Voltage Stability Assessment Of Power Systems With Thyristor Controlled Series Compensator Device

In the recent decades,along with the constant increase of electric requirement and the enhanced electric load,the problem of the voltage stability in the power system stands out day and day.In the world, accidents,such as electric system breakdown and mass electric power cut,occurred time after time because of the voltage lost stability. Voltage insecurity has become one of primary factors that limit the power transmission.The method of enhancing the voltage stability in the power system has become a problem which starves for settling.However,the device of TCSC(thyristor controlled series compensator,TCSC)which is the first applied device of FACTS(flexible alternating current transmission system)attracts the attention of people more and more.The paper studies the case of the voltage stability in the power system when the device of TCSC is connected to the transmission line,and obtains certain results.The paper predigests the device of TCSC to a fixed repay device in series.By this method,the transmission line can be compensated in series.The paper defines the concept of compensatory degree in susceptance,constructs the mathematic models of active power and reactive power on the electric lines,and the mathematic models of the relations between the active power and node voltage.The PU curve graph shows that the voltage stability of the electric power is evidently improved while TCSC is configured.The results are the same with the TCSC device.In order to research the voltage stability of the electric power while TCSC is configured,a measurement is needed.In view of more and more voltage instability caused by the insufficiency of dynamic reactive power,based on power flow calculation method and by means of adding steady state model of thyristor controlled series compensator (TCSC)into power flow equation,the Jacobian matrix with TCSC is derived and applied in the sensitivity calculation of voltage stability. The paper figures the sensitivity index for voltage stability of power system as the obvious functions of burst angle of TCSC.However,how much load the system can endure more,and how far the distance between the current state and the state of the breakdown, the problems still need to settle.So,the paper imports the margin index for voltage stability of power system.The paper equals the load with TCSC by susceptance of TCSC.By computing tidal flow,the paper imports it into margin index.The margin index can show the ameliorative voltage stability with TCSC.On this basis,the voltage stability of the whole power system before and after the installation of TCSC and that of the node where TCSC is configured are compared and analyzed by sensitivity index and margin index.Besides,the paper interconnects two 9-bus systems,and installs the TCSC devices at the weakness nodes and interconnected nodes of the two systems separately,comparing and analyzing by the voltage stability of the whole power system as well.The results show that the sensitivity index of voltage stability is evidently improved while TCSC is configured.The results are the same with the interconnected system, and the effects are better when the TCSC device is installed at the interconnected node which transmits electricity by long line.By use of power system analysis tool PSAT1.3.4,the simulation of WSCC 3-machine 9-bus system is simulated,the correctness,effectiveness and feasibility of the proposed method is validated by simulation results.The correctness of the method provides the theory foundation for the larger-scale interconnect of the complex and huge electric power system...