High-inertia multi-port composite motor for new energy grid connection

Abstract

The invention discloses a high-inertia multi-port composite motor for new energy grid connection. The high-inertia multi-port composite motor comprises a brushless doubly-fed motor, an axial permanent magnet motor and a magnetic gear structure. The brushless doubly-fed motor comprises a radial stator and a squirrel cage rotor, a power winding and a control winding are arranged in the stator and serve as a first electric port and a second electric port respectively, the axial permanent magnet motor comprises an axial stator and an axial permanent magnet rotor, and an armature winding is arranged in the stator and serves as a third electric port. The magnetic gear structure is arranged on the inner side of the squirrel cage rotor and the outer side of the rotating shaft, a brushless doubly-fed motor rotor magnetic field is used as a modulation magnetic source, the phase and amplitude of the magnetic field are adjustable, dynamic adjustment of the transmission ratio of the magnetic gear is achieved through a control winding, and electromagnetic and mechanical dual coupling is achieved. The equivalent rotational inertia of the composite motor is obviously higher than that of a single machine, stronger inertia support and frequency stability can be provided for a power grid in a new energy grid connection process, and the composite motor is provided with three independent electric ports, realizes multi-mode operation, and is compact in structure and high in power density.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of motor and new energy grid connection, and particularly relates to a high-inertia multi-port composite motor for new energy grid connection BACKGROUND

[0002] With the increasing penetration of wind power, photovoltaic and other new energy in the power grid, the proportion of traditional large-inertia synchronous generators gradually decreases, resulting in a significant reduction in the equivalent inertia of the power system. Under the condition of high proportion of new energy grid connection, when the power grid is disturbed (such as wind speed fluctuation, load mutation or short circuit fault), the system frequency fluctuation is more severe, the low-frequency oscillation risk is significantly improved, and even a large-scale power grid instability may be caused.

[0003] In the prior art, in order to improve the inertia support capability of the new energy grid connection system, there are mainly three types of schemes: one type is to provide additional inertia by increasing independent flywheel energy storage devices on the grid side, but this scheme is bulky, high in cost, high in loss and complex in maintenance, and is not suitable for the requirements of new energy devices for compactness and high power density; another type is to simulate the inertia characteristics in the power electronic interface through virtual inertia control, which improves the dynamic response of the power grid to a certain extent, but is limited by the energy storage capacity and control bandwidth, and its inertia support capability is limited, and the performance decreases significantly under large disturbance conditions; the third type is to rely on a single motor to realize inertia support, such as a doubly-fed induction generator (DFIG) or a permanent magnet synchronous generator (PMSG), but due to the physical limitations of rotor mass, number of pole pairs and electromagnetic design, the equivalent inertia of a single machine is insufficient, and it is difficult to meet the demand for inertia of high proportion of new energy grid connection. At the same time, the existing single machine scheme often lacks multi-port energy interaction capability, and it is difficult to balance the multi-source collaborative demand of power generation, grid connection and energy storage.

[0004] Therefore, the prior art cannot simultaneously meet the requirements of high inertia support, multi-port energy flow management and compact high power density design, and therefore, there is an urgent need for a new type of composite motor that can realize high inertia characteristics, support multi-port flexible control and provide real-time inertia adjustment in a limited volume, in order to meet the requirements of high proportion of new energy grid connection system for frequency stability and dynamic response capability. SUMMARY

[0005] The present application aims to provide a high-inertia multi-port composite motor for new energy grid connection, which utilizes the coupling structure of brushless doubly-fed motor + magnetic gear coupling + axial permanent magnet motor, and uses the magnetic gear structure to make the equivalent rotational inertia of the composite motor significantly higher than that of a single machine, thereby significantly improving the dynamic inertia response capability. In a compact volume, high inertia support, multi-port energy flow management and multi-mode operation are realized, and the grid stability and dynamic response capability of the new energy power generation device are improved.

