Intelligent frequency converter control system based on three-level topology circuit

Abstract

The invention discloses an intelligent frequency converter control system based on a three-level topology circuit, which relates to the technical field of power electronics and comprises a main circuit power module, a signal acquisition module, a core control module, a fault diagnosis module, a recovery management module and a case library module. The core control module is used for generating a PWM driving signal according to a system instruction and a feedback signal so as to realize normal speed regulation and control functions of the frequency converter; the fault diagnosis module is used for monitoring the state of the system in real time, and performing diagnosis classification and starting a recovery process when a fault is detected; the recovery management module is used for monitoring and analyzing the coupling relation between the bus voltage recovery speed and the switch tube restart current peak value in real time; when it is judged that the voltage recovery speed exceeds a preset threshold value and the current peak value exceeds a rated value preset proportion, an instruction is sent to the core control module immediately, and a step-by-step restart strategy is switched; and the case library module is used for storing historical fault recovery cases.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of power electronics, and particularly relates to an intelligent frequency converter control system based on a three-level topology circuit. BACKGROUND

[0002] The three-level topology structure has become the preferred circuit scheme for medium and high voltage large capacity frequency converters due to its advantages of small output harmonics and low voltage stress of switching devices. However, the circuit structure is complex, and there are many power switching devices, which are prone to trigger overcurrent and overvoltage faults due to load mutation, power grid fluctuation and other reasons in actual operation. The rapid and stable recovery after the fault occurs is the key to ensure the continuous and reliable operation of the system.

[0003] The traditional three-level frequency converter generally adopts a fixed parameter fault recovery strategy. After detecting the fault, the system undergoes a fixed delay, and then restarts the inverter at a preset and fixed voltage and frequency rise rate. The fixed recovery parameters cannot adapt to the changing fault conditions and load states. If the recovery speed is too fast, it is easy to cause a large impact current, leading to fault recurrence or even damage to power devices. If the recovery speed is too conservative, the recovery time will be prolonged, affecting the production efficiency. The traditional recovery strategy lacks real-time monitoring and adjustment capability of the recovery process itself, and cannot cope with abnormal situations during the recovery process. The fixed parameter fault recovery strategy lacks self-adaptive ability, and it is difficult to achieve dynamic optimal balance between recovery speed, impact current and system stability. SUMMARY

[0004] The present application aims to provide an intelligent frequency converter control system based on a three-level topology circuit to solve the problems in the prior art.

[0005] To achieve the above-mentioned purpose, the present application provides the following technical scheme: an intelligent frequency converter control system based on a three-level topology circuit, which comprises a main circuit power module, a signal acquisition module, a core control module, a fault diagnosis module, a recovery management module and a case library module. The main circuit power module is used to complete AC-DC and DC-AC conversion and provide three-phase AC power for the load. The signal acquisition module is connected with the main circuit power module, and is used to acquire bus voltage, output current, switching tube temperature and output voltage signals in real time, and convert the acquired analog signals into standard signals. The core control module is connected with the signal acquisition module, and generates PWM driving signals according to system instructions and feedback signals to realize normal speed regulation and control functions of the frequency converter. The fault diagnosis module is connected to the signal acquisition module, the core control module and the recovery management module respectively, and is used to monitor the system status in real time, perform diagnosis and classification and start the recovery process when a fault is detected. The recovery management module is connected to the fault diagnosis module and is used to collect the bus voltage recovery rate, the peak value of the switch restart current and the output voltage recovery time in real time, and analyze the coupling relationship between the bus voltage recovery rate and the peak value of the switch restart current. When it is determined that the voltage recovery rate exceeds the preset threshold and the peak current exceeds the preset ratio of the rated value, an instruction is immediately sent to the core control module to switch to a step-by-step restart strategy. The case library module is connected to the fault diagnosis module and the recovery management module, and is used to store historical fault recovery cases.

