CN112230066B - Traction converter direct current bus capacitance health assessment method and system - Google Patents
Traction converter direct current bus capacitance health assessment method and system Download PDFInfo
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Abstract
The invention discloses a traction converter direct current bus capacitance health assessment method and a system, wherein the method comprises the following steps: the method comprises the steps that firstly, direct-current bus voltage of a traction converter, three-phase output current of an inversion module and switching signals of a power switching tube are synchronously sampled and obtained; secondly, respectively calculating ESR and C at the switching frequency of the direct current bus capacitor and the output frequency of the inversion module according to the switching signal and the three-phase output current of the inversion module; thirdly, estimating the central temperature of the direct current bus capacitor according to the surface temperature of the direct current bus capacitor, the three-phase output current of the inversion module and a switching signal; and fourthly, evaluating the health condition of the direct current bus capacitor according to the ESR and C of the direct current bus capacitor and the output frequency in combination with the central temperature. The method provided by the invention can utilize the original sampling point in the traction converter, can accurately monitor ESR and C at two frequencies of the direct current bus capacitor of the traction converter, and effectively evaluate the health condition of the direct current bus capacitor.
Description
Technical Field
The invention relates to the field of on-line monitoring and reliability evaluation of power electronic elements, in particular to a traction converter direct-current bus capacitance health evaluation method and system.
Background
With the improvement of the power supply management standard of the high-speed electrified railway and the passenger dedicated line, higher requirements are put on the safety and the reliability of power supply equipment, and as for the current management mode of the electric equipment of the Chinese electrified railway, the standard requirements are met, and a large amount of operation and maintenance cost is consumed. Therefore, necessary equipment monitoring measures are needed to reduce the accident potential of the power supply system, reduce the accident probability, shorten the time for fault finding and maintenance, ensure the reliable operation of the power supply system, and play an important role in reducing the operation and maintenance cost, improving the economic benefits of transportation and establishing good images of railways.
After a direct-current bus capacitor in a traction system is used for a period of time, the equivalent series resistance ESR of the capacitor can be increased, the capacitance value C of the capacitor can be reduced, and when the equivalent series resistance ESR and the capacitance value C of the capacitor are changed to a certain degree, the capacitor can be considered to be failed, and the failure of the capacitor can cause operation faults of a converter and the system. In industry, the ESR and C of a specific frequency point of an electrolytic capacitor are important indicators for measuring the health condition of the capacitor, so that monitoring the ESR and C of a dc bus capacitor in a traction system is important for evaluating the health condition of the traction system. However, the conventional ESR and C monitoring method mostly adopts a switching ripple, and the switching ripple includes multiple harmonics, so that the identification result is affected by the harmonics, the reference value of the result is affected, and a relatively universal and effective capacitor health monitoring method cannot be provided. Furthermore, both ESR and C of the capacitor are affected by the core temperature, and thus the combined temperature is required to evaluate the state of health of the capacitor. However, most of the current studies are based on surface temperature, and there is an error between the surface temperature and the center temperature, so the confidence of the current evaluation of the capacitance health is not high.
Disclosure of Invention
The invention aims to solve the technical problem of the background art, and provides a traction converter direct current bus capacitor health assessment method and system aiming at the defects in the background art, which can monitor the ESR and C of a switching frequency point and an output frequency point on line in real time, and estimate the central temperature of a capacitor, thereby realizing the health assessment of the direct current bus capacitor in the traction converter.
The invention adopts the following technical scheme for solving the technical problems:
the method for evaluating the health of the direct current bus capacitor of the traction converter comprises the following steps:
step A), synchronously sampling and obtaining the direct-current bus voltage v of the traction converterC(t) inverter Module three-phase output Current iU(t)、iV(t)、iW(T) and T1、T2、T3Of the switching signal s1、s2、s3On is 1 and off is 0, wherein the switching signal s1、s2、s3Can be directly obtained by the control unit of the traction converter;
step B), respectively according to the DC bus voltage v obtained in the step A)C(t) inverter Module three-phase output Current iU(t)、iV(t)、iW(T) and power switch tube T1、T2、T3Of the switching signal s1、s2、s3Calculating the switching frequency fsOutput frequency f of the inverter moduleoESR and C, calculated as follows:
step B1), calculating the input current:
step B2), calculating the integral coefficient at frequency point f:
step B3), calculating the values of ESR and C at the frequency point f of the DC bus capacitor of the traction converter according to the following formula:
wherein f is fsOr foEsr (f) is the equivalent series resistance at the dc bus capacitance frequency f, and c (f) is the capacitance at the dc bus capacitance frequency f.
