A method and system for improving the stability of vehicle-mounted three-phase AC variable speed constant frequency power generation

Abstract

This invention discloses a method and system for improving the stability of vehicle-mounted three-phase AC variable-speed constant-frequency power generation. First, the engine drives a permanent magnet synchronous generator (PMSG) to rotate, and the PMSG outputs variable-frequency and variable-voltage three-phase AC power. Simultaneously, a rotary transformer is used to detect the rotor position of the PMSG, obtaining first detection data. This first detection data is then decoded and fed back to the rectifier control unit. This invention decouples the three-phase active current i from the three-phase load current by using a transformation from a three-phase stationary to a two-phase rotating coordinate system in the phase angle of the three-phase command voltage on the inverter side. dfac With three-phase reactive current i qfac Then, both are fed back to the i in the rectifier-side SVPWM control. d and i q In the loop, a current loop feedforward is constructed on the rectifier side, thereby suppressing the fluctuation of DC side voltage when the AC load current changes abruptly, thus improving the stability of the DC bus voltage on the rectifier side, preventing inverter failure of the power generation system, and making it suitable for widespread promotion and use.

Description

Technical Field

[0001] This invention relates to the field of power generation system technology, specifically to a method and system for improving the stability of vehicle-mounted three-phase AC variable speed constant frequency power generation. Background Technology

[0002] To reduce carbon dioxide emissions and improve energy efficiency, the transportation industry, represented by vehicles, ships, and aviation, is undergoing an electrification transformation. The use of electricity in these devices is increasing, leading to a growing demand for high-quality, stable power, thus requiring independent power supply systems. Given the current limitations of large-capacity energy storage technology, "power take-off" systems, where generators are driven by engines, are an effective solution. Permanent magnet synchronous generators (PMSGs) offer advantages such as high power density, high efficiency, and high speed. Combined with a controllable three-phase two-level back-to-back bridge converter using pulse width modulation (PWM) technology, they have broad application prospects in AC and DC power supply systems.

[0003] The vehicle-mounted permanent magnet motor three-phase AC variable speed constant frequency power generation system is a new type of mobile power supply system proposed by replacing the generator and back-to-back full-bridge converter on the basis of the traditional electrically excited synchronous generator set. This system aims to reduce the weight of the unit, increase energy density, reduce fuel consumption and noise, and increase the number of power supply standards.

[0004] Currently, in the application of vehicle-mounted permanent magnet motor three-phase AC variable speed constant frequency power generation systems, sudden loading on the AC side will cause a sudden increase in AC current and DC bus current, resulting in a sudden drop in DC bus voltage. However, excessive reduction in DC bus voltage will lead to inverter failure on the inverter side, which poses a huge threat to the reliability and stability of the entire system and can easily cause serious damage to the load or equipment, posing potential safety accidents and economic losses. Therefore, it is necessary to design a method and system for improving the stability of vehicle-mounted three-phase AC variable speed constant frequency power generation. Summary of the Invention

[0005] The purpose of this invention is to overcome the shortcomings of the prior art and to better solve the problem that DC-side voltage fluctuations and even divergence are easily caused by sudden load changes, ultimately leading to instability of the inverter system. This invention provides a method and system for improving the stability of vehicle-mounted three-phase AC variable speed constant frequency power generation. It constructs a current loop feedforward on the rectifier side, thereby suppressing the fluctuation of DC-side voltage when AC load current changes suddenly, thus improving the stability of the DC bus voltage on the rectifier side and preventing inverter failure of the power generation system.

[0006] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0007] A method for improving the stability of vehicle-mounted three-phase AC variable speed constant frequency power generation includes the following steps:

[0008] In step (A), the engine drives the permanent magnet synchronous generator to rotate, and the permanent magnet synchronous generator outputs frequency-converted and voltage-converted three-phase AC power. At the same time, a rotary transformer is used to detect the rotor position of the permanent magnet synchronous generator to obtain the first detection data. The first detection data is then decoded and fed back to the rectifier control unit.

