Three-phase four-wire inverters with an independently controlled neutral module have the advantages of small zero-sequence current and mutual decoupling of output neutral point voltage and three-phase voltage control. Maintaining stable neutral point voltage is fundamental to their normal operation. The traditional proportional-integral (PI) dual-loop control strategy is constrained by its limited bandwidth

resulting in inadequate suppression of midpoint voltage fluctuations. This can easily cause output common-mode disturbances and degrade waveform quality. To address this

this paper proposes a neutral point voltage control strategy based on the inner-loop state feedback (SF) and outer-loop PI composite

as well as a control parameter optimization design method driven by target response. The proposed control strategy establishes a refined mathematical model of the controlled object in the discrete domain. Based on a holistic system design philosophy

it derives analytical expressions for all control parameters by reverse-engineering the preset target transfer function. Furthermore

it quantifies the relationship between the system control bandwidth and the positions of closed-loop zeros and poles. Based on this

the system’s ability to suppress low-frequency components of zero-sequence current under different control bandwidths is investigated

as well as the effects of sampling delay and measurement noise on control system performance. This provides guidance for the optimal design of control parameters in practical applications. At the same time

the impact of wide variations in filter parameters on the closed-loop control performance of the system is analyzed. Experimental results demonstrate that the proposed method can significantly increase the control bandwidth without amplifying noise

thereby effectively suppressing midpoint voltage fluctuations under asymmetric/ harmonic load disturbances and improving output waveform quality

while exhibiting high parameter robustness.