Environmental Engineering Reference
In-Depth Information
Electrical Power Generated (mW) vs. Load Resistance (Ω)
100
Vo = 1.3 m/s
Vo = 2.3 m/s
Vo = 3.5 m/s
Vo = 3.8 m/s
Vo = 4.5 m/s
Vo = 5.6 m/s
Vo = 6.3 m/s
Vo = 7 m/s
Vo = 8.5 m/s
80
60
40
20
0 0
100Ω
200
400
Load Resistance (Ω)
600
800
1000
FIGURE 2.4
Power curves of a wind turbine generator over a range of load resistances.
employed to decouple the interrelationship between the fluctuating energy
supply of the wind turbine generator and the duty-cycling operation of the
wireless sensor node. It is necessary to optimize the power management unit
with consideration of the characteristic of the wind turbine generator and the
performance of the sensor node in order to meet the application requirement.
As such, a WEH system optimized using a specially designed ultralow-power
management circuit with two distinct highlights has been presented: (1) an
AC-DC active rectifier using MOSFETs in place of diodes for rectifying the
low-amplitude AC voltage generated by the wind turbine generator under a
low wind condition and (2) a DC-DC boost converter with a resistor emulation
algorithm to perform MPPT.
2.1.2.1 Active AC-DC Converter
The active AC-DC converter can be separated into two stages: the negative
voltage converter and the active diode. The first stage of the active rectifier
circuit, as seen in Figure 2.5 , is made up of four standard MOSFETs: two
high-side P-type MOSFETs, PMOS1 and PMOS2, employed to deliver the
positive and negative half cycles v 1 and v 2 ,respectively, of the AC voltage
to the output DC voltage V dc ; and two low-side N-type MOSFETs (NMOS1
and NMOS2) that provide a path for the ground node V gnd to return to the
lower potential of either v 2 or v 1 ,respectively. By doing so, the first stage
of the active rectifier converts the negative half wave of the input sinu-
soidal wave into a positive one. Moreover, no additional start-up circuit is
 
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