2019 Volume 8 Issue 6 Pages 884-892
An auto-tuning damper for grid-connected converters (GCs) is proposed in this paper to improve the stability of GCs when there is an increase in the penetration of renewable energy sources (RES). Increasing number of GCs are being connected to the power grid for supporting the power generation of RES systems, and this makes the equivalent output impedance of GCs becomes closer to the system impedance of the power grid. This increases the influences of the operation of GCs on the output voltage, and there is a greater risk of GCs becoming instable. In addition, system operations such as switching of transmission lines will result in larger variations in the system impedance than before in this situation. This could induce large changes in the resonance characteristics between the system and GCs. In this situation, conventional active damping control, which is designed based on the known conditions of system impedance, could have less controllability due to the changes in resonance characteristics. The harmonic resonance could become instable if the active damping control has insufficient damping effect. For this reason, an auto-tuning damper for harmonic resonance is proposed in this paper. It makes the active damping control capable of taking action in response to the changes in resonance characteristics. Therefore, it can improve the stability of operation of GCs. The operational principle, simulation, and scale-down prototype validation are presented to show the improvements achieved by the proposed solution. In addition, a problem investigated during prototype validation is explained and described.
