New Busbar Automatics Transfer Switch Scheme For New Energy Access

Under the influence of energy crisis and environmental pollution,the gradual low-carbon of power system will be the key direction of energy development in China in the future.Therefore,the power system will gradually show the "double high" characteristics of high proportion of renewable energy and high proportion of power electronic equipment.In terms of stability,the "double high" characteristics will have essential changes to the dynamic characteristics of the system and even the system itself.Unlike the traditional synchronous generator-based power system in the past,the "double-high" power system has more complex dynamic characteristics.For example,the randomness of the output of new energy,the low inertia brought by the use of power electronic interfaces,and the low short circuit current when the power electronic equipment is short-circuited will seriously affect the stability of power system operation and the reliability of power supply.In order to improve the reliability of power supply of the system,the automatic switching device for equipment power supply(hereinafter referred to as standby automatic switching)is often installed in the system.Its function is to automatically switch on the standby power supply to ensure the continuous power supply of the load when the main power supply fails.The operation of standby automatic switch shall generally meet the voltage free condition of the incoming bus of the main power supply.However,the low voltage ride through control of the new energy itself has always played a supporting role on the bus voltage,which leads to the failure of the voltage free operation condition of the standby automatic switch bus,and the standby automatic switch cannot work normally to recover the system power supply.However,the existing standby automatic switching scheme adopts to cut off the new energy first to meet the bus voltage free action conditions in the standby automatic switching scheme,and then put the standby power supply into operation through the standby automatic switching.Although this method is effective,it takes a long time to split the new energy,resulting in a large number of load losses;In addition,it is difficult for new energy units to be connected to the grid again.Therefore,the main research goal of this paper is how to solve the problem that the standby automatic switching device cannot operate without splitting the new energy.At first,this paper briefly introduces the operation principle,basic structure and different classification of the standby automatic switching device,analyzes and considers that the "low penetration" characteristic of new energy makes the operation conditions of the standby automatic switching device not satisfied,points out that all the existing standby automatic switching devices need to cut off new energy,and puts forward three major problems faced by the standby automatic switching device to achieve the goal of not cutting off new energy.Secondly,focusing on these three problems,this paper focuses on the change of electrical quantity in the island,especially at the island connection point,after the fault is removed,and points out that the power imbalance in the island is the main reason for the change of electrical quantity,laying a theoretical foundation for limiting the closing impulse current.At the same time,according to the relative relationship between fan output power and load power before opening,the island is divided into "source greater than load" and"source less than load" scenarios,paving the way for the proposal of a new standby automatic switching scheme.Finally,the action principle and action logic of the new backup automatic switching scheme are introduced.At the same time,in order to verify the effectiveness of the new scheme,the internal load of the island is simulated and verified by using pure resistance,pure inductance,pure capacitance and induction motor type load respectively.The simulation results show that the scheme is practical.In addition,this paper also uses the IEEE39 for simulation,which shows the effectiveness of the scheme from the system level.