Study Of Middle&Low-voltage Line DC Ice-melting Based On Movable Battery Storage System For Fujian Hilly Terrain

Transmission line icing is one of the major natural disasters in power system,severe icing can cause ice flashover,pole(tower)collapse and broken line accident.The current ice-melting is the most widely used and most effective method of melting ice.At present,because of no special ice-melting power and low construction standard in most rural distribution lines of 35kV/10kV voltage level,the efficiency and range of ice-melting are limited and the damage caused by ice cover is also serious.In the light of insufficient of the middle&low voltage distribution network line ice-melting technology and large capacity,large reactive power consumption of the AC short circuit ice-melting,this paper put forward the middle&low-voltage line DC ice-melting technology based on the movable battery storage system.With the energy storage battery as a power source,it can be used to melt the icing of the middle and low voltage power distribution line neatly and efficiently.Firstly,according to the meteorological environment conditions over the years and the ice distribution maps of Fujian power grid,the necessity of ice-melting technology research on Fujian Hilly Terrain and the regularities of Fujian power grid ice distribution was analyzed.A place in Fujian hilly terrain was also decided to be demonstration place of DC ice-melting system based on the survey results.Secondly,combined with the thermal balance during ice-melting,the basic principle and merits and drawbacks of the static model,dynamic model,oval-shaped model and empirical model of ice-melting were comparative analyzed.The empirical model was finally used to calculate the related parameters in ice melting progress.In order to increase the flexibility and economy of the DC ice-melting system,the optimization design for the system capacity and power have been discussed from the angle of the DC ice-melting mode and system cost.The capacity and power of the ice-melting system was finally determined.Under the results of optimization,the ice-melting system was designed as the structure with bi-directional AC/DC converter,DC/DC converter,lithium-ion battery energy storage system,distribution system and monitor.After the design of DC ice-melting system,the operational principle and control strategy of three modules which include bi-directional AC/DC converter,DC/DC converter and lithium-ion battery energy storage system were analyzed.The result demonstrated that single loop control with the AC current was adopt for grid connected operation of AC/DC converter.On the other hand,the outer-loop with voltage and the inner-loop with current was used to control AC/DC converter in the island operation.The battery energy storage system used the bi-directional fast balance control strategy to achieve the energy balance between each of the cell.The forecast-current method combined with the deadbeat control that was used to control the DC/DC convert at the same time.After the hardware and software designs finished,the ice-melting testing program of demonstration line was compiled and the ice-melting system was test for the demonstration line,in order to verify the effectiveness of the DC ice-melting system based on the movable battery storage device.