DISTRIBUTION SYSTEM

BUS ARCHITECTURE

            There are two ways for power transfer

·         DET (direct energy transfer)

·         PPT (peak point tracking)

In DET solar is connected to loads directly without any series components in between. This method requires a solar array, loads and battery voltage to be matched. This method has higher efficiency as compared to PPT because there is no series component which can dissipate power. PPT architecture is often used for long mission duration where solar array degradation is significant over a long time.

For simple LEO mission DET architecture is suitable. Because the mission life is short and the area required for sufficient power generation is very less than the area available. So extra solar panel can be added for redundancy purpose and EOL (end of life) power requirements.

                DET is further divided into two type

·         Fully regulated (regulated)

·         Sun regulated (unregulated)

Sun regulated bus is simple and reliable. The battery voltage is set at the bus voltage which means there is no discharge regulator. The unregulated voltage is usually higher than the subsequent regulated voltage which reduces the I2R loss for the same amount of power transfer.

In the regulated bus, there is a discharge converter which boosts the voltage to meet the voltage requirement during an eclipse. This boost converter reduces the efficiency of the system. To use this regulator, the power loss due to the regulator should be less than the power which can be saved by using a regulator.

According to the power generation capability of the satellite, bus preference is decided. Usually, the unregulated bus is preferred for the satellite.