A method and system for commutation failure detection for forced commutation phase

Abstract

This application proposes a method and system for detecting commutation failure during forced commutation. The method includes: monitoring key electrical quantities on the machine bridge side and network bridge side of the static frequency converter during forced commutation; determining whether the target thyristor on the machine bridge side has been turned off based on the key electrical quantities; after determining that the target thyristor has been turned off, monitoring whether the three-phase current on the machine bridge side meets preset abnormal conditions; if the three-phase current simultaneously meets the abnormal conditions, then executing a preset fault protection operation. The technical solution proposed in this application can improve the reliability of commutation failure detection during forced commutation, reduce the risk of misjudgment through dual criteria, and achieve rapid fault response to protect equipment safety.

Description

Technical Field

[0001] This application relates to the field of detection technology, and in particular to a method and system for detecting commutation failure in the forced commutation stage. Background Technology

[0002] As the core power equipment for gas-steam combined cycle power generation, the reliable startup of heavy-duty gas turbines is a crucial prerequisite for ensuring stable unit operation. Among related technologies, the static frequency converter (SFC) constructs a complete variable frequency startup system that drives the unit from standstill to self-sustaining speed through the coordinated operation of grid-side converter, turbine-side inverter, and trigger control. Specifically, the SFC calculates the triggering time based on the turbine-side voltage phase and supplies two-phase current to the motor stator to generate a stator rotating magnetic field that leads the rotor magnetic field, thereby generating driving electromagnetic torque. When the motor speed is below 10% of the rated speed, due to insufficient back electromotive force at the turbine terminals, forced commutation technology is required. This involves controlling the grid-side converter to invert the circuit current to zero and maintain it for a time Δt to ensure the thyristors regain their blocking capability.

[0003] Current forced commutation completion detection methods typically rely solely on whether the grid-side current drops below a threshold as the single criterion. Since this approach depends solely on grid-side current information, if a bridge arm shoot-through fault occurs in the grid-side converter during forced commutation, the fault current will idle in the loop formed by the faulty bridge arm on both the generator bridge side and the grid bridge side, causing grid-side current detection to fail. In this situation, the system will misjudge commutation success and continue executing subsequent sequential control commands, potentially leading to equipment oscillations, power device damage, or even unplanned unit shutdowns, severely threatening production continuity and economic efficiency. Therefore, there is an urgent need for a solution that can accurately detect whether commutation has failed during the forced commutation phase. Summary of the Invention

[0004] This application provides a method and system for detecting commutation failure during the forced commutation stage, in order to at least solve one of the technical problems in the related art.

[0005] The first aspect of this application provides a method for detecting commutation failure during forced commutation, the method comprising:

[0006] During the forced commutation operation of the static inverter, key electrical quantities on the machine bridge side and network bridge side of the static inverter are monitored; Based on the key electrical quantities, determine whether the target thyristor on the bridge side has been turned off; After determining that the target thyristor has been turned off, monitor whether the three-phase current on the bridge side meets the preset abnormal conditions. If the three-phase currents are detected to simultaneously meet the abnormal conditions, then a preset fault protection operation is executed.

[0007] Preferably, during the forced commutation operation of the static inverter, monitoring the key electrical quantities on the bridge side of the static inverter includes: The amplitudes of the three-phase current on the bridge side and the three-phase current on the machine bridge side, as well as the output voltage on the machine bridge side, of the static inverter are collected. The maximum value among the six sets of currents is determined based on the three-phase current on the bridge side and the three-phase current on the machine bridge side.

[0008] Furthermore, the step of determining whether the target thyristor on the bridge side has been turned off based on the key electrical quantity includes: Determine whether the maximum value is less than a preset turn-off threshold, and use the determination that the maximum value is less than the preset turn-off threshold as the main criterion for determining that the target thyristor has been turned off; Determine whether the amplitude of the output voltage on the bridge side is less than a preset voltage target value, and use the determination of whether the amplitude of the output voltage on the bridge side is less than the preset voltage target value as an auxiliary criterion for determining that the target thyristor has been turned off; If the maximum value is less than the turn-off threshold and the amplitude is less than the voltage target value, then the target thyristor is determined to be turned off.

[0009] Furthermore, after determining that the target thyristor has been turned off, monitoring whether the three-phase current on the bridge side meets preset abnormal conditions includes: Determine whether the current value of each phase of the three-phase current on the bridge side is greater than the preset abnormal current threshold. If so, determine that the three-phase current on the bridge side meets the preset abnormal conditions.

