Research On Fast Frequency Regulation Strategy Based On The Combination Of Supercapacitor And Hydraulic Unit

The foreground of renewable energy has appealed to vigorous development and application of many regions globally.Wind power,photovoltaic power generation and other generating sets with random charactcristics do not respond to the fluctuation of system frequency,and their integration into the power grid will result in insufficient inertial response of the system and bring about frequency stability problems of the power system.Synchronous hydraulic units themselves undertake the task of frequency modulation.and occupy a large proportion of clean energy,but their regulatory capacity can not meet the needs of new power grid construction,and their response capacity to wind-wind grid connection is gradually insufficient.At present,the research on the frequency regulation performance of synchronous hydraulic units is mainly focused on the optimization of controller parameters and the improvement of control strategy,but the improved regulation capacity of synchronous hydraulic units still fail to meet the regulation needs of the power grid with increasing wind and photovoltaic percentage.External energy storage equipment is needed to make up for the lack of inertia response of the system caused by wind and photovoltaic units and improve the fast response capacity of conventional hydropower units.The addition of supercapacitor energy storage device with fast response characteristics can coordinate the operation with the synchronous hydraulic unit and enhance the rapid regulation ability of the synchronous hydraulic unit,which has important application value for the large-scale access of new energy.The thesis mainly completed the following work:First of all,through the study of the energy storage theory and working mode of the supercapacitor,the Simulink simulation model of the supercapacitor energy storage device is set up,in which the bi-directional DC-DC converter controls the working state of supercapacitor,and the voltage converter keeps the DC voltage on the high voltage side stable during charge and discharge.The correctness of the model is proved by charge and discharge simulation experiments.Secondly,the model of hydraulic unit regulation system is established,and the supercapacitor-hydraulic unit coordinated control strategy is proposed to improve the frequency regulation characteristics of the unit by adding supercapacitor virtual inertia control and virtual droop control,the former aims at the change rate of frequency deviation,while the latter aims at frequency deviation,this improved control method will not cause supercapacitor overcharge and discharge while improving the effect of frequency regutation..Then,the capacity distribution principle of the supereapacitor energy storage device is analyzed and studied,and the economic feasibility of the supercapacitor energy storage device is verified through the calculation formula of the economic benefit index of the large-scale energy storage device.Finally,on the basis of Matlab/simulink platform,the simulation experiment is carried out.actual capacity configuration of supercapacitor according to capacity con figuration principle and capacity of the hydraulic unit,calculate the cost of the actual supercapacitor sets,and compare the frequency response characteristics of the unit under load disturbance under the condition of single unit and grid connection with or without supercapacitor auxiliary frequency regulation,which proves that the supercapacitor can indeed assist the frequency regulation of synchronous hydraulic units and verifies the effectiveness of the proposed control strategy.