<p>Brushless dual-electrical-port and dual-mechanical-port (BLDD) machine have received increasing attention due to its advantages of torque and speed decoupling, as well as contactless multi-port collaborative operation. However, conventional BLDD machine generally suffer from low torque density due to low working flux density. This paper proposes a stator-excited dual flux modulation BLDD machine with a dual-flux-modulation effect to enhance the working flux density, thereby significantly improving torque density. The proposed BLDD machine can be considered a combination of flux-reversal machine and magnetic geared machine. In addition, two mechanical ports are connected to the vertical axis wind turbine and the turbine respectively, which can absorb both wind energy and ocean current energy to further improve the energy conversion efficiency, and there are two sets of windings in the stator, which can optimize the torque of the inner and outer rotors of the machine by adjusting the currents of the two sets of windings. Therefore, the proposed BLDD machine is more suitable for direct-drive co-generation system. The topology and working principles of this machine are detailed, and its advantages are validated through quantitative performance comparisons with conventional BLDD machines. Results show that the back electromotive force amplitude of winding I increases by approximately 2.7&#xa0;times, while that of winding II rises by around 15.8&#xa0;times; the output torque of the inner rotor improves by 146.8%, and that of the outer rotor by 312.3%. Finally, an optimization analysis using the response surface methodology identifies the optimal structural parameters, reducing the inner rotor’s fluctuation from 18.4 to 7.4% and the outer rotor’s fluctuation from 62 to 24.7%. Additionally, the stator core loss was reduced by 20.9%, and the outer rotor core loss decreased by 44%.</p>