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Using Simulation to Determine the Maneuvering Performance of the WAGB‐20

The WAGB-20 is a U. S. Coast Guard polar icebreaker with an integrated diesel-electric propulsion system. Power is generated by four main diesel engines driving AC generators. Two main 15,000-HP AC synchronous propulsion motors are directly coupled to the port and starboard propellers. Two cycloconverters provide variable-voltage, variable-frequency power for controlling each propulsion motor. The simulation of the electric propulsion system is being developed to analyze the steady- state and transient performance of the system during open water and icebreaking operations. The objectives of the analysis are to support propulsion plant design, aid in the integration of system components, develop control system algorithms, predict system performance, and determine the requirements for dynamic braking resistors. The analysis consists of mathematical models for the ship, shaft systems, propellers, AC synchronous propulsion motors, motor controllers, cycloconverters, generators, generator exciters, voltage regulators, diesel engines, and engine governors. These models are based on actual machinery data. The WAGB-20 specification requires the propulsion system to have the capability of going from full power ahead to full power astern in open water in 25 seconds or less. This paper presents the simulation results which show that by controlling the regenerative power the crash astern maneuver can be performed to meet this requirement without the need for dynamic braking resistors.