Continuous order identification of PHWR models under step-back for the design of hyper-damped power tracking controller with enhanced reactor safety

Abstract

Abstract:In this paper, discrete time higher integer order linear transfer function models have been identified first for a 500 MWe Pressurized Heavy Water Reactor (PHWR) which has highly nonlinear dynamical nature. Linear discrete time models of the nonlinear nuclear reactor have been identified around eight different operating points (power reduction or step-back conditions) with least square estimator (LSE) and its four variants. From the synthetic frequency domain data of these identified discrete time models, fractional order (FO) models with sampled continuous order distribution are identified for the nuclear reactor. This enables design of continuous order Proportional-Integral-Derivative (PID) like compensators in the complex w-plane for global power tracking at a wide range of operating conditions. Modeling of the PHWR is attempted with various levels of discrete commensurate-orders and the achievable accuracies are also elucidated along with the hidden issues, regarding modeling and controller design. Credible simulation studies are presented to show the effectiveness of the proposed reactor modeling and power level controller design. The controller pushes the reactor poles in higher Riemann sheets and thus makes the closed loop system hyper-damped which ensures safer reactor operation at varying dc-gain while making the power tracking temporal response slightly sluggish; but ensuring greater safety margin.

Review on Application of Control Algorithms to Power Regulations of Reactor Cores

“…Saha et al [37][38][39] devised a fractional order PID controller of the identification model and reduced order model for a CANDU type pressurized heavy water reactor with practical test data in order to regulate this reactor power. The combination of the fractional order PID control and the new neural network algorithm to optimize controller parameters was effectively exploited by Zhao et al [40] to develop a PWR core power control system.…”

“…Improving power regulation technology of cores by the introduction of control algorithms is an important measure for safety and availability of NPPs. Over the decades, many control algorithms have been exploited and applied by researchers to core power regulations, which are the stateor output-feedback control with a state observer [2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17], the optimal control [18,19], the neural network or fuzzy intelligent control [20][21][22][23][24][25], the model predictive control [26][27][28], the H ∞ robust control [29][30][31], the sliding model control [32][33][34][35], the fractional order control [36][37][38][39][40][41] and other control algorithms [42][43][44][45][46][47]…”

Multi-objective active control policy design for commensurate and incommensurate fractional order chaotic financial systems

“…This enables design of a relatively fast control system as opposed to the safe but very slow control operation when all the closed loop poles are pushed to the higher Riemann sheet (i.e. hyper-damped and ultra-damped roots) in the study by Das et al [42].…”

“…During the optimization based controller design for both the commensurate and incommensurate FO systems, a constraint is imposed such that at least two roots lie in the stable region of the primary Riemann sheet This enables design of a relatively fast control system as opposed to the safe but very slow control operation when all the closed loop poles are pushed to the higher Riemann sheet (i.e. hyper-damped and ultra-damped roots) in the study by Das et al[42].…”