Current Research
PhD Thesis: Power Electronics Converters Onboard an EV
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The Government of India has set a target of achieving 30% electric vehicle (EV) penetration by 2030. Attaining this goal is expected to reduce primary particulate matter (PM) emissions by 17% and greenhouse gas emissions by 4%. However, two major challenges hinder this transition: (i) limited EV driving range and (ii) long charging times. Enhancing the driving range necessitates larger battery capacities, which in turn lead to longer charging durations. Addressing these issues requires higher power-rated chargers and a reduction in the size of onboard components to lower vehicle weight and, consequently, the load on the battery. This research focuses on minimizing the size of onboard power electronic converters and improving their efficiency to support this objective.
The current work primarily focuses on light electric vehicles. Fig. 1 illustrates a typical EV architecture highlighting the key onboard power electronic converters: the onboard charger (OBC), a three-phase inverter, and an auxiliary power module (APM). The OBC is used to charge the high-voltage (HV) traction battery from the utility grid. The three-phase inverter drives the traction motor, while the APM charges the low-voltage (LV) auxiliary battery, which powers auxiliary loads such as the battery management system, display panel, and control electronics.
The OBC operates when the EV is stationary, whereas the inverter and APM function when the vehicle is in motion. However, during OBC operation, certain critical auxiliary loads continue to draw power, leading to the discharge of the LV battery. Therefore, simultaneous charging of both the HV and LV batteries during OBC operation is essential to prevent deep discharge of the LV battery.
Fig. 1: Schematic of a typical two-wheeler EV
Work 1:
Integration of OBC and APM
An integrated topology that combines the onboard charger (OBC) and auxiliary power module (APM) can significantly reduce the size, cost, and weight of electric vehicles, especially as the power rating of APMs is expected to increase in the future. Current industry standards typically employ separate converters for OBC and APM functions. Some research proposes adding a switch to alternate between OBC and APM modes within an integrated circuit. However, such configurations do not support simultaneous operation. Other approaches involve multi-winding transformers, which result in complex designs and increased volume.
Fig. 2: Circuit Diagram
Fig. 3: Developed Hardware Prototype
This work proposes a three-port converter capable of performing both OBC and APM operations without requiring additional switches, relays, or multi-winding transformers. The topology includes three bridge configurations, two transformers, and one or two inductors for power transfer. Detailed waveform-based analysis and component sizing have been carried out.
The developed topology, intended for 2-wheeler and 3-wheeler applications, is shown in Fig. 2. The prototype integrates a 1.5 kW onboard charger (OBC) and a 350 W auxiliary power module (APM). A closed-loop controller was designed and validated through circuit-level simulations using PLECS, and the control was digitally implemented on hardware using the Texas Instruments C2000 Piccolo MCU (F28027F LaunchPad). This work was carried out in collaboration with Varroc Engineering Ltd., which sponsored the project. A patent related to the proposed topology has been granted. The project has been successfully completed, with all deliverables submitted in accordance with the company’s requirements.
Work 2:
Design Methodologies for Three-Port Integrated Power Converter (IPC)
Developed and analyzed three distinct IPC design approaches for two-wheeler EV applications. Each approach was evaluated based on performance, conduction loss, and current cancellation. The methods were compared to identify the most suitable design for compact and efficient onboard integration. The proposed IPC was also benchmarked against two existing commercial solutions. A journal paper detailing the design methodologies and benchmarking results has been submitted.
Work 3:
Light-Load Efficiency Improvement of SDABC (IPC Sub-Circuit)
Investigated the semi-dual active bridge converter (SDABC) shown in Fig. 4, a sub-circuit of the integrated power converter (IPC), and identified notable efficiency degradation under light-load conditions. Proposed design-level strategies to address these losses, targeting improvements in both light-load and overall energy efficiency. The work led to two conference publications—one specifically addressing light-load performance and the other focusing on overall energy efficiency enhancement.
