Research On Simulation Of AC/DC Power Distribution System

Energy shortage and environmental deterioration are the greatest public crisis that human beings have ever encountered.The transition to low-carbon environmental protection electric power has become the trend of the development of electric power industry in China and even in the world.The development and utilization of new energy will be an important pillar of the future electric power industry.However,in the low-voltage distribution network,while the distributed energy grid is increasing rapidly,the new energy types and application forms become more and more complicated.In addition,the large-scale access grid of DC load leads to the increase of the variable energy link of the AC distribution network.The use of DC technology to strengthen the traditional AC distribution network,the construction of AC/DC power distribution system can meet the various types of energy and load access and achieve load control and other purposes.At the same time,it has important practical significance to the power quality,reliability,economy and operation efficiency of the distribution system.This paper presents AC/DC power distribution system,whose basic principle is based on the flexible back-to-back technology and through the multi-port voltage source inverter control to achieve the bus between the energy conversion and control,all kinds of AC-DC grid-connected power supply,and through the coordinated control of DC bus voltage,energy storage,DC load and access of distributed power supply,etc..At the same time,the control strategy of the system is proposed,and the corresponding simulation model is set up in the PSCAD,and the dynamic characteristics of the system are simulated and analyzed.Firstly,the whole structure of AC / DC power distribution system is researched,the principle of voltage source converter is analyzed,and the mathematical model of d-q rotating coordinate system is established by PARK transformation.At the same time,the operating characteristics of wind power generation system,photovoltaic power generation system and energy storage system are also expounded.Next,the central control strategy of AC / DC power distribution system is designed.The control strategy of the two voltage source converters is as follows: one controls active power and reactive power on the AC side,while the other controls the reactive power and DC bus voltage on the AC side,which uses the double closed-loop control system and the inner ring uses the decoupling control strategy.According to the time response and the application scenario,three levels of central control strategies are designed,which are the central control layer,the device control layer and the device control layer,in order to maintain the system power balance and voltage stability.In order to improve the stability of the power distribution system,an additional power control module is added to the central control stage to achieve the purpose of rapid follow power changes and realize the simultaneous adjustment of the power balance of the multi-converter.Finally,a brief introduction is given to the electromagnetic transient simulation program PSCAD,in which the corresponding simulation model is built according to the established mathematical model and the proposed control strategy.At the same time,the dynamic characteristics of the AC / DC power distribution system are simulated and analyzed under various operating modes and disturbance conditions to verify the feasibility of AC / DC power distribution system and the effectiveness of the control strategy.