Closed-Loop Control and Performance Evaluation of Reduced Part Count Multilevel Inverter Interfacing Grid-Connected PV System

Multilevel inverters (MLIs) have drawn a tremendous attention in power sector. Application of MLI has grown extensively to improve the power quality and efficiency of the photovoltaic (PV) system. For an MLI interfacing PV system, the size, cost and voltage stress are the key constraints of the MLI that need to be minimized. This paper presents a novel reduced part count MLI interfacing single-stage grid-tied PV system along with a closed-loop control strategy. The proposed MLI consists of n repeating units and a level boosting circuit (LBC) that assists to generate 4n+7 voltage levels instead of 2n+3 levels. Three different algorithms are proposed for suitable selection of dc-link voltages to further enhance the levels. Comparative analysis is carried out to confirm the superiority of developed MLI. The workability of the proposed MLI is investigated with a 1.3 kW PV system. The closed-loop control strategy ensures the maximum power tracking, dc-link voltage balancing, satisfactory operation of the MLI and injection of clean sinusoidal grid current under any dynamic changes. Comprehensive simulation analysis is carried out considering a 15-level MLI structure. The practicality of the topological advancement for PV system is further confirmed by experimental tests under different dynamic conditions.publishedVersio

A single-source switched-capacitor based step-up multilevel inverter with reduced components

Switched-capacitor based multilevel inverters (SC MLIs) have received a great deal of interest that reduces the dc source requirement and improves the power quality. However, multiple dc sources and requirement of a large number of switches to generate a high-quality boost output are the fundamental issues in the SC MLIs. This paper presents a stepup 17-level SC MLI using reduced number of switches, three capacitors and a single dc source. The steady-state voltage across the capacitors is maintained in the ratio 1:2:0.5 that contributes to quadruple boosting ability without using any auxiliary capacitor voltage balancing circuit. Besides, lower switch count in the conduction path and operation of 50 % of the switches at fundamental frequency ensures total power loss reduction in the proposed circuit. A comparative assessment with recently developed 17-level MLIs in terms of the number of components, gain, stress and cost factor elucidates the advantages of the proposed MLI. After a detailed circuit analysis and loss evaluation, simulations are performed to verify the step-up and inherent balancing features of the proposed MLI. Further, using both the fundamental frequency and high-frequency switching techniques, extensive experimental test results are presented under different transient conditions to validate the operational feasibility of the 17-level prototype

Recently Developed Reduced Switch Multilevel Inverter for Renewable Energy Integration and Drives Application: Topologies, Comprehensive Analysis and Comparative Evaluation

Recently, multilevel inverters (MLIs) have gained lots of interest in industry and academia, as they are changing into a viable technology for numerous applications, such as renewable power conversion system and drives. For these high power and high/medium voltage applications, MLIs are widely used as one of the advanced power converter topologies. To produce high-quality output without the need for a large number of switches, development of reduced switch MLI (RS MLI) topologies has been a major focus of current research. Therefore, this review paper focuses on a number of recently developed MLIs used in various applications. To assist with advanced current research in this field and in the selection of suitable inverter for various applications, significant understanding on these topologies is clearly summarized based on the three categories, i.e., symmetrical, asymmetrical, and modified topologies. This review paper also includes a comparison based on important performance parameters, detailed technical challenges, current focus, and future development trends. By a suitable combination of switches, the MLI produces a staircase output with low harmonic distortion. For a better understanding of the working principle, a single-phase RS MLI topology is experimentally illustrated for different level generation using both fundamental and high switching frequency techniques which will help the readers to gain the utmost knowledge for advance research

HIL based Coordinated Control of grid interfaced Distributed Generation assisted Battery Swapping Station

The large-scale world-wide adoption of Electric Vehicles as a mode of transportation is predicted to create stress on the already loaded power supply network. As such continued efforts in the area of distributed generation assisted charging stations are in full-swing. The paper investigates the outcomes of utilizing a PV assisted Battery Swapping Station to combat and alleviate simultaneously the issues of overburden and energy storage. A BSS can be tethered not only to provide battery swapping services to EVs but also provide for grid support, energy storage, ancillary services, etc. A grid interfaced PV assisted BSS system and its functioning in the smart grid environment has been proposed considering the system has a reliable and secure communication infrastructure. The multiple roles of the BSS and its coordinated functioning with the PV and the grid is examined under various test scenarios. The hardware prototyping of the control strategies for the inverter and the BSS is realized using Virtex-6 FPGA ML605 evaluation kit. The simulation and the hardware co-simulation results are presented to validate the efficacy of the proposed control scheme