A single optocoupler anti-theft detection circuit for single-phase three-wire system
By adopting a single optocouple circuit design in a single-phase three-wire power system, and using the current limit voltage divider, optocouple isolation module and rectifier module to collect and process signals, the problem of difficulty in detecting different power theft methods in the prior art is solved, and a low-cost and reliable anti-power theft detection effect is achieved.
Patent Information
- Application Number
- CN202411904247.6
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2024-12-23
- Publication Date
- 2025-04-08
AI Technical Summary
The prior art is difficult to effectively detect different power theft methods in single-phase three-wire power systems, and the commonly used multi-optocoupling schemes are costly.
The circuit design of a single optocouple is adopted, including a signal acquisition unit and a signal processing unit MCU, and the signal is collected and processed through the current limit voltage divider, optocouple isolation module and rectifier module to detect single contacts and double contacts.
It realizes low-cost and reliable anti-theft detection, can effectively detect the power output status, simplify circuit design, and reduce device quantity and cost.
Smart Images
Figure CN119780494A_ABST
Abstract
Description
Technical Field
[0001] The invention relates to the field of electronic technology, and in particular to an anti-electricity theft detection circuit for a single-phase three-wire electrical system. Background Art
[0002] With the development of automation technology, in order to ensure the safe and stable operation of the power system, the high reliability of power relays plays a vital role in the power system. It can respond quickly and accurately when the power system fails or operates abnormally due to external factors (human power theft), and avoid equipment damage and accidents by operating the circuit breaker or sending a signal to protect the safe operation of the power system.
[0003] At present, the commonly used relay detection methods include: coil power-on state detection, which determines whether the relay is activated by detecting the power-on state of the relay coil, but this method cannot directly detect the contact state, and can only determine whether the coil is driven; or using the characteristics of the auxiliary contacts of the relay being linked with the main contacts, the state of the main contacts can be indirectly determined by detecting the state of the auxiliary contacts, but this method relies on the linkage between the auxiliary contacts and the main contacts, and there is a risk of failure;
[0004] Alternatively, the output signal of the relay can be isolated through an optocoupler, and the microcontroller can perform level processing to determine the state of the external power system. This method can accurately determine the actual state of the relay contacts, and the optocoupler achieves good isolation between the high-voltage and low-voltage circuits. However, multi-phase relays often require a corresponding number of optocouplers, which are relatively expensive. Summary of the invention
[0005] The purpose of the present invention is to provide a single optocoupler circuit to detect single contact and double contact for different electricity theft modes in a single-phase three-wire power system; the circuit is a simple, low-cost and reliable anti-electricity theft detection.
[0006] The technical solution of the present invention is:
[0007] The present invention provides a single optocoupler anti-electricity theft detection circuit applied to a single-phase three-wire system, comprising a signal acquisition unit and a signal processing unit MCU;
[0008] The signal acquisition unit includes a current limiting and voltage dividing module, an optocoupler isolation module and a rectifier module; a single-phase three-wire AC voltage source is divided by the current limiting and voltage dividing module, and the generated voltage signal is connected to the output terminal of the relay contact in the relay switch module through the diode in the optocoupler isolation module, and the transistor collector in the optocoupler isolation module is connected to the base of the transistor in the rectifier module through a resistor; the rectifier module connects the processed signal to the level input terminal of the signal processing unit MCU;
[0009] The signal processing unit MCU periodically scans the collected signal, counts the collected high and low level numbers and level flip numbers, and obtains the signal frequency; determines the relay contact state according to the signal frequency; and determines whether the power theft event is triggered by comparing the relay contact state with the internally configured relay state.
[0010] Furthermore, the current limiting and voltage dividing module includes resistors R1-R6; in a single-phase three-wire application scenario, phases L1 and L2 in the power grid are connected to the two ends of the series resistors R1-R6 of the energy meter, and the neutral line N bypasses the energy meter and is directly connected to the electrical wire PE in the user's home; the middle point UN of the resistors R1-R6 is taken as the reference point of the single-phase three-wire simulated N line, and is connected to the positive pole of the primary side diode of the optocoupler U1 in the optocoupler isolation module.
