Environmental Engineering Reference
In-Depth Information
Main : 125 k
100 us/div
Mean(C1)
85.2735 mA
Mean(C2)
6.75528 V
Mean(C3)
2.15023 V
Freq(C4)
18.30578 kHz
Duty (C4)
86.0%
Mean(M1)
575.484 uEU
Mean(M2)
79.7185 EU
Source Power ( P in )
Source Resistance (
R s
)
PWM Gating Signal
Source Voltage ( V in )
Output Voltage ( V o )
Source Current ( I in )
0
100
200
300
400
500
600
700
800
Time/µsec
FIGURE 3.8
Operation of a resistor emulation-based MPP tracker at 10-k
loading.
varying temperature differences. These observations and analyzes apply to
the decreasing temperature difference condition as well.
Second, the operation of a resistor emulation-based MPP tracker for dif-
ferent loading conditions were experimentally tested, and the experimental
results are shown in Figures 3.8 and 3.9 . Equation 3.10 is used to determine the
duty cycle that emulates the source resistance of the thermal energy harvester
( R s,TEG =82k
) for maximum power transfer between the source and the load.
The operating range of the loading conditions is determined based on the two
extreme ends of the operational bandwidth of the buck converter when con-
nected to a 0.1-F supercapacitor, the initial charging and final charged states
of the supercapacitor can be emulated by two load resistances R L of 10 and
56 k
,respectively. Based on Equation 3.10 , the emulated duty cycles of the
two resistance values (i.e., 10 and 56 k
)are calculated to be 0.14 and 0.27,
respectively.
Referring to Figures 3.8 and 3.9 , the complementary emulated duty cycles
(a P-MOSFET [metal-oxide-semiconductor-field-effect-transistor] [PMOS] is
used instead of an N-MOSFET [NMOS] as the high-side switch of the buck
converter) obtained experimentally are 0.14 and 0.251 for the load resistances
R L of 10 and 56 k
,respectively, and the experimental results tally with
the calculated duty cycles of 0.14 and 0.27. At the emulated duty cycles, it
can be observed in both Figures 3.8 and 3.9 that the approximate desired
R em =82k
is achieved, and the maximum electrical power P MPPT = 580
W
(see Figure 3.3 ) is harvested.
 
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