Power utilization switching control system for thermal power plant

Abstract

The invention discloses a power utilization switching control system for a thermal power plant, which integrates a sensor module, a PLC control module, a change-over switch, an alarm module and a storage module into a unified control system, and replaces a mechanical or analog control mode depending on a hardware relay and a synchronizing device in the prior art by taking a PLC as a built-in preset logic of a core control unit. Hardware intensification and function software are realized; besides, the sensor module collects voltage and current signals, and compared with the prior art that only voltage parameters are monitored, the newly added current signal collection can more accurately recognize serious faults such as short circuit and overcurrent, double data support is provided for subsequent fault judgment, and one-sidedness of single voltage detection is avoided. The system further comprises a storage module, and the storage module records operation data and provides a data basis for fault tracing and system optimization.

Description

Technical Field

[0001] This application relates to the field of power technology, specifically to a power switching control system for thermal power plants. Background Technology

[0002] In a power plant's power system, a stable supply of auxiliary power is a crucial element in ensuring the safe operation of generating units. Auxiliary power switching refers to the timely switching of the power supply from the main power source to the backup power source when an anomaly occurs in the main power source (such as voltage exceeding the rated range or a serious fault). This ensures the continuous and stable operation of equipment within the plant and avoids serious consequences such as abnormal unit operation or even shutdown due to power loss.

[0003] In existing technologies, the plant power switching cabinet is equipped with a SIMENS switching device. This switching device mainly relies on traditional control logic to achieve main and backup power switching, including voltage detection when the main power supply is normal and initiating backup power switching logic when the main power supply is abnormal. However, with the increase in operating time, this device has revealed many shortcomings. On the one hand, the equipment is severely aging, and its operating conditions are difficult to guarantee, leading to unstable device performance and increasing the risk of plant power switching failure. Switching failure may directly cause plant power outage, posing a significant threat to the safe operation of the unit. On the other hand, the corresponding spare parts for this device are no longer in production, making equipment maintenance and fault repair difficult, further affecting the reliability of the system. In addition, the control logic of the existing device may have deficiencies in fault interlocking. When a serious fault occurs in the main power supply or backup power supply (such as short circuit or overcurrent), the interlocking mechanism may not be triggered in a timely and effective manner, posing a risk of further equipment damage due to improper switching. At the same time, this device may rely on relatively complex control loops such as synchronizing devices, increasing the complexity and failure rate of the system, which is not conducive to achieving efficient and accurate switching control.

[0004] Therefore, how to achieve stable switching control between primary and backup power supplies is a problem that urgently needs to be solved by those skilled in the art. Summary of the Invention

[0005] In view of the above-mentioned defects or deficiencies in the prior art, it is desirable to provide a power switching control system for thermal power plants that can realize stable switching control of main and backup power sources.

[0006] This application provides a power supply switching control system for thermal power plants, including:

[0007] The system includes a switch, sensor module, PLC control module, alarm module, and storage module.

[0008] The sensor module is used to collect voltage and current signals from the main power supply and the backup power supply.

[0009] The PLC control module is connected to the sensor module, the switch, the alarm module and the storage module respectively, and is used to control the action of the switch according to preset logic and drive the alarm module to work.

[0010] The storage module is used to record system operation data.

[0011] In one embodiment, the PLC control module is used for:

[0012] If the main power supply voltage is within the rated range, the backup power supply switching command may be executed;

[0013] If the main power supply voltage exceeds the rated range, an alarm trigger signal is generated and the backup power switching submodule is triggered.

[0014] The backup power switching submodule is used to: send a switching command to the switching switch when the backup power voltage is within the rated range and there is no fault signal; and cancel the alarm trigger signal after the backup power switching is successful.

[0015] The alarm module is used to: trigger an alarm upon detecting the alarm trigger signal, and cancel the alarm if the alarm trigger signal disappears.

[0016] In one embodiment, the backup power switching module is further configured to: trigger the PLC control module to collect the voltage of the backup power supply over a period of time and calculate the voltage stability index before performing the switching; and allow the execution of the switching command when the voltage stability index reaches a stability threshold.

[0017] In one embodiment, the PLC control module has a built-in fault lockout submodule, which is used to trigger a lockout state when either the main power supply or the backup power supply experiences any of the following faults:

[0018] The current value exceeds a specified multiple of the rated current, and the duration reaches the first time threshold.

