Method and device for braking an asynchronous motor suitable for a traction system of a rail vehicle

Abstract

The application provides an asynchronous motor braking method and device suitable for a rail vehicle traction system, and the asynchronous motor braking method suitable for the rail vehicle traction system comprises the following steps: determining a stator voltage reference value in a two-phase stationary coordinate system of an asynchronous motor according to a current and a speed of a stator of the asynchronous motor; setting a change range threshold value of a current frequency of the stator of the asynchronous motor when the asynchronous motor is switched from regenerative braking to reverse connection braking; and performing a braking operation on the asynchronous motor according to the stator voltage reference value and the change range threshold value. The application can reduce the brake shoe wear caused by air braking of the rail vehicle traction system, thereby saving the relevant production cost and maintenance cost of the rail vehicle.

Description

TECHNICAL FIELD

[0001] The present application belongs to the field of rail transit technology, and particularly relates to an asynchronous motor braking method and device suitable for a rail vehicle traction system in the field of alternating current motor control technology in the field of power electronics and power transmission. BACKGROUND

[0002] Electrified railway has the advantages of large carrying capacity, high speed, small pollution and low operation cost, and has been highly valued and strongly supported in its investment and construction for a long time. The power core of electrified railway is the electric traction transmission system, among which, the "AC-DC-AC" type electric traction transmission mode has become the mainstream transmission mode of the existing technology of electrified railway. The traction and braking performance of the asynchronous traction motor as the power source of the system is directly related to the transportation capacity and running safety of the train.

[0003] The train includes two core working conditions in the running process: traction working condition and braking working condition. With the continuous improvement of train running speed, how to make the train brake efficiently under the premise of meeting the braking deceleration and braking distance, passenger comfort and safety and reliability has become a technical problem to be solved by those skilled in the art.

[0004] At present, the braking mode of rail transit vehicle is electric-air combined braking. The process of electric-air combined braking is as follows: when the train runs at medium and high speed, the regenerative braking is mainly used; when the train is braked to below 10 km / h, the regenerative braking is gradually cut off and the air braking is gradually put into operation until the train is reliably stopped. The electric-air combined braking characteristic curve is as shown in Figure 1 . Among them, the regenerative braking can be realized by controlling the traction motor to work in the regenerative braking working condition, and the regenerative braking can also convert the kinetic energy in the deceleration process into electric energy and feedback to the traction network through the traction converter, which is an ideal electric braking mode; but the air braking is a mechanical braking mode, which dissipates the energy in the vehicle deceleration process through the friction between the brake shoe and the brake disc or the wheel, so the electric-air combined braking has its own shortcomings which cannot be overcome, specifically:

[0005] (1) The air braking relies on friction to realize braking, which is easy to cause wear of mechanical braking components and has high maintenance cost;

[0006] (2) The controllability of air braking mode is poor, and the stopping position is not accurate after the switching of electric and air braking;

[0007] (3) The response speed of air braking is slower than that of electric braking, and the cooperation of the two braking modes is difficult in the switching process;

[0008] (4) The switching process of electric and air braking may cause acceleration mutation and passenger comfort is reduced. SUMMARY

[0009] The asynchronous motor braking method and device for a rail vehicle traction system can reduce brake shoe wear caused by air braking of the rail vehicle traction system and save production and maintenance costs.

[0010] To solve the technical problems in the background art, the present application provides the following technical solutions:

[0011] In a first aspect, the present application provides an asynchronous motor braking method for a rail vehicle traction system, comprising:

[0012] determining a stator voltage reference value in a two-phase stationary coordinate system of the asynchronous motor according to a current and a speed of the asynchronous motor stator;

[0013] setting a variation range threshold of a current frequency of the asynchronous motor stator when the asynchronous motor is switched from regenerative braking to reverse braking;

[0014] braking the asynchronous motor according to the stator voltage reference value and the variation range threshold.

[0015] In an embodiment, the asynchronous motor braking method for a rail vehicle traction system further comprises:

[0016] correcting the stator voltage reference value according to a three-phase voltage error of the asynchronous motor stator.

[0017] In an embodiment, the braking the asynchronous motor according to the stator voltage reference value and the variation range threshold comprises:

[0018] braking the asynchronous motor according to the corrected stator voltage reference value and the variation range threshold.

[0019] In an embodiment, the determining a stator voltage reference value in a two-phase stationary coordinate system of the asynchronous motor according to a current and a speed of the asynchronous motor stator comprises:

[0020] collecting the current and the speed of the asynchronous motor;

[0021] calculating the stator voltage reference value according to the current and the speed.

[0022] In an embodiment, the correcting the stator voltage reference value according to a three-phase voltage error of the asynchronous motor stator comprises:

[0023] calculating an ideal voltage of the asynchronous motor stator according to the current;

[0024] calculating the three-phase voltage error according to the ideal voltage and an actual voltage of the asynchronous motor stator.

[0025] correcting the stator voltage reference value according to a three-phase voltage error of the asynchronous motor.

[0026] In an embodiment, the braking the asynchronous motor according to the corrected stator voltage reference value and the variation range threshold value comprises:

[0027] generating a pulse signal according to the corrected stator voltage reference value;

[0028] sending the pulse signal to an inverter in a rail vehicle traction system to brake the asynchronous motor; and

[0029] when the asynchronous motor is switched from regenerative braking to reverse braking and the current frequency is not less than the variation range threshold value, setting the value of the current frequency according to the variation range threshold value.

[0030] In a second aspect, the present application provides an asynchronous motor braking device suitable for a rail vehicle traction system, which comprises:

[0031] a reference value determination module configured to determine a stator voltage reference value in a two-phase stationary coordinate system of the asynchronous motor according to a current and a speed of a stator of the asynchronous motor;

[0032] a current frequency setting module configured to set a variation range threshold value of a current frequency of the stator of the asynchronous motor when the asynchronous motor is switched from regenerative braking to reverse braking;

[0033] an asynchronous motor braking module configured to brake the asynchronous motor according to the stator voltage reference value and the variation range threshold value.

