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

Li, Zejie; Ponnaganti, Pavani; Zhao, Fulong; Wang, Xiongfei; Bak‐Jensen, Birgitte; Munk‐Nielsen, Stig; Blaabjerg, Frede

doi:10.23919/ipec-himeji2022-ecce53331.2022.9807056

Cited by 9 publications

(53 citation statements)

References 35 publications

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“…The impact of internal capacitor voltage fluctuations on the external output of CVG can be mitigated by feeding these capacitor voltages forward to the modulation link of CVG [12], [15], [16]. In respect to the voltage imbalance in the internal capacitors, the NPC-, CHB-based grid emulators differ from the MMC-based grid emulators.…”

Section: A Interactions Within Cvg Caused By Fault Current Injection ...mentioning

confidence: 99%

“…1 shows a general diagram of power-electronic-based grid emulators, which is commonly built on a back-to-back power conversion system with an active-front end (AFE) and a controlled voltage generator (CVG) [3]. For scalability, AFE and CVG are generally composed by series/ parallel connected modular power converters, such as the cascaded or interleaved neutral point clamped (NPC) converter [6]- [10], the cascaded H-bridge (CHB) converter [11]- [13], and the modular multilevel converter (MMC) [14]- [17]. Those topologies typically employ several neutral-point (NP), cell or submodule (SM) capacitors as the energy buffer of the power conversion, where low-frequency fluctuations of capacitor voltages are actively regulated, introducing internal dynamics into grid emulators [13], [14], [18].…”

Section: Introductionmentioning

confidence: 99%

“…Those topologies typically employ several neutral-point (NP), cell or submodule (SM) capacitors as the energy buffer of the power conversion, where low-frequency fluctuations of capacitor voltages are actively regulated, introducing internal dynamics into grid emulators [13], [14], [18]. The internal dynamics can interact with the external dynamics of CVG when emulating transient events, causing voltage imbalance or even over-/under-voltage of the internal capacitors, which may, in turn, adversely affect the testing capabilities of CVG, such as the synthesis of harmonic voltages and the emulation of varying grid impedance during a fault ride-through (FRT) test [16].…”

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

Medium-Voltage Megawatt Power-Electronic-Based Grid Emulators: Testing Capability Requirements and Dynamics Challenges—A Review

Zhao

Wang

et al. 2024

IEEE J. Emerg. Sel. Topics Power Electron.

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Power-electronic-based grid emulators are emerging as a promising way to test the grid-code compliance of renewable energy resources. Yet, the ever-increasing power and voltage levels of device under test pose new requirements and challenges to power-electronic-based grid emulators. This paper first gives an overview of testing capability requirements based on the recent grid codes and standards, then discusses the resulted dynamic interactions and solutions for power-electronic-based grid emulators. Perspectives on the open issues and emerging trends of grid emulators are finally shared.

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Section: A Interactions Within Cvg Caused By Fault Current Injection ...mentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Medium-Voltage Megawatt Power-Electronic-Based Grid Emulators: Testing Capability Requirements and Dynamics Challenges—A Review

Zhao

Wang

et al. 2024

IEEE J. Emerg. Sel. Topics Power Electron.

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“…Role of grid emulator functionalities becomes very important when new inverter control schemes are tested before the real-life implementation [31]. Grid emulator needs to be able to represent future low or variable inertia power systems with different share of IBRs and SG as well as emulate also the different shares of GFM-and GFL-based IBR generation.…”

Section: ) Active and Reactive Power Control Schemesmentioning

confidence: 99%

Improvement of Power System Frequency Stability With Universal Grid-Forming Battery Energy Storages

Laaksonen

2023

IEEE Access

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Large-scale integration of inverter-based renewable generation leads to the reduction of power systems' natural inertia. Therefore, the dynamics of the future power systems will be more sensitive than in the traditional systems with high-inertia rotating synchronous generators. This development is a potential risk for frequency stability and requires utilization of rapidly controllable resources for dynamic frequency stability support. Simultaneously, development of new synchronization and control methods for inverterbased resources is needed in order to ensure the frequency and synchronization stability of future power systems. In this paper, a grid-forming and supporting universal frequency-locked-loop -based control and grid synchronization for inverter-based resources is utilized to improve the frequency stability of a small high-voltage network. The simulations are done with PSCAD software and the main focus is on the battery energy storages to evaluate the effect of their location, enhanced control schemes as well as operation mode on frequency stability. In the studies, for example, the effect of battery storages location, active power response related control parameters, communication time delay and input frequency determination on frequency support are studied during charging and discharging of the batteries. Based on the simulations, also new solutions to improve the frequency stability of future variable inertia power systems with universal grid-forming battery storages are proposed.INDEX TERMS Frequency stability, inverter-based resources, grid-forming, battery energy storages, power systems.

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“…Modular Multilevel Converters (MMC) have already been analyzed regarding GEMs for fault ride-through testing [17] and unbalanced scenarios [18]. While MMCs have not yet been installed for ac grid emulation so far, they are used in PHiL experiments to study MVDC systems [19].…”

Section: ~= ~=mentioning

confidence: 99%

A discussion on the characterization of grid emulators by apparent power rating and short-circuit power

Grune¹,

Geske²

2023

Forsch Ingenieurwes

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Wind turbines are a driving force in the change towards renewable energies today. Offshore wind turbines have reached power ratings around 15 MW, and the growth continues. Grid emulators have become inevitable for the test and validation of wind turbines and subsystems at full scale. Yet, large investments for new installations present major challenges.Therefore, the following discussion outlines basic design aspects for the grid emulator main components: converter, transformer, and filter. The aim is to clarify the implications of requirements on the design to exhaust ratings for minimum investments, and to satisfy testing against the most recent standards and grid codes. Appropriate ratings are derived based on steady-state and transient test needs. It is shown how much overrating is specifically needed and why the converter is usually rated a multiple compared to the device under test. Further dimensioning criteria such as power quality, switching frequency, and filter size are discussed in this context.Finally, the capacity of grid emulators is often characterized by the short-circuit power. Two essentially different variants of short-circuit power are introduced, either being dependent on the converter peak current or the passive components impedance. While the first one reveals the overload capability, the latter represents a proper measure for grid strength. However, the emulated grid strength can be adjusted in a limited bandwidth using impedance control. The concept might be confusing at first glance, but it effectively decouples the virtual short-circuit power from the ratings of the power hardware.

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

Cited by 9 publications

References 35 publications

Medium-Voltage Megawatt Power-Electronic-Based Grid Emulators: Testing Capability Requirements and Dynamics Challenges—A Review

Medium-Voltage Megawatt Power-Electronic-Based Grid Emulators: Testing Capability Requirements and Dynamics Challenges—A Review

Improvement of Power System Frequency Stability With Universal Grid-Forming Battery Energy Storages

A discussion on the characterization of grid emulators by apparent power rating and short-circuit power

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