CN116908636A - Spark flashover judging method and circuit based on self-adjusting comparison point - Google Patents
Spark flashover judging method and circuit based on self-adjusting comparison point Download PDFInfo
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- 238000000034 method Methods 0.000 title claims abstract description 29
- 238000005070 sampling Methods 0.000 claims abstract description 35
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- 230000001105 regulatory effect Effects 0.000 abstract description 3
- 239000000428 dust Substances 0.000 description 13
- 238000010586 diagram Methods 0.000 description 6
- 238000001514 detection method Methods 0.000 description 3
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- 238000007781 pre-processing Methods 0.000 description 2
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- 239000012717 electrostatic precipitator Substances 0.000 description 1
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Classifications
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02H—EMERGENCY PROTECTIVE CIRCUIT ARRANGEMENTS
- H02H3/00—Emergency protective circuit arrangements for automatic disconnection directly responsive to an undesired change from normal electric working condition with or without subsequent reconnection ; integrated protection
- H02H3/08—Emergency protective circuit arrangements for automatic disconnection directly responsive to an undesired change from normal electric working condition with or without subsequent reconnection ; integrated protection responsive to excess current
- H02H3/10—Emergency protective circuit arrangements for automatic disconnection directly responsive to an undesired change from normal electric working condition with or without subsequent reconnection ; integrated protection responsive to excess current additionally responsive to some other abnormal electrical conditions
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
- G01R19/00—Arrangements for measuring currents or voltages or for indicating presence or sign thereof
- G01R19/165—Indicating that current or voltage is either above or below a predetermined value or within or outside a predetermined range of values
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
- G01R31/00—Arrangements for testing electric properties; Arrangements for locating electric faults; Arrangements for electrical testing characterised by what is being tested not provided for elsewhere
- G01R31/12—Testing dielectric strength or breakdown voltage ; Testing or monitoring effectiveness or level of insulation, e.g. of a cable or of an apparatus, for example using partial discharge measurements; Electrostatic testing
- G01R31/1227—Testing dielectric strength or breakdown voltage ; Testing or monitoring effectiveness or level of insulation, e.g. of a cable or of an apparatus, for example using partial discharge measurements; Electrostatic testing of components, parts or materials
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
- G01R31/00—Arrangements for testing electric properties; Arrangements for locating electric faults; Arrangements for electrical testing characterised by what is being tested not provided for elsewhere
- G01R31/12—Testing dielectric strength or breakdown voltage ; Testing or monitoring effectiveness or level of insulation, e.g. of a cable or of an apparatus, for example using partial discharge measurements; Electrostatic testing
- G01R31/14—Circuits therefor, e.g. for generating test voltages, sensing circuits
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- H—ELECTRICITY
- H03—ELECTRONIC CIRCUITRY
- H03K—PULSE TECHNIQUE
- H03K5/00—Manipulating of pulses not covered by one of the other main groups of this subclass
- H03K5/22—Circuits having more than one input and one output for comparing pulses or pulse trains with each other according to input signal characteristics, e.g. slope, integral
- H03K5/24—Circuits having more than one input and one output for comparing pulses or pulse trains with each other according to input signal characteristics, e.g. slope, integral the characteristic being amplitude
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- H—ELECTRICITY
- H03—ELECTRONIC CIRCUITRY
- H03M—CODING; DECODING; CODE CONVERSION IN GENERAL
- H03M1/00—Analogue/digital conversion; Digital/analogue conversion
- H03M1/12—Analogue/digital converters
- H03M1/124—Sampling or signal conditioning arrangements specially adapted for A/D converters
- H03M1/1245—Details of sampling arrangements or methods
Abstract
The application discloses a spark flashover judging method and a circuit based on self-adjusting comparison points, wherein the method comprises the following steps: during normal operation, sampling the secondary current of the rectifier; judging whether the secondary current value at the moment t is the maximum value from the starting time to the moment t; if yes, superposing the compensation value on the basis of the maximum value to obtain a comparison point aiming at the t' moment; the time t' is the next sampling time; if not, the comparison point at the moment t' is still the comparison point determined last time; and comparing the secondary current value at the time t 'with the comparison point, and if the secondary current value at the time t' is larger than the comparison point, determining that spark flashover occurs. The spark flashover comparison point is self-regulated based on the determined maximum value of the secondary current, and the comparison point is only slightly higher than the maximum value of the secondary current, so that the judgment time is shorter, the current surge amplitude is smaller, the current impact is not caused, and the stability and the service life of the equipment are improved.