[0006] According to the above scheme, the main circuit power module includes a three-phase rectifier unit, a DC bus support capacitor, a three-level inverter unit, and a midpoint potential balancing circuit. The AC side of the three-phase rectifier unit is connected to a three-phase power supply, and the DC side outputs a pulsating DC voltage. The DC bus support capacitor is connected between the positive and negative terminals of the DC output of the three-phase rectifier unit to stabilize the DC bus voltage. The DC input terminal of the three-level inverter unit is connected in parallel with the DC bus support capacitor, and the AC output terminal of the three-level inverter unit is connected to the load. The three-level inverter unit is composed of three-phase bridge arms, each phase bridge arm includes four power switching transistors connected in series and diodes connected in antiparallel with them, and two clamping diodes are connected across the connection points of the four power switching transistors. The midpoint potential balancing circuit is connected to the midpoint of the DC bus support capacitor and the midpoint potential clamping point of the three-level inverter unit to maintain the voltage balance of the upper and lower capacitors on the DC bus.

[0007] According to the above scheme, the fault diagnosis module includes a signal monitoring module, a fault determination module, and a process triggering module; The signal monitoring module is connected to the signal acquisition module and is used to receive real-time data of bus voltage, output current, switching transistor temperature and output voltage. The fault determination module is connected to the signal monitoring module and is used to compare real-time data with a preset safe operating threshold. When the data continuously exceeds the safe operating threshold, a fault trigger signal is generated, and the fault type is classified and identified to determine the fault attribute. The safe operating thresholds are determined separately for four types of monitoring signals: bus voltage, output current, switching transistor temperature, and output voltage. The safe thresholds for bus voltage and output voltage are obtained based on the rated voltage margin of the switching transistors in the rectifier and inverter units of the main circuit. The safe threshold for output current is calculated by combining the rated current of the power switching transistors and the rated operating current of the load, and analyzing the short-term overload demand. The safe threshold for switching transistor temperature is obtained by referring to the upper limit parameter of the junction temperature of the power switching transistors and deducting the temperature margin of the heat dissipation system. The process triggering module is connected to the fault determination module, the core control module, and the recovery management module. When the fault determination module determines that a fault exists, the process triggering module sends a fault interrupt signal to the core control module, causing the core control module to stop outputting normal PWM drive signals; at the same time, it sends a start signal to the recovery management module to trigger the fault recovery process.

[0008] According to the above scheme, the recovery management module includes a feature extraction module, a risk assessment module, and a control command generation module; The feature extraction module is connected to the signal acquisition module and is used to collect and calculate the instantaneous recovery rate of the bus voltage and the instantaneous peak value of the switching transistor restart current in real time after the fault recovery process is started. The risk assessment module, connected to the feature extraction module, compares the instantaneous recovery rate with a preset voltage rate threshold and compares the instantaneous current peak value with a preset current ratio threshold. When the instantaneous recovery rate exceeds the voltage rate threshold and the instantaneous current peak value exceeds the current ratio threshold, it is determined that there is an overshoot risk in the current recovery process, and a decision instruction to switch to a step-by-step restart strategy is generated. The control command generation module is connected to the risk assessment module and the core control module respectively. It is used to generate corresponding PWM control parameter modification commands according to the received decision commands and send them to the core control module to execute the switch from the current restart strategy to the step restart strategy.

[0009] According to the above scheme, the instantaneous recovery rate of the bus voltage is obtained by continuously sampling the bus voltage signal at a preset first sampling frequency, acquiring the bus voltage difference between adjacent sampling periods, and using the ratio of the difference to the sampling period time as the instantaneous recovery rate. The instantaneous peak value of the restart current of the switching transistor is obtained by continuously sampling the switching transistor current signal at a preset second sampling frequency within a preset time window after the recovery process starts, recording and maintaining the maximum absolute value of the current collected within this time window as the instantaneous peak value of the current.

[0010] According to the above scheme, the risk assessment module receives the instantaneous recovery rate and instantaneous current peak value sent by the feature extraction module; The instantaneous recovery rate is compared with a preset voltage speed threshold, and a first comparison result is output; the instantaneous current peak value is compared with the actual comparison benchmark value of the current ratio threshold, and a second comparison result is output; the actual comparison benchmark value of the current ratio threshold is calculated based on the rated output current and a preset ratio, and the preset ratio is used to set the allowable current overshoot range; the voltage speed threshold is determined based on the electrical parameter characteristics of the DC bus support capacitor and the voltage withstand margin of the switching transistors in the three-level inverter unit; the current ratio threshold is determined based on the rated output current of the inverter, combined with the current withstand characteristics of the power switching transistors and the current surge withstand capability of the load; The first comparison result and the second comparison result are analyzed to generate a risk judgment signal. When the first comparison result is that the instantaneous recovery rate exceeds the voltage speed threshold and the second comparison result is that the instantaneous current peak exceeds the current ratio threshold, it is determined that there is an overshoot risk and a risk judgment signal is generated. At the same time, a decision instruction to switch to the step-by-step restart strategy is generated, and the decision instruction includes the identification information of the step-by-step restart strategy.

