Available online at www.sciencedirect.com ScienceDirect Procedia Engineering 170 (2017 ) 488 495 Engineering Physics International Conference, EPIC 2016 A Study on Integration of 1kW PEM Fuel Cell into a Smart Microgrid System with Programmable Scenario Muhamad Maulanal Haq 1, Irsyad Nashirul Haq 2, Edi Leksono 3, Nugraha Tapran 4,* 1234 Engineering Physics, Faculty of Industrial Technology, Institute Technology Bandung Jalan Ganesha 10, Bandung 40132, Indonesia Abstract Hybrid Renewable Energy System (SHET) is a smart microgrid system that has been implemented in Energy Management Laboratory ITB. The SHET consists of photovoltaic power plant, national electricity grid, battery based energy storage system and hybrid energy controller system. This SHET is operated to supply electricity to the laboratory. In this paper, 1 KW Proton Exchange Membrane Fuel Cell (PEMFC) integrated to the microgrid system is investigated. The PEMFC fuel cell is connected to the SHET through DC coupling method as one input for the hybrid energy controller. To optimize the energy conversion of the PEMFC and also to stabilize the input voltage to the hybrid energy controller, Maximum Power Point Tracker (MPPT) is used. This MPPT also functions as DC-DC converter. In this microgrid system where the PEMFC is also incorporated, the PEMFC will only supply its generated electricity whenever the system is in island mode with additional configured specific conditions such as battery s State of Charge (SoC) is lower than 40% or electricity load of the microgrid system is more than 0.72kW. The result of study showed that the PEMFC only generated 120-160W from its potential maximum power of 1kW. This happened because the battery voltage closes to the PEMFC Open Circuit Voltage (OCV) so the MPPT cannot operate the PEMFC to its Maximum Power Point. The low electrical power is supplied to system makes the battery still on discharge when the electricity load is in high level. This means, the PEMFC and battery work simultaneously at the same time. From this research, it has been found out that other solutions may be implement to maximize the generated power from the PEMFC 2017 The Authors. Published by Elsevier Ltd. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/). 2016 The Authors. Published Elsevier Ltd. Peer-review under responsibility of the organizing committee of the Engineering Physics International Conference 2016 Keywords: SHET, PEM fuel cell, island mode, MPPT, smart microgrid, SoC 1. Introduction Energy is everywhere [1], almost everything that has built in this world used energy. Houses, industrial, even people need energy, especially electricity. With high growth of technology happened, need of electricity will follow. The problem is most of Indonesia s energy resources are nonrenewable like oil and coal. Nowadays renewable energy become choice to replace nonrenewable resource to reduce pollution that made, carbon dioxide. In Indonesia, the use of new and renewable energy (EBT) ruled by Perpres (President Regulation) 5/2006 with vision that Indonesia will be using 17% EBT from total electricity production in 2025 [2]. Not only in Indonesia, many countries all over the world try to use green energy as much as they can to replace dependence of nonrenewable energy such as coal and gas. For this purpose smart microgrid have been used for integrating the existing electricity from grid with some renewable sources. Smart Grid is a system that allows communication between consumer and electric power companies [3], so smart microgrid is the small version of smartgrid. Another definition is distribution grid which can monitor electricity and every important event that disturb the system. In ITB (Management Energy Laboratory) we already used smart microgrid called SHET (Sistem Hibrida Energi Terbarukan) with grid, 48V VRLA battery and photovoltaic 1kWp connected to load that can handle power up to 5kW. For expansion need, fuel cell PEMFC 1kW planned to attach in existing system. Fuel cell is chosen because it s one of renewable resources that has no pollutant product in it [4]. So when the smart microgrid run with many renewable resources, the * Corresponding author. Tel.: +62-85640361050 E-mail address:dana.haq@gmail.com 1877-7058 2017 The Authors. Published by Elsevier Ltd. