CN111007303B - Current distortion identification method - Google Patents
Current distortion identification method Download PDFInfo
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- CN111007303B CN111007303B CN201911340957.XA CN201911340957A CN111007303B CN 111007303 B CN111007303 B CN 111007303B CN 201911340957 A CN201911340957 A CN 201911340957A CN 111007303 B CN111007303 B CN 111007303B
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- G01R19/04—Measuring peak values or amplitude or envelope of ac or of pulses
Abstract
The invention discloses a method for identifying current distortion, which comprises the following steps: 1) sampling an input phase current value of a power supply module in real time; 2) initializing; 3) the time-base variable of the timer begins to accumulate, the timing begins, and the sampling begins at the same time; 4) sampling the input current value once in each sampling period T to obtain a real-time sampling input current value; 5) comparing the current value of the current beat with the current value of the previous beat, and identifying and judging whether the current of the current beat is at a rising edge or a falling edge; 6) judging whether the current has a complete distorted waveform; 7) and when the primary complete distortion waveform is identified, judging whether the input current of the power supply module is distorted. The method judges the waveform distortion of the current by identifying the rising edge and the falling edge of the distorted current, improves the accuracy and the authenticity of a judgment result according to the maximum amplitude of the distorted current, solves the problem of the current distortion by adjusting a matched control algorithm on the basis of the method, and effectively improves the reliability of a power module.
Description
Technical Field
The invention relates to a power supply control technology, in particular to a method for identifying current distortion.
Background
In the field of power supplies at present, in order to avoid pollution to a power grid, all single-phase or three-phase power supply modules with commercial power alternating-current input have strict standard limit values for multiple harmonics of input current, namely (ith of the input current). In order to ensure high-quality ITHD performance of the module, the distortion type of the input current waveform needs to be detected in real time, and a loop control algorithm is determined according to different distortion types, so that ITHD of input current harmonics is optimized.
When the input source changes, the equivalent model of the input source loop is changed, and different types of distortion of the input current are caused. When the input current is distorted, great risk is brought to the reliability of the power supply module, and meanwhile, the power grid is seriously polluted. When the distortion frequency of the input current is in the range of 20 Hz-20 kHz, the human ear identification frequency range carries large noise pollution.
The invention provides a current distortion identification method, which can accurately distinguish and identify the distortion at the zero-crossing point of alternating current input current and can distinguish and identify the distortion existing when the input current is at the peak value; and can distinguish and identify the high-frequency and low-frequency oscillation of the full range of the input current. By identifying the distortion type of the input current, the equivalent model of the input source can be effectively calculated, the current distortion problem can be solved by adjusting a matched control algorithm, and the reliability of a power supply module and the ITHD optimal design of the current harmonic can be greatly improved.
Disclosure of Invention
The technical problem to be solved by the present invention is to provide a method for identifying current distortion, aiming at the defects in the prior art.
