Unbalance load analysis on closed bus electrical system under ship dynamic positioning scenario

Dynamic Positioning (DP) operation on offshore auxiliary vessels emerges as a challenge in need of ensured high-powered bow thruster stability. DP operation is widely adopted under an open electrical system (open bus). Open bus-configured DP usually has low electricity disturbance. However, open bus-configured DP is always attributed to its low efficiency. Our study revealed that DP ships using closed bus configuration are prone to the unbalance three-phase electric load problem. Unbalanced load, which always results in the unbalance three-phase voltage problem, can affect the performance of the motor or another electrical component. Our simulation successfully showed the effect of unbalance load on the ship's electric stability. By using commonly electric ship configuration as simulation testing, the ship grid configuration with the power supply of two generator thruster and one diesel generator with the 2-bow thruster and a static load can indicate unbalanced load on AHTS vessels with variations up to 75%. By minimizing the variation of percentages of the bow thruster operating point and other loads, minimum allowable three-phase deviation of the unbalance, which indicated by the three-phase voltage operating point could be met. The simulation study was done using MATLAB as a tool.