Balancing loads of rotating generators utilizing VSC direct power controllers in a ship AC/DC smartgrid

This paper considers the case of a ship AC/DC smartgrid configured in the docked mode, where a 1 MW diesel-generator is in operation to supply the AC-side of the grid in addition to a battery-bank connected to the DC-side, and a 0.5MVA Voltage Source Converter (VSC) for bridging the two sides of the grid. In this configuration, three-phase power imbalance can easily occur due to unpredictable per-phase consumer-loads, causing generator torque, power-angle and voltage oscillations that lead to increased fuel consumption and potentially to premature failure. To overcome such a condition, the paper proposes a control method for the VSC which implements three power-controllers for re-balancing the loads on the rotating-generator. Firstly, it presents a four-thorder power-model for the VSC microgrid-connection and the DC-link, including a diesel-generator's electromechanical model. Then the model is expanded to allow the design and implementation of the power-controllers based on an inverse-model technique. This process also includes the analysis and design of integrated DC-link voltage and frequency-droop controllers, and a synthetic-inertia provider. Finally, the paper demonstrates the performance of the complete VSC control system and its parts through a detailed system simulation of the microgrid, which covers performance tests and analysis, demonstrating the elimination of generator torque oscillation.