Frequency converter real-time switching intelligent control method and system

Abstract

The invention discloses an intelligent control method and system for real-time switching of a frequency converter, and relates to the field of real-time switching control of the frequency converter, and the method comprises the steps: analyzing the change slope of a frequency deviation time sequence through linear regression based on the phase angle and frequency value of the current output voltage of the frequency converter; meanwhile, the phase angle difference value variation between adjacent sampling points is calculated; the method comprises the following steps of: establishing a state machine of transfer logic, entering a phase angle monitoring state after the frequency is continuously converged, and generating a switching ready signal after judging that a frequency deviation trend and a phase angle difference trend both meet a stable approaching condition; after switching is completed, the switching stability is analyzed through the fluctuation amplitude of the output current and the change trend of the instantaneous rotating speed change rate, a closed-loop correction mechanism is started when the switching stability is detected to be abnormal, the optimal switching moment of the frequency converter is determined, and it is guaranteed that the motor runs stably before and after switching.

Description

Technical Field

[0001] This invention belongs to the field of real-time switching control technology for frequency converters, and relates to an intelligent control method and system for real-time switching of frequency converters. Background Technology

[0002] As control devices for motor drive systems, frequency converters are widely used in speed regulation and operation control of critical loads such as fans and heavy transmission machinery. To ensure production continuity, a smooth switching of frequency converters must be achieved when transferring loads between multiple frequency converters. If the timing of the switching is not properly judged or the switching process is poorly controlled, it may lead to motor shutdown, drastic fluctuations in operating parameters, and consequently, production interruption and equipment damage.

[0003] However, although existing technologies have basic implementation solutions in the field of inverter switching control, the following shortcomings still exist: First, in actual operation, due to factors such as load fluctuations, system inertia and electrical disturbances, the switching-related parameters are often in a state of continuous dynamic change. Existing technologies usually use instantaneous judgment logic, lack analysis of the long-term evolution trend of switching parameters, and are difficult to make accurate decisions when there are oscillations or transient fluctuations in the system, which can easily lead to improper switching timing, thereby causing current surges or even equipment damage.

[0004] Secondly, existing technologies typically detect parameter matching as an isolated condition during the switching operation, ignoring the dynamic continuity of the system state. Due to the open judgment of switching parameters, what is captured are the momentary points of accidental overlap, rather than the truly stable synchronous matching state, which cannot guarantee the continuous and stable operation of the system before and after the switch.

[0005] Finally, after the switchover is completed, existing technologies usually rely on the detection and adjustment of the switchover stability index, which cannot accurately identify the trend of stability fluctuations, or identify and suppress the disturbance trend introduced by the switchover in an early stage. This leads to correction lag, which may cause secondary oscillations, reduce operating efficiency and equipment life. Summary of the Invention

[0006] In view of this, in order to solve the problems mentioned in the background art, the present invention provides a method and system for real-time switching intelligent control of frequency converters.

[0007] The objective of this invention can be achieved through the following technical solutions: In a first aspect, this invention provides a real-time switching intelligent control method for frequency converters, comprising the following steps: based on the phase angle and frequency value of the current frequency converter output voltage, analyzing the changing trend of the deviation between the current frequency converter and the target frequency converter output frequency, and the dynamic difference of the phase angle of their output voltages.

[0008] Based on the changing trend of frequency deviation and the dynamic difference of phase angle, the switching logic is judged by state machine. When the frequency deviation is in a continuous convergence trend and the phase angle difference shows a stable decreasing trend, a switching ready signal is generated.

[0009] Based on the switching readiness signal, the output frequency and phase angle of the target inverter are dynamically adjusted to match the output frequency and phase angle of the current inverter until the frequency difference and phase difference are both kept within the allowable error band.

[0010] After the synchronization control reaches the matching state, the control switching device will switch the motor load from the current frequency converter to the target frequency converter.

[0011] After the switching operation is completed, the motor's operating status is monitored in real time. The switching smoothness is evaluated by analyzing the fluctuation characteristics of the output current and the rate of change of speed. If an abnormality in the switching smoothness is detected, a closed-loop correction mechanism is activated.

[0012] Secondly, the present invention provides an intelligent control system for real-time switching of frequency converters, including the following modules: a synchronization parameter analysis module, used to analyze the changing trend of the deviation between the output frequency of the current frequency converter and the target frequency converter, and the dynamic difference of the phase angle of their output voltages.

[0013] The switching logic judgment module is used to make switching logic judgments based on the changing trend of frequency deviation and the dynamic difference of phase angle through a state machine. When the frequency deviation is in a continuous convergence trend and the phase angle difference shows a stable decreasing trend, a switching ready signal is generated.

