Abstract:
Grid-connected diode rectified adjustable speed drives (ASDs) use electrolytic capacitors with dc-side inductors for dc-link filtering. Stability and power quality determine dc-link filter size. However, the dc-link filter’s reliability depends on both component capability and field operation conditions (e.g., electrothermal stresses). Unbalanced voltage is most common in distribution networks today.
It increases electrical-thermal stress, reducing capacitor reliability. This paper proposes a mission profile-based capacitor reliability evaluation method to quantify LC filter reliability in an ASD system. Long-term estimation uses a nonlinear accumulated damage model that accounts for equivalent series resistor growth and capacitance reduction during degradation.
Based on the proposed lifetime estimation procedure, four case studies are investigated: lifetime benchmarking of capacitors in LC filtering and slim capacitor filtering configurations; scalability analysis for capacitor lifetime in terms of system power rating and grid-unbalanced levels; lifetime estimation of capacitors in the dc-link filter with long-term mission profile; and the impact of capacitor sizing on t The results help choose ASD-specific dc-link configurations and parameters.
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