Power Loss Distribution Research Articles

Power Loss Model and Efficiency Analysis of Three-Phase Inverter Based on SiC MOSFETs for PV Applications

This paper presents the power loss model analysis and efficiency of three-level neutral-point-clamped (3L-NPC) inverter that is widely employed in solar photovoltaic energy conversion system. A silicon carbide (SiC) 3L-NPC inverter is developed in this paper by employing wide bandgap semiconductor power devices, such as SiC MOSFET and SiC diode (SiC D). These devices are used due to their superior characteristics over silicon (Si) semiconductor devices for the reduction of inverter power losses, and as a result, an improving efficiency at the high switching frequency. Accurate and detailed power loss calculation formula and power loss distribution over switching devices of the SiC 3L-NPC inverter are derived according to the modulation technique and inverter operation. The switching energy loss of SiC MOSFET is then measured and determined experimentally via inductive clamp double pulse test (DPT) at the real working condition of the circuit. Afterward, this experimental data is used in the thermal description file of the device’s library of PLECS simulation software to determine the total power loss of SiC 3L-NPC inverter. The developed simulation model replicates the real operating conditions of the 3L-NPC inverter. This method gives results close to the practical test. Finally, the power loss of SiC 3L-NPC inverter is measured and compared with the theoretical results. Furthermore, SiC MOSFET and SiC D are employed to achieve high system efficiency at the high switching frequency. The results verify the features of SiC 3L-NPC inverter, the corresponding modulation technique used and their effects on reducing and improving power loss in solar SiC photovoltaic inverters.

Analysis on the Impact of Geomagnetic Storm on Reactive Power and Voltage in Extrahigh Voltage Power Grid

With the growing scale of the power grid and the improvement of the voltage level, the geomagnetically induced currents (GICs) generated by geomagnetic storms has become one of the leading factors that cause large-scale power outages in power grid. Considering the global simultaneity characteristic of geomagnetic storms, this paper presents the concept of mass reactive power disturbance for the first time, analyzes the mechanism of GIC reactive power loss of transformer and reveals the mechanism of mass reactive power disturbance’s influence on voltage. Finally, combined with the practical situation of 750kV EHV power grid in China, the reactive power loss and voltage distribution under the geomagnetic storms at various intensities are calculated, with the grid operating in two typical modes, and the impact of the geomagnetic storm on voltage is illustrated, which provides the theoretical basis for the study of voltage stability.

Investigation of a New Modular Multilevel Converter With DC Fault Blocking Capability

Modular multilevel converter (MMC) has been a promising candidate in high voltage direct current (HVdc) transmission systems. Due to the features of simple structure, low cost, and low power losses, half-bridge (HB) is usually adopted as the submodule circuit in the traditional MMC. However, an HB submodule circuit-based MMC does not have the capability of blocking dc short-circuit fault, which obstructs the development of low-cost HVdc systems with overhead lines. In order to solve this problem, an MMC with active clamped T-type submodule (ACTSM) to own dc fault blocking capability is proposed in this paper. Compared with other submodule circuits, the proposed ACTSM has many features, such as symmetrical blocking capability, low power losses, low voltage stress, and low amount of independent drive signals. The topology, operation principle, dc fault blocking capability, and distribution of power losses of the ACTSM are presented in this paper. The effectiveness of the ACTSM-based MMC is validated by both simulations and experiments.

Энергосберегающий электропривод для стенда испытаний тракторных шин

The article addresses matters concerned with designing the tractor tire test bench with taking into account the shortcomings of its previous designs and considers the possibility of performing tractor tire tests with better energy efficiency and reliability. The existing domestic and foreign test benches are analyzed. The test bench electric drive power part’s functional diagram is proposed along with the power flows and power loss distribution diagram in the bench drives for estimating their power performance characteristics. From the technical point of view, the aim of the development is to reduce the electricity consumption. To this end, the bench is equipped with two additional electric machines operating in regenerative braking modes, thereby ensuring return of energy back to the network (an individual loading induction motor is provided for each tire). The article describes the bench design, its technical characteristics, requirements for the bench control system, and the technical solution that allows more efficient tire test results to be obtained due to returning energy back to the network and due to the fact that the drive power is now spent only to compensate losses in the bench mechanisms. A vector control system of interconnected electric drives used in the bench is mathematically modeled, and its technical capabilities are investigated. The effectiveness of the proposed solution is proved based on estimating the energy return level to the drive power supply grid.

