Phase-to-ground fault detection circuit based on precise rectification and active filtering

Abstract

The utility model provides a phase-to-ground fault detection circuit based on precision rectification and active filtering. The circuit comprises 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 which are connected in sequence. Wherein the precise rectifying circuit is used for rectifying a sine alternating-current small voltage signal into a direct-current voltage signal; the active low-pass filter circuit is used for filtering the direct-current voltage signal into a low-ripple direct-current signal. According to the circuit, relative fault detection is carried out through a plurality of sub-circuits such as precise rectification and active filtering, the size of the detection circuit is reduced, the fault detection cost is reduced, and the detection efficiency is improved.

Description

Technical Field

[0001] This utility model relates to the field of power electronic equipment technology, and in particular to a ground fault detection circuit based on precision rectification and active filtering. Background Technology

[0002] With the development of new energy technologies, energy storage devices have become crucial for maintaining stable operation in the power sector. Because power systems face complex and ever-changing application environments, energy storage devices must possess a certain level of stability, rapid fault protection capabilities, and real-time monitoring technology. As a bridge connecting the power grid and batteries, energy storage devices bear the responsibility of power conversion; a short-circuit fault to ground on the AC side of the power grid can severely impact these devices.

[0003] Among them, such as Figure 1 As shown, in a grid-side neutral-grounded system, a phase-to-ground short-circuit fault can cause anything from energy storage equipment shutdown to equipment damage and system oscillations, resulting in significant economic losses. Conversely, in a grid-side ungrounded neutral-grounded system, a phase-to-ground short-circuit fault (i.e., a ground fault) will cause the ungrounded phase-to-ground voltage to rise significantly to the line voltage, threatening the insulation capability of grid-side equipment. Therefore, energy storage equipment must possess real-time grid-side voltage monitoring and diagnostic capabilities to quickly detect phase-to-ground short-circuit faults and rapidly disconnect the faulty phase to prevent further escalation of the impact.

[0004] In related technologies, the detection of grid-side ground faults in energy storage devices typically employs a combination of transformers and traditional voltage sampling circuits. The system outputs an analog signal based on the monitored grid-side voltage to the device's control system for decision-making. However, this detection method involves costly and bulky equipment such as transformers, resulting in a complex detection system structure. Furthermore, the control program requires calculation and comparison of analog quantities before outputting execution commands, leading to a slow fault response. Utility Model Content

[0005] This utility model aims to at least partially solve one of the technical problems in the related art.

[0006] Therefore, the purpose of this utility model is to propose a relative ground fault detection circuit based on precision rectification and active filtering. This circuit performs relative ground fault detection through multiple sub-circuits such as precision rectification and active filtering, which reduces the size of the detection circuit, lowers the fault detection cost, and improves the efficiency and accuracy of relative ground fault detection.

[0007] To achieve the above objectives, this utility model proposes a ground fault detection circuit based on precision rectification and active filtering. The circuit includes: a differential voltage sampling circuit, a precision rectification circuit, an active low-pass filter circuit, a voltage bias circuit, an AD sampling module, and a processor; wherein,

[0008] The input terminal of the differential voltage sampling circuit is connected to the single-phase ground voltage of the power grid. The differential voltage sampling circuit is used to reduce the amplitude of the acquired sinusoidal AC voltage signal in order to obtain a small sinusoidal AC voltage signal.

[0009] The input terminal of the precision rectifier circuit is connected to the output terminal of the differential voltage sampling circuit. The precision rectifier circuit is used to rectify the sinusoidal AC small voltage signal into a DC voltage signal.

[0010] The input terminal of the active low-pass filter circuit is connected to the output terminal of the precision rectifier circuit. The active low-pass filter circuit is used to filter the DC voltage signal into a low-ripple DC signal.

[0011] The input terminal of the voltage bias circuit is connected to the output terminal of the active low-pass filter circuit. The voltage bias circuit is used to bias the voltage of the low-ripple DC signal to the voltage range applicable to the AD sampling module.

[0012] The input terminal of the AD sampling module is connected to the output terminal of the voltage bias circuit. The AD sampling module is used to sample the biased voltage signal and convert the sampled voltage into a digital signal.

[0013] The processor's input terminal is connected to the output terminal of the AD sampling module. The processor is used to compare the digital signal with its internally preset fault threshold to determine whether the relative short-circuit fault condition is met.

[0014] Optionally, in one embodiment of this utility model, the differential voltage sampling circuit includes: a first resistor to a fourth resistor, a first feedback capacitor, a second feedback capacitor, and a first operational amplifier; wherein, the input terminals of the first resistor and the second resistor are connected to the single-phase-to-ground voltage of the power grid, the output terminal of the first resistor is connected to the negative input terminal of the first operational amplifier, and the output terminal of the second resistor is connected to the positive input terminal of the first operational amplifier; the first feedback capacitor and the fourth resistor are connected in parallel between the negative input terminal and the output terminal of the first operational amplifier; the input terminals of the third resistor and the second feedback capacitor are connected to the output terminal of the second resistor, and the output terminals 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 values ​​of the third resistor and the fourth resistor are equal.

