Nine Level Symmetrical Modified Multi-Level Cascaded H-Bridge Inverter

 ABSTRACT:

In this paper, a 9-level symmetrical modified multi-level cascaded H-bridge inverter with reduced switch count is considered. The operation and control of 9-level inverter is discussed. This multilevel inverter uses four symmetrical DC input sources and twelve unidirectional power

semiconductor switches. The basic operation with equal width modulation and resistive and Resistive-Inductive loads are verified with the help MATLAB simulation. The simulation outputs are presented and confirm the operation of nine level inverter operations. Together with the traditional topologies and some other inverters, this inverter topology is capable to produce more number of output voltage levels by means of less number of power switches and driver circuits. Simulation results confirm the probability of this inverter topology

KEYWORDS:

1.      Multi-Level inverter

2.      Cascaded H-Bridge (CHB)

3.      Reduced number of switches

4.      Harmonics

5.      Modified H-bridge (MHB)

SOFTWARE: MATLAB/SIMULINK

CONCLUSION:

In this paper, a modified CHB 9-level symmetrical MLI with 4 DC voltage sources and 12 unidirectional switches was successfully studied with the help of MATLAB simulation. The operation of this topology of inverter is analyzed. The simulation results are at satisfactory level.

The harmonics in the output voltages are comparable with the other topologies in the literature. This topology of inverter required less number of switches could assure enhanced performance, efficiency, consistency and decrease in price and volume of the inverter. The performance of this inverter topology can be improved by employing harmonic elimination techniques.

REFERENCES:

 1. Nabae. A, Takahashi. I, and Akagi. H, “A New Neutral-point-clamped PWM inverter,” IEEE Transactions on Industry Applications, Vol. IA-17, pp. 518-523, 1981.

2. Lai. J.S, and Peng. F.z, “Multilevel Converters: A New Breed of Power Converters,” IEEE Transactions on Industry Applications, Vol. 32, pp. 509-517, 1996.

3. Hammond. P.W, “A New Approach to Enhance Power Quality for Medium Voltage AC Drives,” IEEE Transactions on Industry Applications, Vol. 33, pp. 202-208, 1997.

4. C.Ganavel, M. Rajavelan, P. Muthukumar, T. Baldwin Immanuel, “A performance Investigation of a Single Phase Multilevel Inverter Fed Nonlinear loads for Solar PV Applications,” International Journal of Engineering & Technology, Vol. 7, pp. 388-391, 2018.

5. V Kartikeyan, V Jamuna, “Hybrid control strategy for BCD topology based modular multilevel inverter,” Circuits and Systems, Vol.7, pp. 1441-1454, 2016.

A Modified Seven Level Cascaded H Bridge Inverter

ABSTRACT:

Presently Multilevel inverters are extensively used for high-voltage applications and their execution is exceptionally better to that of regular two-level inverters due to minimized harmonic distortion, lower electromagnetic interference and larger DC link voltages. Nevertheless certain shortcomings are faced such as adding in number of components and voltage balancing problem. In order to overcome these, a seven-level hybrid inverter has been proposed. This topology requires a lesser number of power switches which results in the decrease of multifaceted nature, add up to cost and weight of the inverter. Finally this can be able to generate near sinusoidal voltages and approximately fundamental frequency switching. The simulation and the experimental results of a modified cascaded seven level H bridge inverter with and without LC filter are presented for validation.

KEYWORDS:

1.      Cascaded H-bridge inverter (CHBI)

2.      Seven level hybrid inverter

3.      Asymmetrical DC sources

4.      Total harmonic distortion (THD)

5.      Pulse Width modulation (PWM)

6.      Multi-level Inverter

SOFTWARE: MATLAB/SIMULINK

CONCLUSION:

A modified cascaded seven level H-bridge inverter was fabricated which has the benefit of reduced THD, portability, and cost has compared to normal cascaded H-bridge inverter. Since the topology requires minimum switches, and low-cost real time interfacing device (Arduino) compared DSP, DSPACE, FPGA, etc., the overall expenditure for fabrication reduces. This paper envisages the working of proposed structure. An LC filter is introduced which helps in getting nearer to sinusoidal waveform. The concepts which are projected are verified through simulation and experimental results.

REFERENCES:

[1] E. Babaei and S.Hosseini, “Charge balance control methods for asymmetrical cascade multilevel converters”. In Proc. ICEMS, Seoul, Korea, 2007, pp, 74-79.