[0019] The voltage drop is less than a specified percentage of the rated voltage, and the duration reaches a second time threshold.

[0020] A fault signal indicating a short circuit in the line has been detected.

[0021] In the locked state, switching operations are prohibited, and a fault lock signal is generated.

[0022] In one embodiment, the fault-locking submodule is further configured to: release the lockout state when any of the following release conditions occur;

[0023] The conditions for releasing the fault lockout state include:

[0024] Received a manually entered cancellation command;

[0025] The fault that triggered the lockout state has disappeared, and the parameters of the main power supply and the backup power supply remain normal for a continuous period of time.

[0026] In one embodiment, the switching switch is a three-position electric switch, including three positions: main power supply, backup power supply, and maintenance isolation.

[0027] The PLC control module controls the motor drive circuit of the switching switch through a relay group.

[0028] In one embodiment, the alarm module includes a local audible and visual alarm and a remote communication module;

[0029] The alarm module is used to: activate the local audible and visual alarm when an alarm trigger signal is detected, and send a fault code through the remote communication module.

[0030] In one embodiment, the operational data recorded by the storage module includes: real-time voltage / current waveforms of the main / backup power supply, switching time point, switching duration, switching success / failure status, fault lockout triggering reasons, and historical operation records.

[0031] In one embodiment, the PLC control module further includes: a synchronization control submodule;

[0032] The synchronization control submodule is used to: collect the voltage phase difference and frequency difference between the main power supply and the backup power supply in real time; if the phase difference is not higher than the phase difference threshold and the frequency difference is not higher than the frequency difference threshold, the parallel switching command is allowed; if the phase difference is higher than the phase difference threshold or the frequency difference is higher than the frequency difference threshold, the series power-off switching command is executed.

[0033] In one embodiment, the power switching control system for thermal power plants further includes a power supply module. The power supply module adopts a dual-channel AC / DC redundant power supply design, with the main power supply circuit connected to the plant power bus and the backup power supply circuit connected to the UPS power supply.

[0034] The power switching control system for thermal power plants provided in this application integrates sensor modules, PLC control modules, actuators (switching switches), alarm modules, and storage modules into a unified control system, forming a fully closed-loop architecture from data acquisition, logic judgment, execution control to status feedback. By using a PLC as the core control unit with built-in preset logic, it replaces the mechanical / analog control methods in existing technologies that rely on hardware relays and synchronizing devices. This achieves hardware integration and software-based functionality. On the one hand, logic parameters (such as voltage thresholds and switching times) can be adjusted through software configuration without hardware modification, solving the maintenance problems caused by spare parts outages in existing devices. On the other hand, the PLC's digital signal processing capabilities support millisecond-level real-time calculations, resulting in faster response and smaller errors compared to traditional analog circuits. Furthermore, the sensor modules collect voltage and current signals. Compared to existing technologies that may only monitor voltage parameters, the addition of current signal acquisition can more accurately identify serious faults such as short circuits and overcurrents, providing dual data support for subsequent fault diagnosis and avoiding the limitations of single voltage detection. The system also includes a storage module that records operating data, providing a data foundation for fault tracing and system optimization.

[0035] Additional aspects and advantages of the invention will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. Attached Figure Description

[0036] Other features, objects, and advantages of this application will become more apparent from the following detailed description of non-limiting embodiments with reference to the accompanying drawings:

[0037] Figure 1 A schematic diagram of the structure of a power switching control system for a thermal power plant provided in an embodiment of this application is shown. Detailed Implementation

[0038] The present application will now be described in further detail with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and not intended to limit it. Furthermore, it should be noted that, for ease of description, only the parts relevant to the invention are shown in the accompanying drawings.

[0039] It should be noted that, unless otherwise specified, the embodiments and features described in this application can be combined with each other. The present application will now be described in detail with reference to the accompanying drawings and embodiments. Although the embodiments of this application provide method operation instruction steps as shown in the following embodiments or drawings, more or fewer operation instruction steps may be included in the method based on conventional or non-inventive effort. In steps where there is no logically necessary causal relationship, the execution order of these steps is not limited to the execution order provided in the embodiments of this application. In actual processing or when the device executes, the method may be executed sequentially or in parallel according to the method shown in the embodiments or drawings.

