High-reliability overvoltage switch-out detection method for single-phase intelligent electric meter

Abstract

The invention provides a high-reliability overvoltage switching-out detection method for a single-phase intelligent electric meter, and the method comprises the steps: obtaining the state information of a built-in relay, and judging whether the built-in relay is in a switching-on state or not; if the built-in relay is in a closed state, collecting a ripple signal to calculate a current voltage value of an input terminal, and judging whether an overvoltage value exceeds a preset overvoltage threshold value or not; if yes, the built-in relay is controlled to be switched off according to the overvoltage duration; if so, judging whether the overvoltage is recovered or not; and if the overvoltage is recovered, the built-in relay is controlled to be switched on. According to the circuit and the method, when the built-in relay is switched on, whether the voltage of the input terminal is in an overvoltage condition or not can be rapidly detected in real time, the built-in relay is controlled to be switched on after the overvoltage is recovered, user loss can be effectively reduced, and electricity utilization safety is greatly improved.

Description

Technical Field

[0001] The present invention relates to the field of single-phase smart electric meters, and more specifically, to a high-reliability overvoltage switch-off detection method for single-phase smart electric meters. Background Art

[0002] With the development of smart meters, the functional requirements of meters are getting higher and higher. As an important part of the smart grid, smart energy meters are not only used as a measurement tool, but also bear the responsibility of ensuring the safe use of electricity by users. For example, if the user's overload or the voltage of the grid is unstable, affecting the user's power safety, the meter should be turned off in time to disconnect the user from the grid.

[0003] At present, the scheme for protecting the meter is mainly to remotely shut down the meter through the master station. If the user side detects an overload, overvoltage or other event, it will first report to the master station, wait for the master station to respond, and after confirming the fault with the user side, the master station will issue a remote shutdown command to shut down the meter.

[0004] The above-mentioned switching-off methods have low requirements on the switching-off response time, which may cause losses of varying degrees. When the meter is switched off and the fault disappears, when it is necessary to close the switch, there are still problems such as inconvenient closing methods. Summary of the invention

[0005] The purpose of the present invention is to address the control problems in the protection of the existing smart meter opening and closing, and to propose a high-reliability overvoltage switch detection circuit and method for single-phase smart meters. The circuit and method can quickly detect whether the input terminal voltage is overvoltage in real time when the built-in relay is closed, and control the built-in relay to close after the overvoltage is restored.

[0006] The technical solution of the present invention is:

[0007] The present invention provides a high-reliability overvoltage switch detection circuit for a single-phase smart electric meter. Outside the electric energy meter, a wiring terminal L2 is connected to an incoming line contact of a user-side main switch air switch MCB, an outgoing line contact of the user-side main switch air switch MCB is connected in series to one end of an electric load RL, and the other end of the electric load RL is connected to a wiring terminal N4.

[0008] The detection circuit is built into the electric energy meter, including: resistors R1-R5, diodes D1, D2, relays K1, K2 and capacitors C1, C2, among which:

[0009] The wiring terminal L is connected to one end of the parallel resistor R5 and capacitor C1 and is grounded at the same time, the other end of the parallel resistor R5 and capacitor C1 is connected in series with the resistor R1 and the cathode of the diode D1, the anode of the diode D1 is connected to the wiring terminal L2, and the relay K1 is connected between the wiring terminals L and L2;

[0010] The terminal N is connected in series with the resistor R2 and the cathode of the diode D2, the anode of the diode D2 is connected in series with one end of the resistor R3, the other end of the resistor R3 is connected to one end of the parallel resistor R4 and the capacitor C2, the other end of the parallel resistor R4 and the capacitor C2 is grounded, and the relay K2 is connected between the terminal N and N4;

[0011] The non-grounded end of the parallel resistor R5 and capacitor C1 outputs a ripple signal U ADC2 , the parallel resistor R4 and the non-grounded end of the capacitor C2 output ripple signal U ADC4 To the MCU, the MCU determines the state of the built-in relay of the electric energy meter based on the ripple signal, the input terminal voltage in the closed state and the voltage at the output terminal of the electric energy meter in the open state; the control signal end of the relays K1 and K2 is connected to the control signal output end of the MCU.

