Optimal Technical-Economic Design of a DC Microgrid for Electroplating Industry

The paper proposes the implementation of a controlled DC microgrid to supply DC loads in a plating industry. The plating loads, typically from chromium-based surface coating processes, are characterized by low voltage (10-20 V) and high currents (5-10 kA). To adopt renewable sources, the supplying 600 V-DC microgrid is powered by a photovoltaic (PV) system and a Battery Energy Storage (BES) system. Main aim of the work is to develop a smart strategy to reduce energy consumption, while lowering electricity costs, and minimizing the current ripple affecting the loads. Since PV systems cannot provide a continuous power supply, the system also includes an interface with the external AC grid by a bidirectional DC/AC converter. This hybrid converter allows to feed back the PV energy excess to the grid, still ensuring electricity supply when needed. The paper wants to provide a technical-economic overview, from the sizing of PV and BES systems to the voltage control system, including an Energy Management System (EMS). In particular, the study is aimed at determining the optimal PV system size and BES capacity size to maximize the Net Present Value (NPV) of investments-originated savings. Industrial electricity load profiles, PV generation data derived from 18 years of average hourly irradiation, and three years of electricity price profiles are adopted as optimization inputs. Particularly, the BES power is optimized over a one-year period to minimize grid energy exchange, with annual cost curves to maximize the NPV. Finally, with the same MILP approach as sizing, an EMS with real-time control is proposed in the optimization of microgrid devices, while the DC voltage control system is discussed in detail with tests performed on a Hardware In the Loop (HIL) platform in some scenarios among equilibrium conditions. The paper aims to make a contribution to the development of energy management strategies for reducing procurement costs in industries that make extensive use of DC current, suggesting the entire process, from the optimal calculation of the sizing of the components, to the daily management of the microgrid with optimized scheduling of the EMS, including the control system.