A Comparative Study of Energy Management Schemes for a Fuel Cell Hybrid Emergency Power System of More Electric Aircraft

ABSTRACT:

This paper presents a comparative analysis of different energy management schemes for a fuel cell based emergency power system of a more electric aircraft. The fuel cell hybrid system considered in this study consists of fuel cells, lithium-ion batteries and supercapacitors, along with associated DC/DC and DC/AC converters. The energy management schemes addressed are state-of-the-art, most commonly used energy management techniques in fuel cell vehicle applications and include: the state machine control strategy, the rule based fuzzy logic strategy, the classical PI control strategy, the frequency decoupling/fuzzy logic control strategy and the equivalent consumption minimization strategy (ECMS). The main criteria for performance comparison are the hydrogen consumption, the state of charges of the batteries/supercapacitors and the overall system efficiency. Moreover the stresses on each energy source, which impact their life cycle, are measured using a new approach based on the wavelet transform of their instantaneous power. A simulation model and an experimental test bench are developed to validate all analysis and performances.

KEYWORDS:

1.      Fuel cells

2.       Batteries

3.      Supercapacitors

4.      DC-DC converters

5.      Energy management

6.      Hybridization

7.      Optimization

SOFTWARE: MATLAB/SIMULINK

BLOCK DIAGRAM:

                              

Fig. 1. Overall system schematic

 EXPECTED SIMULATION RESULTS:

Fig. 2. Simulation and experimental results for all EMS schemes: (a) Simulation results. State machine control (b) Experimental results. State machine control (c) Simulation results. Rule based fuzzy logic (d) Experimental results. Rule based fuzzy logic (e) Simulation results. Classical PI control (f) Experimental results. Classical PI control (g) Simulation results. Frequency decoupling and fuzzy logic (h) Experimental results. Frequency decoupling and fuzzy logic (i) Simulation results. ECMS (j) Experimental results. ECMS

CONCLUSION:

 

This paper presented a performance comparison of different energy management schemes for a fuel cell hybrid emergency system of more electric aircraft. The hybrid system is modelled and validated with experiments. Five state-of-the art commonly used energy management schemes are studied through simulations and experimental tests on a 14 kW fuel cell hybrid system. The same initial condition is used for all the schemes and the experimental results are close to simulations. The criteria for performance comparison are the hydrogen consumption, the battery state of charge, the overall efficiency and the stress seen by each energy source. The latter is measured using a new approach based on wavelet transform. Compared to the other schemes, the state machine control scheme provided a slightly better efficiency (80.72%) and stresses on the battery and supercapacitor (_ of 21.91 and 34.7 respectively). The classical PI control scheme had the lowest fuel consumption (235 g of H2 consumed) and more use of the battery energy (SOC between 70 - 51 %). As expected, the lowest fuel cell stress (_ of 12.04) and lowest use of the battery energy (SOC between 70 - 59 %) was achieved with the frequency decoupling and fuzzy logic scheme, but at the expense of more fuel consumption (245 g of H2 consumed) and lower overall efficiency (79.32 %). The DC bus or supercapacitor voltage was maintained nearly constant (_ 270 V DC) for all the schemes. To conclude, the energy management system suitable for MEA should be a multi-scheme EMS such that each scheme is chosen based on a specific criterion to prioritize. As an example, depending on the operating life of each energy source, the energy management strategy can be chosen to either minimize the stress on the fuel cell system, the battery system or supercapacitor system, hence maximizing the life cycle of the hybrid power system. Also if the target is to reduce the fuel consumption, the strategy based on the classical PI or ECMS could be selected. An alternative is to design a multi-objective optimization EMS to optimize all the performance criteria, which is the next topic for further studies.

REFERENCES:

 

[1] P. Thounthong and S. Rael, ”The benefits of hybridization”. IEEE Ind. Electron. Mag., vol.3, no.3, pp.25-37, Sept. 2009.

[2] P. Thounthong, S. Rael and B. Davat, ”Control Strategy of Fuel Cell and Supercapacitors Association for a Distributed Generation System,” IEEE Trans. Ind. Electron., vol.54, no.6, pp.3225-3233, Dec. 2007.

