectional structure of an axial double-stator brushless doubly-fed motor of the present invention;

Fig. 3 is a three-dimensional structure diagram of an axial double-stator brushless doubly-fed motor of the present invention;

Fig. 4 is a structural schematic diagram of the left stator core of the axial double-stator brushless doubly-fed motor of the present invention;

Fig. 5 is a schematic cross-sectional view of the left stator shaft of the axial double-stator brushless doubly-fed motor of the present invention;

Fig. 6 is a schematic structural view of the right stator core of the axial dual-stator brushless doubly-fed motor of the present invention;

Fig. 7 is a schematic cross-sectional view of the right stator shaft of the axial double-stator brushless doubly-fed motor of the present invention;

Fig. 8 is a schematic diagram of the rotor structure of the axial dual-stator brushless doubly-fed motor of the present invention;

Fig. 9 is a schematic diagram of the connection and installation structure of the rotor guide bars of the axial double-stator brushless doubly-fed motor of the present invention;

Fig. 10 is a schematic diagram of the operation of the axial dual-stator brushless double-fed motor connected to the grid as a variable-speed constant-frequency generator or motor according to the present invention.

In the figure: 1 is the left stator, 2 is the right stator, 3 is the rotor, 4 is the two-way rectifier inverter, 5 is the gear box, 6 is the fan wheel, 7 is the end cover, 8 is the bearing, 9 is the rotating shaft, 10 is the filter inductance; 11 is the left stator core, 12 is the left stator winding, 13 is the left stator tooth, 14 is the left stator slot, 21 is the right stator core, 22 is the right stator winding, 23 is the right stator tooth, 24 is the right Stator slot, 31 is rotor mechanical support, 32 is left iron core, 33 is left iron core end ring, 34 is left iron core guide bar, 35 is right iron core, 36 is right iron core end ring, 37 is right iron core guide bar.

Detailed ways

Figure 1 shows the double-stator brushless doubly-fed wind power generation system, the motor includes a bidirectional rectifier inverter 4, an end cover 7, a rotating shaft 9, a rotor 3 arranged on the rotating shaft 9, and symmetrically arranged on both axial sides of the rotor 3 left stator 1 and right stator 2. The left stator 1 has a set of left stator windings 12 with 2p poles, and the right stator 2 has a set of right stator windings 22 with 2q poles, where p and q are positive integers respectively. The left stator winding 12 is the main power winding and is directly connected to the grid or the main power supply; the right stator winding 22 is the control winding and is connected to the grid or an external circuit through the bidirectional power converter 4 . The above-mentioned 2p stator winding 12 and the 2q stator winding are all multi-phase symmetrical stator windings. The rotor 3 is mechanically connected to the fan wheel 6 directly or through the gearbox 5 .

The gearbox 5 in FIG. 1 is not necessary for the double-stator brushless doubly-fed wind power generation system. When the fan rotor 6 is connected to the motor rotor 3 through the gearbox 5, the system is a high-speed double-fed wind power generation system; when the fan rotor 6 is directly connected to the motor rotor 3, the system is a low-speed direct drive double-fed wind power generation system .

The magnetic flux distribution direction of the device of the present invention is parallel to the rotating shaft, and a closed loop of magnetic flux is formed in a plane parallel to the shaft.

As shown in Figure 2 and Figure 3, two stators and rotors are arranged axially, the rotor 3 is placed between the left stator 1 and the right stator 2, and the mechanical axes of the stator and rotor coincide. The rotating shaft 9 and the end cover 7 are connected by a bearing 8, and the rotor 3 is connected to the rotating shaft 9. There is an air gap between the two stators and the rotor 3, and the air gap between the stator and the rotor transmits the electromagnetic torque so as to realize the power generation or electric motor of the motor. run.

As shown in Figures 4 and 6, the left stator 1 includes a left stator core 11 and a left stator winding 12 with a pole number of 2p arranged on the left stator core 11, and the right stator 2 includes a right stator core 21 and a left stator winding 12 arranged on the left stator core 11. The right stator winding 22 with the pole number 2q on the right stator core 21 . The stator core is made of laminated stator punches based on double-sided insulated electrical steel sheets, and evenly distributed tooth slots are punched on the surface of the stator facing the rotor.

The role of the stator teeth is magnetic conduction, and the role of the slot is to place the winding. The outer stator winding is a power winding, its current and voltage are relatively high, and it is directly connected to the power grid as the first feed port of the doubly-fed motor. The inner stator winding is the control winding, its voltage and current are small, and it is indirectly connected to the power grid through the bidirectional rectification inverter, as the second feed port of the doubly-fed motor.

