Analysis And Suppression Of Power System Of Low Frequency Oscillation Based On Improved Prony Algorithm

With the development of power industry,the stability,security and economy of power system have been widely concerned.The interconnection of power network makes the power system in different areas more closely connected,but also gives rise to a series of stable operation problems.Low-frequency oscillations occur frequently in interconnected power systems,which seriously restricts the safe and stable operation of power networks.Under the operation condition of long distance heavy load,because the controller is widely used,such as rapid excitation system cause insufficient damping to power system,the weak damping or negative damping mode,when the system failure or disturbance,due to lack of enough to quell the oscillation damping torque,the oscillation will gradually deteriorate,eventually appear low frequency oscillation phenomenon.Low frequency oscillation will damage electrical equipment,cause the power change of the link line and trip,and even make the synchronous operation of the generator set out of step and disassembly,resulting in the power system can not run smoothly and cause great economic losses.Based on this,the low-frequency oscillation and its suppression strategy optimization of interconnected power system are studied as follows.Firstly,the generation mechanism,analysis method and suppression strategy of low frequency oscillation are described.Using the power system module library of Simulink,a single-machine infinite excitation speed regulation system and a typical four-machine two-area power system model are established.Through the single-machine infinite system,it is verified that the high-gain fast excitation system is the main cause of the increase oscillation.In order to analyze and suppress the low-frequency oscillations caused by faults or disturbances,Prony algorithm was used to identify the characteristic parameters of the oscillations.On the basis of analyzing the shortcomings of the traditional Prony algorithm to identify the overdetermined system,polynomial method and matrix beam method were introduced to improve the Prony algorithm in MATLAB.Secondly,by analyzing the mathematical models of different types of power system stabilizer(PSS),the advantages of multi-band PSS are obtained,and the multi-band PSS model is built.In order to improve the performance of PSS in various aspects,the improved Prony algorithm was used to adjust the parameters of multi-band PSS to obtain the improved PSS.On the basis of the two power system models established,different types of faults and disturbances were set up,and the response curves of the operating parameters of the generator set,such as electromagnetic torque,rotor speed and transmission power of the link line,were compared and analyzed respectively in three system operation modes,namely,no PSS,ordinary PSS and improved PSS.The results show that the amplitude and period of low-frequency oscillation caused by the same type of fault or disturbance are significantly attenuated after the addition of improved PSS,and the system can reach the stable state more quickly,which greatly improves the suppression ability of PSS,and verifies the feasibility of the improved Prony algorithm.