This part of IEC TR 62001, which is a Technical Report, provides guidance on the state-of-the art of VSC technology in relation to harmonics and predicted future developments, on the harmonic profile of present and predicted future VSC architectures and how they are characterised and modelled \u2013 as voltage sources, current sources, or otherwise. It also assesses the harmonic impedance of VSC and the possible impact on pre-existing background harmonics emanating from loads or generation units in the supply network and considers how VSC harmonics are assessed under current IEC standards and national regulations, and identify areas where improvements could be made, research can be needed, or other bodies consulted, for example when considering interharmonics. This document can be a reference source on the subject, which will also contain recommendations for use by those charged with modifying existing standards to adapt to VSC HVDC systems.<\/p>\n
Issues relating to harmonics on the DC side of the converters, including DC grids, are deliberately not covered in this document, but are addressed by a separate CIGRE Technical Brochure [1]1<\/sup>.<\/p>\n High-voltage direct current (HVDC) systems. Guidance to the specification and design evaluation of AC filters – AC side harmonics and appropriate harmonic limits for HVDC systems with voltage sourced converters (VSC)<\/b><\/p>\nPDF Catalog<\/h4>\n
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\n PDF Pages<\/th>\n PDF Title<\/th>\n<\/tr>\n \n 2<\/td>\n undefined <\/td>\n<\/tr>\n \n 4<\/td>\n CONTENTS <\/td>\n<\/tr>\n \n 10<\/td>\n FOREWORD <\/td>\n<\/tr>\n \n 12<\/td>\n INTRODUCTION <\/td>\n<\/tr>\n \n 14<\/td>\n 1 Scope
2 Normative references
3 Terms, definitions and abbreviated terms
3.1 Terms and definitions <\/td>\n<\/tr>\n\n 15<\/td>\n 3.2 Abbreviated terms <\/td>\n<\/tr>\n \n 16<\/td>\n 4 Basic aspects of VSC HVDC harmonics
4.1 General <\/td>\n<\/tr>\n\n 17<\/td>\n 4.2 Differences between VSC and LCC harmonic behaviour <\/td>\n<\/tr>\n \n 18<\/td>\n 4.3 Issues relating to VSC harmonics <\/td>\n<\/tr>\n \n 19<\/td>\n 4.4 Range of frequencies considered
Figures
Figure 1 \u2013 Frequency range of VSC waveform <\/td>\n<\/tr>\n\n 20<\/td>\n 4.5 Equivalent circuit of the converter for harmonic analysis
Figure 2 \u2013 Harmonic representation of a VSC station for harmonics analysis <\/td>\n<\/tr>\n\n 21<\/td>\n 4.6 Dual impact of a VSC converter on harmonic distortion at PCC
4.6.1 General
4.6.2 Converter generated harmonics <\/td>\n<\/tr>\n\n 22<\/td>\n 4.6.3 Pre-existing harmonics
Figure 3 \u2013 Harmonic contribution by the converter
Figure 4 \u2013 Amplification of the background harmonics <\/td>\n<\/tr>\n\n 23<\/td>\n 4.6.4 Combining the effects of converter-generated and pre-existing harmonics
Tables
Table 1 \u2013 Indicative summation exponents <\/td>\n<\/tr>\n\n 24<\/td>\n 5 Harmonic generation
5.1 General <\/td>\n<\/tr>\n\n 25<\/td>\n 5.2 Factors influencing harmonic generation
5.2.1 General
5.2.2 Converter topology <\/td>\n<\/tr>\n\n 26<\/td>\n Figure 5 \u2013 Two-level converter
Figure 6 \u2013 Three-level converter
Figure 7 \u2013 Modular multi-level converter (MMC)
Figure 8 \u2013 Cascaded two-level converter (CTL) <\/td>\n<\/tr>\n\n 27<\/td>\n 5.2.3 Control
Figure 9 \u2013 HVDC VSC converter control structure <\/td>\n<\/tr>\n\n 29<\/td>\n 5.2.4 Power electronics hardware <\/td>\n<\/tr>\n \n 30<\/td>\n Figure 10 \u2013 Interlocking example <\/td>\n<\/tr>\n \n 31<\/td>\n 5.3 Harmonic generation
5.3.1 General
5.3.2 Harmonic generation from VSC using switch type valves
Figure 11 \u2013 Semiconductor voltage drop <\/td>\n<\/tr>\n\n 32<\/td>\n Figure 12 \u2013 References and carrier for a two level converterusing PWM with pulse number of 9
