Study On Automatic Paralleling And Coordinated Protection For Shipboard Power Systems

As the shipboard becoming more automated and large, the quality, continuity and reliability of electric energy will directly affect the economic operation and the vitality of the shipboard. Simple traditional relay protection scheme which formed by fuse and current protection could not satisfy the modern shipboard power requirements. Therefore, the research on auto-parallel, auto-disconnection and the protection of the shipboard is particularly important.Based on the Matlab platform, the paper simulates the shipboard power station which contains two identical generators. Starting the generator waiting for the parallel operation once the load exceeds the capacity of a single generator 80%. It is able to reduce the voltage and frequency of the generator waiting for the parallel operation by adjusting the speed and excitation. Once the load is reduced to 30% of the total capacity of the two generators, in order to move the load of the generator to the other generator, adjustment for one of the generators' rotational speed and excitation is needed When the generator's load is less than 20% of the generator's capacity, the generator will be auto-disconnected. In order to solve the contradiction of the selectivity and rapidity of the traditional shipboard loop power system protection, this paper proposes a method to accelerate the protection. The method by comparing the difference of the current phase at both ends of the line segments to determine the fault zone, then adjusting each circuit breaker tripping time to make the nearest two circuit of the two sides of the fault point to trip at once, so as to achieve the purpose of accelerating the protection. At the same time, so that the each upper grade circuit breakers of the two circuit breakers to trip with delaying 0.3 second, as its backup protection. Aiming at how to solve the two circuit breakers of generator outlet without backup protection problem, three method are put forward. A current protection coordination analysis software is designed for shipboard power system, by using Matlab/Simulink toolbox and friendly graphical user interface GUI. It is able to draw and debug the superior and subordinate protections as well as the current three segment protections cooperation curves based on the requirements of clients. The parameters of relay can be directly transmitted to the corresponding relay in Simulink, so that the clients can analyze the coordination between superior and subordinate protections, as well as the current three segment protections more conveniently. The simulation examples verified the protection coordination analysis function of developed software.Based on the Matlab simulation, the paper successfully simulated the auto-parallel and auto-disconnection of ship power station which contains two identical generators. It can guide the engineering application. The paper proposes a method to accelerate the protection of the shipboard loop power system. This method can instantaneous tripping of the two circuit breakers which nearby the both sides of the fault point, so as to achieve the purpose of accelerating the protection. At the same time, this method also solves the problem of the traditional differential protection without backup protection. Design of current protection software is in order to analysis the coordination and the selectivity of protections.