A direct voltage variable excitation switched reluctance generator power converter and its control method

Abstract

A kind of high-voltage switch reluctance generator power converter and its control method, power converter is composed of ten switch tubes, six inductors, three-phase winding, seven capacitors and eight diodes, and it is specifically divided into main circuit for each phase winding excitation and power generation and variable excitation circuit for realizing variable excitation voltage by feedback power generation energy;Directly realize high-voltage output in excitation and power generation process, the excitation power in the loop also participates in the power generation stage, and then can directly generate control effect in the power generation stage, and when the power generation voltage is too low, there is a loop that increases instantaneous output in excitation and power generation stage;By setting the ratio of two pairs of coupled inductors, and the constraint of the ninth switch tube and the tenth switch tube, the excitation voltage change can be adjusted while realizing overall voltage reduction;The whole power converter has no isolation transformer;It is suitable for small power variable speed wind driven high-speed switch reluctance generator system field application in direct current microgrid.

Description

Technical Field

[0001] This invention relates to the field of switched reluctance motors, specifically to a novel power converter and its control method for a small-power variable-speed wind power generator with direct voltage boost, variable excitation voltage and voltage reduction, adjustable generation voltage, adaptability to low voltage ride-through, no isolation link, and common ground for generation and variable excitation. Background Technology

[0002] Under the "dual-carbon" strategy, the utilization of clean energy power generation, represented by wind power, has received unparalleled attention, which has also spurred the industry's enthusiasm for the research and development of different generator systems. Meanwhile, in order to more effectively utilize the electrical energy of various small and medium-sized distributed power generation devices, DC microgrids have received increasing attention from the industry and have made significant progress. Currently, the industry's wind turbine generator systems are dominated by AC motor systems, represented by asynchronous and permanent magnet synchronous generators. For the application of DC microgrids, a rectification stage is inevitably required. However, switched reluctance generators directly generate DC power, at least eliminating the need for a rectification stage.

[0003] However, although switched reluctance generators directly generate DC power, the grid connection voltage of DC microgrids is generally significantly higher than the output voltage of switched reluctance generators under traditional power converters, requiring the addition of a separate DC / DC boost stage. In order to eliminate or reduce the boost stage, high-gain direct-boost switched reluctance generator power converters are bound to be one of the important directions of research and development.

[0004] In recent years, in the control of switched reluctance generator systems, control methods have emerged that aim to improve system performance by utilizing excitation voltage. For example, maximum power point tracking control of switched reluctance generators under variable wind speed wind power drive conditions has led to the development of circuit structures in power converters that can change the excitation voltage. However, most of these methods change the excitation voltage during the excitation phase when each phase winding of the switched reluctance generator is working. Although the excitation phase is adjusted, it can only indirectly affect the subsequent power generation phase. Although a few methods have emerged that can achieve relatively direct control by changing the excitation voltage during the power generation phase, i.e., full-domain variable excitation voltage control, these methods are often subject to many structural or other constraints.

[0005] To achieve both direct voltage boost and variable excitation voltage, the first consideration is the source of the excitation power supply's input energy. If it comes from a battery, issues arise such as replacing or charging the battery, significantly increasing maintenance costs. Therefore, feedback from the generator output is considered. This raises the question that the circuit system for variable excitation voltage must first achieve voltage reduction; otherwise, it cannot be matched. Then, a certain range of voltage transformation can be achieved on the basis of voltage reduction.

[0006] In the field of DC microgrids, most applications involve small-scale power generation devices with wide coverage and numerous locations, such as photovoltaic, small wind power, or small pumped storage power stations. Switched reluctance motors (SRMs), due to their simple structure, especially the absence of windings and permanent magnets on the rotor, offer convenient heat dissipation and are particularly suitable for high-speed operation, demonstrating their advantages. However, large and medium-sized SRMs face the problem of significantly increased costs at high speeds due to mechanical strength requirements. Therefore, relatively speaking, miniaturized SRMs are easier to achieve high-speed operation at a lower cost. Consequently, low-power, high-speed SRM generator systems are very suitable for DC microgrid applications, especially as variable-speed wind power drives.

