Series compensation on power system with very low harmonic distortion

This paper describes a series compensation scheme employing a capacitor in parallel with two PWM switched reactor modules. The two module PWM switched reactors provide continuously variable reactance by employing simple duty ratio control. The switching instants of the two reactor modules are controlled to have 180° phase shift, but equal duty ratio, to achieve harmonic cancellation. The complete series compensator provides a wide range of capacitive and inductive compensation. The harmonic distortion produced by this series compensation scheme with a single switched reactor and two switched reactors is analyzed and compared. An experimental model of the proposed compensator has been simulated, constructed and tested. In the case of the two module system the voltage harmonics have been found to be well below the IEEE 519-1992 recommended limit with a switching frequency of only 300 Hz. Modulating this new compensator with a swing between minimum capacitive compensation and maximum capacitive compensation at 1 Hz shows its fast dynamic response. The simplicity of the scheme and the quality of the results indicates potential as another useful FACTS controller