Energy control of supercapacitor/fuel cell hybrid power source

This paper deals with a flatness based control principle in a hybrid system utilizing a fuel cell as a main power source and a supercapacitor as an auxiliary power source. The control strategy is based on regulation of the dc bus capacitor energy and, consequently, voltage regulation. The proposed control algorithm does not use a commutation algorithm when the operating mode changes with the load power variation and, thus, avoids chattering effects. Using the flatness based control method, the fuel cell dynamic and its delivered power is perfectly controlled, and the fuel cell can operate in a safe condition. In the hybrid system, the supercapacitor functions during transient energy delivery or during energy recovery situations. To validate the proposed method, the control algorithms are executed in dSPACE hardware, while analogical current loops regulators are employed in the experimental environment. The experimental results prove the validity of the proposed approach.     

Hybrid control approach for PV/FC fed voltage source converter tied to grid

A hybrid and adaptive control approach for solar photovoltaic system and fuel cell fed voltage source converter (VSC) is presented in this work. Further maximum power from solar photovoltaic array is extracted by using incremental conductance (INC) based maximum power point tracking approach. This hybrid approach combines I cos ? technique and gradient descent back propagation learning (GDBP) neural network (NN) to extract fundamental components from load current for efficient harmonics compensation and provides power quality improvement and support the three-phase AC grid by supplying power to the grid and as well as connected loads. The proposed system includes photovoltaic (PV) array, a voltage source converter (VSC), ripple filter and combination of linear and non-linear loads. The proposed control approach provides a fast response during dynamic conditions as well. Results of the proposed control technique also compared with the other available control techniques for its superiority analysis. The developed control technique is demonstrated by using MATLAB/SIMULINK platform.     

A coupled power-voltage equilibrium strategy based on droop control for fuel cell/battery/supercapacitor hybrid tramway

In order to improve the robustness of the energy management system (EMS) and avoid the influence of demand power on the design of EMS, a coupled power-voltage equilibrium strategy based on droop control (CPVE-DC) is proposed in this paper. Making use of the principal that the DC bus can directly reflect the changes of load power, the proposed strategy couples DC bus voltage with output powers through droop control to achieve self-equilibrium. The proposed EMS is applied into a hybrid tramway model configured with multiple proton exchange membrane fuel cell (PEMFC) systems, batteries and super capacitors (SCs). FC systems and SC systems are responsible for satisfying most of the demand power, therefore the CPVE-DC strategy generates FCs and SCs reference power through power-voltage droop control on the primary control. Then batteries supplement the rest part of load power and generate DC bus voltage reference value of the next sampling time. With the gambling between output power and DC bus voltage, the hybrid system achieves self-equilibrium and steps into steady operation by selecting appropriate droop coefficients. Then the secondary control of the proposed strategy allocates power between every single unit. In addition, a penalty coefficient is introduced to balance SOC of SCs. The proposed strategy is tested under a real drive cycle LF-LRV on RT-LAB platform. The results demonstrate that the proposed strategy can achieve self-equilibrium and is effective to allocate demand power among these power sources,achieve active control for the range of DC bus voltage and SOC consensus of SCs as well. In addition, some faults are simulated to verify the robustness of the proposed strategy and it turns out that the CPVE-DC strategy possesses higher robustness. Finally, the CPVE-DC strategy is compared with equivalent consumption minimization strategy (ECMS) and the results shows that the proposed strategy is able to get higher average efficiency and lower equivalent fuel consumption.     

Model-based fault detection of hybrid fuel cell and photovoltaic direct current power sources

Hybrid DC power sources which consist of fuel cells, photovoltaic and lithium-ion batteries provide clean, high efficiency power supply. This hybrid DC power sources can be used in many applications. In this work, a model-based fault detection methodology for this hybrid DC power sources is presented. Firstly, the dynamic models of fuel cells, photovoltaic and lithium-ion batteries are built. The state space model of hybrid DC power sources is obtained by linearizing these dynamic models in operation points. Based on this state space model the fault detection methodology is proposed. Simulation results show that model-based fault detection methodology can find the fault on line, improve the generation time and avoid permanent damage to the equipment.     

