An inclusive review on different multi-level inverter topologies, their modulation and control strategies for a grid connected photo-voltaic system

Fault ride-through control of grid-connected photovoltaic power plants: A review

The installation of photovoltaic (PV) system for electrical power generation has gained a substantial interest in the power system for clean and green energy. However, having the intermittent characteristics of photovoltaic, its integration with the power system may cause certain uncertainties (voltage fluctuations, harmonics in output waveforms, etc.) leading towards reliability and stability issues. In PV systems, the power electronics play a significant role in energy harvesting and integration of grid-friendly power systems. Therefore, the reliability, efficiency, and cost-effectiveness of power converters are of main concern in the system design and are mainly dependent on the applied control strategy. This review article presents a comprehensive review on the grid-connected PV systems. A wide spectrum of different classifications and configurations of grid-connected inverters is presented. Different multi-level inverter topologies along with the modulation techniques are classified into many types and are elaborated in detail. Moreover, different control reference frames used in inverters are presented. In addition, different control strategies applied to inverters are discussed and a concise summary of the related literature review is presented in tabulated form. Finally, the scope of the research is briefly discussed.

https://www.mdpi.com/1996-1073/13/16/4185/pdf

A Comprehensive Review on Grid Connected Photovoltaic Inverters, Their Modulation Techniques, and Control Strategies

Multilevel inverters (MLI) with reduced components are becoming popular to achieve higher voltage levels with lower cost and complexities of the circuit. Most of the reduced switch MLIs use a large number of isolated voltage sources that have a large total standing voltage (TSV) and higher losses. Moreover, many reduced component MLIs have been developed to reduce the number of switches only and have not utilized the dc-link voltages properly. Thus, an inverter needs to be designed in which the number of dc sources is also small and utilized fully. In this paper, a novel single-phase, multicell MLI configuration is presented that can generate a maximum number of output voltage levels using a minimum number of switches and dc sources. Two optimal configurations of the proposed MLI are proposed based on the minimum requirements of components with the optimum voltage stress of the highest rated switches. Moreover, the TSV of the proposed optimal MLI also becomes low. A generalized multicell optimum MLI is presented and the number of components, voltage stress of all the switches, and the TSV of the proposed as well as the other inverters also determined by the generalized expressions for comparison purpose. The prototype of a specimen 15-level inverter and the optimal 75-level inverter cell is further developed and implemented using DS 1103 in the laboratory to show the effectiveness of the proposed configuration. The experimental results corresponding to the different modulation indices are presented here for the verification of the simulation results.

Implementation of an Optimum Reduced Components Multicell Multilevel Inverter (MC-MLI) for Lower Standing Voltage

Renewable energy (RE) has become a focal point of interest as an alternative source of energy to the traditional fossil fuel and other energy sources due to the fact that it is more environmentally friendly, abundant and economically feasible. Many countries aggressively promote feed-in tariff schemes and solar photovoltaic (PV) systems have become one of the fastest growing RE sources that can be integrated into the grid distribution network. This paper reviews the recent development of grid-connected PV (GPV) generation systems comprising of several sub-components such as PV modules, DC-DC converter, maximum power point tracking (MPPT) technique, and an inverter. In addition, various grid synchronization and islanding detection methods are elaborated. The future key challenges to build a smart and efficient GPV generation system were also presented.

https://www.mdpi.com/1996-1073/13/17/4279/pdf

Grid-Connected PV Generation System—Components and Challenges: A Review

This study presents the performance analysis of a new asymmetrical multi-level inverter using reduced number of switches for a single-phase grid-tied photovoltaic (PV) system. The solar PV panels of unequal power rating are connected in an appropriate manner to obtain the DC link voltages of suitable ratio for an asymmetrical cascaded multi-level inverter. The PV power, voltages as well as the current injected into the grid have been controlled using the separate maximum power point tracking, voltage controllers and a current controlled technique to achieve the maximum power with sinusoidal current with a unity power factor. The variations of DC link voltages, inverter voltage and injected grid current are simulated and are experimentally verified under the variable irradiation as well as grid voltage fluctuation. The simulation and the corresponding hardware results of the proposed reduced switch asymmetrical seven-level inverter for a low-power residential grid-tied PV system is also presented.

