Publications
Publications
Peer-reviewed Journals
N. Deshmukh, S. Prabhakar, and S. Anand, “Power loss reduction in buck converter based active power decoupling circuit,” IEEE Transactions on Power Electronics, pp. 1–1, 2020.
Title: Power loss reduction in buck converter based active power decoupling circuit
Authors: Nachiketa Deshmukh; Siva Prabhakar; Sandeep Anand
Published in: IEEE Transactions on Power Electronics ( Volume: 36, Issue: 4, April 2021)
Page(s): 4316 - 4325
INSPEC Accession Number: 20209479
Date of Publication: 18 September 2020
Abstract
Active power decoupling (APD) circuits enable the use of long lifetime capacitors (film or ceramic capacitors) in single-phase power converters. Owing to the inclusion of the APD circuits, the literature reports 1.5%-1.8% drop in efficiency of single-phase converter at rated power. This reduction in conversion efficiency is one of the significant challenges in the practical use of APD circuits. This article proposes an approach to reduce the power loss in the bidirectional buck converter based APD circuit. This approach is presented with the help of analytical calculations and graphical representation of operation of APD circuit. The proposed approach requires rapid variation in the average voltage of the buffer capacitor with a change in inverter power. To achieve this, an enhanced control technique is suggested with a duty ratio injection controller. The steady state and transient response of the proposed control technique are validated with simulation and experimentation. Further, the reduction in power losses realized by the proposed approach is verified with the help of a developed laboratory prototype. The proposed approach obtains up to 1% improvement in efficiency of single-phase converter at rated power, when compared with existing APD approaches.
Patent
Title: On-board charging system for electric vehicles
Inventors: Siva Prabhakar, Nachiketa Deshmukh, Dr. Shiladri Chakraborty, Prof. Sandeep Anand
Applicants: Varroc Engineering Limited, Indian Institute of Technology Bombay
Application No.: PCT/IN2023/051078
Publication No.: WO2024110989A1
Filed: 22 November 2023
Published: 30 May 2024
Jurisdiction: Worldwide (PCT - International Application)
Language: French (among others)
Application Type: International (PCT) – submitted under the Patent Cooperation Treaty for global recognition.
Abstract
Disclosed is an on-board charging system for electric vehicles. The on-board charging system comprises an on-board charger (OBC) having an input AC port, a first output port operatively coupled to a first battery, and a second output port operatively coupled to a second battery. The OBC includes a three-port DC-DC converter coupled to an output of a rectifier stage of the on-board charging system, the first output port, and the second output port; two two-winding transformers; and a power transfer sub-system to transfer power across the three ports of the DC-DC converter. The three-port DC-DC converter comprises a first converter sub-system, a second converter sub-system, and a third converter sub-system connected to the two two-winding transformers and the power transfer sub-system. Further, the power transfer sub-system comprises two inductors or a single inductor.
Non-peer reviewed conference proceedings
S. Prabhakar, N. Deshmukh, and S. Anand, “Stability improvement of series stacked buffer circuit in single phase solar inverter,” 2020 IEEE International Conference on Power Electronics, Drives, and Energy Systems (PEDES), Jaipur, India .
Title: Stability improvement of series stacked buffer circuit in single phase solar inverter
Authors: Siva Prabhakar; Nachiketa Deshmukh; Sandeep Anand
Published in: 2020 IEEE International Conference on Power Electronics, Drives and Energy Systems (PEDES)
Date of Conference: 16-19 Dec. 2020
Date Added to IEEE Xplore: 24 March 2021
DOI: 10.1109/PEDES49360.2020.9379650
Publisher: IEEE Conference Location: Jaipur, India
Abstract
Small scale rooftop solar photovoltaic (PV) installations witnessed significant growth in the past decade. A single phase solar inverter is an integral part of these systems. In single phase systems, there is an instantaneous mismatch between PV power and grid power, which is conventionally supported by Aluminum Electrolytic Capacitors (AECs). These capacitors reduce the expected lifetime of PV inverter due to their rapid degradation at high operating temperatures. Series Stacked Buffer (SSB) circuit is considered as one of the best replacement for these capacitors. The SSB circuit facilitates power dense and reliable realization of solar inverter. However, the operation of SSB circuit is strongly dependent on small signal equivalent series resistance (SS-ESR) value of PV array. This dependence may lead to unstable operation when the value of SS-ESR becomes low. This also reduces the viable range of operation of PV inverter. In this work, the instability issue in the SSB circuit with a source having low SS-ESR is analytically established. Further, a control technique to improve stability of the system is proposed. The proposed controller extends the operation of PV inverter to a wide range of SS-ESR values. The controller performance is validated with the help of circuit simulations in MATLAB/Simulink.
