Power Loss Model Research Articles

Optimal Braking Torque Distribution of Dual-Motor Front-Rear Individually Driven Electric-Hydraulic Hybrid Powertrain Based on Minimal Energy Loss

Regenerative braking is one of the most important methods for improving energy utilization in electric vehicles. Electric vehicles with front-rear, individually driven configurations exhibit significant potential and flexibility for recovering braking energy. To improve the system’s high-power impact tolerance, a high-power density hydraulic energy storage system can be incorporated to facilitate a full-drive dual-motor electric–hydraulic hybrid (DMEHH) powertrain. The DMEHH system is composed of an independently driven electric–hydraulic hybrid front axle and a purely electric rear axle. In this study, a method for distributing braking torque to minimize energy loss was devised based on the proposed DMEHH powertrain. Power loss models for both the electric and hydraulic subsystems have been developed. Loss minimization control was adapted for the power loss model of the permanent magnet synchronous motors in the powertrain, and the front-rear and front electric–hydraulic torque braking distribution maps were calculated using the energy-loss minimization rule. The application of torque distribution maps resulted in energy losses less than those of the general ideal torque distribution for all braking conditions. The energy loss decreased by 27.2% when the loss minimization control method was used in the WLTC cycle, and decreased by 29.1%, 25.5%, and 21.6% in UDDS, NEDC, and US06 driving cycles, respectively.

Preliminary modelling of power losses in roller chain drive: application to single speed cycling

A quasi-static chain drive model is proposed. This model, consistent with single speed cycling application, applies to simple two sprocket drives. The kinematics of the transmission is determined, including the capture and release positions of the rollers and the influence of the polygonal effect. The tensions into the links and the contact forces (between rollers and sprocket) are then calculated based on the results of the kinematic analysis. Both chain strands are assumed to be straight and their tension are considered as imposed. An estimate of the roller displacement is proposed using existing studies on the relationship between loading conditions and roller positions along the sprocket tooth profile. The presented model, is then used to assess the contribution of both meshing and roller motion on the global efficiency of the drive. Calculations show that the magnitude of both loss sources is similar for a wide range of gear ratios and loading conditions. According to the presented results, the relative motion between the rollers and the sprocket tooth profile should be considered in future studies dedicated to chain drive efficiency.

Real-time estimation of junction temperature in IGBT inverter with a simple parameterized power loss model

System-level thermal modelling of electric drive systems requires simple thermal models coupled with each other by the operation parameters of the drive systems. This paper presents a simple parameterized power loss model for insulated gate bipolar transistor (IGBT) inverters, in which variables are relevant to the powertrain operation conditions and are routinely monitored. Combined with a two-impedance thermal model of the inverter with parameters fitted to the results of computation fluid dynamics (CFD) simulations, the resulted real-time model can provide accurate estimations of the junction temperature. The present power loss model combined with the simple two-impedance thermal model is very suitable to be used in system-level real-time thermal monitoring of an integrated electric drive system.

Investigation of the Influences of Thrust Loads Resulted by Helix Angle Directions of Planetary Gear Sets on Bearing Power Losses in Automotive Planetary Gear Trains

In the recent automotive industries, automotive technologies for improving fuel efficiency have focused on the developments of reducing power losses in a transmission. As a well-developed and conventional power transmitting system, an automatic transmission is still widely used in many automotive vehicles. The automatic transmission is co-axially designed with several planetary gear sets and other mechanical parts. The co-axial arrangements and gear helix angles make the transmission necessarily include bearings for supporting loads and allowing relative rotations. In this study, the influences of thrust loads yielded by helix angle directions of planetary gear sets on bearing power losses are presented by performing the structural and power loss analysis. Bearing power losses consist of mechanical and spin power losses. For calculating thrust loads and bearing rotations, a complete transmission model is constructed by using an example structure, and structural analysis is performed for the combinations of helix angle directions of the gear sets. Finally, bearing power losses are computed by using the bearing power loss model, and the results of the entire combinations of helix angle directions are discussed.

