Research On Circulating Current Suppression Method For Parallel-connected Two Inverters During Low Voltage Ride Through

In recent years,with the rapid development of photovoltaic(pv)grid power generation technology,high-power photovoltaic power generation system is more and more tend to have more machine in parallel mode working mode of photovoltaic power generation system has increasingly become the mainstream,multimachine parallel has the advantage of flexibility,high reliability and good fault tolerance,but multimachine parallel work usually exist circulation,this has a certain influence on the performance of photovoltaic power generation system,with the increase of the proportion of the pv system connected to the electricity grid in parallel,especially when a fault is short if not effectively controlled circulation,may therefore and photovoltaic power generation system for trip protection,which can lead to cannot be achieved through the grid fault impact on a paralleling system is becoming more and more big,therefore,this subject mainly research the grid pv paralleling system fault conditions circulation inhibition.First,to analyze the circulation of the normal time of the power grid,to find out the factors that affect the cause.This paper introduces the control pethod and its advantages of parallel system in this paper.Follow the grid voltage failure detection method of voltage,the design method of the three-phase phase-locked loop and parallel system and node reactive power injection to help and the calculation method of node voltage recovery;Secondly,analyzed the influence factors of power grid failure circulation,the circulation is decomposed into positive sequence,negative sequence and zero sequence component,and gives the specific solutions,and grid single-phase fault,three phase fault specific experimental verification;Study a proportion of a plural integral controller(PCI),and use it to replace traditional PI controller for the zero sequence components in circulation suppressed,and through the simulation and test experiment to analysis the control performance of two methods;In the end,the problem of the start-up flow encountered in the experiment was analyzed and verified experimentally.According to the design of circuit and control method of this topic in PSIM 9.0 under the simulation environment under the condition of normal operation of the grid fault and two T tri-level simulation of photovoltaic inverter parallel system;In this paper,the traditional circulation suppression method is simulated with the method of this subject.In this paper,the experimental prototype of two t-type inverter and parallel network system,which is based on STM32F407ZG as the core controller,has been experimentally verified.The simulation and experimental results show that the zero sequence circulation flow in low voltage across process is effectively suppressed,which indicates that the method is feasible.