Design and Implementation of Voltage Controller for Grid-Forming Converters Based Single-Voltage Feedback Active Damping

This work deals with the design and digital implementation of voltage controller for grid-forming voltage source converters with LC output filters. Inspired by the structure diagram of the passive damping method, the virtual resistance concept based only on capacitor voltage feedback is used to actively damp the LC resonance without the need of current sensor, thus reducing the system costs. According to the closed-loop controller analysis, it is revealed that the insertion of an extra integrator with a PR controller can significantly improve stability margin and dynamic performance of the system, where only P controller is determined for system stability, which facilitates the controller parameter tuning. A method based on the root contours in the discrete z-domain is proposed to optimize the parameters of the controller. The largest distance between the poles of the close loop gain and the unit circle is achieved with the proposed method, which indicates the fastest dynamic performance under the desired stability margins. In order to evaluate the proposed control approach performance, the system is tested in laboratory setup under different loads conditions. The obtained results verify the effectiveness of the proposed design method and validate the analysis.