[3] Z. Amjadi and S. Williamson, ”Power-Electronics-Based Solutions for Plug-in Hybrid Electric Vehicle Energy Storage and Management Systems,” IEEE Trans. Ind. Electron., vol.57, no.2, pp.608-616, Feb. 2010.

[4] G. Renouard-Vallet ,M. Saballus, G. Schmithals , J. Schirmer, J. Kallo and A. K. Friedrich, ”Improving the environmental impact of civil aircraft by fuel cell technology: concepts and technological progress,” Energy Environ. Sci., 2010,1458-1468.

[5] G. Renouard-Vallet ,M. Saballus, G. Schmithals , J. Schirmer, J. Kallo and A. K. Friedrich, ”Fuel Cells For Aircraft Applications,” ECS Trans., 2011, Volume 30, Issue 1, Pages 271-280.

Direct Torque Control of DFIG Driven by Wind Turbine System Connected to the Grid

ABSTRACT:

This paper described a Direct Torque Control (DTC) applied to a Doubly Fed Induction Generator (DFIG) driven by a Wind Turbine (WT) connected to the grid. This control strategy based on the regulation of the flux and the torque, the currents and voltages are used to estimate the torque and the flux and compare those magnitudes to the reference values, the obtained results will be converted to digital form by hysteresis comparators. The commutation table will use those values and the sector number to choose the voltage vector. The aim of this study is to treat three modes that can drive WT-DFIG system utilizing Maximum Power Point Tracking (MPPT) technique. Computer simulation has carried out under MATALB/Simulink environment and the obtained results demonstrate the effectiveness of the proposed control.

 KEYWORDS:

1.      Direct Torque Control

2.      Doubly Fed Induction Generator

3.      Wind Turbine

4.      Wind Energy

5.      Maximum Power Point Tracking

 SOFTWARE: MATLAB/SIMULINK

 BLOCK DIAGRAM:

Fig.1. DTC Control applied to DFIG connected to the grid.

EXPECTED SIMULATION RESULTS:

Fig.2. Wind speed.

Fig.3. Cp (λ) Characteristic.

Fig.4. Mechanical speed (generator speed).

Fig.5. Waveform of Slip.

Fig.6. Electromagnetic Torque.

Fig.7. Rotor and Reference flux.

Fig.8. The rotor flux.

Fig.9. Wave form of Rotor flux φ_rα and φ_rβ.

Fig.10. Rotor Current Ir(abc)

Fig.11. Rotor Reactive Power

Fig.12. Stator Current Is(abc)

Fig.13. Stator Power

 

Fig.14. Rotor Power

Fig.15. The FFT analysis of phase (a) stator current (Synchronous mode).

CONCLUSION:

A study of Direct Torque Control strategy applied to Doubly Fed Induction Generator used for Wind Turbine Conversation system has been presented in this paper. As known, the wind has a random movement imposing indiscriminate speed for the turbine, therefore driving DFIG in different modes (sub-synchronous, synchronous and super synchronous modes), those modes have been treated in this work. The obtained results show clearly satisfactory performances, they showed a good dynamic of the torque and the flux, low THD in synchronous mode and constant stator frequency, while keeping a better precision of control, as well as the efficiency of the control strategy leading to better performances.

REFERENCES:

 

[1] C. J. Nobles, E. F. Schisterman, Sandie Ha, Keewan Kim, and all, “Ambient air pollution and semen quality,” Environmental Research. 163, 2018, pp. 228-236.

[2] B. Sawetsakulanond, V. Kinnares, “Design, analysis, and construction of a small scale self-excited induction generator for wind energy application,” Energy Journal. 2010, pp. 4975–4985.

[3] A. Tapia, G. Tapia, J.X. Ostolaza, J.R. Saenz, “Modeling and control of a wind turbine driven doubly fed induction generator,” IEEE Trans. Energy Convers. 2003, pp. 194–204.

[4] “GWEC’s Global Wind Report - Annual Market Update,” the Global Wind Energy Council, 2017. Available: http://www.gwec.net.

[5] “Renewables 2017 global status report 2017,” Ren21, 2017.

DTC of DFIG included in a Wind Turbine Connected to the Grid

ABSTRACT:

This article presents a contribution of the application of direct torque control, for the control of the powers of a double power induction generator (DFIG), used in a constant speed wind energy conversion system. This type of control based on two hysteresis band controllers of torque and flux. The simulation results showed that it is possible to control the rotor powers with this method.

