Single Switched Capacitor Battery Balancing

8/13/2019 Single Switched Capacitor Battery Balancing

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Single Switched Capacitor Battery

Balancing

System Enhancements

Mohamed Daowd, Mailier Antoine,

Noshin Omar, Peter van den Bosscheand Joeri van Mierlo


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Double-Tiered Switched

Capacitor(DTSC)

n capacitors

2n bi-directional

switches


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Single switched capacitor(SSC)

single capacitor

n + 5

bi-directional

switches


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Modularized switched capacitor (MSC)

n 1 capacitor low

voltage

1 capacitor high voltage

2n + 4

bi-directional switches


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Figure 6. Switched capacitor balancing simulation

results


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Figure 7. Double-tiered switched capacitor simulation


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Figure 8. Single switched capacitor balancing simulation


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Single Switched Capacitor Control

Strategy

More efficient control strategy, reducing the

capacitor size, the system cost, and the

balancing time

Maximize the shuttling energy transfers

between the cells, and minimizing the

capacitor size and the balancing time


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Factors

Capacitor value (C)

Switching frequency (F)

Series equivalent resistance (Rseq) Voltage difference between the unbalanced

cells (Vdiff)

The duty cycle, on-period, (D)


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SSC Strategy Proceeding

1. Extracting the function of the transferred energy between the cells and

the capacitor.

2. Selecting the optimal capacitor value (minimum) by maximizing the

energy function with respect to the capacitor value at different switching

frequencies. The transferred energy will be a function of (C, F), with any

arbitrary Vdiff and D because the latter two parameters will vary during

balancing periods. 3. Maximizing the energy transfer with the calculated C and RSeq values as

a function of (F, D) at different values of Vdiff.


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SSC Strategy Proceeding

4. Dividing the balancing period into zones according

to voltage difference Vdiff, and decide the required

maximum current allowed through the capacitor and

the corresponding equivalent resistor RSeq value 5. By knowing the higher and lower cell voltage,

applying the corresponding F and D along the

balancing time according to the cell voltages to get

the maximum energy transfer


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Proposed SSC Balancing Simulation


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Experimental results

3.288 and 3.212 V (Vdiff. = 76 mV)

SoCs =35% and 11.3%(difference is 23.7%)

SoC summation was 46.3%

Documents

Single Switched Capacitor Battery Balancing