Study On Digital ATSE Based On Voltage Sag Detection Algorithm

Some important occasions such as hospital and airport are usually equipped with two-way power to ensure uninterrupted power supply. ATSE can automatically switch the power supply when the fault occurs, to ensure the reliability of power supply. Traditional ATSE based on analog circuit controlled by relay has high failure rate, less flexibility and low intelligent level when it detects voltage fault. With the more and more critical requirements of electricity customs and distribution utility in the aspect of reliability and the increasing demand of ATSE in terms of rapid action, the research for the intelligent ATSE and the algorithm of detecting voltage sag has become an important part of the study on distribution automation.Firstly, the paper focuses on studying the basic principle of several kinds of single-phase voltage sag detection algorithms, including RMS algorithm, αβ transformation derivation algorithm, derivation algorithm and wavelet transform. On this basis, the paper analyses and discusses the detection characteristic features of these algorithms, and gives the evaluation results of strengths and weaknesses. The paper then proposes a new algorithm called two-point algorithm, which is based on an equation set constructed by two voltages sampled at the adjacent time. Simulation results show that the detection velocity is fast and the detection precision is high and the algorithm is immune to the effects of sampling rate. However, the biggest disadvantage of this algorithm is that the detection precision is easily affected by harmonic, so it is only available for application with high detection speed requirement and low harmonic content. To solve this problem, the paper further puts forward a kind of algorithm based on sliding window wavelet algorithm and two-point algorithm. Simulation results show that the algorithm has detection precision and eliminates harmonic influence, and its detection time less than one power frequency period, these features satisfy the requirements for the ATSE.On the basis of above algorithm, according to the design requirements of the ATSE, the paper presents the scheme of hardware design, and designs the hardware units of the ATSE including data processing unit, auxiliary power unit, signal acquisition unit, control unit and communication unit. The paper then proposes software design scheme, the software includes micro-controller software and host computer control software. On this basis, the paper develops principle prototype.Finally, the paper gives the experimental results of the principle prototype. The results show that the principle prototype works well and the algorithm meets the demand of engineering computational precision.