https://ietresearch.onlinelibrary.wiley.com/doi/pdf/10.1049/iet-rpg.2016.0895

Performance evaluation of an asymmetrical reduced switched multi-level inverter for a grid-connected PV system

This article presents a generalised asymmetrical cascaded multilevel inverter (MLI) for a single-phase grid-connected photovoltaic (PV) system and their control strategy. The control strategy, including maximum power tracking along with a suitable interface, is implemented for maximum power transfer from the PV source to the single-phase low-power grid. The balancing of DC-link voltages for an asymmetrical MLI under variable solar parameters as well as grid parameter variation is implemented using the proposed control strategy. The voltage controllers maintain the constant DC-link voltage ratio, whereas the current controller injects the sinusoidal current into the grid at unity power factor and track the grid voltage under variation of grid voltage using grid tracker. Stability analysis of the proposed grid-connected asymmetrical inverter system is also incorporated. The whole grid-tied PV system is simulated in the MATLAB/SIMULINK environment and the exhaustive simulation results of the system under different transient conditions are presented. In addition, a laboratory prototype for a low-power grid-tied PV system has been developed and implemented using DS1103. The performance of the system is also tested at varying irradiance conditions and the corresponding experimental results are also presented.

https://ietresearch.onlinelibrary.wiley.com/doi/epdf/10.1049/iet-rpg.2018.5230

Control of asymmetrical cascaded multilevel inverter for a grid-connected photovoltaic system

The major concern with renewable sources of energy, feeding the distributed power generation system, is the power quality, reliability and efficiency of the system. This study proposes a novel topology comprising single-phase, seven-level, grid-connected photovoltaic-fed (PV) inverters in parallel. An important expediency of connecting multilevel inverters (MLIs) in parallel is that the failure of any source or the MLI module itself will never stop the overall generation, leading to improved efficiency and reliability of the system. This study also incorporates a novel controller comprising of two DC and an AC controller that independently controls the DC-link voltage of PV system and AC-side voltage so as to inject a pure sinusoidal current at unity power factor into the grid. Also, the AC controller discussed here is self-synchronising, i.e. aloof of phase-locked loop. The power mismatch problem that basically arises due to partial shading conditions in PV system has also been discussed. The MATLAB/Simulink-based proposed two seven-level grid-connected inverters in parallel are modelled and simulation results are presented. An experimental prototype of the PV-fed grid-connected system comprising two seven-level inverters in parallel is developed and tested to validate the simulation results.

https://ietresearch.onlinelibrary.wiley.com/doi/epdf/10.1049/iet-pel.2019.0379

Control strategy of PV-fed, grid-interfaced, seven-level T-type MLI for distributed power generation

In this article, islanding detection, control, grid synchronization, and power share techniques have been considered for the seamless operation of ac microgrid in grid-connected mode, islanded mode, and during the transition between both modes. A master–slave organization coordinates the power distribution among microgrid sources. The control scheme of each source is designed with a nested loop robust linear quadratic regulator and mixed $H_{2}/H_{\infty }$ optimal controller. The islanding detection algorithm is developed with synchro-extraction transform and optimal support vector machine (OSVM). An optimal linear Kalman filter-based synchronous reference frame phase locked loop (OLKF-SRFPLL) method is considered for the reconnecting of the microgrid to the utility grid. For optimal parameter tuning in the OSVM and LKF-SRFPLL methods, a particle swarm optimization technique is used. The seamless operation of the proposed ac microgrid system is verified in MATLAB/SIMULINK, and the practical feasibility is verified with an experimental photo-type setup and dSPACE 1202 control kit. Simulation and experimental results are presented to illustrate the seamless operation of the proposed ac microgrid system.

Madan Kumar Das

Papers

An inclusive review on different multi-level inverter topologies, their modulation and control strategies for a grid connected photo-voltaic system

Performance evaluation of an asymmetrical reduced switched multi-level inverter for a grid-connected PV system

Control of asymmetrical cascaded multilevel inverter for a grid-connected photovoltaic system

Control strategy of PV-fed, grid-interfaced, seven-level T-type MLI for distributed power generation

Seamless Operation of Master–Slave Organized AC Microgrid With Robust Control, Islanding Detection, and Grid Synchronization