[0012] A high-reliability overvoltage switch-off detection method for a single-phase smart meter, comprising:

[0013] Obtaining status information of built-in relays K1 and K2 to determine whether the built-in relays are in a closed state;

[0014] If the built-in relay is in the closed state, the ripple signal U is collected. ADC4 The voltage value is based on the reference slope K adc Calculate the current voltage value of the input terminal; calculate the overvoltage value based on the current voltage value of the input terminal and the rated voltage; determine whether the overvoltage value exceeds a preset overvoltage threshold; if exceeded, control the built-in relay to switch off according to the overvoltage duration;

[0015] If the built-in relay is in the off state, the current voltage value of the input terminal is collected by the metering chip; it is determined whether the overvoltage is restored; if the overvoltage is restored, the built-in relay is controlled to close.

[0016] Furthermore, the reference slope K adc The acquisition includes:

[0017] Close relays K1 and K2 and input the preset rated voltage U AC Calibrate the meter and detect the ripple signal U ADC4 The voltage value is calculated, and the corresponding slope k is used as the reference slope K adc , U ADC4 ≈kU AC .

[0018] Furthermore, the ripple signal U ASC The cycle is 20ms, sampling is performed once every millisecond, and the average value of 20 samples is calculated as U ADC4 The voltage value is used to calculate the current voltage of the input terminal.

[0019] Further, the ripple signal U is obtained ADC4 The sum of the first-order difference of every two sampling data is within the preset range, according to the reference slope K adc Calculate the current voltage value U of the input terminal AC Use the following formula:

[0020] U AC =U ADC4 ×(K adc +(U ADC4 / 100)-5).

[0021] Furthermore, it is determined every 5 ms whether the overvoltage value exceeds a preset overvoltage threshold.

[0022] Further, controlling the built-in relay to switch off according to the overvoltage duration includes:

[0023] Start the timer and record the duration of overvoltage;

[0024] If the overvoltage duration exceeds a preset time threshold, the built-in relay is controlled to switch off.

[0025] Further, judging whether the overvoltage value exceeds a preset overvoltage threshold; if exceeded, controlling the built-in relay to switch off according to the overvoltage duration includes:

[0026] If the input voltage exceeds 115% of the rated voltage and lasts for more than 15s, the circuit breaker will be turned off;

[0027] If the input voltage exceeds 120% of the rated voltage and lasts for more than 3s, the circuit breaker will be turned off;

[0028] If the input voltage exceeds 130% of the rated voltage and lasts for more than 1s, the circuit breaker will be turned off;

[0029] If the input voltage exceeds 141% of the rated voltage and lasts longer than 0.3s, the circuit breaker will be turned off;

[0030] If the input voltage exceeds 152% of the rated voltage and lasts longer than 0.1s, the circuit breaker will be turned off.

[0031] Furthermore, judging whether the overvoltage is restored is specifically as follows:

[0032] Determining whether the current voltage value of the input terminal is lower than a preset recovery voltage threshold;

[0033] If the current voltage value of the input terminal is lower than the preset recovery voltage threshold, the circuit breaker is restored.

[0034] Furthermore, the sampling interval of the metering chip is 1s;

[0035] When the overvoltage duration is greater than the sampling interval of the metering chip, the current voltage value of the input terminal is obtained through the metering chip;

[0036] When the overvoltage duration is less than or equal to the sampling interval of the metering chip, the ripple signal U is collected. ADC4 The voltage value of the input terminal is calculated based on the voltage value;

[0037] The sampling interval of the metering chip is 1s.

[0038] Beneficial effects of the present invention:

[0039] In the present invention, built-in relays K1 and K2 are used as built-in relays, and their on and off can be uniformly controlled by MCU. The resistor mainly plays the role of resistive voltage division to reduce the AC power signal to an appropriate amplitude. The diode mainly plays the role of half-wave rectification. The capacitor mainly plays the role of energy storage capacitor to convert the half-wave signal into a continuous ripple signal with a stable period. The signal is then transmitted to the MCU for comprehensive judgment to determine the state of the built-in relay of the electric energy meter, the input terminal voltage in the closed state, and the voltage at the output terminal of the electric energy meter in the open state.

[0040] Other features and advantages of the present invention will be described in detail in the following detailed description. BRIEF DESCRIPTION OF THE DRAWINGS

[0041] The above and other objects, features and advantages of the present invention will become more apparent through a more detailed description of exemplary embodiments of the present invention in conjunction with the accompanying drawings, wherein like reference numerals generally represent like components throughout the exemplary embodiments of the present invention.

[0042] Figure 1 The schematic diagram of the overvoltage switch detection circuit of the present invention is shown.

