WO2022237796A1 - 一种漏电检测装置、漏电检测方法和充电设备 - Google Patents

一种漏电检测装置、漏电检测方法和充电设备 Download PDF

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Publication number
WO2022237796A1
WO2022237796A1 PCT/CN2022/092029 CN2022092029W WO2022237796A1 WO 2022237796 A1 WO2022237796 A1 WO 2022237796A1 CN 2022092029 W CN2022092029 W CN 2022092029W WO 2022237796 A1 WO2022237796 A1 WO 2022237796A1
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excitation
frequency
preset
leakage detection
signal
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PCT/CN2022/092029
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English (en)
French (fr)
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杜明胜
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上海盛位电子技术有限公司
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Publication of WO2022237796A1 publication Critical patent/WO2022237796A1/zh

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    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
    • G01R31/00—Arrangements for testing electric properties; Arrangements for locating electric faults; Arrangements for electrical testing characterised by what is being tested not provided for elsewhere
    • G01R31/50—Testing of electric apparatus, lines, cables or components for short-circuits, continuity, leakage current or incorrect line connections
    • G01R31/52—Testing for short-circuits, leakage current or ground faults
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
    • G01R31/00—Arrangements for testing electric properties; Arrangements for locating electric faults; Arrangements for electrical testing characterised by what is being tested not provided for elsewhere
    • G01R31/50—Testing of electric apparatus, lines, cables or components for short-circuits, continuity, leakage current or incorrect line connections
    • G01R31/56—Testing of electric apparatus
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02H—EMERGENCY PROTECTIVE CIRCUIT ARRANGEMENTS
    • H02H3/00—Emergency protective circuit arrangements for automatic disconnection directly responsive to an undesired change from normal electric working condition with or without subsequent reconnection ; integrated protection
    • H02H3/08—Emergency protective circuit arrangements for automatic disconnection directly responsive to an undesired change from normal electric working condition with or without subsequent reconnection ; integrated protection responsive to excess current
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02T—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO TRANSPORTATION
    • Y02T10/00—Road transport of goods or passengers
    • Y02T10/60—Other road transportation technologies with climate change mitigation effect
    • Y02T10/70—Energy storage systems for electromobility, e.g. batteries
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02T—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO TRANSPORTATION
    • Y02T10/00—Road transport of goods or passengers
    • Y02T10/60—Other road transportation technologies with climate change mitigation effect
    • Y02T10/7072—Electromobility specific charging systems or methods for batteries, ultracapacitors, supercapacitors or double-layer capacitors

Definitions

  • the present invention generally relates to the field of leakage detection, and more specifically relates to a leakage detection device, a leakage detection method and a charging device.
  • RCD residual Current Device, residual current detection device
  • residual current detection device is a leakage detection device used to detect the magnitude of the leakage current in the line. If no RCD is installed in the line, when a person or animal is exposed to high voltage, a leakage current will be generated to the ground. When the leakage current exceeds a certain threshold, it will cause the heart of the person or animal to tremble, causing cardiac arrest, and then causing Life is in danger. If a leakage detection device such as RCD is installed in the line, when there is a leakage current in the line and the magnitude of the leakage current signal exceeds the set threshold, the RCD will send an alarm signal to the action mechanism, triggering the action mechanism to quickly break the line , so as to achieve the purpose of protecting life safety.
  • the main purpose of the action mechanism is to break the power supply line at the back end. When the line is broken, there will be no voltage and current at the back end of the breaker, so as to achieve the purpose of protection.
  • RCD on-board leakage module is currently widely used in charging piles and charging guns, which can be directly installed on the circuit board. When the electric vehicle is charging, the RCD is used to detect whether the leakage current exceeds the threshold during the charging process. If it exceeds the threshold , the RCD will send an alarm signal to other devices in the circuit board to execute the command to stop charging and disconnect the charging circuit, such as disconnecting the closed relay or circuit breaker mechanism.
  • An embodiment of the present invention provides an electric leakage detection device on the one hand, and the electric leakage detection device includes:
  • Zero-sequence current transformer for sensing leakage current signal
  • a control circuit is connected to the excitation driver and the sampling resistor, and the control circuit includes:
  • variable frequency excitation circuit connected to the excitation drive is used to generate excitation signals of at least two preset excitation frequencies, and alternately apply the excitation signals of the at least two preset excitation frequencies to the zero sequence through the excitation drive on the current transformer;
  • a frequency-variable sampling circuit connected to the sampling resistor, configured to sample the sampling resistor at a sampling frequency corresponding to the preset excitation frequency, so as to obtain a leakage current signal
  • a comparison circuit connected to the frequency conversion sampling circuit, used to compare the leakage current signal with a preset threshold, and generate an alarm signal when the leakage current signal is greater than the preset threshold;
  • the communication interface is connected with the comparison circuit and is used for outputting the alarm signal.
  • the at least two preset excitation frequencies are the excitation frequencies that cause the zero-sequence current transformer to enter a deep saturation state.
  • At least one of the preset excitation frequencies is an excitation frequency that causes the zero-sequence current transformer to enter a deep saturation state.
  • variable frequency excitation circuit switches the preset excitation frequency every at least one cycle.
  • the sampling frequency is an integer multiple of the preset excitation frequency.
  • control circuit further includes a feedback circuit respectively connected to the variable frequency sampling circuit and the excitation circuit, for comparing the voltage generated by the leakage current signal on the sampling resistor with a preset voltage, to generate a feedback signal, and feed the feedback signal to the excitation circuit; the excitation circuit is used to adjust the frequency of the excitation signal according to the feedback signal.
  • the zero-sequence current transformer includes a magnetic core, a sheath and a coil, and the magnetic core is a nanocrystalline magnetic core.
  • the magnetic saturation of the magnetic core is Bs ⁇ 1.2T, the magnetic permeability u>80000, and the coercive force Hc ⁇ 4.5A/m after adding longitudinal magnetism.
  • variable-frequency sampling circuit includes a digital low-pass filter for filtering information of the excitation signal.
  • Another aspect of the embodiment of the present invention provides a leakage detection method, the method comprising:
  • the alarm signal is output.
  • At least one of the preset excitation frequencies is an excitation frequency that causes the zero-sequence current transformer to enter a deep saturation state.
  • each of the preset excitation frequencies is an excitation frequency that causes the zero-sequence current transformer to enter a deep saturation state.
  • the generating the excitation signals of at least two preset excitation frequencies includes: switching the preset excitation frequencies every at least one cycle.
  • the method also includes:
  • the voltage generated by the leakage current signal is compared with a preset voltage to generate a feedback signal, and the frequency of the excitation signal is adjusted according to the feedback signal.
  • Still another aspect of the embodiments of the present invention provides a charging device, the charging device includes the above leakage detection device; and an action mechanism connected to the leakage detection device for disconnecting the power supply line when the alarm signal is received.
  • the leakage detection device, leakage detection method and charging equipment of the embodiments of the present invention drive the zero-sequence current transformer through excitation signals of at least two preset excitation frequencies, which can improve the accuracy of detection of leakage current signals.
  • Fig. 1 is the circuit diagram of A type and AC type leakage detection device of an embodiment of the present invention
  • Fig. 2 is the schematic diagram of the magnetization curve of the B-type leakage detection device of an embodiment of the present invention
  • Fig. 3 is a schematic diagram of an external magnetic field affecting the magnetization curve according to an embodiment of the present invention.
  • Fig. 4 is the schematic diagram of the leakage detection device of an embodiment of the present invention.
  • Fig. 5 is a waveform diagram of a zero-sequence current transformer entering a deep saturation state according to an embodiment of the present invention
  • Fig. 6 is a waveform diagram of a zero-sequence current transformer entering a shallow saturation state according to an embodiment of the present invention
  • FIG. 7 is a schematic diagram of open-loop frequency hopping according to an embodiment of the present invention.
  • Fig. 8 is a schematic flowchart of a leakage detection method according to an embodiment of the present invention.
  • Leakage detection devices such as RCD (Residual Current Device, residual current detection device) are divided into AC type leakage detection device, A type leakage detection device and B type leakage detection device, among which:
  • the AC-type leakage detection device can detect AC-type AC leakage current. When there is AC-type AC leakage in the line, and the leakage current reaches the set threshold, the AC-type leakage detection device will send a TRIP (tripping) to the external working mechanism. ) alarm signal to disconnect the main line.