[0010] Furthermore, the execution of the preset fault protection operation includes: Generate fault protection instructions, which include instructions to block the trigger pulses of each thyristor in the static frequency converter and to disconnect the relevant circuit breakers; Execute the fault protection command.

[0011] A second aspect of this application provides a commutation failure detection system for the forced commutation stage, comprising: The first monitoring module is used to monitor key electrical quantities on the machine bridge side and network bridge side of the static inverter during the forced commutation operation of the static inverter. The judgment module is used to determine whether the target thyristor on the bridge side has been turned off based on the key electrical quantities. The second monitoring module is used to monitor whether the three-phase current on the bridge side meets the preset abnormal conditions after determining that the target thyristor has been turned off. The execution module is used to execute a preset fault protection operation if the three-phase currents are detected to simultaneously meet the abnormal conditions.

[0012] Preferably, the first monitoring module is further used for: The amplitudes of the three-phase current on the bridge side and the three-phase current on the machine bridge side, as well as the output voltage on the machine bridge side, of the static inverter are collected. The maximum value among the six sets of currents is determined based on the three-phase current on the bridge side and the three-phase current on the machine bridge side.

[0013] Furthermore, the determination module is also used for: Determine whether the maximum value is less than a preset turn-off threshold, and use the determination that the maximum value is less than the preset turn-off threshold as the main criterion for determining that the target thyristor has been turned off; Determine whether the amplitude of the output voltage on the bridge side is less than a preset voltage target value, and use the determination of whether the amplitude of the output voltage on the bridge side is less than the preset voltage target value as an auxiliary criterion for determining that the target thyristor has been turned off; If the maximum value is less than the turn-off threshold and the amplitude is less than the voltage target value, then the target thyristor is determined to be turned off.

[0014] A third aspect of this application provides an electronic device, including: a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein when the processor executes the program, it implements the method described in the first aspect embodiment.

[0015] A fourth aspect of this application provides a computer-readable storage medium having a computer program stored thereon that, when executed by a processor, implements the method described in the first aspect.

[0016] The technical solutions provided by the embodiments of this application bring at least the following beneficial effects: This application proposes a method and system for detecting commutation failure during forced commutation. The method includes: monitoring key electrical quantities on the machine bridge side and network bridge side of the static inverter during forced commutation; determining whether the target thyristor on the machine bridge side has been turned off based on the key electrical quantities; after determining that the target thyristor has been turned off, monitoring whether the three-phase current on the machine bridge side meets preset abnormal conditions; if the three-phase current simultaneously meets the abnormal conditions, then executing a preset fault protection operation. The technical solution proposed in this application can improve the reliability of commutation failure detection during forced commutation, reduce the risk of misjudgment through dual criteria, and achieve rapid fault response to protect equipment safety.

[0017] Additional aspects and advantages of this application 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 this application. Attached Figure Description

[0018] The above and / or additional aspects and advantages of this application will become apparent and readily understood from the following description of the embodiments taken in conjunction with the accompanying drawings, wherein: Figure 1 This is a flowchart of a commutation failure detection method for a forced commutation stage according to an embodiment of this application; Figure 2 This is a schematic diagram of commutation failure detection data acquisition according to an embodiment of this application; Figure 3 This is a structural diagram of a commutation failure detection system for a forced commutation stage according to an embodiment of this application. Detailed Implementation

[0019] The embodiments of this application are described in detail below. Examples of these embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary and intended to explain this application, and should not be construed as limiting this application.

[0020] This application proposes a method and system for detecting commutation failure during forced commutation. The method includes: monitoring key electrical quantities on the machine bridge side and network bridge side of the static frequency converter during forced commutation operation; determining whether the target thyristor on the machine bridge side has been turned off based on the key electrical quantities; after determining that the target thyristor has been turned off, monitoring whether the three-phase current on the machine bridge side meets preset abnormal conditions; if the three-phase current simultaneously meets the abnormal conditions, then executing a preset fault protection operation. The technical solution proposed in this application can improve the reliability of commutation failure detection during forced commutation, reduce the risk of misjudgment through dual criteria, and achieve rapid fault response to protect equipment safety.

[0021] The following description, with reference to the accompanying drawings, describes a method and system for detecting commutation failure during the forced commutation stage, according to an embodiment of this application.

