Browse Topic: High voltage systems
Monitoring power device temperature in an electric vehicle propulsion drive converter is extremely important to achieve full power delivery within the maximum power capability envelope. Usually, on-die temperature sensors are installed on Si-IGBT power devices in electric vehicle propulsion drive converters to enable monitoring device temperature and achieve over-temperature protection. Currently, SiC MOSFET is a promising power device in power converters of electric drives because of its lower loss, higher switching speed, higher voltage capability, and higher junction temperature limit in comparison with the widely used Si-IGBT. However, SiC MOSFET is a more expensive device, installation of an on-die temperature sensor on SiC MOSFET will significantly increase its cost and complexity. So presently, there is no junction temperature sensor installed in SiC MOSFET due to which there is great difficulty protecting SiC MOSFET from over temperature. When a junction temperature estimation method is used to monitor SiC MOSFET temperature, the power loss computation of SiC MOSFET is a key factor. However, the existing loss calculation method assumes electric motors operate at high speed and power loss is computed/estimated with rms current. When the motor operates at low speed, the existing method is not practical because of a long fundamental period of phase current. The instantaneous power losses and hence the junction temperatures of the six power converter switches are not the same under such operating conditions. Hence, the junction temperature obtained with the loss computed from the rms current value does not reflect the actual device junction temperature, which may result in a failure of power device over-temperature (OT). This paper proposes a converter power device OT protection method under low motor speed to solve the above issues. The proposed method allows system cost and complexity reduction. It computes/estimates instantaneous loss and junction temperature for each individual power device of the power converter, which enables the OT detection at the motor low speed and/or imbalance phase operation. The paper presents the technical principle of the proposed instantaneous power loss and junction temperature estimation method, and OT protection for SiC MOSFET. Its model details, simulation, and experimental test results verify the new method.
Reducing the high-voltage BEV to a household level of 120-240 volts is considered in the paper as an effective means of solving the problems of electrical safety, maintenance and minor repairs of an electric vehicle in household conditions, and distributed power supply of BEV within walking distance for the driver. The analysis of the low-voltage electric drive is performed under the assumption that the battery has a nominal voltage of 200 volts. The issues of transforming a high-voltage machine (400 volts) into a low-voltage one (200 volts) by switching the stator phase sections from serial to parallel connection without changing the overall and energy characteristics are considered. It is shown that a two-motor unit with induction machines with a capacity of 50 kilowatts can provide 100 kilowatts in long-term and up to 200 kilowatts in peak modes. The paper considers the issues of implementing a low-voltage inverter and modern trends in distributed power supply for BEVs based on low- and medium-power charging units adapted to household electrical networks. The paper contains an example of a three-phase charging device with adaptive power take-off for each phase, taking into account the instantaneous load of the network by household consumers. The paper considers the issues of implementing a positive energy balance of the BEV-charger-electric grid system using mobile energy storage devices based on the secondary use of car batteries.
Sodium-ion batteries (SIBs) are becoming a strong candidate for large-scale energy storage applications due to their cost-effectiveness and abundant sodium resource reserves. Ether solvents have advantages such as excellent low-temperature performance and good reduction stability. However, poor oxidation stability limits the use of ether-based electrolytes, which need to be addressed urgently. In this study, 1 M sodium tetrafluoroborate (NaBF4) and 0.05 M sodium difluoro(oxalato)borate (NaDFOB) were added in tetraethylene glycol dimethyl ether (G4), which is named “BDG4”. BDG4 electrolyte can promote the formation of cathode electrolyte interface (CEI) layers containing NaF and B─O/B─Na inorganic components on the surface of the cathode. The dense CEI layers can prevent the solvent from undergoing oxidation reactions. Therefore, thanks to the lower highest occupied molecular orbital (HOMO) energy level of G4 and its close coordination structure with Na+, the electrolyte has a high-voltage stability exceeding 4.5 V versus Na+/Na. Therefore, BDG4 electrolyte can be stably cycled on Na3(VO)2(PO4)2F (NVOPF) and NaNi1/3Fe1/3Mn1/3O2 (NFM) cathode for over 250 cycles at room temperature, exhibiting a high Coulombic Efficiency (CE) exceeding 99.8%. Furthermore, BDG4 demonstrated excellent rate performance of NFM cathode, maintaining 75% capacity retention even at 4 C. Due to the stable solid electrolyte interface (SEI) layers formed by the mixture of inorganic and organic components, BDG4 electrolyte can also cycle stably on the Hard Carbon (HC) anode. Therefore, the commercial NFM||HC pouch full cell can cycle stably with 88.3% capacity retention after 80 cycles. This work reveals the role of NaDFOB and provides a feasible approach for the design of high-voltage ether electrolytes of SIBs.
