CN116232168A - Control method and control system for frequency conversion of frequency converter without disturbance - Google Patents
Control method and control system for frequency conversion of frequency converter without disturbance Download PDFInfo
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- CN116232168A CN116232168A CN202211732748.1A CN202211732748A CN116232168A CN 116232168 A CN116232168 A CN 116232168A CN 202211732748 A CN202211732748 A CN 202211732748A CN 116232168 A CN116232168 A CN 116232168A
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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
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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
- H02P1/00—Arrangements for starting electric motors or dynamo-electric converters
- H02P1/16—Arrangements for starting electric motors or dynamo-electric converters for starting dynamo-electric motors or dynamo-electric converters
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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
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Abstract
The invention discloses a control method and a control system for non-disturbance mutual switching of frequency conversion of a frequency converter, which comprise the following steps: the central console sends out a frequency switching command; judging whether the frequency conversion cutting power frequency command or the power frequency cutting frequency command is carried out according to the current working state of the high-voltage motor; the frequency converter performs acceleration and deceleration control according to the current running frequency; the frequency converter starts to execute a phase locking program; the control system executes an action command on the circuit breaker; and completing the frequency switching of the frequency converter. By the method, the motor can be ensured to be switched back and forth between frequency conversion and power frequency under the condition of no shutdown, and the current is smooth and has no impact.
Description
Technical Field
The application belongs to the technical field of high-voltage motor frequency conversion control, and particularly relates to a control method and a control system for frequency conversion and disturbance-free mutual switching of a frequency converter.
Background
In industrial control sites, due to the requirements of the production process, many devices are not allowed to be stopped, otherwise, relatively large economic loss and even safety accidents are caused. At present, the high-voltage frequency converter basically adopts a unit cascading mode, and although the reliability is higher and higher, because the high-voltage frequency converter adopts a plurality of devices, the system is huge, and in order to prevent equipment shutdown caused by high-voltage frequency converter faults, the high-voltage frequency converter needs to be regularly maintained and overhauled, and the like. The traditional method needs to stop the motor firstly, then directly start the motor at the power frequency, stop the motor again after the overhaul of the constant-voltage frequency converter is completed, and then start to operate by the frequency conversion. In order to ensure that the motor is not stopped when the high-voltage frequency converter overhauls and is transited to the high-voltage frequency converter to control the motor after the overhauls are completed, the frequency conversion and power frequency non-disturbance inter-cutting control method of the high-voltage frequency converter is particularly important, the whole-process motor can be ensured not to stop, the current is not impacted, and the switching process is smooth and stable.
Some existing soft start modes have some defects: the thyristor soft starter has the problem of small starting torque, and cannot be applied to some loads needing heavy-load starting or constant-torque starting in industry. The traditional soft start of the frequency converter has the advantages of good performance, high efficiency, automatic smooth acceleration, current impact reduction and the like, and can avoid impact of current on a power grid during starting. The soft start of the frequency converter is generally controlled according to a V/F constant voltage frequency ratio mode, but the constant voltage frequency ratio control method has low-speed load capacity and uncontrollable current, and particularly for a large-inertia and heavy-load system, the constant voltage frequency ratio control method is difficult to achieve ideal starting performance, and reliable starting is often realized by increasing the capacity of the frequency converter. The successful implementation of vector control technology, especially no-code wheel vector control method, makes the mechanical performance and dynamic performance of the AC asynchronous motor after frequency conversion and speed regulation reach the level different from the speed regulation performance of DC motor during voltage regulation. However, although the vector control technique solves the starting problem, one of the main functions of the soft starter is to perform the switching between the power frequency operation and the variable frequency operation. The mutual switching technology between the power frequency operation and the variable frequency operation generally adopts synchronous switching, namely, under the condition of no power failure, the phase-locked loop technology is utilized to ensure that the frequency, the phase and the amplitude of the output voltage of the frequency converter are consistent with the voltage of the power grid, and then the mutual stable switching between the frequency converter and the power grid is carried out. If synchronous switching is directly carried out under the vector control method, the vector control method has the risk of failure under the condition that the frequency converter and the power grid are simultaneously powered. In the running state that the power grid and the frequency converter supply power to the motor simultaneously, as the output voltage of the frequency converter is not smooth sine wave, a certain error exists in the synchronous switching control algorithm, so that a circulation current between the power grid and the frequency converter is certain in the running state, and the circulation current can cause deviation between the output current of the frequency converter and the current of the motor, so that the vector control mode is possibly invalid.
