Narsa Reddy Tummuru

Bio: Narsa Reddy Tummuru is an academic researcher from Indian Institute of Technology Mandi. The author has contributed to research in topics: Microgrid & Photovoltaic system. The author has an hindex of 10, co-authored 43 publications receiving 727 citations. Previous affiliations of Narsa Reddy Tummuru include Nanyang Technological University & Indian Institute of Technology Madras.

Dynamic Energy Management of Renewable Grid Integrated Hybrid Energy Storage System

Abstract: In this paper, a unified energy management scheme is proposed for renewable grid integrated systems with battery–supercapacitor hybrid storage. The intermittent nature of renewable-energy resources (RES), coupled with the unpredictable changes in the load, demands high-power and high-energy-density storage systems to coexist in today's microgrid environment. The proposed scheme dynamically changes the modes of renewable integrated systems based on the availability of RES power and changes in load as well. The participation of battery–supercapacitor storage to handle sudden/average changes in power surges results in fast dc link voltage regulation, effective energy management, and reduced current stress on battery. In addition, the proposed energy management scheme enables the real power transfer along with ancillary services such as current harmonic mitigation, reactive power support, and power factor improvement at the point of common coupling. The proposed scheme is validated through both simulation and experimental studies.

Validation of Faster Joint Control Strategy for Battery- and Supercapacitor-Based Energy Storage System

Abstract: Energy storage system (ESS) is generally used to manage the intermittency of the renewable energy sources (RESs). The proper control strategy is needed to effectively maintain the power balance between the RESs, load demand, and ESS. The conventional control strategy for the hybrid energy storage system (HESS) uses the high-/low-pass filter method for system net power decomposition and the ESS power dispatch. In this paper, a new joint control strategy is proposed for photovoltaic-based dc grid system, with battery and supercapacitor (SC) as a HESS. The new joint control strategy utilizes the uncompensated power from the battery system to increase the performance of the overall HESS. The advantages of the proposed control strategy over the conventional control strategy are faster dc-link voltage restoration and effective power sharing between the battery and the SC. The detailed stability analysis of the proposed control strategy is also presented. The effectiveness of the proposed control strategy over the conventional control strategy is validated with the short-term and long-term experimental studies.

Energy Management and Control for Grid Connected Hybrid Energy Storage System Under Different Operating Modes

Abstract: DC-coupled microgrids are simple as they do not require any synchronization when integrating different distributed energy generations. However, the control and energy management strategy between the renewable energy sources and the energy storages under different operating modes is a challenging task. In this paper, a new energy management scheme is proposed for the grid connected hybrid energy storage with the battery and the supercapacitor under different operating modes. The main advantages of the proposed energy management scheme are effective power sharing between the different energy storage systems, faster dc link voltage regulation to generation and load disturbances, dynamic power sharing between the battery and the grid based on the battery state of charge, reduced rate of charge/discharge of battery current during steady state and transient power fluctuations, improved power quality features in ac grid and seamless mode transitions. The effectiveness of the proposed method is validated by both simulation and experimental studies.

Dynamic Energy Management of Hybrid Energy Storage System With High-Gain PV Converter

Abstract: In this paper, fast acting dc-link voltage-based energy management schemes are proposed for a hybrid energy storage system fed by solar photovoltaic (PV) energy. Using the proposed control schemes, quick fluctuations of load are supplied by the supercapacitors and the average load demand is controlled by the batteries. Fast dc-link voltage, effective energy management, and reduced current stress on battery are the main features achieved from the proposed control schemes. The effectiveness of the proposed control schemes are compared with the unified cascaded control. Small-signal control gains are formulated to design the voltage and current loops of the proposed energy management schemes. Detailed stability analysis is also presented to find the boundary values of compensator gains. In addition, a high-gain PV converter is proposed for extraction of maximum power from the solar panels. High voltage gain, reduced reverse recovery of diodes, and less duty cycle operation are the key features obtained from the proposed high-gain converter. The validity of the proposed energy management schemes with high-gain converter is verified by the detailed simulation and experimental studies.

Multifunctional VSC Controlled Microgrid Using Instantaneous Symmetrical Components Theory

Abstract: This paper proposes a control scheme to control the microgrid side voltage-source converter (μG-VSC) using instantaneous symmetrical components theory. The μ G-VSC with proposed control can be utilized 1) as a bidirectional power sharing converter to control the power flow from the dc side to the ac side and vice versa, based on renewable power available at the dc link; 2) as a power quality compensator with the features of reactive power compensation, load balancing, and mitigation of current harmonics generated by nonlinear loads at the point of common coupling, thus enabling the grid to supply only sinusoidal current at unity power factor; and 3) to damp out the oscillations in the μG-VSC currents effectively using damping filter in the control algorithm. The mathematical models are derived and stability aspects are analyzed in detail through the frequency domain approach. The multifunctional features of the proposed control algorithm are demonstrated using extensive simulation studies and are also validated through experimental results.

