The distribution grid is under major transformation due to the increasing dependency on renewable energy resources (RES) and electric vehicle (EV) charging stations. For accommodating such sources and loads in an existing AC distribution system without violating the voltage and current quality limits, various strategies such as modifying the control methodologies, structural reconfiguration of the grids, etc., are identified as suitable options. The power electronic converters play a significant role in integrating these features to the distribution grid. Unified power quality conditioner (UPQC) is a preferred choice to control quality of both currents and voltages. In this paper, the operation of a meshed hybrid microgrid is realized using UPQC. The DC link of UPQC is used to form a low voltage (LV) DC line. This LVDC line is connected parallel to the LVAC lines. The loads and distribution generation units are integrated to AC and DC lines using power electronic converters. The improved performance during adverse operating conditions show the superior reliability for the proposed system. In addition, the analysis verifies the enhanced capability of the proposed system in accommodating new DC loads to the existing system. Both simulation and experimental results are demonstrated to evaluate the performance of the proposed system.

The increasing need of cost-effective and large-scale energy storage systems is motivating a strong focus on the deployment of hydrogen based conversion and storage. Hence, the potential of achieving fast dynamic response and high efficiency of electrolyzers makes them attractive to support the mitigation of reliability and stability threats due to the inherent variable power supply from renewables. Suitable dynamic models of new combined solutions, i.e. renewable generation with electrolyzers, are urgently needed to properly characterize and mitigate such threats. Therefore, this paper presents an EMT real-time simulation model of an electrolyzer connected to an offshore 20 MW DC wind power generation system. The envisioned power electronic layout along with the necessary controlling actions are explained in detail. Two modes of electrolyzer operation are proposed the master and slave mode. Based on whether hydrogen production is the priority or grid power injection is priority, the controlling action of the proposed model can be switched. The proposed model is developed as a building block for the study and design of multi-gigawatt scale offshore wind power plants, with stability support from electrolyzers.

As modern trends demand efficient methods to massively and promptly exploit clean energy, there is an urgent need of solutions that can help the ambition of accelerating the development and integration of larger scale energy systems with the capacity to extract, store, and utilize huge amounts of renewable energy sources. In view of this, the rated power output of the wind generation technology is expected to significantly increase in the near future to enable multi-gigawatt roll outs, e.g. the European plans for Offshore infrastructure development in the North-Sea. Besides, gigantic energy systems shall transmit the power to onshore interconnected systems via HVDC transmission. This paper introduces an EMT model of a 20 MW wind generation system with the conventional back-to-back converter replaced by a combination of an AC to DC converter and a DC to DC converter. While the need of such systems is acknowledged in the literature, the design and performance analysis of high power implementation of such systems have not been addressed yet. The proposed system operates at a voltage level of 100 kV, which can directly transfer power through HVDC interconnection. The designed control aspects are outlined and the resulting dynamic response obtained from realtime digital simulation (RTDS) are discussed. The presented wind generator concept can help in reducing the size of a planned energy system by requiring lesser system components. Also, the system efficiency can be enhanced by decreasing the number of power conversion stages.

The Nordic Power System is undergoing significant transformation and development in the coming years. A driving factor for this is the increased dependency on renewable energy sources and high voltage direct current transmission (HVDC). Various stability challenges due to the dynamics of reactive power - voltage (Q-V) balancing and active power - frequency (P-f) balancing seep into the system with such rise of non-synchronous generation (NSG). This paper investigates the projected impact of NSGs on the P-f dynamic performance of Nordic power system in 2030. As NSGs are systems with low inertia, power discrepancies lead to larger oscillations, higher Rate of Change of Frequency (RoCoF) and bigger maximum frequency deviation (MFD) values. To address these issues, Emulated Inertia (EI) control for wind turbines and Synthetic Inertia (SI) control for VSC-HVDC links are proposed in this paper. The simulation is carried out using DIgSILENT PowerFactory 2022 SP1 simulation software. The results obtained confirm the Effectiveness of the proposed EI and SI methods to enhance frequency response and mitigate deviations.