An improved current mode control of a three-phase rectifier based on positive-sequence detection

In this paper an improved current mode control for a three-phase rectifier is presented which is able to compensate the line currents under unbalanced operation of the supplied grid voltage. Instrumental for the controller design is the computation of the current reference, where, the key point is the use of the positive-sequence of the grid voltage to construct it. The control scheme is designed to guarantee current tracking of the positive-sequence of the grid voltage and the average voltage regulation at the output towards the desired voltage reference. The overall resulting controller is composed by two main control loops, namely, current (or inner), the voltage (or outer) control loops and additionally a positive-sequence estimator of the grid is used to compute the current reference. The current control loop is designed as a proportional controller with a couple of adaptive estimators which have been added to cope with parameter uncertainties of the filter. The voltage control loop consists of an Integral plus a Proportional controller whose output signal acts as a modulating signal of the current reference.