Power Loss Calculation Research Articles

Methods Improving Energy Efficiency of Photovoltaic Systems Operating under Partial Shading

This article is devoted to the relevant problem of increasing the efficiency of PV systems. The presented analysis discusses the available methods for improving the power generation of PV modules under partial shading. Mathematical models for power loss calculation were compiled based on the results of this analysis. The proposed approach minimizes the negative impact of partial shading on the energy production of PV modules. It is based on the equalization of voltages of parallel-connected arrays of modules by installing additional power elements in them. The proposed solution is promising for various areas; it allows for the minimization of the unfavorable influence of existing urban objects (buildings, trees, communications, etc.) on the energy efficiency of PV modules. The obtained results are useful for the sustainable development of the urban environment in the context of digital transformation. They are the basis for the promising methodology of the parametric optimization of power plants using renewable energy sources.

Optimal Design of Computational Fluid Dynamics: Numerical Calculation and Simulation Analysis of Windage Power Losses in the Aviation

Based on the theory of computational fluid dynamics (CFD), with the help of the Fluent software and the powerful parallel computing capability of the super cloud computer, the single-phase flow transient simulation calculation of the windage power loss of the engagement spiral bevel gear pair (SBGP) was performed. The two-equation SST k-ω turbulence model based on the assumption of eddy viscosity was adopted, which was improved from the standard k-ε model combined with the Wilcox k-ω model. The SST k-ω turbulence model inherited the respective advantages of the Wilcox k-ω model in the near-wall region and the k-ε model in the free shear layer and could more accurately describe the resistance and separation effect of the gear tooth surface on the airflow. The simulation analyzed the airflow characteristics around SBGP and the mechanism of the windshield to reduce the windage loss of the gear. It also studied the influence of the windshield clearance and opening size on the windage power loss. Then the orthogonal experimental analysis method was adopted to perform numerical simulation analysis. The windage torque was studied under different clearance values between the windshield and the gear tooth surface, as well as the large end and the small end. The variance analysis was performed on the numerical simulation data. The results showed that when the windshield clearance value was 1 mm and the engagement opening was 30°, the windage torque was the smallest, and the effect of reducing the windage power loss was the best. According to the changes in the pressure, velocity, and turbulent kinetic energy cloud diagram of the flow field in the reducer during multi-group simulation tests, the local optimal windshield configuration was obtained, which provided a method for further research on the multi-objective optimization of the windshield and the windage loss of the gear pair under the oil–gas two-phase flow and also provided a reference for the practical engineering application of the windshield.

Elementwise power losses calculation in complex distribution power networks represented by hierarchical-multilevel topology structure

Wydawnictwo SIGMA-NOT wydaje czasopisma fachowe informujące swoich czytelników o najnowszych osiągnięciach naukowych i nowoczesnych rozwiązaniach technicznych w Polsce i na świecie, popularyzuje problemy techniczne oraz poszerza wiedzę i kulturę techniczną.

Transient Electro-Thermal Coupled Modeling of Three-Phase Power MOSFET Inverter during Load Cycles.

This study introduces an effective and efficient dynamic electro-thermal coupling analysis (ETCA) approach to explore the electro-thermal behavior of a three-phase power metal–oxide–semiconductor field-effect transistor (MOSFET) inverter for brushless direct current motor drive under natural and forced convection during a six-step operation. This coupling analysis integrates three-dimensional electromagnetic simulation for parasitic parameter extraction, simplified equivalent circuit simulation for power loss calculation, and a compact Foster thermal network model for junction temperature prediction, constructed through parametric transient computational fluid dynamics (CFD) thermal analysis. In the proposed ETCA approach, the interactions between the junction temperature and the power losses (conduction and switching losses) and between the parasitics and the switching transients and power losses are all accounted for. The proposed Foster thermal network model and ETCA approach are validated with the CFD thermal analysis and the standard ETCA approach, respectively. The analysis results demonstrate how the proposed models can be used as an effective and efficient means of analysis to characterize the system-level electro-thermal performance of a three-phase bridge inverter.

