A nonlinear control of the instantaneous power in dq synchronous frame for PWM AC/DC converter under generalized unbalanced operating conditions

This paper proposes a new control scheme for regulating the instantaneous power for PWM AC/DC type rectifiers under generalized unbalanced operating conditions. By nullifying the oscillating components of instantaneous power at the poles of the converter instead of the front-end through solving a set of nonlinear control equations in real time, the harmonics in the output DC voltage can be eliminated more effectively under generalized unbalanced operating conditions on the AC input side. The control scheme allows the PWM rectifier to generate a DC output without substantial even-order harmonics and to maintain nearly unity power factor under generalized unbalanced operating conditions, which makes it possible to reduce the size of the DC-link capacitor and AC inductors leading to the possibility of reduced total cost. Simulation results along with experimental results under the two examples of the unbalanced operating conditions confirm the feasibility of the new control method.