CN117517784B - Insulation resistance detection device and method for mining high-voltage frequency converter and optimization method - Google Patents
Insulation resistance detection device and method for mining high-voltage frequency converter and optimization method Download PDFInfo
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Abstract
The invention discloses a device and method for detecting and optimizing insulation resistance of a mining high-voltage frequency converter, and relates to the technical field of high-voltage frequency converter detection. The device comprises a voltage attenuation module, a voltage detection module and a voltage detection module, wherein the voltage attenuation module is used for attenuating a high-voltage signal at a neutral point position of the high-voltage frequency converter and transmitting the high-voltage signal to the insulation detection module; the high-voltage isolation power supply is used for providing a high-voltage power supply for the insulation detection module; the insulation detection module is used for generating positive and negative low-frequency signals and injecting the positive and negative low-frequency signals into the high-voltage frequency converter shell, and determining the insulation resistance value of the high-voltage frequency converter through the voltage of the neutral point position of the high-voltage frequency converter and the voltage of the positive and negative low-frequency signal injection point. The invention can improve the insulation resistance detection efficiency and the detection safety.
Description
Technical Field
The invention relates to the technical field of high-voltage frequency converter detection, in particular to a device and method for detecting insulation resistance of a mining high-voltage frequency converter and an optimization method.
Background
The application occasion of the mining high-voltage frequency converter has the characteristics of high voltage (up to 10 KV), high electromagnetic interference, direct current and alternating current working conditions, motor rotation and the like, and has urgent requirements for online insulation detection.
In the prior art, a megger is generally adopted to measure the insulation resistance state of a motor relative to the ground, the measurement is needed for a plurality of times, the time and the labor are wasted, but the insulation state of the middle position of a device (such as an IGBT (insulated gate bipolar transistor) and a rectifier diode) relative to the ground cannot be detected.
In the prior art, in the insulation on-line detection of the mining frequency converter, an additional direct current (or direct current superposition) is adopted for insulation resistance detection, direct current voltage is required to be directly superposed in a cable or a main loop, and the insulation resistance is calculated by detecting the direct current size, so that the insulation resistance is easily influenced by factors such as distributed capacitance and the like, and is easily influenced by electromagnetic interference.
The traditional low-frequency pulse injection method has long test time, and when the insulation value of a system is reduced and the ground fault occurs, a plurality of periods (more than 20 s) are needed to be passed to determine whether the insulation value is normal or not.
The traditional low-frequency injection method insulation detection device is mainly applied to insulation detection of electric vehicles, the detection voltage is less than 800V, and the traditional low-frequency injection method insulation detection device is mainly applied to direct current detection and is not used in the environment of a high-voltage frequency converter.
Disclosure of Invention
Aiming at the defects in the prior art, the invention provides a device, a method and an optimization method for detecting the insulation resistance of a mining high-voltage frequency converter, so as to improve the insulation resistance detection efficiency and the detection safety.
In order to achieve the aim of the invention, the invention adopts the following technical scheme:
in a first aspect, the present invention provides a mining high-voltage inverter insulation resistance detection device, including:
the voltage attenuation module is used for attenuating a high-voltage signal at the neutral point position of the high-voltage frequency converter and transmitting the high-voltage signal to the insulation detection module;
the high-voltage isolation power supply is used for providing a high-voltage power supply for the insulation detection module;
the insulation detection module is used for generating positive and negative low-frequency signals and injecting the positive and negative low-frequency signals into the high-voltage frequency converter shell, and determining the insulation resistance value of the high-voltage frequency converter through the voltage of the neutral point position of the high-voltage frequency converter and the voltage of the positive and negative low-frequency signal injection point.
In a second aspect, the invention provides a mining high-voltage frequency converter insulation resistance detection method applying the device, which comprises the following steps:
s101, initializing power-on reset and reading parameter configuration; the parameter configuration comprises an insulation alarm value, a positive voltage threshold, a negative voltage threshold and a delay threshold;
s102, starting delay timing, and judging whether the delay timing reaches a delay threshold; if yes, go to step S103; otherwise, adding 1 to the clock cycle time, and continuing to delay time;
s103, utilizing a main control chip to control a positive and negative pressure generating circuit to generate a positive and negative pressure low-frequency signal, and judging whether the positive and negative pressure value of the positive and negative pressure low-frequency signal is within the limit range of a positive and negative pressure threshold value; if yes, go to step S104; otherwise, outputting a positive and negative voltage fault signal;
s104, detecting positive and negative voltage values of sampling signals of the high-voltage frequency converter, and judging whether the voltage value is equal to 0; if yes, outputting a detection result as a maximum insulation value; otherwise, executing step S105;
s105, judging whether the voltage value has positive and negative direction conversion; if yes, executing step S106; otherwise, outputting a fault signal;
s106, carrying out digital filtering on the voltage value, calculating the insulation resistance value of the high-voltage frequency converter according to the internal impedance of the high-voltage frequency converter, and outputting a detection result;
s107, judging whether the calculated insulation resistance value of the high-voltage frequency converter is smaller than an insulation alarm value; if yes, return to step S103; otherwise, outputting an alarm signal.