[0034] In an embodiment, the asynchronous motor braking device suitable for the rail vehicle traction system further comprises:

[0035] a reference value correction module configured to correct the stator voltage reference value according to a three-phase voltage error of the stator of the asynchronous motor.

[0036] In an embodiment, the asynchronous motor braking module comprises:

[0037] an asynchronous motor braking unit configured to brake the asynchronous motor according to the corrected stator voltage reference value and the variation range threshold value.

[0038] In an embodiment, the reference value determination module comprises:

[0039] a data acquisition unit configured to acquire the current and the speed of the electronic of the asynchronous motor;

[0040] The reference value calculation unit is configured to calculate the stator voltage reference value according to the current and the speed.

[0041] In an embodiment, the reference value correction module comprises:

[0042] The ideal voltage calculation unit is configured to calculate an ideal voltage of the asynchronous motor stator according to the current.

[0043] The error calculation unit is configured to calculate a three-phase voltage error according to the ideal voltage and an actual voltage of the asynchronous motor stator.

[0044] The reference value correction unit is configured to correct the stator voltage reference value according to the three-phase voltage error.

[0045] In an embodiment, the asynchronous motor braking unit comprises:

[0046] The pulse signal generation unit is configured to generate a pulse signal according to the corrected stator voltage reference value.

[0047] The asynchronous motor braking sub-unit is configured to send the pulse signal to an inverter in the rail vehicle traction system to brake the asynchronous motor.

[0048] The current frequency forced setting unit is configured to set a value of the current frequency according to the change range threshold value when the asynchronous motor is switched from regenerative braking to reverse braking and the current frequency is not less than the change range threshold value.

[0049] In a third aspect, the present application provides a computer program product comprising computer programs / instructions, which, when executed by a processor, implement the steps of the asynchronous motor braking method for the rail vehicle traction system.

[0050] In a fourth aspect, the present application provides an electronic device comprising a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein the processor implements the steps of the asynchronous motor braking method for the rail vehicle traction system when executing the program.

[0051] In a fifth aspect, the present application provides a computer-readable storage medium having a computer program stored thereon, wherein the computer program, when executed by a processor, implements the steps of the asynchronous motor braking method for the rail vehicle traction system.

[0052] From the above description, the embodiment of the application provides an asynchronous motor braking method and device suitable for a rail vehicle traction system, and the corresponding method comprises the following steps: firstly, determining the stator voltage reference value in the two-phase stationary coordinate system of the asynchronous motor according to the current and speed of the stator of the asynchronous motor; then, setting the variation range threshold of the current frequency of the stator of the asynchronous motor when the asynchronous motor is switched from regenerative braking to reverse braking; finally, braking the asynchronous motor according to the stator voltage reference value and the variation range threshold. The beneficial effects of the application are as follows:

[0053] 1) An improved Sigmoid function is used to calculate the compensation voltage, which solves the problem of dead zone voltage miscompensation caused by current polarity misjudgment, and effectively improves the steady-state performance of the asynchronous motor in the low-speed running stage.

[0054] 2) A special amplitude limiting processing method is used to solve the stator zero frequency "crossing" problem, thereby reducing the current and torque impact when the asynchronous motor is switched from regenerative braking to reverse braking, and realizing smooth switching of the two braking modes;

[0055] 3) The full-electric braking function of the asynchronous motor is realized, which can provide a better reference for realizing full-electric braking operation of the train in the rail transit industry; BRIEF DESCRIPTION OF DRAWINGS

[0056] In order to more clearly illustrate the technical solutions in the embodiments of the application or the prior art, the following will briefly introduce the drawings needed to be used in the embodiment or prior art description. Obviously, the drawings in the following description are some embodiments of the application, and other drawings can also be obtained by those skilled in the art without creative labor.

[0057] Figure 1 It is the braking characteristic curve diagram of the electric-pneumatic combined braking mode in the prior art;

[0058] Figure 2 It is the flowchart of the asynchronous motor braking method suitable for the rail vehicle traction system in the embodiment of the application Figure 1 ;

[0059] Figure 3 It is the flowchart of the asynchronous motor braking method suitable for the rail vehicle traction system in the embodiment of the application Figure 2 ;

[0060] Figure 4 It is the pulse signal and output voltage waveform diagram of the a-phase bridge arm in one switching period in the embodiment of the application;

[0061] Figure 5 It is the torque diagram when there is no dead zone compensation in the embodiment of the application;

[0062] Figure 6 Current waveform diagram without dead-time compensation in the embodiment of the present application;

[0063] Figure 7 Torque diagram with dead-time compensation in the embodiment of the present application;

[0064] Figure 8 Current waveform diagram with dead-time compensation in the embodiment of the present application;

[0065] Figure 9 Flow chart of step 200 in the embodiment of the present application;

[0066] Figure 10 Flow chart of step 100 in the embodiment of the present application;

[0067] Figure 11 Asynchronous motor direct rotor field orientation control block diagram in the embodiment of the present application;

[0068] Figure 12 Flow chart of step 400 in the embodiment of the present application;

[0069] Figure 13 Flow chart of step 401 in the embodiment of the present application;

[0070] Figure 14 Flow chart of step 201 in the embodiment of the present application;

[0071] Figure 15 Flow chart of asynchronous motor braking method suitable for rail vehicle traction system in the specific embodiment of the present application;

[0072] Figure 16 Three-phase two-level inverter-asynchronous motor traction system topology diagram in the specific embodiment of the present application;

[0073] Figure 17 New sigmoid function and traditional switching function curve diagram in the specific embodiment of the present application;

[0074] Figure 18 Asynchronous motor regenerative braking to reverse braking schematic diagram in the specific embodiment of the present application;