  • TRIP tripping
  • the A-type leakage detection device can also detect pulsating DC leakage such as A0, A90, and A135.
  • pulsating DC leakage such as A0, A90, and A135.
  • Type B leakage detection device not only has the detection function of AC type and A type leakage module, but also has the detection function of 2P-DC (two-phase rectification), 3P-DC (three-phase rectification), S-DC (smooth direct current) and F type ( 10Hz, 50Hz, 1000Hz) complex wave capability, when the above-mentioned leakage current value reaches the preset threshold, the B-type leakage detection device will send a TRIP alarm signal to the external trigger mechanism to disconnect the main line.
  • 2P-DC two-phase rectification
  • 3P-DC three-phase rectification
  • S-DC smooth direct current
  • F type 10Hz, 50Hz, 1000Hz
  • the detection principle of B-type leakage detection device is completely different from that of A-type and AC-type leakage detection devices.
  • the principle of A-type and AC-type leakage detection devices is to detect the leakage current in the line completely passively; while the B-type leakage detection device needs an external excitation frequency to drive ZCT (zero sequence current transformer)
  • ZCT zero sequence current transformer
  • the coil makes its core magnetized, and the magnetization curve is shown in Figure 2.
  • the principle of the B-type leakage current detection device is shown in FIG. 3 .
  • the influence of the external magnetic field is reflected in the change on the H axis, which means that the current changes when the excitation signal drives the magnetization of the ZCT core.
  • the voltage information including the excitation signal can be obtained.
  • the information also includes the information of the external magnetic field generated by the leakage current; by filtering out the information of the excitation signal, the information of the external magnetic field can be obtained, thereby obtaining the information of the leakage current signal, and realizing the detection function of the AC and DC leakage current signal.
  • the principle of B-type leakage detection device can be divided into open-loop and closed-loop, among which:
  • the principle of open-loop leakage detection is: the excitation frequency of the excitation circuit is generated by the oscillation circuit, and the oscillation frequency is determined comprehensively according to the characteristics of different transformers and the magnitude of the driving current.
  • the excitation frequency is fixed, and the excitation cannot be adjusted in real time during the application process. frequency;
  • the principle of closed-loop leakage detection is: the excitation frequency of the excitation circuit is related to the parameters of ZCT. During the application process, a feedback signal is generated according to the magnitude of the current, and the frequency of the excitation current is adjusted according to the feedback signal until the circuit is in a stable state.
  • the open-loop leakage detection device cannot adjust the excitation frequency in real time during the application process.
  • the leakage current is sampled through the sampling resistor, it will face the problem that the TRIP current threshold is too small when the leakage current frequency is relatively high (for example, greater than 1K Hz).
  • the excitation circuit of the closed-loop leakage detection device is greatly affected by the residual magnetism Br, especially after a large leakage current impact, and then continuously measures the leakage current value, there will be a large deviation, which seriously affects the accuracy; in addition , after a large leakage current occurs, the closed-loop leakage detection device will have the problem that the excitation cannot start to vibrate.
  • the embodiment of the present invention applies the frequency hopping technology to the leakage detection device, specifically to the B-type leakage detection module that requires an excitation signal, where the frequency hopping mainly refers to the application of excitation frequency hopping.
  • a frequency conversion excitation circuit is used to drive the ZCT coil.
  • the excitation circuit can generate excitation signals of various frequencies, and the excitation signals of various frequencies are used to alternately drive the ZCT to perform periodic magnetization in time intervals, and ensure that the excitation signals at different excitation frequencies ZCT can well complete periodic magnetization, thereby solving the problems existing in the above-mentioned open-loop and closed-loop leakage detection devices.
  • the leakage detection device of the embodiment of the present invention includes at least a zero-sequence current transformer 401, a sampling resistor 402, an excitation drive 403 and a control circuit 404, wherein the zero-sequence current transformer 401 is used for sensing leakage current signals; the excitation drive 403 and sampling resistor 402 are respectively connected to zero-sequence current transformer 401; control circuit 404 is respectively connected to excitation drive 403 and sampling resistor 402, and control circuit 404 includes: a variable frequency excitation circuit connected to excitation drive 403 for generating at least two preset The excitation signal of the excitation frequency is set, and the excitation signals of at least two preset excitation frequencies are alternately applied to the zero-sequence current transformer 401 by the excitation driver 403; Sampling the sampling resistor 402 at the corresponding sampling frequency to obtain the leakage current signal; connecting the comparison circuit of the frequency conversion sampling circuit for comparing the leakage current signal with the preset threshold, and generating an
  • the leakage detection device of the embodiment of the present invention adopts a forced excitation circuit structure, and uses frequency hopping technology to alternately generate excitation signals of different preset excitation frequencies to excite the zero-sequence current transformer 401, it can solve the problem of open-loop In the leakage detection device, when the leakage current frequency is relatively high under a single excitation frequency, it is easy to identify the AC leakage current signal as a DC leakage current signal, and the problem that the preset threshold is too low; due to the implementation of the present invention
  • the example uses a forced excitation circuit, so there is no problem that the excitation in the closed-loop leakage detection device cannot start to vibrate.
  • the leakage detection device of the embodiment of the present invention is a B-type leakage detection device, and the frequency conversion excitation circuit generates an excitation signal to drive the coil of the zero-sequence current transformer 401 to magnetize its magnetic core.
  • the zero-sequence current transformer 401 is used to detect the magnitude of the leakage current in the line, and specifically includes a magnetic core, a sheath and a coil.
  • the magnetic core of the zero-sequence current transformer 401 in the embodiment of the present invention satisfies the following conditions: Magnetic saturation Bs ⁇ 1.2T, magnetic permeability u>80000, coercive force Hc ⁇ 4.5A/m after adding longitudinal magnetism. Further, the size of the cross-sectional area Ac of the magnetic core matches the size of the sampling resistor, the size of the excitation frequency and the working voltage, which can be calculated by the following formula:
  • f is the excitation frequency
  • V ext is the excitation voltage amplitude of the excitation signal
  • Ac is the cross-sectional area of the magnetic core
  • N is the turn ratio coefficient of the magnetic core
  • B m is the maximum magnetic induction intensity.
  • the leakage detection device of the embodiment of the present invention adopts the fluxgate technology, and the magnetic core is magnetized by the excitation signal; at the same time, when the leakage current signal generates an external magnetic field, the information of the external magnetic field can be obtained by filtering out the information of the excitation signal, In order to obtain the information of the leakage current signal.
  • the principle of the magnetization process is: if the ferromagnetic material is magnetized from a completely demagnetized state to saturated Bs along the magnetization curve OS, if the external magnetic field H is reduced at this time, the value of B will no longer follow the original The initial magnetization curve (OS) decreases for , but more slowly along higher B, because the rigidly rotating domains retain the direction of the external field.
  • a magnetic field strength -H opposite to the direction of the original magnetic field must be applied.
  • B 0 in the magnetic medium. This does not mean that the magnetic medium has returned to a disorderly state, but that a part of the magnetic domains still retains the direction of the original magnetized magnetic field, while the other part changes to the direction of the external magnetic field under the action of the reverse magnetic field.
  • the two parts are equal, the combined magnetic induction intensity is zero. If the strength of the reverse magnetic field continues to increase, the reverse magnetic domains in the ferromagnetic material will increase, and the reverse magnetic induction will increase. With the increase of the -H value, the reverse B will also increase.
  • At least two excitation signals with different preset excitation frequencies are used to alternately excite the zero-sequence current transformer 401 .
  • the zero-sequence current transformer 401 is connected to the control circuit 404, the control circuit 404 can be implemented as an MCU (micro control unit), and can also be implemented as other control units or circuits with similar functions, and the excitation signal is generated by the frequency conversion excitation circuit in the control circuit 404 , The start output and stop output of each frequency are precisely controlled by the frequency conversion excitation circuit, and the switching between different frequencies is seamlessly switched.
  • MCU micro control unit
  • an excitation driver 403 is connected between the frequency conversion excitation circuit and the zero-sequence current transformer 401, and the current output capability is increased by the excitation driver 403 to realize the function similar to an amplifier.
  • the embodiment of the present invention can specifically adopt the open-loop fluxgate technology, that is, use fixed excitation signals of at least two preset excitation frequencies to excite the zero-sequence current transformer 401, thereby avoiding the failure of the closed-loop fluxgate technology. Existing excitation can not start the problem.
