Optimal Control of Active Damping on the DC Side of Front-to-Front DC-DC Converter Based on MMC

The front-to-front direct current(DC) converter based on modular multilevel converters (MMC) is a highvoltage, high-power converter, which is capable of applying to the new energy full dc technology of dc convergence-dc delivery, and only needs to maintain the de voltage stability to achieve system stability. However, insufficient damping of the dc system can cause de-side oscillations, which is highly related to the control strategy adopted by the converter. For this reason, in order to improve the damping and dynamic characteristics of the system with a view to suppressing oscillations, the an optimal control strategy with active damping on the DC side is proposed, where damping is introduced for the correction of the inner-loop reference current, and the damping mechanism is analyzed. The optimal damping coefficient calculation method is derived, and when the damping is the optimal damping coefficient, the model can be equivalently downgraded, which significantly enhances the voltage control characteristics. The stability and control characteristics of the de side before and after the introduction of damping are compared and analyzed, and the results show that the system has better stability and control characteristics after the introduction of damping, which effectively improves the voltage stability under the fluctuation of the dc bus. Finally, the effectiveness of the damping optimization control strategy is verified by MATLAB/Simulink simulation.