CN111509958A - Cascade type frequency converter bypass method and cascade type frequency converter - Google Patents
Cascade type frequency converter bypass method and cascade type frequency converter Download PDFInfo
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- CN111509958A CN111509958A CN202010352160.8A CN202010352160A CN111509958A CN 111509958 A CN111509958 A CN 111509958A CN 202010352160 A CN202010352160 A CN 202010352160A CN 111509958 A CN111509958 A CN 111509958A
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
- H02M1/00—Details of apparatus for conversion
- H02M1/32—Means for protecting converters other than automatic disconnection
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
- H02M1/00—Details of apparatus for conversion
- H02M1/32—Means for protecting converters other than automatic disconnection
- H02M1/325—Means for protecting converters other than automatic disconnection with means for allowing continuous operation despite a fault, i.e. fault tolerant converters
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Abstract
A cascade type frequency converter bypass method comprises the following steps: detecting the running states of all power units of the frequency converter; determining the phase and the stage number of a fault power unit in a frequency converter; and bypassing the fault power unit, and bypassing the normal power units of which the other phases are the same as the fault power unit in the same stage. The embodiment of the invention avoids the situation that the position of a fault power unit cannot be found in time by detecting the running states of all power units simultaneously; after the fault position is determined, the time difference is eliminated by simultaneously bypassing the fault power unit and other phases of normal power units with the same stage number as the fault power unit, and the problems of 3-phase imbalance and even secondary damage caused by successive bypassing are avoided.
Description
Technical Field
The invention belongs to the field of high-voltage power transmission, and particularly relates to a cascade type frequency converter bypass method and a cascade type frequency converter.
Background
With the frequency converter being applied in various industries more and more frequently, in order to improve the reliability of field devices, the frequency of the frequency converter having faults is required to be reduced to the minimum, so as to ensure that the frequency converter has no faults as much as possible, and also ensure that when the frequency converter has faults, an electronic bypass mode is adopted, that is, the operation of the frequency converter is ensured by reducing the operation stages of power units, thereby improving the production efficiency of the whole factory devices.
The current bypass method mainly adopts: when the power unit fails, the power unit with the failure is bypassed firstly, then a failure signal is uploaded to the main control board, and finally, the main control board issues a bypass instruction and bypasses other same-stage power units.
However, after the above method is adopted, in practical application, it is found that after the frequency converter has a fault bypass, an overcurrent fault of the IGBT is often reported in the bypass process. Analysis shows that when the power unit fails, the power unit at the same level is bypassed first, so that the us-level time difference exists between two bypasses, and the time difference during bypassing cannot be controlled, so that the IGBT explosion phenomenon easily occurs to the power unit which normally operates originally, and the reliability of the frequency converter is reduced.
Disclosure of Invention
The present invention is directed to solving at least one of the problems of the prior art. Therefore, the cascade frequency converter bypass method is simple in steps, solves the problem that the IGBT (insulated gate bipolar translator) is overcurrent after a power unit is bypassed, and improves the reliability of the frequency converter. The invention also provides a cascade frequency converter.
According to the first aspect of the invention, the bypass method of the cascade frequency converter comprises the following steps: detecting the running states of all power units of the frequency converter; determining the phase and the stage number of a fault power unit in the frequency converter; and bypassing the fault power unit, and bypassing the normal power units of which the other phases are the same as the fault power unit in the same stage.
The bypass method of the cascade frequency converter according to the embodiment of the invention at least has the following technical effects: the operating states of all the power units are detected simultaneously, so that the situation that the positions of the fault power units cannot be found in time is avoided; after the fault position is determined, the time difference is eliminated by simultaneously bypassing the fault power unit and other phases of normal power units with the same stage number as the fault power unit, and the problems of 3-phase imbalance and even secondary damage caused by successive bypassing are avoided.
According to some embodiments of the present invention, the above-mentioned cascade-type frequency converter bypass method further comprises the steps of: and after the bypassed fault power unit is bypassed, the fault power unit is failed again, and pulses of all power units of the frequency converter are blocked.
According to some embodiments of the present invention, the above-mentioned cascade-type frequency converter bypass method further comprises the steps of: and after the normal power unit which is bypassed, a fault occurs, and the pulse of all power units of the frequency converter is blocked.