[0009] Step (B) involves receiving the variable frequency and variable voltage three-phase AC power output from the permanent magnet synchronous generator through the rectifier unit and converting it into constant voltage DC power. At the same time, the first current sensor is used to detect the current of the variable frequency and variable voltage three-phase AC power to obtain the second detection data, and the second detection data is fed back to the rectifier control unit.

[0010] Step (C) uses the inverter side to convert the constant voltage DC power output from the rectifier unit into three-phase AC power with a neutral point and constant voltage at the power frequency. At the same time, a voltage sensor is used to detect the voltage of the constant voltage DC power to obtain the third detection data, and the third detection data is fed back to the rectifier control unit.

[0011] Step (D) involves receiving the three-phase AC power output from the inverter side via a three-phase load, and simultaneously using a second current sensor to detect the current of the three-phase AC power output from the inverter side via a three-phase load, obtaining fourth detection data, and feeding the fourth detection data back to the rectifier control unit.

[0012] In step (E), the rectifier control unit processes the first detection data, the second detection data, the third detection data, and the fourth detection data, and outputs a control signal to the rectifier unit for control, thereby completing the stability improvement operation of the vehicle-mounted three-phase AC variable speed constant frequency power generation.

[0013] In the aforementioned method for improving the stability of vehicle-mounted three-phase AC variable speed constant frequency power generation, the decoding in step (A) involves using a decoding circuit to decode the first detection data and feeding back the rotor position angle θ to the rectifier control unit.

[0014] In the aforementioned method for improving the stability of a vehicle-mounted three-phase AC variable-speed constant-frequency generator, the rectifier unit in step (B) adopts a three-phase full-bridge circuit, and the rectifier unit is internally equipped with six switching transistors T with anti-parallel diodes. 1_1 T 1_2 T 1_3 T 1_4 T 1_5 and T 1_6 Furthermore, all six switching transistors are electrically connected to the rectifier control unit, and the second detection data is the three-phase armature current i. a i b and i c .

[0015] The aforementioned method for improving the stability of on-board three-phase AC variable speed constant frequency power generation includes an inverter unit and an LC filter in step (C). The inverter unit adopts a three-phase four-bridge-arm circuit and internally contains eight switching transistors T with anti-parallel diodes. 2_1 T 2_2 T 2_3 T 2_4 T 2_5 T 2_6 T 2_7 and T 2_8 The third detection data is the DC bus voltage U. dcfdb .

[0016] In the aforementioned method for improving the stability of vehicle-mounted three-phase AC variable-speed constant-frequency power generation, the fourth detection data in step (D) is the three-phase AC load current i. rn i yn and i bn .

[0017] The aforementioned method for improving the stability of a vehicle-mounted three-phase AC variable-speed constant-frequency generator, specifically the rectifier control unit in step (E), involves the following processing steps.

[0018] Step (E1) involves relating the rotor position angle θ to the three-phase armature current i. a i b and i c Perform a quadrature-direct axis coordinate transformation to obtain the quadrature-axis current feedback value i of the three-phase windings of the permanent magnet synchronous generator. qfdb and direct-axis current feedback value i dfdb ;

[0019] Step (E2) involves integrating the three-phase power frequency angular velocity ω to obtain the commanded phase angle wt, and then using the commanded phase angle wt and the three-phase AC load current i rn i yn and i bn Perform a quadrature-axis coordinate transformation to obtain the quadrature-axis current feedback value i of the load. qfac and direct-axis current feedback value i dfac ;

[0020] Step (E3), let the desired value of the DC bus voltage be U. dcref and the expected value U dcref With DC bus voltage U dcfdb Take the difference to obtain the difference ΔU dc Then the difference ΔU dc The DC voltage command U before limiting is obtained by inputting it to the first PI regulator. dcpre Then, the first limiting module will change the DC voltage command U before limiting. dcpre With DC voltage command minimum limit value Udcmin and DC voltage command maximum limit value U dcmax Limit the amplitude and obtain the actual DC voltage control command U. dccmd The specific process of limiting the amplitude is as follows: If U dcpre Less than U dcmin , then U dccmd equal to U dcmin , if U dcpre Greater than U dcmax , then U dccmd equal to U dcmax ;

