Fault recording method for low-voltage frequency conversion equipment

Abstract

The invention relates to the technical field of power system fault recording, and particularly discloses a low-voltage frequency conversion equipment fault recording method, which comprises the following steps of: changing a data acquisition time interval according to three-phase voltage and current data acquired in real time and calculated time of a zero crossing point, and adopting an effective value and real-time value double recording mode to obtain a fault recording result; millisecond-level wave recording at the fault moment and long-time effective value data wave recording before and after the fault are achieved. Compared with the prior art, the method has the advantages that the recording time interval period can be automatically adjusted when the frequency conversion equipment is started and fails in work, recording data integrity is guaranteed, storage requirements are lowered, maintenance is simple, and analysis of fault types and pre-judgment of fault development trends after events are facilitated.

Description

Technical Field

[0001] The invention relates to the technical field of power system fault recording, and in particular to a method for recording fault of low-voltage frequency conversion equipment. Background Art

[0002] When the frequency conversion equipment is started and working, the voltage and current frequency will change. If the fixed-time recording method is used, the number of collection points per unit time will decrease as the frequency decreases at low frequencies, which can easily lead to missing fault data information. If the fixed-time recording is reduced, the recorded data will increase sharply when working at high or normal frequencies, resulting in a waste of storage resources and not conducive to saving more fault development trend data. Summary of the invention

[0003] The purpose of the present invention is to overcome the defects of the above-mentioned existing frequency conversion equipment fault recording technology and provide a low-voltage frequency conversion equipment fault recording method.

[0004] The purpose of the present invention can be achieved by the following technical solutions:

[0005] A method for recording faults of low-voltage frequency conversion equipment, the method comprising the following steps:

[0006] Step 1, initialize the effective value data cache period, the real-time value data sampling period, the real-time value cache array Yas and the effective value cache array Has;

[0007] Step 2: Obtain the real-time voltage value of the device at the current calculation time. When the voltage crosses zero, calculate the effective value of the voltage at the current time and the time period P1(i) when the voltage crosses zero.

[0008] When the current voltage effective value is greater than the set voltage threshold, the current voltage effective value flag Uflag[i] is set to 1, otherwise Uflag[i] is set to 0;

[0009] Step 3: Get the current real-time value of the device at the current calculation time. When the current crosses zero, calculate the effective value of the current at the current time.

[0010] If the current voltage effective value flag Uflag[i]==1, go to step 4, otherwise calculate the time period P2(i) of the current current zero-crossing moment;

[0011] When the effective current value at the current moment is greater than the set current threshold, the current effective current value flag Iflag[i] is set to 1, otherwise, flag[i] is set to 0;

[0012] Step 4: Based on the current voltage and current RMS value flags and the time period of the voltage and current zero-crossing moment, set the RMS data cache period T at time i p ;

[0013] Step 5: Change the effective value data cache period to T p , the real-time value data sampling period is 2T p / m; and cache the effective value and real-time value of voltage and current into the effective value cache array Has and the real-time value cache array Yas respectively;

[0014] Step 6: When the system finds an abnormality, it triggers the recording, and stores the voltage and current effective value cache array Has and the real-time value cache array Yas data to the disk in chronological order; otherwise, go to step 2;

[0015] Step 7: Continue sampling, repeat steps 2 to 5, and update the effective value data cache period T p ; and save the effective value and real-time value of voltage and current to the disk respectively until the effective value and real-time value of the recorded data reach the number of cycles to be saved.