[0015] Optionally, in one embodiment of this utility model, the precision rectifier circuit includes: a fifth to a ninth resistor, a second operational amplifier, a third operational amplifier, a first rectifier diode, a second rectifier diode, and a third feedback capacitor; wherein the input terminals of the fifth and eighth resistors are connected to the output terminal of the first operational amplifier, the output terminal of the fifth resistor is connected to the negative input terminal of the second operational amplifier, and the positive input terminal of the second operational amplifier is grounded; the sixth, seventh, and ninth resistors are connected in series, the input terminal of the sixth resistor is connected to the output terminal of the fifth resistor, and the output terminal of the ninth resistor is connected to the output terminal of the third operational amplifier; the first rectifier diode and the second rectifier diode are connected in series, and the third feedback capacitor... The connection point of the sixth resistor and the seventh resistor is connected to the positive terminal of the first rectifier diode; the negative terminal of the second rectifier diode is connected to the output terminal of the fifth resistor; the connection point of the first rectifier diode and the second rectifier diode is connected to the output terminal of the second operational amplifier; the output terminal of the eighth resistor is connected to the input terminal of the third feedback capacitor; the third feedback capacitor and the ninth resistor are connected in parallel between the negative input terminal and the output terminal of the third operational amplifier; the positive input terminal of the third operational amplifier is grounded; the resistance values ​​of the fifth, sixth, and eighth resistors are equal and twice the resistance value of the seventh resistor; the second and third operational amplifiers are used to compensate for the voltage drop of each rectifier diode during the full-wave rectification process.

[0016] Optionally, in one embodiment of this utility model, the active low-pass filter circuit includes: a tenth resistor, a first filter capacitor, and a fourth operational amplifier; wherein, the input terminal of the tenth resistor is connected to the output terminal of the third operational amplifier, and the output terminal of the tenth resistor is connected to the input terminal of the first filter capacitor and the positive input terminal of the fourth operational amplifier respectively; the output terminal of the first filter capacitor is grounded, and the negative input terminal of the fourth operational amplifier is connected to the output terminal of the fourth operational amplifier, so that the input impedance of the fourth operational amplifier is infinite.

[0017] Optionally, in one embodiment of this utility model, the voltage bias circuit includes: an eleventh resistor, a twelfth resistor, a positive power supply voltage, and a fifth operational amplifier; wherein, the input terminal of the eleventh resistor is connected to the output terminal of the fourth operational amplifier, and the output terminal of the eleventh resistor is connected to both the input terminal of the twelfth resistor and the positive input terminal of the fifth operational amplifier; the output terminal of the twelfth resistor is connected to the positive power supply voltage, and the negative input terminal of the fifth operational amplifier is connected to its output terminal; the output terminal of the fifth operational amplifier is also connected to the AD sampling module.

[0018] Optionally, in one embodiment of this utility model, the relative ground fault detection circuit calculates the acquired input voltage value using the following formula:

[0019]

[0020] Among them, U in It is the input voltage value, U o R1 is the output voltage value of the circuit, R4 is the first resistor in the differential voltage sampling circuit, R8 is the eighth resistor in the precision rectifier circuit, and R9 is the ninth resistor in the precision rectifier circuit. 11 It is the eleventh resistor in the voltage bias circuit, R 12 It is the twelfth resistor in the voltage bias circuit, V CC It is the positive power supply voltage in the voltage biasing circuit.

[0021] The technical solution provided by the embodiments of this utility model brings at least the following beneficial effects: This utility model constructs a novel phase-to-ground fault detection circuit through four sub-circuits: a differential voltage sampling circuit, a precision rectification circuit, an active low-pass filter circuit, and a voltage bias circuit. This utility model avoids the use of large equipment such as transformers, thereby reducing the size of the detection circuit, lowering its hardware cost, and improving its practicality and manufacturability, making it suitable for energy storage devices in different working scenarios. Furthermore, the detection process of this utility model does not require complex logic operations, and the fault judgment procedure is relatively simple. The speed of phase-to-ground fault detection is improved through digital comparison, thereby increasing the overall speed from the start of voltage data sampling to the execution of protection actions. This allows for faster protection of the equipment when a fault occurs, improving the efficiency of phase-to-ground fault detection. By setting up an operational amplifier, this utility model can compensate for the diode voltage drop in traditional full-wave rectification schemes, resulting in higher rectification accuracy. Moreover, by setting up an active filter circuit, it can effectively avoid the problem of decreased filtering capability of passive RC filter circuits under load, thereby improving the accuracy of phase-to-ground fault detection. Therefore, this invention can accurately, efficiently and cost-effectively detect phase-to-ground faults on the AC side of the power grid, which is beneficial to ensuring the safe and stable operation of energy storage equipment.

