Steady-state Performance Analysis Research Articles

Steady-state analysis of a hybrid power supply system using an induction generator with a shunt AC/DC converter

Hybrid power supply systems (HPSSs) are considered as a good option for electric power supply of remotely located from the grid consumers due to significant fuel savings compared to diesel sets. Quick development and improvement of HPSSs may be achieved using specialized methodologies and programs. In the paper a schematic diagram is proposed and operation principles of a 400 V / 50 Hz HPSS were developed. The system’s main component is the master generating unit of the hydropower plant using a 250 kW induction generator (IG). The voltage of the system is controlled by the controller of the AC/DC power converter. The electrical frequency of the system is controlled by the speed controller of the hydropower turbine. A wind turbine, an energy storage system and a regulated dump load are connected to the IG through the AC/DC converter. Goal. The paper aims to develop a methodology for steady state performance analysis of the hydraulic turbine driven isolated IG operating in parallel through an AC/DC power converter with additional sources and consumers of active power. Methodology. The methodology for evaluation of performance characteristics of the IG operating in the proposed system has been developed. The methodology is based on the equivalent circuit of the system, equations of active and reactive power balance in the system and the superposition method. Results. The equations of frequency, voltage and power regulators of the system are given. The performance characteristics of the IG operating in the system supplying resistive and RL load in «constant voltage – constant frequency» mode are obtained. Novelty. The developed methodology is innovative in taking into account the control algorithms of the system. The comparative analysis of the IG’s performance operating in the stand-alone generating unit and in the generating unit connected to the proposed system is performed. Practical value. The developed methodology can be used for development and performance improvement of hybrid AC power systems.

Steady-state fuel performance analyses for the preliminary fuel concept of general atomics fast modular reactor

This manuscript presents the fuel performance analysis results of the General Atomics Fast Modular Reactor (FMR) based on an axi-symmetric (2D-RZ) geometry. Three fuel performance model sets that fit the FMR fuel specifications best, i.e., a BISON baseline model set, a BISON diffusion enhancement model set, and a BISON-FASTGRASS model set, were identified and evaluated against a series of relevant experimental cases featuring high burnup and low irradiation temperature conditions. The three BISON-based model sets were then utilized to conduct a comprehensive fuel performance analysis of the FMR fuel under normal operation including the shutdown/restarting periods for refueling. The evaluation of the fuel performance parameters, represented by temperature, internal pressure, stress, and strain, shows that the FMR fuel maintains its thermal and mechanical integrity during normal operation. Technology gaps and limitations are also discussed to guide future efforts for extending the performance analysis to transient scenarios as well as improving the fuel performance evaluation through experiments.

Managing cutoff-based shipment promises for order fulfilment processes in warehousing

AbstractWarehouses recently face increasing stress imposed by a volatile customer demand and increasing customer expectations in terms of ever shorter order response times. In that respect, warehouses more and more offer same-day and next-day shipment conditions. However, same-day shipment promises are challenging to fulfil, especially as the order fulfilment process operates against fixed deadlines imposed by the predefined truck departure times. As a natural mitigation strategy, warehouses set a cutoff point and offer same-day shipment only to customers that order until the cutoff point, but next-day shipment to all customers ordering thereafter. Setting an appropriate cutoff point is challenging as it affects multiple facets of the service quality, such as the order response time and the service level. In this paper, we study the design of cutoff-based shipment promises for stochastic deadline-oriented order fulfilment processes in warehouses. We present a discrete-time Markov chain model for exact steady-state performance analysis and propose two novel performance measures – $$\alpha-$$ α - and $$\beta-$$ β - cutoff service level – for service level measurement in these systems. We numerically show the benefit of cutoff-based shipment promises. Even with a late cutoff point, there is a significant gain in the system performance. Furthermore, we find that warehouses should set the cutoff point such that it balances customer expectations in terms of service level and order response time. Finally, warehouses can improve their shipment promises when referring to $$\beta-$$ β - instead of $$\alpha-$$ α - cutoff service level and by implementing measures reducing the utilisation and the variabilities of the order fulfilment process.

