Power Electronics

Silicon Carbide (SIC) Power Module

In general terms, Power Electronics refers to switching devices that control and convert electrical power flow from one form to another, according to a user’s need. “Convert,” in power electronics, describes the process of changing power from one form to another (for example, from the direct current used in long-distance transmission to the alternating current used in commercial and residential applications). The piece of hardware that performs this process is generally called a “converter.”

Converters can perform the following processes/conversions (each process/conversion is referred to with a commonly used name):

* The most common type of conversion is DC-to-AC (inversion); e.g., converting DC power from a storage device into AC power for use by a utility grid or other end-user.

Performing conversions requires some essential hardware:

• a control system,
• semiconductor switches,
• thermal management devices,
• protection devices,
• magnetics such as transformers and filters,
• DC and AC disconnects, and
• enclosures.

Power Conversion System (PCS)

The PCS is a vital part of all energy storage systems. It interfaces energy storage, the energy-storage device, and the load (the end-user). PCS costs are significant and can be greater than 25% of the overall storage system. PCS costs range from $100/kW for uninterruptible power supply (UPS) markets to $1200/kW for standalone markets.

Some of the major PCS markets include:

• motor drives,
• power supplies,
• UPSs,
• electric vehicles,
• DC and AC disconnects, and
• inverters/converters for solar hybrid systems, micro-turbines, fuel cells, and wind turbines.

However, PCS technology has been evolving slowly, due to the limited distributed energy resource (DER) market. As a result, PCS costs have been high, with low profit margins; and the manufacturing volume has lowered, which has impacted reliability and quality of the PCS designs.

PCS needs a significant reduction in overall cost, with improved reliability, and development of state-of-the-art, multiple-use systems. This would increase production volumes for DER applications, improve controls and adaptability, and improve manufacturing.

DOE Energy Storage Systems Program Involvement

Sandia represents the DOE Energy Storage Systems Program (DOE/ESS) and collaborates with the DOE Power Electronics Program in partnerships with industry and educational institutions to develop state-of-the-art PCS. DOE/ESS goals include lower cost, increased reliability, improved control philosophy, better integration to energy storage devices, and more efficient packaging and manufacturing for the PCS. Efforts by the DOE/ESS are instrumental in providing benefits for all energy users and helping to secure our nation’s energy supply.

Current PCS projects include: