Jong-Min Cheon

Design of a pitch controller using disturbance accommodating control for wind turbines under stochastic environments

This paper describes a design of a wind turbine pitch controller based on the disturbance accommodating control (DAC) theory. Wind turbine systems generally operate under stochastic environments, such as random wind inputs and noise corrupted sensor signals. Especially wind inputs can be treated as persistent disturbances and DAC can play a role in reducing effects of wind disturbances. By doing this, wind turbines suffer less from mechanical fatigue loads and their lifespan can be increased. Because wind disturbances we must accommodate are stochastic, we design DAC for stochastic plants and compare with other controllers not considering stochastic conditions to verify the performances of our proposed controller.

A Design and Implementation of a Fault-Tolerant Rod Control System for Nuclear Power Plants

The design and implementation of a fault-tolerant control rod control system for nuclear power plants is described. High reliability and safety are necessary for the instrumentation and control systems for safety-critical plants such as nuclear power plants. For a control rod control system that controls the nuclear reactivity inside the reactor by inserting or withdrawing the rods into or from the reactor, the reliability is more critical than the safety since its malfunction directly results in an unexpected shutdown of the power plant. This paper deals with a design and implementation practice to enhance the reliability of the control system. The reliability enhancement is basically achieved by adopting hardware redundancy in its structure. The reliability is evaluated quantitatively to check if the designed and implemented system is reliable enough to be applied to commercial plants. The ability of fault detection realized in the system is expected to give a further reliability enhancement by means of software. The bumpless control problem that can be arisen from adopting hardware redundancy is discussed here. Also a new algorithm for the rod movement detection is briefly introduced and demonstrated with a test result

Multi-Objective Controller Design using a Rank-Constrained Linear Matrix Inequality Method

This paper presents a rank-constrained linear matrix inequality (LMI) approach to the design of a multi-objective controller such as control. Multi-objective control is formulated as an LMI optimization problem with a nonconvex rank condition, which is imposed on the controller gain matirx not Lyapunov matrices. With this rank-constrained formulation, we can expect to reduce conservatism because we can use separate Lyapunov matrices for different control objectives. An iterative penalty method is applied to solve this rank-constrained LMI optimization problem. Numerical experiments are performed to illustrate the proposed method.

Rank-constrained LMI Approach to Simultaneous Linear Quadratic Optimal Control Design

This paper presents a rank-constrained linear matrix inequality(LMI) approach to simultaneous linear-quadratic(LQ) optimal control by static output feedback. Simultaneous LQ optimal control is formulated as an LMI optimization problem with a nonconvex rank condition. An iterative penalty method recently developed is applied to solve this rank-constrained LMI optimization problem. Numerical experiments are performed to illustrate the proposed method, and the results are compared with those of previous work.

New Method for Detecting Failures of Power Converter Module in Control Rod Control System

In this paper, we introduce a new method for detecting failures of a power converter module in control rod control system of a nuclear power plant. The failure called the phase failure and occurring in a power converter module can exert harmful influence upon the operation of the associated control rod drive mechanism for driving neutron-absorbing control rods controlling the thermal output of the reactor. Because of this adverse condition, it is necessary that the phase failure should be detected quickly and correctly. We devised a new method for detecting the phase failure for the digital power controller and solved the drawbacks of the existing failure detector

A New Fault Detectior for Three-Phase Half-Wave Converter Using Wavelet Transform

Abstract In this paper, we introduce a new method of detecting faults in a three-phase half-wave converter used to transmit DC power into Control Rod Drive Mechanisms (CRDMs) in a Nuclear Power Plant (NPP). The failures in a three-phase half-wave converter can have a bad influence upon the operation of CRDM. This situation makes the system generate the urgent alarm and stop the movement of control rods. Existing systems use complex analogue circuits, but we adopt simple and efficient digital technology, in accordance with a current tendency. The digital system needs a new algorithm for fault detection and the wavelet transform is used to design the new fault detector and improve the ripple detector of Westing house type NPP.