To address these requirements, the exploration of power electronic devices based on Wide band gap semiconductors like Silicon Carbide and gallium nitride are gaining immense popularity and interest. The recent commercialization of these WBG semiconductors is thought to bring about a transformation in the power electronics industry as the new and improved Silicon devices encounter limitations in terms of maximum junction temperature of 135°C, switching frequency, breakdown voltage, and power density. Silicon-carbide devices offer lower volume and higher efficiency or a combination of both due to their higher breakdown field. This allows the development of switches with superior voltage-blocking capability compared to traditional silicon switches with the use of 3L-BS NPC topology instead of the 3L-DNPC topology to leverage the advantages of SiC devices. PV-inverter companies have already begun producing converters based on the 3L-BS NPC topology with SiC devices to achieve higher efficiency.

In the pursuit of cost reduction in photovoltaic systems, a converter utilizing Silicon Gate Bipolar Transistors and neutral point clamping has achieved an impressive market-leading efficiency of 98.5%. However, the drawback lies in its relatively high cost compared to Si-based alternatives that involve returning to the 2L-Full Bridge with a split capacitor, aiming to maintain comparable efficiency while reducing overall costs. Moreover, it is also important to evaluate efficiency, thermal loading distribution, and costs associated with both PV-Inverter topologies and provide insights into the trade-offs and advantages of each approach. The below Figure 1 shows various applications that utilize and integrate SiC and GaN-based power devices into the current commercial market.

Figure 1: Graph Showing Integration of GaN and SiC Power Devices in the Market for Various Applications

Exploring In-depth Analysis and Application of Wide Band-Gap Devices in Photo Voltaic Inverter Systems

The current state of technology has achieved the maximum potential and development level of Silicon, which is almost equivalent to its theoretical maturity, therefore the new age Wide Bandgap devices are sought to replace these traditional and outdated silicon-based devices. Wide Band-Gap devices exhibit superior electro-thermal properties and are believed to be potential replacements for Silicon in certain applications. Their advantages over Si-based devices include the ability to operate at higher temperature levels without compromising electrical characteristics, which is possible only due to the wider bandgap.

WBG devices also boast higher breakdown voltages due to a superior electric breakdown field, enabling the use of thinner semiconductor chips with lower on-resistance and reduced conduction losses. Additionally, higher power density is achievable through enhanced thermal conductivity, although Gallium Nitride is proven to be an exception. Despite these superior advantages, challenges and barriers exist, such as the limitation imposed by current high temperature packaging techniques, obstructing the full exploitation of WBG semiconductors. These limitations include the need for packaging with a power density of 1000 W/cm² and a temperature exceeding 300°C, while current techniques offer only 280 W/cm² and a maximum temperature below 125°C.

Furthermore, the short-circuit capability of commercialized Silicon Carbide devices lags Si-based devices, prompting ongoing research to enhance this aspect. Despite these challenges, the technology has matured over the years, with the commercial availability of SiC diodes for over a decade and the introduction of various SiC switches in the past 3-4 years. Moreover, with the entry of low-voltage GaN devices into the market, the scope of Wide Bandgap devices is very extensive.

Power electronics play a pivotal role in facilitating the integration of photovoltaic systems with the electrical grid. In Figure 3, a typical grid-connected PV system is illustrated, comprising components such as the voltage source inverter, buck-boost DC-DC converter, PV-string, and output LCL filter. The decision to include the DC-DC converter stage is mostly dependent upon the power output of the PV system. Additionally, Figure 3 outlines the essential control blocks necessary for achieving the intended system functionality.

Given the high cost of solar electricity technology, the utilization of high-efficiency inverters emerges as a critical requirement. In the realm of silicon-based inverters, the switching frequency is typically limited to 16 kHz due to switching losses, leading to heightened cooling and magnetic demands. To enhance the efficiency of PV systems, many solutions for Si-based PV inverters have transitioned to 3L structures, attaining efficiencies of up to 98%. This is primarily attributed to the low switching losses of 600V Si IGBT or MOSFET and reduced core losses in the filter.

Figure 2: Typical Layout of a Grid-Connected Photo Voltaic System

The current state of silicon technology has reached its theoretical maturity, prompting the exploration of Wide Bandgap devices as a potential candidate for replacement due to their superior electro-thermal properties. These devices operate at higher temperatures without compromising electrical characteristics, mostly due to their wider bandgap. WBG devices also offer higher breakdown voltages, thinner semiconductor chips, and enhanced thermal conductivity, although challenges exist, such as limitations in high-temperature packaging techniques. Despite obstacles, WBG technology has matured over the years, with the commercial availability of Silicon Carbide diodes for over a decade and the introduction of various SiC switches in recent years. The entry of low-voltage Gallium Nitride devices into the market further expands the scope of WBG devices. In the field of power electronics, advancements in semiconductor devices, particularly WBG devices like SiC and GaN, play a crucial role.

Traditional Silicon-based devices face challenges in meeting market demands for applications such as electric vehicles and photovoltaic systems. The recent commercialization of SiC and GaN semiconductors is expected to transform the power electronics industry, addressing limitations faced by Silicon devices. SiC devices, in particular, offer higher efficiency and power density, allowing for the development of converters with superior voltage-blocking capability. PV-inverter companies are already adopting SiC devices in their products to achieve higher efficiency.

While converters utilizing Silicon Gate Bipolar Transistors and neutral point clamping have achieved impressive efficiency, cost considerations drive the exploration of alternative topologies, such as the 2L-Full Bridge with a split capacitor. Evaluating efficiency, thermal loading distribution, and costs associated with different PV-inverter topologies is essential for understanding trade-offs and advantages.