A device and method for automatic switching of three-phase load in a low-voltage single-phase meter box

Abstract

The application discloses a device and method for automatically switching three-phase load in a low-voltage single-phase electric meter box, which comprises a commutation executing unit, an MCU control unit and a communication interface unit; the commutation executing unit is composed of bidirectional thyristors and magnetic latching relays in parallel connection for A, B and C three phases, and the three-phase output ends are short-circuited to form a common output node connected to the incoming line firewire end of the single-phase electric energy meter; the MCU control unit integrates phase voltage comparators and current comparators and is used for zero-crossing detection; the application adopts the double-criterion zero-crossing detection scheme composed of the voltage comparator and the current comparator to perform switching when the voltage is zero-crossed and the current tends to be zero, so that the non-inductive switching with a commutation time less than 0.01 second is realized; the device is all integrated on a PCB board and is suitable for a standard electric meter box; and the application can realize automatic optimization adjustment of the three-phase load in a transformer area and effectively solve the problems of voltage out-of-limit and three-phase imbalance.

Description

Technical Field

[0001] This invention belongs to the field of low-voltage power distribution network energy metering and load balancing technology, and particularly relates to a device and method for automatic switching of three-phase loads in a low-voltage single-phase meter box. Background Technology

[0002] Currently, three-phase load imbalance is a common problem in rural and urban power distribution areas, leading to voltage exceeding the upper and lower limits. Even if the initial installation strictly distributes the three phases evenly according to the number of households, the imbalance can still occur due to differences in actual load and working hours, resulting in the following problems: Residential users all use single-phase electricity, and the load distribution is uneven, which can easily cause overload of a certain phase, voltage exceeding the limit on the user side, resulting in individual electrical appliances failing to operate normally, causing user complaints, transformer overheating, and increased line loss; The current three-phase balance adjustment method at the very end of the power supply system is as follows: 1. Traditional methods rely on manual on-site wiring and phase replacement for each household, which involves a large workload, requires power outages, poses high safety risks, is inefficient, and has high maintenance costs. 2. External three-phase balancing devices are bulky and costly, and cannot be directly integrated into standard meter boxes; 3. With the continuous upgrading and iteration of household appliances, and the ongoing application of more efficient and long-life energy-saving products (such as LED energy-saving lamps, induction cookers, microwave ovens, inverter air conditioners, electric bicycle chargers, etc.), these loads can cause voltage fluctuations, current distortions, and waveform harmonics. These practical problems mean that existing automatic commutation methods applied to the power distribution end cannot completely achieve safe and reliable commutation with less than 0.01 seconds of non-inductive power interruption.

[0003] Therefore, there is an urgent need for a three-phase load balancing device that can be directly integrated into a standard meter box without modifying the box structure, supports remote automatic control, and can achieve safe, reliable, and seamless phase commutation in complex harmonic environments. Summary of the Invention

[0004] To address the shortcomings of existing technologies, this invention provides a three-phase balancing mechanism that is directly integrated inside the meter box, enabling seamless power cut-off and automatic phase switching. This effectively solves the problems of voltage exceeding the upper and lower limits. Inside the single-phase meter box, a miniaturized three-phase load balancing mechanism is integrated, enabling automatic, seamless power cut-off and safe switching between phases A, B, and C for single-phase users. This reduces three-phase imbalance in the distribution area from the source, effectively reducing voltage exceeding limits, ensuring the lifespan of household appliances, reducing the frequency and duration of power outages, significantly reducing manual phase switching maintenance costs, maximizing the utilization rate of distribution transformers, optimizing power supply conductor utilization, improving power supply reliability, and reducing losses while increasing efficiency.

[0005] The present invention adopts the following technical solution.

[0006] This invention proposes a device for automatic three-phase load switching within a low-voltage single-phase meter box, comprising: The commutation execution unit includes an A-phase commutation execution module, a B-phase commutation execution module, and a C-phase commutation execution module. Each commutation execution module consists of a bidirectional thyristor and a magnetic latching relay connected in parallel. The A-phase, B-phase, and C-phase phase lines are respectively connected to the input terminals of the A-phase, B-phase, and C-phase commutation execution modules. The output terminals of the A, B, and C phase commutation execution modules are short-circuited to form a common output node, which is connected to the incoming live wire terminal of the single-phase energy meter. The three-phase neutral wires are directly connected to the incoming neutral wire terminal of the single-phase energy meter. The MCU control unit includes three corresponding voltage comparators and current comparators, A, B, and C. The input terminals of each phase voltage comparator are connected to the corresponding phase line, and each phase current comparator is connected in series in the corresponding phase sampling circuit. The MCU control unit is connected to each voltage comparator, each current comparator, the trigger terminal of each bidirectional thyristor, the drive terminal of each magnetic latching relay, and the communication interface unit. The communication interface unit is used to receive external commutation commands and forward them to the MCU control unit. The MCU control unit performs the following operations according to the commutation command: controls the bidirectional thyristor of the currently connected phase to conduct, and disconnects the main contacts of the magnetic latching relay of the currently connected phase after confirming conduction; tracks the current and voltage through the current comparator and voltage comparator of the currently connected phase, and turns off the bidirectional thyristor of the currently connected phase when the voltage of the currently connected phase crosses zero and the current meets the conditions, and triggers the bidirectional thyristor of the target phase to conduct when the voltage of the target phase crosses zero after confirming turn-off; after confirming that all the main contacts of the three-phase magnetic latching relays are open and only the bidirectional thyristor of the target phase is conducting, closes the main contacts of the magnetic latching relay of the target phase, and turns off the bidirectional thyristor of the target phase after confirming that the contacts are in place.