I and i

Abstract: There is, I think, something ethereal about i —the square root of minus one. I remember first hearing about it at school. It seemed an odd beast at that time—an intruder hovering on the edge of reality. Usually familiarity dulls this sense of the bizarre, but in the case of i it was the reverse: over the years the sense of its surreal nature intensified. It seemed that it was impossible to write mathematics that described the real world in …

A review of supercapacitor modeling, estimation, and applications: A control/management perspective

Abstract: Supercapacitors (SCs) have high power density and exceptional durability. Progress has been made in their materials and chemistries, while extensive research has been carried out to address challenges of SC management. The potential engineering applications of SCs are being continually explored. This paper presents a review of SC modeling, state estimation, and industrial applications reported in the literature, with the overarching goal to summarize recent research progress and stimulate innovative thoughts for SC control/management. For SC modeling, the state-of-the-art models for electrical, self-discharge, and thermal behaviors are systematically reviewed, where electrochemical, equivalent circuit, intelligent, and fractional-order models for electrical behavior simulation are highlighted. For SC state estimation, methods for State-of-Charge (SOC) estimation and State-of-Health (SOH) monitoring are covered, together with an underlying analysis of aging mechanism and its influencing factors. Finally, a wide range of potential SC applications is summarized. Particularly, co-working with high energy-density devices constitutes hybrid energy storage for renewable energy systems and electric vehicles (EVs), sufficiently reaping synergistic benefits of multiple energy-storage units.

Emerging Power Quality Challenges Due to Integration of Renewable Energy Sources

Abstract: Renewable energy becomes a key contributor to our modern society, but their integration to power grid poses significant technical challenges. Power quality is an important aspect of renewable energy integration. The major power quality concerns are: 1) Voltage and frequency fluctuations, which are caused by noncontrollable variability of renewable energy resources. The intermittent nature of renewable energy resources due to ever-changing weather conditions leads to voltage and frequency fluctuations at the interconnected power grid. 2) Harmonics, which are introduced by power electronic devices utilized in renewable energy generation. When penetration level of renewable energy is high, the influence of harmonics could be significant. In this paper, an extensive literature review is conducted on emerging power quality challenges due to renewable energy integration. This paper consists of two sections: 1) Power quality problem definition. Wind turbines and solar photovoltaic systems and their power quality issues are summarized. 2) Existing approaches to improve power quality. Various methods are reviewed, and the control-technology-based power quality improvement is the major focus of this paper. The future research directions for emerging power quality challenges for renewable energy integration are recommended.

Adaptive Droop Control Strategy for Load Sharing and Circulating Current Minimization in Low-Voltage Standalone DC Microgrid

Abstract: This paper addresses load current sharing and cir- culating current issues of parallel-connected dc-dc converters in low-voltage dc microgrid. Droop control is the popular technique for load current sharing in dc microgrid. The main drawbacks of the conventional droop method are poor current sharing and drop in dcgrid voltage due tothe droop action. Circulating current issue will also arise due to mismatch in the converters output voltages. In this work, a figure of merit called droop index (DI) is introduced in order to improve the performance of dc microgrid, which is a function of normalized current sharing difference and losses in the output side of the converters. This proposed adaptive droop con- trol method minimizes the circulating current and current sharing difference between the converters based on instantaneous virtual resistance Rdroop .U singRdroop shifting, the proposed method also eliminates the tradeoff between current sharing difference and voltage regulation. The detailed analysis and design procedure are explained for two dc-dc boost converters connected in paral- lel. The effectiveness of the proposed method is verified by detailed simulation and experimental studies.

Hybrid energy storage system for microgrids applications: A review

Abstract: Energy storages introduce many advantages such as balancing generation and demand, power quality improvement, smoothing the renewable resource’s intermittency, and enabling ancillary services like frequency and voltage regulation in microgrid (MG) operation. Hybrid energy storage systems (HESSs) characterized by coupling of two or more energy storage technologies are emerged as a solution to achieve the desired performance by combining the appropriate features of different technologies. A single ESS technology cannot fulfill the desired operation due to its limited capability and potency in terms of lifespan, cost, energy and power density, and dynamic response. Hence, different configurations of HESSs considering storage type, interface, control method, and the provided service have been proposed in the literature. This paper comprehensively reviews the state of the art of HESSs system for MG applications and presents a general outlook of developing HESS industry. Important aspects of HESS utilization in MGs including capacity sizing methods, power converter topologies for HESS interface, architecture, controlling, and energy management of HESS in MGs are reviewed and classified. An economic analysis along with design methodology is also included to point out the HESS from investor and distribution systems engineers view. Regarding literature review and available shortcomings, future trends of HESS in MGs are proposed.