Sandra Zeljkovic

A three phase bidirectional V2G interface converter based on SiC JFETs

This paper presents a 10kW three phase bidirectional on-board battery charger for use as a V2G interface in electric vehicles (EVs). The interface to the grid in the on-board charger is a three phase IGBT-based boost converter, being in charge of the power factor correction (PFC). The interface to the battery is an isolated dual active bridge (DAB) converter based on the silicon carbide (SiC) JFETs. 1200V rated SiC JFETs enable both the operation at high voltage values in the DC link (above 500V) and high switching frequencies in the range from 50 to 150 kHz. Both high converter efficiency and compact converter design can be achieved thanks to the application of these wide band gap components. The control algorithm where PFC stage can control the flow of reactive power and the DAB the flow of active power between traction battery and the grid is presented and analyzed.

Control of SiC-based dual active bridge in high power three phase on-board charger of EVs

This paper presents a control algorithm of active power flow between traction battery and grid in a dual active bridge converter (DAB). Here, DAB is a part of a three phase 10kW bidirectional on-board charger in electric vehicles (EVs). It is an isolated interface to the battery placed after a three phase power factor correction (PFC) stage. 1200V rated SiC JFETs in the H-bridge at the DC link side of DAB enable operation at high voltage values of the DC link (above 500V) with high switching frequencies in the range from 50 to 150 kHz. Both high converter efficiency and simplified, compact converter design can be achieved thanks to the application of these wide band gap (WBG) devices. Furthermore, the control algorithm is presented to achieve the fast reference tracking even in the case when, due to simplicity of sensing, only average values of currents of both battery and DC link are being regulated.

Efficiency Optimized Single-Stage Reconfigurable DC/DC Converter for Hybrid and Electric Vehicles

This paper proposes a single-stage reconfigurable topology for an isolated dc/dc converter that supplies the 12 V power net from high voltage (HV) battery pack in hybrid and electric vehicles. The proposed topology solves the problem of reduced converter efficiency in the upper range of HV battery voltages. The converter is based on a zero voltage transition (ZVT) phase shift (PS) full bridge dc/dc converter that is during its operation, depending on the instantaneous value of battery voltage, reconfigured into a push-pull converter. The more efficient ZVT PS configuration covers the upper range of input voltages whereas the hard-switching push-pull configuration covers the lower, less significant range. The ZVT PS configuration, due to tighter voltage range, operates with reduced turn-off losses, significantly decreased circulating current in the freewheeling period as well as improved efficiency of the rectifier stage. The point of reconfiguration is chosen to maximize the average efficiency according to the histogram of HV battery voltage during a typical driving cycle. The operation of the proposed converter and the efficiency improvement are validated experimentally.

Analysis of rectifier topologies for automotive HV to LV phase shift ZVT DC/DC converter

Full bridge phase shift zero voltage transition (ZVT) converter is a standard topology for the automotive high voltage (HV) to low voltage (LV) DC/DC converter. One of the major issues due to the required wide input and output voltage range is the voltage overshoot during the turn-off process of rectifier MOSFET switches. This paper presents a model to simulate turn-off voltage waveforms of switches for different rectifier topologies. Experimental verification on a 3kW converter prototype shows that the model is accurate regarding voltage overshoot value and the oscillation frequency, and that reverse recovery of body diodes has no significant effect on the overshoot. In comparison to two other rectifier topologies, the bridge rectifier has the lowest requirements regarding the switch breakdown voltage, resulting in decreased power losses and eliminating the need for complex clamping/snubber circuits in this specific application.

An applicability study of LV battery on-board chargers for high power EVs

This paper analyzes an 11kW three phase on-board charger in case of prospective high power electric vehicles powered by low voltage traction battery (LV, e.g. 24V or 48V). The charger design is compared to the one in present-day electric passenger vehicles that use high voltage batteries (e.g. Tesla Model S). The analyses show that the main difference appears in the design and operation of the output stage of the isolated DC/DC converter, whereas performance of the PFC stage in both cases is comparable. First, the assessment of differences in the topology choice and in related design considerations is given. Consequently, the selection of semiconductor components for an exemplary topology is presented, followed by the efficiency-to-cost ratio analysis. Although no significant cost change is to be expected in case of LV battery chargers for high power vehicles, the LV system introduces distinguishing advantage by eliminating the need for an isolated HV to LV DC/DC converter, followed by the possibility for the space, loss and cost reduction.

A 2kW, 100kHz high speed IGBT based HV-LV DC/DC converter for electric vehicle

This paper presents a design of IGBT-based zero voltage transition (ZVT) phase shift full bridge (PSFB) synchronous rectification (SR) DC/DC converter. PSFB is frequently used topology for the high voltage to low voltage (HV-LV) DC/DC converter in electric and hybrid electric vehicle (EV/HEV). This paper evaluates the suitability of high speed IGBTs and rapid diodes for application in HV-LV DC/DC converter at 100kHz as an alternative to standard solution such as superjunction MOSFETs. Experimental measurements are obtained using prototype designed for input voltage range of 220V~400V and output ratings of 14V 145A. The efficiency over 90%is achieved in the wide range of input voltages and load currents.

Soft Switching of IGBTs in Lagging Lag of ZVT Phase Shift DC/DC Converter

Abstract The additional effort to achieve zero voltage transition (ZVT) in the lagging leg of a frequently used ZVT phase shift full bridge converter can be avoided by designing the converter with ‘high speed’ trench fieldstop IGBTs. Thanks to their reduced turn-off but at the same time low turn-on losses, the loss of ZVT in the lagging leg is not anymore critical to converter’s efficiency. Moreover, it can be beneficial due to their improved ‘switching to conduction loss’ ratio. Based on that conclusion, a simple method to maximize their efficiency by minimizing the resonant inductance is proposed.

Single-stage reconfigurable DC/DC converter for wide input voltage range operation in HEVs

This paper proposes a single-stage reconfigurable topology (1) for an isolated DC/DC converter that supplies the 12V power net from a HV-battery pack in hybrid and electric vehicles. The proposed topology solves the problem of reduced converter efficiency in the upper range of HV-battery voltages. The converter is based on the ZVT phase shift full bridge DC/DC converter that is depending on the instantaneous value of battery voltage reconfigured into the push-pull converter. The ZVT phase shift configuration covers upper range of input voltages whereas it is reconfigured into the less efficient, hard- switching, push-pull configuration to cover the lower range. The point of reconfiguration is chosen to maximize the average efficiency according to the histogram of HV-battery voltage during typical driving cycle. Experimental validation of the proposed converter and the efficiency improvement is also presented.