Monitoring synchronous motor
By monitoring the power factor of the synchronous motor, forming automated monitoring values, identifying and solving excitation device failures, it solves the problem of difficulty in monitoring excitation device failures in the prior art, and realizes efficient energy utilization and energy saving of the motor.
Patent Information
- Application Number
- CN202380043395.0
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Priority Date
- 2022-05-30
- Filing Date
- 2023-04-14
- Publication Date
- 2025-01-10
AI Technical Summary
The prior art is difficult to effectively identify and monitor the failure of the excitation device of the synchronous motor, resulting in abnormal power factor and affecting the torque performance and energy utilization efficiency of the motor.
By measuring and monitoring the power factor of the synchronous motor, an automated monitoring value is formed, and the weighting mechanism of multiple single-value and time periods is used to identify abnormal states, and the operating status of the excitation device is automatically evaluated during long-term operation to reduce manual monitoring and errors Rate of return.
Automatic identification and repair of excitation device faults is realized, the energy utilization efficiency of the motor is improved, and a large amount of energy consumption is saved, especially in the operation of large motors, which significantly reduces losses.
Smart Images
Figure CN119301866A_ABST
Abstract
Description
Technical Field
[0001] The present invention relates to a method or a device for monitoring a synchronous motor, in particular a method or a device for monitoring an excitation device of a synchronous motor. In particular, the present invention relates to a method for identifying an excitation device fault when a synchronous motor is operated in a power grid or a frequency converter, wherein power grid operation is also referred to as DOL operation (directly connected to the grid). Background Art
[0002] A synchronous machine is an electric machine that can be used as a synchronous motor or a synchronous generator. Synchronous machines can be self-excited or externally excited. Externally excited synchronous machines have an excitation device. Self-excited synchronous machines, in particular, use permanent magnets for excitation. When operating synchronous machines, attention should be paid to the power factor. The power factor (also called active power factor) in alternating current technology is the ratio of the numerical value of the active power P to the apparent power S. In the case of sinusoidal alternating current variables, the power factor is defined as the ratio of the active power P to the apparent power S. This is also called In case of synchronous motors operating in the grid or with a frequency converter, the power factor can be adjusted or set by means of the excitation device. In general, a power factor of 1 can be assumed, since this is the optimal value from the point of view of losses and torque provision. In principle, the motor can also be operated at other operating points, but this must be taken into account accordingly in the algorithm (variable or static prescribed target value of the power factor). During the commissioning phase, the excitation circuit is usually not optimally set, since not all points can be reached during the test run. If the torque performance is sufficient, a suboptimal setting is not an immediate problem for the operator. In this case, the excitation closed-loop control circuit can be considered a secondary problem in certain specific scenarios. Faults or incorrect parameter settings of the excitation device, or a damaged excitation device, can lead in particular to abnormalities in the power factor. Summary of the invention
[0003] An object of the invention is to identify errors, anomalies or defects. The errors relate in particular to an erroneously and / or incorrectly parameterized excitation device and / or a damaged excitation device. The object relates in particular to synchronous motors.
[0004] The object is achieved by a method according to claim 1 , a monitoring device according to claim 11 or a computer program product according to claim 12 .
[0005] In terms of a method for monitoring a synchronous machine (in particular a synchronous motor), in particular in terms of a method for monitoring an excitation device of a synchronous machine (in particular a synchronous motor), a single value depending on the power factor of the synchronous machine or the synchronous motor is measured, wherein a monitoring value is formed from a plurality of single values and / or values depending on these single values. Therefore, a single value can be, for example, the power factor itself. A single value can also be composed of a plurality of single values. By monitoring a single value and generating a monitoring value from a single value, anomalies can be automatically identified. This is also possible during long-term operation of the synchronous machine. Therefore, in long-term monitoring, in particular, the power factor is not monitored from one grid cycle to the next cycle, but a longer period of minutes, hours, days, weeks or months. Therefore, for example, a synchronous motor with an excitation device can automatically identify anomalies during long-term operation. A "normal" or "abnormal" state describing the current operating status of the excitation device can be provided. For larger motors, the potential for saving in terms of losses alone is as high as 50,000 kWh per year. In the life cycle, this means a considerable potential for saving. Therefore, monitoring is particularly important for synchronous electric machines with relatively large output powers of hundreds of kilowatts or several megawatts.
