DC Bus Physical Implementation

[newbie28]

Hi.. I am trying to imagine how a DC bus looks like physically. I have just seen DC bus as a "line"in diagrams. But in real life how does it look? Also, the voltage of a DC bus remains constant. How? Isnt it a waste of energy to have a constant supply to a DC Bus just to maintain the voltage? I am considering a PV system, a Wind turbine with rectifier and grid - all connected to a DC bus. The purpose of the DC bus is to charge a battery. Not able to imagine how it will work physically and how the use of DC bus can be justified. Any help is really appreciated. Thanks in advance!

 

[mtwieg]

It depends on what power/voltage level you're talking about, and the function of the bus. Could be a small copper trace on a PCB, or a slab of copper busbar.

In general at some point in a power conversion system, you'll have one point where the voltage is well-regulated. For example in a PV battery charger, the battery voltage will be controlled, though it certainly won't be absolutely fixed since the battery EMF has to change. Other times you might have an intermediate DC bus which actually will be regulated to a fixed voltage, before being used for the next conversion stage. For example, to interface a turbine generator to the grid you usually use a AC-DC rectifier stage, then a DC-AC grid tie inverter stage to interface with the grid.

 

[YanivS]

Think of a DC bus as a water pipes. There is always pressure(voltage) in the pipes but as long as the tap is closed no waters(current/energy) is being lost.

 

[nuflia]

what Yanivs says is completely true, the DC bus should be always kept constant, otherwise the load may not get the enough power, so the need of storage energy is necessary in order to keep the dc-bus voltage constant, this can be achieved by bi-directional dc-dc converter that can charge a battery when there is sufficient voltage and discharge the battery when the voltage gets bellow pre-determined level