  • the embodiment of the present invention can also adopt the closed-loop fluxgate technology, that is, the control circuit 404 also includes a feedback circuit respectively connected to the variable frequency sampling circuit and the excitation circuit, which is used to generate the leakage current signal on the sampling resistor. The voltage is compared with the preset voltage to generate a feedback signal, and the feedback signal is fed back to the excitation circuit; the excitation circuit is used to adjust the magnitude of the preset excitation frequency according to the feedback signal.
  • the embodiment of the present invention combines the open-loop frequency hopping technology with the deep saturation performance of the zero-sequence current transformer to improve the performance of the leakage detection device.
  • at least one preset excitation frequency is an excitation frequency that causes the zero-sequence current transformer 401 to enter a deep saturation state.
  • each preset excitation frequency generated by the variable frequency excitation circuit is an excitation frequency that causes the zero-sequence current transformer 401 to enter a deep saturation state.
  • the performance of the zero-sequence current transformer 401 will be very little affected by the residual magnetism Br, and can even be ignored, so there is no measurement after a large leakage current
  • the problem that the accuracy is affected can reduce the measurement error caused by the residual magnetism in the open-loop and closed-loop leakage detection, and improve the measurement accuracy.
  • Figure 5 is the waveform information captured on the sampling resistor 402 when the zero-sequence current transformer 401 enters a deep saturation state
  • Figure 6 shows that the zero-sequence current transformer 401 enters shallow saturation state, the waveform information captured on the sampling resistor 402.
  • the waveform captured on the sampling resistor 402 shows that there is a flat area on the vertical axis, and the positive and negative half axes of the vertical axis There is a period of leveling time.
  • the theoretical values of the entire flat area are symmetrically distributed, and the time length of the flat area is generally greater than 5% of the current excitation frequency period.
  • the voltage reaches the highest output voltage of the excitation drive 403, and it will last for a period of time, and the time length is generally greater than 5% of the current excitation frequency period; the waveform reflected on the sampling resistor in the shallow saturation state has at most only one peak time to reach the excitation drive 403
  • the highest output voltage which means that the highest output voltage of the waveform reflected on the sampling resistor in the shallow saturation state must be smaller than the waveform voltage reflected on the sampling resistor in the deep saturation state, at most there is only a moment at the peak (less than the excitation frequency 5% of the period) is equal to the voltage at deep saturation.
  • the zero-sequence current transformer 401 Due to the deep saturation state, the zero-sequence current transformer 401 is always in saturation for a period of time (greater than 5%) in one excitation cycle, so the zero-sequence current transformer 401 itself will be very little affected by the remanence, so that in After a very large (above tens or hundreds of amperes) leakage current impacts the zero-sequence current transformer 401, since the frequency conversion excitation circuit will force the zero-sequence current transformer 401 to be magnetized in a manner similar to that shown in Figure 2, the drive transformer reaches Deep saturation state, thereby eliminating the adverse effects of remanence and avoiding the deviation of the magnetization curve caused by remanence.
  • each excitation frequency generated by the frequency-variable excitation circuit can ensure sufficient capacity to drive the zero-sequence current transformer 401 into the above-mentioned deep saturation state.
  • some of the excitation frequencies can drive the zero-sequence current transformer 401 into a deep saturation state, and the rest of the excitation frequencies can drive the zero-sequence current transformer 401 into a shallow saturation state.
  • the excitation frequency at which the device 401 enters a deep saturation state is used to eliminate the influence of remanence.
  • the three preset excitation frequencies are the excitation frequencies at which the zero-sequence current transformer 401 enters the deep saturation state, or it may be that the two preset excitation frequencies work in the deep saturation state , one of the preset excitation frequencies works in a shallow saturation state.
  • the zero-sequence current sensor 401 is also connected to the sampling resistor 402, which is connected to the frequency conversion sampling circuit in the control circuit 404.
  • the frequency conversion sampling circuit is used to collect the voltage signal on the sampling resistor 402, and convert the voltage signal to obtain the magnitude of the current signal.
  • variable frequency sampling circuit While the excitation circuit outputs different excitation frequencies, the variable frequency sampling circuit also collects the voltage on the sampling resistor according to the sampling frequency corresponding to the output preset excitation frequency.
  • the sampling frequency is equal to the preset excitation frequency, or the sampling frequency is N times the preset excitation frequency, and N is an integer not less than 2.
  • sampling on the sampling resistor is a frequency-variable sampling, there are different sampling frequencies under different preset excitation frequencies, and this variable-frequency sampling method is continuously repeated. If there are three different preset excitation frequencies, It means that there are at least three different sampling frequencies. Similarly, if there are five or more preset excitation frequencies, it means that there are five or more sampling frequencies.
  • variable frequency sampling circuit also includes a digital low-pass filter, which is used to filter out the information of the excitation signal from the received signal and retain the information of the leakage current signal.
  • a digital low-pass filter which is used to filter out the information of the excitation signal from the received signal and retain the information of the leakage current signal.
  • the leakage detection device of the embodiment of the present invention does not need a high-order low-pass filter, and the function of an external hardware high-order low-pass filter can be realized based on a digital low-pass filter, saving The cost of the hardware circuit and the space of the PCB board are reduced.
  • the variable frequency excitation circuit can alternately generate excitation signals of at least three different preset excitation frequencies, and each excitation signal outputs one or more cycles, that is, the variable frequency excitation circuit switches the preset once every at least one cycle. Excitation frequency, seamlessly switch between the excitation signals of each preset excitation frequency. Taking three preset excitation frequencies of 1K Hz, 2K Hz and 3K Hz as an example, the frequency conversion excitation circuit alternately outputs the excitation frequencies of 1K Hz, 2K Hz and 3K Hz, and the zero-sequence current transformer 401 enters the above-mentioned The state of deep saturation.
  • the working logic of the excitation signals of three excitation frequencies is as follows: first, output the excitation signal of 1K Hz for three cycles, then output the excitation signal of 2K Hz for three cycles, and then output the excitation signal of 3K Hz for three cycles , and then re-output the excitation signal of 1K Hz for three cycles, and repeat in turn.
  • the preset excitation frequencies in the embodiment of the present invention are not limited to three types, and may also be two or more types, and the embodiment of the present invention does not limit the output sequence of the preset excitation frequencies, for example, it may be As shown in Figure 7, the order of 1KHz, 2KHz, and 3KHz is frequency hopping, or it can be the order of 2KHz, 1KHz, 3KHz or the order of 3KHz, 2KHz, 1KHz.
  • the order of frequency hopping can be fixed or random.
  • the number of output cycles of each preset excitation frequency may be three cycles, or one, two or more cycles, and the number of output cycles of each preset frequency may be the same or different.
  • the frequency conversion sampling circuit is connected to the comparison circuit, and the comparison circuit judges whether there is a leakage current flowing in the zero-sequence current transformer 401 according to the leakage current signal obtained by sampling, and judges whether the magnitude of the leakage current signal is greater than a preset threshold.
  • the comparison circuit outputs an alarm signal.
  • the alarm signal may include a TRIP signal, which is used to control the action mechanism to disconnect the power supply line.
  • the action mechanism is the mechanism used to trigger the external mechanical tripping device.
  • the action mechanism can be purely mechanical, or a combination of mechanical and electronic, or purely electronic.
  • the action mechanism can be directly connected to the control circuit 404, or can be connected to an external device.
  • the control circuit 404 may also include an external communication interface for realizing communication with external equipment, receiving and sending various information between the leakage detection device and external equipment, and the alarm signal may also include an alarm signal sent to external equipment.
  • the comparison circuit is further connected to an analog-to-digital conversion circuit for performing analog-to-digital conversion according to the type and magnitude of the leakage current signal to generate an analog signal representing the magnitude of the leakage current signal, that is, a pulse signal.
  • the pulse signal can also indicate the waveform information of the leakage current signal, the frequency of the leakage current signal, and the like.
  • the analog-to-digital conversion circuit may generate a PWM (Pulse Width Modulation, pulse width modulation) signal with a corresponding duty cycle according to the magnitude of the leakage current signal.
  • the duty cycle of the PWM signal is the proportion of the high level in the entire cycle in one pulse cycle.
  • the duty cycle of the PWM signal can determine the magnitude of the leakage current signal.
  • PWM signals can be output through different external communication ports, so that external devices can determine the type of leakage current signals according to the external communication ports outputting PWM signals, thereby realizing the representation of leakage current signals through digital signals size and signal type purposes, without configuring additional algorithms on the client side.