[0043] Figure 2 The overvoltage switch detection circuit diagram of the present invention is shown. DETAILED DESCRIPTION

[0044] The preferred embodiments of the present invention will be described in more detail below with reference to the accompanying drawings. Although the preferred embodiments of the present invention are shown in the accompanying drawings, it should be understood that the present invention can be implemented in various forms and should not be limited to the embodiments set forth herein.

[0045] Example 1

[0046] like Figure 1 , 2 , showing the principle block diagram and circuit diagram of the overvoltage switch detection circuit of the present invention.

[0047] The present invention provides a high-reliability overvoltage switch detection circuit for a single-phase smart electric meter. Outside the electric energy meter, a wiring terminal L2 is connected to an incoming line contact of a user-side main switch air switch MCB, an outgoing line contact of the user-side main switch air switch MCB is connected in series to one end of an electric load RL, and the other end of the electric load RL is connected to a wiring terminal N4.

[0048] The detection circuit is built into the electric energy meter, including: resistors R1-R5, diodes D1, D2, relays K1, K2 and capacitors C1, C2, among which:

[0049] The wiring terminal L is connected to one end of the parallel resistor R5 and capacitor C1 and is grounded at the same time, the other end of the parallel resistor R5 and capacitor C1 is connected in series with the resistor R1 and the cathode of the diode D1, the anode of the diode D1 is connected to the wiring terminal L2, and the relay K1 is connected between the wiring terminals L and L2;

[0050] The terminal N is connected in series with the resistor R2 and the cathode of the diode D2, the anode of the diode D2 is connected in series with one end of the resistor R3, the other end of the resistor R3 is connected to one end of the parallel resistor R4 and the capacitor C2, the other end of the parallel resistor R4 and the capacitor C2 is grounded, and the relay K2 is connected between the terminal N and N4;

[0051] The non-grounded end of the parallel resistor R5 and capacitor C1 outputs a ripple signal U ADC2 , the parallel resistor R4 and the non-grounded end of the capacitor C2 output ripple signal U ADC4 To the MCU, the MCU determines the state of the built-in relay of the electric energy meter based on the ripple signal, the input terminal voltage in the closed state and the voltage at the output terminal of the electric energy meter in the open state; the control signal end of the relays K1 and K2 is connected to the control signal output end of the MCU.

[0052] Example 2

[0053] The present invention provides a high-reliability overvoltage switch-off detection method for a single-phase smart meter, comprising:

[0054] Obtaining status information of built-in relays K1 and K2 to determine whether the built-in relays are in a closed state;

[0055] If the built-in relay is in the closed state, the ripple signal U is collected. ADC4 The voltage value is based on the reference slope K adc Calculate the current voltage value of the input terminal; calculate the overvoltage value based on the current voltage value of the input terminal and the rated voltage; determine whether the overvoltage value exceeds a preset overvoltage threshold; if exceeded, control the built-in relay to switch off according to the overvoltage duration;

[0056] If the built-in relay is in the off state, the current voltage value of the input terminal is collected by the metering chip; whether the overvoltage is restored is determined; if the overvoltage is restored, the built-in relay is controlled to close. ;

[0057] The specific method for judging whether the overvoltage is restored is as follows:

[0058] Determining whether the current voltage value of the input terminal is lower than a preset recovery voltage threshold;

[0059] If the current voltage value of the input terminal is lower than the preset recovery voltage threshold, the circuit breaker is restored.

[0060] Among them, the reference slope K adc The acquisition includes: closing relays K1 and K2, inputting the preset rated voltage U AC Calibrate the meter and detect the ripple signal U ADC4 The voltage value is calculated, and the corresponding slope k is used as the reference slope K adc , U ADC4 ≈kU AC .

[0061] In one example, the ripple signal U ADC The cycle is 20ms, sampling is performed once every millisecond, and the average value of 20 samples is calculated as U ADC4 The voltage value is used to calculate the current voltage of the input terminal;

[0062] In order to avoid abnormal signals caused by power failure and manual drop, misjudgment of overvoltage conditions, and obtain the ripple signal U ASC4 The sum of the first-order difference of every two sampling data is within the preset range, according to the reference slope K adc Calculate the current voltage value U of the input terminal AC Use the following formula:

[0063] U AC =U ADC4 ×(K adc +(U ADC4 / 100)-5).

[0064] In one example, whether the overvoltage value exceeds a preset overvoltage threshold is determined every 5 ms; controlling the built-in relay to shut down according to the overvoltage duration includes: starting a timer to record the overvoltage duration; if the overvoltage duration exceeds the preset time threshold, controlling the built-in relay to shut down.

