The escalating penetration of distributed photovoltaic (PV) systems has intensified grid-connected voltage violations, posing severe challenges to the stability of distribution networks. This paper first investigates the mechanisms of voltage violations at 35 kV substations and 380 V consumer-side terminals under high-penetration scenarios. It is demonstrated that PV integration elevates line voltage, with the voltage profile at any given node being governed by the equivalent net load—defined as the offset between total demand and PV generation—downstream of that node. Subsequently, the impacts of critical operating conditions, including PV penetration levels, line impedance, and dynamic meteorological variations, are quantitatively analyzed. Simulation results characterize voltage fluctuation patterns under diverse variables, such as varying PV outputs, line parameters, and interconnection points, thereby validating the theoretical derivation. Finally, an integrated management strategy, coupling coordinated reactor compensation with voltage-source inverter (VSI) control, is proposed. Simulation results across multi-dimensional complex scenarios verify the effectiveness of the proposed strategy in suppressing voltage violations and enhancing grid resilience.

The escalating penetration of distributed photovoltaic (PV) systems has intensified grid-connected voltage violations, posing severe challenges to the stability of distribution networks. This paper first investigates the mechanisms of voltage violations at 35 kV substations and 380 V consumer-side terminals under high-penetration scenarios. It is demonstrated that PV integration elevates line voltage, with the voltage profile at any given node being governed by the equivalent net load—defined as the offset between total demand and PV generation—downstream of that node. Subsequently, the impacts of critical operating conditions, including PV penetration levels, line impedance, and dynamic meteorological variations, are quantitatively analyzed. Simulation results characterize voltage fluctuation patterns under diverse variables, such as varying PV outputs, line parameters, and interconnection points, thereby validating the theoretical derivation. Finally, an integrated management strategy, coupling coordinated reactor compensation with voltage-source inverter (VSI) control, is proposed. Simulation results across multi-dimensional complex scenarios verify the effectiveness of the proposed strategy in suppressing voltage violations and enhancing grid resilience.

To address the issues of thermal non-uniformity and insulation aging of converter transformers operating under long-term high electric field and high-temperature conditions in ultra-high-voltage direct current (UHVDC) transmission systems, this paper investigates the temperature field distribution characteristics of converter transformers based on electro–thermal–mechanical multiphysics coupling. By establishing a full-scale multiphysics simulation model of a ±800 kV converter transformer, the interactions among the electric field, temperature field, and mechanical stress field are comprehensively considered. The temperature gradient distribution and hotspot formation mechanisms within the valve-side winding and the lead-out structure are revealed. The results show that the internal temperature distribution of the converter transformer is non-uniform, resulting in a nonlinear distribution of material parameters in oil-paper insulation, which significantly affects the insulation performance. The research findings provide a theoretical basis and engineering reference for the structural optimization and thermal stability improvement of the main insulation system of converter transformers.