阅读说明：本技术 用于大功率永磁直驱系统的牵引变流器及其控制方法 (Traction converter for high-power permanent magnet direct drive system and control method thereof ) 是由 梁镇中 刘鹏 张佳峰 于 2018-08-30 设计创作，主要内容包括：本公开提供一种用于大功率永磁直驱系统的牵引变流器及其控制方法,牵引变流器包括三个牵引变流单元以及辅助变流单元,其中,每一所述牵引变流单元包括预充电回路、四象限整流电路、中间直流回路、逆变器电路以及牵引控制单元,所述牵引控制单元包括用于控制所述四象限整流电路运行的四象限脉冲整流器以及用于控制所述逆变器电路运行的逆变器控制电路。本公开提供的牵引变流器可以应用于大功率永磁直驱系统。(The traction converter comprises three traction current conversion units and an auxiliary current conversion unit, wherein each traction current conversion unit comprises a pre-charging loop, a four-quadrant rectifying circuit, a middle direct current loop, an inverter circuit and a traction control unit, and the traction control unit comprises a four-quadrant pulse rectifier for controlling the four-quadrant rectifying circuit to operate and an inverter control circuit for controlling the inverter circuit to operate. The traction converter provided by the disclosure can be applied to a high-power permanent magnet direct drive system.)

1. A traction converter for a high-power permanent-magnet direct-drive system is characterized by comprising three traction converter units, wherein each traction converter unit comprises:

a pre-charge loop;

a four-quadrant rectifier circuit;

an intermediate DC loop;

the inverter circuit comprises a driving plate, and the dynamic active clamping voltage of the driving plate is divided into two stages of 3700V and 4400V; and

a traction control unit comprising:

the four-quadrant pulse rectifier is coupled to the four-quadrant rectifying circuit and used for controlling the four-quadrant rectifying circuit to operate;

and the inverter control circuit is coupled with the motor and the inverter circuit and used for controlling the operation of the inverter circuit according to the rotating speed of the motor.

2. The traction converter as claimed in claim 1, wherein the inverter control circuit comprises:

the rotating speed judging module is used for detecting the rotating speed of the motor, sending a first signal when the rotating speed of the motor is less than or equal to a preset value, and sending a second signal when the rotating speed of the motor is greater than the preset value;

the MTPA control signal generating module is used for responding to the first signal and generating a control signal in an MTPA mode;

and the weak magnetic control signal generation module is used for responding to the second signal and generating the control signal in a weak magnetic mode.

3. The traction converter of claim 2, wherein the inverter control circuit further comprises:

the signal modulation module is used for determining the modulation frequency for modulating the control signal by adopting an asynchronous modulation mode according to the motor rotating speed when the motor rotating speed is in a first value area, determining the modulation frequency for modulating the control signal by adopting a middle 60-degree synchronous modulation mode according to the motor rotating speed when the motor rotating speed is in a second value area, and determining the modulation frequency for modulating the control signal by adopting a square wave modulation mode according to the motor rotating speed when the motor rotating speed is in a third value area.

4. The traction converter as claimed in claim 1, wherein said four-quadrant pulse rectifier comprises:

the voltage control closed-loop circuit is used for controlling the voltage of the direct-current bus to be a preset voltage value;

and the current control closed-loop circuit is used for controlling the current waveform of the alternating current to be a sine wave.

5. The traction converter according to any one of claims 1 to 4, further comprising:

an isolation contactor coupled to the inverter circuit.

6. The traction converter of claim 1, further comprising:

auxiliary converter unit, comprising:

an auxiliary pre-charge loop;

an auxiliary four-quadrant rectifier circuit;

the auxiliary intermediate direct current loop comprises an energy storage circuit and a measurement protection circuit;

an auxiliary inverter circuit; and

an auxiliary control unit comprising:

the auxiliary four-quadrant pulse rectifier is used for controlling the auxiliary four-quadrant rectifying circuit to operate;

and the auxiliary inverter control circuit is used for controlling the auxiliary inverter circuit to operate.

7. The traction converter of claim 6, further comprising:

and the water cooling system is coupled to the traction converter unit and the auxiliary converter unit.

8. A high-power permanent magnet direct drive system is characterized by comprising:

the traction converter of claims 1-7;

a permanent magnet synchronous motor coupled to the traction converter;

and the flexible coupling is coupled to the permanent magnet synchronous motor and the wheel pair of the locomotive.

