Multi-input single-inductor dc-dc converter for MPPT in parallel-connected photovoltaic applications

This paper focuses on photovoltaic systems with multiple parallel-connected panels. It is shown that distributed MPPT must be performed on each panel to maintain maximum power harvesting in partial shading conditions. This is especially true for PV systems made with panels having different electrical parameters. The multi-input, single-output (MISO) dc-dc converter provides a low-cost implementation of distributed MPPT for solar applications. A controller with digital peak and valley current control is used to operate the MISO converter in pseudo-CCM mode. A digital input current estimation algorithm based on the inductor current is proposed to iteratively reach DMPPT for each input, while eliminating the need for several current sensors in the system. The overall power benefit from the MISO converter ranges from 7% to 43% in the experimental MISO buck prototype. The proposed low-cost DMPPT solution and control algorithm provide very promising power savings compared to the conventional MPPT approach. The novel solution allows PV systems to be easily expanded without being restricted to panels from a single manufacturer.