Time-keeping improving method applied to voltage recording device of power distribution station house

Abstract

The invention provides a punctuality improving method applied to a voltage recording device of a power distribution station house. The voltage recording device comprises a GPS time service module, a zero-cross detection module and a communication module. Wherein the GPS time service module is used for realizing accurate clock time synchronization of the voltage recording device; when the GPS cannot capture satellite signals in time, the zero-crossing detection module is started and directly extracts power frequency signals of the power distribution station house system so as to determine a voltage zero-crossing point; the time interval between the last zero crossing point and the current zero crossing point is set, the zero crossing points are counted through the single-chip microcomputer, and the time keeping of the clock of the single-chip microcomputer is controlled, so that the time keeping reliability of the voltage wave recording device is improved; and the communication module is used for communication of a plurality of voltage recording devices in the power distribution station room so as to ensure time synchronization of each device. According to the invention, accurate clock signal output can still be ensured when the voltage recording GPS time service module fails.

Description

Technical Field

[0001] The invention relates to the field of power distribution network safety, and in particular to a timekeeping improvement method applied to a voltage recording device in a distribution station. Background Art

[0002] The distribution network voltage recording device is mainly used to record and analyze the voltage waveform of the power system to determine system oscillations, line faults, voltage over-limit faults and other faults, which is crucial to the safe operation of the substation.

[0003] The premise for the reliable operation of the distribution network voltage recording device is the need for accurate time synchronization to ensure the accuracy of the device's collection of three-phase voltage signals in order to analyze and judge the fault. The current time synchronization method of the voltage recording device is mainly based on the use of GPS standard second pulse signals as the synchronous clock and the Beidou navigation system to achieve clock synchronization, mark the measured current information with a time stamp, and achieve three-phase synchronous sampling. However, due to the installation of a variety of electrical equipment in the distribution station room, the small space, and the complex and harsh electrical conditions, the signal interference is serious, and the GPS cannot capture satellite signals and cannot receive data, which poses a challenge to the timekeeping technology of the distribution network voltage recording device.

[0004] Therefore, it is urgent to study methods to ensure the output of accurate clock signals after GPS loses lock. Summary of the invention

[0005] The purpose of the present invention is to propose a timekeeping improvement method for a voltage recording device in a power distribution station. When the GPS is locked, the device can still ensure the output of an accurate clock signal to improve the timekeeping ability of the voltage recording device in the power distribution network under severe working conditions.

[0006] To achieve the above purpose, the technical solution of the present invention is: a method for improving the timekeeping of a voltage recording device applied to a power distribution station; the voltage recording device includes a GPS timing module, a zero-crossing detection module and a communication module; the method is specifically: Use GPS timing module to synchronize the clock of voltage recording device; When the GPS fails to capture satellite signals in time, the zero-crossing detection module is started; the zero-crossing detection module detects the zero-crossing point of the system voltage of the power distribution station and records the number of zero-crossing points, and realizes clock punctuality according to the preset time interval between two adjacent zero-crossing points and the recorded number of zero-crossing points; The communication module is used to communicate with multiple voltage recording devices in the distribution station to achieve the timing of each device.

[0007] Preferably, the zero-crossing detection module includes a zero-crossing detection circuit and a single-chip microcomputer; the zero-crossing detection circuit is respectively connected to the substation building system and the single-chip microcomputer. The zero-crossing detection circuit detects the zero-crossing point of the voltage of the substation building system and sends a zero-point signal to the single-chip microcomputer when the voltage passes through the zero-crossing point. The single-chip microcomputer counts the zero-point signals and calculates the time based on the preset time interval between two adjacent zero-crossing points and the zero-crossing count, so as to achieve the timekeeping of the internal clock of the single-chip microcomputer.

[0008] Preferably, for the preset time interval between two adjacent zero-crossing points, the time interval between the previous zero-crossing point and the current zero-crossing point is set to 10 ms according to the voltage frequency of the substation building system.

[0009] Preferably, the zero-crossing detection circuit includes a step-down transformer, a dual-limit zero-crossing comparison circuit based on LM339M, and a 7408N dual-input four-AND gate circuit. The input end of the step-down transformer is connected to the substation building system. The input end and the output end of the dual-limit zero-crossing comparison circuit based on LM339M are respectively connected to the output end of the step-down transformer and the input end of the 7408N dual-input four-AND gate circuit. The output end of the 7408N dual-input four-AND gate circuit is connected to the single-chip microcomputer.