[0007] More preferably, the voltage comparator and the current comparator are integrated quad comparator chips; The communication interface unit establishes a communication connection with the acquisition terminal via HPLC low-voltage power line carrier; The MCU control unit, communication interface unit, and A, B, and C three-phase commutation execution modules are integrated on the same PCB board.

[0008] More preferably, the bidirectional thyristor turn-off method of the target phase is as follows: The MCU controller stops outputting trigger signals to the target phase bidirectional thyristor and turns it off by taking advantage of the characteristic that the thyristor turns off naturally when the AC current crosses zero. The MCU controller detects the current of the target phase bidirectional thyristor through the current comparator of the target phase and determines that the commutation operation is complete after confirming that it has been turned off.

[0009] More preferably, the MCU controller is also used to execute security logic: Only one of the three phases can be connected at any given time; If any step in the commutation process fails, the device will be restored to the initial phase before commutation.

[0010] More preferably, the MCU controller is also used to execute security logic: If the main contacts of the magnetic latching relay and the bidirectional thyristor in the same phase are simultaneously in the on state and the duration exceeds the set time, it is determined that the thyristor in that phase has a short circuit fault, and a thyristor fault work order is generated.

[0011] More preferably, the MCU controller is also used to execute security logic: If the magnetic latching relay fails to engage or disengage within the specified time during the commutation process, it is determined to be a mechanical fault of the relay. The commutation operation is immediately terminated and the device is restored to the initial phase before the commutation. At the same time, a relay fault alarm is generated.

[0012] This invention also proposes a method for automatic three-phase load switching, implemented by a device for automatic three-phase load switching within a low-voltage single-phase meter box, comprising: The data acquisition system master station determines the target meters that need to be switched according to preset priority filtering rules based on events such as voltage exceeding the upper limit, voltage exceeding the lower limit, or three-phase current imbalance in the distribution area. The data acquisition system master station sends a phase switching command to the three-phase load automatic balancing switching mechanism associated with the target meter, authorizing it to perform the phase switching operation; After receiving the phase switching command, the three-phase load automatic balancing switching mechanism autonomously completes the phase switching operation from the current connected phase to the target phase and reports the execution result to the main station of the acquisition system. The data acquisition system master station rechecks the voltage status or three-phase current balance of all meters in the area. If there are still voltage over-limit or three-phase current imbalances, the above steps are repeated until all are qualified.

[0013] More preferably, the preset priority filtering rules include: The first priority event is voltage exceeding the upper limit, the second priority event is voltage exceeding the lower limit, and the third priority event is three-phase current imbalance in the transformer area.

[0014] More preferably, when both voltage exceeding the upper limit and voltage exceeding the lower limit events exist simultaneously in the same transformer area, the system prioritizes processing the voltage exceeding the upper limit event, and processes the voltage exceeding the lower limit event only after all upper limit events have been eliminated.

[0015] More preferably, during the execution of any priority adjustment, if a higher priority event is detected, the system suspends the remaining adjustment tasks of the current priority and instead processes the newly triggered high-priority event. After the high-priority event is processed, the remaining adjustment tasks of the original priority are resumed.

[0016] More preferably, the criteria for determining the target meter in the preset priority screening rules include: The voltage deviation of the current phase connected to the meter, the real-time load of the meter on the current phase, and whether the meter and the voltage over-limit meter belong to the same branch line and different phases.

[0017] More preferably, when the number of consecutive adjustments reaches the preset maximum value and the voltage is still not fully qualified, the system stops automatic adjustment and sends an alarm to the maintenance personnel.

[0018] The present invention also proposes a terminal, including a processor and a storage medium: The storage medium is used to store instructions. The processor is used to perform the steps of the above method according to the instructions.

[0019] The present invention also proposes a computer-readable storage medium having a computer program stored thereon, which, when executed by a processor, implements the steps of the above-described method.

[0020] Compared with the prior art, the beneficial effects of the present invention are as follows: 1. No power outages or manual pole climbing for phase switching are required, significantly reducing maintenance workload and safety risks; 2. By promptly switching phases to adjust the load based on voltage exceeding the upper and lower limits, the three-phase imbalance in the distribution area is significantly reduced, line losses decrease, transformer lifespan is extended, voltage quality is improved, and the lifespan of users' household appliances is extended. 3. The structure is highly integrated, with low cost and small size, and can be directly installed inside the existing meter box, making it suitable for bulk bidding; 4. Supports remote centralized control, enabling intelligent, automated, and lean operation of the transformer area, reducing costs and increasing efficiency.

[0021] 5. Mass production feasibility: All core components use mature and common materials from State Grid. Magnetic latching relays, bidirectional thyristors, MCUs, and carrier modules all have stable State Grid supplier supply chains, eliminating the need for customized development and possessing a strong cost advantage.

[0022] 6. Significant economic benefits: It can stably control the three-phase imbalance of the meter box within 20%, reduce the line loss of the transformer area by more than 30%, reduce copper and iron losses of the transformer, and extend the service life of the equipment; at the same time, it completely replaces manual phase adjustment, significantly reduces the operation and maintenance costs of grassroots power supply stations, and fully meets the State Grid's management requirements for cost reduction and efficiency improvement.

