Using Smart PV Inverters for Reactive Power Management in Distribution Grids

Due to changing behavior of loads, enhanced installation of underground cables and increased amount of renewable energy sources connected with both transmission and distribution grids the flow of capacitive reactive power (CRP) is becoming difficult to manage. Several control measures are taken to keep CRP within limits but these control measures are expensive. These control measures are normally taken at transmission level while high proportion of CRP sources reside in distribution level. PV inverters are used in the distribution grids to generate active power during day and remain idle for nighttime. The remaining available capacity of smart PV inverters apart from the capacity used for active power generation could be considered as an asset to handle the CRP issue. This paper introduces a solution based on smart PV inverters to keep CRP within limits in the distribution grid and controlling its flow at T-D interface. To validate this concept smart PV inverter control is developed for inverters to work as reactive power compensation device for daytime and nigttime operation. During the daytime PV inverter works in active power priority mode and at the nighttime the full capacity of the inverter can be utilized for reactive power control. To analyze the impact of this control strategy on a larger network a simplified model of proposed strategy is used on a case study network. The results show that CRP flow can be managed in distribution grids with the smart inverters.