An optimal power sharing and power control strategy of photovoltaic/fuel cell/ultra-capacitor hybrid power system

Abstract

Renewable energy sources experience problems such as deregulation when they are used as stand-alone energy sources. This paper presents an optimal power sharing and power control strategy combining a photovoltaic (PV) array, a fuel cell (FC) stack, an ultra-capacitor (UC) module, and a set of loads. The photovoltaic is the prior energy source while the fuel cell (FC) system is added as a backup source to meet the excess power demand. The ultra-capacitor (UC) is utilized as a buffer storage to compensate the slow dynamic response of the FC during transient and regulate the DC-bus voltage. The power control strategy is designed to work on a two-level arrangement. The top level controls the entire power management, which generates references to low level individual subsystems depending upon solar radiation, temperature, and load conditions. Based on the command signals, each local controller controls the PV, FC, electrolyzer, and UC. The top level also controls the load scheduling during low solar radiation in order to sustain the system operation for 24 h. The performance of the system is tested under real-world record of solar radiation, temperature, and load conditions for Bahria town at Islamabad, Pakistan. The effectiveness of the proposed model in terms of voltage regulation, power transfer, load tracking, and grid stability is verified by Matlab simulation results.

A novel low-voltage ride-through capable energy management scheme for a grid-connected hybrid photovoltaic-fuel cell power source

“…Fuel cell–based power solutions have garnered a lot of interest in recent years . In existing literature, a variety of energy management control solutions have been proposed for hybrid power systems containing FCs where energy output is managed between the FCs and other sources to smoothen the power output, follow a desired load profile, or optimize energy production/consumption.…”

“…While the control techniques proposed in some of the aforementioned literature are quite interesting and efficient, they largely deal with the operation and energy management (EM) of hybrid DG sources under normal conditions (eg, Mohammadi and Nafar, Eid, Patra et al, and Kamal et al ). They do not address the special requirements associated with LVRT capability, modern grid code directives, and equipment protective measures discussed earlier.…”

“…The key contributions of this work are as follows: A unique EMS is proposed that allows the intermittent PV resource to actively participate in the grid by hybridizing and coordinating it with a controllable FC generator, under both the normal operating conditions and voltage sags. Unlike some existing power‐sharing solutions for hybrid systems, the proposed EM control strategy enables the hybrid power source to provide dynamic active and reactive power support to the grid in case of symmetrical and asymmetrical voltage sags. A novel combination of disturbance rejection control (DRC) and repetitive control is employed to design a robust control system for the hybrid PV‐FC power source. Uncertainties, unmodeled dynamics, and disturbances are formally treated in design to robustify the control system.…”

“…1,2 SABIR Fuel cell-based power solutions have garnered a lot of interest in recent years. 1,[3][4][5][6][7][8][9][10][11] In existing literature, a variety of energy management control solutions have been proposed for hybrid power systems containing FCs where energy output is managed between the FCs and other sources to smoothen the power output, follow a desired load profile, or optimize energy production/consumption. The feasibility of the hybrid PV-FC concept has been investigated in some of the earlier works (see Rahman and Tam 1 and the references therein).…”

“…• A unique EMS is proposed that allows the intermittent PV resource to actively participate in the grid by hybridizing and coordinating it with a controllable FC generator, under both the normal operating conditions and voltage sags. Unlike some existing power-sharing solutions for hybrid systems, [4][5][6]11 the proposed EM control strategy enables the hybrid power source to provide dynamic active and reactive power support to the grid in case of symmetrical and asymmetrical voltage sags.…”