[0011] Furthermore, the optocoupler isolation module includes an optocoupler U1, resistors R7-R11, and diodes D1 and D2; the cathode of the primary side diode of the optocoupler U1 is connected to the L1 phase contact output terminal through resistors R9-R10 and diode D2, and is connected to the L2 phase contact output terminal through resistors R7-R8 and diode D1; the optocoupler U1 is turned on and off by closing the L1 phase and L2 phase relays, and the signal output by the secondary side transistor is sent to the rectifier module.
[0012] Furthermore, the rectifier module includes resistors R12-R13, capacitor C1 and transistor Q1, the resistor R12 and capacitor C1 are connected in parallel, one of the parallel connection points is connected to the signal output after optocoupler isolation, and the other parallel connection point is connected to the base of the transistor Q1. The collector of the transistor Q1 is connected in series with the resistor R13 and then connected to the signal processing unit MCU as an output. The emitter of the transistor Q1 is grounded. The rectifier module is used to shape the signal output after optocoupler isolation and transmit it to the signal processing for signal processing judgment.
[0013] Furthermore, the detection circuit further includes an electricity theft simulation unit, the electricity theft simulation unit uses a relay switch module, and the relay switch module includes switches S1-S8; wherein,
[0014] The two ends of the switch S1 are respectively connected to the L1 line input end and the L1 line output end, and are used to control the on and off of the L1 line;
[0015] The two ends of the switch S2 are respectively connected to the input end of the L2 line and the output end of the L2 line, and are used to control the on and off of the L2 line;
[0016] The two ends of the switch S3 are respectively connected to the output end of the L1 line and the input end of the L2 line, so as to simulate the scenario where the L1 line and the L2 line are reversely connected;
[0017] The two ends of the switch S4 are respectively connected to the output end of the L2 line and the input end of the L1 line, so as to simulate the scenario where the L1 line and the L2 line are reversely connected;
[0018] The switch S5 and the switch S7 are connected to the output end of L2 and the N line respectively through the resistor R15, so as to simulate the use of a real load by a household user;
[0019] The switch S5 and the switch S6 connect the output end of L1 and the output end of L2 via the resistor R14, so as to simulate the use of a real load by a household user;
[0020] The two ends of the switch S8 are connected to the output end of L2 and the N line respectively through a resistor R16, so as to simulate a home user using a real load.
[0021] Furthermore, in the signal processing unit MCU, if a consistent frequency is continuously determined, the state of the relay contact is further determined based on the frequency;
[0022] If the signal frequency is less than the first threshold, it is determined that both the L1 and L2 phase relays are in the disconnected state;
[0023] If the signal frequency is between the first threshold and the second threshold, it is determined that one phase of the two-phase relays L1 and L2 is in the disconnected state and the other phase is in the closed state;
[0024] If the signal frequency is greater than the second threshold, it is determined that both the L1 and L2 phase relays are in the closed state.
[0025] Furthermore, if the determined relay contact state does not match the internally configured relay state, an electricity theft event is triggered.
[0026] Beneficial effects of the present invention:
[0027] The single optocoupler anti-electricity theft detection circuit applied to a single-phase three-wire system of the present invention can effectively detect the power output state, and has the advantages of simple overall circuit, few components, low cost, strong practicability and easy implementation.
[0028] The circuit for detecting power theft of the present invention collects the relay contact state signal and uses the MCU to process the signal; first, the AC voltage source signal is subjected to voltage division and optical coupling isolation processing, and then the contact state signal is obtained through rectification and shaping. The MCU periodically scans the collected signal and counts its frequency or duty cycle characteristics. If consistent characteristics are obtained for multiple consecutive times, the current contact state is determined according to a preset threshold. The determination result is compared with the pre-configured state. If there is any inconsistency, it is determined that power theft has occurred and an alarm is triggered.
