Research On Suppression Technology Of Sub-synchronous/Super-Synchronous Oscillation Of Variable Speed Pumped Storage Unit

As the most widely used generator set at present,the double-fed induction generator set is connected with the AC power grid through the conventional line,the seriescompensated line,the DC transmission device and the phase-locked loop.Causes sub/super synchronous oscillation problems.Therefore,based on the eigenvalue analysis method combined with the time-domain simulation verification method,this paper conducts an in-depth discussion on the variation law of the oscillation mode and stability of the grid-connected system,and proposes an additional damping controller based on the converter and the phase-locked loop to suppress the secondary /Super-synchronous oscillation strategy,the simulation verifies the effectiveness of the proposed strategy.The main research work and results of this paper are as follows:Firstly,the dynamic model of the whole system considering the series compensation line is constructed,and the active power and reactive power decoupling control of the doubly-fed induction generator set is realized.Taking the doubly-fed induction generator set considering the dynamic characteristics of the phase-locked loop as the research object,the original dynamic modeling of the system is completed in the dq synchronous rotating coordinate system.Based on the analysis and research,the small-signal model under the AC control time scale is obtained.Secondly,the characteristics of sub/super-synchronous oscillation of the variable speed system are analyzed,and the participation factors of different oscillation modes and the corresponding strongly correlated state variables are obtained.The eigenvalue sensitivity analysis is carried out on the controller parameters and system structure parameters,and the dominant parameter characteristics of different oscillation modes are judged.Domain simulations verify the correctness of the proposed analysis method.Finally,a strategy for suppressing sub/super-synchronous oscillations with additional damping controllers based on converters and phase-locked loops is proposed.According to the characteristics of converter control,in order to increase the equivalent resistance of the system,the stator current disturbance is selected as the input of the control signal of the additional damping controller on the rotor side,and the state current disturbance on the grid side is selected as the additional damping controller.It is verified that the additional damping control can improve the stability of the system from three aspects: the introduction of the rotor-side converter,the grid-side converter alone,and the coordinated control of the two.According to the control characteristics of the phase-locked loop,combined with The phase compensation method is beneficial to improve the phase in the oscillation frequency band of the phase-locked loop;a time-domain simulation model is built in Matlab,and the two types of damping controllers proposed in this paper are compared.The converter and the grid-side converter cooperate with the additional controller to have the strongest suppression effect.The research results in this paper provide engineering application reference value for the application of sub-/super-synchronous oscillation suppression technology for variable-speed pumped-storage units,and have general applicability.