Railway energy consumption and its environmental repercussions, alongside operational costs, are pivotal concerns necessitating attention. With escalating energy prices, renewable energy sources emerge as compelling alternatives to traditional systems, offering clean and cost-effective solutions while advancing decarbonization efforts. This study delves into the integration of photovoltaic (PV) and energy storage systems (ESS) into AC railway traction power supply systems (TPSS) with Direct Feed (DF) and Autotransformer (AT) configurations. The aim is to evaluate energy performance, overhead line current distribution, and conductor temperature. A case study is conducted on a 100 km AC rail route with six passenger stations and suburban trains operational throughout a full day, illustrating the impact of PV and ESS integration in both DF and AT setups. Findings reveal improved voltage drops and significant reductions in substation supply power, energy consumption, contact wire current, and temperature. Notably, a 6.5% and 9.6% reduction in supply energy is observed with PV and ESS integration for DF and AT configurations, respectively. These results underscore the imperative of the integration to optimize energy management in railway systems, fostering efficient energy utilization, potential cost savings, and environmental sustainability.

A proportional–integral repetitive controller (PIRC) can be employed in hybrid distribution transformers (HDTs) to control voltages and currents across multiple frequencies for the steady-state performance improvement. However, the transient performance of a PIRC under grid faults or step change conditions deteriorates due to the coupling effect between its proportional and repetitive components. Based on the derived transfer function of the PIRC in relation to the HDT, this article reveals that the mismatched dynamic response speeds between the PI and RC loops are the primary cause of the control coupling effect. This mismatch leads to the accumulation of step tracking errors into the next fundamental frequency cycle in the RC loop. To address this issue, a novel event-triggered PIRC (ET-PIRC) scheme is proposed to eliminate the control coupling effect and enhance the HDT’s transient performance. The main contribution of this article is the adoption of an event-triggered control based on the principle of dynamically adjusting the control efforts of the PI and RC loops in response to the step tracking errors, thereby mitigating the inherent coupling between them. During step changes, this approach accelerates the transient response of the PI loop while driving the step tracking error in the RC loop to zero, effectively decoupling the two control loops. The robustness and stability of the ET-PIRC are also examined. Comparative simulation and experimental results validate the feasibility of the proposed control method and its superior transient response performance.

This paper presents the findings from the initial phases of the SIF BLADE project, focused on demonstrating the capabilities of an offshore wind power plant (OWPP) for power system restoration (PSR). It provides an overview of PSR, highlighting its challenges and operational requirements, alongside the various scenarios considered in the project. The study includes a steady-state analysis to assess whether the OWPP can meet local network demands for both active and reactive power. Results indicate that the OWPP can operate within an envelope that covers all local power requirements. Additionally, electromagnetic transient (EMT) analysis was conducted to evaluate different percentages of grid-forming (GFM) converter penetration during the energisation process. These analyses aimed to determine compliance with transmission system operator (TSO) requirements. Findings demonstrate that all GFM penetration levels met the necessary TSO standards. Furthermore, a novel small-signal analysis was performed to identify the optimal percentage of GFM converters for enhancing system stability during block loading. The analysis suggests that for top-up scenarios, a GFM penetration between 20% and 40% is optimal, while for anchor scenarios, 40% to 60% GFM penetration enhances stability and robustness.

A hybrid offshore rectifier system, consisting of a Diode Rectifier and a Modular Multilevel Converter (DR-MMC), is attracting attention in High Voltage Direct Current (HVDC) transmission systems, as it combines the high efficiency and low cost of the DR with the control capabilities of the MMC. It is also applied to offshore wind farms (OWF). The application of offshore DR-MMC rectifiers necessitates a thorough evaluation of system stability. A small-signal DC impedance model for the DR-MMC rectifier is proposed. It includes the impact of the OWF, transformers, AC cable and the DR-MMC rectifier. This model is then used for developing the AC impedance model as seen from the onshore converter station. The OWF is represented using an aggregated model for simplification. Utilizing these small-signal impedance models, the paper explores the effects of the OWF’s control parameter, control parameters of the DR-MMC, and MMC/DR rated capacity ratio on the AC impedance of onshore converter and the onshore stability. Moreover, this paper compares the stability of HVDC systems utilizing the DR-MMC and the conventional MMC, and evaluates the validity of modeling the offshore system using an ideal source in stability analyses of the onshore system. It finds that the DR-MMC offers better stability than the conventional MMC, and modeling the offshore system as a simple DC voltage source leads to inaccurate onshore stability assessments.

This paper presents the findings from the initial phases of the SIF BLADE project, focused on demonstrating the capabilities of an offshore wind power plant (OWPP) for power system restoration (PSR). It provides an overview of PSR, highlighting its challenges and operational requirements, alongside the various scenarios considered in the project. The study includes a steady-state analysis to assess whether the OWPP can meet local network demands for both active and reactive power. Results indicate that the OWPP can operate within an envelope that covers all local power requirements. Additionally, EMT analysis were conducted to evaluate different percentages of grid-forming (GFM) converter penetration during the energization process. These analyses aimed to determine compliance with Transmission System Operator (TSO) requirements. Findings demonstrate that all GFM penetration levels met the necessary TSO standards. Furthermore, a novel small signal analysis was performed to identify the optimal percentage of GFM converters for enhancing system stability during block loading. The analysis suggests that for top-up scenarios, a GFM penetration between 20% to 40% is optimal, while for anchor scenarios, 40% to 60% GFM penetration enhances stability and robustness.