Controller Hardware in loop Implementation of Unified Virtual Oscillator with Improved Frequency Droop

Abstract

Unified Virtual Oscillator Control (uVOC) is a decentralized control strategy used in power systems to manage inverter-based resources. In grid forming (GFM) converter operation, non-linear droop relations of uVOC require setpoints for active and reactive power to be close to the operating point. Determining setpoints for GFM converters operating in islanded mode under varying load conditions is challenging, and the absence of setpoints can cause increased frequency deviations. To address this issue, a reactive power-dependent non-linear frequency droop is proposed that minimizes frequency deviation and nearly restores the frequency to its nominal value without using any setpoints. Additionally, the proposed modification makes virtual impedance more effective in enhancing reactive power sharing among Distributed Generations (DG). Although there is a slight deviation in active power sharing under highly inductive load conditions, the reactive power sharing remains proportionate. Extensive simulations and controller hardware-in-loop (CHIL) results validate the proposed method. © 2024 IEEE.