Description
Technical Field
The application belongs to the technical field of latch circuits, and particularly relates to a method and a circuit for judging spark flashover.
Background
The electric dust collector is a dust collector which makes charged dust adsorbed on a dust collecting electrode under the action of high-voltage electric field force so as to strip solid dust particles from dust-containing gas, and is widely applied to industries such as electric power, metallurgy, building materials, chemical industry, petroleum, textile, boilers, steel and the like. Because the cathode and the anode in the electric dust remover are influenced by a plurality of factors, the interval between the cathode and the anode is changed, the withstand voltage between the cathode and the anode is changed, and the spark flashover, also called discharge phenomenon, occurs in the electric dust remover. At this time, the power supply device must timely judge the spark flashover, and close the power module, stop supplying power to the electric dust collector, prevent to cause electric energy waste, resume dust collection efficiency and protect the reliable operation of the power supply, therefore, can accurately and reliably judge the spark flashover to become the key technical point of the power supply device of the dust collector.
In the prior art, the spark flashover is generally judged by utilizing the instantaneous secondary current surge of the spark flashover, and is generally judged by the following two modes: firstly, a specific comparison point is preset by artificial experience, and when the secondary current exceeds the comparison point, the spark flashover is judged to occur. However, the secondary current comparison point must be set above the rated current, as shown in fig. 1, otherwise, false detection is caused when the equipment is in normal operation, and if the comparison point is above the rated current, the primary current exceeds the rated current every time the spark is flashover, so that the stability and the service life of the equipment are affected. Secondly, converting the secondary current and the secondary voltage into digital quantities through AD sampling and processing the digital quantities by a CPU to judge spark flashover, but the CPU in the mode needs to continuously calculate, compare and judge the collected secondary current and secondary voltage, so that a large amount of resources of the CPU are occupied, and the normal operation of other programs is easily influenced; and the program processing requires time, and the judgment time cannot ensure that hysteresis exists in detecting spark flashover.
Disclosure of Invention
Based on the above technical problems, a spark flashover judging method and a circuit based on self-adjusting comparison points are provided, so that the timeliness of the spark flashover judgment is improved, and the stability and the service life of equipment are improved.
In a first aspect, a method for determining spark flashover based on self-adjusting comparison points, the method comprising:
during normal operation, sampling the secondary current of the rectifier;
judging whether the secondary current value at the moment t is the maximum value from the starting time to the moment t; if yes, superposing the compensation value on the basis of the maximum value to obtain a comparison point aiming at the t' moment; the time t' is the next sampling time; if not, the comparison point at the moment t' is still the comparison point determined last time;
and comparing the secondary current value at the time t 'with the comparison point, and if the secondary current value at the time t' is larger than the comparison point, determining that spark flashover occurs.
In the above scheme, optionally, the interval time of the sampling is 5-10 μs.
In the above scheme, optionally, the value range of the compensation value is 0-1V.
In the above aspect, optionally, after the real-time sampling of the secondary current of the rectifier, the pre-processing of the sampled secondary current includes: and removing burrs of the secondary current signal.
In a second aspect, a spark flashover judging circuit based on a self-adjusting comparison point comprises a rectifier transformer and a sampling unit connected with the rectifier transformer, wherein the output end of the sampling unit is respectively connected with the input end of a maximum value acquisition and holding circuit, the first input end of a first comparator and the first input end of a second comparator, the output end of the maximum value acquisition and holding circuit is connected with the second input end of the first comparator, the maximum value acquisition and holding circuit is used for detecting the current secondary current and outputting the maximum value of the secondary current in the starting process, and the sampling state and the holding state of the maximum value acquisition and holding circuit are controlled by utilizing the potential change of the output end of the first comparator; the output end of the maximum value acquisition and holding circuit is connected with the input end of the adder, and the output end of the adder is connected with the second input end of the second comparator.
In the above scheme, optionally, the sampling unit is connected with the maximum value acquisition and holding circuit through the signal isolation unit.