[2] K. Wang, Y. Li, Z. Zheng, and L. Xu, “Voltage balancing and fluctuation suppression methods of floating capacitors in a new modular multilevel converter,” IEEE Trans. Ind. Electron., vol. 60, no. 5, pp. 1943–1954,May 2013

[3] J. Napoles, A. J. Watson, and J. J. Padilla, “Selective harmonic mitigation technique for cascaded H-bridge converter with nonequal dc link voltages,” IEEE Trans. Ind. Electron., vol. 60, no. 5, pp. 1963–1971, May 2013.

[4] N. Farokhnia, S. H. Fathi, N. Yousefpoor, and M. K. Bakhshizadeh, “Minimisation of total harmonic distortion in a cascaded multilevel inverter by regulating of voltages dc sources,” IET Power Electron., vol. 5, no. 1, pp. 106–114, Jan. 2012.

[5] S. Mekhilef, M. N. Abdul Kadir, and Z. Salam, “Digital control of three phase three-stage hybrid multilevel inverter,” IEEE Trans. Ind. Informat., vol. 9, no. 2, pp. 719–727, May 2013.

Design and Performance Analysis of Three-Phase Solar PV Integrated UPQC

 ABSTRACT:

In this paper, the design and performance of a three phase solar PV (photovoltaic) integrated UPQC (PV-UPQC) are presented. The proposed system combines both the benefits of distributed generation and active power filtering. The shunt compensator of the PV-UPQC compensates for the load current harmonics and reactive power. The shunt compensator is also extracting maximum power from solar PV array by operating it at its maximum power point (MPP). The series compensator compensates for the grid side power quality problems such as grid voltage sags/swells by injecting appropriate voltage in phase with the grid voltage. The dynamic performance of the proposed system is simulated in Matlab-Simulink under a nonlinear load consisting of a bridge rectifier with voltage-fed load.

 KEYWORDS:

1.      Power Quality

2.      DSTATCOM

3.       DVR

4.       UPQC

5.      Solar PV

6.      MPPT

 SOFTWARE: MATLAB/SIMULINK

CONCLUSION:

The dynamic performance of three-phase PV-UPQC has been analyzed under conditions of variable irradiation and grid voltage sags/swells. It is observed that PV-UPQC mitigates the harmonics caused by nonlinear and maintains the THD of grid voltage, load voltage and grid current under limits of IEEE-519 standard. The system is found to be stable under variation of irradiation from 1000𝑊/𝑚2 to 600𝑊/𝑚2. It can be seen that PV-UPQC is a good solution for modern distribution system by integrating distributed generation with power quality improvement.

 REFERENCES:

[1] Y. Yang, P. Enjeti, F. Blaabjerg, and H. Wang, “Wide-scale adoption of photovoltaic energy: Grid code modifications are explored in the distribution grid,” IEEE Ind. Appl. Mag., vol. 21, no. 5, pp. 21–31, Sept 2015.

[2] B. Singh, A. Chandra and K. A. Haddad, Power Quality: Problems and Mitigation Techniques. London: Wiley, 2015.

[3] M. Bollen and I. Guo, Signal Processing of Power Quality Disturbances. Hoboken: Johm Wiley, 2006.

[4] P. Jayaprakash, B. Singh, D. Kothari, A. Chandra, and K. Al-Haddad, “Control of reduced-rating dynamic voltage restorer with a battery energy storage system,” IEEE Trans. Ind. Appl., vol. 50, no. 2, pp. 1295– 1303, March 2014.

[5] M. Badoni, A. Singh, and B. Singh, “Variable forgetting factor recursive least square control algorithm for DSTATCOM,” IEEE Trans. Power Del., vol. 30, no. 5, pp. 2353–2361, Oct 2015.

Design and Performance Analysis of Three-PhaseSolar PV Integrated UPQC

ABSTRACT:

This paper deals with the design and performance analysis of a three-phase single stage solar photovoltaic integrated unified power quality conditioner (PV-UPQC). The PV-UPQC consists of a shunt and series connected voltage compensators connected back to back with common DC-link.The shunt compensator performs the dual function of extracting power from PV array apart from compensating for load current harmonics. An improved synchronous reference frame control based on moving average filter is used for extraction of load active current component for improved performance of the PVUPQC. The series compensator compensates for the grid side power quality problems such as grid voltage sags/swells. The compensator injects voltage in-phase/out of phase with point of common coupling (PCC) voltage during sag and swell conditions respectively. The proposed system combines both the benefits of clean energy generation along with improving power quality. The steady state and dynamic performance of the system are evaluated by simulating in Matlab-Simulink under a nonlinear load. The system performance is then verified using a scaled down laboratory prototype under a number of disturbances such as load unbalancing, PCC voltage sags/swells and irradiation variation.