[0022] Additional aspects and advantages of this invention will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. Attached Figure Description

[0023] The above and / or additional aspects and advantages of this utility model will become apparent and readily understood from the following description of the embodiments taken in conjunction with the accompanying drawings, in which:

[0024] Figure 1This is a schematic diagram illustrating the impact of a relative short-circuit fault on an energy storage device.

[0025] Figure 2 This is a flowchart illustrating a method for detecting a relative short-circuit fault in a related embodiment;

[0026] Figure 3 A schematic diagram of a ground fault detection circuit based on precision rectification and active filtering, as proposed in an embodiment of this utility model;

[0027] Figure 4 This is a schematic diagram of the various sub-circuits included in a relative ground fault detection circuit proposed in an embodiment of the present invention;

[0028] Figure 5 A structural diagram of a specific ground fault detection circuit based on precision rectification and active filtering proposed in an embodiment of this utility model;

[0029] Figure 6 A flowchart illustrating a ground fault detection method based on precision rectification and active filtering, as proposed in an embodiment of this utility model;

[0030] Figure 7 This is a flowchart illustrating a specific ground fault detection method based on precision rectification and active filtering, as proposed in an embodiment of this utility model. Detailed Implementation

[0031] The embodiments of this utility model are described in detail below. Examples of these embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary and intended to explain this utility model, and should not be construed as limiting this utility model.

[0032] It should be noted that, in the relevant embodiments, when performing phase-to-ground fault detection on the AC side of the power grid, the following methods are typically used: Figure 2 The detection method shown first converts the high voltage of the power grid into a low voltage using a transformer, and then outputs it to a conventional voltage sampling circuit. The conventional voltage sampling circuit then outputs an analog signal suitable for the control system's calculations based on the low voltage. The control system then compares and calculates the obtained analog signal to determine whether a relative ground fault has occurred.

[0033] However, the transformers and other equipment used in this detection method are costly and bulky, and have a slow fault response and low detection efficiency. Therefore, this invention proposes a ground fault detection circuit and method based on precision rectification and active filtering, which reduces the size of the detection circuit, lowers the fault detection cost, and improves the efficiency and accuracy of ground fault detection.

[0034] The following describes in detail, with reference to the accompanying drawings, a ground fault detection circuit and method based on precision rectification and active filtering proposed in the embodiments of this utility model.

[0035] Figure 3 This is a schematic diagram of a ground fault detection circuit based on precision rectification and active filtering, as proposed in an embodiment of this utility model. Figure 3 As shown, the fault detection circuit includes: a differential voltage sampling circuit 10, a precision rectifier circuit 20, an active low-pass filter circuit 30, a voltage bias circuit 40, an AD sampling module 50, and a processor 60. The connection method of each sub-circuit in this fault detection circuit is as follows: Figure 1 As shown.

[0036] The input terminal of the differential voltage sampling circuit 10 is connected to the single-phase ground voltage of the power grid. The differential voltage sampling circuit 10 is used to reduce the amplitude of the acquired sinusoidal AC voltage signal in order to obtain a small sinusoidal AC voltage signal.

[0037] Specifically, according to the front-end design of the differential voltage sampling circuit 10, the phase-to-ground voltage of a certain phase in the power grid acquired by the sampling circuit can be regarded as a sinusoidal AC signal. The differential voltage sampling circuit 10 of this invention can reduce the amplitude of the acquired sinusoidal AC voltage signal, that is, convert the voltage signal with a large amplitude into a small voltage signal.

[0038] The input terminal of the precision rectifier circuit 20 is connected to the output terminal of the differential voltage sampling circuit 10. The precision rectifier circuit is used to rectify a small sinusoidal AC voltage signal into a DC voltage signal.

[0039] Specifically, the precision rectifier circuit 20 can rectify a small sinusoidal AC voltage signal into a DC signal with larger ripple. The precision rectifier circuit 20 of this invention can reduce the deviation in the rectification process.

[0040] The input terminal of the active low-pass filter circuit 30 is connected to the output terminal of the precision rectifier circuit 20. The active low-pass filter circuit 30 is used to filter the DC voltage signal into a low-ripple DC signal.

[0041] Specifically, the active low-pass filter circuit 30 can filter a DC signal with large ripple into a DC signal with very small ripple (i.e., a low-ripple DC signal). Compared with passive filter circuits in related technologies, the active low-pass filter circuit 30 of this invention can maintain strong filtering capability even under load. In practical applications, an RC first-order active low-pass filter circuit can be used.

[0042] The input terminal of the voltage bias circuit 40 is connected to the output terminal of the active low-pass filter circuit 30. The voltage bias circuit 40 is used to bias the voltage of the low-ripple DC signal to the voltage range applicable to the AD sampling module 50.

