Soft Switched Interleaved DC/DC Converter as front-end of Multi Inverter Structure for Micro Grid Applications

ABSTRACT:

An isolated four channel DC/ DC converter with zero voltage switching (ZVS) is proposed as front-end of multiple inverter structures to integrate renewable and other low voltage energy sources to micro grid. Interleaving technique is adopted to connect each module of proposed converter to a common dc source. This dc source can be a fuel cell stack, PV panels,  battery or any other low voltage dc source. All four channels are interleaved and phase shift of 90o is provided between the gate signals of each channels which reduces the input current ripple.Output port of the proposed converter provide four isolated and regulated dc voltages. These isolated dc sources can be connected in series or parallel or series-parallel manner to obtain required dc link voltage of various inverter structure. Issues like capacitor voltage balancing of diode clamped multilevel inverters can overcome through proposed converter. By incorporating coupled inductor for isolation and energy storage along with voltage multiplier circuit, proposed converter can achieve higher voltage step up with lower turns ratio and lower voltage stress at moderate duty ratio. Hence MOSFETs of low voltage rating (low RDS(ON)) can be utilized to reduce conduction loss. A 2kW prototype of proposed interleaved DC/DC converter is developed and tested with diode clamped three level inverter, five level inverter and three phase two level inverter to verify the design.

 

KEYWORDS:

  1. DC-DC Converter
  2. Zero voltage switching
  3. Active clamp
  4. Interleaving
  5. Coupled inductor
  6. High voltage gain

SOFTWARE: MATLAB/SIMULINK

BLOCK DIAGRAM:

Fig. 1. Proposed Interleaved DC/DC Converter.

 

EXPECTED SIMULATION RESULTS

 Fig. 2. Experimental results at full load for Vin = 55V, (a) Gate signals for main switches of all four channels which are phase shifted by 90o (b) Gate signals for main and clamp switches of channel-a and channel-b. (c) Input current drawn by individual channels at full load (d) Resultant input current drawn from the input source at full load by interleaving operation of all four channels (e) Voltage stress across the main switches of all four channels at full load (f) Soft turn on (ZVS) of main and clamp switches of channel-a, ZVS turn on region is highlighted (g) Voltage stress across the voltage multiplier diodes Da1 and Da2 of channel-a along with input current of same channel (h) Voltage stress across the output diode Dao of channel-a along with voltage stress of diode Da1.

Fig. 3. Experimental results: (a) Phase voltage and current of three level inverter feeding R-L load of 0.85 power factor (b) Regulated and balanced dc link voltage of 3 level diode clamped inverter (c) Phase voltage and current of 5 level diode clamped inverter feeding to R-L load of 0.85 power factor (d) Balanced DC link voltage of five level diode clamped inverter which is regulated by proposed converter (e) Line voltage and current of 2 level full bridge inverter feeding R-L load of 0.85 power Factor.

 

CONCLUSION:

An isolated 4-channel interleaved dc/dc converter with soft switching and high voltage step up gain is proposed as a front end of multiple inverter structures. Proposed converter makes use of isolated coupled inductor and dual voltage multiplier circuit to achieve voltage step up with lower voltage stress on devices. Active clamp circuit is used to clamp the voltage spike on MOSFETs and also to provide soft turn on for MOSFET switches. Interleaved operation enhanced the power output and reduces the input current ripple. Modularity of proposed converter is an added advantage. Four isolated output port of proposed converter can be connected in series, parallel or series-parallel combination to obtain required dc link voltages of multiple commonly used inverter structures like three phase two level inverter, three level NPC and five level NPC inverter structures. Proposed converter can overcome the capacitor voltage balancing issues of five level and three level NPC inverters without any additional voltage balancing circuits. Feasibility of same is experimentally verified and results are shown. By using MOSFETs of low on state resistance, conduction losses are reduced in proposed converter. A 2kW prototype of proposed converter is build and results are verified. Maximum efficiency of proposed converter is found to be 95.83%.

 

REFERENCES:

  • Blaabjerg, Z. Chen, and S. B. Kjaer, “Power electronics as efficient interface in dispersed power generation systems,” IEEE Trans. Power Electron., vol. 19, no. 5, pp. 1184–1194, Sept 2004.
  • Liserre, T. Sauter, and J. Y. Hung, “Future energy systems: Integrating renewable energy sources into the smart power grid through industrial electronics,” IEEE Ind. Electron. Mag., vol. 4, no. 1, pp. 18– 37, March 2010.
  • Zhao, X. Xiang, W. Li, X. He, and C. Xia, “Advanced symmetrical voltage quadrupler rectifiers for high step-up and high output-voltage converters,” IEEE Trans. Power Electron, vol. 28, no. 4, pp. 1622–1631, 2013.
  • S. Solanki, Solar photovoltaics: fundamentals, technologies and applications. PHI Learning Pvt. Ltd., 2011.
  • Sharma and V. Agarwal, “Exact maximum power point tracking of grid-connected partially shaded pv source using current compensation concept,” IEEE Trans. Power Electron., vol. 29, no. 9, pp. 4684–4692, Sept 2014.

