CN107947645B - High-voltage frequency converter rapid braking system and control method - Google Patents
High-voltage frequency converter rapid braking system and control method Download PDFInfo
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- CN107947645B CN107947645B CN201711224465.5A CN201711224465A CN107947645B CN 107947645 B CN107947645 B CN 107947645B CN 201711224465 A CN201711224465 A CN 201711224465A CN 107947645 B CN107947645 B CN 107947645B
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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
- H02P3/22—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 by short-circuit or resistive braking
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Abstract
The invention provides a high-voltage frequency converter rapid braking system and a control method, wherein the high-voltage frequency converter comprises a phase-shifting transformation unit and a plurality of power units, the rapid braking system comprises a braking energy absorption unit and a braking control unit, and the braking energy absorption unit comprises: the braking energy absorption unit comprises a three-phase contactor and three braking resistors; the first ends of the three-phase contactors are respectively connected to three-phase output lines of a high-voltage frequency converter, and the three brake resistors are connected to the second ends of the three-phase contactors in a star or triangle connection mode; and the brake control unit controls the three-phase contactor to be closed according to the received quick brake signal and controls the three-phase contactor to be disconnected when the output frequency of the high-voltage frequency converter reaches the target frequency. According to the invention, the three braking resistors are connected to the three-phase output line of the high-voltage frequency converter, so that the energy generated by braking of the motor can be quickly absorbed without adding a braking module in the power unit, and the structure is simple and reliable.
Description
Technical Field
The invention relates to the field of high-voltage frequency converters, in particular to a high-voltage frequency converter rapid braking system and a control method.
Background
At present, high-voltage high-power motors are widely used in industrial fields, such as rolling mills for the steel industry, compressors for petrochemical production, feed pumps and induced draft fans for the power industry, and the like. The power unit cascade type high-voltage frequency converter is widely applied to the field of variable frequency speed regulation of high-voltage high-power motors due to high reliability and perfect output voltage waveform.
In induced draft fan applications in power plants, there is a FCB (FAST CUT BACK) requirement. The basic functions of FCB control are: when the unit operates under normal working conditions, if the generator is cracked, the FCB function of the unit is automatically put into operation, load is quickly removed, and stable operation is achieved with service power. In the process of load shedding of the unit, the change of the operation parameters of the unit can be ensured within a safety range, the shutdown and blowing protection action is not caused, and the equipment safety is not endangered, so that the grid connection power generation can be carried out quickly. Taking the induced draft fan as an example, when the induced draft fan is in normal production, the frequency is usually 45Hz, if the generator is cracked, the load needs to be quickly thrown, that is, the speed is quickly reduced, the target frequency is usually below 20Hz, and the whole braking time is generally within 30 s.
Generally, when the two-quadrant frequency converter is applied to a rapid braking occasion, if the frequency converter does not perform any treatment, the voltage of a power unit bus is increased due to the feedback of the generated energy of the motor, and overvoltage faults of the power unit bus are caused.
In order to avoid the above problems, the current main practice is to install a braking device inside the power unit to absorb the power generated by the motor. However, this solution requires a braking energy absorption device to be installed inside each power unit to absorb the power generated by the motor, thereby greatly increasing the complexity of the system, and greatly increasing the cost and volume. In addition, because of the high-voltage system, after the braking energy absorption device is additionally arranged in the power unit, the insulation and reliability of the system are also great problems.
There is also a method of injecting a high-frequency signal to the stator side of the motor to increase the internal resistance of the motor due to an internal skin effect, thereby consuming the generated energy of the motor in the motor winding, which is also called a superposition braking method. However, during the stacked frequency braking process, the heat generation of the motor is increased in proportion to the absorbed energy, and the noise of the motor is high during the braking process; the scheme is only suitable for short-time braking of the motor, and the temperature rise inside the motor winding needs to be monitored in real time, otherwise the motor winding is burnt out.
In addition, a four-quadrant frequency converter is used, and after the FCB brake signal is effective, energy generated by rapid braking of the induced draft fan is fed back to the power grid through the four-quadrant frequency converter. Although the scheme can well solve the problem of the rise of the bus voltage of the power unit, the power unit in the scheme adopts a back-to-back structure, and the number of power devices is doubled, thereby increasing the cost and complicating the system control.
Disclosure of Invention
The invention aims to solve the technical problems of complex control process and high cost when the motor is switched back quickly, and provides a novel high-voltage inverter quick braking system and a control method.