[0043] Specifically, the voltage biasing circuit 40 can bias the filtered voltage to a voltage range that can be input to the AD sampling module 50. For example, the applicable voltage range of the AD sampling module 50 can be 0-3V, and the voltage biasing circuit 40 can bias a DC voltage signal with very small ripple to this voltage range.

[0044] The input terminal of the AD sampling module 50 is connected to the output terminal of the voltage bias circuit 40. The AD sampling module 50 is used to sample the biased voltage signal and convert the sampled voltage into a digital signal.

[0045] Specifically, the AD sampling module 50 of this utility model first samples the voltage within the above-mentioned applicable range, and then converts the sampled analog voltage into a digital voltage so that it can be used for subsequent logic operations.

[0046] The input terminal of the processor 60 is connected to the output terminal of the AD sampling module 50. The processor 60 is used to compare the digital signal with its internally preset fault threshold to determine whether the relative short-circuit fault condition is met.

[0047] The processor 60 can be any type of device capable of processing digital voltage signals, such as a digital signal processor (DSP) or a microcontroller.

[0048] For example, the AD sampling module sends the converted digital voltage signal to the subsequent DSP module. The DSP module compares the digital signal with its internally preset fault threshold to determine whether a short-circuit fault condition to ground is met. The DSP module then sends the result to the control module in the energy storage device's control system. The control module issues a command: if the short-circuit fault condition to ground is met, the device shuts down for protection; otherwise, it continues monitoring. Specifically, if the digital voltage signal is less than the preset fault threshold, the short-circuit fault condition to ground is determined to be met; otherwise, the short-circuit fault condition to ground is determined not to be met.

[0049] It should be noted that this invention converts the sampled analog voltage signal into a digital signal using the AD sampling module 50 before performing calculations and judgments. Compared to related technologies that calculate and compare analog signals, this invention improves the speed of fault detection. Therefore, as... Figure 4 As shown, the novel phase-to-ground fault detection circuit of this utility model realizes its own function through the various sub-circuits it includes, and can detect whether a phase-to-ground short-circuit fault has occurred in the phase-to-ground voltage of each phase of the power grid.

[0050] In order to realize the function of the above-mentioned short-circuit fault detection circuit, as a possible implementation method, a specific circuit structure of the short-circuit fault detection circuit is proposed in one embodiment of the present invention.

[0051] like Figure 5 As shown, in this embodiment, the differential voltage sampling circuit includes: a first resistor R1, a second resistor R2, a third resistor R3, a fourth resistor R4, a first feedback capacitor C1, a second feedback capacitor C2, and a first operational amplifier U1. The input terminals of the first resistor R1 and the second resistor R2 are connected to the single-phase-to-ground voltage AC of the power grid; the output terminal of the first resistor R1 is connected to the negative input terminal of the first operational amplifier U1; the output terminal of the second resistor R2 is connected to the positive input terminal of the first operational amplifier U1; the first feedback capacitor C1 and the fourth resistor R4 are connected in parallel between the negative input terminal and the output terminal of the first operational amplifier U1; the input terminals of the third resistor R3 and the second feedback capacitor C2 are connected to the output terminal of the second resistor R2; and the output terminals of the third resistor R3 and the second feedback capacitor C2 are grounded.

[0052] In this circuit, the first resistor has the same resistance value as the second resistor, and the third resistor has the same resistance value as the fourth resistor, i.e., R1 = R2 and R3 = R4. The input terminal of this differential voltage sampling circuit is connected to the single-phase-to-ground voltage AC of the power grid to acquire this single-phase-to-ground voltage. This allows for the conversion of a large voltage signal into a small voltage signal.

[0053] In this embodiment, refer to Figure 5 As shown, the precision rectifier circuit includes: fifth resistor R5, eighth resistor R8, sixth resistor R6, seventh resistor R7, ninth resistor R9, second operational amplifier U2, third operational amplifier U3, first rectifier diode D1, second rectifier diode D2, and third feedback capacitor C3.

[0054] The input terminals of the fifth resistor R5 and the eighth resistor R8 are connected to the output terminal of the first operational amplifier U1, the output terminal of the fifth resistor R5 is connected to the negative input terminal of the second operational amplifier U2, and the positive input terminal of the second operational amplifier U2 is grounded.

[0055] The sixth resistor R6, the seventh resistor R7, and the ninth resistor R9 are connected in series. The input terminal of the sixth resistor R6 is connected to the output terminal of the fifth resistor R5, and the output terminal of the ninth resistor R9 is connected to the output terminal of the third operational amplifier U3.

[0056] The first rectifier diode D1 and the second rectifier diode D2 are connected in series. The connection point of the sixth resistor R6 and the seventh resistor R7 is connected to the positive terminal of the first rectifier diode D1. The negative terminal of the second rectifier diode D2 is connected to the output terminal of the fifth resistor R5. The connection point of the first rectifier diode D1 and the second rectifier diode D2 is connected to the output terminal of the second operational amplifier U2.