[0022] Example 1 Figure 1 This is a flowchart of a commutation failure detection method for a forced commutation stage according to an embodiment of this application, as shown below. Figure 1 As shown, the method includes: Step 1: During the forced commutation operation of the static inverter, monitor the key electrical quantities on the machine bridge side and network bridge side of the static inverter; In this embodiment of the disclosure, step 1 specifically includes: The amplitudes of the three-phase current on the bridge side and the three-phase current on the machine bridge side, as well as the output voltage on the machine bridge side, of the static inverter are collected. The maximum value among the six sets of currents is determined based on the three-phase current on the bridge side and the three-phase current on the machine bridge side.

[0023] It should be noted that during the forced commutation operation of the static inverter, in order to obtain information reflecting the electrical status of the bridge side to support subsequent commutation completion judgment, this step involves monitoring key electrical quantities on the bridge side of the static inverter. These key electrical quantities refer to electrical parameters that characterize the on / off state of the thyristors on the bridge side or reflect the progress of the forced commutation process. Monitoring can be achieved through sensors or detection devices installed in the bridge side circuit. The monitoring operation covers the entire duration of forced commutation to ensure the acquisition of dynamic electrical data related to the commutation process. These electrical quantities typically include, but are not limited to, current and voltage. By acquiring these quantities in real time, a real-time perception of the bridge side's electrical behavior can be established. For example, as a specific implementation, the current flowing through the target thyristor on the bridge side and the output voltage on the bridge side can be monitored, where the current is used to directly determine whether the thyristor is turned off, and the voltage is used to assist in verifying the commutation status.

[0024] By monitoring key electrical quantities on the bridge side, this step provides a comprehensive and direct electrical data foundation for subsequent commutation status judgment, thereby enhancing the reliability of data sources and monitoring coverage of the entire detection scheme and helping to improve the accuracy of forced commutation process status perception.

[0025] Specifically, first, sub-step S11 is executed, which involves real-time acquisition of the three-phase current on the bridge side using the current transformers configured on the bridge side and the machine bridge side of the static inverter. , , Three-phase current on the bridge side , , These six current signals are transmitted as inputs to the controller of the static inverter. The processing unit inside the controller continuously compares and calculates the instantaneous or effective values ​​of these six currents in real time, and selects the current value with the largest absolute value, which is recorded as the maximum value. The maximum value The calculated output is intended to characterize the peak value that the loop current may reach during forced commutation, which will serve as a key input quantity for subsequent determination of whether the target thyristor on the bridge side has been turned off. Next, sub-step S12 is executed, specifically, by using a voltage transformer configured at the bridge-side outlet of the static inverter to collect the three-phase line voltage on the bridge side in real time and measure its amplitude. The voltage amplitude As an output, it will serve as a key input quantity for assisting in verifying the turn-off state of the thyristors on the bridge side. Thus, through sub-steps S11 and S12, the key electrical quantity on the bridge side—namely, the maximum loop current—has been verified. With the amplitude of the output voltage on the bridge side The specific monitoring and acquisition of electrical quantities provide a direct and accurate basis for subsequent reliable shutdown judgments.

[0026] This specific implementation provides a dual and direct monitoring data source for determining thyristor turn-off by explicitly collecting the six-phase current from both sides of the bridge and the machine arm and calculating the maximum value, as well as directly collecting the output voltage amplitude from the machine arm side. This overcomes the deficiency that monitoring only a single location current may fail due to a bridge arm shoot-through fault, laying the foundation for reliability judgment from the data acquisition level.

[0027] Step 2: Determine whether the target thyristor on the bridge side has been turned off based on the key electrical quantities; In this embodiment of the disclosure, step 2 specifically includes: Determine whether the maximum value is less than a preset turn-off threshold, and use the determination that the maximum value is less than the preset turn-off threshold as the main criterion for determining that the target thyristor has been turned off; Determine whether the amplitude of the output voltage on the bridge side is less than a preset voltage target value, and use the determination of whether the amplitude of the output voltage on the bridge side is less than the preset voltage target value as an auxiliary criterion for determining that the target thyristor has been turned off; If the maximum value is less than the turn-off threshold and the amplitude is less than the voltage target value, then the target thyristor is determined to be turned off.

