3. Static voltage support based on reactive power
In order to protect the connected loads, the voltage must be kept within defined limits – that applies to the distribution grid in particular. With their ability to provided controlled inductive or capacitive reactive power, PV inverters can help guarantee the voltage quality required in EN 50160. Reason: the increasing feed-in at low and medium-voltage levels can result in voltage increases which caused problems for the grid operation method used so far (flow of energy from central generator to decentralized loads). Using reactive power, PV inverters can now reduce undesirable voltage increases significantly. Reactive power-compatible inverters can also be used to compensate for existing phase shift. As even reactive power reduces efficiency, this reduces the load on the grid infrastructure, whose capacity limits may already have been reached. Typical causes of phase shifts include transformers, large motors or even simply long cable sections.
There are several options for adjusting the percentage of reactive power: Plant operators can use set points specified by utility operator, or various reactive power values can be set via an agreed schedule or remotely programmed via the SMA Power Reducer Box. The third option is regulation of the percentage of reactive power via a characteristic curve depending on the grid voltage measured at the connection point or the active power output of the inverter.