Auxiliary power of Three-phase photovoltaic inverter is supplied by solar cells with wide input ranging from 140V to 1000V.The conventional single-switch flyback converter exists too high voltage stress in power switch to be applied in this inverter. This paper presents a dual-switch flyback converter in which the voltage stress of each switch is slightly higher than the input voltage when switches turn off, at the same time , the leakage inductance energy is recycled back into the inputside; otherwise, this topology needs no snubber circuit, so it is much more efficient than single switch flyback. The dual switch flyback converter with seven outputs is successfully applied in 10KW three phase PV inverter.
Under three-phase grid asymmetric fault conditions, use traditional PI controller of PV inverters to inject symmetric current positive sequence into the grid, ignoring the impact of the negative sequence current on LVRT, thus traditional PI controller does not apply to three-phase grid asymmetric faults. The paper proposes the decoupling dual synchronous current controller to reject positive, negative sequence current into the grid simultaneously and adopt positive and negative sequence flexible control to determine the active current reference and reactive current reference, avoiding the various drawbacks such as power control, totally positive sequence control bringing. Experiment verify the science and feasibility that decoupling dual synchronous current controller applies to asymmetric faults riding-through.
In this paper, 10KW three-phase three-level photovoltaic grid-tied inverter is applied as hardware platform. Considering the insufficiency of PV arrays power output and low overall efficiency due to grid voltage falls asymmetrically, P-R current controller is used to provide unsymmetrical positive and negative sequence current to the grid so that low voltage ride through (LVPT) in photovoltaic inverter can be achieved. Through the implement of experiments, it is well proved that the requirement of LVPT when the grid voltage falls asymmetrically can be met by applying the solution proposed in this paper.
This paper proposed a kind of analysis method for the aluminium alloy welding quality based on current sample entropy to solve the difficulties in the quantitative analysis for the welding stability of aluminium alloy. With the decrease of electrical signal stability, the sample entropy mean increased, and the standard deviation of sample entropy increased. The welding stability was evaluated by the product of the sample entropy mean and the standard deviation, and this was verified well by the test.
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