Abstract: Abstract: With the widely uses of power electronic devices, harmonic has got more concerns in power system. Traditionally, negative impedances of synchronous generation units are widely used to describe the characteristics of synchronous machines during harmonic analysis. Recently, some practical cases call our attention to the impact of control strategies on the model of synchronous machines in power system harmonic analysis. In this paper, firstly, a synchronous model has been built based on PSCAD. The exciter, governor and power system stabilizer are integrated in our model. Then, the harmonic impedance are studied with Fourier algorithm on the basis of superposition principle. Two methods are used to calculate the impedance of different harmonic: One is current injection method, the other is voltage source method. Many cases are considered in this paper, including normal operation conditions, power system dynamic, unbalance, etc. Finally, some analysis are conducted according to the simulation results.