Direct current (DC) systems are increasingly used in small power system applications ranging from combined heat and power plants aided with photovoltaic (PV) installations to powertrains of small electric vehicles. A critical safety issue in these systems is the occurrence of series arc faults, which can lead to fires due to high temperatures. This paper presents a model-based method for detecting such faults in medium- and high-voltage DC circuits. Unlike traditional approaches that rely on high-frequency signal analysis, the proposed method uses a physical circuit model and a high-gain observer to estimate deviations from nominal operation. The detection criterion is based on the variance of a disturbance estimate, allowing fast and reliable fault identification. Experimental validation is conducted using a PV system with an arc generator to simulate faults. The results demonstrate the effectiveness of the method in distinguishing fault events from normal operating variations. The method is compared with a recursive least squares estimator, showing improved performance in terms of sensitivity. The approach offers a cost-effective and robust solution to improve safety in DC power systems, particularly in PV and electric mobility applications.
Zero emission vehicles are essential for achieving sustainable and clean transportation. Hybrid vehicles such as Fuel Cell Electric Vehicles (FCEVs) use multiple energy sources like batteries and fuel cell stacks to offer extended driving range without emitting greenhouse gases. Optimal performance and extended life of the important components like the high voltage battery and fuel-cell stack go a long way in achieving cost benefits as well as environmental safety. For this, energy management in FCEVs, particularly thermal management, is crucial for maintaining the temperature of these components within their specified range. The fuel cell stack generates a significant amount of waste heat, which needs to be dissipated to maintain optimal performance and prevent degradation, whereas the battery system needs to be operated within an optimal temperature range for its better performance and longevity. Overheating of batteries can lead to reduced efficiency and potential safety hazards, while low temperatures can decrease battery performance and range. The multiple temperature control loops in the thermal system design of the current FCEVs require significant energy for continuous heating and cooling. This is due to the fact that each of them exchanges energy directly with an external source or sink without redistributing energy among themselves. This can lead to energy losses during the heat exchange process. Our goal is to optimize thermal energy usage while maintaining the same performance and efficiency of both battery electric system and the fuel cell stack in a vehicle. In this paper, an analysis of thermal energy utilization of a single system is compared to the exchange of thermal energy across multiple systems, considering various heating and cooling scenarios. We compare our proposed strategy (with redistribution) with the existing strategy (without redistribution) quantitatively with respect to controller effort/ energy spent in achieving thermal target.
Increasing the mission capability of ground combat and tactical vehicles can lead to new concepts of operation that enhance safety and effectiveness of warfighters. High-temperature power electronics enabled by wide-bandgap semiconductors such as silicon carbide can provide the required power density to package new capabilities into space-constrained vehicles and provide features including silent mobility, boost acceleration, regenerative braking, adaptive cooling, and power for future protection systems and command and control (C2) on the move. An architecture using high voltage [1] would best satisfy the ever-increasing power demands to enable defense against unmanned aerial systems (UAS) and offensive directed energy (DE) systems for advanced survivability and lethality capabilities.
The interaction of electric, electronic (E/E) and mechanical components defines the quality of a BEV’s powertrain. Component selection, their integration and calibration aim at meeting legal requirements for EMC and safety as well as competitive targets for efficiency, NVH and driving comfort. These tasks in particular need attention on electromagnetic events on the DC bus, the high-power electronics of inverters, the e-motors, and the drive shaft. Each component within this environment is defined by its electromechanical features with variabilities selected from a large set of operating parameters. Consequently, a complete powertrain and its controllers give rise to endless combinations for powertrain operation. How to understand and avoid risk laden and ineffective parameter options, how to find powertrain control parameters for safe, efficient and comfortable operation? And how to find solutions within competitive development timeframes? Particular issues include high voltage risks on AC and DC bus, AC resonant ripple currents on the DC lines, or risks arising from powertrain dynamics and impacting NVH quality and driving comfort. Such issues are addressed with extensive system simulations and, finally, with comprehensive testing a powertrain’s electric, electronic and mechanical behavior. The focus of this paper is on E/E and NVH signal analytics guiding the integration of powertrain modules: E/E challenges arise from voltage bursts at MHz frequencies endangering insulation of stator windings and cables. Current ripples on the HV-DC bus may endanger auxiliary components. Motor operation and drive shaft dynamics must not compromise NVH quality and component durability.
