Power Level Control Research Articles

Pressurized Water reactor power level control: A nonlinear generalized predictive control with extended Kalman filter method

Reactor power level control is an effective way to achieve load tracking of Pressurized Water Reactor (PWR) in a nuclear power station. A novel Nonlinear Generalized Predictive Control with Extended Kalman Filter (NGPC + EKF) is proposed to solve the problem that discrete predictive model mismatch in noisy environment. In this paper, an NGPC controller is developed to realize the reactor load tracking, and an EKF is used to estimate reactor states and suppress noise. Finally, the control methods of PID, MPC, NGPC and NGPC + EKF are compared by two simulation experiments, load tracking experiment and step response experiment. The load tracking experiment results show that NGPC + EKF method obtains better noise suppression ability and tracking effect. In the step response experiment, the proposed NGPC + EKF scheme is also proved to have better step response performance than others.

Analyzing the Automatic Power Level Control Effect of a Signal Generator in RF Power Sensor Calibration by a Direct Comparison Transfer Method and a Millimeter Wave Application.

Most calibration laboratories prefer the Direct Comparison Transfer Method (DCTM) for a reliable and accurate calibration of power sensors in the radio frequency (RF) scope. Most studies suggest using this calibration method, with its automatic power level control (APLC) of RF signal generators. The APLC is preferred to keep the output power level of the signal generator the same, while the power sensor is calibrated and the reference power sensor is connected to the measurement system. The known APLC mechanisms are also explained for the DCTM, and a comparison of the calibration factor values carried out with and without the automatic power level control process in the DCTM is also given in this study. RF power sensor calibrations with coaxial and waveguide connector types are examined with DCTM in this study as well. This study shows that the DCTM, unless with APLC, should be applied for the waveguide power sensor's calibration at millimeter wave frequencies.

Control of small pressurized water reactors under single-loop operation based on MFAPC theory

Small pressurized water reactors can supply power to ships, and single-loop operation is adopted to improve maneuverability under some abnormal conditions. Large key parameter fluctuations and the potential risk of human errors occur in conventional single-loop operation. Therefore, an automatic rapid power reduction method is proposed to improve the control performance of single-loop operation. An automatic rapid power-reduction method based on conventional control systems was tested. Poor power control performance and large fluctuations in steam generator water level were observed. Reactor power and steam generator water level control systems improved by the model-free adaptive predictive control (MFAPC) theory were developed, and the parameters of the MFAPC controller were optimized by the differential evolution method. The simulation results under single-loop operation show that the improved control systems reduce the overshoot of the reactor power and effectively suppress the water level fluctuation of the steam generator.

Power Level Control of Nuclear Power Plants During Load Following Operation Using Fractional Order Controller Based on a Modified Algorithm

Power Level Control of Nuclear Power Plants During Load Following Operation Using Fractional Order Controller Based on a Modified Algorithm

Energy efficient two-stage capacity allocation scheme for WBAN healthcare applications

Co-channel interference occurs in coexisting Wireless Body Area Networks (WBANs) and has an impact on the capacity allocation of the networks. The proposed Two Stage Capacity Allocation (TSCA) mitigates interference and maximizes the capacity of poor channel quality WBANs with high priority data. It uses traditional interference mitigation schemes such as transmission power level control, channel switching and relay-aided transmission in each instant of pause time. The proposed work introduces a metric called Emergency Residual Index (ER-Index) and chooses any one of the mitigation schemes. The ER Index value provides a trade-off between residual energy, emergency factor and channel metrics. Further, TSCA executes a two-stage capacity allocation method. The TSCA scheme is a combination of the Nash bargaining solution and the Min-Max algorithm. The mitigated interference is 45% compared to Dynamic link quality-based Sub Channel Allocation (DSCA) and 60% compared to Traffic Aware Medium Access Control (TA-MAC). The average energy consumption is decreased up to 37.82% compared to TA-MAC and 25.59% compared to the DSCA algorithm.