Improved Dual Active Bridge DC–DC Converter With Symmetric Bipolar Output by Utilizing a Switched-Capacitor Circuit for Bipolar DC Distribution System

The bipolar dc distribution system is a promising solution due to its advantages in efficiency and reliability, but there are also challenges of pole voltage imbalance. By using a simple switched-capacitor circuit, this paper presents a semi-dual active bridge converter with symmetrical bipolar output characteristics. The converter is capable of single-stage power conversion, offering the advantages of low cost and high-power conversion efficiency. Moreover, the symmetrical bipolar output voltage can be achieved without an additional voltage balancer and feedback control under unbalanced load conditions, which reduces system cost and control system complexity. In addition, the proposed converter also has a significant advantage over existing solutions in terms of the number of semiconductor devices and magnetic components. A detailed analysis of the proposed converter is presented, including the operation principle, steady-state performance, soft-switching performance, voltage gain, voltage/current stresses, efficiency and loss analysis, and control method. Finally, a 1-kW prototype is developed and tested to verify the performance of the proposed converter.

Piecewise Linear Power Flow Algorithm of DC Distribution Networks Considering Automatic Adjustment of VSC Control Strategy

Voltage source converter (VSC)-based DC distribution networks (DCDNs) can automatically adjust the control strategy of overloaded VSCs to adapt to the variation in renewable energy power, but it brings difficulties to the steady-state performance analysis of DCDNs. This paper presents a piecewise linear power flow (PLPF) algorithm to estimate the joint effect of power disturbance and VSC control strategy adjustment on steady-state performance. Firstly, according to the VSC power balance, the critical point of the VSC hitting the capacity limit is directly determined, and the power variations in each node before VSC control strategy adjustment are obtained. Then, the linear power flow is revised considering the VSC control strategy adjustment. Inversion of the block Jacobian matrix is used to improve the calculation speed of linear power flow revision. Finally, linear power flow calculation is performed in each stage, and the steady-state performance is obtained by using the superposition method. Simulation results show that the proposed PLPF model can estimate the steady-state performance faster and more simply.

Dynamic and steady-state performance analysis of a linear solenoid parallel elastic actuator with nonlinear stiffness

Dynamic and steady-state performance analysis of a linear solenoid parallel elastic actuator with nonlinear stiffness

Aero-Engine Preliminary Design Optimization and Operability Studies Supported by a Compressor Mean-Line Design Module

An approach for preliminary aero-engine design, incorporating a mean-line code for the design of axial-flow, multi-stage compressors, is presented. The compressor mean-line code is developed and integrated within a framework for the preliminary design and assessment of aero-engine concepts. It is then combined with modules for compressor map generation, multi-point engine design, steady-state and transient engine off-design performance and aircraft mission analysis. Implementation examples are presented, demonstrating the determination of the optimal combination of compressor and engine design parameters for achieving minimum fuel burn over a specific aircraft mission, while obeying constraints that guarantee operability over the entire flight envelope. Constraints related to compressor stability during transient maneuvers between idle and static take-off conditions and engine temperature limits at maximum take-off are respected by the final design. The results demonstrate the potential for design trade-offs between engine performance at the aircraft mission level and compressor aerodynamic stability.

The nature of silica-to-alumina ratio effect on lean methane oxidation over Pd/Beta zeolite catalysts

The silica-to-alumina ratio (SAR) effect on lean methane oxidation over Pd/Beta catalysts was investigated. Light-off test, steady-state performance and kinetic analysis demonstrate the activity of Pd/Beta catalysts shows a volcano-shaped dependence on SAR. Pd/Beta402 presents the highest activity among all samples, regardless of the presence of water. By the employment of H2-TPR, CO-chemisorption, STEM-EDS, TGA and NH3-TPD, it is found that the activity of Pd/Beta catalysts is essentially influenced by their acidity, which is the nature of the SAR effect on methane oxidation. Increasing SAR leads to lower acidity, resulting in less formation of inactive Pd2+ and higher hydrophobicity which benefit methane oxidation. However, the larger PdO particles are formed at the same time, leading to a decrease in the amount of exposed PdO which is detrimental to methane oxidation. This work can guide the design of state-of-the-art zeolite-supported Pd-based methane oxidation catalysts.

