Research On Bus Voltage Stability Control Of DC Distribution Network Based On Energy Storage Converter

With the increase of the proportion of new energy such as wind power connected to the DC distribution system,the DC distribution system presents the characteristics of weak damping and low inertia,and the anti-interference ability of the system gradually becomes weak.When the power grid failure,large capacity load switching or harmonic imbalance,the DC bus voltage will also have an impact.DC distribution system does not have the problem of power angle and frequency stability,so it is very important to maintain the voltage stability of DC bus for the stable and reliable operation of DC distribution system.If the voltage of the DC busbar fluctuates greatly and measures are not taken to suppress it in time,the voltage protection device in the system may misoperate or refuse to operate,or even trigger voltage collapse,which seriously threatens the safe and stable operation of the DC power distribution system.Based on the analysis of the voltage fluctuation of the DC bus in the traditional voltage source converter DC distribution network,this thesis studies the method to stabilize the DC bus voltage.A DC distribution network model with an energy storage converter is built,and the effectiveness of the energy storage converter to stabilize DC bus voltage is simulated and verified.Firstly,the voltage fluctuation of DC bus in DC distribution network with traditional voltage source converter is analyzed,and the method of DC bus voltage stabilization is studied.According to the fluctuation frequency and period,the causes of voltage fluctuation of DC bus are divided into disturbance type and oscillation type.The influence mechanism of these two types of factors on DC bus voltage is analyzed,and the harm of DC bus voltage fluctuation not controlled in time is emphasized.From the point of view of improving the converter control strategy,the methods to stabilize the DC bus voltage are analyzed,and the disadvantages of these methods are pointed out.Secondly,the DC distribution network model with energy storage converter is designed and built.Aiming at the main components of DC distribution network,including voltage source converter,energy storage system,bidirectional DC converter and photovoltaic unit,the mathematical model of each component is established and the corresponding control strategy is designed according to the role of each part in the network.The energy storage unit capacity is configured according to the maximum power deviation caused by the most serious case.PSCAD/EMTDC simulation software is used to verify the stability of the designed energy storage converter in DC distribution network.Finally,PSCAD/EMTDC simulation software is used to verify the efficiency of the accumulator converter to stabilize the DC bus voltage.From two aspects of simulation output waveform and DC voltage evaluation index,it is verified that the energy storage converter has significant voltage stabilization effect,which greatly improves the power quality of DC distribution system,and has certain reference value for ensuring the stable and reliable operation of DC distribution engineering.The thesis contains 64 figures,5 tables,and 82 references.