Resonant AC-AC Converter With Multi-Power Level Controller for Inductive EV Charging Systems

Design of Inductive Power Transfer (IPT) controller to tune EV charging level in a wide range is of great importance. The IPT power level controller is proposed to regulate the power transfer rate by modulating the active state and zero state counts of the converter. During active states, energy injection is applied to the IPT compensation tank which increases the IPT resonant current; during the zero state; no injection occurs, and the resonant current of IPT tank is in free oscillation. The FPGA-based IPT power controller is designed to be applied on single stage AC-AC matrix converter which allows direct connection to the main grid without any need of DC conversion; the controller is also operational in dual-stage AC-DC-AC topologies. The proposed IPT power controller is self-tuned without any need to wireless communication channel and offers more simplicity, higher speed, ease of implementation and lower cost. The efficiency up to 90.73% is achieved for the proposed IPT controller thanks to soft-switching (ZCS and ZVS). Finally, ModelSim-Quartus simulation results as well as experimental validation results are provided.

Passivity-Based Power-Level Control of Nuclear Reactors

Nonlinear power-level control of nuclear reactors can guarantee wide-range closed-loop stability that is positive for plant load-following capability. Nuclear reactor power dynamics are the tight interconnection of both neutron kinetics and thermal hydraulics, which determines that the corresponding control design model is a complex nonlinear system with large uncertainty. Although nuclear reactor dynamics are complex, it is meaningful to develop simple but effective power-level control methods for easy practical implementation and commissioning. In this paper, a passivity-based control (PBC) is proposed for nuclear reactor power-level dynamics, which has a simple form and relies on the measurement of both neutron flux and average primary coolant temperature. By constructing the Lyapunov function based on the shifted ectropies of neutron kinetics and reactor core thermal hydraulics, the sufficient condition for globally asymptotic closed-loop stability is further given. Finally, this PBC is applied to the power-level control of a nuclear heating reactor, and simulation results show the feasibility and satisfactory performance.

Output power control of nuclear reactor using ant lion optimization-based controller

Power level control is a <span>critical issue in nuclear power stations due to its nonlinear dynamics. One of the most commonly used controllers is fractional order proportional–integral–derivative (FOPID). The FOPID is an enhanced and modern controlling system that has two additional added parameters. In this paper, comparison between particle swarm, gray wolf and ant lion optimization techniques is performed to determine the FOPID controller parameters. The nuclear reactor is a pressurized water reactor which is a fifth order nonlinear reactor model and is simulated using MATLAB software based on the point kinetic model. The integral square error (ISE) performance index is used to evaluate the performance of the three optimization techniques. The simulation results show that ant lion optimization for tuning the FOPID controller parameters gives the best performance and integral square error index better than the two other optimization techniques.</span>

Port-Hamiltonian Control of Nuclear Reactors

The port-Hamiltonian form (PHF) of nuclear reactor dynamics is first given with the corresponding Hamiltonian function determined by the shifted-ectropies of neutron kinetics and reactor thermal-hydraulics. Then, a passivity-based control (PBC) is proposed by adding extra damping injections to the PHF, and it is shown by theoretical analysis that satisfactory closed-loop stability can be guaranteed. The newly designed control law is applied to a nuclear heating reactor, and the simulation results not only verify the theoretical analysis but also show the satisfactory reactor power-level control performance.

Nuclear Reactor Power Level Model Predictive Control: A Consideration of Coolant Outlet Temperature Relaxation Tracking Method

Nuclear reactor core power level control and the average coolant temperature usually adopt independent control strategies, but tracking only one single core power makes the coolant temperature control risky in a disturbance situation. To solve this problem, a reference trajectory calculation based on the coolant outlet temperature under the steady state of the reactor power is designed; then, a model predictive controller with a dual objective optimization function, which also includes a relaxation factor, is constructed. By setting the tracking weight matrix in the controller, the tendency setting of dual target trajectory tracking can be realized. Simulation experiments verify the effectiveness of core power level control considering the coolant outlet temperature trajectory tracking. Furthermore, the tracking effect of different weight matrices is simulated and analyzed. The results show that the developed control strategy is more flexible than a single control scheme.

