Ruoyu Hou

A topological evaluation of isolated DC/DC converters for Auxiliary Power Modules in Electrified Vehicle applications

This paper presents a comparative evaluation of the suitable isolated DC-DC converters for the Auxiliary Power Module (APM) in Electrified Vehicle applications. The basic Single-Input-Single-Output (SISO) DC-DC converter topologies are reviewed. Different configurations of Single-Input-Multiple-Output (SIMO) and Multiple-Input-Multiple-Output (MIMO) topologies and their control strategies are presented. By applying full bridge current doubler as the base topology, different multiple topology configurations are compared from a MOSFET switch efficiency drop and cost aspect. Results of the study show that the Input-Series-Output-Parallel (ISOP) topology configuration presents better performance for the APM application in terms of switch efficiency and cost.

Applied Integrated Active Filter Auxiliary Power Module for Electrified Vehicles With Single-Phase Onboard Chargers

In single-phase onboard chargers for electrified vehicles, second-order harmonic currents and corresponding ripple voltages exist on the dc bus. The low-frequency harmonic current is normally filtered using a bulk film capacitor or an additional active filter (AF) circuit. This presents an obstacle for improving the power density as well as reducing the cost. This paper proposes a simple and effective method that reduces the bulk capacitor in single-phase chargers and alleviates the low-frequency sinusoidal harmonic current in automotive applications. It applies the low-voltage (LV) battery charger auxiliary power module as an AF to filter the low-frequency harmonic currents in the high-voltage (HV) battery charger when the HV battery is charging. Hence, the integrated active filter auxiliary power module (AFAPM)-based dual-voltage charging system can achieve the AF function without extra power switches, heat sinks, and corresponding gate-drive circuits. In addition, the proposed AFAPM converter can obtain an almost unchanged switch rating to achieve 2.4-kW LV battery charging and 6.6-kW HV active filtering functions. Therefore, the proposed method can reduce the cost for the dual-voltage charging system in electrified vehicles. A 1.2-kW proof-of-concept prototype has also been built and experiments show promising results confirming the effectiveness of the proposed concept.

A Primary Full-Integrated Active Filter Auxiliary Power Module in Electrified Vehicles With Single-Phase Onboard Chargers

In single-phase ac high-voltage (HV) battery chargers, as the input current is enforced to be varying sinusoidally in phase with the input voltage, the pulsating power at two times of the line frequency will be seen on the dc-link. Bulky capacitor bank or extra active filter (AF) circuits are needed to assimilate this harmonic current, which become a major barrier in terms of power density and cost. Sinusoidal charging method can be applied, while this might affect the charging efficiency and a deep study is still needed to further investigate on the impact to the Lithium-ion battery. An active filter auxiliary power module (AFAPM) based dual-mode dual-voltage charging system for vehicle application has been proposed. The AFAPM converter has two modes: the HV active filtering mode, in which the vehicle is connected to the grid and the converter assimilates the significant second-order harmonic current; and the low-voltage (LV) battery charging mode, in which the vehicle is running and the converter charges the LV battery from HV battery. However, a relay and inductors are still required in that converter to achieve the dual-mode operation. This paper proposes a primary full-integrated AFAPM for electrified vehicle applications with single-phase onboard chargers. The proposed AFAPM converter is composed of a two-phase bidirectional buck converter to work as an AF and a dual-active-bridge to operate as a LV battery charger auxiliary power module (APM). With the proposed converter, only an extra active energy storage capacitor is needed to achieve the active filtering. All the switches and inductors on the primary stage are shared between the AF and APM. Therefore, the use of a bulky capacitor bank or an additional AF circuit is avoided and, thus, the cost, size, and weight of the dual-voltage charging system in the electrified vehicle applications can be reduced. A 720-W prototype has been built to confirm the effectiveness of the proposed converter.

Dual active bridge-based full-integrated active filter auxiliary power module for electrified vehicle applications with single-phase onboard chargers

In single-phase AC onboard chargers for electrified vehicles, second-order harmonic current and corresponding ripple voltage exist on the DC bus. The low-frequency harmonic current is normally filtered using a bulk capacitor or an additional active filter (AF) circuit. This presents an obstacle for improving the power density as well as reducing the cost. In this paper, a dual active bridge (DAB)-based full-integrated active filter auxiliary power module (AFAPM) is presented so that when the high-voltage (HV) battery is charging, the DAB converter acts as an active filter; and when the low-voltage (LV) battery needs to be charged, the DAB converter works as a LV battery charger. Therefore, the required DC-link capacitance in the HV battery can be reduced significantly and, hence, the cost and volume of the dual-voltage system in the electrified vehicle applications can be reduced. The effectiveness of the proposed method is verified by simulation results.

