CN107707158B - Frequency converter comprehensive braking system and working method thereof - Google Patents
Frequency converter comprehensive braking system and working method thereof Download PDFInfo
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- CN107707158B CN107707158B CN201711032510.7A CN201711032510A CN107707158B CN 107707158 B CN107707158 B CN 107707158B CN 201711032510 A CN201711032510 A CN 201711032510A CN 107707158 B CN107707158 B CN 107707158B
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02P—CONTROL OR REGULATION OF ELECTRIC MOTORS, ELECTRIC GENERATORS OR DYNAMO-ELECTRIC CONVERTERS; CONTROLLING TRANSFORMERS, REACTORS OR CHOKE COILS
- H02P3/00—Arrangements for stopping or slowing electric motors, generators, or dynamo-electric converters
- H02P3/06—Arrangements for stopping or slowing electric motors, generators, or dynamo-electric converters for stopping or slowing an individual dynamo-electric motor or dynamo-electric converter
- H02P3/18—Arrangements for stopping or slowing electric motors, generators, or dynamo-electric converters for stopping or slowing an individual dynamo-electric motor or dynamo-electric converter for stopping or slowing an ac motor
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02P—CONTROL OR REGULATION OF ELECTRIC MOTORS, ELECTRIC GENERATORS OR DYNAMO-ELECTRIC CONVERTERS; CONTROLLING TRANSFORMERS, REACTORS OR CHOKE COILS
- H02P25/00—Arrangements or methods for the control of AC motors characterised by the kind of AC motor or by structural details
- H02P25/02—Arrangements or methods for the control of AC motors characterised by the kind of AC motor or by structural details characterised by the kind of motor
- H02P25/022—Synchronous motors
- H02P25/024—Synchronous motors controlled by supply frequency
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02P—CONTROL OR REGULATION OF ELECTRIC MOTORS, ELECTRIC GENERATORS OR DYNAMO-ELECTRIC CONVERTERS; CONTROLLING TRANSFORMERS, REACTORS OR CHOKE COILS
- H02P27/00—Arrangements or methods for the control of AC motors characterised by the kind of supply voltage
- H02P27/04—Arrangements or methods for the control of AC motors characterised by the kind of supply voltage using variable-frequency supply voltage, e.g. inverter or converter supply voltage
- H02P27/06—Arrangements or methods for the control of AC motors characterised by the kind of supply voltage using variable-frequency supply voltage, e.g. inverter or converter supply voltage using dc to ac converters or inverters
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- Stopping Of Electric Motors (AREA)
Abstract
The invention relates to a frequency converter comprehensive braking system and a working method thereof, which are characterized in that: the frequency converter comprehensive braking system comprises a frequency converter and an alternating current braking unit, wherein the output end of the frequency converter is connected with the motor, and the alternating current braking unit is connected to the output end of the frequency converter; in the motor braking process, the alternating current braking unit and the frequency converter work cooperatively to generate braking torque simultaneously or in a time-sharing manner; the frequency converter comprehensive braking system has three working modes in the motor braking process: the frequency converter comprehensive braking system comprises an alternating current braking mode, a comprehensive braking mode and a frequency conversion braking mode, wherein when the frequency converter comprehensive braking system is in the alternating current braking mode, the alternating current braking unit generates braking torque, and the frequency converter does not generate braking torque; when the frequency converter comprehensive braking system is in a comprehensive braking mode, the alternating current braking unit and the frequency converter both generate braking torque; when the frequency converter comprehensive braking system is in a frequency conversion braking mode, the frequency converter generates braking torque, and the alternating current braking unit does not generate braking torque.
Description
Technical Field
The invention relates to a frequency converter braking system and a working method thereof, in particular to a frequency converter comprehensive braking system and a working method thereof, which are applied to the field of motor frequency conversion driving.
