Dynamic Optimization of a Subcritical Steam Power Plant Under Time-Varying Power Load

Abstract

The increasing variability in power plant load in response to a wildly uncertain electricity market and the need to to mitigate CO2 emissions, lead power plant operators to explore advanced options for efficiency optimization. Model-based, system-scale dynamic simulation and optimization are useful tools in this effort and are the subjects of the work presented here. In prior work, a dynamic model validated against steady-state data from a 605 MW subcritical power plant was presented. This power plant model was used as a test-bed for dynamic simulations, in which the coal load was regulated to satisfy a varying power demand. Plant-level control regulated the plant load to match an anticipated trajectory of the power demand. The efficiency of the power plant’s operation at varying loads was optimized through a supervisory control architecture that performs set point optimization on the regulatory controllers. Dynamic optimization problems were formulated to search for optimal time-varying input trajectories that satisfy operability and safety constraints during the transition between plant states. An improvement in time-averaged efficiency of up to 1.8% points was shown to be feasible with corresponding savings in coal consumption of 184.8 tons/day and a carbon footprint decrease of 0.035 kg/kWh.

Review of Process Modeling of Solid-Fuel Thermal Power Plants for Flexible and Off-Design Operation

“…The model was equipped with fuel mass flow-rate characteristics to simulate rapid load changes, boiler equipment failures, and different sliding curves (Figure 6). On the same lines, a dynamic plant operation optimization control system was simulated in [71]. A coal-fired subcritical power plant was modeled in the Modelica ® /Dymola language and Modelon ThermalPower library.…”

Dynamic modeling for assessment of steam cycle operation in waste-fired combined heat and power plants

“…The dynamic CHP plant model is constructed in the commercial software Dymola [36], which is based on the modeling language Modelica [37], using the component library ThermalPower from Modelon [38], which has been used to model power plants in a number of previous studies [18,19,22,[24][25][26]. The components are modeled based on differential and/or algebraic mass and energy balance equations.…”

“…Chen et al [18] developed a dynamic model and studied the implementation of a regulatory control structure in a 605 MW coal-fired plant, followed up by development of dynamic supervisory control schemes for plant efficiency optimization [19]. Coal-fired plant responses to step and ramp changes in load were analyzed by Oko and Wang [20].…”

Dynamic modeling, simulation and optimization of a subcritical steam power plant. Part I: Plant model and regulatory control

“…In the plant description by Singer [40], only the open-loop configuration is presented (for design analyses). Therefore, common power plant control configurations [43,44] were used in this work, which enabled the study of the closed-loop performance of the plant, as well as the analysis of benefits of supervisory control (based on set-point optimization) presented in Part II of this work [45]. Basic control logic to serve the requirements for dynamic per- Figure 4.…”

“…In summary, the model responses to step changes in the coal load illustrate the robustness of the controllers, and the value of the dynamic model of the power plant in tuning the controllers to maintain the regulated variables at set point, even for sudden (and somewhat unrealistic) changes in coal load. This power plant model, validated quantitatively at steady state and qualitatively in terms of closed-loop dynamic performance, can be used as a robust test bed for dynamic simulation and optimization of power plants, which is the focus of Part II of this series[45]. Response of the power plant model with control design to -5%, -10% and -15% step changes in coal load, in terms of (a) T SH , (b) the liquid level of the Drum, (c) the liquid level of the condenser, (d) the liquid level of the deaerator and (e) power generation.…”