Flexibility Services Management Under Uncertainties for Power Distribution Systems: Stochastic Scheduling and Predictive Real-Time Dispatch

Abstract

Over the last years, the role of the distribution system operator (DSO) has largely expanded. This is necessitated by the increased penetration of intermittent energy resources at the distribution level, as well as the new, more complex interactions with the transmission system operator (TSO). As such, to properly manage its system and to have an effective joint cooperation with the TSO, the DSO is required to procure and carefully manage flexibility services from distributed energy resources (DER). This paper introduces a thorough framework on optimal operational planning (day-ahead scheduling) and operational management (real-time dispatch) of active distribution systems under uncertainties, to avoid line congestions and voltage limit violations, and efficiently balance the distribution system. A two-stage stochastic programming model based on weighted scenarios is proposed to optimize the multi-period optimal power flow day-ahead scheduling, i.e., scheduled power flows at the TSO-DSO interface and reserved DER flexibility services. Subsequently, the operational management, realized with a predictive real-time dispatch model based on a constantly updated rolling horizon, aims to efficiently activate the available flexibility services to minimize deviations from the committed schedule. Different sources of flexibility are considered, with their respective response times also taken into account at real-time dispatch. The proposed framework is applied on two distribution systems and investigates the DSO's level of risk exposure while minimizing its total cost (reservation and activation expenses). The results indicate that a less conservative approach at planning stage, despite the potential risk exposure, can lead to significant reduction in total expenses. INDEX TERMS Battery storage systems, distributed energy resources, flexibility services management, real-time dispatch, renewable energy sources, stochastic day-ahead scheduling, stochastic programming. NOMENCLATURE ACRONYMS & ABBREVIATIONS ANM Active network management BSS Battery storage systems DAS Day-ahead scheduling DER Distributed energy resources DERA DER aggregators DSO Distribution system operator FSD Flexibility service downward-regulated The associate editor coordinating the review of this manuscript and approving it for publication was Pierluigi Siano .

A Local Capacity Market Providing Local and System-Wide Flexibility Services

“…Comprehensive research is needed to analyze the potential of distribution network-connected resources to provide local and system-wide services simultaneously. In this regard, [32] introduced the participation of DSOs in providing balancing services as well as line congestion and voltage regulation services of the distribution network. However, currently the balancing service is not the responsibility of the DSO.…”

Planning Flexibility With Non-Deferrable Loads Considering Distribution Grid Limitations

“…Certain controllable power plants have been traditionally responsible for balancing supply and demand by adjusting their power output, so as to maintain the system frequency within a predefined acceptable band. Although such practice still continues today, the introduction of renewable energy resources and plug-in electric vehicles (PEVs) increases the need for flexibility in the power system [1], [2]. Integrating more variable resources into the power system significantly increases supply and demand uncertainty.…”

A Novel Formulation to Compute Sensitivities to Solve Congestions and Voltage Problems in Active Distribution Networks

“…The new paradigm difficult distribution system operation that becomes as complex as transmission operation, and new initiatives are being proposed to tackle the emerging problems. For instance, distribution networks may also need to combine day-ahead scheduling with real-time dispatch [10] as in transmission. Besides, some authors point out that coordinated actions between both operators would allow to achieve effective and efficient voltage control and congestion management [11] as well as regulate active and reactive power exchange at frontier nodes [12,13] to guarantee security, reliability, and cost-efficiency.…”