A ZVS Grid-Connected Three-Phase Inverter

ABSTRACT:

A six-switch three-phase inverter is widely used in a high-power grid-connected system. However, the anti parallel diodes in the topology operate in the hard-switching state under the traditional control method causing severe switch loss and high electromagnetic interference problems. In order to solve the problem, this paper proposes a topology of the traditional six-switch three-phase inverter but with an additional switch and gave a new space vector modulation (SVM) scheme. In this way, the inverter can realize zero-voltage switching (ZVS) operation in all switching devices and suppress the reverse recovery current in all anti parallel diodes very well. And all the switches can operate at a fixed frequency with the new SVM scheme and have the same voltage stress as the dc-link voltage. In grid-connected application, the inverter can achieve ZVS in all the switches under the load with unity power factor or less. The aforementioned theory is verified in a 30-kW inverter prototype..

KEYWORDS:

  1. Grid connected
  2. soft switching
  3. space vector modulation (SVM)
  4. three-phase inverter
  5. zero-voltage switching (ZVS)

 SOFTWARE: MATLAB/SIMULINK

 BLOCK DIAGRAM:

 Fig. 1. ZVS three-phase inverter.

 EXPECTED SIMULATION RESULTS:

 

 Fig. 2. Inverter output current and grid voltage (10 ms/div): (a) φu = φi , (b), φuφi = π/6, (c) φuφi = π/6.

Fig. 3. CE voltage and current of S6 (IGBT on) (5 μs/div).

Fig. 4. CE voltage and current of S6 (diode on) (2.5 μs/div).

 

 Fig. 5. CE voltage and current of S7 (25 μs/div).

Fig. 6. CE voltage and current of S7 , ibus, and iLr (10 μs/div).

 

Fig. 7. VCc and iLr (50 μs/div).

Fig. 8. Efficiency curve.

CONCLUSION:

In order to speed up the market acceptance of EVs/HEVs, the capital cost in charging infrastructure needs to lower as much as possible. This paper has presented an improved asymmetric half-bridge converter-fed SRM drive to provide both driving and on-board DC and AC charging functions so that the reliance on off-board charging stations is reduced.  The main contributions of this paper are: (i) it combines the split converter topology with central tapped SRM windings to improve the system reliability. (ii) the developed control strategy enables the vehicle to be charged by both DC and AC power subject to availability of power sources. (iii) the battery energy balance strategy is developed to handle unequal SoC scenarios. Even through a voltage imbalance of up to 20% in the battery occurs, the impact on the driving performance is rather limited. (iv) the state-of-charge of the batteries is coordinated by the hysteresis control to optimize the battery performance; the THD of the grid-side current is 3.7% with a lower switching frequency.  It needs to point out that this is a proof-of-concept study based on a 150 W SRM and low-voltage power for simulation and experiments. In the further work, the test facility will be scaled up to 50 kW.

REFERENCES:

[1] B. K. Bose, “Global energy scenario and impact of power electronics in 21st Century,” IEEE Trans. Ind. Electron., vol. 60, no. 7, pp. 2638- 2651, Jul. 2013.

[2] J. de Santiago, H. Bernhoff, B. Ekergård, S. Eriksson, S. Ferhatovic, R. Waters, and M. Leijon, “Electrical motor drivelines in commercial all-electric vehicles: a review,” IEEE Trans. Veh. Technol., vol. 61, no. 2, pp. 475-484, Feb. 2012.

[3] A. Chiba, K. Kiyota, N. Hoshi, M. Takemoto, S. Ogasawara, “Development of a rare-earth-free SR motor with high torque density for hybrid vehicles,” IEEE Trans. Energy Convers., vol. 30, no. 1, pp.175-182, Mar. 2015.

[4] K. Kiyota, and A. Chiba, “Design of switched reluctance motor competitive to 60-Kw IPMSM in third-generation hybrid electric vehicle,” IEEE Trans. Ind. Appl., vol. 48, no. 6, pp. 2303-2309, Nov./Dec. 2012.