[0014] The synchronization adjustment module is used to dynamically adjust the output frequency and phase angle of the target frequency converter according to the switching readiness signal, and to achieve synchronous matching.

[0015] The switching control module is used to control the switching device to complete the load transfer after synchronization and matching are achieved.

[0016] The smoothness correction module is used to analyze the fluctuation characteristics of the output current and the rate of change of speed after the switching operation is completed to evaluate the smoothness of the switching. If an abnormality in the smoothness of the switching is detected, the closed-loop correction mechanism is activated.

[0017] Compared with the prior art, the beneficial effects of the present invention are as follows: (1) The present invention uses linear regression analysis of the change slope of the frequency deviation time series based on the phase angle and frequency value of the current inverter output voltage, and calculates the change of phase angle difference between adjacent sampling points to realize dynamic analysis of the long-term evolution trend of switching parameters, effectively distinguishing whether the system is in a true synchronous convergence process or transient oscillation, thereby achieving the best switching timing and reducing the risk of current impact and equipment damage caused by improper switching timing.

[0018] This invention constructs a state machine for the transfer logic. After the frequency continues to converge, it enters the phase angle monitoring state. Only after both the frequency deviation trend judgment and the phase angle difference trend meet the stable approach condition is a switching ready signal generated. This ensures the continuity of the switching and avoids misjudging the instantaneous point when the frequency and phase accidentally enter the threshold simultaneously as a stable synchronization state. This ensures continuous operation before and after the switching and improves the reliability of synchronization matching.

[0019] After the switching is completed, this invention analyzes the switching smoothness by measuring the fluctuation amplitude of the output current and the changing trend of the instantaneous speed change rate. If an abnormality in switching smoothness is detected, a closed-loop correction mechanism is activated, realizing pre-emptive trend intervention. This can suppress the trend in the early stages of development, avoid correction lag and large-scale adjustment, and prevent secondary oscillations. Attached Figure Description

[0020] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0021] Figure 1 This is a diagram illustrating the implementation steps of the method of the present invention.

[0022] Figure 2 This is a flowchart illustrating the frequency and phase synchronization adjustment process before frequency switching in the inverter of this invention.

[0023] Figure 3 This is a schematic diagram showing the connections of the various modules in the system of the present invention. Detailed Implementation

[0024] 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. Example 1

[0025] Please see Figure 1 As shown, the present invention provides a real-time switching intelligent control method for frequency converters, including: S1, analyzing the changing trend of the deviation between the output frequency of the current frequency converter and the target frequency converter, and the dynamic difference of the phase angle of their output voltages, based on the phase angle and frequency value of the current frequency converter output voltage.

[0026] To address the issue that insufficient accuracy in judging frequency deviation trends in real-time switching control of frequency converters can easily lead to improper selection of switching timing, resulting in problems such as motor load impact and decreased operational stability.

[0027] Therefore, the steps to analyze the changing trend of the deviation between the current inverter and the target inverter output frequency are as follows: obtain the output frequency value of the current inverter and the output frequency value of the target inverter, and sample them at a predetermined sampling period to obtain frequency data of multiple sampling points.

[0028] The frequency detection module integrated into the inverter directly collects the output frequency value of the inverter, and through the synchronous trigger signal of the control system, it ensures that the frequency value collected by the current inverter for the target inverter is consistent, so as to avoid the distortion of subsequent frequency deviation calculation due to the timing deviation of the collection.

[0029] The calculation process for the aforementioned predetermined sampling period is as follows: First, calculate the maximum allowable period that matches the inverter's response speed. Because there is a minimum response time when the frequency converter adjusts the output frequency, that is, the shortest time from when the frequency converter receives the adjustment command to when the frequency actually changes, if the sampling period is longer than this time, it will not be able to keep up with the real-time frequency adjustment process, resulting in the frequency data being lagging. Therefore, the sampling period should be controlled within 1 / 5 of the response speed in order to leave enough redundancy and ensure that the sampling can track the adjustment in real time.

[0030] Next, calculate the maximum allowable period that can capture the smallest deviation change. , The minimum identifiable deviation is calculated as the ratio of the minimum identifiable deviation to the maximum rate of change. The minimum identifiable deviation is obtained directly from the minimum measurement accuracy specified in the manufacturer's technical parameters of the measuring equipment, and then combined with the minimum effective deviation threshold defined in the inverter switching control specifications of the relevant industry; the larger of these two values ​​is taken as the minimum identifiable deviation. The maximum rate of change is obtained by measuring the deviation change data of the inverter under full load as it adjusts from 10% of the rated frequency back to the rated frequency. The maximum change in frequency deviation per unit time is recorded, and the ratio of this change to time is the maximum rate of change. To determine the trend of frequency deviation change, it is necessary to identify the change in the minimum effective deviation. If the sampling period is too long, the deviation change within the interval between two samplings may have exceeded the minimum effective value without being detected.

