A Method Of The Electrolytic Capacitor Parameter Prediction In Boost Type Converter Based On The Frequency Components

With the rapid development of modern electronic technology, application field of converter is more and more widely, and requirement of converter reliability becomes stricter. High failure rate of the electrolytic capacitors in converter has been the bottle neck problem of its devolpment all the time. In order to improve the converter reliability, condition of the electrolytic capacitor must be monitored effectively. But there is still not a proven and simple method to measure the electrolytic capacitor parameters accurately in real time. Therefore, predict the degraded condition of the electrolytic capacitor parameters in operational process simply and accurately is an urgent problem to solve, and also an effective way to improve the reliability of the converter.This paper puts forward a new method to predict the output electrolytic capacitor parameters in Boost converter. Take typical Boost converter in the DC-DC converter as an example and establish its non-ideal small signal model under CCM mode. Parasitic parameters of various elements in the model are considered in the so-called non-ideal small signal model when model established, and it is more accurate and closer to the real conditions. Calculate the transfer function between different variables based on the small signal model and plot Bode diagrams, then change the capacitance parameters and plot corresponding Bode diagram. Since only capacitor parameters changed, effection of capacitor parameters on frequency response can be reflected intuitively from Bode diagram. Through the theoretical analysis and the change of the Bode diagram, frequency band in which system is sensitive to capacitor parameters is found. Load square wave to the converter, and detect the reponse of sensitive frequency band at the ouput, record reponse data of sensitive band under different capacitor parameter, and then regression model is built between capacitor and the output reponse.Load the same signal to the converter during the operation time, then capacitor parameter can be real-time predicted through pluging corresponding reponse data to the previous established regression model. This method is simple, accurate, need not change the structure of the converter, and has good practicle value.This paper builds Boost converter simulink circuit in MATLAB and a multiple regression predict model is established through simulation data, which predict electrolytic capacitor parameters successfully and get good result. Then take real product as an example and predict electrolytic capacitor parameters accurately without knowing too much parameters of converter, which proves the method practicable.Three-phase voltage source rectifier is also called Boost rectifier because of the similar topology with Boost converter. This paper builds a non-ideal small signal model of three-phase voltage source rectifier, and set up a corresponding three-phase voltage source rectifier simulation circuit in MATLAB. Then establish a multiple regression predict model by using simulation data to predict electrolytic capacitor parameters under different aging conditions accurately. New method is successfully popularized to three-phase voltage source rectifier. Finally, analyze the effection on predict result of capacitor parameters under different load, and conclude that the method is still applicable under changing load, which proves the accuracy and feasibility of the method when applicated online in three-phase voltage source rectifier.