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

Abstract

Please cite the original version:Kukkola, Jarno & Hinkkanen, Marko. 2015 All material supplied via Aaltodoc is protected by copyright and other intellectual property rights, and duplication or sale of all or part of any of the repository collections is not permitted, except that material may be duplicated by you for your research use or educational purposes in electronic or print form. You must obtain permission for any other use. Electronic or print copies may not be offered, whether for sale or otherwise to anyone who is not an authorised user. Abstract-Synchronization with the power system is an essential part of control of grid-connected converters. This paper proposes a grid-voltage sensorless synchronization and control scheme for a grid-connected converter equipped with an LCL filter, measuring only the converter currents and the DC voltage. A discrete-time pole-placement design method is used to formulate an adaptive full-order observer for estimation of the angle and magnitude of the grid voltage. The analytically derived design is experimentally validated, and the results demonstrate rapid convergence of the estimated angle and magnitude.

State Observer for Grid-Voltage Sensorless Control of a Converter Equipped With an LCL Filter: Direct Discrete-Time Design

“…As revealed in (19), the real part of the estimation error i c of the converter current is strongly affected by the voltage differenceũ g . On the other hand, the imaginary part ofĩ c is strongly affected by the angle differenceθ g .…”

“…4 shows the linearized adaptation loops, when the proposed adaptation laws are used. Considering the quasisteady-state relationships G iu (1) and G iϑ (1) according to (19), two separate feedback loops are obtained. The closedloop transfer function of the linearized grid-voltage magnitude adaptation loop becomes…”

“…This work deals with grid-voltage sensorless control of a converter equipped with an LCL filter [19]. Main contributions of this paper are: 1) A direct discrete-time design method is proposed for an adaptive full-order observer enabling gridvoltage sensorless control; 2) Estimation-error dynamics of the observer are analyzed by means of small-signal linearization; 3) The proposed observer is experimentally tested as a part of a grid-voltage sensorless control system under balanced and unbalanced grid disturbances.…”