Integrated active power filter auxiliary power modules for electrified vehicle applications with single-phase on-board chargers

In single-phase on-board charger for the electrified vehicles, second-order harmonic currents and corresponding ripple voltages exist on the dc bus. The low-frequency harmonic current is normally filtered using a bulk film capacitor or additional active power filter (APF) circuit. This presents an obstacle for improving the power density as well as reducing the cost. This paper presents a new method for reducing the bulk capacitor in the single-phase charger. It applies the low voltage (LV) battery charger auxiliary power module (APM) as an APF to filter the low-frequency harmonic currents in the high voltage (HV) battery charger when the HV battery is charging. Hence, the integrated APM can achieve the APF function without extra power switches, heat sinks and corresponding gate drivers. Therefore, the proposed method can reduce the cost and volume for the dual-voltage charging system in the electrified vehicle applications. The effectiveness of the proposed method is verified by simulation results.

Dynamic analysis of the interaction between an Interleaved Boost Converter with Coupled Inductor and a Constant Power Load

This paper presents the dynamic analysis of the interaction between an Interleaved Boost Converter with Coupled Inductor (DPCI) and a Constant Power Load (CPL). In order to perform the analysis, the analytical determination of the output impedance of the DPCI is presented, as well as the input impedance of CPL. Then, the same analysis is proposed for a conventional Boost Converter in order to compare the two topologies. Based on identical specifications and operating conditions corresponding to an electrified vehicle, the two cascaded systems are analyzed and compared. The impedance and stability analysis are given by small-signal approach. Accuracy of the analyses is verified using MATLAB/Simulink simulations. Results of the study show that the DPCI presents better output impedance characteristics than the conventional topology. Therefore, considering similar specifications and controller, asymptotic stability and power quality of the DC-bus is improved by using DPCI.

Evaluation of integrated active filter auxiliary power modules in electrified vehicle applications

In electrified vehicles, distinct harmonic currents and corresponding ripple voltages exist mainly on the DC-links of the traction inverter and single-phase high voltage (HV) battery charger. Those harmonic currents are normally filtered by a bulk capacitor or an additional active filter (AF) circuit. This presents an obstacle for improving the power density as well as reducing the cost. This paper explores and evaluates a new method for reducing the bulk film capacitors in electrified vehicles. It applies a proposed integrated active filter auxiliary power module (AFAPM) to fulfill both the low voltage (LV) battery charging mode and the active filtering mode functions. Hence, the integrated AFAPM can achieve the AF function without extra power switches, heat sinks, and corresponding gate drivers. Therefore, the proposed method can reduce the cost and volume of the power electronics system in electrified vehicle applications. The evaluation results show that using the AFAPM to mitigate the single-phase HV battery chargers second-order harmonic current is promising and easy to achieve.

Hybrid electric locomotive powertrains

With the increasing awareness of fuel consumption and combustion engine exhaust emissions, more electrified locomotives emerge as promising solutions to fulfill the new requirements of being “Green”. This paper aims at reviewing the present situation and development of hybrid electric locomotive powertrains. The present diesel-electric locomotive powertrains, motor-assist locomotive powertrains as well as their alternators and traction motors are reviewed. Various other locomotive hybrid powertrains are also presented with the future trends discussed.

Power Electronic Systems and Control in Automobiles

Abstract Electrified transportation is the outcome of the paradigm shift from conventional internal combustion engine (ICE)-based vehicles to more efficient and cleaner electrified vehicles. Power electronics plays an increasingly important role in the electrified vehicle applications. In this chapter, the functions and requirements of the power electronic systems and their main converters in electrified vehicles are given. The modeling of the cascading system and the control of the traction inverter, the boost converter, and the low-voltage (LV) DC/DC auxiliary power module (APM) are presented. Some design examples are also given to support the control theory and show the design performance.

Improved combined modulation strategy for dual active bridge converter in electrified vehicles

The dual active bridge (DAB) converter is ideally suited for electrified vehicle applications for its galvanic isolation, bidirectional power flow and inherent soft-switching capability. However, when conventional single-phase-shift (SPS) modulation is applied, zero-voltage switching operation is limited by wide voltage range of high voltage and low voltage batteries, especially under light load condition. A combined modulation strategy including triangular, trapezoidal and SPS modulation has been proposed to extend soft switching range by realizing zero-current switching. In this paper, the current stress of each modulation method is analyzed comprehensively. It is observed that the boundaries applied in the traditional combined modulation strategy result in higher current stress in some operation area. A new boundary between the trapezoidal and SPS modulation is proposed to improve the combined modulation strategy. Current stress is reduced considerably in the area between traditional boundary and the new boundary. Simulation results are provided to validate the proposed boundary.