Step C), obtaining the DC bus voltage v according to the step A)C(t) inverter Module three-phase output Current iU(t)、iV(t)、iW(T) and power switch tube T1、T2、T3Of the switching signal s1、s2、s3Combining the measured surface temperature t of the DC bus capacitorCEstimating the central temperature of the direct current bus capacitor, wherein the estimation process comprises the following steps:
step C1), obtaining the DC bus voltage v through the same high-pass filterC(t) and the input current iinAlternating current component in (t): v. ofC_ac(t) and iin_ac(t)；
Step C2), according to vC_ac(t) and iin_ac(t) calculating the ac power on the dc bus capacitance:
step C3) of the method,obtaining p by a high pass filterCDirect current component in (t): pC；
Step C4), combining the measured surface temperature t of the direct current bus capacitorCAnd calculating the central temperature of the direct current bus capacitor:
wherein R isCThe thermal resistance between the center and the surface of the direct current bus capacitor is obtained through data manual inquiry or advanced measurement.
Step D) of calculating the frequency f according to step B)sAt frequency foAnd (C) evaluating the health condition of the direct current bus capacitor by combining the ESR and the C with the central temperature estimated in the step C): respectively comparing the calculated ESR (f), C (f) and the calculated ESR (f) with the temperature T of the capacitor at the time of factory shipment or before installationjAnd comparing the data measured at the frequency f, and evaluating the health condition of the direct current bus capacitor according to the magnitude of the variable quantity.
A traction converter dc bus capacitance health assessment system, the system comprising:
the information acquisition unit is used for acquiring a plurality of items of attribute information of the traction converter in a sampling manner;
the ESR and C calculating unit is used for calculating ESR and C at two frequencies of the direct current bus capacitor of the traction converter according to the attribute information;
the central temperature estimation unit is used for estimating the central temperature of the direct current bus capacitor according to the attribute information;
and the health evaluation unit is used for evaluating the health condition of the direct current bus capacitor according to the ESR and the C in combination with the central temperature.
Compared with the prior art, the invention adopting the technical scheme has the following technical effects:
1. the method can effectively remove interference components in the voltage and the output current of the direct current bus, and accurately monitor the ESR and C values of the capacitance switching frequency point and the output frequency point of the direct current bus;
2. the invention is suitable for online real-time monitoring;
3. for a common traction converter, a new sampling point is not required to be introduced;
4. the error of using the surface temperature of the capacitor is avoided, and the central temperature of the direct current bus capacitor can be estimated more accurately;
5. the circuit is simple, the health condition of the direct current bus capacitor can be effectively evaluated on the basis of not increasing electronic components, and the direct current bus capacitor has important practical application value.
Drawings
FIG. 1 is a schematic diagram of a traction converter DC bus capacitance health assessment system according to the present invention;
FIG. 2 is a diagram of one implementation of a health assessment unit of the present invention;
fig. 3 is a waveform diagram illustrating simulation of the operation of the traction converter according to the present invention.
Detailed Description
The technical scheme of the invention is further explained in detail by combining the attached drawings:
with reference to a schematic diagram of a principle of an evaluation system and an implementation method diagram of an evaluation unit respectively corresponding to fig. 1 and fig. 2, the invention discloses a traction converter direct current bus capacitance health evaluation method, which comprises the following steps:
step A), synchronously sampling and obtaining the direct-current bus voltage v of the traction converterC(t) inverter Module three-phase output Current iU(t)、iV(t)、iW(T) and power switch tube T1、T2、T3Of the switching signal s1、s2、s3(1 for on, 0 for off);
step B), respectively according to the DC bus voltage v obtained in the step A)C(t) inverter Module three-phase output Current iU(t)、iV(t)、iW(T) and power switch tube T1、T2、T3Of the switching signal s1、s2、s3Calculating the switching frequency fsOutput frequency f of the inverter moduleoESR and C, calculated as follows:
step B1), calculating the input current:
step B2), calculating the integral coefficient at frequency point f:
step B3), calculating the values of ESR and C at the frequency point f of the DC bus capacitor of the traction converter according to the following formula:
wherein f is fsOr foEsr (f) is the equivalent series resistance at the dc bus capacitance frequency f, and c (f) is the capacitance at the dc bus capacitance frequency f.