Figure 13 \u2013 Reference, carrier and the resulting phase voltage for one phase of a two level converter using PWM with pulse number of 9 <\/td>\n<\/tr>\n\n 33<\/td>\n Figure 14 \u2013 Harmonic spectrum, phase to ground, of a two level converterusing PWM with pulse number of 39
Figure 15 \u2013 Harmonic spectrum, phase to ground, of a two level converter using PWM with pulse number 39 after removal of the zero sequence orders <\/td>\n<\/tr>\n\n 34<\/td>\n Figure 16 \u2013 Extended harmonic spectrum of a two level converter using PWM with pulse number 39 after removal of the zero sequence orders <\/td>\n<\/tr>\n \n 35<\/td>\n Figure 17 \u2013 Fundamental and phase voltage for one phaseof a two-level converter using OPWM
Figure 18 \u2013 Harmonic spectrum, phase to ground, of a two-level converter using OPWM <\/td>\n<\/tr>\n\n 36<\/td>\n Figure 19 \u2013 Harmonic spectrum, phase to ground, of a two level converterusing OPWM after removal of the zero sequence
Figure 20 \u2013 Extended harmonic spectrum, phase to ground, of a two-level converter using OPWM after removal of the zero sequence <\/td>\n<\/tr>\n\n 37<\/td>\n Figure 21 \u2013 References and carriers for a three level converter with pulse number of 9 <\/td>\n<\/tr>\n \n 38<\/td>\n Figure 22 \u2013 Reference, carriers and the resulting phase voltagefor one phase of a three level converter with pulse number of 9
Figure 23 \u2013 Harmonic spectrum, phase-ground, of a three level converter,pulse number of 39 <\/td>\n<\/tr>\n\n 39<\/td>\n Figure 24 \u2013 Harmonic spectrum, phase to ground, of a three level converterwith pulse number of 39 after removal of the zero sequence
Figure 25 \u2013 Extended harmonic spectrum, phase to ground, of a three level converter with pulse number of 39 after removal of the zero sequence <\/td>\n<\/tr>\n\n 40<\/td>\n 5.3.3 Harmonic generation from VSC using controllable voltage source type valves
Figure 26 \u2013 Voltage source representation of the MMC <\/td>\n<\/tr>\n\n 42<\/td>\n Figure 27 \u2013 Valve voltage generation
Figure 28 \u2013 Harmonic spectrum for one arm of the MMC converter <\/td>\n<\/tr>\n\n 43<\/td>\n Figure 29 \u2013 Harmonic spectrum for one arm of the MMC converter(extended frequency range) <\/td>\n<\/tr>\n \n 44<\/td>\n Figure 30 \u2013 Reference and carriers for three adjacent cells <\/td>\n<\/tr>\n \n 45<\/td>\n Figure 31 \u2013 Zoomed \u2013 reference and carriers for three adjacentcells and resulting voltage
Figure 32 \u2013 Reference and voltage for one arm <\/td>\n<\/tr>\n\n 46<\/td>\n 5.4 Interharmonics
Figure 33 \u2013 Harmonic spectrum for one arm of a CTL converter
Figure 34 \u2013 Harmonic spectrum for one arm of a CTL converter \u2013extended frequency range <\/td>\n<\/tr>\n\n 47<\/td>\n Figure 35 \u2013 Voltage synthesization with optimum time stepof the valve control operation <\/td>\n<\/tr>\n \n 48<\/td>\n Figure 36 \u2013 Voltage synthesization with an alternative time stepof the valve control operation
Figure 37 \u2013 Illustrative impact of sorting and selection algorithmson interharmonic generation <\/td>\n<\/tr>\n\n 49<\/td>\n 5.5 Impact of non-ideal conditions on harmonic generation <\/td>\n<\/tr>\n \n 50<\/td>\n 6 VSC HVDC as a harmonic impedance
6.1 General <\/td>\n<\/tr>\n\n 51<\/td>\n 6.2 Passive impedance
6.3 Active impedance
6.3.1 General
6.3.2 Ideal VSC behaviour
Figure 38 \u2013 Active and passive impedance elements <\/td>\n<\/tr>\n\n 52<\/td>\n 6.3.3 Impact of practical control system features
Figure 39 \u2013 Control of AC voltage or current <\/td>\n<\/tr>\n\n 53<\/td>\n 6.3.4 Example of impact of control <\/td>\n<\/tr>\n \n 54<\/td>\n 6.4 Impact on amplification of pre-existing harmonics
