Order reduction and dynamic performance of hydropower system with surge tank for grid-connected operation

Abstract

This paper aims to study the order reduction and dynamic performance of hydropower system with surge tank (HSST) for grid-connected operation. Firstly, for the hydropower system, the basic equations are presented, and the overall transfer function is derived. Then, a novel order reduction method for high order dynamic system is proposed to study the dynamic performance. The low order equivalent systems under different-scaled power grids are obtained based on order reduction method. Finally, the dynamic performance of hydropower system is studied. The time domain formula for the dynamic response of unit frequency is derived and verified. The results indicate that the overall transfer function for the HSST for grid-connected operation is a ninth-order linear dynamic system. Dominant poles and dominant zeros are the basis of the novel order reduction method. The low order equivalent system is a fourth-order linear dynamic system, which can be analytically solved and represent the dynamic performance of original system. The time domain formulas for the dynamic response of unit frequency are reasonable and have a high precision. The power grid has an obvious effect on the dynamic performance. A larger scale grid leads to a hydropower system with better dynamic performance.