Performance of Distributed Power Flow Controller on System Behavior under Unbalance Fault Condition



Recently, within the family of FACTS, the distributed power flow controller is an additional device. This paper highlights on voltage sag mitigation which is one of the burgeoning power quality issues. It deals with the working concept of distributed power flow controller for compensating unbalanced three phase line currents in the transmission system. The single phase series converters of DPFC are able to compensate active as well as reactive, negative and zero sequence unbalanced currents. In this paper the performance of the DPFC has been studied by considering line to ground fault near the load end. The MATLAB/SIMULINK results obtained shows an improved performance in voltage sag mitigation, unbalance compensation, remarkable reduction in load voltage harmonics and also enhanced power flow control.


  1. DPFC
  2. Power flow control
  3. Reduction of load voltage harmonics
  4. Reliability improvement
  5. Voltage sag mitigation
  6. Unbalance fault condition



Fig. 1. Basic DPFC structure.


 Fig. 2. Load voltage sag waveform during unbalance fault.

Fig. 3. Mitigation of load voltage sag wave form during unbalance fault with DPFC.



Fig. 4. Load voltage. (a) Signal selected for calculating THD without DPFC.

(b) THD without DPFC.



Fig. 5. Load voltage. (a) Signal selected for calculating THD with DPFC.

(b) THD with DPFC.

Fig. 6. Capacitor dc voltage in dc side of shunt converter within DPFC.


This paper introduces the unbalance compensation and the voltage sag mitigation during unbalance fault condition by utilizing a recent additional FACTS device which is distributed power flow controller (DPFC) adopting sequence analysis technique. The DPFC is designed by employing three control loops. The simulated system has two machine systems, in presence and absence of the DPFC in the system. To examine the capability of the DPFC, an unsymmetrical L-G fault is taken into account near the load end side. In this paper simulation done verifies that the adopted control is able to give unbalance compensation and mitigation of voltage sag.


[1] N. G. Hingorani and L. Gyugyi, Understanding FACTS : Concepts And Technology of Flexible AC Transmission Systems. New York: IEEE Press, 2000.

[2] L. Gyugyi, C. D. Schauder, S. L. Williams, T. R. Rietman, D. R. Torgerson, and A. Edris, “The Unified Power Flow Controller: A New Approach to Power Transmission Control,” IEEE Trans. Power Del., vol. 10, no. 2, pp. 1085–1097, April 1995.

[3] Y. H. Song, and A. Johns, “Flexible AC Transmission Systems (FACTS),” Institution of Electrical Engineers (IEE Power and Energy Series), London, U.K:, vol. 30, 1999.

[4] K. Ramya and C. Christober Asir Rajan, “Analysis And Regulation of System Parameters Using DPFC,” IEEE International Conference on Advances in Engineering, Science And Management (ICAESM), March 2012, pp. 505-509.

[5] M. D. Deepak, E. B. William, S. S. Robert, K. Bill, W. G. Randal, T. B. Dale, R. I. Michael, and S. G. Ian, “A Distributed Static Series Compensator System For Realizing Active Power Flow Control on Existing Power Lines,” IEEE Trans. Power Del., vol. 22, pp. 642-649, Jan. 2007.

Analysis and Design of Three-Level, 24-Pulse Double Bridge Voltage Source Converter Based HVDC System for Active and Reactive Power Control


This paper deals with the analysis, design and control of a three-level 24-pulse Voltage Source Converter (VSC) based High Voltage Direct Current (HVDC) system. A three level VSC operating at fundamental frequency switching (FFS) is proposed with 24-pulse VSC structure to improve the power quality and reduce the converter switching losses for high power applications. The design of three-level VSC converter and system parameters such as ac inductor and dc capacitor is presented for the proposed VSC based HVDC system. It consists of two converter stations fed from two different ac systems. The active power is transferred between the stations either way. The reactive power is independently controlled in each converter station. The three-level VSC is operated at optimized dead angle (β). A coordinated control algorithm for both the rectifier and an inverter stations for bidirectional active power flow is developed based on FFS and local reactive power generation. This results in a substantial reduction in switching losses and avoiding the reactive power plant. Simulation is carried to verify the performance of the proposed control algorithm of the VSC based HVDC system for bidirectional active power flow and their independent reactive power control.



Voltage Source Converter (VSC), Three-level VSC, Fundamental Frequency Switching (FFS), HVDC System, Power Flow Control, Reactive Power Control, Power Quality, Total Harmonic Distortion (THD), Dead Angle (β).






Fig. 1 Three-level 24-pulse double bridge VSC based HVDC system




Fig. 2a Performance of rectifier station during reactive power control of three level 24-pulse VSC HVDC system


Fig. 2b Performance of Inverter station during reactive power control at rectifier station of three-level 24 pulse VSC HVDC system


Fig. 2c Variation of (δ) and (α) values for rectifier and inverter Stations for reactive power variation of a three-level 24-pulse VSC HVDC system


Fig. 3a Rectifier station during active power reversal of three-level 24-pulse VSC HVDC system


Fig. 3b Inverter station during active power reversal of three-level 24-pulse VSC HVDC system


Fig. 3c Variation of (δ) and (α) values during active power reversal of three level 24-pulse VSC HVDC system.



A new three-level, 24-pulse voltage source converter based HVDC system operating at fundamental frequency switching has been designed and its model has been developed and it is successfully tested for the independent control of active and reactive powers and acceptable level harmonic requirements. The reactive power has been controlled independent of the active power at both conditions. The converter has been successfully operated in all four quadrants of active and reactive powers with the proposed control. The reversal of the active power flow has been implemented by reversing the direction of dc current without changing the polarity of dc voltage which is very difficult in conventional HVDC systems. The power quality of the HVDC system has also improved with three-level 24-pulse converter operation. The harmonic performance of this three-level, 24-pulse VSC has been observed to an equivalent to two-level 48-pulse voltage source converter.



[1] “It’s time to connect,” Technical description of HVDC Light Technology, ABB HVDC Library.

[2] J. Arrillaga, “High Voltage Direct Current Transmission,” 2nd Edition, IEE Power and Energy Series 29, London, 1998.

[3] Vijay K. Sood, “HVDC and FACTS Controllers – Applications of Static Converters in Power Systems,” Kluwer Academic Publishers, Masachusetts, 2004.

[4] J. Arrillaga, Y. H. Liu and N. R. Waston, “Flexible Power Transmission- The HVDC Options,” John Wiley & Sons, Ltd, Chichester, UK, 2007.

[5] J. Arrillaga and M. E. Villablanca, “A modified parallel HVDC convertor for 24 pulse operation,” IEEE Trans. on Power Delivery, vol. 6, no. 1, pp. 231-237, Jan 1991.