Hourly Economic Dispatch Optimization of Interconnected Multi-Zone Power Systems with Renewable Generation and Battery Energy Storage via Nonlinear Programming

This study presents a nonlinear optimization framework for the hourly economic dispatch of interconnected multi-zone power systems integrating thermal, hydroelectric, wind, photovoltaic, and battery energy storage resources. The proposed formulation explicitly models zonal power balance, interzonal power exchange, thermal ramp-rate limits, battery state-of-charge dynamics, storage operating bounds, and hydroelectric energy quotas in order to minimize total system operating cost while preserving technical feasibility. The methodology was implemented in MATLAB and applied to a three-zone interconnected test system under two operating conditions: autonomous zonal operation and coordinated interconnected operation with battery storage support. The results show that the coordinated strategy reduces total operating cost from USD 8.23 million/day to USD 6.60 million/day, corresponding to a 19.8% reduction and an estimated annual saving of USD 595 million. In parallel, the optimized interconnected dispatch increases wind generation from 14.46 to 16.44 GWh/day and reduces thermal generation from 8.12 to 6.08 GWh/day, thereby improving the effective use of renewable resources. A complementary sustainability assessment further shows that coordinated operation increases the renewable share from 71.81% to 78.68%, decreases the carbon intensity of supplied electricity from 189.4 to 146.3 kgCO₂-e/MWh, and yields estimated avoided emissions of 1241.0 tCO₂-e/day. These findings demonstrate that the joint use of interzonal coordination and battery energy storage provides simultaneous economic, operational, and environmental benefits, thereby supporting sustainability-oriented operation of modern multi-zone power systems.