Zhe Dong

Physically-Based Power-Level Control for Modular High Temperature Gas-Cooled Reactors

Because of its strong inherent safety, the modular high temperature gas-cooled nuclear reactor (MHTGR) has been regarded as the central part of the next generation nuclear plants (NGNPs). Power-level control is one of the key techniques which provide safe, stable and efficient operation for the MHTGRs. The physically-based regulation theory is definitely a promising trend of modern control theory and provides a control design method that can suppress the unstable part of the system dynamics and remain the stable part. Usually, the control law designed by the physically-based control theory has a simple form and high performance. Stimulated by this, a novel nonlinear dynamic output feedback power-level control is established in this paper for the MHTGR based upon its own dynamic features. This newly-built control strategy guarantees the globally asymptotic stability and provides a satisfactory transient performance through properly adjusting the feedback gains. Simulation results not only verify the correctness of the theoretical results but also illustrate the high control performance.

Dissipation-Based High Gain Filter for Monitoring Nuclear Reactors

Growing electricity requirement and the serious pollution caused by burning petroleum and coal give the current rebirth of nuclear energy industry. State observation is one of the key and basic technologies of system monitoring which is very necessary to the safe and effective operation of todays nuclear reactors. Since nuclear reactors are complex and nonlinear systems, it is quite necessary to design a nonlinear state-observer with high-performance for nuclear reactors. A dissipation-based high gain filter (DHGF) is presented for nonlinear systems in this paper, and robustness analysis is also given. The DHGF is then applied to the state-observation for a nuclear heating reactor (NHR), and simulation results show the feasibility of the DHGF.

Nonlinear adaptive power-level control for the modular high temperature gas-cooled reactors

After the Fukushima nuclear accident, much more attention has to be drawn on the safety issues. The improvement of safety has already become the focus of the developing trend of the nuclear energy systems. Due to the inherent safety feature and the potential economic competitiveness, the modular high temperature gas-cooled reactor (MHTGR) has been seen as the central part of the next generation of nuclear plant (NGNP). Power-level control is one of the key techniques that guarantee the safe, stable and efficient operation for nuclear reactors. Since the MHTGR dynamics has the features of strong nonlinearity and uncertainty, in order to improve the operation performance, it is meaningful to develop the nonlinear adaptive power-level control law for the MHTGR. Based on using the natural dynamic features beneficial to system stabilization, a novel nonlinear adaptive power-level control is given for the MHTGR in this paper. It is theoretically proved that this newly-built controller does not only provide globally asymptotic closed-loop stability but is also adaptive to the system uncertainty. This control law is then applied to the power-level regulation of the pebble-bed MHTGR of the HTR-PM power plant. Numerical simulation results show the feasibility of this control law and the relationship between the performance and controller parameters.

PD Power-Level Control Design for PWRs: A Physically-Based Approach

Pressurized water reactor (PWR) is the most widely used nuclear fission reactor, and the renaissance of fission energy industry needs the safe, stable and efficient operation of PWRs. Power-level control technique which strengthens the closed-loop stability and dynamic performance is meaningful to build a strong operation strategy for PWRs. In this paper, after extending the shifted-ectropy of thermodynamic systems to that of transport systems, a proportional-differential (PD) power-level controller is proposed for PWRs based on the physically-based approach. A sufficient condition for this PD controller to provide the globally asymptotic stability of those reactor state variables is established. Numerical simulation results not only verify the correctness of the theoretic results but also illustrate the relationship between the control performance and controller parameters. The meaning of this result is giving a theoretic explanation to why the simple PD control is effective for PWR power-level regulation practically.

Saturated Output Feedback Dissipation Steam Temperature Control for the OTSG of MHTGRs

The modular high-temperature gas-cooled nuclear reactor (MHTGR) is seen as one of the best candidates for the next generation of nuclear power plants. The once through steam generator (OTSG) is a crucial element for any MHTGR power plants with steam cycle. In order to guarantee the efficient and safe operation of the power plant, the outlet steam temperature of the OTSG should be well controlled. In this paper, a saturated output feedback dissipation control (SOFDC) law is presented for regulating the outlet steam temperature of OTSGs, and the corresponding robustness analysis is also given. In the numerical study, the SOFDC is applied to the outlet steam temperature control for the OTSG of Chinese high temperature gas-cooled reactor pebble-bed module (HTR-PM) project. Numerical simulation results show not only feasibility but also good control performance of this regulator, and the influence of its parameters to the regulation performance is also discussed.

Power-Level Control of Nuclear Reactors Based on Feedback Dissipation and Backstepping

Due to the existing serious climate and environment problems caused by burning fossil fuels, nuclear energy is now under rapid development. As a crucial technology in the field of nuclear energy, power-level control for nuclear power plants is significant for not only regular operating but also safety issues. A nonlinear controller based on feedback dissipation and backstepping (FDBC) is presented in this paper. This new controller can guarantee not only globally closed-loop asymptotic stability but also robustness to the uncertainties of the control rod dynamics. Numerical simulation results show the high performance of this controller. Moreover, this newly built controller is simplified to a proportional power-level controller under the assumption of no modeling error in control rod dynamics. The characteristics of these two power-level controllers are given by theoretic analysis and numerical simulation.

Module Coordination Control of MHTGR-Based Multi-Modular Nuclear Plants

Based on the multi-modular scheme, modular high temperature gas-cooled reactor (MHTGR) can be used to build large-scale nuclear power plants with inherent safety feature at any desired power ratings. It is so clear that module coordinated control is very crucial for the safe and stable operation of multi-modular MHTGR plants, which induces the importance of the study in module coordination. Motivated by this, it is revealed in this paper that coordinated control of multiple MHTGR-based NSSS modules is essentially the flowrate-pressure regulation of a fluid flow network (FFN). A novel pressure-flowrate control with the proportional-integral (PI) form is then proposed for the FFN that couples

Model-Free Power-Level Control of MHTGRs Against Input Saturation and Dead-Zone

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Nonlinear Coordinated Control for MHTGR-Based Nuclear Steam Supply Systems

MHTGR-based NSSS modules. This control provides the input-to-state stability (ISS) of the closed-loop system. Numerical simulation results not only verify the theoretic results but also show the satisfactory control performance.

Coordination Control of SMR-Based NSSS Modules Integrated by Feedwater Distribution

The modular high temperature gas-cooled reactor (MHTGR) is an important type of small modular reactors (SMRs) with inherent safety. It is clear that power-level control is crucial in providing safe and stable operation as well as in realizing load-following function so that the MHTGRs can be grid-appropriate. However, there always exists the reactor parameter uncertainty and control input nonlinearity such as saturation and dead-zone practically, which seriously intensify the difficulty in designing power-level control. Thus, it is quite necessary to study MHTGR power-level control method against reactor parameter variation as well as control input saturation and dead-zone. Motivated by this, model-free MHTGR power-level control laws against the input saturation, dead-zone and both saturation and dead-zone are proposed in this paper, which are not only insensitive to reactor parameter but also able to compensate the control input nonlinearities. It is proved theoretically that these newly-built MHTGR power-level control laws guarantee strong closed-loop stability. Numerical simulation results illustrate the relationship between the control performance and some parameters of the controllers and input nonlinearities.