In the above scheme, optionally, the maximum value collection and holding circuit includes a triode Q1, a resistor R4, a charging capacitor C1, a discharging resistor R1, a resistor R5 and an operational amplifier U6, an E emitter of the triode Q1 is respectively connected with one end of the charging capacitor C1 and one end of the resistor R5 through the resistor R4, the other end of the charging capacitor C1 is grounded, the charging capacitor C1 is connected in parallel with the resistor R1, the other end of the resistor R5 is connected with a non-inverting input end of the operational amplifier U6, an inverting input end of the operational amplifier U6 is connected with an output end of the operational amplifier U6, and an output end of the operational amplifier U6 is connected with the adder.
In the above scheme, further optionally, the first comparator is a comparator U7A, a non-inverting input end of the comparator U7A is connected to an output end of the signal isolation unit, an output end of the operational amplifier U6 is connected to a inverting input end of the comparator U7A through a resistor R3, and an output end of the comparator U7A is connected to a B base of the triode Q1.
In the above solution, optionally, the adder includes a resistor R12, a resistor R15, a resistor R16, a resistor R17, an adjustable resistor R11, and an operational amplifier U8; the resistor R12 is connected with the output end of the maximum value acquisition and holding circuit in series and then is connected with the non-inverting input end of the operational amplifier U8; the resistor R15 is connected with the non-inverting input end of the operational amplifier U8 after being connected with the adjustable resistor R11 in series; one end of the resistor R16 is connected with the inverting input end of the operational amplifier U8, and the other end of the resistor R16 is grounded; one end of a resistor R17 is connected with one end of the operational amplifier U8 in series, and the other end of the resistor R17 is connected with the output end of the operational amplifier U8.
In the above solution, further optionally, the second comparator is a comparator U7B, an inverting input end of the comparator U7B is connected to an output end of the operational amplifier U8 through a resistor R13, and a non-inverting input end of the comparator U7B is connected to an output end of the signal isolation unit.
The application has at least the following beneficial effects:
the application realizes the self-adjustment of the spark flashover comparison point by taking the maximum value of the secondary current in the current starting process as the basis, the comparison point is only slightly higher than the maximum value of the secondary current, when the spark appears, the secondary current suddenly increases and can rapidly exceed the comparison point.
Drawings
FIG. 1 is a prior art waveform diagram of determining a comparison point to determine a spark flashover secondary current;
FIG. 2 is a schematic flow chart of a spark flashover determination method based on self-adjusting comparison points according to an embodiment of the present application;
FIG. 3 is a block diagram of a spark flashover determination circuit system based on self-adjusting comparison points according to one embodiment of the present application;
FIG. 4 is a schematic diagram of a signal sampling isolation circuit according to an embodiment of the present application;
FIG. 5 is a circuit diagram of a system for determining a spark-over based on self-adjusting comparison points in accordance with one embodiment of the present application;
FIG. 6 is a schematic diagram of a CPU and driver circuit according to one embodiment of the present application;
FIG. 7 is a schematic diagram of a determined comparison point utilizing a method for determining spark flashover based on self-adjusting comparison points, in accordance with one embodiment of the present application.
Detailed Description
The present application will be described in further detail with reference to the drawings and examples, in order to make the objects, technical solutions and advantages of the present application more apparent. It should be understood that the specific embodiments described herein are for purposes of illustration only and are not intended to limit the scope of the application.
The application is applied to the spark flashover judgment of a high-voltage electrostatic dust collection power supply, and is characterized in that after the spark flashover occurs in the electrostatic precipitator, the application comprises the following steps: the output voltage decreases instantaneously and the output current increases instantaneously. Based on the characteristics, the circuit is applied to a high-voltage electrostatic dust removal power supply, so that the spark flashover can be judged in extremely short time, a hardware signal wire is used for directly locking a driving loop, the impact of circuit current surge on equipment power components during the spark flashover can be effectively prevented, the tube explosion of the IGBT caused by the high current of the spark flashover is prevented, and the service life of the components is ensured. It is also possible to prevent the CPU from being halted due to strong disturbance caused at the time of high voltage breakdown.
In one embodiment, as shown in fig. 2, a spark flashover determination method based on self-adjusting comparison points is provided, comprising the steps of:
step S101, during normal operation, sampling the secondary current of the rectifier;
in step S101, the secondary current signal is sampled to convert the current signal into a voltage signal.
