Available Transmission Capacity Of Power System Voltage Stability Constraints

The power industry worldwide is experiencing unprecedented restructuring for establishing power markets and the power industry in China is now under the way of restructuring. At the same time large area interconnected system is forming, which will get the benefit of network being the stand-by for each other, exigent accident supporting and promoting the development of the power market etc. Due to the introducing of the power market mechanism, the development of large area interconnected system, the environment protection and the restriction of using the land and so on, the conflict between security and economic operation of the power system is more severe. Power tranfer capability provides valuable measurement to the security and reliability of interconnected power systems. The magnitude of available transfer capability (ATC) reflects the interconnection intensity and the structural quality of a power transmission network. It can not only instruct the dispatch of the dispatcher to confirm the stability and security of the power system, but also it is seen as a market signal to instruct trade actions of market participant. So it is theoretically and practically important and necessary to evaluate ATC calculating methods.The calculation of available transfer capability is a very complicated issue. This dissertation conducts systematical research work on ATC calculation constrained by static voltage stability:First, the status quo of transfer capability of the power system in and out of China is introduced. Voltage stability of the power system is one of the conditions that ensure its operational security. It is more and more prominent because of the power markets, the development of the network and applications of new techniques etc. The concept, status quo and the available methods of voltage stability are discussed. Then three kinds of static voltage stability index are compared and they are used for contingency ranking in the IEEE30 bus system.Secondly, it is discussed that available transfer capability considering the static voltage stability with continuation power flow method (CPF method) The Jacobian matrix of a normal power flow equation is singular at the saddle-node bifurcation point. The CPF met- hod is free from the illness associated with the singularity of power flow Jacobian matrix at the sadele-node bifurcation point by introducing a one dimension equation, which results in accurately calculating the saddle-node bifurcation point. This method is predominant in solving the voltage stability problem. This paper discusses the principle of the CPF method in detail, establishes the mathematical model of calculating ATC considering the restriction of static voltage stability. Finally the IEEE39 bus system is simulated to prove the validity of this method. Due to the increasing direction of the outputs of generators and loads confirmed in the continuation power flow method, reactive power and voltage can't be distributed reasonably.Then, an optimal power flow method: the prime-dual interior point method is introduced. The prime-dual interior point method is polynomial timing complex, converging fast and it has good Robustness. This method is not sensitive to the original value and is has already been widely used in the optimization area and it is one of the most potential algorithm. This method is used to get a model of generator dispatching, which will increase the power system transfer capability to a maximum one. Samples illustrate that the prime-dual interior point method can elevate the power system transfer capability compared with the CPF method. IEEE30 bus system is simulated to prove this method.This paper concludes with summarizing the whole paper and pointing out the future direction of the transfer capability.