In a third aspect, the invention provides a mining high-voltage frequency converter insulation resistance detection optimization method applying the method, which comprises the following steps:
s201, initializing power-on reset;
s202, when the high-voltage frequency converter is not started and has no high voltage, a test resistor is put into, the time from 0 to stable voltage of the voltage at two ends of the test resistor and the stable voltage are recorded, and a distributed capacitance value is calculated;
s203, comparing the distributed capacitance value with the capacitance value in the recorded table, matching the capacitance value in the table, and compensating the running capacitance value according to the environmental temperature and humidity parameters;
s204, when the high-voltage frequency converter is started and has high voltage, calculating the insulation resistance value of the high-voltage frequency converter according to the method;
s205, adjusting control signals sent to the positive and negative voltage generating circuit by using the main control chip at set frequency intervals so as to increase positive and negative voltage output frequency and record a first frequency value;
s206, acquiring a loop voltage value of the filtering sampling circuit by using the main control chip, and recording voltage period change time to obtain a second frequency value;
s207, judging whether the first frequency value is equal to the second frequency value; if yes, fitting the maximum voltage value of the distributed capacitor, and calculating the insulation resistance value of the high-voltage frequency converter according to the method; otherwise, the value returns to step S205.
The invention has the following beneficial effects:
1. after improvement, the measured voltage is attenuated by adjusting the resistance value in the voltage attenuation module, the transmission energy is small, the safety is high, and the online insulation resistance detection of the 10kV frequency converter can be realized at most.
2. The internal output voltage VP and the sampling resistor RK of the insulation detection module can be adjusted according to the actual return detection signal; and adjusting the gain so that the sampling loop works in an optimal amplification interval, and further ensuring that each module and the accuracy of the ground insulation value between the modules are accurately measured under the cascade state of the high-voltage multi-module.
3. The anti-interference performance is strong, and the accuracy of the data collected by the frequency converter is effectively ensured. 1) The filter circuit adopts a seven-order low-pass filter circuit design, so that the interference signals above 10Hz can be effectively filtered. 2) The low-frequency interference during the starting of the frequency converter is avoided through the delay design in the program. The delay subprogram can be called, and the insulation detection module can be electrified firstly, so that the insulation detection module works when the frequency converter is not started, and when the frequency converter needs to be started, the main control only needs to send a starting instruction to the insulation detection module through the communication circuit, and the delay subprogram can be called. 3) Digital filtering, compensation and the like in the program.
4. The data acquisition is more accurate. And adding a distributed capacitance compensation function, recording test data in a dot form, comparing the test data with calculation data, and compensating a capacitance value during operation.
5. By detecting the rise time and voltage of the distributed capacitor, the fault reporting time is shortened.
Drawings
FIG. 1 is a schematic diagram of a mining high-voltage frequency converter insulation resistance detection device;
fig. 2 is a schematic diagram of a mining high-voltage inverter insulation resistance detection device;
FIG. 3 is a schematic diagram of an insulation detection module;
FIG. 4 is a schematic diagram of a filtered sampling circuit;
FIG. 5 is a schematic diagram of a BOOST circuit;
FIG. 6 is a schematic diagram of a BUCK step-down circuit;
FIG. 7 is a schematic diagram of a push-pull control circuit;
FIG. 8 is a schematic flow chart of a method for detecting insulation resistance of a mining high-voltage frequency converter;
FIG. 9 is a schematic flow chart of a method for optimizing insulation resistance detection of a mining high-voltage frequency converter;
fig. 10 is a schematic diagram of a transformation principle of a device for detecting insulation resistance of a mining high-voltage frequency converter.
Detailed Description
The following description of the specific embodiments of the present invention is provided to facilitate understanding of the present invention by those skilled in the art, but it should be understood that the present invention is not limited to the scope of the specific embodiments, and all the inventions which make use of the inventive concept are protected by the following description as long as they are within the spirit and scope of the present invention as defined by the appended claims.
Example 1:
as shown in fig. 1, an embodiment of the present invention provides a device for detecting insulation resistance of a mining high-voltage frequency converter, including:
the voltage attenuation module is used for attenuating a high-voltage signal at the neutral point position of the high-voltage frequency converter and transmitting the high-voltage signal to the insulation detection module;
the high-voltage isolation power supply is used for providing a high-voltage power supply for the insulation detection module;
the insulation detection module is used for generating positive and negative low-frequency signals and injecting the positive and negative low-frequency signals into the high-voltage frequency converter shell, and determining the insulation resistance value of the high-voltage frequency converter through the voltage of the neutral point position of the high-voltage frequency converter and the voltage of the positive and negative low-frequency signal injection point.
As shown in fig. 1, inside the dashed box is the internal electrical topology of the high voltage inverter, and the solid box area represents the equipment housing. The device comprises 3 modules, (1) an insulation detection module, a core acquisition processing module, an insulation resistance acquisition processing module and an upper control unit, wherein after the MCU processes, data are uploaded to the upper control unit for judgment; (2) The high-voltage isolation power supply can provide 14kV electrical isolation, so that the power supply safety of equipment is ensured, and high-voltage serial-in is prevented; (3) And the voltage attenuation module is used for attenuating the high-voltage signal, reducing energy transmission and reducing high-voltage influence.
When the insulation resistance is measured, the device can supply power to the insulation detection module through the high-voltage isolation power supply, and the insulation detection module generates a 1Hz low-frequency signal after self-checking is normal and is injected into the equipment shell, namely the ground. And meanwhile, the voltage attenuation module is connected into the bus plus, the bus minus or the neutral point position. When the method is used, the voltage attenuation module is connected to the neutral point position because the device voltage is high and a three-level or higher multi-level topology is adopted.