Step S102, judging whether the secondary current value at the moment t is the maximum value from the starting time to the moment t; if yes, superposing the compensation value on the basis of the maximum value to obtain a comparison point aiming at the t' moment; the time t' is the next sampling time; if not, the comparison point at the moment t' is still the comparison point determined last time;
in step S102, since the calculation time is required for adding the compensation value to the maximum value, if it is determined at the time t that the secondary current at the time t is the maximum value in the current starting process, the comparison point obtained by using the secondary current at the time t is taken as the comparison point at the time t', and therefore the interval of the sampling time may be the calculation time for adding the compensation value to the maximum value.
And step S103, comparing the secondary current value at the time t 'with the comparison point, and if the secondary current value at the time t' is larger than the comparison point, determining that the spark flashover occurs.
In this embodiment, after the secondary current signal is processed by the sampling isolation circuit, the maximum value of the secondary current in the current starting process is collected by the maximum value collection and holding circuit, the maximum value is compared with the real-time secondary current through the comparator, and the sampling state and the holding state of the maximum value collection and holding circuit are controlled by using the potential change of the output end of the comparator, so as to track the maximum value of each waveform of the secondary current (the maximum value of the secondary current changes in the boosting stage of the equipment, namely the peak value of the secondary current in the steady operation stage of the equipment). The maximum value of the secondary current and the voltage compensation circuit (the voltage output by the voltage compensation circuit is regulated by a potentiometer) are taken out and added by an adder, a comparison point slightly higher than the maximum value of the secondary current is obtained, the comparison point changes along with the change of the secondary current, the self-adjustment of the spark comparison point is realized, the potentiometer of the voltage compensation circuit is regulated, the obtained comparison point is larger than the increase amplitude of the secondary current when the equipment is normally boosted, and the false detection during the cold state boosting and the recovery stage after the spark flashover of the equipment is prevented. The obtained comparison point and the real-time value of the secondary current are compared by a primary comparator, when the spark flashover is generated, the real-time value of the secondary current suddenly increases, and exceeds the comparison point, the level of the output end of the comparator is inverted, the rear-end latch receives the level inversion signal, and continuously outputs an effective level signal, and the effective level signal is respectively input into the IGBT driver and the CPU: the output to the IGBT driver immediately turns off the IGBT and stops supplying power to the rectifier transformer. And outputting to a CPU, entering a spark flashover program, and after the subsequent processing of the spark flashover is completed, outputting a reset signal to a latch and an IGBT driver by the CPU to supply power to the rectifier transformer again.
Specifically, as shown in fig. 7, when the device starts boosting, the secondary current generates a first waveform, and the maximum value of the secondary current changes in real time with time during the rising edge of the first waveform, so that the size of the comparison point also changes with the change of the maximum value; when the first waveform of the secondary current reaches the peak value, the secondary current value in the section does not exceed the peak value of the first waveform from the falling edge of the first waveform to the part of the rising edge of the second waveform which does not exceed the peak value of the first waveform, so that the comparison points are all based on the comparison points calculated by the peak value of the first waveform; the maximum value of the secondary current changes again with time at the portion where the rising edge of the second waveform exceeds the peak of the first waveform, and thus the comparison point also changes with the change of the maximum value.
According to the spark flashover judging method based on the self-adjusting comparison point, the self-adjusting of the spark flashover comparison point is realized by taking the maximum value of the secondary current in the starting process in real time as a basis, the comparison point is only slightly higher than the maximum value of the secondary current, when sparks occur, the secondary current suddenly increases and can rapidly exceed the comparison point, compared with the spark flashover judging method based on the preset comparison point, the judging time is shorter, the current suddenly increases in amplitude and cannot cause current impact, so that the stability and the service life of equipment are improved, the IGBT is directly turned off after the sparks are judged, CPU (Central processing unit) judgment is not needed, the time for judging the sparks is further reduced while CPU resources are not occupied, and the timeliness of the spark flashover judgment is improved.
In one embodiment, the sampling is spaced 5-10 μs apart.
In one embodiment, the compensation value ranges from 0V to 1V.
In one embodiment, after the real-time sampling of the secondary current of the rectifier, the sampled secondary current is preprocessed, and the preprocessing includes: and removing burrs of the secondary current signal.
