This paper evaluates the performance of coordinated control across advanced distribution management systems (ADMS), distributed energy resources (DERs), and distributed energy resource management systems (DERMS) using an advanced hardware-in-the-loop (HIL) platform. This platform provides a realistic laboratory testing environment, including accurate dynamic modeling of a real-world distribution system from a utility partner, real controllers (ADMS and DERMS), physical power hardware (DERs), and standard communications protocols. One grid service—voltage regulation—is evaluated to show the performance of the coordinated grid automation system. The testing results demonstrate that the coordinated DERMS and ADMS system can effectively regulate system voltages within target operation limits using DERs. The realistic laboratory HIL testing results give utilities confidence in adopting the grid automation systems to manage DERs to achieve system-level control and operation objectives (e.g., voltage regulation). This helps utilities mitigate potential risks (e.g., instability) prior to field deployment.

Seamless recovery and sustained power to critical infrastructures (CIs), after grid failure, is a crucial need arising in disaster scenarios that are increasingly becoming more frequent. Accreditation standards recommend CIs to have emergency power supply system (EPSS) in order to form a local microgrid network with backup resources (generation units/renewable resources) in case of sudden power blackouts of main grid supply. The standards also recommend enhancements such as seamless transition capability during on-grid to off-grid jump and vice versa, efficient and optimal operation while maintaining the standard regulation and power quality limits during power contingencies, and operation with sustenance of reliable power for long periods of time. This article is proposing a comprehensive design of the EPSS for uninterrupted operation of CIs by employing novel techniques, such as 1) mode-dependent droop controlled grid-forming inverters for seamless transition capability; 2) fast-acting optimal net-load management engine for efficient and optimal operations maintaining regulation and power quality limits; 3) optimization-based horizon of viability engine for longer, sustained and viable operation in the aftermath of grid failure as recommended in standards. Two stage validations are conducted using defined test cases while considering various types of contingencies on a 3-ϕ, 60 Hz, 480 V, 450 kVA test system based on a realistic electrical network of a commercial scale medical center. The comprehensive controller-hardware-in-loop and power-hardware-in-the-loop based experiments corroborate the efficacy and robustness of the proposed strategy for EPSS employed in the CI. The mode-dependent droop controller enables seamless transition of the critical infrastructure between the off-grid and the on-grid modes. Inverters operate in the gird-forming mode when the CI is off-grid and also when the CI is on-grid while keeping frequency and voltage regulated between ±0.5 Hz and ±10% of the nominal respectively. The fast-acting net-load management engine maintains the balance in total available generation and the power demand by determining the optimal decisions within 100 ms during various contingencies while regulating the voltage, frequency, and total harmonic distortion (THD) of the system under the strict limit recommended by the grid codes. The horizon of viability optimization engine showcases advantages over conventional scheduling engines with higher utilization of critical loads and maintaining higher energy at the end of an 1-hour experiment.

Nowadays, a large number of inverter-based resources (IBRs) are integrated into the grid at a single connection point as an IBR plant. In this article, a virtual dynamic grid impedance concept is introduced to evaluate the harmonics and stability for grid integration of an IBR plant containing multiple IBRs. First, a detailed theoretical study is conducted to build a foundation of the virtual grid impedance concept, which is a dynamic impedance that changes with the number of IBRs added into an IBR plant. Then, based on the new virtual dynamic grid impedance concept, frequency spectrum analysis is performed to explore harmonic impact at the interconnection point for an IBR plant with IBRs having L, LC, and LCL filters, respectively. An electromagnetic transient (EMT) simulation model of a grid-connected IBR plant is developed to explore the harmonics and stability of the IBR plant connected to the grid as well as the reliable operation of IBRs within the plant from the novel virtual equivalent dynamic grid impedance point of view. Hardware experiments are conducted to validate the EMT simulation evaluation. The results show that the number of IBRs added into an IBR plant influences the grid impedance, i.e., grid strength, and the grid impedance variation has multiple impacts on the IBR plant and IBRs within the plant depending on the grid-connected filters of the IBRs.

Nowadays, inverter-based resources are rapidly growing in electric power systems. On the other side, abnormal inverter operations are also occurring more often. Traditionally, inverter PQ capability charts are employed by electric utility companies to ensure safe and reliable operations of inverter-based resources. However, it is found in this paper that existing inverter PQ capability charts do not address the operating characteristics of an inverter correctly, which can result in irregular and unstable inverter operations. In this paper, a novel study is conducted to investigate inverter PQ capability charts, where constraints that are specific to an inverter are considered. It is found in this paper that the inverter PQ capability charts exhibit a unique dynamic nature under uncertain grid conditions. This dynamic nature has not been considered by the industry in managing, designing, and controlling an inverter as well as in developing international standards for inverter-based resources. Via both electromagnetic transient simulation and hardware experimental investigations, it is found that the dynamic PQ capability nature, together with the limitations of the existing control methods, are the underlying causes of many unusual inverter operations that have been reported in the literature.

The reliable operation of islanded microgrids increasingly depends on secondary controls that restore voltage and frequency to nominal values and ensure accurate active and reactive power sharing. Centralized secondary control architectures achieve high accuracy through global coordination at the cost of single-point failures and limited scalability compared with decentralized/distributed approaches. But a critical gap remains in addressing the interoperability and vendor-agnostic operation of secondary controls in real-world microgrids where heterogeneous diesel generator(s) and grid-forming (GFM) inverter(s) from multiple manufacturers always coexist. Practical and vendor-agnostic interoperability guidelines for the secondary control architecture of microgrids with multiple GFM units have not yet been developed; therefore, this paper proposes an interoperable and vendor-agnostic secondary control framework that operates seamlessly across GFM units from different vendors without relying on proprietary controls and protocols, hardware, or lock-ins. The framework leverages existing communication infrastructures (e.g., Modbus TCP/IP) to enable cost-effective deployment while addressing practical challenges, such as packet loss and quantization errors. Mitigation strategies—including data averaging, situational event-triggered control, and finite-iteration execution—are introduced to enhance reliability under real-world conditions. A generalized modeling and design framework is also presented, supported by robustness analysis to demonstrate independence from vendor-specific implementations. The proposed framework is validated through a large-scale hardware demonstration using a 3-φ, 480-V, 60-Hz, 713-kVA laboratory hardware microgrid involving a heterogeneous diesel generator and multiple GFM inverters, showcasing its effectiveness in achieving stable voltage and frequency restoration and accurate power sharing under practical constraints. The results highlight the framework’s potential as a scalable and practical solution for next-generation microgrids requiring openness, standard framework, and interoperability.