  • the frequencies of the PWM signals generated by different analog-to-digital conversion circuits may be the same or different.
  • the frequency of the PWM signal may also be Frequency represents the frequency of the AC leakage current signal.
  • control circuit 404 further includes a self-test circuit for performing system self-test to obtain a fault status signal. Further, the control circuit 404 also includes a logic circuit, connected to the self-test circuit, used to generate a combination signal of a high level signal and/or a low level signal according to the fault status signal, and output the combination signal through an external communication port to prompt the external Device failure status type.
  • the leakage detection device of the embodiment of the present invention drives the zero-sequence current transformer through at least two excitation signals of preset excitation frequencies, which can avoid misdetecting the AC signal as a DC signal when the frequency of the AC leakage current signal is high , thereby avoiding the problem that the threshold value is too small in the high-frequency band, and improving the accuracy of leakage current signal detection.
  • Another aspect of the embodiments of the present invention provides a leakage detection method, which can be implemented by the leakage detection device described with reference to FIG. 4 .
  • Fig. 8 shows a schematic flowchart of a leakage detection method 800 according to an embodiment of the present invention.
  • the leakage detection method 800 of the embodiment of the present invention includes the following steps:
  • step S810 the leakage current signal induced by the zero-sequence current transformer is obtained
  • step S820 generating excitation signals of at least two preset excitation frequencies, and applying the excitation signals of at least two preset excitation frequencies to the zero-sequence current transformer alternately;
  • step S830 sampling is performed at a sampling frequency corresponding to the preset excitation frequency to obtain a leakage current signal
  • step S840 comparing the leakage current signal with a preset threshold, and generating an alarm signal when the leakage current signal is greater than the preset threshold;
  • step S850 the alarm signal is output.
  • At least one preset excitation frequency is an excitation frequency that causes the zero-sequence current transformer to enter a deep saturation state. Further, each preset frequency is an excitation frequency for making the zero-sequence current transformer enter a deep saturation state.
  • generating the excitation signals of at least two preset excitation frequencies includes: switching the preset excitation frequencies every at least one cycle.
  • the method further includes: comparing the voltage generated by the leakage current signal with a preset voltage to generate a feedback signal, and adjusting the frequency of the excitation signal according to the feedback signal.
  • the leakage detection method drives the zero-sequence current transformer through at least two excitation signals with preset excitation frequencies, which can avoid misdetecting the AC signal as a DC signal when the frequency of the AC leakage current signal is high, thereby avoiding The problem that the threshold value is too small in the high-frequency band improves the accuracy of leakage current signal detection.
  • An embodiment of the present invention also provides a charging device, including the leakage detection device as described above and an action mechanism connected to the leakage detection device.
  • the action structure is used to detect that the magnitude of the leakage current signal is greater than a preset threshold. Disconnect the power supply line.
  • the charging equipment in the embodiment of the present invention can be implemented as charging equipment for charging vehicles such as charging piles and charging guns, and the leakage detection device can be an on-board leakage detection device, which can be directly installed on the PCB board of the charging equipment.