While electric powertrains are driving 48V adoption, OEMs are realizing that xEV and ICE vehicles can benefit from a shift away from 12-volt architectures. In every corner of the automotive power engineering world, there are discussions and debates over the merits of 48V power networks vs. legacy 12V power networks. The dialogue started over 20 years ago, but now the tone is more serious. It's not a case of everything old is new again, but the result of a growing appetite for more electrical power in vehicles. Today's vehicles - and the coming generations - require more power for their ADAS and other safety systems, infotainment systems and overall passenger comfort systems. To satisfy the growing demand for low-voltage power, it is necessary to boost the capacity of the low-voltage power network by two or three times that of the late 20th century. Delivering power is more efficient at a higher voltage, and today, 48V is the consensus voltage for that higher level.
Precision flight in windy conditions is a common challenge for multirotor UAS. It is especially challenging for in contact tasks that require high-precision positioning and good disturbance rejection capabilities. Such tasks include landing on high-voltage powerlines for in-contact inspections. This paper presents the implementation of small lateral thrusters to improve the lateral position hold ability of a large power line inspection UAS in windy conditions. Arranged in antagonistic pairs on each side, the lateral thrusters handle the high-frequency but smaller-amplitude wind turbulence components with a frequency split control. Using an identified model of the UAS flight dynamics alongside flight data in high-wind conditions, a control architecture with a frequency split in the lateral axis was optimized to increase the disturbance rejection. Experimental tests showed a 67% reduction in lateral position error with the proposed approach in high-wind conditions.
Sound power is a commonly used metric to quantify acoustic sources like AC motor in electrified powertrain. Testing for sound power determination is often performed in an anechoic environment to create free-field conditions around the unit. To eliminate the influence of extraneous noise sources, the anechoic facilities must be further isolated from driver and absorber dynamometers. These dynamometers are needed for running the AC motors in the desired speed and load conditions. For early detection of potential issues, it is advantageous to have the capability for engineers to conduct acoustic tests in standard laboratory environments. These may include non-acoustically treated rooms, presence of extraneous noise sources (e.g., driver and absorber dynos), etc. In such environments, sound intensity-based sound power determination methods could be utilized. The sound intensity-based approach is covered in ISO 9614 standard. The norm is to sweep an intensity probe on a sound source in constant speed condition to cover all the surfaces around the source. However, standing next to a high speed, high voltage electric motor to perform intensity probe sweep poses safety risks. To counter this challenge, a different approach is applied using Pressure Velocity (p-u) intensity probe array around the test subject. In this alternative approach, the use of intensity probe array to calculate sound power of AC motor is discussed. Also detailed is how the measurements are validated to ensure they conform to ISO field indicators. The validation process included considerations such as size of the array, distance from the array and number of probes in the array. The key advantage of this approach is the ability to perform speed sweeps on the motor in semi-reverberant acoustic environment, which could help in identifying potential issues early on in the development.
Improving the efficiency of Battery Electric Vehicles (BEVs) is crucial for enhancing their range and performance. This paper explores the use of virtual tools to integrate and optimise various systems, with a particular focus on thermal management. The study considers global legislative drive cycles and real-world scenarios, including hot and cold weather conditions, charging cycles, and towing. A virtual vehicle model is developed to include major contributors to range prediction and optimisation, such as thermal systems. Key components analysed include high voltage (HV) and low voltage (LV) consumers (compressors, pumps, fans), thermal system performance and behaviour (including cabin climate control), thermal controllers, and thermal plant models. The emergent behaviour resulting from the interaction between hardware and control systems is also examined. The methodology involves co-simulation of hardware and control models, encompassing thermal systems (coolant, refrigerant, cabin) and the vehicle propulsion domain (driveline, powertrain). This is achieved using a combination of 1D thermos-fluid simulation tools, multi-domain simulation, model-based design block diagram environments, and virtual ECU simulation platform models. The approach can run the entire vehicle operating range and capturing the main HV and LV consumers. The findings demonstrate that integrating thermal system plant and controls through virtual tools can significantly enhance BEV efficiency, providing a comprehensive framework for future developments in electric vehicle technology.
To promote the electric performance and safety of development for EV mobility, optimization methodology and design guide of high voltage bolted joint should be newly developed. This paper describes the development process of multi-physics (electrical, mechanical, thermal) FEA methodology, various experimental tests and establishment of optimization methodology of busbar bolted joint design in terms of bolt preload validation and joint temperature rise. The various key factors on high voltage joint tightening are quantitatively studied by utilizing this optimized methodology.
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