High-Efficiency MOSFET Transformerless Inverter for Non-isolated Microinverter Applications

ABSTRACT

State-of-the-art low-power-level metal–oxide–semiconductor field-effect transistor (MOSFET)-based transformerless photovoltaic (PV) inverters can achieve high efficiency by using latest super junction MOSFETs. However, these MOSFET-based inverter topologies suffer from one or more of these drawbacks: MOSFET failure risk from body diode reverse recovery, increased conduction losses due to more devices, or low magnetics utilization. By splitting the conventional MOSFET based phase leg with an optimized inductor, this paper proposes a novel MOSFET-based phase leg configuration to minimize these drawbacks. Based on the proposed phase leg configuration, a high efficiency single-phase MOSFET transformerless inverter is presented for the PV microinverter applications. The pulsewidth modulation (PWM) modulation and circuit operation principle are then described. The common-mode and differential-mode voltage model is then presented and analyzed for circuit design. Experimental results of a 250W hardware prototype are shown to demonstrate the merits of the proposed transformerless inverter on non-isolated two-stage PV microinverter application.

KEYWORDS: Microinverter, MOSFET inverters, photovoltaic (PV) inverter, transformerless inverter.

SOFTWARE: MATLAB/SIMULINK

   

BLOCK DIAGRAM:

Fig. 1. Two-stage nonisolated PV microinverter.

CIRCUIT DIAGRAM:

Fig. 2. Proposed transformerless inverter topology with (a) separated magnetic and (b) integrated magnetics.

EXPERIMENTAL RESULTS:

Fig. 3. Output voltage and current waveforms.

Fig. 4. PWM gate signals waveforms.

Fig. 5. Inverter splitting inductor current waveform.

Fig. 6. Waveforms of voltage between grid ground and DC ground (VEG ).

 CONCLUSION

This paper proposes a MOSFET transformerless inverter with a novel MOSFET-based phase leg, which achieves:

1) high efficiency by using super junction MOSFETs and SiC diodes;

2) minimized risks from the MOSFET phase leg by splitting the MOSFET phase leg with optimized inductor and minimizing the di/dt from MOSFET body diode reverse recovery;

3) high magnetics utilization compared with previous high efficiency MOSFET transformerless inverters in [21], [22], [25], which only have 50% magnetics utilization.

The proposed transformerless inverter has no dead-time requirement, simple PWM modulation for implementation, and minimized high-frequency CMissue. A 250Whardware prototype has been designed, fabricated, and tested in two-stage nonisolated microinverter application. Experimental results demonstrate that the proposed MOSFET transformerless inverter achieves 99.01% peak efficiency at full load condition and 98.8% CEC efficiency and also achieves around 98% magnetic utilization. Due to the advantages of high efficiency, low CM voltage, and improved magnetic utilization, the proposed topology is attractive for two-stage nonisolated PV microinverter applications and transformerless string inverter applications.

REFERENCES

 [1] F. 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, Sep. 2004.

[2] S. B. Kjaer, J. K. Pedersen, and F. Blaabjerg, “A review of singlephase grid-connected inverters for photovoltaic modules,” IEEE Trans. Ind. Appl., vol. 41, no. 5, p. 1292, Sep. 2005.

[3] Q. Li and P. Wolfs, “A review of the single phase photovoltaic module integrated converter topologies with three different dc link configurations,” IEEE Trans. Power Electron., vol. 23, no. 3, pp. 1320–1333, May 2008.

[4] Y. Xue, L. Chang, S. B. Kjaer, J. Bordonau, and T. Shimizu, “Topologies of single-phase inverters for small distributed power generators: An overview,” IEEE Trans. Power Electron., vol. 19, no. 5, pp. 1305–1314, 2004.

[5] W. Yu, J. S. Lai, H. Qian, and C. Hutchens, “High-efficiency MOSFET inverter with H6-type configuration for photovoltaic non-isolated AC-module applications,” IEEE Trans. Power Electron., vol. 56, no. 4, pp. 1253–1260, Apr. 2011.

A High Step-Up DC to DC Converter Under Alternating Phase Shift Control for Fuel Cell Power System

ABSTRACT

This paper investigates a novel pulse width modulation (PWM) scheme for two-phase interleaved boost converter with voltage multiplier for fuel cell power system by combining alternating phase shift (APS) control and traditional interleaving PWM control. The APS control is used to reduce the voltage stress on switches in light load while the traditional interleaving control is used to keep better performance in heavy load. The boundary condition for swapping between APS and traditional interleaving PWM control is derived. Based on the aforementioned analysis, a full power range control combining APS and traditional interleaving control is proposed. Loss breakdown analysis is also given to explore the efficiency of the converter. Finally, it is verified by experimental results.