At present, the traditional synchronous switching technology is not truly undisturbed switching, and the following problems generally exist: when the variable frequency operation is switched to the power frequency operation, the power grid current can generate a certain degree of impact at the switching moment, and the impact current is related to the load of the motor; when the power frequency operation is switched to the variable frequency operation, the output current of the frequency converter can generate a certain degree of impact at the switching moment, and the impact current is also related to the load of the motor. However, up to now, no technology has been presented which can truly realize undisturbed handover.
Disclosure of Invention
In order to overcome the defects of the prior art, the embodiment of the application provides a control method and a control system for frequency conversion and disturbance-free mutual switching of a frequency converter.
The embodiment of the invention provides a control method for non-disturbance mutual cutting of frequency conversion of a frequency converter, which comprises the following steps:
step 4, the frequency converter starts to execute a phase locking program;
and 6, completing frequency switching of the frequency converter.
According to the method for controlling the frequency conversion and non-disturbance inter-cutting of the frequency converter provided by the embodiment of the invention, in the step 2, whether the frequency conversion and cutting power frequency command or the power frequency and cutting frequency command is judged according to the current working state of the frequency converter further comprises:
step 2.1, when the current running state of the high-voltage motor is variable frequency running, the frequency converter executes a frequency conversion cutting frequency command;
and 2.2, when the current running state of the high-voltage motor is the power frequency running state, the frequency converter executes a power frequency shear frequency command.
According to the method for controlling the frequency converter to perform the frequency conversion without disturbance and mutual switching, in the step 3, the frequency converter further comprises the following steps:
the frequency converter smoothly adjusts the output frequency of the frequency converter to be near the frequency of the power grid according to the current operating frequency.
According to the method for controlling the frequency converter to perform the frequency conversion without disturbance, the step 4, the step of starting the frequency converter to perform the phase locking program, further comprises:
the output frequency, phase, and amplitude of the frequency converter are adjusted to be consistent with the grid.
According to the method for controlling the disturbance-free inter-switching of the frequency converter in the frequency conversion provided by the embodiment of the invention, in the step 5, the control system executes the action command to the circuit breaker, the method further comprises the following steps:
step 5.1, when the frequency converter is switched from frequency conversion to power frequency, the control system controls the bypass breaker to be closed, at the moment, the frequency converter and the power grid supply power to the motor together, then the action command of the breaker sends out the switch-off command of the frequency converter output breaker, the frequency converter stops, and the frequency conversion of the frequency converter is completed;
and 5.2, when the frequency converter is switched by the power frequency, the control system sends out an output breaker closing command, the frequency converter and the power grid supply power to the motor at the moment, and then the breaker action command sends out a bypass breaker opening command of the frequency converter to open the power frequency of the power grid and finish the power frequency shearing frequency of the frequency converter.
According to the control method for the frequency conversion of the frequency converter without disturbance, which is provided by the embodiment of the invention, when the frequency conversion of the frequency converter is performed, the processing logic of the control system is as follows:
when the bypass breaker is in an open state and the control system receives a command of power frequency power grid access, the control system sends a command of closing the bypass breaker;
after the bypass breaker is closed, the control system confirms that the bypass breaker is closed after detecting feedback of the bypass breaker, and a power frequency power grid is connected to a motor for supplying power;
when the bypass breaker is confirmed to be closed and the frequency converter output breaker is in a closed state, the control system outputs an open command for opening the output breaker.
