Control of a voltage-source converter connected to the grid through an LCL-filter-application to active filtering

In this paper, a control principle for a voltage source converter connected to the grid through an LCL-filter is presented. The dynamic performance is compared with the performance obtained with an L-filter and a dead-beat vector control system. Measured frequency responses and an active filtering operation verify the control principle. By using an LCL-filter, high attenuation of harmonics caused by the PWM and high dynamic performance can be obtained simultaneously. Different methods for active filtering are compared. It is advantageous to use a Fourier-method since it allows for compensation for time delays occurring in the control system in the frequency domain. By using the LCL-filter along with compensation for time delays in the frequency domain, active filtering can be performed at moderate switching frequencies. This is a major advantage in systems, such as a rectifier with an active filtering option.