Ship harmonics of sub-synchronous vibration

Modern ships have been widely equipped with electric propulsion system. With the ships becoming larger, the load also being larger and more modern equipments, the micro-grid system is also more complex. Therefore, the stability of the micro-grid requirements is increasing. This article firstly describes that the structure of marine power system is a multi-motor structure which is the hybrid system of the AC load and DC load, so the ship micro-grid harmonic problem is serious. The harmonics and other instability reasons can cause sub-synchronous oscillation in the micro-grid system. Then the article describes the mechanism of sub-synchronous oscillations, and, starting from the principle, innovatively establishes a gas turbine five-axis model under the PSCAD simulation. Through the simulation, it can be found that generators are prone to torsional vibration. To avoid this situation, the article analyzes the advantages and disadvantages of the common methods. Serial capacitors are used to eliminate some harmonics and to compensate the line. By taking this reliable way to eliminate and reduce sub-synchronous oscillation, it is finally verified on simulation and demonstrated feasible.