[0040] Example 1:

[0041] This embodiment proposes a power supply switching control system for thermal power plants. Please refer to [reference needed]. Figure 1 , Figure 1 A structural block diagram of the power switching control system for thermal power plants provided in this embodiment is shown. Figure 1 As shown, the system mainly includes: a switching switch, a sensor module, a PLC control module, an alarm module, and a storage module. These five core modules enable stable switching control between the main and backup power supplies.

[0042] The sensor module, as the data acquisition layer, mainly includes a main power supply voltage sensor, a main power supply current sensor, a backup power supply voltage sensor, and a backup power supply current sensor. It is used to collect the voltage and current of the main power supply and backup power supply, and can also collect frequency signals, etc. Sensor components can be added according to actual usage needs.

[0043] The sensor module and the PLC control module can be connected through an isolated signal transmitter to ensure strong and weak current isolation and improve anti-interference capability.

[0044] The PLC control module, serving as the logic control layer, employs an industrial-grade PLC controller with a built-in high-speed CPU and dedicated signal processing module. It connects to the sensor module, switching switch, alarm module, and storage module, primarily controlling the switching switch's operation according to preset logic and driving the alarm module. Its core functions include: 1. Data processing: Receiving voltage / current signals from the sensor module and calculating parameters such as voltage deviation (e.g., ±15% of rated value), frequency difference, and phase difference in real time; 2. Logic execution: A built-in core algorithm (master / standby switching logic) outputs control commands based on preset thresholds (e.g., voltage 85% / 115%, current 1.5 times rated value); 3. Timing control: Precisely controlling the switching switch's action sequence (e.g., switching wait time ≤200ms), with built-in protection against frequent switching (interval ≥30 seconds); 4. Communication interface: Supporting industrial buses such as Modbus RTU and Profibus for communication with the alarm module, storage module, and external DCS system.

[0045] As the execution layer, the transfer switch is the core component for switching power between the main power supply and the backup power supply. A transfer switch is a switching device with bidirectional or multi-channel switching capabilities, typically employing mechanical contacts or electronic switches (such as solid-state relays). Under the command of the PLC control module, it can disconnect the main power supply circuit and connect the backup power supply circuit, or vice versa, thereby achieving automatic power supply switching and ensuring continuous power supply to the system when the main power supply is abnormal. Specifically, under normal conditions, the main power supply circuit is closed and the backup power supply circuit is disconnected, allowing the power plant's electrical equipment to be powered by the main power supply. Under fault conditions, when the sensor module detects abnormal main power supply voltage (such as below 85% or above 115% of the rated value), current overload, short circuit, or other fault signals, the PLC control module sends a command to the transfer switch to disconnect the main power supply and connect the backup power supply, preventing equipment shutdown due to power failure.

[0046] The alarm module, as the human-machine interface layer, is a key functional unit for fault early warning, status indication, and anomaly notification. Its core function is to transmit system anomaly information to operators through audible and visual signals or communication methods, ensuring timely fault handling and preventing the escalation of accidents. This embodiment does not limit the specific hardware composition of the alarm module or the corresponding alerting methods; these can be set according to the actual application scenario's requirements, and will not be elaborated upon in this embodiment.

[0047] As the data management layer, the storage module is a key unit for realizing data recording, historical tracing, and system status analysis. Its core function is to persistently store system operating data, fault information, operation records, and other system status data through hardware storage media and software management programs, providing data support for equipment maintenance, fault analysis, and system optimization.

[0048] In this embodiment, the specific data types recorded by the storage module are not limited. They can be configured according to the maintenance needs of the actual application scenario. One type of data recorded by the storage module includes: real-time voltage / current waveforms of the main / backup power supply, switching time points, switching duration, switching success / failure status, fault lockout trigger reasons, and historical operation records. Specifically, it records the dynamic curves of the electrical signals of the main and backup power supplies, reflecting instantaneous characteristics such as voltage fluctuations and current distortions. Waveform data can identify power quality problems (e.g., whether a voltage drop is caused by lightning strikes). Fault cause records can directly point to the source of the anomaly, shortening troubleshooting time. It marks the start and end times of the main / backup power supply switching, as well as the switching process time, and records the results of each switching operation. This can be used to evaluate the efficiency and reliability of power switching, providing data support for optimizing PLC control logic. It marks the specific fault type (e.g., overcurrent, undervoltage, short circuit) and trigger time that causes the system to enter a lockout state, and saves manual or automatic control operation logs (e.g., manual switching, fault reset commands), tracing the operation trajectory and facilitating accident tracing and responsibility determination. Furthermore, it can also record equipment status parameters, load data, environmental parameters, energy consumption statistics, etc.

