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As a consequence of the transition to distributed and renewable energy systems, some distribution system operators are increasingly concerned about power quality, including steady-state voltage volatility. In this paper, we study the control of real and reactive power injections by inverter-based distributed energy resources to regulate voltage magnitudes and phase angles measured by sensors positioned across 3-phase unbalanced distribution grids. Our proposed controllers are agnostic to the location and type of communications supporting energy resource operations. To design the controllers, we apply the Gershgorin Disc Theorem and determine analytic stability regions in terms of renewable energy operating parameters and grid impedances. The stability regions yield direct relationships between renewable energy system siting and the convergence of voltage phasors to references. Beyond defining stability regions, we compute ranges of stable operating parameters for renewable energy systems that promote operational flexibility by including customer economics. By means of a case study on the IEEE 123-node test circuit, we observe our approach to coordinating renewable energy systems achieves non-oscillatory voltage regulation and reduces the duration of voltage violations by 26%., Comment: 10 pages, 9 figures, submitted to IEEE Transactions on Power Systems

In this paper, we introduce Voltage Phasor Control (VPC), also known as Phasor Based Control, as a novel way of implementing Optimal Power Flow (OPF). Unlike conventional OPF, in which the power flow optimization broadcasts power injections, the VPC power flow optimization broadcasts voltage phasor setpoints to feedback controllers distributed throughout the network which respond to disturbances in real time. In this paper, we demonstrate that VPC can actively manage distributed energy resources to avoid voltage magnitude and line flow constraint violations in power distribution networks. We provide sensitivities and bounds that quantify how the distributed voltage phasor feedback control reduces the effect of disturbances on the network voltages and line flows. Using simulations, we compare the performance of VPC with the related but more conventional Voltage Magnitude Control (VMC). The sensitivities, bounds, and simulations provide implementation insights, which we highlight, for how distribution network operators can use VPC and VMC to avoid constraint violations., Comment: 9 pages, 8 figures. Pre-print submitted to the 2022 Power Systems Computation Conference

As more distributed energy resources (DERs) are connected to the power grid, it becomes increasingly important to ensure safe and effective coordination between legacy voltage regulation devices and inverter-based DERs. In this work, we show how a distribution circuit model, composed of two LTCs and two inverter devices, can create voltage oscillations even with reasonable choices of control parameters. By modeling the four-device circuit as a switched affine hybrid system, we analyze the system's oscillatory behavior, both during normal operation and after a cyber-physical attack. Through the analysis we determine the specific region of the voltage state space where oscillations are possible and derive conditions on the control parameters to guarantee against the oscillations. Finally, we project the derived parameter conditions onto 2D spaces, and describe the application of our problem formulation to grids with many devices., Comment: 9 pages, 8 figures, accepted to European Control Conference (ECC2022); compared to version 1, reviewer comments have been incorporated and typos have been corrected