Steady-state performance analysis of loop heat pipe radiator in space reactor

The loop heat pipe has a good application prospect in the field of space reactor radiator because of its characteristics of the separation of gas/liquid pipelines and the long-distance efficient heat transfer. The comprehensive performance analysis of loop heat pipe radiator for space reactor is carried out by the heat balance calculation method based on energy coupling iteration proposed in this paper. The loop heat pipe radiator models of different configurations were developed using the mass and energy conservation theory. The models were validated by experimental data of the loop heat pipe under various heat loads. The model in this paper can correctly simulate the steady-state operation characteristics of loop heat pipe, and evaluate the design of loop heat pipe radiator for space reactor. The performance of loop heat pipe radiator was analyzed in this paper under various design conditions such as power, evaporation temperature, and heat sink temperature. The results show that the thermal operating parameters have significant effect on characteristics of loop heat pipe radiator. The design length of the condenser pipe was considered as an important factor to achieve steady state heat balance under different design power. Meanwhile, the operation characteristics of loop heat pipe radiator with different configurations were compared, which demonstrated that the performance of panel-type radiator was better than fin-type radiator.

Steady-State Performance Analysis of the Arctangent LMS Algorithm With Gaussian Input

The adaptive filtering algorithms based on the arctangent cost function framework have shown robustness against impulsive noise. In this brief, the standard least mean square (LMS) algorithm under this framework is concentrated on, which is called the arctangent LMS (ATLMS) algorithm. The steady-state excess mean square error (EMSE) and mean square deviation (MSD) of the ATLMS algorithm are analyzed using the energy conservation relation. In stationary environment, both Gaussian and non-Gaussian situations are discussed. The closed-form expressions of the steady-state EMSE and MSD are obtained using Taylor’s expansion. In non-stationary environment, a first-order random-walk model is used for modeling the time-varying optimal weight. Theoretical steady-state performance and the optimal step size are derived. Simulation results under different noise environments verify the validity of our theoretical findings.

Simulation and Analysis of Steady-State and Dynamic Performance of Asymmetric Half Bridge Converter-Fed SRM using Finite Element Analysis

Variable reluctance motor is becoming a competitive candidate among all other machines available due to its added features. The development of variable reluctance motor is simple due to the simple construction of rotor without any permanent magnets. Reduced complexity in structure paves the way for low-cost motor and it also leads to the application of SRM in a wide manner. In order that the machine could be used in various applications, it is much necessary to have a suitable driving system (converter configuration). The best choice of converter for SRM would pave the way for desirable control of the machine. The proposed work includes the design and analyses of an appropriate driver configuration for SRM and interface it with the motor which is already designed and analyzed using ANSYS Maxwell. The design and analysis of the converter are carried out using the ANSYS Simplorer tool box.

Electromagnetic design and performance analysis of coreless superconducting machine

With the development of offshore wind power generation, there is an urgent demand for high-power wind turbines. Superconducting machines with high power density and efficiency are one of the solutions for wind turbines of 10 MW and above. This paper summarizes the existing superconducting synchronous generators in several structural forms and features, and considers that the coreless machine can avoid the impact of core oversaturation on the power density increase of the machine, which is the development direction of the superconducting machine. In this paper, the structural topology of a coreless superconducting machine is established and the similarities and differences between its structure and that of a conventional one are analyzed. Since the conventional magnetic circuit method is no longer applicable, a designing model based on the analytical method is established for the designing of coreless machines, which considers the effects of slotless armature, the superconducting excitation winding thickness and the nonlinearity of the ferromagnetic material. Based on this method, the magnetic field distribution is solved and verified with the finite element method. Further, the effect of the superconducting excitation winding opening angle on the magnetic field in the air gap of the machine is investigated, and the machine structure is optimized based on this. The steady-state and transient performance analysis of the machine is carried out to illustrate the operating characteristics of the coreless superconducting machine. The design method and analysis results of this paper can provide a reference for building higher power density coreless superconducting wind turbines.

