Active power control of a PV generator for large scale photovoltaic power plant without energy storage

The increasing renewable energy penetration together with the price reduction of photovoltaic modules is supporting the development of photovoltaic power plants connected to the medium and low voltage grid. Many concerns are emerging about the electrical system stability when it is connected to renewable sources. Usually, photovoltaic power plants are thought to reach always the maximum power point and to extract the maximum power available. However, due to the new grid codes as the ones from Puerto Rico and South Africa, the photovoltaic power plants should not always extract the maximum power available. Instead it is necessary to follow a fix reference due to power curtailment, power reserve or ramp rate. Thus, this article proposes a control method to comply active power requirements by modifying a tracking algorithm. For this purpose, a photovoltaic generator is modelled and controlled in DIgSILENT PowerFactory. The results show that the control proposed can follow a given active power reference despite the ambient conditions.