Electricity Production from Renewables Energies

6.3 Connection constraints

6.3.1. Voltage control

6.3.1.1. Connection to the distribution network

The connection of a production power station can change the voltage plan, especially around the connection point. This should not prevent the network operator from respecting the ranges defined by norms (of about ± 5% of the contractual voltage, often 20 kV). Thus, power stations with a power higher than 1 MW must be able to adjust their output voltage at the operators request, whereas power stations with a power higher than 10 MW must be equipped with an output voltage controller.

In order to illustrate the impact of a generator dispersed on the voltage plan of a distribution network, the integration of a photovoltaic generator of 55 kW in an LV network is considered in Figures 6.7 and 6.8 [PAN 03]. When the photovoltaic generator is placed at the end of the line at node 4, the voltage along the line is increased in comparison to a situation without generator. A similar result is obtained when the photovoltaic generator is replaced by a conventional generator, such as an electric generating set. This situation can be interesting in some cases, but can also lead to dangerous over-voltages in low load period, if the voltage control transformers upstream of the distribution network do not include in their adjustment strategy, the presence of decentralized production (“rise in power”).

Figure 6.7. Radial structure of a low voltage network

In some cases, decentralized production can ...