Power Flow Solvability with Volt-Var Controlled Inverter-Based Resources

TL;DR

This paper derives a sufficient condition for power flow solvability in distribution grids with inverter-based resources under Volt-Var control, ensuring voltage stability and aiding real-time voltage regulation.

Contribution

It introduces a fixed point formulation of power flow equations with Volt-Var control and applies Brouwer's fixed-point theorem to establish solvability conditions.

Findings

The conditions are validated through simulations on distribution test feeders.

The approach helps prevent voltage collapse by identifying operational limits.

It supports real-time decision-making for voltage regulation.

Abstract

This paper establishes a sufficient condition for guaranteeing power flow solvability in distribution grids with inverter-based resources (IBRs) operating under IEEE 1547 compliant Volt-Var control. While designed to improve voltage profiles, reactive power injection can drive the system toward its operational limits. Under these stressed conditions, any further incremental reactive power injection can trigger voltage collapse, the point at which a power flow solution ceases to exist. In this paper, by leveraging a phasor-based voltage representation, the power flow equations with Volt-Var control are developed in the complex fixed point form, enabling a compact formulation and the rigorous application of fixed-point theorems. Addressing the challenges posed by the non-holomorphicity of the complex power flow equations due to the Volt-Var function's dependence on voltage magnitude, the solvability conditions are then developed using the Brouwer fixed-point theorem. The proposed conditions are validated through simulations on distribution test feeders, with a primary focus on their application to real-time decision-making for voltage regulation services.