SMES for protection of distributed critical loads

This paper proposes the use of a micro high-temperature superconducting magnetic energy storage system (HTS-SMES) to support critical industrial loads connected to the customer´s 11 kV load bus with a ride-through capability of around 20 cycles. With the advances of power electronics and digital signal processing technology, such a system can also be utilized to improve the power quality of the power system. A novel control methodology is proposed to regulate the SMES discharge to extend the support time to critical loads during a short-term disturbance in the distribution network. Using a P-Q diagram, the analysis of the power flow from the energy storage system to the power system is presented. The proposed hysteresis controller with SMES increases the operating area in P-Q plane as compared to the conventional d-q controlled scheme used in the literature. This allows the system capability to be utilized to its maximum thermal limits. The scheme also has the capability to control the real and reactive power flow through the converter using the proposed hysteresis current control scheme. This provides the capability to optimize the available energy storage by using load priority scheduling. The detailed three-phase system simulation is carried out using realistic models of the power electronics components used in the converters. Laboratory test results on the prototype are presented to validate the proposed control scheme.