9. A traction converter control method, comprising:

detecting the rotating speed of the motor;

when the rotating speed of the motor is less than or equal to a preset value, generating a control signal for controlling the operation of the inverter by adopting an MTPA (maximum Transmission Power Amplifier) mode;

and when the rotating speed of the motor is greater than the preset value, a flux weakening mode is adopted to control and generate a control signal for controlling the operation of the inverter.

10. The traction converter control method of claim 9 further comprising:

when the rotating speed of the motor is in a first value area, determining the modulation frequency for modulating the control signal in an asynchronous modulation mode according to the rotating speed of the motor;

when the motor rotating speed is in a second value area, determining the modulation frequency for modulating the control signal by adopting a middle 60-degree synchronous modulation mode according to the motor rotating speed;

and when the rotating speed of the motor is in a third value area, determining the modulation frequency for modulating the control signal by adopting a square wave modulation mode according to the rotating speed of the motor.

Technical Field

The disclosure relates to the technical field of motors, in particular to a traction converter for a high-power permanent magnet direct drive system and a control method.

Background

With the development of high-performance permanent magnet material technology and the deepening of industry, the technology and products of permanent magnet motors are developing from the basic research stage to the directions of high power, applicability, wide range and multiple fields.

At present, the railway locomotive in China generally adopts an asynchronous motor driving technology. In asynchronous motor drive technology, there is a loss of gearing efficiency of about 2% in operation due to the presence of components such as gearboxes in asynchronous motors. In addition, the asynchronous motor also has the problems of large driving noise, inconvenient lubrication, poor sealing and the like. The permanent magnet motor has the advantages of simple structure, high power factor and the like, so that the permanent magnet motor is used for replacing an asynchronous motor and is an important future development direction in the field of locomotive research and development.

Because the traction converters in the existing high-power driving system are all used by matching with asynchronous motors, the traction converter for the high-power permanent magnet direct drive system needs to be designed to be matched with a permanent magnet synchronous motor to operate, and the technical development requirement is met.

It is to be noted that the information disclosed in the above background section is only for enhancement of understanding of the background of the present disclosure, and thus may include information that does not constitute prior art known to those of ordinary skill in the art.

Disclosure of Invention

The present disclosure is directed to a traction converter for a high power permanent magnet direct drive system and a control method thereof, which overcome, at least to some extent, the technical blank problem of the traction converter for a high power permanent magnet direct drive system due to the limitations and disadvantages of the related art.

According to a first aspect of the embodiments of the present disclosure, there is provided a traction converter for a high-power permanent-magnet direct drive system, including three traction converter units, each traction converter unit including:

a pre-charge loop;

a four-quadrant rectifier circuit;

an intermediate DC loop;

the inverter circuit comprises a driving plate, and the dynamic active clamping voltage of the driving plate is divided into two stages of 3700V and 4400V; and

a traction control unit comprising:

the four-quadrant pulse rectifier is coupled to the four-quadrant rectifying circuit and used for controlling the four-quadrant rectifying circuit to operate;

and the inverter control circuit is coupled with the motor and the inverter circuit and used for controlling the operation of the inverter circuit according to the rotating speed of the motor.

Optionally, the inverter control circuit includes:

the rotating speed judging module is used for detecting the rotating speed of the motor, sending a first signal when the rotating speed of the motor is less than or equal to a preset value, and sending a second signal when the rotating speed of the motor is greater than the preset value;

the MTPA control signal generating module is used for responding to the first signal and generating a control signal in an MTPA mode;

and the weak magnetic control signal generation module is used for responding to the second signal and generating a control signal in a weak magnetic mode.

Optionally, the inverter control circuit further includes:

the signal modulation module is used for determining the modulation frequency for modulating the control signal by adopting an asynchronous modulation mode according to the rotating speed of the motor when the rotating speed of the motor is in a first value area, determining the modulation frequency for modulating the control signal by adopting a middle 60-degree synchronous modulation mode according to the rotating speed of the motor when the rotating speed of the motor is in a second value area, and determining the modulation frequency for modulating the control signal by adopting a square wave modulation mode according to the rotating speed of the motor when the rotating speed of the motor is in a third value area.

