CN110794291A - Method and device for checking charging pile filter capacitor - Google Patents
Method and device for checking charging pile filter capacitor Download PDFInfo
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Abstract
The invention relates to a method and a device for checking a charging pile filter capacitor. The method comprises the following steps: acquiring a maximum fundamental current effective value and each harmonic current effective value injected into the filter capacitor; calculating rated phase current of the filter capacitor according to rated voltage and rated installation capacity of the filter capacitor; calculating an equivalent value of a fundamental wave current equivalent to the H-th harmonic according to the equivalent resistance of the H-th harmonic active loss of the filter capacitor and the rated phase current of the filter capacitor, wherein H is the maximum harmonic frequency generated by the charging pile, H is [2, H ], H and H are positive integers, and H is less than or equal to H; and performing overcurrent check on the filter capacitor according to the rated phase current of the filter capacitor, the effective value of the equivalent fundamental current of the h-th harmonic wave and the maximum effective value of the fundamental current of the filter capacitor.
Description
Technical Field
The invention relates to the technical field of harmonic filtering of a power system, in particular to a method and a device for checking a charging pile filter capacitor.
Background
With the rapid development of electric vehicles and charging piles thereof, the charging piles of the electric vehicles become important nonlinear harmonic sources in a power grid. In the charging process of the electric vehicle, three-phase alternating current is reduced in voltage by a distribution transformer, then is changed into direct current by a rectifying device, is converted by a DC/DC high-frequency power converter to output direct current, and is filtered again to charge an electric vehicle storage battery, wherein higher harmonics can be injected into a power grid in the working processes of switching components of a rectifying link, a DC/DC conversion link and the like, and the switching frequency of a power electronic converter applied in a charging pile is higher and higher along with the development of a power electronic technology, so that the harmonic frequency injected into the power grid by the charging pile is higher and higher; simultaneously along with filling the increase of electric pile quantity, the electric wire netting with fill electric pile interactive influence, lead to filling electric pile harmonic emission level also corresponding rising, fill the high frequency harmonic problem that electric pile brought and receive people's concern day by day.
In order to reduce the pollution of high-frequency harmonics of the charging pile to a power grid, the charging pile is merged into an alternating-current power grid and is connected with an inlet filter in series, the common type of the charging pile is an L-shaped filter and an LCL filter, the suppression effect of the LCL filter on the high-frequency harmonics is more ideal, and the charging pile system is more widely applied. The capacitor in the LCL filter is one of key components, and the safe and stable operation of the capacitor is the key for ensuring the safe and stable operation of the LCL filter and even a charging pile system. When a large amount of high frequency harmonics are injected into the LCL filter capacitor, the power capacitor generates power loss due to the high frequency harmonics and generates heat, the heat is continuously accumulated to cause the power capacitor to break down due to overhigh temperature, the capacitor is burnt out under severe conditions, and the safe and stable operation of the charging pile is directly influenced.
In order to ensure good filtering effect of the LCL filter and to enable long-term safe and stable operation, the design and the safety check method thereof are very important. In order to ensure the safety and reliability of the application of the low-voltage parallel capacitor, a power capacitor standardization organization writes and releases a plurality of national standards and industrial standards related to capacitor design and check, for example, the provision given by 21 maximum allowable current in the national standard GB12747.1-2017 nominal voltage 1000V and self-healing parallel capacitors for the following alternating current power system is that 'a capacitor unit is adapted to continuously operate … … under the current generated by the unit under the rated sinusoidal voltage and the rated frequency when the square root mean value of the line current is 1.3 times', and the difference of fundamental current and harmonic current on the heating of the capacitor is not considered in the standard. In 6.7.1.2 overcurrent check formula in GB/T26868-2011-high-voltage filter design and application guide rule, harmonic current and fundamental current are considered equally to perform capacitor overcurrent check, and in low-voltage system engineering application, overcurrent safety check is performed on a capacitor according to the method.