[0031] Then calculate the maximum allowable period for the linear regression sample size. , The value is obtained by the ratio of the observation time window length to the minimum sample size, where the minimum sample size is generally taken as 5 to 10. To analyze the trend of frequency deviation, linear regression is required, and regression analysis requires a sufficient sample size, and the samples must be collected within a fixed observation time window.

[0032] Finally select , , The minimum value is taken as the final sampling period.

[0033] For each sampling point, the difference between the current inverter output frequency value and the target inverter output frequency value is calculated to obtain the frequency deviation value, and the time series of the frequency deviation value is obtained.

[0034] Perform linear regression analysis on the frequency deviation time series and calculate its slope of change.

[0035] If the slope of change remains negative within a predetermined observation time window and its absolute value is greater than a preset slope threshold, then the frequency deviation is determined to be in a continuous convergence trend; otherwise, the frequency deviation is determined not to be in a continuous convergence trend.

[0036] It should be noted that if the slope of change remains negative within the predetermined observation time window, it indicates that the frequency deviation decreases monotonically over time, which meets the requirements for deviation convergence. Furthermore, the window constraint can eliminate trend anomalies caused by instantaneous disturbances, ensuring trend stability. The absolute value of the slope is greater than the preset threshold to select an effective convergence rate that meets the real-time requirements of industrial control, avoiding slow rates that could lead to switching timeouts or convergence interruptions, and ensuring that the deviation approaches zero within a reasonable time. This ensures both the correct convergence direction and the achievement of convergence efficiency standards, avoiding the shortcomings of judgment under a single constraint.

[0037] The preset slope threshold is based on the inverter switching control specifications of the relevant industry. The minimum convergence rate index of frequency deviation in the specifications is extracted. Then, combined with the frequency corresponding to the rated speed of the inverter and the motor, the minimum convergence rate is mapped to the slope threshold. For example, a convergence rate of 0.5Hz / s corresponds to an absolute slope value greater than or equal to 0.5Hz / s. If the observation time window is 100ms, the threshold can be converted to a corresponding absolute slope value greater than or equal to 0.05Hz / 100ms.

[0038] Considering that during the real-time switching control of the frequency converter, if the phase angle deviation between the current frequency converter and the target frequency converter is too large, direct switching will cause the output voltage of the two frequency converters to form an instantaneous potential difference at the load end, triggering an inrush current, causing a sudden change in motor speed, and increasing the mechanical stress of the equipment.

[0039] Therefore, the steps for calculating the dynamic difference of the output voltage phase angle are as follows: synchronously obtain the instantaneous phase angle of the output voltage of the current inverter and the target inverter.

[0040] Specifically, a Hall voltage sensor is used to collect the high voltage signal of the PWM output side of the frequency converter and directly convert it into a low-amplitude analog signal. The analog signal is then conditioned by a comparator and converted into a digital signal by an ADC analog-to-digital converter. The DSP digital signal processor then performs zero-crossing detection to extract the time of voltage zero crossing and finally calculates the phase angle in conjunction with a timer.

[0041] Calculate the instantaneous phase angle difference between the current inverter and the target inverter at the same sampling time.

[0042] Calculate the change in phase angle difference between adjacent sampling points. If the change in phase angle difference is negative for multiple consecutive sampling periods, and the number of sampling points with negative phase angle difference changes is greater than the number of sampling points with non-negative phase angle difference changes, then it is determined that the phase angle difference shows a stable decreasing trend.

[0043] It should be noted that the negative change in phase angle difference between adjacent sampling points indicates that the phase angle difference is decreasing in each sampling period, which is consistent with the requirement of phase synchronization convergence. The requirement that the change in phase angle difference be negative for multiple consecutive sampling periods is to eliminate accidental situations caused by voltage fluctuations and temporary load changes, and to ensure that this decreasing trend is not occasional. The fact that there are more sampling points with negative changes than non-negative changes is to confirm that even if the phase difference does not decrease in a few periods throughout the observation time, it will not change the overall direction of convergence.

[0044] S2. Based on the changing trend of frequency deviation and the dynamic difference of phase angle, the switching logic is judged through the state machine. When the frequency deviation is in a continuous convergence trend and the phase angle difference shows a stable decreasing trend, a switching ready signal is generated.

[0045] The switching logic judgments made by the state machine are as follows: The state machine has multiple preset states, including initialization state, frequency monitoring state, phase monitoring state, preparation state, and switching state.

[0046] In the initialization state, the state machine waits to receive the output frequency and phase angle data of the current inverter and the target inverter.

