Research On Control Strategy Of Distributed Photovoltaic Grid-connected Inverter With Active Filtering Function

At the end of 2020,China proposed the "30 60" carbon neutrality goal,which means to take more favorable plans and measures to make Chinese carbon dioxide emissions peak before 2030 and strive to achieve carbon neutrality before 2060 This means that China solemnly promises to greatly increase the proportion of renewable energy in the total energy consumption in the future and accelerate the transform the energy production and consumption structure into the green environmental protection mode,and the photovoltaic industry in China is about to meet the greater development opportunities and bright prospects However,the change of weather and day alternates with night,photovoltaic power generation has intermittent and nonlinear problems,photovoltaic grid-related equipment has high cost and low utilization rate,these factors have great limitations to the promotion and application of photovoltaic Due to the rapid development,the power electronic equipment of gridconnected inverter circuit always causes harmonic current,which makes a large number of harmonic components injected into the power system that cause harmonic pollutions With the increase of the application rate of distributed photovoltaic power generation in the power grid,how to use the residual capacity of inverter to deal with the power quality problem has become a research hotspot at home and abroadActive power filter is a kind of dynamic harmonic suppression and reactive power compensation equipment which relevant theoretical research has been very complete,but the promotion and application of APF is still under the restriction of its expensive price and single function There are still much room for improvement in its practicability and the control strategy remains to be optimized and improvedIn this paper,the advantages with disadvantages and similarities with differences of photovoltaic grid-connected power generation system and APF system from the structure and control strategy are respectively analyzed in detail Exploring the feasibility of unified control of APF and photovoltaic grid-connected system and analyzing the synthesis of grid-connected command current reference signal of unified control of photovoltaic grid-connected power generation with APF function In this paper,different fundamental active power signals are used to make the current at the gird side change with the rise and fall of illumination Based on instantaneous reactive power theory,the harmonic and reactive power detection method is improved to enhance the compensation of specific odd harmonic compoents Designing the corresponding ways of capture process of the harmonic compensation component with the reactive power compensation component and synthesize mode of the gridconnected command current reference signal with the photovoltaic active power component by classifying the working state of the system based on different application scenarios In addition,the problem about the traditional perturbation and observation method of photovoltaic maximum power peak tracking control can lead to continuously fluctuate of steady-state output current in photovoltaic cell which will affect the harmonic suppression and reactive power compensation components to deviate from the original detection accuracy According to the traditional perturbation observation method and traditional incremental conductance method on the maximum power peak tracking control of photovoltaic cells,this paper adopts an improved incremental conductance method with piecewise variable step size which can adaptat and track the change of external environment conditions faster and more accurately with the steadied state accuracy of maximum power tracking and the reduced oscillation of the output current of the photovoltaic cells which will improve the effect of harmonic suppression Finally,the unified system control simulation model built on Matlab/Simulink simulation platform,which includes the main circuit,photovoltaic module,harmonic and reactive current detection module,command current reference signal synthesis module,current tracking control module,etc The triple functions of photovoltaic gridconnection,harmonic suppression and reactive power compensation of the system are verified under the conditions of continuous switching of illumination load...