Renewable energy sources that power residences and small businesses are usually integrated into small networks known as microgrids. Microgrids operate as a unit and traditionally use alternating current (AC) oscillating at 60 cycles per second (hertz). Alternative energy sources typically generate power at 0 hertz (fuel cells) or at variable frequencies (wind), and require inefficient frequency converters to connect to the 60-hertz microgrid. Power systems that operate at frequencies above 400 hertz, such as those in air and spacecraft, offer significant benefits over 60-hertz systems, including improved power quality and reduced electrical component size, weight, and cost.
NSF-funded researchers at the Colorado School of Mines are investigating the benefits of microgrids that operate at 500 hertz instead of 60 hertz. Their efforts in theory and simulation have demonstrated the viability and efficiency of 500-hertz single-phase power systems. Experimental results using a test bed built by the researchers have confirmed that the high frequency alternating current (HFAC) microgrid is a practical method for integrating renewable energy sources into the power grid.
With advances in power electronics, devices, and controls, the utilization of much higher frequencies in the microgrid will significantly reduce the size, weight, and power loss of the energy conversion system. The paradigm shift from centrally controlled, three-phase 60-hertz systems to HFAC single-phase microgrids will dramatically change the way electric distribution systems are operated and will increase their energy efficiency, economy, and resilience. The effort also enables future large-scale integration of renewable energy resources in the U.S. energy portfolio.