Multi-parameter Saddle-node Bifurcation Analysis Of Wind Power System Containing Static Synchronous Compensator

With the development of grid-connected wind farms，it makes an increasing influence ongrid stability and power quality, especially voltage stability. As a new dynamic reactivecompensation device, static synchronous compensator (STATCOM) has a better reactivepower compensation effect such as small in size, capacity, continuous adjusting, fast responseand economic performance. It is suitable to be used in large-scale wind farms to improve thevoltage stability of wind power system. In this dissertation, STATCOM is used for thereactive power compensation of wind power system. Saddle-node bifurcation participationfactor is used to choose the installation location of STATCOM in wind power system. Voltagestability mechanism of wind power system containing STATCOM was revealed bymulti-parameter analysis of saddle-node bifurcation based on bifurcation theory. The mainresearch results and conclusions are seen below:（1）The nodes that have the greatest impact on voltage stability of wind power systemwere found by saddle-node bifurcation participation factor based on 3-machine 9-bus systemmodel. Compensation mode of STATCOM in wind power system was determined by thismeans. Then load margin index was used to verify the effectiveness of this compensationmode.（2）In order to reveal the voltage stability mechanism affected by the parameters ofwind power system and consider the dynamic characteristics of STATCOM, active powerinjection of wind power system Pinand STATCOM internal parameters (DC voltage gain KMdcand DC reference voltage Urefdc) were chosen as the bifurcation control parameters.Two-dimensional saddle-node bifurcation boundary of wind power system was tracked basedon the direct method and continuation method. It can be concluded by analysis that DCvoltage gain KMdcis more effective than DC reference voltage Urefdcto increase the activepower injection limit and improve the voltage stability of wind power system.（3）Based on two-dimensional saddle-node bifurcation boundary, active power injectionof wind power system Pinand STATCOM internal parameters (DC voltage gain KMdcand ACvoltage gain KMac) were chosen as the bifurcation control parameters and the saddle-nodebifurcation surface of wind power system was obtained. Multi-parameter bifurcation controlis more effective to expand the saddle-node bifurcation boundary and reveal the voltagestability mechanism of wind power system than the two-dimensional saddle-node bifurcationboundary analysis. With the joint action of Pin、KMdcand KMac, saddle-node bifurcationboundary of wind power system was expanded effectively. By coordinating three controlparameters, the voltage of wind power system tends to rated value, which proves that thevoltage stability of wind power system is improved.