In one embodiment, as shown in fig. 3, a spark flashover judging circuit based on a self-adjusting comparison point comprises a rectifier transformer and a sampling unit connected with the rectifier transformer, wherein the output end of the sampling unit is respectively connected with the input end of a maximum value acquisition and holding circuit, the first input end of a first comparator and the first input end of a second comparator, the output end of the maximum value acquisition and holding circuit is connected with the second input end of the first comparator, the maximum value acquisition and holding circuit is used for detecting the current secondary current and outputting the maximum value of the secondary current in the current starting process, and the potential change of the output end of the first comparator is used for controlling the sampling state and the holding state of the maximum value acquisition and holding circuit; the output end of the maximum value acquisition and holding circuit is connected with the input end of the adder, and the output end of the adder is connected with the second input end of the second comparator.
In the embodiment, the secondary current signal output by the rectifier transformer is processed by devices such as a sampling unit, a maximum value acquisition and holding circuit and the like, after the spark flashover signal is judged at the moment of the spark flashover, the IGBT driver is directly turned off through a locking signal wire, the power supply to the rectifier transformer is stopped, and the spark flashover signal is output to the CPU. At this time, the CPU can run the spark flashover processing flow, after the spark flashover processing flow, the CPU outputs a reset signal to the latch and the IGBT driver, and the power supply of the power supply is restored again.
In one embodiment, the sampling unit is connected to the maximum value acquisition and holding circuit through a signal isolation unit.
In this embodiment, the sampling unit is connected to the signal isolation unit to eliminate signal glitches of the output secondary current and to eliminate high frequency noise generated by the linear optocoupler in the circuit, and then the maximum value of the secondary current is collected by connecting the isolation unit to the maximum value collection and holding circuit.
As shown in the signal sampling isolation circuit in fig. 4, the secondary current is taken out through the rectifier transformer and is connected into the signal isolation circuit composed of U2, U3 and U4 through the follower U1 to be output: the secondary current signal is connected with the in-phase input end of the operational amplifier U1, the reverse input end of the U1 is connected with the output end of the U1 to form a follower, the output end of the U1 is connected with the reverse input end of the U2 through a resistor R7, the reverse input end of the U2 is connected with the output end U2 through a capacitor C2 to prevent circuit signal oscillation and remove signal burrs, the output end of the U2 is connected with the cathode of a light emitting diode of the linear optocoupler U3 through a resistor R8, the anode of the diode is connected with a power supply, the anode and the cathode of the photosensitive diode of the linear optocoupler U3 are respectively connected with the in-phase input end of the operational amplifier U4 and the reverse input end of the U4, the resistor R10 and the capacitor C3 form low-pass filtering to eliminate high-frequency noise generated by the linear optocoupler, and the secondary current signal is output through the reverse input end of the U4 and connected with the self-adjusting comparison point to judge the spark flashover hardware circuit.
In one embodiment, the maximum value collection and holding circuit includes a triode Q1, a resistor R4, a charging capacitor C1, a discharging resistor R1, a resistor R5 and an operational amplifier U6, where an E emitter of the triode Q1 is connected to one end of the charging capacitor C1 and one end of the resistor R5 through the resistor R4, the other end of the charging capacitor C1 is grounded, the charging capacitor C1 is connected in parallel with the resistor R1, the other end of the resistor R5 is connected to a non-inverting input end of the operational amplifier U6, an inverting input end of the operational amplifier U6 is connected to an output end of the operational amplifier U6, and an output end of the operational amplifier U6 is connected to the adder.
The first comparator is a comparator U7A, the non-inverting input end of the comparator U7A is connected with the output end of the signal isolation unit, the output end of the operational amplifier U6 is connected with the inverting input end of the comparator U7A through a resistor R3, and the output end of the comparator U7A is connected with the B base electrode of the triode Q1.
The adder comprises a resistor R12, a resistor R15, a resistor R16, a resistor R17, an adjustable resistor R11 and an operational amplifier U8; the resistor R12 is connected with the output end of the maximum value acquisition and holding circuit in series and then is connected with the non-inverting input end of the operational amplifier U8; the resistor R15 is connected with the non-inverting input end of the operational amplifier U8 after being connected with the adjustable resistor R11 in series; one end of the resistor R16 is connected with the inverting input end of the operational amplifier U8, and the other end of the resistor R16 is grounded; one end of a resistor R17 is connected with one end of the operational amplifier U8 in series, and the other end of the resistor R17 is connected with the output end of the operational amplifier U8.
The second comparator is a comparator U7B, the inverting input end of the comparator U7B is connected with the output end of the operational amplifier U8 through a resistor R13, and the non-inverting input end of the comparator U7B is connected with the output end of the signal isolation unit.