KEYWORDS: Boost converter, Fuel cell, Interleaved, Loss breakdown, Voltage multiplier.

SOFTWARE: MATLAB/SIMULINK

BLOCK DIAGRAM:

Fig. 1. Grid-connected power system based on fuel cell.

Fig. 2. Main theoretical waveforms at boundary condition.

EXPERIMENTAL RESULTS:

 Fig.3 Experimental results at boundary condition with traditional interleaving control (L = 1158 μH, R = 2023 Ω, and D = 0.448). (a) CH1-S1 Driver Voltage, CH2 − L1 Current, CH3-S1 Voltage Stress, CH4-Output Voltage, (b) CH1-S1 Driver Voltage, CH2 − C1 Current, CH3-S1 Voltage Stress, CH4-OutputVoltage, (c) CH1-S1 DriverVoltage,CH2 − D1 Current,CH3-S1 Voltage Stress, CH4-Output Voltage, (d) CH1-S1 Driver Voltage, CH2 −DM1 Current, CH3-S1 Voltage Stress, CH4-Output Voltage.

Fig. 4. Traditional interleaving control at nominal load (L = 1158 μH and R = 478 Ω).

Fig. 5. Traditional interleaving control in Zone A (L = 1158 μH and R = 1658 Ω).

Fig. 6. Traditional interleaving control in Zone B (L = 1158 μH and R = 3460 Ω).

Fig. 7. APS control in Zone B (L = 1158 μH and R = 3460 Ω).

 CONCLUSION

The boundary condition is derived after stage analysis in this paper. The boundary condition classifies the operating states into two zones, i.e., Zone A and Zone B. The traditional interleaving control is used in Zone A while APS control is used in Zone B. And the swapping function is achieved by a logic unit. With the proposed control scheme, the converter can achieve low voltage stress on switches in all power range of the load, which is verified by experimental results.

REFERENCES

[1] N. Sammes, Fuel Cell Technology: Reaching Towards Commercialization. London, U.K.: Springer-Verlag, 2006.

[2] G. Fontes, C. Turpin, S. Astier, and T. A. Meynard, “Interactions between fuel cells 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.

[3] P. Thounthong, B. Davat, S. Rael, and P. Sethakul, “Fuel starvation,” IEEE Ind. Appl. Mag., vol. 15, no. 4, pp. 52–59, Jul./Aug. 2009.

[4] S.Wang,Y.Kenarangui, and B. Fahimi, “Impact of boost converter switching frequency on optimal operation of fuel cell systems,” in Proc. IEEE Vehicle Power Propulsion Conf., 2006, pp. 1–5.

[5] S. K. Mazumder, R. K. Burra, and K. Acharya, “A ripple-mitigating and energy-efficient fuel cell power-conditioning system,” IEEE Trans. Power Electron., vol. 22, no. 4, pp. 1437–1452, Jul. 2007.

New AC-DC Power Factor Correction Architecture Suitable for High Frequency Operation

ABSTRACT:

This paper presents a novel ac-dc power factor correction (PFC) power conversion architecture for single-phase grid interface. The proposed architecture has significant advantages for achieving high efficiency, good power factor, and converter miniaturization, especially in low-to-medium power applications. The architecture enables twice-line-frequency energy to be buffered at high voltage with a large voltage swing, enabling reduction in the energy buffer capacitor size, and elimination of electrolytic capacitors. While this architecture can be beneficial with a variety of converter topologies, it is especially suited for system miniaturization by enabling designs that operate at high frequency (HF, 3 – 30 MHz). Moreover, we introduce circuit implementations that provide efficient operation in this range. The proposed approach is demonstrated for an LED driver converter operating at a (variable) HF switching frequency (3 – 10 MHz) from 120Vac, and supplying a 35Vdc output at up to 30W. The prototype converter achieves high efficiency (92 %) and power factor (0.89), and maintains good performance over a wide load range. Owing to architecture and HF operation, the prototype achieves a high ‘box’ power density of 50W/ in3 (‘displacement’ power density of 130W/ in3), with miniaturized inductors, ceramic energy buffer capacitors, and a small-volume EMI filter.