[5] S. E. Schulz, and K. M. Rahman, “High-performance digital PI current regulator for EV switched reluctance motor drives,” IEEE Trans. Ind. Appl., vol. 39, no. 4, pp. 1118-1126, Jul./Aug. 2003.

A Frequency Adaptive Phase Shift Modulation Control Based LLC Series Resonant Converter for Wide Input Voltage Applications

ABSTRACT

This paper presents an isolated LLC series resonant DC/DC converter with novel frequency adaptive phase shift modulation control, which suitable for wide input voltage (200-400V) applications. The proposed topology integrates two half-bridge in series on the primary side to reduce the switching stress to half of the input voltage. Unlike the conventional converter, this control strategy increases the voltage gain range with ZVS to all switches under all operating voltage and load variations. Adaptive frequency control is used to secure ZVS in the primary bridge with regards to load change. To do so, the voltage gain becomes independent of the loaded quality factor. In addition, the phase shift control is used to regulate the output voltage as constant under all possible inputs. The control of these two variables also significantly minimizes the circulating current, especially from the low voltage side, which increases the efficiency as compared to a conventional converter. Experimental results of a 1Kw prototype converter with 200-400V input and 48V output are presented to verify all theoretical analysis and characteristics.

KEYWORDS:

  1. LLC
  2. Resonant converter
  3. Frequency adaptive phase shift modulation control (FAPSM)
  4. Zero-Voltage-Switching (ZVS)
  5. Wide gain range.

SOFTWARE: MATLAB/SIMULINK

CIRCUIT DIAGRAM:

Fig. 1. Proposed LLC resonant converter.

EXPECTED SIMULATION RESULTS:

Fig. 2(a). Simulation waveforms of proposed converter under 400V input, 48V output and full load condition.

Fig. 2(b). Simulation waveforms of proposed converter under 200V input, 48V output and full load condition.

Fig. 2(c). Simulation waveforms of proposed converter under 400V input, 48V output and 20% load condition.

Fig. 2(d). Simulation waveforms of proposed converter under 200V input, 48V output and 20% load condition.

CONCLUSION

In this paper, a variable frequency phase shift modulation control for a DAB LLC resonant converter has been incorporated. This control strategy makes the converter operating at a wide gain range with ZVS over all load conditions. The combination of two half bridge connected in series on the inverter side reduces the voltage stress across each switch, which also makes the converter capable of operating at high-voltage applications. The voltage stresses remain half of the input voltage over all load variations. With the proposed control, the voltage gain becomes independent of Q and K values. Thus, the process of parameter design can be simplified. The magnetizing inductance has been calculated as high to reduce the conduction loss. It also reduced the circulating current (or, reactive power) from the secondary side even at light load condition, which increased the efficiency as compared to conventional DAB LLC resonant converter. The performance of the proposed LLC resonant converter is experimentally verified with 200-400V input and 48V output converter prototype. Therefore, the proposed converter becomes a good candidate for variable input and constant output voltage applications.

REFERENCES

  • Costinett, D. Maksimovic, and R. Zane, “Design and Control for High Efficiency in High Step-Down Dual Active Bridge Converters Operating at High Switching Frequency,” IEEE Transactions on Power Electronics, vol. 28, pp. 3931-3940, 2013.
  • P. Engel, N. Soltau, H. Stagge, and R. W. D. Doncker, “Dynamic and Balanced Control of Three-Phase High-Power Dual-Active Bridge DC-DC Converters in DC-Grid Applications,” IEEE Transactions on Power Electronics, vol. 28, pp. 1880-1889, 2013.
  • Krismer and J. W. Kolar, “Efficiency-Optimized High-Current Dual Active Bridge Converter for Automotive Applications,” IEEE Transactions on Industrial Electronics, vol. 59, pp. 2745-2760, 2012.
  • Z. Peng, L. Hui, S. Gui-Jia, and J. S. Lawler, “A new ZVS bidirectional DC-DC converter for fuel cell and battery application,” IEEE Transactions on Power Electronics, vol. 19, pp. 54-65, 2004.
  • Inoue and H. Akagi, “A Bidirectional DC-DC Converter for an Energy Storage System With Galvanic Isolation,” IEEE Transactions on Power Electronics, vol. 22, pp. 2299-2306, 2007.

