Monitoring device and method for AC leakage into DC system

Abstract

The present invention discloses a monitoring device and method for AC intrusion into a DC system. The monitoring device includes: an AC signal separation and amplification module, a control module, and an output drive module. The control module is used to determine whether the AC component corresponding to the converted AC signal exceeds the limit based on a preset rectangular algorithm, and output a drive signal to the output drive module when the limit is exceeded. The rectangular algorithm includes marking the converted AC signal with a set time period as the rectangular length, marking the absolute value of the difference between the voltage amplitude of the converted AC signal at the end time point and the start time point of the set time period as the rectangular width, calculating the rectangular area corresponding to the set time period, and calculating the cumulative sum of the rectangular areas corresponding to each set time period within a cycle. The preset rectangular algorithm of the present invention can monitor both fixed-frequency AC components and variable-frequency AC components, thereby improving the accuracy of the monitoring device.

Description

Technical Field

[0001] Embodiments of the present invention relate to the technical field of DC power equipment monitoring, and in particular to a monitoring device and method for monitoring AC leakage into a DC system. Background Art

[0002] The safe and reliable operation of the secondary DC systems at each substation in a power system is crucial for its safe and reliable operation. In actual operation, due to the presence of both AC and DC power within a single cabinet, long power cables, and close proximity between AC and DC terminals, AC power can enter the DC system due to wiring errors, insulation degradation, and other factors. The "DL / T1392-2014 Technical Specifications for Insulation Monitoring Devices for DC Power Systems" stipulates that "substation DC systems must have an AC power inrush alarm function. When an AC power inrush fault of 10V RMS or greater occurs in the DC system, an AC power inrush fault alarm should be issued and the magnitude of the incoming AC voltage should be displayed."

[0003] Current monitoring devices for AC leakage into DC systems use an instantaneous value acquisition method to compare the amplitude of all cycles of the AC current in the DC system's ground voltage with a voltage threshold to determine whether the AC component in the DC system exceeds the limit.

[0004] Existing monitoring devices for AC leakage into DC systems can only monitor AC components with fixed frequencies, but cannot monitor AC components with variable frequencies. Summary of the Invention

[0005] The present invention provides a monitoring device and a monitoring method for AC leakage into a DC system, which can monitor both fixed-frequency AC components and variable-frequency AC components, thereby improving the accuracy of the monitoring device.

[0006] In a first aspect, an embodiment of the present invention provides a monitoring device for AC leakage into a DC system, comprising: an AC signal separation and amplification module, a control module, and an output driver module; the input end of the AC signal separation and amplification module is connected to the DC system, and the output end of the AC signal separation and amplification module is electrically connected to the control module; the AC signal separation and amplification module is used to separate the AC component in the DC system, and isolate, amplify, and filter the separated AC component to obtain a converted AC signal, which is output to the control module; the control module is used to determine whether the AC component corresponding to the converted AC signal exceeds a limit based on a preset rectangular algorithm, and output a drive signal to the output driver module if the limit is exceeded; wherein the rectangular algorithm includes: marking the converted AC signal with a set time period as the rectangle length, marking the absolute value of the difference between the voltage amplitude of the converted AC signal at the end time point and the start time point of the set time period as the rectangle width, calculating the rectangle area corresponding to the set time period, and calculating the cumulative sum of the rectangle areas corresponding to each set time period within a cycle; the input end of the output driver module is electrically connected to the control module, and is used to output an alarm indication signal based on the output drive signal.

[0007] Optionally, the AC signal separation and amplification module includes an AC signal separation circuit and a linear optocoupler isolation amplifier circuit; the input end of the AC signal separation circuit is connected to the DC system, the output end of the AC signal separation circuit is electrically connected to the input end of the linear isolation optocoupler amplifier circuit, and the output end of the linear isolation optocoupler amplifier circuit is electrically connected to the control module; the AC signal separation circuit is used to separate the AC component in the DC system; the linear isolation optocoupler amplifier circuit is used to isolate and amplify the AC component separated by the AC signal separation circuit and obtain a converted AC signal output after filtering.

[0008] Optionally, the AC signal separation circuit includes a first capacitor, a second capacitor, a first resistor separation unit and a second resistor separation unit; wherein, the first end of the first capacitor is connected to the positive power supply terminal of the DC system, the second end of the first capacitor is connected to the first end of the first resistor separation unit, and the second end of the first resistor separation unit serves as the first output end of the AC signal separation circuit; the first end of the second capacitor is connected to the negative power supply terminal of the DC system, the second end of the second capacitor is connected to the first end of the second resistor separation unit, and the second end of the second resistor separation unit serves as the second output end of the AC signal separation circuit; wherein, the first resistor separation unit and the second resistor separation unit each include at least one resistor connected in series between their own first end and second end.

