Impact of Power Plant Controller on Voltage Oscillations in RE complex: Insights from Hardware-in-the-Loop Simulation

Power Plant Controller (PPC) is used to control the individual inverters in the RE plant based on the grid operator requirements. The real and reactive power set points of individual inverters are decided by PPC based on the voltage and frequency parameters at the Point of Connection/Interest (POC/I). The delay between the instant of measurements at POI and the corresponding command signal from PPC reaching inverters may exist due to communication delays, poor PQ meter sampling rates, and inverter polling rates. Due to the same reasons, the inverters respond to the changes in grid parameters with the corresponding delays. These delays can result in oscillations as each plant responds differently to changes in its POI voltage. Such delays can amplify certain oscillation modes as the PPC attempts to respond to voltage fluctuations. This paper analyzes the effect of PPC on voltage oscillations at the POI of the PV plant. A hardware-in-loop simulation study is done where the solar power plant is modelled in a Real-Time Digital Simulator (RTDS), and PPC hardware controls the plant model. The study is carried out on the actual PPC hardware, being developed for deployment in a renewable energy plant. The paper gives insights into the effect of PPC settings on the voltage oscillations in the PV power plant.