An Improved Non-Isolated Quadratic DC-DC Boost Converter With Ultra High Gain Ability

This paper introduces an improved quadratic DC-DC boost converter to provide an ultra-high level voltage gain with the switched-capacitor cell based structure. The proposed converter has the ability to excel the output voltage gain to the ultra-high level without any voltage doubler circuit. Hence, the total number of components is less compared to the conventional topologies. The proposed converter offers reduced voltage stress on the capacitors, diodes, and semiconductor switches while generating a high voltage gain effect with a low duty cycle. In addition, the continuous source current (CSC) and input-to-output side ground-sharing features are also available for renewable energy applications. The steady-state and comparative performance analysis with similar topologies and power loss calculations are presented in this paper. Furthermore, the simulation results extracted from the Matlab/Simulink are compared and analyzed with the conventional topology. Finally, the experiments are carried out by designing a 150 W laboratory prototype where the peak efficiency is found 90% while delivering 80 W power to the load side.

Diffusion Mixture Minimum Total Error Entropy Adaptive Filtering Algorithm and Its Performance Analysis

The distributed adaptive filtering algorithms applied in the error-in-variables (EIV) model consider that both input and output signals suffer from noise disturbance for practical applications. However, the traditional distributed adaptive filtering algorithms applied in the EIV model cannot combat non-Gaussian noises well. To address this issue, this paper develops a mixture minimum total error entropy (MMTE) method and its diffusion mixture minimum total error entropy (DMMTE) algorithm. The proposed DMMTE has the significant performance improvement in non-Gaussian noises, and is more general than the diffusion minimum total error entropy (DMTE) algorithm. To select mixture coefficient effectively, a variable mixture coefficient method is further proposed to generate a variable DMMTE (VDMMTE) algorithm. Moreover, the local mean stability analysis and steady-state performance analysis of DMMTE are presented. Simulations verify the correctness of the theoretical analysis and illustrate the performance superiority of the proposed DMMTE.

Thermo-enviro-exergoeconomic analysis and multi-objective optimization of a novel geothermal-solar-wind micro-multi-energy system for cleaner energy production

Renewable energy- based multigeneration systems have been proposed as a viable means of achieving a net-zero future as these systems can decarbonize the power and energy sector simultaneously. Although there has been significant development in this research field, the large sizes of the existing systems in literature are a major setback in the adoption/implementation of these systems. Furthermore, the unavailability of solar and wind energy during some hours daily makes solar or wind energy-based multigeneration systems undesirable in many applications. Considering the urgency/importance of attaining a net-zero emission future, this study presents a novel multi-energy system that can bridge the existing gaps in literature. Therefore, the thermodynamics, economic, and environmental analysis novel CO2-based geothermal micro-multi-energy system that is hybridized with a concentrated solar photovoltaic/thermal system and wind turbine is presented in this paper. The proposed energy system presents an innovative method that can be effectively used to decarbonize future energy production. The multi-energy system is modeled to produce electricity, refrigeration effect, space heating, hydrogen, and hot water. The economic study in this paper also analyzed the Levelized cost of electricity (LCOE), Levelized cost of cooling (LCOC), and Levelized cost of hydrogen (LCOH). A multi-objective optimization operation is also carried out on the modeled system in order to determine the optimal exergy efficiency and total product unit cost. The steady-state performance analyses showed that the overall energetic and exergetic efficiencies of the system are 48,61% and 88.31% and these efficiencies can be as high as 51.76% and 95.08% respectively when the system is optimized with reference to exergy efficiency. The LCOE, LCOC, and LCOH at the optimal total product unit cost are 0.04529 $/kWh, 0.004564 $/kWh, and 28.86 $/kg.

Thermionic conversion performance analysis of the single-cell thermionic fuel element based on FROBA-THERMION code

The thermionic conversion performance of the single-cell thermionic fuel element (TFE) is influenced by fuel mass transfer and other parameters. With the consideration of current flow and heat transfer, the thermionic conversion model and the modified heat transfer model were implemented in FROBA-THERMION, a steady-state performance analysis code for the single-cell TFE. Afterward, both implemented models were verified by comparing with experiments or calculation results of KATET (a complex code developed by the Research Inst of SIA 'Lutch' of Russia to simulate single-cell TFE life behavior). Further, a steady-state performance simulation of the single-cell TFE was carried out. The results indicate that the thermionic conversion efficiency will be decreased due to the emitter temperature flattening caused by fuel mass transfer. In addition, the influence of several key parameters on thermionic conversion efficiency and measures to improve the thermionic conversion efficiency were analyzed.