Background
When adopting converter driving motor, if the motor needs quick braking, the scheme that currently commonly uses has two kinds: scheme 1 adopts a frequency converter to realize rapid braking, for example, chopping braking is added on a direct current side of the frequency converter or active front end rectification is adopted; scheme 2 connects ac switch and resistance at the motor end, is usually used for the braking of synchronous machine, closes ac switch when the motor brakes, puts into the resistance, the motor is in the power generation state, realizes the braking through the energy consumption of resistance, when the motor is the excitation synchronous machine, still can realize quick braking through the power that the control motor end voltage thereby control ac resistance absorbs. These two solutions each have advantages and disadvantages: the scheme 1 can realize constant power braking in the whole speed reduction process, and can still provide enough braking torque when the motor speed is low, but if the scheme 1 adopts active front end rectification, the system is complex and the cost is high; if direct current chopping braking is adopted, energy consumption is large, in addition, when the frequency converter does not have a concentrated direct current bus, for example, a frequency converter with unit series connection multi-level topology needs to be added with direct current chopping braking on each power unit, and in the application occasion of high-power braking, the structure of the power unit is complex, and the practicability is not high. The scheme 2 adopts concentrated alternating current resistance braking, does not need additional devices of a frequency converter, has a simple system structure, is suitable for all frequency converter topologies, but the braking torque of the scheme 2 is directly related to the terminal voltage of the motor, the terminal voltage of the motor is related to the rotating speed of the motor, and when the rotating speed of the motor is lower, the sufficient braking torque cannot be provided, and the speed reduction time is difficult to guarantee.
Disclosure of Invention
The invention aims to overcome the problems in the prior art and discloses a frequency converter comprehensive braking system and a working method thereof.
The invention is realized by the following steps: a working method of a frequency converter comprehensive braking system is characterized by comprising the following steps: the frequency converter comprehensive braking system comprises a frequency converter and an alternating current braking unit, wherein the output end of the frequency converter is connected with a motor, the alternating current braking unit is connected to the output end of the frequency converter, and the frequency converter is a three-phase voltage source type frequency converter and comprises a rectifying unit, a direct current component unit and an inversion unit which are sequentially connected; the alternating current brake unit comprises an alternating current switch and an alternating current brake resistor which are connected, the alternating current switch and the alternating current brake resistor are both three phases, the alternating current switch is connected with the alternating current brake resistor in series and then connected to the output end of the frequency converter, when the alternating current brake unit operates, the alternating current switch is closed, and when the alternating current switch is open, the alternating current brake unit does not operate; in the motor braking process, the alternating current braking unit and the frequency converter work cooperatively to generate braking torque simultaneously or in a time-sharing manner; the frequency converter comprehensive braking system has three working modes in the motor braking process: an alternating current braking mode, a comprehensive braking mode and a variable frequency braking mode; when the frequency converter comprehensive braking system is in an alternating current braking mode, the alternating current braking unit generates braking torque, an alternating current switch of the alternating current braking unit is closed, and the frequency converter does not generate braking torque; when the frequency converter comprehensive braking system is in a comprehensive braking mode, the alternating current braking unit and the frequency converter are both in a running state and generate braking torque, and an alternating current switch of the alternating current braking unit is closed; when the frequency converter comprehensive braking system is in a frequency conversion braking mode, the frequency converter is in a running state and generates braking torque, an alternating current switch of the alternating current braking unit is disconnected, and the alternating current braking unit does not run and does not generate braking torque.
When the frequency converter comprehensive braking system is in a comprehensive braking mode, an alternating current switch of the alternating current braking unit is closed, the frequency converter generates braking torque, and the frequency converter controls the alternating current braking unit to generate braking torque by controlling the terminal voltage of the motor.
When the frequency converter comprehensive braking system is in an alternating current braking mode, an alternating current switch of the alternating current braking unit is closed, the frequency converter controls the voltage of a motor terminal by controlling the exciting current of the motor, so that the alternating current braking unit is controlled to generate braking torque, the frequency converter does not generate driving torque or controls the torque current of the motor to generate driving torque at the same time, the frequency converter does not generate braking torque, the driving torque generated by the frequency converter is smaller than the braking torque generated by the alternating current braking unit, and the frequency converter comprehensive braking system outputs the braking torque.
The frequency converter comprehensive braking system at least comprises a comprehensive braking mode in the motor braking process or only comprises an alternating current braking mode and a frequency conversion braking mode in the motor braking process.
In the motor braking process, when the rotating speed of the motor is greater than a rotating speed threshold value n1, the frequency converter comprehensive braking system operates in an alternating current braking mode; when the rotating speed of the motor is less than a rotating speed threshold value n2, the frequency converter comprehensive braking system operates in a frequency conversion braking mode; when the motor rotating speed is between a rotating speed threshold value n1 and a rotating speed threshold value n2, the frequency converter comprehensive braking system operates in a comprehensive braking mode; the rotation speed threshold n1 is greater than or equal to the rotation speed threshold n 2.
In the simple application of the frequency converter comprehensive braking system, the rotation speed of the motor does not need to be judged, and the frequency converter comprehensive braking system always operates in a comprehensive braking mode in the braking process of the motor.