[0047] After entering the frequency monitoring state, the state machine monitors the changing trend of the frequency deviation. When the frequency deviation is in a continuous convergence trend, the state machine automatically switches to the phase monitoring state.

[0048] In phase monitoring mode, the state machine monitors the dynamic difference of the phase angle difference. When the phase angle difference shows a stable decreasing trend, the state machine automatically transitions to the ready state.

[0049] In the ready state, the state machine generates a switch ready signal and waits for a switch trigger command; this waiting switch trigger command is obtained by receiving a manual trigger command from the host computer.

[0050] When a switch trigger command is received, the state machine transitions to the switch state and outputs a switch execution command.

[0051] By using a state machine for switching logic, synchronization conditions can be verified step by step according to the priority of frequency first and then phase angle. State transitions are strictly controlled by condition triggers, and a preparation state is reserved to wait for trigger commands. This not only avoids erroneous switching, but also makes the switching process controllable and traceable, ensuring the safe and stable switching of the frequency converter.

[0052] The specific steps for generating the switching readiness signal are as follows: when the frequency deviation is determined to be in a continuous convergence trend and the phase angle difference is determined to be in a stable decreasing trend, the synchronization conditions are confirmed to be met simultaneously.

[0053] It should be noted that the continuous convergence of frequency deviation indicates that the current output frequency is getting closer to that of the target frequency inverter. If the frequencies are different, the phase difference will continue to diverge, resulting in unstable alignment. The stable decrease in the phase angle difference indicates that, under the premise of close frequencies, the phases of the two are getting closer.

[0054] Set an internal frequency convergence flag to active state, and simultaneously set an internal phase stability decrease flag to active state.

[0055] If the frequency convergence flag and the phase stability reduction flag are detected to be continuously active simultaneously within a signal generation cycle, a high-level switching ready signal is generated, which includes a frequency matching flag, a phase matching flag, and a switching enable flag.

[0056] The frequency matching flag indicates that the frequency deviation has converged, the phase matching flag indicates that the phase angle difference has decreased, and the handover permission flag indicates that the handover operation is permitted.

[0057] The generated handover readiness signal is output to the handover logic control unit, and the handover readiness signal is kept valid until the handover action is detected to begin.

[0058] S3. Based on the switching readiness signal, dynamically adjust the output frequency and phase angle of the target inverter to match the output frequency and phase angle of the current inverter until the frequency difference and phase difference are both maintained within the allowable error band.

[0059] See Figure 2 As shown, the steps for dynamically adjusting the output frequency and phase angle of the target inverter are as follows: After receiving the switching ready signal, the output frequency difference and phase difference between the current inverter and the target inverter are compared in real time.

[0060] If the frequency difference is positive, the target inverter is controlled to increase its output frequency; if the frequency difference is negative, the target inverter is controlled to decrease its output frequency.

[0061] It should be noted that if the frequency difference is positive, it means that the output frequency of the target inverter is lower than that of the current inverter, so the target inverter is controlled to increase its output frequency; if the frequency difference is negative, it means that the output frequency of the target inverter is higher than that of the current inverter, so the target inverter is controlled to decrease its output frequency.

[0062] If the phase difference is positive, the phase angle of the output voltage of the target frequency converter will change ahead; if the phase difference is negative, the phase angle of the output voltage of the target frequency converter will change lag.

[0063] If the phase difference is positive, it means that the phase of the target inverter is lagging behind the current inverter, so the target inverter is controlled to make its output voltage phase angle change ahead; if the phase difference is negative, it means that the phase of the target inverter is ahead of the current inverter, so the target inverter is controlled to make its output voltage phase angle change behind.

[0064] After performing frequency and phase adjustments, the latest output frequency difference and phase difference are recalculated to determine whether both the frequency difference and phase difference are kept within the allowable error band. If they are not within the allowable error band, the adjustment steps described above are returned.

[0065] It should be added that the method for determining the allowable error band is as follows: First, establish a simulation model that includes the inverter output filter and the equivalent circuit of the motor. Specifically, integrate the equivalent circuit of the inverter output filter and the equivalent circuit of the motor, and assign values ​​to the key parameters of the model according to the actual rated parameters of the inverter and the motor.

[0066] Secondly, fix the output of a frequency converter in the model, and apply stepped frequency deviation and phase deviation respectively. For example, increase the frequency deviation in steps of 0.1Hz or the phase deviation in steps of 1°, and monitor the peak value of the motor stator current after each deviation step stabilizes.