For reactive compensation and harmonic wave filtering devices arranged at medium voltage and low voltage, harmonic current flowing into a capacitor of the reactive compensation and harmonic wave filtering device is mainly low frequency, the problem of capacitor overcurrent checking is not big according to the standard GB/T26868 plus 2011, but the current flowing into an LCL filtering capacitor of a charging pile not only contains fundamental wave current, but also contains a large amount of high-frequency harmonic current, the heating level of the capacitor has great difference due to equivalent high-frequency and low-frequency harmonic current, if the overcurrent checking of the LCL filtering capacitor of the electric automobile charging pile is checked according to a method given by the national standard, the safety checking of the capacitor can pass, but the risk of serious heating and even burning in actual operation exists.
Disclosure of Invention
Therefore, it is necessary to provide a method and a device for checking a charging pile filter capacitor, which consider the influence of the amplitude and frequency of the high-frequency harmonic current on the LCL filter capacitor and can check the capacitor more scientifically and reasonably, so as to ensure that the LCL filter capacitor and the charging pile can operate safely, stably and reliably for a long time.
The embodiment of the invention provides a method for checking a charging pile filter capacitor, which comprises the following steps:
acquiring a maximum fundamental current effective value and each harmonic current effective value injected into the filter capacitor;
calculating rated phase current of the filter capacitor according to rated voltage and rated installation capacity of the filter capacitor;
calculating an equivalent value of a fundamental wave current equivalent to the H-th harmonic according to the equivalent resistance of the H-th harmonic active loss of the filter capacitor and the rated phase current of the filter capacitor, wherein H is the maximum harmonic frequency generated by the charging pile, H is [2, H ], H and H are positive integers, and H is less than or equal to H;
and performing overcurrent check on the filter capacitor according to the rated phase current of the filter capacitor, the effective value of the equivalent fundamental current of the h-th harmonic wave and the maximum effective value of the fundamental current of the filter capacitor.
In one embodiment, obtaining the effective value of each harmonic current of the filter capacitor comprises:
obtaining a large 95% probability value of each harmonic current generated by the charging pile power electronic converter from a manufacturer;
and carrying out simulation calculation according to the 95% probability large value of each harmonic current generated by the charging pile to obtain the fundamental current effective value and each harmonic current effective value injected into the filter capacitor.
In one embodiment, obtaining the effective value of each harmonic current injected into the filter capacitor comprises:
carrying out electric energy quality test on the charging pile with the test condition to obtain a 95% probability large value of each harmonic current generated by the charging pile;
and carrying out simulation calculation according to the 95% probability large value of each harmonic current generated by the charging pile to obtain the fundamental current effective value and each harmonic current effective value injected into the filter capacitor.
In one embodiment, obtaining the effective value of each harmonic current of the filter capacitor comprises:
and testing the electric energy quality of the charging pile with the testing conditions to obtain the fundamental wave current effective value and each harmonic current effective value of the filter capacitor.
In one embodiment, the rated phase currents of the filter capacitors are:
wherein Q isC,NFor rated installation capacity, UC,NIs a rated voltage.
In one embodiment, the checking method further includes:
and before calculating the equivalent value of the fundamental current of the h harmonic, determining the equivalent resistance of the h harmonic active loss of the filter capacitor.
In one embodiment, the performing the overcurrent check on the smoothing capacitor according to the rated phase current of the smoothing capacitor, the effective value of the fundamental current equivalent to the h-th harmonic, and the effective value of the maximum fundamental current of the smoothing capacitor includes:
judging whether a preset formula is established or not according to the rated phase current of the filter capacitor, the equivalent fundamental wave current effective value of the h-th harmonic wave and the maximum fundamental wave current effective value of the filter capacitor;
when the formula is satisfied, judging that the filter capacitor can safely and stably operate;
otherwise, judging that the filter capacitor has potential safety and stability operation hazards.
