An inner winding magnetism regulating type double-stator high-voltage grid-connected generator based on an oriented silicon steel magnetism regulating bridge

Abstract

The application discloses a kind of inner winding magnetism regulating type double-stator high-voltage grid-connected generator based on orientation silicon steel magnetic bridge and working method thereof.The generator includes coaxial nested outer stator, inner stator and rotor, high-voltage three-phase alternating current winding is embedded in the slot of outer stator, and output end is directly connected to power grid;Inner stator winding is arranged in the slot of inner stator, and is connected with low-voltage side variable current voltage regulating unit, induction electromotive force is generated, and power supply is provided to load, and simultaneously generating magnetizing magnetic potential or demagnetizing magnetic potential;Rotor adopts split permanent magnet structure, each pole is composed of two same polarity permanent magnet units, orientation silicon steel magnetic bridge is embedded between units, easy magnetization direction is arranged along magnetic pole center line, and low magnetic resistance channel is formed, for magnetizing magnetic potential to enter outer air gap main magnetic circuit.High-voltage alternating current energy output by outer stator winding of the generator does not pass through high-voltage full-power converter, and magnetism regulating control is realized through small-capacity variable current voltage regulating unit on inner stator side, which effectively reduces system cost and complexity.

Description

Technical Field

[0001] This invention relates to the field of motor technology, and in particular to an internal winding magnetic adjustment type double-stator high-voltage grid-connected generator based on an oriented silicon steel magnetic bridge and its working method. Background Technology

[0002] With the development of wind power, distributed energy supply, high-speed power generation, and large-capacity industrial power generation systems, high-voltage, high-power generators are gradually evolving towards higher power density, higher efficiency, higher reliability, and lower cost. Permanent magnet synchronous generators, due to their advantages such as high efficiency, low rotor loss, compact structure, and low maintenance, have been widely used in large-capacity power generation systems.

[0003] In high-voltage grid-connected power generation applications, the generator output winding typically needs to pass through a rectifier, inverter, or full-power converter before being connected to the grid to achieve voltage regulation, frequency control, reactive power regulation, and grid-connected control. However, in large-capacity high-voltage power generation systems, high-voltage full-power converters suffer from problems such as high cost, large size, difficult heat dissipation, high insulation requirements, and limited reliability. Since all the generator's output power must pass through high-voltage power devices, the converter not only bears high voltage and high current stress but also introduces switching losses, electromagnetic interference, and harmonic pollution. Especially in megawatt-level and above high-voltage power generation systems, the difficulty of selecting components, insulation protection, cooling design, and fault protection for high-voltage converters increases significantly, restricting the system's economic efficiency and long-term operational reliability.

[0004] On the other hand, in addition to the high-voltage main power output, large-capacity power generation systems typically need to provide low-voltage power to controllers, sensors, protection devices, cooling systems, excitation regulation units, and auxiliary electrical loads. Existing systems usually require additional low-voltage auxiliary power supplies, isolation transformers, or DC / DC converters, which not only increases the number of system components and connection complexity but also reduces system integration and operational reliability.

[0005] Traditional electrically excited synchronous generators can control terminal voltage and reactive power by adjusting the excitation current, but their excitation system structure is complex, and they suffer from problems such as rotor winding losses, slip ring maintenance, and reliability issues with the excitation device. While permanent magnet synchronous generators eliminate the excitation winding, improving efficiency and power density, their main magnetic field is primarily provided by permanent magnets, resulting in weak flux linkage regulation. When the generator is directly connected to the grid, the output voltage is significantly affected by speed, load, grid voltage, and permanent magnet flux linkage, making it difficult to flexibly achieve magnetization, magnetization weakening, voltage stabilization, and reactive power regulation. Under high-speed, wide-range operating conditions, or grid disturbances, permanent magnet generators may also experience problems such as excessively high terminal voltage, large short-circuit current, and fault braking torque impact.