According to the control method for the frequency converter industrial frequency conversion non-disturbance mutual switching provided by the embodiment of the invention, when the frequency converter is subjected to frequency conversion by industrial frequency switching, the processing logic of the control system is as follows:
when the output circuit breaker is in an open state and the control system receives a command that the power frequency power grid exits and is switched to a variable frequency state, the control system sends a command of closing the output circuit breaker;
after the output circuit breaker is closed, the control system confirms that the output circuit breaker is closed after detecting feedback of the output circuit breaker, and the frequency converter is connected with the motor for supplying power;
when the output circuit breaker is confirmed to be closed and the bypass circuit breaker is in a closed state, the control system outputs an open command for opening the bypass circuit breaker.
According to the method for controlling the frequency converter to perform frequency conversion without disturbance, in the step 2, whether the frequency conversion is a frequency conversion and frequency conversion command or not is judged according to the current working state of the high-voltage motor:
when the input breaker and the output breaker of the frequency converter are in a closed state and the bypass breaker is in an open state, the high-voltage motor is considered to be in a frequency conversion running state currently;
when the output circuit breaker of the frequency converter is in an open state and the bypass circuit breaker is in a closed state, the current power frequency running state of the high-voltage motor is determined.
The embodiment of the invention also provides a control system based on the control method for the disturbance-free mutual switching of the frequency converter industrial frequency conversion provided by the embodiment, which comprises the following steps: the high-voltage frequency converter, the high-voltage input of high-voltage frequency converter is connected with high-voltage power frequency electric wire netting by input circuit breaker, the high-voltage output of high-voltage frequency converter is connected with the high-voltage motor via output circuit breaker, the high-voltage power frequency electric wire netting with be connected with the bypass circuit breaker between the high-voltage motor, input circuit breaker high-voltage frequency converter and output circuit breaker constitutes the serial circuit with connect in parallel between the bypass circuit breaker, the circuit control system control of high-voltage frequency converter, control system is the PLC controller.
According to the control system for the frequency converter industrial frequency conversion non-disturbance mutual switching, which is provided by the embodiment of the invention, the input circuit breaker, the output circuit breaker and the bypass circuit breaker are vacuum circuit breakers or contactors.
The beneficial effects of the invention are as follows: the control method and the control system for the frequency converter industrial frequency conversion undisturbed mutual switching realize the smooth, stable and undisturbed synchronous switching function between the industrial frequency operation and the frequency conversion operation in a real sense. The current at the switching moment does not exceed the real-time current of the high-voltage motor, so that the impulse current and torque fluctuation are effectively restrained, and smooth current transfer is realized in the switching process. The control method provided by the embodiment is suitable for any application occasion needing soft start of the high-voltage motor.
Drawings
Technical solutions and other advantageous effects of the present application will be made apparent from the following detailed description of specific embodiments of the present application with reference to the accompanying drawings.
Fig. 1 is a schematic diagram of a control method for non-disturbance inter-switching of frequency conversion of a frequency converter according to an embodiment of the present invention.
Fig. 2 is a flowchart of a control method for non-disturbance inter-switching of frequency conversion of a frequency converter according to an embodiment of the present invention.
Fig. 3 is a schematic structural diagram of a control system for non-disturbance inter-switching of frequency conversion of a frequency converter according to an embodiment of the present invention.
The reference numerals of the components in the drawings are as follows: the power frequency power grid comprises a power frequency power grid 1, an input breaker 2, a high-voltage frequency converter 3, an output breaker 4, a bypass breaker 5 and a high-voltage motor 7.
Detailed Description
The technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the drawings in the embodiments of the present application. It will be apparent that the described embodiments are only some, but not all, of the embodiments of the present application. All other embodiments, which can be made by those skilled in the art based on the embodiments herein without making any inventive effort, are intended to be within the scope of the present application.
