Control strategy to alleviate PV power output fluctuations through a superconducting coil

During the last decade, the significant incentives that many countries provided worldwide led to a rapid increase in the deployment of renewable energy sources and especially of photovoltaics (PV). However, PV power output is highly volatile and may drastically change the power output within a few seconds. Therefore, voltage and frequency stability in an electric power system is brought under compromise. Power conditioning, using efficient and highly responsive means of energy storage, such as Superconducting Magnetic Energy Storage (SMES), may be the solution to that problem. Although this technology is still not competitive in market terms, its main advantage being the fastest response of all energy storage options has led many researchers to investigate the technical aspects of SMES utilization. This paper investigates the use of a Current Source Converter (CSC)-based SMES system in the power conditioning of a PV power plant output. The charging and discharging of a superconducting coil is controlled in order to compensate for power fluctuations from the PV plant, caused by unexpected phenomena such as cloud shading. A parallel active filter topology is utilized and a control strategy based on the instantaneous ABC power theory is proposed to separate the power fluctuations from a constant power reference. The corresponding currents are then used as reference inputs to a space vector modulation, where the switching patterns for the CSC are produced. Finally, simulations are carried out using the PSIM software. The system capability to control and stabilize the power delivered to the grid for several seconds is investigated.