Research On Energy Management Of Household Type Off-grid Photovoltaic Power System

Currently fossil fuels are depleted, and the photovoltaic industry as an importantpart of today’s energy sector, is becoming a research hotspot. In this thesis, some ofoff-grid PV system key technologies were studied.To better understand the off-grid photovoltaic systems, analysis and comparisonof its structural framework; Using Matlab/Simulink to build the simulation model ofsolar cell, and the model simulation results and its equivalent circuit is analyzed.Lithium-ion batteries as the energy storage element, are an important part of thesystem; This article use Ann measurement and EMF method to estimate battery stateof charge (SOC), the battery monomer equalization control will use PWMcontrollable active balancing method, using the four sections of the charging methodfor charging the battery pack.The maximum power point tracking (MPPT) technique is an important methodto improve energy utilization efficiency of the photovoltaic system; this thesisintroduces the common MPPT control strategy, on the basis of the solar cell modelsimulation results analysis, using Matlab/Simulink and improved variable step sizeperturbation and observation method, the establishment of a photovoltaic array MPPTsimulation model. Simulation results show that: This improved MPPT controlalgorithm can achieve the desired goal-fast and stable track maximum power point,for off-grid PV system has good practicability.This thesis uses the VISUAL BASIC6.0design the associated matchingsoftware to optimize the system, and gives the realization of hardware circuit andsoftware based on STM32F103C8T6. This thesis proposes energy coordinated controlscheme, when the external environment temperature, solar radiation intensity or loadpower change, the system can reasonably regulate energy flow mode and manner, inorder to maintain normal operation of the system.