Optionally, the four-quadrant pulse rectifier includes:

the voltage control closed-loop circuit is used for controlling the voltage of the direct-current bus to be a preset voltage value;

and the current control closed-loop circuit is used for controlling the current waveform of the alternating current to be a sine wave.

Optionally, the method further includes:

and the isolation contactor is coupled to the inverter circuit.

Optionally, the method further includes:

auxiliary converter unit, comprising:

an auxiliary pre-charge loop;

an auxiliary four-quadrant rectifier circuit;

the auxiliary intermediate direct current loop comprises an energy storage circuit and a measurement protection circuit;

an auxiliary inverter circuit; and

an auxiliary control unit comprising:

the auxiliary four-quadrant pulse rectifier is used for controlling the auxiliary four-quadrant rectifying circuit to operate;

and the auxiliary inverter control circuit is used for controlling the auxiliary inverter circuit to operate.

Optionally, the method further includes:

the water cooling system is coupled to the traction converter unit and the auxiliary converter unit.

According to a second aspect of the embodiments of the present disclosure, there is provided a high-power permanent-magnet direct drive system, including:

a traction converter as above;

the permanent magnet synchronous motor is coupled to the traction converter;

and the flexible coupling is coupled to the permanent magnet synchronous motor and the wheel pair of the locomotive.

According to a third aspect of the embodiments of the present disclosure, there is provided a traction converter control method, including:

detecting the rotating speed of the motor;

when the rotating speed of the motor is less than or equal to a preset value, generating a control signal for controlling the operation of the inverter by adopting an MTPA mode;

and when the rotating speed of the motor is greater than a preset value, a flux weakening mode is adopted to control and generate a control signal for controlling the operation of the inverter.

The traction converter control method according to any one of the above, further comprising:

when the rotating speed of the motor is in the first value area, determining the modulation frequency for modulating the control signal in an asynchronous modulation mode according to the rotating speed of the motor;

when the rotating speed of the motor is in the second value area, determining the modulation frequency for modulating the control signal by adopting a middle 60-degree synchronous modulation mode according to the rotating speed of the motor;

and when the rotating speed of the motor is in the third value area, determining the modulation frequency for modulating the control signal by adopting a square wave modulation mode according to the rotating speed of the motor.

The traction converter for the high-power permanent-magnet direct drive system and the control method thereof provided by the disclosure at least have the following advantages:

firstly, three traction current transformation units are integrated to transform the output alternating voltage of a traction current transformer into a three-phase alternating current power supply with variable voltage and frequency, so that the characteristic control of a permanent magnet motor can be realized;

secondly, the traction converter is isolated from the motor through an isolation contactor, so that the counter electromotive force problem of the permanent magnet synchronous motor can be solved, and the fault expansion is avoided;

thirdly, the four-quadrant rectification control is controlled by adopting a double closed-loop control strategy, and the inverter is controlled to operate by adopting an optimized weak magnetic control strategy above the rated rotating speed of the motor, so that the back electromotive force of the motor can be inhibited, and the reliability of the system is ensured.

It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory only and are not restrictive of the disclosure.

Drawings

The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments consistent with the present disclosure and together with the description, serve to explain the principles of the disclosure. It is to be understood that the drawings in the following description are merely exemplary of the disclosure, and that other drawings may be derived from those drawings by one of ordinary skill in the art without the exercise of inventive faculty.

Fig. 1 is a block diagram of a traction converter in an exemplary embodiment of the present disclosure.

Fig. 2A is a schematic circuit diagram of a traction converter unit in an exemplary embodiment of the present disclosure.

Fig. 2B is a circuit schematic of a traction converter in an exemplary embodiment of the present disclosure.

Fig. 3 is a circuit schematic of a four-quadrant pulse rectifier.

Fig. 4A is a block diagram of an inverter control circuit.

Fig. 4B is a schematic diagram of an inverter control circuit.

Fig. 5 is a schematic diagram of a variation of the inverter modulation scheme.

Fig. 6A is another schematic diagram of a traction converter provided in an embodiment of the present disclosure.

Fig. 6B is a circuit schematic diagram of an auxiliary variable current unit in an exemplary embodiment of the present disclosure.

Fig. 7A is a block diagram of a traction converter according to an embodiment of the present disclosure.

Fig. 7B is a mechanical schematic diagram of a traction converter provided in an embodiment of the present disclosure.

Fig. 8 is a flowchart of a traction converter control method according to an embodiment of the present disclosure.

