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50 kW Power Block for Distributed Energy Applications

National Renewable Energy Laboratory

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Actual prototype
Actual prototype

Technology Marketing Summary


Distributed energy (DE) systems have begun to make a significant impact on energy supply and will certainly affect energy needs in the future. These systems include, but are not limited to, photovoltaics (PV), wind turbines, micro-turbines, fuel cells, and internal combustion (IC) engines.  Beyond these generation systems, energy storage and electric vehicles are expected to have an increasing impact. The PV-inverter market alone totaled $7.2 billion in 2011 and is expected to surpass $19 billion by 2017.

In order to integrate distributed energy systems into the electric grid, advanced power electronics are required. While power electronics are not new technology, their applicability and range of use have expanded with wider acceptance of DE systems. These power electronics, given the right design, can be applied to DE systems, electric car and rail transport, energy storage, and a number of other applications.

Considering power electronics can account for anywhere between 20% - 40% of the total cost of a DE system, there is the potential for significant cost savings if the cost of the power electronics can be reduced. The traditional method of creating power electronics, such as inverters, has been to make equipment for the specific purpose of each individual system.  While this method has upfront cost savings, it eliminates the possibility for economies of scale and varied applications for a given power electronics technology. By building a modular, scalable power block, there is potential for cost savings from economies of scale, multiple applications, and increased functionality.

Because of the potential to lower costs and increase functionality of power electronics for DE systems, the California Energy Commission (CEC) sponsored an initiative in partnership with NREL to develop a modular, scalable power block based on off-shelf or readily available components. The project included the CEC, National Instruments, Semikron and NREL researchers in a public-private partnership in order to develop and test a modular, scalable power inverter system.


Power Block

The Modular 50 kW Power Block comprises a Semikron SKiiP3 module with 1200V insulated gate bipolar transistor (IGBT) switches and anti-parallel diodes arranged in three-phase bridges. It includes gate drivers, DC bus film capacitors, current sensors, a DC voltage sensor, a temperature sensor, a digital controller board, connectors, and bussing—all mounted on an air-cooled heat sink. The Semikron SkiiP3 IGBT module has features such as pressure contact technology, an integrated driver, and protection that have been fully integrated and tested by NREL researchers.

Advanced Power Electronics Controller

NREL worked with National Instruments to develop a state-of-the-art controller board for these power blocks. The controller board was based on National Instruments’ single-board RIO platform, which is commercially available and, for this project, included a 400 MHz PowerPC processor and Xilinx Spartan-6 LX45 FPGA.

The deployment-ready controller board has been designed for high-volume production of grid-tied inverter, DC-DC converter, and motor/generator drives and has input-output signal compatibility with most standard IGBT intelligent power modules. The controller board provides advanced programming capability for use in Smart Grid applications and a wireless user interface.

Software Development

In order for the power block and controller components to work correctly to be grid-ready, advanced code was developed at NREL to meet the unique design. The developed software implements complete control algorithms in LabVIEW FPGA for a three-phase IEEE 1547-compliant grid connected inverter. The software includes: feedback control loops, actual pulse-width modulated gate-drive output and more. The algorithms allow for AC current and DC voltage feedback control loops, phase-lock loop (PLL), and island detection and all other IEEE 1547 requirements. While space in FPGAs can be limited, the software was designed for individual users to add their own customized capabilities, such as Maximum Power Point Tracking (MPPT) or a battery management system. The software is not specific to any energy source or load, and can therefore be applied in a variety of applications. And while the code was written specifically for an inverter control platform, it could readily be modified to work with other NI RIO platforms or general purpose controllers.

Partnership Success

The resulting prototype included benefits such as: improved operating efficiencies and power quality, IEEE 1547 standard compliance, VAR support, reduction of distributed energy fault currents, among others. The complete system was built and tested in a grid-like setup in NREL labs with both technical and commercial support from Semikron, National Instruments and NREL staff. NREL was instrumental in developing the advanced software as well as grid-like testing and validation in real-world simulations. Furthermore, NREL’s ability to test at megawatt levels with grid simulation has grown significantly with the recent addition of the Energy Systems Integration Facility (ESIF). Please visit for more information.

While the modular power block is just one example of what can be created with NREL and industry partnerships, NREL is looking to further develop new and innovative integrated systems technologies with commercial partners.

  • A crosscutting, standardized interface for utility grid-tied and smart grid DE applications                                                            
  • Scalable and modular design
  • High reliability with a mean time between failures of at least 10 years
  • Low cost and manufacturability in high volume
  • Ways to address, improve and lower costs for UL certification
Applications and Industries
  • Solar, Photovoltaics
  • Small Wind
  • Energy Storage
  • Power electronics
  • Electric Vehicle
  • Rail transportation
Technology Status
Technology IDDevelopment StageAvailabilityPublishedLast Updated
ROI 12-37, 12-52, 12-53, 12-61, SWR 12-11, 12-12, 12-14, 13-02, 13-03PrototypeAvailable08/05/201308/05/2013

Contact NREL About This Technology

To: Erin Beaumont<>