Motor driver monitoring method based on transient signals

Abstract

A motor driver monitoring method based on transient signals relates to the technical field of crane control, and comprises the following steps: establishing a common node inductance-capacitance equivalent transient model; according to the state of a switching tube on the inverter side and a system signal, a direct-current bus capacitive current is reconstructed, and average filtering is carried out on the voltage and the current to reduce interference; a long-period transient signal during load switching is analyzed, an equivalent series capacitor expression is deduced, a final ESC result is obtained through multiple times of monitoring and averaging, and a polynomial baseline calibration method is used for adjusting and reconstructing a capacitance current baseline; calculating transient process time based on the transient model, determining monitoring starting duration, and setting starting time by using a slope monitoring method; when load switching occurs, the aging monitoring program is started, and a capacitor aging result is output; the method is economical and efficient, computing resources can be saved, and a powerful guarantee is provided for reliability and safety of a crane driving system.

Description

Technical Field

[0001] The invention relates to the technical field of crane control, and in particular to a motor driver monitoring method based on transient signals. Background Art

[0002] In crane drive systems, DC bus capacitors play an indispensable role in power electronic converters. These capacitors not only balance power differences and reduce voltage fluctuations, but also protect the entire system from external grid interference. However, as the use time increases, the performance of capacitors will gradually degrade, which not only threatens the reliability of the system, but also increases potential safety risks.

[0003] With the development of the crane industry, especially the increasing demand for large and sophisticated lifting equipment, the reliability of crane motor drive systems has become increasingly critical. In order to meet the various load requirements in different operating environments, such as lifting, moving and placing goods, crane motors need to frequently change speed and load. This change in electromagnetic torque may cause instantaneous changes in the DC bus voltage and current of the power converter, resulting in transient phenomena and may accelerate the aging process of the DC bus capacitor.

[0004] Therefore, it is particularly important to conduct real-time status monitoring of the DC bus capacitor in the crane motor drive converter. Timely detection of capacitor aging failure and maintenance can avoid the expansion of faults, reduce unnecessary economic losses, and ensure the safe operation of the crane. At present, the mainstream online monitoring methods are mainly divided into two schemes: circuit model-based and fuzzy model-based. The former is further divided into steady-state ripple-based and disturbance signal-based methods. Although circuit model-based monitoring schemes are more popular, they usually require high-precision sensors and occupy more computing resources, while disturbance signal-based methods face the challenge of selecting appropriate frequency and amplitude injection signals, because improper signals may violate technical standards and affect the power quality of the power grid. Summary of the invention

[0005] In order to overcome the shortcomings of the background technology, the present invention discloses a motor drive monitoring method based on transient signals; it aims to use the long-period transient analysis generated when the converter switches the load to economically and reliably estimate the ESC of the DC bus capacitor; at the same time, a polynomial-based current baseline calibration method is proposed to improve the accuracy of state monitoring.

[0006] In order to achieve the above-mentioned invention object, the present invention adopts the following technical scheme:

[0007] A motor driver monitoring method based on transient signals comprises the following steps:

[0008] S1. Establish a common-node inductance-capacitance equivalent transient model of the crane motor driver, which is equivalent to a second-order dynamic circuit that connects the inductor and capacitor at the same node;

[0009] S2, based on the state of the inverter-side switch tube and the signal acquisition required by the system's own control, the DC bus capacitor current i dc Refactoring

[0010] S3, taking average filtering processing on the DC bus voltage and the reconstructed DC bus current;

[0011] S4. Analyze the long-period transient signal generated during load switching to obtain the theoretical expression of the equivalent series capacitor ESC;

[0012] S5. Derive the monitoring expression of the capacitor ESC, discretize the current integral in the expression using the complex Simpson algorithm, and obtain the final monitoring expression of the capacitor ESC by averaging multiple monitorings;

[0013] S6. Calibrate the reconstructed capacitor current baseline based on a polynomial baseline calibration method so that its average value is corrected to 0;

[0014] S7. Calculate the transient process time based on the common node inductance-capacitance equivalent transient model to determine the monitoring start duration ;

[0015] S8, based on the slope monitoring method, determining the start time t0 of the monitoring program;

[0016] S9: When the load switching occurs on the crane motor driver, the aging monitoring program is started and lasts for a period of time. Duration, output capacitor aging monitoring results.

