Abstract : Various electric propulsion systems are widely used in diesel-electric propulsion ships. Their power electronics add harmonic currents to the power grid. When shipboard equipment, such as speed control drives, frequency converters, power supplies, and flashers, is combined with line impedance, harmonic voltage drops occur, interfering with the power supply voltage sine wave. Due to higher losses, equipment lifespan may be shortened, the circuit power factor (λ) may decrease, and sensitive loads may fail or even be damaged. Therefore, a high-quality power grid is essential for an operating "electric ship." To ensure the ship meets the specific power quality requirements of the shipowner, calculations and simulations are necessary before ship construction. Taking the basic principles of various electric propulsion systems and frequency converters as examples, a matching simulation device is described, and the simulation results are compared with measured values ​​on some diesel-electric propulsion ships. This demonstrates that the simulation results have high accuracy and conform to actual measurements. Keywords : Propulsion system, frequency converter, model simulation, ship 1 Introduction Various electric propulsion systems are widely used in diesel-electric propulsion ships. The propulsion motor can be synchronous or asynchronous, and permanent magnet motors can also operate. These motors are powered by different frequency converters (such as Hz converters, current source converters, and pulse width modulation converters). Various propulsion systems can be built using these components. Limitations on the power quality of the ship's electrical grid are determined according to standards, classification societies, and shipowner requirements. To achieve high-performance power quality, manufacturers use multi-pulse converters, filter cabinets, and additional rotary transformers. Simulation is essential for finding the optimal electric propulsion design concept and determining the optimization parameters of complex systems. Proper use of simulation during the design phase can reduce the time and cost of engineering planning. The simulation equipment used is an internal device specifically developed for electric propulsion and power electronics equipment. This paper describes the simulation equipment in conjunction with the basic principles of different electric propulsion systems and frequency converters. Simulation results regarding power quality are compared with corresponding measurements for some diesel-electric propulsion ships. 2. Description of the Simulation Equipment Used The state of electrical and mechanical equipment is difficult to reliably extrapolate using approximations or mathematical equations. Since accurate calculations of the system's response to potential faults are as important as dynamic characteristic data, simulation methods are necessary from the design phase to the commissioning phase to obtain accurate information about complex systems. [b][align=center]For details, please click: Simulation of Ship Electric Propulsion Systems[/align][/b]