Changes In Power Level Research Articles

A Fuzzy-Logic Based Control Methodology in Microgrids in the Presence of Renewable Energy Units

The mix of conveyed ages, for example, photovoltaic and wind and additionally substantial load varieties prompts the significant issue of recurrence soundness issue. This paper shows a multi-arrange recurrence control for microgrids. Vitality stockpiling frameworks, for example, BESSs are chosen as an adaptable and quick reaction gadget for this application. In the main stage, a PI control strategy in view of PSO for the BESS is connected so as to limit the recurrence deviations. Also, in possibility modes, in which the BESS with the enhanced PI control application can't balance out the framework because of the uneven circumstance of free market activity, quick response of the focal control framework administrator is essential so as to shield the system from crumple. Thus, in the second phase of the control, a Fuzzy-rationale recurrence controller as a brilliant controller is outlined. This controller proposes arrangements through power level change, for example, stack shedding in a brief time frame to save the system from instability. The proposed technique is approved by an arrangement of reproductions on a delegate microgrid. The viability of the proposed multi-organize control is delineated through the correlation with the one-arrange controller without the Fuzzy-rationale part.

Control of the reactor core power in PWR using optimized PID controller with the real-coded GA

Load following is an importance topic in the Nuclear Power Plants (NPPs). One of the conventional and simplest ways is the use of Proportional-Integral-Derivative (PID) controller. The reactor power is simulated based on the point kinetic model. PID gains of a nonlinear time-varying system (a PWR NPP) are optimized and scheduled using real-coded genetic algorithm (GA). To this end, the objective function of the decision variables, include the overshoot, settling time and stabilization time (based on the Lyapunov approach) of the system is minimized. The presented control system track demand power level change within a wide range of time. The simulation results demonstrate good stability of this method and show high performance of the optimized PID gains to adapt any changes in the output power.

Minor actinide transmutation characteristics in AP1000

We study the minor actinide transmutation characteristics by coating different thickness minor actinide on fuel pellets of the AP1000. The calculation results indicate that the more minor actinide is loaded to AP1000, the more boric acid concentration need to be reduced from coolant to let keff return criticality. The relationship between the reduced boric acid concentrations in AP1000 coolant with minor actinide loading amount is not linear. The reduced boric acid concentration in coolant approaches a saturation level after about 300.0 kg minor actinide loading amount. This implies that too much minor actinide loading amount in a single AP1000 fuel loading is meaningless.Our simulation results also denote that loading minor actinide to AP1000 core does affect the power distribution of AP1000 in some way, we need to reduce the boric acid concentration and rearrange the burnable poison rods in the core simultaneously to achieve the purpose of flatting the power distribution. So a moderate minor actinide loading in AP1000 will not adversely affect the core power distribution strikingly.Our calculation results also display that fuel temperature coefficient (FTC) is still negative after adding minor actinide to reactor. In comparison with the standard AP1000 reactor core, the extent of the negative feedback effect of FTC after loading minor actinides is reduced to some extent; the moderator temperature coefficient (MTC) improves the negative feedback effect of the reactor core to a great extent. Taking into account all analytical results about FTC and MTC, the total negative feedback effect on reactor power level changes is improved after loading minor actinides to AP1000 reactor for transmutation. The transmutation rate calculation results show that AP1000 reactor can incinerate 44.0 kg MA nuclides after one year fuel cycle. So AP1000 reactor can incinerate almost 2 times the annual MA yield from a typical PWR reactor.

Calculation of sound power level of tandem axial fan

A numerical simulation of the flow in axial fans with single and tandem geometrically equivalent blade rows was carried out. During the research, the sound power level of the fans was calculated. The acoustic characteristics of the single fan obtained in the numerical experiment were compared with the results of the physical experiment. The divergence between the results of the physical and numerical experiments on the sound power level for the first harmonic is 0.08 %, for the second harmonic – 0.35 %. In order to reduce the acoustic emission, a 3D model of the axial fan with the geometrically equivalent tandem row was constructed. The results showed that at the fan rotation frequency of 900 rpm, the sound power level on the first two harmonics is reduced by more than 7 dB. Also, the change in the total sound power level for axial single and tandem fans in the rotation frequency range of 900 to 1,500 rpm was investigated. The fan with the geometrically equivalent tandem blade row has the total sound power level by 6.9...7.4 dB lower than the single fan. The use of the tandem axial fan allows improving acoustic characteristics

Utilization of District Heating Networks to Provide Flexibility in CHP Production

