Abstract
Renewable energy generators (REGs) usually employ power electronic devices for connecting with the grid, which makes their fault characteristics completely different from those of conventional synchronous generators. In the existing studies, the simulation methods are mainly adopted to analyze fault current contribution from REG. As a result, the explanations on the fault current show diversity and cannot reach a recognized standard. The REGs’ mathematical model in relay-setting calculations is unknown. Thus, this paper theoretically analyses the fault current characteristics of inverter-interfaced REGs (IIREGs) with fault-ride-through (FRT) ability. In order to understand the fault current characteristics, the FRT control strategy for IIREGs is firstly studied. Then the characteristics of high-frequency and fundamental-frequency fault currents from IIREGs are theoretically analyzed after and during the faults. The affecting factors and duration time of different frequency fault currents are, respectively, revealed. Further, the mathematical expression of fundamental fault currents from IIREGs are derived and verified based on the experimental test bench. The results can be used in estimating the IIREGs’ fault contributions and developing the fault calculation model.
Highlights
With the worldwide concern on environment pollution and the crisis on traditional fossil energy, renewable-energy penetration in power grids is expected to grow spectacularly [1]
To ensure that the inverter-interfaced REGs (IIREGs) ride through the asymmetrical faults, the control strategy based on dual vector current controller (DVCC) for the grid-tie inverter has been widely used
The proposed strategy can help the IIREGs to ride through the severe symmetrical faults
Summary
With the worldwide concern on environment pollution and the crisis on traditional fossil energy, renewable-energy penetration in power grids is expected to grow spectacularly [1]. In order to enhance the asymmetrical FRT ability, some control strategies have been proposed, such as the single vector current controller with feed forward negative-sequence grid-side voltage [16], dual vector current controller (DVCC) in a positive and negative synchronously rotating frame [17], and proportional-resonant controllers in a two-phase stationary frame [18,19] Their main concerns are how to eliminate the DC-link fluctuation or to decrease the negative fault current. [23,24,25] studies the fault current characteristics of IIREGs by considering the FRT control strategy. The two-times frequency component of active power Po1ut yields a 100-Hz DC-link voltage ripple Such a pulsating voltage causes detrimental effects on the control system of the grid-tied inverter and even leads to tripping off of the IIREG from the grid
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