Power Level Control Research Articles

Computational effort comparison of genetic algorithm and particle swarm optimization algorithms for the proportional–integral–derivative controller tuning of a pressurized water nuclear reactor

Power level control is important in nuclear power plants, and some dynamic parameters depend on the output power. One of the popular controllers is proportional–integral–derivative (PID), that the researchers are interested in tuning its gains. In this paper, computational effort comparison of genetic algorithm (GA) and particle swarm optimization (PSO) algorithm is aimed to tune the PID gains for the typical pressurized water reactor (PWR) load-following, based on the point kinetics model with and without the parametric uncertainties. The integral of time-weighted square error (ITSE) performance index is used in the GA and PSO metaheuristic algorithms. The number of function evaluations (NFE) is used for the computational effort comparison as the novelty of this work. The results of both optimization methods show the high performance of the closed-loop metaheuristic–PID controller for the desired load-following with robustness to the parametric uncertainties. However, PSO achieves the optimal solution in less NFE.

Adaptive vibration control on electrohydraulic shaking table system with an expanded frequency range: Theory analysis and experimental study

Abstract Active vibration control using electrohydraulic shaking table (EHST) system is widely applied in civil engineering, automotive industry, environmental vibration testing and other situations where large actuating forces are needed. However, the electrohydraulic actuators (actuating systems) often suffer from drawbacks of limited frequency bandwidth, varying system parameters and so forth. In view of the limits mentioned above, this study hopes to seek out proper solutions to minimize the influence from those drawbacks. We first design a full state feedback-feedforward servo controller, which is able to extend the frequency bandwidth of EHST system, by constructing the analytical models of the servo valve and hydraulic cylinder. Numerical simulations show that the proposed servo controller is able to compensate for the attenuation-band of hydraulic cylinder and thus improve the upper frequency limit of the whole system to a degree that is higher than the natural frequency of servo valve. Afterwards, we propose a frequency domain adaptive power level control (APLC) algorithm for solving the problem of parametric variations of EHST system in application of power level control (i.e., simulate vibration based on certain power spectrum). Numerical simulations show that although APLC algorithm is not able to get exactly same spectrum and waveform at every independent trial, the power level of every trail will finally converge to the target power spectrum. Finally, an experimental validation was conducted based on an EHST system with 3 ton maximum force and 1.2 m × 1.2 m horizontal table. The results show that the proposed algorithms have greatly improved the effective bandwidth and the power level of the controlled system response can finally match the target power spectrum within an accuracy of ±3 dB.

Design an anti-windup controller for a PWR power-level control in the presence of control rod speed saturation

Control input saturation can cause severe performance degradation and possible instability in a Pressurized Water Reactor (PWR). Therefore, some form of limit protection is needed. This study proposes a dynamic compensation design problem for a PWR subject to control rod speed saturation. Design of this dynamic compensator is based on minimization of a performance index. First, a nonlinear dynamic feedback controller is designed based on feedback linearization. Then based on Parseval's theorem, the dynamic compensator is design such that the auxiliary control law is the same as that without control rod speed saturation. The proposed control approach is applied to a PWR. Simulation results show that the proposed anti-windup scheme is quite effective in presence of input saturation and it has a remarkable performance for tracking reference trajectory.

Robust tuned PID controller with PSO based on two-point kinetic model and adaptive disturbance rejection for a PWR-type reactor

Nonlinear systems such as nuclear reactor dynamics are associated with parametric uncertainties and stability conditions. These properties must be taken into account in controller design. In this paper, an effective and robust Proportional–Integral–Derivative (PID) controller is designed and tuned. Particle Swarm Optimization (PSO) is used as a metaheuristic algorithm to optimize PID gains. The PSO–PID controller is scheduled based on the power level control of a PWR-type reactor. According to Axial Offset (AO) power-distribution characteristics in the PWRs, the two-point kinetic model is used with a constant AO strategy. Lyapunov stability synthesis is intended to guarantee the stability condition of the system at various time intervals. Disturbance Rejection System (DRS) is designed based on a Lyapunov approach to avoid output disturbance. The control signal disturbance is properly removed by the designed DRS. Simulation results show output performance and robustness of the tuned PSO–PID controller against parametric uncertainties.