Fig. 9 is a block diagram of a high-power permanent-magnet direct drive system provided by the embodiment of the disclosure.

Detailed Description

Example embodiments will now be described more fully with reference to the accompanying drawings. Example embodiments may, however, be embodied in many different forms and should not be construed as limited to the examples set forth herein; rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the concept of example embodiments to those skilled in the art. The described features, structures, or characteristics may be combined in any suitable manner in one or more embodiments. In the following description, numerous specific details are provided to give a thorough understanding of embodiments of the disclosure. One skilled in the relevant art will recognize, however, that the subject matter of the present disclosure can be practiced without one or more of the specific details, or with other methods, components, devices, steps, and the like. In other instances, well-known technical solutions have not been shown or described in detail to avoid obscuring aspects of the present disclosure.

Further, the drawings are merely schematic illustrations of the present disclosure, in which the same reference numerals denote the same or similar parts, and thus, a repetitive description thereof will be omitted. Some of the block diagrams shown in the figures are functional entities and do not necessarily correspond to physically or logically separate entities. These functional entities may be implemented in the form of software, or in one or more hardware modules or integrated circuits, or in different networks and/or inverter control circuit means and/or microcontroller means.

The following detailed description of exemplary embodiments of the disclosure refers to the accompanying drawings.

Fig. 1 is a block diagram of a traction converter for a high power permanent magnet direct drive system according to the present disclosure.

Referring to fig. 1, the traction converter 1 may comprise three traction converter units 11.

Wherein, each traction converter unit 11 may include:

the pre-charging loop 111 is coupled to the direct-current voltage input end and used for receiving the alternating current at the grid side and limiting the current of the alternating current within a preset safety range so as to prevent the device of the traction converter from being damaged by sudden large current when the alternating current at the grid side is initially connected;

a four-quadrant rectifying circuit 112, coupled to the pre-charging circuit 111, for rectifying the input grid-side ac power to output a dc power;

the intermediate dc loop 113 is coupled to the four-quadrant rectifying circuit 112, and may include an energy storage circuit and a measurement protection circuit, and is configured to store dc energy and implement a protection function;

the inverter circuit 114 is located at the output end of the traction converter 1, and may include a photoelectric conversion board, a driving power supply, a driving board, and three power modules of U-phase, V-phase, and W-phase, where each power module may be composed of two sets of IGBT elements and anti-parallel diodes of upper and lower bridge arms, and is configured to convert a direct current into a three-phase alternating current and output the three-phase alternating current to an external permanent magnet synchronous motor to drive the permanent magnet synchronous motor to operate;

the traction control unit 115 is coupled to the pre-charge circuit 111, the four-quadrant rectifying circuit 112, the intermediate dc circuit 113, and the inverter circuit 114, and configured to receive signals from the circuits and output control signals to the circuits. The traction control unit 115 may include at least:

a four-quadrant pulse rectifier 1151, coupled to the four-quadrant rectifying circuit 112, for controlling the four-quadrant rectifying circuit 112 to operate;

the inverter control circuit 1152 is coupled to the permanent magnet synchronous motor outside the traction converter 1 and the inverter circuit 114 inside the traction converter 1, and is used for controlling the operation of the inverter circuit 114 according to the rotation speed of the permanent magnet synchronous motor.

In the embodiment of the present disclosure, to better protect the IGBT device from different application conditions of the permanent magnet synchronous motor, the dynamic active clamping voltage of the driving board of the inverter circuit 114 may be set to two stages of 3700V (low threshold) and 4400V (high threshold).

During the turn-off of the IGBT elements of the power module in the inverter circuit 114, the inverter control circuit 1152 controls the active clamp voltage of the drive board to be a low threshold (3700V) to clamp the collector potential of the IGBT elements, so that the IGBT elements are prevented from being damaged due to an excessively high voltage spike. When the IGBT element is continuously kept to be turned off, the inverter control circuit 1152 controls the active clamping voltage of the driving plate to be a high threshold value (4400V) so as to clamp the collector potential of the IGBT element, so that the IGBT is prevented from being damaged due to overhigh voltage peak, and the internal voltage of the traction converter for the high-power permanent magnet direct drive system can not reach the high threshold value even if the traction converter has extreme special working conditions.

Fig. 2A is a circuit schematic of the traction converter unit, and fig. 2B is a circuit schematic of the traction converter.

