Recently, the penetration of renewable energy sources (RESs) into electrical power systems is witnessing a large attention due to their inexhaustibility, environmental benefits, storage capabilities, lower maintenance and stronger economy, etc. Among these RESs, offshore wind power plants (OWPP) are ones of the most widespread power plants that have emerged with regard to being competitive with other energy technologies. However, the application of power electronic converters (PECs), offshore transmission lines and large substation transformers result in considerable power quality (PQ) issues in grid connected OWPP. Moreover, due to the installation of filters for each OWPP, some other challenges such as voltage and frequency stability arise. In this regard, various customs power devices along with integration control methodologies have been implemented to deal with stated issues. Furthermore, for a smooth and reliable operation of the system, each country established various grid codes. Although various mitigation schemes and related standards for OWPP are documented separately, a comprehensive review covering these aspects has not yet addressed in the literature. The objective of this study is to compare and relate prior as well as latest developments on PQ and stability challenges and their solutions. Low voltage ride through (LVRT) schemes and associated grid codes prevalent for the interconnection of OWPP based power grid have been deliberated. In addition, various PQ issues and mitigation options such as FACTS based filters, DFIG based adaptive and conventional control algorithms, ESS based methods and LVRT requirements have been summarized and compared. Finally, recommendations and future trends for PQ improvement are highlighted at the end.

A benchmark distribution system is developed for investigating control and energy management of distributed generation (DG) at a residential level in the form of three single-phase microgrids. The benchmark is derived from a typical distribution network architecture with common parameters found in North-America systems including wiring specifications, line impedances and connection details for rooftop PV systems. This benchmark system can accommodate microgrids operating in both grid-connected and islanded modes. Within this benchmark, multiple single-phase DG sources located in different phases can be coordinated to form a dynamically balanced three phase system under different load and generation profiles in different phases. The coordination of DG sources in a particular phase is achieved through an intra-phase power management device, while mitigating loads and generation imbalance among all phases are done by an inter-phase power management scheme. It is expected that this benchmark system will facilitate investigation of impacts posed by proliferation of single-phase distributed generation devices and local storage systems in private residences. Three case studies have been carried out to demonstrate the versatility and effectiveness of this benchmark system.

A power control and management strategy for islanded residential microgrids is presented. A three-phase residential microgrid can be viewed as three separate single-phase systems. Within each phase, there are PV systems, battery storage devices and droop controlled dispatchable units. Connections among phases are made through back-to-back converters to allow for power transfer between the phases. Hence, voltage and frequency control and power management must be carried out at intra-phase and inter-phase levels. The intra-phase power control and management system uses a modified vector control with a multi-segment (P/f) droop strategy. In the case where such a balance cannot be maintained locally, the inter-phase power can be transferred through the back-to-back converters. Both intra-phase and inter-phase power control and management scenarios have been considered. To demonstrate the effectiveness of the strategy, a detailed three-phase residential microgrid model is developed in PSCAD/EMTDC environment, including switching models of the back-to-back converters. The results have shown that the proposed strategies can effectively maintain desired voltage and frequency profiles for each phase-wise and the overall microgrid, frequency, and power balance in each phase can be effectively managed for stable operation.

With the increased installation of single-phase rooftop PV systems, in-house battery storage units, and high-power plug-in loads (i.e., EVs) at single-phase residential sites, it is prevalent that an increasing number of residential distribution systems are becoming severely unbalanced, causing power quality problems and thermal risks at distribution sub-stations. While different techniques have been investigated to resolve this issue, there is still a lack of adequate theoretical foundations to guide these approaches. In this study, a detailed analytical analysis is carried out for a typical North American residential community with single-phase power generation, storage, and high-power random plug-in loads. This analysis has laid the foundation for a class of operating scenarios and provides an essential theoretical basis to unify different techniques for dynamically balancing single-phase microgrids connected to three-phase distribution systems. Detailed formulations have been developed for the first time to draw explicit power transfer relationships among power surplus and power-deficient phases to achieve an overall dynamic balance. A user-friendly, free interactive online tool has also been developed for potential users to evaluate their own application scenarios.

As the penetration of renewable energy resources has increased over the years, the need to reduce high-frequency switching harmonics and distortion in the power grid has become more important than ever before. The LCL filter in a voltage source converter (VSC) has been introduced as a solution to this problem. This paper provides a comprehensive mathematical approach that has been established to design LCL filters for various applications. By applying the conventional methodology to design an LCL filter, a comparative study is presented with the main objective of finding the optimal sizes for the filter components, while ensuring filter stability and efficiency. The proposed design process is tested using PSCAD/EMTDC and MATLAB/Simulink-based models. An averaging mathematical approach was used to balance the component sizes and the filter’s stability. The simulation results indicate that a computational iteration could enhance the system’s performance through further optimization. Four cases are studied for a typical VSC system with an LCL filter. These cases include studying and analyzing the voltage and current signals and their THDs. The proposed design respects the limits on voltage and current distortion to comply with IEEE standards.