The technical scheme adopted by the invention for solving the technical problems is as follows: a method of identifying current distortion, comprising the steps of:
1) sampling an input phase current value of a power supply module in real time; the sampling frequency is f;
2) initializing, and enabling the input current value of the current beat sample to be Ia; the input current value sampled in the previous beat is Ia 1; the difference between the input current value sampled by the current beat and the input current value sampled by the previous beat is delta I; the maximum amplitude of the identified distorted rising and falling edges of the input current is Imax; current distortion identification count N; a settable number of times determination value Nset of current distortion; detecting the current rise times count CNT _ up; detecting the current drop times count CNT _ down; the total rising amplitude of the current which is accumulated to rise is Iup; the total decreasing amplitude of the accumulated decreasing current is Idown; BaseTime is the time base of the timer; iset is a settable distortion current identification amplitude;
clearing all variables Ia, Ia1, delta I, Imax, N, CNT _ up, CNT _ down, Iup, Idown and BaseTime;
3) the time-base variable of the timer begins to accumulate, the timing begins, and the sampling begins at the same time; judging the time of the timer, clearing the time base variable of the timer, clearing the distortion count N, clearing the maximum Imax amplitude record when the time is more than 3ms (1/6 of 20ms of the AC input power frequency period), and then returning to continue timing; when the time is less than 3ms, returning to continue timing;
4) sampling the input current value Ia in real time according to the sampling frequency f;
5) comparing the sampling current value Ia of the current beat with the sampling current value Ia1 of the previous beat, and identifying and judging whether the current beat is at a rising edge or a falling edge;
6) if the current beat current is at the rising edge, adding 1 to the rising count CNT _ up, recording the amplitude of single rising by delta I, and accumulating the amplitude of single rising by Iup;
when the rising count CNT _ up is more than or equal to 3 times, recognizing that the current beat current is at the falling edge and recognizing that the current beat current is at the rising edge next time, recording the value of the falling edge falling count CNT _ down,
if CNT _ down > is 3, judging that the current has a complete distorted waveform once, comparing the maximum value Imax of the counting current distortion with the total current increasing amplitude Iup of the current accumulated increasing after identifying the complete distorted waveform once, and updating the maximum value Imax of the counting current distortion to be Iup if Iup > Imax;
clearing the falling count CNT _ down and the falling edge amplitude Idown if CNT _ down is less than 3; returning to continuously identify the sampling value of the input current;
if the current beat current is at a falling edge, adding 1 to a falling count CNT _ down, recording the amplitude of single falling by delta I, and accumulating the amplitude of single falling by Idown;
when the falling count CNT _ down is more than or equal to 3 times, identifying and judging that the current beat is at the rising edge and identifying the current beat is before the falling edge next time, recording the rising times CNT _ up of the current at the rising edge,
if CNT _ up > is 3, judging that the current has a complete distorted waveform once, comparing the maximum value Imax of the counting current distortion with the total current descending amplitude Idown of the current accumulated descending, and if Idown is greater than Imax, updating the maximum value Imax of the counting current distortion to Idown;
clearing the rising count CNT _ up and the rising edge amplitude Iup if CNT _ up < 3; returning to continuously identify the sampling value of the input current;
7) when a complete distortion waveform is identified, adding 1 to the distortion count N, judging the value N of the distortion count, and returning to continuously identify the sampling value of the input current when N is less than Nset; and when N > is Nset, judging the maximum amplitude Imax of the distorted waveform, when Imax is less than Iset, returning to continuously identify the input current sampling value, and when Imax > is Iset, judging that the input current of the power supply module is distorted.
According to the scheme, the input phase current value of the real-time sampling power module in the step 1) is the input phase current value of the real-time sampling power module through an ADC sampling port of the digital control chip.
According to the scheme, the power module in the step 1) is a single-phase or three-phase power module.
According to the scheme, the sampling period T in the step 4) is 1/f, the sampling period is set to be less than 33us, and the accuracy of identifying the distortion is higher when the set sampling period is shorter. .
According to the scheme, the step 6) of judging the current to have the complete distorted waveform further comprises the step of judging the current distortion type, and the method specifically comprises the following steps:
after the current is judged to have a complete distortion waveform, judging the type of the current distortion according to the phase angle of a sine wave which appears in the current distortion: when the current distortion is near the zero crossing point phase, identifying the current distortion as type I distortion-zero crossing point current distortion; class II distortion-distortion at the current peak is identified when the current distortion occurs at 90 degrees phase, i.e., near the current peak.
According to the scheme, the distortion current identification amplitude Iset in the step 2) is set according to the input power of the power supply module.
According to the scheme, the distortion current identification amplitude Iset in the step 2) comprises a class I distortion current identification amplitude IsetIAnd class II distortion current identification magnitude IsetII。
The invention has the following beneficial effects: according to the method, the waveform of the input current is detected in real time, the maximum amplitude of the waveform of the distorted current is recorded while the rising edge and the falling edge of the distorted current are identified, and the accuracy and the authenticity of judging the waveform distortion of the input current of the power supply module are improved; on the basis of the method, the problem of current distortion is solved by adjusting a matched control algorithm, and the reliability of a power supply module and the optimal design of current harmonic ITHD can be greatly improved.