[0017] Preferably, in step S2, the capacitor current is obtained by reconstructing the signal:

[0018]

[0019] in is the input current of the inverter, expressed as:

[0020]

[0021] in, Represent the output current of three phases ABC respectively; and Indicates the switching state of the inverter upper bridge arm IGBT, where "1" indicates the on state and "0" indicates the off state.

[0022] Preferably, in step S3, the signal collected within one window period is assumed to be , then their arithmetic mean M is calculated as follows:

[0023] .

[0024] Preferably, in step S4, the ESC is calculated once according to the current integral and the start-end voltage difference between every two sampling times, and the calculation formula is as follows:

[0025] .

[0026] Preferably, in step S5, all the collected group data (end) are divided into multiple parts (parts); each part contains multiple groups of data, and an ESC calculation is performed; the number of data groups in each part is:

[0027]

[0028] In each portion, the formula can be rewritten as:

[0029]

[0030] In the formula Indicates the collection time of group 1 in a data set; Indicates the collection time of the first group in a data set; represent The voltage collected at all times; represent The voltage collected at the moment; m represents the mth result in a certain long-period transient signal analysis;

[0031] According to the composite Simpson algorithm, the above formula can be rewritten as:

[0032] E S C ( m ) = t g r o u p − t 1 _ g r o u p 6 n [ i ( t 1 _ g r o u p ) + 4 ∑ k = 0 g r o u p − 1 i ( t k + 1 / 2 ) + 2 ∑ k = 1 g r o u p − 1 i ( t k ) + i ( t g r o u p ) ] / ( v g r o u p − v 1 _ g r o u p )

[0033] in, and express and The time points between parts; the average value of ESC of parts is obtained to get the final monitoring result:

[0034] .

[0035] Preferably, in step S6, the fitting form of the current baseline is as follows:

[0036]

[0037] In the formula is the polynomial fitting coefficient, m is the polynomial coefficient, m≤1.

[0038] Preferably, in step S7, during the delay After that, the control monitoring signal jumps from "1" back to "0", at which time the monitoring program is locked and one state monitoring ends; the state of the monitoring program is automatically reset to zero to wait for the next load switching to start automatically;

[0039] Based on the equivalent circuit, the time constant of the DC bus capacitor transient signal is calculated ;

[0040] ;

[0041] Estimate Size:

[0042] t d e l a y ∈ [ 6 π L e q C , 1 0 π L e q C ] .

[0043] Preferably, in step S8, the least square method is used for fitting to calculate the slope k of the fitting curve;

[0044]

[0045] According to the calculated slope k and the set threshold For comparison, when the absolute value of the slope is greater than or equal to the threshold, it is considered that the crane motor drive system has undergone load switching, and the online monitoring program is started at this time; the judgment conditions for starting the monitoring program are:

[0046]

[0047] When the above equation is satisfied, the monitoring signal jumps from "0" to "1", starting status monitoring.

[0048] Due to the adoption of the above-mentioned technical solution, the present invention has the following beneficial effects:

[0049] The present invention discloses a motor driver monitoring method based on transient signals. The method can start the monitoring program when the load of the converter changes without adding additional components and without affecting the normal operation of the main power circuit. The effective series resistance ESC of the DC bus capacitor is estimated by analyzing the long-period transient signal, and the capacitor current baseline is calibrated using a digital processing method of polynomial reconstruction to improve the monitoring accuracy. The present invention is not only economical and efficient, but also saves computing resources, providing a strong guarantee for the reliability and safety of the crane drive system. BRIEF DESCRIPTION OF THE DRAWINGS