[0016] Compared with the prior art, the present invention has the following beneficial effects:

[0017] The present invention changes the data collection time interval according to the real-time collected three-phase voltage and current data and the calculated zero-crossing time, and adopts the effective value and real-time value dual recording mode to realize millisecond-level recording at the time of the fault and long-time effective value data recording before and after the fault. The method can automatically adjust the recording time interval cycle when the frequency conversion equipment is started or a fault occurs during operation, ensure the integrity of the recorded data, reduce storage requirements, simplify maintenance, and facilitate post-fault type analysis and prediction of fault development trends. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 The present invention is a flowchart of the steps of a method for recording faults of low-voltage frequency conversion equipment. DETAILED DESCRIPTION

[0019] The present invention is described in detail below in conjunction with the accompanying drawings and specific embodiments. This embodiment is implemented based on the technical solution of the present invention, and provides a detailed implementation method and specific operation process, but the protection scope of the present invention is not limited to the following embodiments.

[0020] Example 1

[0021] The present invention proposes a method for recording faults of low-voltage frequency conversion equipment. According to the real-time collected three-phase voltage and current data and the calculated zero-crossing time, the data collection time interval is changed, and the effective value and real-time value dual recording methods are adopted to achieve millisecond-level recording at the time of the fault and long-term effective value data recording before and after the fault. The method proposed by the present invention can automatically adjust the recording time interval when the frequency conversion equipment is started or a fault occurs during operation, so as to ensure the integrity of the recorded data and reduce the storage requirements. Figure 1 As shown, the specific steps of this method are as follows:

[0022] Step 1) Set the effective value data cache period initialization value T p =1 / 4 / f, the real-time data sampling period is initialized to 2T p / m, f is the grid frequency;

[0023] Set the number of real-time value sampling points per cycle m, the real-time value cache array Yas, the size is mYas; the current real-time value cache point is iYas=0, the effective value cache array Has, the size is mHas, and the current effective value cache point is iHas=0.

[0024] Step 2) Get the real-time voltage value of the device at the current calculation time t. If the voltage sampling value at this moment is opposite to the voltage value of the previous collection point, record it as the calculation point of the current i-th voltage zero crossing point. For this voltage, take half of the average value of the absolute value of all collection point data from the previous zero crossing point to the current zero crossing point (excluding the current zero crossing point) as the current effective value U(i), and set the voltage threshold value U m , the zero-crossing time T(i) of the i-th zero-crossing point is calculated as follows:

[0025]

[0026] Wherein, D1 and D2 are the voltage values ​​at adjacent moments t1 and t2 respectively, and t1<t2.

[0027] Calculate the i-th voltage zero-crossing time period P1(i):

[0028] P1(i)=T(i)-T(i-1)

[0029] Where: T(i-1) is the i-1th zero-crossing moment adjacent to T(i).

[0030] When U(i)>U m When the current voltage effective value flag Uflag[i] is set to 1, otherwise Uflag[i] is set to 0.

[0031] Step 3) Get the current value of the device at the current calculation time t. The current sampling value at this moment has the opposite sign to the current value of the previous acquisition point. Use it as the calculation point of the current i-th current zero-crossing point. Take 1 / 2 of the average value of the absolute value of all acquisition point data from the previous zero-crossing point to the current zero-crossing point (excluding the current zero-crossing point) as the current effective value I(i), and set the current threshold value Im.

[0032] When Uflag[i]==1, go to step 4), otherwise use the method in step 2) to calculate the i-th current zero-crossing time period P2(i);

[0033] When I(i)>Im, the current effective value flag is set, flag[i]=1, otherwise, flag[i]=0.

[0034] Step 4) If Uflag[i]==1, then the time period T at time i p =P1(i);

[0035] If Uflag[i]==0, Iflag[i]==1, then the time period T at time i p =P2(i);

[0036] Step 5) Modify the effective value data cache period to T p , modify the real-time value data sampling period to 2T p / m:

[0037] If the time from the last valid cache data is greater than or equal to T p , then cache the effective value of voltage and current at time i into Has[iHas], iHas=iHas+1, if iHas==mHas, then set iHas=0;

[0038] Cache the real-time voltage and current values ​​at time i into Yas[iYas], iYas=iYas+1. If iYas==mYas, set iYas=0;

[0039] Step 6) When the system finds an abnormality, trigger the recording; otherwise go to step 2)

[0040] Store the voltage and current effective value cache array Has data to the disk in chronological order, set the remaining storage quantity aHas of the recorded effective value, and record the effective value storage time as the current time;

[0041] aHas=4*maxHas-mHas

[0042] Where maxHas is the number of cycles for which the effective value of the recorded data is stored, which is a fixed value.