[0009] Optionally, the linear isolated optocoupler amplifier circuit includes a current-type converter, a first operational amplifier, a linear photoelectric coupler and a second operational amplifier; wherein, the primary side of the current-type converter is respectively connected to the first output end and the second output end, the inverting input end of the first operational amplifier is electrically connected to the secondary side of the current-type converter, the non-inverting input end of the first operational amplifier is grounded through a resistor, the output end of the first operational amplifier is connected to the first input end of the linear photoelectric coupler, the second input end of the linear photoelectric coupler is grounded, the third input end of the linear photoelectric coupler is connected to the power supply voltage, the fourth input end of the linear photoelectric coupler is connected to the non-inverting input end of the first operational amplifier, the output end of the linear photoelectric coupler is electrically connected to the non-inverting input end of the second operational amplifier, the inverting input end of the second operational amplifier is electrically connected to the output end of the second operational amplifier, and the output end of the second operational amplifier is connected to the output end of the linear optocoupler amplifier circuit through a filtering circuit.

[0010] Optionally, the linear photocoupler includes a light-emitting diode, a first photosensitive diode and a second photosensitive diode, the cathode of the light-emitting diode is connected to the first input terminal of the linear photocoupler, and the anode of the light-emitting diode is connected to the second input terminal of the linear photocoupler; the cathode of the first photosensitive diode is connected to the third input terminal of the linear photocoupler, and the anode of the first photosensitive diode is connected to the fourth input terminal of the linear photocoupler; and the anode of the second photosensitive diode is connected to the output terminal of the linear photocoupler.

[0011] Optionally, the output drive module includes a switch unit, a relay and an external control unit; the control end and the first end of the switch unit are electrically connected to the control module, the second end of the switch unit is connected to the first end of the relay coil, the second end of the relay coil is connected to the power supply, and the two ends of the normally open contact of the relay are respectively connected to the external circuit control unit, and the external circuit control unit is used to control the external circuit connected to itself to operate when the normally open contact is closed; the switch unit is used to turn on or off according to the drive signal output by the control module received by its own control end.

[0012] Optionally, the output driving module further includes an optocoupler, and the control module connects the control end and the first end of the switch unit via the optocoupler.

[0013] Optionally, it also includes a power generation module, the input end of the power generation module is connected to the DC system, and the output end of the power generation module is connected to the AC signal separation and amplification module, the control module and the output drive module. The power generation module is used to process and convert the power signal input from the DC system to power the AC signal separation and amplification module, the control module and the output drive module.

[0014] Optionally, the power generation module includes a step-down circuit and a rectifier circuit, the input end of the step-down circuit is connected to the input end of the power generation module, the output end of the step-down circuit is connected to the input end of the rectifier circuit, and the output end of the rectifier circuit is connected to the output end of the power generation module. The step-down circuit is used to step down the power signal of the DC system, and the rectifier circuit is used to rectify the output signal of the step-down circuit and output it to the AC signal separation and amplification module, the control module and the output drive module.

[0015] In a second aspect, an embodiment of the present invention further provides a method for monitoring AC intrusion into a DC system, comprising: determining whether the AC component corresponding to the converted AC signal output by the AC signal separation and amplification module exceeds the limit based on a preset rectangular algorithm, and outputting a drive signal to the output drive module when the limit is exceeded; wherein the rectangular algorithm comprises labeling the converted AC signal with a set time period as the rectangle length, taking the difference between the voltage amplitude of the converted AC signal at the end time point and the start time point of the set time period as the rectangle width, calculating the rectangle area corresponding to the set time period, and calculating the cumulative sum of the rectangle areas corresponding to each set time period within one cycle.

[0016] The monitoring device for AC intrusion into a DC system according to an embodiment of the present invention includes an AC signal separation and amplification module, a control module, and an output drive module. The multiple linear isolation and safety protection of the AC separation and amplification module can avoid operational safety risks, thereby improving the safety and stability of the monitoring device for AC intrusion into a DC system. The preset rectangular algorithm in the control module can determine whether the AC component corresponding to the converted AC signal exceeds the limit, and output a drive signal to the output drive module when the limit is exceeded. The preset rectangular algorithm can monitor both fixed-frequency AC components and variable-frequency AC components, thereby improving the accuracy of the monitoring device. The output drive module can realize various forms of fault alarm outputs such as screens and signal indicator lights. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 1 is a schematic structural diagram of a monitoring device for AC leakage into a DC system provided by an embodiment of the present invention;

