With the evolution of the distribution network to an active bidirectional interactive system, as an important active load interface in the distribution network, the large-scale access of charging piles not only brings challenges to the power quality of the distribution network but also provides opportunities for power quality regulation and optimization. This paper discusses the main factors affecting the power quality of the distribution network due to charging piles. The power quality problems such as voltage fluctuation and harmonics caused by charging piles are described. Then, the key technologies and potential of charging piles in power quality management are summarized, focusing on the technical progress in harmonic suppression and voltage regulation. Finally, the paper provides an outlook on the optimization directions of related technologies. This paper reveals the positive role of charging piles in power quality management of distribution networks from the perspective of devices. It provides a reference for future research on the participation of large-scale charging pile integration in power quality management.

With the expansion of renewable energy sources, the stable and high-quality operation of microgrids composed of new energy sources has attracted widespread attention. Among them, the power conversion system (PCS), as an important part of microgrids, plays a crucial role in their operation and management. The PCS operation modes are classified into grid-connected and off-grid modes. However, in off-grid mode, due to the access of nonlinear and unbalanced loads, the output voltage quality of a PCS is worse, and the voltage waveform distortion is serious. To solve these problems, a fast repetitive control (FRC) strategy is proposed for a power conversion system with an Active Neutral Point Clamped (ANPC) architecture of three levels. The voltage loop control strategy can be applied to the voltage/frequency ($V/f$) mode and the grid-forming mode. The control strategy can effectively realize the suppression of the harmonics of the output voltage and has a 100% capability to carry unbalanced loads. Finally, a 1725 kVA PCS prototype is developed, and the proposed control strategy is verified using the MT3200 HIL semiphysical simulator of ModelingTech in the $V/f$ mode as an example. This practically verifies the feasibility and validity of the proposed control strategy, which has a certain degree of engineering practicability and reference due to the simplicity of the design and the ease of realization.

To address the challenge of virtual synchronous generator (VSG) control technology in simultaneously achieving transient oscillation suppression and steady-state accuracy, as well as the poor anti-interference capability of fixed damping parameters under scenarios such as sudden changes in the short-circuit ratio (SCR), this paper proposes a transient damping optimization VSG control strategy based on a dissipative Hamiltonian neural network (DHNN) adaptive mechanism. Without affecting the original droop characteristics and rotational inertia, a transient damping feedback (TDF) branch is introduced to provide an additional damping ratio for the system to suppress low-frequency oscillations. The TDF control directly acts on the rotor motion equation through active-power low-frequency component feedback, featuring a simple structure without requiring complex computations. A small-signal model was established to quantitatively analyze the oscillation suppression mechanism. Furthermore, the dissipative Hamiltonian neural network (DHNN) was employed to dynamically optimize TDF parameters, ensuring a robust system performance under disturbances. The simulation and experimental results ultimately validated the effectiveness of the proposed control strategy.

Under the background of vigorously promoting the construction of new power system，the power conversion system(PCS) plays an important role to transfer high reliable electrical power quality to grid. However, the system is sensitive to the voltage deviation on both side of point of common coupling(PCC) when switching from off-grid mode to grid-connected mode directly, it leads to surge currents or even threaten system stability.In this paper, an improved grid-connected pre-synchronization method for smooth grid connection is proposed. The system adds a pre-synchronization module on the basis of virtual synchronous generator(VSG) control to synchronize the voltage between the PCS and the grid. In addition, a slope control unit is introduced to further avoid the potential surge current problem at the moment of grid connection. Finally, the experimental results of simulation is verified the effectiveness and feasibility of the proposed scheme.