[0049] It should be noted that this embodiment only uses the above data types as examples for introduction, but is not limited to them. The system structure and functions under other record data types can refer to the introduction of this embodiment, and will not be repeated here.

[0050] The power switching control system for thermal power plants provided in this embodiment integrates sensor modules, PLC control modules, switching switches, alarm modules, and storage modules into a unified control system, forming a fully closed-loop architecture from data acquisition, logic judgment, execution control to status feedback. By using a PLC as the core control unit with built-in preset logic, it replaces the mechanical or analog control methods in existing technologies that rely on hardware relays and synchronizing devices. This achieves hardware integration and software-based functionality. On the one hand, logic parameters can be adjusted through software configuration without hardware modification, solving the maintenance problems caused by spare parts outages in existing devices. On the other hand, the PLC's digital signal processing capability supports millisecond-level real-time calculations, resulting in faster response and smaller errors compared to traditional analog circuits. Furthermore, the sensor modules collect voltage and current signals. Compared to existing technologies that only monitor voltage parameters, the addition of current signal acquisition can more accurately identify serious faults such as short circuits and overcurrents, providing dual data support for subsequent fault diagnosis and avoiding the limitations of single voltage detection. The system also includes a storage module that records operating data, providing a data foundation for fault tracing and system optimization. In summary, the power switching control system for thermal power plants provided in this embodiment has a fast response speed, is easy to maintain, has high monitoring accuracy, and high stability during main and backup power switching.

[0051] Example 2:

[0052] To deepen the understanding of the collaboration between modules, this embodiment introduces two working scenarios.

[0053] Normal operating scenario (mains power supply):

[0054] 1. The sensor module collects the main power supply voltage (e.g., 400V±10%) and current signal in real time and transmits them to the PLC control module;

[0055] 2. The PLC control module determines that the main power parameters are normal, outputs a command to keep the switch in the main power position, and the alarm module is in standby mode.

[0056] 3. The storage module records the main power parameters at 1-second intervals to form a real-time operating curve.

[0057] Main power supply abnormal switching scenarios (such as voltage suddenly dropping to 70% of rated value):

[0058] 1. The sensor detects that the main power supply voltage is less than 85% of the rated value, triggering the PLC's standby switching logic;

[0059] 2. PLC startup backup power supply pre-verification: detect backup power supply voltage (e.g., 390V), frequency (50±0.2Hz), and calculate phase difference (<15°);

[0060] 3. After the verification is passed, the PLC sends a "switch to backup power" command to the switch and at the same time drives the alarm module to issue an audible and visual alarm (such as "main power undervoltage" code 0x01).

[0061] 4. After the switch is activated, a status signal is fed back. The PLC confirms that the switch is successful (backup power supply voltage signal is connected), cancels the alarm, and the storage module records the switch time (e.g., 14:23:15) and duration (75ms).

[0062] Example 3:

[0063] To ensure automatic and stable switching between primary and backup power supplies in different application scenarios, this embodiment proposes a specific control logic setting in the PLC control module. Specifically, the control logic in the PLC control module can be set as follows:

[0064] 1. If the main power supply voltage is within the rated range, the backup power supply switching command is permitted;

[0065] 2. If the main power supply voltage exceeds the rated range, an alarm trigger signal is generated and the backup power supply switching submodule is triggered. The backup power supply switching submodule is used to: send a switching command to the switching switch when the backup power supply voltage is within the rated range and there is no fault signal; and cancel the alarm trigger signal after the backup power supply is successfully switched.

[0066] The alarm module is used to: trigger an alarm upon detecting an alarm trigger signal, and cancel the alarm if the alarm trigger signal disappears.

[0067] In the above control logic, the main power supply voltage is continuously monitored. If the voltage is within the rated range (e.g., 380V±10%), it indicates that the main power supply is in a normal state, and the backup power supply switching command is allowed to be executed, but the switching is not actively triggered.