  • the leakage detection device can be used to detect whether the leakage current exceeds the threshold during the charging process, and when the leakage current exceeds the threshold, an alarm signal is sent to the MCU or other devices on the PCB board to Execute the command to stop charging, and disconnect the charging circuit through the action mechanism, such as disconnecting the closed relay or circuit breaker mechanism, etc.

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  • Physics & Mathematics (AREA)
  • General Physics & Mathematics (AREA)
  • Engineering & Computer Science (AREA)
  • Power Engineering (AREA)
  • Testing Of Short-Circuits, Discontinuities, Leakage, Or Incorrect Line Connections (AREA)
  • Emergency Protection Circuit Devices (AREA)

Abstract

一种漏电检测装置、漏电检测方法和充电设备，该装置包括：零序电流互感器(401)，用于感应漏电电流信号；激励驱动(403)和采样电阻(402)，分别连接零序电流互感器(401)；控制电路(404)，包括：连接激励驱动(403)的变频激励电路，用于产生至少两种预设激励频率的激励信号，并通过激励驱动(403)将其交替施加在零序电流互感器(401)上；连接采样电阻(402)的变频采样电路，用于以与激励频率相对应的采样频率对采样电阻(402)进行采样，以获得漏电电流信号；连接变频采样电路的比较电路，用于在漏电电流信号大于预设阈值时生成报警信号；通信接口，连接比较电路，用于输出报警信号。该漏电检测装置通过至少两种预设激励频率的激励信号驱动零序电流互感器，能够提高漏电电流信号检测的准确性。

Description

一种漏电检测装置、漏电检测方法和充电设备
说明书
技术领域
本发明总地涉及漏电检测领域，更具体地涉及一种漏电检测装置、漏电检测方法和充电设备。
背景技术
RCD(Residual Current Device，剩余电流检测器件)是用来检测线路中的漏电电流大小的漏电检测装置。若线路中没有安装RCD，当有人或者动物接触到高电压时，会对地产生漏电电流，当漏电电流超过一定的阈值后，会造成人或动物的心脏的颤动，引起心脏骤停，进而造成生命危险。若线路中安装了RCD这样的漏电检测装置，当线路中存在泄漏电流、并且漏电电流信号的大小超过设定的阈值时，RCD就会发出报警信号给动作机构，触发动作机构去快速地分断线路，从而实现保护生命安全的目的。
动作机构的主要目的是用来分断后端供电的线路，当线路分断后，分断器后端将不存在电压和电流，从而实现保护的目的。RCD板载式的漏电模块目前广泛应用于充电桩和充电枪，其可以被直接安装在电路板上，当电动汽车进行充电时，RCD用于检测充电过程中漏电电流是否超过阈值，如果超过阈值，则RCD会发出报警信号给电路板中的其它器件，去执行停止充电的命令，并断开充电的线路，例如断开已闭合的继电器或断路器机构等。
发明内容
在发明内容部分中引入了一系列简化形式的概念，这将在具体实施方式部分中进一步详细说明。本申请的发明内容部分并不意味着要试图限定出所要求保护的技术方案的关键特征和必要技术特征，更不意味着试图确定所要求保护的技术方案的保护范围。
本发明实施例一方面提供了一种漏电检测装置，所述漏电检测装置包括：
零序电流互感器，用于感应漏电电流信号；
连接所述零序电流互感器的激励驱动和采样电阻；
控制电路，连接所述激励驱动和所述采样电阻，所述控制电路包括：
连接所述激励驱动的变频激励电路，用于产生至少两种预设激励频率的激励信号，并通过所述激励驱动将所述至少两种预设激励频率的激励信号交替施加在所述零序电流互感器上；
连接所述采样电阻的变频采样电路，用于以与所述预设激励频率相对应的采样频率对所述采样电阻进行采样，以获得漏电电流信号；
连接所述变频采样电路的比较电路，用于将所述漏电电流信号与预设阈值进行比较，并在所述漏电电流信号大于所述预设阈值时生成报警信号；
通信接口，连接所述比较电路，用于输出所述报警信号。
在一个实施例中，所述至少两种预设激励频率均为使所述零序电流互感器进入深度饱和状态的激励频率。
在一个实施例中，至少一种所述预设激励频率为使所述零序电流互感器进入深度饱和状态的激励频率。
在一个实施例中，所述变频激励电路每隔至少一个周期切换一次所述预设激励频率。
在一个实施例中，所述采样频率为所述预设激励频率的整数倍。
在一个实施例中，所述控制电路还包括分别连接所述变频采样电路和所述激励电路的反馈电路，用于将所述漏电电流信号在采样电阻上产生的电压与预设电压相比较，以产生反馈信号，并将所述反馈信号反馈至所述激励电路；所述激励电路用于根据所述反馈信号调节所述激励信号的频率。
在一个实施例中，所述零序电流互感器包括磁芯、护壳和线圈，所述磁芯为纳米晶磁芯。
在一个实施例中，所述磁芯的磁饱和强度Bs≤1.2T，磁导率u>80000，加纵磁后的矫顽力Hc<4.5A/m。
在一个实施例中，所述变频采样电路包括数字低通滤波器，用于滤除所述激励信号的信息。
本发明实施例另一方面提供一种漏电检测方法，所述方法包括：
获取零序电流互感器感应的漏电电流信号；
产生至少两种预设激励频率的激励信号，并将所述至少两种预设激励频率的激励信号交替施加在所述零序电流互感器上；
以与所述预设激励频率相对应的采样频率进行采样，以获得漏电电流信 号；
将所述漏电电流信号与预设阈值进行比较，并在所述漏电电流信号大于所述预设阈值时生成报警信号；
输出所述报警信号。
在一个实施例中，至少一种所述预设激励频率为使所述零序电流互感器进入深度饱和状态的激励频率。
在一个实施例中，每种所述预设激励频率均为使所述零序电流互感器进入深度饱和状态的激励频率。
在一个实施例中，所述产生至少两种预设激励频率的激励信号包括：每隔至少一个周期切换一次所述预设激励频率。
在一个实施例中，所述方法还包括：
将所述漏电电流信号产生的电压与预设电压相比较，以产生反馈信号，根据所述反馈信号调节所述激励信号的频率。
本发明实施例又一方面提供一种充电设备，所述充电设备包括上述漏电检测装置；以及，连接所述漏电检测装置的动作机构，用于在接收到所述报警信号时分断供电线路。
本发明实施例的漏电检测装置、漏电检测方法和充电设备通过至少两种预设激励频率的激励信号驱动零序电流互感器，能够提高漏电电流信号检测的准确性。
附图说明
通过结合附图对本申请实施例进行更详细的描述，本申请的上述以及其它目的、特征和优势将变得更加明显。附图用来提供对本申请实施例的进一步理解，并且构成说明书的一部分，与本申请实施例一起用于解释本申请，并不构成对本申请的限制。在附图中，相同的参考标号通常代表相同部件或步骤。
图1是本发明一个实施例的A型和AC型漏电检测装置的电路图；
图2是本发明一个实施例的B型漏电检测装置的磁化曲线的示意图；
图3是本发明一个实施例的外部磁场影响磁化曲线的示意图；
图4是本发明一个实施例的漏电检测装置的示意图；
图5是本发明一个实施例的零序电流互感器进入深度饱和状态的波形图；
图6是本发明一个实施例的零序电流互感器进入浅饱和状态的波形图；
图7是本发明一个实施例的开环跳频的示意图；
图8是本发明一个实施例的漏电检测方法的示意性流程图。
具体实施方式
在下文的描述中，给出了大量具体的细节以便提供对本发明更为彻底的理解。然而，对于本领域技术人员而言显而易见的是，本发明可以无需一个或多个这些细节而得以实施。在其他的例子中，为了避免与本发明发生混淆，对于本领域公知的一些技术特征未进行描述。
应当理解的是，本发明能够以不同形式实施，而不应当解释为局限于这里提出的实施例。相反地，提供这些实施例将使公开彻底和完全，并且将本发明的范围完全地传递给本领域技术人员。在附图中，为了清楚，层和区的尺寸以及相对尺寸可能被夸大。自始至终相同附图标记表示相同的元件。
