HARMONIC

The European Green Deal has set the clear objective for the European Union to become climate neutral by 2050 (net-zero). An essential element to reach this objective in the (Belgian) industry will be electrification of industrial processes. According to the study “Powering industry towards net-zero” -, industrial electric energy consumption is expected to increase with 40 % by 2030 in Belgium, which will allow the Belgian industry to not only significantly decarbonize but also realize considerable savings on the final energy consumption. The demand for electricity will grow tremendously throughout the Belgian industry, regardless of measures to decarbonize (electrification, carbon capture and storage (CCS) or hydrogen), will result in significant more stress on the Belgian transmission system and industry-internal power systems. For example, the electricity consumption of BASF is projected to double from 400MW to approximately 800MW
by 2030. Where the first 400MW of electric consumption has gradually increased over a period of approximately 60 years, the next 400MW need to be integrated in one tenth of that time, i.e., approximately six years. As similar electrification efforts will occur throughout the whole Belgian industry, it will be of utmost importance to understand and eliminate the technical constraints that might negatively influence (hinder or slow down) this crucial electrification.

Considerable electrification and CCS efforts as well as future electrolysis which will become a significant electricity consumer in the Belgian industry will require large-scale electrical drives, i.e., with a nominal power exceeding 5MW. Electric drives, electrolysis but also the newest types of wind turbines and large-scale PV installations will require large-scale power electronic converters, converting alternating current (AC) into direct current (DC). The increased use of power-electronic
converters may result in an increased risk for the Belgian transmission system and the industry internal power systems as it is well established that large-scale converters are a source of harmonic pollution. Harmonic pollution (or harmonics) are voltages and currents injected into the network at a multiple of the fundamental frequency of 50 Hz. This pollution decreases power quality and leads to higher losses, increased risk of equipment failure, equipment damage and
fire hazard. Decreased reliability of equipment has a detrimental effect on the reliability and availability of the power system, which in turn has an impact of the competitiveness of the Belgian industry. As the number of converters is set to significantly increase, so will the harmonic pollution in the system. The characteristics and negative consequences of this pollution depend on a combination of the behavior of the harmonic polluters (whether they act as voltage or current
sources) and the power system characteristics, e.g., its individual components and operating points. These characteristics include uncertainty, e.g., unknown component parameters or a wide variation, e.g., a lot of operating states.

A transmission system operator’s main objective of is to ensure the availability and safe operation of its power system. Managing harmonic pollution is an essential priority, especially given that it is expected to increase together with increased electrification. Although in presence of a few harmonic pollutants, local management can be sufficient; in presence of many pollutants harmonics management requires a system-wide approach, as local harmonic pollution could also have a significant impact elsewhere in the system. The system-wide amplification of harmonics has been identified as a topic of concern, as e.g., reported by the Danish system operator Energinet -. Energinet found that, when integrating underground cables into the system, the observed harmonic spectrum was profoundly changed. This led to system-wide amplification of harmonic injections, where local injections were amplified to substations up to 90 km away from the cable.
Considering continuous grid improvements, system-wide management of harmonics will thus be essential of ensuring the reliability of electricity supply. In conclusion, to achieve the European CO2 reduction goals, the essential integration of
renewables and electrification of industry needs to be facilitated by guaranteeing safe and available operation of the power systems. For the future power system with large power electronic converters, it will be of utmost importance to determine the hosting capacity of the transmission system with respect to large-scale converters, i.e., harmonic pollution. This way,
through alignment of the converter technology and the transmission system characteristics, the number of large-scale converters that can be economically hosted in a transmission system can be maximized, reducing the overall cost of electrification for the Belgian industry.

EnergyVille/KU Leuven, as research institute; BASF as one of the largest chemical companies and frontrunner regarding sustainability and implementing solutions; and Elia, the Belgian high-voltage (HV) grid operator want to accelerate the electrification of industrial processes and, in general, the uptake of large-scale power-electronic converters. This main objective will be achieved by researching following three essential and specific objectives:

1. To improve current practices of harmonic modeling for converter-interfaced grid components by providing guidelines for selecting the most suited converter representation based on the required modeling complexity. A hierarchy will be
   developed of harmonic models of power electronic converters available in the literature and based on their modelling complexity. This hierarchy will then allow to provide recommendations on the required modeling accuracy for converters depending on the frequency range of interest. In a later stage of HARMONIC, these guidelines will be implemented to select the most suited converter representation for harmonic studies and assessing the harmonic hosting capacity of power systems.
2. To improve the accuracy and to provide a measure of uncertainty of harmonic modeling of an electric network through reinventing the practices of model selection and validation, which will needed as an input to fulfil the first objective. During HARMONIC, uncertainties related to electrical network modeling will be defined first. Subsequently, it will be investigated how these uncertainties propagate to the uncertainty on the harmonic impedances. The developed methodology will take up a system-wide rather than a component view, as the harmonic network impedance is by large determined through interactions between components.
3. To develop an optimization framework to determine the harmonic hosting capacity of a given power system, accounting for uncertainty on component model, component parameters and power system exploitation. To this end, a robust optimization paradigm will be used to ensure that the resulting hosting capacity is valid for all possible realizations of the uncertainties. The objective of the optimization model is to determine the maximum number of harmonics, i.e., number of large-scale converters, that can be hosted without violating the harmonic distortion limits, equitably distributed over the power system users. Furthermore, by considering the entire power system in a single model, the interaction between different harmonic polluters will be directly included into the optimization approach. In a final step, the method will be applied in studies on the electrical network in the Antwerp Harbor region.