[0006] In order to achieve the above-mentioned purpose, the present application provides the following scheme:

[0007] The application provides a high-inertia multi-port composite motor for grid connection of new energy, comprising a brushless doubly-fed motor, an axial permanent magnet motor and a magnetic gear structure.

[0008] The brushless doubly-fed motor comprises a radial stator and a squirrel cage rotor, two sets of windings are arranged in the radial stator, one set is a power winding (electric port one), the pole pair number is Pp, and the frequency is fp, and the other set is a control winding (electric port two), the pole pair number is Pc, and the frequency is fc, the two sets of windings are distributed in the stator slot; the pole pair number of the squirrel cage rotor is Ps, and the frequency is fs, the relationship between the pole pair numbers is Pp=Pc+Ps, and the relationship between the frequencies is fp=fc+fs.

[0009] The axial permanent magnet motor comprises an axial stator and an axial permanent magnet rotor, and one set of armature winding (electric port three) is arranged in the axial stator, the pole pair number is Pa, and the pole pair number of the axial permanent magnet rotor is Pa.

[0010] The magnetic gear structure is distributed inside the squirrel cage rotor and outside the rotating shaft, the pole pair number of the magnetic gear inside the squirrel cage rotor is Pm1, the pole pair number of the magnetic gear outside the rotating shaft is Pm2, and the relationship between the pole pair numbers is Pm2=Pm1+Ps.

[0011] The brushless doubly-fed motor has the characteristics of constant frequency power generation, that is, the frequency fc of the control winding and the frequency fs of the squirrel cage rotor are changed respectively, so that the frequency fp of the power winding remains constant, therefore, the power winding can be directly connected to the large power grid without passing through the current conversion device, and the control winding is connected to the new energy power grid through the current converter. The rated output power of the brushless doubly-fed motor is Pew, the power of the power winding is Pewp, the power of the control winding is Pewc, and the mechanical power of the rotor is Pewm. The relationship between the powers is Pew=Pewp+Pewc+Pewm.

[0012] The armature winding of the axial permanent magnet motor is connected to the new energy power grid or the energy storage system through the current converter, converts the electric energy into mechanical energy, and provides the mechanical power Pewm for the brushless doubly-fed motor through the magnetic gear structure.

[0013] The rotor magnetic field of the brushless doubly-fed motor is a modulating magnetic source of the magnetic gear structure, and by adjusting and controlling the current amplitude and frequency of the control winding, dynamic control of the rotor magnetic field can be realized, an adjustable magnetic field is provided for the magnetic gear, and transmission ratio control of the magnetic gear is realized. When it is necessary to increase the system inertia to enhance the grid connection stability under low-frequency disturbance, the control winding outputs a low-frequency large-amplitude magnetic field, the equivalent transmission ratio of the magnetic gear is increased, and the rotational inertia of the axial permanent magnet motor is efficiently superimposed on the doubly-fed motor side through the magnetic gear, so that the equivalent inertia of the system is significantly increased. When it is necessary to reduce the system inertia to improve the fast dynamic response, the control winding outputs a high-frequency low-amplitude magnetic field, the transmission ratio of the magnetic gear is reduced, and the equivalent inertia coupling of the axial permanent magnet motor is reduced, so that the system is accelerated or braked quickly. By adjusting the current of the control winding, the system can be switched between the "high inertia mode" and the "low inertia mode", so that the system inertia is real-time controllable, and the needs of different working conditions of new energy grid connection are met.

[0014] The power winding has a working state of sending power to the large power grid, the control winding has two working states, the first working state is to use power from the new energy grid, and the second working state is to send power to the new energy grid. The armature winding has a working state of using power from the new energy grid or the energy storage system.

[0015] When the rotor speed of the brushless doubly-fed motor is higher than the synchronous speed, the control winding sends power to the new energy grid, and when the rotor speed of the brushless doubly-fed motor is lower than the synchronous speed, the control winding uses power from the new energy grid, and by controlling the mechanical power Pewm output by the axial permanent magnet motor, the rotor speed of the brushless doubly-fed motor can be adjusted. When the frequency or voltage of the large power grid fluctuates, the kinetic energy of the squirrel-cage rotor can be controlled to support the frequency or voltage of the large power grid.

