CN-224231941-U - Relative ground fault detection circuit based on precision rectification and active filtering

CN224231941UCN 224231941 UCN224231941 UCN 224231941UCN-224231941-U

Abstract

The utility model provides a relative ground fault detection circuit based on precise rectification and active filtering, which comprises a differential voltage sampling circuit, a precise rectification circuit, an active low-pass filtering circuit, a voltage bias circuit, an AD sampling module and a processor which are sequentially connected, wherein the precise rectification circuit is used for rectifying a sinusoidal alternating-current small voltage signal into a direct-current voltage signal, and the active low-pass filtering circuit is used for filtering the direct-current voltage signal into a low-ripple direct-current signal. The circuit carries out relative ground fault detection through a plurality of sub-circuits such as precise rectification, active filtering and the like, reduces the volume of a detection circuit, reduces the fault detection cost and improves the detection efficiency.

Inventors

Zhang Huaida
ZHANG XINTAO

Assignees

西安奇点能源股份有限公司

Dates

Publication Date: 20260512
Application Date: 20250117

Claims (6)

1. A relative ground fault detection circuit based on precision rectification and active filtering is characterized by comprising a differential voltage sampling circuit, a precision rectification circuit, an active low-pass filtering circuit, a voltage bias circuit, an AD sampling module and a processor, The input end of the differential voltage sampling circuit is connected with the single-phase ground voltage of the power grid, and the differential voltage sampling circuit is used for reducing the amplitude of the acquired sinusoidal alternating-current voltage signal so as to obtain a sinusoidal alternating-current small-voltage signal; the input end of the precise rectification circuit is connected with the output end of the differential voltage sampling circuit, and the precise rectification circuit is used for rectifying the sinusoidal alternating-current small voltage signal into a direct-current voltage signal; The input end of the active low-pass filter circuit is connected with the output end of the precise rectification circuit, and the active low-pass filter circuit is used for filtering the direct-current voltage signal into a low-ripple direct-current signal; the input end of the voltage bias circuit is connected with the output end of the active low-pass filter circuit, and the voltage bias circuit is used for biasing the voltage of the low-ripple direct current signal into a voltage range applicable to the AD sampling module; The input end of the AD sampling module is connected with the output end of the voltage bias circuit, and the AD sampling module is used for sampling the biased voltage signal and converting the sampled voltage into a digital signal; The input end of the processor is connected with the output end of the AD sampling module, and the processor is used for comparing the digital signal with a fault threshold preset in the processor to judge whether the relative ground short circuit fault condition is met.
2. The circuit of claim 1, wherein the differential voltage sampling circuit comprises first through fourth resistors, a first feedback capacitor, a second feedback capacitor, and a first operational amplifier, wherein, The input ends of the first resistor and the second resistor are connected with the single-phase voltage to ground of the power grid, the output end of the first resistor is connected with the negative input end of the first operational amplifier, and the output end of the second resistor is connected with the positive input end of the first operational amplifier; The first feedback capacitor and the fourth resistor are connected in parallel between the negative input end and the output end of the first operational amplifier; The input ends of the third resistor and the second feedback capacitor are connected with the output end of the second resistor, and the output ends of the third resistor and the second feedback capacitor are grounded; The resistance values of the first resistor and the second resistor are equal, and the resistance value of the third resistor and the fourth resistor are equal.
3. The circuit of claim 2, wherein the precision rectifying circuit comprises a fifth resistor through a ninth resistor, a second operational amplifier, a third operational amplifier, a first rectifying diode, a second rectifying diode, and a third feedback capacitor, wherein, The input ends of the fifth resistor and the eighth resistor are connected with the output end of the first operational amplifier, the output end of the fifth resistor is connected with the negative input end of the second operational amplifier, and the positive input end of the second operational amplifier is grounded; The input end of the sixth resistor is connected with the output end of the fifth resistor, and the output end of the ninth resistor is connected with the output end of the third operational amplifier; The first rectifying diode is connected with the second rectifying diode in series, the connection point of the sixth resistor and the seventh resistor is connected with the positive electrode of the first rectifying diode, the negative electrode of the second rectifying diode is connected with the output end of the fifth resistor, and the connection point of the first rectifying diode and the second rectifying diode is connected with the output end of the second operational amplifier; The output end of the eighth resistor is connected with the input end of the third feedback capacitor, the third feedback capacitor and the ninth resistor are connected in parallel between the negative input end and the output end of the third operational amplifier, and the positive input end of the third operational amplifier is grounded; The resistance values of the fifth resistor, the sixth resistor and the eighth resistor are equal and are equal to twice the resistance value of the seventh resistor; the second operational amplifier and the third operational amplifier are used for compensating the voltage drop of each rectifier diode in the full-wave rectification process.
4. The circuit of claim 3, wherein the active low pass filter circuit comprises a tenth resistor, a first filter capacitor, and a fourth operational amplifier, wherein, The input end of the tenth resistor is connected with the output end of the third operational amplifier, and the output end of the tenth resistor is respectively connected with the input end of the first filter capacitor and the positive electrode input end of the fourth operational amplifier; The output end of the first filter capacitor is grounded, and the negative input end of the fourth operational amplifier is connected with the output end of the fourth operational amplifier, so that the input impedance of the fourth operational amplifier is infinite.
5. The circuit of claim 4, wherein the voltage bias circuit comprises an eleventh resistor, a twelfth resistor, a positive supply voltage, and a fifth operational amplifier, wherein, The input end of the eleventh resistor is connected with the output end of the fourth operational amplifier, and the output end of the eleventh resistor is respectively connected with the input end of the twelfth resistor and the positive electrode input end of the fifth operational amplifier; The output end of the twelfth resistor is connected with the positive power supply voltage, and the negative input end of the fifth operational amplifier is connected with the output end of the fifth operational amplifier; The output end of the fifth operational amplifier is also connected with the AD sampling module.
6. The circuit of claim 5, wherein the relative ground fault detection circuit operates on the collected input voltage value by: Wherein U in is an input voltage value, U o is an output voltage value of the circuit, R 1 is a first resistor in the differential voltage sampling circuit, R 4 is a fourth resistor in the differential voltage sampling circuit, R 8 is an eighth resistor in the precision rectifying circuit, R 9 is a ninth resistor in the precision rectifying circuit, R 11 is an eleventh resistor in the voltage biasing circuit, R 12 is a twelfth resistor in the voltage biasing circuit, and V CC is a positive power supply voltage in the voltage biasing circuit.