[0075] Figure 19 Regenerative braking switched to reverse braking torque diagram without amplitude limiting processing in the specific embodiment of the present application;

[0076] Figure 20 Regenerative braking switched to reverse braking current waveform diagram without amplitude limiting processing in the specific embodiment of the present application;

[0077] Figure 21 FIG. 6 is a graph of regenerative braking torque when the limit processing is performed in the embodiment of the present application;

[0078] Figure 22 FIG. 7 is a graph of regenerative braking current when the limit processing is performed in the embodiment of the present application;

[0079] Figure 23 FIG. 8 is a block diagram of an asynchronous motor braking device for a railcar traction system in the embodiment of the present application; Figure 1 ;

[0080] Figure 24 FIG. 8 is a block diagram of an asynchronous motor braking device for a railcar traction system in the embodiment of the present application; Figure 2 ;

[0081] Figure 25 FIG. 9 is a block diagram of the asynchronous motor braking module 30 in the embodiment of the present application;

[0082] Figure 26 FIG. 10 is a block diagram of the reference value determination module 10 in the embodiment of the present application;

[0083] Figure 27 FIG. 11 is a block diagram of the reference value correction module 40 in the embodiment of the present application;

[0084] Figure 28 FIG. 12 is a block diagram of the asynchronous motor braking unit 301 in the embodiment of the present application;

[0085] Figure 29 FIG. 13 is a structural schematic diagram of an electronic device in the embodiment of the present application. DETAILED DESCRIPTION

[0086] In order to make the objects, technical solutions and advantages of the embodiments of the present application clearer, the following will clearly and completely describe the technical solutions in the embodiments of the present application with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are some but not all of the embodiments of the present application. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative work fall within the scope of the present application.

[0087] Those skilled in the art should understand that the embodiments of the present application can be provided as a method, a system or a computer program product. Therefore, the present application can take the form of an entirely hardware embodiment, an entirely software embodiment or an embodiment combining software and hardware aspects. Moreover, the present application can take the form of a computer program product implemented on one or more computer-usable storage media (including but not limited to disk storage, CD-ROM, optical storage etc.) containing computer-usable program code.

[0088] It should be noted that the terms "comprising" and "having" and any variations thereof in the specification and claims and the above description of the drawings are intended to cover not only the listed steps or units but also other non-listed steps or units that are inherent to the process, method, system, product or device. The embodiments in the present application and the features in the embodiments can be combined with each other without conflict. The present application will be described in detail below with reference to the accompanying drawings and in combination with the embodiments.

[0089] Based on the technical problems in the prior art described above, the embodiment of the present application provides a specific embodiment of an asynchronous motor braking method suitable for a rail vehicle traction system, referring to Figure 2 The method specifically includes the following contents:

[0090] Step 100: determining the stator voltage reference value of the asynchronous motor in the two-phase stationary coordinate system according to the current and speed of the stator of the asynchronous motor;

[0091] Specifically, first, the stator current and speed information of the traction asynchronous motor are sampled, and then the two-phase voltage reference value of the stator of the asynchronous motor is determined by using the rotor field-oriented control method.

[0092] Step 200: setting the change range threshold of the frequency of the stator current of the asynchronous motor when the asynchronous motor is converted from regenerative braking to reverse braking;

[0093] Specifically, when the stator current frequency is less than a positive set value (one end point of the change range threshold), the stator current frequency value is forced to be equal to the positive set value; when the stator current frequency is less than a negative set value (one end point of the change range threshold), the stator current frequency value is forced to be equal to the negative set value; the selection of the set value is determined according to actual debugging, so as to ensure that the stator current frequency value will not frequently jump between positive and negative.

[0094] Step 300: braking operation of the asynchronous motor according to the stator voltage reference value and the change range threshold.

[0095] Specifically, the space vector pulse width modulation method is adopted, and pulses are sent to the inverter to drive the asynchronous motor to operate normally according to the corrected two-phase voltage reference value, wherein the inverter is connected with the asynchronous motor.

[0096] From the above description, the asynchronous motor braking method suitable for the rail vehicle traction system provided by the embodiment of the application comprises the following steps: firstly, determining the stator voltage reference value in the two-phase stationary coordinate system of the asynchronous motor stator according to the current and speed of the asynchronous motor stator; then, setting the variation range threshold of the current frequency of the asynchronous motor stator when the asynchronous motor is switched from regenerative braking to reverse braking; and finally, braking the asynchronous motor according to the stator voltage reference value and the variation range threshold. The beneficial effects of the application are as follows:

[0097] 1) An improved Sigmoid function is used to calculate the compensation voltage, which solves the problem of dead zone voltage miscompensation caused by current polarity misjudgment, and effectively improves the steady-state performance of the asynchronous motor in the low-speed running stage.

[0098] 2) A special amplitude limiting processing method is used to solve the problem of stator zero frequency “crossing”, thereby reducing the current and torque impact when the asynchronous motor is switched from regenerative braking to reverse braking, and achieving smooth switching of the two braking modes;

[0099] 3) The full-electric braking function of the asynchronous motor is realized, which can provide a better reference for the full-electric braking operation of the train in the rail transit industry.

[0100] In an embodiment, referring to Figure 3 , the asynchronous motor braking method suitable for the rail vehicle traction system further comprises:

[0101] Step 400: correcting the stator voltage reference value according to the three-phase voltage error of the asynchronous motor stator.

[0102] Based on the influence of the “dead zone effect” on the output voltage of the inverter, the error between the ideal output voltage and the actual voltage is calculated by using the sigmoid function, and then the two-phase voltage reference value in step 100 is corrected according to the error.