[0011] According to the above scheme, the control command generation module receives and parses the decision command sent by the risk assessment module, and identifies the step-by-step restart strategy identifier contained therein; based on the step-by-step restart strategy identifier, it generates a corresponding PWM control parameter modification command, which includes a new parameter value for setting the voltage ramp rise slope and a time parameter value for setting the duration of each stage; and sends the PWM control parameter modification command to the core control module.

[0012] According to the above scheme, the step-by-step restart strategy divides the fault recovery process into two sequentially executed voltage recovery stages; The first stage is the pre-charging stage, in which the motor is energized with a first preset voltage slope and a first preset frequency. The first preset voltage slope is less than the voltage slope when the system is starting normally. The second stage is the smooth transition stage. Once the output current is detected to be stable within the rated range, the voltage slope is switched from the first preset voltage slope to the second preset voltage slope, and the output frequency is gradually increased to the target value to complete the recovery process. The first preset voltage slope and the first preset frequency are determined based on the excitation and starting characteristics of the load; the second preset voltage slope is obtained based on the speed increase characteristics and power requirements of the load. According to the above scheme, the case library module includes a case storage module, a fault feature matching module, and a strategy recommendation module; The case storage module is connected to the fault diagnosis module and the recovery management module, and is used to store historical fault case records in a data table structure. The fault case record includes a fault type identifier, a set of recovery strategy parameters used, and a comprehensive performance score for the recovery. The fault feature matching module is connected to the fault diagnosis module and the case storage module, and is used to receive the type identifier of the current fault and query historical case records with the same or similar fault type identifiers in the case storage module. The strategy recommendation module is connected to the fault feature matching module and the recovery management module, respectively. It is used to filter out the record with the highest comprehensive performance score from the matched historical case records, and output the corresponding recovery strategy parameter set to the recovery management module as the initial parameters for fault recovery.

[0013] After a fault recovery process is completed, the recovery management module feeds back the key performance data of this recovery process to the case storage module; the case storage module then generates a comprehensive performance score for the recovery case and updates or adds the corresponding historical fault case records.

[0014] According to the above scheme, the comprehensive performance score is obtained by weighted calculation based on evaluation indicators; the evaluation indicators include the maximum current impact coefficient of the recovery process, the voltage recovery stabilization time, and the total recovery time. The maximum current surge coefficient is the ratio of the measured peak current to the rated current during the recovery process; the voltage recovery stabilization time is the time elapsed from the start of the recovery process to the bus voltage fluctuation rate remaining below a set threshold; the bus voltage fluctuation rate threshold is obtained based on the load's requirements for voltage stability and the adjustment capability of the core control module; the total recovery process time is the time elapsed from the start of the recovery process to the output frequency reaching the target value.

[0015] Compared with the prior art, the beneficial effects of the present invention are: 1. This invention monitors the coupling relationship between the bus voltage recovery rate and the peak value of the switching transistor restart current in real time through the recovery management module, which can accurately identify the risk of recovery overshoot, effectively suppress the inrush current, and reduce the risk of secondary faults caused by improper recovery; 2. This invention constructs a control system for real-time perception and intelligent decision-making, making optimal decisions based on the actual recovery situation, and achieving a dynamic optimal balance between efficiency and stability in the recovery process; 3. This invention introduces a case library module to continuously accumulate data, optimize parameter recommendation accuracy, improve the system's adaptability under different operating conditions, and realize continuous self-optimization of fault recovery strategies, thereby improving the long-term operational stability and maintenance efficiency of the equipment. Attached Figure Description

[0016] Figure 1 This is a schematic diagram of the structure of an intelligent frequency converter control system based on a three-level topology circuit according to the present invention. Detailed Implementation