[0007] A crucial issue that cannot be avoided in a complete grid-connected wind power generation system is low-voltage ride-through (LVRT). In the conventional wind power industry, dedicated hardware converters and fast software algorithms are designed for LVRT. Therefore, for switched reluctance generator (SRG) systems connected to the grid under variable-speed wind power, in order to protect the grid, it is essential to design a LVRT solution that can efficiently utilize the power generation system, rather than simply shutting down the system when voltage drops suddenly. At this point, there is inevitably a cost-effectiveness issue, that is, the cost of LVRT must be lower than the power generation lost by direct shutdown. Therefore, it is also important to have a simple, low-cost, and fast LVRT recovery capability in the SRG power converter system.

[0008] Among the many development trends of switched reluctance generators and their power converter systems, one issue that cannot be ignored is that, since the phase winding excitation and power generation processes of a switched reluctance generator are not in the same loop as the variable excitation process, the question of whether or not to isolate the power converter and the grounding issue will also cause problems in the cost and control complexity of the power converter. In particular, adding isolation devices will inevitably increase the size, weight, cost, and losses. Summary of the Invention

[0009] Based on the above background technology, this invention proposes a novel power converter and its control method for a variable-speed switched reluctance generator. This converter can directly boost the voltage output by relying on the excitation and power generation processes themselves. It can achieve variable excitation voltage and directly affect the power generation stage. When the power output feedback is used as the input of the variable excitation circuit, the corresponding voltage reduction stage can be completed first. It fully utilizes the inherent advantage of high-speed operation of the switched reluctance motor. It can also help low voltage ride-through in both the excitation and power generation stages. Furthermore, the entire power converter has no isolation stage and is grounded. This invention is suitable for application in the field of small-power switched reluctance wind turbine generator systems in DC microgrids.

[0010] The technical solution of this invention is as follows:

[0011] A step-up variable-excitation switched reluctance generator power converter comprises a first switch, a second switch, a third switch, a fourth switch, a fifth switch, a sixth switch, a seventh switch, an eighth switch, a ninth switch, a tenth switch, a first inductor, a second inductor, a third inductor, a fourth inductor, a fifth inductor, a sixth inductor, a first phase winding, a second phase winding, a third phase winding, a first capacitor, a second capacitor, a third capacitor, a fourth capacitor, a fifth capacitor, a sixth capacitor, a seventh capacitor, a first diode, a second diode, a third diode, a fourth diode, a fifth diode, a sixth diode, a seventh diode, and an eighth diode. The anode of the switching transistor is connected to the anodes of the second and third switching transistors, one end of the first inductor, one end of the second inductor, one end of the fourth inductor, one end of the sixth inductor, and one end of the seventh capacitor, serving as the positive terminal of the excitation power input for the switched reluctance generator. The cathode of the first switching transistor is connected to one end of the first phase winding, the cathode of the second switching transistor is connected to one end of the second phase winding, and the cathode of the third switching transistor is connected to one end of the third phase winding. The other end of the first phase winding is connected to the other end of the second and third phase windings, the anode of the fourth switching transistor, the anode of the first diode, and the anode of the second diode. The other end of the first inductor is connected to the anode of the fifth switching transistor and one end of the first capacitor, and the other end of the second inductor is connected to the eighth switching transistor. The anode is connected to one end of the third capacitor. The other end of the third capacitor is connected to the cathode of the third diode and the anode of the fourth diode. The anode of the third diode is connected to the cathode of the second diode and one end of the second capacitor. The other end of the second capacitor is connected to the cathode of the sixth switch and the anode of the seventh switch. The anode of the sixth switch is connected to the other end of the first capacitor and the cathode of the first diode. The cathode of the fourth diode is connected to one end of the fourth capacitor, one end of the third inductor, and the cathode of the fifth diode, and serves as the positive terminal of the switched reluctance generator output. The cathode of the fourth switch is connected to the cathodes of the fifth, seventh, and eighth switches, the other end of the fourth and seventh capacitors, and the anode of the sixth diode. The anodes of the seventh and eighth diodes serve as the negative input and output terminals of the switched reluctance generator's excitation power supply. The other end of the third inductor is connected to one end of the fifth inductor and one end of the fifth capacitor. The other end of the fifth capacitor is connected to the anode of the fifth diode and the cathode of the sixth diode. The other end of the fifth inductor is connected to the anode of the ninth switching transistor. The cathode of the ninth switching transistor is connected to the anode of the tenth switching transistor and one end of the sixth capacitor. The other end of the sixth capacitor is connected to the other end of the fourth inductor and the cathode of the seventh diode. The cathode of the tenth switching transistor is connected to the other end of the sixth inductor and the cathode of the eighth diode. The third and fourth inductors form a pair of coupled inductors. The fifth and sixth inductors form a pair of coupled inductors.

