Investigation on cascade multilevel inverter with symmetric, asymmetric, hybrid and multi-cell configurations

 ABSTRACT:  

In recent past, numerous multilevel architectures came into existence. In this background, cascaded multilevel inverter (CMLI) is the promising structure. This type of multilevel inverters synthesizes a medium voltage output based on a series connection of power cells which use standard low-voltage component configurations. This characteristic allows one to achieve high-quality output voltage and current waveforms. However, when the number of levels increases switching components and the count of dc sources are also increased. This issue became a key motivation for the present paper. The present paper is devoted to investigate different types of CMLI which use less number of switching components and dc sources and finally proposed a new version of Multi-cell based CMLI. In order to verify the proposed topology, MATLAB – simulations and hardware verifications are carried out and results are presented.

KEYWORDS:

1.      Cascade multilevel inverter

2.      Multi-cell

3.      Switching components

4.      High quality output voltages

SOFTWARE: MATLAB/SIMULINK

 INVESTIGATION ON CASCADE MULTILEVEL INVERTER:

Figure 1 (a) CHB multilevel inverter, (b) key waveform for seven-level inverter, (c) CHB multilevel inverter by employing single-phase transformers, (d) simulation verification of seven-level CHB multilevel inverter, (e) FFT spectrum.

Figure 2 (a) Asymmetrical thirteen-level CHB inverter, (b) simulation verification of thirteen-level CHB multilevel inverter, (c) FFT spectrum.

Figure 3 (a) Asymmetrical CHB multilevel inverter, (b) output voltages of each H-bridge module, (c) twenty-seven level output voltage waveform, (d) FFT spectrum.

Figure 4 (a) Asymmetrical CHB multilevel inverter using sub-cells, (b) output voltage of sub-cells, (c) thirty-one level output voltage waveform, (d) FFT spectrum.

Figure 5 (a) Hybrid CHB multilevel inverter, (b) output voltage of each H-bridge and load voltage (nine-level) waveform, (c) FFT spectrum.

Figure 6 (a) Hybrid multilevel inverter using traditional inverter, (b) output voltage waveform, (c) FFT Spectrum.

Figure 7 The proposed multi-cell CMLI.

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Figure 8 (a) The proposed 25-level asymmetric multi-cell CMLI, (b) key waveforms.

Figure 9 (a) Output voltage of first H-bridge, (b) output voltage of second H-bridge, (c) resultant output voltage with 25-levels, (d) FFT spectrum.

CONCLUSION:

In this paper CMLI with sub-cells is proposed with less number of switches. To highlight the merits of proposed inverter, an in-depth investigation is carried out on symmetric, asymmetric and hybrid multilevel inverters based on CHB topologies. Symmetric configuration has capacity to produce only limited number of levels in output voltage. On the counter side, symmetrical configuration can be operated in asymmetrical mode with different DC sources. However, asymmetrical configurations can produce higher number of output levels and thereby qualitative output waveforms could be generated. Later, hybrid CHB inverters are also introduced, which utilizes single DC source for entire structure. Thus complexity and voltage balancing issues can be reduced. Finally proposed inverter is introduced with less number of switching components and able to produce qualitative output waveforms. To verify the proposed inverter adequate simulation is done with help of MATLAB simulink. Later on, hardware variations are carried out in laboratory. Verifications are quite impressive with greater number of levels in the output voltage and lower harmonic content in FFT spectrums. Spectrums indicate that, low order harmonics are drastically reduced. Thus power quality is significantly enhanced. Thus proposed inverter shows some promising attributes when compared with traditional CHB based architectures.

REFERENCES:

[1] Babaei E, Alilu S, Laali S. A new general topology for cascaded multilevel inverters with reduced number of components based on developed H-bridge. IEEE Trans Ind Electron 2014;61(8):3932–9.

[2] Malinowski Mariusz, Gopakumar K, Rodriguez Jose, Pe´rez Marcelo A. A survey on cascaded multilevel inverters. IEEE Trans Ind Electron 2010;57(7):2197–205.

[3] Wu JC, Wu KD, Jou HL, Xiao ST. Diode-clamped multi-level power converter with a zero-sequence current loop for three-phase three-wire hybrid power filter. Elsevier J Electr Power Syst Res2011;81(2):263–70.