[0006] In existing technologies, to address the issue of the unadjustable magnetic field of permanent magnet generators, hybrid excitation structures, additional excitation windings, or power electronic converters are typically employed for regulation. However, some hybrid excitation structures require excitation components on the rotor side, resulting in complex structures and limitations on mechanical reliability and heat dissipation. While some solutions can achieve magnetic field regulation, the coupling between the regulating winding and the main power winding is insufficient, limiting the regulation range. Furthermore, solutions using full-power converters still require high-voltage, high-capacity power electronic devices, failing to effectively reduce system costs and complicate high-voltage insulation protection.

[0007] In recent years, dual-stator motor structures have been extensively studied in the field of permanent magnet power generation. These motors typically employ a coaxial nested structure of inner and outer stators and a central rotor, forming inner and outer dual air-gap magnetic circuits to achieve coordinated output of high and low voltage electrical energy or magnetic field regulation. In dual-stator permanent magnet motor structures, existing technologies usually use an integral permanent magnet rotor. The magnetic field generated on the inner stator side is difficult to effectively couple to the outer air-gap main magnetic circuit, resulting in low magnetic field transmission efficiency between the inner and outer magnetic circuits and significant magnetic leakage between adjacent magnetic poles, leading to effective magnetic flux leakage and insufficient flux linkage utilization.

[0008] Therefore, how to improve the magnetic field coupling efficiency of the internal and external magnetic circuits and reduce magnetic flux leakage in a dual-stator permanent magnet generator is a technical problem that urgently needs to be solved in this field. Summary of the Invention

[0009] The technical problem to be solved by the present invention is to provide an internal winding magnetic adjustment type double-stator high-voltage grid-connected generator based on oriented silicon steel magnetic bridge and its working method, so as to solve the technical problems of low magnetic field coupling efficiency, serious magnetic flux leakage and insufficient magnetic adjustment capability of existing double-stator permanent magnet generators.

[0010] The technical solution adopted by this invention to solve the technical problem is as follows: An internal winding magnetic adjustment type dual-stator high-voltage grid-connected generator based on a grain-oriented silicon steel magnetic bridge includes a coaxially nested outer stator, an inner stator, and a rotor located between the outer stator and the inner stator; The outer stator slot is embedded with an outer stator winding, which is a high-voltage three-phase AC winding used to sense high-voltage AC electromotive force and output high-voltage AC power. The output end of the outer stator winding is directly connected to the power grid. The inner stator slot is provided with an inner stator winding, which is connected to the low-voltage side converter voltage regulation unit. It is used to sense electromotive force and output electrical energy to supply power to the load. It is also used to generate magnetizing or demagnetizing magnetizing force under the control of the low-voltage side converter voltage regulation unit to adjust the effective magnetic flux of the outer air gap corresponding to the outer stator winding. The rotor includes a rotor core and permanent magnets arranged at intervals along the circumference of the rotor. The rotor adopts a split permanent magnet structure. Each pole of the permanent magnet is composed of two permanent magnet units with the same magnetization direction and the same outer polarity. A magnetic adjustment embedding gap is formed between the two permanent magnet units. An oriented silicon steel magnetic adjustment bridge is provided in the magnetic adjustment embedding gap. The radial inner side of the oriented silicon steel magnetic bridge is connected to the rotor core magnetic circuit, and the radial outer side faces the outer air gap between the outer stator and the rotor. The easy magnetization direction of the oriented silicon steel magnetic bridge is arranged along the direction of the rotor's magnetic pole center line. The oriented silicon steel magnetic bridge forms a low magnetic resistance channel, and the magnetomotive force of the inner stator winding enters the main magnetic circuit of the outer air gap through the low magnetic resistance channel.

[0011] Preferably, the number of pole pairs of the outer stator winding and the inner stator winding are the same, and there is no direct electrical connection between the outer stator winding and the inner stator winding. The two are coupled through the magnetic field formed by the permanent magnet of the rotor and the magnetic bridge of the oriented silicon steel.

