Adaptive robust optimization (ARO) is a well-known technique to deal with the parameter uncertainty in optimization problems. While the ARO framework can actually be borrowed to solve some special problems without uncertain parameters, such as the power flexibility aggregation problem studied in this paper. To effectively harness the significant flexibility from massive distributed energy resources (DERs), power flexibility aggregation is performed for a distribution system to compute the feasible region of the exchanged power at the substation over time. Based on two-stage ARO, this paper proposes a novel method to aggregate system-level multi-period power flexibility, considering heterogeneous DER facilities, network operational constraints, and an unbalanced power flow model. This method is applicable to aggregate only the active (or reactive) power, and the joint active-reactive power domain. Accordingly, two power aggregation models with two-stage optimization are developed: one focuses on aggregating active power and computes its optimal feasible intervals over multiple periods, and the other solves the optimal elliptical feasible regions for the aggregate active-reactive power. By leveraging the ARO technique, the disaggregation feasibility of the obtained feasible regions is guaranteed with optimality. Numerical simulations on a real-world distribution feeder with 126 multi-phase nodes demonstrate the effectiveness of the proposed method.
In this paper we introduce a method for performance quantification of flexibility aggregation in flexibility coordination schemes (FCS), with a focus on privacy preserving hierarchical FCS. The quantification is based on two performance metrics: The aggregation error and the aggregation efficiency. We present the simulation framework and the modelling of one complex type of flexibility providing units (FPUs), namely energy storage systems (ESS). ESS cause intertemporal constraints for flexibility coordination that lead to aggregation errors in case flexibility is aggregated from heterogeneous …
Exposing Barriers to Flexibility Aggregation in Unbalanced Distribution Networks
Imperial College London（帝国理工学院）；National Grid Electricity Transmission（国家电网输电公司）；the University of Manchester（曼彻斯特大学）；the University of Melbourne（墨尔本大学）
The energy transition towards renewable based power provision requires improved monitoring and control of distributed energy resources (DERs), installed predominantly at the distribution grid level. Due to the gradual phase out of thermal generation, a shift of ancillary services provision like voltage control, congestion management and dynamic support from DERs is underway. Increased planning for procurement of ancillary services from underlying grid levels is required. Therefore, provision of flexible active and reactive power potentials from distribution system operators to transmission sys…
Cost-Informed Learning for Aggregating Building HVAC Flexibility
State Key Laboratory of Advanced Electromagnetic Technology, Huazhong University of Science and Technology（华中科技大学先进电磁技术国家重点实验室）；Thayer School of Engineering, Dartmouth College（达特茅斯学院塔克工程学院）；HyperStrong Technology Co., Ltd.（HyperStrong科技有限公司）
The increase of generation capacity in the area of responsibility of the distribution system operator (DSO) requires strengthening of coordination between transmission system operator (TSO) and DSO in order to prevent conflicting or counteracting use of flexibility options. For this purpose, methods for the standardized description and identification of the aggregated flexibility potential of distribution grids (DGs) are developed. Approaches for identifying the feasible operation region (FOR) of DGs can be categorized into two main classes: Data-driven/stochastic approaches and optimization b…
Hierarchical multi-(voltage-)level grid control strategies are an appropriate design concept for the coordination of future TSO/DSO- and DSO/DSO-interactions. Hierarchical approaches are based on the aggregation of decentralized ancillary service potentials, represented by converter-coupled, communicable active and reactive power flexibility providing units (FPU) (e.g. wind turbines) at vertical system interfaces. The resulting PQ-polygon made available by the DSO for a potential request of ancillary service flexibilities by the TSO is called feasible operation region (FOR). A monetarization o…
