The rapid development of the digital economy and the deployment of large-scale electricity big-data platforms have highlighted both the opportunities and risks associated with energy data circulation. Conventional identity management frameworks in the energy sector suffer from weak authentication, fragmented governance, and high compliance costs, limiting the secure and efficient realization of data value. This paper proposes a decentralized digital identity (DID) management framework tailored for the energy data space. By integrating blockchain-based traceability, verifiable credentials, and smart-contract-driven privacy protection, the framework establishes a sovereign, interoperable, and privacy-preserving identity infrastructure. Through simulation experiments using Monte Carlo modeling, we evaluate the performance of the proposed system under different blockchain infrastructures (Fabric vs. EVM) and disclosure mechanisms (plain vs. zero-knowledge proofs). The results demonstrate that Fabric achieves lower latency and higher throughput compared to EVM, while zero-knowledge proofs introduce moderate but acceptable overhead, enabling stronger privacy guarantees. The proposed framework effectively tackles the key challenges of secure identity verification, fine-grained and dynamic authorization, and tamper-resistant auditing, thereby establishing a scalable and reliable foundation for trusted circulation of energy data.