[0028] It should be noted that, addressing the risk of misjudgment inherent in existing technologies that rely solely on a single electrical quantity to determine the completion of forced commutation, this step aims to provide a more reliable scheme for determining the turn-off state of the target thyristor on the bridge side. The core of this scheme lies in utilizing at least one key electrical quantity obtained from the bridge side of the static inverter during forced commutation to comprehensively evaluate whether the target thyristor has recovered its blocking capability, i.e., reached a reliable turn-off state. The key electrical quantities include, but are not limited to, current signals that directly reflect the thyristor's conduction state, and voltage signals that indirectly characterize its turn-off conditions. By constructing the judgment logic based on one or more such electrical quantities, the actual decay and zeroing process of the current within the target thyristor can be captured more directly and accurately, thereby overcoming the problem that a single signal source may fail due to the measurement point location or system faults (such as bridge arm shoot-through), and achieving multi-dimensional verification of the turn-off state. For example, in one specific implementation, relevant current signals on the bridge side can be collected to determine whether they have dropped below a preset reliable turn-off threshold, which serves as the main criterion for determining that the thyristor has been turned off; at the same time, the output voltage signal on the bridge side can be monitored to determine whether it is lower than a preset target voltage value, which serves as an auxiliary verification of the current criterion.

[0029] By employing the aforementioned technical approach based on comprehensive judgment of multiple key electrical quantities on the bridge side, this step significantly improves the accuracy of determining whether the target thyristor has been reliably turned off during forced commutation. This effectively avoids misjudgments caused by the failure of a single criterion, providing a more reliable prerequisite for the smooth execution of subsequent processes, thereby reducing the risk of equipment failure caused by unreliable thyristor turn-off from the source.

[0030] Step 3: After determining that the target thyristor has been turned off, monitor whether the three-phase current on the bridge side meets the preset abnormal conditions; In this embodiment of the disclosure, step 3 specifically includes: Determine whether the current value of each phase of the three-phase current on the bridge side is greater than the preset abnormal current threshold. If so, determine that the three-phase current on the bridge side meets the preset abnormal conditions.

[0031] It should be noted that after determining that the target thyristor has been reliably turned off, in order to ensure the normal operation of the subsequent drive process of the static inverter and prevent potential commutation failure risks, continuous or periodic monitoring of the three-phase current state on the bridge side is performed to determine whether it simultaneously meets preset abnormal conditions. The core of this step lies in constructing a monitoring logic for identifying abnormal conduction modes based on the basic conduction principle of the bridge-side converter of the static inverter under normal drive conditions—that is, at any given time, only two specific phases on the bridge side should be in an effective conducting state to form a unique current loop—. Specifically, by real-time acquisition or acquisition of the three-phase current signals on the bridge side, and based on preset electrical conditions used to characterize abnormal conduction features, the state of these three-phase currents is analyzed and judged collaboratively. The preset abnormal conditions aim to define an electrical state characteristic that can indicate the occurrence of unexpected simultaneous conduction of multiple phases or abnormal current increase on the bridge side. When the electrical quantities of the three-phase current simultaneously meet the abnormal condition, it indicates that an abnormal operating condition may have occurred on the bridge side, violating the normal two-phase conduction mode. This could be due to three-phase short-circuiting caused by commutation failure or other serious fault conditions, thus triggering subsequent fault determination. For example, as one implementation method, the preset abnormal condition can be specified as determining whether the instantaneous or effective value of the three-phase current simultaneously exceeds a preset abnormal current threshold.

[0032] By implementing this monitoring procedure, multi-phase abnormal conduction faults, such as commutation failure, can be quickly and directly identified based on the coordinated abnormal state of the three-phase currents on the bridge side. This significantly shortens the time window from fault occurrence to system identification, creating conditions for timely execution of protection operations and disconnection of the fault current loop, thereby effectively preventing fault escalation and reducing the risk of equipment damage.

[0033] Specifically, first, sub-step S31 is executed: acquiring the three-phase current values ​​on the bridge side. Specifically, the three-phase current analog signals on the bridge side are acquired in real time using current transformers installed on the three-phase output circuit of the static inverter bridge. These analog signals are transmitted to the analog input module of the inverter controller, and after analog-to-digital conversion (ADC) and necessary filtering and sampling processing, digitized instantaneous or effective values ​​of the three-phase current are obtained, denoted as follows: , , This serves as the input data source for subsequent judgments. Next, sub-step S32 is executed: based on the three-phase current values, it is determined whether the current of each phase exceeds a preset abnormal current threshold. The input for this sub-step is the three-phase current value obtained in the previous sub-step. , , In one specific implementation, a preset abnormal current threshold is used. The value stored in the controller's memory can be set based on the system's rated current and experience, for example, to a small current value slightly above zero to characterize the "current present" state. The processing actions include comparing the current value of each phase with the abnormal current threshold. Real-time comparisons are performed. Specifically, the comparison logic unit or software algorithm in the controller executes sequentially. , , The comparison operation is performed. Based on these parallel comparison results, a comprehensive judgment is made: if all three comparison results are true simultaneously, then the condition is satisfied. , and If the three-phase currents simultaneously exceed the abnormal current threshold, it is determined that the three-phase currents simultaneously meet the abnormal conditions, and a corresponding fault flag signal is output; otherwise, it is determined that the abnormal conditions are not met.

