B.S. Prasad

Bio: B.S. Prasad is an academic researcher from Indian Institutes of Technology. The author has contributed to research in topics: Inverter & Waveform. The author has an hindex of 1, co-authored 1 publications receiving 138 citations.

Universal Single-Stage Grid-Connected Inverter

Abstract: A new single-stage grid-connected inverter, suitable for distributed generation applications, is proposed. The inverter is universal in the sense that it can be switched between buck, boost, and buck--boost configurations by appropriately altering the pulse width modular (PWM) control. Discontinuous current mode (DCM) operation is implemented to facilitate shuffling between configurations during the converter operation. Such flexibility ensures maximum benefit of the buck, boost, and the buck--boost operations (e.g., low device stresses, higher efficiency, higher boosting capability, etc.). The PWM is achieved by comparing a high frequency carrier (triangular) waveform with a suitable reference waveform, which is not necessarily sinusoidal, but has a shape specific to the individual configuration and is derived by equating the power fed into the grid with that extracted from the source during each switching cycle. The values of the components (inductors and capacitors) need to be optimized so that DCM is maintained and the required amount of energy is transferred to the grid in all the three configurations during their respective operation. All the design expressions have been derived. A salient feature of this inverter is its compatibility with various types of sources (PV array, fuel cell, etc.) with varying voltage levels and control requirements. Being single-stage, the proposed topology offers additional advantages like modularity, compactness, and low cost. All the details of simulation and experimental work are presented.

Topology Review and Derivation Methodology of Single-Phase Transformerless Photovoltaic Inverters for Leakage Current Suppression

Abstract: Single-phase voltage source transformerless inverters have been developed for many years and have been successful commercial applications in the distributed photovoltaic (PV) grid-connected systems. Moreover, many advanced industrial topologies and recent innovations have been published in the last few years. The objective of this paper is to classify and review these recent contributions to establish the present state of the art and trends of the transformerless inverters. This can provide a comprehensive and insightful overview of this technology. First, the generation mechanism of leakage current is investigated to divide the transformerless inverters into asymmetrical inductor-based and symmetrical inductor-based groups. Then, the concepts of dc-based and ac-based decoupling networks are proposed to not only cover the published symmetrical inductor-based topologies but also offer an innovative strategy to derive advanced inverters. Furthermore, the transformation principle between the dc-based and ac-based topologies is explored to make a clear picture on the general law and framework for the recent advances and future trend in this area. Finally, a family of clamped highly efficient and reliable inverter concept transformerless inverters is derived and tested to offer some excellent candidates for next-generation high-efficiency and cost-effective PV grid-tie inverters.

Review and Comparison of Step-Up Transformerless Topologies for Photovoltaic AC-Module Application

Abstract: This paper presents a comprehensive review of step-up single-phase non-isolated inverters suitable for ac-module applications. In order to compare the most feasible solutions of the reviewed topologies, a benchmark is set. This benchmark is based on a typical ac-module application considering the requirements for the solar panels and the grid. The selected solutions are designed and simulated complying with the benchmark obtaining passive and semiconductor components ratings in order to perform a comparison in terms of size and cost. A discussion of the analyzed topologies regarding the obtained ratings as well as ground currents is presented. Recommendations for topological solutions complying with the application benchmark are provided.

Fuel cell hybrid electric vehicles: A review on power conditioning units and topologies

Abstract: Fuel cell (FC) application in vehicular technology has gained much popularity since the past few years. Typically, fuel Cell Hybrid Electric Vehicle (FCHEV) consists of fuel cell, battery and/or ultracapacitor (UC) as the power sources. The power converter is integrated to the power sources to form the hybrid FC system. This helps to compensate the drawback of individual power sources. Apart from the technical efficiency of power sources itself, the performance of an FCHEV is governed by the efficiency of power electronics and associated controller. In this paper, a state-of-the-art of vehicle classification is reviewed, in which the focus is placed on the deployment of fuel cell, battery, ultracapacitor and flywheel. The configurations used in FCHEV, followed by the updated power converter topologies, are also discussed. The topologies are categorized and discussed according to the power stages and control techniques used in the configurations. Then, multiple stages conversion and single stage topologies are described chronologically. The advantages and disadvantages of each topology, safety standards, current situation and environmental impact of FCHEV are also discussed. In addition, the current development of FCHEV, challenges and future prospects are also elaborated. The rapid growth of FC based research and technology has paved great prospects for FCHEVs in the near future, with the prediction of the competitive cost of hydrogen as compared to gasoline.

Resistor Emulation Approach to Low-Power Energy Harvesting

Abstract: This paper presents an approach and associated circuitry for harvesting near maximum output from low power sources in the 100 μW range for miniature wireless devices. A set of converter topologies and control approaches are presented together with detailed efficiency analysis and a design example for a buck-boost based energy harvesting converter using commercially available discrete circuitry. Experimental results are presented for harvesting energy from miniature RF and wind power sources operating over a 10:1 input power range from 500 μW to 50 μW. A closed-system efficiency of 65 % at 50 μW output power is achieved, including all control and converter losses. The results demonstrate that useful energy, sufficient to power typical wireless sensors, can be harvested from miniature sources that output less than 100 μW at a few hundred mV.

Constant-Frequency Hysteresis Current Control of Grid-Connected VSI Without Bandwidth Control

Abstract: The theory, design, and implementation of a constant-frequency hysteresis current control for grid-connected voltage source inverter (VSI) is presented. The proposed control technique retains the benefit of the hysteresis control having fast dynamic response and tackles the drawback of the standard hysteresis control having variable switching frequency. The concept is based on predicting the current reference, system dynamic behavior, and past time to formulate the switching function for dictating the switching times of the switches in the inverter within a predefined switching period. Of particular importance, no hysteresis bandwidth (a challenge in the practical implementation) is needed in the entire control method. The operating principles of the proposed technique and mathematical derivation of the switching functions will be given. The proposed method is successfully applied to a 300 W, 110 V, 60 Hz grid-connected VSI prototype with the controller implemented by a simple analog circuit. The steady-state and large-signal dynamic response of the VSI are studied. Experimental results show that the inverter can reach the steady state in two switching actions after the inverter is subject to large-signal input and output disturbances.