Fig. 1 is a main topology, which is electrically connected, so the topology of fig. 1 is appropriately simplified as shown in fig. 2. Rm is the voltage decay module resistance, which is known; RK is an internal divider resistor of the insulation detection module, and is adjustable and known; r1 and R2 are the impedance existing in the equipment, are uncertain, but the same equipment is basically consistent, and can be obtained through measurement; different devices can respectively measure, make a point table, and the program is internally provided for calling; the voltage of the V2 point is the voltage of the rechecking end in the insulation detection module and the voltage of the VP point is the voltage generated in the insulation detection meter, and the voltage is designed to be adjustable in the insulation detection module and can be automatically adjusted according to the rechecking result; rf is the insulation resistance to be measured. By detecting the voltage of the V2 point and the voltage of the Vp point, the Rf insulation resistance value can be calculated through a node voltage formula.
In an alternative embodiment of the present invention, the insulation detection module specifically includes:
the system comprises a main control chip, a filtering sampling circuit, a positive and negative voltage generating circuit and a parameter setting circuit, wherein the filtering sampling circuit, the positive and negative voltage generating circuit and the parameter setting circuit are respectively connected with the main control chip;
the filtering sampling circuit is used for filtering high-frequency signals from sampling signals of the high-voltage frequency converter by adopting a multi-stage high-order low-pass filtering circuit and amplifying low-frequency signals at the same time; then digital filtering is carried out outputting to a main control chip;
the positive and negative voltage generating circuit is used for generating an adjustable positive and negative voltage low-frequency signal according to a switch control signal issued by the main control chip and returning an output voltage rechecking signal to the main control chip;
the parameter setting circuit is used for setting working state parameters of the main control chip; the working state parameters comprise working voltage, RF insulation alarm value, power-on delay action parameter, communication carrier frequency and the like;
the main control chip is used for determining the voltage of the low-frequency signal injection point according to the output voltage rechecking signal and determining the insulation resistance value of the high-voltage frequency converter by combining the detected neutral point position voltage of the high-voltage frequency converter.
As shown in fig. 3, the present embodiment includes, in addition to the above main structure, a power supply circuit for supplying power at 24V, and the power supply circuit is internally converted into power supply for each functional part; the communication circuit is used for designing communication modes such as CAN, analog quantity, serial port and the like and outputting a test value; and the alarm circuit is designed to be an indication loop and a relay loop.
In an alternative embodiment of the present invention, the filtering sampling circuit specifically includes:
a four-stage seven-order Butterworth filter circuit and an ADC sampling circuit;
the four-stage seven-order Butterworth filter circuit is used for filtering and proportional amplifying high-frequency signals through the RC low-pass filter circuit, then suppressing the high-frequency signals through the active second-order filter circuit, and finally suppressing the high-frequency signals through the two-stage homodromous amplifying filter circuit and amplifying low-frequency signals at the same time;
the ADC sampling circuit is used for carrying out analog-to-digital conversion on the low-frequency signal output by the four-stage seven-order Butterworth filter circuit, and outputting the low-frequency signal to the main control chip after digital filtering.
As shown in fig. 4, the filter circuit adopts the design of a Butterworth low-pass filter circuit, the circuit is designed into a 4-level seven-order, so that interference signals above 10Hz can be effectively filtered, and the gain is designed to be 40dB. The phase A, R1 and C4 form an RC low-pass filter circuit, bypass high-frequency signals, have a certain buffer left and right for the high-frequency high-voltage signals, and R8 and R11 form a homodromous proportional amplifying circuit, so that the input weak signals are amplified proportionally, and the subsequent operation is facilitated; the stage B, R2, R3, C1 and C5 form an active second-order filter loop, and parameters are adjusted to inhibit high-frequency signals; and a stage C, D, wherein the homodromous amplifying circuit is added on the basis of the stage A, so that the high-frequency signal suppression intensity is improved, and the low-frequency signal is amplified, thereby being convenient for the use of a subsequent sampling circuit.
The sampling circuit adopts a high-precision ADC to perform high-speed conversion and analog-to-digital conversion, and performs digital filtering processing on data by means of an internal chip filtering measure.
In the embodiment, the weak sampling signal INV2 of the high-voltage frequency converter of the filtering sampling circuit is amplified to the signal V2 which can be received by the ADC, so that loop signal detection is realized.
In an optional embodiment of the present invention, the positive and negative voltage generating circuit specifically includes:
a BOOST circuit and a BUCK circuit respectively connected with the main control chip, and a push-pull control circuit respectively connected with the BOOST circuit and the BUCK circuit;
the BOOST circuit is used for controlling the switching state of the first selection switch according to a BOOST signal issued by the main control chip so as to generate an adjustable positive-pressure low-frequency signal and outputting the adjustable positive-pressure low-frequency signal to the push-pull control circuit;
the BUCK step-down circuit is used for controlling the switching state of the second selection switch according to a BUCK signal issued by the main control chip so as to generate an adjustable negative pressure low-frequency signal and output the adjustable negative pressure low-frequency signal to the push-pull control circuit;
the push-pull control circuit is used for controlling the alternate output of the positive pressure low-frequency signal and the negative pressure low-frequency signal according to the push-pull control signal issued by the main control chip.
As shown in FIG. 3, the positive and negative voltage generating circuit consists of 3 parts, namely a BOOST circuit, a BUCK circuit and a push-pull control circuit. VP voltage is designed to be three gears of + -48V, + -72V and + -96V in design; the gear selection is determined by the size of a return checking signal V2 during testing, and when the return checking signal is small, the gear can be automatically switched, so that the return checking signal can be effectively obtained when a plurality of devices are ensured.
