Design Consideration of a High-Temperature Superconducting Magnet for Energy Storage in an Active Power Filter

Installing active power filters (sometimes called active harmonic filters or line conditioners) in an electric power network can improve the quality of electricity supply. A shunt active power filter, with a current-source PWM inverter and a conventional copper inductor as its energy storage, has a significant power loss. The power loss in this copper inductor can be substantially reduced by replacing the inductor with a high-temperature superconducting (HTS) magnet. Several solenoid design alternatives using silver-sheathed BSCCO-2223 tape have been made for the HTS magnet that has an inductance of 0.5 H for this application. A liquid-nitrogen-cooled HTS magnet has been built and tested for use in an active power filter. The loss-reduction effect of using the HTS magnet with the current-source active power filter has been investigated experimentally, and the results are compared with those when using a conventional copper inductor. Practical issues such as air-core design versus iron-core design and using liquid-nitrogen cooling or a cryocooling are analyzed and discussed.