Middle And High Frequency Resonance Analysis Model And Suppression Strategy Of Wimd Farm

With the increasing proportion of wind power installed in the power system,the stability of new energy power systems caused by nonlinear components of wind power grid-connected technology has become a hot topic of research.At present,the oscillation and resonance caused by the wind power connected to the traditional power grid has become an urgent and serious problem.This paper aims at the high frequency resonance of doubly fed-back induction generator(DFIG)in the field of renewable power generation.Firstly,by analyzing control strategy of the grid side c3onvertor(GSC)and the rotor-side converter(RSC)which is connected to the doubly fed-back induction generator(DFIG),the impedance model of two converters can be obtained;By establish the dq rotational coordinate system of ideal and actual coordinate,the small-signal analysis model of the phase-locked loop can be obtained.By analyzing the relationship of harmonic disturbance and q-axis of voltage component,closed-loop transfer function between the voltage component and rotation angle shows that the phase-locked loop does not affect the impedance modeling in the high-frequency range.Firstly,by analyzing the control strategies of two converters,the impedance models of two converters can be obtained respectively.Secondly,by analyzing the frequency response curves of the grid with various compensation forms,the topology of the parallel compensation grid which can generate high frequency resonance is selected for the research emphasis.Then,by plotting the impedance Bode diagram of DFIG and the parallel compensation grid,the frequency response margin phase can be obtained according to the intersection of two impedance magnitude curves when high frequency resonance occur.The impedance analysis method can explain the mechanism of high-frequency resonance.The impedance open-loop transfer function of the doubly fed-back connected system and the parallel compensation grid is established.The influence of the PI parameters of the controller,the internal resistance of the grid and the wind speed on the stability of the two impedance systems is studied.Aiming at the high-frequency resonance phenomenon caused by the impedance interaction between the parallel compensation grid and the doubly-fed grid-connected system,an additional damping control based on vector control is proposed.The control strategy proposed in this paper can effectively solve the problem of under-damping in the high-frequency region,and suppress the occurrence of high-frequency resonance by improving the control strategy of the converter.Finally,the simulation model is built in PSCAD.The simulation results verifies that the occurrence mechanism of high frequen-cy resonance in DFIG has good rationality and the suppression control of high frequency resonance has effectiveness.