Research On Unified Control Strategy Of Photovoltaic Grid Connection And APF Based On Feedforward Control

The output power of the photovoltaic array is related to external environmental factors such as light,temperature,and climate.External environment mutation make the system's DC side voltage oscillate,causing the operation to be unstable.so,a new photovoltaic grid-connected and active power filter(APF)unified control strategy based on current feedforward control is eliminated in this paper.The photovoltaic grid-connected system with APF function can not provide sufficient capacity in the case of the photovoltaic grid-connected system and harmonic and reactive power compensation at the same time.In order to prevent the system capacity from exceeding the limit and causing an irreversible impact on the inverter,the size of the grid-connected current must be limited.However,the traditional capacity limitation strategy may cause secondary pollution of harmonics and the decrease of compensation effect.The capacity restriction policies called Dual-Value Current Limiting is eliminated in paper to solve the above problems.This paper focuses on the problem that caused by external environment mutation of system DC bus voltage oscillation,a current feedforward control strategy to act on the photovoltaic grid-connected and APF unified control system is eliminated.The current feedforward control strategy is equivalent to pre-estimating the grid-connectable energy in the photovoltaic PV array by participating in the calculation of the grid-connected command current,which accelerates the calculation of the effective current of the three-level converter integrated into the power grid,as a result,the dynamic response speed of the DC side voltage is improved,and its voltage oscillation is suppressed.In this paper,the voltage and current double-closed-loop control strategy are used in the photovoltaic grid-connected and APF unified control method.The required voltage can be tracked through the DC side voltage in voltage outer loop control,which ensures the relative stability of the DC side voltage and providing the current inner loop grid-connected command current component at the same time;Current inner loop adopts PIMR controller,which make the multiple AC sinusoidal be tracked without static error.Finally,the simulation experiment is carried out through MATLAB / Simulink platform,the correctness and feasibility of the strategy be proved by the result.The paper has 58 pictures,2 tables and 52 references.