Design and realization of a differential power processor with bidirectional DC/DC converter in photovoltaic systems

A photovoltaic system is an energy generation system that converts solar energy into electrical energy. It is the fastest-developing energy source among renewable energy types and receives the largest investments. Photovoltaic systems are usually used by connecting a number of modules in series. The biggest disadvantage of this connection structure is the occurrence of mismatch situations. When different powers occur between photovoltaic modules due to partial shading, contamination, temperature difference, etc., a large drop in output power occurs. Conventional bypass diodes solve this problem to some extent but cannot ensure that all power is transferred to the output. Differential power processing has emerged as a widely used solution to mitigate this effect. However, the implementation of differential power processing architectures brings challenges such as system cost, reliability, control implementation, and modularity. This research proposes a simplified voltage equalization algorithm that is implemented on a low-cost and modular differential power processing architecture using bidirectional flyback converters. In particular, under light to moderate mismatch conditions, the output power of the photovoltaic system shows a significant increase compared to the conventional string configuration with bypass diodes. A methodology adapted to the voltage equalization algorithm is proposed to optimize the system performance, minimizing the power dissipated while increasing overall efficiency. The proposed solutions have been extensively tested through simulations and experiments. The results confirm that the system efficiency reaches about 90% under partial shading conditions.