[0034] Through the above specific implementation method, using simple current amplitude comparison logic, an abnormal conduction state in which three-phase currents coexist on the bridge side can be quickly and directly identified. This state is a typical and dangerous characteristic of commutation failure. The method has clear logic and low computational load, enabling very early and rapid detection of commutation failure faults. This buys critical time for subsequent immediate execution of protection actions and effectively reduces the risk of equipment damage caused by prolonged fault duration.

[0035] Step 4: If the three-phase currents are detected to simultaneously meet the abnormal conditions, then execute the preset fault protection operation.

[0036] In this embodiment of the disclosure, performing the preset fault protection operation includes: Generate fault protection instructions, which include instructions to block the trigger pulses of each thyristor in the static frequency converter and to disconnect the relevant circuit breakers; Execute the fault protection command.

[0037] It should be noted that when the three-phase currents on the bridge side simultaneously meet preset abnormal conditions, the system determines that the commutation process has failed or entered a serious abnormal operating state, and immediately executes preset fault protection operations. This fault protection operation aims to respond quickly to the detected abnormality, actively intervening to cut off potential fault current paths or stop the abnormal operating mode of the system, thereby preventing the expansion of the fault's impact range and avoiding damage to power devices and related equipment in the system. The specific form of the fault protection operation can be preset according to system configuration and protection requirements; its core lies in generating and implementing protection commands that can effectively terminate the current abnormal state. For example, as a specific implementation, the fault protection operation may include immediately blocking the trigger pulses of all thyristors in the static inverter and controlling the disconnection of related electrical circuit breakers, thereby completely cutting off the fault circuit from both the trigger signal and main circuit levels.

[0038] By executing preset fault protection operations, the system can respond to detected commutation failures or severe abnormal conditions in a timely manner, greatly shortening the duration of fault current and the duration of abnormal conditions. This effectively limits the scope of potential damage caused by the fault, significantly reducing the risk of permanent damage to critical power devices (such as thyristors) and other system equipment, thereby improving the operational safety and reliability of the entire system.

[0039] Specifically, when step S3 determines that the three-phase currents on the bridge side simultaneously meet the abnormal conditions (i.e., all three-phase currents exceed the preset abnormal current threshold), the control system of the Static Variable Frequency Drive (SFC) immediately responds and generates a fault protection command containing specific control actions. The input source of this command is the abnormal judgment logic signal output in step S3. The processing action involves the protection logic module in the control system assembling and generating a digital command data packet based on this signal. This command data packet explicitly contains two core operation commands: the first is to send a blocking signal to the gate drive circuits of all thyristors (including those on the bridge side and the machine side) within the SFC to immediately stop the issuance of all trigger pulses; the second is to issue a disconnection command to the control circuit of the relevant circuit breaker electrically connected to the SFC system (e.g., the grid-side incoming circuit breaker or the machine-side output circuit breaker). The output result is the generated fault protection command data stream ready to be sent.

[0040] Subsequently, the system executes the fault protection command. The input source for this sub-step is the fault protection command data stream generated in the previous step. The processing action involves the SFC control system's command output interface parsing and power-driving the command data stream, sending it to the corresponding actuators. Specifically, the command to block the trigger pulse is sent to the gate drive unit of each thyristor via a digital optocoupler or level conversion circuit, forcing its output to a low level or high impedance state, thereby achieving instantaneous and synchronous blocking of all thyristor trigger pulses. Simultaneously, the command to disconnect the circuit breaker is sent to the intelligent operating box or protection device of the relevant circuit breaker via hard-wiring or a communication bus (such as hard-contact signals or GOOSE messages), driving its trip coil to operate. The output result is that the trigger pulses of all thyristors are actually blocked, and the main contacts of the relevant circuit breakers are actually disconnected, thereby completely cutting off the fault current path and forcing the system into a safe isolation state.

[0041] This specific implementation, through a clear and rapid instruction generation and execution mechanism, can immediately take the most effective isolation measures after detecting serious anomalies such as commutation failure, greatly shortening the duration of fault current, thereby effectively protecting expensive power devices such as thyristors and other system equipment, and significantly reducing the risk of equipment damage and failure losses.

[0042] The following section provides a detailed description of the complete implementation of the commutation failure detection method used in the forced commutation stage.

