Voltage support in open pit mining power systems using electric drill rigs

Abstract

The electrification of mining operations presents significant challenges in power quality, particularly in remote open-pit mines where limited grid connectivity results in reduced short-circuit capacity and increased susceptibility to voltage instability. High-power induction motor startups in drilling equipment frequently generate significant voltage sags, that compromise operational continuity and compliance with power quality standards. This thesis examines different configurations of the motor and drive system for electric drilling units and their impact on voltage profiles in mining grids. The study aims to determine how electric drillers can provide voltage support to improve grid voltage stability. A comprehensive electrical distribution grid model was developed in MATLAB/Simulink, incorporating typical mining environment loads. Critical scenarios were identified through parametric sweeps across different grid strengths to assess voltage sag depth, duration, and reactive power demand under multiple operational scenarios. Simulation results demonstrate that Active Front End (AFE) drives significantly reduce the severity of voltage sag, improve steady-state voltage profiles, and maintain system stability under weak grid conditions. When AFE control is modified to provide dynamic reactive power compensation, additional voltage support is achieved, further mitigating voltage sags and enabling stable operation under even weaker grid conditions while maintaining voltage performance comparable to full AFE implementation. A key contribution of this work is to demonstrate that a single AFE-equipped driller with compensation capability can effectively support multiple Direct-On-Line (DOL) drillers during simultaneous operation, keeping Point-of-Common Coupling (PCC) voltages within acceptable limits without requiring full fleet AFE conversion. This selective deployment approach represents a technically robust and operationally viable solution to enhance power quality and resilience in mining electrical systems.