Abstract
In this paper, a systematic analysis of seven control topologies is performed, based on three possible control variables of the power generated by the Fuel Cell (FC) system: the reference input of the controller for the FC boost converter, and the two reference inputs used by the air regulator and the fuel regulator. The FC system will generate power based on the Required-Power-Following (RPF) control mode in order to ensure the load demand, operating as the main energy source in an FC hybrid power system. The FC system will operate as a backup energy source in an FC renewable Hybrid Power System (by ensuring the lack of power on the DC bus, which is given by the load power minus the renewable power). Thus, power requested from the batteries’ stack will be almost zero during operation of the FC hybrid power system based on RPF-control mode. If the FC hybrid power system operates with a variable load demand, then the lack or excess of power on the DC bus will be dynamically ensured by the hybrid battery/ultracapacitor energy storage system for a safe transition of the FC system under the RPF-control mode. The RPF-control mode will ensure a fair comparison of the seven control topologies based on the same optimization function to improve the fuel savings. The main objective of this paper is to compare the fuel economy obtained by using each strategy under different load cycles in order to identify which is the best strategy operating across entire loading or the best switching strategy using two strategies: one strategy for high load and the other on the rest of the load range. Based on the preliminary results, the fuel consumption using these best strategies can be reduced by more than 15%, compared to commercial strategies.
Highlights
The very fast increase of global energy demand over recent decades calls for a new approach to energy sustainable development based on Hybrid Power Systems (HPS) combining RenewableEnergy Sources (RESs) and Fuel Cell (FC) systems [1,2,3]
Power Point Tracking (GMPPT) control algorithms [19,20,21] applied to available RenewableEnergy Sources (RESs) in order to optimally ensure the power flow balance on the DC bus [22,23,24] and improve the harvested energy from the RESs [25,26,27]; Hybridization of the RES HPS with an FC system as backup energy source (FC/RES HPS) to mitigate the RES power variability and load dynamics by controlling the generated FC power at the level of the required power on the DC bus [28,29,30]
Seven control topologies are identified based on the three ways to regulate the FC
Summary
The very fast increase of global energy demand over recent decades calls for a new approach to energy sustainable development based on Hybrid Power Systems (HPS) combining Renewable. Solid Oxide Electrolyzer/Fuel Cells [15]: Proposal of innovative stand-alone or grid-connected RES HPS architectures, which can be optimized based on advanced Energy Management Strategies (EMSs) [16,17,18] and Global Maximum. If the FCHPS is operated using the best RTO strategy for high values of the load demand and another one which is best in the rest of the load range, more combinations are possible (which we refer to as the switching strategies). This is because two RTO strategies are identified as best for high levels of load and two others as best for low load. Th final section concludes the performed study by highlighting the main findings and work
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