Research on the Mechanism of Affecting the Transmission Capability of HVDC Connected to Weak AC System Considering STATCOM

With the power consumption increasing of the West-to-East project year by year, the power flow of long transmission lines changes greatly and rapidly under different operation mode, leading the system voltage regulation becoming more difficult. China Southern Power Grid faces operation problems of HVDC feeding weak AC systems decided by the actual structural characteristics in the power grid. Static synchronous compensator(STATCOM) is an important method to improve the characteristic of the operation in weak AC systems which has been applied to many electric substations and converter stations. The mechanism of STATCOM affecting the weak system connected to the inverter of HVDC is studied in this paper based on modeling and analytic solution. Firstly, the DC and AC system model including STATCOM are built, and the unique solution of the model is solved. Then the mechanism of affecting the transmission capability of HVDC connected to weak ac system considering STATCOM or not is analyzed in detail. And the quantitative calculation method of DC power transmission limit considering STATCOM is proposed. At last, the accuracy and effectiveness of the mechanism studied in this paper are verified in the simulations of one actual region model built in the PSCAD/EMTDC programme.