And according to different configurations of the rectifying unit and the direct current assembly unit, the frequency converter realizes the braking function of the frequency converter in different modes.
(1) The rectification unit of the frequency converter adopts a diode rectification unit, the direct current component unit comprises a direct current energy storage capacitor, a direct current brake resistor and a direct current switch, the direct current switch is connected with the direct current energy storage capacitor in parallel after being connected with the direct current brake resistor in series, and the direct current switch is an electronic switch or a mechanical switch; the frequency converter comprehensive braking system has three working modes in the motor braking process: the frequency converter comprehensive braking system comprises an alternating current braking mode, a comprehensive braking mode and a frequency conversion braking mode, when the frequency converter comprehensive braking system is in the frequency conversion braking mode and the comprehensive braking mode, the frequency converter outputs current to enable the output end of the frequency converter to absorb energy, the direct current bus voltage of the frequency converter is greater than the rectification voltage, a diode of a rectification unit is in a cut-off state, a direct current switch is always closed or periodically closed, kinetic energy of a motor is converted into heat energy of a direct current braking resistor and is dissipated, and the frequency converter generates braking torque.
(2) The rectification unit of the frequency converter adopts an active front end rectification unit, and the direct current component unit comprises a direct current energy storage capacitor; the frequency converter comprehensive braking system has three working modes in the motor braking process: the frequency converter comprehensive braking system comprises an alternating current braking mode, a comprehensive braking mode and a frequency conversion braking mode, when the frequency converter comprehensive braking system is in the frequency conversion braking mode and the comprehensive braking mode, the frequency converter outputs current to enable the output end of the frequency converter to absorb energy, the direct current bus voltage of the frequency converter is larger than the rectified voltage, the active front end rectifying unit is in an energy feedback mode to convert motor kinetic energy into electric energy to be fed back to a power grid, and the frequency converter generates braking torque.
(3) The rectifying unit of the frequency converter adopts a diode rectifying unit, and the direct current component unit comprises a direct current energy storage capacitor; the frequency converter comprehensive braking system has three different conditions in the braking process of the motor, which are respectively as follows:
the first method comprises the following steps: the frequency converter comprehensive braking system has three working modes in the motor braking process: when the frequency converter comprehensive braking system is in the frequency conversion braking mode and the comprehensive braking mode, the output current of the frequency converter enables the output end of the frequency converter to absorb energy, the energy absorbed by the output end of the frequency converter is balanced with the loss of the frequency converter, the voltage of a direct current bus of the frequency converter is stable, a diode is enabled to be in a cut-off state, and meanwhile, overvoltage of the direct current bus cannot be caused.
And the second method comprises the following steps: the frequency converter comprehensive braking system has three working modes in the motor braking process: the frequency converter comprehensive braking system comprises an alternating current braking mode, a comprehensive braking mode and a variable frequency braking mode, wherein when the frequency converter comprehensive braking system is in the variable frequency braking mode and the comprehensive braking mode, an inverter unit of the frequency converter outputs high-frequency alternating current voltage, and the frequency converter controls a motor to generate slip so as to generate braking torque.
And the third is that: the frequency converter comprehensive braking system has two working modes in the motor braking process: the frequency converter comprehensive braking system comprises an alternating current braking mode and a variable frequency braking mode, wherein when the frequency converter comprehensive braking system is in the variable frequency braking mode, an alternating current switch of an alternating current braking unit is disconnected, an inversion unit of the frequency converter outputs direct current voltage, and the frequency converter controls a motor to generate slip so as to generate braking torque.
The utility model provides a braking system is synthesized to converter which characterized in that: the frequency converter comprehensive braking system comprises a frequency converter and an alternating current braking unit, wherein the output end of the frequency converter is connected with a motor, the alternating current braking unit is connected to the output end of the frequency converter, the motor is an asynchronous motor or a synchronous motor, the synchronous motor comprises a permanent magnet synchronous motor and an excitation synchronous motor, and the motor is a single-winding motor or a double-winding motor; the frequency converter is a three-phase voltage source type frequency converter and comprises a rectifying unit, a direct current component unit and an inverter unit which are sequentially connected, wherein the rectifying unit is a diode rectifying unit or an active front end rectifying unit and is used for converting alternating voltage of a power grid into direct voltage; the direct current component unit comprises a direct current energy storage capacitor, a direct current brake resistor and a direct current switch, the direct current switch is connected with the direct current energy storage capacitor in parallel after being connected with the direct current brake resistor in series, and the direct current switch is an electronic switch or a mechanical switch; the inverter unit is used for converting the direct-current voltage into alternating-current voltage with variable frequency and amplitude, and the output end of the inverter unit is respectively connected with the motor and the alternating-current brake unit; the alternating current brake unit comprises an alternating current switch and an alternating current brake resistor which are connected, the alternating current switch and the alternating current brake resistor are three phases, the alternating current switch and the alternating current brake resistor are connected in series and then connected to the output end of the frequency converter, and the alternating current switch is a contactor or a circuit breaker.