Increasing penetration of intermittent renewable energy production in power systems will remarkably increase the need of flexible and controllable power generation. As numerous existing thermal power generation units have been closed down, all the possible flexibility available in power systems should be harnessed to stabilize the power systems. Combined heat and power (CHP) generation is widely used in district heating (DH) systems. As total heat production into the DH network needs to be balanced with the total heat consumption, this sets significant limitations to the long-term power production. However, the heat load and electric production can be decoupled temporarily by using the heat storage capacity of DH networks and heat accumulators. This paper presents an analysis of dynamic operability of interconnected CHP plants and district heating networks. The flexibility of generation capacity was compared with the requirements set when attending the Automatic Frequency Restoration Reserve (FRR-A) market. For that, two case studies were presented that include FRR-A tests in two municipal CHP plants. The results indicate that both cases fulfil the requirements and that the DH network operation is affected only slightly. However, the rapid power level changes are disturbances to CHP boilers and DH networks that the process components and automation systems must adapt to. Therefore, these aspects must be considered carefully when applying such new operation practises in existing CHP plants.

Multi-stage Frequency Control of a Microgrid in the Presence of Renewable Energy Units

The integration of distributed generations such as photovoltaic and wind as well as large load variations leads to the significant issue of frequency stability problem. This paper presents a multi-stage frequency control for microgrids. Energy storage systems such as BESSs are selected as a flexible and fast-response device for this application. In the first stage, a PI control method based on PSO for the BESS is applied in order to minimize the frequency deviations. Moreover, in contingency modes, in which the BESS with the optimized PI control application cannot stabilize the system due to the unbalanced situation of supply and demand, fast reaction of the central control system operator is necessary in order to protect the network from collapse. Hence, in the second stage of the control, a Fuzzy-logic frequency controller as a smart controller is designed. This controller proposes solutions through power level change such as load shedding in a short time to rescue the network from instability. The proposed method is validated by a set of simulations on a representative microgrid. The effectiveness of the proposed multi-stage control is illustrated through the comparison to the one-stage controller without the Fuzzy-logic part.

Evaluation of missing pellet surface geometry on cladding stress distribution and magnitude

Missing pellet surface (MPS) defects are local geometric defects in nuclear fuel pellets that result from pellet mishandling or manufacturing. The presence of MPS defects can cause significant clad stress concentrations that can lead to through-wall cladding failure for certain combinations of fuel burnup, and reactor power level or power change. Consequently, the impact of MPS defects has limited the rate of power increase, or ramp rate, in both pressurized and boiling water reactors (PWRs and BWRs, respectively). Improved three-dimensional (3-D) fuel performance models of MPS defect geometry can provide better understanding of the probability for pellet clad mechanical interaction (PCMI), and correspondingly the available margin against cladding failure by stress corrosion cracking (SCC). The Consortium of Advanced Simulations of Light Water Reactors (CASL) has been developing the Bison-CASL fuel performance code to consider the inherently multi-physics and multi-dimensional mechanisms that control fuel behavior, including cladding stress concentrations resulting from MPS defects. This paper evaluates the cladding hoop stress distributions as a function of MPS defect geometry with discrete pellet radial cracks for a set of typical operating conditions in a PWR fuel rod. The results provide a first step toward a probabilistic approach to assess cladding failure during power maneuvers. This analysis provides insight into how varying pellet defect geometries affect the distribution of the cladding stress, as well as the temperature distributions within the fuel and clad; and are used to develop stress concentration factors for comparing 2-D and 3-D models.

Linearisation of radio frequency power amplifiers exhibiting memory effects using direct learning‐based adaptive digital predistoriton

This study presents an adaptive predistortion algorithm based on direct learning approach to compensate for the non-linearities of a power amplifier (PA) exhibiting memory effects. The proposed algorithm implements the steepest descent technique on an odd-order memory polynomial model to optimise the predistorter coefficients. The performance of the proposed algorithm is validated using a harmonically tuned broadband PA driven by long-term evolution 20 MHz signal. Measurement results confirmed the robustness of the proposed technique by adapting the coefficients of the predistorter to the changes in average input power, drain bias, and gate bias of the PA. The linearisation using the proposed algorithm is compared to the traditional uncompensated case and results are presented. For changes in average input power, gate bias and drain bias levels, the normalised mean square error shows substantial enhancement when the predistortion coefficients are updated using the proposed algorithm.

The impact of medium frequency pulsed magnetron discharge power on the single probe Langmuir measurements and resulted plasma parameters

AbstractThe resonant type power supplies of medium frequency designed for magnetron sputtering processes often use pulse density modulation to regulate the average discharge power level. While the output power level changes then number of pulses in a group changes, but the discharge current pulses are the same from pulse to pulse: their parameters (duration time, amplitude) do not change with the discharge power. The goal of this paper is to present the influence of medium frequency discharge power level on the direct current I-V characteristics of a single Langmuir probe and resulting plasma parameters caused by the pulse density modulation. The sputtering processes of titanium and copper were diagnosed at two spatial positions. The measured Langmuir probe I-V characteristics showed strong dependence on the discharge power. As the discharge powering pulses stay the same with the discharge power level change, such influence was unlikely to occur. Using time-resolved analysis of probe current waveforms the origin of this influence was indicated. The influence of discharge power level on the single probe Langmuir I-V characteristics and resulting plasma parameters was eliminated using a simple method of scaling the results. Finally, the reliable plasma parameters were calculated.