[0010] Preferably, the turns ratio of the step-down transformer is 220 / 5.

[0011] Preferably, the zero-crossing detection circuit detects the zero-crossing point of the voltage of the substation building system and sends a zero-point signal to the single-chip microcomputer when the voltage passes through the zero-crossing point. Specifically: Zero-crossing detection is performed according to the preset upper limit value V2 and lower limit value V3 of the dual-limit zero-crossing comparison circuit. When the voltage of the substation building system passes through the zero-crossing point, the output signal V11 of the step-down transformer satisfies V3 < V11 < V2. Both output pins of the dual-limit zero-crossing comparison circuit output high levels. The two high-level signals pass through the AND gate of 7408N and then output a high level, which is sent to the single-chip microcomputer as a zero-point signal. The single-chip microcomputer counts. Otherwise, the output signal V11 of the step-down transformer is in the state of V11 < V3 or V11 > V2. One output pin of the dual-limit zero-crossing comparison circuit outputs a high level and the other outputs a low level. The two signals pass through the AND gate of 7408N and then output a low level to the single-chip microcomputer. At this time, the single-chip microcomputer does not count.

[0012] Preferably, the preset values of the upper limit value V2 and the lower limit value V3 of the reference voltage of the dual-limit comparator are 0.1 V and -0.1 V.

[0013] Compared with the prior art, the present invention has the following beneficial effects: The present invention is based on maintaining a constant voltage frequency of the power distribution station system, by setting a zero-crossing detection module, detecting the zero-crossing point of the power distribution station system voltage when the GPS is invalid, and realizing the timekeeping of the power distribution station voltage recording device according to the preset time interval between the last zero-crossing point and the current zero-crossing point and the zero-crossing point count, thereby ensuring accurate clock signal output when the GPS of the voltage recording device fails. The detection circuit of the present invention adopts a double-limit comparator, which can prevent the signal from erroneously crossing zero to a certain extent and causing system malfunction, thereby improving the reliability of detection. The present invention is easy to implement, has strong stability, high reliability, and good anti-interference ability. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1 A voltage diagram of a power distribution station system in one embodiment of the present invention; Figure 2 A circuit model diagram based on LM339M dual-limit zero-crossing comparison in one embodiment of the present invention; Figure 3 Graph showing simulation results of zero-crossing detection in one embodiment of the present invention. DETAILED DESCRIPTION

[0015] The following is combined with Figure 1-3 , the technical solution of the present invention is specifically described.

[0016] The present invention proposes a method for improving the timekeeping of a voltage recording device in a power distribution station; the voltage recording device includes a GPS timing module, a zero-crossing detection module and an upper communication module. The method is specifically as follows: Use GPS timing module to achieve accurate clock synchronization of voltage recording device; When the GPS fails to capture satellite signals in time, the zero-crossing detection module is started; the zero-crossing detection module detects the zero-crossing point of the system voltage of the power distribution station and records the number of zero-crossing points, and realizes clock punctuality according to the preset time interval between two adjacent zero-crossing points and the recorded number of zero-crossing points; The communication module is used to communicate with multiple voltage recording devices in the distribution station to achieve the timing of each device.

[0017] In this embodiment, the zero-crossing detection module includes a zero-crossing detection circuit and a single-chip microcomputer; the zero-crossing detection circuit is connected to the power distribution station system and the single-chip microcomputer respectively, the zero-crossing detection circuit detects the zero-crossing point of the power distribution station system voltage, and sends a zero-point signal to the single-chip microcomputer when the voltage crosses zero; the single-chip microcomputer counts the zero-point signal, and calculates the time according to the preset time interval between two adjacent zero-crossing points and the zero-crossing point count, so as to realize the internal clock timekeeping of the single-chip microcomputer.

[0018] In this embodiment, for the preset time interval between two adjacent zero crossings, the time interval between the last zero crossing and the current zero crossing is set to 10 ms according to the voltage frequency of the substation building system.

[0019] In this embodiment, the zero-crossing detection circuit includes a step-down transformer, a dual-limit zero-crossing comparison circuit based on LM339M, and a 7408N dual-input four AND gate circuit; the input end of the step-down transformer is connected to the substation building system, specifically, it is connected to the secondary side of the voltage transformer on the bus side of the substation building system; the input end and the output end of the dual-limit zero-crossing comparison circuit based on LM339M are respectively connected to the output end of the step-down transformer and the input end of the 7408N dual-input four AND gate circuit; the output end of the 7408N dual-input four AND gate circuit is connected to the single-chip microcomputer.