When the motor is a double-winding motor, each set of winding of the double-winding motor is respectively connected with one set of frequency converter comprehensive braking system, each set of frequency converter comprehensive braking system comprises a frequency converter and an alternating current braking unit, the output ends of the two frequency converters are respectively connected with the double-winding motor, and the two alternating current braking units are respectively connected to the output ends of the respective corresponding frequency converters.
The invention has the beneficial effects that:
1) the invention combines the traditional two frequency converter driving motor braking modes, can provide enough braking torque in the whole braking process by configuring proper alternating current braking resistor and frequency converter, ensures the speed reduction time, can realize constant power braking in the whole speed reduction process, and can still provide enough braking torque when the motor speed is lower.
2) The invention can be suitable for all frequency converter topologies, is particularly suitable for application occasions where the frequency converter does not have a concentrated direct current bus and needs high-power braking, and is suitable for asynchronous motors and synchronous motors.
Drawings
FIG. 1 is a block diagram of the present invention.
Fig. 2 is a schematic block diagram of a motor using double windings according to the present invention.
Fig. 3 is a schematic block diagram of the frequency converter of the present invention.
Fig. 4 is a block structural schematic diagram of the alternating current brake unit of the invention.
Fig. 5 is a schematic block diagram of a first embodiment of a rectifying unit and a dc component unit of the frequency converter of the present invention.
Fig. 6 is a schematic block diagram of a second embodiment of the rectifying unit and the dc component unit of the frequency converter of the present invention.
Fig. 7 is a schematic block diagram of a third embodiment of a rectifying unit and a dc component unit of the frequency converter of the present invention.
In the figure: 1. a frequency converter; 11. A rectifying unit; 12. A direct current component unit; 121. A direct current energy storage capacitor; 122. A DC switch; 123. A direct current brake resistor; 13. An inversion unit;
2. an alternating current braking unit; 21. An AC switch; 22. An alternating current brake resistor;
3. an electric motor.
Detailed Description
According to the attached figures 1-4, the frequency converter comprehensive braking system comprises a frequency converter 1 and an alternating current braking unit 2, wherein the output end of the frequency converter 1 is connected with a motor 3, the alternating current braking unit 2 is connected to the output end of the frequency converter 1, the motor 3 is an asynchronous motor or a synchronous motor, the synchronous motor comprises a permanent magnet synchronous motor and an excitation synchronous motor, and the motor 3 is a single-winding motor or a double-winding motor; the frequency converter 1 is a three-phase voltage source type frequency converter and comprises a rectifying unit 11, a direct current component unit 12 and an inverting unit 13 which are connected in sequence; the ac brake unit 2 includes an ac switch 21 and an ac brake resistor 22 connected to each other.
When the motor 3 is a double-winding motor, each set of winding of the double-winding motor is respectively connected with one set of frequency converter comprehensive braking system, each set of frequency converter comprehensive braking system comprises a frequency converter 1 and an alternating current braking unit 2, the output ends of the two frequency converters are respectively connected with the double-winding motor, and the two alternating current braking units are respectively connected to the output ends of the respective corresponding frequency converters.
The alternating current switch 21 and the alternating current brake resistor 22 are both three phases, the alternating current switch 21 and the alternating current brake resistor 22 are connected in series and then connected to the output end of the frequency converter 1, the alternating current switch 21 is a contactor, a circuit breaker or other electronic switches, and the alternating current brake resistor 22 can be provided with overload, overheat or other protection according to needs; when the alternating current brake unit 2 is operated, the alternating current switch 21 is closed, and when the alternating current switch 21 is opened, the alternating current brake unit 2 is not operated.
The rectifying unit 11 is a diode rectifying unit or an active front end rectifying unit, and the rectifying unit 11 is used for converting the alternating-current voltage of the power grid into direct-current voltage; the dc component unit 12 includes a dc energy storage capacitor 121, a dc braking resistor 123, and a dc switch 122, the dc switch 122 is connected in series with the dc braking resistor 123 and then connected in parallel with the dc energy storage capacitor 121, and the dc switch 122 is an electronic switch or a mechanical switch; the inverter unit 13 is used for converting the direct-current voltage into alternating-current voltage with variable frequency and amplitude, and the output end of the inverter unit 13 is respectively connected with the motor 3 and the alternating-current brake unit 2.