[0068] When the main power supply voltage is less than the lower limit (e.g., 342V = 380V × 90%) or greater than the upper limit (e.g., 418V = 380V × 110%), it indicates an abnormal state of the main power supply, and an alarm trigger signal is immediately generated (e.g., digital output DO1 = 1); at the same time, the backup power supply switching submodule is triggered to start assessing the availability of the backup power supply.

[0069] The control logic of a backup power switching submodule is as follows:

[0070] 1. Check if the backup power supply voltage is within the rated range (e.g., 380V±10%);

[0071] 2. Confirm that the backup power supply has no fault signals (such as no overcurrent, short circuit, or other fault alarms);

[0072] If conditions 3, 1, and 2 are met, a switching command (such as digital output DO2 = 1) is sent to the switch to drive the switch to switch from the main power supply to the backup power supply.

[0073] The control logic settings of the PLC control module provided in this embodiment immediately trigger an alarm when the main power supply voltage exceeds the rated range, and simultaneously initiate a backup power supply switching assessment to prevent the abnormal state from escalating. At the same time, the backup power supply must meet the dual conditions of normal voltage and no fault signal before switching, eliminating the risk of switching to a faulty power supply, which is safer than the traditional single voltage detection logic. After a successful switch, the alarm trigger signal is canceled by delaying the effect of transient interference, ensuring that the system truly enters a stable state, significantly improving the success rate of plant power supply switching and the anti-maloperation capability of the alarm system, and providing a high reliability guarantee for the continuous power supply of critical loads in thermal power plants.

[0074] To improve the reliability of switching decisions, in addition to the aforementioned backup power supply switching logic, dynamic characteristic analysis of the backup power supply can be further added. By introducing a voltage stability index evaluation mechanism, switching to a pseudo-normal power supply can be avoided. Specifically, before executing the switch, the PLC control module can be triggered to collect the voltage of the backup power supply over a period of time and calculate the voltage stability index; when the voltage stability index reaches the stability threshold, the switching command is allowed to be executed.

[0075] By analyzing the fluctuation characteristics of the backup power supply voltage over a short period (e.g., 500ms to 2s), its dynamic stability is quantified. The voltage stability index can be calculated using indicators such as voltage fluctuation rate, voltage change rate, or standard deviation; this embodiment does not limit the specific metrics. The calculated results are compared with preset stability thresholds (e.g., voltage fluctuation rate ≤ 2%, standard deviation ≤ 0.5V) to determine whether switching is permissible. This method, through voltage stability index assessment, can identify backup power supply voltage amplitudes that are normal but exhibit hidden fluctuations (e.g., harmonic interference, voltage oscillations) and other dynamic defects, preventing switching to a seemingly normal but actually unstable backup power supply. This makes backup power supply switching decisions more scientific, particularly suitable for critical loads in thermal power plants with stringent power quality requirements; moreover, it can avoid switching during voltage transients, extending equipment lifespan.

[0076] Example 4:

[0077] To prevent system malfunctions under hazardous conditions and ensure equipment safety and power supply reliability, this embodiment proposes to incorporate a fault-locking submodule into the PLC control module. This submodule is used to trigger a lockout state when any of the following faults occur in the main power supply or backup power supply:

[0078] 1. The current value exceeds a specified multiple of the rated current, and the duration reaches the first time threshold;

[0079] One parameter configuration is as follows: rated current 100A, trigger value 150A / 500ms.

[0080] 2. The voltage drop is less than a specified percentage of the rated voltage, and the duration reaches the second time threshold.

[0081] One parameter configuration is as follows: rated voltage 400V, trigger value 340V / 200ms.

[0082] 3. A fault signal indicating a short circuit in the line was detected;

[0083] Fault signals for line short circuits include: the detection of short circuit protection device (such as circuit breaker) operation signal or current change rate exceeding a threshold.

[0084] Once the interlock is triggered, the PLC immediately cuts off all switching command outputs (including manual operation) to prevent the switching switch from operating, and generates a fault lockout signal (such as DO3=1), driving the alarm module to issue a specific alarm (such as system interlock - overcurrent fault), and uploads it to the system through a communication interface (such as Modbus).