Повышение коэффициента полезного действия внецентроидного циклоидального зацепления

Gears with eccentric cycloidal engagement have large gear ratios, small overall dimensions, low noise and vibration levels. A relatively low efficiency factor limits their use in transmissions mechanisms, where involute gearing with gear ratios up to 10 and high efficiency (over 0.98) are in demand. The power losses of the eccentric cycloidal engagement are caused by friction in the jointly working kinematic pairs, which are formed by the gear with at least half of the pins, and the latter form the pairs with axles or sockets in the housing. It is possible to reduce the power loss by reducing the number of jointly working kinematic gear-pin pairs, which is done by modifying the theoretical profile of the gear. The modified profile is obtained from the theoretical one by removing the tops of the protrusions so that the remaining parts of the profile provide a smooth transfer of the load to a given number of pins. The study introduces a method for calculating power losses and the efficiency of eccentric cycloidal gearing for theoretical and modified gear profiles. Findings of research show that the modification of the cycloidal gear makes it possible to reduce the power loss in the engagement by more than 60% and to increase the efficiency by 0.03 ... 0.04 without a significant decrease in the strength of the working surfaces. The obtained result confirmed the possibility of increasing the efficiency of eccentric cycloidal gearing for it to be used in transmissions of transport vehicles.

Analytical Winding Power Loss Calculation in Gapped Magnetic Components

The analytical calculation of winding loss in gapped magnetic components is complex, and numerical analysis tools, such as finite elements analysis (FEA) tools, are commonly needed to characterize the windings. As FEA tools are used, the required design time of these types of components increases greatly when many simulations are needed to select the appropriate component for a given application, and simple analytical models become necessary to reduce the design time. In this paper, some analytical approaches for winding loss calculation in gapped magnetic components are reviewed and a general two-dimensional equivalent method, which aims to consider the frequency effects in conductors in a simplified manner, is proposed afterward. Due to its simplicity, it can be integrated into design and optimization tools in order to evaluate the influence of the air gap over the winding loss even at the early stages of the design process. The presented model shows good agreement with FEA simulations and measurements.

Calculation of power losses at given loads and source voltage in radial networks of 35 kV and above by hierarchical-multilevel structured topology representation

Wydawnictwo SIGMA-NOT wydaje czasopisma fachowe informujące swoich czytelników o najnowszych osiągnięciach naukowych i nowoczesnych rozwiązaniach technicznych w Polsce i na świecie, popularyzuje problemy techniczne oraz poszerza wiedzę i kulturę techniczną.

Design and Implementation a Single-Switch Step-Up DC-DC Converter Based on Cascaded Boost and Luo Converters

We designed and implemented a single-switch step-up DC-DC converter based on cascaded boost and Luo converters. The proposed converter demonstrated a quadratic voltage gain and a high efficiency, which makes it suitable for renewable energy applications, where a high voltage gain ratio is desired without imposing a high number of bulky items or employing a high duty cycle of the active switches. This converter benefits from the continuity of the input current waveform, which equips the maximum utilisation of renewable energy sources. While a transformer-less high voltage-gain was achieved, the voltage and current stresses of the power switch and diodes were kept low in comparison with the existing quadratic DC-DC converters. We analysed the converter in both continuous and discontinuous conduction modes. A non-ideal model of components was considered for power loss and efficiency calculations and comparisons. Finally, the simulation results were extracted with PLECS and validated with experiments on a 120 W prototype.

Selection of an IGCT for multilevel converters dedicated to high‐voltage direct current grid connection of offshore wind‐farms

Grid connection of remote offshore wind-parks uses high-voltage direct current technology and in order to reduce costs and losses and maximise profitability, semiconductor power losses must be minimised. To properly choose the semiconductors, it is necessary to estimate their losses for a large number of operating conditions. This article deals with a modelling approach to calculate power losses for many such operating conditions, based on measured semiconductor characteristics and the chosen multilevel modulation strategy. The case of the integrated gate-commutated thyristor is considered because, for a given device rating, it is possible to select an integrated gate-commutated thyristor benefiting from the best trade-off between on-state losses and turn-off losses, thus minimising the power losses of the two end-stations.

