A Comparison of Half Bridge & Full Bridge Isolated DC-DC Converters for Electrolysis Application

ABSTRACT:

This paper presents a comparison of half bridge and full bridge isolated, soft-switched, DC-DC converters for Electrolysis application. An electrolyser is a part of renewable energy system which generates hydrogen from water electrolysis that used in fuel cells. A DC-DC converter is required to couple electrolyser to system DC bus. The proposed DC-DC converter is realized in both full-bridge and half-bridge topology in order to achieve zero voltage switching for the power switches and to regulate the output voltage. Switching losses are reduced by zero voltage switching. Switching stresses are reduced by using resonant inductor and capacitor. The proposed DC-DC converter has advantages like high power density, low EMI, reduced switching stresses, high circuit efficiency and stable output voltage. The MATLAB simulation results show that the output of converter is free from the ripples and regulated output voltage and this type of converter can be used for electrolyser application. Experimental results are obtained from a MOSFET based DC-DC Converter with LC filter. The simulation results are verified with the experimental results.

KEYWORDS:

  1. DC-DC converter
  2. Electrolyser
  3. Renewable energy sources
  4. Resonant converter
  5. TDR

SOFTWARE: MATLAB/SIMULINK

CIRCUIT DIAGRAM:

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Fig 1. Half Bridge DC-DC Converter.

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Fig 2. Full Bridge DC-DC Converter.

 EXPECTED SIMULATION RESULTS:

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Fig 3 (b) Driving Pulses

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Fig 4 (c) Inverter output voltage with LC filter

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Fig 5 (d) Transformer secondary voltages

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Fig 6 (e) Output voltage and current

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Fig 7 (b) Driving Pulses

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Fig 8 (c) Inverter output voltage with LC filter

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Fig 9 (d) Transformer secondary voltage

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Fig 10 (e) Output voltage and current

 CONCLUSION:

 A comparison of half bridge and full bridge isolated DC-DC converters for Electrolysis application are presented. DC-DC converters for electrolyser system is simulated and tested with LC filter at the output. The electrical performances of the converter have been analyzed. The simulation and experimental results indicate that the output of the inverter is nearly sinusoidal. The output of rectifier is pure DC due to the presence of LC filter at the output. Switching losses are reduced by zero voltage switching. Switching stresses are reduced by using resonant inductor and capacitor The advantages of resonant converter are reduced (di/dt), low switching losses and high efficiency. Switching losses are reduced by zero voltage switching. Switching stresses are reduced by using resonant inductor and capacitor The converter maximizes the efficiency through the zero voltage switching and the use of super-junction MOSFET as switching devices with high dynamic characteristics and low direct voltage drop. Half bridge converter is found to be better than that of full bridge converter.

REFERENCES:

[1] E.J.Miller, “Resonant switching power conversion,”in Power Electronics Specialists Conf.Rec., 1976, pp. 206-211.

[2] V. Volperian and S. Cuk , “A complete DC analysis of the series resonant converter”, in IEEE power electronics specialists conf. Rec. 1982, pp. 85-100.

[3] R.L. Steigerwald, “High-Frequency Resonant Transistor DC-DC Converters”, IEEE Trans. On Industrial Electronics, vol.31, no.2, May1984, pp. 181-191.

[4] D.J. Shortt, W.T. Michael, R.L. Avert, and R.E. Palma, “A 600 W four stage phase-shifted parallel DC-DC converter,”, IEEE Power Electronics Specialists Conf., 1985, pp. 136-143.

[5] V. Nguyen, J. Dhayanchand, and P. Thollot, “A multiphase topology series-resonant DC-DC converter,” in Proceedings of Power Conversion International, 1985, pp. 45-53.

A Multi-Input Bridgeless Resonant AC-DC Converter for Electromagnetic Energy Harvesting

ABSTRACT

Flapping electromagnetic-reed generators are investigated to harvest wind energy, even at low cut-off wind speeds. Power electronic interfaces are intended to address ac-dc conversion and power conditioning for single- or multiple-channel systems. However, the generated voltage of each generator reed at low wind speed is usually below the threshold voltage of power electronic semiconductor devices, increasing the difficulty and inefficiency of rectification, particularly at relatively low output powers. This manuscript proposes a multi-input bridgeless resonant ac-dc converter to achieve ac-dc conversion, step up voltage and match optimal impedance for a multi-channel electromagnetic energy harvesting system. Alternating voltage of each generator is stepped up through the switching LC network and then rectified by a freewheeling diode. Its resonant operation enhances efficiency and enables miniaturization through high frequency switching. The optimal electrical impedance can be adjusted through resonance impedance matching and pulse-frequency-modulation (PFM) control. A 5-cm×3-cm, six-input standalone prototype is fabricated to address power conditioning for a six-channel BreezBee® wind panel.

 KEYWORDS:

AC-DC conversion, electromagnetic energy harvesting, multi-input converter, resonant converter, wind energy.