The technical scheme for solving the technical problems is to provide a high-voltage frequency converter rapid braking system, wherein the high-voltage frequency converter comprises a phase-shifting transformation unit and a plurality of power units, the input ends of the power units are respectively connected to a plurality of output ends on the secondary side of the phase-shifting transformation unit, and the output ends of the power units are connected in series in groups and then are connected to a three-phase output line of the high-voltage frequency converter; the rapid braking system comprises a braking energy absorption unit and a braking control unit, wherein: the braking energy absorption unit comprises a three-phase contactor and three braking resistors; the first ends of the three-phase contactors are respectively connected to three-phase output lines of the high-voltage frequency converter, and the three braking resistors are connected to the second ends of the three-phase contactors in a star or triangle connection mode; and the brake control unit controls the three-phase contactor to be closed according to the received quick brake signal and controls the three-phase contactor to be disconnected when the output frequency of the high-voltage frequency converter reaches the target frequency.
In the high-voltage frequency converter rapid braking system, the rapid braking system comprises a voltage detection unit, wherein the voltage detection unit is used for detecting the direct-current bus voltage of a power unit; and when the three-phase contactor is closed, the main control board of the high-voltage frequency converter adjusts the output voltage of each power unit according to the maximum value in the detected direct-current bus voltage so as to adjust the output torque.
In the high-voltage inverter rapid braking system, a main control board of the high-voltage inverter comprises a flux linkage regulator, a first current regulator, a speed regulator, a second current regulator and a direct-current bus voltage regulator;
when the three-phase contactor is disconnected, the flux linkage regulator generates an exciting current instruction according to stator flux linkage setting and a stator flux linkage feedback value, and the first current regulator generates a first output voltage instruction according to the exciting current instruction and the exciting current feedback value; the speed regulator generates a first torque current instruction according to a given speed and a feedback speed value, and the second current regulator generates a second output voltage instruction according to the first torque current instruction and the feedback torque current value; and the power unit control board of the high-voltage frequency converter controls the inversion operation of the power unit according to the first output voltage instruction and the second output voltage instruction.
In the high-voltage inverter rapid braking system, the main control board comprises a bus voltage regulator;
when the three-phase contactor is closed, the bus voltage regulator generates a second torque current instruction according to a given value of bus voltage and a difference value of maximum values in direct current bus voltages of all power units detected and obtained by the voltage detection unit, and generates a third output voltage instruction according to the second torque current instruction and a torque current feedback value by the second current regulator; and the power unit control board of the high-voltage frequency converter controls the inversion operation of the power unit according to the first output voltage instruction and the third output voltage instruction.
In the high-voltage inverter rapid braking system according to the present invention, the main control board makes the output torque T of the high-voltage inverter when the three-phase contactor is closedMComprises the following steps:
wherein U isNIs rated voltage of a motor connected with the high-voltage frequency converter, R is resistance value of a brake resistor, n is current rotating speed of the motor, and n iseIs the rated speed of the motor.
The invention also provides a high-voltage frequency converter rapid braking control method, wherein the high-voltage frequency converter comprises a phase-shifting transformation unit and a plurality of power units, the input ends of the power units are respectively connected to a plurality of output ends of the secondary side of the phase-shifting transformation unit, and the output ends of the power units are connected in series in groups and then are connected to a three-phase output line of the high-voltage frequency converter; the control method comprises the following steps:
controlling a three-phase contactor of a braking energy absorption unit to be closed according to a received quick braking signal, wherein in the braking energy absorption unit, a first end of the three-phase contactor is respectively connected to a three-phase output line of the high-voltage frequency converter, and a second end of the three-phase contactor is provided with three braking resistors connected in a star-shaped or triangular connection manner;
and when the output frequency of the high-voltage frequency converter reaches the target frequency, controlling the three-phase contactor to be disconnected.
In the method for controlling rapid braking of a high-voltage inverter, the method further comprises:
detecting the direct current bus voltage of each power unit, and obtaining the maximum value of the direct current bus voltages of the plurality of power units;
when the three-phase contactor is closed, the output voltage of each power unit is adjusted according to the maximum value in the direct-current bus voltage so as to adjust the output torque.
In the method for controlling the rapid braking of the high-voltage frequency converter, the control method comprises the following steps: when the three-phase contactor is opened,
generating an exciting current instruction according to a stator flux linkage given value and a stator flux linkage feedback value, and generating a first output voltage instruction according to the exciting current instruction and the exciting current feedback value;
generating a first torque current instruction according to the speed given value and the speed feedback value, and generating a second output voltage instruction according to the first torque current instruction and the torque current feedback value;
and controlling the inversion operation of the power unit according to the first output voltage instruction and the second output voltage instruction.