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/). Peer-review under responsibility of the organizing committee of the Engineering Physics International Conference 2016 doi:10.1016/j.proeng.2017.03.078
Muhamad Maulanal Haq et al. / Procedia Engineering 170 ( 2017 ) 488 495 489 load will need less electricity from grid which is produced by non-renewable plants and will be using more renewable s energy to fulfill demand. This paper explains the design of integration method between fuel cell and microgrid. We managed all of renewable sources to create the rules of what the first one will supply power. 2. Devices Hybrid Renewable Energy System (SHET) consist of 1kWp photovoltaic (PV) that supply power directly to load through an inverter and connected to Hybrid Energy Controller (HEC). HEC is device that manage all energy productions and storage in SHET including monitoring system. A national distribution grid (PLN) connected to SHET and supply more power to fulfill demand when PV and battery were not enough. Battery that used as storage device is VRLA with 48 Volt nominal voltage connected to HEC. Battery will be used when load excess PV production or when SHET in island mode that disconnect from grid. 3. Methods 3.1. System and Topology Design The installed SHET has included Hybrid Energy Controller (HEC) that control its power management depend on how much power produced and power demand in load. HEC has 3 connection lines which are AC1, AC2 and DC. AC1 connected to load and renewable sources that has AC Coupled, AC 2 connected to distribution grid or generator, and DC connected to batteries or renewables that has DC coupled. Fig. 1 Topology Design Fuel Cell integration designed to connect at DC port together with 48V VRLA battery. The open circuit voltage of fuel cell is 59V and the battery is 48. The design used MPPT (Maximum Power Point Tracker) battery charge controller to manage the power supply from fuel cell to DC port, and MPPT will maximize power produced from fuel cell and prevent over chargingdischarging on battery [5]. Fig. 1 shows the line fuel cell and MPPT are between battery and HEC, its DC coupling integration to connect fuel cell in the system. 3.2. Operation Management Design HEC is device that manage produced power and power consume in system with priority rules. This priority defined which source will use to fit demand. Rules defined by time, State of Charge (SoC) battery and load. Old system has been started with solar cell was the first priority, then battery used as second priority to help supply when its SoC and load are in good area. If battery s SoC out of defined area or load excess limit then grid used as third priority to help supply and charge battery. Fuel cell designed to be a backup source when grid is down, then replacing grid in the third priority. That condition make system move to Island Mode, meant the smart microgrid off from distribution grid and running by its own produced and backup energies. Fuel cell will begin to start operating when the conditions are met. This condition defined in HEC with some parameters. These parameters are SoC and power that showed in Table 1 and Table 2. Fuel cell will need to start if SoC below 40% or load power above 0.72kW, and need to shut down when SoC back to 80% or load down to below 0.48kW. Based on these parameters HEC will send signal on/off through relay, so when the signal ON then fuel cell will begin to start and when its off then fuel cell shutting down.
