Large-Signal Stability of Grid-Forming and Grid-Following Controls in Voltage Source Converter: A Comparative Study

Fu, Xikun; Sun, Jianjun; Tian, Zhen; Yan, Han; Iu, Herbert Ho-Ching; Hu, Pan; Zha, Xiaoming

doi:10.1109/tpel.2020.3047480

Cited by 135 publications

(26 citation statements)

References 18 publications

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“…Moreover, frequency dynamics are also analyzed by proposing a motion equation, where the stiffness is defined to illustrate the synchronizing capability of VSG with weak grids. Large-signal stability of GFMI and GFD VSG are compared using energy function modeling by the authors in [90]. The results show that compared to a GFMI, the GFLI loses stability by exhibiting a varying damping coefficient.…”

Section: ) Transient Stabilitymentioning

confidence: 99%

Grid Forming Inverter Modeling, Control, and Applications

et al. 2021

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This paper surveys current literature on modeling methods, control techniques, protection schemes, applications, and real-world implementations pertaining to grid forming inverters (GFMIs). Electric power systems are increasingly being augmented with inverter-based resources (IBRs). While having a growing share of IBRs, conventional synchronous generator-based voltage and frequency control mechanisms are still prevalent in the power industry. Therefore, IBRs are experiencing a growing demand for mimicking the behavior of synchronous generators, which is not possible with conventional grid following inverters (GFLIs). As a solution, the concept of GFMIs is currently emerging, which is drawing increased attention from academia and the industry. This paper presents a comprehensive review of GFMIs covering recent advancements in control technologies, fault ride-through capabilities, stability enhancement measures, and practical implementations. Moreover, the challenges in adding GFMIs into existing power systems, including a seamless transition from grid-connected mode to the standalone mode and vice versa, are also discussed in detail. Recently commissioned projects in Australia, the UK, and the US are taken as examples to highlight the trend in the power industry in adding GFMIs to address issues related to weak grid scenarios. Research directions in terms of voltage control, frequency control, system strength improvement, and regulatory framework are also discussed. This paper serves as a resource for researchers and power system engineers exploring solutions to the emerging problems with high penetration of IBRs, focusing on GFMIs.INDEX TERMS Current control, fault ride-through, grid forming inverters, power synchronization control, small-signal and transient stability, virtual inertia.

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Section: ) Transient Stabilitymentioning

confidence: 99%

Grid Forming Inverter Modeling, Control, and Applications

et al. 2021

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“…Growing levels of converter-interfaced generation, such as HVDC systems and renewables, are connected each year to power systems around the globe. Therefore, the modeling, control, and stability of the power converters are now one of the main focuses of attention for researchers (see [2,3,[34][35][36][37][78][79][80]). Specifically, stability analysis using energy functions were provided in [34,37] for single-machine, single-converter systems and in [2,3] for multi-machine, multi-HVDC systems.…”

Section: Modeling Of a Multi-machine Multi-converter Power Systemmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

“…Therefore, stability analysis is of interest given the expected growth in GFM applications in power systems (see [34][35][36][37]). In [34], a stability analysis was conducted for GFL and GFM converters connected to a synchronous generator, one at a time. The study established a comparison between both energy functions and transient stability for GFL and GFM converters, compared through an experimental setup.…”

Section: Introductionmentioning

confidence: 99%

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Stability Analysis of Grid-Forming MMC-HVDC Transmission Connected to Legacy Power Systems

et al. 2021

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The power system is going through a change in its very foundations. More and more power converters are being integrated into the electric grid to interface renewable energy resources and in high-voltage direct-current (HVDC) transmission systems. This article presents a discussion on the stability of power systems when HVDC transmission systems based on modular multilevel converters (MMC) are connected in grid-forming (GFM) mode to the legacy power system using concepts of energy functions and Lyapunov stability theory and considering aspects of the interoperability between GFM converter technologies. As a base for the stability analysis, we review the main GFM converter technologies (droop and virtual synchronous machine), highlighting their differences. Then, we present a model using the center-of-inertia formulation for a multi-machine/multi-GFM converter power system representing a close future scenario of power systems where GFM converters might adopt different technologies. To illustrate the theoretical Lyapunov-based stability analysis, simulations performed in Matlab/Simulink showed the behavior of a 12-bus test system during a frequency disturbance that originated from the sudden connection of a load. To reflect the interoperability of different GFM technologies and the power system, scenarios with one single GFM technology and a scenario with mixed technologies were investigated. For the test system considered, the frequency response with fewer oscillations and a higher frequency nadir was obtained when all GFM converters were operated as VSMs that have a higher inertial response contribution.

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“…The grid-friendly control scheme is mainly concerned for improving the interaction performance between the grid and the inverter. Traditionally, the control schemes for grid-connected inverter include gridfollowing control and grid-forming control [1]. The former, which includes constant current control, constant power control [2,3], cannot support the power grid during the transient process.…”

Section: Introductionmentioning

confidence: 99%

The Strategy of Active Grid Frequency Support for Virtual Synchronous Generator

Yang

Wang

et al. 2021

Electronics

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Virtual synchronous generator (VSG) control is a promising control approach for voltage source converters as an interface between new energy sources and the power grid. VSG is a grid-friendly control scheme, which can imitate the mechanical inertia of the synchronous generator (SG) and the power droop characteristics. Yet, the droop characteristics imitation of SG induces the frequency variation of the grid-connected inverter along with the droop characteristic curve, which will deteriorate the performance of the grid frequency support during the transient process. In this paper, a control scheme, which shapes the droop curve during the disturbance, is proposed for active grid frequency support. First, a load disturbance extraction strategy with a high-pass filter is applied in the proposed method, and the disturbance component is effectively extracted to compensate for the frequency reference variation in traditional VSG control. The grid frequency is actively supported by shaping the droop curve of active power to the frequency of VSG during the disturbance. Afterward, H∞ and H2 norms are used as the objective function to quantify the control performance of the proposed method, and the particle swarm optimization (PSO) algorithm is applied to optimize the control parameters of the proposed method. With a well-optimized high-pass filter, the active support performance is further improved. Finally, the simulation results and hardware in the loop (HIL) tests verify the effectiveness of the proposed method.

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Large-Signal Stability of Grid-Forming and Grid-Following Controls in Voltage Source Converter: A Comparative Study

Cited by 135 publications

References 18 publications

Grid Forming Inverter Modeling, Control, and Applications

Grid Forming Inverter Modeling, Control, and Applications

Stability Analysis of Grid-Forming MMC-HVDC Transmission Connected to Legacy Power Systems

The Strategy of Active Grid Frequency Support for Virtual Synchronous Generator

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