[0012] The first capacitor and the second capacitor are exactly the same; the first inductor and the second inductor are exactly the same; the number of turns of the third inductor divided by the number of turns of the fourth inductor should be greater than 1, and equal to the number of turns of the fifth inductor divided by the number of turns of the sixth inductor. The inductance values ​​and number of turns of the third inductor and the fifth inductor are equal, and the inductance values ​​and number of turns of the fourth inductor and the sixth inductor are equal.

[0013] A control method for a direct-drive variable-excitation switched reluctance generator power converter includes a variable excitation circuit composed of a fifth diode, a sixth diode, a seventh diode, an eighth diode, a third inductor, a fourth inductor, a fifth inductor, a sixth inductor, a fifth capacitor, a sixth capacitor, a seventh capacitor, a ninth switch, and a tenth switch. The fifth and sixth diodes are connected in series to receive the electrical energy fed back from the generator output terminal as input. The seventh capacitor outputs excitation energy. The magnitude of the excitation voltage is determined by the duty cycle of the two switches, namely the ninth and tenth switches.

[0014] According to the working principle of a switched reluctance generator, when the first phase winding needs to be engaged based on the rotor position information, the first, fourth, sixth, and eighth switches are closed first, and the first phase winding enters the excitation stage. The excitation power supply powers the first phase winding through the first and fourth switches, and simultaneously charges the second inductor through the eighth switch. The excitation power supply, together with the first inductor, the first capacitor, and the second capacitor, is connected in series and charges the third capacitor through the sixth and eighth switches. When the excitation stage of the first phase winding needs to end based on the rotor position information, the fourth and sixth switches are opened. The eighth switch is closed, and the fifth and seventh switches are closed simultaneously to enter the power generation stage. At this time, the first phase winding and the excitation power supply are connected in series to charge the first capacitor through the first and fifth switches. The first phase winding and the excitation power supply are also connected in series to charge the second capacitor through the first and seventh switches. The excitation power supply, together with the second inductor and the third capacitor, outputs electrical energy to the power generation output terminal. The excitation power supply also charges the first inductor through the fifth switch. According to the rotor position information, when the power generation stage of the first phase winding needs to end, all previously closed switches are disconnected, and the power generation stage ends, that is, the operation of the first phase winding ends.

[0015] Based on the rotor position information, when the second and third phase windings need to be put into operation, the operating mode is the same as that of the first phase winding. The first switching transistor is simply replaced by the second and third switching transistors respectively.

[0016] During the excitation and generation phases of each phase winding, the fifth, sixth, seventh, and eighth switching transistors all implement PWM control mode during the closed conduction phase.