Optical Rogue Waves by Random Dissipative Soliton Buildup in a Fiber Laser

We report on the generation of optical rogue waves (RWs) during the process of the random dissipative soliton buildup in an ultrafast net-normal dispersion fiber laser. It is demonstrated that the random dissipative soliton buildup can be achieved under the multi-pulse regime by properly adjusting the cavity parameters, i.e., pump power level and polarization controller. The high amplitude waves accompanying with the dissipative soliton buildup process are analyzed by plotting the real-time spectral dynamics and the temporal pulse evolution, which is further confirmed as optical RWs by the statistical method. The obtained results provide a promising alternative for investigating the phenomenon of optical RW in ultrafast fiber lasers, and will be beneficial for further unveiling the physical mechanism of optical RWs.

Control of the pressurized water nuclear reactors power using optimized proportional–integral–derivative controller with particle swarm optimization algorithm

Abstract Various controllers such as proportional–integral–derivative (PID) controllers have been designed and optimized for load-following issues in nuclear reactors. To achieve high performance, gain tuning is of great importance in PID controllers. In this work, gains of a PID controller are optimized for power-level control of a typical pressurized water reactor using particle swarm optimization (PSO) algorithm. The point kinetic is used as a reactor power model. In PSO, the objective (cost) function defined by decision variables including overshoot, settling time, and stabilization time (stability condition) must be minimized (optimized). Stability condition is guaranteed by Lyapunov synthesis. The simulation results demonstrated good stability and high performance of the closed-loop PSO–PID controller to response power demand.

Multi-layer perception based model predictive control for the thermal power of nuclear superheated-steam supply systems

Nuclear superheated-steam supply systems (Su-NSSS) produces superheated steam flow for electricity generation or process heat. Although the current Su-NSSS control law can guarantee satisfactory closed-loop stability, which regulates the neutron flux, primary coolant temperature and live steam temperature by adjusting the control rod speed as well as primary and secondary flowrates, however, the control performance needs to be further optimized. Motivated by the necessity of optimizing the thermal power response, a novel multi-layer perception (MLP) based model predictive control (MPC) is proposed in this paper, which is constituted by a MLP-based prediction model and the control input designed along the direction opposite to the gradient of a given performance index. It is proved theoretically that this MLP-based MPC guarantees globally-bounded closed-loop stability. Finally, this newly-built MLP-based MPC is applied to the thermal power control of a Su-NSSS, whose implementation is given by forming a cascaded feedback control loop with the currently existing Su-NSSS power-level control in the inner loop for stabilization and with this new MPC in the outer loop for optimization. Numerical simulation results verify the correctness of theoretical result, and show the satisfactory improvement in optimizing the thermal power response.

A Scalable and Hybrid Location Estimation Algorithm for Long-Range RFID Systems

Localization of assets is a critical component of smart building applications. This problem involves a lot of challenges and gets even more challenging when a consistently high level of accuracy has to be ensured while employing long-range RFID readers. In general, these antennas are placed so that there is some level of overlap of their ranges of influence, in order to support asset tracking with high precision. However, it is desirable to reduce the level of overlap when employing multiple readers for large-scale asset tracking, due to the high cost of these RFID readers and antennas. In such scenarios, it is important to maintain accuracy while increasing the coverage area of the readers, and for this a robust localization algorithm is necessary. This paper describes a novel hybrid indoor localization algorithm that combines the transmission power level control and the signal strength information in an intelligent manner to locate assets accurately. The algorithm does not require much calibration and is easily scalable. Additionally, it allows for both coarse and fine-grained location estimation depending on application requirements. Our experiments in real indoor environments, and with different degrees of overlap between long-range RFID antennas show that our algorithm provides higher accuracy in comparison to other algorithms, and is also consistent.