[0021] Step (E4) involves transferring the actual DC voltage control command U. dccmd The desired value of the quadrature current i is obtained after a gain of -1. qref And let the desired value of the direct-axis current be i. dref Next, the desired value of the quadrature-axis current i qref The feedback values ​​of the quadrature axis currents of the three-phase windings of the permanent magnet synchronous generator are respectively compared with those of the feedback values ​​of the quadrature axis currents of the three-phase windings. qfdb and load cross-axis current feedback value i qfa Take the difference and obtain the difference value Δi. q Then, the desired value of the direct-axis current i dref The feedback values ​​of the direct-axis current of the three-phase windings of the permanent magnet synchronous generator are respectively compared with those of the two phases. dfdb and load direct-axis current feedback value i dfac Take the difference and obtain the difference value Δi. d The difference Δi q Sum and difference Δi d The specific steps for inputting the second PI regulator and the second limiting module are as follows.

[0022] Step (E41) involves setting the difference Δi q Input the second PI regulator and obtain the quadrature axis current command value i before limiting. qpre Then the second limiting module will adjust the quadrature axis current command value i before limiting. qpre Each is compared with the minimum limit value u of the AC voltage command. qmin and AC voltage command maximum limit value u qmax Apply amplitude limiting and obtain the actual quadrature-axis voltage command value u. qcmd The specific process of limiting the amplitude is as follows: if i qpre Less than u qmin , then u qcmd equal to u qmin , if i qpre Greater than u qmax , then u qcmd equal to u qmax ;

[0023] Step (E42) involves calculating the difference Δi. dInput the second PI regulator and obtain the direct-axis current command value i before limiting. dpre Then the second limiting module will adjust the direct-axis current command value i before limiting. dpre Each is compared with the minimum limit value u of the DC voltage command. dmin and DC voltage command maximum limit value u dmax Apply amplitude limiting and obtain the actual direct-axis voltage command value u. dcmd The specific process of limiting the amplitude is as follows: if i dpre Less than u dmin , then u dcmd equal to u dmin , if i dpre Greater than u dmax , then u dcmd equal to u dmax ;

[0024] Step (E5) involves obtaining the actual quadrature axis voltage command value u. qcmd and the actual direct-axis voltage command value u dcmd The input is fed to the Space Vector Modulation (SVPWM) module, and then converted by the SVPWM module into the switching transistor T of the rectifier unit. 1_1 T 1_2 T 1_3 T 1_4 T 1_5 and T 1_6 The control signal.

[0025] A vehicle-mounted three-phase AC variable-speed constant-frequency power generation system includes an engine, a rotary transformer, a permanent magnet synchronous generator, a first current sensor, a rectifier unit, a voltage sensor, an inverter unit, an LC filter, a second current sensor, a three-phase load, and a rectifier control unit. The engine drives the permanent magnet synchronous generator to rotate. The rotary transformer detects the rotor position of the permanent magnet synchronous generator, obtains first detection data, decodes the first detection data, and feeds it back to the rectifier control unit. The permanent magnet synchronous generator outputs variable-frequency and variable-voltage three-phase AC power. The first current sensor detects the current of the variable-frequency and variable-voltage three-phase AC power, obtains second detection data, and feeds the second detection data back to the rectifier control unit. The rectifier unit processes the variable-frequency and variable-voltage three-phase AC power output by the permanent magnet synchronous generator. The system can receive and convert the DC power into constant voltage. The voltage sensor detects the voltage of the constant voltage DC power, obtains third detection data, and feeds the third detection data back to the rectifier control unit. The inverter side, composed of the inverter unit and the LC filter, converts the constant voltage DC power output from the rectifier unit into three-phase AC power with a neutral point at the power frequency. The second current sensor detects the current of the three-phase AC power with a neutral point at the power frequency, obtains fourth detection data, and feeds the fourth detection data back to the rectifier control unit. The three-phase load receives the three-phase AC power with a neutral point at the power frequency output from the inverter side. The rectifier control unit processes the first, second, third, and fourth detection data and outputs control signals to the rectifier unit for control.