[0050] Figure 1 It is a topological diagram of the crane motor driver of the present invention;

[0051] Figure 2Establish a common node inductance-capacitance equivalent transient circuit diagram and DC bus voltage and reconstructed current average filter diagram for the driver during load change;

[0052] Figure 3 To reconstruct the capacitance current baseline calibration map;

[0053] Figure 4 A graph for selecting the start time of the monitoring program based on slope comparison;

[0054] Figure 5 This is the simulation diagram of the proposed online status monitoring technology of the DC bus capacitor of the crane motor drive. DETAILED DESCRIPTION

[0055] The present invention can be explained in detail through the following embodiments. The purpose of disclosing the present invention is to protect all technical improvements within the scope of the present invention. In the description of the present invention, it should be understood that if there are terms such as "upper", "lower", "front", "back", "left", "right", etc. indicating directions or positional relationships, they only correspond to the drawings of the present application for the convenience of describing the present invention, and do not indicate or imply that the device or element referred to must have a specific direction.

[0056] Embodiment 1, in combination with Figures 1 to 5 , a motor driver monitoring method based on transient signals, comprising the following steps:

[0057] S1. Modeling the crane motor drive under load switching conditions, where the system can be considered as a second-order dynamic circuit connecting the inductor and capacitor at the same node.

[0058] Typical topology of crane motor drive system is as follows: Figure 1 During the normal operation of the crane motor drive system, the sensor collects and provides the DC bus voltage. , Rectifier side output current , Crane motor angular velocity and angle , and the three-phase output current on the inverter side , these data are used in the system control loop. At the same time, the control loop can obtain the switching status of the inverter.

[0059] The DC equivalent circuit of the crane motor drive system is as follows Figure 2 As shown, Represents the rectified output voltage, is the equivalent inductance of the three-phase AC input induction in the DC circuit, is the equivalent load current. When the system is operating normally, and equal, the average value of the capacitor current is 0. Assuming that the switching element is an ideal switch, the system can be regarded as a second-order dynamic circuit that connects the inductor and capacitor at the same node. When the load torque changes suddenly or quickly, the DC bus capacitor will charge and discharge, resulting in instantaneous fluctuations in voltage and current. This is because at the moment of load change, the DC side equivalent load current A current change occurs The average current through the capacitor is no longer zero, and the additional energy provided by the current is stored in the capacitor and released after the load change ends.

[0060] S2. Since the DC circuit is not equipped with a current sensor, the capacitor current is obtained by reconstructing the signal:

[0061]

[0062] is the input current of the inverter, expressed as:

[0063]

[0064] In this process, Represent the output current of three phases ABC respectively; and Indicates the switching state of the inverter upper bridge arm IGBT, where "1" indicates the on state and "0" indicates the off state.

[0065] S3. In the actual system, due to the existence of various harmonic interferences, the monitoring results of two adjacent samplings cannot meet the required accuracy. In order to reduce the impact of ripple on the monitoring results, the voltage and current of the DC bus capacitor are averaged and filtered, and the average value is used for the online status monitoring of the system.

[0066] Assume that the signal collected within one window period is , then their arithmetic mean M is calculated as follows:

[0067] .

[0068] S4. The ESC can be calculated once according to the current integral between every two sampling times and the start-end voltage difference. The calculation formula is as follows:

[0069]

[0070] S5. In order to avoid the DC bus current integral error being too large due to the short time interval between two samplings, all groups of data (end) are divided into multiple parts (parts); each part contains multiple groups of data and performs an ESC calculation; the number of data groups in each part is:

[0071]

[0072] In each portion, the formula can be rewritten as

[0073]

[0074] In the formula Indicates the collection time of group 1 in a data set; Indicates the collection time of the first group in a data set; represent The voltage collected at any time, represent The voltage collected at the moment; m represents the mth result in a certain long-period transient signal analysis.