应当明白，当元件或层被称为“在...上”、“与...相邻”、“连接到”或“耦合到”其它元件或层时，其可以直接地在其它元件或层上、与之相邻、连接或耦合到其它元件或层，或者可以存在居间的元件或层。相反，当元件被称为“直接在...上”、“与...直接相邻”、“直接连接到”或“直接耦合到”其它元件或层时，则不存在居间的元件或层。应当明白，尽管可使用术语第一、第二、第三等描述各种元件、部件、区、层和/或部分，这些元件、部件、区、层和/或部分不应当被这些术语限制。这些术语仅仅用来区分一个元件、部件、区、层或部分与另一个元件、部件、区、层或部分。因此，在不脱离本发明教导之下，下面讨论的第一元件、部件、区、层或部分可表示为第二元件、部件、区、层或部分。
空间关系术语例如“在...下”、“在...下面”、“下面的”、“在...之下”、“在...之上”、“上面的”等，在这里可为了方便描述而被使用从而描述图中所示的一个元件或特征与其它元件或特征的关系。应当明白，除了图中所示的取向以外，空间关系术语意图还包括使用和操作中的器件的不同取向。例如，如果附图中的器件翻转，然后，描述为“在其它元件下面”或“在其之下”或“在其下”元件或特征将取向为在其它元件或特征“上”。因此，示例性术语“在...下面”和“在...下”可包括上和下两个取向。器件可以另外地取向(旋转90度或其它取向)并且在此使用的空间描述语相应地被解释。
在此使用的术语的目的仅在于描述具体实施例并且不作为本发明的限制。在此使用时，单数形式的“一”、“一个”和“所述/该”也意图包括复数形式，除非上下文清楚指出另外的方式。还应明白术语“组成”和/或“包括”，当在该说明书中使用时，确定所述特征、整数、步骤、操作、元件和/或部件的存在，但不排除一个或更多其它的特征、整数、步骤、操作、元件、部件和/或组的存在或添加。在此使用时，术语“和/或”包括相关所列项目的任何及所有组合。
为了彻底理解本发明，将在下列的描述中提出详细的结构，以便阐释本发明提出的技术方案。本发明的优选实施例详细描述如下，然而除了这些详细描述外，本发明还可以具有其他实施方式。
RCD(Residual Current Device，剩余电流检测器件)等漏电检测装置分为AC型漏电检测装置、A型漏电检测装置和B型漏电检测装置，其中：
AC型漏电检测装置能够检测AC型的交流漏电电流，当线路中存在AC型的交流漏电，并且漏电电流达到设定的阈值后，AC型漏电检测装置会向外部的工作机构发出TRIP(脱扣)报警信号，以分断主线路。
A型漏电检测装置除了能够检测AC型的交流漏电外，还能检测A0、A90、A135等脉动直流漏电，当线路中的AC型漏电或A型漏电电流达到所设定的阈值时，A型漏电检测装置会向外部的触发机构发出TRIP报警信号，以分断主线路；
B型漏电检测装置既有AC型和A型漏电模块的检测功能，又具有检测2P-DC(两相整流)、3P-DC(三相整流)、S-DC(平滑直流)以及F型(10Hz、50Hz、1000Hz)复合波的能力，当上述的漏电电流值达到预设阈值时，B型漏电检测装置会向外部的触发机构发出TRIP报警信号，以分断主线路。
B型漏电检测装置的检测原理完全不同于A型和AC型的漏电检测装置。如图1所示，A型和AC型的漏电检测装置的原理是完全被动式地检测线路中的漏电电流；而B型漏电检测装置需要有外部的激励频率去驱动ZCT(零序电流互感器)线圈，使得其磁芯磁化，磁化曲线如图2所示。
因此，B型漏电电流检测装置的原理如图3所示。外部磁场的影响体现在H轴上的变化，就意味着激励信号驱动ZCT磁芯磁化时电流发生了变化，通过检测采样电阻上的电压，就可以获得包含激励信号在内的电压信息，这个电压信息同样包含了漏电电流产生的外部磁场的信息；通过滤除激励信号 的信息，就可以获得外部磁场的信息，从而获得漏电电流信号的信息，实现了交直流漏电电流信号检测的功能。
根据激励频率是否存在反馈，B型漏电检测装置的原理可分为开环式和闭环式，其中：
开环式的漏电检测原理为：激励电路的激励频率由振荡电路产生，振荡的频率根据不同互感器的特性和驱动电流的大小来综合决定，激励频率固定，无法在应用的过程中实时调整激励频率；
闭环式的漏电检测原理为：激励电路的激励频率与ZCT的参数相关，在应用的过程中根据电流的大小产生反馈信号，并根据反馈信号调整激励电流的频率，直到电路处于稳定状态。
开环式的漏电检测装置无法在应用的过程中实时调整激励频率，当通过采样电阻采样漏电电流时，就会面临漏电电流频率较大(例如大于1K Hz)时TRIP电流阈值过小的问题。
闭环式的漏电检测装置的激励电路受剩磁Br的影响较大，尤其是在大的漏电电流冲击后，再去连续地测量漏电电流值，会有较大的偏差存在，严重影响精度；另外，在出现较大漏电电流后，闭环式的漏电检测装置的会发生激励无法起振的问题。
基于此，本发明实施例将跳频技术应用在漏电检测装置中，具体应用于需要有激励信号的B型漏电检测模块，其中跳频主要是指激励频率的跳动应用。本发明实施例用变频激励电路去驱动ZCT线圈，激励电路能够产生多种频率的激励信号，用多种频率的激励信号分时段地、交替地驱动ZCT进行周期性磁化，并保证不同激励频率下ZCT都能很好地完成周期性的磁化，从而解决上述开环式和闭环式漏电检测装置中存在的问题。
下面结合附图，对本发明实施例的漏电检测装置、漏电检测方法和充电设备进行详细说明。在不冲突的情况下，下述的实施例及实施方式中的特征可以相互组合。
参见图4，本发明实施例的漏电检测装置至少包括零序电流互感器401、采样电阻402、激励驱动403和控制电路404，其中，零序电流互感器401用于感应漏电电流信号；激励驱动403和采样电阻402，分别连接零序电流互感器401；控制电路404，分别连接激励驱动403和采样电阻402，控制电路 404包括：连接激励驱动403的变频激励电路，用于产生至少两种预设激励频率的激励信号，并通过激励驱动403将至少两种预设激励频率的激励信号交替施加在零序电流互感器401上；连接采样电阻402的变频采样电路，用于以与激励频率相对应的采样频率对采样电阻402进行采样，以获得漏电电流信号；连接变频采样电路的比较电路，用于将漏电电流信号与预设阈值进行比较，并在漏电电流信号大于预设阈值时生成报警信号。
由于本发明实施例的漏电检测装置采用的是强制激励电路结构，且采用跳频技术、交替性地产生不同预设激励频率的激励信号去激励零序电流互感器401，因此能够解决开环式漏电检测装置中存在的、在单一激励频率下漏电电流频率较大时容易将交流漏电电流信号识别为直流漏电电流信号的问题，以及由此导致的预设阈值过低的问题；由于本发明实施例采用的是强制激励电路，因而也不存在闭环式漏电检测装置中存在的激励无法起振的问题。
本发明实施例的漏电检测装置为B型漏电检测装置，变频激励电路生成激励信号去驱动零序电流互感器401的线圈，使得其磁芯磁化。其中，零序电流互感器401用于检测线路中的漏电电流大小，具体包括磁芯、护壳和线圈。为了使零序电流互感器401能够更适用于调频式的激励方式，更易于进入下文所述的深度饱和状态，本发明实施例的零序电流互感器401的磁芯满足以下条件：磁芯的磁饱和强度Bs≤1.2T，磁导率u>80000，加纵磁后的矫顽力Hc<4.5A/m。进一步地，磁芯的横截面积Ac的大小与采样电阻的大小、激励频率的大小以及工作电压相匹配，具体可以通过以下公式计算：
Figure PCTCN2022092029-appb-000001
在公式(1)中，f为激励频率，V ext为激励信号的激励电压幅值，A c为磁芯的横截面积，N为磁芯的匝比系数，B m为最大磁感应强度。
本发明实施例的漏电检测装置采用磁通门技术，通过激励信号使得其磁芯磁化；同时，当漏电电流信号产生外部磁场时，通过滤除激励信号的信息，就可以获得外部磁场的信息，从而获得漏电电流信号的信息。参见图2，示例性地，磁化过程的原理为：如果将铁磁物质沿磁化曲线OS由完全去磁状态磁化到饱和Bs，此时如将外磁场H减小，B值将不再按照原来的初始磁化曲线(OS)减小，而是更加缓慢地沿较高的B减小，这是因为发生刚性转动的磁畴保留了外磁场方向。即使外磁场H＝0时，B也不等于0，即尚有剩余的磁感应强度Br存在。这种磁化曲线与退磁曲线不重合特性称为磁化的不可 逆性。磁感应强度B的改变滞后于磁场强度H的现象称为磁滞现象。
如要使B减少，必须施加一个与原磁场方向相反的磁场强度-H，当这个反向磁场强度增加到-Hc时，才能使磁介质中B＝0。这并不意味着磁介质恢复了杂乱无章状态，而是一部分磁畴仍保留原磁化磁场方向，而另一部分在反向磁场作用下改变为外磁场方向，两部分相等时，合成磁感应强度为零。如果再继续增大反向磁场强度，铁磁物质中反转的磁畴增多，反向磁感应强度增加，随着-H值的增加，反向的B也增加。当反向磁场强度增加到-Hs时，则B＝-Bs达到反向饱和。如果使-H＝0，B＝-Br，要使-Br为零，必须加正向HC。如H再增大到Hs时，B达到最大值Bs，磁介质又达到正向饱和。这样磁场强度的变化过程为Hs—0—-HC—-Hs—0—HC—Hs,相应地,磁感应强度的变化过程为Bs—Br—0—-BS—-Br—0—Bs，从而形成了一个对原点对称的回线，称为饱和磁滞回线，或最大磁滞回线。
如图3所示，在磁化过程中，若没有外部磁场影响，则磁场始终处于平衡状态，当由于漏电电流信号I(交流漏电电流信号或直流漏电电流信号)的存在而产生外部磁场时，外部磁场会打破磁化原有的磁场平衡，磁化曲线会在横轴(H轴)上左右移动。磁场的变化会影响会导致零序电流互感器401的线圈中产生的电流发生变化。