In the method for controlling the rapid braking of the high-voltage frequency converter, the control method comprises the following steps: when the three-phase contactor is closed,
generating a second torque current instruction according to the bus voltage given value and the difference value of the maximum value in the direct current bus voltages of the plurality of power units, and generating a third output voltage instruction according to the second torque current instruction and the torque current feedback value;
and controlling the inversion operation of the power unit according to the first output voltage instruction and the third output voltage instruction.
In the method for controlling the rapid braking of the high-voltage frequency converter, when the three-phase contactor is closed, the output torque T of the driving motor of the high-voltage frequency converterMComprises the following steps:
wherein U isNIs rated voltage of a motor connected with the high-voltage frequency converter, R is resistance value of a brake resistor, n is current rotating speed of the motor, and n iseIs the rated speed of the motor.
According to the high-voltage frequency converter rapid braking system and the control method, the three braking resistors are connected to the three-phase output line of the high-voltage frequency converter, energy generated by braking of the motor can be absorbed rapidly without adding a braking module in the power unit, and the structure is simple and reliable.
Drawings
FIG. 1 is a schematic diagram of an embodiment of a high voltage inverter quick braking system of the present invention;
FIG. 2 is a schematic diagram of an embodiment of a braking energy absorption unit in a fast braking system of a high-voltage inverter according to the invention;
FIG. 3 is a schematic diagram of another embodiment of a braking energy absorption unit in the fast braking system of the high-voltage inverter according to the invention;
FIG. 4 is a schematic diagram of a power unit control structure in the fast braking system of the high-voltage inverter according to the present invention;
FIG. 5 is a schematic diagram of the power unit control signal generation in the high-voltage inverter fast braking system according to the present invention;
FIG. 6 is a schematic diagram of a control signal in a fast braking state in a fast braking system of a high-voltage inverter according to the present invention;
fig. 7 is a schematic flow chart of an embodiment of a fast braking control method of a high-voltage inverter according to the invention.
Detailed Description
In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention is described in further detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.
As shown in fig. 1 and 2, the high-voltage inverter rapid braking system according to an embodiment of the present invention is schematically illustrated, and can be applied to a compressor for petrochemical production, a feed pump for power industry, and a high-voltage high-power three-phase asynchronous motor control of an induced draft fan, so as to realize rapid switch-back control of a high-voltage high-power motor. The high-voltage frequency converter for controlling the high-voltage high-power three-phase asynchronous motor comprises a phase-shifting transformation unit 1 and a plurality of power units 2, wherein the input ends of the power units 2 are respectively connected to a plurality of output ends on the secondary side of the phase-shifting transformation unit 1, the output ends of the power units 2 are divided into three groups, and the three groups of power units 2 are respectively connected to a three-phase output line (the three-phase output line is connected to a three-phase asynchronous motor 3) of the high-voltage frequency converter in series.
The high-voltage frequency converter rapid braking system comprises a braking energy absorption unit 4 and a braking control unit 5, wherein the braking energy absorption unit 4 comprises a three-phase contactor KM and three braking resistors R; the first end of the three-phase contactor KM is respectively connected to a three-phase output line of the high-voltage frequency converter, and the three braking resistors R are connected to the second end of the three-phase contactor KM in a star-shaped mode; the brake control unit 5 controls the three-phase contactor KM to be closed according to the received fast braking signal (which is generated when the generator is cracked and at which the output frequency of the high-voltage inverter is greater than a preset frequency), and controls the three-phase contactor to be opened when the output frequency of the high-voltage inverter reaches a target frequency. In particular, the brake control unit 5 may be integrated into the main control board 7 of the high voltage inverter shown in fig. 4, or may be independent of the main control board 7.
The motion equation of the high-voltage high-power three-phase asynchronous motor is as follows:
wherein, G is multiplied by D 24 × g × J, J is the moment of inertia, unit: kg.m 2, GxD2Flywheel torque (G represents the mass of the object in kg, D represents the diameter of the object in m); t isMFor electromagnetic torque, TfAt a rated rotation speed neThe load torque during the process, F is the friction coefficient, n is the current rotating speed, the unit: and rotating/minute.