[0016] Optionally, a flywheel can be installed at both ends of the rotating shaft to additionally increase the equivalent rotational inertia of the composite motor, so as to improve the dynamic stability of the system under large disturbance conditions.

[0017] Advantages: The composite integration design of the brushless doubly-fed motor, the axial permanent magnet motor and the magnetic gear is adopted, mechanical and electromagnetic double coupling is realized, the equivalent rotational inertia of the system is significantly increased, stronger inertia support and frequency stability can be provided for the power grid during the new energy grid connection process. By using the rotor magnetic field of the brushless doubly-fed motor as the modulating magnetic source of the magnetic gear, and by dynamically adjusting the current of the control winding, the transmission ratio of the magnetic gear and the real-time controllability of the system inertia can be realized, high inertia support can be provided under different working conditions, and high-efficiency energy conversion can be realized, so that the composite motor is suitable for high-proportion new energy grid connection scenes. BRIEF DESCRIPTION OF DRAWINGS

[0018] In order to make the technical solutions in the embodiments of the present application or the prior art clearer, the accompanying drawings needed in the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below only represent some of the embodiments of the present application, and all other embodiments obtained by a person of ordinary skill in the art without any creative effort on the basis of the embodiments of the present application also belong to the protection scope of the present application.

[0019] Figure 1 Structure schematic diagram of a high-inertia multi-port composite motor for an embodiment

[0020] Figure 2 Structure schematic diagram of a magnetic gear of a high-inertia multi-port composite motor for an embodiment

[0021] Figure 3 System block diagram for an embodiment when new energy is connected to a grid

[0022] Figure 4 Supporting effect of a large power grid frequency for an embodiment

[0023] In the figure: 1 - machine shell; 11 - machine shell main body; 12 - rear end cover; 13 - front end cover; 2 - brushless doubly-fed motor; 21 - brushless doubly-fed motor stator; 22 - brushless doubly-fed motor squirrel cage rotor; 23 - power winding (electric port one); 24 - control winding (electric port two); 3 - axial permanent magnet motor; 31 - axial permanent magnet motor rotor; 32 - axial permanent magnet motor stator; 33 - armature winding (electric port three); 4 - magnetic gear; 41 - magnetic gear outer permanent magnet; 42 - magnetic gear inner permanent magnet; 5 - rotating shaft; 51 - front end bearing; 52 - rear end bearing. DETAILED DESCRIPTION

[0024] The technical solutions in the embodiments of the present application will be described clearly and completely below with reference to the accompanying drawings. Obviously, the described embodiments only represent some of the embodiments of the present application, rather than all the embodiments. Based on the embodiments of the present application, all other embodiments obtained by a person of ordinary skill in the art without any creative effort also belong to the protection scope of the present application.

[0025] The present application provides a high-inertia multi-port composite motor for new energy grid connection, such as Figure 1As shown, including the shell 1, brushless doubly-fed motor 2, axial flux permanent magnet motor 3, magnetic gear 4, shaft 5; brushless doubly-fed motor 2, axial flux permanent magnet motor 3, magnetic gear 4, shaft 5 are located in the shell 1, the shell 1 is composed of shell body 11, rear end cover 12, front end cover 13; brushless doubly-fed motor stator 21 is fixed on the shell body 11, the doubly-fed motor stator 21 is evenly placed power winding (electric port one) 23 and control winding (electric port two) 24, brushless doubly-fed motor rotor 22 is fixed on the magnetic gear 4; axial flux permanent magnet motor stator 32 is fixed on the rear end cover 12, the axial flux permanent magnet motor stator 32 is placed in the armature winding (electric port three) 33, the axial flux permanent magnet motor rotor 31 is fixed on the shaft 5; the magnetic gear outside permanent magnet 41 is placed in the brushless doubly-fed motor rotor 22 inside, the magnetic gear inside permanent magnet 42 is placed on the shaft 5; the shaft 5 is fixed on the shell 1 through the front end bearing 51 and the rear end bearing 52.