[0018] Figure 2 2 is a schematic structural diagram of another device for monitoring AC leakage into a DC system provided by an embodiment of the present invention;

[0019] Figure 3 2 is a schematic structural diagram of another device for monitoring AC leakage into a DC system provided by an embodiment of the present invention;

[0020] Figure 4 2 is a schematic structural diagram of another device for monitoring AC leakage into a DC system provided by an embodiment of the present invention;

[0021] Figure 5This is a flow chart of a method for monitoring AC leakage into a DC system provided by an embodiment of the present invention. DETAILED DESCRIPTION

[0022] The present invention will be further described in detail below with reference to the accompanying drawings and examples. It will be understood that the specific embodiments described herein are intended only to illustrate the present invention and are not intended to limit the present invention. It should also be noted that, for ease of description, the accompanying drawings only illustrate portions relevant to the present invention, not all structures.

[0023] Figure 1 This is a schematic diagram of the structure of a monitoring device for AC leakage into a DC system provided by an embodiment of the present invention. This embodiment is applicable to monitoring the situation where AC leakage into a DC system.

[0024] like Figure 1 As shown, the monitoring device for AC leakage into a DC system includes an AC signal separation and amplification module 10 , a control module 20 and an output drive module 30 .

[0025] The input end of the AC signal separation and amplification module 10 is connected to the DC system, and the output end of the AC signal separation and amplification module 10 is electrically connected to the control module 20. The AC signal separation and amplification module 10 is used to separate the AC component in the DC system, and isolate, amplify and filter the separated AC component to obtain a converted AC signal, which is output to the control module 20. The control module 20 is used to determine whether the AC component corresponding to the converted AC signal exceeds the limit based on a preset rectangular algorithm, and output a drive signal to the output driver module 30 when the limit is exceeded. The rectangular algorithm includes: marking the converted AC signal with a set time period as the rectangle length, marking the absolute value of the difference between the voltage amplitude of the converted AC signal at the end time point and the start time point of the set time period as the rectangle width, calculating the rectangle area corresponding to the set time period, and calculating the cumulative sum of the rectangle areas corresponding to each set time period within a cycle. The input end of the output driver module 30 is electrically connected to the control module 20, and is used to output an alarm indication signal based on the output drive signal.

[0026] Optionally, the AC signal separation and amplification module 10 may include a capacitor, an operational amplifier, and a linear optocoupler isolation chip.

[0027] Optionally, the control module 20 may include a microcontroller. Optionally, the control module 20 may include a single chip microcomputer, a digital signal processor (DSP) or a field programmable gate array (FPGA).

[0028] Optionally, the output driving module 30 may include an optocoupler isolation chip, a transistor and a current limiting resistor. After receiving the control command from the control module 20, the output driving module 30 outputs a driving signal by controlling the on and off of the transistor.

[0029] The area of ​​the rectangle represents the voltage change of the converted AC signal within the set time period. Rectangle length = set time period = T2 - T1, where T1 represents the start time and T2 represents the end time. Rectangle width = |U2 - U1|, where U2 represents the voltage amplitude at the end time and U1 represents the voltage amplitude at the start time.

[0030] The time it takes for AC power to complete one complete change (i.e., one sinusoidal waveform) is called a cycle, and the time it takes for each cycle to complete is called a period. A cycle consists of multiple set time periods. The set time period is fixed and unchanging.

[0031] The AC-to-DC system monitoring device operates as follows: the AC signal separation and amplification module 10 separates the AC component in the DC system, then isolates, amplifies, and filters the separated AC component to generate a converted AC signal, which is then output to the control module 20. The control module 20 collects the instantaneous value of the converted AC signal at set time intervals, calculates the rectangular area corresponding to the set time period, and then calculates the cumulative sum of the rectangular areas corresponding to each set time period within a cycle. The cumulative sum of all the rectangular areas within a cycle is then compared with a preset rectangular area to determine whether the AC component corresponding to the converted AC signal exceeds a limit. When the cumulative sum of the rectangular areas corresponding to each set time period within a cycle is greater than or equal to the preset rectangular area, the AC component corresponding to the converted AC signal is determined to have exceeded a limit, and the output driver module 30 then outputs an alarm indication signal. When the cumulative sum of the rectangular areas corresponding to each set time period within a cycle is less than the preset rectangular area, the AC component corresponding to the converted AC signal is determined to have not exceeded a limit, and the output driver module 30 then does not output an alarm indication signal.