Because the high-voltage high-power three-phase asynchronous motor has large inertia, the speed change rate is small during braking, and a long period of time is needed for braking. According to the motion equation (1), the braking capacity of the system is smaller and the system is harder to brake at low-speed braking. And because of the energy stored by the flywheel, the three-phase asynchronous motor can be in a power generation state during rapid deceleration braking, and for the two-quadrant frequency converter, the energy generated by rapid braking is enough to enable the high-voltage frequency converter to generate overvoltage faults.
The braking control unit 5 can access the three braking resistors R after the FCB emergency state signal is effective, so that the high-voltage frequency converter enters an energy consumption braking mode, the energy stored in the flywheel is rapidly consumed through the energy consumption braking of the braking resistors R, and the effect of rapid braking is achieved.
In particular, as shown in fig. 3, the braking resistor R in the braking energy absorption unit 4 may be connected to the second end of the three-phase contactor KM in a delta connection manner, in addition to the star connection manner. In addition, a current sensor 41 and an isolation switch QS can be added to the braking energy absorption unit 4, so that the three-phase contactor KM can be prevented from being touched by mistake on one hand, and the current in the braking resistor R can be detected on the other hand, so that the braking resistor R can be prevented from being burnt due to overlarge current.
In order to further improve the braking effect, the inherent maximum braking capability of the high-voltage frequency converter can be utilized, namely, the control system of the high-voltage frequency converter is switched from the normal driving mode to the energy consumption braking mode, and the current with the maximum braking torque is output by the power unit 2 through the maximum bus voltage regulation. Specifically, a voltage detection unit 6 may be added, as shown in fig. 4, the voltage detection unit 6 being connected between the rectifier 21 and the inverter 22 of the power unit 2 and used to detect the dc bus voltage of the power unit 2. Specifically, one voltage detection unit 6 may be provided for each power unit 2 to detect the dc bus voltage of each power unit, only one voltage detection unit 6 may be provided and the voltage detection unit 6 may detect the dc bus voltages of all the power units 2, and the voltage detection unit 6 may be integrated into the power unit control board 8.
Each power unit control board 8 transmits the dc bus voltage of all the power units 2 detected by the voltage detection unit 6 to the main control board 8, and the main control board 8 selects the maximum value of the dc bus voltage to adjust the output voltage of each power unit 2 (different switch tube driving signals are output by each power unit control board 8) so as to maximize the braking torque output by the high-voltage inverter.
As shown in fig. 5, the main control board 7 may include a flux linkage adjuster 71, a first current adjuster 72, a speed adjuster 73, and a second current adjuster 74, and stator flux linkage closed-loop vector control and speed closed-loop control are performed by the flux linkage adjuster 71, the first current adjuster 72, the speed adjuster 73, and the second current adjuster 74.
Specifically, when the three-phase contactor KM is turned off (i.e., when the three-phase asynchronous motor operates normally), the flux linkage regulator 71 generates an excitation current command according to a stator flux linkage setting and a stator flux linkage feedback value, and the first current regulator 72 generates a first output voltage command according to the excitation current command and the excitation current feedback value; the speed regulator 73 generates a first torque current command according to the speed setting and the speed feedback value, and the second current regulator 74 generates a second output voltage command according to the first torque current command and the torque current feedback value; each power unit control board 8 controls the inverter operation of each power unit 2 according to the above-described first output voltage command and second output voltage command.
As shown in fig. 6, in order for the main control board 7 to output the maximum braking torque, a bus voltage regulator 75 may be added to the main control board 7.
When the three-phase contactor is closed (at this time, the three-phase asynchronous motor is in a rapid braking state), the bus voltage regulator 75 generates a second torque current command according to a difference value between a given bus voltage value (which is generally a safer bus voltage value and generally takes a 90% bus overvoltage detection point voltage value) and a maximum value of the dc bus voltage, and generates a third output voltage command according to the second torque current command and a torque current feedback value by the second current regulator 74; each power unit control board 8 controls the inverter operation of the power unit 2 according to the first output voltage command and the third output voltage command.
