Reactive current arises with PV systemsas soon as the inverters convert the direct current from the solar modules into alternating current. As reactive currents only form in AC or three-phase grids, this phenomenon does not occur in the cables that connect the modules to each other and the string cables that connect the strings to the inverter. The DC side Wiring of PV modules is therefore not affected by reactive current, which is also referred to as reactive current.
Reactive current briefly explained
Reactive current is a term used in electrical engineering and describes the part of the electrical current that does not perform any useful work in an alternating current system or is not converted by a consumer. According to the inverter of a PV system, there are therefore two types of current: Active currentthe current actually used, which performs work, and reactive current, which performs no work but is necessary to maintain the electric and magnetic field and maintain it.
It is caused by inductive and capacitive loads, such as those found in coils (inductances) and capacitors (capacitances). It is used due to the constant Field structure of the alternating currentwhich oscillates at a frequency of 50 Hz in Europe. If there are phase shifts between current and voltage or due to a high number of installed coils and capacitors, the proportion of reactive current increases.
PV systems must provide reactive current
Although reactive current basically represents an additional load for the overall system, it is not a problem for PV systems that are connected to the public grid, obligatory. Such systems must be located at the Mains support through a Static voltage maintenance or by a so-called Provision of reactive power participate. The decisive factors here are Inverter.
This is regulated for PV systems from 135 kW by VDE-AR-N 4105 from November 2018. The application rule states that the respective grid operator can provide the system operator with four different options for providing reactive power.
- Reactive power voltage characteristic Q(U)
- Reactive power characteristic curve as a function
- Reactive power with voltage limiting function
- Fixed displacement factor cos phi
Some distribution grid operators also require combinations of these specifications. To ensure that the exact specifications of the grid operator can be met, a measuring unit constantly measures the actual values of the voltage, active power and reactive current at the Grid connection point. A controller then transmits the setpoints to the inverters. In almost all cases, operators of larger PV systems therefore cannot do without Telecontrol technology out. The interaction of the individual components ensures that the reactive power is constantly optimized, thereby increasing the power factor of the overall system.
Inverters regulate the reactive current of PV systems
Due to the increased proportion of decentralized energy producers such as PV and wind power plants, the reactive power in the grid can no longer be controlled centrally, as was still possible with individual large coal and nuclear power plants. Therefore Inverter They have to provide capacitive and inductive reactive power with the help of capacitors and coils, which also contributes to voltage regulation in the grid. This is particularly important for grids with extreme voltage and frequency levels. With the help of the components of the telecontrol technology, the inverters always provide the Optimum and maximum AC output power as apparent power, while the power generated by the PV modules represents active power.
Reactive current in PV systems is unavoidable, but controllable and sometimes useful
Reactive current plays an important role in the integration of PV systems into the public power grid. Although it does not perform any useful work, it is necessary for the generation and maintenance of electric and magnetic fields in AC systems. Reactive current is an unavoidable but controllable part of the operation of PV systems that are connected to the grid.
Due to the increased proportion of decentralized energy generators such as PV and wind power plants, central control of reactive power is no longer possible. Inverters therefore take on this task and provide the necessary capacitive and inductive reactive power, which also contributes to voltage regulation in the grid. This is particularly important for grids with extreme voltage and frequency levels.
The provision and optimal adjustment of reactive power by inverters and telecontrol technology are crucial to increasing the power factor of PV systems and meeting the requirements of grid operators. Overall, this contributes significantly to the stability and efficiency of the electricity grid.