[0012] Preferably, the inner stator winding also functions as a low-voltage power generation winding, supplying power to the low-voltage side load through magnetic field coupling of the rotor.

[0013] Preferably, the radial width of the oriented silicon steel magnetic bridge is smaller than the radial width of the permanent magnet unit.

[0014] Preferably, both the outer stator winding and the inner stator winding are three-phase AC windings; adjacent permanent magnets are connected by a magnetic circuit formed by the salient poles of the rotor core.

[0015] This invention also provides a method for operating an internal winding magnetic adjustment type double-stator high-voltage grid-connected generator based on a grain-oriented silicon steel magnetic bridge, using the above-mentioned generator, including the following steps: When the rotor rotates, the permanent magnet generates a main excitation magnetic field, which acts on the outer air gap and the inner air gap respectively, causing the outer stator winding to induce a high voltage AC electromotive force and output high voltage AC power, while causing the inner stator winding to induce low voltage power. When it is necessary to increase the output voltage of the outer stator winding, a magnetizing current is injected into the inner stator winding through the low-voltage side converter voltage regulation unit, so that the inner stator winding generates a magnetizing magnetomotive force. The magnetizing magnetomotive force enters the main magnetic circuit of the outer air gap through the oriented silicon steel magnet bridge along the direction of the rotor's magnetic pole center line, thereby increasing the effective magnetic flux of the outer air gap. When it is necessary to reduce the output voltage of the outer stator winding, a demagnetizing current is injected into the inner stator winding through the low-voltage side converter voltage regulation unit, so that the inner stator winding generates a demagnetizing magnetomotive force. The demagnetizing magnetomotive force acts on the main magnetic circuit of the outer air gap along the direction of the magnetic pole center line of the rotor through the oriented silicon steel magnetic adjustment bridge, thereby weakening the effective magnetic flux of the outer air gap.

[0016] Preferably, the inner stator winding outputs a magnetic adjustment current while outputting low-voltage electrical energy, and the power of the magnetic adjustment current is lower than the high-voltage power output by the outer stator winding.

[0017] Preferably, the low-voltage side converter voltage regulation unit adjusts the amplitude and phase of the inner stator winding current according to the terminal voltage of the outer stator winding, the grid voltage, and the rotor speed signal.

[0018] Preferably, when a short-circuit fault occurs in the power grid, the low-voltage side converter voltage regulation unit injects the maximum permissible demagnetizing current into the inner stator winding to reduce the effective magnetic flux in the outer air gap and limit the fault current in the outer stator winding.

[0019] The working principle of this invention is as follows: This invention adopts a coaxial nested structure of outer stator-rotor-inner stator to form two air gaps, inner and outer. When the rotor rotates, the main excitation magnetic field generated by the permanent magnet passes through the outer air gap and the inner air gap at the same time, and links with the outer stator winding and the inner stator winding respectively to realize dual-path power generation.

[0020] The outer stator winding is a high-voltage three-phase AC winding, and its output terminal is directly connected to the power grid. The main power does not pass through the high-voltage full-power converter. The inner stator winding is connected to the low-voltage side converter voltage regulation unit. On the one hand, it induces low-voltage power to supply power to auxiliary loads such as controllers, sensors, and protection devices. On the other hand, it generates a magnetizing current under the control of the low-voltage side converter voltage regulation unit to achieve magnetization or demagnetization.

[0021] Two permanent magnet units of the same polarity are set on each pole of the rotor, and a grain-oriented silicon steel magnetic bridge is embedded between the two permanent magnet units. The easy magnetization direction of the grain-oriented silicon steel magnetic bridge is arranged along the center line of the rotor magnetic pole. This direction has high magnetic permeability and forms a low magnetic reluctance channel. The magnetomotive force generated by the inner stator winding enters the main magnetic circuit of the outer air gap through this low magnetic reluctance channel and directly acts on the linkage of the outer stator winding.