Power Loss Minimization in Islanded Microgrids: A Communication-Free Decentralized Power Control Approach Using Extremum Seeking

This paper focuses on islanded microgrids and presents a method to allocate power among the distributed generation units (DGs) to minimize the distribution power loss. Motivated by the need for decentralized control strategies with minimal communication among grid components to support a robust and plug-and-play operation, a communication-free decentralized power control approach is developed for power loss minimization based on the extremum-seeking (ES) method. In this approach, the DGs implement ES simultaneously and separately to minimize their current outputs by controlling the active power. The total power loss is thus reduced without the need for any grid structure information or communication in the optimization process. This approach results in a non-cooperative game. The existence of a Nash equilibrium to this game and its stability are proved. The numerical simulations are conducted to demonstrate the performance of the proposed approach and show its ability to maintain low-power loss under different operating conditions in a plug-and-play manner.

Raising Power Loss Equalizing Degree of Coil Array by Convex Quadratic Optimization Commutation for Magnetic Levitation Planar Motors

This paper proposes a convex quadratic optimization commutation method to raise the equalization degree of power loss distribution of coil array for magnetic levitation planar motors. Starting with the modeling of electromagnetic forces/torques and commutation of coil array, the global power loss and the local power losses of coil array are analyzed, and the power loss equalizing degree is defined to evaluate the power loss distribution of coil array being commutated dynamically. Then, in consideration of the fact that the global power loss is the quadratic function of commutated coil currents, the convex quadratic function optimization with equality constraint and boundary constraints is applied to commutate the coil array, and the power loss equalizing degree is raised by decreasing the boundary constraints of optimization. Taking the magnetically levitated planar motor under investigation as examples and using quadprog routine in Matlab Optimization Toolbox, which is a dedicated quadratic optimization routine, it is verified that the power loss equalizing the degree of coil array is raised gradually and the power loss distribution of coil array becomes more uniform along with decrease of the boundary constraints. The convex quadratic optimization commutation is verified experimentally on a constructed multi-dimension force/torque measurement platform. Using the convex quadratic optimization commutation can not only improve the power loss distribution of coil array of magnetically levitated planar motors, but also make it possible to select lower capacity power amplifiers to produce the identical desired electromagnetic forces and torques.

An analysis of the decoupling relationship between CO2 emission in power industry and GDP in China based on LMDI method

China predominantly relies on thermal power generation to meet its power requirement, which has led to a major increase in total CO2 emission and poses a huge threat to the development of power industry. In order to reduce CO2 emission in power industry and develop economy simultaneously, it is necessary to study how to achieve the strong decoupling relationship between CO2 emission in power industry and GDP in China. However, such studies are relatively limited so far. Thus, this paper mainly inquiries the major driving factors on the decoupling during the period of 1985–2016. First, the decoupling state in China is quantified by using the Tapio decoupling indicator. Then, this paper carries out the decomposition of the decoupling index to explore the driving factors affecting the decoupling by the logarithmic mean divisia index (LMDI) method and Kaya identity equation. Finally, energy consumption in power generation, thermal power structure, power generation structure, transmission and distribution loss, electrification, energy intensity and economic scale are explored to discuss the decoupling relationship with respect to the CO2 emission reduction. The results show that the decoupling relationship is in an alternating state between weak decoupling and expansive negative decoupling in 1985–2016. And the influences of seven factors on the decoupling relationship are of difference. Wherein, energy intensity as well as energy consumption in power generation, promotes the decoupling while both the economic scale and electrification are the two main factors that inhibit the decoupling. The other three factors have relatively weak effects. Therefore, based on the empirical results, this paper puts forward some policy suggestions to effectively promote the decoupling between China’s electric CO2 emission and economic growth.

Power transmission and distribution losses – A model based on available empirical data and future trends for all countries globally

This article aims at the creation of a holistic and analytic function for describing the transmission and distribution (T&D) grid power loss for all countries globally based on economical, geographical, political and technical available data. The created function is the very first of its kind, it is statistically well validated, and several examples are discussed. The function based on empirical data describes the dependence of the T&D grid power loss level on widely available metrics, such as GDP per capita, corruption perception index, area of the country, temperature, grid organization parameter and level of urbanization. The same function can also be used by modellers to anticipate the development of the T&D grid power loss in the years and decades to come. The suggested methodology could be easily reproduced and tuned to precise environmental conditions, what can be helpful for research in countries without available data.