A cascade-type frequency converter according to an embodiment of the second aspect of the present invention includes: the multi-secondary-side transformer is used for connecting an external three-phase power supply; the three power unit series structures are connected between the multi-secondary-side transformer and external electrical equipment, each power unit series structure comprises power units with the same number, and each power unit is respectively connected with one group of secondary sides of the multi-secondary-side transformer; the driving plate is used for detecting the running states of all the power units and driving the on-off of all the power units; and the main control board is used for receiving the running state information sent by the drive board to determine the phase and the stage number of the fault power unit in the frequency converter and control the drive board to bypass the fault power unit and normal power units of other phases and the fault power unit in the same stage number.
The cascade frequency converter according to the embodiment of the invention at least has the following technical effects: the on-off control of all power units can be realized through the main control board and the drive board, then the bypass control of all power units is realized, and the bypass control of the power units of the same level in the three power unit series structures can be realized through the main control board and the drive board, so that the effect of higher stability is realized compared with the traditional frequency converter which cannot bypass.
According to some embodiments of the invention, the main control board is further configured to control the drive board to block the pulses of all of the power cells.
According to some embodiments of the invention, the multi-secondary transformer is a phase-shifting transformer.
According to some embodiments of the invention, the power cell series configuration employs a 5-stage series.
Additional aspects and advantages of the invention will be set forth in part in the description which follows and, in part, will be obvious from the description, or may be learned by practice of the invention.
Drawings
The following further describes embodiments of the present invention with reference to the drawings.
FIG. 1 is a block flow diagram of an embodiment of a first aspect of the present invention;
FIG. 2 is a schematic diagram of a frequency converter according to an embodiment of the second aspect of the present invention;
fig. 3 is a schematic circuit diagram of a power cell in accordance with an embodiment of the second aspect of the present invention.
Detailed Description
Reference will now be made in detail to embodiments of the present invention, examples of which are illustrated in the accompanying drawings, wherein like or similar reference numerals refer to the same or similar elements or elements having the same or similar function throughout. The embodiments described below with reference to the accompanying drawings are illustrative only for the purpose of explaining the present invention, and are not to be construed as limiting the present invention.
In the description of the present invention, if there are first, second, third, fourth, etc. described only for the purpose of distinguishing technical features, they are not to be interpreted as indicating or implying relative importance or implying number of indicated technical features or implying precedence of indicated technical features.
In the description of the present invention, unless otherwise explicitly defined, terms such as arrangement, connection and the like should be broadly construed, and those skilled in the art can reasonably determine the specific meanings of the above terms in the present invention in combination with the detailed contents of the technical solutions.
A cascaded frequency converter bypass method according to an embodiment of the first aspect of the invention is described below with reference to fig. 1 to 3.
According to the first aspect of the invention, the bypass method of the cascade frequency converter comprises the following steps: detecting the running states of all power units of the frequency converter; determining the phase and the stage number of a fault power unit in a frequency converter; and bypassing the fault power unit, and bypassing the normal power units of which the other phases are the same as the fault power unit in the same stage.
Referring to fig. 1 to 3, after the frequency converter starts to operate, the operation states of all power units in the frequency converter need to be continuously detected, when it is found that one power unit fails, it is required to first confirm which stage of which specific phase the failed power unit is in the frequency converter, and then bypass the failed power unit and other normal power units having the same stage as the failed power unit at the same time, so that the problem of three-phase imbalance caused by bypassing only one phase can be effectively avoided. Meanwhile, because the fault power unit and the other normal power units with the same stage as the fault power unit are bypassed simultaneously, the time difference caused by bypassing the fault power unit and the normal power units successively can be effectively eliminated, and the problem of over-current alarm and even secondary damage of the IGBT is further avoided.
To facilitate an understanding of the method of the embodiment of the first aspect of the invention, a brief description of the converter-related principles follows. Referring to fig. 2 and 3, a schematic diagram of a single power unit is shown in fig. 2, the power unit is three-phase R, S, and T input, and outputs a dc voltage after an external voltage signal is input and rectified, and finally a single-phase output PWM signal can be realized. The adjacent power unit cascade can form the high-voltage output of the frequency converter, and the output end is directly connected with external electrical equipment (such as a motor). Generally, each phase of a high-voltage frequency converter with 6kV voltage level is formed by connecting 5 power units in series, and the output voltage can meet the requirement of 6000V. High-voltage output of different voltage grades can be realized by adjusting the serial number of the power units or the output voltage grades of the power units. During normal work, the PWM waveforms of the 5-level power unit are superposed together to obtain output voltage; when a certain power unit in the 5-level fails, the main control initiates a bypass instruction after receiving the failure information, and the 5-level system becomes a 4-level system to operate after bypassing the first level, so that the normal operation of the frequency converter can be ensured although the harmonic waves of the output voltage and the current are increased.