490 Muhamad Maulanal Haq et al. / Procedia Engineering 170 ( 2017 ) 488 495 Table 1 SoC Parameters Table 2 Load Power Parameters 3.3. Fuel Cell Integration and Manual Operation Integration of fuel cell into exist system using automatic startup generator (AutoGn) that built inside HEC. This AutoGn worked with parameters that have described before and will send a signal to relay when conditions are meet. This signal called GnReq and connected to LED which used as indicator. When LED ON means that system need fuel cell to produce power, vice versa. User will be warned by this indicator and must manually start fuel cell. Fuel cell PEMFC 1kW that used in this research already have instrumentation system to manage its operations, including PLC and microcontroller. PLC manage sequence to define start up and shut down procedure, microcontroller to control fan that supply oxygen. In this fuel cell integration, the startup procedure begin after LED indicator ON. 4. Results and Discussion 4.1. Fuel Cell Performance The experiments tried to find V-I curve of fuel cell that used in this research. This experiments used fuel cell to charge the batteries in different voltage with MPPT and the result is shown by Error! Reference source not found. Open circuit voltage of fuel cell is 59V and the voltage turn down when more current applied. The max output power happened when charging 24V battery is around 500W, but less than 200W when charging 48V battery. This is because MPPT operating fuel cell above battery voltage, so the higher voltage applied the lower current and power produced. Fig. 2 V-I Curve
Muhamad Maulanal Haq et al. / Procedia Engineering 170 ( 2017 ) 488 495 491 Fig. 3 P-I Curve Fig. 4 Voltage at DC Hub In showed battery/mppt output and fuel cell voltage when current was flowing to DC hub. Operation started at battery s voltage 47V. The difference between fuel cell and battery voltage is around 3V, this caused by MPPT s capability to track fuel cell s MPP. Higher battery voltage makes fuel cell work at above it so the voltage closer to OCV and depend on I-V curve the power generated fall off. 4.2. DC Coupling In this experiment used 3 initial conditions of battery before fuel cell supplying power to DC hub including 47V, 48V and 49V while the load applied around 10A. The result showed in that battery voltage falling down when fuel cell have been started. MPPT output steady around 2-3 ampere and battery output current add some current to fulfill current demand. Because battery still discharging and MPPT output didn t fulfill the demand of HEC, SoC battery will down to the limit of allowable SoC and can shut down the system. Fig. 5 Battery Fluctuation
492 Muhamad Maulanal Haq et al. / Procedia Engineering 170 ( 2017 ) 488 495 Fig. 6 Current Comparison at Fluctuating Load Fig. 7 Fuel Cell Production Another experiment with applied fluctuating load showed in Fig. 6, MPPT distribute the current in steady value at 2.7-3 ampere. Battery output become a backup source when demand (INV(IN)) from HEC exceed produced power from fuel cell so current out from battery have a similar fluctuation as load current. Fuel cell voltage depend on how MPPT track it, and MPPT voltage depend on battery voltage. When more current discharged from battery, this made battery voltage drop and then MPPT voltage drop too. In this case we found out that fuel cell will produce more power when the voltage battery drop happened, but not significant. Fuel cell production and MPPT conditions can be found out from Fig. 7. With fluctuating significant load and the maximum is 1.3kW made battery/mppt voltage drop. The fuel cell voltage following it with higher voltage that looked unsteady because the operation method of MPPT. Lower voltage of fuel cell cause more current and power generated, but because value of voltage drop not much so the risen current. When fuel cell start producing, it becomes the second priority and battery third. In the DC hub more current discharged when load rising and fuel cell can t generate maximum power because its voltage operation cause by MPPT. MPPT was operating depend on battery voltage, and its voltage near to fuel cell OCV far from MPP. 4.3. MPPT Performance In this research MPPT used for DC-DC converter to manage voltage operation between fuel cell and battery. The MPPT algorithm of this device used to maximizing power generated. From experiments that have done MPPT cannot positioning fuel cell to its MPPT, because battery have 48V nominal voltage and this closer to OCV not the Vmpp. When MPPT try tracking close to MPP, the voltage cannot lower than battery voltage, and always around 3 volts above its value. So the MPPT that used is buck converter which can only step down the voltage input (fuel cell). Depend on P-I curve, higher voltage operation result less power generated from fuel cell. Another MPPT performance analysis is from its efficiency. The experiments have done with three different battery voltage conditions, BatVtg 47V 48V and 49V. MPPT efficiency calculate from power input and output through MPPT when supplying power to DC hub. The result given almost similar but have small gap. Fig. 8, Fig. 9 and Fig. 10 showed three different graphs that looked fluctuating at 93-96%. The calculation in Table 3 with mean and standard deviation conclude that lower battery voltage
