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.

A reverse startup procedure for a multi terminal smart transformer (MTST) supplying data centres, transitioning from islanded operation to grid connected operation is proposed in this paper. During islanded operation, the MTST low voltage (LV) converter remains active, while the MTST multi active bridge (MAB) converter is partially active and MTST medium voltage (MV) converter is inactive. To facilitate reconnection to the MV grid from the LV side, these converters need to be activated to allow the power flow. In this operation, the power is drawn from a battery energy storage system (BESS) connected to LVdc-1 bus to charge the MTST MVdc bus. Once the MVdc bus is sufficiently charged, the MTST-MV converter is initiated to establish the connection between the LV side and the MV grid. Simulation is performed in PSCAD and the results are provided to validate the effectiveness of this startup operation.

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.