Design Optimisation of a Current-Fed Solid-State Transformer for MV Grid-Connected Applications

For integrating large batteries in the medium voltage grid, current fed solid-state transformers offer galvanic isolation and a significant weight and size reduction. While the power losses increase with frequency and flux density, the core volume is contrariwise. Therefore, a design optimisation to achieve minimum losses and/or a minimum volume is essential. An optimisation strategy is proposed in this paper to find the optimum operating frequency and core flux density under certain practical constraints such as winding voltage per turn, clearance between transformer windings, saturation flux density and minimum efficiency. Differently from previous works, the proposed strategy provides a holistic approach for the design considering all main power losses from all main components using nonsinusoidal voltage waveforms and different operating conditions. Analytical equations for the power losses calculation and the cores design are derived and validated using ANSYS and MATLAB Simulink software packages. Simulation results of the power loss calculation under different operating frequencies and duty cycles are presented and compared with the analytical results. A case study for designing a 1.0 MW, 0.6/18 kV current fed solid-state transformer is presented. The results of two optimisation objectives, minimum power losses or minimum total cores housing volume are also shown.

Analysis of hybrid switches symmetric flying capacitor multilevel inverter based STATCOM

Static compensator (STATCOM) based on cascaded H-bridge (CHB) multilevel inverter (MLI) uses a lower number of switches compared to the other topologies. Therefore, it is preferred due to lower switch losses. However, it is possible to reduce further the number of switches and its losses in cascaded STATCOM. In this context, a STATCOM based on a cascaded symmetric flying capacitor (SFC) constituted by IGBT and IGCT is presented in this paper. Furthermore, the common issue of imbalance due to asymmetric switch losses has been resolved by proposing and implementing multistage feedback voltage control with a combination of level-shifted and phase-shifted LS-PS PWM switching techniques. Moreover, the switching and conduction power losses calculations and efficiencies of SFC-MLI based on these semiconductors are also presented. Finally, the experimental results show the effectiveness of the proposed topology and the control strategy.

A Dumbbell Type (D-Type) multilevel inverter based on switched capacitor concept

ABSTRACT In this paper, a new single-phase seven level inverter with reduced device count is introduced. The structure can boost the input voltage by synthesising the capacitors’ voltages in predetermined current paths. A single DC voltage source is utilised to generate the output AC staircase waveform, which is facilitated via Nearest Level Control. Self-voltage balancing ability, less number of semiconductor devices, high efficiency and control simplicity are the most significant inherent attributes of the proposed circuit. It is also noticeable that in this configuration neither bulky transformer/inductor nor filters are applied. Power loss calculation and required capacitance of the proposed inverter are investigated and theoretical efficiency of 93.31% was reached. Moreover, the proposed converter operates under various load conditions with lower Total Harmonic Distortion compared to recent topologies. Ultimately, operating principles of the proposed D-Type seven-level Inverter and simulation results in MATLAB SIMULINK environment are validated by experimental ones obtained from the laboratory prototype.

A Study on Real Time IGBT Junction Temperature Estimation Using the NTC and Calculation of Power Losses in the Automotive Inverter System.

This paper proposes a junction temperature estimation algorithm for the insulated gate bipolar transistor (IGBT) based on a power loss calculation and a thermal impedance model for inverter systems. The Simulink model was designed to calculate the power losses of power semiconductor devices and to estimate the junction temperature with a simplified thermal impedance model. This model can estimate the junction temperature up to the transient state, including the steady state. The parameters used to calculate the power losses, the thermal resistance, and the thermal capacitance were optimized for a given inverter to be tested for improving the accuracy. The simulation results and experimental measurement data were compared to verify the proposed junction temperature estimation algorithm. Finally, the algorithm was installed on the inverter controller, and the performance was verified by comparing the real time estimation result with the measured temperature.