In particular, the maximum braking voltage T of the high-voltage frequency converter can be obtained by deducting according to the motion equation (1) of the high-voltage high-power three-phase asynchronous motorM：
Wherein U isNIs rated voltage of a motor connected with the high-voltage frequency converter, R is resistance value of a brake resistor, n is current rotating speed of the motor, and n iseIs the rated speed of the motor. That is, after the three-phase contactor is closed, the main control board makes the output torque of the high-voltage frequency converter be T in the formula (2)M。
As shown in fig. 7, the present invention further provides a high voltage inverter rapid braking control method, and the high voltage inverter for driving the three-phase asynchronous motor to operate includes a phase-shifting transformation unit and a plurality of power units, wherein input ends of the plurality of power units are respectively connected to a plurality of output ends of a secondary side of the phase-shifting transformation unit, and output ends of the plurality of power units are connected in series in groups and then connected to a three-phase output line of the high voltage inverter. The control method comprises the following steps:
step S71: and controlling the three-phase contactor of the braking energy absorption unit to be closed according to the received quick braking signal (and the output frequency of the high-voltage frequency converter is greater than a preset value, such as 45Hz), wherein in the braking energy absorption unit, the first ends of the three-phase contactors are respectively connected to the three-phase output lines of the high-voltage frequency converter, and the second ends of the three-phase contactors are provided with three braking resistors connected in a star-shaped or triangular connection manner.
In order to improve the rapid braking effect, the steps can further comprise: detecting the direct current bus voltage of each power unit, and obtaining the maximum value of the direct current bus voltages of the plurality of power units; and adjusting the output voltage of each power unit according to the maximum value in the DC bus voltage so as to realize the output torque adjustment of the high-voltage frequency converter.
Step S72: it is determined whether the output frequency of the high voltage inverter reaches a target frequency (e.g., 30Hz) and step S74 is performed when the output frequency of the high voltage inverter reaches the target frequency, otherwise step S73 is performed.
Step S73: the three-phase contactor is kept closed and the process returns to step S72.
This step may also include: detecting the direct current bus voltage of each power unit, and obtaining the maximum value of the direct current bus voltages of the plurality of power units; and adjusting the output voltage of each power unit according to the maximum value in the direct current bus voltage.
Step S74: and controlling the three-phase contactor to be disconnected, and operating the high-voltage frequency converter in a normal working mode. At the moment, the high-voltage frequency converter generates an exciting current instruction according to the stator flux linkage given value and the stator flux linkage feedback value, and generates a first output voltage instruction according to the exciting current instruction and the exciting current feedback value; generating a first torque current instruction according to the speed given value and the speed feedback value, and generating a second output voltage instruction according to the first torque current instruction and the torque current feedback value; meanwhile, the high-voltage frequency converter controls the inversion operation of the power unit according to the first output voltage instruction and the second output voltage instruction.
In the above steps S71 and S73, the high-voltage inverter generates a second torque current command according to the bus voltage set value and the difference value between the maximum values of the dc bus voltage, and generates a third output voltage command according to the second torque current command and the torque current feedback value; and simultaneously controlling the inversion operation of the power unit according to the first output voltage instruction and the third output voltage instruction.
Specifically, in the above steps S71 and S73, the output torque T of the high voltage inverter driving motorMComprises the following steps:
wherein U isNIs rated voltage of a motor connected with the high-voltage frequency converter, R is resistance value of a brake resistor, n is current rotating speed of the motor, and n iseIs the rated speed of the motor.
The above description is only for the preferred embodiment of the present invention, but the scope of the present invention is not limited thereto, and any changes or substitutions that can be easily conceived by those skilled in the art within the technical scope of the present invention are included in the scope of the present invention. Therefore, the protection scope of the present invention shall be subject to the protection scope of the claims.
Claims (6)
1. A high-voltage frequency converter rapid braking system comprises a phase-shifting transformation unit and a plurality of power units, wherein the input ends of the power units are respectively connected to a plurality of output ends of the secondary side of the phase-shifting transformation unit, and the output ends of the power units are connected in series in groups and then connected to a three-phase output line of the high-voltage frequency converter; the quick braking system is characterized by comprising a braking energy absorption unit and a braking control unit, wherein: the braking energy absorption unit comprises a three-phase contactor and three braking resistors; the first ends of the three-phase contactors are respectively connected to three-phase output lines of the high-voltage frequency converter, and the three braking resistors are connected to the second ends of the three-phase contactors in a star or triangle connection mode; the brake control unit controls the three-phase contactor to be closed according to the received rapid brake signal and controls the three-phase contactor to be opened when the output frequency of the high-voltage frequency converter reaches a target frequency;
the rapid braking system comprises a voltage detection unit, wherein the voltage detection unit is used for detecting the direct-current bus voltage of the power unit; when the three-phase contactor is closed, a main control board of the high-voltage frequency converter adjusts the output voltage of each power unit according to the maximum value in the detected direct-current bus voltage so as to adjust the output torque;
the main control board of the high-voltage frequency converter comprises a flux linkage regulator, a first current regulator and a second current regulator, wherein the flux linkage regulator is used for generating an exciting current instruction according to stator flux linkage setting and a stator flux linkage feedback value, and the first current regulator generates a first output voltage instruction according to the exciting current instruction and the exciting current feedback value; the main control board comprises a bus voltage regulator;
when the three-phase contactor is closed, the bus voltage regulator generates a second torque current instruction according to a given value of bus voltage and a difference value of maximum values in direct current bus voltages of all power units detected and obtained by the voltage detection unit, and generates a third output voltage instruction according to the second torque current instruction and a torque current feedback value by the second current regulator; and the power unit control board of the high-voltage frequency converter controls the inversion operation of the power unit according to the first output voltage instruction and the third output voltage instruction.
