Probabilistic Reactive Power Capability Charts at DSO/TSO Interface

Abstract

Hosting an increasing share of distributed generation and flexible consumers, distribution systems are being more often considered as providers of ancillary services among which are reactive power support and voltage control. For the purpose of reliable and efficient planning and operation of a transmission system, information about reactive power capabilities of connected distribution systems would be beneficial. These capabilities are subject to uncertainties especially with a presence of intermittent distributed generation and stochastic loads. To capture these uncertainties, this paper introduces probabilistic capability charts using the concept of probabilistic curves. These curves analytically represent reactive power support limits of distribution systems as a family of random variables with their associated probabilistic density functions. As such, they carry more information about states of the system than deterministic curves. The proposed capability charts can be easily applied in probabilistic studies of the overlaying transmission system. By providing analytical expressions of stochastic power injections of connected distribution systems, the use of these charts can speed up time and memory demanding probabilistic calculations of transmission systems planning and operation studies. Not containing sensitive system information, the charts can be used to exchange data between distribution and transmission system operators.

Coordination of DERs and Flexible Loads to Support Transmission Voltages in Emergency Conditions

“…The coordination of DERs and FLs is carried out at stepdown substations where the DN can provide active and reactive power support. To ensure that the DN has enough flexibility, the methodologies from [19]- [21], [23], [36] can be employed. There might be as many coordinators as TN load buses, and they are independent from each other.…”

“…New methodologies based on AC Optimal Power Flow (AC-OPF) formulations are used to estimate the flexibility of Active Distribution Networks (ADNs) at the TSO-DSO interface. The works in [19]- [21] estimate the flexibility range of active and reactive power at the TSO-DSO interface by means of capability charts of DNs to aid the operation of TNs. The impact of grid topology changes and transformer's tap position changes on the flexibility provision from ADNs is analyzed in [22], and the value of the flexibility at the TSO-DSO interface is measured in [23] by computing the DSO capability curves and the TSO desirability surfaces.…”

Characterizing Power Support from Distribution Networks via Flexibility Area Segmentation

“…However, few attempts have been made to characterize the structure of ADN flexibility and incorporate the contributions and uncertainties associated with flexible units activation. To capture the uncertainties related to DERs, Stanković and Söder [16] proposed probabilistic reactive power capability charts that represent reactive power support limits of distribution systems as families of random variables with their associ-ated probabilistic density functions. Thus, this approach is able to identify different levels of flexibility with associated uncertainties.…”

Enlarging flexibility region of virtual power plant via dynamic line rating

“…In [16], the robust flexibility region of the VPP is proposed to secure the operation of the internal distribution system immunizing any possible renewable generation fluctuation within the uncertainty set. In [23], the probabilistic flexibility region is studied to estimate the probability distribution of the capability limits of the VPP. Temporal-coupled constraints are also considered in the recent literature when characterizing the aggregated flexibility region of DERs [17,24].…”