Research On Oscillating Characteristics Of Parameter Coupling For Hydraulic Generating Unit

The efficiency, cavitation and stability of the hydraulic generating units is important indexes to measure the function of the unit. Efficiency is related to utilization of hydraulic unit; Cavitation is related to the life of unit; stability is related to the unit whether to operate safely, vibration is one of the important indexes of measuring unit stability, Researching the coupling and oscillation characteristic of unit parameters provides the basis for controlling design and it is also one of the effective ways to ameliorate the system stability of operation. The main work of this paper is following:(1)In order to extract the hydraulic generator oscillation characteristics of main parameters(turbine output, flow, head, generator active power, power angle, angular velocity) from oscillator signal, this paper uses the nonlinear model of hydraulic turbine, and the hydraulic system adopts the elastic water hammer nonlinear differential equation model; turbine model uses the turbine model proposed by IEEE Working Group; the generator adopts single-machine infinite three-class model; the control system model adopts the typical parallel PID governor and PI excitation controller. These sub-models form a complete hydraulic generating set nonlinear system model.(2)The extraction methods of oscillation characteristics. Through comparing and analyzing the matrix pencil algorithm and prony algorithm, the matrix pencil algorithm is selected as the extraction method in this paper.(3)Under various disturbance, based on the established nonlinear model of hydraulic generator set to the main parameters of the one carry on simulation calculation. Applying matrix algorithm extracts oscillation modal information of main parameters of hydraulic generator sets and establishes mathematic model.(4)The disturbance type of the research includes1).when hydraulic generator set carry on the active regulation, the influence of initial operating point, positive disturbance, negative disturbance on amplitude, frequency, damping factor are analyzed.2).when the grid-side has short circuit fault, influence of initial operating point, clearing time, the removal of impedance strength on amplitude frequency, attenuation factor are analyzed.3).When the grid side occurs low frequency oscillation, influence of initial operating point, disturbance frequency, disturbance amplitude on amplitude, frequency, attenuation factor are analyzed.(5)Exploring the coupling relationship among oscillation modes information of the parameters as well as the motion model whether to change affected by each factors.The simulation results show:①When hydraulic generating units subject to various disturbances, the application of matrix pencil algorithm to extract oscillation modes information of the ones main parameters are effective and intuitive.②When hydraulic generating unit subject to various disturbances, the motion model of each parameter established won’t change because of affecting factors and that is further illustrated with versatility and value, the motion model of the electrical parameters in the form is consistent; the motion model of the hydraulic parameters in the form is also consistent, however, the motion model of the electrical parameters and hydraulic parameters is not all the same in their forms.③When hydraulic generating unit subject to various disturbances, amplitude, frequency, attenuator of parameters with each variation influencing factor are analyzed.④When hydraulic generating unit subject to various disturbances, the coupling relationships among the electrical parameters, among the hydraulic parameter, between the electrical parameters and the hydraulic parameters. Those above all-mentioned conclusion can provide theoretical basis for controlling design.