Investigation of MPPT in photovoltaic systems with step-down DC-DC converter and supercapacitor energy storage

Abstract

This study explores the implementation of Maximum Power Point Tracking (MPPT) in photovoltaic (PV) systems integrated with a step-down DC-DC converter and supercapacitor (SC) based energy storage. The integration of renewable energy sources, particularly solar power, necessitates highly efficient energy conversion and storage mechanisms to maximise the utility of the harvested energy. MPPT techniques play a pivotal role in optimising the power output of PV systems by dynamically adjusting the operating point to extract the maximum possible power under varying environmental conditions. SCs, with their high charge and discharge rates and high power density, emerge as a promising storage solution to manage the intermittent and variable energy output characteristic of PV systems. A Constant Voltage (CV) MPPT algorithm is employed to fine-tune the power output and ensure maximum energy efficiency. The experimental setup comprises a Solar Array Simulator simulating the PV array, interfaced with a step-down DC-DC converter, and an SC configured as the load. The system's performance is analysed by observing the available, actual and output power using a power analyser and evaluated to ascertain the robustness and effectiveness of the MPPT algorithm. The research distinguishes itself by utilising SCs as the primary load, an approach not commonly adopted in previous studies. Few studies have investigated the use of SCs exclusively as the load, and those that have indicated that MPPT is not efficiently achieved under such conditions. However, the analysed results affirm that the system proficiently tracks the maximum power point, attaining an average MPPT efficiency of 94.88% when the system is integrated with the CV MPPT algorithm. The average conversion efficiency attained was 75.62% with a basic DC-DC step-down converter constructed on a solderless board. It is anticipated that this MPPT efficiency will further improve with the application of more sophisticated MPPT algorithms such as Perturb and Observe (P&O), Incremental Conductance (IncCond), and Hill Climbing (HC). The average conversion efficiency can be increased by fine-tuning the converter and implementing more advanced topologies of DC-DC stepdown converters. This research makes a substantial contribution to advancing high-efficiency and dependable PV energy storage systems, underscoring the practical viability of SCs as an energy storage device. Furthermore, these findings have significant implications for SC-assisted Heating, Ventilation, and Air Conditioning (HVAC) systems integrated with PV systems, where efficient MPPT can enhance overall system performance as MPPT can be tracked when using the SC as the storage. Prospective studies will examine the long-term stability and scalability of this innovative approach in larger-scale PV installations, paving the way for more resilient and efficient renewable energy systems.