Operation Of Proposed Strategy Research Articles

An improved operation strategy of combined cooling heating and power system following electrical load

The operation strategy of CCHP (combined cooling heating and power) system is a vital factor governing its overall performance. This paper proposed an improved operation strategy of CCHP system FEL (following electrical load) to minimize primary energy consumption. In this strategy, the generated electricity of PGU (power generation unit) is optimized to improve the average generation efficiency at the lower electrical load of building. Battery is cooperated with PGU to finish a charge and discharge cycle in 24 hours so as to limit the size of battery. Different operation logics of the proposed operation strategy are presented with the combination of PGU and battery. The energetic performance analysis demonstrates the feasibility of the improved operation strategy. The energy saving potential influenced by fluctuation characteristic of electrical load is discussed to find out the impact relationship of PGU average generation factor, charge factor and supplementary electricity factor on primary energy saving ratio. The comparison results between four types of building indicated that the proposed strategy can achieve more energy saving in the building where the electrical demand has dramatic fluctuation during a day, whereas it is not suitable to the buildings with stable electrical load.

계통연계형 직렬운전 소형풍력발전시스템의 해석 및 운전방안 연구

This paper proposes an analysis and operation strategy of a grid-connected wind turbine system using a diode rectifier. The currents of generators are the same as that of a small wind turbine system. Therefore, the analysis of generator torque is required as opposed to an analysis of blade speed. In this paper, the appropriate MPPT control method is proposed to control generator torque. Usefulness of the proposed operation strategy is verified by simulations and experiments.

A novel operation strategy for CCHP systems based on minimum distance

Abstract A novel operation strategy based on minimum distance was proposed. Also, an integrated evaluation criterion which can reflect the matching performance between the CCHP (combined cooling, heating and power) system and the building was presented. A hospital in Shanghai was used to evaluate the CCHP system with the proposed strategy using the proposed evaluation criterion. The proposed operation strategy was compared with FEL (following the electric load), FTL (following the thermal load) and FHL (following hybrid electric-thermal load) strategies. The results show that the matching performance evaluation criterion is reasonable and integrated. The system with a better matching performance would be fully used and maintain high efficiency. Compared with FEL, FTL and FHL strategies, the proposed operation strategy is flexible and adaptable, which can lead to a better matching performance for a CCHP system. In the case study, the optimized power generation unit capacity and weightings of the optimized operation strategy are 900 kW and w1,above equals to 0.4, w1,below equals to 0.1, respectively.

3-D Cross-Point Array Operation on <inline-formula> <tex-math notation="TeX">${\rm AlO}_{y}/{\rm HfO}_{x}$ </tex-math></inline-formula>-Based Vertical Resistive Switching Memory

A comprehensive array operation scheme for a multilayer stacked 3-D vertical resistive random access memory (RRAM) cross-point array architecture is developed. Based on the proposed READ/WRITE scheme, each memory cell in the 3-D array can be randomly accessed. The fabricated AlOy\HfOx-based bilayer vertical RRAM array with excellent device-to-device and layer-to-layer uniformity is applied to demonstrate the feasibility of the proposed operation scheme.

Optimal scheduling and operation of battery/wind generation system in response to real‐time market prices

AbstractThis paper addresses the scheduling and operation problem of a combined battery and wind generation system (BWGS) in real‐time market. The proposed operation scheme consists of two control mechanisms: (i) offline scheduling according to the estimation of the market prices and the stochastic information of wind generation, and (ii) online dispatching based on the updated system state in real time. The analysis in this paper is different from the previous studies by taking into account the expense of battery energy storage under a newly defined term: cost of lifetime losses (CLLs). Thus the optimal scheduling and operation of BWGS not only gives maximum profit to the owner but also avoids the abusive operation of the battery. The case study provides a comparison of the proposed operation scheme with other approaches. It is shown that the proposed scheme considering the CLLs can significantly change the optimal charging/discharging of battery energy storage, and the increase in profit obtained in this case is about 9%. © 2014 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.