[0103] The dead zone effect is divided into: taking the a-phase bridge arm as an example to analyze the dead zone effect of the inverter, Figure 4 The ideal pulse signal of the a-phase bridge arm in a switching period, the pulse signal considering the dead zone time, the pulse signal considering the dead zone time and the switching delay, the ideal output voltage waveform and the actual output voltage waveform are given. S+ and S- are the upper and lower bridge arm pulse signals respectively, and 1 and 0 represent the turn-on and turn-off of the power devices respectively. As can be seen from part (a) of Figure 4 , the pulse signals of the upper and lower bridge arms are complementary in the ideal case. As shown in part (b) of Figure 4 , in order to avoid short circuit caused by the simultaneous turn-on of the upper and lower bridge arm power devices, a certain dead zone time t d is inserted in the pulse signal. During t d , the power devices of the upper and lower bridge arms are in the turn-off state.Figure 4 As shown in part (c), since the power device requires time to turn on and off, when a pulse signal with added dead time is applied to the power device, after the turn-on delay t... r and shutdown delay t f Only when the power device is turned on or off can it truly achieve this; therefore, the pulse after the delay can be considered a valid pulse. Figure 4 The middle (d) section represents the voltage U between phase a of the inverter and the negative terminal n of the power supply under ideal pulse action. an waveform, U dc This is a DC voltage. The direction of current flow is defined as positive for the load and negative for the inverter. Figure 4 part (e) and Figure 4 The (f) part in the middle represents i a ≥0 and i a When <0, Figure 4 The pulse U shown in part (c) is applied in the middle. an The actual waveform.

[0104] Figure 5 to Figure 8 This more clearly reflects the impact of the dead-time effect on the inverter. Figure 5 as well as Figure 6 The waveforms of torque and current when there is no dead zone compensation are shown. Figure 7 as well as Figure 8 (This is a waveform diagram of torque and current with dead zone compensation).

[0105] In one embodiment, see Figure 9 Step 200 includes:

[0106] Step 201: Perform braking operation on the asynchronous motor according to the corrected stator voltage reference value and the change range threshold.

[0107] Specifically, a space vector pulse width modulation method is used to send pulses to the inverter based on the corrected two-phase voltage reference value to drive the asynchronous motor to operate normally. The inverter is connected to the asynchronous motor.

[0108] In one embodiment, see Figure 10 Step 100 specifically includes:

[0109] Step 101: Collect the current and speed of the asynchronous motor's electronic components;

[0110] Step 102: Calculate the stator voltage reference value based on the current and speed.

[0111] In steps 101 and 102, the stator current and speed information of the traction asynchronous motor are sampled, and the stator voltage reference value u in the two-phase stationary coordinate system is obtained using the direct rotor field-oriented control method. αand u β The direct rotor flux orientation control block diagram of the asynchronous motor is shown in FIG. 3. Figure 11

[0112] In one embodiment, referring to FIG. 4, step 400 specifically comprises: Figure 12

[0113] Step 401: calculating the ideal voltage of the stator of the asynchronous motor according to the current;

[0114] Specifically, the sigmoid function is used to calculate the error between the ideal output voltage and the actual voltage.

[0115] Step 402: calculating the three-phase voltage error according to the ideal voltage and the actual voltage of the stator of the asynchronous motor;

[0116] In step 201 and step 202, the three-phase stator current of the asynchronous motor is first sampled, and then the dead-time effect of the inverter is analyzed to calculate the three-phase voltage error.

[0117] Step 403: correcting the stator voltage reference value according to the three-phase voltage error.

[0118] In one embodiment, referring to FIG. 4, step 401 further comprises: Figure 13

[0119] Step 4011: calculating the three-phase ideal voltage of the stator of the asynchronous motor according to the current by using the sigmoid function.

[0120] First, define the voltage error as the ideal voltage minus the actual voltage, and the a-phase voltage error can be expressed as

[0121]

[0122] Wherein

[0123]

[0124] In the formula, U dc is the DC bus voltage, t d is the dead-time, t r is the IGBT turn-on delay, t f is the turn-off delay, i a is the a-phase stator current. Similarly, the b-phase and c-phase voltage errors Δu b and Δu c can be calculated according to the current polarity of the b-phase and c-phase.

[0125] In one embodiment, referring to FIG. 2, step 201 specifically comprises: Figure 14

[0126] ​​​​Step 2011: generating a pulse signal according to the modified stator voltage reference value;

[0127] Step 2012: sending the pulse signal to an inverter in a rail vehicle traction system to brake the asynchronous motor;

[0128] Specifically, in step 2011 and step 2012, a space vector pulse width modulation method is used to send a pulse to the inverter to drive the asynchronous motor to operate normally;

[0129] Step 2013: when the asynchronous motor is converted from regenerative braking to reverse braking and the current frequency is not less than the change range threshold value, setting the value of the current frequency according to the change range threshold value.

[0130] Specifically, when the stator current frequency is less than a positive set value, the stator current frequency value is forced to be equal to the positive set value; when the stator current frequency is less than a negative set value, the stator current frequency value is forced to be equal to the negative set value; the selection of the set value is determined according to actual debugging, to ensure that the stator current frequency value does not frequently jump between positive and negative.

[0131] In one specific embodiment, the present application also takes a three-phase two-level inverter-asynchronous motor traction system as the research object, and provides a specific embodiment of an asynchronous motor braking method suitable for a rail vehicle traction system, referring to Figure 15 and Figure 16 , specifically including the following contents.

[0132] To solve the problems existing in the electric-pneumatic combined braking, some scholars have proposed a method of naturally transitioning from regenerative braking to reverse braking to realize full electric braking, that is, only using the electrical braking mode of the traction motor in the normal braking of the train, without the intervention of air braking. Although full electric braking has many advantages, but at present, full electric braking is rarely used in external rail transit vehicles. Affected by the factors of low-speed area speed measurement accuracy, flux observation and field orientation accuracy, and inverter nonlinearity, it is easy to lead to insufficient electrical braking force or poor braking performance of the asynchronous traction motor, which is not enough to make the train stop safely and reliably. Therefore, at present, the mainstream braking mode of the train in the low-speed area is still air braking.