[0022] During magnetization, the low-voltage side converter voltage regulating unit injects a magnetizing current in the same direction as the main magnetomotive force of the permanent magnet into the inner stator winding. The magnetizing magnetomotive force enters the main magnetic circuit of the outer air gap through the grain-oriented silicon steel magnet regulating bridge, increasing the effective magnetic flux linkage in the outer air gap and raising the induced voltage of the outer stator winding. During demagnetization, a reverse demagnetizing current is injected, weakening the effective magnetic flux linkage in the outer air gap. Part of the magnetic flux is closed through the internal bypass of the rotor core, reducing the induced voltage of the outer stator winding.

[0023] The magnetic permeability of the grain-oriented silicon steel magnetic bridge is low in the non-magnetizing direction, which has a certain suppressive effect on circumferential leakage magnetic flux. It can reduce the ineffective magnetic flux leakage between adjacent magnetic poles, allowing more effective magnetic flux to enter the outer and inner air gaps, and improving the utilization rate of permanent magnet flux linkage.

[0024] When a short-circuit fault occurs in the power grid, the low-voltage side converter voltage regulation unit quickly injects the maximum demagnetizing current into the inner stator winding, reduces the effective magnetic flux in the outer air gap, and limits the fault current and electromagnetic braking torque of the outer stator winding from the source.

[0025] Compared with the prior art, the present invention has the following advantages: 1. The external stator winding of the present invention is directly connected to the power grid, and the main power does not pass through the high-voltage full-power converter. Therefore, the high-cost, large-volume, and heat-dissipating high-voltage full-power converter in the prior art can be eliminated, reducing system cost and insulation design difficulty, while avoiding switching losses, electromagnetic interference and harmonic pollution introduced by the converter.

[0026] 2. In this invention, the inner stator winding is connected to the low-voltage side converter voltage regulation unit. By injecting magnetizing or demagnetizing current, the effective magnetic flux linkage of the corresponding outer air gap of the outer stator winding can be adjusted, achieving magnetization, demagnetization, and voltage stabilization control. Since the low-voltage side converter voltage regulation unit only needs to provide magnetizing current, its capacity is much smaller than the high-voltage power output of the outer stator winding. Therefore, a small-capacity low-voltage controller can be used to achieve magnetic field regulation of a large-capacity high-voltage power generation system, significantly reducing the capacity requirements and cost of power electronic devices.

[0027] 3. The inner stator winding of the present invention, while participating in magnetic regulation, also generates low-voltage electrical energy through rotor magnetic field coupling induction to supply power to the low-voltage side load. It has the dual functions of low-voltage power generation and magnetic regulation, eliminating the need for additional low-voltage auxiliary power supply or isolation transformer, reducing the number of system components and improving system integration.

[0028] 4. The rotor of this invention adopts a split permanent magnet structure, with each pole consisting of two permanent magnet units of the same polarity. A grain-oriented silicon steel tuning bridge is embedded between the permanent magnet units. The easy magnetization direction of the grain-oriented silicon steel tuning bridge is arranged along the center line of the rotor poles. This direction has high permeability, forming a low magnetic reluctance channel, allowing the tuning magnetomotive force generated by the inner stator windings to efficiently enter the main magnetic circuit of the outer air gap. Simultaneously, the grain-oriented silicon steel has lower permeability in the non-easy magnetization direction, which can suppress circumferential leakage between adjacent poles, reduce effective magnetic flux leakage, and improve the utilization rate of the permanent magnet flux linkage. This invention improves tuning efficiency while also enhancing flux linkage utilization.

