Development of an IEC 61850 based power quality monitoring device

Abstract

The term “Smart Grid” holds varying definitions in the increasingly digitised technological landscape of energy generation, distribution, control and monitoring. Three defining characteristics of the “Smart Grid” that are common among existing definitions are the following: 1) The integration of Information and Communications Technology (ICT) to improve grid reliability, efficiency and situational awareness. 2) To utilise advanced metering infrastructure (AMI) for bidirectional communications with customer meters and encourage customer participation. 3) To enhance the control, monitoring and optimisation of distributed energy resources (DERs) and bidirectional power flow in an increasingly decentralised electric power grid. The decentralisation of generation plants mainly stems from the adoption of Small-scale Embedded Generators (SSEG), or Distributed Energy Resources (DERs) as they are more commonly known. DERs pose a unique challenge to Network Operators within the “Smart Grid” and may potentially jeopardise grid reliability. The use of power electronic converters coupled with the often-bidirectional nature of DERs power flow, along with the inconsistent and intermittent generation characteristics of renewable energy offer unique challenges in maintaining and monitoring power quality. Due to recent regulatory changes and the increasingly constrained ESKOM generation infrastructure; South African municipalities have seen the benefit of employing more renewable energy and encourage customer participation to lessen the strain and improve grid reliability. The increasing number of small-scale generation plants in South Africa would, in future, require a solution that is interoperable with existing substation automation hardware and communications infrastructure, but also cost-effective. This research project presents a methodology for designing, modelling and implementing an IEC 61850-based power quality monitoring embedded systems device. Primarily aimed at systems with a large number of low-voltage Small-scale Embedded Generation plants; the goal is to achieve a balance between cost-effectiveness and power quality monitoring standards compliant performance, while crucially maintaining full interoperability with existing grid infrastructure. The thesis deliverables provide a novel proof of concept for a power quality monitoring device that may be deployed and modified depending on the use case and specific application. The following research contributions are identified: 1) Modelling and implementation of a viable, interoperable and low-cost IEC 61850- based power quality monitoring device using off-the-shelf components and an open-source software library. The implementation of this device provides a platform that is easily modifiable for use in a range of applications. 2) The method of modelling IEC 61850 logical nodes and functions to analogue frontend measurement registers presented in this research demonstrates how to design and map information to equivalent logical nodes. The knowledge demonstrated shows how device modelling techniques can be used to extract additional information for mapping to existing logical nodes or to develop new ones. The thesis findings and deliverables result in a low-cost IEC 61850-based power quality monitoring device. The device may additionally be used for general utility-scale monitoring of DER plants, check metering, IEC 61850-based power quality mitigation algorithms and short-term power quality studies. It may also function as a low-cost entry point to IEC 61850-based communications in smaller municipalities, and additionally as a lab test and prototyping tool for technicians and engineers. The research work may also contribute to educating university student on topics such as Linux operating systems, networking, embedded systems, substation automation and the IEC 61850 standard. It may also find use as a prototyping platform for new logical nodes. The device proposed in this research project has the potential to act as an enabling technology for the adoption of DERs due to lowering the barriers of entry in terms of cost and functionality.