[0023] 7. Enhanced User Experience: The entire phase switching process is seamless and shock-free, leaving users completely unaware. This completely solves the problems of appliance restarting and damage caused by traditional phase switching, significantly reducing user complaints and improving the quality of power supply services. Attached Figure Description

[0024] Figure 1 This is a schematic diagram of the overall structure of a three-phase load automatic switching device in a low-voltage single-phase meter box according to the present invention. Figure 2 This is an electrical connection diagram of an automatic three-phase load switching device in a low-voltage single-phase meter box according to the present invention; Figure 3 This is a schematic diagram of the data and instruction flow for an automatic three-phase load switching method in a low-voltage single-phase meter box according to the present invention. Detailed Implementation

[0025] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions of this invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of this invention. The embodiments described in this application are merely some embodiments of this invention, and not all embodiments. Based on the spirit of this invention, all other embodiments obtained by those skilled in the art without creative effort are within the protection scope of this invention.

[0026] The present invention proposes the following technical solution: This invention proposes a device for automatic three-phase load switching within a low-voltage single-phase meter box, comprising: The commutation execution unit includes an A-phase commutation execution module, a B-phase commutation execution module, and a C-phase commutation execution module. Each commutation execution module consists of a bidirectional thyristor and a magnetic latching relay connected in parallel. The A-phase, B-phase, and C-phase phase lines are respectively connected to the input terminals of the A-phase, B-phase, and C-phase commutation execution modules. The output terminals of the A, B, and C phase commutation execution modules are short-circuited to form a common output node, which is connected to the incoming live wire terminal of the single-phase energy meter. The three-phase neutral wires are directly connected to the incoming neutral wire terminal of the single-phase energy meter. The MCU control unit includes three corresponding voltage comparators and current comparators, A, B, and C. The input terminals of each phase voltage comparator are connected to the corresponding phase line, and each phase current comparator is connected in series in the corresponding phase sampling circuit. The MCU control unit is connected to each voltage comparator, each current comparator, the trigger terminal of each bidirectional thyristor, the drive terminal of each magnetic latching relay, and the communication interface unit. The voltage comparator and current comparator are integrated quad comparator chips; The communication interface unit is used to receive external commutation commands and forward them to the MCU control unit. The MCU control unit performs the following operations according to the commutation command: controls the bidirectional thyristor of the currently connected phase to conduct, and disconnects the main contacts of the magnetic latching relay of the currently connected phase after confirming conduction; tracks the current and voltage through the current comparator and voltage comparator of the currently connected phase, and turns off the bidirectional thyristor of the currently connected phase when the voltage of the currently connected phase crosses zero and the current meets the conditions, and triggers the bidirectional thyristor of the target phase to conduct when the voltage of the target phase crosses zero after confirming turn-off; after confirming that all the main contacts of the three-phase magnetic latching relays are open and only the bidirectional thyristor of the target phase is conducting, closes the main contacts of the magnetic latching relay of the target phase, and turns off the bidirectional thyristor of the target phase after confirming that the contacts are in place.

[0027] The bidirectional thyristor turn-off method for the target phase is as follows: The MCU controller stops outputting trigger signals to the target phase bidirectional thyristor and turns it off by taking advantage of the characteristic that the thyristor turns off naturally when the AC current crosses zero. The MCU controller detects the current of the target phase bidirectional thyristor through the current comparator of the target phase and determines that the commutation operation is complete after confirming that it has been turned off.

[0028] The communication interface unit establishes a communication connection with the acquisition terminal via HPLC low-voltage power line carrier; The MCU control unit, communication interface unit, and A, B, and C three-phase commutation execution modules are integrated on the same PCB board.

[0029] The MCU controller is also used to execute security logic: Only one of the three phases can be connected at any given time; If any step in the commutation process fails, the device will be restored to the initial phase before commutation.

[0030] If the magnetic latching relay fails to engage or disengage within the specified time during the commutation process, it is determined to be a mechanical fault of the relay. The commutation operation is immediately terminated and the device is restored to the initial phase before the commutation. At the same time, a relay fault alarm is generated.

[0031] This invention also proposes a method for automatic switching of three-phase loads within a low-voltage single-phase meter box, comprising the following steps: The data acquisition system master station determines the target meters that need to be switched according to preset priority filtering rules based on events such as voltage exceeding the upper limit, voltage exceeding the lower limit, or three-phase current imbalance in the distribution area. The preset priority filtering rules include: The first priority event is voltage exceeding the upper limit, the second priority event is voltage exceeding the lower limit, and the third priority event is three-phase current imbalance in the transformer area.

[0032] When both voltage exceeding the upper limit and voltage exceeding the lower limit events exist simultaneously in the same transformer area, the system prioritizes processing the voltage exceeding the upper limit event, and processes the voltage exceeding the lower limit event only after all upper limit events have been eliminated.

[0033] If a higher priority event is detected during the execution of any priority adjustment, the system will pause the remaining adjustment tasks of the current priority and start processing the newly triggered high priority event. The remaining adjustment tasks of the original priority will resume execution after the high priority event has been processed.

[0034] The preset priority filtering rules determine the target electricity meter based on the following criteria: The voltage deviation of the current phase connected to the meter, the real-time load of the meter on the current phase, and whether the meter and the voltage over-limit meter belong to the same branch line and different phases.

