Research On Photovoltaic Grid-Connected Power Generation System With Active Filter Function

In recent years,in order to deal with the energy crisis and environmental pollution,solar energy as a green,clean,pollution-free renewable energy has been widely concerned.Grid-connected photovoltaic power generation is a technology that effectively utilizes solar energy resources and occupies an increasing proportion in the power industry.At the same time,the use of a large number of nonlinear loads leads to the sharp increase of harmonic content in the power grid side,which will threaten the safe and stable operation of the power grid.Therefore,some measures should be taken to limit the harmonic content within a reasonable range.Aiming at the low utilization rate of photovoltaic grid-connected inverter and harmonic problems in power grid,this paper studies a harmonic suppression scheme combining photovoltaic grid-connected power generation system and source power filter.The work is as follows:1)In this paper,the engineering mathematical model of photovoltaic cell module is derived,its output characteristics are verified,the photovoltaic MPPT control algorithm based on disturbance observation method is introduced,and the pre-stage analysis of photovoltaic grid-connected system is completed.On this basis,the similarity of photovoltaic grid-connected system and APF in topology structure and control method is compared,so that the same grid-connected device can realize two functions of photovoltaic grid-connected power generation and active filter at the same time.The structure scheme and overall topology of the unified control system are analyzed,and the two key links of the system are harmonic current detection and the control technology of the main circuit.2)The main structure of photovoltaic grid-connected system is introduced,the mathematical model of photovoltaic cell module is deduced,the photovoltaic output characteristics under different light and temperature are verified by simulation,and the disturbance observation method is selected as the MPPT control algorithm of the front stage system.Then introduces the working principle of the active power filter with the contrast analysis of photovoltaic(pv)grid system,and a unified control system of the fusion is put forward,make the photovoltaic(pv)grid power generation system with active filtering functions,has been clear about the two key links of the system is the harmonic current detection and tracking control of instruction current signal.3)For unified control system of the synthetic model of instruction current,voltage and current double closed-loop control strategy is analyzed,according to the characteristics of the dc side voltage,choose PI controller to control,considering the current loop is used in the PI controller can’t to zero tracking error of the harmonic signal,so designed a PI control and repetitive control parallel compound control manner,In order to better control the harmonic signal.Finally,a simulation model of the unified control system was built using Matlab/ Simulink platform,and three different operating conditions of single photovoltaic grid-connected,single active filter and photovoltaic grid-connected and active filter in the model were tested and analyzed,which verified the effectiveness and feasibility of the system designed in this paper.