Estimation of the state-of-charge of gel lead-acid batteries and application to the control of a stand-alone wind-solar test-bed with hydrogen support

In hybrid renewable energy systems, batteries act as a DC bus to provide constant voltage and to smooth out commutations between the generating devices. These batteries are usually of a lead-acid type and operate under harsh variable conditions due to fluctuations of both solar radiation and wind speed. Precise knowledge of the state-of-charge of the batteries, and hence of their available energy, play a key role in effecting efficient control and energy management of the installation. The present study had a twofold aim. One objective was to adjust and validate a method based on coulomb counting to estimate the state-of-charge (SOC) of a gelled lead-acid battery which is the DC bus of a hybrid wind-solar system with hydrogen storage. Other works evaluate SOC models based on several parameters, however, the present proposal based on experimental measurements involves only a few parameters. The second objective was to modify the installation's control algorithm to use the battery's calculated SOC as control parameter instead of its voltage. The results of a test-bed system, showing how the system evolved under real operating conditions, constitute a proof-of-concept of the validity of the method.     

Energy management of fuel cell/solar cell/supercapacitor hybrid power source

This study presents an original control algorithm for a hybrid energy system with a renewable energy source, namely, a polymer electrolyte membrane fuel cell (PEMFC) and a photovoltaic (PV) array. A single storage device, i.e., a supercapacitor (ultracapacitor) module, is in the proposed structure. The main weak point of fuel cells (FCs) is slow dynamics because the power slope is limited to prevent fuel starvation problems, improve performance and increase lifetime. The very fast power response and high specific power of a supercapacitor complements the slower power output of the main source to produce the compatibility and performance characteristics needed in a load. The energy in the system is balanced by d.c.-bus energy regulation (or indirect voltage regulation). A supercapacitor module functions by supplying energy to regulate the d.c.-bus energy. The fuel cell, as a slow dynamic source in this system, supplies energy to the supercapacitor module in order to keep it charged. The photovoltaic array assists the fuel cell during daytime. To verify the proposed principle, a hardware system is realized with analog circuits for the fuel cell, solar cell and supercapacitor current control loops, and with numerical calculation (dSPACE) for the energy control loops. Experimental results with small-scale devices, namely, a PEMFC (1200 W, 46 A) manufactured by the Ballard Power System Company, a photovoltaic array (800 W, 31 A) manufactured by the Ekarat Solar Company and a supercapacitor module (100 F, 32 V) manufactured by the Maxwell Technologies Company, illustrate the excellent energy-management scheme during load cycles.     

Fuel cell/battery passive hybrid power source for electric powertrains

The concept of passive hybrid, i.e. the direct electrical coupling between a fuel cell system and a battery without using a power converter, is presented as a feasible solution for powertrain applications. As there are no DC/DC converters, the passive hybrid is a cheap and simple solution and the power losses in the electronic hardware are eliminated. In such a powertrain topology where the two devices always have the same voltage, the active power sharing between the two energy sources can not be done in the conventional way. As an alternative, control of the fuel cell power by adjusting its operating pressure is elaborated. Only pure H₂/O₂ fuel cell systems are considered in this approach. Simulation and hardware in the loop (HIL) results for the powertrain show that this hybrid power source is able to satisfy the power demand of an electric vehicle while sustaining the battery state of charge.     

Energy management of fuel cell/battery/supercapacitor hybrid power source for vehicle applications

This paper proposes a perfect energy source supplied by a polymer electrolyte membrane fuel cell (PEMFC) as a main power source and storage devices: battery and supercapacitor, for modern distributed generation system, particularly for future fuel cell vehicle applications. The energy in hybrid system is balanced by the dc bus voltage regulation. A supercapacitor module, as a high dynamic and high power density device, functions for supplying energy to regulate a dc bus voltage. A battery module, as a high energy density device, operates for supplying energy to a supercapacitor bank to keep it charged. A FC, as a slowest dynamic source in this system, functions to supply energy to a battery bank in order to keep it charged. Therefore, there are three voltage control loops: dc bus voltage regulated by a supercapacitor bank, supercapacitor voltage regulated by a battery bank, and battery voltage regulated by a FC. To authenticate the proposed control algorithm, a hardware system in our laboratory is realized by analog circuits and numerical calculation by dSPACE. Experimental results with small-scale devices (a PEMFC: 500-W, 50-A; a battery bank: 68-Ah, 24-V; and a supercapacitor bank: 292-F, 30-V, 500-A) corroborate the excellent control principle during motor drive cycle.     

