Minimum Total Power Loss Research Articles

Voltage Zoning Regulation Method of Distribution Network with High Proportion of Photovoltaic Considering Energy Storage Configuration

Photovoltaics have uncertain characteristics. If a high proportion of photovoltaics are connected to the distribution network, the voltage will exceed the limit. In order to solve this problem, a voltage regulation method of a distribution network considering energy storage partition configuration is proposed. Taking the minimum total voltage deviation, the minimum total cost, the minimum total power loss, and the minimum energy storage device installation ratio as the objective function, and considering various conditions, such as voltage deviation constraint and energy storage constraint, a mathematical model of voltage regulation is established. Firstly, a high proportion of photovoltaics are connected to the distribution network, and the voltage deviation curve is obtained. The optimal k value is determined by the elbow rule. The voltage deviation curve of each node is clustered by the k-means algorithm so as to determine the energy storage device partition. The energy storage device is connected to various clustering centers, and then the weighting factor of each objective function is determined by the fuzzy comprehensive evaluation method. For comparison and analysis, (k + 1) schemes are determined through the partition configuration of (k + 1) energy storage devices. Then, the model is solved by particle swarm optimization, and the unit output result and the minimum objective function value are obtained. Finally, an example of IEEE33 is used to verify the effectiveness of the proposed model.

Optimization Method of Energy Storage Configuration for Distribution Network with High Proportion of Photovoltaic Based on Source–Load Imbalance

After a high proportion of photovoltaic is connected to the distribution network, it will bring some problems, such as an unbalanced source and load and voltage exceeding the limit. In order to solve them, this paper proposes an optimization method of energy storage configuration for a high-proportion photovoltaic distribution network considering source–load imbalance clustering. Taking the minimum total voltage deviation, the minimum total power loss and the minimum total operating cost as the objective function, and considering various constraints such as power balance constraints and energy storage operation constraints, a mathematical model for energy storage configuration optimization is established. Firstly, the source–load imbalance of the distribution network with a high proportion of photovoltaic is defined. Therefore, according to the 24 h photovoltaic and load data, the 24 h source–load imbalance can be obtained, and the optimal k value can be determined by the elbow rule, so that 24 h a day can be clustered into k periods by the k-means algorithm. Then, the fuzzy comprehensive evaluation method is used to determine the weight factors of each objective function in each period, and three scenes are determined according to the different amount of energy storage. Then, the hybrid particle swarm optimization algorithm proposed in this paper is used to solve the model, and the minimum objective function value, optimal position and optimal capacity of each energy storage grid in each scene are obtained. Finally, it is applied to an example of IEEE33. In the results, the total voltage deviation is increased by more than 10%, the total power loss is increased by more than 8% and the total operating cost is increased by more than 12%, which verifies the effectiveness of the proposed model.

Optimization and Influence of Micro-Chamfering on Oil Film Lubrication Characteristics of Slipper/Swashplate Interface within Axial Piston Pump

The overturning and eccentric abrasion of the slipper worsens the lubrication characteristics and increases the friction power loss and kinetic energy consumption of the slipper/swashplate interface to reduce the axial piston pump efficiency. A coupling lubrication numerical model and algorithm and a micro-chamfering structure are developed and proposed to predict more precisely and improve the lubrication characteristics of the slipper/swashplate interface. The simulation results reveal that the slipper without micro-chamfering overturns and contacts with the swashplate, while the one with micro-chamfering forms a certain oil film thickness to prevent this contact effectively. The minimum total power loss of the slipper/swashplate interface has to be effectively ensured under the worst working conditions, such as the high pressure, the low speed, the maximum swashplate inclination angle and the minimum house pressure. The optimal micro-chamfering width and depth are 1.2 mm and 3.5 μm or C1.2-3.5, the simulation average oil film thickness of which is approximately equal to the optimal analytical value. The experimental friction power loss of the slipper/swashplate interface is basically consistent with the simulation one, confirming the correctness and effectiveness of the coupling lubrication numerical model, and the optimization method and providing the further design direction of axial piston pumps.

