Characteristic model based micro-grid equivalent modeling

With the development of distributed and micro-grid technology, more and more micro-grid will connect into the power system. The dynamic simulation of distributed network should consider the affection of micro-grid. This paper proposes a micro-grid equivalent modeling method based on the characteristic model. The characteristic model can simplify the detailed model of micro-grid without missing the characteristic information under connected mode. Characteristic model is presented by a low-order time-varying difference equation and the difference equations are equal to the micro-grid dynamic characteristic. Voltage and power of the Point of Common Couple(PCC) are collected for the input and output of the characteristic model respectively. Recursive damped least square algorithm is used for the parameter estimation and the measured vector is normalized for improving the convergence of the algorithm. An micro-grid system is built for the simulation of micro-grid in DIgSILENT, and simulation results show that the dynamic equivalent based on characteristic model can well describe the dynamic characteristic of the detailed model of micro-grid, and the modeling method is validity.