[0026] The beneficial effects of this invention are as follows: The method and system for improving the stability of on-board three-phase AC variable-speed constant-frequency power generation firstly decouples the three-phase load current i by transforming the phase angle of the three-phase command voltage on the inverter side to a two-phase rotating coordinate system. dfac With three-phase reactive current i qfac Then, both are fed back to the i in the rectifier-side SVPWM control. d and i qIn the loop, a current loop feedforward is constructed on the rectifier side to suppress the fluctuation of DC side voltage when the AC load current changes abruptly, thereby improving the stability of the DC bus voltage on the rectifier side, preventing inverter failure of the power generation system, and effectively realizing the function of improving DC voltage stability by adding feedforward to the current loop in the closed-loop space vector pulse width modulation control on the rectifier side. It can also dynamically calculate the size of the current loop feedforward according to the magnitude of different load currents, thereby improving the system's ability to suppress DC bus voltage fluctuations, ensuring the reliability and stability of the system, and realizing the ability to treat the inverter side full bridge and load as a whole, and from the perspective of the rectifier side, this whole is a constant power load. After decoupling the three-phase current on the inverter side and incorporating it into the rectifier side current loop feedback, the stability of the DC bus voltage on the inverter side is improved, the maximum power supply of the power supply system is increased, and the DC bus voltage fluctuation caused by load abrupt changes is reduced. Attached Figure Description

[0027] Figure 1 This is a flowchart of the vehicle-mounted three-phase AC variable speed constant frequency power generation system of the present invention;

[0028] Figure 2 This is a schematic diagram of the control principle of the sorting and control unit of the present invention;

[0029] Figure 3 This is a schematic diagram of the dynamic waveform of the DC bus voltage in an embodiment of the present invention. Detailed Implementation

[0030] The present invention will now be further described with reference to the accompanying drawings.

[0031] like Figure 1 As shown, the present invention provides a method for improving the stability of a vehicle-mounted three-phase AC variable-speed constant-frequency power generation system, comprising the following steps:

[0032] In step (A), the engine drives the permanent magnet synchronous generator to rotate, and the permanent magnet synchronous generator outputs frequency-converted and voltage-converted three-phase AC power. At the same time, a rotary transformer is used to detect the rotor position of the permanent magnet synchronous generator to obtain the first detection data. The first detection data is then decoded and fed back to the rectifier control unit.

[0033] The decoding process involves using a decoding circuit to decode the first detection data and feeding back the rotor position angle θ to the rectifier control unit.

[0034] Step (B) involves receiving the variable frequency and variable voltage three-phase AC power output from the permanent magnet synchronous generator through the rectifier unit and converting it into constant voltage DC power. At the same time, the first current sensor is used to detect the current of the variable frequency and variable voltage three-phase AC power to obtain the second detection data, and the second detection data is fed back to the rectifier control unit.

[0035] The rectifier unit adopts a three-phase full-bridge circuit, and the rectifier unit is equipped with six switching transistors T with anti-parallel diodes. 1_1 T 1_2 T 1_3 T 1_4 T 1_5 and T 1_6 Furthermore, all six switching transistors are electrically connected to the rectifier control unit, and the second detection data is the three-phase armature current i. a i b and i c .

[0036] Step (C) uses the inverter side to convert the constant voltage DC power output from the rectifier unit into three-phase AC power with a neutral point and constant voltage at the power frequency. At the same time, a voltage sensor is used to detect the voltage of the constant voltage DC power to obtain the third detection data, and the third detection data is fed back to the rectifier control unit.

[0037] The inverter side includes an inverter unit and an LC filter. The inverter unit adopts a three-phase four-bridge circuit and internally contains eight switching transistors T with anti-parallel diodes. 2_1 T 2_2 T 2_3 T 2_4 T 2_5 T 2_6 T 2_7 and T 2_8 The third detection data is the DC bus voltage U. dcfdb .

[0038] Step (D) involves receiving the three-phase AC power output from the inverter side via a three-phase load, and simultaneously using a second current sensor to detect the current of the three-phase AC power output from the inverter side via a three-phase load, obtaining fourth detection data, and feeding the fourth detection data back to the rectifier control unit.

[0039] The fourth detection data is the three-phase AC load current i. rn i yn and i bn .