Magnetic Design and Experimental Evaluation of a Commercially Available Single Integrated Transformer in Three-Phase <italic>LLC</italic> Resonant Converter

Multiphase topologies are preferably employed in power conversion systems to lessen the per-phase circuit current, conduction losses, devices thermal stresses, and to reduce the output current ripples. A multiphase LLC resonant dc/dc converter usually possesses a number of magnetic cores equal to the number of phases. These magnetic cores are the major contributors to supply volume, weight, and size. For these reasons, circuit designers tend to select the topologies that have a minimal number of magnetic cores. In this paper, the authors aim to promote the industrial applications of the three-phase LLC resonant converter by integrating three transformers into a single commercially available magnetic core to reduce the volume, weight, and cost of the power converter. A comprehensive magnetic analysis for the three-phase-integrated transformer is conducted. Finite element method (FEM) simulation and experimental tests are carried out to validate the proper operation of the integrated transformer utilized in a 390-/12-V to 500-W prototype. Furthermore, the power losses distribution has been presented. The proposed integrated transformer has been proven effective, and it realized a uniform thermal distribution along the core compared to the three-discrete transformers.

Mitigating Distribution Power Loss of DC Microgrids With DC Electric Springs

DC microgrids fed with substantial intermittent renewable energy sources face the immediate problem of power imbalance and the subsequent dc bus voltage fluctuation problem (that can easily breach power system standards). It has recently been demonstrated that dc electric springs (DCES), when connected with series non-critical loads, are capable of stabilizing the voltage of local nodes and improving the power quality of dc microgrids without large energy storage. In this paper, two centralized model predictive control (CMPC) schemes with: 1) non-adaptive weighting factors and 2) adaptive weighting factors are proposed to extend the existing functions of the DCES in the microgrid. The control schemes coordinate the DCES to mitigate the distribution power loss in the dc microgrids, while simultaneously providing their original function of dc bus voltage regulation. Using the DCES model that was previously validated with experiments, simulations based on MATLAB/Simulink platform are conducted to validate the control schemes. The results show that with the proposed CMPC schemes, the DCES are capable of eliminating the bus voltage offsets as well as reducing the distribution power loss of the dc microgrid.

The effect of respiration-driven flow waveforms on hemodynamic metrics used in Fontan surgical planning

ObjectivePoor total cavopulmonary connection (TCPC) hemodynamics have been hypothesized to be associated with long-term complications in Fontan patients. Image-based Fontan surgical planning has shown great potential as a clinical tool because it can pre-operatively evaluate patient-specific hemodynamics. Current surgical planning paradigms commonly utilize cardiac-gated phase contrast magnetic resonance (MR) imaging to acquire vessel flows. These acquisitions are often taken under breath-held (BH) conditions and ignore the effect of respiration on blood flow waveforms. This study investigates the effect of respiration-driven flow waveforms on patient-specific hemodynamics using real-time MR acquisitions. MethodsPatient-specific TCPCs were reconstructed from cardiovascular MR images. Real-time phase contrast MR images were acquired under both free-breathing (FB) and breath-held conditions for 9 patients. Numerical simulations were employed to assess flow structures and hemodynamics used in Fontan surgical planning including hepatic flow distribution (HFD) and indexed power loss (iPL), which were then compared between FB and BH conditions. ResultsDifferences in TCPC flow structures between FB and BH conditions were observed throughout the respiratory cycle. However, the average differences (BH – FB values for each patient, which are then averaged) in iPL and HFD between these conditions were 0.002 ± 0.011 (p = 0.40) and 1 ± 3% (p = 0.28), respectively, indicating no significant difference in clinically important hemodynamic metrics. ConclusionsRespiration affects blood flow waveforms and flow structures, but might not significantly influence the values of iPL or HFD. Therefore, breath-held MR acquisition can be adequate for Fontan surgical planning when focusing on iPL and HFD.

Bulk temperature prediction of a two-speed automatic transmission for electric vehicles using thermal network method and experimental validation

Nowadays, the development of electric vehicle equipped with a two-speed automatic transmission has become a hotspot. As well known, the automatic transmission operates with power loss including gear meshing loss, bearing loss, and oil churning loss. This paper focuses on the bulk temperature prediction of a two-speed automatic transmission using thermal network method. An integrated model, including an efficiency model and a heat balance model, is proposed, which makes it possible to predict power loss, bulk temperature, and temperature distributions under different conditions. In the efficiency model, each part of power losses from gear meshes is studied to calculate the summation of mechanical power losses in the transmission, including losses of gear meshing, bearing and oil churning. In the heat balance model, the entire gearbox is divided into elements with a uniform temperature connected by thermal resistances which account for conduction, convection, and radiation, based upon the first law of thermodynamics for transient conditions. The effectiveness of bulk temperature prediction using thermal network method is validated by the comparison between simulation results and the experimental data. Consequently, this study on heat transfer characteristics, thermal characteristics, and bulk temperature prediction of the two-speed automatic transmission has significant academic and application values.

