Discrete time modeling and control of the voltage source converterfor improved disturbance rejection

摘要

A new voltage source converter control approach is presented,nbased on multivariable z-domain control techniques. Using time-averagingntheory in the synchronous reference frame, a linear time-varying modelnof the converter is developed. The new model may be directly employed asnan efficient simulation tool and used as a basis for developing discretentime inverter controls. Application of digital control techniquesnresults in current step tracking in one switching period, with zeronovershoot. While DC load fluctuations are rapidly compensated throughnnonlinear feedforward, AC system voltage disturbances are rejectednthrough a positive and negative sequence bias estimation scheme. As anresult, the converter may operate at its current limit under even severenAC voltage unbalance and only a balanced AC current will flow, thusnensuring full protection of the semiconductor devices in all threenconverter legs. Experimental results validate both the time-varyingnsimulation model as well as the proposed control design