The bypass process of the first embodiment of the present invention is briefly described below in conjunction with the above.
Referring to fig. 3, in the operation process of the frequency converter, it is assumed that a VI4 of the power unit a3 fails first, the drive board detects the failure, and the drive board uploads a failure signal to the main control board first; after receiving a fault signal uploaded by a drive board, a main control board immediately issues instructions of bypass power units A3, B3 and C3 to the drive board, the power units A3, B3 and C3 simultaneously open upper bridge arms VI1 and VI3 and block lower bridge arms VI2 and VI4, and at the moment, the power units A3, B3 and C3 do not output pulse signals any more, are only responsible for connecting adjacent power units and share corresponding voltages; at the moment, the main control board sends a bypass success command, the drive board cancels the IGBT fault signal, and uploads a bypass success signal.
According to the cascade frequency converter bypass method provided by the embodiment of the invention, the situation that the position of a fault power unit cannot be found in time is avoided by detecting the running states of all power units at the same time; after the fault position is determined, the time difference is eliminated by simultaneously bypassing the fault power unit and other phases of normal power units with the same stage number as the fault power unit, and the problems of 3-phase imbalance and even secondary damage caused by successive bypassing are avoided.
In some embodiments of the present invention, the above-mentioned cascade-type frequency converter bypass method further comprises the steps of: and the bypassed fault power unit is bypassed, and then the fault occurs again, and the pulse of all power units of the frequency converter is blocked. In practical application, the frequency converter which has bypassed may also have a fault again, and if the power unit which has not bypassed originally has a fault, the bypass method may be directly applied, but when the power unit which has bypassed has a fault again, the method may not be applied. The problem is directly solved by blocking the pulses of all power units of the frequency converter, and after the pulses of all power units are blocked, all power units stop outputting, so that the frequency converter is protected from further damage.
In some embodiments of the present invention, the above-mentioned cascade-type frequency converter bypass method further comprises the steps of: and after the bypassed normal power unit is bypassed, the fault occurs, and the pulse of all power units of the frequency converter is blocked. In practical application, when the normal power unit which is bypassed has a fault again, the same coping method as that when the fault power unit which is bypassed has a fault again is adopted, namely, the problem is solved by blocking the pulses of all the power units of the frequency converter. After the pulses of all the power units are blocked, all the power units stop outputting, thereby protecting the frequency converter from further damage.
A cascade-type frequency converter according to an embodiment of the second aspect of the present invention includes: the multi-secondary-side transformer, the driving board, the main control board and the three power units are connected in series. The multi-secondary-side transformer is used for connecting an external three-phase power supply; the three power unit series structures are connected between the multi-secondary-side transformer and external electrical equipment, each power unit series structure comprises power units with the same number, and each power unit is respectively connected with one group of secondary sides of the multi-secondary-side transformer; the driving board is used for detecting the running states of all the power units and driving the on-off of all the power units; and the main control board is used for receiving the running state information sent by the drive board to determine the phase and the stage number of the fault power unit in the frequency converter and control the drive board to bypass the fault power unit and normal power units with the same stage number as the fault power unit and other phases.
Referring to fig. 2 and 3, each power unit is respectively supplied with power by a set of secondary sides of the multi-secondary-side transformer, so that mutual insulation between the power units and between secondary windings of the transformer can be realized. The driving board is controlled by the main control board and is used for driving each bridge arm of each power unit to be switched on and off, so that any one power unit is bypassed, for example: when VI4 of the power unit A3 fails first, the bypass can be realized by switching on the upper bridge arms VI1 and VI3 of the power unit A3 and blocking the lower bridge arms VI2 and VI 4.
The working process of the cascaded frequency converter according to the embodiment of the present invention is briefly described below.
The method comprises the steps that a drive board collects the running states of all power units in real time and uploads the running states to a main control board, the main control board analyzes the running states in real time, when the drive board detects that a certain power unit breaks down in running, the main control board receives a running fault signal sent by the drive board at the moment, then the main control board sends a bypass instruction to the drive board, and the drive board simultaneously controls a fault power unit which breaks down and normal power units which have the same stage number as other same-phase fault power units to be in one-pass bypass. And then the drive board controls the power unit to start bypassing, and after the bypassing is successful, the drive board sends information of successful bypassing to the main control board.