[0057] The output terminal of the eighth resistor R8 is connected to the input terminal of the third feedback capacitor C3. The third feedback capacitor C3 and the ninth resistor R9 are connected in parallel between the negative input terminal and the output terminal of the third operational amplifier U3. The positive input terminal of the third operational amplifier U3 is grounded.

[0058] Among them, the fifth, sixth, and eighth resistors have equal resistance values, and are twice the resistance value of the seventh resistor, i.e., R5 = R8 = R6 = 2R7. The second operational amplifier U2 and the third operational amplifier U3 are used to compensate for the voltage drop of each rectifier diode during the full-wave rectification process.

[0059] Therefore, through the compensation effect of the operational amplifier, the precision rectifier circuit in this embodiment does not have the error caused by the diode voltage drop. During full-wave rectification, the voltage drop generated by the first rectifier diode D1 and the second rectifier diode D2 is compensated by the relevant operational amplifier, thereby improving the rectification accuracy and ensuring the accuracy of the rectified DC voltage signal.

[0060] In this embodiment, refer to Figure 5 As shown, the active low-pass filter circuit includes: a tenth resistor R10, a first filter capacitor C4, and a fourth operational amplifier U4. The input terminal of the tenth resistor R10 is connected to the output terminal of the third operational amplifier U3, and the output terminal of the tenth resistor R10 is connected to both the input terminal of the first filter capacitor C4 and the positive input terminal of the fourth operational amplifier U4. The output terminal of the first filter capacitor C4 is grounded, and the negative input terminal of the fourth operational amplifier U4 is connected to its output terminal.

[0061] Therefore, by using the configuration of the first-order RC active low-pass filter circuit in this embodiment, the input impedance of the fourth operational amplifier U4 can be made infinite. Thus, this filter circuit can effectively improve the problem of the filtering capability deteriorating after the traditional passive RC filter circuit is loaded, and can still maintain a strong filtering capability after being loaded.

[0062] In this embodiment, refer to Figure 5 As shown, the voltage bias circuit includes: eleventh resistor R11, twelfth resistor R12, positive power supply voltage VCC, and fifth operational amplifier U5.

[0063] The input terminal of the eleventh resistor R11 is connected to the output terminal of the fourth operational amplifier U4, and the output terminal of the eleventh resistor R11 is connected to the input terminal of the twelfth resistor R12 and the positive input terminal of the fifth operational amplifier U5.

[0064] The output terminal of the twelfth resistor R12 is connected to the positive power supply voltage VCC, and the negative input terminal of the fifth operational amplifier U5 is connected to the output terminal of the fifth operational amplifier U5.

[0065] The output of the fifth operational amplifier U5 is also connected to the AD sampling module.

[0066] Therefore, through this voltage biasing circuit, the filtered voltage can be biased to a voltage range that can be input into the AD sampling module of the control system.

[0067] Based on the above Figure 5 The specific structure of the relative-to-ground fault detection circuit shown is used to calculate the acquired input voltage value using the following formula:

[0068]

[0069] Among them, U in It is the input voltage value, U o This refers to the output voltage value of the circuit. R1 is the first resistor, R4 is the fourth resistor, R8 is the eighth resistor, R9 is the ninth resistor, and R... 11 It is the eleventh resistor, R 12 It is the twelfth resistor, V CC It is the positive power supply voltage.

[0070] The above formula reflects the input-output relationship of the circuit. The input voltage value is the single-phase-to-ground voltage of the power grid collected above. In the formula, 2 / π means that the average value after full-wave rectification is 0.637 times the amplitude.

[0071] In one embodiment of this utility model, Figure 5 The phase-to-ground fault detection circuit shown can be configured in an energy storage device connected to the power grid, and a control program can be configured in the relevant components of the energy storage device's control system to realize real-time detection of phase-to-ground short-circuit faults on the AC side of the power grid, so as to ensure the safety of the energy storage device.

[0072] In summary, the ground fault detection circuit based on precision rectification and active filtering in this embodiment of the invention comprises four sub-circuits: a differential voltage sampling circuit, a precision rectification circuit, an active low-pass filter circuit, and a voltage bias circuit. This circuit avoids the use of large devices such as transformers, thereby reducing the size of the detection circuit, lowering its hardware cost, and improving its practicality and manufacturability, making it suitable for energy storage devices in various operating scenarios. Furthermore, the detection process of this circuit does not require complex logic operations, and the fault judgment procedure is relatively simple. The speed of ground fault detection is improved through digital comparison, thereby increasing the overall speed from initial voltage data sampling to execution of protection actions. This allows for faster protection of the device when a fault occurs, improving the efficiency of ground fault detection. By incorporating an operational amplifier, the circuit can compensate for the diode voltage drop in traditional full-wave rectification schemes, resulting in higher rectification accuracy. Moreover, the active filter circuit effectively avoids the problem of decreased filtering capability of passive RC filters under load, thus improving the accuracy of ground fault detection. Therefore, this circuit can accurately, efficiently and cost-effectively detect phase-to-ground faults on the AC side of the power grid, which is beneficial to ensuring the safe and stable operation of energy storage equipment.

