Flexible Power Control of Photovoltaic Systems

With a still increasing penetration level of grid-connected photovoltaic (PV) systems, more advanced and flexible control functionalities are demanded. To ensure a smooth and friendly integration between the PV systems and the grid, the power generated by the PV system needs to be flexible and capable of (1) limiting the maximum feed-in power, (2) limiting the maximum power change rate, and (3) providing active power reserve during the operation. This chapter explores the possible solutions to realize the flexible power control requirements. Among other possible approaches, modifying the Maximum Power Point Tracking (MPPT) control algorithm of the power converter can realize the flexible power control requirement by regulating the operating point of the PV system below the maximum available power of the PV arrays. Therefore, this approach does not require an extra component, being a cost-effective solution in terms of component cost and at the same time offering high reliability. The operational principle of the PV systems with the modifying MPPT algorithm is discussed in this chapter, where the flexible active power control functionalities are demonstrate via experiments on a two-stage grid-connected PV system. The experimental results verify that the power-limiting control, power ramp-rate control, and power reserve control functionalities can be achieved upon demands.