Multi-Timescale Control of Smart Inverters for Optimal Operation of Low-Inertia Grids

Abstract

This article proposes a novel frequency and voltage control scheme for low-inertia electrical systems with high penetration of renewable energy sources (RES). A multi-timescale coordinated control scheme was proposed to optimally control inverter-based resources in different timescales. Accordingly, a two-stage stochastic optimisation framework has been developed for optimal operation of battery energy storage system (BESS) and voltage source converters (VSC) in hour-ahead and intra-hourly timescales, to counteract the effects of uncertainties in solar photovoltaic (PV) and load. Additionally, a novel real-time coordination framework was developed for fast frequency control, triggered by appliance switching/scheduling information through energy internet. Thus, real-time control is implemented as a pre-disturbance preventive action, appropriately acting with the load switching event. Furthermore, the proposed real-time frequency control is developed as a coordination strategy for primary regulation by adaptive VSC control and recovery control by the grid. Extensive simulations were performed to verify suitability of the proposed optimisation and control strategy in mitigating the effects of unforeseen uncertainties and scheduled events on system stability. Effectiveness of the proposed control is further verified by experimental validation on laboratory-scale hardware test setup.