In an alternative embodiment of the present invention, the BOOST circuit specifically includes:
a BOOST control chip;
the starting signal end of the BOOST control chip is connected with the main control chip, the output end of the BOOST control chip is connected with the grid electrode of a first MOS switch tube, the source electrode of the first MOS switch tube is grounded through a first resistor and is connected with the current sampling end of the BOOST control chip, the drain electrode of the first MOS switch tube is respectively connected with the positive electrode of a first energy storage capacitor and a first rectifying diode, the other end of the first energy storage capacitor is used as a voltage input end, the negative electrode of the first rectifying diode is respectively connected with a first energy storage filter capacitor and a first resistor, the other end of the first energy storage filter capacitor is grounded, the other end of the first resistor is respectively connected with the first end of a first selection switch and the voltage division signal end of the BOOST control chip, the second end, the third end and the fourth end of the first selection switch are respectively grounded through a second resistor, a third resistor and a fourth resistor, and the BOOST signal control end of the first selection switch is connected with the main control chip.
As shown in fig. 5, positive voltage vp+ is generated by the BOOST circuit, and the main control chip adjusts the voltage of the sampling resistor to control the vp+ voltage value, and monitors the vp+ voltage in real time. The boost control chip receives control of the main control signal and has protection functions of overvoltage, overcurrent and the like; l1 is a BOOST circuit energy storage capacitor; d7 is a rectifier diode, which is responsible for rectifying and anti-reversing the pulse current; q10 is a SiCmos switch tube, so that heating power consumption is greatly reduced; r1 is a current sampling resistor and is responsible for converting a current signal into a voltage signal, and transmitting the voltage signal into a control chip to be used as an overcurrent protection reference; c1 is an energy storage filter capacitor; the selection switch K1 is an analog switch chip, has small internal resistance, receives a control instruction of the main control chip, and switches different voltage dividing resistors; r2, R3 and R4 are reference resistors under different voltages; r5 is a fixed resistance resistor, forms different voltage division parameters with R2, R3 and R4, and feeds back the parameters to the boost chip side to output VP+ with three voltage levels. In the design, a programmable control switch chip is utilized to combine with system logic, so that the aim of adjusting the output positive pressure VP+ is fulfilled, and the output positive pressure VP+ is not fixed.
In an alternative embodiment of the present invention, the BUCK circuit specifically includes:
a BUCK control chip;
the starting signal end of the BUCK control chip is connected with the main control chip, the output end of the BUCK control chip is connected with the grid electrode of the second MOS switch tube, the drain electrode of the BUCK control chip is used as a voltage input end, the source electrode of the BUCK control chip is respectively connected with the second energy storage capacitor and the cathode of the second rectifier diode, the other end of the second energy storage capacitor is respectively connected with the second energy storage filter capacitor and the fifth resistor and grounded, the other end of the fifth resistor is respectively connected with the first end of the second selection switch and the voltage division signal end of the BUCK control chip, the second end, the third end and the fourth end of the second selection switch are respectively connected with the anode of the second rectifier diode and the other end of the second energy storage capacitor through the sixth resistor, the seventh resistor and the eighth resistor, and the BOOST signal control end of the first selection switch is connected with the main control chip.
As shown in FIG. 6, the negative pressure VP-is generated by the BUCK step-down circuit, the main control chip adjusts the voltage of the sampling resistor, the VP-voltage value is controlled, and the VP-voltage is monitored in real time. Wherein the BUCK chip is controlled by a main control signal; l2 is a BUCK circuit energy storage filter capacitor; d8 is a freewheeling diode; q11 is a SICMOS tube, so that heating power consumption is reduced; r6, R7 and R8 are reference resistors under different voltages, R9 is a fixed resistance resistor, and forms different voltage dividing parameters with R6, R7 and R8, and the different voltage dividing parameters are fed back to the BUCK chip side to output VP-of three voltage levels; in the design, a programmable switch chip is utilized to combine with system logic, so that the aim of adjusting the output negative pressure VP-is fulfilled instead of being fixed.
In an alternative embodiment of the present invention, the push-pull control circuit specifically includes:
the third MOS switch tube and the fourth MOS switch tube;
the grid electrode of the third MOS switch tube is used as a positive-voltage low-frequency signal input end, the drain electrode of the third MOS switch tube is used as a positive-voltage low-frequency signal input end, the positive-voltage signal control end is connected with the positive-voltage low-frequency signal input end through a ninth resistor, and the source electrode of the third MOS switch tube is connected with a tenth resistor; the grid electrode of the fourth MOS switch tube is used as a negative electrode signal control end, the source electrode of the fourth MOS switch tube is used as a negative voltage low-frequency signal input end, the negative electrode signal control end is connected with the negative voltage low-frequency signal input end through an eleventh resistor, the drain electrode of the fourth MOS switch tube is connected with a twelfth resistor, and the other end of the tenth resistor is connected with the other end of the twelfth resistor to serve as a positive voltage low-frequency signal output end and is grounded through a third energy storage filter capacitor and a first voltage stabilizing diode which are connected in parallel.
As shown in FIG. 7, the main control chip controls VP+ and VP-to be alternately output through a P+ and P-control signal circuit, wherein Q12 is Pmos, Q13 is Nmos, and as a switch for generating positive and negative pressure VP+ -switching, a mos tube is adopted instead of a triode in the traditional design, so that the purposes of reducing the heating of a device, reducing the difficulty of matching an opening resistor and improving the reliability are achieved; p+ and P-are positive and negative voltage control signals for controlling the on and off of Q12 and Q13; r11 and R12 are limiting resistors, so that VP+ and VP-are directly conducted when control is abnormal, and a short circuit phenomenon is caused; r10 pulls up the Q12 gate voltage to VP+ and R13 pulls down the Q13 gate voltage to VP-, which is designed to ensure that Q12 and Q13 are in an off state when the master control unit is not issuing control commands.