Power Quality and Power Interruption Enhancement by Universal Power Quality Conditioning System with Storage Device

 

ABSTRACT:

In this paper a novel design of Universal Power Quality Conditioning System (UPQS) is proposed which is composed of the DC/DC converter and the storage device connected to the DC link of UPQS for balancing the voltage interruption. The proposed UPQS can balance the reactive power, harmonic current, voltage sag and swell, voltage unbalance, and the voltage interruption. The performance of proposed system was analyzed through simulations with MATLAB\SIMULINK software. The proposed system can improve the power quality at the common connection point of the non-linear load and the sensitive load.

KEYWORDS:

  1. Universal Power Quality Conditioning System (UPQS)
  2. Voltage interruption
  3. DC/DC converter
  4. Super-capacitor

SOFTWARE: MATLAB/SIMULINK

BLOCK DIAGRAM:

 

Fig. 1: Configuration of proposed UPQC with energy storage.

 EXPECTED SIMULATION RESULTS:

                  Fig. 2: Nonlinear load current.

Fig. 3: Active and reactive power consumed by load.

    Fig. 4: Voltage sag compensation. (a) Source voltage. (b) Load voltage.

CONCLUSION:

This paper proposes a new configuration of UPQC that consists of the DC/DC converter and the super capacitors for compensating the voltage interruption. The proposed UPQC can compensate the reactive power, harmonic current, voltage sag and swell, voltage unbalance, and the voltage interruption. The control strategy for the proposed UPQC was derived based on the Synchronous reference frame method. The operation of proposed system was verified through simulations with MATLAB/SIMULINK software. The proposed UPQC has the ultimate capability of improving the power quality at the installation point in the distribution system. The proposed system can replace the UPS, which is effective for the long duration of voltage interruption, because the long duration of voltage interruption is very rare in the present power system.

REFERENCES:

[1]        Akagi, H., Y. Kanazawa and A. Nabae, 2007. Instantaneous reactive power compensator comprising switching devices without energy storage components. IEEE Transactions on Industry Application, 20: 625-630.

[2]        Aredes, M., K. Heumann, E.H. Watanabe, 1998. An universal active power line conditioner. IEEE Transactions on Power Delivery, 13(2): 545-551.

[3]        Aredes, M. and E.H. Watanabe, 1995. New control algorithms for series and shunt three-phase four-wire active power Filters. IEEE Transactions on Power Delivery, 10: 1649-1656.

[4]        Arrillaga, J., M.H.J. Bollen, N.R. Watson, 2000. Power quality following deregulation. Proceedings of the IEEE, 88(2): 246-261.

[5]        Bendre, A., S. Norris, D. Divan, I. Wallace, 2003. New high power DC/DC converter with loss limited switching and lossless secondary clamp. IEEE Transactions on Power Electronics, 18(4):1020-1027.

 

Power Management Strategy for a Multi-Hybrid Fuel Cell/Energy Storage Power Generation Systems

 

 ABSTRACT:

This paper depicts a new configuration for modular hybrid power conversion systems, namely, multi-hybrid generation system (MHGS), and parallel connection at the output, such that the converter of each unit shares the load current equally. This is a significant step towards realizing a modular power conversion system architecture, where smaller units can be connected in any series/parallel grouping to realize any required unit specifications. The supercapacitor (SC) as a complementary source is used to compensate for the slow transient response of the fuel cell (FC) as a main power source. It assists the Fe to meet the grid power demand in order to achieve a better performance and dynamic behavior. Reliable control of the proposed MHGS with multiple units is also a challenging issue. In this paper, a simple control method to achieve active sharing of load current among MHGS modules is proposed. The simulation results verify the performance of the proposed structure and control scheme.

KEYWORDS:

  1. Multi-hybrid generation system (MHGS)
  2. Fuel cell (FC)
  3. Dc/dc converter
  4. Supercapacitor (SC)
  5. Average load sharing (ALS)

 SOFTWARE: MATLAB/SIMULINK

 CIRCUIT DIAGRAM:

 image001

Figure 1. Configuration of the FC/SC hybrid system.