Power Loss Modes of Building-Integrated Photovoltaic Modules: An Analytical Approach Using Outdoor $I-V$ Curves

Using outdoor time-series I-V curves, the analytic I <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">sc</sub> -V <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">oc</sub> method was applied to glass/backsheet and glass/glass crystalline silicon module constructions with ventilated and insulated mounting configurations in order to explore contributing factors to degradation in the power performance. The rates of power loss modes; namely uniform current, recombination, series resistance, and current mismatch, were assessed for each module and configuration. The effect of thermal insulation was evident in the glass/backsheet module with an ethylene-vinyl acetate type encapsulant: the observed loss in the performance was chiefly originated from the resistive loss. The cell and metallization defects induced by thermo-mechanical stresses were believed to be main reasons. However, the double glass module with a polyvinyl-butyral type encapsulant was more resistant to thermal effects: a large increase in the uniform current, compensated by the resistive loss, was the main driver for the observed gain in the performance. For all modules and configurations, the calculated power loss mode rates were compared with the reported performance loss rates and they were found to be in close agreement. This analytic technique was found to be a powerful method in order to determine and quantify the individual contributions from specific power loss modes to overall module performance.

The Power Losses in Cable Lines Supplying Nonlinear Loads

This paper presents the skin effect impact on the active power losses in the sheathless single-core cables/wires supplying nonlinear loads. There are significant conductor losses when the current has a distorted waveform (e.g., the current supplying diode rectifiers). The authors present a new method for active power loss calculation. The obtained results have been compared to the IEC-60287-1-1:2006 + A1:2014 standard method and the method based on the Bessel function. For all methods, the active power loss results were convergent for small-cable cross-section areas. The proposed method gives smaller power loss values for these cable sizes than the IEC and Bessel function methods. For cable cross-section areas greater than 185 mm2, the obtained results were better than those for the other methods. There were also analyses of extra power losses for distorted currents compared to an ideal 50 Hz sine wave for all methods. The new method is based on the current penetration depth factor calculated for every considered current harmonics, which allows us to calculate the precise equivalent resistance for any cable size. This research is part of our work on a cable thermal analysis method that has been developed.

Systematic photovoltaic system power losses calculation and modeling using computational intelligence techniques

The performance of a photovoltaic (PV) system is highly affected by different types of power losses which are incurred by electrical equipment or altering weather conditions. In this context, an accurate analysis of power losses for a PV system is of significant importance. Hence, the systematic calculation of the PV system power losses based on recorded data of the main electrical and meteorological parameters is investigated in this paper. The proposed approach for power losses calculation investigates both array capture losses (e.g. losses resulted from cell temperature, soiling, low irradiance, snow cover, mismatching, and module quality degradation) and system losses (e.g. losses resulted from cabling, inverter, etc.). Moreover, according to the best of our knowledge, the paper proposes for the first time in the literature the modeling of all types of losses based on computational intelligence techniques. The proposed models can predict the future daily values for each type of loss solely based on the main meteorological parameters. The proposed losses calculation approach is applied to 8 years of recorded data for a 1.44 kWp rooftop PV system located in Denver, CO. Several prediction models are built based on the calculated values of the losses. The models are not only validated on the PV system itself, but also on another PV system with different electrical characteristics in Las Vegas, NV. As the results show, the loss prediction models developed in this paper perform accurately for the main PV system and are also applicable to other PV systems.

Operation and design analysis of an interleaved high step‐up DC–DC converter with improved harnessing of magnetic energy

SummaryIn this paper, a new interleaved DC–DC converter based on a coupled and a single input inductor is proposed. The suggested high step‐up converter utilizes various inductive and capacitive methods to transfer magnetic energy more efficiently. The output voltage is regulated with the switches' duty cycle and the coupled inductor (CI) turns ratio, which provide a wide output voltage range. Interleaving improves the converter reliability, employs both the first and third areas of CI's B‐H plane, cancels DC component of the CI, and reduces the input current ripple of the proposed converter with twice switching frequency. Utilization of two output ports for voltage stress and ripple reduction in each port, recycling the stored energy of inductances in both forward and flyback mechanisms, alleviation of switch voltage spikes, operation without circulating current, high power density, independency of switch voltage stress to the CI turns ratio, and continuous input current can be mentioned as other features. In this paper, continuous and discontinuous conduction modes' steady‐state analytics, power loss calculations, and design procedure of the proposed converter are followed with comprehensive comparisons to evaluate the capabilities. Eventually, experimental results are presented to validate theoretical calculations.