In an optional embodiment of the present invention, the calculation formula for determining the insulation resistance value of the high-voltage frequency converter by the insulation detection module through detecting the voltage at the neutral point position of the high-voltage frequency converter and the voltage at the injection point of the positive and negative low-frequency signals is:
，
wherein,indicating the insulation resistance value to be measured of the high-voltage frequency converter, < >>Indicating the positive value of the voltage signal of the return detection end of the insulation module, < + >>Indicating the negative value of the voltage signal of the return detection end of the insulation module, < + >>Indicating that the positive value of the detection voltage is generated inside the insulation detection table,indicating that the insulation detection table generates a negative value of the detection voltage, < + >>Representing the voltage division detection resistance within the insulation detection module,，/>represents the internal impedance of the high voltage frequency converter, +.>Representing the resistance of the voltage decay module.
Example 2:
the embodiment further provides a method for detecting insulation resistance of a mining high-voltage frequency converter by using the device on the basis of the insulation resistance detection device of the mining high-voltage frequency converter provided by the embodiment 1, as shown in fig. 8, comprising the following steps S101 to S107:
s101, initializing power-on reset and reading parameter configuration; the parameter configuration comprises an insulation alarm value, a positive voltage threshold, a negative voltage threshold and a delay threshold;
specifically, in this embodiment, through step S101, the power-on reset, the initialization procedure, the parameter configuration, the insulation alarm value RF, the positive and negative voltage VP delay T0, and the like are read.
S102, starting delay timing, and judging whether the delay timing reaches a delay threshold; if yes, go to step S103; otherwise, adding 1 to the clock cycle time, and continuing to delay time;
specifically, in the stage of starting the frequency converter, low-frequency interference is generated, so in this embodiment, the time T0 of the detection signal is designed to be a fixed value through step S102, the time T0 is delayed to be counted, when T is detected to be smaller than T0, the time of each clock cycle in the program can be automatically +1, and when T is larger than or equal to T0, the insulation detection module formally works, so that the design purpose is to avoid the low-frequency interference at the moment of starting the frequency converter, and the accuracy of the measurement result is ensured.
S103, utilizing a main control chip to control a positive and negative pressure generating circuit to generate a positive and negative pressure low-frequency signal, and judging whether the positive and negative pressure value of the positive and negative pressure low-frequency signal is within the limit range of a positive and negative pressure threshold value; if yes, go to step S104; otherwise, outputting a positive and negative voltage fault signal;
specifically, in this embodiment, after the delay is finished in step S103, the control chip sends out a p+ and P-control signal circuit to the push-pull control circuit in the positive and negative voltage generating circuit to control vp+ and VP-to be alternately output and sent out, and at the same time, detects whether vp+ and VP-voltages are within a preset error of 10%, if the error exceeds a preset parameter, a fault is reported to the main control chip, and the main control chip displays the current fault or sends the current fault to the upper computer through communication; if the error is within the range, then the next step is performed.
S104, detecting positive and negative voltage values of sampling signals of the high-voltage frequency converter, and judging whether the voltage value is equal to 0; if yes, outputting a detection result as a maximum insulation value; otherwise, executing step S105;
specifically, in this embodiment, step S104 is performed on the positive and negative voltage values of the signal V2 received by the filtering and sampling circuit, if V2 is 0, it indicates that the insulation resistance is infinite at this time, and the maximum insulation value is set at this time for convenience of display; if v2+.0, then proceed to the next step.
S105, judging whether the voltage value has positive and negative direction conversion; if yes, executing step S106; otherwise, outputting a fault signal;
specifically, in this embodiment, step S105 is used to determine whether V2 has ±direction conversion, and V2 does not have ±direction conversion, so that internal rechecking circuit faults or other reasons may be required to report rechecking faults to the main control chip, and the main control chip displays the current faults or sends the current faults to the upper computer through communication.
S106, carrying out digital filtering on the voltage value, calculating the insulation resistance value of the high-voltage frequency converter according to the internal impedance of the high-voltage frequency converter, and outputting a detection result;
specifically, in the present embodiment, when V2 has ±conversion in step S106, the value of V2 is read, digital filtering is performed, and the internal compensation parameter R1/R2 is called to calculate the Rf insulation resistance value. The obtained insulation value is uploaded to a display screen and an upper computer control center through communication, and the upper computer judges the insulation value.
S107, judging whether the calculated insulation resistance value of the high-voltage frequency converter is smaller than an insulation alarm value; if yes, return to step S103; otherwise, outputting an alarm signal.
Specifically, in the present embodiment, the calculated Rf value is compared with the insulation alarm value Rf in step S107, and if Rf < Rf, the process returns to step S103; otherwise, sending out an alarm signal to trigger an alarm loop, wherein the insulation value is low.
Example 3:
the embodiment further provides a mining high-voltage frequency converter insulation resistance detection optimization method applying the method on the basis of the mining high-voltage frequency converter insulation resistance detection method provided in embodiment 2, as shown in fig. 9, comprising the following steps S201 to S207:
s201, initializing power-on reset;
specifically, the present embodiment first performs power-on reset and initializes the procedure through step S201.
S202, when the high-voltage frequency converter is not started and has no high voltage, a test resistor is put into, the time from 0 to stable voltage of the voltage at two ends of the test resistor and the stable voltage are recorded, and a distributed capacitance value is calculated;
specifically, in this embodiment, step S202 is used to determine whether the complete machine system is working, and when the complete machine system is not started and has no high voltage, the test resistor Rf1 is put into, the time t from 0 to the stable voltage of the voltage at two ends of Rf1 and the stable voltage are recorded, and the distributed capacitance Cf value can be calculated by back-pushing in combination with the capacitance charging model.