Description

Relative ground fault detection circuit based on precision rectification and active filtering Technical Field The utility model relates to the technical field of power electronic equipment, in particular to a relative ground fault detection circuit based on precise rectification and active filtering. Background With the development of new energy technology, energy storage devices have become important devices in the power field to keep smooth operation. Because the power system faces complex and changeable application environments, the energy storage device is required to have certain stability, rapid fault protection capability and real-time monitoring technology. The energy storage device is used as a bridge for connecting the power grid and the battery, bears the responsibility of power conversion, and can be seriously influenced if the AC side of the power grid has a relative ground short circuit fault. In the system with the grounded neutral point at the grid side, as shown in fig. 1, if a short circuit fault occurs, the energy storage equipment is stopped due to light weight, and equipment damage and system oscillation are caused due to heavy weight, so that a large amount of economic loss is caused. In a system in which the neutral point on the power grid side is not grounded, if a relative ground short circuit fault, namely a ground fault occurs, the non-grounded relative ground voltage can obviously rise to a line voltage, which threatens the insulation capability of equipment on the power grid side. Therefore, the energy storage device is required to have the functions of monitoring and diagnosing the voltage of the power grid side in real time, and the phase-to-ground short circuit fault can be detected rapidly, so that the fault phase can be removed rapidly, and further expansion of influence is avoided. In the related art, for the detection of a grid-side relative ground fault in an energy storage device, a mode of combining a transformer and a traditional voltage sampling circuit is generally adopted, and an analog signal is output to a control system of the device to make a decision according to the monitored grid-side voltage. However, the cost of the equipment such as the transformer adopted in the detection mode is high, the volume is large, the detection system structure is complex, the control program can output the execution instruction after calculating and comparing the analog quantity, and the fault response is slow. Disclosure of utility model The present utility model aims to solve at least one of the technical problems in the related art to some extent. Therefore, the utility model aims to provide a relative ground fault detection circuit based on precise rectification and active filtering, which performs relative ground fault detection through a plurality of sub-circuits such as precise rectification and active filtering, reduces the size of the detection circuit, reduces the fault detection cost and improves the efficiency and accuracy of relative ground fault detection. In order to achieve the aim, the utility model provides a relative ground fault detection circuit based on precise rectification and active filtering, which comprises a differential voltage sampling circuit, a precise rectification circuit, an active low-pass filter circuit, a voltage bias circuit, an AD sampling module and a processor, wherein, The input end of the differential voltage sampling circuit is connected with the single-phase ground voltage of the power grid, and the differential voltage sampling circuit is used for reducing the amplitude of the acquired sinusoidal alternating-current voltage signal so as to obtain a sinusoidal alternating-current small-voltage signal; the input end of the precise rectification circuit is connected with the output end of the differential voltage sampling circuit, and the precise rectification circuit is used for rectifying the sinusoidal alternating-current small voltage signal into a direct-current voltage signal; The input end of the active low-pass filter circuit is connected with the output end of the precise rectification circuit, and the active low-pass filter circuit is used for filtering the direct-current voltage signal into a low-ripple direct-current signal; the input end of the voltage bias circuit is connected with the output end of the active low-pass filter circuit, and the voltage bias circuit is used for biasing the voltage of the low-ripple direct current signal into a voltage range applicable to the AD sampling module; The input end of the AD sampling module is connected with the output end of the voltage bias circuit, and the AD sampling module is used for sampling the biased voltage signal and converting the sampled voltage into a digital signal; The input end of the processor is connected with the output end of the AD sampling module, and the processor is used for comparing the digital signal with a fault threshold preset in the processor to jud