[0032] The monitoring device for AC intrusion into a DC system according to an embodiment of the present invention includes an AC signal separation and amplification module, a control module, and an output drive module. The multiple linear isolation and safety protection of the AC separation and amplification module can avoid operational safety risks, thereby improving the safety and stability of the monitoring device for AC intrusion into a DC system. The preset rectangular algorithm in the control module can determine whether the AC component corresponding to the converted AC signal exceeds the limit, and output a drive signal to the output drive module when the limit is exceeded. The preset rectangular algorithm can monitor both fixed-frequency AC components and variable-frequency AC components, thereby improving the accuracy of the monitoring device. The output drive module can realize various forms of fault alarm outputs such as screens and signal indicator lights.

[0033] Figure 2 FIG. 1 is a structural diagram of another AC-to-DC system monitoring device provided by an embodiment of the present invention. This embodiment is based on the above embodiment. Figure 2 As shown, optionally, the AC signal separation and amplification module 10 includes an AC signal separation circuit 101 and a linear optocoupler isolation amplifier circuit 102 .

[0034] The input end of the AC signal separation circuit 101 is connected to the DC system, the output end of the AC signal separation circuit 101 is electrically connected to the input end of the linear isolation optocoupler amplifier circuit 102 , and the output end 102 of the linear isolation optocoupler amplifier circuit is electrically connected to the control module 20 .

[0035] The AC signal separation circuit 101 is used to separate the AC component in the DC system;

[0036] The linear isolation optocoupler amplifier circuit 102 is used to isolate, amplify, and filter the AC component separated by the AC signal separation circuit to produce a converted AC signal output. By separating high voltage from low voltage, the linear isolation optocoupler amplifier circuit 102 can improve the safety and stability of the AC-to-DC system monitoring device.

[0037] The AC signal separation circuit 101 includes a first capacitor C1, a second capacitor C2, a first resistor separation unit 103, and a second resistor separation unit 104. The first end of the first capacitor C1 is connected to the positive terminal of the DC power supply, the second end of the first capacitor C1 is connected to the first end of the first resistor separation unit 103, and the second end of the first resistor separation unit 103 serves as the first output terminal of the AC signal separation circuit 101. The first end of the second capacitor C2 is connected to the negative terminal of the DC power supply, the second end of the second capacitor C2 is connected to the first end of the second resistor separation unit 104, and the second end of the second resistor separation unit 104 serves as the second output terminal of the AC signal separation circuit 101. The first resistor separation unit 103 and the second resistor separation unit 104 each include at least one resistor connected in series between their first and second ends. Figure 2 Schematically shows a case where the first resistor separation unit 103 includes a first resistor R1 and a second resistor R2, and the second resistor separation unit 104 includes a third resistor R3 and a fourth resistor R4.

[0038] The first capacitor C1 and the second capacitor C2 are DC blocking capacitors. By utilizing the capacitance characteristics of the first capacitor C1 and the second capacitor C2 that block DC and pass AC, the DC voltage on the DC bus can be isolated.

[0039] The linear isolated optocoupler amplifier circuit 102 includes a current-source converter TA1 , a first operational amplifier U1 , a linear optocoupler U2 , and a second operational amplifier U3 .

[0040] Among them, the primary side of the current-source converter TA1 is respectively connected to the first output end and the second output end, the inverting input end IN1- of the first operational amplifier U1 is electrically connected to the secondary side of the current-source converter TA1, the non-inverting input end IN1+ of the first operational amplifier U1 is grounded to GND through a resistor R5, the output end of the first operational amplifier U1 is connected to the first input end AIN1 of the linear optocoupler U2, the second input end AIN2 of the linear optocoupler U2 is grounded to GND, the third input end AIN3 of the linear optocoupler U2 is connected to the power supply voltage VCC, the fourth input end AIN4 of the linear optocoupler U2 is connected to the non-inverting input end IN1+ of the first operational amplifier U1, the output end of the linear optocoupler U2 is electrically connected to the non-inverting input end IN2+ of the second operational amplifier U3, the inverting input end IN2- of the second operational amplifier U3 is electrically connected to the output end of the second operational amplifier U3, and the output end of the second operational amplifier U3 is connected to the output end of the linear optocoupler amplifier circuit 102 through a filter circuit 105.

[0041] The current-source converter TA1 may be a milliampere-level current-source converter, which has a high-precision electromagnetic isolation function and can block strong electrical interference on the DC bus.

[0042] Specifically, the linear isolation optocoupler amplifier circuit 102 further includes a first diode D1 , a second diode D2 , a sixth resistor R6 , a seventh resistor R7 , an eighth resistor R8 , a ninth resistor R9 , a third capacitor C3 , and a fourth capacitor C4 .