[0017] In the operation of the variable excitation circuit, the ninth and tenth switching transistors have the same switching frequency, the same duty cycle (less than 0.5), and a phase difference of 180 degrees. The specific duty cycle is determined according to the excitation voltage required by the power converter across the seventh capacitor.

[0018] The main technical effects of this invention are:

[0019] When the switched reluctance generator operates in two stages—excitation and generation—through the windings of each phase, the power converter can directly and simultaneously achieve a generation voltage at the output end that is much higher than the excitation voltage on the input side, thus directly achieving high-gain voltage output and saving the need for a dedicated boost stage.

[0020] Besides the need for maximum power point tracking control in variable speed wind power operation through variable excitation voltage in the variable excitation circuit, the excitation power supply participates in the current conversion process of each phase winding of the switched reluctance generator during both the excitation and generation stages. The generation voltage can be directly affected by adjusting the excitation voltage. In particular, it has pioneered the ability to directly affect the generation voltage and operating performance by adjusting the excitation voltage during the generation stage. According to the mathematical model of the switched reluctance generator, the direct controllability of the generation stage has a crucial impact on the generation efficiency of the switched reluctance generator.

[0021] The power converter directly boosts the voltage output, while the variable excitation circuit can achieve a step-down output, that is, the generator voltage at the input is stepped down to the excitation voltage. When the duty cycles of the two pairs of coupled inductors and the ninth and tenth switching transistors are adjusted to a suitable range, a certain width of step-down output can be achieved.

[0022] This invention is very suitable for low-power, high-speed and ultra-high-speed switched reluctance generators, and can give full play to the advantages of high-speed operation of switched reluctance motors.

[0023] When the voltage on the generator output side drops suddenly, especially when a voltage drop fault occurs after connecting to a DC microgrid, if the voltage cannot be restored quickly, it is very likely to cause damage to the components in the line, or even grid paralysis. In the operation of the switched reluctance generator of the present invention, whether in the excitation stage or the generation stage, there is an ability to adapt to the sudden drop in generation voltage, and the original circuit can instantly change the current to increase the power output capacity, thereby enhancing the ability to resist voltage drops and quickly help restore voltage. This is the enhanced low voltage ride-through capability commonly seen in the wind power industry.

[0024] While achieving the above-mentioned multiple technical effects, the power converter of this invention does not have the common isolation links in its structure, and the main circuit and the variable excitation circuit and each phase winding share a common ground when they are working. Attached Figure Description

[0025] Figure 1 The diagram shown is a circuit structure diagram of a direct-drive variable-excitation switched reluctance generator power converter according to the present invention. Detailed Implementation