Power management of PV/battery hybrid power source via passivity-based control

In this paper, the power electronic interface between a DC hybrid power source with a photovoltaic main source and a Li-ion battery storage as the secondary power source is modelled based on the Euler–Lagrange framework. Subsequently, passivity-based controllers are synthesised using the energy shaping and damping injection techniques. Local asymptotic stability is ensured as well. In addition, the power management system is designed to manage power flow between components.Evaluation of the proposed system and simulation of the hybrid system are accomplished using MATLAB/Simulink. The results show that the outputs of the hybrid system have good tracking response, low overshoot, short settling time and zero steady-state error. Afterwards, linear PI controllers are provided to compare the results with those of passivity-based controller responses. This comparison demonstrates the robustness of the proposed controllers for reference DC voltage and load resistance changes.     

Control Algorithm of Fuel Cell and Batteries for Distributed Generation System

This paper intends to propose a novel control algorithm for utilizing a polymer electrolyte membrane fuel cell (PEMFC) as a main power source and batteries as a complementary source, for hybrid power sources for distributed generation system, particularly for future electric vehicle applications. The control, which takes into account the slow dynamics of a fuel cell (FC) in order to avoid fuel (hydrogen and air) starvation problems, is obviously simpler than state machines used for hybrid source control. The control strategy lies in using an FC for supplying energy to battery and load at the dc bus. The structure is an FC current, battery current, and battery state-of-charge (SOC) cascade control. To validate the proposed principle, a hardware system is realized by analogical circuits for the FC current loop and numerical calculation (dSPACE) for the battery current and SOC loops. Experimental results with small-scale devices (a 500 W PEM FC and 33 Ah, 48 V lead-acid battery bank) illustrate the excellent control scheme during motor drive cycles.     

Modeling,control and simulation of a photovoltaic /hydrogen/ supercapacitor hybrid power generation system for grid-connected applications

Hybrid renewable energy systems (HRES) should be designed appropriately with an adequate combination of different renewable sources and various energy storage methods to overcome the problem of intermittency of renewable energy resources. Focusing on the inevitable impact on the grid caused by strong randomicity and apparent intermittency of photovoltaic (PV) generation system, modeling and control strategy of pure green and grid-friendly hybrid power generation system based on hydrogen energy storage and supercapacitor (SC) is proposed in this paper. Aiming at smoothing grid-connected power fluctuations of PV and meeting load demand, the alkaline electrolyzer (AE) and proton exchange membrane fuel cell (PEMFC) and SC are connected to DC bus of photovoltaic grid-connected generation system. Through coordinated control and power management of PV, AE, PEMFC and SC, hybrid power generation system friendliness and active grid-connection are realized. The validity and correctness of modeling and control strategies referred in this paper are verified through simulation results based on PSCAD/EMTDC software platform.     

Energy management of fuel cell/battery/ultracapacitor in electrical hybrid vehicle

This paper describes an energy management algorithm for an electrical hybrid vehicle. The proposed hybrid vehicle presents a fuel cell as the main energy source and the storage system, composed of a battery and a supercapacitor as the secondary energy source. The main source must produce the necessary energy to the electrical vehicle. The secondary energy source produces the lacking power in acceleration and absorbs excess power in braking operation. The addition of a supercapacitor and battery in fuel cell-based vehicles has a great potential because it allows a significant reduction of the hydrogen consumption and an improvement of the vehicle efficiency. Other the energy sources, the electrical vehicle composed of a traction motor drive, Inverter and power conditioning. The last is composed of three DC/DC converters: the first converter interfaces the fuel cell and the DC link. For the second and the third converter, two buck boost are used in order to interface respectively the ultracapacitor and the battery with the DC link. The energy management algorithm determines the currents of the converters in order to regulate accurately the power provided from the three electrical sources. This algorithm is simulated with MATLAB_Simulink and implemented experimentally with a real-time system controller based on dSPACE. In this paper, the proposed algorithm is evaluated for the New European Driving Cycle (NEDC). The experimental results validate the effectiveness of the proposed energy management algorithm.     