Referring to fig. 2A and 2B, in some embodiments, the traction converter unit 11 may include an isolation contactor 116 coupled to the inverter circuit 114, and the traction converter 1 may be coupled to the permanent magnet synchronous machine through the isolation contactor 116.

In order to solve the back electromotive force problem of the permanent magnet synchronous motor, an isolation contactor can be designed and installed behind the inverter to isolate the motor from the traction converter when necessary. The isolation contactor is designed behind the inverter, on one hand, the isolation contactor can be used for electric transmission system control logic, for example, in high-speed restarting of a motor, when a locomotive is dragged (braked) by idling above a rated rotating speed, the isolation contactor needs to be closed to output torque after weak magnetic field suppression counter potential is established. On the other hand, the permanent magnet motor can generate higher back electromotive force to damage middle loop parts, and when the back electromotive force exceeds a preset threshold value due to system failure, the traction converter can be isolated from the motor through the isolation contactor, so that the failure expansion can be avoided.

The traction control unit 115 provided by the embodiment of the present disclosure can realize four-quadrant rectification control, inverter output control, chopping control, anti-slip anti-idle-rotation adhesion control, and protection functions such as overvoltage, undervoltage, overcurrent, overload, grounding, and the like. The four-quadrant rectification control adopts a double closed-loop control strategy, and when the rated rotation speed of the motor is higher than the rated rotation speed, the inverter output control adopts an optimized weak magnetic control strategy so as to inhibit the back electromotive force of the motor and ensure the reliable operation of the system.

Fig. 3 is a control block diagram of the four-quadrant pulse rectifier 1151.

Referring to fig. 3, the four-quadrant pulse rectifier 1151 includes: a voltage control closed-loop circuit 11511, configured to control the dc bus voltage to a preset voltage value; and a current control closed-loop circuit 11512 for controlling the current waveform of the alternating current to be a sine wave.

The voltage control closed loop circuit 11511 includes a phase locked loop PLL coupled to the dc bus and a PI controller coupled to the four-quadrant rectification circuit 112, and output currents of the phase locked loop PLL and the PI controller are input to the multiplier a to input the current control closed loop circuit 11512.

In the current control closed-loop circuit 11512, the PR controller receives the output current of the multiplier a and the output current of the dc bus at the same time, the output voltage of the PR controller is input together with the dc bus voltage to generate an SPWM modulation wave, so as to implement double closed-loop control, the dc bus voltage is controlled to a preset value, the control network side current waveform is a sine wave, and the power factor is close to 1.

The inverter control circuit 1152 may be mainly divided into a control section and a modulation section. The control part is responsible for generating a voltage command, the modulation part is responsible for realizing the voltage command in a pulse form through hardware, and the voltage command and the modulation part are independent and adopt different calculation frequencies. The control part adopts fixed calculation frequency to complete AD sampling, instruction receiving and vector control algorithm realization, and the modulation part is limited by the highest switching frequency and needs to adopt a variable carrier period according to different motor rotating speeds in the whole motor rotating speed range through a multi-mode modulation strategy.

Fig. 4A is a block diagram of the inverter control circuit 1152.

Referring to fig. 4A, in an exemplary embodiment of the present disclosure, the inverter control circuit 1152 may include:

the rotating speed judging module 11521 is coupled to a speed sensor connected to the permanent magnet synchronous motor, and is configured to detect a rotating speed of the motor, send a first signal when the rotating speed of the motor is less than or equal to a preset value, and send a second signal when the rotating speed of the motor is greater than the preset value;

an MTPA control signal generation module 11522, configured to generate a control signal in an MTPA manner in response to the first signal;

and a field weakening control signal generating module 11523, configured to generate the control signal in a field weakening manner in response to the second signal.

The signal modulation module 11524 is coupled to the rotation speed determination module 11521, the MTPA control signal generation module 11522, and the flux-weakening control signal generation module 11523, and is configured to determine a modulation frequency for modulating the control signal in an asynchronous modulation manner according to the rotation speed of the motor when the rotation speed of the motor is in a first value-taking region, determine a modulation frequency for modulating the control signal in a middle 60-degree synchronous modulation manner according to the rotation speed of the motor when the rotation speed of the motor is in a second value-taking region, and determine a modulation frequency for modulating the control signal in a square wave modulation manner according to the rotation speed of the motor when the rotation speed of the motor is in a third value-taking region.