Survey and Taxonomy of Transmissions Power Control Mechanisms for Wireless Body Area Networks

Wireless body area networks (WBANs) comprise several sensor nodes equipped with a short range radio-frequency transceiver, implanted and/or attached to the human body. Their low form-factor and localization imply less resources available and limited energy capabilities. Therefore, energy efficiency of WBANs is a critical issue since, in many cases, batteries cannot be replaced or recharged, requiring mechanisms to extend their life-time. The aim of transmission power control (TPC) mechanisms, which can be combined with other energy-saving mechanisms, is to reduce the energy consumption, external interferences, and specific-observation-rate in wireless communications by dynamically adjusting the transmission power output of data transmission, with the minimum effect on other performance aspects, such as reliability and latency. This paper describes and analyzes the TPCs developed as a result of a synergy created by two mechanisms, a link quality estimator and the transmission power level control. Design choices, in terms of the solutions devised to each mechanism, as well as, the strategy adopted to combine them in a TPC, are highlighted. A comparison between the newest and the most relevant research works in this area is provided as a guideline to future research. A taxonomy to classify the different TPC mechanisms developed is proposed.

Linear active disturbance rejection control for pressurized water reactor power

Since dynamic of pressurized water reactor (PWR) power is quite nonlinear, uncertain and time-varying, the reliable power-level control of PWR is necessary to guarantee high efficiency and safety of nuclear power plant. In this paper, a robust power-level regulation scheme based on linear active disturbance rejection control (LADRC) is presented for PWR. Its structure is simple and the Bandwidth-Parameterization based controller tuning is easy. First, the second order model with uncertainty is derived from a 18th order nonlinear model of PWR. And based on the derived model, two LADRC systems are designed for power control with and without model information respectively. Simulation results show the designed controllers both have satisfactory performance over the wide range of reactor operating conditions, while LADRC with model information has faster response, less overshoot, better disturbance rejection ability and robustness.

Mechanical Shim core operational strategy designed for CPR1000 nuclear power plant

The CPR1000, one of the water-cooled reactor types in China, employ MODE-G core control strategy through control rods and soluble boron to control the reactivity change during load follow operation, In spite of this, it has load follow capability for only 80% of cycle life, and also a large amount of radioactive waste liquid will be produced. In order to solve this problem, the MSHIM core control strategy was designed for CPR1000 in this paper. The MSHIM core control strategy has two independently moving RCCA groups are utilized for essentially simultaneous control of reactivity/temperature control and axial power distribution with complete boron-adjustment free load follow operation for up to more than 95% of cycle life.The prime objective of core control is to simultaneously manage core power level and power distribution to ensure the reactor operation safety. In the MSHIM core control strategy in CPR1000, reactor power control includes power level control and power distribution control. Power level control uses the reactivity balance analysis method; the objective of power distribution control is to ensure the safety related parameters, such as DNBRs and FQ within its design limit, AO control analysis method is used. According to the reactivity balance analysis method, the control rods inserted in reactor core to offset the positive reactivity during load follow operation, and in CPR1000 core, part G1-bank is lifted to supply the positive reactivity prior to load follow operation. AO analysis result shows that the axial burnup distribution can affect the AO target value, AO control ability is enhanced with the increase of R-bank worth. Changing burnup history and redesigning the RCCAs are employed.

