Dynamic dead angle control of three-level voltage source converter based HVDC system

This paper presents a dynamic dead angle control of three-level voltage source converter based HVDC system for real and reactive power control operating at Fundamental Frequency Switching (FFS). A three-level voltage source converter replaces the conventional two-level VSC and it is designed for the active and reactive power control is all four quadrants operation. A new control method is developed for achieving the reactive power control by varying the pulse width and by keeping the dc link voltage constant. The steady state and dynamic performances of HVDC system interconnecting two different frequencies network are demonstrated for active and reactive powers control. Total numbers of transformers used in the system are reduced to half in comparison to two level VSCs. The performance of the HVDC system is also improved in terms of reduced harmonics level even at fundamental frequency switching.