Step C), obtaining the DC bus voltage v according to the step A)C(t) inverter Module three-phase output Current iU(t)、iV(t)、iW(T) and power switch tube T1、T2、T3Of the switching signal s1、s2、s3Combining the measured surface temperature t of the DC bus capacitorCEstimating the central temperature of the direct current bus capacitor, wherein the estimation process comprises the following steps:
step C1), obtaining the DC bus voltage v through the same high-pass filterC(t) and the input current iinAlternating current component in (t): v. ofC_ac(t) and iin_ac(t)；
Step C2), according to vC_ac(t) and iin_ac(t) calculating the ac power on the dc bus capacitance:
step C3), obtaining p by a high-pass filterCDirect current component in (t): pC；
Step C4), combining the measured surface temperature t of the direct current bus capacitorCAnd calculating the central temperature of the direct current bus capacitor:
wherein R isCThe thermal resistance between the center and the surface of the direct current bus capacitor is obtained through data manual inquiry or advanced measurement.
Step D) of calculating the frequency f according to step B)sAt frequency foAnd (C) evaluating the health condition of the direct current bus capacitor by combining the ESR and the C with the central temperature estimated in the step C):
step D1), according to the switching frequency fsOutput frequency foAnd the estimated central temperature T of the DC bus capacitorjEsr and c of the direct current bus capacitance under the health condition are obtained through table lookup: esr (f)s,Tj)、esr(fo,Tj)、c(fs,Tj)、c(fo,Tj)；
Step D2), based on the on-line calculated ESR (f)s)、ESR(fo)、C(fs)、C(fo) Are respectively connected with esr (f)s,Tj)、esr(fo,Tj)、c(fs,Tj)、c(fo,Tj) Comparing if it is satisfied
And judging that the direct current bus capacitor needs to be replaced, otherwise, judging that the direct current bus capacitor does not need to be replaced.
Fig. 3 is a waveform diagram illustrating the operation of the traction converter according to the present invention. The invention provides a simulation result of a traction converter ESR and C calculation unit, and the simulation conditions are as follows: DC network voltage of 1000V and switching frequency fs=2kHz, samplingFrequency fp=500 kHz. Firstly, carrying out circuit operation simulation, and after the operation is stopped, carrying out direct-current bus voltage vC(t) inverter Module three-phase output Current iU(t)、iV(t)、iW(T) and power switch tube T1、T2、T3Of the switching signal s1、s2、s3The method is introduced into Matlab Workspace for data processing, simulation results under different capacitance parameters are shown in table 1 (because ESR and C values at different frequencies of simulation species are the same, only simulation results at switching frequencies are given), and therefore the calculation method of the ESR and C of the direct current bus capacitor of the traction converter provided by the invention has higher monitoring precision.
TABLE 1
| Actual value of C/. mu.F | 500 | 1000 | 500 |
| Actual value of ESR/Ω | 0.1 | 0.1 | 0.2 |
| Calculated C/. mu.F | 495.48 | 999.95 | 502.84 |
| Calculated ESR/Ω | 0.1009 | 0.0998 | 0.2021 |
The traction converter direct-current bus capacitance health assessment method and system provided by the invention have the advantages that the interference of other sub-harmonics can be eliminated, the ESR and C values of specific frequency points can be accurately monitored, no new measuring point needs to be introduced, the method is simple and easy to implement, and the traction converter direct-current bus capacitance health assessment method and system are simultaneously suitable for traction converters under different working conditions.
