The Probabilistic Stability Research For Hybrid AC/DC Power System

This paper focuses attention on the modeling as well as computer algorithms for PSA of hybrid AC/DC power system by the Non-sequential Monte-Carlo simulation . The following is the work reported in summary.1.Having consummated the models of HVDC systems and the emulation of control systems. This paper takes the negative impedance into consideration on the basis of QSS(Quasi Steady State Model) model of converter, and the results of computation can meet the need of speed and precision for a mixed AC/DC system when asymmetric faults happened.2.Having completed the modeling and software design of power flow computation and stability analysis for hybrid AC/DC power systems. The package can deal with three types of loads and generator models up to sixth orders.3.A simulation method and probabilistic modeling of transmission systems is built, which can deal with the different failure modes, such as the open circuit and short circuit of transmission lines, short circuit contingencies of bus frame, common-mode failure, correlated faults, grounding faults of breakers, fail to trip and false tripping of breakers , recloser failures commutation failure,3-4 operation mode etc.4. The proposed method can simulate many emergency control measures ,such as under frequency/under voltage load shedding ,generator shedding, fast valve control, excitation control ,VDCL,DC restart etc.5 This paper rebuilds a set of new risk indices on the basis of system level and substation levels, such as Loss Of Stability Probability ,Loss of Stability Frequency ,Dynamic Loss Of Load, Dynamic Loss Of Energy, Probability of Generator Shedding ,Mean Time to Unstable etc. We have investigated the effects of different ECMs statistically. It is demonstrated that ECMs may have positive or negative effects on the transient stability under different conditions.Several sample systems are used to verify the accuracy of modeling and the effectiveness of algorithm implementation . The computation results show that the work is fruitful and the software can meet the need of engineering and research.The research work is financially supported by the National Natural Science Foundation of China (NSFC) under the grant No.59977004, the Natural Science Foundation of Anhui Province under the grant No.00104421 and the Outstanding Teacher Projects financially supported by the Education Ministry of China.