Power-Agnostic Approach for Surface Drill Rigs

Abstract

The mining industry’s transition towards low-carbon operations requires electrification strategies that remain reliable under weak grids, variable renewable output, and highly dynamic drilling loads. This thesis proposes and evaluates a power-agnostic electrical architecture for surface drill rigs that enables operation across AC grids, DC microgrids, and hybrid renewable-storage systems without major system redesign. The work develops a conceptual multi-source architecture, assesses technology maturity through TRL mapping, and outlines a road-map for the evolution of converters, batteries, and control systems that can be substituted or upgraded without redesigning the system between the grid interface and the motor. The study proceeds in two parts. The first decomposes the rig power supply into its functional subsystems and assesses each against technology readiness and S-curve maturity, producing evolution matrices for cables, transformers, filters, rectifiers, grid-forming converters, DC-DC converters, batteries and inverters. A cross-impact analysis then examines how those subsystems constrain one another, and three candidate architectures are derived from the matrices. The second part evaluates the selected architecture, a grid-forming converter with a common DC bus and DClink battery storage, in time-domain simulation over four supply scenarios spanning short-circuit ratios from 20 to 2 and four disturbance families. The technology assessment finds the constituent hardware mature and the integration immature: active front ends and medium-voltage converters sit at readiness levels 8 to 9, while the supervisory and analytics layers that would make an architecture genuinely source-agnostic remain at 5 to 7. The simulations show that DC-link storage decouples the rig from the supply almost completely. A load variation of 290.5 kW across the drilling cycle reaches the point of common coupling as 0.13 kW on the stiffest connection, and the machine side registers no measurable response to any grid disturbance applied. As the connection weakens, more of the load variation reaches the grid, rising to 2.2 % of it on the weakest supply. The converter also meets its active-power droop once the frequency has settled, although the power swings well beyond the droop value while the frequency is still changing. The main limitation lies in the converter current. Three of the sixteen disturbance cases took it above the 1.50 pu rating. In the 60◦ phase jumps the current rose faster than the virtual-impedance current limit could act, reaching 1.97 pu on the stiffest supply, so a higher converter rating or a different current-limiting method is needed. In the zero-voltage sag on the weakest supply, the converter took 2.2 s to regain synchronism, because the angle correction applied after fault ride-through has no output limit. Overall, the architecture can keep a drill rig running across a wide range of grid strengths, provided the grid-side converter is rated and controlled for the disturbances. Based on these results, the thesis recommends limiting the output of the angle correction and selecting the converter rating or current-limiting method with phase steps in mind. It further proposes simulating a full working shift to size the storage by energy, using a switching converter model to assess harmonics and semiconductor losses, quantifying total cost of ownership and CO2 emissions, and checking the technology assessment for design evolution and implementation strategies to support OEMs in advancing sustainable, future-ready drilling systems.