[0043] The anode of the first diode D1 is connected to the second end of the secondary side of the current-type converter TA1 and to the ground GND; the cathode of the first diode D1 is connected to the first end of the secondary side of the current-type converter TA1; the anode of the second diode D2 is connected to the first end of the secondary side of the current-type converter TA1, and the cathode of the second diode D2 is connected to the second end of the secondary side of the current-type converter TA1; the sixth resistor R6 is connected between the first end and the second end of the secondary side of the current-type converter TA1; the first end of the seventh resistor R7 is connected to the first end of the sixth resistor R6, and the second end of the seventh resistor R7 is connected to the first end of the first capacitor C1; the second end of the third capacitor C3 is connected to the second end of the secondary side of the current-type converter TA1; the first end of the eighth resistor R8 is connected to the first end of the third capacitor C3, and the second end of the eighth resistor R8 is connected to the inverting input terminal IN1- of the first operational amplifier U1; the ninth resistor R9 is connected between the output terminal of the first operational amplifier U1 and the inverting input terminal IN- of the first operational amplifier U1; the fourth capacitor C4 is connected in parallel across the ninth resistor R9.

[0044] The first diode D1 is a freewheeling diode connected in parallel across the current-source converter TA1 to prevent the third capacitor C3 from discharging the current-source converter TA1 after power failure. The second diode D2 is a rectifier diode.

[0045] The absorption circuit formed by the third capacitor C3, the sixth resistor R6 and the seventh resistor R7 connected in series behind the current-type converter TA1 is connected in parallel with the second diode D2. Its function is to suppress the influence of the reverse peak voltage (surge voltage) on the second diode D2 and prevent the second diode D2 from being damaged.

[0046] The linear optocoupler U2 includes a light-emitting diode (LED), a first photosensitive diode (PD1), and a second photosensitive diode (PD2). The cathode of the LED is connected to the first input terminal AIN1 of the linear optocoupler U2, and the anode of the LED is connected to the second input terminal AIN2 of the linear optocoupler U2. The cathode of the first photosensitive diode (D1) is connected to the third input terminal AIN3 of the linear optocoupler U2, and the anode of the first photosensitive diode (PD1) is connected to the fourth input terminal AIN4 of the linear optocoupler U2. The anode of the second photosensitive diode (PD2) is connected to the output terminal of the linear optocoupler U2. The linear optocoupler U2 eliminates direct electrical connection between the DC system and the AC signal separation and amplification module 10, preventing interference caused by electrical connection. The third input terminal AIN3 of the linear optocoupler U2 is connected to the power supply VCC.

[0047] The linear isolation optocoupler amplifier circuit 102 further includes a tenth resistor R10 , an eleventh resistor R11 , and a twelfth resistor R12 .

[0048] The tenth resistor R10 is connected between the output end of the first operational amplifier U1 and the first input end AIN1 of the linear optocoupler U2; the eleventh resistor R11 is connected between the output end of the linear optocoupler U2 and the ground end GND; the twelfth resistor R12 is connected between the output end of the linear optocoupler U2 and the non-inverting input end IN2+ of the second operational amplifier U3.

[0049] The output end of the second operational amplifier U3 is connected to the inverting input end IN2- of the second operational amplifier U3; it is used as a buffer, and its output always follows the input. Its main function is to further improve the output power of the converted AC signal, reduce the output impedance, reduce the distortion of the converted AC signal, and improve the stability of the converted AC signal.

[0050] The filter circuit 105 includes a thirteenth resistor R13, a fifth capacitor C5, and a sixth capacitor C6. A first end of the thirteenth resistor R13 is connected to a first end of the fifth capacitor C5, and a second end of the thirteenth resistor R13 is connected to a second end of the sixth capacitor C6. The fifth capacitor C5 is connected between the output terminal of the second operational amplifier U3 and the ground terminal GND. The sixth capacitor C6 is connected between the output terminal of the second operational amplifier U3 and the ground terminal.

[0051] In this embodiment, the working process of the monitoring device for AC leakage into the DC system is as follows: first, the "DC isolation and AC passing" characteristics of the first capacitor C1 and the second capacitor C2 are used to extract the AC component, and the power supply is isolated by the current-type converter TA1. The obtained signal is amplified by the first operational amplifier U1 and then transmitted to the linear optocoupler U2 for isolation again. The AC component after doubly isolation is filtered by the second operational amplifier U3 and the filter circuit 105, and finally transmitted to the control module 20 for analysis and calculation. The preset rectangular algorithm in the control module 20 can determine whether the AC component corresponding to the converted AC signal exceeds the limit, and output a drive signal to the output drive module 30 when the limit is exceeded.

