Study On Multifunctional Grid Connected Photovoltaic Inverter Technology Based On LCL

Photovoltaic grid connected power system and active power filter (APF) has broadprospects for development, but there are restricting their development obstacles. Activefilter function into the photovoltaic grid connected system, become research focus inrecent years, scholars to solve the low actual utilization, expensive, single function,difficult to promote. At present, multifunctional grid connected photovoltaic systemwith active filtering method mainly has the dual inverter structure method, time-sharingreuse, according to the condition of light switch mode three methods. Dual invertermethod is expensive, and inverter capacity utilization rate is not high. Time-sharingreuse requires frequent switching power switch, will increase the burden and theinverter power utilization rate is not high. Third methods are better than the former twohas the advantages of low price, does not need to frequently switch and can make fulluse of the residual capacity of the inverter. But do not consider eliminating harmonicsand reactive power compensation equence problem of the current control strategy, alsodoes not take into account the goal of eliminating harmonics and reactive powercompensation.In view of the PV grid connected system active power filter function controlstrategy on the basis of the residual capacity, without considering the order ofeliminating harmonics and reactive power compensation and compensation problem,this paper has done the following work:First, from the photovoltaic grid connected system and APF structure, workingprinciple and control strategy discussed will implement the principle of unified controltwo, master of the given system strategy.Second, grid connected inverter capacity constraints based on maximum power,photovoltaic power generation, in the calculation of harmonics elimination and reactivepower command current, priority compensation from the national standard of powerquality indexes (harmonic content of THD is less than or equal to5%, specific harmoniccontent THD1is less than or equal to4%, power factor is greater than or equal to0.9),make full use of the inverter capacity.Third, according to the national standard of power quality indexes, this paperdesigns a compensation calculation algorithm, and studies the realization of thisalgorithm in different conditions.Fourth, in order to compensate the order of real-time and accurate for determiningthe amount of compensation, this paper improved the algorithm of the ip-iq based oninstantaneous reactive power,and to detect specific time harmonics, reduce the delaytime and the calculation of eliminating harmonics and reactive power detection,improve the compensation amount of detection speed and accuracy. Fifth, in order to eliminate harmonic interference in the inverter on compensationrate, the LCL filter is applied to this system, and studied the effect to multifunctionalgrid connected photovoltaic system, design the corresponding LCL parameters.Finally, through the MATLAB/Simulink simulation of the multifunctional gridconnected photovoltaic system based on LCL, built America TI based productioncompany DSP (TMS320LF28335) for the effectiveness and correctness of theparameter and control strategy design of prototype verification system of control core.