# Review of Power Electronics Technologies in the Integration of Renewable Energy Systems
## 1 Introduction  
Power electronics technology plays a key role in renewable energy applications, authorizing the efficient control, conversion, and integration of RE sources into the electric utility grid. The demand for electrical energy is at the highest point ever globally, and since fossil fuels are starting to run out, experts are constantly searching for the most efficient alternative energy sources to support sustainable growth. In addition, the main drivers of carbon emissions, which add to global warming, are conventional power plants. Renewable energy sources (RESs) have gained attention as well, and are widely recognized as the best alternative energy sources available today [1, 2, 3]. The depletion of raw materials and environmental pollution caused by conventional energy sources, such as coal and oil, present significant barriers to achieving global sustainability goals. In alignment with the 2015 Paris Agreement, there is a pressing need to transition towards renewable energy sources (RESs) to support global energy sustainability. In response, many nations are intensifying their efforts to shift their energy paradigms, significantly increasing the integration of RESs--such as wind, solar photovoltaics (PV), bioenergy, and ocean wave energy--into their national energy systems [1; 2; 3]. For example, Denmark aims to achieve 100% energy independence from fossil fuels and become carbon-neutral through the use of RESs by 2050 [2]. The International Energy Agency (IEA) reported that Germany has significantly expanded its share of renewable energy in its electricity generation due to robust policy support [3]. Over the past two decades, the RES capacity has surged significantly far and wide, as shown in Figure 1[4]. Furthermore, the growth rates of wind and solar PV technologies have been most rapid among RES systems developed between 2000 and 2020 [4]. Despite this progress, the widespread integration of RESs presents two primary challenges. The first is ensuring the integration of large-scale RESs into the electrical grid while maintaining the system's reliability during fluctuations in renewable energy power generation. Second, the use of improved power electronics can help with the efficient, intelligent, and sustainable conversion, transmission, distribution, and consumption of electrical power. Consequently, power electronics technologies have evolved rapidly, and the grid integration standards for RESs, particularly for wind and PV systems, are continuously being updated [5; 6; 7; 8; 9; 10; 11; 12; 13]. The cumulative capacity of RESs is depicted in Figure 2.  
The development of power electronics technologies has been closely linked to advancements in power semiconductor devices, as shown in Figure 3[14]. From the introduction of thyristors in 1957 to the third-generation of fully controlled semiconductor devices, such as insulated gate bipolar transistors (IGBTs) and metal-oxide semiconductor field-effect transistors (MOSFETs), in the 2000s [15; 16], the research has focused on the gate drivers, circuit configuration, design, and control performance to achieve high switching frequencies, low losses, and high power handling capability in power-electronics-based converters. The advent of wide-bandgap (WBG) devices, including with silicon carbide (SiC) and gallium nitride (GaN), has marked a second revolution in power electronics, offering superior results in all aspects of the system's performance [17; 18]. However, WBG devices also introduce new challenges related to their packaging, thermal management, and electromagnetic interference (EMI). Figure 1: RES installed capacity. Although reducing system costs remains an issue, technological advances in semiconductor technology have made integrating RESs into the grid on a wide scale easier. In the past, the emphasis for small-scale RES power converter architectures was attaining high power densities and efficiency to preserve the electrical isolation between the grid and the low-voltage side [19].