[0073] Based on the above embodiments, to more clearly illustrate the specific implementation process of the fault detection based on the precision rectification and active filtering relative-to-ground fault detection circuit, a relative-to-ground fault detection method based on precision rectification and active filtering proposed in this application embodiment will be described in detail below. This method is applied to the relative-to-ground fault detection circuit based on precision rectification and active filtering in the above embodiments, that is, controlling the relevant devices in the detection circuit of the above embodiments to implement the detection method of this embodiment. The executing entity of the detection method in this embodiment includes the above-mentioned detection circuit and the control system of the detection circuit.

[0074] Figure 6 This is a flowchart illustrating a ground fault detection method based on precision rectification and active filtering, as proposed in an embodiment of this utility model. Figure 6 As shown, the method includes the following steps:

[0075] Step S101: The acquired sinusoidal AC high voltage signal is converted into a sinusoidal AC low voltage signal through a differential voltage sampling circuit, and the sinusoidal AC low voltage signal is rectified into a DC voltage signal through a precision rectifier circuit.

[0076] In this embodiment, see Figure 7 The workflow shown involves first converting the acquired high-voltage signal into a low-voltage signal using a differential voltage sampling circuit, and then inputting the converted low-voltage signal into a precision rectifier circuit. The precision rectifier circuit then rectifies the AC voltage into a DC voltage.

[0077] Step S102: The pulsating waveform of the DC voltage signal is filtered by an active low-pass filter circuit to obtain a low-ripple DC signal, and the voltage of the low-ripple DC signal is biased to a preset voltage range by a voltage bias circuit.

[0078] Continue to refer to Figure 7 For example, the DC pulsating waveform is first filtered into a DC signal with very small ripple through an active low-pass filter circuit, and then the DC signal with very small ripple is biased into a signal that can be input to the control system through a voltage bias circuit. The voltage of the signal that can be input to the control system is within a preset voltage range, that is, within the voltage range that the AD sampling module of the control system can receive, for example, 0-3V.

[0079] Step S103: Sample the biased voltage signal, convert the sampled voltage into a digital voltage signal, and determine whether the conditions for a short circuit to ground are met based on the digital voltage signal.

[0080] Continue to refer to Figure 7 For example, after the sampled voltage is converted into a digital voltage signal, logical operations are performed through relevant programs to determine whether the digital voltage signal meets the conditions for a short-circuit fault to ground.

[0081] In one embodiment of this utility model, determining whether the conditions for a relative short-circuit fault are met based on a digital voltage signal includes: comparing the digital voltage signal with a preset fault threshold, and determining whether the conditions for a relative short-circuit fault are met based on the comparison result.

[0082] For example, the built-in program compares the digital value of the current sampled voltage with a preset 0V or a certain threshold to determine whether the fault condition for a short circuit to ground is met. If the voltage value of the digital voltage signal is less than the preset fault threshold, the condition for a short circuit to ground is determined to be met; otherwise, the condition for a short circuit to ground is determined not to be met.

[0083] Step S104: If the conditions for a relative short-circuit fault to ground are not met, the voltage signal of the power grid is collected again through the differential voltage sampling circuit to perform relative fault detection cyclically. If the conditions for a relative short-circuit fault to ground are met, the relative fault protection operation is executed.

[0084] Specifically, if the conditions for a relative-to-ground short-circuit fault are not met, the process returns to step S101 and restarts by acquiring the grid voltage signal through the differential voltage sampling circuit, repeatedly executing steps S101 to S104 to continuously detect relative-to-ground faults. If the conditions for a relative-to-ground short-circuit fault are met, a relative-to-ground fault protection operation is performed to protect the safety of equipment connected to the grid.

[0085] In one embodiment of this utility model, performing a relative fault protection operation includes: controlling the shutdown of an energy storage device connected to the power grid and disconnecting the energy storage device from the power grid.

[0086] For example, after detecting a phase-to-ground short-circuit fault, the control program in this embodiment immediately outputs an execution command to perform shutdown protection on the energy storage device connected to the power grid and disconnect the connection between the energy storage device and the power grid, thereby quickly disconnecting the connection between the faulty phase of the power grid and the energy storage device and avoiding further impact of the phase-to-ground short-circuit fault of the power grid on the energy storage device.