[0026] This embodiment describes a step-up variable-excitation switched reluctance generator power converter, the circuit structure of which is shown in the attached figure. Figure 1As shown, the switched reluctance generator is a three-phase 6 / 4-pole structure. The power converter consists of the following components: first switch V1, second switch V2, third switch V3, fourth switch V4, fifth switch V5, sixth switch V6, seventh switch V7, eighth switch V8, ninth switch V9, tenth switch V10; first inductor L1, second inductor L2, third inductor L3, fourth inductor L4, fifth inductor L5, sixth inductor L6; first phase winding M, second phase winding N, third phase winding P; first capacitor C1, second capacitor C2, third capacitor C3, fourth capacitor C4, fifth capacitor C5, sixth capacitor C6, seventh capacitor C7; first diode D1, second diode D2, third diode D3, fourth diode D4, fifth diode D5, sixth diode D6, seventh diode D7, and fourth diode D8. The system consists of diodes D3, D4, D5, D6, D7, and D8. The anode of the first switching transistor V1 is connected to the anodes of the second and third switching transistors V2 and V3, one end of the first inductor L1, one end of the second inductor L2, one end of the fourth inductor L4, one end of the sixth inductor L6, and one end of the seventh capacitor C7, serving as the positive terminal of the excitation power input for the switched reluctance generator. The cathode of the first switching transistor V1 is connected to one end of the first phase winding M, the cathode of the second switching transistor V2 is connected to one end of the second phase winding N, and the cathode of the third switching transistor V3 is connected to one end of the third phase winding P. The other end of the first phase winding M is connected to the other end of the second phase winding N, the other end of the third phase winding P, and the fourth switching transistor... The anodes of diodes V4, D1, and D2 are connected. The other end of the first inductor L1 is connected to the anode of the fifth switch V5 and one end of the first capacitor C1. The other end of the second inductor L2 is connected to the anode of the eighth switch V8 and one end of the third capacitor C3. The other end of the third capacitor C3 is connected to the cathode of the third diode D3 and the anode of the fourth diode D4. The anode of the third diode D3 is connected to the cathode of the second diode D2 and one end of the second capacitor C2. The other end of the second capacitor C2 is connected to the cathode of the sixth switch V6 and the anode of the seventh switch V7. The anode of the sixth switch V6 is connected to the other end of the first capacitor C1 and the cathode of the first diode D1. The cathode of the fourth diode D4 is connected to one end of the fourth capacitor C4 and one end of the third inductor L3. The fourth switch transistor V4 is connected to the cathodes of the fifth switch transistor V5, the seventh switch transistor V7, and the eighth switch transistor V8, as well as the other end of the fourth capacitor C4 and the seventh capacitor C7, the anodes of the sixth diode D6, the seventh diode D7, and the eighth diode D8. This connection serves as the negative input terminal and the negative output terminal of the switched reluctance generator. The other end of the third inductor L3 is connected to one end of the fifth inductor L5 and one end of the fifth capacitor C5. The other end of the fifth capacitor C5 is connected to the anode of the fifth diode D5 and the cathode of the sixth diode D6. The other end of the fifth inductor L5 is connected to the anode of the ninth switch transistor V9.The cathode of the ninth switch V9 is connected to the anode of the tenth switch V10 and one end of the sixth capacitor C6. The other end of the sixth capacitor C6 is connected to the other end of the fourth inductor L4 and the cathode of the seventh diode D7. The cathode of the tenth switch V10 is connected to the other end of the sixth inductor L6 and the cathode of the eighth diode D8. The third inductor L3 and the fourth inductor L4 form a pair of coupled inductors, with their corresponding terminals as shown in the attached diagram. Figure 1 As shown; the fifth inductor L5 and the sixth inductor L6 form a pair of coupled inductors, with their corresponding terminals as shown in the attached diagram. Figure 1 As shown.

[0027] The first capacitor C1 and the second capacitor C2 are identical; the first inductor L1 and the second inductor L2 are identical; the number of turns of the third inductor L3 divided by the number of turns of the fourth inductor L4 should be greater than 1, and equal to the number of turns of the fifth inductor L5 divided by the number of turns of the sixth inductor L6. In this embodiment, it equals 5. That is, the variable excitation circuit should first achieve a certain high voltage drop capability to match the feedback after the direct voltage boost during the excitation of each phase winding and the power generation operation. The inductance value of the third inductor L3 is equal to the inductance value and the number of turns of the fifth inductor L5, and the inductance value of the fourth inductor L4 is equal to the inductance value and the number of turns of the sixth inductor L6.

[0028] This embodiment provides a control method for a direct-drive variable-excitation switched reluctance generator power converter. A variable excitation circuit is composed of a fifth diode D5, a sixth diode D6, a seventh diode D7, an eighth diode D8, a third inductor L3, a fourth inductor L4, a fifth inductor L5, a sixth inductor L6, a fifth capacitor C5, a sixth capacitor C6, a seventh capacitor C7, a ninth switch V9, and a tenth switch V10. The fifth diode D5 and the sixth diode D6 are connected in series to receive the electrical energy fed back from the generator's output terminal as input. The seventh capacitor C7 outputs excitation energy. The magnitude of the excitation voltage is determined by the duty cycle of the two switches, namely the ninth switch V9 and the tenth switch V10. The ninth switch V9 and the tenth switch V10 operate independently relative to the other switches.