[0035] The data acquisition system master station sends a phase switching command to the three-phase load automatic balancing switching mechanism associated with the target meter, authorizing it to perform the phase switching operation; After receiving the phase switching command, the three-phase load automatic balancing switching mechanism autonomously completes the phase switching operation from the current connected phase to the target phase and reports the execution result to the main station of the acquisition system. The data acquisition system master station rechecks the voltage status or three-phase current balance of all meters in the area. If there are still voltage over-limit or three-phase current imbalances, the above steps are repeated until all are qualified.

[0036] If the voltage is still not fully qualified after the number of consecutive adjustments reaches the preset maximum value, the system will stop automatic adjustment and send an alarm to the maintenance personnel.

[0037] The present invention also proposes a terminal, including a processor and a storage medium: The storage medium is used to store instructions. The processor is used to perform the steps of the above method according to the instructions.

[0038] The present invention also proposes a computer-readable storage medium having a computer program stored thereon, which, when executed by a processor, implements the steps of the above-described method.

[0039] Example 1 This invention provides a three-phase load automatic switching device in a low-voltage single-phase meter box, comprising: a commutation execution unit, a communication interface unit (HPLC power line carrier), and an MCU control unit (including voltage and current comparators).

[0040] The specific electrical connection method of the device of the present invention is as follows: Figure 1 As shown, specifically: 1. The three-phase four-wire power supply is directly introduced into the low-voltage multi-position single-phase meter box through the power supply inlet isolating switch.

[0041] 2. All three phase lines (A, B, and C) and the neutral line are connected to the automatic balancing phase-commutation device. The output lines of the three phase lines (A, B, and C) after being combined by the phase-commutation execution unit inside the automatic balancing phase-commutation device are connected to the power meter's inlet; the main neutral line of the power supply is connected to the power meter's neutral line.

[0042] 3. After the three phase lines A, B, and C are connected to the automatic balancing commutation device, they are respectively connected to the A, B, and C phase commutation execution modules of the commutation execution unit. The A, B, and C phase commutation execution modules operate in parallel. Each phase execution module consists of one thyristor and one magnetic latching relay connected in parallel. The output terminals of the A, B, and C phase commutation execution modules are short-circuited to form a common output node, which is connected to the incoming live wire terminal of the single-phase energy meter via a wire. The three-phase neutral wire is directly connected to the incoming neutral wire terminal of the energy meter.

[0043] 4. The MCU control unit and communication interface unit are directly connected to the main neutral line and the three phase lines of A, B, and C as the working power supply. At the same time, the MCU control unit integrates voltage comparators and current comparators for the three phases of A, B, and C.

[0044] For detailed commutation operation procedures, please refer to [link / reference]. Figure 2 The electrical connection diagram is shown. When a substation in a certain area triggers a three-phase voltage imbalance threshold (or similarly, a three-phase current condition), the system, based on a preset priority selection rule, determines the target meter for phase switching from the meters equipped with automatic phase balancing devices. This selection rule considers the following factors: the degree of voltage deviation of the current phase connected to the meter (beyond the upper or lower limit), the real-time load on the current phase, and whether the meter and the meter with the voltage exceeding the limit belong to the same branch line but different phases. The system selects the meter that contributes most to improving the current three-phase imbalance as the target, determines the address of its associated automatic phase balancing device and the phase switching target (e.g., switching from phase A to phase B), and issues a phase switching command. After receiving the phase switching command from A to B, the automatic phase balancing device of the meter reports back to the master station that it has received the command and begins execution.

[0045] The meter's automatic balancing and commutation device is authorized by the main station and autonomously completes the commutation operation locally. Step 1: Primary Phase (A Phase) Thyristor Power Supply: The MCU controller controls the A Phase parallel bidirectional thyristor to conduct. After the A Phase parallel bidirectional thyristor is successfully conducted, the main contacts of the A Phase magnetic latching relay are disconnected, and the power supply of A Phase is switched from the original A Phase magnetic latching relay main contacts to the temporary power supply of the A Phase bidirectional thyristor.

[0046] More preferably, when the acquisition system determines and issues a commutation permission command, the authorized target MCU control unit completes the local operation command. At this time, the specific operation is entirely executed by the local MCU control unit, which maximizes the principle of ensuring the fastest possible timeliness and is a key factor in achieving a commutation time of less than 0.01 seconds.

[0047] Step 2: Instantaneous Switching: The MCU controller tracks the instantaneous value of the phase A current in real time through the phase A current comparator and the phase A voltage comparator (in one specific implementation, the voltage and current comparators can be integrated four-channel comparator chips, such as the LM339, whose typical response time is 1.3 microseconds, which is sufficient to meet the accuracy requirements of zero-crossing detection). When the phase A voltage instantaneously crosses zero and the phase A current approaches zero, the phase A parallel bidirectional thyristor is triggered to turn off. After the MCU controller confirms that the phase A parallel bidirectional thyristor is turned off, it immediately triggers the phase B parallel bidirectional thyristor to turn on at the instant the phase B voltage crosses zero. Since the phase A thyristor turn-off and phase B thyristor turn-on are both performed near the voltage zero-crossing point, and the interrupt response time of the MCU controller is in the microsecond range, the time difference between the two is less than 10 microseconds. During this extremely short time, the load is maintained by energy storage elements (such as parallel capacitors on the load side), achieving uninterrupted voltage at the load end.