Drawings
The invention will be further described with reference to the accompanying drawings and examples, in which:
FIG. 1 is a flow chart of a method of an embodiment of the present invention;
FIG. 2 is a schematic diagram of input current distortion detection according to an embodiment of the present invention;
FIG. 3 is a schematic illustration of class I distortion for an embodiment of the present invention;
FIG. 4 is a schematic illustration of class II distortion for an embodiment of the present invention;
FIG. 5 is a schematic illustration of class III distortion for embodiments of the present invention.
Detailed Description
In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention is further described in detail with reference to the following embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.
As shown in fig. 1, a method for identifying current distortion includes the following steps:
(1) the power module is electrified, an input phase current value is sampled in real time through an ADC (analog to digital converter) sampling port of the digital control chip, ADC sampling of the digital control chip is not completely continuous, a designed sampling frequency f exists, and the digital chip can sample the input current value once in each sampling period T (1/f); as shown in fig. 2;
(2) initializing, and enabling the input current value of the current beat sample to be Ia; the input current value sampled in the previous beat is Ia 1; the difference between the input current value sampled by the current beat and the input current value sampled by the previous beat is delta I; the maximum amplitude of the identified distorted rising and falling edges of the input current is Imax; current distortion identification count N; a settable number of times determination value Nset of current distortion; detecting the current rise times count CNT _ up; detecting the current drop times count CNT _ down; the total rising amplitude of the current which is accumulated to rise is Iup; the total decreasing amplitude of the accumulated decreasing current is Idown; BaseTime is the time base of the timer; iset is a settable distortion current identification amplitude;
clearing all variables Ia, Ia1, delta I, Imax, N, CNT _ up, CNT _ down, Iup, Idown and BaseTime;
(3) after the module is started to run, the time-base variable of the timer begins to accumulate, and the timing begins;
(4) - (5): judging the time of the timer, clearing the time-base variable of the timer, clearing the distortion count N, clearing the maximum amplitude record of Imax when the time is more than 3ms (1/6 considering the power frequency period), and then returning to continue timing; when the time is less than 3ms, returning to continue timing;
(6) sampling the input current value Ia in real time with the sampling frequency f;
(7) identifying the current row of the sampled current value Ia and comparing the current row of the sampled current value Ia with the sampled current value Ia1 of the previous beat, and judging the rising and falling of the current;
(8) - (10) when Ia > Ia1, the module identifies a current rise, the rise count CNT _ up is incremented by 1, Δ I records the amplitude of the single rise, Iup accumulates the amplitude of the single rise;
(11) - (13) when the up count CNT _ up is less than 3 times, returning to continue identifying the input current sample value;
when the rising count CNT _ up is more than or equal to 3 times, entering the next step, identifying whether a falling edge of at least continuous 3 times of current falling exists before the current rising edge (namely, judging that CNT _ down > is 3), judging that a complete distorted waveform exists once if the CNT _ down > is 3, and clearing the falling count CNT _ down and the falling edge amplitude Idown if the CNT _ down < 3; returning to continuously identify the sampling value of the input current;
(14) after a complete distortion waveform is identified, the magnitude of Imax and Iup is judged, and the Imax counts the maximum value of current distortion;
(15) - (17) when Ia < Ia1, the module identifies a current drop, the drop count CNT _ down is incremented by 1, Δ I records the amplitude of the single drop, Idown accumulates the amplitude of the single drop;
(18) - (20) when the falling count CNT _ down is less than 3 times, returning to continuously identify the input current sample value;
when the falling count CNT _ down is more than or equal to 3 times, entering the next step, identifying whether a rising edge of at least continuous 3 times of current rising exists before the current falling edge (namely, judging that CNT _ up > is equal to 3), judging that a complete distorted waveform exists once if the CNT _ up > is equal to 3, and clearing the rising count CNT _ up and the rising edge amplitude Iup if the CNT _ up < 3; returning to continuously identify the sampling value of the input current;
(21) after a complete distortion waveform is identified, judging the magnitude of Imax and Idown, and counting the maximum value of current distortion by Imax;
(22) - (25) when a complete distortion waveform is identified, adding 1 to the distortion count N, judging the value N of the distortion count, and when N < Nset, returning to continuously identify the sampling value of the input current; and when N > is Nset, judging the maximum amplitude Imax of the distorted waveform, when Imax is less than Iset, returning to continuously identify the input current sampling value, and when Imax > is Iset, judging that the input current of the power supply module is distorted.