In one embodiment, the preset formula is:
wherein, IC,NFor the rated phase current of the filter capacitor, IC，1,maxIs the maximum fundamental current of the filter capacitor, IC,h,1The effective value of the fundamental current equivalent to the h-th harmonic is α harmonic coefficients of the equivalent resistance of the filter capacitor.
In one embodiment, the effective value of the fundamental current equivalent to the h-th harmonic
Wherein, IC,hAnd α is the harmonic coefficient of the equivalent resistance of the filter capacitor, which is the effective value of the h-th harmonic current.
Based on the same inventive concept, the embodiment of the invention also provides a checking device of the charging pile filter capacitor, which comprises:
the acquisition module is used for acquiring the maximum fundamental current effective value and each harmonic current effective value injected into the filter capacitor;
the data processing module is used for calculating rated phase current of the filter capacitor according to rated voltage and rated installation capacity of the filter capacitor, and calculating equivalent fundamental wave current effective value of the H-th harmonic according to equivalent resistance of H-th harmonic active loss of the filter capacitor and rated phase current of the filter capacitor, wherein H is the maximum harmonic frequency generated by the charging pile, H is [2, H ], H and H are positive integers, and H is less than or equal to H; and
and the judging module is used for performing overcurrent check on the filter capacitor according to the rated phase current of the filter capacitor, the equivalent fundamental wave current effective value of the h-th harmonic wave and the maximum fundamental wave current effective value of the filter capacitor.
In one embodiment, the determining module is specifically configured to:
judging whether a preset formula is established or not according to the rated phase current of the filter capacitor, the equivalent fundamental wave current effective value of the h-th harmonic wave and the maximum fundamental wave current effective value of the filter capacitor;
when the formula is satisfied, judging that the filter capacitor can safely and stably operate;
otherwise, judging that the filter capacitor has potential safety and stability operation hazards.
In one embodiment, the preset formula is:
wherein, IC,NFor the rated phase current of the filter capacitor, IC，1,maxIs the maximum fundamental current of the filter capacitor, IC,h,1The effective value of the fundamental current equivalent to the h-th harmonic is α harmonic coefficients of the equivalent resistance of the filter capacitor.
In summary, the invention provides a method and a device for checking a charging pile filter capacitor. The method comprises the following steps: acquiring a maximum fundamental current effective value and each harmonic current effective value injected into the filter capacitor; calculating rated phase current of the filter capacitor according to rated voltage and rated installation capacity of the filter capacitor; calculating an equivalent value of a fundamental wave current equivalent to the H-th harmonic according to the equivalent resistance of the H-th harmonic active loss of the filter capacitor and the rated phase current of the filter capacitor, wherein H is the maximum harmonic frequency generated by the charging pile, H is [2, H ], H and H are positive integers, and H is less than or equal to H; and performing overcurrent check on the filter capacitor according to the rated phase current of the filter capacitor, the effective value of the equivalent fundamental current of the h-th harmonic wave and the maximum effective value of the fundamental current of the filter capacitor. In the invention, the h-th harmonic current effective value is equivalent to the fundamental current effective value, the LCL filter capacitor is subjected to overcurrent check by using the fundamental current of the filter capacitor and the h-th harmonic equivalent fundamental current, the influence of the amplitude and the frequency of the high-frequency harmonic current on the LCL filter capacitor is comprehensively considered, and the capacitor can be checked more scientifically and reasonably, so that the LCL filter capacitor and the charging pile can be ensured to run safely, stably and reliably for a long time.
Drawings
Fig. 1 is a schematic flowchart of a method for checking a charging pile filter capacitor according to an embodiment of the present invention;
FIG. 2 is a schematic diagram of a three-phase electric vehicle charging pile connected to an AC power grid through an LCL inlet filter;
FIG. 3 is an equivalent circuit diagram of a capacitor considering the effect of harmonic frequencies according to an embodiment of the present invention;
fig. 4 is an electrical structure schematic diagram of a checking apparatus of a charging pile filter capacitor according to an embodiment of the present invention.