[0048] In this invention, the instantaneous switching process takes less than 0.01 seconds. The normal commutation time of 0.02 seconds is the critical value at which most household appliances restart or freeze. The specific reason why this invention can achieve a commutation switching time of less than 0.01 seconds is as follows: 1. This invention uses an MCU controller to perform operations locally authorized by the master station, which ensures zero signal transmission delay and reliably guarantees the shortest possible time. 2. This invention uses an MCU controller that integrates voltage and current comparators for phases A, B, and C using the same motherboard surface mount technology. This results in more accurate data acquisition and zero-delay transmission, further ensuring the shortest possible lead time. 3. The present invention uses voltage comparators and current comparators as zero-crossing voltage and current judgment tools, which is more accurate than the traditional method of using current transformers and voltage transformers as zero-crossing voltage and current judgment tools. It can better cope with various complex harmonic scenarios generated by modern household appliances, and has no magnetic field induction delay, further ensuring safe commutation.

[0049] Step 3: Target Phase Main Contact Closure: After the MCU controller confirms that all main contacts of the three-phase magnetic latching relays are open and that only the B-phase bidirectional thyristor is conducting normally, it closes the main contacts of the B-phase magnetic latching relay. Once the contacts are confirmed to be fully engaged, the B-phase bidirectional thyristor is turned off. The MCU controller stops outputting trigger signals to the B-phase bidirectional thyristor, utilizing the thyristor's natural turn-off characteristic when the AC current crosses zero. The MCU controller detects the current of the B-phase bidirectional thyristor through the B-phase current comparator. Only after confirming that it has been reliably turned off does it determine that the commutation operation is complete, and the successful execution result is reported to the master station via the RS485 communication interface unit.

[0050] Step 4: The main station analyzes the data again to see if the voltage values ​​of the electricity meters of each branch user in the distribution area exceed the limit. If it is still necessary to continue adjusting, the system will issue a switching command again to the automatic balancing switching device associated with another electricity meter that meets the switching conditions, until the power supply voltage of all electricity meters in the distribution area is qualified and meets the standard.

[0051] The key technologies that enable this invention to achieve rapid, miniaturized, and high-precision commutation are as follows: 1. Guaranteed commutation speed (<0.01 seconds seamless switching): The commutation switching time of this invention is less than 0.01 seconds, which is lower than the critical value (about 0.02 seconds) for most household appliances to restart or crash, achieving a completely imperceptible commutation experience for users. This speed indicator is ensured by the following three measures: (1) The MCU controller adopts the local autonomous execution method after authorization by the master station, which eliminates the communication delay of remote real-time interaction; (2) The voltage comparators and current comparators of the three phases A, B, and C adopt the same motherboard surface mount technology, which has the shortest data acquisition and transmission path and no delay; (3) The voltage comparators and current comparators are used to replace the traditional voltage transformers and current transformers as zero-crossing detection tools, which have fast response speed, no magnetic field induction delay, and can accurately capture the zero-crossing point in complex harmonic environments.

[0052] 2. Miniaturized integrated protection (compatible with standard meter boxes): This invention integrates the commutation execution unit (magnetic latching relay and bidirectional thyristor), MCU control unit, and communication interface unit onto a single PCB board. The overall size is compatible with the internal space of existing standard single-phase meter boxes, allowing for direct installation without modifying the meter box structure. All core components use standard materials from the State Grid, eliminating the need for custom development and offering cost advantages for mass production.

[0053] 3. Commutation accuracy assurance (precise zero-crossing switching): This invention employs a dual-criteria zero-crossing detection scheme using both voltage and current comparators. It simultaneously monitors both voltage and current zero-crossing points to ensure switching occurs at the optimal moment when the voltage instantaneously crosses zero and the current approaches zero. Compared to a single-criteria scheme, this dual-criteria approach effectively addresses harmonics and current distortions generated by modern household appliances (such as LED lights, inverter air conditioners, and induction cookers), avoiding misjudgments caused by waveform distortion and ensuring that each commutation is completed under optimal electrical conditions, minimizing arcing and impact.

[0054] The electrical logic that ensures safety during commutation includes: 1. Only one of the three phases can be connected at any given time; 2. If any step in the automatic commutation process fails, it will return to the initial state; 3. During automatic phase switching, if the main contact of the magnetic latching relay and the bidirectional thyristor of the same phase are simultaneously in the conducting state for more than 30 minutes (this threshold is calculated based on the thermal capacity and heat dissipation conditions of the thyristor to ensure that it will not be damaged due to overheating within this time), it is determined that the thyristor of that phase has a short circuit fault. The system triggers the generation of a thyristor fault work order and notifies the maintenance personnel to handle it on-site within 3 days.

[0055] 4. If the magnetic latching relay fails to engage or disengage within the specified time during the commutation process (determined by the MCU through auxiliary contacts or current detection), the system determines it to be a mechanical fault of the relay, immediately terminates the commutation operation, restores the device to the initial phase before commutation, and generates a relay fault alarm to report to the master station.

