Flexible control of nuclear cogeneration plants for balancing intermittent renewables

Abstract

Both intermittent renewable energy (IRE) and nuclear fission energy can provide carbon-free electric power to the grid. The electric power generation from the intermittent renewable energy (IRE) sources such as the wind and solar are strongly dependent on the climatic conditions, geographical location and large land footprint. While, nuclear plants can provide consistent and clean power supply with small land footprint. Due to the strong complementarity between the IRE and nuclear, it is attractive to interconnect them to build nuclear-renewable hybrid energy systems (NRHESs) which are defined as the integrated facilities comprised of nuclear reactors, renewable energy generation and industrial processes. The flexibility of a NRHES for grid balance can be provided by actively adjusting the electric power output of nuclear cogeneration plants (NCPs), which leads to the frequent redistribution of main steam flow to the turbine and cogeneration process. For the main steam redistribution, it is necessary to guarantee the stability of grid frequency and main steam pressure, which heavily relies on the flexible control strategy of NCPs. In this paper, a new flexible control of NCPs with saturated main steam is proposed based on the idea of actively suppressing the total disturbance to the dynamics of grid frequency and main steam pressure. The stabilization problems of pressure and frequency are transferred to the disturbance attenuation Problem of a second-order disturbed dynamical system, and an active disturbance rejection control (ADRC) is then originally proposed for system stabilization. This ADRC is applied to the flexible control of a NCP composed of a nuclear heating reactor (NHR), a turbine-generator set and a multi-effect-desalination and thermal-vapor-compression (MED-TVC) process for seawater desalination. Numerical simulation results in the cases of load stepping and maneuvering show that the flexibility of this NCP is satisfactory in balancing the grid.