Detailed Description
In order to make the aforementioned objects, features and advantages of the present invention comprehensible, embodiments accompanied with figures are described in detail below. In the following description, numerous specific details are set forth in order to provide a thorough understanding of the present invention. This invention may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein, but rather should be construed as broadly as the present invention is capable of modification in various respects, all without departing from the spirit and scope of the present invention.
Referring to fig. 1, an embodiment of the present invention provides a method for checking a charging pile filter capacitor, including:
step S110, obtaining the maximum fundamental current effective value and each harmonic current effective value injected into the filter capacitor;
step S120, calculating rated phase current of the filter capacitor according to rated voltage and rated installation capacity of the filter capacitor;
step S130, calculating an equivalent value of a fundamental wave current equivalent to the H-th harmonic according to an equivalent resistance of the H-th harmonic active loss of the filter capacitor and a rated phase current of the filter capacitor, wherein H is the maximum harmonic frequency generated by the charging pile, H is [2, H ], H and H are positive integers, and H is less than or equal to H;
and step S140, performing overcurrent check on the filter capacitor according to the rated phase current of the filter capacitor, the effective value of the equivalent fundamental current of the h-th harmonic and the effective value of the maximum fundamental current of the filter capacitor.
It can be understood that in order to reduce the pollution of the high-frequency harmonic waves of the charging pile to the power grid, the charging pile is merged into the alternating-current power grid and is connected with the LCL filter in series. Because the current flowing into the charging pile LCL filter capacitor not only contains fundamental wave current, but also contains a large amount of high-frequency harmonic current, the heating level of the capacitor has larger difference due to equivalent high-frequency and low-frequency harmonic current, and if the overcurrent checking of the charging pile LCL filter capacitor of the electric automobile is checked according to a method given by national standards, the risk that the safety checking of the capacitor can pass, but the actual operation generates heat seriously and even burns out exists. Based on this, through being equivalent to the fundamental wave current effective value with h harmonic current effective value in this embodiment, utilize filter capacitor's fundamental wave current and the equivalent fundamental wave current of h harmonic carry out the overcurrent check to LCL filter capacitor, synthesize the influence of considering high frequency harmonic current's amplitude and frequency to LCL filter capacitor, can check the condenser more scientifically and reasonably to guarantee LCL filter capacitor and fill electric pile can long-term safe and stable reliable operation.
In one embodiment, obtaining the effective value of each harmonic current of the filter capacitor comprises:
obtaining a large 95% probability value of each harmonic current generated by the charging pile power electronic converter from a manufacturer;
and carrying out simulation calculation according to the 95% probability large value of each harmonic current generated by the charging pile to obtain the fundamental current effective value and each harmonic current effective value injected into the filter capacitor.
It can be understood that the charging pile is subjected to various tests before leaving the factory, so that data such as harmonic currents generated by the charging pile power electronic converter can be directly obtained from a manufacturer, and the safety check time is saved.
In one embodiment, obtaining the effective value of each harmonic current of the filter capacitor comprises:
and testing the electric energy quality of the charging pile with the testing conditions to obtain the fundamental wave current effective value and each harmonic current effective value of the filter capacitor.
In one embodiment, obtaining the effective value of each harmonic current injected into the filter capacitor comprises:
carrying out electric energy quality test on the charging pile with the test condition to obtain a 95% probability large value of each harmonic current generated by the charging pile;
and carrying out simulation calculation according to the 95% probability large value of each harmonic current generated by the charging pile to obtain the fundamental current effective value and each harmonic current effective value injected into the filter capacitor.
In this embodiment, the charging pile with the test condition is subjected to the power quality test to obtain each harmonic current generated by the charging pile, see table 1, and then the large 95% probability value of each harmonic current output by the charging pile is used as the effective value of each harmonic current of the filter capacitor.
