Advanced Power Electronics and Smart Inverters

To enable the integration of hundreds of gigawatts of solar generation into the U.S. electric power system, NREL is designing a PV inverter that combines high-voltage silicon carbide with revolutionary concepts such as additive manufacturing and multi-objective magnetic design optimization to achieve better performance and reliability at lower cost. This project includes a high-voltage silicon carbide-based power block, advanced gate driver, flexible controller board, advanced grid-support control algorithms, communications interface for interoperability, multi-objective magnetic design tools, high-power-density inverter design, prototyping, and grid integration testing of the new inverter.

Advanced Energy Industries validated its advanced PV inverter technology using NREL's power hardware-in-the-loop system and megawatt-scale grid simulators. Our utility-scale power hardware-in-the-loop capability allowed Advanced Energy to loop its inverter into a real-world simulation environment so researchers could see the impact of the inverter's advanced features on power reliability and quality. Advanced Energy's inverter will help support a smarter grid that can handle two-way flow of power and communication while reducing hardware costs.

Florida Power and Light commissioned a 1.1-MW AC PV solar canopy that shades parking spaces at the Daytona Motor Speedway in Daytona Beach, Florida. In addition to generating clean solar electricity, the site serves as a test platform for solar inverters. Thirty-six grid-connected inverters from eight inverter manufacturers are installed on site, allowing Florida Power and Light to gain insight into the products' efficiency, grid support performance, reliability, and cost.

Florida Power and Light partnered with NREL to provide performance evaluations of several of the inverter types installed at this site. In the Energy Systems Integration Facility, NREL researchers are able to test the inverters under a range of operating conditions in a controlled laboratory environment. Nine types of tests were run in this study: voltage ride-through, frequency ride-through, fixed power factor operation, frequency-watt control, volt/VAR control, efficiency, anti-islanding, load rejection overvoltage, and single- and three-phase faults.

Reaching Department of Energy goals of 20% wind energy by 2030 and 35% by 2050 requires a better understanding of power system reliability at high levels of wind energy penetration. These important questions need to be addressed to enable high-penetration scenarios:

• What is the role for short-term power storage to provide power variability smoothing for wind turbine drivetrain loads?
• How can advanced wind plant controls contribute to grid reliability enhancements?
• Can system stability and reliability be maintained with high instantaneous wind penetrations?
• What is the role of energy storage to firm wind power ability to provide such controls?
• How can other enabling technologies, such as response loads, help integrate high levels of variable power?
• What testing needs to be done to enable this transformation?

The goal of this project is to develop and test coordinated controls of active power by wind generation, short-term energy storage, and large industrial motor drives to provide ancillary services to the grid and minimize loading impacts, thereby reducing operation and maintenance costs and the cost of energy generated by wind power.

NREL is collaborating with SolarCity to address the safety, reliability, and stability challenges of interconnecting high penetrations of distributed PV with the electric power system. This work includes collaborating with the Hawaiian Electric Companies to analyze high-penetration solar scenarios using advanced modeling and inverter testing.

NREL partnered with Solectria to develop PV inverters with advanced features that can support the electric grid. To get more solar power onto the grid, researchers are working to find ways to tame solar power's variable nature. Solar inverters offer the potential to help with this, and manufacturers such as Solectria are developing advanced inverters that can better manage solar power reliability and quality.