Research On Voltage Level Sequence And Line Protection Principle Of DC Distribution Network

The rapid development of power electronics technology and control strategies,the general trend of energy interconnection,and the problems faced by existing communication systems have prompted new development opportunities for DC distribution networks.The standardization of the voltage level sequence is the basis for problems such as equipment development and power grid planning and operation.The protection technology is a technical guarantee for the safe and stable operation of the DC distribution network.Therefore,the in-depth study of the above two issues are of great significance in promoting the theorization and engineering of DC distribution.In this paper,double terminal power distribution network is the main research object.First,the typical topology and typical application scenarios of DC distribution network are analyzed.A±10kV double terminal DC distribution network model is set up in the RT-LAB environment.The transient and steady-state operation is analyzed for the preparation of later.Secondly,in view of the problem of DC distribution voltage level,the internal and external factors affecting the voltage grade sequence and the constraint principle of voltage level are mainly analyzed,and a method for determining the voltage level sequence for DC distribution network is formed in all aspects.Based on the method above,a voltage level sequence for DC distribution network is given.In order to evaluate the performance of the sequence,the power supply performance and consideration factors is mainly analyzed.The results show that many factors are considered and adapt to the development trend of the power grid in the future.On the other hand,the protection scheme for DC line in the dual end power supply DC distribution network is carried out.The protection scheme is mainly composed of non-communication protection technology and two times slope characteristics of capacitance discharge.Based on the non-communication protection technology with reasonable delay,the fault section is determined by the initial value of two times slope of capacitance discharge.And also it is used as the acceleration criterion for the acceleration action of the circuit breaker.For the fault that can start the acceleration criterion,the action of protections act in accelerating mode,for those unable to start the acceleration criterion,protection scheme act in the mode of scheduled delay.In the end,the proposed protection method is tested on the basis of the built±10kV two end power supply direct current distribution demonstration project.The results prove that the non-communication protection scheme combined with the characteristics of discharge is correct.