Detailed analysis and experimental results of the control system of a UPFC

Abstract

This paper explains the decoupled control of the power flow through a transmission line using a PWM based Unified Power Flow Controler (UPFC). The dynamic model of the UPFC has been developed using the space-vector representation of the instantaneous three-phase variables. The Park´s transformation and the reference frame selected reduce the control of the real and reactive-power flows to the control of the d- and q-axis currents, respectively. The proposed control scheme produces fast and decoupled response of the real and the reactive-power flow through a transmission line. It also achieves tight control of the d.c.-link capacitor voltage, thanks to the careful coordination between the control of the series and shunt compensators of the UPFX. A 15 kVA prototype with 750 Hz switching frequency has been built to illustrate the main contributions. Experiemental results agree closely with the theoretical analysis.This paper explains the decoupled control of the power flow through a transmission line using a PWM based Unified Power Flow Controler (UPFC). The dynamic model of the UPFC has been developed using the space-vector representation of the instantaneous three-phase variables. The Park´s transformation and the reference frame selected reduce the control of the real and reactive-power flows to the control of the d- and q-axis currents, respectively. The proposed control scheme produces fast and decoupled response of the real and the reactive-power flow through a transmission line. It also achieves tight control of the d.c.-link capacitor voltage, thanks to the careful coordination between the control of the series and shunt compensators of the UPFX. A 15 kVA prototype with 750 Hz switching frequency has been built to illustrate the main contributions. Experiemental results agree closely with the theoretical analysis.