Unified Power Flow Controller: Comparison of Two Advanced Control Schemes and Performance Analysis for Power Flow Control

In this paper real, reactive power and voltage balance of the UPFC system is analyzed. Two advanced control schemes of UPFC have been proposed. One is the conventional coordination control scheme. In this scheme, the shunt converter of the UPFC controls the UPFC bus voltage and the DC-link voltage. The series converter controls the transmission line real and reactive power flow. By analysis, it is indicated that the shunt converter provides all the required reactive power during the power flow changes if the UPFC bus voltage is constant. The UPFC bus voltage can be control both from the sending side and from the receiving side. So a modified control scheme is presented. In this scheme, the shunt converter controls the transmission line reactive power flow and the DC-link voltage. The series converter controls the transmission line real power flow and the UPFC bus voltage. The conventional coordination controllers in the UPFC control system can get good performance, and the modified controller has an improved performance. Operation of UPFC using the proposed two control schemes is presented by experimental laboratory results