2. N. Deshmukh, S. Prabhakar, and S. Anand, “Conductance emulation based control for series stacked energy buffer,” 2020 IEEE International Conference on Power Electronics, Drives, and Energy Systems (PEDES), Jaipur, India.
Title: Conductance emulation based control for series stacked energy buffer
Authors: Nachiketa Deshmukh; Siva Prabhakar; Sandeep Anand
Published in: 2020 IEEE International Conference on Power Electronics, Drives and Energy Systems (PEDES)
Date of Conference: 16-19 Dec. 2020
Date Added to IEEE Xplore: 24 March 2021
DOI: 10.1109/PEDES49360.2020.9379869
Publisher: IEEE Conference Location: Jaipur, India
Abstract
In single phase power conversion, an energy storage is required to supply the power mismatch between instantaneous ac power and dc power. The Series Stacked Energy Buffer (SSEB) is an active energy storage that requires a low value of capacitance to support the said power mismatch and ensure a ripple free voltage at dc port. The SSEB also incurs small power losses and occupies low volume. However, the existing control techniques for SSEB require dc-link current sensing and noise-prone differentiation function. To address these challenges, this paper proposes a conductance emulation control for SSEB circuit. The value of emulated conductance is changed to control the real power absorbed by the SSEB circuit. In result, the entire SSEB network becomes equivalent to a controlled frequency dependent conductance. This facilitates a straightforward analysis and intuitive understanding on the effect of SSEB topology on the operation of the system. This effect is further examined with a small signal model of SSEB circuit. The load transient and steady-state performance of the proposed controller are supported by simulation studies using MATLAB/Simulink.
3. N. Deshmukh, S. Prabhakar, and S. Anand, “DC-link voltage feed forward controller for buck active power decoupling circuit,” 2020 IEEE International Conference on Power Electronics, Drives, and Energy Systems (PEDES), Jaipur, India.
Title: Stability Improvement of Series Stacked Buffer Circuit in Single Phase Solar Inverter
Published in: 2020 IEEE International Conference on Power Electronics, Drives and Energy Systems (PEDES)
Date of Conference: 16-19 Dec. 2020
Date Added to IEEE Xplore: 24 March 2021
DOI: 10.1109/PEDES49360.2020.9379485
Publisher: IEEE Conference Location: Jaipur, India
Abstract
Single phase ac to dc power converter generally requires an energy storage element to support instantaneous power difference between dc side and ac side. An option to use a large value of electrolytic capacitors as energy storage is not viable due to their limited lifetime and poor reliability. Hence, in reliable rectifier designs, Active Power Decoupling (APD) circuits are preferred to allow the use of long life ceramic or film capacitors. The use of bidirectional buck converter as APD circuit is advantageous due to its simple control and low switch count. With conventional controller for buck APD circuit, dc-link voltage fluctuations during load changes are often large. This may result in maloperation of dc loads and increase the voltage rating of power devices in rectifier. To address said challenges, this study ideates a dc-link voltage feed
4. N. Deshmukh, S. R. Sahoo, S. Prabhakar and S. Anand, "A Three Terminal Active Power Decoupling Circuit for Single-Phase Single-Stage On-Board Charger," 2021 National Power Electronics Conference (NPEC), 2021, pp. 1-6, doi: 10.1109/NPEC52100.2021.9672515.
Title: A Three Terminal Active Power Decoupling Circuit for Single-Phase Single-Stage On-Board Charger
Published in: 2021 National Power Electronics Conference (NPEC)
Date of Conference: 15-17 December 2021
INSPEC Accession Number: 21573189
Date Added to IEEE Xplore: 17 January 2022
DOI: 10.1109/NPEC52100.2021.9672515
Publisher: IEEE
Conference Location: Bhubaneswar, India
Abstract
Single-phase single-stage On-Board Charger (OBC) for Electric Vehicles (EVs) are advantageous due to their high efficiency and low component count. The output power provided by this OBC has a second harmonic ripple component. This ripple component of power causes overheating of the Li-ion battery pack and reduces its round trip efficiency by up to 2 % as reported in literature. The conventional techniques for decoupling the second harmonic ripple power may not work satisfactorily due to very low impedance of battery pack. This paper proposes a Three Terminal Active Power Decoupling Circuit (3T-APDC) to decouple the second harmonic ripple power. The proposed circuit ensures charging of battery pack with almost ripple free power. It consists of a series blocking capacitor and two bidirectional power converters. These converters process a fraction of total power supplied to the battery pack. This significantly limits the additional power loss and cost of the proposed 3T-APDC. Simulation studies are conducted to evaluate the proposed circuit in accordance with TATA Nexon EV's specifications for single-phase OBC. As per the reported simulation results, the proposed circuit limits the ripple in battery current close to 5 %
5. S. Prabhakar, N. Deshmukh, S. Anand, S. Chakraborty, M. Deo and P. Chaudhary, "Design Methodology to Improve Efficiency of Semi-dual Active Bridge Converter," 2024 IEEE Transportation Electrification Conference and Expo (ITEC), Chicago, IL, USA, 2024, pp. 1-6, doi: 10.1109/ITEC60657.2024.10598930.