 KEYWORDS:

1.      DFIG

2.      DTC

3.      WIND TURBINE

4.      GRID

 SOFTWARE: MATLAB/SIMULINK

 BLOCK DIAGRAM:

Fig.1. Block diagram of DTC.

 EXPECTED SIMULATION RESULTS:

Fig.2. The rotor flux sector location.

Fig.3. evolution of rotor flux estimated components.

Fig.4. Waveform of the alpha/beta rotor flux (Wb).

Fig.5. The rotor flux  (Wb).

Fig.6. Waveform of the alpha/beta rotor currents

Fig.7. Waveform of the rotor currents and voltages.

CONCLUSION:

This paper presents the simulation of the direct torque control for a doubly fed induction generator connected to the grid. The results obtained confirm the theoretical studies of this commande, and show the effectiveness of the proposed control strategy.

REFERENCES:

[1] A. Kadri , H. Marzougui , K. Omrani , F. Bacha, “DTC of Doubly Fed Induction Generator for Wind Power System based on Rotor Flux Estimation,” International Confernece on Control Engineering Information Technology. Tunisia, vol. 34, pp. 33-38, December 2017.

[2] Y. Sahri, S.Tamalouzt, S. L. Belaid, “Direct Torque Control of DFIG Driven by Wind Turbine System Connected to the Grid,” International Conference on Wind Energy and Applications in Algeria. Algeria, pp. 88-93, November 2018.

[3] N. El Ouanjli1 , A. Derouich , A. El Ghzizal , M. Taoussi , Y. El Mourabit, “Direct torque control of doubly fed induction motor using three-level NPC inverter,” Protection and Control of Modern Power Systems 4. October 2019

[4] G.Naveen, P.K.S.Sarvesh, B.Rama Krishna, “DTC Control Strategy for Doubly Fed Induction Machine,” International Journal of Engineering and Advanced Technology. India, vol. 3, pp. 92-95, October 2013.

[5] A. Bakouri, H. Mahmoudi, A. Abbou, “Intelligent Control for Doubly Fed Induction Generator Connected to the Electrical Network,” International Journal of Power Electronics and Drive System. Indonesia, vol. 7, pp. 688-700, September 2016.

Seven-Level Packed U-Cell (PUC) Converter with Natural Balancing of Capacitor Voltages

 ABSTRACT:

A seven-level Packed U-Cell inverter is presented in this paper. The converter uses a single dc source and two floating capacitors, whose voltages are balanced in open loop, to produce multilevel output voltage. Peak magnitude of the output phase voltage is equal to the magnitude of dc source. Voltages across floating capacitors add intermediate voltage-levels by establishing an asymmetric ratio (with respect to the available dc voltage in the circuit). The average energy exchange (when the network is in steady state) of the capacitors with the rest of the inverter-circuit will be zero. This helps the capacitors to maintain desired voltages and thus create intermediate levels of steady dc voltages. Performance of the converter is validated in simulation by MATLAB/Simulink and testing of the converter is done for resistive as well as inductive loads. Experimental verification of the converter is carried out on a laboratory prototype and the obtained results match well with the simulation.

KEYWORDS:

1.      PUC converter

2.      Natural balancing

3.      Open-loop control

SOFTWARE: MATLAB/SIMULINK

CONCLUSION:

 

A seven-level Packed U-Cell converter is presented. The converter contains only one dc source and two floating capacitors. Voltages of floating capacitors along with the available dc voltage source establish a ratio of 3:2:1. Floating capacitors work by the principle of current-sec balance and therefore have natural balancing capability. Concept of natural balancing works regardless of the modulation index and load power factor. Time-domain expressions for the capacitor voltages are derived considering a specific switching operation of the converter. This helped in analytically validating the concept of natural balancing. Capacitor requirement in terms of kJ/MVA is discussed which forms an important aspect of the converter. Losses and efficiency of the converter are presented in comparison with few basic topologies including a standard two-level inverter. Performance of the inverter is validated through extensive simulations in MATLAB/Simulink. Experimental verification is done by developing a laboratory prototype to confirm the usefulness of the proposed concept.