[0085] This embodiment features fault interlocking design under three conditions: overcurrent fault, undervoltage fault, and short circuit fault. It replaces passive remediation with active defense, elevating the safety of the power switching system in thermal power plants to a new level. It is particularly suitable for 300MW and above units with extremely high requirements for power supply continuity, such as turbine lubricating oil pumps and boiler feedwater pumps.

[0086] Under the aforementioned fault-locked state triggering conditions, for maintenance or system operation purposes, it is necessary to set conditions for releasing the lockout state. In order to ensure the safety and flexibility of the release process, and to avoid the impact of repeated faults on the stability of system operation, this embodiment further proposes a lockout state release method, which can release the lockout state when either of the following two situations occurs.

[0087] 1. Received a manually entered cancellation command;

[0088] Granting maintenance personnel final decision-making authority is suitable for complex faults that require manual confirmation, such as testing insulation resistance after cable replacement.

[0089] 2. The fault that triggered the interlocking state has disappeared, and the parameters of the main power supply and the backup power supply remain normal for a continuous period of time.

[0090] For temporary faults that can be recovered quickly, such as a sudden voltage drop caused by lightning strikes, reduce the delay of manual operation and improve the efficiency of power restoration. In order to avoid repeated faults, continuous monitoring is required over a continuous period of time to ensure that the system truly enters a stable state and avoid misdiagnosis caused by transient fault recovery, such as when the short circuit point is not completely repaired and the voltage temporarily returns to normal.

[0091] This mechanism, through closed-loop control of fault troubleshooting, status confirmation, and safety recovery, not only avoids erroneous operation of the system when the fault is not repaired, but also prevents long-term lockout from affecting the continuity of power supply. It is an important component of the reliability design of the power switching system in thermal power plants.

[0092] Example 5:

[0093] To enhance the safety of switching control, this embodiment proposes a specific type of switching switch. Specifically, the switching switch can be a three-position electric switch, including three positions: main power supply, backup power supply, and maintenance isolation. The switch contacts connect to the main power circuit, supplying power to the load from the main power source. When switching to the backup power circuit, power is supplied in case of a main power failure. When switching from the main power supply to the backup power supply, the switch first disconnects the main power contact (0.1s) and then connects the backup power contact (0.2s), forming a zero-dead-time switching zone. The switch contacts are completely disconnected, and both the main and backup power circuits are electrically isolated. The PLC control module controls the motor drive circuit of the switching switch through a relay group.

[0094] The maintenance position of the three-position electric switch forms an independent isolation break, allowing for live maintenance of other circuits. When a withstand voltage test is required on the main power circuit, placing the switch in the maintenance isolation position prevents the test voltage from entering the backup power system and thus preventing equipment damage. Furthermore, the mechanical interlock structure ensures that the three positions cannot be connected simultaneously, eliminating the risk of short circuits caused by parallel power supply operation. This achieves a balance between safety, reliability, and maintenance efficiency in the power switching system, making it particularly suitable for scenarios with extremely high requirements for power supply continuity, such as thermal power plants and data centers.

[0095] The three-position electric switch provided in this embodiment achieves clear zoning and safe isolation of power supply status through the design of three independent workstations: main power supply, backup power supply, and maintenance isolation. The main and backup power supply workstations can achieve automatic and seamless switching through the PLC control module to ensure power supply continuity. The maintenance isolation workstation can physically disconnect the power supply during equipment maintenance to avoid the risk of live operation and significantly improve system safety. Compared with traditional two-position switches or manual switches, its electric drive mode is linked with the PLC through a relay group, supporting remote control and automatic logic triggering. This reduces the cost of manual intervention and prevents misoperation through the mechanical interlocking mechanism of the workstations. It is especially suitable for industrial power supply scenarios with high requirements for reliability, safety, and automation.

[0096] The above embodiments do not limit the specific hardware components in the alarm module. This embodiment further proposes a hardware structure composition of the alarm module, which specifically includes a local audible and visual alarm and a remote communication module. When the system detects an alarm trigger signal (such as a main or backup power failure, switching abnormality, parameter over-limit, etc.), it simultaneously starts the local audible and visual alarm and remote fault information transmission.

