# Review of Power Electronics Technologies in the Integration of Renewable Energy Systems
## 1 Introduction
Transformer-based and transformer-less topologies are the two primary groups into which these grid-connected converters fall. Transformer-less topologies are now preferred over transformer-based converters due to their increased efficiency, affordability, and simplicity. The other benefits of microinverters for low-power PV systems include their plug-and-play capability, high voltage gains, and capacity to track each PV panel's maximum power point (MPPT) [20]. For large-scale RESs, such as wind power facilities, the power converters provide high power levels, high voltages, and high reliability [21]. Despite allowing more control and flexibility, the use of power electronics in wind turbine systems has evolved from partial-scale to full-scale systems in practical applications. Multiport converters have been looked into for use with energy storage devices to improve the grid integration even more [22]. These converters are becoming increasingly popular because of their capacity for increased system efficiency and flexibility. They are primarily created for low-power, grid-connected RESs. The key research investigations are as follows:  
Figure 3: Advancements in power semiconductor devices. Figure 2: Share of RES in energy generation. * Several investigations (e.g., [3; 6; 10; 22]) highlight grid instability and low inertia as impediments to integrating high-penetration renewables. The importance of mitigation techniques (grid-forming inverters, smart loads, and hybrid control) is escalating. * The development of boost converter topologies [23; 24] and multilevel and switched-capacitor inverters [2; 8] is remarkable. * Conventional MPPT methodologies [25; 26] are progressively giving way to AI/ML-based strategies [27; 28; 29]. Standardized benchmarking within different MPPT scenarios appears to be lacking, according to comparative reviews [29; 30; 31]. A number of studies emphasize converter design, control under grid failures, and PMSG-based wind systems [32; 33]. Vehicle applications, cold starts, and hybridization with batteries or ultracapacitors are the main priorities of fuel cell research [34; 35; 36; 37; 38; 39; 40; 41; 42; 43]. The major research gaps are found to be as follows:
* Power electronics converters have failed to provide high efficiency under fluctuating or variable conditions. * There is not much in the literature on coordinated control for multi-source hybrid systems, despite the fact that many studies prioritize single systems (PV, wind, and FC). * The demand-side management and power flow in both directions play important roles and act as the functionalities in smart grid integration; however, many power electronics converters have not shown good compatibility over attaining these functionalities. * Additionally, it was found that there is a need of to achieve proper coordination between the energy storage phenomenon and power converters in order to avoid reliability issues. As the smart grid is highly associated with IOT platforms, proper monitoring devices have to be installed to avoid safety issues. * A lack of validation and real-world datasets for AI-based MPPT [28]. With an emphasis on wind and solar power technologies, this article thoroughly reviews the advancements in power electronics for dependable and effective energy conversion from RESs. The reference papers have been chosen and categorized as follows: (a) Grid connectivity and the stability of clean energy sources with a primary emphasis on the following topics: power system operation under high RE penetration, mitigating techniques, and challenges. (b) Inverters and power electronics for renewable inclusion, with a particular emphasis on grid converters, fault-handling, control strategies, and switched-capacitor inverters. (c) MPPT methods for solar PV systems, with a particular emphasis on hybrid, AI-based, traditional, and comparative MPPT approaches. (d) Energy storage systems and hybrid configurations, with a focus on supercapacitors, hydrogen, battery integration, and hybrid storage.