Control of the nuclear steam generators using adaptive dynamic sliding mode method based on the nonlinear model

The water level control problem of steam generators has been a main cause of unexpected shutdowns of nuclear power plants which must be considered for plant safety and availability. The control problem is challenging, especially at low power levels due to shrink and swell phenomena and flow measurement errors. Moreover, the dynamics of steam generator vary as the power level changes. Therefore, it is necessary to improve the water level control system of SG. In this paper, at the first a nonlinear model based on the fundamental conservation equations for mass, energy and momentum is presented for the nuclear steam generator which is validated with other computer programs and experimental results and then, an adaptive dynamic sliding mode control method is applied for the level control problem of U-tube steam generators based on the presented nonlinear model. The proposed method exhibits the desired dynamic properties during the entire output tracking process independent of perturbations. Simulation results are presented to demonstrate the effectiveness of the proposed controller in terms of performance, robustness and stability. Simulation results confirm the improvement in transient response obtained by using the proposed controller.

Why Engaging with More Institutions?: Changes in Economic Power Distribution and Levels of Economic Cooperation

What is the effect of changing economic power on the level of institutional cooperation? The existing literature provides contradictory theories. Some posit that power preponderance, such as the presence of hegemony, is the key to greater cooperation, whereas others such as neofunctionalists contend that power parity is a more favorable condition for deeper integration. Unlike these monotonous and static proposals, this article argues for the presence of a curvilinear and dynamic relationship between changes in power ratios and levels of formal economic integration, showing extensive cooperation at large and small power gap differences but less cooperation at the status quo. In addition, states’ concern for the distributive consequences of formal economic integration is considered a key condition in the development of the integration. This power gap difference hypothesis is tested with my original data set of four-tier preferential trade agreements (PTAs) from 1950 to 2005. The analysis employs models for ordered outcomes. The research findings largely support the power gap difference hypothesis and add to our knowledge that the dynamic shift of economic power and distribution gives incentives to states to develop certain levels of formal integration.

An Efficient Power Management for Wireless Sensor Systems

Devices existing within a wireless sensor system are small in size and their battery capacities are very limited. In addition, diverse channel environments may be configured for them. To overcome various constraints and efficiently utilize the energy of sensor nodes, transmission power control (TPC) technology may be employed. This paper describes our attempt to resolve problems with existing TPC algorithms, reduce the number of unnecessary changes in transmission power level (TPL) using the slope value of linear regressed equation, and present an algorithm for deriving TPL in a fast and appropriate manner. Through an experiment, in this study, we not only derive proper weight value of the proposed algorithm but also compare its performance with that of existing algorithms by analyzing the numbers of control packets, drop packets, and energy consumption.

Refractive index sensor based on stress-induced long period grating

We proposed a novel refractive index sensor based on a side-polishing fiber to be cascaded with a stress-induced long period fiber grating (LPG), which is created by applying a force to a V-grooved plate on the single mode fiber with micro-bending deformation. When the refractive index (RI) surrounding the side-polishing surface is changed, the LPG-induced cladding mode light could be coupled back to the core mode, so that it will result in the magnitude variation of LPG loss-peak. This property of index sensing based on the stress-induced LPG by monitoring the power-level change may be exploited in chemical sensing and environmental monitoring applications.

Nuclear Reactor Doubling Time Calculation Using FIR Filter

In nuclear reactor engineering, reactor doubling time is generally applied to indicate the change of power level and usually provided by a nuclear instrumentation system (NIS). In a digital NIS, current signal from neutron detector is pre-amplified and conditioned into voltage signal which is proportional to the power level of nuclear reactor, and then is acquired and processed by a digital computer in the NIS. The measurement noise contained in the acquired voltage signal will cause a lot of uncertainty in the reactor doubling time calculation result. In this paper, the sensitivity analysis of nuclear reactor doubling time calculation is investigated. A calculation algorithm of reactor doubling time for digital NIS is proposed based on FIR Filtering techniques, and two filtering schemas to calculation reactor doubling time are given based on the FIR filter. A Hard-In-Loop (HIL) experiment environment was built to verify the discussed calculation algorithm. The experimental results show that the calculation algorithm developed can suppress the influence of measurement noise on calculation result to recover the signal's original features, and can provide us with good on-line calculation result.

