Complex state variables modeling and nonlinear control of PWM voltage- and current-source rectifiers

This paper proposes the use of complex state variables to model and control PWM voltage- and current-source rectifiers, a technique originally developed for AC machines based on space vector theory. This technique employs complex signal flow graphs to model systems of differential equations, hence rendering them intelligible by visual inspection. Moreover, it allows nonlinear control laws to be directly obtained from converter models, further simplifying the control system design. Feedback linearization is herein used, a nonlinear strategy of great simplicity and intuitiveness. Under the proposed control schemes both rectifiers attained fully decoupled d-q axes dynamics, thus enabling them as VAr compensators, and also achieved a constant dynamic response totally independent from the drive operating point. The latter is highly desirable for high-performance drives featuring continual accelerations and decelerations. The paper includes a detailed modeling and nonlinear control law design-procedure for both PWM rectifiers, together with experimental results from 10 kVA TMS320C32 DSP-based laboratory prototypes used for evaluation purposes.