In the description of the present application, it should be understood that the terms "center," "longitudinal," "transverse," "length," "width," "thickness," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "outer," "clockwise," "counterclockwise," etc. indicate or are based on the orientation or positional relationship shown in the drawings, merely for convenience of description and to simplify the description, and do not indicate or imply that the devices or elements referred to must have a specific orientation, be configured and operated in a specific orientation, and thus should not be construed as limiting the present application. Furthermore, the terms "first," "second," and the like, are used for descriptive purposes only and are not to be construed as indicating or implying a relative importance or implicitly indicating the number of technical features indicated. Thus, a feature defining "a first" or "a second" may explicitly or implicitly include one or more of the described features. In the description of the present application, the meaning of "a plurality" is two or more, unless explicitly defined otherwise.
The following disclosure provides many different embodiments or examples for implementing different structures of the present application. In order to simplify the disclosure of the present application, the components and arrangements of specific examples are described below. Of course, they are merely examples and are not intended to limit the present application. Furthermore, the present application may repeat reference numerals and/or letters in the various examples, which are for the purpose of brevity and clarity, and which do not in themselves indicate the relationship between the various embodiments and/or arrangements discussed. In addition, the present application provides examples of various specific processes and materials, but one of ordinary skill in the art may recognize the application of other processes and/or the use of other materials.
The embodiment of the application provides a control method and a control system for frequency conversion and disturbance-free mutual switching of a frequency converter, by the method, the motor can be ensured to be switched back and forth between frequency conversion and power frequency under the condition of no shutdown, and current is smooth and impact-free.
Fig. 1 and fig. 2 are schematic flow diagrams of a control method for non-disturbance mutual switching of frequency conversion of a frequency converter according to an embodiment of the present invention. The method comprises the following steps:
step 4, the frequency converter starts to execute a phase locking program;
and 6, completing frequency switching of the frequency converter.
Specifically, in one embodiment, in the step 2, determining whether the frequency conversion cutting power frequency command or the power frequency cutting frequency command is determined according to the current working state of the frequency converter further includes:
step 2.1, when the current running state of the high-voltage motor 7 is variable frequency running, the frequency converter executes a frequency conversion power frequency switching command;
and 2.2, when the current running state of the high-voltage motor 7 is the power frequency running, the frequency converter executes a power frequency shear frequency command.
Specifically, when the high-voltage frequency converter 3 needs maintenance, the high-voltage frequency converter 3 needs to exit from the power supply of the high-voltage motor 7 and power the high-voltage motor 7 by the power frequency power grid 1, and the central console sends a frequency conversion power frequency switching command to the frequency converter. When the high-voltage frequency converter 3 receives the frequency conversion and power frequency cutting command of the central console, the control system controls the high-voltage frequency converter 3 to start acceleration control according to the current operating frequency, and the output frequency of the high-voltage frequency converter 3 is smoothly adjusted to be close to the frequency of the power frequency power grid 1. Then the control system starts to execute the phase locking program, and adjusts the output frequency, phase and amplitude of the high-voltage frequency converter 3 to be consistent with the power frequency power grid 1. At this time, the control system sends out a command to close the bypass breaker 5, and at this time, the high-voltage frequency converter 3 and the power frequency grid 1 supply power to the high-voltage motor 7 at the same time, and the current will not impact the high-voltage motor 7 because the frequency, the phase and the amplitude of the two are consistent. When the control system detects the closing feedback of the bypass breaker 5, i.e. after confirming that the bypass breaker 5 is closed, the control system issues an opening command of the inverter output breaker 4 and the high voltage inverter 3 is shut down. The high-voltage frequency converter 3 frequency conversion is completed, the high-voltage frequency converter 3 is withdrawn from working, the high-voltage motor 7 is powered by the power frequency power grid 1 to operate, and the high-voltage frequency converter 3 can be maintained and overhauled. The whole process realizes undisturbed switching, and the motor has no shutdown process.
