PWM-controlled series compensation on a radial feed power system

A series compensation scheme is described employing two pulse width modulat ion (PWM) switched reactor modules in parallel with a capacitor. The two-mo dule PWM-switched reactors provide continuously variable reactance by emplo ying simple duty ratio control. The switching instants of the two reactor m odules are controlled to have 180 degrees phase shift, but equal duty ratio , to achieve harmonic cancellation. The complete series compensator provide s a wide range of capacitive and inductive compensation. The harmonic disto rtion produced by this series compensation scheme with multiple-controlled reactors is analysed. An experimental model of the proposed compensator has been constructed and tested; this was inserted in a radial feed transmissi on line, to reduce the level of fluctuation of the receiving power on a nom inal load subjected to another large load switching. For the two-module sys tem, the voltage harmonics have been found to be well below the IEEE 519-19 92 recommended limit, with a switching frequency of only 300Hz. At the same time, the influence of the large load switching can be significantly reduc ed by the application of this compensator. The simplicity of the scheme and the quality of the results indicates its potential as another useful power quality controller.