Pw. Lehn et Mr. Iravani, Discrete time modeling and control of the voltage source converter for improved disturbance rejection, IEEE POW E, 14(6), 1999, pp. 1028-1036
A new voltage source converter control approach is presented, based on mult
ivariable z-domain control techniques. Using time-averaging theory in the s
ynchronous reference frame, a linear time-varying model of the converter is
developed. The new model may be directly employed as an efficient simulati
on tool and used as a basis for developing discrete time inverter controls.
Application of digital control techniques results in current step tracking
in one switching period, with zero overshoot, While die load fluctuations
are rapidly compensated through nonlinear feedforward, ac system voltage di
sturbances are rejected through a positive and negative sequence bias estim
ation scheme, sis a result, the converter may operate at its current limit
under even severe ac voltage unbalance and only a balanced ae current will
flow, thus ensuring full protection of the semiconductor devices in all thr
ee converter legs. Experimental results validate both the time-varying simu
lation model as well as the proposed control design.