KEYWORDS:

1.      Power Quality

2.      Shunt compensator

3.      Series compensator

4.      UPQC

5.      Solar PV

6.      MPPT

SOFTWARE: MATLAB/SIMULINK

CONCLUSION:

The design and dynamic performance of three-phase PVUPQC have been analyzed under conditions of variable irradiation and grid voltage sags/swells. The performance of the system has been validated through experimentation on scaled down laboratory prototype. It is observed that PVUPQC mitigates the harmonics caused by nonlinear load and maintains the THD of grid current under limits of IEEE-519 standard. The system is found to be stable under variation of irradiation, voltage sags/swell and load unbalance. The performance of d-q control particularly in load unbalanced condition has been improved through the use of moving average filter. It can be seen that PV-UPQC is a good solution for modern distribution system by integrating distributed generation with power quality improvement.

REFERENCES:

[1] B. Mountain and P. Szuster, “Solar, solar everywhere: Opportunities and challenges for australia’s rooftop pv systems,” IEEE Power and Energy Magazine, vol. 13, no. 4, pp. 53–60, July 2015.

[2] A. R. Malekpour, A. Pahwa, A. Malekpour, and B. Natarajan, “Hierarchical architecture for integration of rooftop pv in smart distribution systems,” IEEE Transactions on Smart Grid, vol. PP, no. 99, pp. 1–1, 2017.

[3] Y. Yang, P. Enjeti, F. Blaabjerg, and H. Wang, “Wide-scale adoption of photovoltaic energy: Grid code modifications are explored in the distribution grid,” IEEE Ind. Appl. Mag., vol. 21, no. 5, pp. 21–31, Sept 2015.

[4] M. J. E. Alam, K. M. Muttaqi, and D. Sutanto, “An approach for online assessment of rooftop solar pv impacts on low-voltage distribution  networks,” IEEE Transactions on Sustainable Energy, vol. 5, no. 2, pp.663–672, April 2014.

[5] J. Jayachandran and R. M. Sachithanandam, “Neural network-based control algorithm for DSTATCOM under nonideal source voltage and varying load conditions,” Canadian Journal of Electrical and Computer Engineering, vol. 38, no. 4, pp. 307–317, Fall 2015.

Active Power Filter for Power Quality in Grid Connected PV-System using an Improved Fuzzy Logic Control MPPT

ABSTRACT:

 Photovoltaic (PV) system is one of the most important and fastest developing renewable energy sources in the globe recently. Since most of the grids contain a power converter system based on power electronic components and several nonlinear loads, which deteriorate power quality. In this paper, the aim is to propose a solution to solve this problem using a shunt active filter SAPF based on efficiency method called Synchronous Detection Method SDM, in the identification of the harmonic currents. The SAPF controller consists of an inverter which works as a multi-functional device, it adopted to interface PV system with the electrical grid and at the same time, to eliminate harmonics generated by nonlinear loads with reactive power compensation. To extract the maximum power in photovoltaic system a fuzzy logic control is proposed to solve a fast irradiation change problem which is compared to the conventional P&O algorithm. The simulation results using Matlab /Simulink show that the fuzzy logic control MPPT gives the best performance with small oscillation in output power, at the same time. The proposed control strategy of SAPF performs the power quality in grid-connected photovoltaic system with smaller total harmonic distortion, grid synchronization and unity power factor.

KEYWORDS:

 

1.      Shunt Active Power Filter

2.      Grid connected PV system

3.      MPPT (P&O)

4.       Fuzzy Logic controller

5.       Power quality enhancement

SOFTWARE: MATLAB/SIMULINK

CONCLUSION:

This paper presents the simulation performance of a three-phase inverter-based multifunction PV power system with shunt active filtering capability. The simulation results show that the proposed multifunctional grid-connected PV power system is efficient for maximum PV power injection to the grid while filtering the current harmonics and compensating reactive power caused by nonlinear loads. Furthermore, a fuzzy logic controller based on P&O MPPT is applied in the PV system and compared with the conventional P&O algorithm. Under fast irradiation this FLC technique represents a good performance and increases the system efficiency. The simulation results show that the power control with multifunctional inverter is mostly achieved because in the daytime with intensive irradiation, the solar PV power system provides active power together with active power filter functionality. At night and/or during poor irradiation times, the active power required by the loads is supplied from the utility and the power quality is improving by SAPF.