 

Extended Range ZVS Active-Clamped Current-Fed Full-Bridge Isolated DC/DC Converter for Fuel Cell Applications: Analysis, Design, and Experimental Results

 

ABSTRACT:

This paper presents analysis and design of zero voltage switching (ZVS) active-clamped current-fed full-bridge isolated dc/dc converter for fuel cell applications. The designed converter maintains ZVS of all switches from full load down to very light load condition over wide input voltage variation. Detailed operation, analysis, design, simulation, and experimental results for the proposed design are presented. The additional auxiliary active clamping circuit absorbs the turn-off voltage spike limiting the peak voltage across the devices allowing the selection and use of low-voltage devices with low on-state resistance. In addition, it also assists in achieving ZVS of semiconductor devices. The converter utilizes the energy stored in the transformer leakage inductance aided by its magnetizing inductance to maintain ZVS. ZVS range depends upon the design, in particular the ratio of leakage and magnetizing inductances of the transformer. Rectifier diodes operate with zero-current switching. An experimental converter prototype rated at 500 W has been designed, built, and tested in the laboratory to verify the analysis, design, and performance for wide variations in input voltage and load.

KEYWORDS:

  1. Fuel cells
  2. High-frequency (HF) dc/dc converter
  3. Renewable energy systems
  4. Zero voltage switching (ZVS)

SOFTWARE: MATLAB/SIMULINK

CIRCUIT DIAGRAM:

Fig. 1. Active-clamped ZVS current-fed full-bridge dc-dc converter.

EXPECTED SIMULATION RESULTS:

Fig. 2. Simulation waveforms at Vin = 22 V and full load: (a) voltage vAB, leakage inductance current ilk, and magnetizing inductance current iLm (b) main switches’ currents iS1 and iS2, auxiliary switch’s current iSax and voltage across auxiliary capacitor VCa.

Fig. 3. Simulation waveforms at Vin = 41 V and 10% load: (a) voltage vAB, leakage inductance current ilk, and magnetizing inductance current iLm (b) main switches’ currents iS1 and iS2, auxiliary switch’s current iSax and voltage across auxiliary capacitor VCa.

Fig. 4. Experimental waveforms at Vin = 22 V and full load: (a) Voltage vAB (100 V/div) and leakage inductance current ilk (50 A/div), (b) main switch voltage vDS (50 V/div) and gate voltage vGS (10 V/div), (c) auxiliary switch voltage vDS (50 V/div) and gate voltage vGS (20 V/div), (d) main switch current iS1 (20 A/div), (e) auxiliary switch current iSax (20 A/div) and (f) magnetizing inductance current iLm (0.5 A/div).

Fig. 5. Experimental waveforms at Vin = 41 V and full load: (a) Voltage vAB (50 V/div) and leakage inductance current ilk (50 A/div), (b) main switch voltage vDS (50 V/div) and gate voltage vGS (10 V/div), (c) auxiliary switch voltage vDS (50 V/div) and gate voltage vGS (20 V/div), (d) main switch current iS1 (20 A/div), (e) auxiliary switch current iSax (10 A/div) and (f) magnetizing inductance current iLm (1 A/div).

Fig. 6. Experimental waveforms at Vin = 22 V and 20% load: (a) Voltage vAB (50 V/div) and leakage inductance current ilk (10 A/div), (b) main switch voltage vDS (50 V/div), gate voltage vGS (20 V/div) and current iS1 (10 A/div), (c) auxiliary switch voltage vDS (50 V/div) and gate voltage Vgs (10 V/div), (d) auxiliary switch current iSax (5 A/div) and (e) magnetizing inductance current iLm (0.5 A/div).

