real-time simulation of electric vehicle battery charging...

9-11 September 2018 - 50th North American Power Symposium

Real-Time Simulation of Electric Vehicle Battery Charging Systems

Authors: Li Bao, Lingling Fan and Zhixin Miao

Presented by: Li Bao

[email protected]

University of South Florida

mailto:[email protected]


Outline

• Introduction

• Level 1 and Level 2 charging systems

- Battery model

- Power factor correction boost circuit

- Constant current/constant voltage control

• Level 3 charging system

- VDC/Q control method

• Simulation Results


Introduction

Fig. 1 Evolution of the global electric car stock, 2013-2017 [1]

[1] I. E. Agency, “Global ev outlook 2018,” May 2018. [Online]. Available: https://webstore.iea.org/global-ev-outlook-2018

The sale of electric vehicles (EV) is rapidly increasing around the world due to EV’s efficiency and energy security.


Introduction

According to the Society of Automatic Engineers (SAE)’s chargingstandard, there are three levels of charging based on power rating.

Table 1. Charging levels summarization [2]

[2] J. Y. Yong, V. K. Ramachandaramurthy, K. M. Tan, and N. Mithulananthan, “A review on the state-of-the-art technologies of electric vehicle, its impacts and prospects,” Renewable and Sustainable Energy Reviews, vol. 49, pp. 365 – 385, 2015.


Level 1 and Level 2 charging

A single-phase AC input is used for both Level 1 and Level 2 charging.

The charging circuit includes:

• A diode rectifier;

• A power factor correction (PFC) boost DC/DC converter;

• A DC/AC converter

• A LLC resonant converter

• Diode-based AC/DC converter


Level 1 and Level 2 charging

Fig. 2 Topology of a Level 1 and Level 2 charging system


Battery modelIn this paper, a lithium-ion (Li-ion) battery is used and its electriccircuit model is adopted for simulation.

Fig. 3 Li-ion battery non-linear model [3]

[3] O. Tremblay and L.-A. Dessaint, “Experimental validation of a battery dynamic model for ev applications,” World Electric Vehicle Journal, vol. 3, no. 1, pp. 1–10, 2009.


Battery model

𝑓1 𝑖𝑡, 𝑖∗

is for charging and 𝑓2 𝑖𝑡, 𝑖∗

for discharging. They are defined as follows.


Battery model

In this paper, the parameters are from MATLAB/SimPowerSystem and are shown in below Table.

Table. 2 Battery Parameters


PFC boost circuit

Since the battery voltage is up to 400𝑉 [4], we can choose this value asPFC boost circuit output.

According the Table 1, the maximum rating power for Level 2 chargingis 14.4 𝑘𝑊. Hence, the DC output current is:

𝐼𝑜𝑢𝑡 =14.4 𝑘𝑊

400 𝑉= 36 𝐴

[4] P. T. Krein, Elements of power electronics. Oxford University Press New York, 1998, vol. 126.


PFC boost circuitAssuming the unity power factor, the single-phase ac circuit has thefollowing form of instantaneous power:

𝑝 𝑡 =𝑃

2+𝑃

2cos(2𝜔t)

where 𝜔 is 377 𝑟𝑎𝑑/𝑠 and 𝑃 is the active power.

The current through the capacitor is:

𝑖𝑐 𝑡 =𝑃cos(2𝜔t)

2𝑉𝐷𝐶

= Ioutcos(2𝜔t)


PFC boost circuit

The capacitor voltage is:

The peak-to-peak voltage ripple can be expressed as:

If the peak-to-peak voltage ripple is less than 10 𝑉, and current is 36 𝐴, the capacitor is chosen as 9.5 𝑚𝐹.


PFC boost circuit

The Level 1 charging voltage is 120 𝑉 and the output voltage is designed as 400 𝑉. Then the duty ratio is:

𝐷 =𝑉𝑜𝑢𝑡 − 𝑉𝑖𝑛

𝑉𝑜𝑢𝑡

= 0.7

The relationship between the current and voltage of the inductor is:

where T is switching time as 5 × 10−4

If 1 𝐴 ripple is allowed, then the inductor can be chosen as 95 𝑚𝐻.


PFC boost circuit

Below figure shows a PFC controller block.

Fig. 4 PFC boost circuit control block [5]

[5] C. Zhou, R. B. Ridley, and F. C. Lee, “Design and analysis of a hysteretic boost power factor correction circuit,” in 21st Annual IEEE Conference on Power Electronics Specialists, 1990, pp. 800–807.


PFC boost circuitBelow figure illustrates the impact of PFC control.

Fig. 5 Comparison of boost converter performancewith PFC control and without PFC control


CC/CV charging algorithm

Three basic charging method applied in EV battery charging [6]:

• Constant-current (CC)

• Constant-voltage (CV)

• Taper-current (TC)

CC/CV charging is combination of CC and CV.

[6] C. H. Dharmakeerthi, N. Mithulananthan, and T. K. Saha, “Modeling and planning of ev fast charging station in power grid,” in 2012 IEEE Power and Energy Society General Meeting, July 2012, pp. 1–8.



Below figure shows a simple illustration of CC/CV charging.

Fig. 6 Illustration of CC/CV charging



Below figure shows the control block implementation.

Fig. 7 CC/CV charging control structure


Level 3 charging circuit topology

The topology of Level 3 charger is shown in below figure.

Fig. 8 Topology of Level 3 charging system, bold element mean three-phase form


VDC/Q control

The VDC/Q control is shown in below figure.

Fig. 9 VDC/Q control method applied to the three-phase rectifier


Phase-locked-loop (PLL)A second-order PLL is modeled in this paper. Its control block is shown in Fig. 10.

Fig. 11 shows the diagram block of a PI controller.

Fig. 10 Block diagram of a PLL [7] Fig. 11 Block diagram of a discrete PI controller

[7] L. Fan, Control and Dynamics in Power Systems and Microgrids. CRC Press, 2017.


Simulation results

Fig. 12 Level 1 charging process Fig. 13 Level 2 charging process


Simulation results

Fig. 14 Level 3 charging process Fig. 15 SOC comparison of three level charging


Simulation analysis

Table. 3 Simulation Analysis


Thanks.

real-time simulation of electric vehicle battery charging...

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