It is undeniable that marine vessel systems play an 6 important role to transfer huge loads and weapons with low cost. 7 However, ship power systems produce a lot of greenhouse gases, 8 which in turn lead to serious environmental pollution. Hence, the 9 utilizing of wind turbines (WTs), solar generation, sea wave en-10 ergy (SWE), and energy storage systems (ESSs) in marine vessel 11 power systems have been attracting a lot of attention in recent 12 years. In this paper, it is assumed that a marine vessel power system 13 with photovoltaic (PV), WT, SWE, and ESS can be regarded as a 14 mobile-islanded MG. Then, a novel topology for hybrid shipboard 15 microgrids (MGs) is presented. Next, in order to make a balance 16 between consumption and power generation in shipboard MGs, 17 an optimal modified model-free nonlinear sliding mode controller 18 is introduced for the secondary load frequency control. Since the 19 quality of the control actions of the proposed model-free approach 20 depends on its parameters, a hybrid version of the sine-cosine al-21 gorithm (SCA) and wavelet-mutation (WM), called SCAWM, is 22 employed to find the best value of these coefficients. Comparisons 23 are conducted with other existing methodologies, such as model 24 predictive control, interval type-2 fuzzy logic controller, and con-25 ventional PI (PI) to establish the supremacy of the newly suggested 26 control strategy. Finally, a real-time hardware-in-the-loop (HIL) 27 simulation based on OPAL-RT is accomplished to affirm the ap-28 plicability of the suggested controller, from a systemic perspective, 29 for the load frequency control problem in the shipboard MG. 30 Index Terms-Frequency regulation, model-free nonlinear slid-31 ing mode controller (MFNSMC), on-board power grid, sine-cosine 32 algorithm (SCA), wavelet mutation (WM).