Table 1 shows the 95% probability maximum value of each harmonic current of the charging pile obtained by the test
Then, a simulation calculation method is used for obtaining a fundamental wave current effective value and each harmonic wave current effective value I which are injected into the LCL filter capacitorC,hAnd H is 1,2 … H. Considering that the effective value of the harmonic current decreases as the number of harmonics increases, H is generally taken to be 50. In this embodiment, simulation is performed according to the 95% probability maximum value of each sub-harmonic current of the charging pile in table 1, and the result obtained by calculation is shown in table 2.
TABLE 2 simulation of effective value of each harmonic current of the injection capacitor
Further, the rated voltage U of the LCL inlet filter capacitor is obtained according to the design result or the manufacturing parameterC,NRated capacity QC,N. From the rated parameters of the power capacitor, the capacitor rated line current is calculated:
considering the losses caused by the current flowing through the LCL filter capacitor, the LCL filter capacitor equivalent impedance is a resistor and capacitor in series, as shown in fig. 2 and 3.
The fundamental wave active loss corresponding to the LCL filter capacitor fundamental wave tangent loss angle tan delta is
PC,1＝QC,N×tanδ (2)
Where tan δ is an inherent property of a material, and its value differs at different frequencies.
LCL filter capacitor fundamental wave active loss equivalent resistance RC,1Determined according to the following formula:
considering that the loss generated by leakage current, medium absorption, lead resistance and the like of the LCL filter capacitor has a relation with the frequency of harmonic current injected into the LCL filter capacitor under the harmonic condition, in order to quantitatively calculate the influence of high-frequency harmonic current on the heating of the LCL filter capacitor, the h-th harmonic current causes the harmonic loss P of the capacitorC,hCalculated according to the following formula:
in the formula IC,hFor h-th harmonic current flowing into the capacitor, RC,hThe equivalent resistance of h harmonic active loss of the LCL filter capacitor.
The h-th harmonic current loss is equivalent to the fundamental current loss according to the following formula:
in the formula IC,h,1Is the h-th harmonic IC,hThe equivalent fundamental current, α, is the harmonic coefficient of the equivalent resistance of the LCL filter capacitor.
Considering the influence of harmonic current on the heating of LCL filter capacitor, the h-th harmonic I can be obtained from the formula (5)C,hWave current I of equivalent baseC,h,1Calculated using the formula:
the equivalent fundamental current value of each harmonic current of the capacitor obtained in this embodiment is shown in table 3 according to table 2 and equation (6).
TABLE 3 fundamental current value equivalent to each harmonic current of injection capacitor
After obtaining the effective value of the fundamental current equivalent to the h-th harmonic, performing over-current correction on the LCL filter capacitor by using the calculated fundamental current and harmonic current according to the table 3 and a preset formula (7), wherein the preset formula (7) is
Wherein, IC,NFor the rated phase current of the filter capacitor, IC，1,maxIs the maximum fundamental current of the filter capacitor, IC,h,1The effective value of the fundamental current equivalent to the h-th harmonic is α harmonic coefficients of the equivalent resistance of the filter capacitor.
Overcurrent correction is performed on the LCL filter capacitor for the calculated fundamental and harmonic currents according to table 3 and equation (7):
according to the checking result, the potential safety and stability operation hazard of the charging pile filter capacitor exists.
In addition, it can be understood that the overcurrent checking formula of 6.7.1.2 in GB/T26868-:
in the formula IC,1,maxThe capacitor is the maximum fundamental current flowing through the capacitor, IC,hIs a simulated value or a 95% probability maximum value of the h harmonic current flowing through the capacitor.