In one embodiment, in the step 3, the step of performing acceleration and deceleration control by the frequency converter according to the current operating frequency further includes:
the frequency converter smoothly adjusts the output frequency of the frequency converter to be near the frequency of the power grid according to the current operating frequency.
The step 4, the step of starting the phase locking procedure by the frequency converter further includes:
the output frequency, phase, and amplitude of the frequency converter are adjusted to be consistent with the grid.
The step 5, the control system executing action command to the breaker further includes:
step 5.1, when the frequency converter is switched from frequency conversion to power frequency, the control system controls the bypass breaker 5 to be closed, at the moment, the frequency converter and the power grid supply power to the motor together, then a breaker action command sends a frequency converter output breaker 4 opening command, the frequency converter stops, and the frequency conversion of the frequency converter is completed;
and 5.2, when the frequency converter is switched by power frequency, the control system sends out an output breaker 4 closing command, the frequency converter and the power grid supply power to the motor at the moment, and then the breaker action command sends out a frequency converter bypass breaker 5 opening command to open the power frequency of the power grid and complete the power frequency switching of the frequency converter.
When the frequency converter is switched from frequency conversion to power frequency, the processing logic of the control system is as follows:
when the bypass breaker 5 is in an open state and the control system receives a command for accessing the power frequency power grid 1, the control system sends a command for closing the bypass breaker 5;
after the bypass breaker 5 is closed, the control system confirms that the bypass breaker 5 is closed after detecting feedback of the bypass breaker 5, and the power frequency power grid 1 is connected with a motor for supplying power;
when it is confirmed that the bypass breaker 5 has been closed and the inverter output breaker 4 is in the closed state, the control system outputs an open command to open the output breaker 4.
Specifically, when the maintenance and repair of the high-voltage frequency converter 3 is completed, the high-voltage frequency converter 3 needs to be connected to the high-voltage motor 7, the high-voltage frequency converter 3 supplies power to the high-voltage motor 7, and the central console sends a power frequency shear frequency command to the high-voltage frequency converter 3. When the high-voltage frequency converter 3 receives the power frequency switching command of the central console, the frequency converter is started by wave generation, the control system controls the high-voltage frequency converter 3 to start to perform acceleration control, the output frequency of the high-voltage frequency converter 3 is smoothly adjusted to be near the frequency of the power frequency power grid 1, and then the control system starts to perform a phase locking program to adjust the output frequency, the phase and the amplitude of the high-voltage frequency converter 3 to be consistent with the power frequency power grid 1. At this time, the control system sends out a closing command of the output breaker 4 to close the output breaker 4, and at this time, the high-voltage frequency converter 3 and the power frequency grid 1 supply power to the high-voltage motor 7 at the same time, and the frequency, the phase and the amplitude of the high-voltage frequency converter 3 and the power frequency grid 1 are consistent, so that the current cannot impact the high-voltage motor 7. When the control system detects the closing feedback of the output circuit breaker 4, namely, confirms that the output circuit breaker 4 is closed, the control system sends a frequency converter bypass circuit breaker 5 opening command to open a power frequency power supply line, so that the power frequency switching of the high-voltage frequency converter 3 is completed, and the high-voltage motor 7 is controlled to run by the power supply of the high-voltage frequency converter 3. The whole process realizes undisturbed switching, and the motor has no shutdown process.
Specifically, when the frequency converter is switched from power frequency to variable frequency, the processing logic of the control system is as follows:
when the output circuit breaker 4 is in an open state and the control system receives a command that the power frequency power grid 1 exits and is switched to a variable frequency state, the control system sends a command of closing the output circuit breaker 4;
after the output circuit breaker 4 is closed, the control system confirms that the output circuit breaker 4 is closed after detecting feedback of the output circuit breaker 4, and the frequency converter is connected with the motor for supplying power;
when it is confirmed that the output breaker 4 has been closed and the bypass breaker 5 is in the closed state, the control system outputs an open command to open the bypass breaker 5.