[0020] In this embodiment, the turns ratio of the step-down transformer is 220 / 5.

[0021] In this embodiment, the zero-crossing detection circuit detects the zero crossing of the voltage of the substation building system and sends a zero-point signal to the single-chip microcomputer when the voltage passes through the zero point. Specifically: Zero-crossing detection is performed according to the preset upper limit value V2 and lower limit value V3 of the dual-limit zero-crossing comparison circuit; When the voltage of the substation building system passes through the zero point, the output signal V11 of the step-down transformer satisfies V3 < V11 < V2, and both output pins of the dual-limit zero-crossing comparison circuit output high levels. The two high-level signals pass through the AND gate of 7408N and then output a high level, which is sent to the single-chip microcomputer as a zero-point signal; the single-chip microcomputer performs counting; Otherwise, the output signal V11 of the step-down transformer is in the state of V11 < V3 or V11 > V2, and one of the two output pins of the dual-limit zero-crossing comparison circuit outputs a high level and the other outputs a low level. The two signals pass through the AND gate of 7408N and then output a low level to the single-chip microcomputer. At this time, the single-chip microcomputer does not count.

[0022] In this embodiment, the preset values of the upper limit value V2 and the lower limit value V3 of the reference voltage of the dual-limit comparator are 0.1 V and -0.1 V.

[0023] When the voltage recording device can receive satellite signals, the GPS timing module is used to achieve clock synchronization to facilitate the device to collect three-phase voltage signals simultaneously. When GPS is invalid, a timekeeping technology needs to be adopted. Since the system voltage frequency in the substation building remains constant, the present invention combines the zero-crossing detection module to achieve the timekeeping of GPS. As Figure 1As shown, the system voltage frequency in the distribution substation room remains at 50 Hz. That is, the time for one cycle is 20 ms, and 50 cycles are 1 s. Therefore, the voltage recording device in the distribution substation room can keep time by recording the number of cycles of the system voltage; the power frequency signal of the distribution substation room system is directly extracted by the zero-crossing detection module to determine the voltage zero-crossing point. At the same time, the single-chip microcomputer counts the zero-crossing points, and the time interval between the previous zero-crossing point and the current zero-crossing point is set to 10 ms.

[0024] The zero-crossing detection module determines the position of the system voltage zero-crossing point through the zero-crossing detection circuit, which can be divided into single-direction zero-crossing detection and two-direction zero-crossing detection. In this embodiment, a double-limit zero-crossing comparison circuit based on LM339M is adopted, and the circuit model built by Multisim simulation software is as Figure 2 shown.

[0025] Among them, T1 is a step-down transformer, U1A and U1B are two comparators used to detect and compare AC signals, V1 is the input signal, V11 is the output signal of the transformer, V22 is the output signal of the zero-crossing comparison, V2 and V3 are respectively the upper limit value and the lower limit value of the reference voltage of the double-limit comparator, and 7408 is an integrated dual-input four AND gate circuit.

[0026] The working principle of the double-limit zero-crossing comparison circuit is as follows: when the signal V11 > V2, the outputs of the 1st and 2nd pins of the comparator are high level and low level respectively. After the two signals pass through the 7408N AND gate, the output is low level; when V3 < V11 < V2, the output of the 1st pin of the comparator is still high level, and the output of the 2nd pin also becomes high level. After the two signals pass through 7408N, the output becomes high level; when V11 < V3, the output of the 1st pin of the comparator becomes low level, while the output of the 2nd pin is still high level. After the two signals pass through the 7408N AND gate, the output becomes low level.

[0027] Set the effective value of the input signal V1 to 220 V and the frequency to 50 Hz; the turns ratio of T1 is 220 / 5; V2 and V3 are 0.1 V and -0.1 V respectively. The simulation result of the zero-crossing detection circuit is as Figure 3 shown, where the green line is the input signal V1, the red line is the output signal V22, and the blue line is the zero-crossing duration (i.e., the zero-crossing detection result).

[0028] The present invention can achieve fast detection of the zero point of the AC signal. Among them, the zero-crossing signal lasts about 100 us and has high accuracy. Since the detection circuit uses a double-limit comparator, it can prevent the system from malfunctioning due to the signal accidentally crossing zero to a certain extent, thus improving the reliability of the detection. This method is easy to implement, has strong stability and high reliability, and has good anti-interference ability.