The preset value of the motor rotation speed may be selected according to the motor characteristics, but the disclosure is not limited thereto.

The signal modulation module 11524, after determining the modulation frequency, modulates the control signal at the modulation frequency to output the control signal to the coupled inverter.

In order to improve the precision and stability of the control system, the embodiment of the disclosure adopts an independent control mode of a control algorithm and a modulation algorithm.

For the control algorithm, an MTPA (Maximum torque per amp, Maximum torque current ratio) control mode and a weak magnetic control mode can be adopted according to the difference of the motor rotation speed.

The MTPA control mode is a control strategy applicable to a non-flux weakening state. Because the direct-axis inductance of the salient pole motor is smaller than the quadrature-axis inductance, when the salient pole motor operates in a range below the basic speed, a higher torque current ratio can be obtained by utilizing the reluctance torque generated by the salient pole effect of the motor. When the control mode is used, the given voltage command value can be realized by adopting double-current closed-loop control.

When the weak magnetic control mode is adopted, the given voltage instruction value can be realized by adopting double-current closed-loop control. In addition, because the voltage at the input end of the motor is limited by the voltage output capacity of the inverter at the moment, a voltage feedforward control loop can be arranged to correct the given value of the current so as to further accurately give the voltage command value, and the voltage requirement at the input end of the motor is within the voltage output capacity of the inverter.

Fig. 4B is a circuit schematic of the inverter control circuit 1152.

Referring to fig. 4A and 4B, in an exemplary embodiment of the present disclosure, the circuitry of the inverter control circuit may generally include one speed control outer loop, one voltage control outer loop, and two current control inner loops; logically divided, the system may include a rotation speed determination module 11521, an MTPA control signal generation module 11522, a field weakening control signal generation module 11523, and a signal modulation module 11524.

The inverter control circuit 1152 obtains the measured rotation speed ω through the speed outer ring based on the rotation speed set value, and outputs a set torque command T to the MTPA control signal generation module 11522 and the field weakening control signal generation module 11523 through the PI controller after comparing the measured rotation speed ω with the set rotation speed ω.

The rotation speed determination module 11521 can determine the selected control mode according to the measured rotation speed ω of the motor, and switch the control mode by sending different signals to control the operations of the MTPA control signal generation module 11522 and the flux weakening control signal generation module 11523, wherein the switching speeds of the first signal S1 and the second signal S2 can be determined according to the inverter characteristics and the parameters of the pmsm.

In a low-speed stage (the rotating speed is less than or equal to a preset value), the MTPA control signal generation module 11522 responds to the first signal S1 to operate, and the given value i x of the quadrature-direct axis current is calculated by adopting an MTPA control algorithm_dAnd i_qTwo current control inner loops will feed back current i_qAnd i_dRespectively corresponding to given current i_dAnd i_qAfter comparison, a given AC-DC axis voltage command u is output through a corresponding PI controller_dAnd u_q。

In a high-speed stage (the rotating speed is greater than the preset value), the weak magnetic control signal generation module 11523 responds to the second signal S2 to operate, and the weak magnetic control algorithm is adopted to calculate the set value i of the quadrature-direct axis current_dAnd i_qTwo current control inner loops will feed back current i_qAnd i_dRespectively corresponding to given current i_dAnd i_qAfter comparison, a given AC-DC axis voltage command u is output through a corresponding PI controller_dAnd u_q。

Since the motor terminal voltage will gradually approach the inverter output voltage limit during operation of the permanent magnet synchronous motor, in the disclosed embodiment, a voltage feedforward control loop is provided to correct a given i x of the d-axis current_d. The voltage feedforward control loop receives a given AC-DC axis voltage command u_dAnd u_qTo it proceed with

And outputting a voltage limit value u through the inverter_satCorrecting the calculated value, and obtaining a current correction quantity delta i after the corrected value passes through a PI regulator_d. Voltage feedforward control loop output Δ i_dAs an additional component of the d-axis current, i x calculated by a flux weakening algorithm_d1Added as d-axis current set value i_dAt correction of i_dWhile also corresponding to i_qThe correction is made.