[4] Khoucha Farid, Lagoun Mouna Soumia, Kheloui Abdelaziz, Benbouzid Mohamed El Hachemi. A comparison of symmetrical and asymmetrical three-phase H-bridge multilevel inverter for DTC induction motor drives. IEEE Trans Energy Convers 2011;26(1):64–72.

[5] Ebrahimi J, Babaei E, Gharehpetian GB. A new topology of cascaded multilevel converters with reduced number of components for high-voltage applications. IEEE Trans Power Electron 2011;26(11):3119–30.

Analysis and Implementation of a Novel Bidirectional DC–DC Converter

ABSTRACT:  

A novel bidirectional dc–dc converter is presented in this paper. The circuit configuration of the proposed converter is very simple. The proposed converter employs a coupled inductor with same winding turns in the primary and secondary sides. In step-up mode, the primary and secondary windings of the coupled inductor are operated in parallel charge and series discharge to achieve high step-up voltage gain. In step-down mode, the primary and secondary windings of the coupled inductor are operated in series charge and parallel discharge to achieve high step-down voltage gain. Thus, the proposed converter has higher step-up and step-down voltage gains than the conventional bidirectional dc–dc boost/buck converter. Under same electric specifications for the proposed converter and the conventional bidirectional boost/buck converter, the average value of the switch current in the proposed converter is less than the conventional bidirectional boost/buck converter. The operating principle and steady-state analysis are discussed in detail. Finally, a 14/42-V prototype circuit is implemented to verify the performance for the automobile dual-battery system.

KEYWORDS:

1.      Bidirectional dc–dc converter

2.      Coupled inductor

SOFTWARE: MATLAB/SIMULINK

 CIRCUIT DIAGRAM:

Fig. 1. Proposed bidirectional dc–dc converter.

 EXPECTED SIMULATION RESULTS:

Fig. 2. Some experimental waveforms of the proposed converter in step-up

mode. (a) i_L1, i_L2, and i_L, (b) i_S1, i_S2, and i_S3. (c) v_DS1, v_DS2, and v_DS3.

Fig. 3. Dynamic response of the proposed converter in step-up mode for the

output power variation between 20 and 200 W.

Fig. 4. Some experimental waveforms of the proposed converter in step down

mode. (a) i_LL, i_L1, and i_L2, (b) i_S3, i_S1, and i_S2. (c) v_DS3, v_DS1, and v_DS2.

Fig. 5. Dynamic response of the proposed converter in step-down mode for

the output power variation between 20 and 200 W.

CONCLUSION:

This paper researches a novel bidirectional dc–dc converter. The circuit configuration of the proposed converter is very simple. The proposed converter has higher step-up and step-down voltage gains and lower average value of the switch current than the conventional bidirectional boost/buck converter. From the experimental results, it is see that the experimental waveforms agree with the operating principle and steady-state analysis. At full-load condition, the measured efficiency is 92.7% in stepup mode and is 93.7% in step-down mode. Also, the measured efficiency is around 92.7%–96.2% in step-up mode and is around 93.7%–96.7% in step-down mode, which are higher than the conventional bidirectional boost/buck converter.

REFERENCES:

[1] M. B. Camara, H. Gualous, F. Gustin, A. Berthon, and B. Dakyo, “DC/DC converter design for supercapacitor and battery power management in hybrid vehicle applications—Polynomial control strategy,” IEEE Trans. Ind. Electron., vol. 57, no. 2, pp. 587–597, Feb. 2010.

[2] T. Bhattacharya, V. S. Giri, K. Mathew, and L. Umanand, “Multiphase bidirectional flyback converter topology for hybrid electric vehicles,” IEEE Trans. Ind. Electron., vol. 56, no. 1, pp. 78–84, Jan. 2009.

[3] Z. Amjadi and S. S. Williamson, “A novel control technique for a switched-capacitor-converter-based hybrid electric vehicle energy storage system,” IEEE Trans. Ind. Electron., vol. 57, no. 3, pp. 926–934, Mar. 2010.

[4] F. Z. Peng, F. Zhang, and Z. Qian, “A magnetic-less dc–dc converter for dual-voltage automotive systems,” IEEE Trans. Ind. Appl., vol. 39, no. 2, pp. 511–518, Mar./Apr. 2003.

