The four-switch Buck-Boost (FSBB) converter can produce voltage conversion within a wide input voltage range, which is suitable for variable-speed permanent magnet synchronous generator (PMSG) energy storage systems with AC inputs and DC outputs. To reduce the interference of input voltage fluctuation on the performance of the FSBB converter, an input voltage feedforward (IVFF) compensation method is proposed in this paper. The switching synchronization strategy is simple. Using the switching average model, the small signal model of a non-ideal FSBB converter in all working modes is established. The effects of input voltage, load current, damping coefficient and right half plane (RHP) zero on the stability of the control system are analyzed in detail. The transfer function of the IVFF of the FSBB converter is derived, and the relationship between input voltage, load current and duty cycle is analyzed. Finally, the design of the parameters of the converter control system is presented. The simulation and experimental results show that this FSBB converter has high efficiency and a good transient response.

A novel strategy of three-vector-based model predictive direct power control (MPDPC) is proposed for three-phase Pulse-width Modulation (PWM) rectifier. Under ideal grid conditions, three-vector MPDPC is studied, and a good control effect has been achieved. However, under the unbalanced power grid condition, the traditional control strategy has some problems, such as a high harmonic content of current and large instantaneous power pulsation. A new three-vector model predictive control is proposed based on the new instantaneous power theory, and the objective function is established by instantaneous power error. The duty cycle of the selected vector is calculated by solving the optimal objective function. Under an unbalanced power grid, this paper takes a three-phase PWM rectifier as a research object, and carries out simulation and experimental tests on the traditional and new control strategies. The experimental results show that the new control strategy has lower current harmonics, and eliminates the twice grid-frequency oscillation of the grid in instantaneous power.

Single metal droplets are widely used in electronic packaging and flexible circuit printing. However, the high density and interfacial tension of liquid metals make it difficult for the jet to stably generate single metal droplets, which greatly restricts the development of pneumatic drop-on-demand metal droplet ejection technology. In this paper, through experiments and numerical simulations, the jet motion states and internal fluid flow transition mechanisms during metal droplet generation are systematically investigated, and a dimensionless limiting jet length prediction model for stable single metal Sn droplet generation is established. The results show that the dynamic competition and dominance transition between inertial force and interfacial capillary force fundamentally determine the jet motion states and internal fluid transition mechanisms. The pulse width is responsible for “activating” and “sustaining” the jet behavior, while the limiting jet length is primarily governed by the velocity provided by the supply pressure. The predictions of the dimensionless limiting jet length model are consistent with the experimental results, indicating that the model can effectively predict the limiting jet length for generating single metal droplets. The findings of this study are of significant importance for revealing the evolution mechanism of the jet during pneumatic drop-on-demand metal droplet generation and for achieving stable generation of single metal droplets, providing a theoretical basis for the further development of pneumatic drop-on-demand metal droplet additive manufacturing technology.

Single metal droplets are widely used in electronic packaging and flexible circuit printing. However, the high density and interfacial tension of liquid metals make it difficult for the jet to stably generate single metal droplets, which greatly restricts the development of pneumatic drop on demand metal droplet ejection technology. In this paper, through experiments and numerical simulations, the jet motion states and internal fluid flow transition mechanisms during metal droplet generation are systematically investigated, and a dimensionless limiting jet length prediction model for stable single metal droplet generation is established. The results show that the dynamic competition and dominance transition between inertial force and interfacial capillary force fundamentally determine the jet motion states and internal fluid transition mechanisms. The pulse width is responsible for “activating” and “sustaining” the jet behavior, while the limiting jet length is primarily governed by the velocity provided by the supply pressure. The predictions of the dimensionless limiting jet length model are consistent with the experimental results, indicating that the model can effectively predict the limiting jet length for generating single metal droplets. The findings of this study are of significant importance for revealing the evolution mechanism of the jet during pneumatic drop on demand metal droplet generation and for achieving stable generation of single metal droplets, providing a theoretical basis for the further development of pneumatic drop on demand metal droplet additive manufacturing technology.