[0133] Nowadays, urban rail transit is developing rapidly, and the demand for full electric braking technology is urgent. The development of new generation high-speed trains with a speed of 400 km / h has also been put on the agenda, and full electric braking technology is one of the important technical indicators. Therefore, it is of great significance to carry out research on the full electric braking technology of the asynchronous traction motor in the low-speed braking stage of the train.

[0134] S1: Sampling the stator current and speed information of the traction asynchronous motor, and using the rotor field oriented control method to obtain the stator voltage reference value u in the two-phase static coordinate system α and u β ;

[0135] S2: Using Sigmoid function to calculate the error between ideal output voltage and actual voltage, correcting u α and u β calculated in step S1;

[0136] The influence of dead-time effect on the output voltage of the inverter is analyzed, the error between ideal output voltage and actual voltage is calculated by using sigmoid function, u α and u β calculated in step S1 are corrected to obtain the corrected values u αe and u βe , and the space vector pulse width modulation method is used to send pulses to the inverter to drive the asynchronous motor to run normally;

[0137] The voltage error is defined as the ideal voltage minus the actual voltage, that is Figure 4 , so when i a ≥0, the a-phase voltage error is

[0138]

[0139] When i a <0, the a-phase voltage error is

[0140]

[0141] The a-phase voltage error can be expressed as

[0142]

[0143] Where

[0144]

[0145] Similarly, the b-phase and c-phase voltage errors Δu b and Δu c can be calculated according to the current polarity of b-phase and c-phase.

[0146] Since the error voltage caused by "dead-time effect" is related to the current polarity, in order to reduce the voltage error compensation problem caused by polarity misjudgment, the above S(i x )(x=a, b, c) function is modified, and the new S(i x ) function is designed as sigmoid function, that is

[0147]

[0148] wherein k is a constant, and the specific value of k is determined according to the effect of experimental debugging. Specifically: from the above analysis, it can be known that the error voltage generated by the dead zone is related to the current polarity. In the traditional dead zone compensation method, the calculation of the compensation voltage is usually carried out by using a switching function S(i a ). However, due to the switching noise of the power device and the zero-current clamping phenomenon, the current polarity is difficult to accurately determine. If the switching function is used to calculate the compensation voltage, in the case of incorrect judgment of the current polarity, it will lead to incorrect dead zone compensation, and the compensation voltage will be suddenly changed at the zero-crossing point, further leading to current distortion. In order to reduce the problems caused by polarity misjudgment and sudden change of compensation voltage, a new sigmoid function is designed to replace the traditional switching function. By judging the size of the three-phase current, the three-phase voltage error can be calculated as

[0149]

[0150] Let the compensation voltage in the two-phase stationary coordinate system be equal to the voltage error value. In order to more obviously show the difference between the new sigmoid function and the traditional switching function, taking k=20 as an example, Figure 17 the comparison curves of the sigmoid function designed in the application and the traditional switching function are given. It can be seen from Figure 17 that the compensation voltage value corresponding to the traditional switching function will be suddenly changed at the current zero point, and once the current polarity is misjudged, the miscompensated voltage value will be large, which is easy to cause current distortion. The compensation voltage value corresponding to the sigmoid function is slowly distributed, and even if the current polarity is misjudged, the error voltage value after misjudgment is small, and the influence on the system can be ignored, and the compensation voltage can be smoothly transitioned near the zero point, without voltage mutation.

[0151] then the compensation voltage in the two-phase stationary coordinate system is

[0152]

[0153] Further, from step S1, the stator voltage reference value u α and u β in the two-phase stationary coordinate system without considering the influence of the dead zone effect can be obtained, and from step S2, the compensation voltage in the two-phase stationary coordinate system under the influence of the dead zone effect can be obtained, and the corrected voltage reference value in the two-phase stationary coordinate system can be expressed as

[0154]

[0155] After the voltage reference value is corrected, the space vector pulse width modulation method is used to send pulses to the inverter to drive the asynchronous motor to run.

[0156] S3: setting a variation range threshold of the current frequency of the stator of the asynchronous motor when the asynchronous motor is switched from regenerative braking to reverse braking.

[0157] In the process of braking of the rail vehicle, a special limiting processing method is used to solve the problem of stator zero frequency "crossing" so as to realize smooth switching of the asynchronous motor from regenerative braking to reverse braking.

[0158] It is known that the output torque of the asynchronous motor can be expressed as

[0159]

[0160] In the formula, T e is the output torque of the asynchronous motor, n p is the number of rotor pole pairs, R r is the rotor resistance, ω sl is the slip frequency, ψ r is the rotor flux, ω s is the stator frequency, and ω r is the rotor frequency.

[0161] It can be seen that the output torque of the asynchronous motor is proportional to the slip frequency. In the process of braking of the motor, the output torque and the slip frequency are both negative. With the decrease of the speed of the motor, ω r decreases. If the motor is only allowed to work in the regenerative braking condition, that is, ω s is always greater than 0, the absolute value of the slip frequency will gradually decrease with the decrease of the speed, thereby limiting the large torque output of the asynchronous motor in the low-speed braking condition. In view of this problem, some scholars have proposed to remove the restriction that ω s is greater than 0, and to use the method of natural transition from regenerative braking (ω s > 0) to reverse braking (ω s < 0) to realize the output of large torque at low speed. However, in the process of switching from regenerative braking to reverse braking, torque oscillation problem will occur near ω s = 0. In order to better explain and illustrate this problem, Figure 18 the waveforms of the rotor flux, the rotor flux angle, the speed and the slip frequency in the process of switching from regenerative braking to reverse braking are given. As can be seen from the waveforms, Figure 18 when the motor is switched from regenerative braking to reverse braking, the phases of ψ rα and ψ rβ will change, and ψ rα leads ψ rβ is switched to ψ rβ leads ψ rα, and the rotor flux angle θ also changes, indicating that the direction of the synchronous rotating magnetic field has changed, and the motor enters the reverse braking state. Since there is a certain error in the rotor flux observation at low speed, and the stator frequency ω s Nearby 0, the frequent jump between positive and negative values is inevitable, that is, the stator zero frequency "crossing" problem occurs, thereby causing the frequent change of the rotor flux angle, resulting in the instability of the rotor field orientation system and causing torque shock.