Оценка погрешности расчета нагрузочных потерь электроэнергии в распределительных электрических сетях напряжением 6—10 кВ

The aim of the study is to estimate the level of load losses for actual (nonuniform) loading of transformer substations in comparison with the load loss level under the conditions of their being uniformly loaded for a typical 6 kV urban distribution electric network. The extent to which such networks are equipped with automated information and measurement systems for fiscal electricity metering is extremely poor. Therefore, not only the load curves of the 6--10/0.4 kV substation transformers, but also their load factors are unknown in the majority of cases. Under these conditions, in calculating the load losses in 6--10 kV distribution electric networks, it is assumed that all substation transformers are uniformly (equally) loaded. The load losses in these electrical networks are calculated with a certain error associated with the assumption according to which the substation transformers are supposed to be uniformly loaded. Under these conditions, estimation of this error becomes of issue. The article describes the modeling, calculation and analysis of technical losses of electricity under the conditions of nonuniformly loaded transformers of a typical urban distribution network consisting of four transformers and four cables interconnecting them. The modeling and calculation of power losses were carried out using the RAP-10-st computer program for several different groups of transformer loading factors. Within each group, different subgroups were produced by rearranging the group loading factors. Each subgroup modeled a nonuniform transformers loading mode in the studied network. For each of these modes, the power losses were calculated and studied with the use of the RAP-10-st computer program. A conclusion has been drawn from the obtained analysis results regarding the error in determining the load losses associated with the assumption about the uniform loading of the substation transformers in the network. The obtained results may prompt electric grid companies to increase the extent of fitting their networks with automated information and measurement systems for fiscal electricity metering to improve the accuracy of determining the load losses.

A Switched-DC Source Sub-Module Multilevel Inverter Topology for Renewable Energy Source Applications

This article presents a sub-module topology for switched DC source cascaded multilevel inverter configurations that require fewer switching devices and can generate a high number of voltage levels that are suitable for renewable energy sources. The proposed sub-module topology comprises eight semiconductor switches and four DC voltage sources that generate fifteen voltage levels. Furthermore, the cascaded topology is presented to increase the output voltage levels and to minimize the number of components. The proposed sub-module inverter and its cascaded topology are compared with several multilevel inverters to indicate the advantages and drawbacks of the proposal. The comparison studies show that the proposed topologies require fewer switching devices and gate drivers in comparison with other multilevel inverter topologies. In addition, the proposed cascaded topology reduces the cost of the inverter when compared to other multilevel inverter configurations. Furthermore, the power loss calculations and the implementation of the proposed topology in grid-connected photovoltaic applications are simulated and analyzed. Finally, the performance of the proposal is verified by simulation and experimental results for both symmetric and asymmetric sub-module topologies as well as for the proposed cascaded topology.

A New High Gain Active Switched Network-Based Boost Converter for DC Microgrid Application

This paper deals with an active switched inductor network-based high gain boost converter. By using less number of components in circuit topology, a higher gain in voltage can be attained at a small duty cycle value by using the proposed converter, which helps in reducing the switch voltage stress and conduction loss. In addition, it draws continuous input current, has lower diode voltage stress, and lower passive component voltage ratings. The operating principles and key waveforms in Continuous Conduction Mode (CCM) and Discontinuous Conduction Mode (DCM) are presented. Parameter design, power loss calculation, characteristics, and comparative study with other non-isolated converters have been presented. Finally, a 200W hardware prototype is constructed and the viability of the proposed converter is verified through the experimentally obtained results.