An investigation on IGBT junction temperature estimation using online regression method

In order to obtain junction temperature of insulated-gate bipolar transistor (IGBT) on electric vehicle, a number of studies have proposed junction temperature (Tj) estimation methods. However, some of these methods require additional circuits which lead to cost increase, some methods simulate the IGBT thermal process with thermal model, which induces a deviation between real functional results and simulation, and the other algorithm based methods may involve upgrading the main control unit (MCU) with increased costs. This paper proposes a method of IGBT Tj estimation with regression analysis. The presented method firstly extracts the most sensitive factors from IGBT power loss model, and then the factors are applied in a data fitting function to characterize Tj. After that, the mentioned fitting function is validated by regression analysis with statistics Anderson – Darling (AD) and P-value. Finally the Tj estimation fitting function is demarcated by the negative thermal coefficient (NTC) measured temperature (TNTC). With the method using TNTC demarcation, the error bandwidth between estimated Tj and measured Tj is 3.4 °C in total. Compared with the Tj estimation without TNTC demarcation, the error bandwidth of Tj decreased from 6.9°C to 3.4 °C. The Tj estimation method with TNTC demarcation is efficient for an online Tj estimation of IGBT modules without increased costs.

Droop control design to minimize losses in DC microgrid for more electric aircraft

Droop control has been widely used as a load-sharing method between paralleled power sources in DC microgrid due to its modularity and reliability. Existing droop gains design methods rely on computationally intensive supervisory control algorithms and knowledge of sub-system parameters.This paper presents a streamlined design approach for optimal droop gains, relying only on the knowledge of the parameters of the local converter power losses model in order to achieve minimum power losses for a More Electric Aircraft (MEA) DC microgrid. Additionally, a simplified, but sufficiently accurate, converter losses model is proposed in this paper for optimal droop gains design. The proposed converter losses model consists of two parts; no-load losses, and losses which are represented by Equivalent Series Resistance (ESR). The proposed design approach analyses show that setting the optimal droop gains equal to the converter ESR will achieve minimum overall DC microgrid power losses without the need for any additional information on the DC transmission line parameters. The effectiveness of the optimal droop gains design method is tested in a simulation environment and evaluated experimentally using a laboratory DC microgrid test rig.

Real-time rolling bearing power loss in wind turbine gearbox modeling and prediction based on calculations and artificial neural network

This paper investigates the bearing power loss in gearbox for wind turbines under actual operating wind speed. Actual power loss values are calculated using calibrated SKF model for three different wind turbine gearbox oils. The gearbox applied load at each operating step is determined by using the wind turbine power curve. Wind data from experiments in Cameroon are used for validation. The back-propagation neural network is designed for actual power loss modeling and predicting desired values. The achieved results revealed that the bearing power loss is highly influenced by the wind turbine operating parameters, capacity, and oil. The difference between actual and neural network predicted bearing power loss values under real-time operating parameters showed the effectiveness of the proposed approach.

Improved switching transient model suitable for power loss evaluation of SiC-based asymmetric H-bridge power converters in SRGs

This paper presented an improved switching transient model of silicon carbide (SiC)-based asymmetric H-bridge (AHB) power converter for a switched reluctance generator (SRG), which takes the nonlinear phase inductance of the SRG into consideration. First, a systematic mathematic derivation is carried out and the switching transient model is established. Second, the impact of the nonlinear phase inductance of the SRG on switching transients is verified by PSpice & Simulink co-simulations. Third, a power loss model is established by the transient model through PSpice & Simulink co-simulations. The model is conducted to indicate the power loss characteristics of the SiC-based AHB power converter. Simulation results indicate that the nonlinear phase inductance of the SRG is able to accelerate the switching speed of SiC-MOSFETs, and that the SiC converter is advantageous in terms of power loss. Experimental results illustrate that the established power loss model experiences high accuracy. In addition, SiC devices are able to strengthen the power density and efficiency of a converter while reducing its heat dissipation requirements.

PERMANENT MAGNET SYNCHRONOUS MACHINE TEMPERATURE ESTIMATION USING LOW-ORDER LUMPED-PARAMETER THERMAL NETWORK WITH EXTENDED IRON LOSS MODEL

Since temperature rise in electric machines is mainly due to power losses during electro-mechanical power conversion, temperature estimation is highly attached to power loss modelling. In this contribution, an extended iron loss model is introduced with a direct identification methodology in the context of temperature estimation. The iron loss model is implemented as part of a fourth-order lumped-parameter thermal network (LPTN), which is parametrised using empirical measurements and global identification. Once parameters are identified using training data, the LPTN model is validated using three unseen profiles cross-validation. Satisfactory estimation is achieved with the average mean squared error of 2.1 K2 and the error bias close to zero.