Muhamad Maulanal Haq et al. / Procedia Engineering 170 ( 2017 ) 488 495 493 gave higher efficiency with small SD. Higher efficiency not because the voltage operation but how much power converted, we know from previous experiments. Fig. 8 Efficiency at BatVtg 47V Fig. 9 Efficiency at BatVtg 48V Fig. 10 Efficiency at BatVtg 49V Table 3 Mean of Efficiency Experiment Mean SD BatVtg 47V 95.12 % 0.62 % BatVtg 48V 94.68 % 0.57 % BatVtg 49V 94.64 % 0.55 % 4.4. Operation Management Overload power and critical SoC applied to knew how new system response. In overload experiment, the load rising from below load limit around 0.5kW then to 1.2kW. GenReq signal change value in 205 seconds after load pass the limit, that response showed by Fig. 11. Manual start up need 50 seconds until fuel cell producing power and supply it to DC hub through MPPT. Fig. 12 shows MPPT respond when load triggered GenReq. When battery discharging with more current, the voltage falling from its current state so we can track down when higher current happened. In this experiment found GenReq behavior that it triggered to
494 Muhamad Maulanal Haq et al. / Procedia Engineering 170 ( 2017 ) 488 495 change value not in the same time when conditions out of its safe area. This response need 10-40 seconds until GenReq give request. Fig. 11 GenReq Respons Fig. 12 MPPT Respons Fig. 13 GenReq Respon depend SoC
Muhamad Maulanal Haq et al. / Procedia Engineering 170 ( 2017 ) 488 495 495 Fig. 14 DC Hub Respons depend SoC Fig. 13 and Fig. 14 shows response from SoC limit experiments. When SoC of battery start falling below 40% which is the limit, GenReq appeared in 1 second after SoC reach 40%. Manual operation start and after 25 seconds fuel cell producing power then 15 seconds later MPPT supplying. In this experiment output of MPPT only gave 2-3 ampere while fuel cell can only producing power around 150W. That made battery discharging because demand was more than MPPT s supply and then SoC keep falling. In this case GenReq still ON because its limit to change value is 80%. 4.5. Design Improvement Analysis The integration design that has implemented still have many problems especially with the maximum power of fuel cell that can be generated. It because MPP voltage of fuel cell lower than battery voltage, and MPPT cannot operate fuel cell under battery voltage. So there are many optional solution or design that can be implemented on smart microgrid, 1. Use fuel cell with higher OCV 2. AC Coupling design that use AC converter 5. Conclusion 1. The design have implemented on SHET through DC coupling with MPPT as its converter. The given result is fuel cell can only generate 120-160W power to system. 2. Management operation have made by using AC Generator Start Up function to call fuel cell with SoC and Load parameter. Call function through relay that connected to LED for indicator. SoC limit is 40% and load power limit is 0.72kW. 3. From analysis we found out that system with 48V battery and fuel cell with 59V OCV made MPPT cannot operate fuel cell to its MPP (1kW) then only generated 120-160W. DC Coupling method made fuel cell became stable energy source that supply power according battery voltage conditions. Acknowledgments This work is full supported by Management Energy Laboratory, Engineering Physics, Industry Technology Faculty, Institute Technology Bandung, Indonesia. References [1] Why is energy important? Sciencelearn Hub. [Online]. Available on: http://sciencelearn.org.nz/contexts/future-fuels/sci-media/video/why-is-energyimportant. [accessed: 29-Jul-2016]. [2] Blueprint Pengelolaan Energi Naional 2006-2025. ESDM, 2006. [3] G. S. Lamba, Smart Grid and its Develpment Prospects In the Asia-Pasific Region, CIS J., 2011. [4] M. W. Ellis, M. R. von Spakovsky, dan D. J. Nelson, Fuel cell systems: efficient, flexible energy conversion for the 21st century, Proc. IEEE, vol. 89, no. 12, hal. 1808 1818, Des 2001. [5] Z. Zhong, H. Huo, X. Zhu, G. Cao, dan Y. Ren, Adaptive maximum power point tracking control of fuel cell power plants, J. Power Sources, vol. 176, no. 1, page. 259 269, Jan 2008.