Considering that the high-frequency harmonic current has a more serious heating effect on the capacitor than the fundamental wave, the h-th order high-frequency harmonic current and the fundamental wave current cannot be considered equally according to the formula (8). For example, if the LCL filter capacitor is still over-current corrected according to table 2 and equation (8), then:
therefore, when 6.7.1.2 overcurrent check formula in GB/T26868-2011 high-voltage filter design and application guide rules is adopted for checking, the charging pile filter capacitor can safely and stably operate, the difference of the heating effect of high-frequency harmonic current on the capacitor and fundamental current is ignored, and the risk that the capacitor can safely check and pass, but the actual operation is serious in heating and even is burnt out exists.
Based on the same inventive concept, an embodiment of the present invention further provides a device for checking a charging pile filter capacitor, please refer to fig. 4, where the device for checking includes an acquisition module 410, a data processing module 420, and a determination module 430.
The acquisition module 410 is configured to obtain a maximum fundamental current effective value and each harmonic current effective value injected into the filter capacitor.
The data processing module 420 is configured to calculate a rated phase current of the filter capacitor according to a rated voltage and a rated installation capacity of the filter capacitor, and calculate an equivalent fundamental current effective value of the H-th harmonic according to an equivalent resistance of H-th harmonic active loss of the filter capacitor and the rated phase current of the filter capacitor, where H is a maximum harmonic frequency generated by the charging pile, H is [2, H ], H and H are positive integers, and H is not greater than H.
The judging module is used for performing overcurrent check on the filter capacitor according to the rated phase current of the filter capacitor, the equivalent fundamental wave current effective value of the h-th harmonic wave and the maximum fundamental wave current effective value of the filter capacitor.
It can be understood that in order to reduce the pollution of the high-frequency harmonic waves of the charging pile to the power grid, the charging pile is merged into the alternating-current power grid and is connected with the LCL filter in series. Because the current flowing into the charging pile LCL filter capacitor not only contains fundamental wave current, but also contains a large amount of high-frequency harmonic current, the heating level of the capacitor has larger difference due to equivalent high-frequency and low-frequency harmonic current, and if the overcurrent checking of the charging pile LCL filter capacitor of the electric automobile is checked according to a method given by national standards, the risk that the safety checking of the capacitor can pass, but the actual operation generates heat seriously and even burns out exists. Based on this, through being equivalent to the fundamental wave current effective value with h harmonic current effective value in this embodiment, utilize filter capacitor's fundamental wave current and the equivalent fundamental wave current of h harmonic carry out the overcurrent check to LCL filter capacitor, synthesize the influence of considering high frequency harmonic current's amplitude and frequency to LCL filter capacitor, can check the condenser more scientifically and reasonably to guarantee LCL filter capacitor and fill electric pile can long-term safe and stable reliable operation.
In one embodiment, the determining module 430 is specifically configured to:
judging whether a preset formula is established or not according to the rated phase current of the filter capacitor, the equivalent fundamental wave current effective value of the h-th harmonic wave and the maximum fundamental wave current effective value of the filter capacitor;
when the formula is satisfied, judging that the filter capacitor can safely and stably operate;
otherwise, judging that the filter capacitor has potential safety and stability operation hazards.
In one embodiment, the preset formula is:
wherein, IC,NFor the rated phase current of the filter capacitor, IC，1,maxIs the maximum fundamental current of the filter capacitor, IC,h,1The effective value of the fundamental current equivalent to the h-th harmonic is α harmonic coefficients of the equivalent resistance of the filter capacitor.
It is understood that the high-frequency harmonic current is considered to have a more serious effect on the heating of the capacitor than the fundamental wave, and the h-order high-frequency harmonic current and the fundamental wave current cannot be considered equally according to the formula (8). For example, if the LCL filter capacitor is still over-current corrected according to table 2 and equation (8), then:
therefore, when 6.7.1.2 overcurrent check formula in GB/T26868-2011 high-voltage filter design and application guide rules is adopted for checking, the charging pile filter capacitor can safely and stably operate, the difference of the heating effect of high-frequency harmonic current on the capacitor and fundamental current is ignored, and the risk that the capacitor can safely check and pass, but the actual operation is serious in heating and even is burnt out exists.