The invention detects the waveform of the input current in real time through the digital control chip, and records the maximum amplitude of the waveform of the distorted current while identifying the rising edge and the falling edge of the distorted current, so as to judge the authenticity of the waveform distortion of the input current of the power module. While identifying the current distortion, the type of the current distortion can be judged by the phase angle of the sine wave in which the current distortion appears. When the current distortion is near the zero crossing point phase, identifying the current distortion as the I-type zero crossing point current distortion; distortion at the class II current peak is identified when current distortion occurs at 90 degrees phase, i.e., near the current peak. The power module can correspondingly adjust the control strategy of the power module according to the distortion types of different phase points.
When the power supply module identifies the distortion of the input current, the set current amplitude comparison value Iset can be switched according to the position identified by the distortion of the input current, and the zero-crossing distortion and the peak distortion of the input current are distinguished and identified. As shown in fig. 3-5;
type I distortion: when the input current distortion of the power supply module is in a phase near a zero crossing point, switching to a comparison value Iset of the current zero crossing point;
distortion of class II: when the input current distortion of the power supply module is near the peak value, switching to a comparison value Iset of the peak current;
type III distortion: including both class I and class II distortions.
In practical application, the invention can change the following parameters according to the requirement of identifying distortion of input current:
1. the number of points of continuous rising edges and continuous falling edges of the actual current is changed, 3 times is used in the example, and 3 times or more is recommended to be designed in order to ensure the accuracy of the current distortion identification. This value determines the identification of the maximum distortion frequency, which, when designed n times, is 1/2n times the input current sampling frequency f; if the distortion of the current with higher frequency is identified and needs to be improved, the sampling detection frequency f of the input current can be changed and improved;
2. changing the recorded Nset of times of the complete distorted waveform, wherein the value determines the number of recognized current distorted waveforms;
3. changing a maximum amplitude judgment value Iset of input current distortion, wherein the maximum current amplitude judgment value can be dynamically adjusted according to the input power of a power supply module and can also be dynamically adjusted through a phase angle of sine wave current, and the value determines the amplitude of the distortion current;
4. the detected timebase count is changed to a clear value (3 ms in the example, which may be most appropriately adjusted based on the actual power module).
The self-identification strategy for detecting the current distortion provided by the invention has the advantages that the variable design values mentioned in the specific strategy can be freely adjusted, and other combined counts for identifying the continuously rising edge and the continuously falling edge can be derived through the identification mode, so that the input current distortion is identified, and the self-identification strategy also belongs to the protection range of the patent.
It will be understood that modifications and variations can be made by persons skilled in the art in light of the above teachings and all such modifications and variations are intended to be included within the scope of the invention as defined in the appended claims.
Claims (8)
1. A method for identifying current distortion, comprising the steps of:
1) sampling an input phase current value of a power supply module in real time; the sampling frequency is f;
2) initializing, and enabling the input current value of the current beat sample to be Ia; the input current value sampled in the previous beat is Ia 1; the difference between the input current value sampled by the current beat and the input current value sampled by the previous beat is delta I; the maximum amplitude of the identified distorted rising and falling edges of the input current is Imax; current distortion identification count N; a settable number of times determination value Nset of current distortion; detecting the current rise times count CNT _ up; detecting the current drop times count CNT _ down; the total rising amplitude of the current which is accumulated to rise is Iup; the total decreasing amplitude of the accumulated decreasing current is Idown; BaseTime is the time base of the timer; iset identifies the amplitude for the set distortion current;
powering on a power supply module, and clearing all variables Ia, Ia1, delta I, Imax, N, CNT _ up, CNT _ down, Iup, Idown and BaseTime;
3) the time-base variable of the timer begins to accumulate, the timing begins, and the sampling begins at the same time; judging the timing time of the timer, when the timing time is greater than 1/6 of the AC input power frequency period, clearing a time base variable of the timer, clearing a distortion count N, clearing an Imax maximum amplitude record, and then returning to the timing again;
4) sampling the input current value once in each sampling period T according to the sampling frequency f to obtain a real-time sampling input current value Ia;
5) comparing the sampling current value Ia of the current beat with the sampling current value Ia1 of the previous beat, and identifying and judging whether the current beat is at a rising edge or a falling edge;
6) identifying and judging the result that the current beat current is at the rising edge or the falling edge according to the step 5), and judging whether the current has a complete distorted waveform;
7) when a complete distortion waveform is identified, adding 1 to the distortion count N, judging the value N of the distortion count, and returning to continuously identify the sampling value of the input current when N is less than Nset; and when N > = Nset, judging the maximum amplitude Imax stored in the distorted waveform, returning to continuously identifying the input current sampling value when Imax is less than Iset, and judging that the input current of the power module is distorted when Imax > = Iset.
