According to the International Energy Agency’s (IEA)s latest research, 74% of renewable capacity additions in 2028 will be solar energy, with an impressive 540 gigawatts (GW) of capacity added annually. As one of the most abundant and sustainable sources of power, solar energy harnesses the sun's energy and converts it into electricity using photovoltaic (PV) systems. At the heart of these systems is the solar inverter, a critical component that transforms the direct current (DC) generated by solar panels into alternating current (AC) suitable for use in homes and on the grid. Semiconductors play a pivotal role in the operation of solar inverters, and we explore their functions, benefits, and latest advancements.
Solar inverters are essential for the functioning of PV systems, acting as the bridge between solar panels and the electrical grid or home power systems. The conversion process involves two main stages:
- DC/DC conversion stage: where the Maximum Power Point Tracking (MPPT) algorithm optimizes the power output from the solar panels by adjusting the voltage to ensure maximum efficiency.
- DC/AC conversion stage: the optimized DC power is then converted into AC electricity, making it suitable for household use or feeding into the grid.
This dual-stage process ensures that the power generated by the solar panels is efficiently converted, minimizing energy losses and enhancing overall system performance.
Inverter topologies and functionality
Solar inverters utilize various topologies to achieve best efficiencies, with two-level and three-level topologies being the most common. Two-level inverters, which are simpler and widely used in smaller systems, switch between two voltage levels to produce AC power. Three-level topologies provide a more refined output by introducing an additional voltage level, resulting in lower harmonic distortion, reduced stress on components, and improved overall efficiency. That makes them ideal for larger, more demanding solar systems. These topologies allow solar inverters to cater to a wide range of applications, from small residential setups to large-scale solar farms. To maximize the efficiency of the solar power system, inverters use Maximum Power Point Tracking (MPPT) algorithms, ensuring that the solar panels operate at their peak power output.
In grid-tied systems, inverters manage the interaction with the electrical grid, ensuring synchronization and safe operation, while also having the capability to shut down automatically during grid outages to protect utility workers. Additionally, modern inverters often come equipped with monitoring and communication features, allowing users to track their system’s performance and receive alerts in case of issues, further enhancing the reliability and convenience of solar energy systems.
Different inverters for different applications
Since photovoltaic installations come in different sizes ranging from small residential units to grid-tied solar power plants there are different types of inverters for every application case.
- The smallest inverter, mainly used for residential installations, is the micro solar inverter. Power conversion is performed at the individual PV panel level, and they can handle power from 200 W up to 3 kW. Having a microinverter on each panel allows MPPT per panel, resulting in higher efficiency and flexibility particularly in installations with shading issues.
- Another inverter commonly used in households is the hybrid solar inverter. These devices are designed to integrate solar electricity along with battery energy storage systems and EV charging infrastructure, managing all power conversion bi-directionally. To cover today’s residential purposes, the current power range for hybrid inverters typically goes from 1 kW up to 50 kW.
- Often the preferred option for larger residential installations as well as commercial projects is the photovoltaic string inverter. This connects multiple panels in series (string) and converts the combined DC output into AC. These systems typically operate in power range of a few kilowatts up to several hundred kilowatts.
- For the biggest utility and grid-tied solar projects one central inverter is at the heart of the solar power conversion process. These large box-shaped devices handle output power ranges from a few hundred to several thousand kilowatts.
Semiconductors in solar inverters
Semiconductors are the backbone of solar inverters, playing a crucial role in the conversion and management of electrical energy within PV systems. Key semiconductor components like IGBTs, MOSFETs, diodes and bipolar transistors are integral to the inverter's operation.
- IGBTs are widely used in solar inverters for their ability to efficiently handle high voltages and currents, making them ideal for power conversion tasks. They offer the benefits of both high-speed switching and low conduction losses, which are essential for both MPPT and DC-AC conversion process.
- MOSFETs, on the other hand, are mainly employed in lower power applications within solar inverters due to their superior switching speeds and lower gate drive power requirements, which contribute to overall efficiency improvements, especially in smaller, high-frequency inverter designs.
- Bipolar Junction Transistors (BJTs) are vital in small signal control applications within solar inverters, where they ensure precise switching and amplification of signals, maintaining stable inverter operation by efficiently controlling low-level currents and voltages in various circuits
- Diodes, another critical component, facilitate the smooth flow of electricity by allowing current to flow in a single direction, preventing backfeed that could potentially damage the inverter and other connected components.
Wide bandgap a game changer
The introduction of wide bandgap (WBG) semiconductors, specifically Silicon Carbide (SiC) and Gallium Nitride (GaN), has revolutionized solar inverter technology by offering significant advantages over traditional silicon-based semiconductors. GaN High Electron-Mobility Transistors (HEMTs) and SiC MOSFETs provide superior electrical properties, including lower on-resistance, faster switching capabilities, higher breakdown voltages, and the ability to operate at elevated temperatures. These characteristics lead to significantly lower power losses, higher efficiency, and more compact designs due to reduced cooling and passive component requirements.
In solar inverter applications, especially in small-scale photovoltaic (PV) systems for homes and commercial buildings, GaN and SiC devices enable more efficient energy conversion and higher power densities. For instance, GaN-based designs, such as those using Nexperia’s GAN041-650WSB, can achieve switching frequencies between 100 kHz and 300 kHz, which is a substantial increase compared to the 15 kHz to 30 kHz range of traditional IGBT-based solutions. This increase in frequency allows for smaller and lighter output filters, reduced harmonic distortion, and an overall more compact and cost-effective design with power densities that have increased from 0.5 W/in³ with IGBT modules to as much as 4 W/in³ with the latest WBG devices.
In single-phase string inverter configurations, where PV panels are connected in series to generate a DC voltage, the higher efficiency of GaN and SiC technologies is critical. These configurations typically involve a DC/DC boost circuit controlled by a microcontroller or system-on-chip (SoC) that also manages maximum power point tracking (MPPT). The output feeds DC link bulk capacitors, which can then supply power to an energy storage system (ESS) or a DC/AC inverter to provide single-phase AC for local use or the grid.
The future is bright for solar inverters
The shift toward GaN and SiC technologies not only improves the size, weight, and cost-effectiveness of solar inverters but also enhances their efficiency, potentially breaking through the 99% efficiency barrier. This leap in performance makes solar energy systems more accessible and viable, ultimately lowering the total cost of ownership and paving the way for the next generation of highly efficient and resilient renewable energy solutions.
In the future, we can expect inverters to integrate even more advanced features like smart grid compatibility, enhanced monitoring, and AI-driven energy management. These advancements will enable greater energy optimization, accelerate response times, and improve integration with energy storage systems. Further transforming the landscape for distributed energy generation and accelerating the transition to clean, efficient solar power. All enabled by advances in power semiconductor technology.
