Abstract
Currently, two maximum power point tracking (MPPT) units are used in hybrid photovoltaic (PV)/fuel cell (FC) systems, one for the PV subsystem and the other one for the FC stack, which significantly complicates the system implementation, and increases cost. This paper addresses this problem by presenting a novel fast and highly accurate unified MPPT technique for extracting maximum output power from hybrid PV/FC energy conversion systems. It is the only unified MPPT technique reported in the literature that uses a single algorithm to concurrently track the maximum power points (MPPs) of both PV module and FC stack used in a hybrid PV/FC system. A hybrid PV/FC energy conversion system has been built to evaluate the performance of the method. It is experimentally verified that the proposed MPPT method performs a very fast and highly accurate MPPT process, so that, the MPPT efficiency in the PV and FC subsystems is more than 99.60% and 99.41%, respectively, along with a very short convergence time of at most 12 ms and 33 s, respectively. Comparison between the MPPT method presented in this work and the state-of-the-art MPPT methods has been also performed that explicitly demonstrates the method has the highest MPPT efficiencies (99.60%, and 99.41%) along with the shortest convergence time (12 ms) compared to the state-of-the-art MPPT methods, while it concurrently performs two tasks (tracking two MPPs) but others perform only one task (tracking one MPP).
1. Introduction
Recently, there has been a rapid increase in the use of renewable energy resources, in particular, solar and wind energy [1,2], due to the problems such as reduction in fossil fuels availability and environmental issues. In practice, to increase rated power and reliability, renewable power sources are often combined with other power sources to arrange a hybrid energy conversion system such as a hybrid photovoltaic (PV)/fuel cell (FC) system [3]. A hybrid PV/ FC system consists of a PV subsystem used as the main power source and a FC stack which is usually used as a standby power source. This configuration makes a hybrid PV/FC energy conversion system more reliable and applicable to industrial applications [4]. Currently, two maximum power point tracking (MPPT) units are used in a hybrid PV/FC system, one for the PV subsystem and the other one for the FC stack that significantly complicates the system implementation. In this study, a novel fast and highly accurate unified MPPT technique applicable to hybrid PV/FC systems is presented to address this problem. The technique uses a single algorithm to concurrently track the maximum power points (MPPs) of both PV module and FC stack.
5. Conclusion
Two MPPT units are currently used in hybrid PV/FC systems, one for the PV subsystem and the other one for the FC stack, which significantly increases the system cost and complication. This study addressed this problem by presenting a novel fast and highly accurate unified MPPT technique that is the only unified MPPT technique reported in the literature. It was shown that the method only uses the output voltages and currents of the PV module and FC stack used in a hybrid PV/FC system to concurrently track the MPPs of both PV module and FC stack. A hybrid PV/FC power generation system was constructed, and the excellent performance of the unified MPPT method was experimentally verified, so that, the MPPT efficiency in the PV and FC subsystems was measured as 99.60% and 99.41%, respectively, along with the convergence time of respectively 12 ms and 33 s. The method was compared to the state-of-the-art MPPT methods that demonstrated it provides the highest MPPT efficiencies along with the shortest convergence time. Furthermore, the MPPT technique presented in this study is applicable to both standalone and grid-connected versions of PV, FC and hybrid PV/FC systems.