2. The method for identifying current distortion as claimed in claim 1, wherein the input phase current value of the real-time sampling power module in step 1) is the input phase current value of the real-time sampling power module through an ADC sampling port of the digital control chip.
3. The method for identifying current distortion as claimed in claim 1, wherein the power module in step 1) is a single-phase or three-phase power module.
4. The method for identifying current distortion according to claim 1, wherein the step 6) is as follows:
if the current beat current is at the rising edge, adding 1 to the rising count CNT _ up, recording the amplitude of single rising as delta I, and accumulating the amplitude of single rising as Iup;
when the rising count CNT _ up is more than or equal to 3 times, recognizing that the current beat current is at the falling edge and recognizing that the current beat current is at the rising edge next time, recording the value of the falling edge falling count CNT _ down,
if CNT _ down > =3, judging that the current has a complete distorted waveform once, comparing the maximum value Imax of the counting current distortion with the total current increasing amplitude Iup of the current accumulated increasing after identifying the complete distorted waveform once, and updating the maximum value Imax of the counting current distortion to be Iup if Iup > Imax;
clearing the falling count CNT _ down and the falling edge amplitude Idown if CNT _ down is less than 3; returning to continuously identify the sampling value of the input current;
if the current beat current is at a falling edge, adding 1 to a falling count CNT _ down, recording the amplitude of single falling as delta I, and accumulating the amplitude of single falling as Idown;
when the falling count CNT _ down is more than or equal to 3 times, identifying and judging that the current beat is at the rising edge and identifying the current beat is before the falling edge next time, recording the rising times CNT _ up of the current at the rising edge,
if CNT _ up > =3, judging that the current has a complete distorted waveform once, comparing the maximum value Imax of the distortion of the counting current with the total current descending amplitude Idown of the current accumulated descending, and if Idown is larger than Imax, updating the maximum value Imax of the distortion of the counting current to be Idown;
clearing the rising count CNT _ up and the rising edge amplitude Iup if CNT _ up < 3; returning to continue identifying input current sample values.
5. The method for identifying current distortion according to claim 1, wherein the sampling period T =1/f in the step 4) is set to be less than 33us, and the distortion is identified with higher accuracy when the set sampling period is shorter.
6. The method for identifying current distortion according to claim 1, wherein the step 6) of judging the occurrence of the complete distortion waveform of the current further comprises a step of judging the type of current distortion, specifically as follows:
after the current is judged to have a complete distortion waveform, judging the type of the current distortion according to the phase angle of a sine wave which appears in the current distortion: when the current distortion is near the zero crossing point phase, identifying the current distortion as type I distortion-zero crossing point current distortion; class II distortion-distortion at the current peak is identified when the current distortion occurs at 90 degrees phase, i.e., near the current peak.
7. The method for identifying current distortion according to claim 1, wherein the distortion current identification magnitude Iset in step 2) is set according to the input power of the power supply module.
8. The method for identifying current distortion of claim 6, wherein the distortion current identification magnitude Iset in step 2) comprises a class I distortion current identification magnitude IsetIAnd class II distortion current identification magnitude IsetII。
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