Title: Design Methodology to Improve Efficiency of Semi-dual Active Bridge Converter
Published in: 2024 IEEE Transportation Electrification Conference and Expo (ITEC)
Date of Conference: 19-21 June 2024
Date Added to IEEE Xplore: 24 July 2024
DOI: 10.1109/ITEC60657.2024.10598930
Publisher: IEEE
Conference Location: Chicago, IL, USA
Abstract:
Semi-dual active bridge converters (SDABCs) find their use in cost-competitive applications requiring unidirectional power flow. However, the efficiency of SDABC with single phase shift (SPS) control is poor at light-load conditions. In this paper, a design approach is suggested to improve the light-load efficiency of SDABC. Here, transformer turns ratio and leakage inductance are selected to achieve a relatively flat efficiency profile over a wide load range. The proposed design approach utilizes the capability of SDABC to operate in a discontinuous conduction state to improve the light-load efficiency. The efficiency improvement of SDABC with the proposed methodology is validated using analytical calculations and experimentation studies. For 1.5 kW laboratory prototype, SDABC with conventional design has 48 % efficiency at 44 % load. At the same operating conditions, SDABC with the proposed design has 97 % efficiency.
6. N. Deshmukh et al., "Extended High Efficiency Operation of Semi - Active Half-Bridge DC-DC Converter," 2024 IEEE International Communications Energy Conference (INTELEC), Bengaluru, India, 2024, pp. 1-6, doi: 10.1109/INTELEC60315.2024.10679037.
Title: Extended High Efficiency Operation of Semi - Active Half-Bridge DC-DC Converter
Published in: 2024 IEEE International Communications Energy Conference (INTELEC)
Date of Conference: 04-07 August 2024
Date Added to IEEE Xplore: 24 September 2024
DOI: 10.1109/INTELEC60315.2024.10679037
Publisher: IEEE
Conference Location: Bengaluru, India
Abstract:
The semi-active half-bridge converter (SAHBC) is a promising option for cost-competitive electric vehicle (EV) charging systems. However, the conversion efficiency of SAHBC is poor at part load conditions. This is attributed to the small duration of current supply to the output and large duration of circulating current in the transformer. This paper proposes an efficiency improvement technique to address this issue. The proposed technique is a combination of design of SAHBC and strategic changes in its switching frequency. The design of SAHBC selects the turns ratio and leakage inductance. Whereas, the switching frequency of SAHBC is strategically increased to enhance the duration of output current transfer. This increase in switching frequency is easily implementable due to complete ZVS and ZCS operation of the power devices. A step-by-step methodology for the proposed technique and its application to a 2.4 kW EV charger are included in the paper. The presented analysis shows that the proposed technique achieves up to 9.3 % improvement in conversion efficiency at part load conditions. The operation of proposed technique is also validated with the help of a 2.4 kW laboratory prototype.
7. N. Deshmukh et al., "Diode Emulation Control for Efficiency Improvement of Dual Active Bridge Converters," 2024 IEEE International Communications Energy Conference (INTELEC), Bengaluru, India, 2024, pp. 1-6, doi: 10.1109/INTELEC60315.2024.10679038.
Title: Diode Emulation Control for Efficiency Improvement of Dual Active Bridge Converters
Published in: 2024 IEEE International Communications Energy Conference (INTELEC)
Date of Conference: 04-07 August 2024
Date Added to IEEE Xplore: 24 September 2024
DOI: 10.1109/INTELEC60315.2024.10679038
Publisher: IEEE
Conference Location: Bengaluru, India
Abstract:
The literature suggests discontinuous conduction mode (DCM) operation for efficiency improvement of dual active bridge (DAB) converters. These techniques require zero voltage across the primary side of the transformer to ensure DCM at part load conditions. Hence, these techniques are not implementable in cost-competitive DAB converters with half-bridge circuit on the primary side (cost-effective up to few kWs). This paper proposes diode emulation control (DEC) for DAB with half-bridge circuit on the primary side. The proposed technique ensures DCM at part load with a simple single phase shift control. The DEC is easily implemented with synchronous rectifier ICs, which are simple to use and popularly available. The design of transformer turns ratio and leakage inductance as per proposed technique are also added. The changes required in the closed loop control of the DAB due to diode emulation on secondary side are also highlighted. When compared to the conventional control, the proposed technique achieves up to 2.5 % improvement in efficiency at part load conditions. The proposed technique is experimentally validated with a 440 W laboratory prototype.