[0026] The pole pair number of power winding 23 is Pp, the pole pair number of control winding 24 is Pc, the pole pair number of squirrel cage rotor 22 is Ps, and they satisfy the relationship Pp=Pc+Ps; the working frequency of power winding 23 is fp, the working frequency of control winding 24 is fc, the working frequency of squirrel cage rotor 22 is fs, and they satisfy the relationship fp=fc+fs. The pole pair number of axial flux permanent magnet motor armature winding 33 is Pa, and the pole pair number of axial flux permanent magnet motor rotor 31 is also Pa. The magnetic gear 4 is distributed inside the squirrel cage rotor 22 and outside the shaft 5, the pole pair number of the magnetic gear inside the squirrel cage rotor 22 is Pm1, the pole pair number of the magnetic gear outside the shaft 5 is Pm2, and they satisfy the relationship Pm2=Pm1+Ps.

[0027] The brushless doubly-fed motor 2 has the characteristics of constant frequency power generation, that is, by adjusting the frequency fc of the control winding 24 and the frequency fs of the squirrel cage rotor 22 respectively, the frequency fp of the power winding 23 can be fixed as a set value, so the power winding 23 does not need to pass through the variable flow device and can be directly connected to the large power grid, and the control winding 24 is connected to the new energy power grid through the converter. The axial flux permanent magnet motor armature winding 33 is connected to the new energy power grid or energy storage system through the converter, converts electrical energy into mechanical energy, provides mechanical power Pewm for the brushless doubly-fed motor 2 through the magnetic gear 4, and realizes power balance and multi-port collaborative work.

[0028] The magnetic field of the brushless doubly-fed motor squirrel cage rotor 22 serves as a modulated magnetic source of the magnetic gear 4. By adjusting the current amplitude and frequency of the control winding 24, the magnetic field of the squirrel cage rotor 22 can be dynamically adjusted to provide a controllable modulated magnetic field for the magnetic gear 4, thereby realizing real-time adjustment of the effective transmission ratio of the magnetic gear. When it is necessary to increase the system inertia to enhance the grid stability under low-frequency disturbance, the control winding 24 outputs a low-frequency large-amplitude magnetic field, so that the equivalent transmission ratio of the magnetic gear 4 increases, and the rotational inertia of the axial permanent magnet motor rotor 31 is efficiently superimposed on the brushless doubly-fed motor 2 side through the magnetic gear 4, thereby significantly improving the equivalent rotational inertia of the system. When it is necessary to reduce the system inertia to improve the fast dynamic response, the control winding 24 outputs a high-frequency low-amplitude magnetic field, so that the transmission ratio of the magnetic gear 4 decreases, and the inertia coupling of the axial permanent magnet motor 3 is reduced, thereby realizing fast acceleration or braking of the system. By adjusting the current of the control winding 24, the system can flexibly switch between the high-inertia mode and the low-inertia mode, thereby realizing real-time controllable system inertia to adapt to different operating conditions of the new energy grid connection.

[0029] Figure 3 The system block diagram for the new energy grid connection is shown. The three-port design supports multiple energy interaction modes. The power winding (electrical port one) 23 has one working state for sending power to the power grid. The control winding (electrical port two) 24 has two working states, in the first state, it takes power from the new energy grid, and in the second state, it sends power to the new energy grid. The armature winding (electrical port three) 33 has one working state, taking power from the new energy grid or energy storage system and converting it into mechanical power to assist the operation of the brushless doubly-fed motor 2 through the magnetic gear 4. When the frequency or voltage of the power grid fluctuates, the system can dynamically adjust the kinetic energy of the squirrel cage rotor 22 and the transmission ratio of the magnetic gear 4, thereby effectively supporting the frequency and voltage of the power grid and improving the stability and dynamic response capability of the power grid.

