Unbalanced Network Harmonic Analysis
Unbalanced Network Harmonic Analysis
The high-demand on current power system infrastructure for EVs, distributed generation and inverter-based resource integration introduces the need for unbalanced network harmonic analysis. Single-phase charging vehicles and inverter positive and negative sequence voltage and current controls require the evaluation of harmonic content on a per-phase basis.
ETAP Unbalanced Harmonic Analysis module performs harmonic load flow and frequency scan analyses on unbalanced networks with balanced and unbalanced current/voltage harmonic sources in the network.
Compliant Harmonic Standards:
- IEEE 519-2014 and IEEE 519-2022
- IEC 61000-3-6
- ANSI/IEEE 399
- IEEE 3002.8-2018
Key Features
- Harmonic Load Flow Analysis on unbalanced networks.
- Harmonic Load Flow Analysis with single phase loads.
- Modeling balanced and unbalanced harmonic current and voltage source libraries.
- Graphical one-line display of harmonic results per phase and sequence.
- Rule books for voltage and current distortion limits based on various available standards.
- Alerts per phase for harmonic limit violations.
- Includes phase shifting transformers.
- Current-injection method.
- Total harmonic voltage, current distortion evaluation on phase & sequence networks.
- Time-domain waveform plots.
- Frequency-domain harmonic spectrum plots.
- Voltage & Current harmonic spectrum plots per phase.
- Multiple plot database comparison in single window using Plot Analyzer™ tool
- IEEE 519 defined harmonic indices.
- Skin effect models for motors transformers & branch elements.
- Short line and Long line modeling for cables and transmission lines.
Unbalanced Network Harmonic Analysis can be performed on phase and sequence networks. The module considers single phase loads and also the loads on the secondary of transformers with center tap.
This module allows modeling of unbalanced harmonic current and voltage source harmonic libraries and to use them as harmonic sources in the network harmonic analysis.
Harmonic distortion mitigation can be achieved using Active Harmonic Filter. Frequency and time domain simulations can be performed to observe harmonic mitigation.
Harmonic Frequency Scan in UBHA
The Harmonic Frequency Scan in the UBHA module calculates and plots the magnitudes and phase angles of bus driving point impedance over a user-specified frequency range for both phase and sequence networks. This study aims to identify any parallel resonance conditions, and the predicted resonant frequency is displayed in alerts and plots.Frequency Scan plots, which include self impedance and mutual impedance results, can be generated for phase and sequence networks using the plot view and plot analyzer tools.
Key Features
- Frequency Scan study on phase and sequence networks.
- Display of phase and sequence impedance results on Frequency Scan plots
- Resonance condition identification.
- User-definable harmonic frequency scan range and step.
- Slider bar for displaying bus driving point impedance magnitude and phase angle at selected frequencies.
Active Harmonic Filter
Generic and AccuSine Active harmonic filter models are available for modeling. Both frequency and time domain simulations can be performed to observe harmonic mitigation in the AccuSine filter models.
Key Features
- Generic AHF model for harmonic mitigation with harmonic order priority and target limits.
- Active Harmonic Filter models: SE PCSn and SE PCS+
- Harmonic distortion mitigation based on predefined logic for prioritizing specific harmonic orders.
- Frequency and time domain simulations.
- User-definable step and simulation time in cycles.
Videos
How Unbalanced Harmonics from EV Charging Stations Impact Supply & Distribution Equipment
The escalating demand for fleet electrification across the U.S. presents a significant challenge to existing distribution infrastructure, necessitating EV charging management strategies to meet electrical energy demands and address power quality issues. Level 2 and Level 3 EV chargers, equipped with power electronic converters and PWM technology, generate non-sinusoidal currents, exacerbating power quality concerns at individual sites. The effect of rapid voltage changes (RVC) introduced by this equipment is also discussed. This case study features insights and observations from field-recorded measurements of unbalanced (per-phase) harmonic distortions at a site with over 300 electric van charging stations. The unbalanced harmonic analysis (UBHA) conducted by Eradeh Power Consulting using ETAP Software for the site, revealed distortion limits being exceeded for individual phase currents and voltages as well as power distribution equipment rating overloads (such as transformer K-rating and cable thermal limits). The presentation also discusses how unbalanced harmonic distortions calculated within the site and at the point of common coupling (PCC) can be mitigated using techniques such as the use of active / passive harmonic filters amongst others.
Unbalanced Network Harmonic Analysis: Power System Infrastructure Challenges & Active Filter Technology
The integration of electric vehicles (EVs), PV systems, battery energy storage systems (BESS), and more has presented us with exciting opportunities and challenges. One such challenge is the need for unbalanced network harmonic analysis, especially when dealing with single-phase charging vehicles and inverter controls.
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