Power optimizers are MLPE (module level power electronics) devices that allow individual maximum power point tracking (MPPT) of photovoltaic modules.
There are two major advantages to using optimizers in photovoltaic systems: reduction of losses due to module power mismatch and immunity of the system to shadows. Power mismatch occurs because the modules in the string are not identical. Even when using modules from the same manufacturer, model and power, there are always slight differences between them.
These differences can result in losses of a few percentage points in photovoltaic installations. The individualization of modules provided by optimizers allows the effect of mismatch to be mitigated, providing greater energy generation.
The problem of partial shadows on PV strings is a major nightmare in PV systems. Conventional inverters (not equipped with intelligent MPPT algorithms) are not able to guarantee the tracking of the global maximum power point of the system when a part of the modules is shaded.
The individualization of modules made possible by optimizers also solves this problem. In addition, the use of optimizers also has the advantage of allowing connections such as the one seen in the following figure, in which the various modules of the system are installed with different inclinations and orientations. This type of series connection of modules would be impossible with conventional string inverters.
Configuration on PVSyst
To configure systems with optimizers in PVSyst, you must select the “Use optimizer” option in the “PV module selection” section. Then, you must choose an optimizer model that has a nominal power compatible with the photovoltaic module used. In this example, we chose an optimizer SolarEdge 400 W. After selecting the optimizer, PVSyst automatically provides a list containing SolarEdge brand inverters.
This manufacturer's technology requires the use of optimizers and inverters from the same brand, so the only option in this case is to use an inverter from SolarEdge. We chose an inverter with a nominal power of 8 kW. After choosing the inverter, the strings must be configured. In this example, we will use 2 strings with 15 modules in each.
Finally, the string configuration in the inverter must be completed using the “String configuration” button. In the configuration window, the easiest option is to use the “Adjust sub-arrays” automatic adjustment tool. The objective of this step is to configure the inverter inputs, distributing the strings of a given sub-group among the inverter inputs. In this project example, we have only 1 sub-group with 2 strings, which results in the configuration shown in the figure below.