[0043] In this embodiment, as Figure 2 As shown, the method is applied to a starting system consisting of a heavy-duty gas turbine, a synchronous generator, and a static frequency converter (SFC). The SFC typically includes a grid-side converter (grid bridge) and a generator-side converter (machine bridge), connected via a DC link. The output of the machine bridge is connected to the stator windings of the synchronous generator. When the unit's starting speed is below 10% of its rated speed, due to the excessively low back EMF of the motor, the SFC controller will initiate a forced commutation operation: controlling the grid bridge inverter to force the DC loop current to drop to zero and maintain this state for a period of time. This ensures that the thyristors that need to be turned off on the bridge side (i.e., the target thyristor) regain their blocking capability. To detect the commutation status in this process in real time and accurately, this embodiment performs the following specific steps.

[0044] First, throughout the entire process of the SFC controller executing the forced commutation operation command, key electrical quantities are simultaneously acquired and monitored. Specifically, the three-phase current on the bridge side is acquired in real time using a three-phase current transformer installed on the AC side of the bridge. Simultaneously, the three-phase current on the machine bridge side is acquired in real time using a three-phase current transformer installed at the output end of the machine bridge. Furthermore, the line voltage amplitude at the machine bridge side outlet is acquired using a voltage transformer. All acquired analog signals are converted into digital signals by an analog-to-digital converter (ADC) after passing through signal conditioning circuits (such as filtering, isolation, and amplification), and then input to the digital signal processor (DSP) of the SFC controller.

[0045] Next, based on the collected electrical quantities, it is determined whether forced commutation has been completed, i.e., whether the target thyristor on the bridge side has been reliably turned off. The determination process employs a dual verification mechanism combining primary and secondary criteria. For the primary criterion, the SFC controller compares six sets of current values ​​collected in each control cycle and selects the maximum value. The controller is preset with a near-zero reliable shutdown current threshold. For example, it can be set to a fixed, tiny positive value. Then determine... Is this condition met? If it is, it indicates that there is no significant current flowing in the entire circuit (including the network bridge and the machine bridge), providing a direct current criterion for turning off the target thyristor. For auxiliary criteria, the controller simultaneously judges the amplitude of the acquired machine bridge-side output voltage. Is it less than the preset voltage target value? . This criterion can be set according to system parameters, for example, to a low voltage value close to zero. This criterion is used to assist in verifying whether the electrical environment on the bridge side has reached a stable state. Only when both the main criterion and the auxiliary criterion are simultaneously satisfied, i.e. and Only then does the controller finally determine that the forced commutation is complete and the target thyristor has been reliably turned off. This "current-based judgment + voltage-based auxiliary judgment" mechanism effectively avoids the risk of current detection failure and subsequent misjudgment of commutation completion due to a bridge arm shoot-through fault when only monitoring the bridge-side current.

[0046] Then, after determining that the forced commutation is complete and the SFC controller issues subsequent trigger pulse commands to continue driving the motor according to the control algorithm, the system immediately enters the abnormal operation state monitoring stage after commutation. According to the normal drive principle of SFC, at any given time, only two thyristors belonging to the common cathode group and the common anode group should be conducting in the bridge, forming a unique current path. Therefore, only two phases of the three-phase current on the bridge side should have current, and the current in the other phase should theoretically be zero. Based on this, this embodiment monitors the three-phase current on the bridge side in real time. The controller presets an abnormal current threshold. This threshold is greater than the phase current value during normal motor operation and can be set empirically. In each monitoring cycle, it is determined whether the following conditions are met simultaneously. , , If the absolute values ​​of the three-phase currents simultaneously exceed This indicates a serious abnormal state such as unexpected simultaneous conduction of three phases or bridge arm shoot-through, which is a typical characteristic of commutation failure. Once this condition is detected, the controller immediately determines that a commutation failure has occurred.

[0047] Finally, upon determining that a commutation failure has occurred, the controller immediately executes preset fault protection operations to maximize equipment protection. Specifically, within the same control cycle, the controller generates and issues a fault protection command. This command includes: immediately blocking the trigger pulses of all thyristors in the SFC bridge and the machine bridge, fundamentally cutting off any new conduction possibilities; simultaneously, issuing a disconnection command to the relevant circuit breakers (such as the SFC input circuit breaker or output circuit breaker) to physically disconnect the fault current path. Through these rapid protection actions, the duration of the fault current can be minimized, effectively preventing damage to expensive power devices (such as thyristors) due to overcurrent, and reducing the risk of system oscillation or equipment shutdown.

