Marcos Pereira

A current based model for load flow studies with UPFC

This paper deals with an alternative proposition for the steady state modeling of unified power flow controller (UPFC). Since current limitations are determinant to FACTS apparatus design, the proposed current based model (CBM) assumes the current as variable, allowing easy manipulation of current restrictions in optimal power flow evaluations. The performance of the proposed model and of the power injection model (PIM) are compared through a Quasi-Newton optimization approach. Two operating situations of a medium size network with 39 busbars were studied from the point of view of optimization and current limits, observing the performance of the UPFC modeling.

Harmonic transfer in HVDC systems under unbalanced conditions

The harmonic interaction between AC- and DC-systems has been discussed in various publications with respect to both characteristic and noncharacteristic harmonics injected into AC-power transmission systems by HVDC converters. This paper presents a method to determine the transfer of harmonics from the supplying AC network to the DC system and vice versa. The imbalance in both fundamental and harmonic voltages is introduced in the mathematical model by the corresponding symmetrical components, e.g. by their positive and negative components. The method presented is valid for both power flow directions.