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Research On Power Quality Problems Detection And Control Of Distributed New Energy DC Power Supply System

Posted on:2019-03-18Degree:MasterType:Thesis
Country:ChinaCandidate:L ZhangFull Text:PDF
GTID:2382330590475498Subject:Embedded Systems
Abstract/Summary:PDF Full Text Request
As the global energy supply structure changes and the impact of environmental pollution becomes more and more significant,the use of renewable energy sources is receiving more and more attention.Distributed generation(DG)grid-connected technologies including photovoltaic and wind power have been obtained.Rapid development.DC power supply system has the advantages of convenient access control,high conversion efficiency,and few intermediate conversion links,and is also being emphasized.The distributed DC power supply system not only overcomes some defects of the traditional centralized power supply,such as redundant power supply and uninterrupted power supply,but also has a higher degree of modularity,ease of expansion,and higher reliability.However,the distributed DC power supply system has its own small capacity,and the distributed power supply is vulnerable to the external environment,making the distributed DC power supply vulnerable to degradation of its own power quality due to system operation changes.In order to ensure that the distributed DC power supply system can supply normal and effective power to the load,it is essential to study the power quality problem in the distributed DC power supply system.This paper focuses on the study of the power quality problems of distributed DC power supply systems,focusing on the detection and management of power quality problems.By comparing and analyzing different power quality detection methods,the source of power quality problems is detected by wavelet transform.By analyzing the power relations and control methods of distributed DC power supply system,a hierarchical control strategy based on DC bus voltage is proposed.Finally,a simulation model was built to analyze and verify the simulation results,which laid the foundation for more in-depth study.The specific research content is as follows:Firstly,a distributed DC power supply system composed of a photovoltaic power generation unit,a battery and a super-capacitor hybrid energy storage device,and a DC load is constructed,that is,a DC micro-grid system.The characteristics of each component unit and its interface control were analyzed,including the mathematical model and control method of photovoltaic power generation unit,hybrid energy storage device super capacitor and battery,and grid-connected converter.Then the causes of the power quality problems existing in the distributed DC power supply system are analyzed,mainly including the influences from the photovoltaic power generation unit,switching of large loads when off-grid,and off-grid switching.The wavelet transform method is used to detect the power quality problem of distributed DC power supply system.According to the good time-frequency adaptive characteristics of wavelet transform and the modulus maximum principle,the pollution source of DC bus voltage at the corresponding time is determined.Then,the energy storage method using a lithium battery and a super capacitor is combined,and a bi-directional DC/DC topology circuit is used to realize the interaction of the active power between the energy storage device and the system.A comprehensive analysis of the entire system has various working modes,and a DC bus based on the DC bus is proposed.Voltage stratified area coordination control strategy.According to the range of the bus voltage,a corresponding control method is applied to the distributed DC power supply system to ensure stable operation when the system operation mode is changed.Finally,a simulation model including photovoltaic power generation module,energy storage module,resistance load module,system monitoring module and system control module was built through Matlab/Simulink platform,and the power quality problems brought by micro-source and load end were simulated.The power quality detection method and the layered control strategy based on the DC bus voltage were verified.Experimental results verify the effectiveness of the proposed method for power quality problems of distributed DC power systems.
Keywords/Search Tags:distributed DC power system, power quality, wavelet analysis, hybrid energy storage, operation mode, control strategy
PDF Full Text Request
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