[0017] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0018] Example: Figure 1 As shown, the present invention provides a technical solution: an intelligent frequency converter control system based on a three-level topology circuit. The system includes a main circuit power module, a signal acquisition module, a core control module, a fault diagnosis module, a recovery management module, and a case library module. The main circuit power module is used to perform AC-DC and DC-AC conversion, providing three-phase AC power to the load. The main circuit power module includes a three-phase rectifier unit, a DC bus support capacitor, a three-level inverter unit, and a midpoint potential balancing circuit. The AC side of the three-phase rectifier unit is connected to the three-phase power supply, and the DC side outputs a pulsating DC voltage. The DC bus support capacitor is connected between the positive and negative terminals of the DC output of the three-phase rectifier unit to stabilize the DC bus voltage. The DC input of the three-level inverter unit is connected in parallel with the DC bus support capacitor, and the AC output of the three-level inverter unit is connected to the load. The three-level inverter unit consists of three-phase bridge arms, each containing four series-connected power switches and diodes connected in anti-parallel. Two clamping diodes are connected across the connection points of the four power switches. The midpoint potential balancing circuit is connected to the midpoint of the DC bus support capacitor and the midpoint potential clamping point of the three-level inverter unit to maintain the voltage balance between the upper and lower capacitors on the DC bus.

[0019] The signal acquisition module is connected to the main circuit power module and is used to acquire bus voltage, output current, switching transistor temperature and output voltage signals in real time, and convert the acquired analog signals into standard signals. The core control module, connected to the signal acquisition module, generates PWM drive signals based on system commands and feedback signals to realize the normal speed regulation and control functions of the frequency converter. The fault diagnosis module, connected to the signal acquisition module, core control module, and recovery management module, monitors the system status in real time. Upon detecting a fault, it performs diagnostic classification and initiates the recovery process. The fault diagnosis module includes a signal monitoring module, a fault determination module, and a process triggering module. The signal monitoring module, connected to the signal acquisition module, receives real-time data on bus voltage, output current, switching transistor temperature, and output voltage. The fault determination module, connected to the signal monitoring module, compares the real-time data with preset safe operating thresholds. When the data consistently exceeds the safe operating thresholds, it generates a fault trigger signal, classifies and identifies the fault type, and determines the fault attribute. The safe operating thresholds are set for four parameters: bus voltage, output current, switching transistor temperature, and output voltage. The monitoring signals are determined separately; the bus voltage and output voltage safety thresholds are obtained based on the rated voltage margin of the switching transistors of the rectifier unit and inverter unit in the main circuit; the output current safety threshold is calculated by combining the rated current of the power switching transistor and the rated operating current of the load, and analyzing the short-term overload demand; the switching transistor temperature safety threshold is obtained by referring to the upper limit parameter of the junction temperature of the power switching transistor and deducting the temperature margin of the heat dissipation system; the process triggering module is connected to the fault judgment module, the core control module and the recovery management module respectively. When the fault judgment module determines that a fault exists, the process triggering module sends a fault interrupt signal to the core control module, causing the core control module to stop outputting the normal PWM drive signal; at the same time, it sends a start signal to the recovery management module to trigger the fault recovery process.

[0020] The recovery management module, connected to the fault diagnosis module, is used to collect the bus voltage recovery rate, the peak value of the switching transistor restart current, and the output voltage recovery time in real time, and analyze the coupling relationship between the bus voltage recovery rate and the peak value of the switching transistor restart current. When it is determined that the voltage recovery rate exceeds a preset threshold and the peak current exceeds a preset proportion of the rated value, an instruction is immediately issued to the core control module to switch to a step-by-step restart strategy. The recovery management module includes a feature extraction module, a risk assessment module, and a control instruction generation module. The feature extraction module, connected to the signal acquisition module, is used to collect and calculate the instantaneous bus voltage recovery rate and the peak value of the switching transistor restart current in real time after the fault recovery process is started. Instantaneous peak value; Risk assessment module, connected to feature extraction module, compares instantaneous recovery rate with preset voltage rate threshold and instantaneous current peak value with preset current ratio threshold; when instantaneous recovery rate exceeds voltage rate threshold and instantaneous current peak value exceeds current ratio threshold, it determines that there is overshoot risk in the current recovery process and generates a decision instruction to switch to a step-by-step restart strategy; Control instruction generation module, connected to risk assessment module and core control module respectively, is used to generate corresponding PWM control parameter modification commands based on the received decision instruction and send them to core control module to execute the switch from the current restart strategy to a step-by-step restart strategy.