Optimized fractional-order PID controller based on nonlinear point kinetic model for VVER-1000 reactor

Abstract Nuclear reactor dynamics are nonlinear and time-varying, so the power level control is a challenging problem in nuclear power plants (NPPs) to ensure both its operation stability and efficiency. An important measure to improve the safety of the reactor core of NPP is the implementation of robust control for the core by adjusting the inserted reactivity of the control rods. Thus in the present paper, fractional-order PID (FOPID) controller is developed as it is well known for its simplicity and robustness against disturbances. A Genetic Algorithm (GA) is used to determine FOPID controller parameters to achieve the desired power level for the generation III+ reactor VVER-1000. Implementing the GA, a suitable objective function is proposed to search for the optimal FOPID parameters. The nonlinear model of the VVER-1000 nuclear reactor is presented based on the point kinetic equations with six delayed neutron groups and temperature feedback from lumped fuel and coolant temperatures. Two cases for the VVER-1000 reactor are investigated; the changes in the power loads and the control rod withdrawal that leads to reactivity disturbance. Moreover, the uncertainties that result from model parameters perturbation are added to examine the controller robustness. The simulation results show that the proposed optimized FOPID controller can track the desired power level of the VVER-1000 reactor and robustly cope with any load changes, disturbances, or any parameters uncertainties. Also, it proves the superiority of the proposed optimized FOPID controller over other PID controllers in ensuring the safe and effective operation of the VVER-1000 reactor.

Online learning based neural network adaptive controller for efficient power tracking of PWR type reactor with unknown internal dynamics

An online learning neural network (NN) based adaptive scheme has been proposed for tracking the power level of higher order point kinetic pressurized water reactor (PWR) with unknown dynamics under local and global load following conditions and emergency conditions. The PWR type of nuclear reactors are linear parameter varying (LPV) systems whose parameters vary with power, ageing effects and changes in nuclear core reactivity with fuel burn up. The drastic changes in plant parameters should be accommodated in a reactor control system through on-line identification to ensures safe operation for the power plant which demands for adaptive control system. To track the demand changes which happens during the load following and emergency conditions considered, the PID controller parameters needs to be varied. However, the proposed NN controller is based on feedback linearisation of nonlinear discrete time system with unknown internal dynamics by using a multilayer neural network acting as function approximator. Online weight tuning algorithm based on a modified delta rule and projection algorithm are used for the update of the weights of the proposed neural network controller along with conventional PID controller. Simulation studies with the proposed controller on a non linear PWR core shows that the proposed algorithm exhibits improved performance in terms of lesser ISE/ IAE/ ITAE over using PID controller under load following conditions. This new proposed power level controller has self learning capability and it needs the measurement of all the state variables and the desired trajectory.

Adaptive second-order nonsingular terminal sliding mode power-level control for nuclear power plants

This paper focuses on the power-level control of nuclear power plants (NPPs) in the presence of lumped disturbances. An adaptive second-order nonsingular terminal sliding mode control (ASONTSMC) scheme is proposed by resorting to the second-order nonsingular terminal sliding mode. The pre-existing mathematical model of the nuclear reactor system is firstly described based on point-reactor kinetics equations with six delayed neutron groups. Then, a second-order sliding mode control approach is proposed by integrating a proportional-derivative sliding mode (PDSM) manifold with a nonsingular terminal sliding mode (NTSM) manifold. An adaptive mechanism is designed to estimate the unknown upper bound of a lumped uncertain term that is composed of lumped disturbances and system states real-timely. The estimated values are then added to the controller, resulting in the control system capable of compensating the adverse effects of the lumped disturbances efficiently. Since the sign function is contained in the first time derivative of the real control law, the continuous input signal is obtained after integration so that the chattering effects of the conventional sliding mode control are suppressed. The robust stability of the overall control system is demonstrated through Lyapunov stability theory. Finally, the proposed control scheme is validated through simulations and comparisons with a proportional-integral-derivative (PID) controller, a super twisting sliding mode controller (STSMC), and a disturbance observer-based adaptive sliding mode controller (DO-ASMC).