Method for optimization of switching frequency in frequency converters

Purpose. To present a methodology for determining the optimal switching frequency in frequency converters and autonomous voltage inverters, the load of which is an asynchronous electric motor. The methodology is based on determining the dependences of static and dynamic power losses in the power switches of the inverter on the switching frequency and the dependence of power losses in the windings of an induction motor on the higher harmonics of currents, which also depend on the switching frequency. Methodology. Polynomial approximation of the energy characteristics of power transistors. General provisions of the theory of electrical circuits. The determination of additional power losses in the windings of an induction motor from higher harmonics is based on analytical calculation and simulation in the Matlab/Simulink software environment and a specialized program from the manufacturer of power switches Mitsubishi MelcoSim5.1. Findings. A method for optimizing the frequency of pulse-width modulation in frequency converters, the load of which is an asynchronous motor, is presented according to the criterion of the minimum total power losses in the power transistors of the inverter and the resistance of the motor windings. The proposed calculation technique allows determining the dependence of static and dynamic losses in power IGBT-transistors with a sufficiently high accuracy while being in the MelcoSim software environment. To calculate the losses in the motor, it is shown that the switching frequency of the power switches affects the harmonic distortion factor and the average value of the phase current of the induction motor. Provided that only the first harmonic of the current performs the useful action in an asynchronous motor, the dependence of additional power losses on the switching frequency is given. Originality. A method for optimizing the frequency of pulse-width modulation by the criterion of minimum additional power losses in the resistance of the motor windings from higher harmonics of the current and static and dynamic losses in the power transistors of the inverter is presented. An analytical dependence of additional power losses in the active resistance of the windings of induction motors as a function of the harmonic distortion factor of the phase current of an autonomous voltage inverter is presented. Practical value. The presented technique makes it possible to determine the optimal modulation frequency in frequency converters with asynchronous motors and to ensure the minimum total power losses and the maximum value of efficiency in the autonomous voltage inverter asynchronous motor system.

A Joint Control With Variable ZVS Angles for Dynamic Efficiency Optimization in Wireless Power Transfer System

Tight voltage regulation and high efficiency are fundamental objectives of wireless power transfer systems (WPTSs) as power supplies. Although the well-established impedance matching control attempts to achieve high efficiency, the associated extra dc–dc converters or hard switching of converters in WPTSs reduce the overall system efficiency, particularly for high-power applications. In this article, under zero voltage switching (ZVS) conditions, the minimum power loss point is derived and proved in detail with different ZVS angles. Moreover, a joint control with variable ZVS angles (JC-VZA) is proposed to ensure ZVS of all switches and achieve the required output, simultaneously. This control scheme is implemented by use of controllers in both sides of WPTSs, which adjust their respective ZVS angles for dynamic efficiency optimization. Under ZVS conditions, the proposed JC-VZA features an optimal amount of reactive power that achieves the minimum total power loss by significantly reducing the switching loss. As a result, the experimental results obtained from our WPTS prototype verify its superiority. With a coupling coefficient $k$ of 0.2 or 0.15, the maximum efficiency reaches 96.8% or 95.0% under the power rating of 288 W (rated load) as well as 92.4% or 88.7% in the case of light load (9% of 288 W).

Influence of fiber fusion on loss and beam quality in multi-mode injection conditions

A simple model based on coupled-mode theory to describe mode evolution and fiber fusion loss at the fusion splicing point is presented. Using the model, the simulations of fundamental mode loss and total power loss, as well as beam quality evolution generated by the fusion interface under different deviation including offset and tilt, are performed for matched and unmatched fiber splicing. In the simulations we consider three states: minimum total power loss state, minimum fundamental mode loss state, and best beam quality state. From the simulations, some interesting results, such as the fact that with certain fusion offset, the output beam quality will be improved and the ratio of fundamental mode will increase, are predicted. In addition, some references for good beam quality as well as low total power loss fusion employing a balance between axial offset and tilt during the actual fusion splice process are provided.

Power Loss Model and Device Sizing Optimization of Si/SiC Hybrid Switches

Si/SiC hybrid switches of parallel Si insulated-gate bipolar transistor (IGBT) and SiC metal-oxide-semiconductor field-effect transistor (mosfet) offer most of the SiC benefits but at a much lower cost in comparison to a full SiC solution. The hybrid switch can be optimized to achieve a minimum total power loss while utilizing the smallest SiC chip size without exceeding the specified maximum junction temperature. In this article, we first develop a generalized power loss model for Si/SiC hybrid switches with total power loss and junction temperature as outputs and SiC device size as a continuous input variable, and then develop a methodology to minimize SiC device size while optimizing total IGBT/mosfet power loss and ensuring maximum junction temperature still below 150 °C. The power loss model is experimentally validated through both simple double pulse testing and a dc-dc buck converter case study. Using the model and optimization methodology, a minimum SiC device size can be obtained with optimized power loss and safe operation temperature.

