Control system for a three-phase PWM current source line converter with compensating properties

This paper presents a three-phase PWM current source line power converter (CSLC) which, apart from feeding the DC load, also performs the role of a compensator for reactive and distortion power drawn by other neighbouring, nonlinear loads connected to the network. Two types of control systems, with feedback-loop signals proportional to the supply-line voltage (i.e., the input capacitor voltage), were considered. In the first system, the instantaneous value of the input voltage is used as the modulating signal to be compared with a saw-tooth signal in the modulator. Digital simulation and laboratory tests were carried out for this system. As concerns the second control system, the quantity that has influence on the modulator is a signal that sums up all the high-order harmonics of the line voltage. Experiments carried out revealed that the second system had superior properties. The control system was realized with the application of an SAB 80C-166 microprocessor.