The signal modulation module 11524 may include a polar coordinate transformation unit a and a multi-mode modulation unit B. Wherein the polar coordinate transformation unit A is based on the AC/DC axis voltage command u_dAnd u_qCalculated from the angular position theta of the rotorTo rest αβ coordinate system voltage command u_αAnd u_β(ii) a The multi-mode modulation unit B generates pulse waves according to different modulation frequencies determined by the rotating speed of the motor and acts on the inverter to realize terminal voltage. When the rotating speed of the motor is in the first value area, the multi-mode modulation unit B determines the modulation frequency for modulating the control signal in an asynchronous modulation mode according to the rotating speed of the motor; when the rotating speed of the motor is in the second value area, the multi-mode modulation unit B determines the modulation frequency for modulating the control signal by adopting a middle 60-degree synchronous modulation mode according to the rotating speed of the motor; when the motor rotation speed is in the third value area, the multi-mode modulation unit B determines the modulation frequency for modulating the control signal in a square wave modulation manner according to the motor rotation speed, and generates a carrier pulse according to the modulation frequency to send the control signal to the inverter circuit 114.

In the circuit shown in fig. 4B, there are various coordinate system transformation units to realize various types of calculations, wherein abc coordinate system is a three-phase stationary coordinate system, αβ coordinate system is a two-phase stationary coordinate system, dq coordinate system is a two-phase rotating coordinate system, conversion of dq- αβ coordinate system is inverse Park transformation, conversion of abc- αβ coordinate system is Clarke transformation, and conversion of αβ -dq coordinate system is Park transformation.

Fig. 5 is a schematic diagram of a modulation algorithm in the embodiment of the present disclosure, that is, a schematic diagram of inverter modulation mode variation.

In fig. 5, the abscissa is the frequency of the modulation wave, which is control information, and the ordinate is the carrier frequency. Referring to FIG. 5, in an embodiment of the present disclosure, the modulation algorithm may be, for example, a multi-mode modulation algorithm to meet the low switching frequency limit of a high power transmission system.

The multi-mode modulation strategy may include, for example, asynchronous modulation (0 Hz to 20Hz in fig. 5), regular sample synchronous modulation (20 Hz to 30Hz in fig. 5), or may employ piecewise synchronous modulation (30 Hz to 82Hz in fig. 5) with intermediate 60 degree modulation in some frequency segments to suppress back emf of the permanent magnet motor.

Different modulation strategies are designed in different speed sections, so that the step-by-step transition of the single pulse mode under the high carrier ratio square wave in the starting stage can be realized, and the requirement of operation in a full speed range can be met. When the transition is performed between different modulation strategies, it is ensured that no serious current impact occurs in the switching process, i.e. a smooth transition is achieved. When the conditions allow, the modulation mode under the low carrier ratio should be optimized to a certain extent as far as possible so as to improve the performance of the harmonic waves and the like and improve the control performance of the permanent magnet synchronous motor. By adopting the multi-mode synchronous modulation strategy, on one hand, the allowable switching frequency of the inverter can be fully utilized, and on the other hand, the higher direct-current voltage utilization rate is ensured to be realized after the inverter enters a weak magnetic area.

The output alternating-current voltage of the traction converter is modulated by the control algorithm to be converted into a three-phase alternating-current power supply with variable voltage and frequency, and the characteristic control of the permanent magnet motor can be realized.

Fig. 6A and 6B are another schematic diagrams of a traction converter provided in an embodiment of the present disclosure.

Referring to fig. 6A, in one embodiment, the converter 1 may further include an auxiliary converter unit 12 for providing power to loads such as locomotive pumps, fans, and the like.

Referring to fig. 6B, the auxiliary current transformer unit 12 provided in this embodiment may include an auxiliary pre-charge circuit 121, an auxiliary four-quadrant rectification circuit 122, an auxiliary intermediate dc circuit 123, an auxiliary inverter circuit 124, and an auxiliary control unit 125, where the auxiliary intermediate dc circuit 123 may include an energy storage circuit and a measurement protection circuit.

In an exemplary embodiment of the present disclosure, the auxiliary control unit 125 may include an auxiliary four-quadrant pulse rectifier for controlling the operation of the auxiliary four-quadrant rectification circuit 122 and an auxiliary inverter control circuit for controlling the operation of the auxiliary inverter 124 circuit. In addition, the auxiliary control unit 125 can also implement protection against overvoltage, overcurrent, and the like.

