Monitoring method of electrolytic capacitor of converter

Abstract

The invention relates to a monitoring method of the electrolytic capacitor of a converter. The method includes following steps that: step a, a variable capacitor is connected in parallel with two ends of the electrolytic capacitor of a test converter, and a variable resistor is also connected in series with the two ends of the electrolytic capacitor of the test converter; step b, test excitation signals are injected into the input position of the closed loop of the test converter, and the output signals of the output end of the closed loop of the test converter are acquired; step c, harmonic content in the output signals is extracted and recorded; step d, the electrolytic capacitor parameters of the test converter are changed, the step b and the step c are repeated, and a mathematical model between the harmonic content and the capacitor parameters are established, wherein the capacitor parameters include a capacitance value and equivalent series resistance; and step e, test excitation signals which are the same as the test excitation signals in the step b are injected into the input position of the conversion loop of a target converter, and harmonic content of sensitive frequency bands in the output signals of the target converter is extracted, and the harmonic content is introduced into the mathematical model in the step d, and the capacitance value and equivalent series resistance of the electrolytic capacitor of the target converter are calculated. With the monitoring method adopted, the performance status of the electrolytic capacitor of the converter can be accurately obtained.

Description

technical field [0001] The invention relates to the field of electric power, in particular to a method for monitoring electrolytic capacitors of converters. Background technique [0002] Converters are widely used in important fields such as aerospace, ship drive, metallurgical machinery transmission, locomotive traction, electric vehicle drive, etc. However, once the converter fails, it will cause extremely serious consequences. The failure of the converter is mainly Caused by internal components, especially the performance state of the electrolytic capacitor (usually aluminum electrolytic capacitor) of the converter has a very important impact on the reliability and stability of the converter. [0003] The performance state of the electrolytic capacitor is mainly reflected by the capacitance value and the equivalent series resistance. As the electrolytic capacitor ages, the equivalent series resistance will continue to increase, and the capacitance value will continue to d...

AI Technical Summary

Problems solved by technology

[0003] The performance state of the electrolytic capacitor is mainly reflected by the capacitance value and the equivalent series resistance. As the electrolytic capacitor ages, the equivalent series resistance will continue to increase, and the capacitance value will continue to decrease. This is due to the late use of the electrolytic capacitor. The liquid consumes more and becomes thicker, causing its resistivity to rise, resulting in a significant increase in the loss of the capacitor; at the same time, because the electrolyte cannot fully contact the uneven anodic metal oxide film at this time, the effective area of ​​the capacitor plate decreases , will cause a sharp drop in capacitance, so that the electrolytic capacitor will lose its function; therefore, timely monitoring of the capacitance value of the electrolytic capacitor and the change of the equivalent series resistance is the key to ensure the reliability and stability of the converter. In the prior art, the measurement of the electrolytic capacitor needs to modify the structure of the converter, and it is necessary to install high-precision voltage sensors, current sensors and other external devices on the electrolytic capacitor of the converter. According to the voltage and current of the electrolytic capacitor The capacitance of the electrolytic capacitor and the resistance of the equivalent series resistance are calculated according to the situation. However, on the one hand, this method has complicated operation process, low detection accuracy and high cost. More importantly, it changes the structure of the converter and adds components. It is not conducive to the stability and reliability of the converter

[0004] Therefore, a new monitoring method needs to be proposed, which can accurately measure the capacitance value of the electrolytic capacitor of the converter and the resistance value of the equivalent series resistance, so as to accurately obtain the performance change status of the electrolytic capacitor of the converter without Adding additional components can greatly save costs, simplify operations, and effectively avoid the influence of external interference on the stability and reliability of the converter caused by traditional measurement techniques

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