[0087] In summary, the phase-to-ground fault detection method based on precision rectification and active filtering in this embodiment of the invention does not require complex logical operations during the detection process, and the fault judgment procedure is relatively simple. It improves the speed of phase-to-ground fault detection through digital comparison, thereby increasing the overall speed from initial voltage data sampling to execution of protection actions. This allows for faster equipment protection when a fault occurs, improving the efficiency of phase-to-ground fault detection. This method can accurately, efficiently, and cost-effectively detect phase-to-ground faults on the AC side of the power grid, which is beneficial for ensuring the safe and stable operation of energy storage equipment.

[0088] To implement the above embodiments, the present invention also proposes a non-transitory computer-readable storage medium storing a computer program thereon, wherein the computer program, when executed by a processor, implements the relative ground fault detection method based on precision rectification and active filtering as described in the second aspect embodiment of the present invention.

[0089] In the description of this specification, the references to terms such as "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the present invention. In this specification, the use of illustrative expressions of the above terms in multiple embodiments or examples does not imply that these embodiments or examples are identical. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples. Moreover, without contradiction, those skilled in the art can combine and integrate the different embodiments or examples described in this specification, as well as the features of different embodiments or examples.

[0090] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one of that feature. In the description of this utility model, "a plurality of" means at least two, such as two, three, etc., unless otherwise explicitly specified.

[0091] Any process or method described in the flowchart or otherwise herein can be understood as representing a module, segment, or portion of code comprising one or more executable instructions for implementing custom logic functions or processes, and the scope of the preferred embodiments of the present invention includes additional implementations in which functions may be performed not in the order shown or discussed, including substantially simultaneously or in reverse order according to the functions involved, as should be understood by those skilled in the art to which embodiments of the present invention pertain.

[0092] The logic and / or steps represented in the flowchart or otherwise described herein, for example, can be considered as a sequenced list of executable instructions for implementing logical functions, and can be embodied in any computer-readable medium for use by, or in conjunction with, an instruction execution system, apparatus, or device (such as a computer-based system, a processor-included system, or other system that can fetch and execute instructions from, an instruction execution system, apparatus, or device). For the purposes of this specification, "computer-readable medium" can be any means that can contain, store, communicate, propagate, or transmit programs for use by, or in conjunction with, an instruction execution system, apparatus, or device. More specific examples (a non-exhaustive list) of computer-readable media include: an electrical connection having one or more wires (electronic device), a portable computer disk drive (magnetic device), random access memory (RAM), read-only memory (ROM), erasable and editable read-only memory (EPROM or flash memory), fiber optic devices, and portable optical disc read-only memory (CDROM). Alternatively, the computer-readable medium may be paper or other suitable media on which the program can be printed, since the program can be obtained electronically, for example, by optically scanning the paper or other medium, followed by editing, interpreting, or otherwise processing as necessary, and then stored in a computer memory.

[0093] It should be understood that the various parts of this utility model can be implemented using hardware, software, firmware, or a combination thereof. In the above embodiments, multiple steps or methods can be implemented using software or firmware stored in memory and executed by a suitable instruction execution system. For example, if implemented in hardware as in another embodiment, it can be implemented using any one or a combination of the following techniques known in the art: discrete logic circuits having logic gates for implementing logical functions on data signals, application-specific integrated circuits (ASICs) having suitable combinational logic gates, programmable gate arrays (PGAs), field-programmable gate arrays (FPGAs), etc.

[0094] Those skilled in the art will understand that all or part of the steps of the methods described in the above embodiments can be implemented by a program instructing related hardware. The program can be stored in a computer-readable storage medium, and when executed, it includes one or a combination of the steps of the method embodiments.

[0095] Furthermore, the functional units in the various embodiments of this utility model can be integrated into a processing module, or each unit can exist physically separately, or two or more units can be integrated into a module. The integrated module can be implemented in hardware or as a software functional module. If the integrated module is implemented as a software functional module and sold or used as an independent product, it can also be stored in a computer-readable storage medium.

[0096] The storage medium mentioned above can be a read-only memory, a disk, or an optical disk, etc. Although embodiments of the present invention have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting the present invention. Those skilled in the art can make changes, modifications, substitutions, and variations to the above embodiments within the scope of the present invention.

Claims

1. A ground fault detection circuit based on precision rectification and active filtering, characterized in that, include: The circuit includes a differential voltage sampling circuit, a precision rectifier circuit, an active low-pass filter circuit, a voltage bias circuit, an AD sampling module, and a processor; among which, The input terminal of the differential voltage sampling circuit is connected to the single-phase ground voltage of the power grid. The differential voltage sampling circuit is used to reduce the amplitude of the acquired sinusoidal AC voltage signal in order to obtain a small sinusoidal AC voltage signal. The input terminal of the precision rectifier circuit is connected to the output terminal of the differential voltage sampling circuit. The precision rectifier circuit is used to rectify the sinusoidal AC small voltage signal into a DC voltage signal. The input terminal of the active low-pass filter circuit is connected to the output terminal of the precision rectifier circuit. The active low-pass filter circuit is used to filter the DC voltage signal into a low-ripple DC signal. The input terminal of the voltage bias circuit is connected to the output terminal of the active low-pass filter circuit. The voltage bias circuit is used to bias the voltage of the low-ripple DC signal to the voltage range applicable to the AD sampling module. The input terminal of the AD sampling module is connected to the output terminal of the voltage bias circuit. The AD sampling module is used to sample the biased voltage signal and convert the sampled voltage into a digital signal. The processor's input terminal is connected to the output terminal of the AD sampling module. The processor is used to compare the digital signal with its internally preset fault threshold to determine whether the relative short-circuit fault condition is met.