 SOFTWARE: MATLAB/SIMULINK

 BLOCK DIAGRAM:

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Fig. 1. Multi-channel EMR generators and PEI system: (a) conventional PEI; and (b) proposed multi-input PEI.

CIRCUIT DIAGRAM:

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Fig. 2. Illustrative scheme of the proposed multi-input converter (v(i)emf: EMF of #i reed; r(i)EMR: coil resistance; L(i)EMR: self-inductance; i(i)EMR: reed terminal current; v(i)EMR: reed terminal voltage; C(i)r1= C(i)r2: resonant capacitors; Lr: resonant inductor; Q(i)r1, Q(i)r2: MOSFETs; Dr: output diode; Co: output capacitor).

EXPERIMENTAL RESULTS:

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  •                                                             (a)
  • image005                                                                    (b)

Fig. 3. Experimental waveforms of power amplifiers: fin = 20 Hz; X-axis: 10 ms/div; Y-axis: (a) vemf = 3 Vrms; Ch1 = output voltage (Vo), 2.5 V/div; Ch2 = terminal voltage (vEMR) of reed #1, 10 V/div; Ch3 = input current (iEMR) of six reeds, 50 mA/div; and (b) vemf = 0.5 Vrms; Ch1 = output voltage (Vo), 0.5 V/div; Ch2 = terminal voltage (vEMR) of reed #1, 5 V/div; Ch3 = sum of the input currents (iEMR) of six reeds, 10 mA/div.

 image006                                                         (a)

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  •                                                           (b)

Fig. 4. Experimental waveforms of power amplifiers with step change: X-axis: 40 ms/div; Y-axis: (a) vemf = from 1 Vrms to 2 Vrms; Ch1 = output voltage (Vo), 1 V/div; Ch2 = terminal voltage (vEMR) of reed #1, 5 V/div; Ch3 = input current (iEMR) of six reeds, 50 mA/div; and (b) fin = from 20 Hz to 50 Hz; Ch1 = output voltage (Vo), 0.5 V/div; Ch2 = terminal voltage (vEMR) of reed #1, 5 V/div; Ch3 = input current (iEMR) of six reeds, 50 mA/div.

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(a)

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  •                                                                 (b)

Fig. 5. Experimental waveforms of EMR generators: X-axis: (a) 20 ms/div; (b) 100 ms/div; Y-axis: (a) constant wind speed; (b) wind speed step change; Ch1 = terminal voltage (vEMR) of reed #2, 5 V/div; Ch2 = output voltage (Vo), 1 V/div; Ch3 = terminal voltage (vEMR) of reed #1, 10 V/div; Ch4 = input current (iEMR) of reed #1, 10 mA/div.

 CONCLUSION

This manuscript introduces a multi-input bridgeless resonant ac-dc converter suitable for efficient, low-voltage, low-power, ac-dc power conversion of multiple electromagnetic generators. The multi-input single-stage topology is capable of directly converting independent, low-amplitude, alternative voltages of EMR inductive generators to a stepped-up dc output voltage with relatively high efficiency. Low-frequency alternating voltages of EMR generators are first converted into a high-frequency alternating voltage through an LC network and then rectified into a dc output voltage through a soft-switched diode. Optimal electrical impedance matching is achieved through proper LC network design and PFM control to scavenge maximum power of EMR generators. In addition, high-frequency soft-switching increases the potential of size miniaturization without suffering from switching losses. The converter performance is verified through a 5cm×3cm standalone prototype, which converts ac voltages of six-channel generators into a dc output voltage. A maximum PEI conversion efficiency of 86.3% is measured at 27-mW ac-dc power conversion. The topological concept, presented in this manuscript, can be adapted for rectification of any inductive voltage sources or electromagnetic energy-harvesting device.

REFERENCES

[1] A. Khaligh, P. Zeng, and C. Zheng, “Kinetic energy harvesting using piezoelectric and electromagnetic technologies – state of the art,” IEEE Trans. on Industrial Electronics, vol. 57, no. 3, pp. 850-860, Mar. 2010.

[2] Altenera Technology Inc., accessible online at http://altenera.com/products/.

[3] H. Jung, S. Lee, and D. Jang, “Feasibility study on a new energy harvesting electromagnetic device using aerodynamic instability,” IEEE Trans. on Magnetics, vol. 45, no. 10, pp. 4376-4379, Oct. 2009.

[4] A. Bansal, D. A. Howey, and A. S. Holmes, “CM-scale air turbine and generator for energy harvesting from low-speed flows,” in Proc. Solid-State Sensors, Actuators and Microsystems Conf., Jun. 2009, pp. 529-532.

[5] D. Rancourt, A. Tabesh, and L. G. Fréchette, “Evaluation of centimeter-scale micro windmills: aerodynamics and electromagnetic power generation,” in Proc. PowerMEMS, 2007, pp. 93-96.