Research On Multi-objective Dynamic Reconfiguration Control Of Dc Side Of Group-string Pv Power Generation System

The connection method of the conventional distributed photovoltaic power generation system is fixed.Under low light conditions such as rainy days or morning and evening,the inverter works at a low power level,which seriously affects the power generation efficiency of the system and the quality of the output waveform.This paper studies the direct current(DC)side topology of photovoltaic system,analyzes the loss and output harmonics of the system in parallel with multiple inverters of the Group-string photovoltaic system,and proposes a variable topology of the multi-objective control of the photovoltaic array and the DC side of the inverter,aiming to improve the performance of the distributed photovoltaic system in weak light.The main research contents are as follows:Firstly,the power quality and power generation efficiency of the group-string photovoltaic system are analyzed.Based on the research of the DC side structure of the photovoltaic grid connected system,a variable topology structure of the DC side of the photovoltaic system is proposed to improve the system performance.The control method of the variable topology of the photovoltaic array and the DC side of the inverter is designed by applying the group control technology idea of parallel operation of multiple inverters.Then the system losses and output harmonics of the variable topology on the DC side are studied;a multi-objective function is established with the minimum system loss rate and harmonic distortion rate as the goal,and the running algorithm of the DC side multi-target dynamic reconstruction is designed and given solution strategy;In addition,the influence of the control strategy on the DC and AC sides of the photovoltaic system is analyzed from an engineering perspective.Finally,the proposed DC side multi-objective control strategy was applied to the experiment,and a photovoltaic system with 5 photovoltaic arrays and 5 inverters connected to the grid via a variable DC side structure was built.The design of the DC side of the system uses DSP as the controller,including multi-link control devices such as information collection,information processing,switching control and feedback correction;through the design of the hardware system and software algorithm,the internal structure and working principle of the switching device are introduced in detail.The effectiveness of this strategy is verified by comparing and analyzing the strategy of this paper,the conventional grid connection strategy and the control strategy aiming at maximum efficiency.