Abstract
In transformerless grid-connected photovoltaic (PV) systems, leakage currents should be properly addressed. The voltage fluctuations between the neutral point of the grid and the PV array, i.e., common-mode voltage (CMV), will affect the value of the leakage currents. Therefore, the leakage currents can be attenuated through proper control of the CMV. The CMV depends on the converter topology and the modulation strategy. For the quasi-Z-source inverter (qZSI), the amplitude of the high-frequency components in the CMV increases due to the extra shoot-through (ST) state. The CMV reduction strategies for the conventional voltage source inverter (VSI) should be modified when applied to the qZSI. In this paper, an input-split-inductor qZSI is introduced to reduce the CMV, in which all the CMV reduction strategies for the VSI can be used directly with appropriate ST state insertion. Moreover, the proposed method can be extended to impedance source converters with a similar structure. Simulations and experimental tests demonstrate the effectiveness of the proposed strategy for the qZSI in terms of CMV reduction.
Highlights
The interest in renewable power generation systems has been increasing with no signs of slowing down in recent years worldwide
When the prior-state-of-the-art common-mode voltage (CMV) reduction strategies for the conventional voltage source inverter (VSI) are applied to the quasi-Z-source inverter (qZSI), the high-frequency components are still large, which results from the ST state
In light of the above, this paper explores the CMV reduction strategies for the qZSI system based on the methods for the conventional VSI without introducing additional circuits
Summary
The interest in renewable power generation systems has been increasing with no signs of slowing down in recent years worldwide. The high-frequency components in the CMV of the qZSI are much larger than those in the conventional two-stage transformerless inverter when the ST states were adopted [25]. When the prior-state-of-the-art CMV reduction strategies for the conventional voltage source inverter (VSI) are applied to the qZSI, the high-frequency components are still large, which results from the ST state. To address this issue, various strategies have been proposed.
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