Adaptive estimator-based dynamic sliding mode control for the water level of nuclear steam generators

Steam Generator (SG) is a crucial component of nuclear power plant. The proper water level control of a nuclear steam generator is of great importance in order to secure the sufficient cooling source of the nuclear reactor and to prevent damage of turbine blades. The water level control problem of steam generators has been a main cause of unexpected shutdowns of nuclear power plants which must be considered for plant safety and availability. The control problem is challenging, especially at low power levels due to shrink and swell phenomena and flow measurement errors. Moreover, the dynamics of steam generator vary as the power level changes. Therefore, it is necessary to improve the water level control system of SG. In this paper, an adaptive estimator-based dynamic sliding mode control method is developed for the level control problem. The proposed method exhibits the desired dynamic properties during the entire output tracking process independent of perturbations. Simulation results are presented to demonstrate the effectiveness of the proposed controller in terms of performance, robustness and stability. Simulation results confirm the improvement in transient response obtained by using the proposed controller.

Change of the sound power level of road vehicle noise

Change of the sound power level of road vehicle noise

Plasmonic modulation and switching via combined utilization of Young interference and metal–insulator–metal waveguide coupling

We present a new nanoscale modulation scheme based on the formation of a plasmonic Young interference pattern and its collection by an excitation field pattern-sensitive metal–insulator–metal (MIM) waveguide. Our numerical investigations reveal that such a scheme can generate sensitive and quasi-linear changes in the output power level in response to the relative phase difference between the waves in the two Young interferometer branches. Thanks to the asymmetric positioning of the collector waveguide, the response becomes most sensitive and linear when the relative phase difference is close to zero. Such a response characteristic can benefit future plasmonic systems by eliminating the need for phase prebiasing. The strong interactions between the surface plasmon polaritons inside the MIM structures are also utilized for realizing functionalities beyond modulation, such as on/off modulation contrast enhancement and all-plasmonic and logic operation.

Gain scheduled dynamic sliding mode control for nuclear steam generators

U-Tube Steam Generator (UTSG) is one of the most important facilities in a pressurized-water nuclear reactor. Poor control of the Steam Generator (SG) water level in the secondary circuit of a nuclear power plant can lead to frequent reactor shutdowns or damage of turbine blades. The control problem is challenging, especially at low power levels due to shrink and swell phenomena and flow measurement errors. In addition, the dynamics of steam generator vary as the power level changes. Therefore, designing a suitable controller for all power levels is a necessary step to enhance the plant availability factor. The purpose of this paper is to design, analyze and evaluate a water level controller for U-tube steam generators using dynamic sliding mode control. The employed method is easy to implement in practical applications and moreover, the dynamic sliding mode control exhibits the desired dynamic properties during the entire output-tracking process independent of perturbations. Gain scheduling is used to obtain a global water level controller. Simulation results are presented to demonstrate the performance, robustness, and stability of the proposed controller. Computer simulations show that the proposed controller improves the transient response of steam generator water level and demonstrates its superiority to existing controllers.

Estimation of the effect of shadow zone boundary for noise calculation on large wind turbines

The prediction methods of wind turbine noise in common use are valid for weather conditions that correspond to moderate down-wind. In this study the up-wind propagation is examined for a point source (turbine hub) and plane source (turbine blades with the hub). Since the wind turbine noise limits are related either to an average�or the highest noise imission at the receiver, the up-wind propagation is considered for the wind speed of 10 m/s at 10 m above the ground surface (wind class W5). It is shown that the up-wind refraction results in the change of the effective sound power level of the wind turbine. It explains some up-wind measurement data

Modelling of D majority ICRH at JET: impact of absorption at the Doppler-shifted resonance

Recent experiments in JET have provided new information on majority ICRF heating schemes in large tokamak plasmas. Adopting a wide range of available diagnostics, the plasma behaviour in a fundamental D majority ICRF heating scenario was investigated. The main results of the experiments are that, due to the modest RF power available at the frequencies necessary for central D absorption in JET associated with the reduced RF electric field amplitude near the cold ion-cyclotron resonance layer of the D majority ions, ICRH alone is barely capable of heating the plasma. On the other hand, when preheating the plasma using neutral beam injection, the wave–plasma coupling is improved and considerable plasma heating followed by increased neutron yield was observed in several discharges. The enhancement of the ICRH efficiency in the presence of NBI is attributed not only to the lower collisionality of the pre-heated plasma but also to the Doppler-shifted ion-cyclotron resonance absorption of the fast beam ions. This effect has been observed with several diagnostics and was confirmed by numerical simulations. The numerical modelling was done adopting a coupled full wave/quasi-linear Fokker–Planck (QLFP) code that takes into account the non-Maxwellian distributions of the injected beam ions in the wave equation, and the actual local RF electric field structure obtained by the full-wave computations in the Fokker–Planck description. By studying the response of the plasma to sudden changes in the ICRF power level, the experimental RF power deposition profiles were estimated and compared with the theoretical predictions. Finally, a qualitative link between the RF-heated beam distributions obtained in the QLFP simulations and some of the experimental results is also presented.