DET is a power control option for solar arrays that involves a shunt regulator in parallel with a solar array to shunt any excess power back through the array for dissipation when the loads or battery charging doesn’t need power. solar array power is also directly transferred to the loads without any series-connected converter or regular (the solar array is directly tied to the load bus).

Algorithm Breakdown

General DET Algorithm:

1. Current flows from the solar arrays directly through the bus and to the loads (since there are no other series-connected components between the solar arrays and the loads)
2. While current flows from the solar arrays, a shunt regulator parallel to a solar array checks to see if too much current is generated.
3. If there is too much current generated, the shunt regulator turns off or adjusts the current delivered to the bus by each solar cell string. The shunt regulation is determined by the current required for the loads and battery charging. The excess energy is then thermally dissipated by the solar arrays or the shunt circuit components.

Unregulated DET:

• load bus voltage varies by about 20% from charge to discharge because it depends on the battery voltage
• The voltage of the load bus and the battery is the same (in parallel), this limits the power that is supplied to the loads
• the solar arrays are directly fed to power the loads and recharge the battery

Regulated DET:

• the power bus is continuously regulated by the battery charge/discharge elements
• the amount of solar array power generated is determined by the bus voltage controller
• The bus voltage controller monitors the bus voltage which is used to determine the control signals for the battery charger and discharge regulator
• when there is enough solar array current to the loads, but not enough current to charge the batteries at a specific rate, the bus is regulated by controlling the charge current to the batteries
• when sufficient current from solar arrays flows to the batteries at the specified rate, the battery charger regulates the current and the shunt regulator becomes active to regulate the bus voltage.

DET Notes:

• often used for larger loads