In one embodiment, in the step 2, it is determined whether the frequency-conversion power frequency-cutting command or the power frequency-cutting frequency-conversion command is determined according to the current working state of the high-voltage motor 7:
when the input breaker 2 and the output breaker 4 of the frequency converter are in a closed state and the bypass breaker 5 is in an open state, the high-voltage motor 7 is considered to be in a frequency conversion running state currently;
when the frequency converter output circuit breaker 4 is in an open state and the bypass circuit breaker 5 is in a closed state, the high-voltage motor 7 is considered to be in a power frequency running state currently.
Fig. 3 is a schematic structural diagram of the control system according to the present embodiment. The embodiment of the invention also provides a control system based on the control method for the disturbance-free mutual switching of the frequency converter industrial frequency conversion provided by the embodiment, which comprises the following steps: the high-voltage frequency converter 3, the high-voltage input of high-voltage frequency converter 3 is connected with high-voltage power frequency electric wire netting 1 by input circuit breaker 2, the high-voltage output of high-voltage frequency converter 3 is connected with high-voltage motor 7 via output circuit breaker 4, high-voltage power frequency electric wire netting 1 with be connected with bypass circuit breaker 5 between the high-voltage motor 7, input circuit breaker 2 high-voltage frequency converter 3 and output circuit breaker 4 constitutes the series circuit with connect in parallel between the bypass circuit breaker 5, the circuit control system control of high-voltage frequency converter 3, control system is the PLC controller. Wherein the input breaker 2, the output breaker 4 and the bypass breaker 5 are vacuum breakers or contactors.
With reference to fig. 1, fig. 2 and fig. 3, the method and the system for controlling the frequency conversion of the frequency converter without disturbance according to the embodiments of the present invention are further described in detail.
When the high-voltage frequency converter 3 is subjected to frequency conversion and power frequency cutting, and the high-voltage frequency converter 3 receives a frequency conversion and power frequency cutting command (9) of the central console, the control system controls the high-voltage frequency converter 3 to start acceleration and deceleration control (10) according to the current operating frequency, the output frequency of the high-voltage frequency converter 3 is smoothly adjusted to be close to the frequency of the power frequency power grid 1, and then the control system starts to execute a phase locking program (11) to adjust the output frequency, the phase and the amplitude of the high-voltage frequency converter 3 to be consistent with the power frequency power grid 1. Then the control system executes a breaker action command (12) to close the bypass breaker 5, and at the moment, the high-voltage frequency converter 3 and the power frequency power grid 1 supply power to the high-voltage motor 7 simultaneously, and the frequency, the phase and the amplitude of the high-voltage frequency converter 3 and the power frequency power grid 1 are consistent, so that the current does not have impact. After the control system detects feedback of the bypass breaker 5, namely, after the bypass breaker 5 is confirmed to be closed, a breaker action command (12) sends a frequency converter output breaker 4 opening command, the high-voltage frequency converter 3 is stopped, so far, the frequency conversion of the high-voltage frequency converter 3 is completed, the high-voltage frequency converter 3 is stopped, the high-voltage motor 7 is powered by the power frequency power grid 1, and the high-voltage frequency converter 3 can be maintained and overhauled. The whole process realizes undisturbed switching, and the motor has no shutdown process.