[0048] The advantages proposed in this embodiment are as follows: 1. More reliable commutation judgment: Through the dual verification mechanism of "bridge side current (main criterion) + bridge side voltage (auxiliary criterion)," the accuracy of forced commutation completion judgment is significantly improved, effectively preventing the risk of thyristor failure to turn off reliably due to misjudgment.

[0049] 2. Faster fault detection: The "three-phase current anomaly" criterion is designed by utilizing the inherent characteristic that only two phases of the bridge are conducting when the SFC is running normally. The logic is simple and clear, and it can detect the most dangerous abnormal conduction states (such as three-phase shoot-through) such as commutation failure at a very early stage (immediately after the subsequent pulse is issued) and very quickly.

[0050] 3. More timely protection actions: Once an anomaly is detected, the system can immediately take protective measures (blocking pulses, tripping), which greatly shortens the duration of fault current, effectively protects expensive power devices (such as thyristors) and other system equipment, and significantly reduces fault losses and downtime risks.

[0051] 4. Enhanced System Security: The overall solution significantly enhances the operational security and reliability of SFC during the critical stage of forced commutation.

[0052] In summary, the commutation failure detection method proposed in this embodiment can improve the reliability of commutation failure detection in the forced commutation stage, reduce the risk of misjudgment through dual criteria, and achieve rapid fault response to protect equipment safety.

[0053] Example 2 Figure 3 This is a structural diagram of a commutation failure detection system for a forced commutation stage according to an embodiment of this application, as shown below. Figure 3As shown, the system includes: The first monitoring module 100 is used to monitor key electrical quantities on the machine bridge side and network bridge side of the static frequency converter during the forced commutation operation of the static frequency converter. The judgment module 200 is used to determine whether the target thyristor on the bridge side has been turned off based on the key electrical quantity. The second monitoring module 300 is used to monitor whether the three-phase current on the bridge side meets the preset abnormal conditions after determining that the target thyristor has been turned off. The execution module 400 is used to execute a preset fault protection operation if the three-phase currents are detected to simultaneously meet the abnormal conditions.

[0054] In this embodiment of the disclosure, the first monitoring module 100 is further configured to: The amplitudes of the three-phase current on the bridge side and the three-phase current on the machine bridge side, as well as the output voltage on the machine bridge side, of the static inverter are collected. The maximum value among the six sets of currents is determined based on the three-phase current on the bridge side and the three-phase current on the machine bridge side.

[0055] In this embodiment of the disclosure, the determination module 200 is further configured to: Determine whether the maximum value is less than a preset turn-off threshold, and use the determination that the maximum value is less than the preset turn-off threshold as the main criterion for determining that the target thyristor has been turned off; Determine whether the amplitude of the output voltage on the bridge side is less than a preset voltage target value, and use the determination of whether the amplitude of the output voltage on the bridge side is less than the preset voltage target value as an auxiliary criterion for determining that the target thyristor has been turned off; If the maximum value is less than the turn-off threshold and the amplitude is less than the voltage target value, then the target thyristor is determined to be turned off.

[0056] In this embodiment of the disclosure, the second monitoring module 300 is further configured to: Determine whether the current value of each phase of the three-phase current on the bridge side is greater than the preset abnormal current threshold. If so, determine that the three-phase current on the bridge side meets the preset abnormal conditions.

[0057] In this embodiment of the disclosure, the execution module 400 is further configured to: Generate fault protection instructions, which include instructions to block the trigger pulses of each thyristor in the static frequency converter and to disconnect the relevant circuit breakers; Execute the fault protection command.

[0058] In summary, the commutation failure detection system proposed in this embodiment can improve the reliability of commutation failure detection in the forced commutation stage, reduce the risk of misjudgment through dual criteria, and achieve rapid fault response to protect equipment safety.

[0059] Example 3 To implement the above embodiments, this disclosure also proposes an electronic device, including: a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein when the processor executes the program, it implements the method described in Embodiment 1.

[0060] Example 4 To implement the above embodiments, this disclosure also proposes a computer-readable storage medium having a computer program stored thereon, which, when executed by a processor, implements the method described in Embodiment 1.

[0061] In the description of this specification, the references to terms such as "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of this application. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples. Moreover, without contradiction, those skilled in the art can combine and integrate the different embodiments or examples described in this specification, as well as the features of different embodiments or examples.