Technico-economic analysis of off grid solar PV/Fuel cell energy system for residential community in desert region

A technico-economic analysis based on integrated modeling, simulation, and optimization approach is used in this study to design an off grid hybrid solar PV/Fuel Cell power system. The main objective is to optimize the design and develop dispatch control strategies of the standalone hybrid renewable power system to meet the desired electric load of a residential community located in a desert region. The effects of temperature and dust accumulation on the solar PV panels on the design and performance of the hybrid power system in a desert region is investigated. The goal of the proposed off-grid hybrid renewable energy system is to increase the penetration of renewable energy in the energy mix, reduce the greenhouse gas emissions from fossil fuel combustion, and lower the cost of energy from the power systems. Simulation, modeling, optimization and dispatch control strategies were used in this study to determine the performance and the cost of the proposed hybrid renewable power system. The simulation results show that the distributed power generation using solar PV and Fuel Cell energy systems integrated with an electrolyzer for hydrogen production and using cycle charging dispatch control strategy (the fuel cell will operate to meet the AC primary load and the surplus of electrical power is used to run the electrolyzer) offers the best performance. The hybrid power system was designed to meet the energy demand of 4500 kWh/day of the residential community (150 houses). The total power production from the distributed hybrid energy system was 52% from the solar PV, and 48% from the fuel cell. From the total electricity generated from the photovoltaic hydrogen fuel cell hybrid system, 80.70% is used to meet all the AC load of the residential community with negligible unmet AC primary load (0.08%), 14.08% is the input DC power for the electrolyzer for hydrogen production, 3.30% are the losses in the DC/AC inverter, and 1.84% is the excess power (dumped energy). The proposed off-grid hybrid renewable power system has 40.2% renewable fraction, is economically viable with a levelized cost of energy of 145 $/MWh and is environmentally friendly (zero carbon dioxide emissions during the electricity generation from the solar PV and Fuel Cell hybrid power system).     

Lead-acid battery use in the development of renewable energy systems in China

Policies and laws encouraging the development of renewable energy systems in China have led to rapid progress in the past 2 years, particularly in the solar cell (photovoltaic) industry. The development of the photovoltaic (PV) and wind power markets in China is outlined in this paper, with emphasis on the utilization of lead-acid batteries. The storage battery is a key component of PV/wind power systems, yet many deficiencies remain to be resolved. Some experimental results are presented, along with examples of potential applications of valve regulated lead-acid (VRLA) batteries, both the absorbed glass mat (AGM) and gelled types.     

Adaptive fuzzy control with an optimization by using genetic algorithms for grid connected a hybrid photovoltaic–hydrogen generation system

The integration of significant amounts of renewable-storage hybrid power generation systems to the electric grid poses a unique set of challenges to utilities and system operators. This article deals with the designing methodology of an intelligent control based grid-connected a hybrid system composed of renewable energy source (RES) and storage system (SS). RES is a photovoltaic (PV) source and SS is a process of hydrogen transformation system (H₂TS) which composed of alkaline water electrolysis (AWE) for decomposition water by using the PV power, a tank used for gas storage and a proton exchange membrane (PEM) fuel cell (FC) to transform the H₂ to the electrical energy. The interconnection of the grid with the power generation system (PGS) is ensured through using a DC/AC hysteresis converter and it can synchronize current with the grid voltage among an independent control of active (P) and reactive (Q) power through a possibility of the Q compensation. In the proposed system, three algorithms are applied; two used inside generation and the third is used inside the grid. Perturb and observe (P&O) maximum power point tracking (MPPT) control algorithm always finds optimal power in the PV generator. A simple cascade controls loop of DC-DC boost converter and operate the FC generator to ensure maximum power and to regulate the DC Bus voltage. In addition, adaptive fuzzy logic control (FLC) unit is developed to control the DC/AC inverter, with adopting an off-line optimization based on genetic algorithms (GAs) applauded for tune different issues as scaling factors of the FLC and PIDs gains of the PV and the H₂TS control loops. Simulated results prove a big success of the proposed controls of the grid connected the hybrid PV-H₂TS with good performance.     

