A generalized control method for input-output harmonic elimination for the PWM boost rectifier under simultaneous unbalanced input voltages and input impedances

Under severe fault conditions in the distribution system, not only input voltages, but also input impedances must be considered as unbalanced. This paper presents a new control method for input-output harmonic elimination of the PWM boost type rectifier under conditions of both unbalanced input voltages and unbalanced input impedances. The range of unbalance in both input voltages and input impedances, for which the proposed method is valid, is analyzed in detail. An analytical approach for complete harmonic elimination shows that PWM boost type rectifier can operate at unity power factor under extreme unbalanced operating conditions resulting in a smooth (constant) power flow from AC to DC side. Based on the analyses in the open loop configuration, a feed-forward control method is proposed. Elimination of harmonics at AC and DC side of the converter affects the cost of DC link capacitor and AC side filter. The proposed method is very useful when PWM boost type rectifier is subject to extreme unbalance due to severe fault conditions in the power system. In addition, by using the proposed method, the PWM boost type rectifier can be operated from the single-phase supply in cases where three-phase source is not available. Simulation results show excellent response and stable operation of the PWM boost type rectifier under the proposed control algorithm.