In this embodiment, as shown in fig. 5, the isolated secondary current signal is connected to the non-inverting input end of the operational amplifier U5 through the resistor R6, the inverting input end of the amplifier U5 is directly connected to the output end of the amplifier U5, so that the output end of the follower U5 becomes a follower, the output end of the follower U5 is connected to the C collector of the NPN triode Q1, the E emitter of the triode Q1 is connected to the charging capacitor C1 through the resistor R4, the voltage on the capacitor is the maximum voltage of the secondary current, the C1 and the discharging resistor R1 are connected in parallel to ensure that the secondary current is reduced and also follows the maximum value, the resistor is too small to affect the maximum voltage adopted to affect the judgment of the spark flashover, and the voltage should be determined according to the period of the secondary current and the IGBT blocking time after the spark flashover. The resistor R4 is connected with the non-inverting input end of the operational amplifier U6 through the resistor R5, the inverting input end of the U6 is directly connected with the output end of the U6, so that the U6 becomes a follower, the output end of the follower U6 outputs a secondary current maximum value, the non-inverting input end of the comparator U7A is connected with the inverting input end of the comparator U7A through the resistor R3, the non-inverting input end of the comparator U7A is directly isolated with a secondary current signal, the output end of the comparator U7A is connected with the B base electrode of the triode Q1 and the pull-up resistor R2, and the sampling and the holding of the secondary current peak maximum value are controlled through the level conversion of the comparator. The output end of the follower U6 outputs the maximum value of the secondary current, the resistors R12, R15, R16 and R17 and the operational amplifier U7 form an adder, the adjustable resistor R11 is connected with the R15 to form a voltage compensation circuit, the output end of the follower U6 outputs the maximum value of the secondary current and is connected with the resistor R12, the voltage of the maximum value of the secondary current and the voltage of the compensation circuit are calculated by the adder to obtain the comparison point voltage slightly higher than the maximum value of the secondary current, the comparison point voltage is output by the output end of the U8, the resistor R13 is connected with the inverting input end of the comparator U7B, the non-inverting input end of the comparator U7B is connected with an isolated secondary current signal, the output end of the comparator U7B is connected with the pull-up resistor R14, when the spark flashover occurs, the secondary current real-time signal can rapidly rise, the level inversion is realized by the output end of the comparator U7B, the input end of the latch U9A is reached, the spark signal is latched, the latch IGBT is output by one output end of the U9A, the other output end of the latch IGBT is passed by the U9A, the CPU is enabled to execute the spark program, the spark program is executed by the CPU, the execution is waited for the reset signal to enter the latch U9A for completing the flashover once.
As shown in fig. 6, the CPU outputs OUTA, OUTB, OUTC, OUTD four-way trigger signals to connect four and operators, performs and operation with a spark flashover signal output by an output end of U9A of the latch, outputs the spark flashover signal to enter the IGBT to drive, controls the IGBT switch, and when the spark flashover occurs, the trigger signals to stop with the operator output end, the IGBT turns off, so that the spark flashover judging circuit directly turns off the IGBT, and does not occupy CPU resources. And meanwhile, the other output end of the U9A inputs a spark signal into the CPU to execute a spark flashover program. After the spark flashover procedure is executed, a reset signal is output to the latch, and the next spark flashover is waited.
Specific limitations regarding a circuit for spark-over determination based on self-adjusting comparison points can be found in the above description of a method for spark-over determination based on self-adjusting comparison points, and are not described in detail herein.
The application realizes the self-adjustment of the spark flashover comparison point by taking the maximum value of the acquired real-time secondary current as shown in fig. 7; because the comparison point is only slightly higher than the maximum value of the secondary current, when sparks occur, the secondary current suddenly increases and can rapidly exceed the comparison point, and compared with a method for judging sparks by the preset comparison point, the method has the advantages of shorter time, smaller current suddenly increasing amplitude and no current impact; when the spark is judged, the IGBT is directly turned off, the CPU is not required to judge, and the time for judging the spark is further reduced while the CPU resource is not occupied.
The technical key points of the application are as follows:
1. automatically detecting a maximum value of each waveform by using a maximum value detection holding circuit;
2. the self-adjustment of the spark flashover comparison point is realized by using an adder;
3. the spark flashover signal directly turns off the IGBT, so that CPU resources are not occupied;
the technical features of the above embodiments may be arbitrarily combined, and all possible combinations of the technical features in the above embodiments are not described for brevity of description, however, as long as there is no contradiction between the combinations of the technical features, they should be considered as the scope of the description.