REFERENCES:

[1] B. Boukezata, J. P. Gaubert, A. Chaoui and M. Hachemi. “Générateur photovoltaique avec une commande directe de puissance connecté et avec adjonction de services au réseau de distribution,” Symposium de Genie Electrique EE-EPF. 2016 Grenoble

[2] A .Kalair ,N.Abas, A.R.Kalair, Z.Saleem,N.Khan. “Review of harmonic analysis, modeling and mitigation techniques”, 78 pp; 1152-1187 . 2017.

[3] M.TALI, A.Obbadi, A.Elfajri, Y.Errami. “Passive Filter for harmonics mitigation in standalone pv system for nonlinear load”, IRSEC14 ,978- 1-4799-7335-4, october 2014.

[4] B.Singh and K.Al haddad, “A review of active filter for power quality improvement”, IEEE. Vol: 46 , Issue: 5 , pp: 960 – 971.Oct1999.

[5] B.Boukezata, A.Chaoui, “Power Quality Improvement by an Active Power Filter in Grid-connected Photovoltaic systems with Optimized Direct Power Control Strategy”, Electric Power Components and Systems , vol:44, Issue :18 , pp:2036-2047, Oct 2016.

Evaluation of Level-Shifted and Phase-Shifted PWM Schemes for Seven Level Single-Phase Packed U Cell Inverter

ABSTRACT:

 An evaluation of level shifted and phase shifted triangular and saw tooth carrier modulation schemes for a seven level packed U cell (PUC) inverter is presented in this paper. The investigated PUC is the recently introduced topology for multilevel inverter having reduced switch count in comparison to the conventional topologies of multilevel inverters. The PUC inverter has six switches for 7 level inverter which is very less in comparison to the conventional topologies. In this paper, the level-shifted pulse width modulation (LS-PWM) and phase-shifted PWM (PS-PWM) for triangular and saw tooth carrier are presented and compared. A comparative harmonic analysis for all the cases is performed and results are presented in the paper. The difference in harmonics of the two modulation methods given by the theoretical approach for both the carrier is validated by the experimental results. DC voltage controller and load current controller of the PUC inverter are also designed and presented. The investigated PUC topology is tested in dynamic and steady state conditions and results obtained are presented. The analysis is done and validated using simulation in MATLAB® Simulink environment and experimental approaches using FPGA platform.

 KEYWORDS:

1.      Level shift

2.      Multilevel inverter

3.      Modulation

4.       Phase shift

5.       PI controller

6.      PUC inverter

SOFTWARE: MATLAB/SIMULINK

CONCLUSION

The paper has presented the comparison of different PWM schemes which can be applied to the PUC inverter. Investigating the suitable modulation schemes is very essential with respect to local grid integration, as the power quality is directly dependent on THD. Triangular carrier based PWM schemes is exhibiting the better result than the saw tooth carrier based PWM schemes as the triangular level shifted carrier PWM scheme is better as compared to saw tooth level shifted carrier because in triangular level shifted carrier both edges (falling and rising) of pulses are modulated which improves the harmonic spectrum. However, in the saw tooth level shifted carrier only rising edges are modulated. Hence triangular level shifted carrier PWM scheme can be applied for integrating the PUC inverter with PV and local grid systems. Triangular level shifted carrier PWM scheme for PUC inverter has been suggested based on observing the THD in voltage and current which are respectively just 17.92% and 2.43%. The whole system i.e. solar panel, boost converter with PUC inverter will be very cost effective, besides having good reliability and power quality as it has the minimum number of power electronics devices compared to previously introduced multilevel inverter topologies. With reduced number of capacitors and power switches seven levels of voltages have been achieved for PUC inverter.

REFERENCES:

[1] F. A. Rahman, M. M. A. Aziz, R. Saidur, W. A. A. Bakar, M. R. Hainin, R. Putrajaya, and N. A. Hassan, “Pollution to solution: Capture and sequestration of carbon dioxide (CO2) and its utilization as a renewable energy source for a sustainable future”, Renewable and Sustainable Energy Reviews,vol. 71, pp. 112-126, May 2017.