[0021] Furthermore, the instantaneous recovery rate of the bus voltage is obtained by continuously sampling the bus voltage signal at a preset first sampling frequency, acquiring the bus voltage difference within adjacent sampling periods, and using the ratio of this difference to the sampling period time as the instantaneous recovery rate; the instantaneous peak value of the switching transistor restart current is obtained by continuously sampling the switching transistor current signal at a preset second sampling frequency within a preset time window after the recovery process starts, recording and maintaining the maximum absolute value of the current collected within this time window as the instantaneous current peak value.

[0022] Furthermore, the risk assessment module receives the instantaneous recovery rate and instantaneous current peak value sent by the feature extraction module; compares the instantaneous recovery rate with a preset voltage speed threshold and outputs a first comparison result; compares the instantaneous current peak value with the actual comparison benchmark value of the current ratio threshold and outputs a second comparison result; the actual comparison benchmark value of the current ratio threshold is calculated based on the rated output current and a preset ratio, which is used to set the allowable current overshoot range; the voltage speed threshold is determined based on the electrical parameter characteristics of the DC bus support capacitor and the voltage tolerance margin of the switching transistors in the three-level inverter unit; the current ratio threshold is determined based on the rated output current of the inverter, combined with the current tolerance characteristics of the power switching transistors and the current surge tolerance capability of the load; analyzes the first comparison result and the second comparison result to generate a risk judgment signal; when the first comparison result is that the instantaneous recovery rate exceeds the voltage speed threshold, and the second comparison result is that the instantaneous current peak value exceeds the actual comparison benchmark value of the current ratio threshold, it is determined that there is an overshoot risk, a risk judgment signal is generated, and at the same time, a decision instruction to switch to the step-by-step restart strategy is generated, which includes the identification information of the step-by-step restart strategy.

[0023] Furthermore, the control command generation module receives and parses the decision command sent by the risk assessment module, identifies the step-by-step restart strategy identifier contained therein, generates the corresponding PWM control parameter modification command based on the step-by-step restart strategy identifier, the PWM control parameter modification command includes a new parameter value for setting the voltage ramp rise slope and a time parameter value for setting the duration of each stage, and sends the PWM control parameter modification command to the core control module.

[0024] Furthermore, the step-by-step restart strategy divides the fault recovery process into two sequentially executed voltage recovery phases. The first phase is the pre-charging phase, where the motor is energized with a first preset voltage slope and a first preset frequency. The first preset voltage slope is lower than the voltage slope during normal system startup. The second phase is the smooth transition phase, where, after the output current is detected to be stable within the rated range, the voltage slope is switched from the first preset voltage slope to the second preset voltage slope, and the output frequency is gradually increased to the target value to complete the recovery process. The first preset voltage slope and the first preset frequency are determined based on the load's excitation and startup characteristics. The second preset voltage slope is obtained based on the load's speed increase characteristics and power requirements. The case library module, connected to the fault diagnosis and recovery management modules, stores historical fault recovery cases. It includes a case storage module, a fault feature matching module, and a strategy recommendation module. The case storage module, connected to both modules, stores historical fault case records in a table structure. Each record contains a fault type identifier, the set of recovery strategy parameters used, and the overall performance score of the recovery attempt. The fault feature matching module, connected to both modules, receives the current fault type identifier and queries the case storage module for historical case records with the same or similar identifiers. The strategy recommendation module, connected to both modules, selects the record with the highest overall performance score from the matched historical case records and outputs its corresponding recovery strategy parameter set to the recovery management module as the initial parameters for fault recovery. After a fault recovery process is completed, the recovery management module feeds back the key performance data of the recovery process to the case storage module. The case storage module then generates the overall performance score of the recovery case and updates or adds the corresponding historical fault case record.

[0025] Furthermore, the comprehensive performance score is obtained based on a weighted calculation of evaluation indicators. These indicators include the maximum current surge coefficient during the recovery process, the voltage recovery stabilization time, and the total recovery time. The maximum current surge coefficient is the ratio of the measured peak current to the rated current during the recovery process. The voltage recovery stabilization time is the time elapsed from the start of the recovery process until the bus voltage fluctuation rate remains below the set threshold. The bus voltage fluctuation rate threshold is obtained based on the load's requirements for voltage stability and the adjustment capability of the core control module. The total recovery time is the time elapsed from the start of the recovery process until the output frequency reaches the target value.