A Novel Approach Based on Crow Search Algorithm for Solving Reactive Power Dispatch Problem

This paper presents a novel meta-heuristic approach based on the crow search algorithm (CSA) for solving the optimal reactive power dispatch (ORPD) problem. The ORPD is formulated as a nonlinear optimization problem designed to minimize power losses while satisfying the required constraints. The CSA is a recent efficient approach that depends on the intelligent behavior of crows. Nowadays, it has been used to solve many complex engineering optimization problems where it has proven its power and effectiveness. Motivated by the high ability in solving complex optimization problems and faster convergence of CSA, this paper proposes a novel approach to solve the ORPD problem. Furthermore, the settings of control variables such as generator terminal voltage, tap changer positions, and capacitor banks are determined to achieve the minimum total power loss while satisfying a set of nonlinear constraints. The accuracy and the performance of the proposed algorithm were performed and compared to other meta-heuristic algorithms reported in the literature. Several tests are applied on two standard test systems, including IEEE 14-bus and IEEE 30-bus as well as on the large-scale Tunisian 86-bus system. In addition, a sensitivity analysis has been performed to valid the performance of the CSA in solving the ORPD problem. We demonstrate that the proposed CSA provides a supremacy results and statistically significant in solving ORPD problems (for IEEE-14 bus p < 0.0006 , for IEEE-30 bus p < 0.006 , and for Tunisian 86-bus p < 0.0000001 ).

Probabilistic Load Flow Solution Considering Optimal Allocation of SVC in Radial Distribution System

This paper proposes a solution procedure for probabilistic load flow problem considering the optimal allocation of Static Var Compensator (SVC) in radial distribution systems. Pareto Envelope-based Selection Algorithm II (PESA-II) with fuzzy logic decision maker is developed to determine the optimal location and size of SVC based on the minimum total power losses and Voltage Deviation (VD). Combined cumulants and gram-chalier expansion are used for solving the probabilistic load flow problem. The proposed algorithm is tested on 33- bus and 69-bus distribution systems. The developed algorithm gives an acceptable solution with low number of iterations and less computation cost compared with the Monte Carlo method.

Optimal reactive power dispatch solution by loss minimization using moth-flame optimization technique

In this paper, a newly surfaced nature-inspired optimization technique called moth-flame optimization (MFO) algorithm is utilized to address the optimal reactive power dispatch (ORPD) problem. MFO algorithm is inspired by the natural navigation technique of moths when they travel at night, where they use visible light sources as guidance. In this paper, MFO is realized in ORPD problem to investigate the best combination of control variables including generators voltage, transformers tap setting as well as reactive compensators sizing to achieve minimum total power loss and minimum voltage deviation. Furthermore, the effectiveness of MFO algorithm is compared with other identified optimization techniques on three case studies, namely IEEE 30-bus system, IEEE 57-bus system and IEEE 118-bus system. The statistical analysis of this research illustrated that MFO is able to produce competitive results by yielding lower power loss and lower voltage deviation than the selected techniques from literature.

Dependence of energy characteristics of Stirling gas refrigerating machines on external and internal parametric values

The question of forcing the heat engines Stirling is important. The increase of cold-productivity of the refrigeration machine is carried out by means of change of pressure filling and Internal parametric values of refrigerating machines: filling pressure, relative temperature, relative dead volume, the ratio of the maximum described volumes working cavities and external: frequency of rotation effects on the energy characteristics of machines. The article presents the assessment of the impact of these parametric values on the real characteristics of refrigerating machines and identify opportunities and ways of forcing speed of the drive. To work with minimum total power losses and maximum cooling capacity of the filling pressure and speed must not be changed arbitrarily. The relationship between them via the same minimum total losses in the regenerator.

Minimization of the Power Losses in IGBT Multiphase Inverters with Carrier-Based Pulsewidth Modulation

Nowadays, there is an increasing interest toward multiphase drives, particularly for medium- and high-power applications. In this paper, some modulation strategies for multiphase voltage-source inverters are compared and the modulation strategy with the minimum switching losses is determined. If the switching devices of the inverter are insulated-gate bipolar transistors or bipolar junction transistors, this modulation strategy turns out to be the one with the minimum total power losses. Simulation and experimental results confirm the validity of the analytical approach and the feasibility of the proposed modulation strategy.

