Design of a PEV Battery Charger with High Power Factor using Half-bridge LLC-SRC Operating at Resonance Frequency

 ABSTRACT:

This paper presents a two stage battery charger for plug-in electric vehicles (PEV) based on half-bridge LLC series resonant converter (SRC) operating at resonance frequency. The first stage is power factor correction (PFC) stage comprising of boost converter topology using hysteresis band control of inductor current. The PFC stage reduces the total harmonic distortion (THD) of the line current for achieving high power factor and regulates the voltage to follow the battery voltage at DC link capacitor. The input of the boost converter is a single phase 50 Hz, 220V AC from grid. At the second stage, a half bridge LLC-SRC is used for constant-current, constant-voltage (CC-CV) based battery charging and for providing galvanic isolation. The resonant converter is designed to operate around resonance frequency to have maximum efficiency and low turnoff current of power switches to reduce switching losses. The circuit is simulated using MATLAB Simulink with 1.5 kW maximum output power. Simulation results show that the PFC stage achieves THD less than 0.07% and high power factor value as 0.9976. The DC/DC stage meets all the CC-CV charging requirements of the battery over wide voltage range 320V—420V for depleted to fully charged battery.

KEYWORDS:

1.      LLC Resonant converter

2.      PEV battery charger

3.      PFC

4.      Hysteresis band control

5.      FHA

SOFTWARE: MATLAB/SIMULINK

BLOCK DIAGRAM:

Fig. 1. Schematic of the proposed battery charger.

EXPECTED SIMULATION RESULTS:

Fig. 2. Boost inductor current for a half cycle of input voltage.

Fig. 3. AC voltage and current after power factor correction.

Fig. 4. LLC-SRC operating at key point A (V0 = 320V, and I0 = 3.57A).

Fig. 5. LLC-SRC operating at key point B (V0 = 360V, and I0 = 3.57A).

Fig. 6. LLC-SRC operating at key point C (V0 = 420V, and I0 = 3.57A).

Fig. 7. LLC-SRC operating at key point D (V0 = 420V, and I0 = 0.25A).

CONCLUSION:

 In this paper, a 1.5 kW PEV battery charger with emphasis on the design of LLC-SRC for DC-DC stage of the battery charger is presented. A method for improvement in the power factor with boost converter is presented using hysteresis current control to keep line input voltage and current in phase using phase shift in inductor current. Simulation results show that the PFC stage achieves minimum THD as 0.07% and a power factor of 0.9976 having line current and voltage in phase. The LLC-SRC is designed to operate around resonance frequency to achieve maximum benefits of LLC converter, having minimum circulating energy, avoiding hard commutation of secondary rectifier diodes. Simulation results for the converter performance are presented which show that the turning off current of power switches have very low value throughout the charging process and is below 2.4A. Hence, the converter have minimum switching and conduction losses.

REFERENCES:

[1] H. Wang, S. Dusmez, and A. Khaligh, "A novel approach to design EV battery chargers using SEPIC PFC stage and optimal operating point tracking technique for LLC converter," Applied Power Electronics Conference and Exposition (APEC), 2014 Twenty-Ninth Annual IEEE, pp.1683-1689, 16-20 March 2014.

[2] H. Wang, S. Dusmez, and A. Khaligh, "Design and Analysis of a Full-Bridge LLCBased PEV Charger Optimized for Wide Battery Voltage Range," Vehicular Technology, IEEE Transactions on, Vol. 63, No. 4, pp.1603-1613, May 2014.

[3] J. Deng, S. Li, S. Hu, C.C. Mi, and R. Ma, "Design Methodology of LLC Resonant Converters for Electric Vehicle Battery Chargers," Vehicular Technology, IEEE Transactions on, Vol. 63, No. 4, pp.1581-1592, May 2014.

[4] Marian K. Kazimierczuk, "Pulse-width Modulated DC-DC Power Converters," Ohio, USA: John Wiley & Sons Ltd, pp. 129-134, 2008.

[5] H. Wang, and A. Khaligh, "Comprehensive Topological Analyses of Isolated Resonant Converters in PEV Battery Charging Applications," Transportation Electrification Conference and Expo (ITEC), 2013 IEEE, pp.1-7, 16-19 June 2013.