[0040] like Figure 2 As shown, in step (E), the rectifier control unit processes the first detection data, the second detection data, the third detection data, and the fourth detection data, and outputs a control signal to the rectifier unit for control, thereby completing the stability improvement operation of the vehicle-mounted three-phase AC variable speed constant frequency generator.

[0041] The specific processing steps of the rectifier control unit are as follows:

[0042] Step (E1) involves relating the rotor position angle θ to the three-phase armature current i. a i b and i c Perform a quadrature-direct axis coordinate transformation to obtain the quadrature-axis current feedback value i of the three-phase windings of the permanent magnet synchronous generator. qfdb and direct-axis current feedback value i dfdb ;

[0043] Step (E2) involves integrating the three-phase power frequency angular velocity ω to obtain the commanded phase angle wt, and then using the commanded phase angle wt and the three-phase AC load current i rn i yn and i bn Perform a quadrature-axis coordinate transformation to obtain the quadrature-axis current feedback value i of the load. qfac and direct-axis current feedback value i dfac ;

[0044] Step (E3), let the desired value of the DC bus voltage be U. dcref and the expected value U dcref With DC bus voltage U dcfdb Take the difference to obtain the difference ΔU dc Then the difference ΔU dc The DC voltage command U before limiting is obtained by inputting it to the first PI regulator. dcpre Then, the first limiting module will change the DC voltage command U before limiting. dcpre With DC voltage command minimum limit value U dcmin and DC voltage command maximum limit value U dcmax Limit the amplitude and obtain the actual DC voltage control command U. dccmd The specific process of limiting the amplitude is as follows: If U dcpre Less than U dcmin , then U dccmd equal to U dcmin , if U dcpre Greater than U dcmax , then U dccmd equal to U dcmax ;

[0045] Step (E4) involves transferring the actual DC voltage control command U. dccmd The desired value of the quadrature current i is obtained after a gain of -1. qref And let the desired value of the direct-axis current be i. dref Next, the desired value of the quadrature-axis current i qref The feedback values ​​of the quadrature axis currents of the three-phase windings of the permanent magnet synchronous generator are respectively compared with those of the feedback values ​​of the quadrature axis currents of the three-phase windings. qfdb and load cross-axis current feedback value i qfa Take the difference and obtain the difference value Δi. q Then, the desired value of the direct-axis current i drefThe feedback values ​​of the direct-axis current of the three-phase windings of the permanent magnet synchronous generator are respectively compared with those of the two phases. dfdb and load direct-axis current feedback value i dfac Take the difference and obtain the difference value Δi. d The difference Δi q Sum and difference Δi d The specific steps for inputting the second PI regulator and the second limiting module are as follows.

[0046] Step (E41) involves setting the difference Δi q Input the second PI regulator and obtain the quadrature axis current command value i before limiting. qpre Then the second limiting module will adjust the quadrature axis current command value i before limiting. qpre Each is compared with the minimum limit value u of the AC voltage command. qmin and AC voltage command maximum limit value u qmax Apply amplitude limiting and obtain the actual quadrature-axis voltage command value u. qcmd The specific process of limiting the amplitude is as follows: if i qpre Less than u qmin , then u qcmd equal to u qmin , if i qpre Greater than u qmax , then u qcmd equal to u qmax ;

[0047] Step (E42) involves calculating the difference Δi. d Input the second PI regulator and obtain the direct-axis current command value i before limiting. dpre Then the second limiting module will adjust the direct-axis current command value i before limiting. dpre Each is compared with the minimum limit value u of the DC voltage command. dmin and DC voltage command maximum limit value u dmax Apply amplitude limiting and obtain the actual direct-axis voltage command value u. dcmd The specific process of limiting the amplitude is as follows: if i dpre Less than u dmin , then u dcmd equal to u dmin , if i dpre Greater than u dmax , then u dcmd equal to u dmax ;

[0048] Step (E5) involves obtaining the actual quadrature axis voltage command value u. qcmd and the actual direct-axis voltage command value u dcmd The input is fed to the Space Vector Modulation (SVPWM) module, and then converted by the SVPWM module into the switching transistor T of the rectifier unit. 1_1 T 1_2 T1_3 T 1_4 T 1_5 and T 1_6 The control signal.

