Investigation on Common-Mode Voltage Suppression in Smart Transformer-Fed Distributed Hybrid Grids

Zhu, Rongwu; Buticchi, Giampaolo; Liserre, Marco

doi:10.1109/tpel.2017.2779803

Cited by 29 publications

(4 citation statements)

References 29 publications

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“…3, where L f and C f are the inductor and the capacitor of the LC-type filter; L n is the inductor of the neutral line; Z l represents the equivalent line impedance between the ST and the point of common coupling (PCC). A three-phase four-leg converter is selected as the ST LV converter [19]. To achieve sinusoidal and balanced threephase voltage at PCC, the voltage control can be realized with the multiloop voltage control strategy (consisting of a voltage-controlled outer loop and a current-controlled inner loop) in the dq0-frame.…”

Section: A Classification Of Voltage Control Strategy Of St LV Convementioning

confidence: 99%

Stability Assessment of Voltage Control Strategies for Smart Transformer-Fed Distribution Grid

et al. 2020

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The smart transformer (ST), a solid-state-based transformer with control and communication functionalities, determines the voltage of the low voltage (LV) network. Due to the similar control purpose, the classic multiple feedback loop (multiloop) voltage control strategies widely utilized in the uninterruptible power supply (UPS) application, can be considered for the control of ST LV converter. However, a fundamental difference between ST and UPS is the presence in LV grid of distributed generation integrated through power electronics interfaces and the dimension of the supplied grid. Emerging issues like stability and harmonic oscillations challenge the safe operation of the ST-fed grid. In order to explore the problems associated with the grid-converter-based devices, the impacts of the grid converters on various multiloop voltage control strategies have been studied in this paper. Optimal multiloop strategy has been found to offer stable operation to a ST-fed distribution grid under various conditions. Case studies in a CIGRÉ benchmark grid and experimental results are provided to verify the correctness of the theoretical analyses.

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Section: A Classification Of Voltage Control Strategy Of St LV Convementioning

confidence: 99%

Stability Assessment of Voltage Control Strategies for Smart Transformer-Fed Distribution Grid

et al. 2020

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“…This power cannot be fully compensated with only modulation strategies. Steps forward were performed already in [18], where a new modulation strategy is proposed to reduce the DC-link power oscillation in case of unbalanced current. It shows that, in case of 40% higher current in one phase, the oscillation can be decreased from 21% with normal modulation to 9.5% with the proposed strategy.…”

Section: B St-based Single Phase Fault Managementmentioning

confidence: 99%

Smart Transformer-Based Single Phase-To-Neutral Fault Management

Carne

Langwasser

Zhu

et al. 2019

IEEE Trans. Power Delivery

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The Smart Transformer, with its high control capability, offers new features for optimizing the management of the distribution grid. The ST, controlling the voltage in each phase independently, is able to manage the operations during grid faults, and in particular in the single-phase ones. The ST, when a single-phase to ground fault occurs, can rapidly reduce the voltage in the phase under fault. Thus, it guarantees system safety and operates with the remaining two healthy phases to avoid unnecessary interruption in the healthy lines. However, the two-phase asymmetrical operation challenges the system performances due to the high power 2 nd harmonic ripple in the DC voltage, that reduces the capacitors lifespan, and the high current flowing in the neutral conductor. These issues would force the grid operator to increase the ST maintenance, in order to avoid unplanned faults in the ST hardware, due to failure of aged capacitors. This paper presents a flexible control strategy, based on the phase-shift angle control between two healthy-phase voltages, that reduces the impact of the power 2 nd harmonic oscillation and thus can delay the maintenance intervention. The proposed strategy aims to improve system performances by avoiding neutral-line current overload and attenuating AC side active power (low voltage DC-link voltage) oscillation. Depending on the grid conditions (small DC link capacitance or low ampacity of neutral cable), the voltage angle can be adapted, minimizing the impact of the two-phase operation system in the ST-fed grid. The effectiveness and feasibility of the proposed approach have been validated experimentally with a simplified microgrid setup.

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“…This has been used to reduce the active power which is transferred through the ST to avoid the overcurrent [11]. Application of a 4-leg inverter structure [12] at this side allows for voltage control in each phase independently, which can reduce the common-mode harmonics [13], manage the fault [14,15] and minimize the energy losses in the distribution system [16,17].…”

Section: Introductionmentioning

confidence: 99%

Methodology for Assessment of the Impact of Smart Transformers on Power System Reliability

Chen

Nouri

Keane

et al. 2019

IECON 2019 - 45th Annual Conference of the IEEE Industrial Electronics Society

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The smart transformer (ST) has been proposed as an alternative to the traditional low frequency transformer as a means to provide extra control functionality in the smart power system. The ST has merits in terms of reactive power decoupling and voltage decoupling at the primary and secondary side. This provides flexibility for reactive power compensation in the transmission system and demand reduction in the distribution system. Using its ability to control demand through voltage regulation, the ST provides the possibility to reduce demand while keeping the entire load online, which can provide an alternative to load curtailment. Thus, it may provide a means to improve power system reliability. However, no of previous research has investigated these potential system reliability benefits of the ST. The paper presents a methodology which can be used to quantify the system reliability impacts of the use of STs as an interface between the transmission and distribution systems. Using the methodology, the ST impacts on the system reliability are assessed using the IEEE 39-bus system as an example.

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Investigation on Common-Mode Voltage Suppression in Smart Transformer-Fed Distributed Hybrid Grids

Abstract: Index Terms-Common mode voltage, smart transformer, three-phase four-leg converter, three-phase four-wire system, unbalanced three-phase loads

Cited by 29 publications

References 29 publications

Stability Assessment of Voltage Control Strategies for Smart Transformer-Fed Distribution Grid

Stability Assessment of Voltage Control Strategies for Smart Transformer-Fed Distribution Grid

Smart Transformer-Based Single Phase-To-Neutral Fault Management

Methodology for Assessment of the Impact of Smart Transformers on Power System Reliability

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