Photovoltaic applications for off-grid electrification using novel multi-level inverter technology with energy storage

In areas where grid connection is difficult and costly, the use of renewable energy is both economically and environmentally advantageous. Due to typically low system efficiency (similar to 10%) and intermittency of photovoltaic (PV) electricity generation, a new design of multi-level H-bridge inverter technology is considered. This multi-level technology increases DC to AC conversion efficiency and the design includes battery energy storage to enable 24/7 operation. The proposed multi-level inverter is compared and contrasted with other existing designs. The proposed cascaded inverter provides lower switching losses, simple switching techniques, modularity, and simpler charge-balancing approaches than conventional technology. A switching technique was designed for the proposed multi-level inverter to ensure balancing of state of charge of each battery. The effectiveness of the switching was demonstrated via simulations. The simulations also show that the total harmonic voltage distortion of the proposed inverter is less than 6% without any filtering requirements. (C) 2011 Elsevier Ltd. All rights reserved.