[0026] This invention provides another technical solution: an intelligent frequency converter control system based on a three-level topology circuit; In the fault diagnosis module, the preset safe operating thresholds are set as follows: the bus voltage safety threshold is 115% of the rated DC bus voltage, i.e., the rated voltage is 720V. When the DC bus voltage exceeds 828V, it is judged as an overvoltage fault; the output current safety threshold is set to 150% of the rated output current of the inverter, i.e., the rated current is 200A. When the output current exceeds 300A, it is judged as an overcurrent fault; the switching transistor temperature safety threshold is set to 105℃. These are just examples and are not intended to be restrictive.

[0027] In the recovery management module, the preset voltage speed threshold is set to 25V / ms; the preset current ratio threshold is set to 120% of the rated output current, that is, its actual comparison reference value is 200A×120%=240A. The parameters for the step-by-step restart strategy are set as follows: the first preset voltage slope is set to 50V / s, the first preset frequency is set to 5Hz, and the second preset voltage slope is set to 200V / s. During system operation, the signal monitoring module of the fault diagnosis module receives data from the signal acquisition module in real time; the fault determination module detects that the output current exceeds 300A for 10 milliseconds, determines it as an overcurrent fault, generates a fault trigger signal, and classifies and identifies the fault type. After receiving the instruction from the fault determination module, the process triggering module immediately sends a fault interrupt signal to the core control module, and the core control module stops outputting normal PWM drive signals; at the same time, the process triggering module sends a start signal to the recovery management module to trigger the fault recovery process. The feature extraction module of the recovery management module collects the bus voltage signal at a sampling frequency of 10kHz and calculates the instantaneous recovery rate as 30V / ms. At the same time, in the first 50ms time window after the recovery process starts, the current signal of the switching transistor is collected at a sampling frequency of 20kHz. The maximum absolute value of the current recorded is 280A, which is used as the instantaneous current peak value. After receiving the instantaneous recovery rate and instantaneous current peak value from the feature extraction module, the risk assessment module executes comparison logic: it compares 30V / ms with the voltage speed threshold; since 30 > 25, the first comparison result is output as exceeding the limit; it compares 280A with the actual comparison benchmark value of the current ratio threshold; since 280 > 240, the second comparison result is output as exceeding the limit; it performs a logical AND operation on the two comparison results, and if the result is true, it determines that there is an overshoot risk, generates a risk judgment signal, and generates a decision instruction containing a step-by-step restart strategy identifier; After receiving the decision command, the control command generation module parses out that a step-by-step restart strategy needs to be executed, and then generates a PWM control parameter modification command. This command includes instructions to modify the voltage ramp rise rate to 50V / s and 200V / s, as well as to set the minimum duration of each stage, and sends this command to the core control module. The core control module executes a step-by-step restart strategy based on the new PWM parameters: First stage: Excitation is applied to the motor at a voltage slope of 50V / s and a frequency of 5Hz; Second stage: After 100 milliseconds, the recovery management module detects that the output current has stabilized within the 200A rated value range, and then notifies the core control module to switch the voltage slope to 200V / s and gradually increase the output frequency to the target value to complete the recovery process.

[0028] After the recovery process is completed, the recovery management module will send the key performance data of this recovery—maximum inrush current 280A, voltage recovery stabilization time 150ms, and total recovery time 800ms—to the case storage module of the case library module.

[0029] The case storage module generates a comprehensive performance score for this recovery case based on the above data, and stores the type of overcurrent fault, the recovery strategy parameters used, and the comprehensive performance score of 85 points as a new historical fault case record.

[0030] When the system experiences the same type of overcurrent fault again, the fault feature matching module will query the case storage module, and the strategy recommendation module will recommend the recovery strategy parameters corresponding to the record with the highest comprehensive performance score to the recovery management module as the initial optimization parameters for this fault recovery.

[0031] It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above, and that the invention can be implemented in other specific forms without departing from its spirit or essential characteristics. Therefore, the embodiments should be considered in all respects as exemplary and non-limiting, and the scope of the invention is defined by the appended claims rather than the foregoing description. Thus, all variations falling within the meaning and scope of equivalents of the claims are intended to be included within the present invention. No reference numerals in the claims should be construed as limiting the scope of the claims.

