DC optimisers are a pretty new solar technology. Solar panels give us dc power. We need ac power to run most appliances. So there is a need of a device which can change the DC power from panels into AC power. Such a device is known as an inverter.
The voltage level of our grid is around 220 ~ 240 VAC. But the voltage of panels is around 12 ~ 40 VDC. So we also have to change the voltage level apart from converting DC into AC.
In the early days of solar tech we had transformer based inverters. In these inverters 12 VDC was converted in to 12 VAC. Then this 12 VAC was increased up to 240 VAC through a transformer. Such inverters were not efficient and very large in size as well. With the increase in power rating of power systems we had to use a larger transformer.
DC Optimisers – What They Do & Stuff
After this transformer based device, DC optimisers were devised. DC optimisers are also known as “TL” DC inverters. Such inverters do not have any AC transformer. In these inverters, the first stage is of MPPT. MPPT is a maximum power point tracker. As its name suggests, it tracks the maximum power output of solar panels. This maximum power has voltage level of around 12 ~ 24 VDC. After this, we have a switching circuit and a very small ferrite core dc transformer. 12 VDC is converted to 400 VDC through the ferrite core transformer. Then this 400 VDC is converted into 220 VAC through a simple sine wave inverter. In this device we have one single unit of MPPT based solar inverter and all panels are connected to that single inverter.
The Rise of Micro Inverters
These days, modern panels have micro inverters with them. Micro inverters are small MPPT based inverters which are attached to each individual panel. Power from each panel is then added up for its domestic use. In micro inverters, each panel has a separate box attached to its back. That box side has a MPPT and DC-DC converter with an AC sine-wave inverter.
In DC-DC optimisers there is a single inverter unit. This type of power system has a low maintenance cost. But as there is a single inverter, in case of any fault there will be a system black out. With the increase in current, size of cable also increases. In this type of power system all the panels are connected in series and parallel combination. Then power from all panels is transferred to a single inverter unit through a common cable. So we will need thicker cable size. As we have to connect all the panels so there are fewer options in installation.
Micro inverters are more efficient and involve a higher maintenance cost. But there are no chances of black out in case of any inverter or panel. As each panel has an individual inverter, so in case of any fault only a single panel will get affected while others will perform perfectly. Cable size will be small in this type of system.
Keeping in view all the points, micro inverters are the better way to go.