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Current limiting algorithm for three-phase grid-connected inverters

Tran Tho Quang

Archives of Electrical Engineering

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2022

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Vol. 71, nr 3

559--579

EN

Grid-connected inverters are commonly used in systems of renewable energy to convert this energy source into AC power with parameters suitable for connection to the grid. In the normal operating conditions, the grid-connected inverters mainly generate active power to the grid. However, when a voltage sag or voltage imbalance occurs, the grid voltage imbalance in the conventional control methods causes negative sequence components and increases the output current magnitude of inverters. The increase of current can damage power semiconductor devices. This paper presents a strategy to limit the current magnitude of inverters under unbalanced grid voltage conditions. In this strategy, a multiple-complex-coefficient filter is used to eliminate the negative sequence voltage components. This method does not require any additional hardware. A three-phase gridconnected photovoltaic inverter system using a solar array of 20 kWp is also used for the survey. The effectiveness has been validated when comparing the simulation results on Matlab/Simulink of the proposed method with those of the conventional method.

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Non-Cartesian Frame Transformation-Based Control of a Three-Phase Power Converter During Unbalanced Voltage Dip – Part II: Simulation And Experiment

Iwański Grzegorz, Maciejewski Paweł, Łuszczyk Tomasz

Power Electronics and Drives

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2019

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Vol. 4 (39)

63--77

EN

The paper presents a control method for the three-phase power converter operating under unbalanced grid voltage conditions. The method uses a new transformation to the non-Cartesian frame, which makes the controlled current vector components balanced in this frame even if originally the three-phase current is referenced as unbalanced. Furthermore, Park’s transformation makes the controlled variables constant, which allows to apply proportional–integral terms as current controllers independent of the required control target. Several control targets known from literature have been analyzed with regard to the required new transformation parameters, and the transformation parameters for all targets have been found. Simulation results are shown to prove the theoretical analysis, and the experimental test results are presented as practical validation of the proposed use of the non-Cartesian frame in control.

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The Numerical Model of 2G YBCO Superconducting Tape in the Windings of the Transformer

Woźniak Ł., Surdacki P., Jaroszyński L.

Applied Computer Science

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2017

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Vol. 13, no 2

23--38

EN

Computer assisted calculations consists in applying software for the simu-lation of models of certain devices and later analysing their behavior under given conditions corresponding to real working conditions in a specific environment.The paper proposes a circuit model of 2G YBCO super-conducting tape created in the PSpice program. The model consists of passive blocks and active user blocks of analogue behavioural modelling (ABM). ABM blocks calculate the conductances, the currents of the indi-vidual layers of the superconducting tape, its thermal capacity, the heating power, the cooling power and resulting temperature of the tape. The model uses table of thermal power density passed to the liquid nitrogen vs. temperature. Smooth transition of the YBCO superconductor layer into the resistive state is described by Rhyner’s power law. The developed model was used for generating waveforms of thermal and electrical quantities.