2. The circuit according to claim 1, characterized in that, The differential voltage sampling circuit includes: a first resistor to a fourth resistor, a first feedback capacitor, a second feedback capacitor, and a first operational amplifier; wherein, The input terminals of the first resistor and the second resistor are connected to the single-phase-to-ground voltage of the power grid, the output terminal of the first resistor is connected to the negative input terminal of the first operational amplifier, and the output terminal of the second resistor is connected to the positive input terminal of the first operational amplifier. The first feedback capacitor and the fourth resistor are connected in parallel between the negative input terminal and the output terminal of the first operational amplifier; The input terminals of the third resistor and the second feedback capacitor are connected to the output terminal of the second resistor, and the output terminals of the third resistor and the second feedback capacitor are grounded. The first resistor has the same resistance value as the second resistor, and the third resistor has the same resistance value as the fourth resistor.

3. The circuit according to claim 2, characterized in that, The precision rectifier circuit includes: resistors five through nine, a second operational amplifier, a third operational amplifier, a first rectifier diode, a second rectifier diode, and a third feedback capacitor; wherein, The input terminals of the fifth and eighth resistors are connected to the output terminal of the first operational amplifier, the output terminal of the fifth resistor is connected to the negative input terminal of the second operational amplifier, and the positive input terminal of the second operational amplifier is grounded. The sixth resistor, the seventh resistor, and the ninth resistor are connected in series. The input terminal of the sixth resistor is connected to the output terminal of the fifth resistor, and the output terminal of the ninth resistor is connected to the output terminal of the third operational amplifier. The first rectifier diode and the second rectifier diode are connected in series. The connection point of the sixth resistor and the seventh resistor is connected to the positive terminal of the first rectifier diode. The negative terminal of the second rectifier diode is connected to the output terminal of the fifth resistor. The connection point of the first rectifier diode and the second rectifier diode is connected to the output terminal of the second operational amplifier. The output terminal of the eighth resistor is connected to the input terminal of the third feedback capacitor. The third feedback capacitor and the ninth resistor are connected in parallel between the negative input terminal and the output terminal of the third operational amplifier. The positive input terminal of the third operational amplifier is grounded. The resistance values ​​of the fifth, sixth, and eighth resistors are equal, and are twice the resistance value of the seventh resistor. The second operational amplifier and the third operational amplifier are used to compensate for the voltage drop of each rectifier diode during the full-wave rectification process.

4. The circuit according to claim 3, characterized in that, The active low-pass filter circuit includes: a tenth resistor, a first filter capacitor, and a fourth operational amplifier; wherein, The input terminal of the tenth resistor is connected to the output terminal of the third operational amplifier, and the output terminal of the tenth resistor is connected to the input terminal of the first filter capacitor and the positive input terminal of the fourth operational amplifier. The output terminal of the first filter capacitor is grounded, and the negative input terminal of the fourth operational amplifier is connected to the output terminal of the fourth operational amplifier, so that the input impedance of the fourth operational amplifier is infinite.

5. The circuit according to claim 4, characterized in that, The voltage bias circuit includes: an eleventh resistor, a twelfth resistor, a positive power supply voltage, and a fifth operational amplifier; wherein, The input terminal of the eleventh resistor is connected to the output terminal of the fourth operational amplifier, and the output terminal of the eleventh resistor is connected to the input terminal of the twelfth resistor and the positive input terminal of the fifth operational amplifier. The output terminal of the twelfth resistor is connected to the positive power supply voltage, and the negative input terminal of the fifth operational amplifier is connected to the output terminal of the fifth operational amplifier. The output of the fifth operational amplifier is also connected to the AD sampling module.

6. The circuit according to claim 5, characterized in that, The relative ground fault detection circuit calculates the acquired input voltage value using the following formula: in, U in It is the input voltage value. U o It is the output voltage value of the circuit. R 1 is the first resistor in the differential voltage sampling circuit. R 4 is the fourth resistor in the differential voltage sampling circuit. R 8 is the eighth resistor in a precision rectifier circuit. R 9 is the ninth resistor in a precision rectifier circuit. R 11 It is the eleventh resistor in the voltage bias circuit. R 12 It is the twelfth resistor in the voltage bias circuit. V CC It is the positive power supply voltage in the voltage biasing circuit.

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