[0006] The long-term recording of the excitation values of synchronous motors enables or makes possible an automated evaluation of the power factor. Anomalies can be automatically determined within a short time. Changes to the excitation device (e.g. repairs), for example, are also automatically recognized based on the data. Fault states, for example, are reset accordingly.
[0007] The monitoring value is, in particular, the difference between a target value for a power factor and a measured power factor, or is not derived from this difference. The measured power factor is an example of a single value. For example, the monitoring value can be determined as follows. Within a time period, power values L1 to L10 are measured at time intervals. In addition, for example, a target power value L-target is specified as 1, wherein other target values (for example 0.9) can also be set for the power value. Subtracting L1 from L-target results in a first intermediate monitoring value ZW1 (L-target-LI=ZW1). Subtracting L2 from L-target results in a second intermediate monitoring value ZW2. The sum of the intermediate monitoring values ZW1 to ZW10 results in a total fault sum W. The total fault sum W can be regarded as a monitoring value.
[0008] By automating the monitoring, the need for experts to monitor the power factor manually can be eliminated. For example, analyzing time series at irregular time intervals can be used to assess the current state of the operating condition. For monitoring purposes, it is also possible to set static limit values for the power factor in a specific configuration, although this can lead to false alarms at certain operating points. Thus, in a static analysis, for example, a fixed limit value is determined and a warning is issued if the power factor falls below this limit value. Over time, errors can occur when evaluating the limit values manually. Therefore, very specific expertise is required, which in turn requires a high level of data aggregation. The analysis can be associated with a large amount of human effort. For manual monitoring, very long operating periods have to be manually observed during operation and evaluated according to exclusion criteria. This problem can be overcome by creating a monitoring value, which is formed from or depends on a number of individual values, which depend on the power factor of the time period.
[0009] In one embodiment of the method, the monitoring value is formed using a single value, for example by calculation, i.e. in particular using a plurality of single values which are to be determined or have been determined in a stable operating state of the synchronous motor. A stable operating state of the synchronous motor is, for example, an operating state in which the speed of the motor, in particular the target speed, changes only slightly. For example, a slight change is when the speed changes by less than 10 rpm within 1 minute. Another example of a slight change is when the speed changes by less than 1% within 1 minute.
[0010] In one embodiment of the method, individual values which are measured or have been measured in dynamic operating states of the synchronous motor are excluded for forming the monitoring value. A dynamic operating state is, for example, the motor starting or the synchronous motor stopping. A dynamic operating state of the synchronous motor exists when the speed of the synchronous motor changes by more than 10 rpm within 1 minute. Another example of a dynamic operating state is a speed change of more than 1% within 1 minute. Synchronous motors are characterized in particular by providing different target speeds and / or different load influences during operation.
[0011] When monitoring synchronous motors, it is particularly important not to monitor absolutely via limit values. because At different operating points, for example in dynamic operating states, different values may be assumed. For the current monitoring, the development or change of the power factor over time in static states may be important.
[0012] In one embodiment of the method, the synchronous motor has different target speeds during operation. According to the method, it is therefore possible to monitor how the stable operating state of the power factor develops over time at different target speeds. In particular, the synchronous motor is to be kept in an energy-optimized operating state. To this end, the power factor needs to be monitored. In a synchronous motor, when When it is equal to 1, the best utilization of energy is achieved.