Research on non-uniform control rod system of PWR

In order to improve the axial power distribution control performance of PWR power control system and simplify the control strategy, three non-uniform power control rod systems based on the novel non-uniform power control rod and their decoupling mode control strategy (mode D) are proposed. The types A, B, and AB non-uniform control rod systems of Qinshan nuclear power plant in China are established by MCNP5. These three non-uniform power control rod systems adopt mode D to control the core power. The radial and axial neutron flux densities of three non-uniform control rod systems at four rod positions are separately calculated. The simulation results show that types A, B, and AB non-uniform control systems adopting the mode D have good power level control performance, and type AB non-uniform control system has the best axial distribution performance. Compared with the other four control strategies, the mode D is simpler.

Research on non-uniform control rod for PWR

The axial power distribution of the core has a great influence on the operation of PWR. The uneven distribution of the axial power even endangers the safety and economy of the whole nuclear reactor. Due to the coupling of neutron leakage, core power level control and axial power deviation control, it is difficult to obtain satisfactory control performance. In order to improve the axial power distribution in the core, a non-uniform control rod is defined based on the decoupling control idea. By taking advantage of the self-shielding effect and the staggered distribution of neutron and non-neutron absorbers, a single non-uniform control rod can achieve the function of power level and distribution control. A core model is built by MCNP5, and the uniform control rod is replaced by non-uniform control rod of N = 2 and 4 (N is the nonuniformity coefficient of non-uniform control), then the axial neutron flux density distributions at different rod positions are calculated and compared. The simulation results show the non-uniform control rod studied in this paper hardly affect the original axial power distribution when controlling the core power level. In other words, the power level and deviation controls are completely decoupled using non-uniform control rod. Although the reactivity introduced by non-uniform control rod is smaller than that of uniform control rod, it is more uniform. So the research of this paper can provide a direction for the new control rod.

Power Level Control of Nuclear Power Plant Based on Asymptotical State Observer under Neutron Sensor Fault

Power level control is one of the critical functions in the instrument and control system of nuclear power plants (NPPs). In most power level control systems of NPPs, the power level or average neutron flux in reactor cores provided by out-of-core neutron sensors are usually measured as feedback of power control systems, while, as critical measuring devices, there is a risk of damage to out-of-core neutron sensors. For improving the operation reliability of NPPs under the neutron sensors’ failure, a power control system based on power observer is developed in this work. The simulation based on NPP simulator shows the power control system based on the observer is effective when neutron sensors fail.

An Efficient Testing Scheme for Power-Balanceability of Power System Including Controllable and Fluctuating Power Devices

Renewable power sources are environmentally friendly power generation systems, such as wind turbines or photovoltaics; however, the output power fluctuations due to the intermittence and variability of these power systems can greatly affect the quality and stability of the power system network. Furthermore, the power fluctuations that are triggered by power load devices also have similar results on the power system. Therefore, it is essential to introduce power level control for controllable power devices and connection in order to lessen the effects of dynamic power fluctuations that are caused by fluctuating power source devices and load devices. The issue of power balancing as a part of power level control presented in this paper assigns power levels to controllable power devices and connections between power source devices and load devices to absorb dynamic power fluctuations. In this paper, we focus on power conservation law instead of detailed voltage or current-based network characterization and present a new power balanceability test for a power flow system that comprises of both fluctuating and controllable power devices. Our proposed power balanceability test can assure the existence of a power flow assignment of power devices and connections for any value of power generation and/or the consumption of fluctuating power devices. Our proposed power balanceability test method can be expressed as a linear programming problem, and it can be resolved in polynomial time complexity.