[0162] To solve the above problems, a special amplitude limiting method is used here to solve the problem of frequent "crossing" of stator zero frequency, thereby realizing the smooth switching of the asynchronous motor from regenerative braking to reverse braking. Specifically, when the stator current frequency is less than a positive set value, the stator current frequency value is forced to be equal to the positive set value; when the stator current frequency is less than a negative set value, the stator current frequency value is forced to be equal to the negative set value; the selection of the set value is determined according to the actual debugging, so as to ensure that the stator current frequency value will not appear positive and negative frequent jump, but will change from the positive set value to the negative set value, Figure 19 to Figure 22 It is shown whether to perform amplitude limiting, the torque and current waveform change when switching from regenerative braking to reverse braking. As can be seen from the figure, the above method effectively solves the torque shock problem caused by the "crossing" of the stator zero frequency.

[0163] Based on the same inventive concept, the embodiment of the present application also provides an asynchronous motor braking device suitable for a rail vehicle traction system, which can be used to realize the method described in the above embodiments, such as the following embodiments. Since the asynchronous motor braking device suitable for the rail vehicle traction system solves the problem in a similar way to the asynchronous motor braking method suitable for the rail vehicle traction system, the implementation of the asynchronous motor braking device suitable for the rail vehicle traction system can be referred to the implementation of the asynchronous motor braking method suitable for the rail vehicle traction system, and the repeated parts will not be described here. The term "unit" or "module" used below can be a combination of software and / or hardware that realizes a predetermined function. Although the system described in the following embodiments is preferably realized in software, hardware, or a combination of software and hardware is also possible and is conceived.

[0164] The embodiment of the present application provides a specific implementation of an asynchronous motor braking device suitable for a rail vehicle traction system, which can realize the asynchronous motor braking method suitable for a rail vehicle traction system, as described in Figure 23 The asynchronous motor braking device suitable for the rail vehicle traction system specifically includes the following contents:

[0165] The reference value determination module 10 is used to determine the stator voltage reference value in the two-phase stationary coordinate system of the asynchronous motor stator according to the current and speed of the asynchronous motor stator;

[0166] A current frequency setting module 20 is configured to set a variation range threshold of a current frequency of a stator of the asynchronous motor when the asynchronous motor is switched from regenerative braking to reverse braking.

[0167] An asynchronous motor braking module 30 is configured to brake the asynchronous motor according to the stator voltage reference value and the variation range threshold.

[0168] In one embodiment, referring to Figure 24 The asynchronous motor braking device for a rail vehicle traction system further comprises:

[0169] A reference value correction module 40 is configured to correct the stator voltage reference value according to a three-phase voltage error of the stator of the asynchronous motor.

[0170] In one embodiment, referring to Figure 25 The asynchronous motor braking module 30 comprises:

[0171] An asynchronous motor braking unit 301 is configured to brake the asynchronous motor according to the corrected stator voltage reference value and the variation range threshold.

[0172] In one embodiment, referring to Figure 26 The reference value determination module 10 comprises:

[0173] A data acquisition unit 101 is configured to acquire a current and a speed of the asynchronous motor electronics;

[0174] A reference value calculation unit 102 is configured to calculate the stator voltage reference value according to the current and the speed.

[0175] In one embodiment, referring to Figure 27 The reference value correction module 40 comprises:

[0176] An ideal voltage calculation unit 401 is configured to calculate an ideal voltage of the stator of the asynchronous motor according to the current;

[0177] An error calculation unit 402 is configured to calculate the three-phase voltage error according to the ideal voltage and an actual voltage of the stator of the asynchronous motor;

[0178] A reference value correction unit 403 is configured to correct the stator voltage reference value according to the three-phase voltage error.

[0179] In one embodiment, referring to Figure 28 The asynchronous motor braking unit 301 comprises:

[0180] A pulse signal generation unit 3011 is configured to generate a pulse signal according to the corrected stator voltage reference value;

[0181] an asynchronous motor braking subunit 3012, configured to send the pulse signal to an inverter in a rail vehicle traction system to brake the asynchronous motor; and

[0182] a current frequency forced setting unit 3013, configured to set a value of the current frequency according to the change range threshold value when the asynchronous motor is switched from regenerative braking to reverse braking and the current frequency is not less than the change range threshold value.

[0183] From the above description, the embodiment of the application provides an asynchronous motor braking device suitable for a rail vehicle traction system, which comprises the following steps: firstly, determining a stator voltage reference value in a two-phase stationary coordinate system of an asynchronous motor stator according to a current and a speed of the asynchronous motor stator; secondly, setting a change range threshold value of a current frequency of the asynchronous motor stator when the asynchronous motor is switched from regenerative braking to reverse braking; and thirdly, braking the asynchronous motor according to the stator voltage reference value and the change range threshold value. Specifically, the beneficial effects of the application are as follows:

[0184] 1) An improved Sigmoid function is used to calculate a compensation voltage, so that the problem of dead zone voltage miscompensation caused by current polarity misjudgment is solved, and the steady-state performance of the asynchronous motor in a low-speed running stage is effectively improved.

