Reference current generation without PLL for shunt active filter under distorted and unbalanced conditions

The performances of an active power filter depends on many factors, but mainly on the selected reference generation strategy. This paper proposes a new high performances selective band pass filter (SBPF) to extract the fundamental component directly from electrical signals (voltage and current) in alpha-beta reference frame. The major advantages of the proposed SBPF are the following: 1) operating adequately in steady state and transient condition; 2) no phase delay and unity gain at the fundamental frequency; 3) suppression of the negative sequence components; 4) no PLL is required; 5) easy implementation in digital and analogue control system. In this paper the frequency and dynamic response of the SBPF are mathematically analyzed and discussed. More, we propose a modified version of the PQ theory based on SBPF to generate current references for harmonic compensation and mains current balancing. Experimental results by ldquoFPGA in the looprdquo prototyping validate the effectiveness of the proposed reference currents generation strategy in distorted and/or unbalanced conditions.