In the present embodiment, the calculated fundamental current and harmonic current are subjected to overcurrent correction on the LCL filter capacitor according to table 3 and formula (7):
according to the checking result, if the influence of the high-frequency harmonic current on the heating effect of the capacitor is considered, the potential safety and stability operation hazard of the charging pile filter capacitor can be judged, the checking accuracy is further improved, and the safety performance of the charging pile is improved.
In summary, the invention provides a method and a device for checking a charging pile filter capacitor. The method comprises the following steps: acquiring a maximum fundamental current effective value and each harmonic current effective value injected into the filter capacitor; calculating rated phase current of the filter capacitor according to rated voltage and rated installation capacity of the filter capacitor; calculating an equivalent value of a fundamental wave current equivalent to the H-th harmonic according to the equivalent resistance of the H-th harmonic active loss of the filter capacitor and the rated phase current of the filter capacitor, wherein H is the maximum harmonic frequency generated by the charging pile, H is [2, H ], H and H are positive integers, and H is less than or equal to H; and performing overcurrent check on the filter capacitor according to the rated phase current of the filter capacitor, the effective value of the equivalent fundamental current of the h-th harmonic wave and the maximum effective value of the fundamental current of the filter capacitor. In the invention, the h-th harmonic current effective value is equivalent to the fundamental current effective value, the LCL filter capacitor is subjected to overcurrent check by using the fundamental current of the filter capacitor and the h-th harmonic equivalent fundamental current, the influence of the amplitude and the frequency of the high-frequency harmonic current on the LCL filter capacitor is comprehensively considered, and the capacitor can be checked more scientifically and reasonably, so that the LCL filter capacitor and the charging pile can be ensured to run safely, stably and reliably for a long time.
The technical features of the embodiments described above may be arbitrarily combined, and for the sake of brevity, all possible combinations of the technical features in the embodiments described above are not described, but should be considered as being within the scope of the present specification as long as there is no contradiction between the combinations of the technical features.
The above-mentioned embodiments only express several embodiments of the present invention, and the description thereof is more specific and detailed, but not construed as limiting the scope of the invention. It should be noted that, for a person skilled in the art, several variations and modifications can be made without departing from the inventive concept, which falls within the scope of the present invention. Therefore, the protection scope of the present patent shall be subject to the appended claims.
Claims (12)
1. A method for checking a charging pile filter capacitor is characterized by comprising the following steps:
acquiring a maximum fundamental current effective value and each harmonic current effective value injected into the filter capacitor;
calculating rated phase current of the filter capacitor according to rated voltage and rated installation capacity of the filter capacitor;
calculating an equivalent value of a fundamental wave current equivalent to the H-th harmonic according to the equivalent resistance of the H-th harmonic active loss of the filter capacitor and the rated phase current of the filter capacitor, wherein H is the maximum harmonic frequency generated by the charging pile, H is [2, H ], H and H are positive integers, and H is less than or equal to H;
and performing overcurrent check on the filter capacitor according to the rated phase current of the filter capacitor, the effective value of the equivalent fundamental current of the h-th harmonic wave and the maximum effective value of the fundamental current of the filter capacitor.
2. A method of verification as claimed in claim 1, wherein obtaining the effective value of each harmonic current of the filter capacitor comprises:
obtaining a large 95% probability value of each harmonic current generated by the charging pile power electronic converter from a manufacturer;
and carrying out simulation calculation according to the 95% probability large value of each harmonic current generated by the charging pile to obtain the fundamental current effective value and each harmonic current effective value injected into the filter capacitor.
3. A method of calibration as claimed in claim 1 wherein obtaining each harmonic current effective value injected into said filter capacitor comprises:
carrying out electric energy quality test on the charging pile with the test condition to obtain a 95% probability large value of each harmonic current generated by the charging pile;
and carrying out simulation calculation according to the 95% probability large value of each harmonic current generated by the charging pile to obtain the fundamental current effective value and each harmonic current effective value injected into the filter capacitor.