[0067] Finally, the frequency deviation or phase deviation value that causes the peak current to first continuously exceed K times the rated current of the motor is recorded as the critical value. This critical value is multiplied by the safety factor α, where 0 < α < 1. This product is the upper limit of the allowable error band. K is selected based on the instantaneous overload capacity of the motor, typically 1.2 to 1.5; the safety factor α is typically 0.6 to 0.8. The lower limit is set based on 5% of the upper limit.

[0068] The aforementioned safety factor setting can reserve sufficient design margin for the system to cover unavoidable uncertainties in actual operation, such as measurement noise, control delay, and load transients, ensuring that switching commands are triggered under absolutely safe electrical conditions.

[0069] The system records the number of adjustments. If the number of adjustments exceeds the preset maximum, the adjustment step is exited, and the switching process is terminated. This avoids the risk of failure caused by an infinite loop in the synchronization process due to anomalies, ensuring that the system returns to a safe state.

[0070] The preset maximum number of times is calculated based on the single adjustment period, i.e., the time from sampling, calculation to output update, and the maximum allowed total synchronization adjustment time of the system. Specifically, the ratio of the maximum allowed total synchronization adjustment time to the single adjustment period is recorded as the preset maximum number of times. For example, if the synchronization process is required to be no more than 0.5 seconds and the single adjustment period is 10 milliseconds, then the preset maximum number of times is set to 50 times.

[0071] S4. After the synchronous control reaches the matching state, the control switching device will switch the motor load from the current frequency converter to the target frequency converter.

[0072] Specifically, when the synchronization control reaches a matching state, a switching execution instruction is generated.

[0073] The switching execution command is sent to the switching device, which includes an electrical switch or contactor.

[0074] The control switching device first disconnects the power connection between the current frequency converter and the motor load.

[0075] After disconnecting the current inverter, the control switching device immediately establishes a power connection between the target inverter and the motor load.

[0076] It should be added that for switching devices that use the disconnect-before-connect method, the target inverter connection should be established as soon as possible after the current inverter connection is disconnected; for circuits that can use parallel switching or have overlapping switching capabilities, control should be performed according to the corresponding timing sequence to minimize the load power outage time.

[0077] Verify the connection status between the target frequency converter and the motor load. Once the connection is confirmed to be correct, complete the switching operation.

[0078] S5. After the switching operation is completed, the motor's operating status is monitored in real time. The switching smoothness is evaluated by analyzing the fluctuation characteristics of the output current and the rate of change of speed. If an abnormality in the switching smoothness is detected, the closed-loop correction mechanism is activated.

[0079] After the frequency converter switches, the current continues to fluctuate violently, which can easily cause the motor windings to overheat and the power module to be overloaded. If the speed rises or falls suddenly, the mechanical transmission components will be subjected to instantaneous impact, which will aggravate wear and even cause structural failure.

[0080] Therefore, analyzing the fluctuation characteristics of the output current and the rate of change of speed to evaluate the smoothness of switching includes: after the switching operation is completed, synchronously collecting the output current and speed of the motor within the monitoring window.

[0081] Extract the peak and valley values ​​of the output current within the monitoring window, and calculate the difference between the peak and valley values ​​as the fluctuation range.

[0082] Record rotational speed values ​​at fixed time intervals within the monitoring window, calculate the rotational speed change between adjacent recording points, and calculate the instantaneous rotational speed change rate at each point based on the time interval.

[0083] When the fluctuation amplitude of the current is decreasing and the absolute value of the instantaneous speed change rate shows a decaying trend, the switching smoothness is judged to be normal; otherwise, it is judged to be abnormal.

[0084] In the specific implementation of the above scheme, the determination of the decreasing state can be achieved by first obtaining the current fluctuation amplitude of each time interval within the monitoring time window after the switch at a fixed time interval, forming a continuous current fluctuation amplitude dataset. First, the current fluctuation amplitude of at least three consecutive time intervals should show that the current fluctuation amplitude of the later time interval is smaller than that of the previous time interval, eliminating misjudgment caused by one or two accidental fluctuations; and the difference between the current fluctuation amplitudes of adjacent time intervals should account for no less than 5% of the current fluctuation amplitude of the previous time interval, to avoid being misidentified as a decreasing trend due to small amplitude changes; finally, it is determined to be in a decreasing state.

[0085] The attenuation trend can be determined by collecting the absolute value data of the instantaneous speed change rate at the most recent 5 consecutive time points, constructing its time-series change curve, and identifying whether it is monotonically decreasing based on the curve. If it is monotonically decreasing, it is determined that there is an attenuation trend.