Model-free adaptive control law for nuclear superheated-steam supply systems

Nuclear steam supply system (NSSS), which provides saturated or superheated steam to the secondary loop system for electricity or cogeneration, is central in a nuclear plant. The control of NSSS is important for the safe, stable and efficient plant operation. Nuclear superheated-steam supply system (Su-NSSS), which is equipped with an under moderated fission reactor and a once-through steam generator (OTSG) for producing superheated steam flow, is an important type of NSSS that widely applied in the nuclear plants based on the common large pressurized water reactors (PWR) and small modular reactors (SMRs) such as integral PWR (iPWR) and modular high temperature gas-cooled reactor (MHTGR). There is still very limited results for the control of Su-NSSS. Motivated by the gap between the importance and the lack of results in the field of Su-NSSS control, a model-free adaptive power-level control law is developed for Su-NSSSs with forced primary circulation in this paper. This new control law is free from physical and thermal-hydraulic parameters, is in the simple proportional-integral (PI) or proportional-differential (PD) form. To verify the feasibility of the newly-built Su-NSSS controller, it is applied to the NSSS control of a two modular high temperature gas-cooled nuclear plant with comparison to a specific MHTGR-based NSSS control law. Numerical simulation results show that this new control law can improve the transient performance of neutron flux and steam temperature in normal operation case, and can realize system resilience in some abnormal cases.

Particle Swarm Optimization-Based Direct Inverse Control for Controlling the Power Level of the Indonesian Multipurpose Reactor

A neural network-direct inverse control (NN-DIC) has been simulated to automatically control the power level of nuclear reactors. This method has been tested on an Indonesian pool type multipurpose reactor, namely, Reaktor Serba Guna-GA Siwabessy (RSG-GAS). The result confirmed that this method still cannot minimize errors and shorten the learning process time. A new method is therefore needed which will improve the performance of the DIC. The objective of this study is to develop a particle swarm optimization-based direct inverse control (PSO-DIC) to overcome the weaknesses of the NN-DIC. In the proposed PSO-DIC, the PSO algorithm is integrated into the DIC technique to train the weights of the DIC controller. This integration is able to accelerate the learning process. To improve the performance of the system identification, a backpropagation (BP) algorithm is introduced into the PSO algorithm. To show the feasibility and effectiveness of this proposed PSO-DIC technique, a case study on power level control of RSG-GAS is performed. The simulation results confirm that the PSO-DIC has better performance than NN-DIC. The new developed PSO-DIC has smaller steady-state error and less overshoot and oscillation.

Power-level regulation and simulation of nonlinear pressurized water reactor core with xenon oscillation using H-infinity loop shaping control

This investigation is to solve the power-level control issue of a nonlinear pressurized water reactor core with xenon oscillations. A nonlinear pressurized water reactor core is modeled using the lumped parameter method, and a linear model of the core is then obtained through the small perturbation linearization way. The H∞loop shapingcontrolis utilized to design a robust controller of the linearized core model.The calculated H∞loop shaping controller is applied to the nonlinear core model. The nonlinear core model and the H∞ loop shaping controller build the nonlinear core power-level H∞loop shaping control system.Finally, the nonlinear core power-level H∞loop shaping control system is simulatedconsidering two typical load processes that are a step load maneuver and a ramp load maneuver, and simulation results show that the nonlinear control system is effective.

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

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.

Adaptive output-feedback power-level control for modular high temperature gas-cooled reactors

Small modular reactors (SMRs) are beneficial in providing electricity power safely and viable for specific applications such as seawater desalination and heat production. Due to its inherent safety feature, the modular high temperature gas-cooled reactor (MHTGR) is considered as one of the best candidates for SMR-based nuclear power plants. Since its dynamics presents high nonlinearity and parameter uncertainty, it is necessary to develop adaptive power-level control, which is beneficial to safe, stable, and efficient operation of MHTGR and is easy to be implemented. In this paper, based on the physically-based control design approach, an adaptive output-feedback power-level control is proposed for MHTGRs. This control can guarantee globally bounded closed-loop stability and has a simple form. Numerical simulation results show the correctness of the theoretical analysis and satisfactory regulation performance of this control.

