The enhancement of primary frequency regulation ability of combined water and power plant based on nuclear energy: Dynamic modelling and control strategy optimization

Abstract

The combined water and power plant based on nuclear energy (CWPN) is a potential way with significant economic and environmental benefits. To accommodate high penetration of intermittent renewable power within the power grid, it is essential to enhance the primary frequency regulation (PFR) ability of CWPN, and many factors, including the reactor operation safety, energy efficiency, and the water-power coupling mechanism of CWPN should be considered. In this study, a dynamic model of CWPN was developed, and two new strategies, the constant turbine power method (CPM) and the classic-PI-decoupling method (CDM), were proposed to enhance PFR capability. The results show that both strategies maintain the reactor power at full load during PFR, with CDM providing superior control, as evidenced by a maximum overshoot of 0.56% compared with 3.58% for CPM. Under typical step disturbances of ±1% full power (FP), ±2%FP, and ±3%FP, the PFR performance of the original and new strategies was evaluated on the basis of settling time and the apex/nadir frequency. Compared with the original strategy (OS), the maximum settling time under CDM and CPM was reduced by 3.3 s and 8.8 s, respectively. The proposed strategies demonstrated improved PFR performance, with smaller apex/nadir frequency values than those of the OS.