[en] One of the most important problems in power system dynamic stability is low frequency oscillations. This kind of oscillation has significant effects on the stability and security of the power system. In some previous papers, a fact was introduced that a steam pressure continuous fluctuation in turbine steam inlet pipeline may lead to a kind of low frequency oscillation of power systems. Generally, in a power generation plant, steam turbine system composes of some main components, i.e. a boiler or steam generator, stop valves, control valves and turbines that are connected by piping. In the conventional system, the turbine system is composed with a lot of stop and control valves. The steam is provided by a boiler or steam generator. In an abnormal case, the stop valve shuts of the steal flow to the turbine. The steam flow to the turbine is regulated by controlling the control valves. The control valves are provided to regulate the flow of steam to the turbine for starting, increasing or decreasing the power, and also maintaining speed control with the turbine governor system. Unfortunately, the control valve has inherent static friction (stiction) nonlinearity characteristics. Industrial surveys indicated that about 20-30% of all control loops oscillate due to valve problem caused by this nonlinear characteristic. In this paper, steam turbine control valve stiction effect on power system oscillation is presented. To analyze the stiction characteristic effect, firstly a model of control valve and its stiction characteristic are derived by using Newton's laws. A complete tandem steam prime mover, including a speed governing system, a four-stage steam turbine, and a shaft with up to for masses is adopted to analyze the performance of the steam turbine. The governor system consists of some important parts, i.e. a proportional controller, speed relay, control valve with its stiction characteristic, and stem lift position of control valve controller. The steam turbine has four stages. The steam chest is represented by the first stage. The three other stages represent either reheaters or crossover piping. The shaft model which represents a four-mass system is coupled to the mass in a synchronous machine (generator) for a total of five masses. To analyze the oscillation in power system, an IEEE benchmark is used as reference scenario. In this scenario, a single generator is connected to infinite bus via a transmission line

[en] In the nuclear power plants (NPPs), monitoring system is one of the most important parts in the instrumentation and control (I and C) system. The function of this system is to monitor all of NPP variables and provide data to other I and C systems and to operator for controlling the operation of the NPP. Moreover, it has to provide the operators with accurate and appropriate information during both normal and abnormal operations. Unfortunately, for providing the accurate and appropriate information, the monitoring system should be supported by hundreds of measurements (instruments). Therefore it is important that instrument failures be detected before significant performance degradation. In this paper, an application of nonlinear filter to instrumentation failure detection mechanism is presented. The mechanism uses extended Kalman filters to generate optimal estimates of the states. Most of previous work on failure detection in a NPP used assumption that the dynamic plant that is monitored is linear or linearized

[en] In a number of applications it is required to work for a long periods of time on the ocean, where supply of fuel is complicated and sometimes impossible. Moreover, high efficiency and compactness are the other important requirements in naval application. Therefore, an integrated nuclear electric propulsion system is the best choice to meet all of these requirements. In this paper, a modeling of nuclear electric propulsion for naval application is presented. The model adopted a long-term power system dynamics model to represent the dynamics of nuclear power part

[en] Control valve has an important function in a nuclear power plant to regulate the inlet steam of turbine. Unfortunately, however, the control valve has inherent nonlinearities characteristics such as the static friction (stiction), backlash, and deadband. The presence of nonlinearities in a control valve limits the control loop performance and also causes a stability problem in the system. Moreover, this condition renders the design of control system more complex and hard to be handled. Based on this phenomenon, it is desirable to improve the control systems to compensate for these inherent nonlinear characteristics of the control valve. In this paper, a procedure is presented to compensate for the stiction phenomenon of control valve for a pneumatic control valve type. A computational simulation is also presented to check on the proposed method

[en] A design concept of the electric propulsion system for the Nuclear Operated Vessel Adventure (NOVA) is presented. NOVA employs Battery Omnibus Reactor Integral System (BORIS), a liquid metal cooled small fast integral reactor, and Modular Optimized Brayton Integral System (MOBIS), a supercritical CO ₂ (SCO₂) Brayton cycle as power converter to Naval Application Vessel Integral System (NAVIS)

