The power optimizers, using an input control loop, perform per module MPPT and enable performance monitoring of each module. In an independent process, the power optimizers enable the inverter to automatically maintain a fixed string voltage, at the optimal point for DC-AC conversion by the inverter, regardless of string length and individual module performance.
Each PV module has a power optimizer connected to it, which is essentially a DC/DC buck-boost converter with an MPPT controller. The power optimizers are serially-connected to form a string; multiple strings can be connected in parallel to the same input of the inverter. The inverter is a single stage current source – it continuously adapts the current it draws from the PV array in order to keep the input voltage constant.
The constant string voltage maintained by power optimizers provide multiple benefits:
- Flexible Design – mismatched modules can be serially-connected in a string. The number of modules in a single string is not dependant on module output voltage and therefore a wide string length range is permitted.
- High Inverter Efficiency and Reliability – the inverter components work at a fixed voltage, operating under less stress. The inverter always operates at a voltage that enables optimal DC-AC inversion efficiency, independent of string length or environmental conditions.
- Reduced Installation Cost - longer strings, lower BoS element count and installation cost and labor.
- Temperature Indifference - the SolarEdge fixed string voltage completely removes the temperature constraints which strongly limit string length in traditional systems.
- Improved Safety - all power optimizers start up in "safety (1) Volt output" mode until the power optimizers are connected to a functioning inverter. Additionally, in the event of a grid power shutdown, the modules immediately stop producing power and revert to this mode.