Research On Several Issues Of Power System Security And Stability Control With Large Scale Wind Power Integration

Due to the great contribution to mitigation of climate change,security of national en-ergy system and expansion of energy access,wind power generation,as a representative of renewable power generation,has become an important part in today’s power system,and is expected to maintain rapid growth.However,wind power generation has the characteristics of high randomness and intermittency,and the complicated operating characteristic and transient performance of wind turbine generators(based on maximum wind energy capture,generally connected to power systems through asynchronous/synchronous machine and power converters under unity power factor)are quite different from conventional synchro-nous generators.Therefore,large scale wind power integration would have a huge impact on power system and seriously threaten its stable and safe operation.It can be seen that how to maintain the high wind penetrated power system security and stability will be the major challenge we face for a long time to come.Power system security incidents,at home and abroad,with large scale wind power in-tegration are introduced at first.Then wind power system security and stability problems and conventional control methods are summarized,followed by the research approach of this paper.Specifically,this paper focuses on four typical problems:power fluctuation and fault ride through of DFIG,low voltage ride through(LVRT)of wind farms,wind power system small signal stability and power system transient angle stability after large scale wind power tripping.The main contents and research results are as follows:(1)Wind power fluctuation suppression and fault response characteristic improvement of DFIG by ES and DVR.This paper proposes a novel DFIG based wind energy conversion system,which incorporates ES and DVR.The embedded ES can store the surplus wind power and release it when needed to suppress wind power fluctuation.And the DVR can significantly improve the fault ride through capability of the DFIG under symmetrical and asymmetrical voltage fault.(2)Improvement of LVRT capability of wind farms by ES-DVR.This paper presents a nonlinear adaptive control(NAC)for the ES-DVR in enhancing the LVRT capability of wind farms.Simulation tests investigate the operation performance of the NAC based ES-DVR,and demonstrate the superiority comparing with the conventional vector control(VC)based on fixed gains and the accurate system model based feedback linearizing con-trol(FLC).(3)Implement of adaptive wide area damping controller based on ES.This paper de-signs a novel wide area damping controller for ES,in which an adaptive self optimizing pole shifting control is employed and extended.This control can adaptively identify power system model and provide better damping performance over a wide range of operating con-ditions and time delays.Case studies are undertaken on a simple discrete test system and multi-machine(wind)power system.Simulation results show the satisfactory control per-formance of the adaptive wide area damping controller.(4)Improvement of power system transient angle stability by emergency control of HVDC.To deal with the transient angle instability problem after large scale wind power tripping etc.,this paper proposes a power swing peak value prediction algorithm on tie line and designs an emergency control of HVDC.The simulation conclusions verify the sup-pression of power swing peak value on UHV tie line,which significantly improves the transfer capability of UHV tie line and can also make sure the stable operation of power system.This emergency control of HVDC also passes the field test in Central China Power Grid.The presented studies are expected to provide valuable references for practical appli-cation of power system security and stability control schemes with large scale wind power integration.