High Frequency Power Quality
Dr. Ing. Jos Knockaert, MSc
jos.knockaert@ugent.be
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Project: TETRA HFPQ funded by
Dec 2014 – Nov 2016
Main goals:
- How to measure?
- What are the problems?
- Propagation?
- What are the solutions?
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I. Introduction
Spectral gap
Harmonics / Power
Quality
0 Hz
50 Hz
Spectral
Gap
2kHz
EMC Conducted /
Radiated
150 kHz
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6GHz
- The gap: 2 – 9 kHz and 9 kHz – 150 kHz
- No standards: (except some advisory additions)
- No emission limits
- Immunity test is defined
- Why?
No coupling below 150 kHz
= no EMI?
No propagation in the grid
= no PQ problem?
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Reality:
“Future grid” will encounter more problems in the 2 – 150 kHz region
- Driving forces are:
• Increasing number of renewable energy sources
• Increasing demand for energy efficiency (APFC, modern
lighting)
Result: increasing number of switching power converters
Act now!
• Increasing capacitive behaviour of the loads
Result: increasing HF current due to low impedance of
loads
• “Smart” grid needs communication
Result: increasing use of communication (PLC, home
automation, wireless communication)
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II. Sources
Power line communication
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PLC
EN 50065:
PLC
Signalling on low-voltage electrical installations in the
frequency range 3 kHz – 148,5 kHz
Class 122: general
Class 134: only for industrial environment
Wideband signals: BW >= 5 kHz
Narrowband signals: BW < 5 kHz
For single phase devices:
134dBµV (Class 134)
134dBµV
A 120dBµV
Utilities
3
9
95
B
C
Users
125
D
140
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148,5
122dBµV (Class 122)
kHz
Sources: PV, AFE and Drives
Ref: J. Meyer et al., “Power quality challenges in future distribution networks,” in IEEE PES Innovative Smart Grid Technologies Europe Conference, 2011
Ref: “EMISSION LEVELS ABOVE 2 KHZ – LABORATORY RESULTS AND SURVEY MEASUREMENTS IN PUBLIC LOW VOLTAGE GRIDS “ – TU Dresden – CIRED 2013
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Compact Fluorescent Lamp
Sources: Lighting
Typical around 40 kHz
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LED Light:
Sources: Lighting
- Very divers circuits:
From simple capacitive
voltage dividers + rectifiers
… to active PFC circuits
A lot of LED’s do not comply with CISPR15
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Sources: Electronic Devices
All electronic devices:
- fed by AC
- internal DC
- supplied by SMPS
Forward converter
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Electrical vehicle chargers
Sources: Electronic Devices
Above 1 A at switching frequency
Fundamental switching frequencies from 8 kHz to 50 kHz
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Resonances are mainly due to combination of transformers
(+cables) and power factor correction capacitors
Resonances
Harmonic frequency p.u.
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III. Problems
Main sources in general:
- power conversion harmonics
- power line communication (PLC)
- resonance phenomena
Known problems in practice related to 2 – 150 kHz:
- General malfunction
- Unintentional switching
- Loss of communication
- Audible noise
SC 205A - Study Report on Electromagnetic Interference between Electrical Equipment / Systems in the Frequency Range below 150kHz (Ed.2)
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Main groups of EMI effects
- Emissions from equipment leading to disturbance or loss of MCS (mains
communication systems) communication
- Harmonics of emissions from equipment cause interference with the MCS resulting in
failed communication
- Distortion of the supply voltage due to discontinuous currents/ voltages from
equipment or signal voltages from MCS may lead to degraded performance or
maloperation of equipment
- Equipment representing a low-impedance path at frequencies used for MCS lead to an
attenuation of the intentional MCS signal which might disturb or interrupt
communication (“shunting effect”)
- Emissions from equipment or MCS signal voltages may result in higher currents, leading
to overheating and accelerated ageing of components in equipment
SC 205A - Study Report on Electromagnetic Interference between Electrical Equipment / Systems in the Frequency Range below 150kHz (Ed.2)
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Known sources:
- Inverters (e.g. in PV installations) and variable speed drives (VSD)
- Switch-mode power supplies (SMPS) (TV, DVD, UPS, …)
- Lighting equipment (CFL, LEDs)
- Household equipment (induction cookers, washing machines)
- Automated meter reading using PLC
SC 205A - Study Report on Electromagnetic Interference between Electrical Equipment / Systems in the Frequency Range below 150kHz (Ed.2)
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Known victims:
- AMR-PLC
- Solid state meters displaying wrong values
- Electronic control unintentional switching (e.g. touch-controlled equipment like
Touch Dimmer lamps (TDL), alarm systems, traffic control systems, traffic lights,
in heating systems, street lighting, in urinals, for doors, in kitchen appliances (e.g.