Sensitivity Analysis of Inverse Thermal Modeling to Determine Power Losses in Electrical Machines

Inverse analysis is a known mathematical approach, which has been used to solve physical problems of a particular nature. Nevertheless, it has seldom been applied directly for loss reconstruction of electrical machines. This paper aims to verify the accuracy of an inverse methodology used in mapping power loss distribution in an induction motor. Conjugate gradient method is used to iteratively find the unique inverse solution when simulated temperature measurement data are available. Realistic measurement situations are considered and the measurement errors corresponding to thermographic measurements and temperature sensor measurements are used to generate simulated numerical measurement data. An accurate 2-D finite-element thermal model of a 37 kW cage induction motor serves as the forward solution. The inverse model’s objective is to map the power loss density in the motor accurately from noisy temperature measurements made on the motor housing’s outer surface. Furthermore, the sensitivity of the adopted inverse methodology to variations in the number of available measurements is also considered. Filtering the applied noise to acceptable ranges is shown to improve the inverse mapping results.

Study on the Thermal Distribution Characteristics of High-Speed and Light-Load Rolling Bearing Considering Skidding

Skidding, which frequently occurs in high-speed rolling bearings, has a significant effect on the thermal distribution and service reliability of the bearings. An improved theoretical model of friction power loss distribution in high-speed and light-load rolling bearings (HSLLRBs) considering skidding is established, and the effects of various operating parameters on the friction power loss are investigated. The results show that the friction power loss of the inner ring and outer ring as well as the total friction power loss of the bearing increase as the slip ratio increases, but that the friction power loss of the cage guide surface and roller oil churning show a reverse trend. In addition, the increase in inner ring speed and kinematic viscosity leads to an increase in bearing friction power loss. The steady and transient temperature field distribution of HSLLRBs is obtained by the finite element method (FEM), and the results show that the inner ring raceway has the highest temperature, whereas the cage has the lowest. The temperature distribution test rig of a full-size roller bearing is constructed, and the influence mechanism of the slip ratio, rotation speed, load, lubrication, and surface topography on the bearing temperature distribution are obtained. The experimental results are consistent with the theoretical results, which also validates the theoretical method.

Frequency Regulation in Deregulated Market Using Vehicle-to-Grid Services in Residential Distribution Network

Progress in vehicle-to-grid technology opens market for electric vehicle (EV) users to participate in the emergency reliability services, such as frequency regulation (FR). EVs can be considered as a mobile energy storage, which has the potential to compensate the uncontracted power if the contracts between the market players are breached. As all the EVs will be penetrated to the distribution network, distribution power loss along with the power limit of transformer and lines must be incorporated in the EV model. In this paper, the accuracy of conventional EV model is improved by introducing distributed network characteristics to participate in FR under deregulated environment in the presence of diverse transmission links such as ac/dc links. Fractional order plus proportional plus integral plus derivative (FOPID) controller also abbreviated as PI λ D μ controller is used for coordinated control of conventional units and EVs. Flower pollination algorithm is employed to choose the controller parameters under different scenarios. Extensive simulations have been performed to validate the superiority of the proposed control strategy. Obtained results strongly suggest that FOPID controller is far superior to conventional PID controller.

A method on modelling and analyzing the power losses in vehicle transmission

The efficiency of transmissions is related directly to the energy consumption in vehicle systems. Hence, it is worth a lot researching the overall power losses inside the transmission, in order to modify the transmission performance or optimize the transmission. In most research works, only how to model the component power losses is considered. It is then necessary to put forward a general or standard method to calculate the overall power losses in the transmissions. In this paper, a general model of overall power losses in transmissions is built up, based on the selection of the submodels of component power losses from literature. With the help of the experimental data from the test bench, the methodology of parameter identification is introduced. As a result, more accurate power loss distribution of the transmission is possible to be obtained, through combining the overall efficiency experimental data and the model of overall power losses. In order to validate the methodology, it is applied into two study cases of different transmissions. Through the results of the two study cases, it is concluded that the methodology of modelling of power losses in transmissions with parameter identification is ready to be extended to other transmission study cases. It is expected that with the help of the methodology in this paper, a platform can be built up to benchmark different production transmissions in the future.

