Enhancement of the Transient Stability of Integrated AC/DC Systems Using Active and Reactive Power Modulation

Active power modulation has been successfully used to improve the dynamic performance of interconnected AC/DC systems. This, however, results in uncoordinated reactive power modulation which, in the case of weak systems, reduces the effectiveness of the method. The paper presents the basic design of a DC link controller which, in the presence of major disturbances in the AC system, modulates the active and reactive power of the converters and improves the transient stability of the integrated system. The proposed control method was tested using dynamic simulation techniques and the results obtained are presented in the paper. These results show that the application of the method, under certain conditions, leads to significant improvement of the transient performance of the interconnected AC/DC system.