[0029] 5. When a short-circuit fault occurs in the power grid, the present invention can quickly inject the maximum demagnetizing current into the inner stator winding through the low-voltage side converter voltage regulation unit, reduce the effective magnetic flux of the outer air gap, thereby limiting the fault current and electromagnetic braking torque of the outer stator winding from the source, and improving the fault adaptability and operational reliability of the generator. Attached Figure Description

[0030] Figure 1 This is a schematic diagram of the overall structure of the present invention; Figure 2This is an end view of the generator of the present invention; Figure 3 This is a three-dimensional structural diagram of the rotor in this invention; Figure 4 This is a schematic diagram showing the arrangement of rotor magnetic poles in this invention. Figure 5 This is an enlarged schematic diagram of a partial rotor structure in this invention; In the diagram: 1--Outer stator; 2--Outer stator winding; 3--Inner stator winding; 4--Inner stator; 5--Rotor; 6--Permanent magnet; 7--Oriented silicon steel magnetic bridge; 8--Rotor core. Detailed Implementation

[0031] The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments. These embodiments are only for illustrating the present invention and are not intended to limit the scope of protection of the present invention.

[0032] Example 1, such as Figures 1 to 5 As shown, an inner-winding magnetic-adjusting dual-stator high-voltage grid-connected generator based on a grain-oriented silicon steel magnetic bridge includes a coaxially nested outer stator 1, an inner stator 4, and a rotor 5 located between the outer stator 1 and the inner stator 4.

[0033] The outer stator 1 is located on the outermost side of the motor, and the outer stator winding 2 is embedded in its slot; the outer stator winding 2 is a high-voltage three-phase AC winding, and its output end is directly connected to the power grid.

[0034] The inner stator 4 is located radially inside the rotor 5, and the inner stator winding 3 is installed in its slot. The inner stator winding 3 is connected to the low-voltage side converter voltage regulation unit, and supplies power to the load after inducing electromotive force, while generating magnetomotive force or demagnetizing magnetomotive force. The number of turns of the inner stator winding 3 is less than that of the outer stator winding 2, and the output voltage is lower.

[0035] The rotor 5 includes a rotor core 8, permanent magnets 6, and a silicon-oriented steel magnetic bridge 7. The permanent magnets 6 are arranged at intervals along the circumferential direction on the outside of the rotor core 8. Each pole is composed of two permanent magnet units of the same polarity. A magnetic adjustment gap is left between the units, and the silicon-oriented steel magnetic bridge 7 is set in the gap.

[0036] The radially inner side of the grain-oriented silicon steel adjusting bridge 7 is connected to the magnetic circuit of the rotor core 8, and the radially outer side faces the outer air gap. Its easy magnetization direction is arranged along the center line of the magnetic pole of the rotor 5, forming a low magnetic reluctance channel, allowing the adjusting magnetomotive force of the inner stator winding 3 to enter the main magnetic circuit of the outer air gap; the radial width of the grain-oriented silicon steel adjusting bridge 7 is smaller than that of the permanent magnet unit.

[0037] The outer stator winding 2 and the inner stator winding 3 have the same number of pole pairs and are not directly electrically connected. They are coupled through the magnetic field of the rotor 5. Adjacent permanent magnets 6 are connected by the salient poles of the rotor core 8 to form a magnetic circuit.

[0038] Example 2: The structure of this example is basically the same as that of Example 1. The similarities will not be repeated. The difference is that the number of slots per pole per phase of the inner stator winding 3 is less than that of the outer stator winding 2, which further reduces the output voltage.

[0039] Example 3: The working method of the inner winding magnetic adjustment type double stator high-voltage grid-connected generator based on grain-oriented silicon steel magnetic bridge described in Example 1: When the generator is running, the external power source drives the rotor 5 to rotate, and the main excitation magnetic field generated by the permanent magnet 6 acts on the outer air gap and the inner air gap respectively; the magnetic flux of the outer air gap links with the outer stator winding 2, and after inducing a high-voltage AC electromotive force, it is directly connected to the grid; the magnetic flux of the inner air gap links with the inner stator winding 3, and inducing low-voltage electrical energy to supply power to the load.