[0029] The present invention is provided with an electricity theft simulation unit, adopts a relay switch module, and controls the on and off of the signal according to a preset relay switch wiring method to simulate various electricity theft scenarios. Combined with signal feature analysis, it can accurately identify various complex electricity theft behaviors and effectively verify the reliability of the detection circuit; improve the accuracy of electricity theft detection and effectively prevent the illegal use of power resources.
[0030] Other features and advantages of the present invention will be described in detail in the following detailed description. BRIEF DESCRIPTION OF THE DRAWINGS
[0031] 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.
[0032] Figure 1 This is a logic block diagram of the present invention for realizing anti-electricity theft detection in a single-phase three-wire system through a single optical coupler;
[0033] Figure 2 This is a schematic diagram of the present invention realizing anti-electricity theft detection of a single-phase three-wire system through a single optical coupler;
[0034] Figure 3 It is a reference diagram for different actual wiring methods of single-phase three-wire power system;
[0035] Figure 4 It is a waveform diagram when the contacts of two-phase relays are closed;
[0036] Figure 5 It is a waveform diagram of one phase relay contact closed and one phase relay contact opened;
[0037] Figure 6 This is a waveform diagram when both phase relay contacts are disconnected. DETAILED DESCRIPTION
[0038] 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.
[0039] like Figure 1-2 As shown, the present invention provides an anti-electricity theft detection circuit for a single-phase three-wire power system using a single optocoupler, which is divided into two parts: signal acquisition and signal processing. The signal acquisition part includes a current limiting and voltage dividing module, an optocoupler isolation module and a rectifier module.
[0040] Anti-electricity theft detection circuit, the single-phase three-wire AC voltage source is divided by the current limiting voltage divider module, the generated voltage signal is connected to the output terminal of the relay contact through the diode inside the optocoupler, the transistor collector inside the optocoupler is connected to the base of the transistor of the rectifier module through a resistor, and the processed signal is connected to the interrupt level input terminal of the MCU. The collected signal is scanned regularly at 250us / time inside the MCU, and the number of high and low levels and level flips monitored during the scanning process are counted to obtain the preliminary signal frequency / duty cycle, but in order to improve the accuracy of signal verification, multiple scans are performed. After multiple consecutive judgments of consistent signal frequencies / duty cycles, the frequency / duty cycle is distinguished and compared, and the contact state of the relay at this time is output. In actual applications, the real-time signal state is compared with the internally configured relay state. If it is consistent with the internal configuration, the electricity theft event is not triggered; if it is inconsistent with the internal configuration, the electricity theft event and warning are triggered, thereby realizing relay anti-electricity theft detection.
[0041] The current limiting and voltage dividing module, in common electrical installations, the phase lines L1 and L2 of the single-phase three-wire power system are connected to the electric energy meter, and the neutral line N is connected to the ground line PE in the user's home to protect personal safety. When an electrical device fails, it can provide a safe current return path to the ground to reduce the risk of electric shock. Since the N line in the power grid is not connected to the electric energy meter, the circuit connects L1 and L2 through resistors R1-R6, and takes the middle point UN as the simulated N line of the single-phase three-wire.
[0042] The optical coupler isolation module uses the above-mentioned middle point UN as the positive pole of the optical coupler U1 primary test diode, and connects the resistors R7-R8 and the diode D1 to the output end of the L2 phase relay, and connects the resistors R9 / R10 and the diode D2 to the output end of the L1 phase relay. The optical coupler U1 is turned on and off by pulling and closing the L1 and L2 phase relays, and the secondary-side transistor outputs the corresponding signal to the rectifier module.
[0043] In the current limiting and voltage dividing module and the optocoupler isolation module, the selection of resistors R1-R10 needs to take into account safety requirements. According to different tests in the standard, it should be ensured that the string of resistors can withstand the corresponding current size. The resistance value and quantity of the resistors can be adjusted according to the actual application scenario. Figure 2 The resistance value shown is not a fixed value. Since there may be lightning strikes or abnormal grid signals during the actual use of the energy meter, there is a probability that a reverse voltage will appear on the primary side of the optocoupler. By placing diodes D1 and D2, the optocoupler U1 is protected by reverse cutoff voltage, thereby improving the safety and reliability of the circuit.