[0097] Specifically, the local audible and visual alarm alerts on-site personnel to the fault through flashing lights and audible sounds, facilitating nearby troubleshooting. The remote communication module sends standardized fault codes to the monitoring center or management personnel via preset communication protocols (such as Modbus, 4G / 5G, Ethernet, etc.). These codes contain information such as the fault type, location, and severity, supporting rapid remote problem location. The advantage of this design lies in constructing a dual alarm system of on-site real-time warning and remote intelligent monitoring. Local alarms ensure that on-site personnel respond immediately, preventing the fault from escalating; remote communication breaks spatial limitations, supporting centralized monitoring and cross-regional operation and maintenance, especially suitable for unattended operations and large industrial clusters. Through the digital transmission of fault codes, it can also interface with the host computer management system to achieve automatic recording, analysis, and early warning of fault data, improving the intelligence and efficiency of system operation and maintenance.

[0098] Example 6:

[0099] To ensure power supply continuity while reducing switching impact, this embodiment proposes configuring a synchronization control submodule in the PLC control module.

[0100] The synchronization control submodule is specifically used to: collect the voltage phase difference (Δφ) and frequency difference (Δf) between the main power supply and the backup power supply in real time. The phase difference reflects the degree of synchronization between the two power supplies, and the frequency difference reflects the frequency consistency between the main power supply and the backup power supply. By sampling the frequency difference and phase difference between the main and backup power supplies in real time, the switching timing is determined based on quasi-synchronous conditions (such as Δf≤0.5Hz, Δφ≤15°) to avoid system impact caused by asynchronous parallel operation.

[0101] If the phase difference is not higher than the phase difference threshold and the frequency difference is not higher than the frequency difference threshold, the parallel switching command is allowed to be executed. The system will connect in parallel first and then disconnect. The load will be powered continuously during the parallel switching process. This is suitable for equipment that is sensitive to power outages, such as DCS control systems and boiler feed pumps.

[0102] If the phase difference exceeds the phase difference threshold or the frequency difference exceeds the frequency difference threshold, or if the parameters exceed the limits, the parallel switching will generate an inrush current equivalent to 2 to 3 times the short-circuit current. Therefore, in this embodiment, a series power-off switching command is executed. First, the main power supply is disconnected, the electrical connection of the asynchronous power supply is cut off, and then the backup power supply is closed. At this time, even if the backup power supply parameters are slightly deviated, the inrush current can be controlled within 1.5 times the rated value because there is no grid-connected circulating current. After disconnecting the main power supply, a wait of 200 to 300 ms can be allowed to ensure the discharge of residual charge.

[0103] Example 7:

[0104] The above embodiments do not limit the power source for the power switching control system of thermal power plants. This embodiment provides a power module that adopts a dual-path AC / DC redundant power supply design. The main power supply circuit is connected to the plant's auxiliary power bus to obtain normal operating power; the backup power supply circuit is connected to the UPS power supply, which provides power outage maintenance capability through the UPS's built-in battery energy storage. The two inputs are converted to DC (such as 24VDC) by independent AC / DC modules and then supplied to the downstream load through diode parallel connection or load sharing circuit.

[0105] Under normal conditions, the main circuit supplies power while the backup circuit is in hot standby mode (i.e., the AC / DC module operates under no-load conditions, and the output voltage is consistent with that of the main circuit). When the voltage of the main circuit drops by more than 10% or there is a power outage, the backup circuit automatically takes over the power supply, achieving seamless switching.

[0106] The power module provided in this embodiment, when powered by dual AC / DC, can still provide independent power to the other circuit even if any one power supply fails (such as a power outage or damage to the UPS inverter), thus eliminating the risk of single-point failure and improving reliability. Moreover, the UPS in the backup circuit has an AC-DC-AC conversion process, which can filter out peak pulses (such as lightning surge waveforms of 1.2 / 50μs) and voltage fluctuations in the power grid, and can provide a clean power supply with THD < 3% for the PLC control module.

[0107] The flowcharts and block diagrams in the accompanying drawings illustrate the architecture, functionality, and operational instructions of possible implementations of a system according to various embodiments of this application. In this regard, each block in a flowchart or block diagram may represent a module, segment, or portion of code containing one or more executable instructions for implementing the specified logical function. It should also be noted that in some alternative implementations, the functions indicated in the blocks may occur in a different order than those indicated in the drawings. For example, two connected blocks may actually be executed substantially in parallel, or they may sometimes be executed in reverse order, depending on the functions involved. It should also be noted that each block in the block diagrams and / or flowcharts, and combinations of blocks in the block diagrams and / or flowcharts, can be implemented using a dedicated hardware-based system that performs the specified function or operational instructions, or using a combination of dedicated hardware and computer instructions.