[0029] According to the working principle of a switched reluctance generator, when the first phase winding M needs to be put into operation based on the rotor position information, the first switch V1, the fourth switch V4, the sixth switch V6, and the eighth switch V8 are closed first. The first phase winding M enters the excitation stage, forming three circuits. The first circuit is: C7-V1-M-V4-C7, that is, the excitation power supply supplies power to the first phase winding M for excitation through the first switch V1 and the fourth switch V4. The second circuit is: C7-L2-V8-C7, that is, the excitation power supply charges the second inductor L2 through the eighth switch V8. The third circuit is: C7-L1-C1-V6-C2-D3-C3-V8-C7, that is, the excitation power supply charges the first inductor L1, the first inductor L2, the first inductor L2, the first inductor L2, the first inductor L3, the first inductor L4, the first inductor L5, the first inductor L6, the first inductor L4, the first inductor L5, the first inductor L6, the first inductor L4, the first inductor L5, the first inductor L6, the first inductor L7 ...7, the first inductor L6, the first inductor L7, the first inductor L7, the first inductor L6, the first inductor L7, the first inductor Container C1 and the second capacitor C2 are connected in series and charge the third capacitor C3 together via the sixth switch V6 and the eighth switch V8. At this time, the voltage of the third capacitor C3 is the sum of the excitation power supply voltage (i.e., the excitation voltage), the voltage at the end of the first inductor L1, the voltage at the end of the first capacitor C1, and the voltage at the end of the second capacitor C2, which is much greater than the excitation voltage. When a sudden drop in the generator output voltage occurs, a sequence C7-L1-C1-V6-C2-D3-D4-C4-C7 will be formed, meaning that the excitation power supply, the first inductor L1, the first capacitor C1, and the second capacitor C2 are connected in series and output electrical energy to the generator output terminal via the sixth switch V6, potentially helping to quickly restore the generator voltage. When the excitation phase of the first phase winding M needs to end, the fourth switch V4, the sixth switch V6, and the eighth switch V8 are disconnected, while the fifth switch V5 and the seventh switch V7 are closed, entering the power generation phase. This forms four circuits: the first circuit is C7-V1-M-D1-C1-V5-C7, meaning the first phase winding M is connected in series with the excitation power supply, charging the first capacitor C1 via the first switch V1 and the fifth switch V5; the second circuit is C7-V1-M-D2-C2-V7-C7, meaning the first phase winding M is connected in series with the excitation power supply, charging the second capacitor C2 via the first switch V1 and the seventh switch V7; and the third circuit is C7-L2-C3. -D4-C4 (generator output terminal)-C7, that is, the excitation power supply, together with the second inductor L2 and the third capacitor C3, outputs electrical energy to the generator output terminal. The fourth circuit is: C7-L1-V5-C7, that is, the excitation power supply charges the first inductor L1 through the fifth switch V5. If a sudden drop in generator voltage occurs during the generator generation stage, the C7-V1-M-D2-D3-D4-C4-C7 circuit will be formed, that is, the excitation power supply and the first phase winding M are connected in series and directly generate electricity through the first switch V1, which enhances the ability of the generator voltage to recover quickly. According to the rotor position information, when the generator generation stage of the first phase winding M needs to end, all previously closed switches are disconnected, the generator generation stage ends, that is, the first phase winding M ends its operation.

[0030] According to the rotor position information, when the second phase winding N and the third phase winding P need to be put into operation, the working mode is the same as that of the first phase winding M. It is only necessary to change the first switch V1 to the second switch V2 and the third switch V3 respectively.