[0086] After the switching operation is completed, the motor windings will generate electromagnetic torque fluctuations because the output frequency and voltage phase are temporarily mismatched with the electrical parameters of the motor load. The outward characteristic is a violent fluctuation in the output current. The decreasing amplitude of the current fluctuation indicates that the frequency and voltage phase are gradually matched, the electromagnetic shock is gradually relieved, and the electrical system converges towards a steady state. The absolute value of the instantaneous speed change rate is positively correlated with the inertial shock of the mechanical components. Its decaying trend indicates that the speed is stabilizing, the mechanical stress is decreasing, and the mechanical system is converging towards a steady state.

[0087] The above-mentioned steps for starting the closed-loop correction mechanism are as follows: When the switching stability is judged to be abnormal in multiple consecutive monitoring windows after the switch, the absolute values ​​of the output current fluctuation amplitude and the instantaneous speed change rate are continuously calculated; when the switch is just completed, the system itself is in a transient process, and starting the correction immediately may lead to over-adjustment, which may introduce instability.

[0088] The aforementioned consecutive monitoring windows typically refer to 3 to 5 consecutive monitoring windows. After the closed-loop correction is initiated, the system will continuously monitor the stability index. When the stability is determined to be normal for 2 consecutive monitoring windows, the correction process is considered complete. After the correction is completed, the adjusted controller parameters will be maintained. Alternatively, according to a preset strategy, the parameters can be gradually restored to their initial values ​​after a period of stable operation, in preparation for the next switch.

[0089] If the current fluctuation amplitude does not show a decreasing trend, increase the current loop proportional gain of the target frequency converter or increase the adjustment response strength of the output frequency.

[0090] At this time, the actual value of the inverter output current is collected by the Hall current sensor, and the current command value is obtained from inside the inverter to calculate the instantaneous current deviation between the two.

[0091] First, if the instantaneous current deviation is greater than or equal to 5% of the motor's rated current within 5 consecutive current sampling cycles, and the absolute value of the deviation does not show a stable decreasing trend, then the root cause of the abnormality is determined to be current loop response lag, and the current loop proportional gain is increased.

[0092] Secondly, the current initial current loop proportional gain is read from the inverter register, and 10% to 15% of the initial current loop proportional gain is recorded as the single adjustment amount. A gain adjustment command is sent to the inverter control module to increase the initial current loop proportional gain to the sum of the initial current loop proportional gain and the single adjustment amount. After adjustment, it is maintained for one current sampling period to avoid current oscillation caused by a sudden increase in gain.

[0093] Finally, if the instantaneous current deviation is less than 5% of the motor's rated current, it is determined that the output frequency is lagging behind the load, and the adjustment response strength of the output frequency is increased.

[0094] If the absolute value of the instantaneous speed change rate does not show a decay trend, increase the speed loop proportional gain of the target frequency converter or increase the adjustment step size of the output voltage phase angle.

[0095] At this time, the inverter output speed command value and the actual speed value are collected, and the instantaneous speed deviation between the two is calculated.

[0096] If the instantaneous speed deviation is greater than or equal to 3% of the motor's rated speed within 5 consecutive speed sampling periods, and the deviation value shows a decreasing trend, then the root cause of the abnormality is determined to be a speed loop response lag, which in turn increases the speed loop proportional gain.

[0097] If the instantaneous speed deviation is less than 3% of the motor's rated speed, the root cause of the abnormality is determined to be a lag in the adaptation between the output voltage phase angle and the motor's back electromotive force, which in turn increases the adjustment step size of the output voltage phase angle.

[0098] After performing the above adjustments, continuously monitor the current fluctuation amplitude and speed change rate. When the switching smoothness is detected to be normal, the correction process is complete. Example 2

[0099] See Figure 3 As shown, a second aspect of the present invention provides an intelligent control system for real-time switching of a frequency converter, including a synchronization parameter analysis module, a switching logic judgment module, a synchronization adjustment module, a switching control module, and a smoothing correction module. All modules are connected in the order described above.

[0100] Specifically, the synchronization parameter analysis module is used to analyze the changing trend of the deviation between the output frequency of the current inverter and the target inverter, as well as the dynamic difference in the phase angle of their output voltages.

[0101] The switching logic judgment module is used to make switching logic judgments based on the changing trend of frequency deviation and the dynamic difference of phase angle through a state machine. When the frequency deviation is in a continuous convergence trend and the phase angle difference shows a stable decreasing trend, a switching ready signal is generated.

[0102] The synchronization adjustment module is used to dynamically adjust the output frequency and phase angle of the target frequency converter according to the switching readiness signal, and to achieve synchronous matching.

[0103] The switching control module is used to control the switching device to complete the load transfer after synchronization and matching are achieved.

[0104] The smoothness correction module is used to analyze the fluctuation characteristics of the output current and the rate of change of speed after the switching operation is completed to evaluate the smoothness of the switching. If an abnormality in the smoothness of the switching is detected, the closed-loop correction mechanism is activated.

