An active damping approach for PR-based current control of grid-tied VSI with LCL filter

Abstract

The use of the Voltage Source Inverter (VSI) in Distributed Power Generation Systems (DPGS) and their connection to the utility network requires low pass filters which are typically used for grid current harmonic suppression. The first-order L-filter limits the harmonic current injection generated by the DC-AC converter, but at the expenses of high inverter switching frequency in addition to a bulky and expensive filter inductor. The L-filter may also lead to an increased loss due to a large voltage drop and to a poor dynamic response. For a better performance, the second-order LC filter can be used. The most common solution is to use the third-order LCL filter which reduces the filter size and introduces better dynamics with improved switching harmonic attenuation compared to a simple L-filter. However, this type of filter can be a source of resonance between inverter and grid if no damping method is adopted. Passive and active damping techniques are employed in order to reduce the resonance. Efficiency concerns established active damping technique as a promising solution for the resonance problem compared to the passive damping technique and thus has become of increasing interest. In this paper, the deployment of an additional control loop for active damping technique is investigated through simulation and demonstrated experimentally.