Adaptive Digital Controller and Design Considerations for a Variable Switching Frequency Voltage Regulator

An auto-tuning adaptive digital controller with maximum efficiency point tracking to optimize dc-dc converter switching frequency is presented in this paper. The adaptive-frequency-optimization (AFO) controller adjusts the dc-dc converter switching frequency while tracking the converter minimum input power (maximum efficiency) point under variable operation conditions of the power converter. The AFO digital controller continuously finds the optimum switching frequency that will result in minimum total power loss while converter parameters and conditions vary. Moreover, the presented controller addresses the issues that are associated with implementing variable switching frequency in digital controllers, including limit cycle oscillation and possible performance degradation, by using a dynamic algorithm to maintain converter system stability under variable switching frequency operation. In this paper, the proposed controller is discussed, analyzed, and its digital control algorithms and experimental results are presented.

High Current Tests of Metal Fiber Brushes

Simultaneous measurements Were made of the friction force and electrical contact drop for small metal fiber brushes at high current densities (12.4 MA/m2). Comparative testing was performed with both polarities of copper, silver-plated copper, and silver fiber brushes on copper and On silver-plated copper slip rings in humidified carbon dioxide. Friction increased from 0.3 to 1.4, while the contact drop decreased as more silver was added. At a contact force of 0.23 N and a sliding speed of 12 m/s, minimum total power loss was found for the bare and the silver-plated copper fibers on the copper sllp ring. However, the optimum material selection will depend on current density, sliding speed, and contact force Used for a specific application. Maximum test duration has been extended to almost 500 h, with indications of slight improvement of both contact drop and wear rate as the operating time is increased. Dimensionless wear rate was only 1.9 x 10-11. With added cooling capability, successful Shortterm operation has been achieved with current density in the individual fibers as high as 100 MA/m2 (65 000 A/in2).

Optimal design of front-contact metallization for photovoltaic solar cells

A new approach to the design of the front metal grid in standard photovoltaic solar cells is presented which allows the synthesis of the optimal grid profile for an arbitrary cell geometry. An expression for the total power loss is derived taking into account ohmic losses in the metal grid, losses in the front diffused layer of the cell and losses due to grid shadowing. The loss is minimized by a variational method solving the differential Euler equation and the optimal grid profile is obtained; then the expression for the minimum total power loss is derived. Applications to rectangular and circular solar cells are presented.

Closure to “Discussion of ‘Design of Multi-Recess Hydrostatic Journal Bearings for Minimum Total Power Loss’” (1975, ASME J. Eng. Ind., 97, pp. 383–384)

Closure to “Discussion of ‘Design of Multi-Recess Hydrostatic Journal Bearings for Minimum Total Power Loss’” (1975, ASME J. Eng. Ind., 97, pp. 383–384)

Design of Multi-Recess Hydrostatic Journal Bearings for Minimum Total Power Loss

The design problem is formulated for multi-recess hydrostatic journal bearings with a design criterion of minimum total power loss. The design is subject to the constraints of constant ratio of the recess area to the total bearing area and maximum load capacity for a given recess geometry. The L/D ratio, eccentricity ratio, ratio of recess area to total bearing area, and shaft rotational speed are considered as parameters. The analysis is based on the bearing model of Raimondi and Boyd [1]. This model is generally valid for low-to-moderate speeds and a ratio of recess area-to-total bearing area of approximately 0.5 or greater. Design charts are presented for bearings having a ratio of recess area-to-total bearing area of 0.6 and employing capillary and orifice restrictors, these being the most common types of compensating elements. A design example is given to illustrate the use of the design charts.

Magnetic properties of grain-oriented silicon iron. Part 4: Relationship of domain spacing, grain size, sheet thickness and power loss

Measurements of total power loss and domain spacing have been made on individual grains of varying size in grain-oriented silicon iron at various frequencies (20–150 Hz) at 1.5 Wb/m2, using recently developed experimental techniques, Minimum total power loss occurs in 0.013 in (0.033cm) thick material at a grain size of about 0.7cm. In the grains studied, the walls followed a simple bar arrangement and moved smoothly without jerks, and repetitively, over approximately the same distances, the equilibrium wall spacing was independent of the frequency. The relevance of these results to explanations of the anomalous loss based on domain-wall models is discussed.