[5] A. Nasiri, Z. Nie, S. B. Bekiarov, and A. Emadi, “An on-line UPS system with power factor correction and electric isolation using BIFRED converter,” IEEE Trans. Ind. Electron., vol. 55, no. 2, pp. 722–730, Feb. 2008.

Dynamic Modeling, Design, and Simulation of a Combined PEM Fuel Cell and Ultracapacitor System for Stand-Alone Residential Applications

ABSTRACT:  

The available power generated from a fuel cell (FC) power plant may not be sufficient to meet sustained load demands, especially during peak demand or transient events encountered in stationary power plant applications. An ultracapacitor (UC) bank can supply a large burst of power, but it cannot store a significant amount of energy. The combined use of FC and UC has the potential for better energy efficiency, reducing the cost of FC technology, and improved fuel usage. In this paper, we present an FC that operates in parallel with a UC bank. A new dynamic model and design methodology for an FC- and UC based energy source for stand-alone residential applications has been developed. Simulation results are presented using MATLAB, Simulink, and Sim Power Systems environments based on the mathematical and dynamic electrical models developed for the proposed system.

KEYWORDS:

1.      Combined system

2.      Dynamic modeling

3.      Fuel cell (FC)

4.      Proton exchange membrane fuel cell (PEMFC)

5.      Ultracapacitor (UC)

SOFTWARE: MATLAB/SIMULINK

BLOCK DIAGRAM:

    

Fig. 1. Combination of FC system and UC bank.     

                     

Fig. 2. PCU and load connection diagram.

EXPECTED SIMULATION RESULTS:

Fig. 3. Real power of residential load.

Fig. 4. Variation of FC system output voltage according to load demand.

Fig. 5. Variation of UC bank terminal voltage according to load demand.

Fig. 6. Variation of UC bank charging and discharging current according to load switching.

Fig. 7. Variation of ac output power.

Fig. 8. Variation of ac load voltage.

Fig. 9. Variation of modulation index corresponding to load demand.

Fig. 10. Variation of ac voltage phase angle.

Fig. 11. Variation of FC system dc output power.

Fig. 12. Variation of hydrogen flow rate.

CONCLUSION:

A UC-based storage system is designed for a PEMFC operated grid independent home to supply the extra power required during peak demand periods. The parallel combination of the FC system and UC bank exhibits good performance for the stand-alone residential applications during the steady-state, load-switching, and peak power demand. Without the UC bank, the FC system must supply this extra power, thereby increasing the size and cost of the FC system. The results corresponding to high peak load demand during short time periods are not shown in order to simulate more realistic load profile. The load profile was created by measuring data at 15-s sampling interval. However, the proposed model can be used for different load profiles consisting of different transients and short-time interruption. Also, it can be extended for use in many areas such as portable devices, heavy vehicles, and aerospace applications. The lifetime of an FC system can be increased if combined FC system and UC bank is used instead of a stand-alone FC system or a hybrid FC and standby battery system.

REFERENCES:

[1] L. Gao, Z. Jiang, and R. A. Dougal, “An actively controlled fuel cell/battery hybrid to meet pulsed power demands,” J. Power Sources, vol. 130, no. 1–2, pp. 202–207, May 2004.

 [2] T. S. Key, H. E. Sitzlar, and T. D. Geist, “Fast response, load-matching hybrid fuel cell,” Final Tech. Prog. Rep., EPRI PEAC Corp., Knoxville,TN NREL/SR-560-32743, Jun. 2003.

[3] S. Buller, E. Karden, D. Kok, and R. W. De Doncker, “Modeling the dynamic behavior of supercapacitors using impedance spectroscopy,” IEEE Trans. Ind. Appl., vol. 38, no. 6, pp. 1622–1626, Nov. 2002.

[4] J. L. Duran-Gomez, P. N. Enjeti, and A. Von Jouanne, “An approach to achieve ride-through of an adjustable-speed drive with flyback converter modules powered by super capacitors,” IEEE Trans. Ind. Appl., vol. 38, no. 2, pp. 514–522, Mar.–Apr. 2002.

[5] A. Burke, “Ultracapacitors: Why, how, and where is the technology,” J. Power Sources, vol. 91, no. 1, pp. 37–50, Nov. 2000.