Showing papers by "Narsa Reddy Tummuru published in 2023"

PV-Grid Integrated Hybrid Charger for EV s with Contactless and Conductive Charging Capability

Abstract: The imminent global fossil fuel crisis and ever-increasing global warming have opened up opportunities for green and energy efficient electric vehicles (EV). With the prevalence of EV in automobile market the charging infrastructure also needs to grow in parity. The objective is to provide a reliable, resilient and adaptive charging solution for existing and future EVs. Due to various pros and cons of plug-in as well as contactless charging both need to coexist in the same system for greater flexibility in charging. In this paper a solar PV -grid integrated hybrid EV charger is presented. The hybrid charger shares the same stages of power electronic converters for both conductive and contactless charging there by reducing the overall component count with reduced losses as compared to existing grid connected hybrid charging schemes. The proposed topology is simulated in MATLAB/Simulink platform for power same as that of standard level1 charger i.e., 3.3 kW. Power flow management and performance of the charger under various modes of operation is analyzed.

An Improvised Modulation and Control Approach for Dual Active Bridge DC-DC Converter System

Abstract: Aimed at the control and modulation of dual active bridge bi-directional dc (DAB-BIDC) converter, an unconventional approach is applied to explore its effect in symmetrical wave-based isolated dc-dc converters. The existing control schemes of DAB-BIDC converter with unified or optimal phase shift (UPS/OPS) modulation have the constraints like complex control schemes, light load efficiency, current stress, and reactive power. Since a 50 Hz, grid-connected conventional converter system uses the sinusoidal pulse width modulation method to minimize the requirement for passive filters. Similarly, this work investigates the same analogy for the high-frequency (HF) symmetrical wave converters to get effective modulation and control scheme for the DAB-BIDC converter. Furthermore, the proposed sinusoidal pulse width-phase shift (SPW-PS) modulation scheme has been implemented by the optimally derived control parameters using Lagrange's Multiplier Method (LMM) to minimize the reactive power flow and current stress reduction at the HF link. Therefore, the DAB-BIDC converter with the proposed modulation and control approach can be used for EV charging and solid-state transformers applications. Finally, the proposed work is validated using MATLAB simulation and experimental setup having turn ratio 36/12 V, fundamental frequency 5-kHz, and switching frequency 100-kHz for the experimental validation using OPAL-RT.

A ZPE Based Frequency Control Approach to Realize Soft Switching in Contactless Power Transfer of Energy Storage System Applications

Abstract: This paper proposes a zero phase angle error (ZPE) based frequency control approach to realize soft switching in inductive power transfer (IPT) charging of energy storage system applications. IPT is influenced by many parameters, such as the coupling coefficient between the transmitting and receiving coils and the load power requirement. This introduces new challenges, such as hard switching of the power converters in the system, which increases the power losses and degrades the power conversion efficiency. Furthermore, the switching devices need to be selected with higher ratings which increases the cost of the converters. To address these issues, an optimal frequency operation of the converter is proposed to achieve soft switching and transmit the maximum power to the load. The optimal frequency control is developed by minimizing the ZPE between the excitation voltage and current from the transmitting side. This makes the controller not require information on the IPT system's receiver side voltages and currents to achieve the aforementioned goals. Furthermore, the performance of the proposed control algorithm is validated using digital simulations. Finally, the IPT system is developed and tested for a maximum power of $1.7\text{kW}$ under open loop conditions, with experimental results presented in this paper.

Filter Capacitor Current Dynamics-Based Frequency-Domain Fault Detection Approach for Grid-Connected Low-Voltage DC Microgrid

Abstract: In this article, we propose a cost-effective short-circuit fault detection method for a distribution network in the ac grid-connected low-voltage dc (LVdc) microgrid. In this method, a typical dc system is considered where a number of dc/dc, ac/dc power converters, and loads are interfaced to the dc link. Furthermore, these loads are dedicated as local loads to the converter based on the locality of the same. The discharge of a filter capacitor (FC) in power converters in the dc system is the foremost indicator of a fault. Such dynamic behavior of FC can be utilized in the identification of a fault. This method is a time–frequency-domain-based wavelet transform (WT), which utilize the current dynamics of an FC for quantitative analysis of a fault current. Additionally, a detailed thresholds selection process is also explained. MATLAB/Simulink model is used to carry out simulation studies. The experimental validation of WT-based fault detection method is executed on the ac grid-connected LVdc microgrid testbed interfaced to the dSPACE 1104 controller.