[0044] The rectifier module, since the signal generated after the optocoupler isolation is not a standard square wave signal, cannot accurately enable the MCU to make accurate judgments. Therefore, the signal is shaped by resistors R12-R13, capacitor C1 and transistor Q1, and then transmitted to the MCU interrupt level input port for signal judgment.
[0045] The detection circuit also includes an electricity theft simulation unit, which uses a relay switch module. The relay switch module is used to control the on-off of the circuit to simulate the actual electricity theft scenario on site of a single-phase three-wire. The relay switch includes switches S1-S8. The two ends of the S1 switch are respectively connected to the input end of the L1 line and the output end of the L1 line to control the on and off of the L1 line; the two ends of the S2 switch are respectively connected to the input end of the L2 line and the output end of the L2 line to control the on and off of the L2 line; the two ends of the S3 switch are respectively connected to the output end of the L1 line and the input end of the L2 line to simulate the scenario of reverse connection of the L1 line and the L2 line; the two ends of the S4 switch are respectively connected to the output end of the L2 line and the input end of the L1 line to simulate the scenario of reverse connection of the L1 line and the L2 line; the S5 switch and the S7 switch are respectively connected to the output end of the L2 and the N line through the resistor R15 to simulate the use of a real load by a home user; the S5 switch and the S6 switch connect the output end of the L1 and the output end of the L2 through the resistor R14 to simulate the use of a real load by a home user; the two ends of the S8 switch are respectively connected to the output end of the L2 and the N line to simulate the use of a real load by a home user.
[0046] Based on the above modules, the specific circuit principle of the present invention is as follows:
[0047] When the two-phase relays L1 and L2 are closed, the contacts are closed, that is, switches S1 and S2 are closed, and the optocoupler U1 is turned on. Since the voltage phase line angle is 180° in the single-phase three-wire power system, the signal after passing through the optocoupler is a 120Hz half-wave (the single-phase three-wire power system described in the present invention is 60Hz, if it is a 50Hz power system, it should be a 100Hz half-wave). After the 120Hz half-wave is shaped by the transistor Q1, a 120Hz square wave is output to the interrupt input port of the MCU, such as Figure 4 As shown, it means that when the two-phase relays are closed normally, the MCU detects a 120Hz square wave signal.
[0048] When the L1 phase relay is closed and the L2 phase relay is disconnected, that is, switch S1 is closed and switch S2 is disconnected, the optocoupler U1 can still be turned on, but because only the L1 phase is closed, the signal after passing through the optocoupler is a 60Hz half-wave (the single-phase three-wire power system described in the present invention is 60Hz, if it is a 50Hz power system, it should be a 50Hz half-wave). The 50Hz half-wave is shaped by the transistor Q1 and outputs a 50Hz square wave to the interrupt input port of the MCU, such as Figure 5As shown, it means that when the L1 phase relay is closed normally, the MCU detects a 60Hz square wave signal.
[0049] When the L2 phase relay is closed and the L1 phase relay is disconnected, that is, switch S2 is closed and switch S1 is disconnected, the output signal is the same as when the L1 phase relay is closed and the L2 phase relay is disconnected, such as Figure 5 As shown, it means that when the L2 phase relay is closed normally, the MCU detects a 60Hz square wave signal.
[0050] When both L1 and L2 phase relays are switched off, the contacts are disconnected, that is, switches S1 and S2 are disconnected, the optocoupler U1 is not conducting, and the transistor Q1 is not conducting, which means that when both phase relays are switched off, the MCU end should be a high level signal, such as Figure 6 shown.
[0051] The signal processing methods for the above four situations are as follows: Figure 1 As shown:
[0052] The MCU scans the collected signal regularly every 250us, and then counts the number of high and low levels and the number of level flips to calculate the frequency / duty cycle of the signal. To ensure the accuracy of the judgment, after a consistent frequency / duty cycle is judged for many consecutive times, the relay contact state is judged, and then the actual read signal is compared with the default relay configuration to determine whether to trigger a power theft event and warning.