[0049] A vehicle-mounted three-phase AC variable-speed constant-frequency power generation system includes an engine, a rotary transformer, a permanent magnet synchronous generator, a first current sensor, a rectifier unit, a voltage sensor, an inverter unit, an LC filter, a second current sensor, a three-phase load, and a rectifier control unit. The engine drives the permanent magnet synchronous generator to rotate. The rotary transformer detects the rotor position of the permanent magnet synchronous generator, obtains first detection data, decodes the first detection data, and feeds it back to the rectifier control unit. The permanent magnet synchronous generator outputs variable-frequency and variable-voltage three-phase AC power. The first current sensor detects the current of the variable-frequency and variable-voltage three-phase AC power, obtains second detection data, and feeds the second detection data back to the rectifier control unit. The rectifier unit processes the variable-frequency and variable-voltage three-phase AC power output by the permanent magnet synchronous generator. The system can receive and convert the DC power into constant voltage. The voltage sensor detects the voltage of the constant voltage DC power, obtains third detection data, and feeds the third detection data back to the rectifier control unit. The inverter side, composed of the inverter unit and the LC filter, converts the constant voltage DC power output from the rectifier unit into three-phase AC power with a neutral point at the power frequency. The second current sensor detects the current of the three-phase AC power with a neutral point at the power frequency, obtains fourth detection data, and feeds the fourth detection data back to the rectifier control unit. The three-phase load receives the three-phase AC power with a neutral point at the power frequency output from the inverter side. The rectifier control unit processes the first, second, third, and fourth detection data and outputs control signals to the rectifier unit for control.

[0050] To better illustrate the effects of the present invention, a specific embodiment of the present invention is described below;

[0051] The dynamic waveform of the DC bus voltage during AC side sudden loading in the embodiment is as follows: Figure 3 As shown in the figure, the horizontal axis represents time t (in seconds), and the vertical axis represents the DC bus voltage U. dc (unit: v)

[0052] In this embodiment, a 3Ω three-phase symmetrical resistive load and a 3Ω single-phase resistive load were applied during time periods of 0.05s to 0.4s and 0.1s to 0.3s, respectively, to observe the system's suppression effect on DC bus voltage drop during sudden load application and removal; the solid line in the figure represents the area without load application. qfac and i dfac The curve showing the decrease in DC bus voltage during feedback under sudden load; the dashed line represents the increase in i. qfac and idfac The curve showing the decrease in DC bus voltage during feedback under sudden loading indicates that the stability of the DC bus voltage is significantly improved in the latter case.

[0053] In summary, the present invention provides a method and system for improving the stability of a vehicle-mounted three-phase AC variable-speed constant-frequency power generation system. By constructing a current loop feedforward on the rectifier side, it suppresses the fluctuation of DC-side voltage when the AC load current changes abruptly, thereby improving the stability of the DC bus voltage on the rectifier side and preventing inverter failure of the power generation system. It effectively realizes the function of improving DC voltage stability by adding feedforward to the current loop in the closed-loop space vector pulse width modulation control on the rectifier side. Furthermore, it can dynamically calculate the size of the current loop feedforward based on the magnitude of different load currents, thereby improving the system's ability to suppress DC bus voltage fluctuations, ensuring the system's reliability and stability. It also enables the inverter-side full-bridge and the load to be considered as a whole, and from the rectifier side, this whole is a constant power load. After decoupling the three-phase current on the inverter side and incorporating it into the rectifier-side current loop feedback, it improves the stability of the DC bus voltage on the inverter side, increases the maximum power supply of the power supply system, and reduces DC bus voltage fluctuations caused by load abrupt changes.

[0054] The foregoing has shown and described the basic principles, main features, and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The embodiments and descriptions in the specification are merely illustrative of the principles of the invention. Various changes and modifications can be made to the invention without departing from its spirit and scope, and all such changes and modifications fall within the scope of the present invention as claimed. The scope of protection of the present invention is defined by the appended claims and their equivalents.

