Modern energy systems require efficient power management, making multi-active bridge (MAB) converters ideal for EV charging and DC microgrids. However, higher port counts lead to magnetic coupling and non-linear dynamics, complicating independent control. This paper proposes a generalized power flow decoupling strategy for a 5-port Modular Multi-Active Bridge (MMAB) converter using the Newton-Raphson (NR) method. Unlike traditional reduced-order models, a current-based model is employed to maintain modularity. A key contribution is the integration of the Moore-Penrose pseudoinverse into the NR solver to mitigate Jacobian singularities and ensure numerical stability. The algorithm is implemented on a dual-core CPU, achieving a deterministic 40 µs execution time. Furthermore, this study identifies performance degradation caused by parasitic inductances in the modular AC bus and proposes an optimized design using magnetic flux cancellation. Modeling precision is further refined through offline FFT-based parameter identification. Experimental validation on a 5-port MMAB prototype confirms that the proposed method provides superior steady-state accuracy and robust dynamic decoupling during rapid transient load transitions.