[0062] Any process or method description in the flowchart or otherwise herein can be understood as representing a module, segment, or portion of code comprising one or more executable instructions for implementing custom logic functions or processes, and the scope of the preferred embodiments of this application includes additional implementations in which functions may be performed not in the order shown or discussed, including substantially simultaneously or in reverse order depending on the functions involved, as should be understood by those skilled in the art to which embodiments of this application pertain.

[0063] Although embodiments of this application have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting this application. Those skilled in the art can make changes, modifications, substitutions and variations to the above embodiments within the scope of this application.

Claims

1. A commutation failure detection method for a forced commutation phase, characterized by, The method includes: During the forced commutation operation of the static inverter, key electrical quantities on the machine bridge side and network bridge side of the static inverter are monitored; Based on the key electrical quantities, determine whether the target thyristor on the bridge side has been turned off; After determining that the target thyristor has been turned off, monitor whether the three-phase current on the bridge side meets the preset abnormal conditions. If the three-phase currents are detected to simultaneously meet the abnormal conditions, then a preset fault protection operation is executed.

2. The method of claim 1, wherein, During the forced commutation operation of the static inverter, the monitoring of key electrical quantities on the bridge side of the static inverter includes: The amplitudes of the three-phase current on the bridge side and the three-phase current on the machine bridge side, as well as the output voltage on the machine bridge side, of the static inverter are collected. The maximum value among the six sets of currents is determined based on the three-phase current on the bridge side and the three-phase current on the machine bridge side.

3. The method of claim 2, wherein, The step of determining whether the target thyristor on the bridge side has been turned off based on the key electrical quantity includes: Determine whether the maximum value is less than a preset turn-off threshold, and use the determination that the maximum value is less than the preset turn-off threshold as the main criterion for determining that the target thyristor has been turned off; Determine whether the amplitude of the output voltage on the bridge side is less than a preset voltage target value, and use the determination of whether the amplitude of the output voltage on the bridge side is less than the preset voltage target value as an auxiliary criterion for determining that the target thyristor has been turned off; If the maximum value is less than the turn-off threshold and the amplitude is less than the voltage target value, then the target thyristor is determined to be turned off.

4. The method of claim 3, wherein, After determining that the target thyristor has been turned off, monitoring whether the three-phase current on the bridge side meets preset abnormal conditions includes: Determine whether the current value of each phase of the three-phase current on the bridge side is greater than the preset abnormal current threshold. If so, determine that the three-phase current on the bridge side meets the preset abnormal conditions.

5. The method of claim 4, wherein, The execution of the preset fault protection operation includes: Generate fault protection instructions, which include instructions to block the trigger pulses of each thyristor in the static frequency converter and to disconnect the relevant circuit breakers; Execute the fault protection command.

6. A commutation failure detection system for the forced commutation stage, characterized in that, The system includes: The first monitoring module is used to monitor key electrical quantities on the machine bridge side and network bridge side of the static inverter during the forced commutation operation of the static inverter. The judgment module is used to determine whether the target thyristor on the bridge side has been turned off based on the key electrical quantities. The second monitoring module is used to monitor whether the three-phase current on the bridge side meets the preset abnormal conditions after determining that the target thyristor has been turned off. The execution module is used to execute a preset fault protection operation if the three-phase currents are detected to simultaneously meet the abnormal conditions.

7. The system as described in claim 6, characterized in that, The first monitoring module is also used for: The amplitudes of the three-phase current on the bridge side and the three-phase current on the machine bridge side, as well as the output voltage on the machine bridge side, of the static inverter are collected. The maximum value among the six sets of currents is determined based on the three-phase current on the bridge side and the three-phase current on the machine bridge side.

8. The system as described in claim 7, characterized in that, The judgment module is also used for: Determine whether the maximum value is less than a preset turn-off threshold, and use the determination that the maximum value is less than the preset turn-off threshold as the main criterion for determining that the target thyristor has been turned off; Determine whether the amplitude of the output voltage on the bridge side is less than a preset voltage target value, and use the determination of whether the amplitude of the output voltage on the bridge side is less than the preset voltage target value as an auxiliary criterion for determining that the target thyristor has been turned off; If the maximum value is less than the turn-off threshold and the amplitude is less than the voltage target value, then the target thyristor is determined to be turned off.

9. An electronic device, characterized in that, include: A memory, a processor, and a computer program stored in the memory and capable of running on the processor, wherein the processor, when executing the program, implements the method as described in any one of claims 1-5.

10. A computer-readable storage medium having a computer program stored thereon, characterized in that, When the program is executed by the processor, it implements the method as described in any one of claims 1-5.

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