Claims

1. A method for improving the stability of vehicle-mounted three-phase AC variable speed constant frequency power generation, characterized in that: Includes the following steps, Step (A): The engine drives the permanent magnet synchronous generator to rotate, and the permanent magnet synchronous generator outputs frequency-converted and voltage-converted three-phase AC power. At the same time, a rotary transformer is used to detect the rotor position of the permanent magnet synchronous generator to obtain the first detection data. The first detection data is then decoded and fed back to the rectifier control unit. Step (B): The variable frequency and variable voltage three-phase AC power output from the permanent magnet synchronous generator is received by the rectifier unit and converted into constant voltage DC power. At the same time, the current of the variable frequency and variable voltage three-phase AC power is detected by the first current sensor to obtain the second detection data and feed the second detection data back to the rectifier control unit. Step (C): The constant voltage DC power output from the rectifier unit is converted into three-phase AC power with a neutral point at the power frequency using the inverter side. At the same time, a voltage sensor is used to detect the voltage of the constant voltage DC power to obtain the third detection data, and the third detection data is fed back to the rectifier control unit. Step (D): The three-phase AC power with neutral point output from the inverter side is received by the three-phase load. At the same time, the current of the three-phase AC power with neutral point is detected by the second current sensor to obtain the fourth detection data, and the fourth detection data is fed back to the rectifier control unit. Step (E) involves the rectifier control unit processing the first detection data, the second detection data, the third detection data, and the fourth detection data, and outputting a control signal to the rectifier unit for control, thereby completing the stability improvement operation of the vehicle-mounted three-phase AC variable speed constant frequency generator. The fourth detection data in step (D) is the three-phase AC load current i rn i yn and i bn ; The specific processing steps of the rectifier control unit in step (E) are as follows: Step (E1) involves comparing the rotor position angle θ with the three-phase armature current i a i b and i c Perform a quadrature-direct axis coordinate transformation to obtain the quadrature-axis current feedback value i of the three-phase windings of the permanent magnet synchronous generator. qfdb and direct-axis current feedback value i dfdb ; Step (E2): Integrate the three-phase power frequency angular velocity ω to obtain the commanded phase angle wt, and then use the commanded phase angle wt and the three-phase AC load current i rn i yn and i bn Perform a quadrature-axis coordinate transformation to obtain the quadrature-axis current feedback value i of the load. qfac and direct-axis current feedback value i dfac ; Step (E3): Assume the desired value of the DC bus voltage is U. dcref and the expected value U dcref With DC bus voltage U dcfdb Take the difference to obtain the difference ∆U dc Then the difference ∆U dc The DC voltage command U before limiting is obtained by inputting it to the first PI regulator. dcpre Then, the first limiting module will change the DC voltage command U before limiting. dcpre With DC voltage command minimum limit value U dcmin and the maximum limit value U of DC voltage command dcmax Limit the amplitude and obtain the actual DC voltage control command U. dccmd The specific process of limiting the amplitude is as follows: If U dcpre Less than U dcmin , then U dccmd equal to U dcmin , if U dcpre Greater than U dcmax , then U dccmd equal to U dcmax ; Step (E4) involves transferring the actual DC voltage control command U. dccmd The desired value of the quadrature current i is obtained after a gain of -1. qref And let the desired value of the direct-axis current be i. dref Next, the desired value of the quadrature-axis current i qref The feedback values ​​of the quadrature axis currents of the three-phase windings of the permanent magnet synchronous generator are respectively compared with those of the feedback values ​​of the quadrature axis currents of the three-phase windings. qfdb and load cross-axis current feedback value i qfa Take the difference and obtain the difference value ∆i q Then, the desired value of the direct-axis current i dref The feedback values ​​of the direct-axis current of the three-phase windings of the permanent magnet synchronous generator are respectively compared with those of the two phases. dfdb and load direct-axis current feedback value i dfac Take the difference and obtain the difference value ∆i d The difference ∆i q Sum and difference ∆i d The specific steps for inputting the second PI regulator and the second limiting module are as follows. Step (E41), the difference ∆i q Input the second PI regulator and obtain the quadrature axis current command value i before limiting. qpre Then the second limiting module will adjust the quadrature axis current command value i before limiting. qpre Each is compared with the minimum limit value u of the AC voltage command. qmin and AC voltage command maximum limit value u qmax Apply amplitude limiting and obtain the actual quadrature-axis voltage command value u. qcmd The specific process of limiting the amplitude is as follows: if i qpre Less than u qmin , then u qcmd equal to u qmin , if i qpre Greater than u qmax , then u qcmd equal to u qmax ; Step (E42), the difference ∆i d Input the second PI regulator and obtain the direct-axis current command value i before limiting. dpre Then the second limiting module will adjust the direct-axis current command value i before limiting. dpre Each is compared with the minimum limit value u of the DC voltage command. dmin and the maximum limit value of DC voltage command u dmax Apply amplitude limiting and obtain the actual direct-axis voltage command value u. dcmd The specific process of limiting the amplitude is as follows: if i dpre Less than u dmin , then u dcmd equal to u dmin , if i dpre Greater than u dmax , then u dcmd equal to u dmax ; Step (E5) involves obtaining the actual quadrature axis voltage command value u. qcmd and the actual direct-axis voltage command value u dcmd The input is fed to the Space Vector Modulation (SVPWM) module, and then converted by the SVPWM module into the switching transistor T of the rectifier unit. 1_1 T 1_2 T 1_3 T 1_4 T 1_5 and T 1_6 The control signal.

