Mohammad N. Anwar

Design considerations for high-voltage DC bus architecture and wire mechanization for hybrid and electric vehicle applications

In electric and hybrid electric vehicle applications high-voltage (HV) DC bus is shared by multiple power converter units and energy storage systems. Each of these components should meet a set of common HV bus design requirements besides their own functional requirements. Selection of an appropriate HV DC bus architecture is intertwined with control dynamics and filter component sizing, together with a set of design metric for automotive applications. This paper discusses these items with simulation results and design trade-offs. Some vehicle level test data is also presented here in support. This paper describes HV DC bus architecture and component selection particularly for Extended-Range Electric Vehicle application. The analysis covered in this paper, in deciding an appropriate DC bus architecture, emphasizes on HV DC Bus ripple, resonance and voltage transients during various vehicle drive profiles.

Features and challenges for Auxiliary Power Module (APM) design for hybrid/electric vehicle applications

Electric and hybrid electric vehicle (EV7HEV) architectures require a small DC/DC converter to replace a conventional vehicles alternator. The small DC/DC converter, also described as the vehicle Auxiliary Power Module (APM), provides power flow between the vehicle high voltage (HV) and low voltage (LV) DC bus. The APM HV interface is connected to the HV DC bus that contains energy storage system (e.g., HV Battery) and multiple power conversion units (e.g., Traction Inverters). The APM LV interface is connected to the vehicle LV DC bus along with low voltage battery, and provides power to vehicle 12V accessory loads and other electronic control modules. Therefore, the design and operational features of the APM have significant impact on vehicle performance, overall efficiency, electric range, and to ensure a continuous power source for all the LV DC bus components. In this paper, features, performance, modes of operation, design challenges and system integration of an APM are presented with simulation results. Detail experimental results are also presented with conclusive comparison between design prediction and test data. This paper also describes power flow, load shedding, sizing and other electrical/mechanical design considerations of the APM.

Performance comparison and device analysis Between Si IGBT and SiC MOSFET

The paper presents the characteristics of the latest commercial 1200V 300A SiC MOSFET module and compares its performance with Si IGBT with the same rating using experimental results and the saber software environment. Our SiC MOSFET model in SABER gives accurate results across a wide range of temperatures. The results show that the 1200V SiC MOSFET has faster switching speed and significantly less switching loss compared to the Si IGBT. Moreover, the Si IGBT switching loss will increase significantly for higher operation temperature, while the SiC MOSFET switching loss has little variation over different temperatures. This paper will also investigates the stray inductance effect on the gate, drain, and source side and verifies its performance with Si IGBT. The double pulse test circuit has been implemented in SABER to simulate the dynamic losses and a brief review of the various applications for automotive industry of the SiC MOSFET has been also presented in the paper.

Analysis of ground fault currents in isolated and non-isolated charging modules in electric vehicles

The paper compares generic on board charger module (OBCM) topologies with respect to ground fault current detection and interruption. Ground fault current in isolated charging modules is very small due to the galvanic isolation between the input and output sides. In non-isolated charging modules, the paper shows the contributing components of the system to the generation of ground fault current. The ground fault current interrupt circuit is explained and compared in both topologies. Performance and parametric measures are used to compare the two topologies in MATLAB/Simulink.

Investigation of common mode noise in electric propulsion system high voltage components in an electrified vehicle

Common mode (CM) and differential mode (DM) noises are two of the main considerations in designing high voltage (HV) components, particularly minimizing filter sizing, shielding structure of the cables, grounding layout for circuits and power stage components and finally orientation of magnetics and chokes. This paper will introduce CM noise and electromagnetic interference (EMI) related issues and design guidelines in designing power electronics for Traction Power Inverters. Power module baseplate and mechanical packaging, vehicle and cable shielding and routing of ground paths and their effects on CM noise and EMI together with bands of frequencies are discussed in this paper. Mechanical and packaging considerations are important to keep CM noise within specified limit and this will be shown with simulated and test results.

Compact and high power inverter for the Cadillac CT6 rear wheel drive PHEV

Electric drive system for the Cadillac CT6 plug-in hybrid electric vehicle (PHEV) comprises a power-split hybrid transmission utilizing two motors, a traction power inverter module (TPIM) having two inverters and a liquid-cooled lithiumion battery pack [1, 2]. The resulting propulsion system provides a combination of exceptional fuel economy, crisp acceleration, and strong electric-only driving range. To meet all these performance, reliability and robustness targets and package the TPIM into a compact under hood environment is a challenge. This paper describes indispensable and collaborative design efforts by Hitachi Automotive and General Motors to meet this challenge. Enhancing heat dissipation performance and using high efficient power semiconductor enables reduced inverter size and increased power output. Elimination of heat impeding thermal grease and developing direct water cooled power module made generational improvements in this area. Hitachi went further by developing a direct double-sided cooling power module to achieve ∼35% improvement in heat dissipation utilizing a proprietary cooling structure that immerses the module in coolant [3]. This paper elaborates on the integration, structure and the selection of power transistor switch for this TPIM to meet Cadillac CT6 PHEV tractive and special maneuver needs. Among other coherent steps are to design low inductance busbar, optimize the gate drive circuit elements, provide protection functions for detecting over-temperature, over-current, over-voltage ranges and thus maximizing the performance from the power devices. Design efforts were also directed to surround the Bulk DC capacitor by the vertical water channels of the power module and maintain life expectancy by not exceeding rated hot spot temperature. This paper describes predictions, component and vehicle level test results to justify design competence.

Power electronics laboratory R-L load bank development for traction inverter of hybrid/ electric vehicles

This paper talks about the development of a laboratory test bench, particularly the load bank, for testing Inverter of Hybrid/Electric Vehicle. This paper discusses capabilities, pros and cons of different load bank options, namely, motor dynamometer, active load emulator and inductive load in terms of testing the inverter power module stress. Enhancements to inductive load test bench are discussed with simulation and testing indicating the effectiveness of this inexpensive load bank to achieve module power stress compared to other load banks. This paper explains the importance of load power factor and modulation index that impacts the module power loss and hence the thermal stress. Multiple operating conditions by changing fundamental frequency and phase currents were tested and the results were analyzed against the simulation model for inductive, resistive-inductive load bank and motor dyne.

Development of a power dense and environmentally robust traction power inverter for the second-generatio chevrolet VOLT extended-range EV

By significantly re-engineering to reduce physical size and mass of the traction power inverter module (TPIM) for 2nd generation Chevrolet VOLT Extended-Range EV it is possible to mount the inverter to the transmission and meet all performance targets, maintain high reliability and environmental robustness. The Chevrolet VOLT is an electric vehicle with extended-range. It is capable of operation on battery power alone, and on hybrid/ engine power after depletion of the battery. 1st generation Chevrolet VOLTs (VOLT-1) were driven over half a billion miles in North America from October 2013 through September 2014, 74% of which were all-electric [1, 12]. For 2016, GM has developed the 2nd generation of the VOLT (VOLT-2) vehicle and “Voltec” propulsion system. This effort by GM and Delphi provides a significant cost benefit to the overall system by eliminating costly AC traction cables. Effort was taken to the electrical design of the power switch to achieve efficiency target and thermal challenges. A novel cooling approach enables high power density while maintaining a very high overall conversion efficiency. Design focus was applied to the mechanical design of this TPIM to provide extremely stiff frame required for reliability in the transmission environment and reduce integration cost.