[0031] During the excitation and generation phases of each phase winding, the fifth switch V5, the sixth switch V6, the seventh switch V7, and the eighth switch V8 all implement PWM control mode during the closed conduction phase as described above. The specific duty cycle of each switch is determined according to the state of each component in its respective circuit to meet the charging and discharging requirements as described above.

[0032] In the operation of the variable excitation circuit, the ninth switch V9 and the tenth switch V10 have the same switching frequency (>20kHz) and the same duty cycle (less than 0.5), but their conduction phases differ by 180 degrees. The specific duty cycle depends on the required output excitation voltage, i.e., the voltage requirement on the seventh capacitor C7. When maximum power point tracking control under variable wind speed conditions is achieved by adjusting the excitation voltage, the ninth switch V9 and the tenth switch V10 will continuously adjust the output excitation voltage to meet the requirements according to the wind speed changes. In this variable excitation circuit, the fifth diode D5 and the tenth switch V10... A lossless clamping circuit is formed by six diodes D6 and the fifth capacitor C5. Two pairs of coupled inductors, namely the third inductor L3 and the fourth inductor L4, and the fifth inductor L5 and the sixth inductor L6, are alternately transmitted to the output and input terminals of the variable excitation circuit under the control of the ninth switch V9 and the tenth switch V10. The ninth switch V9 is responsible for transmitting power from the input terminal to the output terminal, while the tenth switch V10 controls the power transmission to the sixth capacitor C6. The seventh diode D7 and the eighth diode D8 provide paths for the output power of the fourth inductor L4 and the sixth inductor L6, respectively.

[0033] In this embodiment, the switched reluctance generator operates at a high speed of over 10,000 revolutions per minute, and all the switching transistors of the power converter are power MOSFETs, IGBTs, or other new high-frequency fast power electronic switching devices.

Claims

1. A step-up variable-excitation switched reluctance generator power converter, comprising a first switch transistor, a second switch transistor, a third switch transistor, a fourth switch transistor, a fifth switch transistor, a sixth switch transistor, a seventh switch transistor, an eighth switch transistor, a ninth switch transistor, a tenth switch transistor, a first inductor, a second inductor, a third inductor, a fourth inductor, a fifth inductor, a sixth inductor, a first phase winding, a second phase winding, a third phase winding, a first capacitor, a second capacitor, a third capacitor, a fourth capacitor, a fifth capacitor, a sixth capacitor, a seventh capacitor, a first diode, a second diode, a third diode, a fourth diode, a fifth diode, a sixth diode, a seventh diode, and an eighth diode, characterized in that the anode of the first switch transistor is connected to the... The anodes of the second and third switching transistors, one end of the first inductor, one end of the second inductor, one end of the fourth inductor, one end of the sixth inductor, and one end of the seventh capacitor are connected as the positive input terminal of the excitation power supply for the switched reluctance generator. The cathode of the first switching transistor is connected to one end of the first phase winding, the cathode of the second switching transistor is connected to one end of the second phase winding, and the cathode of the third switching transistor is connected to one end of the third phase winding. The other end of the first phase winding is connected to the other end of the second phase winding, the other end of the third phase winding, the anode of the fourth switching transistor, the anode of the first diode, and the anode of the second diode. The other end of the first inductor is connected to the anode of the fifth switching transistor and one end of the first capacitor, and the other end of the second inductor is connected to... The anode of the eighth switch is connected to one end of the third capacitor. The other end of the third capacitor is connected to the cathode of the third diode and the anode of the fourth diode. The anode of the third diode is connected to the cathode of the second diode and one end of the second capacitor. The other end of the second capacitor is connected to the cathode of the sixth switch and the anode of the seventh switch. The anode of the sixth switch is connected to the other end of the first capacitor and the cathode of the first diode. The cathode of the fourth diode is connected to one end of the fourth capacitor, one end of the third inductor, and the cathode of the fifth diode, and serves as the positive terminal of the switched reluctance generator output. The cathode of the fourth switch is connected to the cathodes of the fifth, seventh, and eighth switches, the other end of the fourth capacitor, the other end of the seventh capacitor, and the sixth diode. The anodes of the diodes, the seventh diode, and the eighth diode serve as the negative input and negative output terminals of the switched reluctance generator's excitation power supply. The other end of the third inductor is connected to one end of the fifth inductor and one end of the fifth capacitor. The other end of the fifth capacitor is connected to the anode of the fifth diode and the cathode of the sixth diode. The other end of the fifth inductor is connected to the anode of the ninth switching transistor. The cathode of the ninth switching transistor is connected to the anode of the tenth switching transistor and one end of the sixth capacitor. The other end of the sixth capacitor is connected to the other end of the fourth inductor and the cathode of the seventh diode. The cathode of the tenth switching transistor is connected to the other end of the sixth inductor and the cathode of the eighth diode. The third and fourth inductors form a pair of coupled inductors. The fifth and sixth inductors also form a pair of coupled inductors. The first capacitor and the second capacitor are exactly the same; the first inductor and the second inductor are exactly the same; the number of turns of the third inductor divided by the number of turns of the fourth inductor should be greater than 1, and equal to the number of turns of the fifth inductor divided by the number of turns of the sixth inductor. The inductance values ​​and number of turns of the third inductor and the fifth inductor are equal, and the inductance values ​​and number of turns of the fourth inductor and the sixth inductor are equal.

