A fast detection algorithm suitable for mitigation of numerous power quality disturbances

In this paper, a fast detection method for voltage disturbances is explored. The proposed method provides reliable and fast detection for either single-phase or polyphase voltage disturbances such as voltage sags, voltage swells, flicker, frequency change in the utility voltage, and harmonic distortion. The algorithm is based on the theory that allows a set of three-phase voltages be represented as dc voltages in a d-q synchronous rotating frame. In this case, the utility input voltages are sensed and then converted to dc quantities in the d-q reference frame. Thus, any disturbance at the utility input voltages will be promptly reflected as disturbances in the d-q values. Further processing of the signals minimizes the point-on-wave effect and yields a trip signal indicating if the disturbance is a voltage sag or a voltage swell. Analysis, simulation, and experimental results are presented for a three-phase system. The proposed algorithm is implemented on a digital signal processor (DSP)-based system to provide ride-through for critical loads.