A novel variable reactor with transformer and inverter control

In the paper, a novel principle of variable reactor with a transformer and inverter control is proposed. A transformer with air gap is chosen and its primary winding is connected in series or parallel in power utility, the primary winding current of the transformer is detected and functioned as the reference signal. A voltage source PWM inverter is applied to produce a voltage, which is a controlled voltage and energized across the secondary winding of the transformer. According to the transformerpsilas voltage equations, when the controllable voltage and the primary winding current satisfied a certain condition, the equivalent impedance of primary winding varies continuously along with the controlled voltagepsilas amplitude. Many types of flexible ac transmission system (FACTS) equipments, e.g., fault current limiter (FCL), power system unified load flow controller (UPFC), thyristor controlled series capacitor (TCSC), can be implemented in terms of the novel principle. Besides this, the stability condition is analyzed when the variable reactor is connected in series with a resistance-inductive load. The validity of the theory is proved by the simulation results.