It will be understood by those skilled in the art that, unless otherwise defined, all terms (including technical and scientific terms) used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. It will be further understood that terms, such as those defined in commonly used dictionaries, should be interpreted as having a meaning that is consistent with their meaning in the context of the prior art and will not be interpreted in an idealized or overly formal sense unless expressly so defined herein.
The above-mentioned embodiments, objects, technical solutions and advantages of the present invention are further described in detail, it should be understood that the above-mentioned embodiments are only illustrative of the present invention and are not intended to limit the present invention, and any modifications, equivalents, improvements and the like made within the spirit and principle of the present invention should be included in the protection scope of the present invention.
Claims (3)
1. A traction converter direct current bus capacitance health assessment method is characterized by comprising the following steps:
step A), synchronously sampling and obtaining the direct-current bus voltage v of the traction converterC(t) inverter Module three-phase output Current iU(t)、iV(t)、iW(T) and power switch tube T on three-phase bridge arm of inversion module1、T2、T3Of the switching signal s1、s2、s3Turning on is 1 and turning off is 0;
step B), respectively according to the DC bus voltage v obtained in the step A)C(t) inverter Module three-phase output Current iU(t)、iV(t)、iW(T) and power switch tube T1、T2、T3Of the switching signal s1、s2、s3Calculating the switching frequency fsOutput frequency f of the inverter moduleoESR and C; the calculation process is as follows:
step B1), calculating the input current:
step B2), calculating the integral coefficient at frequency point f:
step B3), calculating the values of ESR and C at the frequency point f of the DC bus capacitor of the traction converter according to the following formula:
wherein f is fsOr foEsr (f) is the equivalent series resistance at the dc bus capacitance frequency f, and c (f) is the capacitance at the dc bus capacitance frequency f;
step C), obtaining the DC bus voltage v according to the step A)C(t) inverter Module three-phase output Current iU(t)、iV(t)、iW(T) and power switch tube T1、T2、T3Of the switching signal s1、s2、s3Combining the measured surface temperature t of the DC bus capacitorCEstimating the central temperature of the direct current bus capacitor;
step D) of calculating the frequency f according to step B)sAt frequency offoAnd (C) evaluating the health condition of the direct current bus capacitor by combining the ESR and the C estimated in the step C).
2. The method for health assessment of the dc bus capacitor of the traction converter according to claim 1, wherein the estimation process of the temperature of the center of the dc bus capacitor in step C) is as follows:
step C1), obtaining the DC bus voltage v through the same high-pass filterC(t) and the input current iinAlternating current component in (t): v. ofC_ac(t) and iin_ac(t)；
Step C2), according to vC_ac(t) and iin_ac(t) calculating the ac power on the dc bus capacitance:
step C3), obtaining p by a high-pass filterCDirect current component in (t): pC；
Step C4), combining the measured surface temperature t of the direct current bus capacitorCAnd calculating the central temperature of the direct current bus capacitor:
wherein R isCThe thermal resistance between the center and the surface of the direct current bus capacitor is obtained through data manual inquiry or advanced measurement.
3. The method for health assessment of the dc bus capacitor of the traction converter according to claim 1, wherein the health assessment process of the dc bus capacitor in step D) is as follows:
respectively comparing the calculated ESR (f), C (f) and the calculated ESR (f) with the temperature T of the capacitor at the time of factory shipment or before installationjAnd comparing the data measured at the frequency f, and evaluating the health condition of the direct current bus capacitor according to the magnitude of the variable quantity.
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Denomination of invention: A method and system for evaluating the health of DC bus capacitors of traction converters Effective date of registration: 20220809 Granted publication date: 20210309 Pledgee: Zheshang Bank Co.,Ltd. Nanjing Branch Pledgor: NANJING HUASHI ELECTRONIC SCIENTIFIC Co.,Ltd. Registration number: Y2022320000447 |
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Denomination of invention: A Method and System for Health Assessment of DC Bus Capacitors in Traction Converters Effective date of registration: 20230921 Granted publication date: 20210309 Pledgee: Zheshang Bank Co.,Ltd. Nanjing Branch Pledgor: NANJING HUASHI ELECTRONIC SCIENTIFIC Co.,Ltd. Registration number: Y2023980058154 |
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