An actively controlled fuel cell/battery hybrid to meet pulsed power demands

This paper presents the experimental results of an actively controlled fuel cell/battery hybrid power source topology that can be widely used in many applications, such as portable electronic devices, communication equipment, spacecraft power systems, and electric vehicles, in which the power demand is impulsive rather than constant. A step-down DC/DC power converter is incorporated to actively control the power flow between the fuel cell and the battery to achieve both high power and high energy densities. The results show that the hybrid power source can achieve much greater specific power and power density than the fuel cell alone. This paper first demonstrates that an actively controlled hybrid with a 35 W hydrogen-fueled polymer electrolyte membrane fuel cell and a lithium-ion battery pack of six cells yielded a peak power of 100 W, about three times as high as the fuel cell alone can supply, while causing a very limited (10%) weight increase to the whole system. After that, another hybrid source using a different battery array (eight cells) was investigated to further validate the control strategy and to show the flexibility and generality of the hybrid source design. The experimental data show that the hybrid source using an eight-cell battery supplied a peak power of 135 W, about four times that of the fuel cell alone. Finally, three power sources including the fuel cell alone and the two hybrids studied were compared in terms of specific power, power density, volume, weight, etc. The design presented here can be scaled to larger or smaller power capacities for a variety of applications.     

Fuzzy neural control of a hybrid fuel cell/battery distributed power generation system

An innovative control strategy is proposed of hybrid distributed generation (HDG) systems, including solid oxide fuel cell (SOFC) as the main energy source and battery energy storage as the auxiliary power source. The overall configuration of the HDG system is given, and dynamic models for the SOFC power plant, battery bank and its power electronic interfacing are briefly described, and controller design methodologies for the power conditioning units and fuel cell to control the power flow from the hybrid power plant to the utility grid are presented. To distribute the power between power sources, the fuzzy switching controller has been developed. Then, a Lyapunov based-neuro fuzzy algorithm is presented for designing the controllers of fuel cell power plant, DC/DC and DC/AC converters; to regulate the input fuel flow and meet a desirable output power demand. Simulation results are given to show the overall system performance including load-following and power management of the system.     

Vehicle hybridization with fuel cell,supercapacitors and batteries by sliding mode control

This paper treats the design and control of two hybrid source using supercapacitors, fuel cell, with and without batteries on the DC link. A fuel cell, as a slowest dynamic source in these systems (because of its auxiliaries) acts to supply the permanent energy. The supercapacitors, as a high dynamic and high power density device, compensate the intrinsic limitations in embedded sources and shave transient power peaks. The batteries module, as a high energy density device, operates for supplying energy if limitations of the power and energy sources occur. The load is a single phase DC machine connected directly in the DC bus. Our interest is focused on the comparison of the two structures and on the principles of control of this two hybrid power sources. Some results are presented and discussed.     

Development of hybrid photovoltaic-fuel cell system for stand-alone application

In this paper we present firstly the different hybrid systems with fuel cell. Then, the study is given with a hybrid fuel cell–photovoltaic generator. The role of this system is the production of electricity without interruption in remote areas. It consists generally of a photovoltaic generator (PV), an alkaline water electrolyzer, a storage gas tank, a proton exchange membrane fuel cell (PEMFC), and power conditioning units (PCU) to manage the system operation of the hybrid system. Different topologies are competing for an optimal design of the hybrid photovoltaic–electrolyzer–fuel cell system. The studied system is proposed. PV subsystem work as a primary source, converting solar irradiation into electricity that is given to a DC bus. The second working subsystem is the electrolyzer which produces hydrogen and oxygen from water as a result of an electrochemical process. When there is an excess of solar generation available, the electrolyzer is turned on to begin producing hydrogen which is sent to a storage tank. The produced hydrogen is used by the third working subsystem (the fuel cell stack) which produces electrical energy to supply the DC bus. The modelisation of the global system is given and the obtained results are presented and discussed.     

Design and experimental tests of control strategies for active hybrid fuel cell/battery power sources

Twenty-first century handheld electronic devices and new generations of electric vehicles or electric airplanes have fueled a need for new high-energy, high-power, small-volume, and lightweight power sources. Current battery technology by itself is insufficient to provide the mandatory long-term power these systems require. Fuel cells are also unable to provide the essentially high peak power demanded by these systems. Hybrid systems composed of fuel cells and secondary batteries could combine the high power density of clean fuel cells and the high energy density of convenient batteries. This paper presents an experimental study on control strategies for active power sharing in such a hybrid fuel cell/battery power source. These control strategies limited the fuel cell current to safe values while also regulating the charging current or voltage of the battery. The several tested control strategies were implemented in MATLAB/Simulink and then tested under the pulsed-current load condition through experiments. Experimental tests were conducted with three control objectives: maximum fuel cell power, maximum fuel cell efficiency, and adaptive.