Method for monitoring service life of DC-side electrolytic capacitor of active power filter in real time

Abstract

The invention provides a method for monitoring the service life of a DC-side electrolytic capacitor of an active power filter in real time. The method comprises the steps of: obtaining a switching function and a switching current frequency spectrum of a switching device through the calculation of a controller according to the actual output compensation current of the active power filter a controlinstruction, and calculating the current frequency spectrum of the capacitor; controlling the switching device and the capacitor to form an RLC loop, and calculating and fitting to obtain the equivalent series resistance of the capacitor under different frequencies by measuring the oscillation period and amplitude; calculating the capacitance loss according to the current spectrum of the capacitorand the equivalent series resistance, combining the capacitance loss, the ambient temperature measured by a temperature sensor near the capacitor and the thermal resistance model of the capacitor, tocalculate the temperature rise in the capacitor; and according to the temperature rise, the environment temperature and an established capacitor service life calculation formula, enabling the controller to calculate the service life loss condition of the capacitor and give an early warning. Parameters in an actual application device and the frequency characteristics of the ESR are considered, andthe reliability and accuracy of detection are improved.

Description

technical field [0001] The invention relates to the technical field of active power filters, in particular to a method for real-time monitoring of the life of an electrolytic capacitor on the DC side of an active power filter. Background technique [0002] With the rapid development of power electronics technology, converter equipment has been widely used, but its nonlinear characteristics not only reduce the power factor of the grid, but also bring a lot of harmonic interference, which affects the normal operation of power equipment, so Harmonic compensation and power factor improvement of power system has become an urgent need. Active Power Filter (APF) is an effective device to solve these problems. [0003] figure 1 The overall structure of the active power filter is shown in , which is mainly composed of current and voltage transformers, signal conditioning and data acquisition circuits, harmonic detection modules, current tracking control modules and PWM inverters. ...

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Problems solved by technology

[0010] At present, the detection of electrolytic capacitor life is mostly based on the model of ambient temperature and internal temperature rise, but this detection method is not combined with the parameters of the actual application device, so it cannot provide reference for the design and selection of the DC side capacitor of the APF device; There are also some patents and literatures that equate the capacitor to a constant ESR, and then use the capacitor current and ESR to solve the internal temperature rise, so that the life of the capacitor can be obtained. This detection method ignores the change of the equivalent series resistance of the capacitor as the frequency changes. Varying properties and therefore less accurate

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