Steady-state performance analysis of permanent magnet synchronous generator with capacitive assistance

This paper presents the steady-state performance analysis of an electrical connection scheme that improves the power factor and output power of a three-phase interior-rotor permanent magnet generator (IPMSG). The inverse saliency ratio ranges from 1 to 6. A three-phase capacitor is connected across the stator winding, close to the generator load, for each ratio. Leading current from the capacitor was used to improve the lagging power factor of the machine, maintain the load voltage under varying load conditions, and enhance the output power conversion ability, which the inverse saliency ratio scheme could not do alone, and without the need for external power electronics control circuitry. The numerical solution of the study was implemented in MATLAB®. The proposed IPMSG performance curves were enhanced with the generator yielding an improved output power of about 11.1% when compared with the inverse saliency ratio scheme without capacitors.

Robust adaptive filtering algorithms based on the half‐quadratic criterion

Recently, robust adaptive filtering algorithms have attracted the interest of researchers and have been extensively studied. However, most of these methods suffer from the non-convexity of their performance surfaces, which results in reduced convergence rate and filtering accuracy. To address this problem, we present a novel robust half-quadratic criterion (HQC) adaptive filtering algorithm by utilizing a convex cost function. In contrast with conventional methods, the proposed HQC can introduce a more effective performance surface, allowing a gradient-based strategy to provide significant performance improvements in convergence speed and robustness against impulsive noise. Furthermore, to enhance the performance of the HQC adaptive filter, a variable step-size (VSS) version, the VSS-HQC algorithm, has also been introduced. Using the energy conservation method, the theoretical expressions for the transient, steady-state, and tracking performance analysis of the proposed HQC algorithm are studied under the Gaussian noise assumption. Then, we examined the theoretical analysis of the HQC using various numerical simulations for system identification to validate the findings. Finally, we compared the performance of the HQC and VSS-HQC algorithms to their competitors in both Gaussian noise and non-Gaussian noise scenarios through numerical experiments.

Diffusion adagrad minimum kernel risk sensitive mean p-power loss algorithm

The most diffusion algorithms based on the mean square error (MSE) criterion generally have good performance in the presence of Gaussian noise, however suffer from performance deterioration under non-Gaussian noises. To combat non-Gaussian noises, a diffusion minimum kernel risk sensitive mean p-power loss (DMKRSP) algorithm is first designed using a generalized robust kernel risk sensitive mean p-power loss (KRSP) criterion combined with stochastic gradient descent (SGD). Then, due to more error information than SGD, the adaptive gradient (Adagrad) is used in DMKRSP to generate a diffusion Adagrad minimum kernel risk sensitive mean p-power loss (DAMKRSP) algorithm. Finally, the theoretical analysis of DMKRSP and DAMKRSP is presented for steady-state performance analysis. Simulations on system identification show that both DMKRSP and DAMKRSP are superior to other classical algorithms in term of robustness and filtering accuracy.

Adaptive Control with Switched Reference Models: Application to Learn-to-Fly

Learn-to-Fly (L2F) is a new framework that aims to replace the traditional iterative development paradigm for aerial vehicles with a combination of real-time aerodynamic modeling, guidance, and learning control. To ensure safe learning of the vehicle dynamics on the fly, this paper presents an adaptive control ()-based scheme, which actively estimates and compensates for the discrepancy between the intermediately learned dynamics and the actual dynamics. First, to incorporate the periodic update of the learned model within the L2F framework, this paper extends the architecture to handle a switched reference system subject to unknown time-varying parameters and disturbances. The paper also includes analysis of both transient and steady-state performance of the architecture in the presence of nonzero initialization error for the state predictor. Second, the paper presents how the proposed scheme is integrated into the L2F framework, including its interaction with the baseline controller and the real-time modeling module. Finally, flight tests on an unmanned aerial vehicle validate the efficacy of the proposed control and learning scheme.