Switching strategy for improving the lifetime of dc-link capacitor in a fault-tolerant active power decoupling topology

Reliability is an important requirement for a grid-connected photovoltaic (PV) system in remote military-secured areas, which are difficult to access for system maintenance. However, the reliability of the PV system is reduced by the use of electrolytic capacitors in inverters. Active power decoupling (APD) topologies eliminate the need for these capacitors by using an additional decoupling circuit. However, the vulnerability of switching devices to failure is another reason for reduced reliability of inverters, which is not addressed in these topologies. Several fault-tolerant topologies are proposed in literature to address this limitation. However, these topologies use electrolytic capacitors in dc-link, which affects the overall reliability of inverter. To address these limitations, a fault-tolerant strategy is proposed in this study. In the proposed strategy, a conventional APD topology is used along with an electrolytic capacitor in the dc-link. The lifetime of the capacitor is improved using the decoupling circuit of the APD topology. In this regard, a switching strategy is proposed, using which the current flowing through dc-link capacitor is reduced. Furthermore, in the event of a device fault, the topology continues to function like the conventional H-bridge inverter. The operation of proposed strategy is validated through simulation and experimental studies