T. Sreekanth

Bio: T. Sreekanth is an academic researcher from University of Minnesota. The author has contributed to research in topics: Inverter & Maximum power point tracking. The author has an hindex of 6, co-authored 14 publications receiving 98 citations. Previous affiliations of T. Sreekanth include Indian Institute of Technology Delhi & Indian Institute of Technology Madras.

A Single-Stage Grid-Connected High Gain Buck–Boost Inverter With Maximum Power Point Tracking

Abstract: Converter system that does both dc–dc conversion and dc–ac conversion in a single stage is called a single-stage converter system (SSCS). Compared to a two-stage converter, SSCS is more efficient and compact in size. In this paper, a grid-connected SSCS (GCSS) system for photovoltaic (PV) applications is presented. This GCSS transfers power from PV to grid while tracking maximum power point (MPP) continuously. The proposed system has several desirable features such as low switching loss, high gain, and compact size that makes this GCSS suitable for PV systems, where the PV system output voltage is low and varies with time. Design of the presented GCSS components with necessary equations and derivation of both current control loop and voltage control loop required for operation are given. Proposed GCSS is simulated using MATLAB/SIMULINK. Detailed simulation and experimental results are given to verify the efficacy of the proposed GCSS.

Coupled inductor-based single-stage high gain DC–AC buck–boost inverter

Abstract: Two stage conversion systems (TSCSs) normally use either boost converter or high gain dc-dc converter along with dc-ac inverter in order to transfer power from low input voltage dc source to high voltage ac load. When these TSCSs operate at extremely low input voltages, the boost converter has to operate at extremely high duty ratios. This in turn results in more losses and reverse recovery problems. Usage of high gain dc-dc converter results in more number of components, increase in control complexity and decrease in reliability. Single-stage conversion systems (SSCSs) are formed by merging both dc-dc and dc-ac conversion processes. These SSCSs have advantages like low loss, more compactness and less reverse recovery problems. In this study, a high gain coupled inductor-based single-phase SSCS is presented. This SSCS topology has many desirable features such as high gain, less switching losses, free from leakage inductance adverse effects and compact. Principle of operation, steady-state analysis and design of the proposed topology are described in detail. MATLAB simulation results of the proposed topology and experimental results using DSP28335-based experimental setup are presented to validate the proposed scheme.

Grid tied single-stage inverter for low-voltage PV systems with reactive power control

Abstract: Single-stage DC-AC converter systems (SSCSs) are developed by merging both DC-DC and DC-AC conversion processes. These SSCS transfer power from photovoltaics (PV) to loads/grid in one stage. In this study, a PV-based grid tied single-stage DC-AC converter system (GTSS) for low-voltage PV systems is presented. Generally, when SSCSs are connected to the grid, grid voltage template is used to generate reference current which is to be tracked. In doing so, the GTSS delivers power to the grid at a power factor other than unity. A suitable control scheme is implemented in this study to control active and reactive powers' flow from the GTSS to the grid while continuously operating PV at maximum power point. The proposed control scheme of GTSS has attributes such as less complexity and requires simple proportional integral controller. Modelling of control loops in the proposed control scheme is mentioned. A detailed MATLAB/SIMULINK-based simulation and experimental studies are conducted to validate the proposed control scheme.

A single stage high gain buck-boost inverter with coupled inductor

Abstract: Output dc voltage from Fuel Cell (FC)/Photo Voltaics (PV) needs to be conditioned and converted into ac form before integrating to grid Normally, two stage converters are used for this purpose Two stage converters have several disadvantages like low efficiency, more number of components, big size, etc especially when they are operated at low input voltages In this paper, a coupled inductor based high performance, high gain, single-stage inverter topology, which can be used for grid connected FC/PV applications or stand-alone applications is proposed In the proposed topology, dc-dc power conversion and dc-ac power conversion can be done in a single stage The proposed topology has several features such as high gain, low cost and compact size This topology suits well for low power applications The principle of operation, steady state analysis of the proposed topology is presented in this paper The steady state analysis is verified by a simulation, simulation results of the proposed converter for an ac load is presented

A single stage coupled inductor based high gain DC-AC buck-boost inverter for photovoltaic (PV) applications

Abstract: Normally, a two stage power conversion system is used to convert a low dc voltage to high amplitude ac voltage. These two stage power conversion systems are very bulky, more complex in control and less efficient, etc when they are used, especially for low input dc voltages. In this paper a high gain dc-ac inverter topology is presented, which can produce an instantaneous output voltage higher or lower than the input dc voltage without any intermediate power conversion stage or transformers. Coupled inductor is used in this circuit in order to achieve high gain. The two stage power conversion will be done in a single stage by this converter. The proposed topology posses several desirable features like high gain, less loss and less size etc. The various modes of operation and steady state analysis of the proposed topology are presented. The proposed topology is simulated using MATLAB/SIMULINK, simulation results are presented to validate the proposed idea.

