On Accurate and Compact Model of High DER-Penetrated Sub-Transmission/Primary Distribution Systems in ISO Energy Market

In Independent System Operator's (ISO) energy market clearing process, sub-transmission/primary distribution systems are usually modeled as simplified fixed or flexible loads. This simplification, however, may not be proper for emerging distribution systems with an increasing penetration of distributed energy resources (DER). As a matter of fact, scheduling results from the simplified model could induce power flow violations of distribution lines, while also misrepresenting contributions of DERs on economic operations of the entire grid. To this end, this paper proposes a multi-port power exchange model and associated bidding strategies, in order to accurately and compactly formulate the contribution of highly DER-penetrated sub-transmission/distribution systems in the ISO energy market while resolving computational complexity. The proposed models can effectively capture physical and economic impacts of sub-transmission/distribution systems in the ISO market clearing, while respecting their internal physical limits. Numerical studies show that, with proper settings, the proposed approach can accurately reflect impacts of DER-penetrated distribution networks on market clearing results and power flows, while presenting high computational performance.