A 10kW Solar-Powered Bidirectional EV Charger Compatible with Chademo and COMBO

Abstract

 Charging electric vehicles (EVs) from photovoltaic panels (PV) provides a sustainable future for transportation. This paper presents the development of a 10kW EV charger that can be powered from both a PV array and the three-phase AC grid. The goal is to realize a high power density and high-efficiency three-port power converter that integrates the EV, PV, grid and meets the Chademo and CCS/Combo EV charging standards. The EV port is designed to be isolated and bidirectional, so that both charging and vehicle-to-Grid (V2G) can be implemented. As PV and EV are both DC by nature, the converter uses a central DC-link to exchange power between the EV and PV, thereby increasing efficiency. The use of silicon carbide devices and powdered alloy core inductors enables high switching frequency and power density. The closed-loop control allows four different power flows: PVàEV, EVàgrid, gridàEV and PVàgrid. Hence the converter operates as a PV inverter, a bidirectional EV charger and a combination of both. A 10kW prototype has been successfully tested, and its experimental waveforms and measured efficiency are presented. It has three times the power density and higher partial and peak load efficiency when compared to existing solutions.

Index Terms

1.      Electric vehicle

2.      Charging

3.      powered alloy core

4.      photovoltaic systems (PV)

5.      silicon carbide (SiC)

6.      Paper produced in Windows/Microsoft Word

Block Diagram:

Fig. 1 – Block diagram of the grid connected bidirectional 10kW three–port EV-PV charger

Expected Simulation Results:

 

 

Fig. 2 – (a) Waveforms for the PV IBC for the phase shifted gate voltage VGS, Inductor current IL and MOSFET drainsource voltage Vds for (a) CCM mode (VPV=700 V, IPV=10 A); (b) DCM mode (VPV=400 V, IPV=10.75 A)

Fig. 3 – Drain-source voltage Vds and gate voltage Vgs for one phase of the IBFC for CH: (a) Quasi resonant operation LVS for Vev=250V, Iev=5A (b) Valley skipping and DCM operation at low powers for Vev=100V, Iev=1A

Conclusions

 

This paper presents the development of a 10kW, three-port, bidirectional converter for direct DC charging of EV from PV. The developed converter is compatible with CCS and Chademo EV charging standard and can operate with a PV array of wide voltage and power range. Interleaving of converters, Silicon carbide (SiC) devices, and powdered alloy core inductors are extensively used to increase the switching frequency, while keeping the converter losses within limits. This has helped to increase the power density by a factor of three when compared to conventional designs and reduce the voltage ripple at the EV, PV ports. The converter is modularly designed with three sub-converters connected on a 750V central DC-link: interleaved boost converter for PV, a three-phase inverter for the AC grid and an interleaved flyback converter for EV. While the flyback is traditionally considered suitable only for low powers, this paper shows how the use of SiC devices in a QR mode flyback converter can achieve high efficiency even at high powers. Three closed loop controls were developed and tested for the three sub-converter which enables four power flows: PVàEV, EVàgrid, gridàEV and PVàgrid. A 10kW prototype was built and tested and exhibits a peak efficiency of 95.2% for PVàEV, 95.4% for GridàEV, 96.4% for PVàGrid. The developed prototype has a much higher peak efficiency, higher partial load efficiency and three times higher power density than currently existing solutions based on AC power exchange. The charge and V2G operation at 10kW were tested with a Nissan Leaf EV with a Chademo charge controller.

References

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