Environmental Engineering Reference
In-Depth Information
module, each set to an initial SOC of 80%, it is shown that a charge sustaining
mode can be realized for the battery, in the presence of random passenger loading
overdrive cycle noted in Figure 4.28. However, the ultra-capacitor bank will be in
charge depletion over this cycle for the selected strategy.
Figure 4.34 illustrates the city bus drive schedule already defined, the pro-
pulsion power, energy storage system SOC, plus the battery and ultra-capacitor
pulse power. The drive schedule specifications are listed in Table 4.14 for the
110 min urban and highway fixed route (total stopped time = 48.5 min or 44% of
total time).
Table 4.14 City bus drive schedule
Event #
t1
t2
t3
t4
t5
t6
t7
t8
t9
t10
Event mark (min) 12
26
40
47
62
72
84
95
103
110
Event time (min)
12
14
14
7
15
10
12
11
8
7
Number pass
43
39
31
20
9
28
37
41
36
30
Accel (m/s
2
)
0.174 0.149 0.10 0.199 0.093 0.139 0.116 0.126 0.174 0.199
Stop time (s)
330
370
370
180
400
260
320
290
210
180
Note:
The number of passengers,
N
p
, is a random number with mean value according to (4.11).
In Figure 4.34 the battery SOC sags noticeably during the highway and early
urban stop-go events because of the extended stop times and the burden of a
constant accessory load for cabin climate control and entertainment features.
Propulsion power
City bus drive schedule
100
300.0
200.0
100.0
0.0
−100.0
−200.0
50
0
0
2,000
4,000
6,000
8,000
0
2,000
4,000
6,000
8,000
-50
Time (s)
Time (s)
Battery and UC SOC
Pulse power, battery and UC
1.0
150.0
100.0
0.5
50.0
0.0
0.0
0
2,000
4,000
6,000
8,000
0
2,000
4,000
6,000
8,000
-0.5
−50.0
Time (s)
Time (s)
Figure 4.34 City bus simulation of propulsion power and energy storage
system performance
For the engine driven generator strategy selected the city bus returns to its
starting point with the battery replenished, but with the ultra-capacitor depleted. It
is clear from the drive schedule that the second, third and fourth stop-go events
