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2015 Sensata Technologies
Introduction
4.
Frequency disturbance/shift from the battery-based inverter:
When the battery voltage
rises above a maximum setpoint, a battery-based inverter changes its output frequency to cause
the grid-tie inverter to limit the energy from the renewable energy source to the battery.
Disadvantages:
• Generated power from the renewable energy is limited/wasted during the frequency shift.
• Batteries are cycled, not regulated—does not allow the batteries to get properly charged
1
.
• The frequency-shift setpoint must be set higher than required to ensure it doesn’t interfere
with normal charging (from the battery-based inverter) or any sell back voltage settings
once the utility power returns
1
.
• No temperature compensated regulation while charging
1
.
Note
1
– May not occur if networked to the grid-tie inverter
5.
AC diversion driven by DC controlled relays:
A battery voltage controlled relay is used
to switch on a dedicated AC diversion load (i.e., space heater, air conditioner, etc.) to consume
any excess power when the battery voltage rises above a maximum setpoint. When the battery
voltage falls to the low setpoint, the dedicated diversion load turns off. If the battery voltage rises
again, this cycle repeats.
Disadvantages:
• Batteries are cycled, not regulated—does not allow the batteries to be properly charged.
• AC diversion loads must be sized to absorb the full output of the renewable energy source
and con
fi
gured to always be on (no temperature or thermostat turn-off control).
• AC diversion loads, when activated, can cause enough AC line drop/disturbance to disconnect
the grid-tie inverter—wasting generated energy.
• No temperature compensated regulation while charging.
6.
AC Load Diversion Controller (ACLD-40):
When the battery voltage rises above a voltage
regulation setpoint, the ACLD-40 begins to send excess current to a dedicated AC diversion load
to maintain the battery voltage. When the battery voltage falls below the regulation setpoint,
current is no longer sent to the dedicated diversion load.
Advantages:
• Batteries are properly charged/regulated - true three-stage charging to batteries during
power outage.
• Easier to source and size AC diversion loads to absorb the full output of the renewable
energy source.
• Primary AC diversion loads can be con
fi
gured for temperature/thermostat turn-off—primary
loads are not required to always be on.
• AC diversion loads are isolated from the grid-tie inverter’s output to provide a smooth turn-
on transition—prevents the inverter from disconnecting due to AC line drop/disturbance.
• ACLD-40 communicates with the MS-PAE Series inverter, this provides:
o No confusion or interference trying to coordinate the inverter’s and controller’s setpoints
once the utility power returns—controller uses same charge setpoints as the MS-PAE
Series inverter for regulation.
o Temperature compensated regulation while charging—uses temperature sensor readings
from the MS-PAE Series inverter.
o Information on diverted power and the controller’s status can be displayed using a
remote control.
o Knows when grid power returns—ensures the renewable energy is not being diverted
and is available to be fed back to the utility grid.
• Does not require multiple current sensors and devices—all current
fl
ow is monitored at the
controller to determine when to divert excess current.
• No AC to DC energy conversion loss when trying to regulate battery voltage—excess power
is regulated on the AC side.