| The Yunnan power grid after asynchronous networking has complex security and stability issues,such as low frequency oscillations.Considering the actual characteristics of the majority of hydropower units in Yunnan Power Grid,the governor model of the turbine unit is studied,and a multi-machine system model conforming to the actual situation of Yunnan Power Grid is constructed.This paper studies the parameters optimization of the power system stabilizer PSS2 B adopted by Yunnan Power Grid,the research content and results have certain practical value and practical significance.Based on the single-machine infinite model,this paper introduces the influence of excitation system on low-frequency oscillation and analyzes the principle of power system stabilizer(PSS)to suppress low-frequency oscillation.For a linear lowexcitation limiter UEL,the extended Philips-Heffron model with UEL is derived,the influence of relevant parameters in UEL on the PSS output damping torque is described.The paper linearizes the low-excitation limiter UEL adopted by Yunnan Power Grid,derives linearized differential equations,and determines the relevant parameters of UEL.Firstly,the governor model of type 1 turbine in PSASP is studied,the influence of water hammer effect time constant on the output damping of turbine governor is analyzed,then a new simplified PSS2 B model considering the influence of governor is proposed.The self-excitation excitation system,the turbine governor and the PSS2 B model adopted by Yunnan Power Grid are linearized to establish a system-wide state matrix,and the low-frequency oscillation mode is found to pave the way for the optimization of the objective function.Secondly,the basic principle of the grey wolf optimization algorithm is briefly introduced,the dynamic weight strategy is used to improve the GWO algorithm and improve its global search ability.In order to maintain the difference of the grey wolf population,the DE algorithm is combined with the GWO algorithm to obtain the DEGWO algorithm,the verification of the four benchmark functions shows that the DEGWO algorithm has certain advantages over the basic GWO algorithm in terms of global search ability,convergence speed and optimization time,which is better applied to PSS2 B parameters optimization.The fitness function based on damping coefficient is constructed,the process of optimizing PSS2 B by DEGWO algorithm is briefly described,and the related parameters of the algorithm are initialized.Finally,a partial area model of Yunnan Power Grid is built in PSASP,such as 3-machine 9-node and 4-machine 2 area system.The conventional PSS2 B,DEGWOSPSS2B and DEGWO-MPSS2 B are selected for comparative analysis,by setting different disturbances and faults,it is verified that the optimized PSS2 B can better suppress low-frequency oscillation in multi-operation mode,which can effectively improve the damping of the system and improve the weak damping of the system.It indicates that the optimization parameters of this paper are reasonable and have certain applicability. |
