| With the exploitation of hydropower resources in Yunnan Province and the increasing power transmission capability of the West to East channel,the operation risk of hybrid AC/DC operation power network is gradually increasing,which poses a great threat to the safe and stable operation of the Southern Power Grid.In order to solve this problem,the Southern Power Grid has implemented asynchronous networking project.By this way,only DC link is connected between main networks of the Yunnan Power Grid and the Southern Power Grid,which makes the Yunnan Power Grid no longer have the electrical conditions of synchronous operation with the Southern Power Grid.The main research contents of this thesis are as follows:(1)This article briefly outlines the relevant background of the asynchronous networking between Yunnan Power Grid and China Southern Power Grid,and the research status of asynchronous interconnection and speed governor parameter setting optimization is introduced.From the basic mathematical model of power system components related to hydroelectric power generation,an equivalent model for the frequency analysis of power grids is established,and the analytical form of the grid frequency in a stand-alone system is quantified.Then the power system simulation software is used for the stand-alone system.The frequency dynamic characteristics are simulated and analyzed,and the influencing factors in the primary frequency modulation process of the power system are qualitatively analyzed.(2)The primary frequency modulation model of single-machine and grid-connected operation system with DC frequency controller was deduced theoretically,and the stability of grid frequency regulation system with DC frequency controller was theoretically deduced and analyzed,including stand-alone operation and multi-machine operation.Analysis of network operation stability.A four-machine two-area system model was built through PSS/E,which is a power system simulation software,and the two areas were connected with a DC line to form a small asynchronous network system.According to the small-scale asynchronous networking model,the simulation verified the frequency changes of the two areas after the disturbance in area 1 of the asynchronous interconnected system,and the power changes on the tie-line before and after the asynchronous operation;and the influence of hydro turbine governor parameters on the transient frequency of asynchronous networking is simulated and analyzed.The actual data of Yunnan Power Grid was used for simulation experiments.The turbine governor parameters of several power stations were calibrated to verify the influence of different turbine governor parameter values on the grid frequency in the actual system.(3)This paper introduces an improved method of the cuckoo search algorithm,and uses the ITAE index as the fitness function of the improved cuckoo search algorithm to optimize the parameters of the PID governor of the turbine.The linearized model of the turbine regulating system is established in MATLAB/Simulink.The simulation results show that the improved performance of the improved cuckoo search algorithm is better than the particle swarm optimization and the standard cuckoo search algorithm,and has better dynamic performance. |
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