Fig. 7. Experimental waveforms at Vin = 41 V and 10% load. (a) Voltage vAB (50 V/div) and leakage inductance current ilk (10 A/div), (b) main  switch voltage vDS (50 V/div) and gate voltage vGS (10 V/div), (c) auxiliary  switch voltage vDS (50 V/div) and gate voltage vGS (10 V/div), (d) main switch current iS1 (10 A/div), (e) auxiliary switch current iSax (5 A/div) and (f) magnetizing inductance current iLm (1 A/div).

CONCLUSION:

To achieve ZVS for wide source voltage variation and varying output power/load while maintaining high efficiency has been a challenge, particularly for low-voltage higher current input applications. A ZVS active-clamped current-fed full bridge isolated converter has been restudied in this paper. The magnetizing inductance increases the leakage inductance current value at light load and therefore the energy stored in leakage inductance to maintain ZVS of main switches as well as auxiliary switch.

Detailed steady-state operation and analysis of current-fed full-bridge converter have been presented. Design to attain soft switching over an extended range of input voltage and load i.e., output power has been presented. Simulation results using PSIM 9.0.4 have been presented. An  experimental prototype of. the converter rated at 500Whas been designed, built, and tested for variations in input voltage and load in order to validate the analysis. Experimental results verify the accuracy of the analysis and show that the proposed configuration is able to maintain ZVS of all switches over a wide range of load and input voltage variation due to the variation in fuel flow and stack temperature. Theoretically, the converter is able to maintain ZVS till 20% load at 22 V and 5% load 41 V.

In a practical fuel cell application, when the load current drops due to reduced fuel flow, the light or reduced power below rated power is transferred at higher fuel cell voltage. It can be clearly seen and understood also from the fuel cell V I characteristic. If the load current or power is around 10% of the rated power, then the fuel cell stack voltage increases nearly to 41 V. Hence, the possibility of the condition Vin = 22 V at 10% load is only during transition period when load is suddenly changed from full load to 10% due to fuel flow adjustment. Hence, it is justifiable to have ZVS range of 20% load at low input voltage and below 10% at higher input voltage will cover the operating range at steady state. Rated converter efficiency of 94% is obtained for the developed lab prototype rated at 500 W. The converter has limitation that duty cycle of the main switch should be greater than 50%.

REFERENCES:

[1] S. Jain and V. Agarwal, “An integrated hybrid power supply for distributed generation applications fed by nonconventional energy sources,” IEEE Trans. Energy Convers., vol. 23, no. 2, pp. 622–631, Jun. 2008.

[2] Y. Lembeye, V. D. Bang, G. Lefevre, and J. P. Ferrieux, “Novel half-bridge inductive dc-dc isolated converters for fuel cell applications,” IEEE Trans. Energy Convers., vol. 24, no. 1, pp. 203–210, Mar. 2009.

[3] J. Mazumdar, I. Batarseh, N. Kutkut, and O. Demirci, “High frequency low cost dc-ac inverter design with fuel cell source home applications,” in Conf. Rec. IEEE IAS Annu. Meeting, Oct. 2002, vol. 2, pp. 789–794.

[4] J. Wang, F. Z. Peng, J. Anderson, A. Joseph, and R. Buffenbarger, “Low cost fuel cell converter system for residential power generation,” IEEE Trans. Power Electron., vol. 19, no. 5, pp. 1315–1322, Sep. 2004.

[5] R. Gopinath, S. Kim, J.-H. Hahn, P. N. Enjeti, M. B. Yeary, and J. W. Howze, “Development of a low cost fuel cell inverter system with DSP control,” IEEE Trans. Power Electron., vol. 19, no. 5, pp. 1256–1262, Sep. 2004.