Options for Control of Reactive Power by Distributed Photovoltaic Generators

TL;DR

This paper explores control strategies for reactive power management in distributed photovoltaic inverters to improve voltage regulation and reduce losses in power distribution systems, comparing centralized and local control methods through simulations.

Contribution

It introduces and evaluates various control system designs for reactive power in PV inverters, emphasizing local control schemes and their tuning for different operational conditions.

Findings

Local control schemes effectively maintain voltage within bounds.

Tuning control systems balances voltage stability and loss minimization.

Distributed control offers a practical solution for high PV penetration scenarios.

Abstract

High penetration levels of distributed photovoltaic(PV) generation on an electrical distribution circuit present several challenges and opportunities for distribution utilities. Rapidly varying irradiance conditions may cause voltage sags and swells that cannot be compensated by slowly responding utility equipment resulting in a degradation of power quality. Although not permitted under current standards for interconnection of distributed generation, fast-reacting, VAR-capable PV inverters may provide the necessary reactive power injection or consumption to maintain voltage regulation under difficult transient conditions. As side benefit, the control of reactive power injection at each PV inverter provides an opportunity and a new tool for distribution utilities to optimize the performance of distribution circuits, e.g. by minimizing thermal losses. We discuss and compare via simulation various design options for control systems to manage the reactive power generated by these inverters. An important design decision that weighs on the speed and quality of communication required is whether the control should be centralized or distributed (i.e. local). In general, we find that local control schemes are capable for maintaining voltage within acceptable bounds. We consider the benefits of choosing different local variables on which to control and how the control system can be continuously tuned between robust voltage control, suitable for daytime operation when circuit conditions can change rapidly, and loss minimization better suited for nighttime operation.