The rectifying unit 11 forms a controllable, semi-controllable or uncontrollable rectifying circuit through diodes or other power electronic devices such as IGBTs, IGCTs, IEGTs, SCRs, etc.
The working method of the frequency converter comprehensive braking system comprises the following steps: in the motor braking process, the alternating current braking unit 2 and the frequency converter 1 work cooperatively to generate braking torque simultaneously or in a time-sharing manner; the frequency converter comprehensive braking system has three working modes in the motor braking process: an alternating current braking mode, a comprehensive braking mode and a variable frequency braking mode; when the frequency converter comprehensive braking system is in an alternating current braking mode, the alternating current braking unit 2 generates braking torque, an alternating current switch 21 of the alternating current braking unit 2 is closed, and the frequency converter 1 does not generate braking torque; when the frequency converter comprehensive braking system is in a comprehensive braking mode, the alternating current braking unit 2 and the frequency converter 1 are both in a running state and generate braking torque, and the alternating current switch 21 of the alternating current braking unit 2 is closed; when the frequency converter comprehensive braking system is in a frequency conversion braking mode, the frequency converter 1 is in a running state and generates braking torque, the alternating current switch 21 of the alternating current braking unit 2 is disconnected, and the alternating current braking unit 2 does not run and does not generate braking torque.
When the comprehensive braking system of the frequency converter is in a comprehensive braking mode, the alternating current switch 21 of the alternating current braking unit 2 is closed, the alternating current braking unit 2 and the frequency converter 1 are both in a running state, the control model of the frequency converter 1 is a model formed by connecting the motor 3 and the alternating current braking unit 2 in parallel, the frequency converter 1 generates braking torque, and the frequency converter 1 controls the terminal voltage of the motor 3 to control the alternating current braking unit 2 to also generate braking torque.
When the frequency converter comprehensive braking system is in an alternating current braking mode, an alternating current switch 21 of the alternating current braking unit 2 is closed, and when the motor 3 is an asynchronous motor, the frequency converter 1 controls the terminal voltage of the motor 3 by controlling the stator exciting current of the motor 3, so that the alternating current braking unit 2 is controlled to generate braking torque; when the motor 3 is an excitation synchronous motor, the frequency converter 1 controls the terminal voltage of the motor 3 through the rotor excitation current of the excitation cabinet control motor 3, so as to control the alternating current brake unit 2 to generate brake torque, the frequency converter 1 does not generate drive torque or the frequency converter 1 simultaneously controls the motor torque current to generate drive torque, the frequency converter 1 does not generate brake torque, the drive torque generated by the frequency converter 1 is smaller than the brake torque generated by the alternating current brake unit 2, and the frequency converter comprehensive brake system outputs the brake torque.
The frequency converter comprehensive braking system at least comprises a comprehensive braking mode in the motor braking process or only comprises an alternating current braking mode and a frequency conversion braking mode in the motor braking process.
In the motor braking process, when the rotating speed of the motor is greater than a rotating speed threshold value n1, the frequency converter comprehensive braking system operates in an alternating current braking mode; when the rotating speed of the motor is less than a rotating speed threshold value n2, the frequency converter comprehensive braking system operates in a frequency conversion braking mode; when the motor rotating speed is between a rotating speed threshold value n1 and a rotating speed threshold value n2, the frequency converter comprehensive braking system operates in a comprehensive braking mode; the rotation speed threshold n1 is greater than or equal to the rotation speed threshold n 2.
In the simple application of the frequency converter comprehensive braking system, the rotation speed of the motor does not need to be judged, and the frequency converter comprehensive braking system always operates in a comprehensive braking mode in the braking process of the motor.
According to different configurations of the rectifying unit 11 and the direct current component unit 12, the frequency converter 1 realizes the frequency converter braking function in different modes.