[0029] In summary, after losing the GPS signal, the voltage recording device will automatically start the zero-crossing detection module, collect the zero-crossing point of the distribution station system voltage, and count it. The microcontroller will strictly keep time based on this.

[0030] In addition, there are multiple voltage recording devices in the distribution station. The zero-crossing detection module of each device will detect the zero-crossing point of the system voltage. Although the GPS satellite signal is susceptible to interference, the time is synchronized based on the system voltage signal, so the time of each device remains consistent.

[0031] The above are preferred embodiments of the present invention. Any changes made according to the technical solution of the present invention, as long as the resulting functions do not exceed the scope of the technical solution of the present invention, belong to the protection scope of the present invention.

Claims

1. A method for improving the timekeeping of a voltage recording device in a power distribution station, characterized in that: The voltage recording device includes a GPS timing module, a zero-crossing detection module and a communication module; the specific method is as follows: Use the GPS timing module to achieve clock synchronization of the voltage recording device; When the GPS fails to capture satellite signals in time, start the zero-crossing detection module; the zero-crossing detection module detects the zero-crossing points of the substation house system voltage and records the number of zero-crossing points, and realizes clock keeping according to the preset time interval between two adjacent zero-crossing points and the recorded number of zero-crossing points; Use the communication module to communicate with multiple voltage recording devices in the substation house to achieve the synchronization of each device.

2. A method for improving the timekeeping of a voltage recording device in a power distribution station according to claim 1, characterized in that: The zero-crossing detection module includes a zero-crossing detection circuit and a single-chip microcomputer; the zero-crossing detection circuit is respectively connected to the substation house system and the single-chip microcomputer, the zero-crossing detection circuit detects the zero-crossing points of the substation house system voltage, and sends a zero-point signal to the single-chip microcomputer when the voltage crosses zero; The single-chip microcomputer counts the zero-point signals, and performs time calculation according to the preset time interval between two adjacent zero-crossing points and the zero-crossing point count, so as to realize the clock keeping of the internal clock of the single-chip microcomputer.

3. A method for improving the timekeeping of a voltage recording device in a power distribution station according to claim 1 or 2, characterized in that: For the preset time interval between two adjacent zero-crossing points, the time interval between the previous zero-crossing point and the current zero-crossing point is set to 10 ms according to the voltage frequency of the substation house system.

4. A method for improving the timekeeping of a voltage recording device in a power distribution station according to claim 2, characterized in that: The zero-crossing detection circuit includes a step-down transformer, a double-limit zero-crossing comparison circuit based on LM339M and a 7408N dual-input four AND gate circuit; the input end of the step-down transformer is connected to the substation house system; the input end and the output end of the double-limit zero-crossing comparison circuit based on LM339M are respectively connected to the output end of the step-down transformer and the input end of the 7408N dual-input four AND gate circuit; the output end of the 7408N dual-input four AND gate circuit is connected to the single-chip microcomputer.

5. A method for improving the timekeeping of a voltage recording device in a power distribution station according to claim 4, characterized in that: The turns ratio of the step-down transformer is 220 / 5.

6. A method for improving the timekeeping of a voltage recording device in a power distribution station according to claim 4, characterized in that: The zero-crossing detection circuit detects the zero-crossing points of the substation house system voltage, and sends a zero-point signal to the single-chip microcomputer when the voltage crosses zero, specifically; Perform zero-crossing detection according to the preset upper limit value V2 and lower limit value V3 of the double-limit zero-crossing comparison circuit; When the substation house system voltage crosses zero, the output signal V11 of the step-down transformer satisfies V3 < V11 < V2, and both output pins of the double-limit zero-crossing comparison circuit output high levels. The two high-level signals pass through the 7408N AND gate and then output a high level, which is sent to the single-chip microcomputer as a zero-point signal; Otherwise, the output signal V11 of the step-down transformer is in the state of V11 < V3 or V11 > V2, and one output pin of the double-limit zero-crossing comparison circuit outputs a high level and a low level. The two signals pass through the 7408N AND gate and then output a low level to the single-chip microcomputer.

7. A method for improving the timekeeping of a voltage recording device in a power distribution station according to claim 6, characterized in that: The preset values of the upper limit value V2 and the lower limit value V3 of the reference voltage of the double-limit comparator are 0.1 V and -0.1 V.

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