Automatic RF Input Power Level Control Methodology for SAR Measurement Validation

Evaluation of radiating radiofrequency fields from hand-held and body-mounted wireless communication devices to human bodies are conducted by measuring the specific absorption rate (SAR). The uncertainty of system validation and probe calibration in SAR measurement depend on the variation of RF power used for the validation and calibration. RF input power for system validation or probe calibration is controlled manually during the test process of the existing systems in the laboratories. Consequently, a long time is required to reach the stable power needed for testing that will cause less uncertainty. The standard uncertainty due to this power drift is typically 2.89%, which can be obtained by applying IEC 62209 in a normal operating condition. The principle of the Automatic Input Power Level Control System (AIPLC), which controls the equipment by a program that maintains a stable input power level, is suggested in this paper. The power drift is reduced to less than <TEX>${\pm}1.16dB$</TEX> by AIPLC, which reduces the standard uncertainty of power drift to 0.67%.

Saturated Adaptive Output-Feedback Power-Level Control for Modular High Temperature Gas-Cooled Reactors

Small modular reactors (SMRs) are those nuclear fission reactors with electrical output powers of less than 300 MWe. Due to its inherent safety features, the modular high temperature gas-cooled reactor (MHTGR) has been seen as one of the best candidates for building SMR-based nuclear plants with high safety-level and economical competitive power. Power-level control is crucial in providing grid-appropriation for all types of SMRs. Usually, there exists nonlinearity, parameter uncertainty and control input saturation in the SMR-based plant dynamics. Motivated by this, a novel saturated adaptive output-feedback power-level control of the MHTGR is proposed in this paper. This newly-built control law has the virtues of having relatively neat form, of being strong adaptive to parameter uncertainty and of being able to compensate control input saturation, which are given by constructing Lyapunov functions based upon the shifted-ectropies of neutron kinetics and reactor thermal-hydraulics, giving an online tuning algorithm for the controller parameters and proposing a control input saturation compensator respectively. It is proved theoretically that input-to-state stability (ISS) can be guaranteed for the corresponding closed-loop system. In order to verify the theoretical results, this new control strategy is then applied to the large-range power maneuvering control for the MHTGR of the HTR-PM plant. Numerical simulation results show not only the relationship between regulating performance and control input saturation bound but also the feasibility of applying this saturated adaptive control law practically.

Nonlinear power-level control design for MHTGRs by considering stepper motor dynamics

Due to its inherent nuclear safety, modular high temperature gas-cooled reactor (MHTGR) is promising in building the next generation nuclear plants which provide safe and clean power or heat supply. It is clear that power-level control technique is crucial in guaranteeing safe, stable and efficient operation of MHTGRs. Since MHTGR dynamics is complexly nonlinear, it is necessary to develop nonlinear power-level control laws. The stepper motor is a satisfactory choice for driving the control rods of MHTGRs, and has already been applied to under-construction HTR-PM plant. Since a stepper motor itself is a nonlinear dynamic system that can deeply influence power-level control performance, it is meaningful to develop nonlinear power-level control laws of MHTGRs by considering the stepper motor dynamics. Motivated by this and based upon the backstepping technique and physically-based control design approach, a novel nonlinear power-level control is proposed by regarding the MHTGR and stepper motor as an entire dynamical system. It is proved theoretically that this newly-built power-level controller can guarantee globally asymptotic closed-loop stability by generating proper motor stator voltages. Numerical simulation results show not only the feasibility of this novel control law but also the relationship between regulation performance and controller parameters.

COMPARATIVE ANALYSIS OF NATURAL GAS ENGINE PARAMETERS WITH QUALITY AND QUANTITY CONTROL

Parameters of natural gas engines were calculated with the aim to determine the optimal way of their working process organization. Analysis of calculations results demonstrated that quality power level control ensured the improvement of parameters of investigated engines. Calculations showed that compared with the diesel engine, the gas engine with quantity power level control, internal mixture formation and glow plug ignition of the gas-air mixture ensured the decrease of СО2 emissions by 26.8%, and the natural gas engine with quality power level control, external mixture formation and gas-air mixture ignition by a small pilot portion of fine atomized diesel fuel supplied by a Common Rail fuel system – by 25.5%. Therefore, one can choose one or another method of diesel engine conversion for operation on gas fuel considering available technical opportunities and with minimal expenses.