Research On PSS Parameters Optimization Based On A New Power Grid Dynamic Equivalent Method

Dynamic performance of excitation system significantly affects the safety and stabilityof the power system. As the rapid development of power system, higher requirements areput forward for control of the excitation system. Therefore, in order to build a largeinterconnection grid and high levels of power system, it is necessary to optimize theparameters design of the excitation system in-depth.This paper has done some research and exploration on PSS parameters optimizationbased on a new power grid dynamic equivalent method. First the characteristics andshortcomings of existing grid equivalent methods are analyzed, then a new power griddynamic equivalent method is proposed for better optimizing the parameters of excitationsystem of synchronous generator, that is the external power system is equivalent as asecond-order dynamic synchronous generator branch connected in parallel with an infinitebus branch. This method can both reflect the impact of the distal large grid and theproximal generators on the same bus.Then an exhaustive method is proposed to identifythe parameters of dynamic equivalent model, just through the step disturbance data of thegenerator port the identification can be carried out. Through the simulated data by PSASPsoftware and field measured disturbance data, the identification is run respectively. Thecalculated results demonstrate the effectiveness of the exhaustive identification method. Inorder to validate the superiority of the new dynamic equivalent method, some research onPSS parameter optimization based on this method has been studied. First thePhilips-Heffron model of the three-machine system has been deduced, and we can calculatethe uncompensated phase frequency characteristics. Then based on the phase compensationmethod an exhaustive method and an improved particle swarm algorithm are proposed tooptimize the time constant of PSS. The simulated results show that the optimizedparameters can effectively improve the system damping ratio, thus demonstrate theireffectiveness. PSS parameters are optimized based on the static and dynamic equivalentmethod respectively. The simulated results verify the effectiveness of the dynamicequivalent method.