Optimization of key power loss for LLC circuits with planar transformer in high-frequency and high-power scenarios

An accurate power loss model, for the design of high-efficiency switching power supplies, is difficult to establish due to the complicated magnetic components where the power loss is hard to calculate. This paper proposed a multi-level power loss model of LLC circuits with a planar transformer of high frequency, high power, and low voltage output. The key loss items can be optimized by using this loss model, the accuracy of which and the feasibility of the optimization method are validated by extensive prototype experiments. The experimental results show that the average accuracy of the loss calculation is about 93.6%, and the high efficiency at high-power conversion (95.9% @ 3 kW, 224–16 V) has been realized using an optimized prototype converter.

Analysis of reliability based on thermal cycle and aging effect in electron devices

This paper concentrates on the estimation of reliability of an automotive electronic power device using thermal cycle, aging effect and accumulated damage. Thermal model has been developed for analysing the factors of power loss. A look-up table has been constructed to calculate the power loss and finite-element modelling was used to find out the aging effect. Thermal model was developed by using FLOTHERM. It is in the form of either Foster or Cauer network. Comparison of results from the thermal model has been done. Preprocessing of data by filtration and spectrum truncation was also explored. Reliability can also be estimated by calculating the accumulated damage with the help of Pagoda Roof method and Miner’s rule. Finally, a method was proposed of using Ga NFET instead of MOSFET to calculate power dissipation.

A high-accuracy switching loss model of SiC MOSFETs in a motor drive for electric vehicles

Power loss estimation of power electronic devices is essential to the efficiency optimization of motor drives in electric vehicles. However, most existing power loss models of silicon carbide (SiC) metal-oxidesemiconductor field-effect transistors (MOSFETs) have a low accuracy due to the neglection of parasitic parameters in the motor drive circuitry. In this paper, the voltage and current trajectories of SiC MOSFETs in the switching transition of a motor drive system are analyzed in detail. Based on the analysis, the conduction and switching losses of SiC MOSFETs in the motor drive inverter are modeled. Compared with the traditional power loss models, the proposed analysis model includes parasitic inductances and capacitances in circuitry and the MOSFET, and the reverse recovery loss of the body diode, etc. The experimental results verified that the proposed power loss model has higher accuracy than the conventional model.

Three-Phase Multilevel Inverter Using Selective Harmonic Elimination with Marine Predator Algorithm

In this paper, the marine predator algorithm (MPA) is proposed for solving transcendental nonlinear equations in a selective harmonic elimination technique using a multilevel inverter (MLI). It proved its suitability and supremacy over the other selective harmonic (SHE) techniques used in recent research as it has good precision, high probability of convergence, and improving quality of output voltage. The optimum values of switching angles from MPA are applied to control a three-phase 11-level MLI using cascaded H-bridge (CHB) topology to control the fundamental component and cancel the low order harmonics for all values of modulation index from 0 to 1. Analytical and simulation results demonstrate the robustness and consistency of the technique through the MATLAB simulation platform. The results obtained from simulation show that the MPA algorithm is more efficient and accurate than other algorithms such as teaching-learning-based optimization (TLBO), flower pollination algorithm (FPA), and hybrid particle swarm optimization with gray wolf optimization (PSOGWO). A prototype for a three-phase seven-level cascaded H-bridge inverter (7L-MLI-CHB) experimental setup is carried out. The output of this experimental test validated and supported the results obtained from the simulation analysis. The model of power loss of three-phase 7L-MLI-CHB using the silicon metal-oxide-semiconductor field-effect transistor (MOSFET) is obtained according to the modulation technique. Conduction and switching losses are calculated based on the experimental manufacturer data from the Si-MOSFET using the thermal model of Piecewise Linear Electrical Circuit Simulation (PLECS). Losses and output power are measured at different modulation index values based on the MPA algorithm. Finally, a design of heatsink volume is presented for this design at different temperatures.

