Monte Carlo simulation based assessment of available transfer capability in AC-DC hybrid systems

Available transfer capability (ATC) is defined as a measure of the system´s capability for transfers of power for further commercial activity, over and above already committed uses. In practical power markets, ATC can provide important information for transmission customers, system operators and power marketers. The assessment of ATC should be carried out to assure the secure, economic, stable and reliable operation of power systems. Most of the existing ATC calculation are mainly focused on AC power system and based on deterministic techniques. As high voltage direct current (HVDC) power distribution systems have been extensively used in modem transmission network, less work has been done on evaluation of ATC in AC-DC hybrid power system. This paper is dealing with the evaluation of ATC for the integration of HVDC link with an AC power system. The mathematical model of ATC for AC-DC hybrid power system is proposed. Due to the stochastic nature of power system behaviors, it is important to assess ATC from a statistical and risk analysis point of view. Considering the dynamics, time-varying and uncertainties of hybrid power systems, several statistical indices are presented to evaluate ATC and they are calculated based on Monte Carlo simulation. States of system operation can be simulated, and the algorithm based on MATPOWER (A MATLAB™ Power System Simulation Package) is developed in the environment of MATLAB 7.5. Case study with a modified IEEE 30-bus AC-DC hybrid power system is used to verify the presented approach. Sequential solution method is employed to deal with the AC-DC power flow. Five-number summary and other statistical indices of ATC are calculated. The results show that the proposed method is effective and practical. The research achievements are undergoing to transfer to the application in other hybrid power systems with different control style, and some new problems are suggested at the end of paper.