Electric distribution systems around the world are seeing an increasing number of utility-owned and non-utility-owned (customer-owned) intelligent devices and systems being deployed. New deployments of utility-owned assets include self-healing systems, microgrids, and distribution automation. Non-utility-owned assets include solar photovoltaic generation, behind-the-meter energy storage systems, and electric vehicles. While these deployments provide potential data and control points, existing centralized control architectures do not have the flexibility or the scalability to integrate the increasing number or variety of devices. The communication bandwidth, latency, and the scalability of a centralized control architecture limit the ability of these new devices and systems from being engaged as active resources. This paper presents a standards-based architecture for distributed power system controls that increases operational flexibility by coordinating centralized and distributed control systems. The system actively engages utility and non-utility assets using a distributed architecture to increase reliability during normal operations and resiliency during extreme events. Results from laboratory testing and preliminary field implementations, as well as details of an ongoing full-scale implementation at Duke Energy, are presented.

The focus of this paper is on analyzing the impact of conservation voltage reduction in the presence of active devices such as solar photovoltaic (PV) and developing controls that leverage these distributed energy resources. An event-driven predictive approach for real-time volt/volt-ampere reactive (VAR) optimization, along with a local two-level adaptive volt/VAR droop-based control algorithm for advanced distribution management systems, is introduced. The methodology covers aggregated and autonomous controls under different timescale operations, including the impact and effect of unpredicted events such as cloud transients on PV power production. Besides, the control schemes include the uncertainties in PV power generation and load power demand. The proposed methodology is validated in a real-time framework using the real-time digital simulator platform through co-simulation with models based on Python and OpenDSS (Open Distribution System Simulator). The developed methodology is tested on the modified IEEE 123-feeder test system. The results reveal that the proposed methodology works well in the presence of high penetrations of PV power, produces significant energy savings, and mitigates over-/undervoltage problems.

This paper studies the coordinated use of smart inverters with legacy voltage regulating devices to help increase the energy savings from conservation voltage reduction (CVR) in distribution systems with high photovoltaic penetration. Two voltage optimization algorithms are developed to evaluate the CVR benefit by considering two types of smart inverter functions: aggregated reactive power control and autonomous volt/VAR control. In each algorithm, smart inverters are coordinately controlled with the operation of legacy voltage regulating devices including load tap changers and capacitor banks. Both algorithms are tested on representative utility distribution system models. Simulation results demonstrate that the proposed algorithms can achieve around 1.8%–3.6% energy savings when only using legacy voltage regulating devices and an additional 0.3%–0.9% when adding smart inverters.

A doubly-fed induction generator grid side converter is studied under voltage disturbances. During voltage dips, conventional current control techniques involving the decoupling of d-q axis in the synchronous reference frame (SRF) exhibits oscillations in the stiff dc link voltage, as well as in the active and reactive power outputs of the voltage source converter (VSC). To mitigate the oscillations, an advanced control technique called the sequence domain control (SDC) is evaluated. This approach implements individual controllers in the positive and negative sequence domains and demonstrates stabilization of the dc link voltage to a greater extent during a disturbance, but is more sluggish than the conventional control. An innovative control technique called direct power control (DPC) is also investigated. This control achieves active and reactive power stability with simple active and reactive power control variables replacing the traditional current control loops. The DPC technique is verified using a prototype in the laboratory. A modified DPC algorithm combining the benefits of DPC and SDC to eliminate the current harmonics created by DPC during system disturbances is introduced. The benefits of the proposed controllers are compared using a simulation of voltage dip on a VSC based on the IEC-61400-21 standard.

This paper develops an integrated synchronization control technique for a grid-forming inverter operating within a microgrid that can improve the microgrid's transients during microgrid transition operation. This integrated synchronization control includes the disconnection synchronization control and the reconnection synchronization control. The simulation results show that the developed synchronization control works effectively to smooth the angle change of the grid-forming inverter during microgrid transition operation. Thus, the microgrid's transients are significantly improved compared to the case without synchronization control.