[0075] According to the composite Simpson algorithm, the above formula can be rewritten as:

[0076] E S C ( m ) = t g r o u p − t 1 _ g r o u p 6 n [ i ( t 1 _ g r o u p ) + 4 ∑ k = 0 g r o u p − 1 i ( t k + 1 / 2 ) + 2 ∑ k = 1 g r o u p − 1 i ( t k ) + i ( t g r o u p ) ] / ( v g r o u p − v 1 _ g r o u p )

[0077] in, and express and In order to reduce the overall monitoring error of ESC, the average value of ESC of parts is calculated to obtain the final monitoring result:

[0078] .

[0079] S6. There is an approximate DC error between the calculated capacitor current and the actual capacitor current. In the steady state of the system, the average value of the output current on the rectifier side should be equal to the average value of the input current on the inverter side, so the average value of the capacitor current should be zero. Figure 3 shown.

[0080] Based on this, in the steady state of the system, the baseline of the signal is calculated by the polynomial fitting method and set to zero, so that the average value of the reconstructed capacitor current is closer to the average value of the actual capacitor current; the fitting form of the current baseline is as follows:

[0081]

[0082] In the formula is the polynomial fitting coefficient, m is the polynomial coefficient. Since polynomial fitting is used to remove the DC offset in the signal, m≤1 at this time.

[0083] S7. In order to ensure that the monitoring program works stably after load switching, a timing trigger is set, that is, After that, the control monitoring signal jumps from "1" back to "0", at which time the monitoring program is locked and one state monitoring ends; the state of the monitoring program is automatically reset to zero to wait for automatic start at the next load switching.

[0084] According to the equivalent circuit, calculate the time constant of the transient signal of the DC bus capacitor :

[0085]

[0086] The end of a transient process takes 3 to 5 seconds. time; therefore, it is possible to qualitatively estimate Size:

[0087] t d e l a y ∈ [ 6 π L e q C , 1 0 π L e q C ] .

[0088] When the system load switches, the absolute value of the slope of the voltage and current signals will suddenly increase due to the energy storage effect of the capacitor. In order to further increase the difference between the transient signal and the steady-state signal, a multiplier is used to output the product of the DC bus voltage and current value at each moment. Figure 4 As shown in the figure, assuming that the system load switches in 0.25 seconds, set the slope threshold of the multiplier output signal .

[0089] S8. During the operation of the system, the value of the output signal is collected in real time; once a predetermined amount of data is collected, the least squares method is used for fitting to calculate the slope k of the fitting curve:

[0090]

[0091] According to the calculated slope k and the set threshold By comparison, when the absolute value of the slope is greater than or equal to the threshold, it is considered that the crane motor drive system has undergone load switching, and the online monitoring program is started at this time; the following are the judgment conditions for starting the monitoring program:

[0092]

[0093] When the above equation is satisfied, the monitoring signal will jump from "0" to "1", thus starting the status monitoring. In order to ensure that the monitoring program works stably after the load is switched, the delay After that, the control monitoring signal changes from "1" to "0", at which time the monitoring program is blocked and one state monitoring ends. The state of the monitoring program is automatically reset to zero to wait for the next load switching to start automatically.

[0094] As attached Figure 5As shown in the figure, the system switches to a load of 5 N.m at t = 0.25 s. The system effectively starts online status monitoring. When the DC bus capacitance is 1500μF, the maximum error is 2% when 2N.m unloading occurs. For high-power synchronous crane motors, a larger DC bus capacitance value needs to be set. When the DC bus capacitance is 8000μF, when 10N.m unloading occurs, the error between the simulation result and the set capacitance is only 0.0005. Therefore, in order to obtain better monitoring results, the program is set to Start monitoring when the value is ≥5N.m to ensure that the monitoring error of the DC bus in the crane motor drive system is less than 1%.

[0095] The parts of the present invention that are not described in detail are prior art. It is obvious to those skilled in the art that the present invention is not limited to the details of the above-mentioned exemplary embodiments, and the present invention can be implemented in other specific forms without departing from the spirit or basic characteristics of the present invention; therefore, no matter from which point of view, the embodiments should be regarded as exemplary and non-restrictive, and it is intended that all changes that fall within the meaning and scope of equivalent elements are included in the present invention.

