Condition Monitoring of DC Link Electrolytic Capacitors in Adjustable Speed Drives

Abstract

A new sensorless technique for monitoring the condition of inverter dc link aluminum electrolytic capacitors based on equivalent series resistance, ESR, and capacitance, C, estimation is proposed in this paper. The main concept of the proposed method is to estimate ESR and C of the capacitor using the inverter whenever the motor is stopped. The parameters are estimated from the dc link voltage and stator current measurements available in the inverter with the switched dc link voltage applied to the motor stator winding. The temperature of the capacitor can also be estimated under thermal equilibrium based on the stator resistance estimate to take the influence of temperature variation into account. An experimental study on a 250W permanent magnet synchronous motor performed under accelerated capacitor degradation is presented to verify the proposed technique. It is shown that the proposed method provides a reliable and sensitive indication of capacitor aging without additional hardware requirements.

Perspectives on condition monitoring techniques of wind turbines

“…Tracking variation of those electrical parameters can help detect failure mechanisms (Sankaran et al, 1997). Proper failure detection of DC-link capacitors highly depends on the size of capacitors (Kim et al, 2007). Electrolyte vaporisation is dominant for small capacitors due to limited available surface to temperature dissipation and higher ESR.…”

Online health monitoring of metallized polymer film capacitors for avionics applications

“…From the existing health monitoring techniques, we can mention the research work of [27] and [28] that are not limited to the simple estimation of ESR but also to that of the capacitance C. However, to properly conduct the identification of these two variables, it is necessary to inject an external signal to the system as in [27], or to force a specific configuration of operation as in [28], which make the generalization of such techniques not possible when different systems are studied.…”

Condition monitoring of capacitors in power electronic converters

“…In [30,31], a quasi-online method is proposed which utilises the simplified equivalent circuit of the drive when it is turned off to estimate the ESR and capacitance of the dc-link capacitor in adjustable-speed drives. Whenever the drive is turned off, the input current becomes zero and the capacitor current discharges through the motor windings.…”

“…This method uses a simplified equivalent circuit model of the drive to estimate the parameters by using the recursive least squares (RLS) approach whenever the induction motor is stopped. The use of the RLS approach to estimate the parameters eliminates the sensitivity to switching period and duty ratio in [30,31] and improves the accuracy. Like the previous methods, this method also needs the switching information of the inverter to estimate capacitor current.…”

“…In [30,31], a technique is proposed to normalise the effect of temperature on the estimated capacitance and ESR. The effect of temperature and frequency on the capacitance and ESR of healthy and aged capacitors are analysed.…”