PWM vs MPPT

Traditional PWM vs Morningstar’s TrakStar™ MPPT Technology
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TrakStar™ Maximum Power Point Tracking:
Morningstar MPPT controllers feature TrakStar technology, designed
to quickly and accurately determine the Vmp (maximum power
voltage) of the solar array. TrakStar MPPT controllers ‘sweep’ the
solar input to determine the voltage at which the array is producing
the maximum amount of power. The controller harvests power from
the array at this Vmp voltage and converts it down to battery voltage,
boosting charging current in the process.
Because power in is equal to the power out of the controller (assuming
100% efficiency, neglecting wiring and conversion losses), it follows
that a down-conversion of voltage corresponds to a proportional
increase in current. Power (watts) is equal to the product of voltage
and current, therefore, if voltage is reduced current must be increased
to keep the input/output power equal.
Assuming 100% efficiency:
Input Power = Output Power
Volts In * Amps In = Lower Volts Out * Higher Amps Out For example:
a 100W panel (Vmp of 17V) is used to charge a battery at 12V with a
TrakStar MPPT controller. In ideal conditions, 5.88A of solar current
flow into the MPPT (100W / 17V = 5.88A). But the output voltage
(battery voltage) is 12V, meaning current flow to the battery is 8.33A
(100W / 12V = 8.33A). You can see that the greater the voltage
difference between the Vmp
and the battery, the more
“boost” current the battery will
receive. The graph on the left
illustrates the advantage of
operating at the TrakStar MPPT.
A consequence of getting more “boost” when the voltage
difference is greater: the less charged the batteries are (lower
battery voltage), the more “boost” current they will receive. This
Staying on Track
» Sweeps full array
from 0-150V in one
tenth of a second!
» Some controllers can
take up to 30 seconds,
during which power
levels could change.
» Other controllers use
dynamic tracking,
adjusting locally,
which can result in
missing the true Vmp.
Flexible Sweep Intervals
» Morningstar’s MPPT
charge controllers
sweep the array more
often when array
voltages change.
» Enabling it to spend
more time on the
maximum power
point.