On-line Calibration Distortion Current Sensing Device for Distributed Photovoltaic Grid-connected Power Generation

Abstract

The invention discloses an online distortion current correction sensing device for distributed photovoltaic grid-connected power generation. Due to saturation, magnetic hysteresis and other characteristics of an iron core material, the existing current transformer is low in accuracy when harmonic current is measured. During a long-time use process, a Rogowski coil has problems of cold and thermal expansion, temperature drift of an integral reduction circuit component and the like, and thus accuracy is low and not stable. The device of the invention comprises a first coil, a second coil, a third coil, the iron core, a fourth coil, a first resistor, a first operational amplifier, a second resistor, a third resistor, a capacitor, a second operational amplifier, an analog-to-digital converter, a microprocessor and an RS485 communication interface; the homonymous end of the first coil and the non-homonymous end of the third coil form an input port of the sensing device, and the RS485 communication interface is an output port of the sensing device. Two primary current sensors: the Rogowski coil and the current transformer are provided, operation state monitoring can be carried out mutually, and reliability of the sensing device is improved.

Description

technical field [0001] The invention belongs to the technical field of electromagnetic measurement, in particular to an on-line calibration distortion current sensing device for distributed photovoltaic grid-connected power generation. Background technique [0002] Distributed photovoltaic grid-connected power generation is the main form of solar photovoltaic power generation. At present, most advanced photovoltaic grid-connected power generation systems adopt a modular structure. Each string structure photovoltaic module is connected to the DC bus through a corresponding modular DC / DC converter, and multiple modules are used between the DC bus and the low-voltage distribution network. DC / AC converter power generation system or centralized DC / AC converter power generation system, these DC / AC converters can provide all or part of the reactive power and harmonic current required by local user loads, DC / AC converters need To control the output of each harmonic current, the pho...

AI Technical Summary

Problems solved by technology

Since the current transformer uses an iron core, the fundamental current measurement accuracy is high and the long-term stability is good, but the saturation and hysteresis of the iron core material make the current transformer low in accuracy when measuring harmonic currents

Because the Rogowski coil uses a non-magnetic material skeleton, it has the advantages of unsaturation and wide frequency band. However, there are problems such as thermal expansion of the coil and temperature drift of integral restoration circuit components during long-term use, so the accuracy is low and unstable.

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