[0030] Figure 4 The example supports the frequency effect of the power grid. At 1.2s, the power grid is disturbed by frequency fluctuation, but under the high-inertia support of the composite motor, the frequency quickly recovers to 50Hz and remains stable.

[0031] The above description is only the preferred embodiment of the present application. It should be noted that for ordinary skilled persons in the art, without departing from the principles of the present application, several improvements and refinements can be made, which should also be considered within the protection scope of the present application.

Claims

1. A high-inertia multi-port composite motor for grid connection of new energy sources, comprising a housing, a brushless doubly-fed motor, an axial permanent magnet motor, magnetic gears, and a rotating shaft, characterized in that, The brushless doubly-fed motor includes a radial stator and a squirrel-cage rotor. The radial stator contains a power winding and a control winding. The power winding serves as electrical port one, with Pp pole pairs and an operating frequency of fp. The control winding serves as electrical port two, with Pc pole pairs and an operating frequency of fc. The squirrel-cage rotor has Ps pole pairs and an operating frequency of fs. These three components satisfy the relationships Pp = Pc + Ps and fp = fc + fs. The axial permanent magnet motor includes an axial stator and an axial permanent magnet rotor. The axial stator contains an armature winding, serving as electrical port three, with Pa pole pairs. The number of pole pairs of the rotor is Pa; the magnetic gears are located inside the squirrel-cage rotor and outside the shaft. The number of pole pairs of the magnetic gear inside the squirrel-cage rotor is Pm1, and the number of pole pairs of the magnetic gear outside the shaft is Pm2, satisfying the relationship Pm2=Pm1+Ps; the rotor magnetic field of the brushless doubly fed motor serves as the modulation magnetic source of the magnetic gears. By adjusting the current amplitude and frequency of the control winding, the effective transmission ratio of the magnetic gears can be dynamically adjusted, thereby realizing the electromagnetic and mechanical dual coupling between the brushless doubly fed motor and the axial permanent magnet motor, improving the equivalent rotational inertia of the composite motor, and enabling dynamic adjustment of the system inertia according to the working conditions.

2. The composite motor according to claim 1, characterized in that, The power winding can be directly connected to the main power grid without going through a converter, and the control winding is connected to the new energy grid through a converter to supply power to the new energy grid or draw power from the new energy grid.

3. The composite motor according to claim 1, characterized in that, The armature winding of the axial permanent magnet motor is connected to a new energy grid or energy storage system through a converter to convert electrical energy into mechanical energy, and provides mechanical power to the brushless doubly fed motor through magnetic gears.

4. The composite motor according to claim 1, characterized in that, The control winding is used to provide an adjustable magnetic field. By changing the amplitude and frequency of the output magnetic field, the effective transmission ratio of the magnetic gear is dynamically adjusted, thereby achieving real-time controllability of the system's equivalent rotational inertia.

5. The composite motor according to claim 1, characterized in that, The composite motor has three energy interaction states: the power winding supplies power to the main power grid, the control winding draws power from the new energy grid in the first state and supplies power to the new energy grid in the second state, and the armature winding draws power from the new energy grid or energy storage system and outputs mechanical power.

6. The composite motor according to claim 1, characterized in that, When the rotor speed of the brushless doubly fed motor is higher than the synchronous speed, the control winding supplies power to the new energy grid; when the rotor speed of the brushless doubly fed motor is lower than the synchronous speed, the control winding draws power from the new energy grid and controls the speed of the brushless doubly fed motor by adjusting the output mechanical power of the axial permanent magnet motor.

7. The composite motor according to claim 1, characterized in that, When the frequency or voltage of the main power grid fluctuates, the system dynamically adjusts the kinetic energy of the squirrel-cage rotor and the transmission ratio of the magnetic gears to provide real-time support for the frequency and voltage of the main power grid.

8. The composite motor according to claim 1, characterized in that, Flywheels can be installed at both ends of the shaft to further improve the equivalent rotational inertia of the composite motor and enhance the inertial response performance of new energy grid connection under large disturbance conditions.

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