Leydig, Voit & Mayer, Ltd.
Controller of adjustable DC voltage for a transformerless reactive series compensator
 A controller for controlling a reactive series compensator serially inserted at compensator terminals into a power transmission line for controlling the line current. The controller includes a current control loop and a voltage control loop. A current controller outputs a control voltage (cc.sub.out) indicating a desired compensator terminal output voltage (u.sub.c). A control method selector means generates, in a low output voltage region, a constant reference voltage (u.sub.DC.sup.ref) for the voltage control loop and a variable modulation index mq of a modulation signal m=m.sub.d cos (.omega.t) -m.sub.q sin (.omega.t). In a high output voltage range, the control method selector outputs a constant modulation index m.sub.q and a variable reference voltage (u.sub.DC.sup.ref). The voltage controller outputs the modulation index m.sub.d of the modulation signal m. Furthermore, the control method selector can include a rate limiter for limiting the change rate of the reference voltage (u.sub.DC.sup.ref). In connection with the control method selection and/or the rate limiter, a decoupling control for making the voltage and current control loops independent from each other can be used. The controllers find particular application in transformerless reactive series compensators for single-phase or three-phase control. 
Mitsubishi Denki Kabushiki Kaisha
Y G H
Y02E G05F H02J
additional inventional inventional
Andreas Toshiyuki
Beer Fujii