Transfer Characteristics of Wide-Range Current Transformer Based on Zero-Flux Theorem
Under the background of"Dual Carbon",the large-scale grid connections of new energy distributed power sources are characterized by intermittency and wide range load,which results in a wide dynamic range characteristics of current signals at the new energy grid connection point.Traditional current transformers are prone to exceeding error limits when the primary current is much lower than the rated current due to insufficient excitation of the iron core and low initial magnetic permeability.When the primary current exceeds the rated current,accuracy degradation may occur due to saturation of the iron core,making it difficult to measure power energy accuratly.In order to meet the requirements of high accuracy and wide range for current transformers,a passive zero-flux composite iron core current transformer based on electromotive force compensation is proposed.Through the introduction of unequal secondary windings and compensation windings on the main and auxiliary iron cores and selection of different iron core structure and materials according to the magnetic field distribution characteristics of the main and auxiliary iron cores,the main iron core works in a state of approximately zero magnetic flux.The control block diagram and transfer function of the current transformer with this structure are derived.Combined with simulation analysis and experimental verification,it is shown that the current transformer with this structure meets the accuracy requirements of 0.1 precision current transformer within the range of 0.1%to 200%of the rated primary current.An effective solution is provided for measuring current signals with a wide dynamic range in power systems under the background of new energy.
current transformerwide rangezero-fluxelectromotive force compensationcomposite iron core
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