Векторне керування асинхронним генератором з підвищеним коефіцієнтом корисної дії

Compared to today’s dominant in autonomous wind power, a synchronous generator with permanent magnets, an induction generator (IG) with a short-circuited rotor has such significant advantages as higher reliability and lower cost. But the energy performance in IG is lower, so their improvement is an actual task. To solve this problem, along with search algorithms, systems of no-search optimization of power losses in IG are intensively developed. In these systems, the optimal magnetic flux is determined by the analytical expression obtained from the loss model. The disadvantages of the known works on this topic are that they use various simplified models of losses. Accordingly, this reduces the accuracy of optimization algorithms. The aim of the work is to build the vector control system of IG, in which, due to the optimization of the sum of major power losses, a significant increment in the efficiency of the generator is achieved. The article uses a model of power losses, which includes all the main losses in the IG of electromagnetic nature. These include ohmic losses in the stator and rotor resistances, magnetic losses in the iron and additional losses. By analytical study of the model of losses to the extremum, an expression for determining the optimal flux linking of the rotor by the criterion of minimum total losses in the generator is obtained. The application of this expression allows to increase the accuracy of loss optimization in comparison with known analogues. The procedure for determining the optimal flux uses the signals of the instantaneous component of the stator current and rotor speed and is simple for computer implementation in real time. Numerical studies of steady-state processes in the mode of operation of the generator with a constant output power P2=const for its values from 15 % to 45 % have been conducted. It is established that the efficiency increment obtained due to control with loss optimization has an extreme character with a maximum in the vicinity of the nominal speed. As P2 increases, the loss optimization zone and efficiency increment decrease. The maximum and average efficiency increment obtained in the study reach 19 % and 11 %, respectively. This shows the prospects of the proposed system of energy-efficient vector control of IG.

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.

Switching Time Delay Optimization for “SiC+Si” Hybrid Device in a Phase-Leg Configuration

Compared to SiC MOSFET, the switching loss of Si IGBT is much higher due to its slow switching speed and tail current. Si IGBT/SiC MOSFET hybrid switch device can reach to optimal performance with low static and dynamic loss, which can improve the current capacity of SiC devices and reduce the power loss of Si IGBT based converters. With the separated gate control signals, the switching moments of the two devices can be controlled independently to ensure Si IGBT under zero-voltage switching (ZVS) conditions. This measurement tends to reduce the switching loss of Si IGBT. However, the switching time delay between these two devices has significant impacts on its power loss. In this paper, the switching time delay optimization method is proposed to minimize the power loss of the hybrid switch. The static and dynamic characteristics of Si IGBT/SiC MOSFET hybrid-paralleled switch are studied, and a generalized power loss model for hybrid switch is developed. The influence of switching time delay on the characteristics of hybrid switch is analyzed and verified through double pulse tests in a phase-leg configuration. The experimental results show that the optimal turn-on delay time is that the two devices turn on at the same time and the turn-on loss can be reduced by about 73% compared with the solely Si IGBT and by about 52% compared with the solely SiC MOSFET. While the optimal turn-off sequence is that the Si IGBT turns off ahead of the SiC MOSFET. Under the proposed optimal turn-off delay time of the hybrid switch, the turn-off loss is reduced by about 61.4%. This optimization strategy is used in a Buck converter to verify the superiority of the SiC/Si hybrid switch and the optimal switching sequence. Simulation results show that the optimal switching sequence is consistent with theoretical analysis, and the efficiency is improved by 2.5% compared with Buck converter using solely Si IGBT.

Improvement of the model of power losses in the pulsed current traction motor in an electric locomotive

When studying transients in pulsed current traction motors, it is important to take into consideration the eddy and hysteresis losses in engine steel. Magnetic losses are a function of the magnetization reversal frequency, which, in turn, is a function of the engine shaft rotation frequency. In other words, magnetic losses are a function of time. Existing calculation procedures do not make it possible to derive the instantaneous values of magnetic losses as they are based on determining average losses over a period.This paper proposes an improved model of magnetic losses in the steel of a pulsed current traction motor as a function of time, based on the equations of specific losses.The adequacy criteria of the procedure for determining magnetic losses in electrical steel have been substantiated: the possibility to derive instantaneous values of magnetic losses in the magnetic material as a function of time; the possibility of its application for any magnetic material; and the simplicity of implementation. The procedure for determining magnetic losses in the steel of a pulsed current traction motor has been adapted by taking into consideration the magnetic properties of steel and the geometry of the engine's magnetic circuit. In order to determine the coercive force, the coefficient of accounting for the losses due to eddy currents, as well as the coefficient that considers the losses on hysteresis, the specifications' characteristics of specific losses in steel have been approximated using the pulsed current traction motor as an example. The simulated model of magnetic losses by the pulsed current traction motor has demonstrated the procedure for determining average magnetic losses and time diagrams of magnetic losses.The proposed model for determining magnetic losses could be used for any magnetic material and any engine geometry under the condition of known material properties and the characteristics of change in the magnetic flux density in geometry