Influence of Different Operation Strategies on Transient Solar Thermal Power Plant Simulation Models with Molten Salt as Heat Transfer Fluid

One of the advantages of solar thermal power plants (STPPs) with molten salt as heat transfer fluid is the direct storage system. This means that the thermal energy collected by the solar field and the electric power generation can be fully decoupled. The plant operator must therefore make the daily decision when to start-up or to shut-down the power block (PB). Normally, the solar field of these STPPs is overdesigned which leads to dumping of solar energy during days with high solar radiation, due to the inability of the hot tank and the PB to consume all the collected thermal energy. The PB must therefore start as soon as possible to prevent excessive dumping of solar energy. Contrarily, on days with low solar radiation, the PB should not start too early to prevent a second start-up on this day, because of a low hot tank level. In order to operate within these counter bounds, a fixed and a dynamic operation strategy are proposed. The so-called solar-driven strategy serves as a reference. Using this strategy, the PB operates whenever the solar field is online. The two proposed operation strategies are compared to the reference strategy by means of a transient STPP simulation model. Using the dynamic operation strategy, the annual unnecessary PB start-ups and the auxiliary heater thermal energy for anti-freeze protection are decreased, whereas the annual net electricity is increased.

Operation Schemes of Smart Distribution Networks With Distributed Energy Resources for Loss Reduction and Service Restoration

The integration of Distributed Energy Resources (DERs) into the future Smart Distribution Network (SDN) has challenging issues regarding the successful development of smart grids. The SDN offers new opportunities in the improvement of the efficiency of power distribution networks. The DERs will be distributed in the existing distribution networks, interconnected in customer areas and operated on its own schedule without communication to the control center of the existing distribution system. The DER units have both positive and negative effects regarding SDN operations. With the appropriate operation of the DER units in the SDN, losses can be reduced during normal operations and they can support local loads during abnormal conditions. Thus, the positive effects of the DER units need to be enabled in the SDN by adopting advanced operation schemes. In this paper, the smart control functions for the DER units in the SDN are defined and classified. In addition, the integration schemes for the SDN with DER units are introduced. The proposed operation strategies will be implemented into the Korean Smart Distribution Management System (KSDMS) as operation schemes used for loss reduction and service restoration. A sample case study shows the effectiveness of the proposed operation schemes to achieve smart operation functions for the SDN with DER units.

Adequacy and Economy Analysis of Distribution Systems Integrated With Electric Energy Storage and Renewable Energy Resources

The integration of renewable energy resources (RER) into an existing distribution system is an important topic in dealing with energy challenge the world is facing. With rapid development of electric energy storage (EES) technologies, there is a growing interest in integrating both EES and RER into power systems to improve their reliability and economy. In this paper, the adequacy and economy of distribution systems integrated with both EES and RER are assessed. A novel model predictive control (MPC)-based operation strategy is presented to minimize distribution system energy purchasing cost by coordinating multiple power supplies from EES, RER and external grid. An islanding operation is implemented to improve the distribution system reliability and reduce customer interruption cost. A reliability and economy assessment framework based on sequential Monte Carlo method integrated with the MPC-based operation and islanding operation is proposed. Case studies are conducted to demonstrate the reliability and economy improvement by implementing the proposed operation strategies together with integration of EES and RER, and also investigate how EES capacity, power limit, and wind turbine generation capacity affect system reliability and economy.

A new operation strategy for CCHP systems with hybrid chillers

Performance and economical efficiency of the combined cooling, heating and power (CCHP) system mainly depend on the system structure, operation strategy and choice of facility capacity. This paper proposes a structural configuration of the CCHP system with hybrid chillers, consisting of a combined electric and absorption chiller, whose electric cooling to cool load ratio varies according to different electric and thermal loads in every hour. A new operation strategy, based on the variational electric cooling to cool load ratio, for the CCHP system with unlimited and limited power generation unit (PGU) capacity is investigated. Given the proposed operation strategy, an optimization algorithm is adopted to determine the optimal PGU capacity. In addition, a case study of a hypothetical hotel in Victoria, BC, Canada is conducted to verify the feasibility of the proposed CCHP system structure and the corresponding optimal operation strategy.