S203, comparing the distributed capacitance value with the capacitance value in the recorded table, matching the capacitance value in the table, and compensating the running capacitance value according to the environmental temperature and humidity parameters;
specifically, in this embodiment, the Cf value is compared with the capacitance value in the recorded table in step S203, the capacitance value in the table is matched, and the capacitance value during operation is compensated according to the parameters such as the environmental temperature and the humidity transmitted by the upper computer.
S204, when the high-voltage frequency converter is started and has high voltage, calculating the insulation resistance value of the high-voltage frequency converter according to the method;
specifically, in this embodiment, when the complete machine system is started and there is a high voltage in step S204, V2 voltage dV2 is recorded every dT, a time and voltage matrix record table is constructed, and a charging curve is mapped according to a capacitor charging and discharging model, so as to calculate an Rf value.
S205, adjusting control signals sent to the positive and negative voltage generating circuit by using the main control chip at set frequency intervals so as to increase positive and negative voltage output frequency and record a first frequency value;
specifically, in this embodiment, after Rf is stabilized in step S205, the control logic of the positive and negative voltage output circuit is adjusted at intervals of 0.5Hz by using the main control chip program, so as to increase the positive and negative voltage output frequency, and record the frequency f1.
S206, acquiring a loop voltage value of the filtering sampling circuit by using the main control chip, and recording voltage period change time to obtain a second frequency value;
specifically, in the embodiment, in step S206, the main control chip is utilized to record the voltage period change time t1 and convert the voltage period change time t into the frequency value f2 while collecting the return ADC loop voltage value.
S207, judging whether the first frequency value is equal to the second frequency value; if yes, fitting the maximum voltage value of the distributed capacitor, and calculating the insulation resistance value of the high-voltage frequency converter according to the method; otherwise, the value returns to step S205.
Specifically, the present embodiment iterates the detection process through step S207 until the frequency f2 detected by the recheck loop is not equal to the emission frequency f1, and at this time, the increase of the frequency may cause the distributed capacitor to be underfilled, so that the maximum recheck voltage is not V2. Fitting is required to obtain the maximum voltage value, and then the Rf value is calculated.
When Rf is detected, the positive pressure and the negative pressure need to be detected simultaneously, the Rf detection time is related to the frequency f1, and the faster the f1 is, the shorter the detection time is. When the fault is reported, the Rf value needs to be sampled for multiple times, the Rf value can be reported after multiple times of faults, and the fault is detected in an insulation way. Therefore, the positive and negative voltage output frequency is increased, and the time for reporting the insulation detection fault can be greatly shortened by fitting the curve to be detected.
In the following, the working principle of the insulation resistance detection optimization method of the mining high-voltage frequency converter provided by the embodiment is described, for convenience of understanding, fig. 2 is transformed to be shown in fig. 10, and in theory, the Cf value does not exist, and the Cf value does not appear in an insulation resistance calculation formula. In practice, the frequency converter system has a distributed capacitance Cf, which is smaller and which is constantly changing due to temperature, humidity, etc. during the start-up and normal operation of the frequency converter. Therefore, by means of tools such as an electric bridge, cf values of the same device under different environments are tested, cf of a plurality of groups of different devices are tested, the Cf values are arranged into a data table for query and call, a data point table is prepared during program programming, and a program automatically queries and fits a Cf model meeting the working requirements for test calculation.
The right side in fig. 10 shows the charge and discharge process of the capacitor, and a charge and discharge curve can be fitted according to a charge and discharge equation. VP, rm, rk in FIG. 8 are known; v2 is measured, and CF is tested and used as a point table for query and call. Rf, insulation resistance to be measured; v22 is a temporary reference, which can be deduced from V2.
Cf charge time constant，/>The expression formula is:
，
in the formula, rf is the resistance to be measured. That is, the Rf value can be calculated by measuring the time constant value.
When the capacitor Cf is fully charged, the maximum voltage Uc across Cf is:
，
in this formula, the maximum voltage value Uc across Cf can be calculated.
Then when the capacitor is in a charged state, the instantaneous voltage across the capacitor Uct is:
，
in this formula Uc is known, uct can be calculated and the time period of t charge is programmed. That is, the time constant in the equation of the instantaneous voltage value Uct across the capacitorAs the only unknown, one can solve.
The instantaneous voltage values Uct at the two ends of the capacitor are calculated by a formulaValue of carry-in->And obtaining the Rf value in the expression formula. And the voltage at two ends of the capacitor is not required to be fully charged, so that the detection time is greatly shortened.
The discharge equation can be deduced in the same way. Therefore, a capacitor charge-discharge curve can be obtained by fitting, a parameter model is built, the detection time is shortened, the fault feedback time is shortened, and the test precision is improved.
The present invention is described with reference to flowchart illustrations and/or block diagrams of methods, apparatus (systems) and computer program products according to embodiments of the invention. It will be understood that each flow and/or block of the flowchart illustrations and/or block diagrams, and combinations of flows and/or blocks in the flowchart illustrations and/or block diagrams, can be implemented by computer program instructions. These computer program instructions may be provided to a processor of a general purpose computer, special purpose computer, embedded processor, or other programmable data processing apparatus to produce a machine, such that the instructions, which execute via the processor of the computer or other programmable data processing apparatus, create means for implementing the functions specified in the flowchart flow or flows and/or block diagram block or blocks.
These computer program instructions may also be stored in a computer-readable memory that can direct a computer or other programmable data processing apparatus to function in a particular manner, such that the instructions stored in the computer-readable memory produce an article of manufacture including instruction means which implement the function specified in the flowchart flow or flows and/or block diagram block or blocks.
