An Online Estimation Method of DC Capacitor ESR

Abstract

The invention relates to an online estimation method of DC capacitor ESR, which comprises the following steps: 1) Detecting the initial value R of the loop total resistance of the converter system res0 and the capacitance of the snubber capacitor C s ; 2) Intercept the DC capacitor current high-frequency oscillation signal S sw_res The kth high-frequency oscillation segment S in (t) sw_res (k); 3) Obtain the high-frequency oscillation signal segment S using the half-power method sw_res (k) Oscillation damping ratio and resonance frequency; 4) Calculate the resonance tank resistance R res ; 5) Calculate the ESR variation ΔESR Cdc , which is the online estimate of the DC capacitance ESR. Compared with the prior art, the invention has the advantages of high accuracy, easy implementation, reduced interference and the like.

Description

technical field [0001] The invention relates to the field of DC capacitance monitoring, in particular to an online estimation method of DC capacitance ESR. Background technique [0002] DC capacitors have the functions of filtering, energy storage, and input-output isolation in converters, and are widely used in important fields such as power grids, photovoltaics, and new energy vehicles. In particular, DC capacitors in high-power systems have large operating currents, high power, and severe heat generation. They are one of the most easily degraded components in converters. Therefore, DC capacitor status monitoring is of great significance to the safe and reliable operation of converter systems. [0003] The health status of DC capacitors is generally judged by two indicators: capacitance value and series equivalent resistance ESR. Taking electrolytic capacitors as an example, when the capacitance value decreases by 20% and the ESR increases by 100% to 200%, the capacitor ca...

AI Technical Summary

Problems solved by technology

The existing technology generally monitors the health status of electrolytic capacitors through ESR, and utilizes the capacitor PWM voltage ripple Δu h and current ripple Δi h Estimated ESR = Δu h / Δi h , but the amplitude of PWM ripple voltage and current is very small and changes with the operating conditions, so it is difficult to accurately detect

[0004] Chinese patent 202010070754.X proposes a system and method to obtain the ESR information of the DC capacitor online by detecting the high-frequency oscillation damping characteristics of the DC capacitor switch of the converter. In this patent, the damping characteristics of the switching oscillation are obtained by the method of time domain fitting, but in the actual system, the switching oscillation signal is usually aliased with dynamic DC components and other frequency components, which will affect the Accurate extraction of damping characteristic parameters causes interference

Images