[0105] The above embodiments can be implemented, in whole or in part, by software, hardware, firmware, or any other combination thereof. When implemented using software, the above embodiments can be implemented, in whole or in part, in the form of a computer program product.

[0106] Those skilled in the art will recognize that the modules and algorithm steps of the various examples described in conjunction with the embodiments disclosed herein can be implemented in electronic hardware, or a combination of computer software and electronic hardware. Whether these functions are implemented in hardware or software depends on the specific application and design constraints of the technical solution. Those skilled in the art can use different methods to implement the described functions for each specific application, but such implementation should not be considered beyond the scope of this application.

[0107] In addition, the functional modules in the various embodiments of this application can be integrated into one processing module, or each module can exist physically separately, or two or more modules can be integrated into one module.

[0108] The above description is merely a specific embodiment of this application, but the scope of protection of this application is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in this application should be included within the scope of protection of this application. Therefore, the scope of protection of this application should be determined by the scope of the claims.

[0109] Finally, the above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A real-time switching intelligent control method for frequency converters, characterized in that: include: Based on the phase angle and frequency value of the current inverter output voltage, analyze the changing trend of the deviation between the current inverter and the target inverter output frequency, and the dynamic difference of the phase angle of their output voltages. Based on the changing trend of frequency deviation and the dynamic difference of phase angle, the switching logic is judged through state machine. When the frequency deviation is in a continuous convergence trend and the phase angle difference shows a stable decreasing trend, a switching ready signal is generated. Based on the switching readiness signal, dynamically adjust the output frequency and phase angle of the target inverter to match the output frequency and phase angle of the current inverter until the frequency difference and phase difference are both kept within the allowable error band. After the synchronization control reaches the matching state, the control switching device will switch the motor load from the current frequency converter to the target frequency converter; After the switching operation is completed, the motor's operating status is monitored in real time. The switching smoothness is evaluated by analyzing the fluctuation characteristics of the output current and the rate of change of speed. If an abnormality in the switching smoothness is detected, a closed-loop correction mechanism is activated.

2. The real-time switching intelligent control method for frequency converters according to claim 1, characterized in that: The steps for analyzing the changing trend of the deviation between the current inverter and the target inverter's output frequency are as follows: The current inverter output frequency value and the target inverter output frequency value are obtained, and sampling is performed at a predetermined sampling period to obtain frequency data of multiple sampling points. For each sampling point, the difference between the current inverter output frequency value and the target inverter output frequency value is calculated to obtain the frequency deviation value, and the time series of the frequency deviation value is obtained. Perform linear regression analysis on the frequency deviation time series and calculate its slope of change; If the slope of change remains negative within a predetermined observation time window and its absolute value is greater than a preset slope threshold, then the frequency deviation is determined to be in a continuous convergence trend; otherwise, the frequency deviation is determined not to be in a continuous convergence trend.

3. The real-time switching intelligent control method for a frequency converter according to claim 1, characterized in that: The calculation steps for the dynamic difference of the output voltage phase angle are as follows: Simultaneously acquire the instantaneous phase angle of the output voltage of the current inverter and the target inverter; Calculate the instantaneous phase angle difference between the current inverter and the target inverter at the same sampling time; Calculate the change in phase angle difference between adjacent sampling points. If the change in phase angle difference is negative for multiple consecutive sampling periods, and the number of sampling points with negative phase angle difference changes is greater than the number of sampling points with non-negative phase angle difference changes, then it is determined that the phase angle difference shows a stable decreasing trend.

4. The real-time switching intelligent control method for frequency converters according to claim 1, characterized in that: The switching logic judgment via state machine includes: The state machine has multiple preset states, including initialization state, frequency monitoring state, phase monitoring state, preparation state, and switching state; In the initialization state, the state machine waits to receive the output frequency and phase angle data of the current inverter and the target inverter; After entering the frequency monitoring state, the state machine monitors the changing trend of the frequency deviation. When the frequency deviation is in a continuous convergence trend, the state machine automatically transitions to the phase monitoring state. In phase monitoring mode, the state machine monitors the dynamic difference of the phase angle difference. When the phase angle difference shows a stable decreasing trend, the state machine automatically transitions to the ready state. In the ready state, the state machine generates a switch ready signal and waits for the switch trigger instruction; When a switch trigger command is received, the state machine transitions to the switch state and outputs a switch execution command.

