Robust sensorless control of grid connected converters with LCL line filters using frequency adaptive observers as AC voltage estimators

State Observer for Grid-Voltage Sensorless Control of a Converter Under Unbalanced Conditions

“…Then,ω g+ drives the estimateθ g+ to the correct value. However, the naturally filtered frequency estimateω gf (green dashed line) given by (20) is free of impulses. During the frequency steps, the estimateω g+ converges rapidly whereas the estimateω gf converges slower but it is noise-free.…”

“…Grid-voltage sensorless methods for converters equipped with the LCL filter have been proposed in [5], [8]- [10], [13]- [20]. The sensorless operation can be based on instantaneous power theory [10], virtual This work was supported in part by ABB Oy, in part by Finnish Foundation for Technology Promotion, in part by Emil Aaltonen Foundation, and in part by Walter Ahlström Foundation.…”

“…Grid-voltage sensorless control has been an interesting research topic during the last decades [1]- [20]. Replacing ACvoltage sensors with estimation is a relevant option, e.g., in pulse-width-modulated rectifiers [1]- [6], since reducing the number of the sensors can improve the reliability against electrical noise and reduce costs of the system.…”

“…Kukkola is with ABB Drives, Helsinki, Finland (e-mail: jarno.kukkola@fi.abb.com) M. Hinkkanen is with Aalto University, Department of Electrical Engineering and Automation, Espoo, Finland (e-mail: marko.hinkkanen@aalto.fi). flux models, [5], [14]- [16], and model-based observers [8], [13], [17]- [20]. However, only a few of these methods take unbalanced grid conditions into account [9], [13]- [15], [19].…”