Influence mechanism of backlash nonlinearity on dynamic regulation stability of hydropower units

Abstract

At present, intermittent renewable energy sources, e.g. wind and solar energy, are developing rapidly in the world, and hydropower plays a key role to ensure the security and stability of power system with high-proportion renewable energy sources. Hence, the research of stability in dynamic regulation processes of hydropower system, especially the influence mechanism of nonlinearity, is of great significance. With the increase of service life of hydropower units and the aging of actuators, the influence of the backlash nonlinearity of hydropower systems is becoming more and more obvious and important. Hence, in this paper, the influence of backlash nonlinearity on the stability of islanded hydraulic turbine regulating systems is analyzed based on Nyquist stability criterion and numerical simulation, and the influence mechanism of four important hydraulic-mechanical time constants on the stability of the nonlinear system with backlash is explored. The results show that backlash could induce the limit cycle oscillation, and the stability characteristics of the system are affected by the matching law between the backlash characteristics and the governor parameters as well as the representative time constants. The results could provide theoretical support for the dynamic regulation stability of hydropower units with backlash nonlinearity.