The above examples illustrate only a few embodiments of the application, which are described in detail and are not to be construed as limiting the scope of the application. It should be noted that it will be apparent to those skilled in the art that several variations and modifications can be made without departing from the spirit of the application, which are all within the scope of the application. Accordingly, the scope of protection of the present application is to be determined by the appended claims.
Claims (10)
1. A spark flashover determination method based on self-adjusting comparison points, the method comprising:
during normal operation, sampling the secondary current of the rectifier;
judging whether the secondary current value at the moment t is the maximum value from the starting time to the moment t; if yes, superposing the compensation value on the basis of the maximum value to obtain a comparison point aiming at the t' moment; the time t' is the next sampling time; if not, the comparison point at the moment t' is still the comparison point determined last time;
and comparing the secondary current value at the time t 'with the comparison point, and if the secondary current value at the time t' is larger than the comparison point, determining that spark flashover occurs.
2. The method of claim 1, wherein the sampling is at intervals of 5-10 μs.
3. The method according to claim 1, wherein the compensation value is in the range of 0-1V.
4. The method of claim 1, wherein the sampling of the rectifier secondary current in real time is followed by a pre-treatment of the sampled secondary current, the pre-treatment comprising: and removing burrs of the secondary current signal.
5. The spark flashover judging circuit based on the self-adjusting comparison point comprises a rectifier transformer and a sampling unit connected with the rectifier transformer, and is characterized in that the output end of the sampling unit is respectively connected with the input end of a maximum value acquisition and holding circuit, the first input end of a first comparator and the first input end of a second comparator, the output end of the maximum value acquisition and holding circuit is connected with the second input end of the first comparator, the maximum value acquisition and holding circuit is used for detecting the current secondary current and outputting the maximum value of the secondary current in the starting process, and the sampling state and the holding state of the maximum value acquisition and holding circuit are controlled by utilizing the potential change of the output end of the first comparator; the output end of the maximum value acquisition and holding circuit is connected with the input end of the adder, and the output end of the adder is connected with the second input end of the second comparator.
6. The circuit of claim 5, wherein the sampling unit is connected to the maximum value acquisition and hold circuit through a signal isolation unit.
7. The circuit of claim 6, wherein the maximum value collection and holding circuit comprises a triode Q1, a resistor R4, a charging capacitor C1, a discharging resistor R1, a resistor R5 and an operational amplifier U6, wherein an E emitter of the triode Q1 is respectively connected with one end of the charging capacitor C1 and one end of the resistor R5 through the resistor R4, the other end of the charging capacitor C1 is grounded, the charging capacitor C1 is connected with the resistor R1 in parallel, the other end of the resistor R5 is connected with a non-inverting input end of the operational amplifier U6, an inverting input end of the operational amplifier U6 is connected with an output end of the operational amplifier U6, and the output end of the operational amplifier U6 is connected with the adder.
8. The circuit of claim 7, wherein the first comparator is a comparator U7A, the non-inverting input terminal of the comparator U7A is connected to the output terminal of the signal isolation unit, the output terminal of the operational amplifier U6 is connected to the inverting input terminal of the comparator U7A through a resistor R3, and the output terminal of the comparator U7A is connected to the B base of the transistor Q1.
9. The circuit of claim 6, wherein the adder comprises a resistor R12, a resistor R15, a resistor R16, a resistor R17, an adjustable resistor R11, and an operational amplifier U8; the resistor R12 is connected with the output end of the maximum value acquisition and holding circuit in series and then is connected with the non-inverting input end of the operational amplifier U8; the resistor R15 is connected with the non-inverting input end of the operational amplifier U8 after being connected with the adjustable resistor R11 in series; one end of the resistor R16 is connected with the inverting input end of the operational amplifier U8, and the other end of the resistor R16 is grounded; one end of a resistor R17 is connected with one end of the operational amplifier U8 in series, and the other end of the resistor R17 is connected with the output end of the operational amplifier U8.
10. The circuit of claim 9, wherein the second comparator is a comparator U7B, an inverting input terminal of the comparator U7B is connected to an output terminal of the operational amplifier U8 through a resistor R13, and a non-inverting input terminal of the comparator U7B is connected to the signal isolation unit output terminal.
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