A system identification method for smart distribution grid

With the development of the smart distribution grid, risk assessment, early risk warning, fault diagnosis and self-healing control have put forward a requirement of getting the precise impedance parameters of a distribution line. In order to solve the problem, a method for online virtual metrology of distribution line impedance is proposed. The paper builds the voltage drop linear equivalent computiong model by using probability theory. Then based on the collected three-phase currents and voltages data at the head and end of the line, it uses mathematical method, such as regression analysis method and the average value of solving equations method, to analyze and calculate the coefficients of the voltage drop linear equivalent calculative model. The coefficient of terminal current corresponding is the impedance of the line. The method can be used to calculate the impedance of a running distribution line. The calculation result and the actual impedance were compared and analyzed. The analysis result shows that it is feasible and effective and has the advantages of a fast calculation speed and a good real-time performance.