Medium-voltage (MV) multilevel converters are considered a promising solution for large scale photovoltaic (PV) systems to meet the rapid energy demand. This paper focuses on reviewing the different structures and the technical challenges of modular multilevel topologies and their submodule circuit design for PV applications. The unique structure of the converter’s submodule provides modularity, independent control of maximum power point tracking (MPPT), galvanic isolation, etc. Different submodule circuits and MPPT methods to efficiently extract the PV power are reviewed. The integration of the multilevel converters to PV systems suffers unbalanced power generation during partial PV shading conditions. Several balancing strategies to solve this problem are presented and compared to give a better understanding of the balancing ranges and capabilities of each strategy. In addition, the paper discusses recent research advancements, and possible future directions of MV converters-based large-scale PV systems for grid integration.

Mitigating power quality issues in distribution systems is of utmost importance to both electricity consumers and suppliers as it improves the distribution system’s efficiency, reduces electricity costs, maintains continuous supply, and diminishes the requirement for frequent maintenance. Custom power devices were introduced to eliminate power quality issues like voltage sags, swells, transients, imbalances, and current harmonics arising in distribution systems. Unified power quality conditioner (UPQC) is one such frequently used custom power device that enhances the power quality of distribution systems. Various structural arrangements of UPQCs with improved performance capability were introduced within the last few decades. The main aim of this paper is to review the most frequently explored UPQC models in literature and to observe the impact of these UPQC structural configurations on their performance as well as that of the overall distribution system. Also, this study investigates the properties, applications, and control techniques used by these structural configurations of UPQCs to mitigate power quality issues.

The uses of grid-connected photovoltaic (PV) inverters are increasing day by day due to the scarcity of fossil fuels such as coal and gas. On the other hand, due to their superior efficiency, lower cost, smaller size, and lighter weight when compared to inverters with transformers, transformerless inverters for low-voltage single-phase grid-tied photovoltaic (PV) systems have recently attracted more interest. However, there are some specific challenges, especially leakage current issues, which must be adequately addressed to ensure the safety standards of the grid codes. A variety of topologies has been presented in the literature to eliminate the leakage current using the decoupling or clamping technique. However, choosing an appropriate topology after comparison is challenging because each topology has a unique set of parameters. In this paper, the authors have selected a common set of parameters and simulated all the selected eighteen well-known topologies in MATLAB/Simulink to fairly analyze and compare their common mode characteristics and other output parameters. In addition, the power loss distribution of every switch of each of the eighteen topologies was calculated and presented to better understand the insight of the topologies.

The study presents an optimal control approach for managing a hybrid Photovoltaic/Wind Turbine/Battery system in an isolated area. The system includes multiple energy sources connected to a DC bus through DC/DC converters for maximum power point tracking. The proposed hybrid MPPT approach (HMPPT) manages the energy production from different sources, while the power flow method is used to balance the load and renewable power. The study shows that integrating the HMPPT algorithm and power flow approach results in improved system performance, including increased power generation and reduced stress on the batteries. The study also proposes an accurate sizing method to further improve system efficiency. The study demonstrates the effectiveness of the proposed approach by presenting results for twelve different days with varying weather conditions. The results show that the proposed approach effectively manages the energy production and load, resulting in optimal system performance. This study provides valuable insights into the optimal control of hybrid renewable energy systems, and highlights the importance of considering different energy sources and optimal sizing for maximizing system efficiency.

This article discusses the potential of using modular multilevel converters (MMC)s in large-scale photovoltaic (PV) systems. A novel modular circuit configuration for the integration of the PV system into the grid using MMC is proposed. The proposed circuit is modular, scalable, and has excellent performance during extreme PV shading conditions. Unlike other PV-MMC circuits, this circuit configuration eliminates the power unbalance between the arms of the converter. This feature enables the converter to deal only with the power unbalance occurring between the phases which eases the control process and ensures a wide range of power balancing of the MMC. A control strategy is adopted to provide a balanced operation of the converter under different conditions. It eliminates the power unbalance between the MMC phases by only injecting the dc circulating current component while the ac component is excluded which reduces the internal losses and increases the stability of the converter. The proposed circuit configuration and the control strategy are tested using the RT box Hardware-in-the-Loop technology. The corresponding analysis and results are provided to demonstrate the effectiveness and the excellent dynamic performance of the proposed system during various PV power generation conditions.

The rapid reduction of power transfer efficiency with misalignment is a matter of grave concern for compact high power WPT systems. The misalignment tolerance can be increased by using complex control techniques but the efficient misalignment operation range is still narrow and efficiency drops significantly beyond that range. This paper proposes a novel natural decoupling method to enhance the efficient misalignment operation range for identical symmetrical quadruple-D coils arranged in a dual-transmitter-dual-receiver configuration without requiring any control. Decoupling of multiple transmitters and receivers is essential for efficient zero phase angle (ZPA) operation. At fully aligned condition the experimental prototype of this design exhibits a peak efficiency of 96% at 2.25 kW output power for a vertical distance of 150 mm. The misalignment operation range extends from +300 mm to -100 mm for a 400 mm x 400 mm coil size with almost constant efficiency (94.78% - 96.19%). The rated power operation points occur at 0 mm (fully aligned) and also at +200 mm (50% misaligned position) thus making it possible to obtain full rated power without fully aligning the EV.