MultiDC, Multi-Machine Energy Management, Facilitated by DC Links
: BASF Antwerpen, Bekaert, Blueways International, Flanders Make, Imtech Belgium, and KU Leuven.
: € 2,318,461
: € 1,490,240
Industrial electrical systems have an ever-increasing number of power electronic inverters. Indeed, their use results in more efficient variable-speed machines and facilitates the (future) integration of storage to reduce downtime. In the proposed MultiDC project, we aim to interconnect the internal DC buses of machines to reduce the number of power electronic converters and their respective connection capacities. In the process, efficiency also improves, harmonic contamination due to passive rectifiers decreases, and filters are eliminated. This brings about a much more efficient platform to share energy between machines and enables the effective integration of electrical energy storage.
Compared to the current AC grid, an industrial DC system will result in a halving of the installed power conversion capacity, lower losses (-5%), and higher availability, or in summary a lower total cost of ownership. However, today there are hardly any validated DC system architectures and consequently, there were no methods to evaluate, assess, or compare them; neither between each other nor with the current situation. Secondly, an overlapping control architecture for stable, safe, and effective operation of these systems was also lacking. Consequently, very little experience was available and there were no real-world guidelines for robust industrial DCs.
MultiDC aims to enable the use of industrial DC systems, with lower investment (CAPEX) and operating costs (OPEX) and higher availability, through experimentally validated innovative DC system architectures, integrating modular storage, real-time power management and small-signal stability. MultiDC provided the necessary supported tools to enable performance assessment, design, sizing, and comparison of these innovative DC architectures.
Multiple system architectures were proposed within the project, and ultimately a design tool was created to gather this knowledge and apply it to each generic case through an automatic calculation. The process followed by the algorithm is visualised in Figure 1 below. The user has to specify certain load profiles and the network topology of the system. During each time step, a load flow calculation is made based on the load during that time at the DC level. Then the AC part of the network is calculated in a load flow using the DC load flow as reference. After all the time steps are iterated, the overall result is calculated based on some predefined KPIs which were the result of an extensive discussion between the partners.
Industrial use cases were developed to achieve higher energy efficiency (Bekaert and Imtech) on one hand and higher system availability (BASF) on the other.
For the industrial use case to achieve higher system availability (BASF), a DC battery (NAS, sodium sulfur) was integrated and commissioned into BASF's existing low-voltage infrastructure.