2. The control method for a direct-drive variable-excitation switched reluctance generator power converter according to claim 1, characterized in that: The fifth diode, sixth diode, seventh diode, eighth diode, third inductor, fourth inductor, fifth inductor, sixth inductor, fifth capacitor, sixth capacitor, seventh capacitor, ninth switch, and tenth switch form a variable excitation circuit. The fifth and sixth diodes are connected in series to receive the electrical energy fed back from the output terminal of the switched reluctance generator as input. The seventh capacitor outputs excitation energy. The magnitude of the excitation voltage is determined by the duty cycle of the two switches, namely the ninth and tenth switches. According to the working principle of a switched reluctance generator, and based on the rotor position information, when the first phase winding needs to be engaged, the first, fourth, sixth, and eighth switches are first closed, and the first phase winding enters the excitation stage. The excitation power supply powers the first phase winding through the first and fourth switches, and simultaneously charges the second inductor through the eighth switch. The excitation power supply, together with the first inductor, the first capacitor, and the second capacitor, is connected in series and charges the third capacitor through the sixth and eighth switches. When the excitation stage of the first phase winding needs to end, based on the rotor position information, the fourth and sixth switches are disconnected. The first phase winding and the eighth switch are connected together, and the fifth and seventh switches are closed simultaneously to enter the power generation stage. At this time, the first phase winding and the excitation power supply are connected in series to charge the first capacitor through the first and fifth switches. The first phase winding and the excitation power supply are also connected in series to charge the second capacitor through the first and seventh switches. The excitation power supply, together with the second inductor and the third capacitor, outputs electrical energy to the power generation output terminal. The excitation power supply also charges the first inductor through the fifth switch. According to the rotor position information, when the power generation stage of the first phase winding needs to end, all previously closed switches are disconnected, the power generation stage ends, that is, the operation of the first phase winding ends. According to the rotor position information, when the second phase winding and the third phase winding need to be put into operation, the working mode is the same as that of the first phase winding. Only the first switching transistor needs to be replaced by the second switching transistor and the third switching transistor respectively. During the excitation and power generation phases of each phase winding, the fifth, sixth, seventh, and eighth switching transistors all implement PWM control mode during the closed conduction phase. In the operation of the variable excitation circuit, the ninth and tenth switching transistors have the same switching frequency, the same duty cycle (less than 0.5), and a phase difference of 180 degrees. The specific duty cycle is determined according to the power converter's requirements for the excitation voltage.

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