[en] The monitoring system is one of the most important parts of the instrumentation and control (I and C) of nuclear power plants (NPPs). This system has a function to monitor NPP variables and provide data to other I and C systems and to operator for controlling the operation of the NPP. It has to provide the operators with accurate and appropriate information during both normal and abnormal operations. For providing the accurate and appropriate information, the monitoring system is supported by hundreds of measurements (instruments). Therefore it is important that instrument failures be detected before significant performance degradation. In this paper, an application of nonlinear filter to instrumentation failure detection mechanism is presented. The mechanism uses nonlinear filters to generate optimal estimates of the states. The nonlinear filter can work well for highly nonlinear problem that are difficult for the conventional Kalman filter. Most of previous work on failure detection in a NPP used assumption that the dynamic plant that is monitored is linear or linearized so that conventional Kalman filter can be used as its estimator. This paper reports on an attempt to apply a failure detection mechanism to the model of a pressurized water reactor (PWR) plant that is nonlinear. The proposed mechanism uses a bank of nonlinear filters to generate optimal estimates of the NPP states. A PWR plant can be conveniently divided into components each of which can be modeled in the state space manner used in failure detection mechanism schemes based on the modern estimations theory. One of the important components is the pressurizer and this element was selected for the work reported here. The pressurizer of the loss-of-fluid test (LOFT) reactor was used because there is dynamic information available on this pressurizer. This model has five instruments: a pressurizer sensor, a pressure sensor, a temperature sensor, and redundant level instruments

[en] The Optimized Supercritical Cycle Operation (OSCO) apparatus is being designing at the Seoul National University (SNU). Its main goal is to obtain experimental data of the supercritical carbon dioxide cycle power conversion system in transient states. To make the transient condition, OSCO adopts a controlled dc power supply for its heaters which can generate various transient power patterns to represent the transient phenomena of heat exchangers or heat sources. A simulator of transient dc power supply for nuclear applications was proposed in. This power supply was designed to represent a typical nonlinear decay heat of fission reaction by adopting a simple proportional controller. Because the actual system is not linear, this type controller still generates a significant error. To the nonlinearity system, a nonlinear controller can be adopted. But the controller design will be more complicated. In this paper, a concept to control the load power is proposed. The concept adopts a load power model to estimate the actual power of the load (heater). Thus by relying only on one actual variable value information, the controller can estimate other variables and resistance of heater

[en] The steam turbine control valves play a pivotal role in regulating the output power of the turbine in a commercial nuclear power plant. In this paper the turbine system refers to Ulchin units 3 and 4. The modeling of friction in steam turbine control valve is presented. Instead of a detailed physical model of the control valve friction, the data-driven models are adopted for modeling the friction to obtain an easier friction identification and faster calculation time. Some computational results by using the MARS thermal hydraulic analysis code are presented to show the effect of friction on the total mass flow at the inlet of the high pressure turbine. The computational results demonstrate that the friction will initiate fluctuations on the total mass flow at the turbine inlet

[en] This work centers about advantages of nuclear power propulsion with various naval applications such as military surface ship, submarine, and ice breaker. These applications are required to work for a long periods of time on the ocean, where supply of fuel is complicated and sometimes impracticable. A preliminary design concept is presented of the propulsion system for the Nuclear Operated Vessel Adventurer (NOVA). NOVA employs the Battery Omnibus Reactor Integral System (BORIS), a small fast integral reactor cooled by natural circulation and the Modular Optimized Brayton Integral System (MOBIS), a supercritical carbon dioxide (SCO2) driven Brayton cycle, as power converter to the Naval Application Vessel Integral System (NAVIS)

[en] In this paper the controlled power source converter is computationally analyzed to represent the fusion reactor global decay heat characteristics. The converter is designed to be a miniature of the decay heat source for experimental purposes. This decay heat source exchanger of the cooling system of the fusion reactor under the decay heat power. A standard commercial simulator is used to analyze performance of the controlled power source converter