The invention is further illustrated by the following specific examples:
the first embodiment is as follows:
according to fig. 5, the rectifying unit 11 of the frequency converter 1 of the present invention adopts a diode rectifying unit, the diode rectifying unit includes 6 diodes, the dc component unit 12 includes a dc energy storage capacitor 121, a dc braking resistor 123, and a dc switch 122, the dc switch 122 is connected in series with the dc braking resistor 123 and then connected in parallel with the dc energy storage capacitor 121, and the dc switch 122 is an electronic switch or a mechanical switch; the frequency converter comprehensive braking system has three working modes in the motor braking process: the frequency converter comprehensive braking system comprises an alternating current braking mode, a comprehensive braking mode and a frequency conversion braking mode, when the frequency converter comprehensive braking system is in the frequency conversion braking mode and the comprehensive braking mode, the frequency converter 1 outputs current to enable the output end of the frequency converter 1 to absorb energy, the direct current bus voltage of the frequency converter 1 is larger than the rectification voltage, the diode of the rectification unit 11 is in a cut-off state, the direct current switch 122 is always closed or periodically closed to convert the motor kinetic energy into the heat energy of a direct current braking resistor 123 and dissipate the heat energy, and the frequency converter 1 generates braking torque.
Example two:
according to fig. 6, the rectifying unit 11 of the frequency converter 1 of the present invention adopts an active front-end rectifying unit, the active front-end rectifying unit includes 6 IGBTs, and the dc component unit 12 includes a dc energy storage capacitor 121; the frequency converter comprehensive braking system has three working modes in the motor braking process: the frequency converter comprehensive braking system comprises an alternating current braking mode, a comprehensive braking mode and a variable frequency braking mode, when the frequency converter comprehensive braking system is in the variable frequency braking mode and the comprehensive braking mode, the frequency converter 1 outputs current to enable the output end of the frequency converter 1 to absorb energy, the direct current bus voltage of the frequency converter 1 is larger than the rectification voltage, the active front end rectification unit is in an energy feedback mode to convert motor kinetic energy into electric energy to be fed back to a power grid, and the frequency converter 1 generates braking torque.
Example three:
referring to fig. 7, the rectifying unit 11 of the frequency converter 1 of the present invention is a diode rectifying unit, the diode rectifying unit includes 6 diodes, and the dc component unit 12 includes a dc energy storage capacitor 121.
The frequency converter comprehensive braking system has three different conditions in the braking process of the motor, which are respectively as follows:
the first method comprises the following steps: the frequency converter comprehensive braking system has three working modes in the motor braking process: when the frequency converter comprehensive braking system is in the frequency conversion braking mode and the comprehensive braking mode, the output current of the frequency converter 1 enables the output end of the frequency converter 1 to absorb energy, the energy absorbed by the output end of the frequency converter 1 is balanced with the loss of the frequency converter 1, the voltage of a direct current bus of the frequency converter 1 is stable, a diode is in a cut-off state, and meanwhile, overvoltage of the direct current bus cannot be caused.
And the second method comprises the following steps: the frequency converter comprehensive braking system has three working modes in the motor braking process: the frequency converter comprehensive braking system comprises an alternating current braking mode, a comprehensive braking mode and a variable frequency braking mode, wherein when the frequency converter comprehensive braking system is in the variable frequency braking mode and the comprehensive braking mode, an inverter unit 13 of a frequency converter 1 outputs high-frequency alternating current voltage, and the frequency converter 1 controls a motor 3 to generate slip so as to generate braking torque.
And the third is that: the frequency converter comprehensive braking system has two working modes in the motor braking process: the frequency converter comprehensive braking system comprises an alternating current braking mode and a frequency conversion braking mode, wherein when the frequency converter comprehensive braking system is in the frequency conversion braking mode, an alternating current switch 21 of an alternating current braking unit 2 is switched off, an inverter unit 13 of a frequency converter 1 outputs direct current voltage, and the frequency converter 1 controls a motor 3 to generate slip so as to generate braking torque.
The foregoing detailed description is only preferred embodiments of the present invention for the purpose of illustrating it in detail, and is not to be construed as limiting the present invention, and it will be apparent to those skilled in the art that various equivalent modifications, variations and substitutions can be made in the detailed description of the present invention, which are within the scope of the present invention. The scope of the invention is defined by the description of the claims.