[0052] Figure 3 FIG. 1 is a structural diagram of another AC-to-DC system monitoring device provided by an embodiment of the present invention. This embodiment is based on the above embodiment. Figure 3 As shown, optionally, the output driving module 30 includes a switch unit 301, a relay K1, and an external circuit control unit 302;

[0053] The control end and the first end of the switch unit 301 are electrically connected to the control module 20, the second end of the switch unit 301 is connected to the first end of the relay coil, the second end of the relay coil is connected to the power supply VCC, and the two ends of the normally open contact of the relay are respectively connected to the external circuit control unit 302. The external circuit control unit 302 is used to control the external circuit to which it is connected to to operate when the normally open contact is closed; the switch unit 301 is used to turn on or off according to the drive signal output by the control module 20 received by its own control end.

[0054] The switch unit 301 includes a transistor Q1 , a control end of the transistor Q1 connected to a control end of the switch unit 301 , a first end of the transistor Q1 connected to a first end of the switch unit 301 , and a second end of the transistor Q1 connected to a second end of the switch unit 301 .

[0055] Optionally, the external circuit control unit 302 includes but is not limited to a contactor. The external circuit can be various electrical devices. For example, the external circuit can be an indicator light.

[0056] The output driving module 30 further includes an optical coupler GG, and the control module 20 is connected to the control end and the first end of the switch unit 301 via the optical coupler GG.

[0057] The output driving module 30 further includes a fourteenth resistor R14 , a fifteenth resistor R15 , and a sixteenth resistor R16 .

[0058] Specifically, a first end of the optocoupler GG is connected to the output end of the control module 20, a second end of the optocoupler GG is grounded, a third end of the optocoupler GG is connected to the first end of a fourteenth resistor R14, and a fourth end of the optocoupler GG is connected to the first power supply VCC. A second end of the fourteenth resistor R14 is connected to the control end of the transistor Q1. A first end of a fifteenth resistor R15 is connected to the third end of the optocoupler GG, and a second end of the fifteenth resistor R15 is connected to the first end of the transistor Q1. A first end of a sixteenth resistor R16 is connected to the control end of the transistor Q1, and a second end of the sixteenth resistor R16 is connected to the first power supply VCC.

[0059] Continue to see Figure 3 The working principle of the output driver module 30 provided in the embodiment of the present invention is as follows:

[0060] When the AC component corresponding to the converted AC signal does not exceed the limit, the control module 20 outputs a low level, the transistor Q1 is turned off, and the relay K1 does not work; when the AC component corresponding to the converted AC signal exceeds the limit, that is, the cumulative sum of the rectangular areas corresponding to the set time periods within a cycle is greater than or equal to the preset rectangular area, the control module 20 outputs a high level signal, the transistor Q1 is turned on, the coil of the relay K1 is energized, the normally open contact of the relay K1 is closed, and the external circuit control unit 302 connected to the normally open contact of the relay K1 starts to work and controls the external circuit connected to it to operate. The connection between the AC signal separation and amplification module 10, the control module 20 and the output drive module 30 is the same as Figure 1 The same, no longer repeated here. Figure 3 The schematic diagram includes Figure 1 The AC signal separation and amplification module 10 is shown in FIG.

[0061] Figure 4 FIG. 1 is a structural diagram of another AC-to-DC system monitoring device provided by an embodiment of the present invention. This embodiment is based on the above embodiment. Figure 4 As shown, optionally, the monitoring device for AC entering the DC system also includes a power generation module 40, the input end of the power generation module 40 is connected to the DC system, and the output end of the power generation module 40 is connected to the AC signal separation and amplification module 10, the control module 20 and the output drive module 30. The power generation module 40 is used to process and convert the power signal input from the DC system to supply power to the AC signal separation and amplification module 10, the control module 20 and the output drive module 30.

[0062] The power generation module 40 includes a step-down circuit 401 and a rectifier circuit 402. The input end of the step-down circuit 401 is connected to the input end of the power generation module 40, the output end of the step-down circuit 401 is connected to the input end of the rectifier circuit 402, and the output end of the rectifier circuit 402 is connected to the output end of the power generation module 40. The step-down circuit 401 is used to step down the power signal of the DC system, and the rectifier circuit 402 is used to rectify the output signal of the step-down circuit 401 and output it to the AC signal separation and amplification module 10, the control module 20 and the output drive module 30. Figure 4 The schematic diagram includes Figure 1 The monitoring device for AC leakage into DC system.

[0063] The power generation module 40 further includes an input protection circuit 403 and an output protection circuit 404. The input end of the input protection circuit 403 is connected to the input end of the power generation module 40, and the output end of the input protection circuit 403 is connected to the input end of the step-down circuit 401; the input end of the output protection circuit 404 is connected to the output end of the rectifier circuit 402; and the output end of the output protection circuit 404 is connected to the output end of the power generation module 40.