[0040] Under the magnetization condition, the low-voltage side converter voltage regulation unit injects magnetizing current into the inner stator winding 3, generating a magnetizing magnetomotive force in the same direction as the main magnetomotive force of the permanent magnet 6. This magnetizing current enters the main magnetic circuit of the outer air gap along the magnetic pole center line through the oriented silicon steel magnet bridge 7, increasing the effective magnetic flux linkage of the outer air gap and raising the induced voltage of the outer stator winding 2.

[0041] Under demagnetizing conditions, a demagnetizing current is injected to generate a reverse demagnetizing magnetomotive force, which acts on the main magnetic circuit of the outer air gap through the oriented silicon steel magnetic bridge 7, weakening the effective magnetic flux linkage of the outer air gap and reducing the induced voltage of the outer stator winding 2.

[0042] When the power grid is short-circuited, the low-voltage side converter voltage regulation unit quickly injects the maximum demagnetizing current to reduce the effective magnetic flux in the external air gap and limit the fault current.

[0043] Example 4: The working method of this example is basically the same as that of Example 3. The similarities will not be repeated. The difference is that the low-voltage side converter voltage regulation unit integrates the voltage at the outer stator winding 2 end, the grid voltage, the output current, the reactive power and the rotor speed signal to adjust the amplitude and phase of the current in the inner stator winding 3, so as to achieve precise control of reactive power.

[0044] In summary, this invention achieves low-voltage side magnetization, demagnetization, and voltage stabilization control of a high-voltage power generation system by directly connecting the outer stator high-voltage winding to the grid for power generation and actively adjusting the rotor flux linkage of the inner stator low-voltage winding. The use of split permanent magnets and grain-oriented silicon steel tuning bridges to construct a low-resistivity tuning channel along the magnetic pole centerline improves the coupling efficiency and adjustment capability of the inner and outer air gap flux linkages. The inner stator winding combines low-voltage power generation and magnetization functions, reducing the need for a high-voltage full-power converter and external low-voltage auxiliary power supply, thus improving system integration and operational reliability.

[0045] The above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit the present invention. Those skilled in the art will understand that modifications or equivalent substitutions can be made to the technical solutions of the above embodiments without departing from the essence of the technical solutions of the present invention, and such modified or substituted technical solutions will still fall within the protection scope of the present invention.

Claims

1. A double-stator high-voltage grid-connected generator with inner winding magnetic adjustment based on a grain-oriented silicon steel magnetic bridge, comprising a coaxially nested outer stator (1), an inner stator (4), and a rotor (5) located between the outer stator (1) and the inner stator (4), characterized in that: The outer stator (1) slot is provided with an outer stator winding (2), which is a high-voltage three-phase AC winding used to induce high-voltage AC electromotive force and output high-voltage AC power. The output end of the outer stator winding (2) is directly connected to the power grid. The inner stator (4) slot is provided with an inner stator winding (3), which is connected to the low-voltage side converter voltage regulation unit. It is used to induce electromotive force and output power to supply power to the load. It is also used to generate magnetizing or demagnetizing magnetizing force under the control of the low-voltage side converter voltage regulation unit to adjust the effective magnetic flux of the outer air gap corresponding to the outer stator winding (2). The rotor (5) includes a rotor core (8) and permanent magnets (6) arranged at intervals along the circumference of the rotor (5). The rotor (5) adopts a split permanent magnet structure. The permanent magnet (6) corresponding to each pole is composed of two permanent magnet units with the same magnetization direction and the same outer polarity. A magnetic adjustment fitting gap is formed between the two permanent magnet units. An oriented silicon steel magnetic adjustment bridge (7) is provided in the magnetic adjustment fitting gap. The radial inner side of the oriented silicon steel magnetic adjustment bridge (7) is connected to the magnetic circuit of the rotor core (8). The radial outer side faces the outer air gap between the outer stator (1) and the rotor (5). The easy magnetization direction of the oriented silicon steel magnetic adjustment bridge (7) is arranged along the magnetic pole center line of the rotor (5). The oriented silicon steel magnetic adjustment bridge (7) forms a low magnetic resistance channel. The magnetic adjustment magnetomotive force of the inner stator winding (3) enters the main magnetic circuit of the outer air gap through the low magnetic resistance channel.

