# Predictive Control for Current Distortion Mitigation in Mining Power Grids
## 1 Introduction  
Mining is a critical industry for energy transition because, although it has a considerable environmental footprint, it provides raw materials, such as gold and copper, which are required for electronic devices, transmission lines and electrical machines [1]. Nowadays, the transition of the mining industry towards smarter and cleaner operations includes environment-friendly practices and policies, pursuing an optimal consumption of water and energy, reduction of carbon emissions, and more precise extraction techniques [2]. In this sense, the coexistence of older machinery, such as cycloconverter-based drives in crushers and mills, and newer technologies, such as electrical hauling trucks, is unavoidable during this transition process. In mining facilities, adjustable frequency drives have been used throughout the whole mining process. Historically, cycloconverter topology was a well-accepted solution for low-speed grinding mills control; however, its related harmonics issues in mining power systems are significant [3]. In this sense, the academic community is currently exploring converters based on multilevel topologies in addition to diode-based rectifiers and active front end (AFE) converters. These converters have been used for high-power mills [4], for medium-power conveyor belts [5; 6] and for hauling trucks [7; 8]. In contrast to the academic trend, mining companies' transition towards new technologies is slower becauseadditional business concerns must be considered. Therefore, the coexistence of old and new technologies in mining facilities implies a tough challenge to be overcome in the short term. Although AFE has shown better control capabilities and efficiency than cycloconverters, both of them impact the power quality of the mining power system. For example, cycloconverters inject harmonic distortion to the grid because of the absence of a DC-link or other reactive components that operate as a filter between the machine-side and the grid-side [9]. On the other hand, DC-link and LC-filters of AFE topologies easily reduce high-frequency components, but low-frequency harmonics, below 200 Hz, caused by unbalances, PLLs tracking errors, and nonlinear loads, are reflected in the power system [10]. As a consequence of this low-order harmonics pollution, magnetic flux inside of transformers and motors of mining machinery is affected, and, thus, the damage risks increase [11]. In addition, because of changes in mining facilities over time, long cables and poor design and selection of transformers, the active power transference capacity of the power grid is also reduced. Therefore, mining companies should be aware that power quality improvement at the point of common coupling (PCC) with the utility grid, and other sensitive nodes, represent a more efficient operation of the power system. The IEEE std 1547 [12] states that the reference points into power systems are those where characteristics, such as voltage, frequency, total rated current distortion, and response-to-failure capabilities, meet the standard. Although PCCs are defined as reference points, it is possible to define additional ones to satisfy internal requirements in the microgrid or power system area. For instance, in the mining industry, electric rope shovels used for ore extraction are sensitive to harmonics pollution and voltage sags/swells. In this case, filtering devices are used to reduce the risk of damage and preserve their operational integrity; however, considering that this type of machinery is replaced according to mine expansion, passive filtering is not an optimal solution [13]. There are two main approaches for managing harmonic distortion issues. The first one considers this issue by directly improving control and modulation algorithms over the power converter. In [14], common mode voltage is mitigated by integrating this objective in a primary controller which states the switching pattern, modifying the classical space vector modulation scheme.