5. The real-time switching intelligent control method for a frequency converter according to claim 1, characterized in that: The specific steps for generating the handover readiness signal are as follows: When the frequency deviation is determined to be in a continuous convergence trend and the phase angle difference is determined to be in a stable decreasing trend, the synchronization conditions are confirmed to be met simultaneously. Set an internal frequency convergence flag to active state, and simultaneously set an internal phase stability decrease flag to active state. If the frequency convergence flag and the phase stability reduction flag are detected to be continuously active simultaneously within a signal generation cycle, a high-level switching ready signal is generated, which includes a frequency matching flag, a phase matching flag, and a switching enable flag. The generated handover readiness signal is output to the handover logic control unit, and the handover readiness signal is kept valid until the handover action is detected to begin.

6. The real-time switching intelligent control method for a frequency converter according to claim 1, characterized in that: The steps for dynamically adjusting the output frequency and phase angle of the target frequency converter based on the switching readiness signal are as follows: After receiving the switching ready signal, the current inverter and the target inverter are compared in real time in terms of output frequency difference and phase difference. If the frequency difference is positive, the target inverter is controlled to increase its output frequency; if the frequency difference is negative, the target inverter is controlled to decrease its output frequency. If the phase difference is positive, the phase angle of the output voltage of the target frequency converter will change ahead; if the phase difference is negative, the phase angle of the output voltage of the target frequency converter will change lag. After performing frequency and phase adjustments, recalculate the latest output frequency difference and phase difference, and determine whether both the frequency difference and phase difference are kept within the allowable error band. If they are not within the allowable error band, return to the above adjustment steps. Record the number of adjustments. If the number of adjustments exceeds the preset maximum, exit the adjustment step and stop the switching process.

7. The real-time switching intelligent control method for a frequency converter according to claim 1, characterized in that: The control switching device switches the motor load from the current frequency converter to the target frequency converter in the following steps: When the synchronization control reaches a matching state, a switching execution instruction is generated; The switching execution command is sent to the switching device, which includes an electrical switch or contactor; The control switching device first disconnects the power connection between the current frequency converter and the motor load; After disconnecting the current inverter, the control switching device immediately establishes a power connection between the target inverter and the motor load; Verify the connection status between the target frequency converter and the motor load. Once the connection is confirmed to be correct, complete the switching operation.

8. The real-time switching intelligent control method for a frequency converter according to claim 1, characterized in that: The analysis of the fluctuation characteristics of the output current and the rate of change of rotation speed to evaluate switching smoothness includes: After the switching operation is completed, the motor's output current and speed are simultaneously collected in the monitoring window; Extract the peak and valley values ​​of the output current within the monitoring window, and calculate the difference between the peak and valley values ​​as the fluctuation amplitude; Record rotational speed values ​​at fixed time intervals within the monitoring window, calculate the rotational speed change between adjacent recording points, and calculate the instantaneous rotational speed change rate at each point based on the time interval. When the fluctuation amplitude of the current is decreasing and the absolute value of the instantaneous speed change rate shows a decaying trend, the switching smoothness is judged to be normal; otherwise, it is judged to be abnormal.

9. The real-time switching intelligent control method for a frequency converter according to claim 8, characterized in that: The steps for initiating the closed-loop correction mechanism if an abnormal switching smoothness is detected are as follows: If the switching smoothness is judged to be abnormal in multiple consecutive monitoring windows after switching, the absolute values ​​of the output current fluctuation amplitude and the instantaneous speed change rate are continuously calculated. If the current fluctuation amplitude does not show a decreasing trend, increase the current loop proportional gain of the target frequency converter or increase the adjustment response strength of the output frequency. If the absolute value of the instantaneous speed change rate does not show a decay trend, increase the speed loop proportional gain of the target frequency converter or increase the adjustment step size of the output voltage phase angle. After performing the above adjustments, continuously monitor the current fluctuation amplitude and speed change rate. When the switching smoothness is detected to be normal, the correction process is complete.

10. A real-time switching intelligent control system for frequency converters, characterized in that: include: The synchronous parameter analysis module is used to analyze the changing trend of the deviation between the output frequency of the current inverter and the target inverter, as well as the dynamic difference of the phase angle of their output voltages. The switching logic judgment module is used to make switching logic judgments through a state machine based on the changing trend of frequency deviation and the dynamic difference of phase angle. When the frequency deviation is in a continuous convergence trend and the phase angle difference shows a stable decreasing trend, a switching ready signal is generated. The synchronization adjustment module is used to dynamically adjust the output frequency and phase angle of the target frequency converter according to the switching readiness signal, and to achieve synchronous matching. The switching control module is used to control the switching device to complete the load transfer after synchronization and matching are achieved. The smoothness correction module is used to analyze the fluctuation characteristics of the output current and the rate of change of speed after the switching operation is completed to evaluate the smoothness of the switching. If an abnormality in the smoothness of the switching is detected, the closed-loop correction mechanism is activated.

Images