Solar Interfaced Series Inverter with Provision of Common DC Bus Grounding

Abstract

In this work, a new series solar inverter configuration is proposed to share the power in terms of voltage, unlike parallel inverter configurations. In a single-stage parallel inverter, elevated dc potential and circulating current due to common mode voltage (CMV) would degrade the solar inverter's life. The proposed topology eases the stress on the dc bus and protects the solar inverter from the issues associated with elevated dc potential (potential induced degradation effect, switch operating voltage stress, etc.). The inherent boosting capability of the proposed series inverter with two modular inverters is demonstrated through two switching algorithms. In the first switching algorithm, the switching combinations are devised to yield the maximum voltage across the load. The second switching algorithm demonstrates the method of eliminating CMV by choosing the appropriate switching combination of two inverters. The eliminated instantaneous CMV would give the provision of operating proposed topology with common dc bus along with the flexibility of dc bus grounding. For the proposed configuration with devised switching techniques, the closed-loop controller is designed by computing the plant's equivalent characteristic impedance using a state-space model. The effectiveness of the proposed configuration, along with the closed-loop control, is validated through hardware.