[0064] The input protection circuit 403 is used to implement the over-temperature protection function of the power supply; the output protection circuit 404 is used to implement the overload protection function of the power supply.

[0065] Figure 4 This is a flow chart of a method for monitoring an AC-DC system provided by an embodiment of the present invention. This method can be performed by the monitoring device for an AC-DC system provided by any of the above embodiments. Figure 4 As shown, the monitoring method for AC leakage into DC system includes:

[0066] S401 , separating the AC component in the DC system through an AC signal separation and amplification module.

[0067] The AC signal separation and amplification module includes an AC signal separation circuit and a linear optocoupler isolation amplifier circuit. The AC signal separation circuit is used to separate the AC component in the DC system; the linear isolation optocoupler amplifier circuit is used to isolate, amplify, and filter the AC component separated by the AC signal separation circuit to obtain a converted AC signal output.

[0068] S402 : Determine whether the AC component corresponding to the converted AC signal output by the AC signal separation and amplification module exceeds a limit according to a preset rectangular algorithm, and output a driving signal to the output driving module when the limit is exceeded.

[0069] Among them, the rectangle algorithm includes marking the converted AC signal with a set time period as the rectangle length, taking the difference between the voltage amplitude of the converted AC signal at the end time point and the start time point of the set time period as the rectangle width, calculating the rectangle area corresponding to the set time period, and calculating the cumulative sum of the rectangle areas corresponding to each set time period within one cycle.

[0070] The monitoring device for AC intrusion into a DC system according to an embodiment of the present invention includes an AC signal separation and amplification module, a control module, and an output drive module. The multiple linear isolation and safety protection of the AC separation and amplification module can avoid operational safety risks, thereby improving the safety and stability of the monitoring device for AC intrusion into a DC system. The preset rectangular algorithm in the control module can determine whether the AC component corresponding to the converted AC signal exceeds the limit, and output a drive signal to the output drive module when the limit is exceeded. The preset rectangular algorithm can monitor both fixed-frequency AC components and variable-frequency AC components, thereby improving the accuracy of the monitoring device. The output drive module can realize various forms of fault alarm outputs such as screens and signal indicator lights.

[0071] Note that the above are only preferred embodiments of the present invention and the technical principles employed. Those skilled in the art will understand that the present invention is not limited to the specific embodiments described herein, and that various obvious changes, readjustments, and substitutions can be made by those skilled in the art without departing from the scope of protection of the present invention. Therefore, although the present invention has been described in detail through the above embodiments, the present invention is not limited to the above embodiments and may include many other equivalent embodiments without departing from the concept of the present invention. The scope of the present invention is determined by the scope of the appended claims.

Claims

1. A monitoring device for AC leakage into a DC system, characterized in that: include: AC signal separation and amplification module, control module and output drive module; The input end of the AC signal separation and amplification module is connected to the DC system, and the output end of the AC signal separation and amplification module is electrically connected to the control module; the AC signal separation and amplification module is used to separate the AC component in the DC system, and isolate, amplify and filter the separated AC component to obtain a converted AC signal and output it to the control module; The control module is configured to determine whether the AC component corresponding to the converted AC signal exceeds a limit based on a preset rectangular algorithm, and output a drive signal to the output drive module when the limit is exceeded; wherein the rectangular algorithm includes standardizing the converted AC signal with a set time period as a rectangular length, taking the difference between the voltage amplitudes of the converted AC signal at the end time point and the start time point of the set time period as the rectangular width, calculating the rectangular area corresponding to the set time period, and calculating the cumulative sum of the rectangular areas corresponding to each of the set time periods within a cycle; The input end of the output driving module is electrically connected to the control module, and is used to output an alarm indication signal according to the output driving signal.

2. The monitoring device for AC leakage into DC system according to claim 1, characterized in that: The AC signal separation and amplification module includes an AC signal separation circuit and a linear isolation optocoupler amplifier circuit; The input end of the AC signal separation circuit is connected to the DC system, the output end of the AC signal separation circuit is electrically connected to the input end of the linear isolation optocoupler amplifier circuit, and the output end of the linear isolation optocoupler amplifier circuit is electrically connected to the control module; The AC signal separation circuit is used to separate the AC component in the DC system; The linear isolation optocoupler amplifier circuit is used to isolate, amplify and filter the AC component separated by the AC signal separation circuit to obtain the converted AC signal output.