本发明实施例采用至少两种不同预设激励频率的激励信号交替性地激励零序电流互感器401。零序电流互感器401连接控制电路404，控制电路404可以实现为MCU(微控制单元)，也可以实现为具有类似功能的其它控制单元或者电路，激励信号由控制电路404中的变频激励电路产生，每种频率的开始输出和停止输出由变频激励电路精确控制，不同的频率之间采用无缝切换的方式进行切换。同时，由于变频激励电路自身的电流驱动能力较弱，因此在变频激励电路与零序电流互感器401之间连接有激励驱动403，通过激励驱动403来增加电流输出能力，实现类似放大器的功能。
本发明实施例具体地可以采用开环式的磁通门技术，即采用固定的至少两种预设激励频率的激励信号去激励零序电流互感器401，从而避免闭环式的磁通门技术中存在的激励无法起振的问题。但可选地，本发明实施例也可以采用闭环式的磁通门技术，即控制电路404还包括分别连接变频采样电路和激励电路的反馈电路，用于将漏电电流信号在采样电阻上产生的电压与预设电压相比较，以产生反馈信号，并将反馈信号反馈至激励电路；激励电路 用于根据反馈信号调节预设激励频率的大小。
进一步地，本发明实施例将开环跳频技术与零序电流互感器深度饱和性能相结合，以提高漏电检测装置的性能。具体地，至少一种预设激励频率为使零序电流互感器401进入深度饱和状态的激励频率。进一步地，变频激励电路生成的每种预设激励频率均为使零序电流互感器401进入深度饱和状态的激励频率。当激励信号使零序电流互感器401处于深度饱状态时，零序电流互感器401的性能受剩磁Br的影响就会非常小，甚至可以忽略，因而不存在在大的漏电电流过后，测量精度受影响的问题，从而能够减小开环和闭环式漏电检测中由剩磁导致的测量误差，提高测量精度。
为了便于理解，参见图5、图6，其中图5是零序电流互感器401进入深度饱和状态时，在采样电阻402上抓取的波形信息，图6是零序电流互感器401进入浅饱和状态时，在采样电阻402上抓取的波形信息。
其中，参见图5，当激励信号的驱动使零序电流互感器401进入深度饱和时，采样电阻402上抓取的波形在纵轴上表现为存在平整区域，而且在纵轴的正负半轴上都存在一段平整时间。在纵轴的正负半轴上，整个平整区域的理论值呈对称分布，且平整区域的时间长度一般大于当前激励频率周期的5％。相比而言，参见图6，当激励信号的驱动使零序电流互感器401进入浅饱和时，采样电阻402上抓取的波形中只有一段尖峰区域进入较为深度的饱和，该尖峰区域在纵轴的正负半轴上也呈对称分布，但进入饱和的时间非常短，一般仅占当前激励频率周期的5％以下。
由图5、图6可知，在零序电流互感器401不受外界磁场的影响的情况下(地磁场除外)，其深度饱和状态在采样电阻上体现的波形，必有一段时间内的输出的电压达到激励驱动403的最高输出电压，且会持续一段时间，时间长度一般大于当前激励频率周期的5％以上；浅饱和状态在采样电阻上体现的波形，最多只有一个尖峰的时间达到激励驱动403的最高输出电压，这也就意味着浅饱和状态在采样电阻上体现的波形的最高输出电压必定小于深度饱和时在采样电阻上体现的波形电压，至多仅有峰值时的一瞬间(小于激励频率的周期的5％)等于深度饱和时的电压。
由于在深度饱和状态下，零序电流互感器401在一个激励周期内始终有一段时间(大于5％)处于饱和，因此零序电流互感器401本身受剩磁的影响会非常小，从而使得在非常大(几十、几百安培以上)的漏电电流对零序电 流互感器401冲击以后，由于变频激励电路会强制驱动零序电流互感器401按照类似图2的方式进行磁化，驱动互感器达到深度饱和状态，从而消除了剩磁的不利影响，避免剩磁造成磁化曲线偏移。相比而言，若激励电流使零序电流互感器401进入浅饱和状态，由于激励驱动无法使零序电流互感器401达到100％的深度饱和状态，剩磁的影响将不能完全被磁化掉，如果大的漏电电流此时对零序电流互感器401进行冲击，将造成剩磁不断累积，最终会造成整个被磁化的平衡的磁场在没有外界磁场影响的情况下(地磁场除外)出现如图3所示的偏移，最终导致漏电检测装置出现较大误差，造成动作机构误动作，从而分断本该正常工作的主线路。
由于深度饱和能够保证零序电流互感器401在激励信号的驱动下能100％的进入饱和，而浅饱和是一种峰值饱和方式，不能很好地保证零序电流互感器401完全进入饱和状态，相反，有可能未能进入所需的饱和，例如只进入了80％的饱和状态。因此，较佳地，变频激励电路生成的每种激励频率都能保证有足够的能力去驱动零序电流互感器401进入上文中所述的深度饱和状态。但在一些实施例中，也可以有部分激励频率能够驱动零序电流互感器401进入深度饱和状态，其余激励频率则可以驱动零序电流互感器401进入浅饱和状态，通过能够驱动零序电流互感器401进入深度饱和状态的激励频率去消除剩磁的影响。例如，当存在三种预设激励频率时，可以是三种预设激励频率均为零序电流互感器401进入深度饱和状态的激励频率，也可以是两种预设激励频率工作于深度饱和状态，其中一种预设激励频率工作于浅饱和状态。
零序电流传感器401还连接采样电阻402，采样电阻402连接控制电路404中的变频采样电路，变频采样电路用于采集采样电阻402上的电压信号，通过电压信号换算出电流信号的大小。
在激励电路输出不同的激励频率的同时，变频采样电路也按照与输出的预设激励频率对应的采样频率采集采样电阻上的电压。其中，采样频率与预设激励频率相等，或者采样频率是预设激励频率的N倍，N为不小于2的整数。
由于对采样电阻上的采样是变频方式的采样，不同的预设激励频率下有着不同的采样频率，而且这种变频采样的方式不停地循环往复进行，若有三种不同的预设激励频率，就意味着有至少三种不同的采样频率，类似地，若 有五种甚至更多种预设激励频率，则意味着有五种甚至更多种采样频率。
进一步地，变频采样电路还包括数字低通滤波器，用于在接收到的信号中滤除激励信号的信息，保留漏电电流信号的信息。在以往的漏电检测装置中，若交流漏电电流信号的频率与激励频率相同或交流漏电频率是采样频率的整数倍，则在进行阈值判断时，会出现将交流信号判断成直流信号的问题，因此需要采用高阶滤波器。而根据本发明实施例的漏电检测装置，由于采样频率不断发生变化，相当于以一种自动移频或移相的方式在对漏电电流信号进行着采样，避免了采用同一种采样频率进行采样时，在交流漏电频率是采样频率的整数倍的情况下，将交流漏电误判为直流漏电的可能性，消除了低通数字滤波器在面对与激励频率相同的交流漏电信号时存在的盲区问题，也就消除了漏电电流频率较大(例如大于1K Hz)时出现的某些频段高频阈值过小的问题。由于采用数字滤波器能够解决上述问题，因而本发明实施例的漏电检测装置不需要高阶的低通滤波器，基于数字低通滤波器即可实现外部硬件高阶低通滤波器的功能，节省了硬件电路的成本和PCB板的空间。
参见图7，示例性地，变频激励电路可以交替产生至少三种不同预设激励频率的激励信号，每种激励信号输出一个或多个周期，即变频激励电路每隔至少一个周期切换一次预设激励频率，各个预设激励频率的激励信号之间无缝切换。以1K Hz、2K Hz和3K Hz三种预设激励频率为例，变频激励电路交替式第输出1K Hz、2K Hz和3K Hz的激励频率，通过激励驱动使得零序电流互感器401进入上文中所述的深度饱和状态。示例性地，三种激励频率的激励信号的工作逻辑如下：首先，输出1K Hz的激励信号三个周期，接着输出2K Hz的激励信号三个周期，再接着输出3K Hz的激励信号三个周期，随后重新输出1K Hz的激励信号三个周期，依次循环往复。
需要注意的是，本发明实施例的预设激励频率不限于三种，也可以是两种或更多种，并且，本发明实施例对预设激励频率的输出顺序不做限制，例如可以是如图7所示的1KHz、2KHz、3KHz的顺序依次跳频，也可以是2KHz、1KHz、3KHz的顺序或3KHz、2KHz、1KHz的顺序，跳频的顺序可以是固定的，也可以是随机的。每种预设激励频率的输出周期数可以是三个周期，也可以是一个、两个或更多个周期，并且每种预设频率的输出周期数可以相同，也可以不同。输出的周期数越多，采样时间越长，采样越稳定；输出的周期数越少，频率切换越快，越能避免误检。一般来说，当输出周期数为五至六 个周期时，能在稳定性和准确性之间实现较好的平衡。
变频采样电路连接比较电路，比较电路根据采样得到的漏电电流信号判断零序电流互感器401中是否有漏电电流流过，并判断漏电电流信号的大小是否大于预设阈值。当漏电电流信号大于预设阈值时，比较电路输出报警信号。其中，报警信号可以包括TRIP信号，用于控制动作机构分断供电线路。动作机构是用来触发外部机械脱扣装置的机构，动作机构可以是纯机械类的，也可以是机械和电子混合的，也可以是纯电子类的。动作机构可以与控制电路404直接连接，也可以与外部设备连接。
控制电路404还可以包括外部通信接口，用于实现与外部设备的通信，在漏电检测装置与外部设备之间接收和发送各种信息，报警信号也可以包括发送至外部设备的报警信号。
在一个实施例中，比较电路还连接模数转换电路，模数转换电路用于根据漏电电流信号的类型和大小进行模数转换，以生成表示漏电电流信号大小的模拟信号，即脉冲信号。脉冲信号除了能够表示漏电电流信号大小以外，还能够表示漏电电流信号的波形信息、漏电电流信号的频率等。示例性地，模数转换电路可以根据漏电电流信号的大小生成具有对应占空比的PWM(Pulse Width Modulation，脉宽调制)信号。PWM信号的占空比即一个脉冲周期内高电平在整个周期中所占的比例，漏电电流信号的大小越高，则模数转换电路生成的PWM信号的占空比越高，客户端根据PWM信号的占空比可以确定漏电电流信号的大小。进一步地，针对不同类型的漏电电流信号，可以通过不同的外部通信端口输出PWM信号，使外部设备能够根据输出PWM信号的外部通信端口确定漏电电流信号的类型，从而实现通过数字信号表示漏电电流信号大小和信号类型的目的，无需在客户端配置额外的算法。示例性地，不同模数转换电路生成的PWM信号的频率可以相同，也可以不同，在一些实施例中，除了通过PWM信号的占空比表示漏电电流信号的大小以外，还可以通过PWM信号的频率表示交流漏电电流信号的频率。