[0185] 2) A special amplitude limiting processing method is used to solve the problem of stator zero frequency "crossing", so that the current and torque impact of the asynchronous motor when switched from regenerative braking to reverse braking is reduced, and smooth switching of the two braking modes is realized;

[0186] 3) The full-electric braking function of the asynchronous motor is realized, which can provide a better reference for realizing full-electric braking operation of a train in the rail transit industry;

[0187] The embodiment of the application also provides a specific implementation of an electronic device capable of realizing all steps in the asynchronous motor braking method suitable for a rail vehicle traction system in the above embodiment, as shown in Figure 29 , the electronic device specifically comprises the following contents:

[0188] a processor 1201, a memory 1202, a communications interface 1203 and a bus 1204;

[0189] The processor 1201, the memory 1202 and the communications interface 1203 are connected to each other through the bus 1204; the communications interface 1203 is configured to realize information transmission between the server-side device, the client-side device and other related devices;

[0190] The processor 1201 is configured to invoke a computer program in the memory 1202, and when the processor executes the computer program, all steps in the asynchronous motor braking method for the traction system of the rail vehicle in the above embodiments are implemented, for example, the following steps are implemented when the processor executes the computer program:

[0191] Step 100: determining the stator voltage reference value of the asynchronous motor in the two-phase stationary coordinate system according to the current and speed of the stator of the asynchronous motor;

[0192] Step 200: setting the change range threshold of the current frequency of the stator of the asynchronous motor when the asynchronous motor is switched from regenerative braking to reverse braking;

[0193] Step 300: braking the asynchronous motor according to the stator voltage reference value and the change range threshold.

[0194] The embodiments of the present application also provide a computer readable storage medium capable of implementing all steps in the asynchronous motor braking method for the traction system of the rail vehicle in the above embodiments, and the computer readable storage medium stores a computer program, and when the processor executes the computer program, all steps in the asynchronous motor braking method for the traction system of the rail vehicle in the above embodiments are implemented, for example, the following steps are implemented when the processor executes the computer program:

[0195] Step 100: determining the stator voltage reference value of the asynchronous motor in the two-phase stationary coordinate system according to the current and speed of the stator of the asynchronous motor;

[0196] Step 200: setting the change range threshold of the current frequency of the stator of the asynchronous motor when the asynchronous motor is switched from regenerative braking to reverse braking;

[0197] Step 300: braking the asynchronous motor according to the stator voltage reference value and the change range threshold.

[0198] Each of the embodiments in the specification is described in a progressive manner, and the same and similar parts between the embodiments can be referred to each other, and each embodiment mainly describes the difference from other embodiments. Especially, for the hardware+program type embodiment, since it is basically similar to the method embodiment, the description is relatively simple, and the related parts can be referred to the part of the method embodiment.

[0199] The above-described embodiments of the application have several aspects, no single one of which is solely responsible for the application's desirable attributes. Without limiting the scope of this application as to the particular aspects or features thereof, some advantages are listed below. Other advantages can become apparent from the following description.

[0200] Although this application provides method operations steps as in embodiments or flowcharts, more or less operations steps can be included based on routine or non-creative labor. The order of steps listed in embodiments is only one of many ways to execute the steps, and does not represent the only way to execute the steps. In actual device or client product execution, the method order shown in embodiments or drawings can be executed in sequence or in parallel (for example, in parallel processor or multi-threaded processing environment).

[0201] For the convenience of description, the above device is described as various modules respectively described in function. Of course, in the implementation of the embodiments of the present application, the functions of each module can be implemented in the same or multiple software and / or hardware, or the modules implementing the same function can be implemented by a combination of multiple sub-modules or sub-units. The device embodiments described above are only schematic, for example, the division of the units is only a logical function division, and actual implementation can have another division manner, for example, multiple units or components can be combined or integrated into another system, or some features can be ignored or not executed. In addition, the coupling or direct coupling or communication connection between the displayed or discussed each other can be indirect coupling or communication connection through some interface, device or unit, and can be electrical, mechanical or other forms.

[0202] Those skilled in the art also know that, in addition to implementing the controller in the form of pure computer readable program code, the same function can also be implemented by logically programming the method steps to make the controller in the form of logic gates, switches, application specific integrated circuits, programmable logic controllers and embedded microcontrollers. Therefore, such a controller can be considered as a hardware component, and the devices included therein for implementing various functions can also be considered as structures within the hardware component. Or even, the devices for implementing various functions can be considered as both software modules implementing the method and structures within the hardware component.

[0203] In one typical arrangement, the computing device includes one or more processors (CPUs), input / output interfaces, network interfaces, and memory.

[0204] Memory can include non-persistent memory, Random Access Memory (RAM), and / or non-volatile memory, etc. in the form of a computer-readable medium, such as read only memory (ROM) or flash memory, for example. Memory is an example of a computer-readable medium.

[0205] Embodiments of the present specification can be described in the general context of computer-executable instructions, such as program modules, being executed by a computer. Generally, program modules include routines, programs, objects, components, data structures, etc., that perform particular tasks or implement particular abstract data types. Embodiments of the present specification can also be practiced in distributed computing environments where tasks are performed by remote processing devices that are linked through a communications network. In a distributed computing environment, program modules can be located in both local and remote computer storage media including memory storage devices.

[0206] Each of the embodiments in the present specification is described in a progressive manner, and the same or similar parts between the embodiments can be referred to each other. Each of the embodiments focuses on the difference from other embodiments. In particular, for the system embodiments, since they are basically similar to the method embodiments, the description is relatively simple, and the relevant parts can be referred to the part of the method embodiments. In the description of the present specification, the description of the terms "one embodiment", "some embodiments", "an example", "a specific example", or "some examples" means that the specific features, structures, materials or characteristics described in connection with the embodiment or example are included in at least one embodiment or example of the embodiments of the present specification. In the present specification, the illustrative description of the above terms does not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described can be combined in any appropriate manner in any one or more embodiments or examples. In addition, the person skilled in the art can combine and combine the different embodiments or examples described in the present specification and the features of the different embodiments or examples without contradiction.