Claims

1. A smart frequency converter control system based on a three-level topology circuit, characterized in that: The system includes a main circuit power module, a signal acquisition module, a core control module, a fault diagnosis module, a recovery management module, and a case library module; The main circuit power module is used to perform AC-DC conversion and DC-AC conversion to provide three-phase AC power to the load; The signal acquisition module is connected to the main circuit power module and is used to acquire bus voltage, output current, switching transistor temperature and output voltage signals in real time, and convert the acquired analog signals into standard signals. The core control module is connected to the signal acquisition module and generates PWM drive signals according to system instructions and feedback signals to realize the normal speed regulation and control functions of the frequency converter. The fault diagnosis module is connected to the signal acquisition module, the core control module and the recovery management module respectively, and is used to monitor the system status in real time, perform diagnosis and classification and start the recovery process when a fault is detected. The recovery management module is connected to the fault diagnosis module and is used to collect the bus voltage recovery rate, the peak value of the switch restart current and the output voltage recovery time in real time, and analyze the coupling relationship between the bus voltage recovery rate and the peak value of the switch restart current. When it is determined that the voltage recovery rate exceeds the preset threshold and the peak current exceeds the preset ratio of the rated value, an instruction is immediately sent to the core control module to switch to a step-by-step restart strategy. The case library module is connected to the fault diagnosis module and the recovery management module, and is used to store historical fault recovery cases.

2. The intelligent frequency converter control system based on a three-level topology circuit according to claim 1, characterized in that: The main circuit power module includes a three-phase rectifier unit, a DC bus support capacitor, a three-level inverter unit, and a neutral point potential balancing circuit. The AC side of the three-phase rectifier unit is connected to a three-phase power supply, and the DC side outputs a pulsating DC voltage. The DC bus support capacitor is connected between the positive and negative terminals of the DC output of the three-phase rectifier unit to stabilize the DC bus voltage. The DC input terminal of the three-level inverter unit is connected in parallel with the DC bus support capacitor, and the AC output terminal of the three-level inverter unit is connected to the load. The three-level inverter unit is composed of three-phase bridge arms, each phase bridge arm includes four power switching transistors connected in series and diodes connected in antiparallel with them, and two clamping diodes are connected across the connection points of the four power switching transistors. The midpoint potential balancing circuit is connected to the midpoint of the DC bus support capacitor and the midpoint potential clamping point of the three-level inverter unit to maintain the voltage balance of the upper and lower capacitors on the DC bus.

3. The intelligent frequency converter control system based on a three-level topology circuit according to claim 1, characterized in that: The fault diagnosis module includes a signal monitoring module, a fault determination module, and a process triggering module; The signal monitoring module is connected to the signal acquisition module and is used to receive real-time data of bus voltage, output current, switching transistor temperature and output voltage. The fault determination module is connected to the signal monitoring module and is used to compare real-time data with a preset safe operating threshold. When the data continuously exceeds the safe operating threshold, a fault trigger signal is generated, and the fault type is classified and identified to determine the fault attribute. The process triggering module is connected to the fault determination module, the core control module, and the recovery management module. When the fault determination module determines that a fault exists, the process triggering module sends a fault interrupt signal to the core control module, causing the core control module to stop outputting normal PWM drive signals; at the same time, it sends a start signal to the recovery management module to trigger the fault recovery process.

4. The intelligent frequency converter control system based on a three-level topology circuit according to claim 1, characterized in that: The recovery management module includes a feature extraction module, a risk assessment module, and a control command generation module; The feature extraction module is connected to the signal acquisition module and is used to collect and calculate the instantaneous recovery rate of the bus voltage and the instantaneous peak value of the switching transistor restart current in real time after the fault recovery process is started. The risk assessment module, connected to the feature extraction module, compares the instantaneous recovery rate with a preset voltage rate threshold and compares the instantaneous current peak value with a preset current ratio threshold. When the instantaneous recovery rate exceeds the voltage rate threshold and the instantaneous current peak value exceeds the current ratio threshold, it is determined that there is an overshoot risk in the current recovery process, and a decision instruction to switch to a step-by-step restart strategy is generated. The control command generation module is connected to the risk assessment module and the core control module respectively. It is used to generate corresponding PWM control parameter modification commands according to the received decision commands and send them to the core control module to execute the switch from the current restart strategy to the step restart strategy.