在一些实施例中，控制电路404还包括自检电路，用于进行系统自检，以获得故障状态信号。进一步地，控制电路404还包括逻辑电路，连接自检电路，用于根据故障状态信号生成高电平信号和/或低电平信号的组合信号，并通过外部通信端口输出组合信号，以提示外部设备故障状态类型。
基于上面的描述，本发明实施例的漏电检测装置通过至少两种预设激励 频率的激励信号驱动零序电流互感器，能够避免在交流漏电电流信号频率较高时将交流信号误检为直流信号，进而避免在高频段下阈值过小的问题，提高漏电电流信号检测的准确性。
本发明实施例另一方面提供了一种漏电检测方法，该漏电检测方法可以由参照图4描述的漏电检测装置来实现。以下仅对描述漏电检测方法的主要步骤进行描述，更多的细节可以参照上文。
图8示出了根据本发明一个实施例的漏电检测方法800的示意性流程图。如图8所示，本发明实施例的漏电检测方法800包括如下步骤：
在步骤S810，获取零序电流互感器感应的漏电电流信号；
在步骤S820，产生至少两种预设激励频率的激励信号，并将所述至少两种预设激励频率的激励信号交替施加在所述零序电流互感器上；
在步骤S830，以与所述预设激励频率相对应的采样频率进行采样，以获得漏电电流信号；
在步骤S840，将所述漏电电流信号与预设阈值进行比较，并在所述漏电电流信号大于所述预设阈值时生成报警信号；
在步骤S850，输出所述报警信号。
在一个实施例中，至少一种预设激励频率为使零序电流互感器进入深度饱和状态的激励频率。进一步地，每种预设频率均为使零序电流互感器进入深度饱和状态的激励频率。
在一个实施例中，产生至少两种预设激励频率的激励信号包括：每隔至少一个周期切换一次所述预设激励频率。
在一个实施例中，所述方法还包括：将所述漏电电流信号产生的电压与预设电压相比较，以产生反馈信号，根据所述反馈信号调节所述激励信号的频率。
根据本发明实施例的漏电检测方法通过至少两种预设激励频率的激励信号驱动零序电流互感器，能够避免在交流漏电电流信号频率较高时将交流信号误检为直流信号，进而避免在高频段下阈值过小的问题，提高漏电电流信号检测的准确性。
本发明实施例还提供一种充电设备，包括如上所述的漏电检测装置和连接所述漏电检测装置的动作机构，动作结构用于在漏电检测装置检测到漏电 电流信号的大小大于预设阈值时分断供电线路。本发明实施例的充电设备可以实现为充电桩、充电枪等用于为车辆充电的充电设备，漏电检测装置可以为板载式的漏电检测装置，其可以直接安装在充电设备的PCB板上，当充电设备为电动汽车进行充电时，漏电检测装置可以用来检测充电过程中漏电电流的大小是否超过阈值，在漏电电流的大小超过阈值时向PCB板上的MCU或者其它器件发出报警信号，以执行停止充电的命令，并通过动作机构分断充电线路，例如断开已闭合的继电器或者断路器机构等。
在此处所提供的说明书中，说明了大量具体细节。然而，能够理解，本发明的实施例可以在没有这些具体细节的情况下实践。在一些实例中，并未详细示出公知的方法、结构和技术，以便不模糊对本说明书的理解。
类似地，应当理解，为了精简本发明并帮助理解各个发明方面中的一个或多个，在对本发明的示例性实施例的描述中，本发明的各个特征有时被一起分组到单个实施例、图、或者对其的描述中。然而，并不应将该本发明的方法解释成反映如下意图：即所要求保护的本发明要求比在每个权利要求中所明确记载的特征更多的特征。更确切地说，如相应的权利要求书所反映的那样，其发明点在于可以用少于某个公开的单个实施例的所有特征的特征来解决相应的技术问题。因此，遵循具体实施方式的权利要求书由此明确地并入该具体实施方式，其中每个权利要求本身都作为本发明的单独实施例。
本领域的技术人员可以理解，除了特征之间相互排斥之外，可以采用任何组合对本说明书(包括伴随的权利要求、摘要和附图)中公开的所有特征以及如此公开的任何方法或者设备的所有过程或单元进行组合。除非另外明确陈述，本说明书(包括伴随的权利要求、摘要和附图)中公开的每个特征可以由提供相同、等同或相似目的替代特征来代替。
此外，本领域的技术人员能够理解，尽管在此所述的一些实施例包括其它实施例中所包括的某些特征而不是其它特征，但是不同实施例的特征的组合意味着处于本发明的范围之内并且形成不同的实施例。例如，在权利要求书中，所要求保护的实施例的任意之一都可以以任意的组合方式来使用。
应该注意的是上述实施例对本发明进行说明而不是对本发明进行限制，并且本领域技术人员在不脱离所附权利要求的范围的情况下可设计出替换实施例。在权利要求中，不应将位于括号之间的任何参考符号构造成对权利要求的限制。本发明可以借助于包括有若干不同元件的硬件以及借助于适当编 程的计算机来实现。在列举了若干装置的单元权利要求中，这些装置中的若干个可以是通过同一个硬件项来具体体现。单词第一、第二、以及第三等的使用不表示任何顺序。可将这些单词解释为名称。
以上所述，仅为本发明的具体实施方式或对具体实施方式的说明，本发明的保护范围并不局限于此，任何熟悉本技术领域的技术人员在本发明揭露的技术范围内，可轻易想到变化或替换，都应涵盖在本发明的保护范围之内。本发明的保护范围应以权利要求的保护范围为准。

Claims (15)

  1. 一种漏电检测装置，其特征在于，所述漏电检测装置包括：
    零序电流互感器，用于感应漏电电流信号；
    连接所述零序电流互感器的激励驱动和采样电阻；
    控制电路，连接所述激励驱动和所述采样电阻，所述控制电路包括：
    连接所述激励驱动的变频激励电路，用于产生至少两种预设激励频率的激励信号，并通过所述激励驱动将所述至少两种预设激励频率的激励信号交替施加在所述零序电流互感器上；
    连接所述采样电阻的变频采样电路，用于以与所述预设激励频率相对应的采样频率对所述采样电阻进行采样，以获得漏电电流信号；
    连接所述变频采样电路的比较电路，用于将所述漏电电流信号与预设阈值进行比较，并在所述漏电电流信号大于所述预设阈值时生成报警信号。
  2. 如权利要求1所述的漏电检测装置，其特征在于，至少一种所述预设激励频率为使所述零序电流互感器进入深度饱和状态的激励频率。
  3. 如权利要求2所述的漏电检测装置，其特征在于，每种所述预设激励频率均为使所述零序电流互感器进入深度饱和状态的激励频率。
  4. 如权利要求1所述的漏电检测装置，其特征在于，所述变频激励电路每隔至少一个周期切换一次所述预设激励频率。
  5. 如权利要求1所述的漏电检测装置，其特征在于，所述采样频率为所述预设激励频率的整数倍。
  6. 如权利要求1所述的漏电检测装置，其特征在于，所述零序电流互感器包括磁芯、护壳和线圈，所述磁芯为纳米晶磁芯。
  7. 如权利要求6所述的漏电检测装置，其特征在于，所述磁芯的磁饱和强度Bs≤1.2T，磁导率u>80000，加纵磁后的矫顽力Hc<4.5A/m。
  8. 如权利要求1所述的漏电检测装置，其特征在于，所述变频采样电路包括数字低通滤波器，所述数字低通滤波器用于滤除所述激励信号的信息。
  9. 如权利要求1所述的漏电检测装置，其特征在于，所述控制电路还包括分别连接所述变频采样电路和所述激励电路的反馈电路，用于将所述漏电电流信号在所述采样电阻上产生的电压与预设电压相比较，以产生反馈信号，并将所述反馈信号反馈至所述变频激励电路；所述变频激励电路用于根据所述反馈信号调节所述预设激励频率的大小。
  10. 一种漏电检测方法，其特征在于，所述方法包括：
    获取零序电流互感器感应的漏电电流信号；
    产生至少两种预设激励频率的激励信号，并将所述至少两种预设激励频率的激励信号交替施加在所述零序电流互感器上；
    以与所述预设激励频率相对应的采样频率进行采样，以获得漏电电流信号；
    将所述漏电电流信号与预设阈值进行比较，并在所述漏电电流信号大于所述预设阈值时生成报警信号；
    输出所述报警信号。
  11. 如权利要求10所述的漏电检测方法，其特征在于，至少一种所述预设激励频率为使所述零序电流互感器进入深度饱和状态的激励频率。
  12. 如权利要求11所述的漏电检测方法，其特征在于，每种所述预设激励频率均为使所述零序电流互感器进入深度饱和状态的激励频率。
  13. 如权利要求10所述的漏电检测方法，其特征在于，所述产生至少两种预设激励频率的激励信号包括：每隔至少一个周期切换一次所述预设激励频率。
  14. 如权利要求10所述的漏电检测方法，其特征在于，还包括：
    将所述漏电电流信号产生的电压与预设电压相比较，以产生反馈信号，根据所述反馈信号调节所述激励信号的频率。
  15. 一种充电设备，其特征在于，所述充电设备包括：
    如权利要求1至9中任意一项所述的漏电检测装置；
    以及，连接所述漏电检测装置的动作机构，用于在接收到所述报警信号时分断供电线路。
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