Applicability of Adapted Reservoir Operation for Water Stress Mitigation Under Dry Year Conditions

This paper introduces the conjunctive use of a deterministic water quality model and water balance criteria for supporting the assessment of simulation and to evaluate the effectiveness of proposed operation strategies. By this, the applicability of enhanced reservoir operation strategies addressing both water quality as well as water quantity aspects under water deficit conditions in dry years can be shown. Arguments will be developed to address stakeholders and decision makers in the context of a more conservative past operation regime. Results are presented for the Kaparas reservoir, which is located in the lower Amu Darya River, on the border of Turkmenistan and Uzbekistan. As being one out of four large reservoirs of the Tuyamuyun Hydro Complex (THC), the Kaparas reservoir could be increasingly used for drinking water supply for the lower Amu Darya region. The results for the dry year 2001 indicates that the combination of simulation together with practical assessment criteria confirm the applicability of adapted operation rules for THC reservoirs and ways can be found to supply the local population (of the lower Amu Darya region) with more potable water of higher quality even subject to a parallel reduction of water deficits. Future aggravation of water stress due to increasing population growth and water quality deterioration will require a more comprehensive consideration of water quality aspects in many arid and semi arid regions. The experience gained during this study emphasizes the fact that classical deterministic water quality models provide effective tools to address even more complex water quality problems under water stressed conditions, provided processing of results is performed, to support the decision making process.

A Wide-Dynamic-Range Photodiode-Type Active Pixel Sensor Cell with Seamlessly Combined Logarithmic–Linear–Logarithmic Response

A wide-dynamic-range photodiode-type (PD) active pixel sensor (APS) cell with seamlessly combined logarithmic–linear–logarithmic response is proposed for the first time and its operation is verified by circuit simulation. It has two additional metal–oxide–semiconductor field-effect transistors (MOSFETs) stacked in parallel to the reset MOSFET of conventional three-transistor (3-Tr) PD APS cells. By utilizing our previously proposed operation scheme that achieves automatic linear–logarithmic response switching, the proposed 5-Tr APS cell realizes seamlessly combined logarithmic–linear–logarithmic response.

Bidirectional Data Injection Operation of Hybrid Integrated SOA–MZI All-Optical Wavelength Converter

A bidirectional data signal input scheme of a semiconductor optical amplifier--Mach-Zehnder interferometer (SOA-MZI) wavelength converter was proposed and experimentally verified for a nonreturn-to-zero (NRZ)-format signal. Theoretical analyses reveal that it is possible to mitigate the patterning effect induced by cross-gain modulation (XGM) by utilizing the difference of the ratio between the XGM and cross-phase modulation on the injection directions of data signals. A hybrid integrated SOA-MZI all-optical wavelength converter, in which the coupling loss between the SOA and the silica waveguide was as small as 1 dB owing to a unique active alignment technique, was used for the experiment. We have verified the superior characteristics of the proposed operation scheme for the first time. Error-free wavelength-conversion operation for an NRZ signal at 40 Gb/s was confirmed

04/02399 Poplar growth and yield in short rotation coppice:model simulations using the process model SECRETS: Deckmyn, G. et al. Biomass and Bioenergy, 2004, 26, (3), 221–227

Producing a hydrogen-rich gas from diesel fuel enables the efficient generation of electricity in a fuel-cell-based auxiliary power unit. In recent years, significant progress has been achieved in diesel reforming. One issue encountered is the stable operation of water-gas shift reactors with real reformates. A new fuel processor is developed using a commercial shift catalyst. The system is operated using optimized start-up and shut-down strategies. Experiments with diesel and kerosene fuels show slight performance drops in the shift reactor during continuous operation for 100 h. CO concentrations much lower than the target value are achieved during system operation in auxiliary power unit mode at partial loads of up to 60%. The regeneration leads to full recovery of the shift activity. Finally, a new operation strategy is developed whereby the gas hourly space velocity of the shift stages is re-designed. This strategy is validated using different diesel and kerosene fuels, showing a maximum CO concentration of 1.5% at the fuel processor outlet under extreme conditions, which can be tolerated by a high-temperature PEFC. The proposed operation strategy solves the issue of strong performance drop in the shift reactor and makes this technology available for reducing emissions in the transportation sector.