[0013] In one embodiment of the method, a plurality of individual values are taken from a time period which is in particular freely determinable, wherein the time period in particular has a length of at least one minute or has a length of several minutes to several months. The time intervals of the individual values used within the time period can be, for example, one second or several seconds (in particular longer than one second) or one minute or several minutes (in particular longer than one minute). The intervals are in particular adjustable. The intervals are, for example, between 10 seconds and 120 seconds. In this case, in particular only individual values determined in stationary operation of the synchronous machine or synchronous motor are taken into account.
[0014] In one embodiment of the method, weighting is performed in the monitoring value according to time. Therefore, the monitoring value can be composed of the sum of multiple values, where these values are weighted differently according to their age. For example, given a first value Wn and a second value Wn+1, a new value can be generated by a forgetting factor Alpha: monitoring value = Wn+1+(Wn*(1-Alpha)), where Alpha is less than 1.
[0015] In one embodiment of the method, a single value is used depending on the operating state of the synchronous electric machine or synchronous motor. In particular, the power factor is not taken into account, for example, when the power factor is determined during the start-up of the synchronous electric machine or synchronous motor. The power factor is taken into account, in particular, when it is determined in the steady state of the synchronous electric machine or synchronous motor.
[0016] However, this evaluation requires expert knowledge, because in many operating states the power factor deviates from the setpoint. This is due, for example, to starting and stopping of motors, load changes, changes in the process speed setpoint, etc. These operating states must be included in the evaluation.
[0017] In one embodiment of the method, an anomaly is detected by means of the monitoring value, wherein the anomaly relates in particular to the excitation device. For example, a fault in the excitation device can be detected.
[0018] In one embodiment of the method, the speed of the synchronous electric machine or synchronous motor is also taken into account when recording the individual values. For example, the power factor can be multiplied by the sign of the motor speed. The monitoring is thus dependent on the speed.
[0019] In one embodiment of the method, after the abnormality is detected, the power factor of the synchronous motor is improved. This can be achieved by optimizing the closed-loop control of the excitation device or replacing or repairing components (such as a faulty power semiconductor valve or a closed-loop control module, etc.). In one design solution, the power factor of the synchronous motor is improved by optimizing the closed-loop control of the excitation device. is 1.
[0020] In a monitoring device for a synchronous electric machine or a synchronous motor, in particular for monitoring an excitation device of a synchronous electric machine or a synchronous motor, the monitoring device is integrated in a component of a power converter or a component of a closed-loop control and / or open-loop control of the synchronous electric machine or the synchronous motor, and the monitoring device can be used to perform one of the methods described. The component of the power converter is, for example, a control cabinet or a housing. The component of the closed-loop control and / or open-loop control is, for example, a housing or a printed circuit board.
[0021] A computer program product comprises programming for carrying out one of the methods, wherein the computer program product is in particular executable on a monitoring device. BRIEF DESCRIPTION OF THE DRAWINGS
[0022] The present invention will be shown and explained in more detail below by way of example with reference to a drawing.
[0023] Specific design plan
[0024] According to the invention, continuous and context-dependent monitoring of the power factor can be achieved. The flowchart shows possible individual steps and highlights the feasible advantages over previous manual problem solving (manual expert monitoring or limit value observation). According to the invention, all the steps described below can be performed, or only one step or only a selected part of the steps described below can be performed:
[0025] step
[0026] Preprocessing 1:
[0027] Multiply the new power factor by the sign of the motor speed -
[0028] In the first step, the current power factor is multiplied by the sign of the motor speed. This ensures that a negative power factor is not mistakenly identified as a fault. Compared to the previous problem solution, additional measurements are taken into account here, which reduces the "false alarm" rate ("false alarm" rate: the time point that is mistakenly considered abnormal and thus unnecessarily attracts attention).
[0029] step
[0030] Filter 2:
[0031] Only timestamps when the machine is stationary (e.g. synchronous motors) are considered -
[0032] In a second step, only relevant timestamps of single values are filtered. In particular, those measured values (single values) that have a certain time until the next closed state are considered irrelevant.