steam irons, coffee machines, ceramic hobs)
- Communication systems (e. g. Ethernet-system, ISDN-, ADSL-modems, IP network
branch exchange, routers, LAN)
- Telephone systems including inductive train radio systems
- Earth leakage circuit breakers (ELB)
- Contactless magnetic card readers, credit card terminals
- Notebooks (cursor position)
- TV and radio receivers
- Mobile and amateur radio
SC 205A - Study Report on Electromagnetic Interference between Electrical Equipment / Systems in the Frequency Range below 150kHz (Ed.2)
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IV. Standards
4.1 Compatibility levels
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IEC61000-2-2: Compatibility levels for low-frequency conducted
disturbances and signalling in public low-voltage power supply
systems
- 0 – 9 kHz (in extension to 148,5 kHz)
Definition:
Compatibility level (CL): the specified electromagnetic disturbance
level used as a reference level in a specified environment for coordination in the setting of emission and immunity limits
By convention, the CL is chosen so that there is only a small probability
that it will be exceeded by the actual disturbance level
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All equipment requires to have
immunity at least at that
compatibility level of disturbance.
Emission must be at any time
below CL. This means emission
limits take into account the
number of devices working
together In the same
environment.
Immunity test level = CL + margin
Emission limit = much lower
than CL for individual devices
Probability to exceed: < 5%
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Current valid version IEC61000-2-2: Ed. 2.0 (2002)
“Maintenance” of the standard is expected (TC77 / SC 77A)
Line of thougth:
- 2 – 30 kHz : High emission allowed (power electronics)
- 30 – 150 kHz: Clean area for PLC
Also ongoing work in CIGRE/CIRED/IEEE WORKING GROUP C4.24
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4.2 Immunity Basic Measurement Standard
IEC61000 – 4 - 19: Testing and measurement techniques – Test
for immunity to conducted, differential mode disturbances and
signalling in the frequency range 2 kHz to 150 kHz at AC power
ports
(Edition 1.0 _ 05-2014)
Purpose:
• To demonstrate immunity against DM disturbances
originating from Power Electronics and PLC
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Two types of test
- Continuous wave test (sweep test)
- Rectangular modulated pulses
Both for voltage and current
- Voltage : to apply to all apparatus
- Current: intended only for devices with current measuring
port (= metering)
Type of test and test levels is determined by product committees
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Test levels:
- compatilibility levels under consideration
- voltage
- also defined for current
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IEC61000 – 4 - 16: Testing and measurement techniques – Test
for immunity to conducted, common mode disturbances in the
frequency range 0 Hz to 150 kHz
(Edition 2.0 _ 12-2015)
Purpose:
• To demonstrate immunity against CM disturbances
originating from power line currents and return leakage
currents in grounding systems
• F.i. due to power converters + filters and stray
capacitances
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4.3 Emission Basic Measurement Standards
• Several standards consider 2 – 150 kHz (under consideration)
• Standards on signal leveling are available (= power quality)
• No standards for products (with exceptions)
• Test methods: lot of open questions
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- Questions:
* voltage or current?
* oscilloscope with FFT or EMI-receiver/SA?
* amplitude and/or phase?
* detector?
* bandwidth
* preconditions of the source (!)
* narrowband and/or broadband?
* continuous and/or discontinuous?
* CM and/or DM?
- Conclusion at this moment: it’s complicated
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2 – 150 kHz according to EN61000-4-30:
- informative annex
- 2 - 9 kHz: ‘4-7 can be considered’
- 9 – 150 kHz: 3 options
* CISPR16 (but PQ = in-situ)
* extend 4-7 method to 150 kHz
* alternative method (further mentioned as 4-30 method):
° 10/12 cycle
° use equal segments (e.g. 2 kHz)
° min/avg/max rms voltage
° sampling, filtering given as example
- typical accuracy: 10 mV range
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From SC205A Study Report Version 3
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4.4 Emission
Product (Family) Standards
CISPR 11: Industrial, Scientific and Medical Equipment
- only limits for induction cooking appliances
- QP (no average)
CISPR 15: Electrical lighting and similar equipment
- same limits
- only ‘provisional’
- radiated emission limits are provided
EN50065-1: Signaling on low-voltage electrical installations
- intentional emission
- range > 122 dBµV
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Technical Specification IEC TS62578 Ed. 2.0: Active infeed converter
- 2 to 9 kHz: distortion factor is defined
- 9 to 150 kHz:
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4.5. Conclusion:
Immunity measurement standard
Emission measurement standard:
- measuring apparatus
- preconditions
Compatibility levels
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V. Grid Survey
Voltage probe
PQube3
• Power quality monitoring tool
• 2 – 150 kHz option
• Measurement according to 61000-4-30
(annex C, option 3)
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Purpose of the measurements:
- What are normal levels?
- 0 – 2 kHz
- 2 kHz – 150 kHz
- 5 locations:
- house 1 & 2
- apartment
- office
- industry
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HF-harmonic: mean values (1 min-average)
Grid Survey Location 2
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Conclusion:
- grid survey of months in different environments
- several sources detected
- results are part of Tetra-project
- workshop in October 2016
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Questions?
Jos.knockaert@ugent.be
Ghent University – Campus Kortrijk
Research Group Lemcko
Graaf Karel de Goedelaan 5
8500 Kortrijk
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