REFERENCES:

[1] K. Boora and J. Kumar, “A Novel Cascaded Asymmetrical Multilevel Inverter With Reduced Number of Switches,” in IEEE Transactions on Industry Applications, vol. 55, no. 6, pp. 7389-7399, Nov.-Dec. 2019.

[2] C. W. Flairty, “A 50-kva adjustable-frequency 24-phase controlled rectifier inverter,” IRE Transactions on Industrial Electronics, vol. IE-9, no. 1, pp. 56–60, May 1962.

[3] K. K. Gupta, A. Ranjan, P. Bhatnagar, L. K. Sahu, and S. Jain, “Multilevel inverter topologies with reduced device count: A review,” IEEE Transactions on Power Electronics, vol. 31, no. 1, pp. 135–151, Jan 2016

[4] F. Sebaaly, H. Vahedi, H. Y. Kanaan and K. Al-Haddad, “Experimental Design of Fixed Switching Frequency Model Predictive Control for Sensorless Five-Level Packed U-Cell Inverter,” in IEEE Transactions on Industrial Electronics, vol. 66, no. 5, pp. 3427-3434, May 2019.

[5] A. Routray, R. Singh and R. Mahanty, “Harmonic Reduction in Hybrid Cascaded Multilevel Inverter Using Modified Grey Wolf Optimization,” in IEEE Transactions on Industry Applications.

Robust ANN-Based Control of Modified PUC-5 Inverter for Solar PV Applications

 ABSTRACT:

Conventional PI controllers are vulnerable to changes in parameters and are difficult to tune. In this work, an artificial neural network (ANN) based controller is developed for the robust operation of a single-phase modified packed U-cell five-level inverter (MPUC-5) for solar PV application under variable insolation conditions. An MPUC-5 is a converter with a main and an auxiliary dc link of equal magnitude; although five-level operation is also still feasible with different voltages also. The maximum power point (MPP) of a PV array changes with the variation in the solar insolation. This results in a variable voltage at the output of the boost converter while maintaining the load line at the MPP. Consequently, the fundamental value of the output of the MPUC-5 also tends to change. Thus, it is required to produce angles that commit to an ac output voltage with a constant fundamental value and constrained to a minimum total harmonic distortion along with a third-order harmonic mitigation as per the grid codes, irrespective of the change in the dc-link voltages. A genetic algorithm is employed for this purpose. A large dataset is prepared for two-angle and four-angle operation of MPUC-5 under various dc-link voltages and constraints with which an ANN-based controller is trained. A neural network with a hidden layer is trained with the back propagation technique; and once a correlation is developed, the network can be operated for a wide range of operating conditions. The robustness of the controller is verified through simulation in MATLAB/Simulink environment and validated by experimental emulation in an hardware in loop environment.

KEYWORDS:

1.      Artificial neural network (ANN)

2.      Genetic algorithm (GA)

3.      Modified packed U-cell (MPUC) Inverter

4.      multilevel inverter (MLI)

5.      selective harmonic elimination (SHE)

6.      total harmonic distortion (THD)

SOFTWARE: MATLAB/SIMULINK

CONCLUSION:

 In this work, a five-level modified PUC inverter with a dc link ratio of 1:1 is considered whose switching is controlled by an ANN-based controller. Furthermore, the controller is implemented in a solar PV system where it provides a robust performance by keeping the fundamental value of the voltage across the load constant despite a change in the voltages of the dc links of the converter. GA is employed to furnish the angles that provided such result under constraints of low values of the THD and mitigation of the low-order harmonics, especially the third-order harmonics. A total of 10 201 combinations of such angles were found for two-angle and four-angle operation of the converter separately and were graphically presented. An ANN controller which was based on MLP was then trained on these angles based on the back propagation technique. The robustness of the controller was then verified in Simulink with variations in dc-link voltages. Then, it was also verified for Solar PV application. The output of the converter was of constant fundamental with the THDs and third-order harmonics within the prescribed limits of IEEE. The real-time hardware emulation for the MPUC-5 with the ANN-based controller was successfully performed on Typhoon HIL-402.

 

REFERENCES:

[1] B. Wu and M. Narimani, “High-power converters and AC drives,” in High-Power Converters and AC Drives. Hoboken, NJ, USA:Wiley, 2017, pp. 119–140.

