An official website of the United States government
This paper proposes a control scheme that prevents the adverse dynamic interactions between the heterogeneously controlled grid-forming inverters (GFMI) in power electronics dominated grid (PEDG) towards a resilient self-driving grid. The primary controller of GFMIs in a grid cluster can vary based on their manufacturers such as virtual synchronous generation, droop control, power synchronization control, etc. Therefore, this can introduce heterogeneity among the network of GFMIs in PEDG. Resultantly, during the interconnection of GFMIs that are based on heterogenous primary controller poses various synchronization and dynamic interaction challenges in PEDG. For instance, severe fluctuations in frequency and voltage, high ROCOF, unintended reactive power circulation that poses a threat on the overall transient stability of the PEDG. Therefore, to mitigate these adverse dynamic interactions among the heterogeneously controlled GFMIs, a force enclaved homogenization (FEH) control is proposed in a supervisory level controller. This will autonomously adjust inertia coefficients of the each GFMI to have homogenous transient response and will enforce coherency among the heterogenous DGs. This will prevent the PEDG from the adverse dynamic interactions during an interconnection and load disturbance. Various case studies are presented that validates the effectiveness of the proposed FEH control.
more »
« less
Enabling Aggregation of Heterogenous Grid-Forming Inverters via Enclaved Homogenization
This paper proposes a control scheme to force homogeneity for heterogenous network of the grid-forming (GFM) inverters in power electronics dominated grid (PEDG) to enable their aggregation and coherent dynamic interaction. Increased penetration of the renewable energy in distributed generation (DG) fashion is moving traditional power system to a highly disperse and complex heterogenous system i.e., PEDG with fleet of grid-forming and grid-following inverters. Optimal coordination, stability assessment, and situational awareness of PEDG is challenging due to numerous heterogenous inverters operating at the grid-edge that is outside the traditional utility centric power generation boundaries. Aggregation of these inverters will not be insightful due to their heterogenous characteristics. The proposed control scheme to force enclaved homogeneity (FEH) enables an insightful aggregation of GFM that can fully mimic the given physical system dynamics. The proposed FEH scheme enables coherent and homogenized dynamic interaction of GFM inverters that enhances the PEDG resiliency. Moreover, different cluster of GFM can be merged into single cluster with minimal synchronization time and frequency fluctuations. Accurate reference models can be achieved that enables effective dynamic assessment and optimal coordination which results in resilient PEDG. Several case studies provided to validate the effectiveness of proposed FEH in network of GFM. Then, GFMs aggregation and developed reference model for the PEDG system is validated via multiple comparative case studies.
more »
« less
- Award ID(s):
- 2114442
- PAR ID:
- 10451546
- Date Published:
- Journal Name:
- IEEE access
- Volume:
- 10
- ISSN:
- 2169-3536
- Page Range / eLocation ID:
- 94765-94777
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
More Like this
-
-
This paper discusses the challenges faced by electric power systems due to the increasing use of inverter-based renewable energy resources (IBRs) operating in grid-following mode (GFL) and the limited support they provide for the grid’s reliability and stability. With increased IBRs connected to the grid, electric utilities are increasingly requiring IBRs to behave like traditional grid-forming (GFM) synchronous generators to provide support for inertia, frequency, voltage, black start capability, and more. The paper focuses on developing GFM inverter technologies with L, LC, and LCL filters and investigates the performance of combined GFM and GFL inverters with different filtering mechanisms when supplying different types of loads. It also emphasizes achieving voltage controllability at the point of common coupling of the GFM with the rest of an AC system. EMT simulation is utilized to investigate the interaction of combined GFM and GFL inverters with different filtering mechanisms. The research results will assist electric utilities in ensuring the reliability and stability of electric power systems in the future.more » « less
-
Electrical power systems are transitioning from fuel-based generation to renewable generation and transmission interfaced by power electronics. This transition challenges standard power system modeling, analysis, and control paradigms across timescales from milliseconds to seasons. This tutorial focuses on frequency stability on timescales of milliseconds to seconds. We first review basic results for grid-following (GFL) and grid-forming (GFM) control of voltage source converters (VSCs), typical renewable generation, and high voltage direct current (HVdc) transmission. In this context, it becomes apparent that GFL and GFM control functions are needed to operate emerging power systems. However, combining GFL resources, GFM resources, and legacy generation on the same system results in highly complex dynamics that are a significant obstacle to stability analysis. The remainder of the tutorial provides an overview of recent developments in universal GFM controls that bridge the gap between GFL and GFM control and provide a pathway to a coherent control and analysis framework accounting for power generation, power conversion, and power transmission.more » « less
-
Historically, the power system has relied on synchronous generators (SGs) to provide inertia and maintain grid stability. However, because of the increased integration of power-electronics-interfaced renewable energy sources, the grid’s stability has been challenged in the last decade due to a lack of inertia. Currently, the system predominantly uses grid-following (GFL) converters, built on the assumption that inertial sources regulate the system stability. Such an assumption does not hold for the low-inertia grids of the future. Grid-forming (GFM) converters, which mimic the traditional synchronous machinery’s functionalities, have been identified as a potential solution to support the low-inertia grids. The performance analysis of GFM converters for small-signal instability can be found in the literature, but large-signal instability is still an open research question. Moreover, various topologies and configurations of GFM converters have been proposed. Still, no comparative study combining all GFC configurations from the perspective of large-signal stability issues can be found. This paper combines and compares all the existing GFM control schemes from the perspective of large-signal stability issues to pave the way for future research and development of GFM converters for large-signal stability analysis and stabilization of the future low-inertia grids.more » « less
-
This paper proposes a unified distributed secondary control for the grid-forming (GFM) and grid-feeding (GFE) converters in DC microgrids. An optimization problem is formulated for the secondary control and the objective function considers regulating the global average of the GFM and GFE converter output voltages and proportional current sharing among all GFM and GFE converters. A unified distributed control is then designed to generate voltage and current references respectively for GFM and GFE converters based on the formulated optimization problem. The dynamic model of the DC microgrid under the proposed control is also developed, and steady-state analysis is performed to show that the proposed distributed control can achieve the control objectives in steady state. The performance of the proposed control is validated through real-time simulations in OPAL-RT on an 8-DG DC microgrid system.more » « less
- Free Publicly Accessible Full Text
-
Accepted Manuscript1.0
- Journal Article:
- The DOI is not currently available.