Claims (11)
1. A working method of a frequency converter comprehensive braking system is characterized by comprising the following steps: the frequency converter comprehensive braking system comprises a frequency converter and an alternating current braking unit, wherein the output end of the frequency converter is connected with a motor, the alternating current braking unit is connected to the output end of the frequency converter, and the frequency converter is a three-phase voltage source type frequency converter and comprises a rectifying unit, a direct current component unit and an inversion unit which are sequentially connected; the alternating current brake unit comprises an alternating current switch and an alternating current brake resistor which are connected, the alternating current switch and the alternating current brake resistor are both three phases, the alternating current switch is connected with the alternating current brake resistor in series and then connected to the output end of the frequency converter, when the alternating current brake unit operates, the alternating current switch is closed, and when the alternating current switch is open, the alternating current brake unit does not operate; in the motor braking process, the alternating current braking unit and the frequency converter work cooperatively to generate braking torque simultaneously or in a time-sharing manner; the frequency converter comprehensive braking system has three working modes in the motor braking process: the frequency converter comprehensive braking system at least comprises a comprehensive braking mode in the motor braking process; when the frequency converter comprehensive braking system is in an alternating current braking mode, the alternating current braking unit generates braking torque, an alternating current switch of the alternating current braking unit is closed, and the frequency converter does not generate braking torque; when the frequency converter comprehensive braking system is in a comprehensive braking mode, the alternating current braking unit and the frequency converter are both in a running state and generate braking torque, and an alternating current switch of the alternating current braking unit is closed; when the frequency converter comprehensive braking system is in a frequency conversion braking mode, the frequency converter is in an operating state and generates braking torque, an alternating current switch of the alternating current braking unit is disconnected, the alternating current braking unit does not operate and does not generate braking torque, in the motor braking process, when the rotating speed of the motor is greater than a rotating speed threshold value n1, the frequency converter comprehensive braking system operates in the alternating current braking mode, when the rotating speed of the motor is less than a rotating speed threshold value n2, the frequency converter comprehensive braking system operates in the frequency conversion braking mode, when the rotating speed of the motor is between a rotating speed threshold value n1 and a rotating speed threshold value n2, the frequency converter comprehensive braking system operates in the comprehensive braking mode, and the rotating speed threshold value n1 is greater than or equal to the rotating speed threshold value n 2.
2. The operating method of the frequency converter comprehensive brake system according to claim 1, characterized in that: when the frequency converter comprehensive braking system is in a comprehensive braking mode, an alternating current switch of the alternating current braking unit is closed, the frequency converter generates braking torque, and the frequency converter controls the alternating current braking unit to generate braking torque by controlling the terminal voltage of the motor.
3. The operating method of the frequency converter comprehensive brake system according to claim 1, characterized in that: when the frequency converter comprehensive braking system is in an alternating current braking mode, an alternating current switch of the alternating current braking unit is closed, the frequency converter controls the voltage of a motor terminal by controlling the exciting current of the motor, so that the alternating current braking unit is controlled to generate braking torque, the frequency converter does not generate driving torque or controls the torque current of the motor to generate driving torque at the same time, the frequency converter does not generate braking torque, the driving torque generated by the frequency converter is smaller than the braking torque generated by the alternating current braking unit, and the frequency converter comprehensive braking system outputs the braking torque.
4. The operating method of the frequency converter comprehensive brake system according to claim 1, characterized in that: in the simple application of the frequency converter comprehensive braking system, the rotating speed of the motor does not need to be judged, and the frequency converter comprehensive braking system always operates in a comprehensive braking mode in the braking process of the motor.
5. The operating method of the frequency converter comprehensive brake system according to claim 1, characterized in that: the rectification unit of the frequency converter adopts a diode rectification unit, the direct current component unit comprises a direct current energy storage capacitor, a direct current brake resistor and a direct current switch, the direct current switch is connected with the direct current energy storage capacitor in parallel after being connected with the direct current brake resistor in series, and the direct current switch is an electronic switch or a mechanical switch; the frequency converter comprehensive braking system has three working modes in the motor braking process: the frequency converter comprehensive braking system comprises an alternating current braking mode, a comprehensive braking mode and a frequency conversion braking mode, when the frequency converter comprehensive braking system is in the frequency conversion braking mode and the comprehensive braking mode, the frequency converter outputs current to enable the output end of the frequency converter to absorb energy, the direct current bus voltage of the frequency converter is greater than the rectification voltage, a diode of a rectification unit is in a cut-off state, a direct current switch is always closed or periodically closed, kinetic energy of a motor is converted into heat energy of a direct current braking resistor and is dissipated, and the frequency converter generates braking torque.
6. The operating method of the frequency converter comprehensive brake system according to claim 1, characterized in that: the rectification unit of the frequency converter adopts an active front end rectification unit, and the direct current component unit comprises a direct current energy storage capacitor; the frequency converter comprehensive braking system has three working modes in the motor braking process: the frequency converter comprehensive braking system comprises an alternating current braking mode, a comprehensive braking mode and a frequency conversion braking mode, when the frequency converter comprehensive braking system is in the frequency conversion braking mode and the comprehensive braking mode, the frequency converter outputs current to enable the output end of the frequency converter to absorb energy, the direct current bus voltage of the frequency converter is larger than the rectified voltage, the active front end rectifying unit is in an energy feedback mode to convert motor kinetic energy into electric energy to be fed back to a power grid, and the frequency converter generates braking torque.