[0207] The above only describes the embodiments of the embodiments of the present specification, and is not intended to limit the embodiments of the present specification. The embodiments of the present specification can have various changes and modifications for those skilled in the art. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the embodiments of the present specification shall be included in the scope of claims of the embodiments of the present specification.

Claims

1. A braking method for an asynchronous motor suitable for a rail vehicle traction system, characterized in that, include: Determine the stator voltage reference value in the two-phase stationary coordinate system based on the stator current and speed of the asynchronous motor. When the asynchronous motor transitions from regenerative braking to reverse braking, a threshold value for the variation range of the stator current frequency is set. Specifically, when the stator current frequency is less than a positive set value, the stator current frequency value is forced to equal the positive set value; when the stator current frequency is less than a negative set value, the stator current frequency value is forced to equal the negative set value. The selection of the set value is determined based on actual debugging to ensure that the stator current frequency value does not frequently jump between positive and negative. The positive set value is one end of the variation range threshold value, and the negative set value is the other end of the variation range threshold value. The asynchronous motor is braked based on the stator voltage reference value and the variation range threshold. The stator voltage reference value is corrected based on the three-phase voltage error of the asynchronous motor stator; The step of braking the asynchronous motor based on the stator voltage reference value and the variation range threshold includes: The asynchronous motor is braked based on the corrected stator voltage reference value and the range threshold. Specifically, pulses are sent to the inverter based on the corrected two-phase voltage reference value to drive the asynchronous motor to operate normally. The inverter is connected to the asynchronous motor.

2. The asynchronous motor braking method as described in claim 1, characterized in that, The determination of the stator voltage reference value in the two-phase stationary coordinate system based on the stator current and speed of the asynchronous motor includes: The current and speed of the asynchronous motor are collected; The stator voltage reference value is calculated based on the current and speed.

3. The asynchronous motor braking method as described in claim 2, characterized in that, The step of correcting the stator voltage reference value based on the three-phase voltage error of the asynchronous motor stator includes: Calculate the ideal voltage of the asynchronous motor stator based on the current; The three-phase voltage error is calculated based on the ideal voltage and the actual voltage of the asynchronous motor stator. The stator voltage reference value is corrected based on the three-phase voltage error.

4. The asynchronous motor braking method as described in claim 3, characterized in that, The braking operation of the asynchronous motor based on the corrected stator voltage reference value and the variation range threshold includes: A pulse signal is generated based on the corrected stator voltage reference value; Sending the pulse signal to the inverter in the rail vehicle traction system to brake the asynchronous motor; and When the asynchronous motor transitions from regenerative braking to reverse braking and the current frequency is not less than the change range threshold, the value of the current frequency is set according to the change range threshold.

5. An asynchronous motor braking device suitable for a rail vehicle traction system, characterized in that, include: The reference value determination module is used to determine the stator voltage reference value in the two-phase stationary coordinate system based on the stator current and speed of the asynchronous motor. The current frequency setting module is used to set a threshold value for the variation range of the stator current frequency of the asynchronous motor when the asynchronous motor transitions from regenerative braking to reverse braking. Specifically, when the stator current frequency is less than a positive set value, the stator current frequency value is forced to equal the positive set value; when the stator current frequency is less than a negative set value, the stator current frequency value is forced to equal the negative set value. The selection of the set value is determined based on actual debugging to ensure that the stator current frequency value does not frequently jump between positive and negative. The positive set value is one end of the variation range threshold value, and the negative set value is the other end of the variation range threshold value. An asynchronous motor braking module is used to perform braking operations on the asynchronous motor based on the stator voltage reference value and the variation range threshold. The reference value correction module is used to correct the stator voltage reference value based on the three-phase voltage error of the asynchronous motor stator; The asynchronous motor braking module includes: An asynchronous motor braking unit is used to brake the asynchronous motor according to the corrected stator voltage reference value and the change range threshold. Specifically, it sends pulses to the inverter according to the corrected two-phase voltage reference value to drive the asynchronous motor to operate normally. The inverter is connected to the asynchronous motor.

6. The asynchronous motor braking device as described in claim 5, characterized in that, The reference value determination module includes: The data acquisition unit is used to acquire the current and speed of the asynchronous motor. A reference value calculation unit is used to calculate the stator voltage reference value based on the current and speed.

7. The asynchronous motor braking device as described in claim 6, characterized in that, The reference value correction module includes: An ideal voltage calculation unit is used to calculate the ideal voltage of the asynchronous motor stator based on the current. An error calculation unit is used to calculate the three-phase voltage error based on the ideal voltage and the actual voltage of the asynchronous motor stator. The reference value correction unit is used to correct the stator voltage reference value based on the three-phase voltage error.

8. The asynchronous motor braking device as described in claim 7, characterized in that, The asynchronous motor braking unit includes: A pulse signal generation unit is used to generate a pulse signal based on the corrected stator voltage reference value; An asynchronous motor braking subunit is used to send the pulse signal to the inverter in the rail vehicle traction system to brake the asynchronous motor; and The current frequency forced setting unit is used to set the value of the current frequency according to the change range threshold when the asynchronous motor changes from regenerative braking to reverse braking and the current frequency is not less than the change range threshold.

9. A computer program product comprising a computer program / instructions, characterized in that, When the computer program / instructions are executed by the processor, they implement the steps of the asynchronous motor braking method for a rail vehicle traction system as described in any one of claims 1 to 4.

10. An electronic device comprising a memory, a processor, and a computer program stored in the memory and executable on the processor, characterized in that, When the processor executes the program, it implements the steps of the asynchronous motor braking method for a rail vehicle traction system as described in any one of claims 1 to 4.

11. A computer-readable storage medium having a computer program stored thereon, characterized in that, When executed by a processor, the computer program implements the steps of the asynchronous motor braking method for a rail vehicle traction system as described in any one of claims 1 to 4.

Images