[0053] In order to improve the accuracy of contact judgment, the frequency thresholds under different states are appropriately adjusted. When the signal frequency is greater than 90Hz, it is determined that the L1 / L2 two-phase relays are both in the normal closed working state (corresponding to the 120Hz square wave signal detected by the above-mentioned MCU end); when the signal frequency is greater than 30Hz and less than 90Hz, it is determined that the L1 / L2 two-phase relays have one phase in the open state and the other phase in the closed state (corresponding to the 60Hz square wave signal detected by the above-mentioned MCU end); when the signal frequency is greater than 30Hz, it is determined that the L1 / L2 two-phase relays are both in the open state (corresponding to the high-level signal on the above-mentioned MCU end).
[0054] In the actual use of the electric energy meter, there may be a situation where the power system fails or operates abnormally due to external factors (human power theft). At this time, it is necessary to operate the circuit breaker to switch off or send a signal to avoid equipment damage and accidents, so as to protect the safe operation of the power system. The present invention can realize anti-power theft detection in the following situations:
[0055] like Figure 3As shown in the figure, a total of 7 load wiring conditions are listed. For these load configurations, 9 different voltage changes are listed on the load side L1_OUT and L2_OUT, using the same phase and different phases to check the safety of relay operation. In these test cases, unsafe relay operation must not occur.
[0056] First, make sure that the relay contacts are in the disconnected state. At this time, the MCU interrupt port detects a high-level signal and determines that the relay is in the fully closed state.
[0057] like Figure 3 As shown in sequence number 1, when an external person manually connects L1_OUT to L1 and L2_OUT to L2, the MCU interrupt port signal is read and a 120Hz square wave signal is collected, which is inconsistent with the premise of the high level state, that is, a power theft event and warning are triggered. Whether the actual user's home is connected to a real load will not change the signal and event record, and power theft detection can be realized;
[0058] like Figure 3 As shown in sequence number 2, in the case of 1) above, connecting L1_OUT to L2 and connecting L2_OUT to L1 can also achieve the same situation of power theft detection;
[0059] like Figure 3 As shown in sequence number 3, when an external person manually connects L1_OUT and L2_OUT to L1, the MCU interrupt port signal is read and a 60Hz square wave signal is collected, which is inconsistent with the premise of the high level state, that is, a power theft event and warning are triggered. Whether the actual user's home is connected to a real load will not change the signal and event record, and power theft detection can be realized;
[0060] like Figure 3 As shown in the sequence number 4, in the case of 1) above, connecting L1_OUT and L2_OUT to L2 can also achieve the same situation of power theft detection;
[0061] like Figure 3 As shown in sequence numbers 5 to 8, any phase of L1_OUT / L2_OUT is connected to any phase of L1 / L2, and the output terminal of the remaining phase is not connected to the input terminal of the remaining phase. At this time, the MCU interrupt port signal is read and a 60Hz square wave signal is collected, which is inconsistent with the premise of the high level state, that is, a power theft event and warning are triggered. Whether the actual user's home is connected to a real load will not change the signal and event record, and power theft detection can be realized;
[0062] like Figure 3As shown in sequence number 9, L1_OUT and L2_OUT are not connected to the input terminals L1 / L2. At this time, the signal read from the MCU interrupt port is high level, which is consistent with the default state and does not trigger event recording.
[0063] 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 single optocoupler anti-theft detection circuit applied to a single-phase three-wire system, characterized in that: It includes a signal acquisition unit and a signal processing unit MCU; The signal acquisition unit includes a current limiting and voltage dividing module, an optocoupler isolation module and a rectifier module; a single-phase three-wire AC voltage source is divided by the current limiting and voltage dividing module, and the generated voltage signal is connected to the output terminal of the relay contact in the relay switch module through the diode in the optocoupler isolation module, and the transistor collector in the optocoupler isolation module is connected to the base of the transistor in the rectifier module through a resistor; the rectifier module connects the processed signal to the level input terminal of the signal processing unit MCU; The signal processing unit MCU periodically scans the collected signal, counts the collected high and low level numbers and level flip numbers, and obtains the signal frequency; determines the relay contact state according to the signal frequency; The relay contact status is compared with the internally configured relay status to determine whether an electricity theft event is triggered.
