Transient Voltage Stability Analysis Considering Time-varying Characteristics Of Load Parameter

The power sectors are likely to make decisions and launch plannings about power systems according to results of simulation.As an important element of power systems,load is an equivalent object consuming power from the systems and connected to a bus.Because of its characteristics of randomness,time-dependent nature and complexity,load mode always influences the accuracy and reliability of simulations as a prerequisite that people have made great progress in modeling of the generator,the excitation system and the HVDC system.In usual transient stability analysis,load parameters are constant and load mode with time-varying parameters are hardly used and researched.Load mode is the key factor to voltage stability.This paper launches simulations with time-varying parameters and analysis their influences in transient voltage stability.PSAT(Power System Analysis Toolbox)is used in the paper.Composite load model is modeled in PSAT,and effect of its important parameters to transient voltage stability is analyzed.According to the iteration of time domain simulation in PSAT,this paper analysis the equations and variables(matrixs)related to the parameters of the induction and the static load;proposes the approach to change load parameters in the process of time domain simulation;states how to revise the codes in PSAT.Simulations at system with 4 generators and 11 nodes prove the validity of the approach.The last but not least,an actual grid is analyzed.The simulations with both constant and time-varying modes are run in order to research the influence of time-varying nature of load on transient voltage stability.It can be inferred from the researches that if the system is under critical status,fluctuation in load parameters may change simulation results radically.It is likely to effected transient process of the system.Load mode will reflect load characteristics in an actual system if time-varying parameters load mode is used in transient stability analysis.Load mode play an important role in voltage stability.Time-varying characteristic of load parameters should not be out of considered and those parameters not be resumed to be constant at simulation researches of transient voltage stability analysis.That will provide new ideas for electric power system analysis The simulation will perfectly simulate the transient process of actual power system,and it will improve accuracy and credibility of simulation for transient stability analysis if time-varying nature of load mode is considered.