Claims

1. A motor driver monitoring method based on transient signals, characterized in that: The following steps are involved: S1. Establish a common-node inductance-capacitance equivalent transient model of the crane motor driver, which is equivalent to a second-order dynamic circuit that connects the inductor and capacitor at the same node; S2, based on the state of the inverter-side switch tube and the signal acquisition required by the system's own control, the DC bus capacitor current i dc Refactoring S3, taking average filtering processing on the DC bus voltage and the reconstructed DC bus current; S4. Analyze the long-period transient signal generated during load switching to obtain the theoretical expression of the equivalent series capacitor ESC; S5. Derive the monitoring expression of the capacitor ESC, discretize the current integral in the expression using the complex Simpson algorithm, and obtain the final monitoring expression of the capacitor ESC by averaging multiple monitorings; S6. Calibrate the reconstructed capacitor current baseline based on a polynomial baseline calibration method so that its average value is corrected to 0; S7. Calculate the transient process time based on the common node inductance-capacitance equivalent transient model to determine the monitoring start duration ; S8, based on the slope monitoring method, determining the start time t0 of the monitoring program; S9: When the load switching occurs on the crane motor driver, the aging monitoring program is started and lasts for a period of time. Duration, output capacitor aging monitoring results.

2. The method for monitoring a motor driver based on transient signals according to claim 1, wherein: In step S2, the capacitor current is obtained by reconstructing the signal: in is the input current of the inverter, expressed as: in, Represent the output current of three phases ABC respectively; and Indicates the switching state of the inverter upper bridge arm IGBT, where "1" indicates the on state and "0" indicates the off state.

3. The motor driver monitoring method based on transient signals according to claim 1, characterized in that: In step S3, the signal collected within one window period is assumed to be , then their arithmetic mean M is calculated as follows: 。 4. The method for monitoring a motor driver based on transient signals according to claim 1, wherein: In step S4, the ESC is calculated once according to the current integral between every two sampling times and the start-end voltage difference, and the calculation formula is as follows: 。 5. The method for monitoring a motor driver based on transient signals according to claim 4, characterized in that: In step S5, all the collected group data (end) are divided into multiple parts (parts); each part contains multiple groups of data, and an ESC calculation is performed; the number of data groups in each part is: In each portion, the formula can be rewritten as: In the formula Indicates the collection time of group 1 in a data set; Indicates the collection time of the first group in a data set; represent The voltage collected at all times; represent The voltage collected at the moment; m represents the mth result in a certain long-period transient signal analysis; According to the composite Simpson algorithm, the above formula can be rewritten as: in, and express and The time points between parts; the average value of ESC of parts is obtained to get the final monitoring result: 。 6. The method for monitoring a motor driver based on transient signals according to claim 1, characterized in that: In step S6, the fitting form of the current baseline is as follows: In the formula is the polynomial fitting coefficient, m is the polynomial coefficient, m≤1.

7. The method for monitoring a motor driver based on transient signals according to claim 1, characterized in that: In step S7, during the delay After that, the control monitoring signal jumps from "1" back to "0". At this time, the monitoring program is locked and one state monitoring ends; the state of the monitoring program is automatically reset to zero to wait for the next load switching to start automatically; Based on the equivalent circuit, the time constant of the DC bus capacitor transient signal is calculated ; ； Estimate Size: 。 8. The method for monitoring a motor driver based on transient signals according to claim 1, wherein: In step S8, the least square method is used for fitting to calculate the slope k of the fitting curve; According to the calculated slope k and the set threshold For comparison, when the absolute value of the slope is greater than or equal to the threshold, it is considered that the crane motor drive system has undergone load switching, and the online monitoring program is started at this time; the judgment conditions for starting the monitoring program are: When the above equation is satisfied, the monitoring signal jumps from "0" to "1", starting status monitoring.

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