[2] Y. Yang, A. Sangwongwanich, and F. Blaabjerg, “Design for reliability of power electronics for grid-connected photovoltaic systems,” in CPSS Transactions on Power Electronics and Applications, vol. 1, no. 1, pp. 92-103, Dec. 2016..

[3] J. Rodriguez, J.-S. Lai, and F. Z. Peng, “Multilevel inverters: a survey of topologies, controls, and applications,” Industrial Electronics, IEEE Transactions on, vol. 49, pp. 724-738, 2002.

[4] Q. M. Attique, Y. Li, and K. Wang, “A survey on space-vector pulse width modulation for multilevel inverters,” in CPSS Transactions on Power Electronics and Applications, vol. 2, no. 3, pp. 226-236, Sept. 2017.

[5] Z. Mohzani, B. P. McGrath, and D. G. Holmes, “A generalized natural balance model and balance booster filter design for three-level Neutral- Point-Clamped converters,” in IEEE Transactions on Industry Applications, vol. 51, no. 6, pp. 4605-4613, Nov.-Dec. 2015.

Comprehensive Review on Solar, Wind and Hybrid Wind-PV Water Pumping Systems-An Electrical Engineering Perspective

ABSTRACT:

 In India, the demand for water is continuously increasing due to the growing population. Approximately 16.5% of all country’s electricity used to pump this water is from fossil fuels leading to increased pump Life Cycle Cost (LCC) and Green House Gas (GHG) emissions. With the recent advancement in power electronics and drives, renewables like solar photovoltaic and wind energy are becoming readily available for water pumping applications resulting in the reduction of GHG emissions. Recently, research towards AC motor based Water Pumping Systems (WPS) has received a great emphasis owing to its numerous merits. Further, considering the tremendous acceptance of renewable sources, especially solar and wind, this paper provides a detailed review of single-stage and multi-stage WPS consisting of renewable source powered AC motors. The critical review is performed based on the following figure of merits, including the type of motor, power electronics interface and associated control strategies. Also, to add to the reliability of solar PV WPS, hybrid Wind-PV WPS will be discussed in detail. Readers will be presented with the state-of-the-art technology and research directions in Renewable Energy-based WPS (REWPS) to improve the overall system efficiency and hence reduce the payback period.

KEYWORDS:

 

1.      AC motor

2.       Hybrid wind-PV system

3.       Multi-stage solar water pump

4.      Pump life cycle cost

5.       Single-stage solar water pump

6.       Water pumping system

SOFTWARE: MATLAB/SIMULINK

CONCLUSION

This paper has attempted to consolidate the research in renewable energy-based water pumping systems. Exhaustive research with the primary focus in the field of electrical engineering like power electronics interface, the motor used for pumping and mainly the control strategy employed for the effective energy utilization of the renewables is presented. The following are the conclusions of this work:

• Investigations conducted on multi-stage SPWPSs, single-stage SPWPSs, Wind WPSs and hybrid Wind-PV systems have been reviewed in detail.

• In each of the systems mentioned above, various research avenues have been conferred to the reader namely, the power electronics interface, MPPT algorithms, type of the motor, motor control algorithms and sensors used for the algorithms.

• Findings of several investigations conducted to compare the performance of multi-stage WPS with single-stage WPS have been presented to weigh the performance of the WPSs.

• Niche areas in REWPSs have been indicated to readers to pursue future research.

This review paper is an effort to guide researchers consolidating work in the area of the REWPS with an emphasis on aspects of electrical engineering (type of motor, power electronics interface and control strategies). In a country like India, which suffers irregular monsoons, harnessing renewable energy sources efficiently to fulfill the requirement of water will be the dire need of the near future. Also, the geographical location of the nation is favorable to produce energy from renewable sources like sunlight and wind. Hence, the authors are in the developmental work of control strategies for REWPSs.

 REFERENCES:

[1] K. B. LTD. (2019, Mar. 28). Life Cycle Cost Analysis – Systematic Approach. [Online]. Available: http://ashraeindia.org/pdf/KBL presenta-tion3.pdf/.

[2] C. Gopal, M. Mohanraj, P. Chandramohan, and P. Chandrasekar, “Renewable energy source water pumping systems—A literature review,” in Renewable and Sustainable Energy Reviews, vol. 25, no. 5, pp. 351–370, Sept. 2013.

