Research On The Factors Of Mechanism Of Resonance-type LFO And Strategies Base On Generation-network’s Optimized Coordination

Power system interconnection can improve the economy and reliability of the systemeffectively. However, complex power grid structure also brings more dynamic stabilityproblems after interconnection. And low frequency oscillation (LFO)issues as most likely tooccur in stability issues after large grid interconnection, which is one of the important issuesthat threaten the security and stability of power grid.Currently, the mechanism on negative damping of LFO is common and has sophisticatedtheories. Generally believe that installation of the power system stabilizer (PSS) to provideappropriate damping can inhibit LFO effectively. Actual operating experience shows thatmechanism on negative damping of LFO will be no longer apply in some type oflow-frequency oscillations.This paper analyzes the mechanism of LFO based on tradition, comprehensiveexposition the mechanism of resonance-type low-frequency oscillation and the discriminationof the mechanism on negative damping and resonance-type were studied. Based onconsideration of generation-network’s optimized coordination, the effects of various forms ofdisturbance on low-frequency oscillations both on the networks side and generation side wereanalyzed. Considering the interaction between the turbines, the speed control system andpower systems, looking disturbance source from the turbine governing system ofresonance-type low-frequency oscillation, which may causes of mechanical power fluctuateperiodicity. And obtained the relationship between resonance-type low-frequency oscillationand mechanical power which affected by the turbine speed control system swing and turbinesteam pressure pulsation by simulation.In this paper, breaking the previous studies ignore the effects of turbine governingsystem and thermal system of steam turbine on low-frequency oscillation. And the theoreticalanalysis, simulation studies and examples of analysis pointed out that: various aspects andparameters of the turbine and governing system set improperly may due to some mechanicalfailure, which may lead to mechanism of resonance-type LFO; When the same disturbanceoccurs in different position, effects of generation side is more serious than network side. Theeffect of PSS for this type of LFO is not ideal, it is necessary to design and install GPSS inturbine governing system so achieve better inhibitory effect.