Research On Influence Of Wind Power Integratios On Small Signal Stability Of Power System And The Influence Factors

After a transforming period,wind power industry has shifted from centralized development to decentralized development,from land-based development to offshore development.Wind power will be more widely used in the power system in the future,thus research on impact of wind power integration on system stability is becoming more important.In this paper,the influence of large-scale wind power integration on power system's small-signal angular stability has been studied.Two different factors,which are power inflow changes as well as dynamic interaction between wind turbines and synchronous generators,are considered and deduced through decomposition computation.Based on doubly-fed induction generator(DFIG),dynamic characteristics,machine-side converter,and grid-side converter of this kind of wind turbine are modeled and then linearized.Due to wind turbine can be regarded as a superposition device of a constant power source and a feedback controller,the low frequency oscillation modes of the power system are derived by taking the two parts respectively.The final result,which is the combination of the two modes,is compared with the overall calculation result.The equivalence proves the efficiency of the proposed method.In order to analyze the physical mechanism of influence,this paper adopts the experimental models which are used in the earliest three classic papers in this area to establish some small test systems,such as two-area four-generator system and three-area six-generator system.Experimental scenarios are set according to the literatures to recalculate the proposed model.The results show that the change of low-frequency oscillation damping is mainly caused by power flow changes due to replacement of synchronous generators' output,whereas the variation induced by dynamic interaction is much smaller.In addition,influence on inter-area oscillation is greater than that on intra-area oscillation.Since wind turbines adopt power electronic control device,new oscillation mode will not be introduced into the system.However,wind power integration changes system power distribution,resulting in the change of transmission power on tie lines,increasing or decreasing coupling among synchronous generators,etc.,which may increase or damage power system small-signal angular stability.Furthermore,the New England 39-nodes system is used to analyze the impact of new wind farms' location on power angular stability.The results show that when wind turbines are allocated closer to balancing generators,the change of system low frequency oscillation mode damp with wind turbines' output increasing is smaller in general.