Fig. 7A and 7B are still another schematic diagrams of a traction converter provided in an embodiment of the present disclosure.

Referring to fig. 7A and 7B, in an exemplary embodiment of the present disclosure, the traction converter 1 may further include:

the water cooling system 13 is coupled to the three traction converter units 11 and the auxiliary converter unit 12, and includes but is not limited to a cooling pipeline, a water pump, an expansion tank, a stop valve, a pressure sensor, a temperature sensor, and an external cooling tower.

Referring to fig. 7B, the overall layout of the converter cabinet with the traction converter 1 installed therein may adopt a unitized mode, and integrate 3 groups of traction converter units and 1 group of auxiliary converter units, and is equipped with a cooling system and a protection system. Because three groups of traction converter units and one group of auxiliary converter units are integrated, components in the converter cabinet are compact in layout and large in heat productivity, and cooling can be realized by adopting a water circulation cooling mode.

In the embodiment of the disclosure, the IGBT devices in the traction converter can be arranged on a single surface, and the direct current circuit is connected by the low-inductance composite busbar, so that the layout design of components is compact and the space utilization rate is improved on the premise of meeting the requirement of electromagnetic compatibility.

Fig. 8 is a flow chart of a traction converter control method in an embodiment of the present disclosure.

Referring to fig. 8, in one embodiment, the traction converter control method 100 may include the steps of generating an inverter control signal as a function of motor speed:

step S101, detecting the rotating speed of a motor;

step S102, when the rotating speed of the motor is less than or equal to a preset value, a control signal for controlling the operation of the inverter is generated in an MTPA mode;

and step S103, when the rotating speed of the motor is greater than a preset value, generating a control signal for controlling the operation of the inverter by adopting a field weakening mode.

In an exemplary embodiment of the present disclosure, the traction converter control method 100 may further include determining a modulation frequency at which the control signal is sent based on the motor speed:

step S104, when the rotating speed of the motor is in a first value area, a control signal is sent in an asynchronous modulation mode;

step S105, when the rotating speed of the motor is in a second value area, determining the modulation frequency for modulating the control signal according to the rotating speed of the motor by adopting a middle 60-degree synchronous modulation mode;

and S106, when the rotating speed of the motor is in the third value area, determining the modulation frequency for modulating the control signal according to the rotating speed of the motor by adopting a square wave modulation mode.

Fig. 9 is a schematic diagram of a high-power permanent-magnet direct drive system in an embodiment of the present disclosure.

Referring to fig. 9, the high power permanent magnet direct drive system may include:

the traction converter 1 as before;

a permanent magnet synchronous motor 2 coupled to the traction converter 1;

and the flexible coupling 3 is coupled to the permanent magnet synchronous motor 2.

The inverter of the traction converter 1 has two-stage dynamic drive plate clamping voltage and can output a variable-frequency variable-voltage power supply for the permanent magnet synchronous motor. The flexible coupling 3 can be directly coupled between wheel pairs of the locomotive to realize direct drive.

The high-power permanent magnet direct drive system provided by the disclosure replaces a gear box existing in the locomotive driving technology in the prior art by using the coupler, avoids the problems of power loss, pollution and the like of the gear box, and improves the power conversion rate. In addition, the high-power permanent magnet driving system fills the blank of the field of locomotive driving.

It should be noted that although in the above detailed description several modules or units of the device for action execution are mentioned, such a division is not mandatory. Indeed, the features and functionality of two or more modules or units described above may be embodied in one module or unit, according to embodiments of the present disclosure. Conversely, the features and functions of one module or unit described above may be further divided into embodiments by a plurality of modules or units.

Furthermore, the above-described figures are merely schematic illustrations of processes involved in methods according to exemplary embodiments of the invention, and are not intended to be limiting. It will be readily understood that the processes shown in the above figures are not intended to indicate or limit the chronological order of the processes. In addition, it is also readily understood that these processes may be performed synchronously or asynchronously, e.g., in multiple modules.

Other embodiments of the disclosure will be apparent to those skilled in the art from consideration of the specification and practice of the disclosure disclosed herein. This application is intended to cover any variations, uses, or adaptations of the disclosure following, in general, the principles of the disclosure and including such departures from the present disclosure as come within known or customary practice within the art to which the disclosure pertains. It is intended that the specification and examples be considered as exemplary only, with a true scope and spirit of the disclosure being indicated by the following claims.