[0108] The units or modules described in the embodiments of this application can be implemented in software or hardware. The described units or modules can also be located in a processor. The names of these units or modules do not, in certain circumstances, constitute a limitation on the unit or module itself.

[0109] The above description is merely a preferred embodiment of this application and an explanation of the technical principles employed. Those skilled in the art should understand that the scope of disclosure in this application is not limited to technical solutions formed by specific combinations of the above-described technical features, but should also cover other technical solutions formed by arbitrary combinations of the above-described technical features or their equivalents without departing from the foregoing disclosed concept. For example, technical solutions formed by substituting the above features with (but not limited to) technical features with similar functions disclosed in this application.

Claims

1. A power supply switching control system for a thermal power plant, characterized in that, include: The system includes a switch, sensor module, PLC control module, alarm module, and storage module. The sensor module is used to collect voltage and current signals from the main power supply and the backup power supply. The PLC control module is connected to the sensor module, the switch, the alarm module and the storage module respectively, and is used to control the action of the switch according to preset logic and drive the alarm module to work. The storage module is used to record system operation data.

2. The system as described in claim 1, characterized in that, The PLC control module is used for: If the main power supply voltage is within the rated range, the backup power supply switching command may be executed; If the main power supply voltage exceeds the rated range, an alarm trigger signal is generated and the backup power switching submodule is triggered. The backup power switching submodule is used to: send a switching command to the switching switch when the backup power voltage is within the rated range and there is no fault signal; and cancel the alarm trigger signal after the backup power switching is successful. The alarm module is used to: trigger an alarm upon detecting the alarm trigger signal, and cancel the alarm if the alarm trigger signal disappears.

3. The system as described in claim 2, characterized in that, The backup power switching module is also used to: trigger the PLC control module to collect the voltage of the backup power supply over a period of time before switching is performed, and calculate the voltage stability index; when the voltage stability index reaches the stability threshold, the switching command is allowed to be executed.

4. The system as described in claim 1, characterized in that, The PLC control module has a built-in fault lockout submodule, which is used to trigger a lockout state when either the main power supply or the backup power supply experiences any of the following faults: The current value exceeds a specified multiple of the rated current, and the duration reaches the first time threshold; The voltage drop is less than a specified percentage of the rated voltage, and the duration reaches a second time threshold. A fault signal indicating a short circuit in the line has been detected. In the locked state, switching operations are prohibited, and a fault lock signal is generated.

5. The system as described in claim 4, characterized in that, The fault lockout submodule is also used to: release the lockout state when any of the following release conditions are met; The conditions for releasing the fault lockout state include: Received a manually entered cancellation command; The fault that triggered the lockout state has disappeared, and the parameters of the main power supply and the backup power supply remain normal for a continuous period of time.

6. The system as described in claim 1, characterized in that, The switching switch is a three-position electric switch, including three positions: main power supply, backup power supply, and maintenance isolation. The PLC control module controls the motor drive circuit of the switching switch through a relay group.

7. The system as described in claim 1, characterized in that, The alarm module includes a local audible and visual alarm and a remote communication module; The alarm module is used to: activate the local audible and visual alarm when an alarm trigger signal is detected, and send a fault code through the remote communication module.

8. The system as described in claim 1, characterized in that, The operational data recorded by the storage module includes: real-time voltage / current waveforms of the main / backup power supply, switching time point, switching duration, switching success / failure status, fault lockout triggering reasons, and historical operation records.

9. The system as described in claim 1, characterized in that, The PLC control module further includes: a synchronization control submodule; The synchronization control submodule is used to: collect the voltage phase difference and frequency difference between the main power supply and the backup power supply in real time; if the phase difference is not higher than the phase difference threshold and the frequency difference is not higher than the frequency difference threshold, the parallel switching command is allowed; if the phase difference is higher than the phase difference threshold or the frequency difference is higher than the frequency difference threshold, the series power-off switching command is executed.

10. The system as claimed in claim 1, characterized in that, It also includes a power module, which adopts a dual-circuit AC / DC redundant power supply design. The main power supply circuit is connected to the plant power bus, and the backup power supply circuit is connected to the UPS power supply.

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