In a single-phase charging system of electric vehicles, the current control performance of the single-phase ac–dc factor correction (PFC) converter with a deadbeat predictive current control (DPCC) method is affected by the distorted grid voltage, parameter dependence, and control delay. To tackle these problems, a modified DPCC method is proposed in this article. By introducing a phase adjustment parameter θ _c , which can be directly calculated according to the required power factor, into the grid voltage feedforward of the current loop, an improved input current control performance with lower harmonic components and higher power factor can be achieved when the converter operates at unity power factor. At the same time, compared with the traditional method, a reactive power compensation function is added in the modified DPCC and a deadtime compensation method is adopted in the modulation. Finally, a 7.8-kW single-phase PFC converter prototype is built to verify the feasibility and effectiveness of the proposed control method.

The phase-shifted full-bridge (PSFB) converter is widely adopted in electric vehicles and energy storage applications. However, it suffers from several technical drawbacks such as voltage overshoot, hard switching, severe circulating current, and large reverse power. To address such issues, an improved control scheme is proposed to enhance the performances of bidirectional operation in the PSFB converter. In this method, the precharge stage and the cocharge stage are added by adjusting the phase-shift angle and duty ratio. The reverse power, circulating current, and transformer root mean square current can be reduced with the cocharge stage. And, due to the precharge stage, this method can constrict voltage overshoot very well, while achieving zero current switching on the large current side devices and zero voltage switching on the high-voltage side devices nearly along all the load range. The proposed method is described, analyzed, and validated in a 1-kW prototype, which presents 96.1% peak efficiency and improves average efficiency by about 2% in the experimental results.

In this article, the control stage of an interesting versatile single-/three-phase electric vehicle (EV) charging system is studied in details. Therein, a typical three-phase two-level voltage source rectifier can be reconfigured to operate as a single-phase rectifier where two phase-legs operate with a pulsewidth modulation interleaving method and the grid neutral is connected to the midpoint of the dc-bus capacitors with the third leg operating as an active power decoupling (APD) circuit to reduce the current stress in the capacitors. To improve the performance of the single-phase operation while considering external grid voltage disturbances, first, an improved hybrid current control method combining deadbeat prediction current control (DPCC) with repetitive control (RC) is proposed in this article, where a modified RC is adopted to suppress the influence of the internal dc-bus capacitor voltage disturbance and to improve the harmonic control performance. Thereafter, via introducing the weighting factor K _f of the DPCC and by multiplexing the filter of RC in the DPCC output, the stability of the current loop under the influence of grid voltage distortion and grid impedance can be improved remarkably. Moreover, a grid-frequency voltage ripple suppression function implementing zero-voltage-switching turn- on for the APD circuit is achieved, improving the reliability of the converter. Finally, a 7.4-kW single-phase ac–dc converter prototype is built to verify the feasibility and effectiveness of the proposed method in the single-/three-phase EV charging system.

As the penetration of photovoltaic (PV) sources in the power system continues to rise, it is important for PV converters to operate in grid-forming (GFM) mode. Since the dc voltage is not controlled by the PV side, GFM PVs should have capabilities for dc voltage regulation and ac side support. However, most research on GFM PVs has concentrated on the stability related to dc-link voltage synchronization control (DVSC), neglecting the impact of ac voltage amplitude control (AVC) on the stability of GFM PVs. In this article, a new low-frequency oscillation issue in GFM PVs is first identified. To investigate the destabilization mechanism of this phenomenon, a small-signal model is derived, revealing that the low-pass filter of the reactive power introduced in the AVC loop and the AVC loop coupled into the DVSC loop are two key factors leading to instability. This article proposes an effective approach to suppress the low-frequency oscillations, which feeds forward reactive power dynamics into the DVSC loop through a proportional gain. This strategy not only addresses low-frequency oscillations but also improves the transient performance of the GFM PVs. Moreover, this strategy enables the GFM converter to operate stably across a wide range of short-circuit ratios. Finally, simulation and experimental results validate the accuracy of the theoretical analysis and the effectiveness of the proposed method.

Grid-forming (GFM) converters have emerged as essential technologies for ensuring the stability of power systems dominated by renewable energy sources. Nevertheless, their restricted overcurrent capacity may trigger protection during grid faults. While existing studies emphasize the design and optimization of overcurrent mitigation strategies, precise characterization of fault current and dynamic analysis of transient inrush current are still lacking, leading to occurrences of protection malfunction. To bridge this research gap, this article considers the impact of filter parameters and current loop parameters on the equivalent impedance of the converter, and on this basis, establishes a precise fault current characterization model for GFM converters. Based on the model, the key factors influencing inrush current can be analyzed, including voltage amplitude, impedance magnitude, and power angle. Finally, a precise virtual impedance-based inrush current suppression method is proposed, which effectively limits the inrush current to the desired level while ensuring system stability. Both theoretical analysis and experimental results are carried out to validate the robustness and adaptability of the proposed strategy under various grid strengths and grid voltage sags.