In this paper a 33kVA Active Power Filter (APF) prototype based on the synchronous d-q reference frame (SRF) control method, well-known in the motor drives industry, is presented. The proportional-integral controllers are used for the voltage and current control loops. The proposed scheme employs a pulse-width modulation (PWM) voltage-source inverter. The APF prototype has been developed in order to meet the harmonics limits imposed by the IEEE Standard 519 [1] under all supply and load conditions. The main project objectives have been to design, realize and test an active power filter. In particular, the new apparatus had to have the following features: to control the active filter in a closed loop manner so as to actively shape the source current into the sinusoid; to compensate transient and harmonic components of the load current. The performance evaluation has been done on the basis of the %THD in the load current and the compensated mains current. Experimental results have shown that the APF system meets the IEEE 519 harmonic current limits in the supply.