Characterization and Performance Evaluation of the Superjunction RB-IGBT in Matrix Converter

In this paper, we investigate the performance of the three-phase ac–ac matrix converter (MC) utilizing the novel superjunction (SJ) reverse-blocking (RB)-insulated gate bipolar transistor (IGBT) as switch elements for the first time. The SJ RB-IGBT offers bidirectional blocking capability >1200 V by introducing a shorted-collector trench and n2-layer. The SJ RB-IGBT exhibits bipolar conducting mode in the on-state and the unipolar mode during turn-off. Therefore, both a low on-state voltage ( V on) and a low turnoff energy loss ( E off) can be obtained. The SJ RB-IGBT delivers the E off 80% lower than state-of-the-art RB-IGBTs without penalty in the V on. These merits make the SJ RB-IGBT an attractive candidate for the MC. To address the short circuit arising in commutation of the MC, the split gate is adopted for a low Miller capacitance. The power loss, efficiency, and loss distribution of the three-phase MC with the SJ RB-IGBT and other RB-IGBTs are compared by simulation and calculation. Compared with the MC using conventional nonpunch-through RB-IGBT, the MC with SJ RB-IGBT achieves 85%, 87%, and 56% reductions in the turnoff, reverse recovery, and conduction losses, respectively, yielding 56% reduction in the total loss. The low-power loss and superior dynamic performance of the SJ RB-IGBT enables the MC to operate at higher frequency and higher power density.

Triple‐band polarisation‐independent metamaterial absorber at mm wave frequency band

The authors present a triple-band metamaterial absorber operating at mm wave frequency band. The absorber is composed of periodic unit cells, which consists of a new pattern and a ground plane, placed in two sides of a dielectric substrate made of polyimide film. To best understand the absorption mechanisms, full-wave simulation results for the electric field, surface current, and power loss distributions are presented. The experimental results, for a transverse electric-polarised normal incident wave, show three distinctive absorption peaks, at frequencies 101.25, 108.75, and 129 GHz with absorptivities of 92.5, 94.9, and 88.6%, respectively. The absorber is independent of the wave polarisation, where high absorption is achieved for a wide range of oblique angles of incidence.

A Stochastic Game Approach for PEV Charging Station Operation in Smart Grid

In the future, smart grid charging stations will be critical infrastructures for plug-in electric vehicle (PEV) to replenish their batteries in a convenient way. Due to the ever-increasing penetration rate of PEVs, how to efficiently manage the loads of PEV charging stations to ensure system efficiency and reliability is a major challenge faced by the distribution service providers (DSPs) in the smart grid. This challenge is further complicated by the highly dynamic PEV mobility, which results in random PEV arrivals, departures, and charging demands. In order to address this challenge, a stochastic game approach is proposed in this paper to characterize the interactions among DSP, charging stations, and PEV owners, where the randomness in charging decision making processes of PEV owners is modeled by a Markov decision process. Based on the Nash equilibrium solution of the stochastic game, a real time pricing scheme is proposed for the DSP to minimize power distribution losses while ensuring system reliability. The performance of the proposed approach is evaluated via extensive simulations based on the IEEE 123 bus test feeder with real vehicle mobility data from the 2009 National Household Travel Survey and the 2010 National Travel Survey.

A Tunable Polarization-Dependent Terahertz Metamaterial Absorber Based on Liquid Crystal

In this paper, a tunable polarization-dependent terahertz (THz) metamaterial absorber based on liquid crystal (LC) is presented. The measurement results show that absorption peak is at 239.5 GHz for a TE-polarized wave and 306.6 GHz for a TM-polarized wave, without exerting the bias voltage on the LC layer. An increase in bias voltage affects the orientation of LC molecules and causes redshifted resonant frequencies. By adjusting the bias voltage from 0 to 10 V, frequency tunabilities of 4.7% and 4.1% for TE- and TM-polarized waves, respectively, were experimentally demonstrated. Surface current and power loss distribution was analyzed to explain the physical mechanism of the absorber, while the absorption dependence on geometrical parameters and incident angles was also studied in detail. According to the obtained results, the proposed absorber is shown here to be capable of achieving tunable polarization-dependent absorption, and to have potential application in terahertz polarization imaging, terahertz sensing, and polarization multiplexing.