[0065] In this embodiment, the state information of the relays K1 and K2 in the electric energy meter is obtained through the detection circuit to obtain the relay state data and determine whether the relay is in the closed state.

[0066] If the relay is in the closed state, the ripple signal U is obtained ASC4 , the ripple signal U ASC4 The AC voltage U AC The signal is half-wave rectified by diode D2 and converted into a DC signal by charging and discharging capacitor C2. Resistors R3 and R4 are used to divide the DC signal to reduce the signal amplitude to an appropriate range. The resulting ripple signal U ADC4 .

[0067] With a period of 20ms, the ripple signal U is measured every 1ms. ADC4 Perform one sampling to obtain 20 sampling values ​​within one cycle. Calculate the average value of the 20 sampling values ​​as the ripple signal U ADC4 The voltage value of U ADC4 With input terminal AC voltage U AC According to U ADC4 with U AC The linear relationship is combined with the nonlinear compensation coefficient to calculate the real-time input terminal voltage value.

[0068] U AC =U ADC4 ×(K adc +(U ADC4 / 100)-5)

[0069] The calculated real-time input terminal voltage is compared with the overvoltage threshold to determine whether an overvoltage condition occurs. If the voltage exceeds the threshold, the relay is controlled to perform overvoltage protection.

[0070] Base slope K adc When the input rated voltage is 230V, the signal U ASC4 The voltage value is 0.498V, and the corresponding slope is 461, which is used as the reference slope Kad c .

[0071] On the basis of the linear relationship, the signal U ADC4 For every 0.1V increase in the voltage value, the slope increases by 1 as nonlinear compensation. The real-time input terminal voltage value is calculated according to the above formula, calculated every 5ms, and compared with the overvoltage threshold to determine whether an overvoltage condition occurs.

[0072] In one example, determining whether the overvoltage value exceeds a preset overvoltage threshold; if exceeded, controlling the built-in relay to switch off according to the overvoltage duration includes:

[0073] If the input voltage exceeds 115% of the rated voltage and lasts for more than 15s, the circuit breaker will be turned off;

[0074] If the input voltage exceeds 120% of the rated voltage and lasts for more than 3s, the circuit breaker will be turned off;

[0075] If the input voltage exceeds 130% of the rated voltage and lasts for more than 1s, the circuit breaker will be turned off;

[0076] If the input voltage exceeds 141% of the rated voltage and lasts longer than 0.3s, the circuit breaker will be turned off;

[0077] If the input voltage exceeds 152% of the rated voltage and lasts longer than 0.1s, the circuit breaker will be turned off.

[0078] In one example, the sampling interval of the metering chip is 1s; when the overvoltage duration is greater than the sampling interval of the metering chip, the current voltage value of the input terminal is obtained through the metering chip; when the overvoltage duration is less than or equal to the sampling interval of the metering chip, the voltage value of the ripple signal UADC4 is collected to calculate the current voltage value of the input terminal.

[0079] The embodiments of the present invention have been described above, and the above description is exemplary, not exhaustive, and is not limited to the disclosed embodiments. Many modifications and changes will be apparent to those skilled in the art without departing from the scope and spirit of the described embodiments.

Claims

1. A high-reliability overvoltage switch detection circuit for a single-phase smart meter. Outside the electric energy meter, the terminal L2 is connected to the incoming line contact of the user-side main switch air switch MCB, the outgoing line contact of the user-side main switch air switch MCB is connected in series to one end of the power load RL, and the other end of the power load RL is connected to the terminal N4. It is characterized in that The detection circuit is built into the electric energy meter, including: resistors R1-R5, diodes D1, D2, relays K1, K2 and capacitors C1, C2, among which: The wiring terminal L is connected to one end of the parallel resistor R5 and capacitor C1 and is grounded at the same time, the other end of the parallel resistor R5 and capacitor C1 is connected in series with the resistor R1 and the cathode of the diode D1, the anode of the diode D1 is connected to the wiring terminal L2, and the relay K1 is connected between the wiring terminals L and L2; The terminal N is connected in series with the resistor R2 and the cathode of the diode D2, the anode of the diode D2 is connected in series with one end of the resistor R3, the other end of the resistor R3 is connected to one end of the parallel resistor R4 and the capacitor C2, the other end of the parallel resistor R4 and the capacitor C2 is grounded, and the relay K2 is connected between the terminal N and N4; The non-grounded end of the parallel resistor R5 and capacitor C1 outputs a ripple signal U ADC2 , the parallel resistor R4 and the non-grounded end of the capacitor C2 output the ripple signal U ADC4 To the MCU, the MCU determines the state of the built-in relay of the electric energy meter based on the ripple signal, the input terminal voltage in the closed state and the voltage at the output terminal of the electric energy meter in the open state; the control signal end of the relays K1 and K2 is connected to the control signal output end of the MCU.

