Law Of Steady State Parameters Of Synchronous Generator Changing With Operating Conditions When Considering The Nonlinearity

The mathematical model and parameters of synchronous generator are very important to the operation and analysis of power system. In this paper,300MW turbo-generator as the research object, the analytical method and the finite element method for five kinds of operation characteristics of generator are studied, and the change law of saturation reactance with operating conditions is revealed. Finally, the mathematical model of generator variable parameters is obtained.The main research content of this paper is as follows:1) Established the finite element model of the steady state operation of 300MW turbo generator. Developed a series of the finite element method and the analytical method MATLAB programs for operation characteristics. By comparison, the calculation results of two methods are almost the same when the saturation is not considered. When the saturation is considered, the calculation results are still different from that of the finite element method, even if the analytical method used the saturated reactance.2) Proposed an approximate analytical method for the angle characteristics to solve power angle by the active power. Prepared to traditional analytical method, the approximate analytical method is applicable to turbine generator in normal operating range and hydro generator as the power angle less than 50°. Put forward a precise finite element calculation method of V-curve, and compared with the analytic method, the result is closer to the measured value. Then apply it to limit current calculation of the safe operating limit.3) Revealed the two dimensional variation laws of saturated reactance under different operating characteristics and three dimensional rules with different electrical parameters. Under the condition of given stator voltage and power factor, the saturated reactance decreases with the increase of the stator current. Generator operating under rated voltage, saturated reactance increases and then decreases with the increase of active power and reactive power.4) Using the least square method, the reactance is expressed as the two degree polynomial of active power and reactive power. Presented a mathematical model of generator variable parameters, which is suitable for system analysis, and combined it with the analytic method of V- curve. By comparing the filed current and the power angle calculated by finite element method, analytical method and variable parameter model, the accuracy of the variable parameter mathematical model is verified.