According to the cascade frequency converter provided by the embodiment of the invention, on-off control of all power units can be realized through the main control board and the drive board, so that bypass control of all power units is realized, bypass control of power units of the same stage in a series structure of three power units can be realized through the main control board and the drive board, and the cascade frequency converter has the effect of higher stability compared with a traditional frequency converter which cannot be bypassed.
In some embodiments of the present invention, the main control board is also used to control the drive board to block the pulses of all power cells. In practical application, the frequency converter which has bypassed may also have a fault again, and if the power unit which has not bypassed originally has a fault, the bypass method may be directly applied, but when the power unit which has bypassed has a fault again, the method may not be applied. The problem is directly solved by blocking the pulses of all power units of the frequency converter, and after the pulses of all power units are blocked, all power units stop outputting, so that the frequency converter is protected from further damage. The specific working process is as follows: the running states of all the power units are collected and uploaded to the main control board, the main control board analyzes that the failed power unit is a bypassed power unit, at the moment, the main control board directly sends a blocking pulse instruction to the main control board, and the drive board blocks all the power unit pulses at once.
In some embodiments of the present invention, the multi-secondary transformer employs a phase-shifting transformer. The phase-shifting transformer can be adopted to enable the power unit to work more stably.
In some embodiments of the present invention, the power cell series configuration employs a 5-stage series. 5-stage series connection, i.e. 5 power cells are connected in series. 5 grades of series connection are enough to satisfy the main demand in most markets, adopt 5 grades of series connection simultaneously can not cause too big influence to whole power supply behind a bypass power unit, are enough to guarantee the normal operating of converter.
In the description herein, references to the description of the term "one embodiment," "some embodiments," "an illustrative embodiment," "an example," "a specific example," or "some examples" or the like mean that a particular feature, structure, material, or characteristic described in connection with the embodiment or example is included in at least one embodiment or example of the invention. In this specification, the schematic representations of the terms used above do not necessarily refer to the same embodiment or example. Furthermore, the particular features, structures, materials, or characteristics described may be combined in any suitable manner in any one or more embodiments or examples.
Although the embodiments of the present invention have been described in detail with reference to the accompanying drawings, the present invention is not limited to the embodiments, and those skilled in the art will understand that: various changes, modifications, substitutions and alterations can be made to the embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the claims and their equivalents.
Claims (7)
1. A bypass method of a cascade frequency converter is characterized by comprising the following steps:
detecting the running states of all power units of the frequency converter;
determining the phase and the stage number of a fault power unit in the frequency converter;
and bypassing the fault power unit, and bypassing the normal power units of which the other phases are the same as the fault power unit in the same stage.
2. The cascade-type frequency converter bypass method according to claim 1, further comprising the steps of: and after the bypassed fault power unit is bypassed, the fault power unit is failed again, and pulses of all power units of the frequency converter are blocked.
3. The cascade-type frequency converter bypass method according to claim 1 or 2, further comprising the steps of: and after the normal power unit which is bypassed, a fault occurs, and the pulse of all power units of the frequency converter is blocked.
4. A cascaded frequency converter, comprising:
the multi-secondary-side transformer is used for connecting an external three-phase power supply;
the three power unit series structures are connected between the multi-secondary-side transformer and external electrical equipment, each power unit series structure comprises power units with the same number, and each power unit is respectively connected with one group of secondary sides of the multi-secondary-side transformer;
the driving plate is used for detecting the running states of all the power units and driving the on-off of all the power units;
and the main control board is used for receiving the running state information sent by the drive board to determine the phase and the stage number of the fault power unit in the frequency converter and control the drive board to bypass the fault power unit and normal power units of other phases and the fault power unit in the same stage number.
5. The cascaded frequency converter of claim 4, wherein the main control board is further configured to control the drive board to block pulses of all of the power cells.
6. The cascaded frequency converter of claim 4, wherein the multi-secondary transformer is a phase shifting transformer.
7. Cascaded frequency converter according to claim 4, characterized in that said power cell series configuration is a 5-stage series.
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CN112924797A (en) * | 2021-02-07 | 2021-06-08 | 东方日立(成都)电控设备有限公司 | Fault positioning method and system for high-voltage frequency conversion system |
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