8. S. Prabhakar, S. Chakraborty and S. Anand, "Design of Fully Soft-Switched Semi-Dual Active DC-DC Converter for Battery Charging Application," 2025 IEEE Applied Power Electronics Conference and Exposition (APEC), Atlanta, GA, USA, 2025, pp. 69-76, doi: 10.1109/APEC48143.2025.10977566.
Title: Design of Fully Soft-Switched Semi-Dual Active DC-DC Converter for Battery Charging Application
Published in: 2025 IEEE Applied Power Electronics Conference and Exposition (APEC)
Date of Conference: 16-20 March 2025
Date Added to IEEE Xplore: 01 May 2025
DOI: 10.1109/APEC48143.2025.10977566
Publisher: IEEE
Conference Location: Atlanta, GA, USA
Abstract:
Semi-dual active bridge converter (SDABC), a unidirectional variant of dual active bridge converter, is popular for battery charging applications. However, it suffers an efficiency dip at different charging instants of the constant current-constant voltage (CC-CV) charging profile, especially at low voltage-medium power conditions of CC mode and high voltage-low power conditions of CV mode. These dips are due to the loss of soft switching at these charging instants. To address this, a design-based approach focusing on transformer turns ratio and leakage inductance is proposed in this digest. The proposed design methodology achieves zero-voltage switching (ZVS) under low voltage-medium power conditions by properly selecting leakage inductance and under high voltage-low power conditions by carefully choosing the turns ratio. In addition, the discontinuous conduction property of SDABC is explored to reduce transformer circulating current at light loads, thereby enhancing efficiency by reducing conduction loss. Analytical results demonstrate that the proposed design enables soft switching across the CC-CV profile and improves efficiency. Validation with a 1.5 kW laboratory-developed hardware prototype of OBC charging 96 V battery shows a 61 % efficiency improvement at the start of CC mode and an improvement of 66 % at 30 % loading at CV mode with the proposed design compared to the conventional design.
9. S. De, S. Prabhakar and S. Anand, "A Plug and Play Three Terminal Active Power Decoupling Circuit," PCIM Conference 2025; International Exhibition and Conference for Power Electronics, Intelligent Motion, Renewable Energy and Energy Management, Nürnberg, Germany, 2025, pp. 1431-1438, doi: 10.30420/566541186.
Title: A Plug and Play Three Terminal Active Power Decoupling Circuit
Published in: PCIM Conference 2025; International Exhibition and Conference for Power Electronics, Intelligent Motion, Renewable Energy and Energy Management
Date of Conference: 06-08 May 2025
Date Added to IEEE Xplore: 30 June 2025
Print ISBN:978-3-8007-6541-6
DOI: 10.30420/566541186
Publisher: VDE
Conference Location: Nürnberg, Germany
Abstract:
The widespread adoption of electric vehicles (EVs) and solar photovoltaic (PV) systems has increased the demand for efficient and reliable single-phase inverters. However, these inverters introduce doubleline frequency ripple current, which disrupts maximum power point tracking (MPPT) in PV systems and accelerates battery pack degradation in EVs. Conventional two terminal active power decoupling (APD) circuits create a low-impedance alternate path to divert this ripple current; however, their effectiveness diminishes when the DC source exhibits low-impedance at double-line frequency. To address this, an alternate three terminal APD circuit (TT-APDC) has been proposed in the literature that increases the source impedance by emulating a small impedance in series with the source. However, this approach requires sensing source current, unlike conventional two terminal solutions. This leads to higher cost due to additional sensing circuitry. This work presents a modified control strategy for the TT-APDC that enhances source impedance while maintaining sensing requirements similar to the two terminal APD circuit. This reduces control complexity and cost compared to the conventional control approach used for TT-APDC.The proposed controller incorporates parallel LC resonance emulation strategy to enhance the source impedance at double-line frequency. At the same time, it creates a low-impedance alternate path for the ripple current by emulating series LC resonance behaviour. When compared to the conventional control strategy, the proposed technique reduces the double-line frequency ripple in the source current from 7% to 4%. The steady-state performance of the proposed controller is supported by simulation studies using MATLAB/Simulink. Its effectiveness is further validated through experimental studies on a 1.2 kW laboratory prototype of single-phase inverter incorporating the TT-APDC.