2. The method for improving the stability of vehicle-mounted three-phase AC variable speed constant frequency power generation according to claim 1, characterized in that: The decoding in step (A) involves using a decoding circuit to decode the first detection data and feeding back the rotor position angle θ to the rectifier control unit.

3. The method for improving the stability of vehicle-mounted three-phase AC variable speed constant frequency power generation according to claim 2, characterized in that: The rectifier unit in step (B) adopts a three-phase full-bridge circuit, and the rectifier unit is equipped with six switching transistors T with anti-parallel diodes. 1_1 T 1_2 T 1_3 T 1_4 T 1_5 and T 1_6 Furthermore, all six switching transistors are electrically connected to the rectifier control unit, and the second detection data is the three-phase armature current i. a i b and i c .

4. The method for improving the stability of vehicle-mounted three-phase AC variable speed constant frequency power generation according to claim 3, characterized in that: The inverter side in step (C) includes an inverter unit and an LC filter. The inverter unit adopts a three-phase four-arm bridge circuit and internally contains eight switching transistors T with anti-parallel diodes. 2_1 T 2_2 T 2_3 T 2_4 T 2_5 T 2_6 T 2_7 and T 2_8 The third detection data is the DC bus voltage U. dcfdb .

5. A vehicle-mounted three-phase AC variable speed constant frequency power generation system, wherein the system operates using the method described in any one of claims 1-4, characterized in that: It includes an engine, a rotary transformer, a permanent magnet synchronous generator, a first current sensor, a rectifier unit, a voltage sensor, an inverter unit, an LC filter, a second current sensor, a three-phase load, and a rectifier control unit. The engine is used to drive the permanent magnet synchronous generator to rotate. The rotary transformer is used to detect the rotor position of the permanent magnet synchronous generator, obtain first detection data, decode the first detection data, and feed it back to the rectifier control unit. The permanent magnet synchronous generator is used to output variable frequency and variable voltage three-phase AC power. The first current sensor is used to detect the current of the variable frequency and variable voltage three-phase AC power, obtain the second detection data, and feed the second detection data back to the rectifier control unit; The rectifier unit is used to receive the frequency-converted and voltage-converted three-phase AC power output from the permanent magnet synchronous generator and convert it into constant voltage DC power. The voltage sensor is used to detect the voltage of the constant voltage DC power supply, obtain the third detection data, and feed the third detection data back to the rectifier control unit; The inverter side, consisting of the inverter unit and the LC filter, is used to convert the constant voltage DC power output from the rectifier unit into three-phase AC power with a neutral point at the power frequency. The second current sensor is used to detect the current of the three-phase AC power with neutral point at the power frequency constant voltage, obtain the fourth detection data, and feed the fourth detection data back to the rectifier control unit; The three-phase load is used to receive the power frequency constant voltage three-phase AC power with neutral point output from the inverter side; The rectifier control unit is used to process the first detection data, the second detection data, the third detection data and the fourth detection data, and output control signals to the rectifier unit for control.

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