All SolarEdge string inverters require DC optimisers to operate with PV systems. The reason being is, the inverters do not have a voltage window and instead use a constant DC voltage input from the pv strings. This voltage is maintained by the optimisers through converting the output of each panel within the string. SolarEdge adopted this unique design due to the higher flexibility, wider monitoring features and enhanced safety provided by the DC optimisers.
Unlike other inverter manufacturers, SolarEdge went to the extent of making its panel optimisers an essential component for the inverter to operate. This means the inverters does not require an operating voltage window like most other pv inverters, but instead use a fixed DC voltage input and let the optimisers match the string voltage to it. This design principal was chosen because of the great advantages that the optimisers could offer a pv system.
Having a SolarEdge optimiser for each panel means the mismatching losses are all mitigated, as each panel is operating at its own maximum power point through voltage matching DC/DC conversion. This is extremely useful for systems that experiences partial shading as one shaded panel would drag down the performance of every other panel connected in the same string. The SolarEdge optimisers allow each panel to operate at its own maximum power point, therefore the other panels in the same string don’t need to operate at the same current as the poor performing panel.
Additionally, the optimisers enable individual panel monitoring, which provides great amounts of information to assess the system performance and detect faults. For example, in a normal string inverter configuration, if one bypass diode failed in a particular panel, a technician would have to be sent to the site and test each connection in the string to find the faulty panel. This can be an extremely time consuming task in a large pv system, however, if SolarEdge optimisers are used, it would be easier to detect the faulty panel.
On top of this, the optimisers also offered an additional layer of safety measures to pv systems through the possibility of panel level shutdown. This is done by dropping the output of the optimisers down to just 1V as soon as it detect. As a result, makes the system safe for urgent maintenance services near the panels.
Overall, with better yield, monitoring effectiveness and safety, the SolarEdge optimisers offer great improvements in performance and flexibility for pv systems.