[0043] Store the voltage and current real-time value cache array Yas data to the disk in chronological order, and set the remaining storage quantity aYas of the real-time recording value:

[0044] aYas=m*maxYas-mYas

[0045] Where maxYas is the number of cycles stored in the real-time value of the recorded data, which is a fixed value.

[0046] Step 7) Continue sampling and repeat steps 2) to 5) to calculate the effective value data cache period Tp ;

[0047] If the time since the last valid value storage is greater than T p , and aHas>0, then the effective value of voltage and current at that moment is stored in the disk, aHas=aHas-1;

[0048] If aYas>0, store the real-time voltage and current values ​​at that moment in the disk, aYas=aYas-1;

[0049] If aYas==0 and aHas==0, go to step 2), otherwise go to step 7);

[0050] In this embodiment, the typical value of m is 32, the typical value of f is 50 Hz, and U m The typical value is 10% of the rated voltage, I m The typical value is 5% of the rated current, the typical value of maxHas is 50, and the typical value of maxYas is 20.

[0051] The preferred specific embodiments of the present invention are described in detail above. It should be understood that a person skilled in the art can make many modifications and changes based on the concept of the present invention without creative work. Therefore, any technical solution that can be obtained by a person skilled in the art through logical analysis, reasoning or limited experiments based on the concept of the present invention on the basis of the prior art should be within the scope of protection determined by the claims.

Claims

1. A method for recording faults of low-voltage frequency conversion equipment, characterized in that: The method steps include: Step 1, initialize the effective value data cache period, the real-time value data sampling period, the real-time value cache array Yas and the effective value cache array Has; Step 2: Obtain the real-time voltage value of the device at the current calculation time. When the voltage crosses zero, calculate the effective value of the voltage at the current time and the time period P1(i) when the voltage crosses zero. When the current voltage effective value is greater than the set voltage threshold, the current voltage effective value flag Uflag[i] is set to 1, otherwise Uflag[i] is set to 0; Step 3: Get the current real-time value of the device at the current calculation time. When the current crosses zero, calculate the effective value of the current at the current time. If the current voltage effective value flag Uflag[i]==1, go to step 4, otherwise calculate the time period P2(i) of the current current zero-crossing moment; When the effective current value at the current moment is greater than the set current threshold, the current effective current value flag Iflag[i] is set to 1, otherwise Iflag[i] is set to 0; Step 4: Based on the current voltage and current RMS value flags and the time period of the voltage and current zero-crossing moment, set the RMS data cache period T at time i p ; Step 5: Change the effective value data cache period to T p , the real-time value data sampling period is 2T p / m; and cache the effective value and real-time value of voltage and current into the effective value cache array Has and the real-time value cache array Yas respectively; Step 6: When the system finds an abnormality, it triggers the recording, and stores the voltage and current effective value cache array Has and the real-time value cache array Yas data to the disk in chronological order; otherwise, go to step 2; Step 7: Continue sampling, repeat steps 2 to 5, and update the effective value data cache period T p ; and save the effective value and real-time value of voltage and current to the disk respectively until the effective value and real-time value of the recorded data reach the number of cycles to be saved.

2. A method for recording faults of low-voltage frequency conversion equipment according to claim 1, characterized in that: The effective value data cache period initialization value is T p =1 / 4 / f, the real-time data sampling period initialization value is 2T p / m, f is the grid frequency.

