Research On Control Strategy Of Photovoltaic Power Plants Actively Participating In Power Grid Primary Frequency Regulation

In recent years,with the rapid development of new energy in China and abroad,the installed capacity of centralized photovoltaic power plants(PVPPs)and distributed PVPPs is increasing with years.However,the increase of photovoltaic(PV)permeability in the power grid will reduce the proportion of synchronous generators in the power grid,leading to the decline of the power grid frequency regulation capability.This brings potential threat to the safety and stability of power grid.To improve the power grid’s capacity to absorb new energy,it is urgent for PVPPs to actively participate in the frequency regulation.Therefore,it is necessary to study the primary frequency regulation control strategy of PVPPs.In this paper,for two types of PVPPs(whether to install the energy storage unit),the active power reserve PVPPs control strategy and primary frequency regulation strategy based on photovoltaic and energy storage co-control is proposed.The strategy uses flexible power point tracking(FPPT)algorithm to realize PV power reserve,which provides power support for the power grid.The small-signal model of the PV operating on the left side of the maximum power point is established,and the system’s power response process when the DC reference voltage changes is analyzed.Based on the FPPT evaluation function,the calculation method of the tracking step-size when the PV operates on the left side of the maximum power point is given,which can improve the dynamic and steady-state performance of the FPPT algorithm.The calculation of the tracking step-size is only related to the output characteristics of the PV cell,so this calculation method is applicable to both single-stage and two-stage PVPPs.The photovoltaic and energy storage co-control strategy comprehensively considers the frequency regulation capabilities of PV and energy storage,so that photovoltaics and energy storage are responsible for half of the primary frequency regulation functions.This strategy can not only ensure the economic benefits of PVPPs,but also reduce the energy storage capacity required for primary frequency regulation.Finally,the proposed FPPT control strategy,tracking step-size calculation method and primary frequency regulation control strategy are verified by MATLAB/Simulink simulation platform and d SPACE experimental platform.The experimental results prove the correctness of the proposed strategy and theory.In addition,the proposed primary frequency regulation strategy is verified to be effective for PVPPs to provide active power when frequency disturbance occurs.