Seamless Transfer Scheme With Unified Control Core for Paralleled Systems

Liu, Hongpeng; Zhang, Wei; Sun, Bainan; Loh, Poh Chiang; Wang, Wei; Xu, Dianguo; Blaabjerg, Frede

doi:10.1109/tpel.2018.2872326

Cited by 14 publications

(11 citation statements)

References 33 publications

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“…In the GC state, the inverter is controlled as a current source, and the inductor current references are listed as (1) and (2). The steady state error of inductor current will be zero with the PI controller GI; therefore, the inductor current in the GC state can be represented as…”

Section: ) Analysis Of Operation Pointsmentioning

confidence: 99%

“…3) Regulating the voltage amplitude and frequency in the SA state [1]. Compared with the control objectives )1) and (3) in steady state, a more difficult challenge is the seamless transfer from GC state to SA state, because control targets in the GC and SA states are noticeably different, which may burden the transfers between states with inrush currents and even system crashes [2]. Thus, different kinds of control methods are proposed to realize the seamless transfer from the GC state to SA state, which can be classified into three categories: 1) droop control; 2) hybrid current and voltage mode (HCVM) control; 3) self-adaptive control.…”

Section: Introductionmentioning

confidence: 99%

“…However, if the grid voltage fluctuates in the GC state, the objective (1) may fail and the inverter output power deviates from its set point. Several improved droop control methods have been devised to mitigate the effects of grid fluctuation by adjusting the references or control structure in different operation states [3][4][5][6][7][8][9][10]; yet the adjustment relied on islanding detection. If islanding occurs but has not been detected and the reference and control structure remain constant, undesirable transients may result.…”

Section: Introductionmentioning

confidence: 99%

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A Self-Adaptive Controller for Inverter With Seamless Transfer and Automatic Pre-Synchronization Capability

Meng

Liu

et al. 2020

IEEE Access

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A self-adaptive controller is proposed to operate inverter in both grid-connected (GC) state and stand-alone (SA) state and ensure seamless transfer between them without reconfiguring the control structure. The controller is mainly composed of phase-locked-loop (PLL) and two cascaded control loops. The role of PLL is not only to estimate the frequency but also to generate the reference of voltage loop. When the grid is normal, the reference and the feedback value of voltage loop are always equal and the proposed controller accurately regulates the grid current of inverter. When islanding occurs, the inverter can automatically convert from current control mode to voltage control mode without critical islanding detection. The self-adaptive controller has several advantages. First, compared with direct current control, it can operate in both strong and weak grid conditions. Second, its dynamic performance in the GC state is much better than that of indirect current control. Third, when the grid returns to normal, the presynchronization of inverter's output voltage and grid voltage can be achieved automatically without any extra control algorithm. Finally, simulation and experimental results are provided to verify the effectiveness of proposed self-adaptive controller.

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Section: ) Analysis Of Operation Pointsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

A Self-Adaptive Controller for Inverter With Seamless Transfer and Automatic Pre-Synchronization Capability

Meng

Liu

et al. 2020

IEEE Access

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“…10 Obviously, to achieve a smooth transient process during intended or unintended islanding occurrence is highly expected in order to prevent fault trigger and protect voltage sensitive critical load. [11][12][13][14] However, this is very challenging to handle unintended islanding as a result of the existing "blanking time" by unavoidable delay time with any islanding detection methods and controller mode transfer, which makes such system suffer from distorted PCC voltage and even system instability in case without dedicated design for reliable operation.…”

Section: Introductionmentioning

confidence: 99%

Seamless transfer control for dual‐mode grid‐connected inverter with automatic PCC voltage regulation

Liu

Yuan

2022

Circuit Theory & Apps

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Distributed generators are more expected with the capability to continue supporting power to local critical loads in both intended and unintended islanding conditions, in addition to its house‐keeping functions of grid‐connected condition. With this purpose, this paper proposes a control strategy of single‐phase grid‐connected inverter with both decoupled power control capability for grid‐connected mode and load voltage regulation capability for standalone mode. It also enables automatic voltage regulation on point of common coupling, which enables seamless transfer after islanding occurrence. An impedance model is disclosed to analyze the operation mechanism during transient state, with further investigations on both the effect of system parameters in different modes and the system operating features. Simulation and experimental results are provided to evaluate its effectiveness.

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“…In spite of operating the distribution system in gridconnected and islanded modes, a smooth mode transfer with synchronisation scheme is necessary to improve the reliability of the supply across the emergency loads [8,9]. Therefore, various islanding and synchronisation schemes [10][11][12] have been proposed to synchronise/island the distribution grid. However, developing a robust synchronisation method is still a challenging task as a conventional phase-locked loop (PLL) has a significant phase error during transitions [13].…”

Section: Introductionmentioning

confidence: 99%

Norm combination constrained set‐membership function‐based approach with limit cycle oscillator control of grid‐interactive photovoltaic system

Kumar

Al‐Durra

El-Saadany

2021

IET Renewable Power Gen

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This study presents a norm combination constrained set‐membership function (CCSMF)‐based approach for two‐stage photovoltaic (PV) array to be used in the three‐phase three‐wire system. Here, the norm is introduced in the control technique to improve the response of existing approaches. The norm is the addition of the magnitudes of the load current components in a space. It is the most natural way of evaluating the various magnitude of harmonic components. In addition, the CCSMF technique furnishes harmonics disturbance rejection, current compensation, grid currents stabilisation and correction of power factor performances in order to allocate system integrated with residential non‐linear loads. Further, it is used to extract the fundamental component of load currents for generating the reference currents. The range of the amplitude and frequency of the grid voltages are continuously monitored by the limit cycle oscillator‐based algorithm. Under the outage of PV insolation, the voltage source converter (VSC) is switched to the compensator unit, and grid feeds power to the emergency load, which improves the utilisation factor of VSC. The presented system along with the proposed technique is tested in the laboratory and grid current total harmonic distortion is brought down within the limit of the IEEE‐519 standard.

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Seamless Transfer Scheme With Unified Control Core for Paralleled Systems

Cited by 14 publications

References 33 publications

A Self-Adaptive Controller for Inverter With Seamless Transfer and Automatic Pre-Synchronization Capability

A Self-Adaptive Controller for Inverter With Seamless Transfer and Automatic Pre-Synchronization Capability

Seamless transfer control for dual‐mode grid‐connected inverter with automatic PCC voltage regulation

Norm combination constrained set‐membership function‐based approach with limit cycle oscillator control of grid‐interactive photovoltaic system

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