Distributed Coordination of Multi-Microgrids in Active Distribution Networks for Provisioning Ancillary Services

TL;DR

This work addresses provisioning passive voltage-support ancillary services from a fleet of microgrids interconnected in an active distribution network (ADN) as renewable penetration rises. It proposes a fully distributed optimization framework based on ADMM that decomposes the centralized problem into ADN and microgrid subproblems, communicates only exchange signals for active/reactive power, and enforces feasibility with mixed-integer inequalities for passive voltage support. The formulation combines a linearized DistFlow model, a MILP encoding of voltage-support boundaries, inverter-based reactive power support, and battery storage dynamics over a multi-stage horizon $N_p$, demonstrated on the IEEE 33-bus test system and scaled to larger networks. Results show that the distributed scheme achieves Zone 1 (penalty-free) operation with near-centralized optimality, robust convergence behavior, and scalable performance, while preserving privacy and autonomy of individual microgrids. The approach offers a practical pathway for real-time coordination of MGs to provide ancillary services with low incremental cost and strong convergence properties, and it can be extended to other ancillary-service regimes and to include uncertainty and peer-to-peer trading in future work.

Abstract

With the phenomenal growth in renewable energy generation, the conventional synchronous generator-based power plants are gradually getting replaced by renewable energy sources-based microgrids. Such transition gives rise to the challenges of procuring various ancillary services from microgrids. We propose a distributed optimization framework that coordinates multiple microgrids in an active distribution network for provisioning passive voltage support-based ancillary services while satisfying operational constraints. Specifically, we exploit the reactive power support capability of the inverters and the flexibility offered by storage systems available with microgrids for provisioning ancillary service support to the transmission grid. We develop novel mixed-integer inequalities to represent the set of feasible active and reactive power exchange with the transmission grid that ensures passive voltage support. The proposed alternating direction method of multipliers-based algorithm is fully distributed, and does not require the presence of a centralized entity to achieve coordination among the microgrids. We present detailed numerical results on the IEEE 33-bus distribution test system to demonstrate the effectiveness of the proposed approach and examine the scalability and convergence behavior of the distributed algorithm for different choice of hyperparameters and network sizes.

Figures (9)

• Figure 1: Notations for branch flow model
• Figure 2: Passive voltage support curve by Belgian's TSO proposal (Figure is not drawn to scale).
• Figure 3: Schematic of microgrid.
• Figure 4: Schematic of distributed operation.
• Figure 5: Modified IEEE 33-bus distribution network

Theorems & Definitions (3)

• Remark 1
• Remark 2
• Remark 3