3. A method for recording faults of low-voltage frequency conversion equipment according to claim 1, characterized in that: The calculation of the effective value of the voltage at the current moment is as follows: If the voltage sampling value at this moment has an opposite sign to the voltage value of the previous sampling point, it is recorded as the calculation point of the current i-th voltage zero crossing point. For this voltage, half of the average value of the absolute value of all sampling point data from the previous zero crossing point to the current zero crossing point is taken as the effective value U(i) at the current moment.

4. A method for recording faults of low-voltage frequency conversion equipment according to claim 1, characterized in that: Calculate the effective value of the current at the current moment as follows: If the current sampling value at this moment has an opposite sign to the current value of the previous sampling point, it is used as the calculation point of the current i-th current zero crossing point, and half of the average value of the absolute value of all sampling point data from the previous zero crossing point to the current zero crossing point is taken as the effective value I(i) at the current moment.

5. A method for recording faults of low-voltage frequency conversion equipment according to claim 1, characterized in that: The effective value data cache period at time i is set based on the current voltage and current effective value flags and the time period of the voltage and current zero crossing time, as follows: If the current voltage effective value flag Uflag[i]==1, the effective value data cache T at time i p =P1(i); If the current voltage RMS flag Uflag[i]==0, and the current current RMS flag Iflag[i]==1, then the RMS data cache T at time i p =P2(i).

6. A method for recording faults of low-voltage frequency conversion equipment according to claim 1, characterized in that: The voltage and current effective values ​​are cached in the effective value cache array Has, as follows: If the time from the last valid value cache data is greater than or equal to the valid value data cache period T p , then the effective values ​​of voltage and current at time i are cached into the effective value cache array Has[iHas], and the current cache point iHas count is increased by 1; If the current valid value cache point iHas is equal to the valid value cache array size mHas, then the current valid value cache point iHas=0.

7. A method for recording faults of low-voltage frequency conversion equipment according to claim 1, characterized in that: The real-time values ​​of voltage and current are cached in the real-time value cache array Yas, as follows: The real-time values ​​of voltage and current at time i are cached into the real-time value cache array Yas[iYas], and the count of the current real-time value cache point iYas is increased by 1; If the current real-time value cache point iYas is equal to the real-time value cache array size mYas, then the current real-time value cache point iYas=0.

8. A method for recording faults of low-voltage frequency conversion equipment according to claim 1, characterized in that: The voltage and current effective value cache array Has data is stored to the disk in chronological order, and the effective value storage time is recorded as the current time, and the remaining storage quantity of the recorded effective value is set: aHas=4*maxHas-mHas Where maxHas is the number of cycles for which the effective value of the recorded data is stored.

9. A method for recording faults of low-voltage frequency conversion equipment according to claim 1, characterized in that: The voltage and current effective value cache array Has data is stored to the disk in chronological order, and the remaining storage quantity of the real-time value of the recording is set: aYas=m*maxYas-mYas Where m is the number of sampling points per cycle of the real-time value; maxYas is the number of cycles stored in the real-time value of the recorded data.

10. A method for recording faults of low-voltage frequency conversion equipment according to any one of claims 8-9, characterized in that: The voltage and current effective values ​​and real-time values ​​are stored in the disk respectively until the effective value and real-time value of the recorded data reach the number of cycles to be saved, as follows: If the time from the last valid value storage is greater than the valid value data cache period T p , and the remaining storage quantity aHas of the waveform effective value is greater than 0, then the voltage and current effective values ​​at that moment are stored in the disk, and the remaining storage quantity aHas of the waveform effective value is reduced by 1; If the remaining storage quantity aYas of the real-time waveform value is greater than 0, the real-time voltage and current values ​​at that moment are stored in the disk, and the remaining storage quantity aYas of the real-time waveform value is reduced by 1; If the remaining storage quantity aYas of the real-time recording value is equal to 0 and the remaining storage quantity aHas of the effective recording value is equal to 0, go to step 2), otherwise go to step 7).

Images