4. A method of verification as claimed in claim 1, wherein obtaining the effective value of each harmonic current of the filter capacitor comprises:
and testing the electric energy quality of the charging pile with the testing conditions to obtain the fundamental wave current effective value and each harmonic current effective value of the filter capacitor.
5. A calibration method according to claim 1, wherein the nominal phase currents of the filter capacitors are:
wherein Q isC,NFor rated installation capacity, UC,NIs a rated voltage.
6. A verification method as claimed in claim 1, further comprising:
and before calculating the equivalent value of the fundamental current of the h harmonic, determining the equivalent resistance of the h harmonic active loss of the filter capacitor.
7. The method of checking according to claim 1, wherein the overcurrent checking of the smoothing capacitor based on the rated phase current of the smoothing capacitor, the effective value of the fundamental current equivalent to the h-th harmonic, and the effective value of the maximum fundamental current of the smoothing capacitor comprises:
judging whether a preset formula is established or not according to the rated phase current of the filter capacitor, the equivalent fundamental wave current effective value of the h-th harmonic wave and the maximum fundamental wave current effective value of the filter capacitor;
when the formula is satisfied, judging that the filter capacitor can safely and stably operate;
otherwise, judging that the filter capacitor has potential safety and stability operation hazards.
8. A verification method according to claim 7, wherein the predetermined formula is:
wherein, IC,NFor the rated phase current of the filter capacitor, IC，1,maxIs the maximum fundamental current of the filter capacitor, IC,h,1The effective value of the fundamental current equivalent to the h-th harmonic is α harmonic coefficients of the equivalent resistance of the filter capacitor.
9. A verification method as claimed in claim 1, characterized in that the effective value of the fundamental current equivalent to the h-th harmonic
Wherein, IC,hAnd α is the harmonic coefficient of the equivalent resistance of the filter capacitor, which is the effective value of the h-th harmonic current.
10. The utility model provides a fill electric pile filter capacitor's check device which characterized in that includes:
the acquisition module is used for acquiring the maximum fundamental current effective value and each harmonic current effective value injected into the filter capacitor;
the data processing module is used for calculating rated phase current of the filter capacitor according to rated voltage and rated installation capacity of the filter capacitor, and calculating equivalent fundamental wave current effective value of the H-th harmonic according to equivalent resistance of H-th harmonic active loss of the filter capacitor and rated phase current of the filter capacitor, wherein H is the maximum harmonic frequency generated by the charging pile, H is [2, H ], H and H are positive integers, and H is less than or equal to H; and
and the judging module is used for performing overcurrent check on the filter capacitor according to the rated phase current of the filter capacitor, the equivalent fundamental wave current effective value of the h-th harmonic wave and the maximum fundamental wave current effective value of the filter capacitor.
11. The verification apparatus according to claim 10, wherein the determination module is specifically configured to:
judging whether a preset formula is established or not according to the rated phase current of the filter capacitor, the equivalent fundamental wave current effective value of the h-th harmonic wave and the maximum fundamental wave current effective value of the filter capacitor;
when the formula is satisfied, judging that the filter capacitor can safely and stably operate;
otherwise, judging that the filter capacitor has potential safety and stability operation hazards.
12. A verification apparatus according to claim 11, wherein said predetermined formula is:
wherein, IC,NFor the rated phase current of the filter capacitor, IC，1,maxIs the maximum fundamental current of the filter capacitor, IC,h,1The effective value of the fundamental current equivalent to the h-th harmonic is α harmonic coefficients of the equivalent resistance of the filter capacitor.
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| CN201911095129.4A CN110794291B (en) | 2019-11-11 | 2019-11-11 | Method and device for checking charging pile filter capacitor |
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| CN201911095129.4A CN110794291B (en) | 2019-11-11 | 2019-11-11 | Method and device for checking charging pile filter capacitor |
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