Exploring frequency control capability of a PV system in a hybrid PV-rotating machine-without storage system

• Photovoltaics made to work in deloaded condition to provide reserve in the system.
• Controllers designed for photovoltaics (PVs) to participate in frequency regulation.
• Modes of operation suggested for deloaded PVs.
• Cost analysis done to compare the financial benefit of using a deloaded PV.

When the penetration of inertia-free photovoltaic (PV) system is rapidly increasing, it is of timely importance to make the system capable of handling the disturbances safely so that the system stability can be assured by maintaining the system frequency. In this paper a novel control strategy has been formulated for frequency regulation utilizing the output from the PV generators itself without going for any kind of storage technologies. A multi bus system with two conventional generators and twelve PV systems which are working away from the maximum power point of operation is the system used for the study. Frequency control of the deloaded PVs with frequency controller is simulated using Power Factory Software. An improved controller which considers not only the frequency deviation of the system but also the available reserve in the photovoltaic is proposed. This ensures that the PV with more reserve will participate more in the frequency control compared to those with less reserve so that the frequency control capability is evenly distributed throughout the system. Two modes of operation for deloaded PV is suggested to derive maximum benefit when it is used for frequency regulation. A cost analysis is carried out to show that the concept of deloaded PV is economical when compared to battery usage for frequency control.