2. The high-voltage inverter rapid braking system according to claim 1, wherein a main control board of the high-voltage inverter comprises a speed regulator;
when the three-phase contactor is disconnected, the speed regulator generates a first torque current instruction according to a given speed and a feedback speed value, and the second current regulator generates a second output voltage instruction according to the first torque current instruction and the feedback torque current value; and the power unit control board of the high-voltage frequency converter controls the inversion operation of the power unit according to the first output voltage instruction and the second output voltage instruction.
3. The high-voltage inverter fast braking system as claimed in claim 1The system is characterized in that: when the three-phase contactor is closed, the main control board makes the output torque T of the high-voltage frequency converterMComprises the following steps:
wherein U isNIs rated voltage of a motor connected with the high-voltage frequency converter, R is resistance value of a brake resistor, n is current rotating speed of the motor, and n iseIs the rated speed of the motor.
4. A high-voltage frequency converter rapid braking control method comprises a phase-shifting transformation unit and a plurality of power units, wherein the input ends of the power units are respectively connected to a plurality of output ends of the secondary side of the phase-shifting transformation unit, and the output ends of the power units are connected in series in groups and then connected to a three-phase output line of the high-voltage frequency converter; the control method is characterized by comprising the following steps:
controlling a three-phase contactor of a braking energy absorption unit to be closed according to a received quick braking signal, wherein in the braking energy absorption unit, a first end of the three-phase contactor is respectively connected to a three-phase output line of the high-voltage frequency converter, and a second end of the three-phase contactor is provided with three braking resistors connected in a star-shaped or triangular connection manner;
when the output frequency of the high-voltage frequency converter reaches the target frequency, controlling the three-phase contactor to be disconnected;
the control method further comprises the following steps:
detecting the direct current bus voltage of each power unit, and obtaining the maximum value of the direct current bus voltages of the plurality of power units;
when the three-phase contactor is closed, adjusting the output voltage of each power unit according to the maximum value in the direct-current bus voltage so as to adjust the output torque;
the control method comprises the following steps: generating an exciting current instruction according to a stator flux linkage given value and a stator flux linkage feedback value, and generating a first output voltage instruction according to the exciting current instruction and the exciting current feedback value; and, when the three-phase contactor is closed,
generating a second torque current instruction according to the bus voltage given value and the difference value of the maximum value in the direct current bus voltages of the plurality of power units, and generating a third output voltage instruction according to the second torque current instruction and the torque current feedback value;
and controlling the inversion operation of the power unit according to the first output voltage instruction and the third output voltage instruction.
5. The high-voltage inverter rapid braking control method according to claim 4, wherein the control method comprises: when the three-phase contactor is opened,
generating a first torque current instruction according to the speed given value and the speed feedback value, and generating a second output voltage instruction according to the first torque current instruction and the torque current feedback value;
and controlling the inversion operation of the power unit according to the first output voltage instruction and the second output voltage instruction.
6. The high-voltage inverter rapid braking control method according to claim 4, characterized in that: when the three-phase contactor is closed, the output torque T of the high-voltage frequency converter driving motorMComprises the following steps:
wherein U isNIs rated voltage of a motor connected with the high-voltage frequency converter, R is resistance value of a brake resistor, n is current rotating speed of the motor, and n iseIs the rated speed of the motor.
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| WO2020102508A1 (en) * | 2018-11-15 | 2020-05-22 | Siemens Aktiengesellschaft | Extended braking with variable frequency drive without input power |
| CN111327231B (en) * | 2020-02-26 | 2023-08-18 | 致瞻科技(上海)有限公司 | Motor braking feedback energy absorbing method, device and system based on high-frequency injection |
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