[0033] Periods when the machine is not running (including, for example, startup and shutdown times) are not taken into account, reducing false alarms. Unlike previous approaches to the problem, additional information is taken into account and the power factor is viewed in its overall context rather than just categorized in its raw value.
[0034] Fault sum 3:
[0035] The deviation in power factor is added to the total fault sum which was previously multiplied by a forgetting factor (alpha) -
[0036] After data preparation, the error (difference between the actual power factor and the expected value of 1) is added to the total fault sum. This is first multiplied by a forgetting factor (α < 1) so that previous errors are weighted less. As time goes by, the total fault sum is thus reduced again and past errors are not permanently carried forward.
[0037] step
[0038] Limit value 4:
[0039] Detect anomalies by summing the total faults -
[0040] If the sum of the faults exceeds a certain value, the point in time is considered an anomaly. Individual measurement errors are not classified as an anomaly. Instead, the errors are accumulated and an anomaly is only identified when a limit is exceeded. This approach ensures a low false alarm rate. An anomaly is only identified when a series of unexpected power factors occurs. In addition, larger deviations are more significant because the sum of the faults grows faster at larger deviations.
[0041] step
[0042] Maximum total faults 5:
[0043] Ensure that the sum of faults does not exceed the maximum value -
[0044] The sum of the faults is limited to a maximum value. This ensures that it does not become too large, so that a replacement of a faulty excitation device is detected in time. By means of the forgetting factor, the sum of the faults is reduced during normal operation, so that after a sufficient number of normal measurements, the status is automatically set to normal. An advantage of the invention may be that after repairing an excitation device, there is no need to record the repair manually. After a certain period of time, the algorithm automatically recognizes the changes based on the data.
[0045] By executing the above description, automated monitoring of the power factor is achieved, by context-sensitive summation of faults (e.g., values used only in steady-state operation), in particular ignoring outliers, identifying accumulations, and dynamically determining changes.
Claims
1. A method for monitoring a synchronous motor, in particular a method for monitoring an excitation device of a synchronous motor, wherein: An individual value which is dependent on the power factor of the synchronous motor is measured, wherein a monitoring value (3) is formed from a plurality of individual values and / or values which are dependent on the individual value.
2. The method according to claim 1, wherein: To form the monitoring value (3), a single value is used which is to be determined or has been determined in the steady-state operating state of the synchronous motor.
3. The method according to claim 1 or 2, wherein: Individual values that are to be or have been determined in a dynamic operating state of the synchronous motor are excluded for forming the monitoring value (3).
4. The method according to any one of claims 1 to 3, wherein: Asynchronous motors have different target speeds during operation.
5. The method according to any one of claims 1 to 4, wherein: The plurality of individual values is taken from a time period which is in particular freely definable, wherein the time period in particular has a length of at least one minute or has a length of from several minutes to several months.
6. The method according to any one of claims 1 to 5, wherein: The resulting monitoring value is weighted according to time (3).
7. The method according to any one of claims 1 to 6, wherein: A single value is used depending on the operating state (2) of the synchronous motor.
8. The method according to any one of claims 1 to 7, wherein: An anomaly is detected via the monitoring value, wherein the anomaly relates in particular to the excitation device.
9. The method according to any one of claims 1 to 8, wherein: The rotational speed (1) of the synchronous motor is taken into account together with the individual values.
10. The method according to any one of claims 8 or 9, wherein: The power factor of the synchronous motor is improved after an abnormality is identified.
11. A monitoring device for a synchronous motor, the monitoring device being particularly used for monitoring an excitation device of the synchronous motor, wherein: The monitoring device is integrated into a component of a power converter or into a component of a closed-loop control and / or an open-loop control of the synchronous motor, wherein the monitoring device can be used to carry out the method according to any one of claims 1 to 10 . 12 . A computer program product for executing the method according to claim 1 when the computer program product is run on a monitoring device according to claim 11 .