When the high-voltage frequency converter 3 is subjected to frequency switching by power frequency, after the high-voltage frequency converter 3 is maintained and overhauled, a central console sends a power frequency switching command (9) to the high-voltage frequency converter 3, at the moment, the high-voltage frequency converter 3 starts to send waves, acceleration and deceleration control (10) starts to be executed, the output frequency of the high-voltage frequency converter 3 is adjusted to be near the frequency of a power grid, then a phase locking program (11) starts to be executed, and the output frequency, the phase and the amplitude of the high-voltage frequency converter 3 are adjusted to be consistent with the power grid. At this time, the control system executes the breaker action command (12) and sends out the closing command of the breaker 4, and at this time, the high-voltage frequency converter 3 and the power frequency power grid 1 supply power to the high-voltage motor 7 at the same time, and the frequency, the phase and the amplitude of the high-voltage frequency converter 3 are consistent, so that the current does not have impact. When the control system detects feedback of the output circuit breaker 4, namely, the output circuit breaker 4 is confirmed to be closed, a circuit breaker action command (12) sends a frequency converter bypass circuit breaker 5 opening command to open a power frequency power supply line, so that frequency conversion of frequency converter power frequency switching is completed, and the high-voltage motor 7 is controlled to operate by power supply of the high-voltage frequency converter 3. The whole process realizes undisturbed switching, and the motor has no shutdown process.
The control method and the control system for the frequency converter industrial frequency conversion undisturbed mutual switching realize the smooth, stable and undisturbed synchronous switching function between the industrial frequency operation and the frequency conversion operation in a real sense. The current at the switching moment does not exceed the real-time current of the high-voltage motor 7, so that the surge current and the torque fluctuation are effectively restrained, and smooth current transfer is realized in the switching process. The control method provided in this embodiment is suitable for any application requiring soft start of the high-voltage motor 7.
While preferred embodiments of the present invention have been described, additional variations and modifications in those embodiments may occur to those skilled in the art once they learn of the basic inventive concepts. It is therefore intended that the following claims be interpreted as including the preferred embodiment and all such alterations and modifications as fall within the scope of the embodiments of the invention. Finally, it is further noted that relational terms such as first and second, and the like are used solely to distinguish one entity or action from another entity or action without necessarily requiring or implying any actual such relationship or order between such entities or actions. Moreover, the terms "comprises," "comprising," or any other variation thereof, are intended to cover a non-exclusive inclusion, such that a process, method, article, or terminal that comprises a list of elements does not include only those elements but may include other elements not expressly listed or inherent to such process, method, article, or terminal. Without further limitation, an element defined by the phrase "comprising one … …" does not exclude the presence of other like elements in a process, method, article or terminal device comprising the element.
The method and the system for controlling the frequency conversion of the frequency converter without disturbance and mutual cutting provided by the embodiment of the application are described in detail, and specific examples are applied to the description of the principle and the implementation mode of the application, and the description of the above embodiments is only used for helping to understand the technical scheme and the core idea of the application; those of ordinary skill in the art will appreciate that: the technical scheme described in the foregoing embodiments can be modified or some technical features thereof can be replaced by equivalents; such modifications and substitutions do not depart from the spirit of the corresponding technical solutions from the scope of the technical solutions of the embodiments of the present application.
Claims (10)
1. The method for controlling the frequency conversion of the frequency converter without disturbance mutual cutting is characterized by comprising the following steps of:
step 1, a central console sends out a frequency switching command;
step 2, judging whether the frequency conversion cutting power frequency command or the power frequency shear frequency command is carried out according to the current working state of the high-voltage motor;
step 3, the frequency converter performs acceleration and deceleration control according to the current running frequency;
step 4, the frequency converter starts to execute a phase locking program;
step 5, the control system executes an action command on the circuit breaker;
and 6, completing frequency switching of the frequency converter.
2. The method for controlling the frequency conversion of a frequency converter without disturbance according to claim 1, wherein in the step 2, judging whether the frequency conversion is a frequency conversion command or a frequency conversion command according to the current working state of the frequency converter further comprises:
step 2.1, when the current running state of the high-voltage motor is variable frequency running, the frequency converter executes a frequency conversion cutting frequency command;
and 2.2, when the current running state of the high-voltage motor is the power frequency running state, the frequency converter executes a power frequency shear frequency command.
