Impact Of Doubly Fed Induction Generator Integration On Power System Small-signal Stability

With the depletion of coal energy and deteriorating of natural environment,renewable energy is getting more and more attention as clean energy.The wind power generation is the fastest-growing and most technologically sophisticated among them,and has spread all over the world,occupied a higher proportion of power system.However,because wind power is intermittent and random,and its controllability and reliability is also weaker than conventional units,the small-signal stability of the grid brought by wind power became a new research direction.In this paper,considering the widely used doubly-fed wind generator(DFIG),the single-machine infinite-bus power system integrated with DFIG is studied.The main contents of this paper are listed as follows.Firstly,the physical model of DFIG is given,and a detailed mathematical model of DFIG is set up.Then,complete state space model of DFIG is derived.Proposed DFIG connected to power system as controller of system,we can create a state space model of closed-loop control system with DFIG integrated.Take single-machine infinite-bus power system as an example,the state-space model of single-machine infinite bus sytem with DFIG connected is obtained,and rationality of the model is verified by numerical example.At present,small signal stability analysis of power system widely used include damping torque analysis and model analysis.This paper analysis the impact of DFIG on small signal stability of single-machine infinite bus system based on damping torque analysis.According to the linear model of single-machine infinite-bus power system integrated with DFIG,the figure of Phillips-Heffron model can be drawn.Then,methods of damping torque analysis are used to calculate the damping torque of oscillation circuit of synchronous machine from synchronous generator's excitation and DFIG respectively.The signal pathways and key parameters of damping torque from DFIG areanalized.Finally,the effect of output of generator on damping torque is analized by a numerical study.This paper analysis the impact of DFIG on small signal stability of single-machine infinite bus system based on model analysis.Through analysis of the linear model of single-machine infinite bus power system with DFIG integrated,evaluation index of dynamic interation between DFIG and power system is obtained.Simplify the transfer function in model,then,the evaluation index can be simplified and analized.Finally,the effect of output of generator,RSC,and access location of DFIG on dynamic interation is analized.The contents of this paper have a certain practical significance to the long-distancetransmission of bundled wind and fire power,and have some guiding significance to power system's damping torque analysis and model analysis,and have reference value to the study of impact of DFIG and synchronous machines to small-signal stability.