2. A high-reliability overvoltage shutdown detection method for a single-phase smart meter, using the circuit of claim 1, characterized in that: The method includes: Obtaining status information of built-in relays K1 and K2 to determine whether the built-in relays are in a closed state; If the built-in relay is in the closed state, the ripple signal U is collected. ADC4 The voltage value is based on the reference slope K adc Calculate the current voltage value of the input terminal; calculate the overvoltage value based on the current voltage value of the input terminal and the rated voltage; determine whether the overvoltage value exceeds a preset overvoltage threshold; if exceeded, control the built-in relay to switch off according to the overvoltage duration; If the built-in relay is in the off state, the current voltage value of the input terminal is collected by the metering chip; whether the overvoltage is restored is determined; if the overvoltage is restored, the built-in relay is controlled to close.

3. A high-reliability overvoltage switch-off detection method for a single-phase smart meter according to claim 2, characterized in that The reference slope K adc The acquisition includes: Close relays K1 and K2 and input the preset rated voltage U AC Calibrate the meter and detect the ripple signal U ADC4 The voltage value is calculated, and the corresponding slope k is used as the reference slope K adc ,U ADC4 ≈kU AC .

4. A high-reliability overvoltage shutdown detection method for a single-phase smart meter according to claim 2, characterized in that: The ripple signal U ADC The cycle is 20ms, sampling is performed once every millisecond, and the average value of 20 samples is calculated as U ADC4 The voltage value is used to calculate the current voltage of the input terminal.

5. A high-reliability overvoltage shutdown detection method for a single-phase smart meter according to claim 4, characterized in that Get the ripple signal U ADC4 The sum of the first-order difference of every two sampling data is within the preset range, according to the reference slope K adc Calculate the current voltage value U of the input terminal AC Use the following formula: IN AC =U ADC4 ×(K adc +(In ADC4 / 100)-5).

6. A high-reliability overvoltage shutdown detection method for a single-phase smart meter according to claim 2, characterized in that: Whether the overvoltage value exceeds a preset overvoltage threshold is determined every 5 ms.

7. A high-reliability overvoltage shutdown detection method for a single-phase smart meter according to claim 2, characterized in that: The controlling of the built-in relay to switch off according to the overvoltage duration comprises: Start the timer and record the duration of overvoltage; If the overvoltage duration exceeds a preset time threshold, the built-in relay is controlled to switch off.

8. A high-reliability overvoltage shutdown detection method for a single-phase smart meter according to claim 7, characterized in that: Determining whether the overvoltage value exceeds a preset overvoltage threshold; If the overvoltage is exceeded, the built-in relay is controlled to switch off according to the overvoltage duration, including: If the input voltage exceeds 115% of the rated voltage and lasts for more than 15s, the circuit breaker will be turned off; If the input voltage exceeds 120% of the rated voltage and lasts for more than 3s, the circuit breaker will be turned off; If the input voltage exceeds 130% of the rated voltage and lasts for more than 1s, the circuit breaker will be turned off; If the input voltage exceeds 141% of the rated voltage and lasts longer than 0.3s, the circuit breaker will be turned off; If the input voltage exceeds 152% of the rated voltage and lasts longer than 0.1s, the circuit breaker will be turned off.

9. A high-reliability overvoltage shutdown detection method for a single-phase smart meter according to claim 2, characterized in that: The specific method for judging whether the overvoltage is restored is as follows: Determining whether the current voltage value of the input terminal is lower than a preset recovery voltage threshold; If the current voltage value of the input terminal is lower than the preset recovery voltage threshold, the circuit breaker is restored.

10. A high-reliability overvoltage shutdown detection method for a single-phase smart meter according to claim 8, characterized in that: When the overvoltage duration is greater than the sampling interval of the metering chip, the current voltage value of the input terminal is obtained through the metering chip; When the overvoltage duration is less than or equal to the sampling interval of the metering chip, the ripple signal U is collected. ADC4 The voltage value of the input terminal is calculated.

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