On the Impact of High-Order Harmonic Generation in Electrical Distribution Systems

TL;DR

The paper addresses how high-order harmonics (beyond 1.5 kHz) from residential power electronics interact with feeder resonance to distort voltages and heat transformers. It integrates PSCAD/EMTdc-based load harmonic data with OpenDSS time-series harmonic analysis on a modified IEEE-34 feeder, evaluating THD, transformer eddy-current loss, and harmonic propagation. Key findings show that when harmonics align with bus resonances (notably at 1.5–2 kHz), THD and eddy losses peak, especially under a scenario with substantial 25th–29th harmonic content, and that harmonic propagation is modulated by network damping and load placement. These results underscore the importance of considering high-order harmonics in grid planning and DER integration to mitigate potential reliability and equipment-stress issues.

Abstract

The modern power grid has seen a rise in the integration of non-linear loads, presenting a significant concern for operators. These loads introduce unwanted harmonics, leading to potential issues such as overheating and improper functioning of circuit breakers. In pursuing a more sustainable grid, the adoption of electric vehicles (EVs) and photovoltaic (PV) systems in residential networks has increased. Understanding and examining the effects of high-order harmonic frequencies beyond $1.5$ kHz is crucial to understanding their impact on the operation and planning of electrical distribution systems under varying nonlinear loading conditions. This study investigates a diverse set of critical power electronic loads within a household modeled using PSCAD/EMTdc, analyzing their unique harmonic spectra. This information is utilized to run the time-series harmonic analysis program in OpenDSS on a modified IEEE 34 bus test system model. The impact of high-order harmonics is quantified using metrics that evaluate total harmonic distortion (THD), transformer harmonic-driven eddy current loss component, and propagation of harmonics from the source to the substation transformer.

Figures (16)

• Figure 1: Simulation setup as modeled in PSCAD.
• Figure 2: Current data recorded at the transformer secondary for the three scenarios
• Figure 3: Simple parallel resonant circuit with capacitor bank at the nonlinear load. This case is characterized by high voltage distortion at the load and low voltage distortion upstream.
• Figure 4: Harmonic resonance curves of five buses in the IEEE-34 Bus test system over a frequency range of 60 Hz-3 kHz.
• Figure 5: Nonlinear Harmonic Load Model used in the computation of harmonic flows. A $50/50$ percentage mix of the series and the parallel $R-L$ part of the load is used.