Figure 40 \u2013 Illustrative impact of the I-control inner control loop time response(to 5 % relative error) on the positive sequence converter impedance <\/td>\n<\/tr>\n\n 55<\/td>\n 7 Adverse effects of VSC HVDC harmonics
7.1 General <\/td>\n<\/tr>\n\n 56<\/td>\n 7.2 Telephone interference
7.2.1 General
7.2.2 Extended higher frequency range of VSC harmonics
7.2.3 Interharmonics <\/td>\n<\/tr>\n\n 57<\/td>\n 7.2.4 AC cable connecting HVDC station to the PCC
7.3 PLC, metering and ripple control
7.3.1 General <\/td>\n<\/tr>\n\n 58<\/td>\n 7.3.2 Extended higher frequency range of VSC harmonics
7.3.3 Interharmonics <\/td>\n<\/tr>\n\n 59<\/td>\n 7.4 Railway signal interference
7.5 Digital telecommunications systems <\/td>\n<\/tr>\n\n 60<\/td>\n 8 Harmonic limits
8.1 General
8.2 Deleterious effects of excessively low limits <\/td>\n<\/tr>\n\n 61<\/td>\n 8.3 Standards and practice <\/td>\n<\/tr>\n \n 62<\/td>\n 8.4 Perception of VSC in setting limits
8.5 Emission and amplification limits <\/td>\n<\/tr>\n\n 63<\/td>\n 8.6 Relevance of standards for VSC
8.7 Existing standards
Table 2 \u2013 Indicative planning levels for harmonic voltages (in percent of the fundamental voltage) in MV, HV and EHV power systems <\/td>\n<\/tr>\n\n 64<\/td>\n 8.8 Higher frequency harmonics
8.8.1 General <\/td>\n<\/tr>\n\n 65<\/td>\n 8.8.2 IEEE Std 519-2014 [7]
Table 3 \u2013 Current limits for system rated > 161 kV <\/td>\n<\/tr>\n\n 66<\/td>\n 8.8.3 Shortcomings in the context of VSC
8.9 Even order harmonic limits
8.10 Interharmonics
8.10.1 General <\/td>\n<\/tr>\n\n 67<\/td>\n 8.10.2 Treatment of interharmonics in existing standards
Table 4 \u2013 Summary of IEC TR 61000-3-6 [5] recommended voltage planning levels <\/td>\n<\/tr>\n\n 68<\/td>\n 8.10.3 Discussion and recommendations <\/td>\n<\/tr>\n \n 69<\/td>\n 8.11 Interharmonics discretization and grouping methodologies
8.11.1 Suggested method <\/td>\n<\/tr>\n\n 70<\/td>\n Figure 41 \u2013 Proposed grouping methodology
Figure 42 \u2013 Comparison with grouping methodology of IEC 61000-4-7 [3] <\/td>\n<\/tr>\n\n 71<\/td>\n Figure 43 \u2013 Centred harmonic subgroup <\/td>\n<\/tr>\n \n 72<\/td>\n 8.11.2 Power quality indices for interharmonic grouping
Figure 44 \u2013 Harmonic group <\/td>\n<\/tr>\n\n 73<\/td>\n 8.11.3 Network impedance loci for interharmonic grouping
Figure 45 \u2013 Harmonic impedance frequency ranges for LCC <\/td>\n<\/tr>\n\n 74<\/td>\n 8.12 Assessment as a harmonic voltage or current source
Figure 46 \u2013 Harmonic impedance frequency ranges for VSC with proposed methodology
Figure 47 \u2013 Harmonic impedance frequency ranges for VSCwith IEC 61000-4-7 grouping methodology <\/td>\n<\/tr>\n\n 75<\/td>\n 8.13 Assessment of THD, TIF, THFF, IT <\/td>\n<\/tr>\n \n 76<\/td>\n 8.14 Measurement and verification of harmonic compliance <\/td>\n<\/tr>\n \n 77<\/td>\n 8.15 Recommendations <\/td>\n<\/tr>\n \n 78<\/td>\n 9 Harmonic mitigation techniques
9.1 General
9.2 Passive filtering <\/td>\n<\/tr>\n\n 79<\/td>\n Figure 48 \u2013 AC filter located at primary (network) side of converter transformer
Figure 49 \u2013 AC filter located at the secondary (converter) side of converter transformer <\/td>\n<\/tr>\n\n 80<\/td>\n 9.3 Active damping and active filtering by converter control <\/td>\n<\/tr>\n \n 81<\/td>\n 9.4 Optimization between passive and active mitigation
9.5 Specific mitigation issues and techniques
9.5.1 Unbalanced phase reactances or voltages <\/td>\n<\/tr>\n\n 82<\/td>\n Figure 50 \u2013 Example of a converter station scheme with asymmetrical phase reactances
Figure 51 \u2013 Example of converter plant and control scheme <\/td>\n<\/tr>\n\n 83<\/td>\n Figure 52 \u2013 Current control scheme <\/td>\n<\/tr>\n \n 84<\/td>\n Figure 53 \u2013 Time-domain response of positive and negative sequence voltages and currents and active power when the converter does not compensate for effect of phase reactance unbalances <\/td>\n<\/tr>\n \n 85<\/td>\n 9.5.2 Power oscillations due to AC supply voltage unbalance