 CONTROL SYSTEM:

 image002

Figure 2. Proposed control strategy of hybrid FC/SC power conversion

.EXPECTED SIMULATION RESULTS:

 image003

Figure 3. Dynamic response of MHGS, (a) load active power, (b) output power of hybrid units, (c) FC stack and SC module power of first hybrid umt, and (d) FC stack and SC module power of second hybrid unit.

image004

Figure 4. Output waveform of (a) dc bus voltage, and (b) dc bus current.

image005

Figure 5. Waveforms of unit’s (a) hydrogen input flow, (b) hydrogen partial pressure, and (d) oxygen partial pressure.

CONCLUSION:

This paper proposes a comprehensive and effective multihybrid FC/SC power generation system structure and control strategy. The detailed model of the modular FC/SC hybrid system which includes an FC stack as a main power source and an SC as a complementary source is presented. In order to balance power sharing among the units, average load sharing technique is used. Elimination of outer voltage loop of ALS technique enhances reliability and reduces the complexity of the control structure. To show the superior dynamic behavior and power sharing of the proposed MHGS, results for two parallel hybrid systems are provided. The presented analysis and the simulation results offer a valuable structure with an effective control strategy to enhance power quality and management. These performances allow the integration MHGS into complex distributed generation systems such as microgrids.

REFERENCES:

[1] P. Chiradeja and R. Ramakumar, “An approach to quantify the technical benefits of distributed generation,” IEEE Trans. Energy Convers., voL 19,no. 4,pp. 764-773,Dec,2004.

[2] B. Wojszczyk, R. Uluski, and F. Katiraei, ‘The role of distributed generation and energy storage in utilities of the future,” in Proc. IEEE PES Gen. Meet., 2008, pp. 1-2.

[3] K. Rajashekara, “Hybrid fuel-cell strategies for clean power generation,” IEEE Trans. Ind Appl., voL 41, no. 3, pp. 682-689, May/Jun. 2005.

[4] 1. M. Carrasco, L. G. Franquelo, 1. T. Bialasiewicz, E. Galvan, R. C. PortilloGuisado, M. A M. Prats, 1. L Leon, and N.Moreno-Alfonso, “Power-electronic systems for the grid integration of renewable energy sources: A survey,” IEEE Trans. Ind Electron., voL 53, no. 4, pp. 1002- 1016, Jun. 2006.

[5] Z. Jiang, and R. A Dougal, “A compact digitally controlled fuel cell/battery hybrid power source,” IEEE Trans. Ind Electron., voL 53, no. 4,pp. 1094-1104,Jun. 2006.

A Novel High StepUp DCDC Converter Based on Integrating Coupled Inductor and Switched-Capacitor Techniques for Renewable Energy Applications

ABSTRACT

In this paper, a novel high step-up dc/dc converter is presented for renewable energy applications. The suggested structure consists of a coupled inductor and two voltage multiplier cells, in order to obtain high step-up voltage gain. In addition, two capacitors are charged during the switch-off period, using the energy stored in the coupled inductor which increases the voltage transfer gain. The energy stored in the leakage inductance is recycled with the use of a passive clamp circuit. The voltage stress on the main power switch is also reduced in the proposed topology. Therefore, a main power switch with low resistance RDS(ON) can be used to reduce the conduction losses. The operation principle and the steady-state analyses are discussed thoroughly. To verify the performance of the presented converter, a 300-W laboratory prototype circuit is implemented. The results validate the theoretical analyses and the practicability of the presented high step-up converter.

 KEYWORDS:

Coupled inductor, DC/DC converters, High step-up, Switched capacitor.

 SOFTWARE: MATLAB/SIMULINK

 CIRCUIT DIAGRAM:

image017

Fig. 1. Circuit configuration of the presented high-step-up converter.

SIMULATION RESULTS:

 image018 image019 image020 image021 image022 image023 image024

Fig. 2. Simulation results under load 300 W.

 CONCLUSION

This paper presents a new high-step-up dc/dc converter for renewable energy applications. The suggested converter is suitable for DG systems based on renewable energy sources, which require high-step-up voltage transfer gain. The energy stored in the leakage inductance is recycled to improve the performance of the presented converter. Furthermore, voltage stress on the main power switch is reduced. Therefore, a switch with a low on-state resistance can be chosen. The steady-state operation of the converter has been analyzed in detail. Also, the boundary condition has been obtained. Finally, a hardware prototype is implemented which converts the 40-V input voltage into 400-V output voltage. The results prove the feasibility of the presented converter.

REFERENCES

[1] F.Nejabatkhah, S. Danyali, S. Hosseini, M. Sabahi, and S. Niapour, “Modeling and control of a new three-input DC–DC boost converter for hybrid PV/FC/battery power system,” IEEE Trans. Power Electron., vol. 27, no. 5, pp. 2309–2324, May 2012.