7. The operating method of the frequency converter comprehensive brake system according to claim 1, characterized in that: the rectifying unit of the frequency converter adopts a diode rectifying unit, and the direct current component unit comprises a direct current energy storage capacitor; the frequency converter comprehensive braking system has three working modes in the motor braking process: when the frequency converter comprehensive braking system is in the frequency conversion braking mode and the comprehensive braking mode, the output current of the frequency converter enables the output end of the frequency converter to absorb energy, the energy absorbed by the output end of the frequency converter is balanced with the loss of the frequency converter, the voltage of a direct current bus of the frequency converter is stable, a diode is enabled to be in a cut-off state, and meanwhile, overvoltage of the direct current bus cannot be caused.
8. The operating method of the frequency converter comprehensive brake system according to claim 1, characterized in that: the rectifying unit of the frequency converter adopts a diode rectifying unit, and the direct current component unit comprises a direct current energy storage capacitor; the frequency converter comprehensive braking system has three working modes in the motor braking process: the frequency converter comprehensive braking system comprises an alternating current braking mode, a comprehensive braking mode and a variable frequency braking mode, wherein when the frequency converter comprehensive braking system is in the variable frequency braking mode and the comprehensive braking mode, an inverter unit of the frequency converter outputs high-frequency alternating current voltage, and the frequency converter controls a motor to generate slip so as to generate braking torque.
9. The operating method of the frequency converter comprehensive brake system according to claim 1, characterized in that: the rectifying unit of the frequency converter adopts a diode rectifying unit, and the direct current component unit comprises a direct current energy storage capacitor; the frequency converter comprehensive braking system has two working modes in the motor braking process: the frequency converter comprehensive braking system comprises an alternating current braking mode and a variable frequency braking mode, wherein when the frequency converter comprehensive braking system is in the variable frequency braking mode, an alternating current switch of an alternating current braking unit is disconnected, an inversion unit of the frequency converter outputs direct current voltage, and the frequency converter controls a motor to generate slip so as to generate braking torque.
10. A frequency converter comprehensive braking system applying the working method of the frequency converter comprehensive braking system according to any one of claims 1 to 9, characterized in that: the frequency converter comprehensive braking system comprises a frequency converter and an alternating current braking unit, wherein the output end of the frequency converter is connected with a motor, the alternating current braking unit is connected to the output end of the frequency converter, the motor is an asynchronous motor or a synchronous motor, and the motor is a single-winding motor or a double-winding motor; the frequency converter is a three-phase voltage source type frequency converter and comprises a rectifying unit, a direct current component unit and an inverter unit which are sequentially connected, wherein the rectifying unit is a diode rectifying unit or an active front end rectifying unit and is used for converting alternating voltage of a power grid into direct voltage; the direct current component unit comprises a direct current energy storage capacitor, a direct current brake resistor and a direct current switch, the direct current switch is connected with the direct current energy storage capacitor in parallel after being connected with the direct current brake resistor in series, and the direct current switch is an electronic switch or a mechanical switch; the inverter unit is used for converting the direct-current voltage into alternating-current voltage with variable frequency and amplitude, and the output end of the inverter unit is respectively connected with the motor and the alternating-current brake unit; the alternating current brake unit comprises an alternating current switch and an alternating current brake resistor which are connected, the alternating current switch and the alternating current brake resistor are three phases, the alternating current switch and the alternating current brake resistor are connected in series and then connected to the output end of the frequency converter, and the alternating current switch is a contactor or a circuit breaker.
11. The frequency converter comprehensive brake system according to claim 10, wherein: when the motor is a double-winding motor, each set of winding of the double-winding motor is respectively connected with one set of frequency converter comprehensive braking system, each set of frequency converter comprehensive braking system comprises a frequency converter and an alternating current braking unit, the output ends of the two frequency converters are respectively connected with the double-winding motor, and the two alternating current braking units are respectively connected to the output ends of the respective corresponding frequency converters.
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| CN108988736A (en) * | 2018-07-06 | 2018-12-11 | 珠海格力电器股份有限公司 | A kind of servo-system and its real-time control method of repid discharge |
| CN109687395A (en) * | 2018-11-27 | 2019-04-26 | 河海大学 | A kind of magnetic suspension motor power-off protection apparatus and method based on electric energy feedback |
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