KEYWORDS:

1.      AC-DC

2.       High frequency

3.       Buck

4.       Power factor correction

5.      PFC

6.       Power factor

7.       LED

8.       Electromagnetic interference

9.      EMI

SOFTWARE: MATLAB/SIMULINK

BLOCK DIAGRAM:

Fig. 1: The proposed grid interface power conversion architecture comprises a line-frequency rectifier, a stack of capacitors, a set of regulating converters, and a power combining converter.

EXPECTED SIMULATION RESULTS:

Fig. 2: Operation of the prototype converter from a 120V_ac line voltage to a 35V_dc output. Each figure illustrates voltage and / or current waveforms over the ac line cycle: (a) the measured 120V_ac line input voltage and the measured voltages across the capacitor stack (output of the bridge rectifier) (b) the measured voltages across C₁ and across C₂ for a delivered output power of 29W (c) the measured input current waveform

at 29W output power (d) the measured input current waveform at 20W output power (e) the output voltage waveform at 29W output power (f) the switched capacitor voltage waveform at 29W output power.

             

CONCLUSION:

A new single-phase grid interface ac-dc PFC architecture is introduced and experimentally demonstrated. In addition to enabling high efficiency and good power factor, this PFC architecture is particularly advantageous in that it enables extremely high operating frequencies (into the HF range) and reduction in energy buffer capacitor values, each of which contributes to converter miniaturization. The proposed stacked combined architecture significantly decreases the voltage stress of the active and passive devices and reduces characteristic impedance levels, enabling substantial increases in switching frequency when utilized with appropriate converter topologies. Moreover, good power factor is achieved while dynamically buffering twice-line-frequency ac energy with relatively small capacitors operating with large voltage swing. The prototype converter achieves high efficiency and good power factor over a wide power range, and meets the CISPR Class-B Conducted electromagnetic interference (EMI) Limits. The

Fig. 3: The proposed architecture can be extended to more than two capacitors in the capacitor stack and other correspondingly other system blocks. This is particularly useful for handling universal ac line interface. Moreover, the number of capacitors and sub-regulating converter may be allowed to vary dynamically depending upon whether the circuit is connected to 120 or 240 V_ac.

Fig. 4: The stack of flyback converters can regulate output load voltage and combine power to supply single load with connected secondary wires. Two flyback converters need to be modulated over the line cycle to achieve high power factor and buffer ac energy.

prototype converter based on the architecture and selected high-frequency circuit topology demonstrates an approximate factor of 10 reduction in volume compared to typical designs. The prototype has a very high ‘box’ power density of 50W=in3 (‘displacement’ power density of 130W=in3) with miniaturized inductors, a small volume of EMI filter, and ceramic energy buffer capacitors. Lastly, as described in the appendix, the proposed architecture can be realized in various ways (e.g., with alternative topologies) to realize features such as galvanic isolation and universal input range.

REFERENCES:

[1] O. Garcia, J. Cobos, R. Prieto, P. Alou, and J. Uceda, “Single phase power factor correction: a survey,” Power Electronics, IEEE Transactions on, vol. 18, no. 3, pp. 749–755, May 2003.

[2] G. Moschopoulos and P. Jain, “Single-phase single-stage power-factor corrected converter topologies,” Industrial Electronics, IEEE Transactions on, vol. 52, no. 1, pp. 23–35, Feb 2005.

[3] B. Singh, B. Singh, A. Chandra, K. Al-Haddad, A. Pandey, and D. Kothari, “A review of single-phase improved power quality ac-dc converters,” Industrial Electronics, IEEE Transactions on, vol. 50, no. 5, pp. 962–981, Oct 2003.

[4] Energy Star, “Energy star program requirements for integral LED lamps,” Energy Star, Tech. Rep., Aug. 2010.

[5] ——, “Energy star program requirements for computers,” Energy Star, Tech. Rep., Jun. 2014.

[6] D. Perreault, J. Hu, J. Rivas, Y. Han, O. Leitermann, R. Pilawa- Podgurski, A. Sagneri, and C. Sullivan, “Opportunities and challenges in very high frequency power conversion,” in Applied Power Electronics Conference and Exposition, 2009. APEC 2009. Twenty-Fourth Annual IEEE, Feb 2009, pp. 1–14.