[2] R. J. Wai and K. H. Jheng, “High-efficiency single-input multiple-output DC–DC converter,” IEEE Trans. Power Electron., vol. 28, no. 2, pp. 886–898, Feb. 2013.

[3] Y. Zhao, X. Xiang, C. Li, Y. Gu, W. Li, and X. He, “Single-phase high step-up converter with improved multiplier cell suitable for half- bridgebased PV inverter system,” IEEE Trans. Power Electron., vol. 29, no. 6, pp. 2807–2816, Jun. 2014.

[4] J.H. Lee, T. J. Liang, and J. F. Chen, “Isolated coupled-inductor-integrated DC–DC converter with non-dissipative snubber for solar energy applications,” IEEE Trans. Ind. Electron., vol. 61, no. 7, pp. 3337–3348, Jul.2014.

[5] C.Olalla, C. Delineand, andD.Maksimovic, “Performance of mismatched PV systems withsubmodule integrated converters,” IEEE J. Photovoltaic, vol. 4, no. 1, pp. 396–404, Jan. 2014.

A High Gain Input-Parallel Output-Series DC/DC Converter with Dual Coupled Inductors

ABSTRACT

High voltage gain dc–dc converters are required in many industrial applications such as photovoltaic and fuel cell energy systems, high-intensity discharge lamp (HID), dc back-up energy systems, and electric vehicles. This paper presents a novel input-parallel output-series boost converter with dual coupled inductors and a voltage multiplier module. On the one hand, the primary windings of two coupled inductors are connected in parallel to share the input current and reduce the current ripple at the input. On the other hand, the proposed converter inherits the merits of interleaved series-connected output capacitors for high voltage gain, low output voltage ripple, and low switch voltage stress. Moreover, the secondary sides of two coupled inductors are connected in series to a regenerative capacitor by a diode for extending the voltage gain and balancing the primary-parallel currents. In addition, the active switches are turned on at zero current and the reverse recovery problem of diodes is alleviated by reasonable leakage inductances of the coupled inductors. Besides, the energy of leakage inductances can be recycled. A prototype circuit rated 500-W output power is implemented in the laboratory, and the experimental results shows satisfactory agreement with the theoretical analysis.

 KEYWORDS

  1. DC–DC converter
  2. Dual coupled inductors
  3. High gain
  4. Input-parallel output-series.

SOFTWARE: MATLAB/SIMULINK

CIRCUIT DIAGRAM:

 image002

Fig. 1. Equivalent circuit of the presented converter.

image004

Fig.2 Key theoretical waveforms.

 EXPERIMENTAL VERIFICATIONS:

image006

Fig.3 Key experimental current waveforms.

image008

Fig.4 Voltage stress waveforms of power components.

CONCLUSION

For low input-voltage and high step up power conversion, this paper has successfully developed a high-voltage gain dc–dc converter by input-parallel output-series and inductor techniques. The key theoretical waveforms, steady-state operational principle, and the main circuit performance are discussed to explore the advantages of the proposed converter. Some important characteristics of the proposed converter are as follows: 1) it can achieve a much higher voltage gain and avoid operating at extreme duty cycle and numerous turn ratios; 2) the voltage stresses of the main switches are very low, which are one fourth of the output voltage under N = 1; 3) the input current can be automatically shared by each phase and low ripple currents are obtained at input; 4) the main switches can be turned ON at ZCS so that the main switching losses are reduced; and 5) the current falling rates of the diodes are controlled by the leakage inductance so that the diode reverse-recovery problem is alleviated. At the same time, there is a main disadvantage that the duty cycle of each switch shall be not less than 50% under the interleaved control with 180phase shift.

 REFERENCES

[1] C.Cecati, F. Ciancetta, and P. Siano, “A multilevel inverter for photovoltaic systems with fuzzy logic control,” IEEE Trans. Ind. Electron., vol. 57, no. 12, pp. 4115–4125, Dec. 2010.

[2] X. H. Yu, C. Cecati, T. Dillon, and M. G. Simoes, “The new frontier of smart grid,” IEEE Trans. Ind. Electron. Mag., vol. 15, no. 3, pp. 49–63, Sep. 2011.

[3] G. Fontes, C. Turpin, S. Astier, and T. A. Meynard, “Interactions between fuel cell and power converters: Influence of current harmonics on a fuel cell stack,” IEEE Trans. Power Electron., vol. 22, no. 2, pp. 670–678, Mar. 2007.

[4] J. Y. Lee and S. N. Hwang, “Non-isolated high-gain boost converter using voltage-stacking cell,” Electron. Lett., vol. 44, no. 10, pp. 644–645, May 2008.

[5] Z. Amjadi and S. 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.