International White Book on DER Protection : Review and Testing Procedures

This white book provides an insight into the issues surrounding the impact of increasing levels of DER on the generator and network protection and the resulting necessary improvements in protection testing practices. Particular focus is placed on ever increasing inverter-interfaced DER installations and the challenges of utility network integration. This white book should also serve as a starting point for specifying DER protection testing requirements and procedures. A comprehensive review of international DER protection practices, standards and recommendations is presented. This is accompanied by the identifi cation of the main performance challenges related to these protection schemes under varied network operational conditions and the nature of DER generator and interface technologies. Emphasis is placed on the importance of dynamic testing that can only be delivered through laboratory-based platforms such as real-time simulators, integrated substation automation infrastructure and fl exible, inverter-equipped testing microgrids. To this end, the combination of fl exible network operation and new DER technologies underlines the importance of utilising the laboratory testing facilities available within the DERlab Network of Excellence. This not only informs the shaping of new protection testing and network integration practices by end users but also enables the process of de-risking new DER protection technologies. In order to support the issues discussed in the white paper, a comparative case study between UK and German DER protection and scheme testing practices is presented. This also highlights the level of complexity associated with standardisation and approval mechanisms adopted by different countries

Small Biogas Plant Stability Prediction Model

In this paper stability prediction for a small biogas plant in islanded mode depending on local consumers energy consumption growth is given. Biogas plant with two cogeneration facilities and local consumers is tested for on grid and islanded operation and thus represents a microgrid. Generator and regulator modelling as well as surrounding electrical grid modelling in software package Power World Simulator are described. Expected consumption growth through the period of 20 years in microgrid area is simulated. All generator important variables, i.e. voltage, frequency, real and reactive power in case of islanded mode are examined and explained. Finally, stability prediction analysis of biogas plant and surrounding consumers for 20 years period is given

OFFSHORE WIND ENERGY STUDY AND ITS IMPACT ON SOUTH CAROLINA TRANSMISSION SYSTEM

As one of the renewable resources, wind energy is developing dramatically in last ten years. Offshore wind energy, with more stable speed and less environmental impact than onshore wind, will be the direction of large scale wind industry. Large scale wind farm penetration affects power system operation, planning and control. Studies concerning type III turbine based wind farm integration problems such as wind intermittency, harmonics, low voltage ride through capability have made great progress. However, there are few investigations concerning switching transient impacts of large scale type III turbine based offshore wind farm in transmission systems. This topic will gain more attention as type III wind generator based offshore wind farm capacity is increasing, and most of these large scale offshore wind farms are injected into transmission system. As expected to take one third of the whole wind energy by 2030, the large offshore wind energy need to be thoroughly studied before its integration particularly the switching transient impacts of offshore wind farms. In this dissertation, steady state impact of large scale offshore wind farms on South Carolina transmission system is studied using PSSE software for the first time. At the same time, the offshore wind farm configuration is designed; SC transmission system thermal and voltage limitation are studied with different amount of wind energy injection. The best recommendation is given for the location of wind power injection buses. Switching transient also impacts is also studied in using actual South Carolina transmission system. The equivalent wind farm model for switching transient is developed in PSCAD software and different level of wind farm penetration evaluates the transient performance of the system. A new mathematical method is developed to determine switching transient impact of offshore wind farm into system with less calculation time. This method is based on the frequency domain impedance model. Both machine part and control part are included in this model which makes this representation unique. The new method is compared with a well-established PSCAD method for steady state and transient responses. With this method, the DFIG impact on system transients can be studied without using time-domain simulations, which gives a better understanding of the transient behaviors and parameters involved in them. Additionally, for large scale offshore wind energy, a critical problem is how to transmit large offshore wind energy from the ocean efficiently and ecumenically. The evaluation of different offshore wind farm transmission system such as HVAC and HVDC is investigated in the last chapter

Impacts of the Inclusion of Distributed Generation on Congestion of Distribution Networks and in the Islanding Operation Capability

The growing demand for electricity in the world has led to power systems having to constantly increase their generation capacity and expand their transmission and distribution systems. Consequently, distributed generation has positioned as a technology able to integrate generation close to consumption centers, freeing up capacity in the transport systems, which can be translated into a deferral of investments in network expansion. Therefore, this paper analyzes the impact of the inclusion of distributed generation in the congestion of a typical distribution network and evaluates the potential of providing the island operation capability ancillary service in a section of the system to identify the possible challenges and benefits that the development of this technical support service could have in typical Colombian distribution networks.Universidad Tecnológica de Bolíva

Design, Implementation and Evaluation of a Microgrid in Island and Grid Connected Modes with a Fuel Cell Power Source

The ability to connect a microgrid to the grid is an important step in the development and evolution of the modern power system. The principle objectives of this research are (1) to simulate a simple microgrid consisting of a PEM hydrogen fuel cell, load and connection to the grid and (2) to evaluate the resulting microgrid control system on a corresponding experimental microgrid. The microgrid simulation demonstrated that the control algorithms can operate the microgrid in both islanded (VSC with voltage and frequency regulation) and grid connected (VSC with current control for power transfer). The experimental laboratory microgrid was constructed and operated in real-time performing its black start and managed transitions between island and grid connected modes of operation. The synchronization method adjusted the island microgrid to become in phase with the grid and tracked well under steady state and load changing conditions. The synchronization process brought the island in phase with the grid within 400 ms. Passive island detection was demonstrated with the restoration to grid operation. The grid connected voltage and current THD were under 1%

Saareketilanteet täystehokonvertterilla

A part of smart grid ideology is a new approach to islanding of power system. Smart grids and distributed generation can e.g. enable power flow upstream from distribution network and operation of distribution branch as an individual power system. These scenarios introduce new requirements for protection and control of the power system such as detection of islanding and the ability of distributed generation to maintain voltage and frequency of the power system. Full power converter is the most used way of connecting new distributed generation to power system and it enables implementation of protection functions and grid controlling abilities into distributed generation units. This thesis studies islanding of power systems and related phenomena such as safety aspects and possible benefits of islanding. Islanding detection methods presented in literature and their benefits and downsides are eviewed. Islanding and an anti-islanding method based on frequency diverging by reactive current injection are studied also from practical perspective by a miniature demonstration. Grid codes and standardization related to islanding are utilized in testing and results are studied on the grounds of stand-ardization. Results show the frequency and voltage behavior of the islanded system with different reactive – and active power balances and behavior of the grid interface inverter with and without islanding prevention functionality. On basis of these results the functionality and applicability of this islanding detection method into different environments and compatibility with different grid codes can be evaluated. Functionality of the grid inverter without anti-islanding functionality is verified and as for currently existing products the possibility and probability of unintentional islanding can be assessed