Cascaded HTGR Power-Level Control Only by Regulating Primary Helium Flow Rate

Reactor power-level control is a key technique of enhancing the safety, stability, and efficiency of nuclear plants. Currently, nearly all the power-level control methods are based on the scheme of inducing reactivity directly via control rods. However, the reactivity can also be injected indirectly via the negative temperature feedback effect, which results in the opportunity to develop indirect nuclear reactor power-level control methods. Motivated by this, a cascaded power-level control of high-temperature gas-cooled reactor, which is composed of a helium temperature controller and a neutron flux controller, is proposed based on only regulating the primary helium flow rate. The temperature controller, which is in the inner loop, regulates the primary helium flow rate according to the setpoint of helium temperature. The flux controller, which is in the outer loop, revises the setpoint of the inner-loop controller so as to eliminate the error of reactor neutron flux. It is proved that the closed-loop system can be guaranteed to be globally asymptotically stable. Finally, numerical simulation results corresponding to the application to the high-temperature gas-cooled reactor pebble-bed module (HTR-PM) plant verifies the theoretical result while showing the satisfactory performance as well as the influence of the controller parameters.

HGO-based adaptive super-twisting sliding mode power level control with prescribed performance for modular high-temperature gas-cooled reactors

This paper proposes a high-gain observer-based adaptive super-twisting sliding mode control strategy with prescribed performance (HGO-ASTSMCS-PP) for the power level of a modular high-temperature gas-cooled reactor (MHTGR). The dynamic model of the MHTGR is firstly described. By using this established model, a high-gain observer is constructed to recover the unmeasured states including relative density of delayed neutron precursor and reactor core temperature in real time. On the basis of the recovering values from the HGO, an adaptive super-twisting sliding mode control method with prescribed performance is designed. The super-twisting sliding mode control approach is adopted to improve control performance of power level for a MHTGR and suppress high-frequency chattering effects simultaneously. An adaptive mechanism is introduced to tune the control gains online so as to overcome the overestimation of the unknown disturbance boundary. In addition, by error transformation and introduction of performance function, the prescribed control performance of power level is guaranteed, which implies that the desirable convergence rate, steady power error, and maximum overshoot can be prescribed in advance. It is verified through Lyapunov stability theory that the overall closed-loop control system is globally uniformly ultimately bounded (GUUB). Finally, simulation and comparison results are presented to reveal the effectiveness of the proposed control scheme in terms of the steady and dynamic performance.

Extended state observer-based adaptive dynamic sliding mode control for power level of nuclear power plant

It is well known that nuclear energy is a clean, safe, and reliable energy resource. Nuclear power plant is one of the prominent applications of nuclear energy. In this paper, aiming at improving the control performance for power level of nuclear power plant, an extended state observer-based adaptive dynamic sliding mode control (ESO-ADSMC) scheme is proposed. The mathematical model of nuclear reactor is firstly constructed based on point-reactor kinetics equations. Then, an extended state observer is designed to estimate both unmeasured states and output disturbances in real time, and the asymptotic convergence of the observer error state space is analyzed according to Routh-Hurwitz and Lyapunov stability theory. Subsequently, an adaptive dynamic sliding mode control approach is proposed for power level control of nuclear power plants in the presence of output disturbances, which is a combination of sliding mode control and backstepping control to enhance disturbance rejection ability. In addition, the chattering phenomenon is eliminated due to the discontinuous sign function contained in the first derivative of actual control input. Finally, simulation studies are carried out to demonstrate the feasibility and effectiveness of the proposed control strategy compared with backstepping control method in terms of the accuracy and rapidity of the response of power level, and robustness against output disturbances.