These computer program instructions may also be loaded onto a computer or other programmable data processing apparatus to cause a series of operational steps to be performed on the computer or other programmable apparatus to produce a computer implemented process such that the instructions which execute on the computer or other programmable apparatus provide steps for implementing the functions specified in the flowchart flow or flows and/or block diagram block or blocks.
The principles and embodiments of the present invention have been described in detail with reference to specific examples, which are provided to facilitate understanding of the method and core ideas of the present invention; meanwhile, as those skilled in the art will have variations in the specific embodiments and application scope in accordance with the ideas of the present invention, the present description should not be construed as limiting the present invention in view of the above.
Those of ordinary skill in the art will recognize that the embodiments described herein are for the purpose of aiding the reader in understanding the principles of the present invention and should be understood that the scope of the invention is not limited to such specific statements and embodiments. Those of ordinary skill in the art can make various other specific modifications and combinations from the teachings of the present disclosure without departing from the spirit thereof, and such modifications and combinations remain within the scope of the present disclosure.
Claims (8)
1. The utility model provides a mining high voltage inverter insulation resistance detection device which characterized in that includes:
the voltage attenuation module is used for attenuating a high-voltage signal at the neutral point position of the high-voltage frequency converter and transmitting the high-voltage signal to the insulation detection module;
the high-voltage isolation power supply is used for providing a high-voltage power supply for the insulation detection module;
the insulation detection module is used for generating positive and negative low-frequency signals and injecting the positive and negative low-frequency signals into the high-voltage frequency converter shell, and determining the insulation resistance value of the high-voltage frequency converter through the voltage of the neutral point position of the high-voltage frequency converter and the voltage of the positive and negative low-frequency signal injection point;
the insulation detection module specifically comprises:
the system comprises a main control chip, a filtering sampling circuit, a positive and negative voltage generating circuit and a parameter setting circuit, wherein the filtering sampling circuit, the positive and negative voltage generating circuit and the parameter setting circuit are respectively connected with the main control chip;
the filtering sampling circuit is used for filtering high-frequency signals from sampling signals of the high-voltage frequency converter by adopting a multi-stage high-order low-pass filtering circuit and amplifying low-frequency signals at the same time; then digital filtering is carried out outputting to a main control chip;
the positive and negative voltage generating circuit is used for generating an adjustable positive and negative voltage low-frequency signal according to a switch control signal issued by the main control chip and returning an output voltage rechecking signal to the main control chip;
the parameter setting circuit is used for setting working state parameters of the main control chip;
the main control chip is used for determining the voltage of the low-frequency signal injection point according to the output voltage rechecking signal and determining the insulation resistance value of the high-voltage frequency converter by combining the detected neutral point position voltage of the high-voltage frequency converter;
the insulation detection module determines the calculation formula of the insulation resistance value of the high-voltage frequency converter through detecting the voltage of the neutral point position of the high-voltage frequency converter and the voltage of the injection point of the positive and negative low-frequency signals, wherein the calculation formula is as follows:
，
wherein,indicating the insulation resistance value to be measured of the high-voltage frequency converter, < >>The positive value of the voltage signal of the return checking terminal of the insulation module is indicated,indicating the negative value of the voltage signal of the return detection end of the insulation module, < + >>Indicating that the positive value of the detection voltage is generated inside the insulation detection table,indicating that the insulation detection table generates a negative value of the detection voltage, < + >>Representing the voltage division detection resistance within the insulation detection module,，/>represents the internal impedance of the high voltage frequency converter, +.>Representing the resistance of the voltage decay module.
2. The insulation resistance detection device of a mining high-voltage frequency converter according to claim 1, wherein the filtering sampling circuit specifically comprises:
a four-stage seven-order Butterworth filter circuit and an ADC sampling circuit;
the four-stage seven-order Butterworth filter circuit is used for filtering and proportional amplifying high-frequency signals through the RC low-pass filter circuit, then suppressing the high-frequency signals through the active second-order filter circuit, and finally suppressing the high-frequency signals through the two-stage homodromous amplifying filter circuit and amplifying low-frequency signals at the same time;
the ADC sampling circuit is used for carrying out analog-to-digital conversion on the low-frequency signal output by the four-stage seven-order Butterworth filter circuit, and outputting the low-frequency signal to the main control chip after digital filtering.
3. The insulation resistance detection device of a mining high-voltage frequency converter according to claim 1, wherein the positive and negative voltage generation circuit specifically comprises:
a BOOST circuit and a BUCK circuit respectively connected with the main control chip, and a push-pull control circuit respectively connected with the BOOST circuit and the BUCK circuit;
the BOOST circuit is used for controlling the switching state of the first selection switch according to a BOOST signal issued by the main control chip so as to generate an adjustable positive-pressure low-frequency signal and outputting the adjustable positive-pressure low-frequency signal to the push-pull control circuit;
the BUCK step-down circuit is used for controlling the switching state of the second selection switch according to a BUCK signal issued by the main control chip so as to generate an adjustable negative pressure low-frequency signal and output the adjustable negative pressure low-frequency signal to the push-pull control circuit;
the push-pull control circuit is used for controlling the alternate output of the positive pressure low-frequency signal and the negative pressure low-frequency signal according to the push-pull control signal issued by the main control chip.