Figure 54 \u2013 Time-domain response of positive and negative sequence voltages and currents and the active power when the converter controls phase currents to be balanced <\/td>\n<\/tr>\n\n 86<\/td>\n Figure 55 \u2013 Power oscillations between AC and DC sides due to unbalanced AC conditions when the converter does not control the fluctuations of energy between arms and the grid currents <\/td>\n<\/tr>\n \n 87<\/td>\n 9.5.3 Harmonic cross-modulation between AC and DC sides <\/td>\n<\/tr>\n \n 88<\/td>\n Figure 56 \u2013 Influence of distortions at the AC and DC side voltagesand the propagation through the control
Figure 57 \u2013 6th harmonic content in DC side voltage of MMC <\/td>\n<\/tr>\n\n 89<\/td>\n 9.5.4 Cross-modulation of DC side fundamental frequency current
Figure 58 \u2013 Resulting AC side voltage with modification of control at t = 4 s <\/td>\n<\/tr>\n\n 90<\/td>\n 10 Modelling
10.1 Provision of models
10.2 Time and frequency domain <\/td>\n<\/tr>\n\n 91<\/td>\n 10.3 Modelling of the converter control for harmonic and resonance studies <\/td>\n<\/tr>\n \n 92<\/td>\n 10.4 Converter linearization by analytical approach
10.4.1 General
10.4.2 VSC-MMC linearized model
10.4.3 Input impedance
Figure 59 \u2013 VSC HVDC transmission system
Figure 60 \u2013 VSC station model using the small-signal approach <\/td>\n<\/tr>\n\n 93<\/td>\n 10.4.4 Advantages of analytical method
10.4.5 Drawbacks of analytical method
10.5 Deriving the converter impedance by numerical approach
10.5.1 Methodology <\/td>\n<\/tr>\n\n 94<\/td>\n Figure 61 \u2013 Model evolution in decreasing complexity
Figure 62 \u2013 Switching function model of MMC arm
Figure 63 \u2013 Time domain to frequency domain stratagem <\/td>\n<\/tr>\n\n 95<\/td>\n 10.5.2 Advantages of numerical method
Figure 64 \u2013 Example of a circuit to linearize a network and a VSC including controllers <\/td>\n<\/tr>\n\n 96<\/td>\n 10.5.3 Drawbacks of numerical method
10.6 Choice between analytical and numerical methods
10.7 Model validation <\/td>\n<\/tr>\n\n 97<\/td>\n 10.8 Network impedance modelling <\/td>\n<\/tr>\n \n 99<\/td>\n 11 Harmonic stability
11.1 General <\/td>\n<\/tr>\n\n 100<\/td>\n 11.2 Literature review
Figure 65 \u2013 Dynamic interactions between components and study framework <\/td>\n<\/tr>\n\n 101<\/td>\n 11.3 Definitions <\/td>\n<\/tr>\n \n 102<\/td>\n 11.4 Theory
11.4.1 General
11.4.2 Passive harmonic resonance
Figure 66 \u2013 RLC circuit and time-domain response to a step disturbance <\/td>\n<\/tr>\n\n 103<\/td>\n Figure 67 \u2013 Connection of the converter station to a passive network
Figure 68 \u2013 Bode plot of the converter, network and equivalent impedances <\/td>\n<\/tr>\n\n 104<\/td>\n 11.4.3 Active behaviour of converters
11.4.4 Active impedance of a VSC with a generic current control
Figure 69 \u2013 Dynamic scheme of the current controller and phase reactor <\/td>\n<\/tr>\n\n 105<\/td>\n 11.4.5 Harmonic instability
Figure 70 \u2013 Bode plot of the converter passive and active impedance <\/td>\n<\/tr>\n\n 106<\/td>\n Figure 71 \u2013 Example of a network composed of a VSC and a frequency-dependent AC system for the study of control interactions
Figure 72 \u2013 Dynamic interaction between the active VSC impedanceand the network passive impedance <\/td>\n<\/tr>\n\n 107<\/td>\n Figure 73 \u2013 Bode plot of the VSC and network impedance,including active converter effects <\/td>\n<\/tr>\n \n 108<\/td>\n 11.5 Analysis methods
11.5.1 General
11.5.2 Network impedance scans
