Impact of grid-forming control on the internal energy of a modular multilevel converter

Rokrok, Ebrahim; Qoria, Taoufik; Bruyère, Antoine; Bart, François; Zhang, Haibo; Belhaouane, Moez; Guillaud, Xavier

doi:10.23919/epe20ecceeurope43536.2020.9215646

Cited by 12 publications

(7 citation statements)

References 12 publications

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“…To ease the understanding on the VI design, the MMC referring to [18] can be simply modeled as illustrated in Fig. 3, assuming that the internal energy of the MMC is well regulated and decoupled from the AC side.…”

Section: ) Variable Virtual Impedance For Current Limitation (Vi)mentioning

confidence: 99%

“…This method takes the advantages of dealing with overcurrent issues while keeping the voltage source behavior behind impedance of the power inverter, additionally, it can be adopted for various control structures (i.e., cascaded controls and direct controls [16], [17]). In this paper, Modular Multilevel Inverter (MMC) topology is used, and referring to [18], the MMC could be naturally driven as a controllable AC voltage source in open-loop (i.e., current control-Less), in this case, the VI is the suitable solution for overcurrent protection purpose. The design of the VI basically rests on static considerations and do not take into account the dynamic aspects of the system [12].…”

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Variable Virtual Impedance-Based Overcurrent Protection for Grid-Forming Inverters: Small-Signal, Large-Signal Analysis and Improvement

Qoria

Wang

et al. 2023

IEEE Trans. Smart Grid

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Grid-forming inverters are sensitive to large grid disturbances that may engender overcurrent due to their voltage source behavior. To overcome this critical issue and ensure the safety of the system, current limitation techniques have to be implemented. In this context, the variable virtual impedance (VI) appears as a suitable solution for this problem. The design of the variable virtual impedance basically rests on static considerations, while, its impact on the system stability and dynamics considering both small-signal and large-signal aspects can be significant. This paper proposes small-signal and nonlinear power models to assess the impact of the virtual impedance parameters on the grid current dynamics and on the angle stability. Thanks to the developed theoretical approaches in this paper, the virtual impedance ratio X/R, which is the unique degree of freedom has shown a contradictory effect on the small and large signal stability. To overcome this constraint, a Variable Transient Virtual Resistance (VRTVR) has been proposed as an additional degree of freedom to the variable virtual impedance. It acts as a transient damper to ensure the maximum angle stability margin allowed by the variable virtual impedance. The effectiveness of the proposed control has been proven through time-domain simulations.

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Section: ) Variable Virtual Impedance For Current Limitation (Vi)mentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Variable Virtual Impedance-Based Overcurrent Protection for Grid-Forming Inverters: Small-Signal, Large-Signal Analysis and Improvement

Qoria

Wang

et al. 2023

IEEE Trans. Smart Grid

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“…The combination of energy-based internal control and grid-forming based external control of MMC is discussed in [45], [46]. It has been demonstrated that by controlling MMC internal energy, the grid-forming based MMC is identical to an equivalent 2-level VSI.…”

Section: Internal Control Of MMCmentioning

confidence: 99%

Testing Requirements and Control Strategies of Next-Generation Grid Emulator: A Review

Ponnaganti

Zhao

et al. 2022

2022 International Power Electronics Conference (IPEC-Himeji 2022- ECCE Asia)

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The power-electronic-based grid emulator has been widely used for grid-code compliance testing of wind turbines (WTs). To accommodate the increasing voltage and power levels of WTs, the modular multilevel converter (MMC) emerges as a promising approach for the future grid emulator. This paper provides an overview of testing requirements and control strategies for the MMC-based grid emulator. Specifications, challenges and solutions to implement expected control functionalities of the MMCbased grid emulator are discussed according to testing requirements of WTs. Emerging testing functionalities and future trends of grid emulators conclude this paper.

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“…The function (28) is called an energy function because the first term represents the kinetic energy of the rotating rotor of the electrical machine, and the second term represents the potential energy of the generator.…”

Section: Energy Functions For Synchronous Generators and Gfm Convertersmentioning

confidence: 99%

“…A wide variety of GFM strategies were proposed in the technical literature: the virtual synchronous machine (VSM) [22,23], the synchronverter [24][25][26], droop control [27,28], and others that were reviewed in [21]. Specifically in the context of HVDC, ref.…”

Section: Introductionmentioning

confidence: 99%

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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Impact of grid-forming control on the internal energy of a modular multilevel converter

Cited by 12 publications

References 12 publications

Variable Virtual Impedance-Based Overcurrent Protection for Grid-Forming Inverters: Small-Signal, Large-Signal Analysis and Improvement

Variable Virtual Impedance-Based Overcurrent Protection for Grid-Forming Inverters: Small-Signal, Large-Signal Analysis and Improvement

Testing Requirements and Control Strategies of Next-Generation Grid Emulator: A Review

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

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