[0056] Example 2 This embodiment illustrates the system-level application and control method of the device described in Embodiment 1 in a real distribution network area. This application, through a centralized control algorithm deployed at the master station, coordinates the scheduling of multiple meters equipped with automatic phase-balancing devices within the distribution area, achieving automatic optimization of the three-phase load at the distribution area level. The process of the system master station selecting and executing phase-balancing meters is as follows: Figure 3 As shown: Basic requirements: The installation rate of single-phase meter boxes (generally multi-meter positions) with three-phase load automatic switching devices is no less than 30% for each branch line. A data acquisition terminal is installed at the main meter station of the distribution area. The acquisition terminal establishes a communication connection with the main meter station of the distribution area via a 485 line to achieve data exchange; the acquisition terminal connects with the carrier communication module of each meter in each branch meter box via HPLC low-voltage power line carrier technology to achieve data exchange; the acquisition terminal is responsible for collecting and storing data from all the electricity meters under it, and connects with the main acquisition station via a GPRS channel using an uplink communication module equipped with a SIM card to achieve data exchange; the main acquisition station connects to the intranet of all county company monitoring computers via fiber optic cable to achieve data exchange.

[0057] 1. First Priority: User's electricity meter voltage exceeds the upper limit > 235V (normal value = 220V). Note: Exceeding the upper limit will easily shorten the lifespan of electrical appliances, easily burn out appliances, and easily cause fires. (Currently: The data acquisition system master station generates a voltage upper limit over-limit work order in real time based on the electricity meter's voltage upper limit over-limit event. At this time, the work order status is "pending dispatch"; when the system monitoring personnel discover the voltage upper limit over-limit event, the work order is dispatched to the transformer area manager and the manager is notified to manually adjust the phase on-site. At this time, the work order status is "pending feedback"; after the data acquisition system master station detects that the user's electricity meter voltage is within the acceptable range, it automatically changes the work order status to "archived".) The method is as follows: The data acquisition system master station immediately generates a voltage limit exceedance work order based on the voltage limit exceedance event of the electricity meter (voltage limit exceedance lasting 30 minutes). The master station then queries the voltage and load status of other meters in the same transformer substation and branch line as the meter associated with the voltage limit exceedance event, and performs data statistical analysis. Simultaneously, it analyzes the overall voltage and current situation of the three phases (A, B, and C) in the transformer substation. Since voltage limit exceedance generally occurs when the load on that phase is low, while the load on other phases in the same transformer substation is high, the master station prioritizes meters in different phases, on the same branch line, the nearest meter, and the meter with the highest load (with automatic phase switching device) to locate the associated automatic phase switching device and issues an automatic phase switching command to authorize the automatic phase switching operation. Once the meter completes the automatic phase switching operation, it reports to the master station. The master station then re-checks the voltage status of all meters in the transformer substation. If voltage limit exceedance still exists, the above process is repeated until the voltage of all meters in the transformer substation is within acceptable limits.

[0058] The iteration termination condition is the same as the first priority. When there are meters in the same transformer area that are both above the upper limit and below the lower limit, the system will process the above-upper-limit event first, and then process the below-lower-limit event after all above-upper-limit events are eliminated.

[0059] 2. Second Priority: User's electricity meter voltage below the lower limit (<198V, normal value = 220V). Note: A user's voltage below the lower limit will cause difficulties in starting motor-driven appliances, some appliances will not work properly, appliances will start frequently or freeze, LED lights will flicker, etc.

[0060] The method is as follows: The data acquisition system master station immediately generates a voltage lower limit work order (voltage lower limit lasting 30 minutes) based on the voltage lower limit event of the electricity meter. The master station then queries the voltage and load status of other meters in the same transformer substation and branch line as the meter associated with the voltage lower limit event, and performs data statistical analysis. Simultaneously, it analyzes the overall voltage and current situation of the three phases (A, B, and C) in that transformer substation. Since a voltage lower limit event generally occurs when the load on that phase is high, while the load on other phases in the same transformer substation is low, the master station prioritizes meters in the following order: non-phase, same branch line, nearest meter, and meter with the highest load (with automatic phase switching device), and issues an automatic phase switching command to authorize the automatic phase switching operation. Once the meter completes the automatic phase switching operation, it reports to the master station. The master station then re-checks the voltage status of all meters in the transformer substation. If a voltage lower limit event still exists, the above process is repeated until the voltage of all meters in the transformer substation is within acceptable limits.

[0061] 3. Third Priority: Severe three-phase current imbalance in the transformer substation, with an imbalance degree >25% and a duration exceeding 30 minutes. Severe three-phase current imbalance in the transformer substation will lead to reduced transformer utilization, increased transformer temperature rise and shortened lifespan, increased zero-sequence current and increased line losses, etc.

[0062] The method is as follows: The data acquisition system master station calculates the three-phase current load balance of all transformer substations based on the load values ​​of all energy meters across the region every 15 minutes. For transformer substations with a three-phase current imbalance greater than 25% and a duration exceeding 30 minutes, the data acquisition system master station performs data statistical analysis on all energy meters connected to the three phases A, B, and C of that substation. Prioritizing the meter with the largest load equipped with an automatic phase-switching device, the master station switches the meter from its current connected phase to the phase with the smallest current overall load among phases A, B, and C, and issues an automatic phase-switching command to authorize the automatic phase-switching operation. Once the meter completes the automatic phase-switching operation, it reports back to the master station. The master station then re-checks the overall load balance of the transformer substation and repeats the above process until the overall load balance of the transformer substation reaches a satisfactory level.

