- As a rule of thumb PV capacity in an LV grid segment should not cause any problems, if power is limited to 70 % of the rated power of the feeding transformer. Due to PV power generation, the voltage drop across the branch can change its sign. Adding generation capacity on a feeder formerly used only to supply loads may cause a reverse power flow in that feeder along with a voltage rise due to voltage drops on the power line to the transformer.
- If PV systems are connected with a nominal power of several kW’s at each customer’s installation, problems with the actual voltage level and capacity of the LV cable can occur.It may become critical in rural areas with higher impedance networks.
- Harmonic currents and DC from inverters are no problem with modern inverters, which comply with generic standards of the IEC 61000 series.
- Grid stability is of prime importance. Therefore “fault-ride-through” capabilities are an important feature for PV systems including small ones, due to their large number. Even with little PV capacity on the grid potential effects of large inverter capacities should be taken into account, since the amount of DG capacity will steadily increase and these inverters will operate for the next 10 to 15 years.
- Finally the PV plants contribute to grid security and stability. In case of distributed grid conditions the PV plant has to remain connected and feed into the grid using much wider voltage and frequency bands than the normal central power stations, and for this there will be new guidelines in future are expected from grid authorities for grid connectivity of solar plants.