3. The method for controlling the frequency converter to perform disturbance-free mutual switching according to claim 1, wherein in the step 3, the step of performing acceleration and deceleration control on the frequency converter according to the current operating frequency further comprises:
the frequency converter smoothly adjusts the output frequency of the frequency converter to be near the frequency of the power grid according to the current operating frequency.
4. The method for controlling the non-disturbance inter-switching of the frequency converter according to claim 1, wherein in the step 4, the step of starting the frequency converter to execute the phase-locking procedure further comprises:
the output frequency, phase, and amplitude of the frequency converter are adjusted to be consistent with the grid.
5. The method for controlling the non-disturbance switching of the frequency converter according to claim 1, wherein in the step 5, the control system further includes:
step 5.1, when the frequency converter is switched from frequency conversion to power frequency, the control system controls the bypass breaker to be closed, at the moment, the frequency converter and the power grid supply power to the motor together, then the action command of the breaker sends out the switch-off command of the frequency converter output breaker, the frequency converter stops, and the frequency conversion of the frequency converter is completed;
and 5.2, when the frequency converter is switched by the power frequency, the control system sends out an output breaker closing command, the frequency converter and the power grid supply power to the motor at the moment, and then the breaker action command sends out a bypass breaker opening command of the frequency converter to open the power frequency of the power grid and finish the power frequency shearing frequency of the frequency converter.
6. The method for controlling frequency conversion non-disturbance inter-cutting of a frequency converter according to claim 5, wherein when the frequency conversion of the frequency converter is performed, the processing logic of the control system is as follows:
when the bypass breaker is in an open state and the control system receives a command of power frequency power grid access, the control system sends a command of closing the bypass breaker;
after the bypass breaker is closed, the control system confirms that the bypass breaker is closed after detecting feedback of the bypass breaker, and a power frequency power grid is connected to a motor for supplying power;
when the bypass breaker is confirmed to be closed and the frequency converter output breaker is in a closed state, the control system outputs an open command for opening the output breaker.
7. The method for controlling non-disturbance inter-switching of frequency converter according to claim 5, wherein when the frequency converter is switched from power frequency to frequency, the processing logic of the control system is:
when the output circuit breaker is in an open state and the control system receives a command that the power frequency power grid exits and is switched to a variable frequency state, the control system sends a command of closing the output circuit breaker;
after the output circuit breaker is closed, the control system confirms that the output circuit breaker is closed after detecting feedback of the output circuit breaker, and the frequency converter is connected with the motor for supplying power;
when the output circuit breaker is confirmed to be closed and the bypass circuit breaker is in a closed state, the control system outputs an open command for opening the bypass circuit breaker.
8. The method for controlling the frequency converter to perform frequency conversion without disturbance according to claim 1, wherein in the step 2, whether the frequency conversion and frequency conversion command or the frequency conversion and frequency conversion command is determined according to the current working state of the high-voltage motor:
when the input breaker and the output breaker of the frequency converter are in a closed state and the bypass breaker is in an open state, the high-voltage motor is considered to be in a frequency conversion running state currently;
when the output circuit breaker of the frequency converter is in an open state and the bypass circuit breaker is in a closed state, the current power frequency running state of the high-voltage motor is determined.
9. A control system based on the method for controlling the disturbance-free inter-switching of the frequency converter according to any one of claims 1 to 9, wherein the control system comprises: the high-voltage frequency converter, the high-voltage input of high-voltage frequency converter is connected with high-voltage power frequency electric wire netting by input circuit breaker, the high-voltage output of high-voltage frequency converter is connected with the high-voltage motor via output circuit breaker, the high-voltage power frequency electric wire netting with be connected with the bypass circuit breaker between the high-voltage motor, input circuit breaker high-voltage frequency converter and output circuit breaker constitutes the serial circuit with connect in parallel between the bypass circuit breaker, the circuit control system control of high-voltage frequency converter, control system is the PLC controller.
10. The control system of claim 9, wherein the input circuit breaker, the output circuit breaker, and the bypass circuit breaker are vacuum circuit breakers or contactors.
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