Unidirectional three-phase rectifier with high power factor

A three-phase three-level rectifier with less power switches is proposed. Four power switches with voltage stress of half DC bus voltage are used in the circuit. A carrier-based current control strategy is proposed to draw the sinusoidal line currents with nearly unity power factor. The switching signals for power switches are derived from the DC bus voltage controller and neutral point voltage compensator. The mathematical model of the rectifier is derived and the control scheme is provided. To verify the proposed operation scheme, performance characteristics are given by experimental results.

Current sensorless three-phase NPC converter with less power switches

A three-phase NPC converter with less power switches is presented. Eight power switches and four clamped diodes with voltage stress of half DC bus voltage are used in the adopted circuit topology. A current sensorless control strategy is proposed to draw the balanced sinusoidal line currents in phase with phase voltages respectively. Bidirectional power flow operation is possible in the converter. A voltage-controlled scheme is employed to track the line current commands. The switching signals of the power switches are derived from the DC bus voltage controller and neutral point voltage compensator. A carrier-based PWM scheme is employed to draw the clean sinusoidal line currents with nearly unity power factor. The mathematical model of the converter is derived and the control strategy is provided. To verify the proposed operation scheme, performance characteristics are given by the simulation and experimental results.

Implementation of the AC∕AC converter based on neutral-point switch-clamped topology

A single-phase AC/AC converter based on neutral-point switch-clamped topology is proposed. The adopted AC/DC converter is controlled to have a stable constant DC bus voltage and draw a sinusoidal line current with unity input power factor. The AC side voltage of the AC/DC converter is controlled to generate a unipolar PWM waveform using the conventional half-bridge PWM rectifier and one AC power switch with voltage stress vdc/2. A carrier-based current control scheme is used in the inner control loop to track the line current command. A proportional-integral (PI) control is adopted in the outer control loop to maintain the constant DC bus voltage. On the inverter side, a sinusoidal output voltage is generated to provide a stable and clean source voltage to the critical load. A fixed-frequency current controller is adopted to generate the proper PWM waveform. A conventional half-bridge PWM inverter with one AC power switch is used in the DC/AC converter to generate the unipolar PWM voltage waveform on the AC side. The system model and control algorithm are described and analysed. To verify the effectiveness of the proposed operation scheme, experimental results based on a laboratory prototype were performed.

Half-bridge neutral point diode clamped rectifier for power factor correction

A high power factor rectifier based on neutral point clamped scheme is proposed. The voltage stress of each power semiconductor of the adopted rectifier is equal to the half dc bus voltage instead of full dc link voltage in the conventional switching mode rectifier. The control signals of the power switches are derived from the dc link voltage balance compensator, line current controller, and dc link voltage regulator. The hysteresis current control scheme is employed to draw a clean sinusoidal line current, high input power factor, regulated dc link voltage, and balance capacitor voltages. Three voltage levels are generated on the ac terminal of the adopted rectifier. To verify the proposed operation scheme, performance characteristics are given by the experimental results.

High-efficiency low-stress electronic dimming ballast for multiple fluorescent lamps

An electronic dimming ballast with a lead-lag tank operation (LLTO) having the properties of high efficiency and low stress is introduced in this paper. The ballast is configured with a voltage-fed half-bridge series-resonant parallel-loaded inverter (SRPLI) acting as a lamp driver. It is loaded with resonant tanks which are designed and operated to be capacitive and inductive to theoretically achieve both zero-voltage switching (ZVS) and zero current switching (ZCS) and to eliminate the reactive current circulating through the switches, resulting in low switching and conduction losses. Moreover, the merit of a successive lamp ignition can be attained with the proposed operation scheme so that current stress imposed on the switches can be reduced. With the plasma model of fluorescent lamps, the analysis, operating principle, and dimming control strategy of the electronic ballast are described in detail. On the other hand, the limitations of the proposed scheme are pointed out. Computer simulation results and experimental measurements are used to verify the theoretical prediction and analytical discussion.