Power Electronics Converters Applications And Design

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Review and comparative study of single-stage inverters for a PV system

Abstract: Energy from the sun is harnessed through a photovoltaic (PV) array in form of DC. This available DC voltage is converted into AC for industrial or domestic use as per the requirement. In some topologies the extracted DC voltage is stepped up to a higher level of DC using a boost or a buck-boost converter and then this stepped up DC voltage is converted into AC by the use of an inverter. However this process is pretty costly because of the larger number of components employed. An efficient alternative to this two-stage approach is the Single-Stage Inverter (SSI). SSI does the boosting of DC and inversion of the DC to AC using only a single circuit and hence the name Single-Stage Boost Inverter. SSBI give us the advantage of reduced and robust circuitry along with reliability and efficiency. This paper presents a review of the various (however not all) SSI topologies in PV systems.

A Single-Stage Grid-Connected High Gain Buck–Boost Inverter With Maximum Power Point Tracking

Abstract: Converter system that does both dc–dc conversion and dc–ac conversion in a single stage is called a single-stage converter system (SSCS). Compared to a two-stage converter, SSCS is more efficient and compact in size. In this paper, a grid-connected SSCS (GCSS) system for photovoltaic (PV) applications is presented. This GCSS transfers power from PV to grid while tracking maximum power point (MPP) continuously. The proposed system has several desirable features such as low switching loss, high gain, and compact size that makes this GCSS suitable for PV systems, where the PV system output voltage is low and varies with time. Design of the presented GCSS components with necessary equations and derivation of both current control loop and voltage control loop required for operation are given. Proposed GCSS is simulated using MATLAB/SIMULINK. Detailed simulation and experimental results are given to verify the efficacy of the proposed GCSS.

Seventeen-Level Inverter Formed by Cascading Flying Capacitor and Floating Capacitor H-Bridges

Abstract: A multilevel inverter for generating 17 voltage levels using a three-level flying capacitor inverter and cascaded H-bridge modules with floating capacitors has been proposed. Various as- pects of the proposed inverter like capacitor voltage balancing have been presented in the present paper. Experimental results are presented to study the performance of the proposed converter. The stability of the capacitor balancing algorithm has been verified both during transients and steady-state operation. All the capac- itors in this circuit can be balanced instantaneously by using one of the pole voltage combinations. Another advantage of this topol- ogy is its ability to generate all the voltages from a single dc-link power supply which enables back-to-back operation of converter. Also, the proposed inverter can be operated at all load power fac- tors and modulation indices. Additional advantage is, if one of the H-bridges fail, the inverter can still be operated at full load with reduced number of levels. This configuration has very low dv/dt and common-mode voltage variation.

A Hybrid Photovoltaic-Fuel Cell-Based Single-Stage Grid Integration With Lyapunov Control Scheme

Abstract: This article presents a single-stage hybrid photovoltaic (PV)-fuel cell (FC)-based grid-integrated system with Lyapunov function-based controller design to obtain optimal power extraction from hybrid renewable sources without maximum power point tracking (MPPT) application. The proposed Lyapunov controller performs MPPT function, improves power quality, and forces inverter to inject sinusoidal current to the utility grid. In this proposed approach, the higher switching frequency has been reduced by employing LCL filter inclusion compared to the two-stage hybrid power system. This proposed single-stage system has low cost and improved power quality at the point of common coupling and employed controller injects stable power to the utility grid. In this article, a hybrid overall distributed-particle swarm optimization-based MPPT is employed with FCs and integrated CUK converter. The effectiveness of the employed Lyapunov function-based controller has been tested with dSPACE (DS1104) real-time platform for single-stage hybrid grid-connected power system under varying operating conditions that have high efficiency, reduced harmonic distortion in grid current with the simpler employed power converter. Experimental responses confirm the effectiveness of the proposed controller, which transfers the hybrid power from PV and FC to the utility grid through a single stage.