Performance Improvement of Grid Interfaced Three Level Diode Clamped Inverter Under Various Power Quality Events

Unpredictable power quality (PQ) events such as, balanced and unbalanced voltage sag/swell, frequency shift, phase jump and harmonic distortions in the utility grid voltage drastically affects the performance of a grid interfaced distributed generation (DG) systems due to unreliable synchronization. This paper presents adaptive synchronization based dq-current control technique for three-level NPC grid interfaced inverter DG system. An amplitude adaptive notch filter (AANF) is used for detection of utility voltage phase angle due to its adjustable accuracy and amplitude adaptability. Three phase extension of single phase AANF is developed and its performance is evaluated under aforementioned PQ events. Robust behavior of three phase AANF enhances the control performance of the interfacing inverter in injecting constant current into utility grid under aforementioned PQ events. This technique also operates interfacing inverter close to UPF mode. The efficacy of the proposed control technique in integrating the DG system to the utility grid under aforementioned PQ events is investigated through MATLAB simulation results. The laboratory experimentation is ongoing and can be presented latter.