2. The single optocoupler anti-electricity theft detection circuit applied to a single-phase three-wire system according to claim 1, characterized in that: The current limiting and voltage dividing module includes resistors R1-R6; in a single-phase three-wire application scenario, phases L1 and L2 in the power grid are connected to the two ends of the series resistors R1-R6 of the energy meter, and the neutral line N bypasses the energy meter and is directly connected to the electrical wire PE in the user's home; the middle point UN of the resistors R1-R6 is taken as the reference point of the single-phase three-wire simulated N line, and is connected to the positive pole of the primary side diode of the optocoupler U1 in the optocoupler isolation module.
3. The single optocoupler anti-electricity theft detection circuit applied to a single-phase three-wire system according to claim 2, characterized in that: The optocoupler isolation module includes an optocoupler U1, resistors R7-R11, and diodes D1 and D2; the cathode of the primary-side diode of the optocoupler U1 is connected to the L1 phase contact output terminal through resistors R9-R10 and diode D2, and is connected to the L2 phase contact output terminal through resistors R7-R8 and diode D1; the optocoupler U1 is turned on and off by closing the L1 phase and L2 phase relays, and the signal output by the secondary-side transistor is sent to the rectifier module.
4. The single optocoupler anti-electricity theft detection circuit applied to a single-phase three-wire system according to claim 1, characterized in that: The rectifier module includes resistors R12-R13, capacitor C1 and transistor Q1. The resistor R12 and capacitor C1 are connected in parallel, one of the parallel connection points is connected to the signal output after optical coupling isolation, and the other parallel connection point is connected to the base of the transistor Q1. The collector of the transistor Q1 is connected in series with the resistor R13 and then connected to the signal processing unit MCU as an output. The emitter of the transistor Q1 is grounded. The rectifier module is used to shape the signal output after optical coupling isolation and transmit it to the signal processing for signal processing judgment.
5. The single optocoupler anti-electricity theft detection circuit applied to a single-phase three-wire system according to claim 1, characterized in that: The detection circuit also includes an electricity theft simulation unit, which uses a relay switch module, and the relay switch module includes switches S1-S8; wherein, The two ends of the switch S1 are respectively connected to the L1 line input end and the L1 line output end, and are used to control the on and off of the L1 line; The two ends of the switch S2 are respectively connected to the input end of the L2 line and the output end of the L2 line, and are used to control the on and off of the L2 line; The two ends of the switch S3 are respectively connected to the output end of the L1 line and the input end of the L2 line, so as to simulate the scenario where the L1 line and the L2 line are reversely connected; The two ends of the switch S4 are respectively connected to the output end of the L2 line and the input end of the L1 line, so as to simulate the scenario where the L1 line and the L2 line are reversely connected; The switch S5 and the switch S7 are connected to the output end of L2 and the N line respectively through the resistor R15, so as to simulate the use of a real load by a home user; The switch S5 and the switch S6 connect the output end of L1 and the output end of L2 via the resistor R14, so as to simulate the use of a real load by a household user; The two ends of the switch S8 are connected to the output end of L2 and the N line respectively through a resistor R16, so as to simulate a home user using a real load.
6. The single optocoupler anti-electricity theft detection circuit applied to a single-phase three-wire system according to claim 1, characterized in that: In the signal processing unit MCU, if a consistent frequency is continuously determined, the state of the relay contact is further determined based on the frequency; If the signal frequency is less than the first threshold, it is determined that both the L1 and L2 phase relays are in the disconnected state; If the signal frequency is between the first threshold and the second threshold, it is determined that one phase of the two-phase relays L1 and L2 is in the disconnected state and the other phase is in the closed state; If the signal frequency is greater than the second threshold, it is determined that both the L1 and L2 phase relays are in the closed state.
7. The single optocoupler anti-electricity theft detection circuit applied to a single-phase three-wire system according to claim 6, characterized in that: If the determined relay contact state does not match the internally configured relay state, a power theft event is triggered.