3. The monitoring device for AC leakage into DC system according to claim 2, characterized in that: The AC signal separation circuit includes a first capacitor, a second capacitor, a first resistor separation unit and a second resistor separation unit; Wherein, the first end of the first capacitor is connected to the positive terminal of the power supply of the DC system, the second end of the first capacitor is connected to the first end of the first resistor separation unit, and the second end of the first resistor separation unit serves as the first output end of the AC signal separation circuit; A first end of the second capacitor is connected to the negative terminal of the power supply of the DC system, a second end of the second capacitor is connected to the first end of the second resistor separation unit, and a second end of the second resistor separation unit serves as the second output end of the AC signal separation circuit; Wherein, the first resistor separation unit and the second resistor separation unit each include at least one resistor connected in series between the first end and the second end thereof.

4. The monitoring device for AC leakage into DC system according to claim 3, characterized in that: The linear isolation optocoupler amplifier circuit includes a current-mode converter, a first operational amplifier, a linear photoelectric coupler, and a second operational amplifier; In which, the primary side of the current-type converter is respectively connected to the first output end and the second output end, the inverting input end of the first operational amplifier is electrically connected to the secondary side of the current-type converter, the non-inverting input end of the first operational amplifier is grounded through a resistor, the output end of the first operational amplifier is connected to the first input end of the linear optocoupler, the second input end of the linear optocoupler is grounded, the third input end of the linear optocoupler is connected to the power supply voltage, the fourth input end of the linear optocoupler is connected to the non-inverting input end of the first operational amplifier, the output end of the linear optocoupler is electrically connected to the non-inverting input end of the second operational amplifier, the inverting input end of the second operational amplifier is electrically connected to the output end of the second operational amplifier, and the output end of the second operational amplifier is connected to the output end of the linear optocoupler amplifier circuit through a filter circuit.

5. The monitoring device for AC leakage into DC system according to claim 4, characterized in that: The linear photoelectric coupler includes a light-emitting diode, a first photosensitive diode, and a second photosensitive diode, wherein the cathode of the light-emitting diode is connected to the first input terminal of the linear photoelectric coupler, and the anode of the light-emitting diode is connected to the second input terminal of the linear photoelectric coupler; the cathode of the first photosensitive diode is connected to the third input terminal of the linear photoelectric coupler, and the anode of the first photosensitive diode is connected to the fourth input terminal of the linear photoelectric coupler; An anode of the second photosensitive diode is connected to an output end of the linear photocoupler.

6. The monitoring device for AC leakage into DC system according to claim 1, characterized in that: The output drive module includes a switch unit, a relay, and an external circuit control unit; The control end and the first end of the switch unit are electrically connected to the control module, the second end of the switch unit is connected to the first end of the relay coil, the second end of the relay coil is connected to a power supply, and the two ends of the normally open contact of the relay are respectively connected to the external circuit control unit, and the external circuit control unit is used to control the external circuit connected to it to operate when the normally open contact is closed; The switch unit is used to be turned on or off according to the driving signal output by the control module received by its own control terminal.

7. The monitoring device for AC leakage into DC system according to claim 6, characterized in that: The output driving module further includes an optical coupler, and the control module is connected to the control end and the first end of the switch unit via the optical coupler.

8. The monitoring device for AC leakage into DC system according to claim 1, characterized in that: It also includes a power generation module, the input end of the power generation module is connected to the DC system, the output end of the power generation module is connected to the AC signal separation and amplification module, the control module and the output drive module, and the power generation module is used to process and convert the power signal input from the DC system to supply power to the AC signal separation and amplification module, the control module and the output drive module.

9. The monitoring device for AC leakage into DC system according to claim 8, characterized in that: The power generation module includes a step-down circuit and a rectifier circuit. The input end of the step-down circuit is connected to the input end of the power generation module, the output end of the step-down circuit is connected to the input end of the rectifier circuit, and the output end of the rectifier circuit is connected to the output end of the power generation module. The step-down circuit is used to step down the power signal of the DC system, and the rectifier circuit is used to rectify the output signal of the step-down circuit and output it to the AC signal separation and amplification module, the control module and the output drive module.

10. A method for monitoring AC leakage into a DC system, characterized in that: The monitoring device for AC leakage into a DC system according to any one of claims 1 to 9, wherein the monitoring method comprises: According to a preset rectangular algorithm, it is determined whether the AC component corresponding to the converted AC signal output by the AC signal separation and amplification module exceeds the limit, and a drive signal is output to the output drive module when the limit is exceeded; wherein, the rectangular algorithm includes labeling the converted AC signal with a set time period as the rectangle length, taking the difference between the voltage amplitude of the converted AC signal at the end time point and the start time point of the set time period as the rectangle width, calculating the rectangle area corresponding to the set time period, and calculating the cumulative sum of the rectangle areas corresponding to each of the set time periods within one cycle.

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