2. The internal winding magnetic adjustment type double-stator high-voltage grid-connected generator according to claim 1, characterized in that: The number of pole pairs of the outer stator winding (2) and the inner stator winding (3) are the same, and there is no direct electrical connection between the outer stator winding (2) and the inner stator winding (3). The two are coupled through the magnetic field formed by the permanent magnet (6) of the rotor (5) and the oriented silicon steel magnetic bridge (7).

3. The internal winding magnetic adjustment type double-stator high-voltage grid-connected generator according to claim 2, characterized in that: The inner stator winding (3) also functions as a low-voltage power generation winding, and supplies power to the low-voltage side load through the magnetic field coupling of the rotor (5).

4. The internal winding magnetic adjustment type double-stator high-voltage grid-connected generator according to claim 1, characterized in that: The radial width of the oriented silicon steel magnetic bridge (7) is smaller than the radial width of the permanent magnet unit.

5. The internal winding magnetic adjustment type double-stator high-voltage grid-connected generator according to claim 1, characterized in that: Both the outer stator winding (2) and the inner stator winding (3) are three-phase AC windings; adjacent permanent magnets (6) are connected by a magnetic circuit formed by the salient pole of the rotor core (8).

6. A method for operating an internal winding magnetic-adjusting double-stator high-voltage grid-connected generator based on a grain-oriented silicon steel magnetic bridge, using the generator described in any one of claims 1 to 5, characterized in that... Includes the following steps: When the rotor (5) rotates, the permanent magnet (6) generates the main excitation magnetic field. The main excitation magnetic field acts on the outer air gap and the inner air gap respectively, causing the outer stator winding (2) to induce a high voltage AC electromotive force and output high voltage AC power, while causing the inner stator winding (3) to induce low voltage power. When it is necessary to increase the output voltage of the outer stator winding (2), a magnetizing current is injected into the inner stator winding (3) through the low-voltage side converter voltage regulation unit, so that the inner stator winding (3) generates a magnetizing magnetomotive force. The magnetizing magnetomotive force enters the outer air gap main magnetic circuit along the direction of the magnetic pole center line of the rotor (5) through the oriented silicon steel magnet bridge (7), thereby increasing the effective magnetic flux of the outer air gap. When it is necessary to reduce the output voltage of the outer stator winding (2), a demagnetizing current is injected into the inner stator winding (3) through the low-voltage side converter voltage regulation unit, so that the inner stator winding (3) generates a demagnetizing magnetomotive force. The demagnetizing magnetomotive force acts on the outer air gap main magnetic circuit along the direction of the magnetic pole center line of the rotor (5) through the oriented silicon steel magnetic bridge (7), weakening the effective magnetic flux of the outer air gap.

7. The working method according to claim 6, characterized in that: The inner stator winding (3) outputs a magnetic adjustment current while outputting low-voltage electrical energy. The power of the magnetic adjustment current is lower than the high-voltage power output by the outer stator winding (2).

8. The working method according to claim 6, characterized in that: The low-voltage side converter voltage regulation unit adjusts the amplitude and phase of the current in the inner stator winding (3) according to the terminal voltage of the outer stator winding (2), the grid voltage, and the rotational speed signal of the rotor (5).

9. The working method according to claim 6, characterized in that: When a short-circuit fault occurs in the power grid, the low-voltage side converter voltage regulation unit injects the maximum allowable demagnetizing current into the inner stator winding (3) to reduce the effective magnetic flux of the outer air gap and limit the fault current of the outer stator winding (2).

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