Figure 74 \u2013 Results of EMT simulation study of the investigated system <\/td>\n<\/tr>\n\n 109<\/td>\n 11.5.3 Passivity analysis <\/td>\n<\/tr>\n \n 111<\/td>\n Figure 75 \u2013 Example output of passivity analysis <\/td>\n<\/tr>\n \n 112<\/td>\n 11.5.4 Impedance-based stability analysis
Figure 76 \u2013 Comparison of passivity analysis of converter systemwithout (blue line) and with (red line) harmonic damper <\/td>\n<\/tr>\n\n 113<\/td>\n Figure 77 \u2013 Simple network, consisting of source and load
Figure 78 \u2013 Loop gain of the simple network <\/td>\n<\/tr>\n\n 114<\/td>\n Figure 79 \u2013 Bode diagram of the frequency dependent impedanceof a converter and the grid
Table 5 \u2013 Phase margins at intersections <\/td>\n<\/tr>\n\n 115<\/td>\n Figure 80 \u2013 Small-signal representation of two interconnected AC systems <\/td>\n<\/tr>\n \n 116<\/td>\n 11.5.5 Modal analysis in rotating reference frame
Figure 81 \u2013 Sample impedance stability results <\/td>\n<\/tr>\n\n 118<\/td>\n 11.5.6 Electro-magnetic-transient simulation
Figure 82 \u2013 Sample modal analysis results <\/td>\n<\/tr>\n\n 119<\/td>\n 11.5.7 Recommendations
11.6 System-wide studies <\/td>\n<\/tr>\n\n 120<\/td>\n 11.7 Real experiences of harmonic stability in the context of HVDC systems
11.7.1 General
11.7.2 Case A: High power rating VSC HVDC system <\/td>\n<\/tr>\n\n 121<\/td>\n Figure 83 \u2013 Circuit configuration of the negative resistance test case
Figure 84 \u2013 Frequency response of Network 1 and the converter station <\/td>\n<\/tr>\n\n 122<\/td>\n 11.7.3 Case B: Offshore wind farm
Figure 85 \u2013 Phase angle from Figure 84 zoomed in the y axis
Figure 86 \u2013 AC voltage at PCC1 and zoomed extract <\/td>\n<\/tr>\n\n 123<\/td>\n Figure 87 \u2013 Schematic view of the main componentsof the case B grid connection system <\/td>\n<\/tr>\n \n 124<\/td>\n 11.7.4 Case C: Back-to-back converter in a 500 kV network
Figure 88 \u2013 Example of frequency scan at the offshore substation in case B <\/td>\n<\/tr>\n\n 125<\/td>\n Figure 89 \u2013 Illustrations of the system in case C
Figure 90 \u2013 Bode diagram of converter and grid impedances in case C and time-domain simulation with the control implemented in the EMT tool <\/td>\n<\/tr>\n\n 126<\/td>\n 12 Conclusion <\/td>\n<\/tr>\n \n 128<\/td>\n Bibliography <\/td>\n<\/tr>\n<\/table>\n","protected":false},"excerpt":{"rendered":" \n\n
\n Published By<\/td>\n Publication Date<\/td>\n Number of Pages<\/td>\n<\/tr>\n \n BSI<\/b><\/a><\/td>\n 2021<\/td>\n 136<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n","protected":false},"featured_media":381722,"template":"","meta":{"rank_math_lock_modified_date":false,"ep_exclude_from_search":false},"product_cat":[2641],"product_tag":[],"class_list":{"0":"post-381713","1":"product","2":"type-product","3":"status-publish","4":"has-post-thumbnail","6":"product_cat-bsi","8":"first","9":"instock","10":"sold-individually","11":"shipping-taxable","12":"purchasable","13":"product-type-simple"},"_links":{"self":[{"href":"https:\/\/pdfstandards.shop\/wp-json\/wp\/v2\/product\/381713","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/pdfstandards.shop\/wp-json\/wp\/v2\/product"}],"about":[{"href":"https:\/\/pdfstandards.shop\/wp-json\/wp\/v2\/types\/product"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/pdfstandards.shop\/wp-json\/wp\/v2\/media\/381722"}],"wp:attachment":[{"href":"https:\/\/pdfstandards.shop\/wp-json\/wp\/v2\/media?parent=381713"}],"wp:term":[{"taxonomy":"product_cat","embeddable":true,"href":"https:\/\/pdfstandards.shop\/wp-json\/wp\/v2\/product_cat?post=381713"},{"taxonomy":"product_tag","embeddable":true,"href":"https:\/\/pdfstandards.shop\/wp-json\/wp\/v2\/product_tag?post=381713"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}