Fig. 8 is the rotor 3 of the axial double-stator brushless doubly-fed motor of the present invention, the rotor 3 includes a disc-shaped mechanical support 31 perpendicular to the axial direction of the rotating shaft 9, and the two sides of the mechanical support 31 are symmetrically provided with ring-shaped The left iron core 32 and the right iron core 35 are respectively provided with a left iron core end ring 33 and a right iron core end ring 36 on the inner rings of the left iron core 32 and the right iron core 35 . The two rotor cores are made of double-sided insulated silicon steel sheets, and the punched sheets are punched with evenly distributed holes for placing guide bars.

Fig. 9 is a diagram of the installation structure of the rotor guide bars. On the rings of the left iron core 32 and the right iron core 35, the radial left iron core guide bars 34 and the right iron core guide bars 37 are evenly arranged along the circumferential direction, and one end of the left iron core guide bar 34 is connected to The left iron core end ring 33 is connected, one end of the right iron core guide bar 37 is connected with the right iron core end ring 36, and the left iron core guide bar 34 and the right iron core guide bar 37 are connected at the outer ring side of the left iron core 32 and the right iron core 35.

The speed n _r of the brushless double-fed motor satisfies the relationship with the frequency f _p and f _q of the current in the two stator windings: n _r =60(f _p ±f _q )/(p+q). When the grid frequency f _p is fixed, the variable speed operation of the brushless double-fed motor can be realized by adjusting the frequency f _q of the current in the inner stator winding. Using a certain control method, by controlling the bidirectional rectification inverter to adjust the frequency, magnitude and phase of the current in the control winding, not only can generate constant frequency and constant voltage electric energy, but also can realize flexible adjustment of active power and reactive power.

As a control method for variable-speed constant-frequency generator operation, in the axial double-stator brushless double-fed motor of the present invention, the outer stator winding is directly connected to the power grid, and the inner stator winding is connected to the power grid through a rectifier inverter. When the generator input shaft When the speed changes, the frequency and amplitude of the 2q pole winding current are controlled by the rectifier inverter, so that the 2p pole power winding outputs an alternating current of constant frequency and constant voltage.

As a control method for the operation of variable-speed constant-frequency motors, in the axial double-stator brushless double-fed motor of the present invention, the outer stator windings are directly connected to the power grid, and the inner stator windings are connected to the power grid through a rectifier inverter, and the rectifier inverter regulates Control the frequency and amplitude of the winding current to change the speed and torque of the motor.

Claims (2)

1. An axial double-stator brushless double-fed motor, characterized in that the motor includes a bidirectional rectifier inverter (4), an end cover (7), a rotating shaft (9), and is arranged on the rotating shaft (9) The rotor (3), the left stator (1) and the right stator (2) symmetrically arranged on both axial sides of the rotor (3), the shaft (9) and the end cover (7) through the bearing (8) connection, and there is an air gap between the two stators and the rotor (3); The left stator (1) includes a left stator core (11) and a left stator winding (12) with a pole number of 2p arranged on the left stator core (11), and the right stator (2) includes a right stator core ( 21) and a right stator winding (22) with a pole number of 2q arranged on the right stator core (21), the p and q are positive integers respectively, and p and q are not equal; the left stator winding (12) The three-phase lead-out lines of the right stator winding (22) are connected with the power grid or the main power supply, and the three-phase lead-out lines of the right stator winding (22) are connected with the bidirectional rectification inverter (4); The rotor (3) includes a disc-shaped mechanical support (31) perpendicular to the axial direction of the rotating shaft (9), and the two sides of the mechanical support (31) are symmetrically provided with an annular left iron core (32) and The right iron core (35), the inner rings of the left iron core (32) and the right iron core (35) are respectively provided with a left iron core end ring (33) and a right iron core end ring (36), between the left iron core (32) and the right The circular ring of the iron core (35) is respectively provided with radial left iron core guide bars (34) and right iron core guide bars (37) uniformly arranged in the circumferential direction, and one end of the left iron core guide bar (34) is connected to the left iron core end ring (33), one end of the right core guide bar (37) is connected with the right core end ring (36), the left core guide bar (34) and the right iron core guide bar (37) are connected between the left core (32) and the right The outer ring side of iron core (35) is connected. 2. The axial double-stator brushless doubly-fed motor according to claim 1, characterized in that, the left stator winding (12) and the right stator winding (22) are multi-phase symmetrical stator windings.

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