Flux Error Function Based Controlled Switching Method for Minimizing Inrush Current in 3-Phase Transformer

Pachore, Parvraj; Gupta, Yugal; Anand, Sandeep; Sarkar, Subrata; Mathur, Paresh; Singh, Pushpendra

doi:10.1109/tpwrd.2020.2995519

Cited by 13 publications

(13 citation statements)

References 18 publications

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“…An anchor black-start source is required to energize network segments, connect to loads, and in some cases synchronize to neighboring networks. Network restoration typically involves power transformers energization, a process that can cause very high inrush currents, up to 7-10 times the transformer rating [15]. On the other hand, power converters are also known for their limited overcurrent capabilities.…”

Section: Grid-forming Control Techniquesmentioning

confidence: 99%

Current-Type Power Hardware-in-the-Loop Interface for Black-Start Testing of Grid-Forming Converter

Feng

Alassi

Syed

et al. 2022

IECON 2022 – 48th Annual Conference of the IEEE Industrial Electronics Society

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Grid-forming converter establishes a stable and controllable voltage at its output terminal without requiring external angle reference, which enables the GFC to be a candidate for providing black-start services. However, this attribute poses significant challenges to the conventional power hardware-in-theloop (PHIL) simulation, which incorporates the physical power converter by regulating its voltage angle to be synchronized with that of an interfacing power amplifier mimicking the real-time emulated power grid. The lack of voltage synchronization at the coupling point of GFC and interfacing power amplifier leads to instability. To address this challenge, the current-type interfacing method with compensation and scaling scheme is proposed to interface a GFC with soft black-start capability into a PHIL setup. Analytical assessment and experimental results involving interfacing a 90 kVA power converter implemented with gridforming control are presented to verify the methodology.Index Terms-Power hardware-in-the-loop (PHIL), gridforming converter, soft black-start, current-type power interface.

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Section: Grid-forming Control Techniquesmentioning

confidence: 99%

Current-Type Power Hardware-in-the-Loop Interface for Black-Start Testing of Grid-Forming Converter

Feng

Alassi

Syed

et al. 2022

IECON 2022 – 48th Annual Conference of the IEEE Industrial Electronics Society

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“…The other control modification considers the grid synchronization requirement through adjusting (1) to include a temporary power term 𝑃 𝑠𝑦𝑛𝑐 that is only activated when synchronization is required to influence 𝛿 𝑖 and match it to the grid angle, resulting in (5).…”

Section: Modified Grid-forming Synchronizing Controlmentioning

confidence: 99%

“…This is to avoid sudden jumps in 𝑃 𝑠𝑦𝑛𝑐 to excessive values if the synchronization controller is activated at a time of high error ∆𝛿 𝑔_𝑝𝑐𝑐 . An alternative grid synchronization design supplies the angle synchronizing controller output directly to the angle terms in (5), considering that the angular frequency is the voltage angle derivative. It has been observed through simulations that this option may require a continuously changing PI controller output as the power reference error input is typically a non-zero value.…”

Section: Modified Grid-forming Synchronizing Controlmentioning

confidence: 99%

“…Transformer energization has long been a task associated to conventional synchronous generators (SG) as the dominant power source in public grids. As strong sources with high short-term overcurrent capabilities, SGs can typically withstand the inrush current requirements of a transformer that can be up to 7-10 times the nominal current [5]. On the other hand, power converters have very strict current limits for protection, which are typically limited to 1.5 p.u.…”

Section: Introductionmentioning

confidence: 99%

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Modified Grid-forming Converter Control for Black-Start and Grid-Synchronization Applications

Alassi

Ahmed

Egea‐Àlvarez

et al. 2021

2021 56th International Universities Power Engineering Conference (UPEC)

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The increasing grid integration of converterbased generation and distributed resources is necessitating a review to the classical synchronous generators dominant network models, and to equip converters with the necessary control capabilities such as inertia emulation and black-start to carry on the required ancillary services provision. This paper proposes a modified grid-forming converter control technique based on virtual synchronous machine (VSM). The modified controller uses a ramping voltage reference to achieve soft transformer energization and eliminate high-magnitude inrush current that can traditionally exceed converters rating. Gridsynchronizing functionality is added to the VSM controller to achieve smooth transition from black-start to grid-connected mode while maintaining grid-forming operation. This is achieved by gradually adjusting the power loop reference through a dedicated synchronizing controller, which is disconnected once grid-connection is achieved. A MATLAB/ Simulink case study is presented to illustrate the controller performance with a 40 MVA simulated converter. The results demonstrate successful black-start sequence execution, starting by soft transformer energization, followed by a block load pickup and grid-synchronization. The sequence is achieved with minimal transformer inrush current, and with seamless transition to the grid-connected operating mode.

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“…When the power transformer is cut-out operation and in various test operations [1]- [3], the internal magnetic flux density in the iron core does not fall to zero and thus an unknown residual flux density (Br) is produced, which is resulted by the hysteresis characteristics of iron core materials [4]- [6]. When the transformer is switched to connect with power grid again, a magnetizing inrush current will be produced as the existence of Br [7], [8]. Sometimes this current may be 6 to 8 times higher than the rated state current [9], which will result the transformer failing to connect with the power grid.…”

Section: Introductionmentioning

confidence: 99%

Residual Flux Density Measurement Method of Single-Phase Transformer Core Based on Time Constant

Huo

Yang

et al. 2020

IEEE Access

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Residual flux density in the single-phase transformer core can dramatically increase inrush current when the transformer is energized. To reduce inrush current, it is necessary to study residual flux density measurement. This paper proposes a new residual flux density measurement method based on time constant. Firstly, the generation principle of residual flux density is analyzed under different magnetization states, and it is found that the positive relative differential permeability is smaller than the negative at different residual flux density. To obtain the relative differential permeability, when an appropriate DC excitation is applied, the measurement circuit is equivalent to a first-order RL circuit. Then, combining magnetic circuit and transient circuit analysis, the relationship between time constant and relative differential permeability is obtained. It is conclusion that the positive time constant is less than the negative. Residual flux density direction is determined by comparing the positive and negative time constant, and the magnitude of residual flux density is calculated by the relationship between residual flux density and the difference of the positive and negative time constant. Finally, the empirical formula between residual flux density and time constant difference of the square core is obtained in finite element method, and then verified on the experimental platform. Compared with other measurement methods, the relative error of proposed empirical formula is within 4.58 %, and it has higher accuracy in this paper. The proposed method in this paper can provide a reference for selecting the demagnetization voltage, which improves the effectiveness of demagnetization. INDEX TERMS Residual flux density, relative differential permeability, time constant difference, empirical formula.

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Flux Error Function Based Controlled Switching Method for Minimizing Inrush Current in 3-Phase Transformer

Cited by 13 publications

References 18 publications

Current-Type Power Hardware-in-the-Loop Interface for Black-Start Testing of Grid-Forming Converter

Current-Type Power Hardware-in-the-Loop Interface for Black-Start Testing of Grid-Forming Converter

Modified Grid-forming Converter Control for Black-Start and Grid-Synchronization Applications

Residual Flux Density Measurement Method of Single-Phase Transformer Core Based on Time Constant

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