Distributed-SMES or D-SMES

What is it?

A Superconducting Magnetic Energy Storage (SMES) system is a device for storing and instantaneously discharging large quantities of power. These systems have been in use for several years to solve voltage stability and power quality problems for large industrial customers. A Distributed-SMES (D-SMES) system represents an innovative new application of proven SMES technology, enabling utilities to improve system-level reliability and transfer capacity. D-SMES provides cost-effective grid stabilization for entire electric utility systems.

Where and how are they used?

D-SMES systems are employed by electric utilities and are connected to their grids at substations. D-SMES systems increase transfer capacity and protect utility grids from the destabilizing effects of short-term events such as voltage dips caused by lightning strikes and downed poles, sudden changes in customer demand levels and switching operations. In many cases, D-SMES is a cost-effective way to reinforce a transmission grid without the costly and environmentally intrusive construction of new lines. Rather than protecting one individual customer, a D-SMES system consists of a number of SMES units placed at strategically-selected locations on the utility system. By improving the stability of the entire transmission grid, a D-SMES system can cost-effectively increase system capacity and improve the reliability and quality of electric service to thousands of customers simultaneously.

D-SMES is a shunt connected Flexible AC Transmission (FACTS) device designed to increase grid stability, improve power transfer, and increase reliability. Unlike other FACTS devices, D-SMES injects real power as well as dynamic reactive power to more quickly compensate for disturbances on the utility grid. Fast response time prevents motor stalling, the principal cause of voltage collapse.

At the heart of each D-SMES system are American Superconductor’s (AMSC) PowerModule™ advanced power electronic converters.  PowerModule inverters are an intelligent, fully integrated four-quadrant power converter with high power density.  The D-SMES is composed of rack-able IGBT power module poles capable of producing capacitive and inductive VARs.  It is an air cooled, current source system that, unlike capacitor-based systems, is not subject to the square of voltage de-rating factor at lower voltages.  This advantage reduces the overall level of MVARs needed for some applications.  The inverters also have a short term overload capability of 2.67-3.0x of the continuous rating for up to 2 seconds, providing extra capacity for post-fault voltage recovery.