5. The intelligent frequency converter control system based on a three-level topology circuit according to claim 4, characterized in that: The instantaneous recovery rate of the bus voltage is obtained by continuously sampling the bus voltage signal at a preset first sampling frequency, acquiring the bus voltage difference between adjacent sampling periods, and using the ratio of the difference to the sampling period time as the instantaneous recovery rate. The instantaneous peak value of the restart current of the switching transistor is obtained by continuously sampling the switching transistor current signal at a preset second sampling frequency within a preset time window after the recovery process starts, recording and maintaining the maximum absolute value of the current collected within this time window as the instantaneous peak value of the current.

6. The intelligent frequency converter control system based on a three-level topology circuit according to claim 5, characterized in that: The risk assessment module receives the instantaneous recovery rate and instantaneous current peak value sent by the feature extraction module; The instantaneous recovery rate is compared with a preset voltage rate threshold, and a first comparison result is output; the instantaneous current peak value is compared with the actual comparison benchmark value of the current ratio threshold, and a second comparison result is output. The actual comparison benchmark value of the current ratio threshold is calculated based on the rated output current and the preset ratio, which is used to set the allowable current overshoot range. Analyze the first and second comparison results to generate risk assessment signals; When the first comparison result is that the instantaneous recovery rate exceeds the voltage speed threshold, and the second comparison result is that the instantaneous current peak exceeds the current ratio threshold, an overshoot risk is determined, a risk determination signal is generated, and at the same time, a decision instruction to switch to the step-by-step restart strategy is generated. The decision instruction includes the identification information of the step-by-step restart strategy.

7. The intelligent frequency converter control system based on a three-level topology circuit according to claim 6, characterized in that: The control command generation module receives and parses the decision command sent by the risk assessment module, identifies the step-by-step restart strategy identifier contained therein, generates a corresponding PWM control parameter modification command based on the step-by-step restart strategy identifier, the PWM control parameter modification command includes a new parameter value for setting the voltage ramp rise slope and a time parameter value for setting the duration of each stage, and sends the PWM control parameter modification command to the core control module.

8. The intelligent frequency converter control system based on a three-level topology circuit according to claim 7, characterized in that: The step-by-step restart strategy divides the fault recovery process into two sequentially executed voltage recovery phases; The first stage is the pre-charging stage, in which the motor is energized with a first preset voltage slope and a first preset frequency. The first preset voltage slope is less than the voltage slope when the system is starting normally. The second stage is the smooth transition stage. Once the output current is detected to be stable within the rated range, the voltage slope is switched from the first preset voltage slope to the second preset voltage slope, and the output frequency is gradually increased to the target value to complete the recovery process.

9. The intelligent frequency converter control system based on a three-level topology circuit according to claim 1, characterized in that: The case library module includes a case storage module, a fault feature matching module, and a strategy recommendation module; The case storage module is connected to the fault diagnosis module and the recovery management module, and is used to store historical fault case records in a data table structure. The fault case record includes a fault type identifier, a set of recovery strategy parameters used, and a comprehensive performance score for the recovery. The fault feature matching module is connected to the fault diagnosis module and the case storage module, and is used to receive the type identifier of the current fault and query historical case records with the same or similar fault type identifiers in the case storage module. The strategy recommendation module is connected to the fault feature matching module and the recovery management module, respectively. It is used to filter out the record with the highest comprehensive performance score from the matched historical case records, and output the corresponding recovery strategy parameter set to the recovery management module as the initial parameters for fault recovery.

10. The intelligent frequency converter control system based on a three-level topology circuit according to claim 9, characterized in that: The comprehensive performance score is obtained by weighted calculation based on evaluation indicators, which include the maximum current surge coefficient during the recovery process, the voltage recovery stabilization time, and the total recovery time. The maximum current surge coefficient is the ratio of the measured peak current to the rated current during the recovery process; the voltage recovery stabilization time is the time elapsed from the start of the recovery process to the bus voltage fluctuation rate remaining below the set threshold; the total recovery process time is the time elapsed from the start of the recovery process to the output frequency reaching the target value.

Images