Study And Applications Of Power Coversion And Data Communication Multiplexing Converters In DC Power System

DC power system has been paid much attention in practical projects and academia,which is an effective solution for integrating renewable energy units with energy storage elements,fitting DC type loads and realizing energy management.In the information age,communication systems play a vital role in the control and monitoring of a DC power system.A novel power and communication multiplexing system is investigated,which achieves the integration of power conversion circuit and data communication circuit in hardware level by performing dual modulation strategy for traditional power converters,and gains advantages in integrated control and system overall costs.This dissertation focuses on the power conversion and data communication multiplexing converters used in power and communication multiplexing systems,explores the available control freedom hiding in conventional power control strategies,and first presents a theory of power and signal dual modulation.Based on the dual modulation principle,the influence of the signal modulation on the original power control loop and the stability issues are analyzed,the communication equivalent models are established and discussed.On the receiver side,the signal conditioning method and data demodulation algorithm due to different signal attenuation are studied.At last,the proposed theory are tested in three different application scenarios,which verifies the effectiveness of the methods.Firstly,the dissertation studies the fundamental theory of the power and signal dual modulation methods.By analyzing the basic principles of traditional control strategies in DC-DC converters,two basic type of dual modulation can be concluded,which are the modulation wave based dual modulation and the carrier wave based dual modulation.The issues including modulation principles,spectrum characteristics,carrier wave shape selection and amplitude control are discussed.Furthermore,the influence of the signal modulation on the original power control loop are analyzed,and the communication equivalent models are established.The simulations and experimental results are given to prove the validity of the proposed methods.Secondly,based on the fundamental dual modulation theory,the approaches to adjust the signal amplitude,enhance communication performance in anti-interference ability and communication rate are investigated.Using novel common mode phase disturbance,direct sequence spread spectrum(DSSS)and orthogonal frequency division multiplexing(OFDM),the methods that can realize both decoupled control and adjustable signal amplitude,achieve better anti-interference performance and higher communication rate are proposed separately.The modulation principle and spectrum analysis of the above methods are illustrated.Then the methods are verified by prototype experiments.Besides,the method of improving the communication carrier frequency based on special topology structures of a power circuit or inserting a high frequency resonant unit are studied preliminarily,which broaden the idea of highspeed broadband communication for the embedded communication.Thirdly,from the view of the receivers,the signal attenuation due to different system topologies as well as the interference issue on a DC power line are analyzed.Based on the typical system topologies used in DC power systems,different signal attenuation features with changing number of nodes in different system structures including series,parallel and cascade are calculated,and verified by simulation results.After analyzing the interference component on a DC power line,signal conditioning circuits to filter random interference signal and the noise elimination method using carrier orthogonal decoding algorithm are studied in details.According to the character differences between the communication carriers generated by different principles,the circuit design approach and decoding algorithm are analyzed,which further demonstrates the effectiveness of the proposed embedded communication method.In addition,considering the applicability of the method in practical applications,a communication protocols is discussed.Finally,the applications of power conversion and data communication multiplexing converters in three different DC power systems are demonstrated.The experimental results verify the effectiveness of the proposed theory,and broaden the proposed embedded communication to a wider field like control loop optimization.