Methods for Harmonic Analysis and Reporting in Future Grid Applications

Abstract

The rollout of advanced metering infrastructure, advanced distribution automation schemes, and integration of generation into distribution networks, along with a raising of awareness of power quality (PQ), means that there is an increase in the availability of power system monitoring data. In particular, the data for harmonics, whether it is voltage or current harmonics, is now available from a large number of sites and from a diverse range of PQ instruments. The traditional analysis and reporting of power quality examines harmonic orders to the 50th. This means that the harmonic data available for analysis are significantly larger than, for example, steady-state voltage variations where only a few parameters are examined (e.g., the voltage on each phase). Higher frequency components, sometimes called highfrequency harmonics, in the 10-250 kHz range arising primarily due to power-electronic interfaced generation are also becoming significant. Given the vast amount of harmonic data that will be captured through grid instrumentation, a significant challenge lies in developing methods of analysis and reporting that reduces the data to a form that is easily understood and clearly identifies issues but does not omit important details. This paper introduces a number of novel methods of analysis and reporting which can be used to reduce vast amounts of harmonic data for individual harmonic orders down to a small number of indices or graphical representations which can be used to describe harmonic behavior at an individual site as well as at many sites across an electricity network. The methods presented can be used to rank site performance in order for mitigation strategies. The application of each method described is investigated using real-world data.

A Virtual Tool for Load Flow Analysis in a Micro-Grid

“…To reduce the installation costs, some authors propose to use a few measurement points and to integrate them with load estimations [20][21][22][23][24][25][26][27]; however, when dealing with load estimations (or pseudo-measurements), higher uncertainty levels are generally expected and more sophisticated algorithms can be needed for the distribution system state's estimation, which also may entail higher computational costs. The integration of differently distributed measurement solutions have also been investigated, for example, considering the possibility of smart meter and power quality meter exploitation or SCADA-and PMU-enhanced integration, for a number of applications (load forecasting, optimization, demand side management, fault detection and so on) [28][29][30][31][32][33][34][35][36][37][38][39][40]. If the application of such solutions is envisaged for small distribution networks, such as those addressed in this paper, the main problems are related to the processing of algorithms' accuracy and complexity, considering the reasonable computational capabilities of the DSOs control centers.…”

Design of a Harmonic Filter for a Grid Connected Doubly Fed Induction Generator under Unsymmetrical Fault Conditions

“…Line-to-line faults are one-tenth of the total percentage of faults and lineto-line-to-ground faults are one-fourth of the total percentage of faults. These faults introduce harmonics into the whole power system [3], [4].…”

Dynamic Average Converter Model for MVDC Link Harmonic Analysis

“…Inserting new MVDC links and/or converting existing MVAC lines to MVDC operation have been considered as an emerging approach to uprate the transmission capability [5]- [7]. At present, voltage source converter (VSC) based MVDC technology is widely used in traction applications, shipboard power systems and is identified as a feasible option for offshore wind power collection systems and micro-grid applications [11]- [13]. Besides these, an MVDC system for the conversion of an existing AC line to DC operation has been considered to enhance the utilization of existing assets [4]- [6].…”

“…Distribution level harmonic studies were usually performed using simplified converter models due to the lack of data from the manufacturers [12]. However, a detailed electromagnetic transient (EMT) converter model, where the topology and control systems of the device under test is masked, is typically provided by the developer for transient studies [9]- [13]. The so called 'black-box model', can be used to analyze harmonic interactions, however, requires long simulation time to cope with the power electronic device switching transition which demands very small-time steps [12].…”