[0063] Priority preemption rule: During the execution of any priority adjustment, if a higher priority event is detected (first priority is higher than second priority, second priority is higher than third priority), the system will pause the remaining adjustment tasks of the current priority and start processing the newly triggered high-priority event. After the high-priority event is processed, the remaining adjustment tasks of the original priority will resume execution.

[0064] Note: No full coverage is required. Through simulation verification and field pilot testing, it is only necessary to configure 20% to 30% (25% recommended) of the total number of meter boxes in each branch of the low-voltage power distribution line. This will stabilize the three-phase current imbalance in the distribution area from a typical value of over 40% to within 20%, thus achieving effective automatic adjustment of the three-phase load balance.

[0065] Example 3 The present invention also proposes a terminal, including a processor and a storage medium: The storage medium is used to store instructions. The processor is used to perform the steps of the above method according to the instructions.

[0066] Example 4 The present invention also proposes a computer-readable storage medium having a computer program stored thereon, which, when executed by a processor, implements the steps of the above-described method.

[0067] This disclosure can be a system, method, and / or computer program product. A computer program product may include a computer-readable storage medium having computer-readable program instructions loaded thereon for causing a processor to implement various aspects of this disclosure.

[0068] Computer-readable storage media can be tangible devices capable of holding and storing instructions for use by an instruction execution device. Computer-readable storage media can be, for example—but not limited to—electrical storage devices, magnetic storage devices, optical storage devices, electromagnetic storage devices, semiconductor storage devices, or any suitable combination of the foregoing. More specific examples (a non-exhaustive list) of computer-readable storage media include: portable computer disks, hard disks, random access memory (RAM), read-only memory (ROM), erasable programmable read-only memory (EPROM or flash memory), static random access memory (SRAM), portable compact disc read-only memory (CD-ROM), digital multifunction disc (DVD), memory sticks, floppy disks, mechanical encoding devices, such as punch cards or recessed protrusions storing instructions thereon, and any suitable combination of the foregoing. The computer-readable storage media used herein are not to be construed as transient signals themselves, such as radio waves or other freely propagating electromagnetic waves, electromagnetic waves propagating through waveguides or other transmission media (e.g., light pulses through fiber optic cables), or electrical signals transmitted through wires.

[0069] The computer-readable program instructions described herein can be downloaded from computer-readable storage media to various computing / processing devices, or downloaded via a network, such as the Internet, local area network, wide area network, and / or wireless network, to an external computer or external storage device. The network may include copper transmission cables, fiber optic transmission, wireless transmission, routers, firewalls, switches, gateway computers, and / or edge servers. A network adapter card or network interface in each computing / processing device receives the computer-readable program instructions from the network and forwards them to the computer-readable storage media in the respective computing / processing device.

[0070] Computer program instructions used to perform the operations of this disclosure may be assembly instructions, instruction set architecture (ISA) instructions, machine instructions, machine-dependent instructions, microcode, firmware instructions, status setting data, or source code or object code written in any combination of one or more programming languages, including object-oriented programming languages ​​such as Smalltalk, C++, etc., and conventional procedural programming languages ​​such as the "C" language or similar programming languages. The computer-readable program instructions may execute entirely on the user's computer, partially on the user's computer, as a standalone software package, partially on the user's computer and partially on a remote computer, or entirely on a remote computer or server. In cases involving a remote computer, the remote computer may be connected to the user's computer via any type of network—including a local area network (LAN) or a wide area network (WAN)—or may be connected to an external computer (e.g., via the Internet using an Internet service provider). In some embodiments, electronic circuitry, such as programmable logic circuitry, field-programmable gate arrays (FPGAs), or programmable logic arrays (PLAs), is personalized by utilizing the status information of the computer-readable program instructions to implement various aspects of this disclosure.

[0071] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit it. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that modifications or equivalent substitutions can still be made to the specific implementation of the present invention. Any modifications or equivalent substitutions that do not depart from the spirit and scope of the present invention should be covered within the protection scope of the claims of the present invention.

Claims

1. A device for automatic switching of three-phase loads within a low-voltage single-phase meter box, characterized in that, include: The commutation execution unit includes an A-phase commutation execution module, a B-phase commutation execution module, and a C-phase commutation execution module. Each commutation execution module consists of a bidirectional thyristor and a magnetic latching relay connected in parallel. The A-phase, B-phase, and C-phase phase lines are respectively connected to the input terminals of the A-phase, B-phase, and C-phase commutation execution modules. The output terminals of the A, B, and C phase commutation execution modules are short-circuited to form a common output node, which is connected to the incoming live wire terminal of the single-phase energy meter. The three-phase neutral wires are directly connected to the incoming neutral wire terminal of the single-phase energy meter. The MCU control unit includes three corresponding voltage comparators and current comparators, A, B, and C. The input terminals of each phase voltage comparator are connected to the corresponding phase line, and each phase current comparator is connected in series in the corresponding phase sampling circuit. The MCU control unit is connected to each voltage comparator, each current comparator, the trigger terminal of each bidirectional thyristor, the drive terminal of each magnetic latching relay, and the communication interface unit. The communication interface unit is used to receive external commutation commands and forward them to the MCU control unit. The MCU control unit performs the following operations according to the commutation command: controls the bidirectional thyristor of the currently connected phase to be turned on, and disconnects the main contact of the magnetic latching relay of the currently connected phase after confirming the turn-on; tracks the current and voltage through the current comparator and voltage comparator of the currently connected phase, turns off the bidirectional thyristor of the currently connected phase when the voltage of the currently connected phase crosses zero and the current meets the conditions, and triggers the bidirectional thyristor of the target phase to be turned on when the voltage of the target phase crosses zero after confirming the turn-off. After confirming that all the main contacts of the three-phase magnetic latching relay are open and only the bidirectional thyristor of the target phase is conducting, close the main contacts of the magnetic latching relay of the target phase. After confirming that the contacts are engaged, turn off the bidirectional thyristor of the target phase.

