Research On Fault Ride Through And Frequency Regulation Of PMSG-Based Wind Turbine Generator Based On The Supercapacitor Energy Storage

To accelerate the process of zero carbon dioxide emission,wind power is widely used as clean energy,and the proportion of wind turbine installed capacity in the power system grows unremittingly.However,the randomness of wind power and the electro-mechanical decoupling characteristics of wind turbine bring challenges to the frequency and voltage stability of the power grid.Therefore,more strict technical requirements are presented for grid-connected wind turbines,so that they can have the abilities of frequency regulation and low voltage ride through(LVRT).Aiming at the above problems,this paper proposes an improved control strategy on the basis of additional supercapacitor energy storage(SCES)to improve the grid-connected capacity of the permanent magnet synchronous generator(PMSG).The main contents of this paper are summarized as follows:(1)The model of PMSG system based on SCES is established,and the principle and control strategy of the main components of the machine side converter(MSC)and the grid side converter(GSC)in the model are given.In addition,the principle of maximum power point tracking(MPPT)control is described.Then,the principle of fault ride through and frequency regulation of the PMSG is introduced,which provides a theoretical basis for the improved control method proposed below.(2)Aiming at the LVRT of PMSG under faults,A LVRT control scheme for PMSG based on the coordinated control of rotor overspeed and SCES is proposed named overspeed-while-storing.And it can enhance LVRT capability of PMSG under all conditions of voltage sags.Under the premise of ensuring rotor speed in the allowable limit,the minimum energy storage capacity is configured to improve the stability and economy of the system.Finally.through the simulation comparison with other methods,the obvious advantages of the overspeed-while-storing are verified.(3)Aiming at the frequency fluctuation in wind power system,an integrated inertial control method considering the optimal configuration of SCES is proposed.Variables of the rate of change of frequency(RoCoF)df/dt and frequency deviation△f are introduced into the control strategy of the bi-directional DC-DC converter to simulate inertial response and primary frequency regulation of conventional unit.The SCES is charging or discharging to response to the frequency fluctuations of system,and frequency regulation function is implemented by SCES module completely.PMSG have been running at MPPT mode to realize the maximum utilization of wind power.In the end,the effectiveness of the control method is verified in both simplified model with a grid-connected PMSG and complex model of micro-grid.