Diagnosis of Electrolytic Capacitors in Three-Phase Interleaved Boost Converters Controlled by Mixed Weighted Sensitivity H∞ Design Control

Aluminum electrolytic capacitors (AECs) are widely used in the DC link of power converters, such as the three-phase interleaved boost converter (IBC) which offers many advantages over the conventional amplifier converter. IBCs can operate both in closed- or open-loop systems and any fault in the converter components can reduce significantly the overall system performance. AECs failures represent the major cause for power electronics equipment breakdown, mainly due to both aging and temperature effects involving significant increase on their equivalent series resistance (ESR) parameter. This reveals the importance of developing robust control strategies that allow evaluating the electrolytic capacitor state condition and keeping, at the same time, the performance of the converter controller, even under a capacitor fault occurrence. For that purpose, a fault detection and control strategy is proposed in this paper, for a three-phase interleaved boost converter application. The control task of this strategy uses a mixed sensitivity H∞ controller to ensure fast dynamics and robustness even under failure mode operation, while the fault detection task uses the Short Time Least Square Prony's (STLSP) method to perform an online estimation of the ESR parameter, allowing a continuous evaluation of the electrolytic capacitor state condition, and consequently avoiding a total system failure. The effectiveness of the proposed strategy is verified by several experimental tests.