Power Management of Renewable-Grid Integrated Smart e-Mobility System for Light Electric Vehicles

Abstract: This work proposes an architecture that integrates renewable energy sources or photovoltaic (PV) systems with the dc-link of utility and acts as primary and secondary energy sources to the electric vehicle (EV) load. The proposed architecture contains the dc-link cascaded single-stage conventional H-bridge, which superimposes a dual boost interleaved (DBI) topology with a series-series resonant (SSR) converter system. Further, the SSR side contains a wireless charging system followed by the diode bridge rectifier and a Li-ion battery as an EV load. It is challenging to integrate the above system with reduced power stages. Moreover, achieving power control in an integrated single-stage system makes it more complex. Therefore, this work includes a fundamental operation and analysis of the proposed architecture. A system-level power management scheme is also provided to control the proposed system. This power management scheme includes four basic power modes that comply with different system conditions during its operation. Furthermore, the essential of the power management scheme is to ensure that the utility should support the charging structure during excess or shortage of power flow between PV and EV load. Finally, the proposed architecture has been validated using MATLAB simulation and a 1.2kW hardware prototype.

Modified VOC Using Three Symmetrical Components for Grid-Supporting Operation During Unbalanced Grid Voltages and Grid-Forming Operation in Hybrid Single-Phase/Three-Phase Microgrid

Abstract: Virtual oscillator (VO) control is the most advanced time-domain-based control strategy for grid-supporting and grid-forming inverters. VO Controllers (VOCs) provide better dynamic performance than droop controllers and virtual synchronous machine controllers. However, the existing VOCs can only provide synchronization with the positive-sequence voltages of a connected electrical network. As a result, the existing VOCs cannot operate in an electrical network with unbalanced voltages. This article has introduced the Instantaneous Symmetrical component-based VOC (S-VOC), which can provide continuous synchronization simultaneously with the positive-, negative-, and zero-sequence voltages of a connected electrical network. The proposed S-VOC enables two very important and relevant functionalities for grid-supporting and grid-forming inverters. The functionalities are the grid-supporting operation in the presence of unbalanced grid voltages and the accurate load-sharing in grid-forming mode when single-phase and three-phase sources are integrated into the same hybrid microgrid architecture. At the same time, the proposed S-VOC preserves the superior dynamic performance of the existing VOC. Furthermore, the proposed S-VOC can replace the existing VOC without any extra sensor. The systematic design procedure and mathematical analysis of the proposed S-VOC are presented in this article. Simulation studies and hardware experiments are conducted for validation.

Application of Filter Capacitor Dynamics Based Short-Circuit Fault Detection Method in Ring-Type DC Microgrid

Abstract: A healthy grid always needs precise and fast isolation because this makes the system reliable and improve the power quality. To achieve this, a short-circuit fault detection method is presented for low-voltage ring-type dc microgrid. This method uses the current dynamics of filter capacitors to identify the faulty zone. Along with fault identification, a fault isolation process is also explained decently. In the considered ring- type architecture, active sources, such as ac grid, battery, and solar photovoltaic, are connected to a common dc link via power converters. The proposed method considers an averaged capacitor current as a detection parameter. Additionally, a criterion for thresholds selection is also given in detail. The presented work is validated through both digital simulation and experimental studies. All the results assure that the proposed concept can detect and isolate the fault cable within 1.98 ms.

Power Management of Hybrid Energy Storage System Based Wireless Charging System With Regenerative Braking Capability

Abstract: Electric vehicles (EVs) usually face many challenges such as long charging time, frequent discharging, and battery life deterioration. These can be addressed by introducing the capability of wireless power transfer (WPT) to the unit that can store the regenerative braking energy. A hybrid energy storage system (HESS) model is shown in this research, consisting of a battery and supercapacitor combination, connected through a bi-directional converter. This topology includes three systems connected to the dc-link, namely, BLDC motor drive system, the HESS, and the WPT system where the WPT system supplies power to the system throughout the drive cycle. Battery has limited power density whereas supercapacitors have limited energy density, hence a combination of both the storage units enables us to have an optimized storage system. Apart from that, a supercapacitor also contributes to battery life extension by redirecting the frequent charging and discharging phenomena. The proposed configuration is simulated in MATLAB environment and practically verified by using a BLDC motor. The proposed topology suits low voltage EVs to run in stop-and- go traffic situation or hilly areas. Regenerative braking of BLDC motor allows it to run as a generator for a while allowing the generated power to boost and store back into battery/supercapacitor. This paper proposes a simultaneous wireless charging method to allow the vehicle to charge while in motion. This research is potentially a future prospective of the developing technology in terms of EVs.