The reliable extinguishment of a single phase-to-ground arc is the key issue for safe and reliable operation in the distribution network. However, since the existing arc suppression methods are normally affected by the line parameters, the residual current (RC) at the grounding point still exists, then the grounding arc is hard to be extinguished reliably. Thus, an adaptive active voltage-type arc suppression (AAVAS) strategy that can reliably inhibit the RC at the grounding point is proposed in this article. First, the mechanism of the traditional voltage-type arc extinguishing method affected by the line parameters is proved, and the variation rules are given for the RC under different fault distances and grounding resistance. Second, the variation characteristics are analyzed for the faulty line current before and after arc extinguishing. On this basis, it is proposed to add the residual voltage compensation ring to the traditional voltage-type control strategy, which can effectively offset the influence of voltage drop on faulty-phase line impedance. Then, the Bode diagram analysis shows that the presented strategy performs well regardless of ground-fault conditions. Finally, the feasibility and effectiveness of the proposed AAVAS strategy are verified by the simulation and experiment results.

A soft open point (SOP) can improve the flexibility of power control and thus further enhance the reliability and economy of distribution networks. However, existing SOP regulation strategies have mainly focused on feeder imbalance regulation and line loss optimization in medium-voltage distribution networks, and the loss of SOPs and distribution transformers are often ignored, which has poor applicability in low-voltage distribution network (LDN). Therefore, a novel two-layer control strategy is proposed for SOPs working in LDN, which can improve economy and reliability of the system simultaneously. In terms of the system layer, the proposed load regulation strategy considering the economical operation area of the transformers can improve the system economy while realizing load imbalance regulation. In terms of the equipment layer, the proposed peer-to-peer control of each port in the SOP can effectively suppress the voltage fluctuation on the DC side. Thus, the system layer commands can be quickly tracked and well conducted. Finally, the feasibility and effectiveness of the proposed two-layer control strategy are verified by simulation and experimental results.

Unified power quality conditioner (UPQC) can well achieve comprehensive control for power quality. However, the power rating reductions of the series side and parallel side of the back-to-back connected converters in UPQC are hard to be achieved simultaneously, and they even restrict each other. In this article, a new topology of UPQC is proposed. It has an LC filter coupled with an external capacitor at the series part. Besides, a comprehensive coordination strategy is proposed to operate the improved UPQC (iUPQC) at reactive power compensation (RPC) mode and voltage fluctuation compensation (VC). Specifically, to achieve the low power rating, the proposed control strategy makes the series part undertakes partial reactive power that needs to be compensated at the parallel side in RPC mode. At the same time, it makes the parallel side coordinates the series side to expand the optimal operation range in VC mode. Compared with the conventional UPQCs, the iUPQC can well reduce the power rating of back-to-back connected converters from both parallel and series sides. Moreover, the optimal parameters design method is also provided. Finally, the effectiveness of the proposed topology and control method is validated by both simulation and experimental results.

The advanced cophase traction power supply system (ACTPSS) integrating with photovoltaics (PV) and energy storage (ES) can realize the efficient consumption of regenerative braking energy (RBE) and renewable energy sources. However, the existing single-level energy management strategies for ACTPSS that only focus on the main-station or the sub-station have poor performance in the economy and timeliness. Therefore, a multi-timescale energy management strategy including the minutes-level optimal dispatch for main-station and the seconds-level real-time control for sub-stations is proposed, which can improve the economy and reliability of the ACTPSS with PV and ES simultaneously. In terms of the main-station layer, an min-level optimal dispatch model is established with an objective of minimum operating cost to obtain reference working points of output port converter, PV, and ES in each sub-station. In terms of the sub-station layer, an s-level adaptive working point control strategy based on improved Arctan droop is proposed to ensure the voltage and frequency stability of ACTPSS, while suppressing the PV/RBE power feedback to three-phase power network. Finally, the feasibility and superiority of the proposed multi-timescale energy management strategy are verified by simulations and experiment results.

The advanced cophase power supply system provides an opportunity to eliminate the problems of neutral section and power quality issues. However, the existing schemes still have drawbacks, such as numerous power electronic devices, high initial cost, and poor reliability. Therefore, in this article, a novel hybrid advanced cophase power supply equipment (NH-ACPSE) is proposed based on the existing traction transformer. By the common dc bus of each port, the secondary ripple power of the input ports can be offset. Also, the number of active/passive devices and capacitance capacity can be reduced. Then, aiming at the secondary ripple and load power impact on the dc side, a composite control strategy of NH-ACPSE is proposed to solve the harmonic transmission and impact fluctuation effectively. Finally, the feasibility and reliability of the proposed equipment and its control strategy are verified by simulation and experiment.

The advanced traction power supply equipment (ATPSE) based on power electronics technology presents an opportunity to address issues of negative-sequence power quality and neutral section simultaneously. However, existing power-frequency/high-frequency isolation schemes still face challenges such as low power density and high investment costs. To address these issues, a high-frequency isolated ATPSE (HI-ATPSE) based on triple-port high-frequency isolated dc converter and existing traction transformers is proposed. Compared to existing high-frequency isolation schemes, the device volume and initial cost are effectively reduced by sharing output ports in the proposed HI-ATPSE. In addition, considering the power quality issues within the proposed HI-ATPSE, a control strategy is proposed to suppress the dc side double-frequency ripple and negative-sequence while reducing the dc side's capacitance value. Finally, the feasibility and reliability of the proposed HI-ATPSE and control strategy are validated through simulation and experimental verification.