System-Wide Harmonic Mitigation in a Diesel-Electric Ship by Model Predictive Control

This paper proposes a system-oriented approach for mitigating harmonic distortions by utilizing a single active power filter (APF) in an electrical grid with multiple buses. Common practice for the control of APFs is to locally compensate the load current harmonics or to mitigate voltage harmonics at a single bus. However, the operation of an APF in a multibus system will influence the voltages at neighboring buses. It is, therefore, possible to optimize the APF operation from a system perspective instead of considering only conventional local filtering strategies. For such purposes, model predictive control (MPC) is proposed in this paper as a framework for generating APF current references that will minimize the harmonic distortions of the overall system within a given APF rating. A diesel-electric ship, with two buses supplying separate harmonic loads, with an APF located at one of the buses, is used as study case. The operation with online MPC-based optimization of the APF current references is compared to two benchmark methods based on conventional approaches for APF control. The results demonstrate that the MPC generates current references that better utilize the APF current capability for system-wide harmonic mitigation.