2. The device for automatic switching of three-phase loads in a low-voltage single-phase meter box according to claim 1, characterized in that: The voltage comparator and current comparator are integrated quad comparator chips; The communication interface unit establishes a communication connection with the acquisition terminal via HPLC low-voltage power line carrier; The MCU control unit, communication interface unit, and A, B, and C three-phase commutation execution modules are integrated on the same PCB board.

3. The device for automatic switching of three-phase loads in a low-voltage single-phase meter box according to claim 1, characterized in that: The bidirectional thyristor turn-off method for the target phase is as follows: The MCU controller stops outputting trigger signals to the target phase bidirectional thyristor and turns it off by taking advantage of the characteristic that the thyristor turns off naturally when the AC current crosses zero. The MCU controller detects the current of the target phase bidirectional thyristor through the current comparator of the target phase and determines that the commutation operation is complete after confirming that it has been turned off.

4. The device for automatic switching of three-phase loads in a low-voltage single-phase meter box according to claim 1, characterized in that: The MCU controller is also used to execute security logic: Only one of the three phases can be connected at any given time; If any step in the commutation process fails, the device will be restored to the initial phase before commutation.

5. The device for automatic three-phase load switching in a low-voltage single-phase meter box according to claim 1, characterized in that: The MCU controller is also used to execute security logic: If the main contacts of the magnetic latching relay and the bidirectional thyristor in the same phase are simultaneously in the conducting state and the duration exceeds the set time, it is determined that the thyristor in that phase has a short circuit fault, and a thyristor fault work order is generated.

6. The device for automatic switching of three-phase loads in a low-voltage single-phase meter box according to claim 1, characterized in that: The MCU controller is also used to execute security logic: If the magnetic latching relay fails to engage or disengage within the specified time during the commutation process, it is determined to be a mechanical fault of the relay. The commutation operation is immediately terminated and the device is restored to the initial phase before the commutation. At the same time, a relay fault alarm is generated.

7. A method for automatic switching of three-phase loads in a low-voltage single-phase meter box using the device described in any one of claims 1-6, characterized in that, include: The data acquisition system master station determines the target meters that need to be switched according to preset priority filtering rules based on events such as voltage exceeding the upper limit, voltage exceeding the lower limit, or three-phase current imbalance in the distribution area. The data acquisition system master station sends a phase switching command to the three-phase load automatic balancing switching mechanism associated with the target meter, authorizing it to perform the phase switching operation; After receiving the phase switching command, the three-phase load automatic balancing switching mechanism autonomously completes the phase switching operation from the current connected phase to the target phase and reports the execution result to the main station of the acquisition system. The data acquisition system master station rechecks the voltage status or three-phase current balance of all meters in the area. If there are still voltage over-limit or three-phase current imbalances, the above steps are repeated until all are qualified.

8. A method for automatic switching of three-phase loads in a low-voltage single-phase meter box according to claim 7, characterized in that: The preset priority filtering rules include: The first priority event is voltage exceeding the upper limit, the second priority event is voltage exceeding the lower limit, and the third priority event is three-phase current imbalance in the transformer area.

9. A method for automatic switching of three-phase loads in a low-voltage single-phase meter box according to claim 8, characterized in that: When both voltage exceeding the upper limit and voltage exceeding the lower limit events exist simultaneously in the same transformer area, the system prioritizes processing the voltage exceeding the upper limit event, and processes the voltage exceeding the lower limit event only after all upper limit events have been eliminated.

10. A method for automatic switching of three-phase loads in a low-voltage single-phase meter box according to claim 7, characterized in that: If a higher priority event is detected during the execution of any priority adjustment, the system will pause the remaining adjustment tasks of the current priority and start processing the newly triggered high priority event. The remaining adjustment tasks of the original priority will resume execution after the high priority event has been processed.

11. A method for automatic switching of three-phase loads in a low-voltage single-phase meter box according to claim 7, characterized in that: The preset priority filtering rules determine the target electricity meter based on the following criteria: The voltage deviation of the current phase connected to the meter, the real-time load of the meter on the current phase, and whether the meter and the voltage over-limit meter belong to the same branch line and different phases.

12. A method for automatic switching of three-phase loads in a low-voltage single-phase meter box according to claim 7, characterized in that: If the voltage is still not fully qualified after the number of consecutive adjustments reaches the preset maximum value, the system will stop automatic adjustment and send an alarm to the maintenance personnel.

13. A terminal, comprising a processor and a storage medium; characterized in that: The storage medium is used to store instructions. The processor is configured to operate according to the instructions to perform the steps of the method according to any one of claims 7-12.

14. A computer-readable storage medium having a computer program stored thereon, characterized in that, When executed by a processor, the program implements the steps of the method according to any one of claims 7-12.

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