Title A Comparative Study of Methods for Estimating Virtual Flux at the Point of Common Coupling in Grid-Connected Voltage Source Converters with LCL Filter
External publication No
Means IEEE Trans Ind Appl
Scope Article
Nature Científica
JCR Quartile 1
SJR Quartile 1
JCR Impact 2.74300
SJR Impact 1.02000
Area International
Web https://www.scopus.com/inward/record.uri?eid=2-s2.0-85028508881&doi=10.1109%2fTIA.2017.2743200&partnerID=40&md5=ff0de9bf0fc085e28acaeb7980768dc0
Publication date 01/01/2017
ISI 000416214600068
Scopus Id 2-s2.0-85028508881
DOI 10.1109/TIA.2017.2743200
Abstract Grid synchronization based on virtual flux (VF) estimation allows for control of grid-connected power converter without depending on ac-voltage measurements. This is useful in voltage-sensor-less applications for reducing cost and complexity of the control hardware, and can be utilized in case of limited reliability or availability of voltage measurements at the intended point of synchronization to the grid. However, for voltage source converters (VSC) with LCL filters, the influence of the capacitor current must be taken into account to ensure accurate VF estimation at the point of common coupling (PCC) with the grid. This paper presents a comparative evaluation of three VF-based methods for grid synchronization of VSCs with LCL filters, with three different ways of obtaining the capacitor current. The VF estimation in the first method is based only on the measured converter currents. The second method includes capacitor voltage measurements used for estimating the capacitor currents, while the capacitor currents are measured in the third approach. Comparative results from time-domain simulations are presented, demonstrating good performance of the estimation and accurate control of the active and reactive power at the PCC with all three methods, as long as sufficiently accurate filter parameters and current measurements are available. However, the approach based on capacitor current measurements is sensitive to noise due to the high ripple current compared with the fundamental frequency current in the capacitors. The operation of a converter with VF-based grid synchronization including estimation of the capacitor current is demonstrated by experimental results, verifying the voltage sensor-less operation with LCL filter. © 1972-2012 IEEE.
Keywords Bandpass filters; Capacitors; Electric current control; Electric current measurement; Electric fault currents; Electric power system control; Estimation; Frequency estimation; Natural frequencies; Syn
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