State Observer for Grid-Voltage Sensorless Control of a Grid-Connected Converter Equipped With an LCL Filter

State observer for sensorless control of a grid-connected converter equipped with an LCL filter: Direct discrete-time design

“…An alternative for the proposed direct discrete-time design method is the continuous-time design method with an approximate discretization for digital implementation [11]. In comparison with the direct discrete-time design, continuoustime design is often easier and the models, e.g., system matrices, are simpler.…”

“…Then, the direct discrete-time design is preferable, e.g., in the case of current control [15]. For sensorless control of a converter equipped with the LCL filter, a continuous-time design has been presented for a model-based full-order observer in [11]. However, no analytical direct discrete-time design method has been presented for the adaptive full-order observer in this application.…”

“…Furthermore, the proposed observer is compared with the observer designed in the continuous-time domain [11]. The presented design method retains analytical connection between the physical model parameters of the LCL filter and the observer dynamics.…”

“…However, only a few grid-voltage sensorless synchronization methods have been presented in the case of the LCL filter [4]- [11]. Sensorless synchronization has been obtained using the instantaneous power theory [4] and virtual flux models [5], [6].…”

“…Adaptive observers have been used for estimation of the rotor speed, position, and flux magnitude in motor drives, e.g., in [14], and, correspondingly, for estimation of the grid-voltage frequency, angle, and magnitude in gridconnected converters [8], [10]- [13]. The estimation error of the converter current includes the information of the gridvoltage angle and amplitude [11], [12].…”