Challenges of planning for high renewable futures: Experience in the US midcontinent electricity market

In the last decade, the Midcontinent Independent System Operator (MISO) bulk electric system has experienced a rapid growth of renewable energy within its footprint. To understand the impact of increasing renewable generation on system reliability, MISO developed the Renewable Integration Impact Assessment (RIIA) framework to examine potential high renewable integration scenarios, starting with the current physical infrastructure, operational practices, and regulations of the North American Eastern Interconnection Bulk Electric System. As of November 2019, the RIIA study has completed simulation up to 50% annual aggregate renewable energy penetration from the current 8% level. The RIIA study indicates that the complexity of integrating renewable energy resources across the MISO footprint would increase sharply beyond the 30% penetration level. The existing infrastructure may be inadequate for fully accessing the diverse resources. This paper focuses on the development of the RIIA framework, discusses challenges of simulating high renewable penetration scenarios, and considers policy implications.