[3] P. Periasamy, N. Jain, and I. Singh, “A review on development of photovoltaic water pumping system,” in Renewable and Sustainable Energy Reviews, vol. 43, pp. 918–925, Mar. 2015.

[4] S. Chandel, M. N. Naik, and R. Chandel, “Review of solar photovoltaic water pumping system technology for irrigation and community drinking water supplies,” in Renewable and Sustainable Energy Reviews, vol. 49, no. 9, pp. 1084–1099, May 2015.

[5] R. Rawat, S. Kaushik, and R. Lamba, “A review on modeling, design methodology and size optimization of photovoltaic based water pumping, standalone and grid connected system,” in Renewable and Sustainable Energy Reviews, vol. 57, pp. 1506–1519, Jan. 2016.

Bidirectional Isolated Dual-Active-Bridge (DAB) DC-DC Converters Using 1.2-kV 400-A SiC-MOSFET Dual Modules

 ABSTRACT:

 This paper describes the 750-Vdc, 100-kW, 20- kHz bidirectional isolated dual-active-bridge (DAB) dc dc converters using four 1.2-kV 400-A SiC-MOSFET dual modules with or without Schottky barrier diodes (SBDs). When no SBD is integrated into each dual module, the conversion efficiency from the dc-input to the dc-output terminals is accurately measured to be 98.0% at the rated-power (100 kW) operation, and the maximum conversion efficiency is as high as 98.8% at 41-kW operation, excluding the gate drive and control-circuit losses from the total power loss. The bidirectional isolated DAB dc-dc converters are so flexible that series and/or parallel connections of their individual input and output terminals make it easy to expand the voltage and current ratings for various applications such as the so-called “solid-state transformer” or “power electronic transformer.”

KEYWORDS:

1.      Bidirectional isolated dc-dc converters

2.      Conversion efficiency

3.      Dual-active-bridge configuration

4.      SiC MOSFET modules

SOFTWARE: MATLAB/SIMULINK

CONCLUSION

This paper has designed, built, and tested two 750-Vdc, 100-kW, 20-kHz bidirectional isolated dual-active-bridge (DAB) dc-dc converters using four 1.2-kV, 400-A SiC-MOSFET dual modules with and without SBDs are used, the maximum conversion efficiency from the dc- input terminals to the dc-output terminals is as high as 98.8. at 41 kW, and 98.0% at 100 kW, which are calculated from the accurately-measured overall power loss excluding gate drive and control circuit losses. When the next generation trench-gate Sic-MOSFET modules come across, the conversion efficiency of a well designed DAB dc-dc converter is expected to be higher than 99% in a broad power range, even at the rated power. Series and/or parallel connections of multiple DAB dc-dc converters would make it easy to expand the voltage and/or current ratings as if the converter were operating as a single high-power DAB dc-dc converter. In particular, the input series and output-parallel connections show considerable promise as a dc-dc converter for medium-voltage high power battery energy storage systems and an interface circuit between two dc power networks with different dc voltages.

REFERENCES:

[1] R. W. De Doncker, D. M. Divan, and M. H. Kheraluwala, “A three phase soft-switched high-power-density dc/dc converter for high power applications,” IEEE Trans. Ind. Appl., vol. 27, no. 1, pp.63-73,Jan/Feb.1991.

 [2] M. H. Kheraluwala, R. W. Gascoigne, D. M. Divan, and E. D. Baumann, “Performance characterization of a high-power dual active bridge dctodc converter,” IEEE Trans. Ind. Appl.,vol.28,no.6, pp. 1294–1301, Nov./Dec. 1992.

[3] R. L Steigerwald, R. W. De Doncker, and M. H. Kheraluwala, “A comparison of high-power dc-dc soft-switched converter topologies,” IEEE Trans. Ind. Appl., vol. 32, no. 5, pp. 1139–1145, Sept/Oct.1996.

[4] S. Inoue and H. Akagi, “A bidirectional isolated dc-dc converter as a core circuit of the next-generation medium-voltage power conversion system,” IEEE Trans. Ind. Appl., vol. 22, no. 2, pp. 535–542, Mar. 2007.

[5] S. Inoue and H. Akagi, “A bidirectional dc-dc converter for an energy storage system with galvanic isolation,” IEEE Trans. Power Electron vol.22,no.6,pp.2299-2306.Nov.2007