Impact of digital time delay on the stable grid-hosting capacity of large-scale centralised PV plant

Abstract

Digital control system has been widely used for the inverters in PV plant. However, the effects of digital time delay of digital control system on grid-connected PV plants have not been fully studied. Therefore, in view of the stable grid-hosting capacity is a key parameter in the process of designing and operating of a grid-connected PV plant, this paper investigates in detail the influence of digital time delay on the stable grid-hosting capacity of large-scale centralised PV plant. Considering the practical situation of large-scale centralised PV plants, the stable grid-hosting capacity of plant is discussed with the conditions of inverters in PV plant have the same and different digital time delays. The analysis results revealed that stable grid-hosting capacity is varied with the digital time delay of inverter and the combination of the inverter with different digital time delays. Meanwhile, in order to realize a stable grid-connected PV plant in particular delay case, a procedure on how to determine the exact inverter number that can be used in a specific PV plant is provided. The theoretical analysis is verified by simulation and equivalent experiment results.