Model-Based Design for Control Architecture of Onboard Hybrid Power Systems

Onboard hybrid power systems (OHPS), as a key enabler for the electrification of marine transport, rely on the capabilities of emerging technologies combined with hierarchical control systems. This paper addresses the challenges associated with the control design of OHPS by proposing a practical model-based design approach and performing case studies for validation. Initially, a generic dynamic model for the OHPS is developed including multi-level controllers, such as a power management system (PMS) and low-level controllers, and power components, such as engine generators, power electronics, dc grid, and batteries. Then, the system's stability is investigated thanks to the eigenvalue-based “stability portraits”. Consequently, stability-based design boundaries are identified concerning changes in the control parameters and loading limits. This allows evaluation of the PMS and its associated parameters such as droop coefficients used for load sharing. The analytical model and the designed PMS are validated with time-domain simulations and experimental tests conducted on a laboratory-scale prototype. The results on selected operating points demonstrate good consistency. The proposed method is developed using simplified dynamic models to avoid computational complexities. Yet, it provides insight into the system physics and reduces the uncertainty of the design process allowing for more flexible-, efficient- and cost-effective control scenarios.