An enhanced adaptive filter for orthogonal signal generation in a single-phase DQ current controller

The development of a suitable and feasible direct- quadrature (DQ) transformation theory for a single-phase current controller has always been a challenge for designers, as an additional orthogonal signal generation (OSG) block is required to generate the orthogonal component of the grid current. Several methods have been investigated in the literature that mostly exhibit poor steady-state and dynamic performance. This paper proposes a new method, which uses an enhanced-adaptive-filter algorithm and can address the limitations of existing methods. The proposed technique operates without any delay and demonstrates improved steady- state and dynamic performance. It can reduce the harmonics of the input signal as it generates orthogonal component of the grid current. Its robustness, fast response and particularly its simplicity make the proposed algorithm well-suited to working as an OSG block in the control system of a power electronic appliance (e.g., static synchronous compensator, active power filter, and unified power flow controller). The performance of the proposed algorithm is verified in a single-phase grid- connected voltage-source converter application. Stability analysis, simulation and experimental results verify the efficacy, reliability and contribution of the proposed method.