Minimal-order observer-based coordinated control method for isolated power utility connected multiple photovoltaic systems to reduce frequency deviations

In this study, a simple coordinated control method based on minimal-order observer is proposed for multiple photovoltaic (PV) systems. Here, output power command is generated in two steps: central and local. In the central step, a minimal-order observer estimates load power. Then, load variation index is calculated by subtracting the average of estimated load power from the instantaneous estimated load power. From the available maximum PV power, base PV power is produced by using a low-pass filter and is added with the load variation index to generate the central PV output power command. In the local step, a simple coordination is maintained between the central power command and the local power commands. The proposed method is compared with the method where maximum power point tracking control is used for each of the PV systems. Simulation results show that the proposed method is capable of reducing the frequency deviations of the power utility and also delivers power near maximum PV power.