[2] A. Nabae, I. Takahashi, and H. Akagi, “A new neutral-point-clamped PWM inverter,” IEEE Trans. Ind. Appl., vol. IA- 17, no. 5, pp. 518–523, Sep. 1981. [Online]. Available: http://ieeexplore.ieee.org/xpls/abs_all. jsp?arnumber=645616

[3] T. Meynard and H. Foch, “Multi-level conversion: High voltage choppers and voltage-source inverters,” in Proc. Conf. Rec. 23rd Annu. Power Electronics Specialists, Toledo, Spain, 1992, pp. 397–403.

[4] F. Z. Peng, J.-S. Lai, J.W. McKeever, and J. VanCoevering, “A multilevel voltage-source inverter with separate DC sources for staticVar generation,” IEEE Trans. Ind. Appl., vol. 32, no. 5, pp. 1130–1138, Sep./Oct. 1996.

[5] J.-S. Lai and F. Z. Peng, “Multilevel converters—A new breedof power converters,” IEEE Trans. Ind. Appl., vol. 32, no. 3, pp. 2348–2356, May/Jun. 1996.

Modified Seven-Level Pack U-Cell Inverter for Photovoltaic Applications

 ABSTRACT:

This paper proposes a modified configuration of single-phase Pack U-Cell (PUC) multilevel inverter in which the output voltage has higher amplitude than the maximum DC link value used in the topology as a boost operation. The introduced inverter generates seven-level AC voltage at the output using two DC links and six semiconductor switches. Comparing to cascaded H-bridge and neutral point clamp multilevel inverters, the introduced multilevel inverter produces more voltage levels using less components. The proposed inverter is used in PV system where the green power comes from two separate PV panels connected to the DC links through DC-DC converters to draw the maximum power. Due to boost operation of this inverter, two different PV panels can combine and send their powers to the grid. Simulations and experimental tests are conducted to investigate the good dynamic performance of the inverter in grid-connected PV system.

KEYWORDS:

1.      PV Inverter

2.      Pack U-Cell

3.      Modified Pack U-Cell

4.      PUC5

5.      MPUC5

6.      Power Quality

7.      Renewable Energy Conversion

 SOFTWARE: MATLAB/SIMULINK

CONCLUSION:

  In this paper a modified multilevel inverter topology has been presented. The proposed MPUC inverter can generate 7-level voltage waveform at the output with low harmonic contents. Unlike the reported PUC topology, the 7-level MPUC inverter is capable to produce voltage levels more than the DC sources used in the structure. It can sum up the DC buses amplitudes to deliver more power to the output. The associated switching algorithm has been designed and implemented on the introduced MPUC topology with reduced switching frequency aspect. Moreover, photovoltaic application has been targeted for this inverter to deliver power from PV panels with different voltage/current rating to grid. In this regard, results have been shown to validate the acceptable voltage regulation and current controlling of the grid-connected inverter as well as the implemented P&O MPPT algorithm.

REFERENCES:

 [1] B. Singh, A. Chandra, and K. Al-Haddad, Power Quality: Problems and Mitigation Techniques: John Wiley & Sons, 2014.

[2] I. Gowaid, G. Adam, A. Massoud, S. Ahmed, and B. Williams, "Hybrid and Modular Multilevel Converter Designs for Isolated HVDC-DC Converters," IEEE Journal Emerg. and Select. Topics in Power Electron., vol. PP, no. 99, p. 1, 2017.

[3] H. Vahedi, K. Al-Haddad, Y. Ounejjar, and K. Addoweesh, "Crossover Switches Cell (CSC): A New Multilevel Inverter Topology with Maximum Voltage Levels and Minimum DC Sources," in IECON 2013-39th Annual Conference on IEEE Industrial Electronics Society, Austria, 2013, pp. 54-59.

[4] P. W. Hammond, "A new approach to enhance power quality for medium voltage drives," in Petroleum and Chemical Industry Conference, 1995. Record of Conference Papers., Industry Applications Society 42nd Annual, 1995, pp. 231-235.

[5] A. Nabae, I. Takahashi, and H. Akagi, "A new neutral-point-clamped PWM inverter," IEEE Trans. Ind. Applications, no. 5, pp. 518-523, 1981.