Reactive current measurement circuit

Abstract

The invention relates to a reactive current measurement circuit. The conduction and cut-off of an optical coupler LED1 and an optical coupler LED2 are controlled through voltage signals of a line voltage UBC, and line current IA signals are acquired in a specific conduction interval of the optical couplers, so that an average value, i.e. a reactive current signal, of the line current IA signals inthe conduction interval is obtained. The beneficial effects of the reactive current measurement circuit are that 1, the voltage signals of the line voltage UBC and the line current IA signals are enabled to have no electrical contact due to adoption of the optical coupler devices, so that the mutual interference therebetween is avoided, and the measurement errors of reactive current are reduced;2, the circuit structure is simple, debugging is easy to be performed, and the production cost is low; and 3, an accumulative error is avoided during the formation process of the reactive current because the circuit structure is simple, so that the measurement accuracy of the reactive current is high.

Description

technical field [0001] The invention relates to a reactive current measuring circuit, which is used for measuring the reactive current of a three-phase AC circuit. Background technique [0002] The line current in a three-phase AC circuit, such as the line current IA, contains active current and reactive current. Active current is formed by resistive loads, and reactive current is generally formed by inductive loads; the mathematical expression of active current is IACosφ, and reactive current The mathematical expression of IASinφ is IASinφ, where φ is the phase difference between the line current IA and the active current; the existence of reactive current not only affects the output rate of the power plant but also increases the line loss of the circuit line, so it is necessary to conduct reactive current Compensation (also known as reactive power compensation) to reduce the loss of electric energy; there are usually two reactive power compensation methods, one method is t...

AI Technical Summary

Problems solved by technology

[0002] The line current in a three-phase AC circuit, such as the line current IA, contains active current and reactive current. Active current is formed by resistive loads, and reactive current is generally formed by inductive loads; the mathematical expression of active current is IACosφ, and reactive current The mathematical expression of IASinφ is IASinφ, where φ is the phase difference between the line current IA and the active current; the existence of reactive current not only affects the output rate of the power plant but also increases the line loss of the circuit line, so it is necessary to conduct reactive current Compensation (also known as reactive power compensation) to reduce the loss of electric energy; there are usually two reactive power compensation methods, one method is to detect the power factor cosφ of the three-phase AC circuit or the relationship between the line current and the corresponding active current The phase difference φ, according to the power factor cosφ or phase difference φ, automatically switches the capacitive load power capacitor in the three-phase AC circuit, so that the power factor cosφ is close to 1 or the phase difference φ is close to 0; according to the power factor cosφ or phase The size of the difference φ has a defect in switching power capacitors. When the current in the three-phase AC circuit is small, overcompensation is prone to occur, that is, the current of a single power capacitor is greater than the inductive current. At this time, the phenomenon of repeated switching and cutting of power capacitors will occur, affecting Service life of power capacitors

Another method is to calculate the reactive current according to the phase difference φ and the line current, and switch on and off the power capacitor according to the size of the reactive current, so as to avoid the phenomenon of repeated switching and cutting of the power capacitor; but according to this method, the design The structure of the reactive current measurement circuit is relatively complicated, and the accumulated error is relatively large