Characteristics of the Magnetic Energy Recovery Switch (MERS) as a Series FACTS Controller

Developing active series compensation in transmission systems is challenging due to the large currents and voltage capabilities required. The main purpose of this paper is to show that the magnetic energy recovery switch (MERS) can be an attractive new series compensator by applying appropriate control. The MERS is similar to a single-phase full bridge, meaning that compared to the gate-commutated series capacitor, it has twice the number of active switches. However, advantages, such as the double voltage-current operating range, eliminating the need for reverse blocking switches, zero current turn-on, and a lower current conduction period of each switch can make the MERS an attractive alternative. The basic characteristics of the MERS have been found to be similar to a series connection of a voltage source and a capacitor in steady state. With this dual characteristic, a control method has been developed where the minimization of the harmonics in the series-injected voltage and stable operation during large setpoint changes have been achieved. The resulting subharmonic characteristic also indicates a low risk of subsynchronous resonance. Experimental results verify the proposed configuration and control.