Getting to a Cleaner Future – Design Challenges and Solutions for Solar Inverters

Renewable Energy is the key to a cleaner future and solar energy is leading the way. Designers of solar inverters face a multidimensional challenge to ensure solar power continues to meet the growing demand for clean energy. This article explores these challenges by comparing the latest solutions in terms of efficiency, weight, cost and reliability, and shows that flying capacitor topologies can offer unique opportunities for system optimization.

Climate change is one of the key challenges facing today’s society. The global demand to fight rising carbon dioxide levels, pollu- tion, and to reduce our dependency on fossil fuels, is driving governments towards a clean energy future. Research Institutions and In- dustry are working to identify and deploy new ways to meet the growing demand for clean energy. Renewable power is the key to a clean energy future, already providing almost 25% of the global power demand, and solar power is the fastest growing part of the re- newable energy landscape. In recent years, more solar generation capacity has been added than fossil fuel and nuclear power combined, and almost twice as much as wind power. Solar power generating capacity grew to 48% of all new power installations during 2019-2020, and countries such as Germany, Italy, Greece and Chile are already produc- ing almost 10% of their national demand. Huge investments continue to be made in all segments of the solar market, including the consumer, industrial and utility sectors.

Over 700 GW of solar power has been deployed globally, with more than 100 GW being installed during 2020. Both cumulative and annual power installation are forecast to double in the next 5 years. The majority has been in utility-scale systems (>100 kW) but, increasingly in recent years, the consumer market has seen significant growth, especially when coupled with storage systems. Utility-scale systems are split between central-inverter and string-inverter systems. Historically, central-inverter systems have received the majority of investment. How- ever, string-inverter systems are expected to become the dominant type in the next 5 years due to falling costs, increased flexibility and ease of maintenance. Central-inverter systems are based on multiple PV panels feeding into a single large inverter hub. In contrast, string-inverter systems place the inverters together with smaller “strings” of PV panels. These sub-systems are then combined before output. Consequently, as demand grows, additional string-inverter sub-systems can easily be added. As string -inverters are usually modular in design, maintenance typically involves simple re- placement of the failing inverter module. Lo- cal storage of replacement modules means problems can be quickly resolved. This helps ensure security of power supply, thereby minimizing brown- or blackouts.

High efficiency, maximum power capability, low weight and high reliability are some of the critical requirements designers need to consider to support these key string-inverter system features. High efficiency is needed to maximize the power generated from the PV panels and minimize power loss. This helps reduce heatsink requirements and system weight. Maximizing the power generation per inverter reduces the number of modular sub- systems required for a given power output. This reduces the footprint of an overall sub- system. Low system weight ensures that in- verters can be easily installed and replaced, without the need for special lifting equipment. This enables quick system installation and a rapid response to system failures, especially in difficult-to-reach locations. High system reliability helps reduce maintenance require- ments, even when systems are working in harsh environments, further improving lon- gevity of supply. Vincotech’s latest genera- tion of power modules for the solar market introduces new design concepts which specifically target these design requirements – high efficiency, maximum power density, low weight and high reliability. Careful selec- tion of innovative topologies and the latest semiconductors enables significant system level benefits. The following detailed analysis of the power conversion steps in an inverter system shows how and where Vincotech’s latest modules are addressing these design requirements and the system benefits provided.