Fig. 4: Semi-dual active bridge converter (SDABC)
Work 4:
Soft-Switching Range Extension in SDABC
Analyzed zero-voltage switching (ZVS) loss characteristics in the semi-dual active bridge converter (SDABC) under varying load conditions. Based on this analysis, a design-centric strategy was developed to extend the soft-switching range across the entire battery charging profile, thereby improving switching efficiency and reducing overall power loss.
Previous Research Experience
MTech Thesis: Stability Improvement of Series Stacked Buffer Circuit in Single Phase Solar Inverter
Over the past decade, small-scale rooftop solar PV systems have experienced rapid adoption. A key component of these systems is the single-phase solar inverter. In such systems, an inherent instantaneous power imbalance exists between the PV array and the utility grid, traditionally managed using aluminum electrolytic capacitors (AECs). However, AECs tend to degrade quickly at elevated temperatures, which compromises the reliability and lifespan of the inverter.
To address this, the Series Stacked Buffer (SSB) circuit has emerged as a promising alternative, enabling compact and robust inverter designs. Despite its advantages, the performance of the SSB circuit is highly sensitive to the
Fig. 5: Circuit Diagram
small-signal equivalent series resistance (SS-ESR) of the PV source. A low SS-ESR can lead to system instability, thus narrowing the safe operating region of the inverter. This work analytically investigates the instability challenges associated with low SS-ESR conditions in the SSB circuit. A tailored control strategy is proposed to mitigate this issue, enhancing system stability across a wider range of operating conditions. The effectiveness of the proposed solution is demonstrated through simulation studies in MATLAB/Simulink.
B.Tech Major Project: Unity Power Factor Rectifier with Boost Front End
Simulated a unity power factor rectifier with a diode bridge and boost converter front end using MATLAB/Simulink. Designed and implemented a closed-loop control scheme to ensure sinusoidal input current and regulated DC output voltage. A 350 W, 230 V AC to 400 V DC prototype was developed using an analog controller.
B.Tech Mini Project: Design and Implementation of Marx Generator
Designed and built a Marx generator capable of producing high-voltage pulses from a low-voltage DC source for pulsed power applications.
Collaborative Research
Three-Terminal Active Power Decoupling Circuit
Single-phase converters used in EV and PV systems draw pulsating power, which induces double-line frequency ripple on the DC side. This ripple degrades system performance by affecting MPPT in PV systems and accelerating battery aging in EVs. While conventional two-terminal active power decoupling (APD) circuits offer a solution, they fail when the DC source has low impedance at ripple frequency.
To address this, a modified control strategy for a three-terminal APD circuit is proposed. It effectively suppresses ripple current while maintaining low sensing requirements—comparable to two-terminal APD systems—thus enabling plug-and-play functionality.
Additionally, a novel three-terminal active DC-link architecture is developed. It achieves ripple suppression similar to conventional three-terminal designs but uses the same number of active components as two-terminal circuits and allows full low-side implementation. A dual-converter configuration further improves flexibility and scalability. The effectiveness of the proposed architectures is validated through simulations and hardware experiments.
Single-Stage Onboard Charger
This work explores a bidirectional, single-stage, interleaved totem-pole AC–DC converter with high-frequency isolation and no electrolytic capacitors—ideal for onboard charger applications.
The converter uses a fixed 50% duty interleaved totem-pole stage on the grid side and a full-bridge on the DC side for regulation. This setup enables ripple-free grid current, independent of input inductance values. With proper inductor design, soft switching is achieved across wide voltage and load ranges—without using auxiliary circuits or resonant tanks.
Power factor correction (PFC) is inherently achieved without a current-shaping loop, using phase-shift as the only control variable. This results in a simple, robust, and high-performance charger architecture.
I have also received brief exposure to the reliability of IGBT, reliability of AECs, GaN-based power converters, gate driver for WBG, short circuit protection, trnasformerless solar inverter and microgrid while involving in active discussion with my lab mates.
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