A fast current control technique for active filters with low switching frequency

A dead-beat current control algorithm for a high power active filter is presented. The filter is based on a three-level voltage source inverter operating with carrier PWM. For a harmonic free measurement the VSI current would normally be sampled synchronously with the tips of the triangular carrier. Here, the current sampling is shifted in order to minimize delays in the control loop. It is shown that the VSI generated harmonics can be calculated and subtracted from the current measurement. For the asynchronous sampling a dead-beat control function is derived. The control technique has been verified by simulations and with an experimental setup of a flicker compensator