A High Step-Up Converter with Voltage-Multiplier Modules for Sustainable Energy Applications

ABSTRACT

This paper proposes a novel isolated high step-up converter for sustainable energy applications. Through an adjustable voltage-multiplier module, the proposed converter achieves a high step-up gain without utilizing either a large duty ratio or a high turns ratio. The voltage-multiplier modules are composed of coupled inductors and switched capacitors. Due to the passive lossless clamped performance, leakage energy is recycled, which alleviates a large voltage spike across the main switches and improves efficiency. Thus, power switches with low levels of voltage stress can be adopted for reducing conduction losses. In addition, the isolated topology of the proposed converter satisfies electrical-isolation and safety regulations. The proposed converter also possesses continuous and smooth input current, which decreases the conduction losses, lengthens life time of the input source, and constrains conducted electromagnetic-interference problems. Finally, a prototype circuit with 40 V input voltage, 380 V output, and 500 W maximum output power is operated to verify its performance. The maximum efficiency is 94.71 % at 200 W, and the full-load efficiency is 90.67 % at 500 W.

KEYWORDS

1.      High Step-Up

2.      Voltage-Multiplier Module

3.      Isolated Converter

SOFTWARE: MATLAB/SIMULINK

BLOCK DIAGRAM:

Fig. 1. Block diagram of a typically sustainable energy system.

CIRCUIT DIAGRAM:

Fig. 2. Proposed isolated high step-up converter for sustainable energy applications.

 EXPERIMENTAL RESULTS:

(a) Measured waveforms of v_DS1, v_DS2, i_Lin and i_Lk

(b) Measured waveforms of v_Dc, v_Dr and i_Dr

(C)Measured waveforms of v_Df1, v_Df2, i_Df1 and i_Df2

(d) Measured waveforms of v_Do, i_Do and V_o

Fig.3 The experimental waveforms measured at a full load of 500 W.

CONCLUSION

This paper has presented the theoretical analysis of steady-state and experimental results for the proposed converter, which successfully demonstrates its performance. A prototype isolated converter has been successfully implemented with a high step-up ratio and high efficiency for sustainable energy applications. The presented circuit topology inherently makes the input current continuous and smooth, which decreases the conduction losses, lengthens the life time of the input source, and constrains conducted EMI problems. In addition, the lossless passive clamp function recycles the leakage energy and constrains/lowers the voltage spikes across the power switches. Meanwhile, the voltage stress on the power switch is restricted and is much lower than the output voltage V_o, which is 380 V. Furthermore, the full-load efficiency is 90.67% at P_o =500 W, and the maximum efficiency is 94.71% at P_o = 200 W. Thus, the proposed converter is suitable for renewable-energy applications that need high step-up conversion and have electrical-isolation requirements.

REFERENCES

1.      T. Kefalas, and A. Kladas, “Analysis of transformers working under heavily saturated conditions in grid-connected renewable energy systems,” IEEE Trans. Ind. Electron., vol. 59, no. 5, pp. 2342–2350, May 2012.

2.      Jonghoon Kim, Jaemoon Lee, and B. H. Cho, “Equivalent circuit modeling of pem fuel cell degradation combined with a lfRC,” IEEE Trans. Ind. Electron., vol. 60, no. 11, pp. 5086–5094, Nov. 2013.

3.      Prasanna U R, and Akshay K. Rathore, “Extended range zvs active-clamped current-fed full-bridge isolated dc/dc converter for fuel cell applications: analysis, design, and experimental results,” IEEE Trans. Ind. Electron., vol. 60, no. 7, pp. 2661–2672, July 2013.

4.      Shih-Jen Cheng, Yu-Kang Lo, Huang-Jen Chiu, and Shu-Wei Kuo, “High-efficiency digital-controlled interleaved power converter for high-power pem fuel-cell applications,” IEEE Trans. Ind. Electron., vol. 60, no. 2, pp. 773–780, Feb. 2013.

5.      Changzheng Zhang, Shaowu Du, and Qiaofu Chen, “A novel scheme suitable for high-voltage and large-capacity photovoltaic power stations,” IEEE Trans. Ind. Electron., vol. 60, no. 9, pp. 3775–3783, Sept. 2013.

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:

Fig. 1. Equivalent circuit of the presented converter.

Fig.2 Key theoretical waveforms.

EXPERIMENTAL VERIFICATIONS:

Fig.3 Key experimental current waveforms.

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 180◦ phase 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.