MLD-Based Thermal Behavior Analysis of Traction Converters Under Faulty Conditions

The existing thermal behavior analysis mainly focuses on the normal condition of converter but lacks investigation in the cases of faulty condition and modulation strategy switching. This further leads to inaccuracy and incomprehensive thermal management. In order to address this issue, in this article, a mixed-logical-dynamic (MLD)-based electrothermal model is proposed for a fast observation of the thermal behavior of power devices within converters under both normal case and open-circuit (OC) fault cases. It also has the advantage of applicability to various modulation strategies. To be specific, the switching-logic-mixed (SLM) and transition-logic-mixed (TLM) variables are first defined to analyze the generating conditions of power loss in power modules, where the power loss models considering the normal and OC fault cases are built, after which the MLD-based electrothermal model is established to calculate the junction temperature of power modules, which will be used to obtain the thermal behaviors of converters. Finally, under various OC fault cases, the thermal behavior of traction converters is analyzed by hardware-in-the-loop (HIL) real-time simulation test. The HIL-based results show that the proposed model can be used to analyze the thermal behaviors under various scenarios in real time, which can further offer guidance for thermal management under faulty conditions.

Енергоефективна система керування автономним асинхронним генератором для віддалених поселень

Laying power lines to small settlements and farms away from towns and villages is not always cost-effective. Therefore, autonomous solar and wind energy sources are increasingly used in such settlements. In contrast to the dominant today in wind power plants synchronous generators with permanent magnets, an induction generator (IG) with a short-circuited rotor have such important advantages as higher reliability and lower cost. But the energy performance in IG is lower, so their improvement is an actual task. To solve this problem, systems of no-search optimization of power losses in IG are intensively developed. In these systems, the optimal magnetic flux is determined by the analytical expression obtained from the loss model. The disadvantages of the known works on this topic are that they use various simplified models of losses. Accordingly, this reduces the accuracy of optimization algorithms. The aim of the work is to build the vector control system of IG, in which, due to the optimization of the sum of major power losses, a significant increment in the efficiency of the generator is achieved. The article uses a model of power losses, which includes all the main losses in the IG of electromagnetic nature. These include ohmic losses in the stator and rotor resistances, magnetic losses in the iron and additional losses. By analytical study of the model of losses to the extremum, a expression is obtained to calculate the optimal flux linkage of the rotor by the criterion of minimum total losses in the generator. The application of this expression allows to increase the accuracy of loss optimization in comparison with known analogues. Numerical studies of steady-state processes in the mode of operation of the generator with a constant output power P2=const for its values from 10% to 50% have been conducted. It is established that the efficiency increment obtained due to control with loss optimization has an extreme character with a maximum in the vicinity of the nominal speed. The maximum and average efficiency increment obtained in the study reach 26% and 18%, respectively. This shows the prospects of the proposed system of energy-efficient vector control of IG.

Research on Capacitor-Switching Semi-Full-Bridge Submodule of Modular Multilevel Converter Using Si-IGBT and SiC-MOSFET

This article presents a capacitor-switching semi-full-bridge (CS-SFB) submodule (SM) using Si-IGBT and SiC-MOSFET for a modular multilevel converter (MMC). Compared with the conventional hybrid half-/full-bridge MMC, the CS-SFB MMC has the same dc fault ride-through capability and lower power losses. The conduction loss reduces due to the current sharing phenomenon between Si-IGBTs and SiC-MOSFETs. The switching loss reduces in virtue of the fast recovery characteristic of SiC-diode. The derivation process and working principle of the proposed SM are first introduced. Then, the power loss models are established in the switch, SM, and MMC system levels, respectively. Afterward, the piecewise calculation and simulation results reveal the low-power-loss characteristics of the proposed SM and MMC. Finally, these features are verified by experimental results acquired from a downscaled MMC prototype with Si-IGBTs and SiC-MOSFETs.