4. A mining high-voltage inverter insulation resistance detection device according to claim 3, wherein the BOOST circuit specifically comprises:
a BOOST control chip;
the starting signal end of the BOOST control chip is connected with the main control chip, the output end of the BOOST control chip is connected with the grid electrode of a first MOS switch tube, the source electrode of the first MOS switch tube is grounded through a first resistor and is connected with the current sampling end of the BOOST control chip, the drain electrode of the first MOS switch tube is respectively connected with the positive electrode of a first energy storage capacitor and a first rectifying diode, the other end of the first energy storage capacitor is used as a voltage input end, the negative electrode of the first rectifying diode is respectively connected with a first energy storage filter capacitor and a first resistor, the other end of the first energy storage filter capacitor is grounded, the other end of the first resistor is respectively connected with the first end of a first selection switch and the voltage division signal end of the BOOST control chip, the second end, the third end and the fourth end of the first selection switch are respectively grounded through a second resistor, a third resistor and a fourth resistor, and the BOOST signal control end of the first selection switch is connected with the main control chip.
5. The insulation resistance detection device of a mining high-voltage frequency converter according to claim 3, wherein the BUCK circuit specifically comprises:
a BUCK control chip;
the starting signal end of the BUCK control chip is connected with the main control chip, the output end of the BUCK control chip is connected with the grid electrode of the second MOS switch tube, the drain electrode of the BUCK control chip is used as a voltage input end, the source electrode of the BUCK control chip is respectively connected with the second energy storage capacitor and the cathode of the second rectifier diode, the other end of the second energy storage capacitor is respectively connected with the second energy storage filter capacitor and the fifth resistor and grounded, the other end of the fifth resistor is respectively connected with the first end of the second selection switch and the voltage division signal end of the BUCK control chip, the second end, the third end and the fourth end of the second selection switch are respectively connected with the anode of the second rectifier diode and the other end of the second energy storage capacitor through the sixth resistor, the seventh resistor and the eighth resistor, and the BOOST signal control end of the first selection switch is connected with the main control chip.
6. A mining high-voltage inverter insulation resistance detection device according to claim 3, wherein the push-pull control circuit specifically comprises:
the third MOS switch tube and the fourth MOS switch tube;
the grid electrode of the third MOS switch tube is used as a positive-voltage low-frequency signal input end, the drain electrode of the third MOS switch tube is used as a positive-voltage low-frequency signal input end, the positive-voltage signal control end is connected with the positive-voltage low-frequency signal input end through a ninth resistor, and the source electrode of the third MOS switch tube is connected with a tenth resistor; the grid electrode of the fourth MOS switch tube is used as a negative electrode signal control end, the source electrode of the fourth MOS switch tube is used as a negative voltage low-frequency signal input end, the negative electrode signal control end is connected with the negative voltage low-frequency signal input end through an eleventh resistor, the drain electrode of the fourth MOS switch tube is connected with a twelfth resistor, and the other end of the tenth resistor is connected with the other end of the twelfth resistor to serve as a positive voltage low-frequency signal output end and is grounded through a third energy storage filter capacitor and a first voltage stabilizing diode which are connected in parallel.
7. A mining high-voltage inverter insulation resistance detection method using the device as claimed in any one of claims 1 to 6, comprising the steps of:
s101, initializing power-on reset and reading parameter configuration; the parameter configuration comprises an insulation resistance alarm value, a positive voltage threshold, a negative voltage threshold and a delay threshold;
s102, starting delay timing, and judging whether the delay timing reaches a delay threshold; if yes, go to step S103; otherwise, adding 1 to the clock cycle time, and continuing to delay time;
s103, utilizing a main control chip to control a positive and negative pressure generating circuit to generate a positive and negative pressure low-frequency signal, and judging whether the positive and negative pressure value of the positive and negative pressure low-frequency signal is within the limit range of a positive and negative pressure threshold value; if yes, go to step S104; otherwise, outputting a positive and negative voltage fault signal;
s104, detecting positive and negative voltage values of sampling signals of the high-voltage frequency converter, and judging whether the voltage value is equal to 0; if yes, outputting a detection result as a maximum insulation resistance value; otherwise, executing step S105;
s105, judging whether the voltage value has positive and negative direction conversion; if yes, executing step S106; otherwise, outputting a fault signal;
s106, carrying out digital filtering on the voltage value, calculating the insulation resistance value of the high-voltage frequency converter according to the voltage of the neutral point position of the high-voltage frequency converter and the voltage of the positive and negative low-frequency signal injection point, and outputting a detection result;
s107, judging whether the calculated insulation resistance value of the high-voltage frequency converter is smaller than an insulation resistance alarm value; if yes, return to step S103; otherwise, outputting an alarm signal.
8. A mining high-voltage frequency converter insulation resistance detection optimization method applying the method of claim 7, which is characterized by comprising the following steps:
s201, initializing power-on reset;
s202, when the high-voltage frequency converter is not started and has no high voltage, a test resistor is put into, the time from 0 to stable voltage of the voltage at two ends of the test resistor and the stable voltage are recorded, and a distributed capacitance value is calculated;
s203, comparing the distributed capacitance value with the capacitance value in the recorded table, matching the capacitance value in the table, and compensating the running capacitance value according to the environmental temperature and humidity parameters;
s204, when the high-voltage frequency converter is started and has high voltage, calculating the insulation resistance value of the high-voltage frequency converter according to the method of claim 7;
s205, adjusting control signals sent to the positive and negative voltage generating circuit by using the main control chip at set frequency intervals so as to increase positive and negative voltage output frequency and record a first frequency value;
s206, acquiring a loop voltage value of the filtering sampling circuit by using the main control chip, and recording voltage period change time to obtain a second frequency value;
s207, judging whether the first frequency value is equal to the second frequency value; if yes, fitting the maximum voltage value of the distributed capacitor, and calculating the insulation resistance value of the high-voltage frequency converter according to the method of claim 7; otherwise, the process returns to step S205.
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