阅读说明：本技术 电机驱动适配 (Motor drive adaptation ) 是由 西莫·哈克利 尼克拉斯·索多 于 2017-07-27 设计创作，主要内容包括：描述了一种用于适配电机驱动系统的方法和装置。该方法包括：向电机驱动系统施加小信号扫频,其中,该电机驱动系统包括逆变器、输出滤波器(例如,正弦滤波器)和电机；响应于所述扫频而获取频率响应数据；以及根据所获取的频率响应数据来设置该电机驱动系统的参数。(A method and apparatus for adapting a motor drive system is described. The method comprises the following steps: applying a small signal sweep to a motor drive system, wherein the motor drive system comprises an inverter, an output filter (e.g., a sine filter), and a motor; acquiring frequency response data in response to the frequency sweep; and setting parameters of the motor drive system based on the acquired frequency response data.)

1. A method, comprising:

applying a small signal frequency sweep to a motor drive system, wherein the motor drive system comprises an inverter, an output filter and a motor;

acquiring frequency response data in response to the frequency sweep to determine resonance in the motor drive system; and

parameters of the motor drive system are set based on the acquired frequency response data.

2. The method of claim 1, wherein applying a small signal sweep comprises applying a low voltage amplitude signal to the motor over a frequency range.

3. A method as claimed in claim 1 or claim 2, wherein the acquired frequency response data comprises current data as a function of frequency generated by the applied frequency sweep.

4. The method of any one of claims 1 to 3, wherein:

applying the small-signal sweep comprises applying a plurality of small-signal sweeps at different DC offset levels; and is

Acquiring frequency response data includes acquiring frequency response data for each of the plurality of small signal sweeps.

5. The method of any of the preceding claims, further comprising:

a DC magnetization pulse is applied and the sweep frequency applying step and frequency response data acquisition step are repeated.

6. The method of any preceding claim, further comprising periodically repeating the sweep frequency applying step and frequency response data acquiring step.

7. The method of claim 6, further comprising determining whether a change in the frequency response data indicates a significant performance change.

8. The method of any one of the preceding claims, wherein the parameters include one or more of a minimum switching frequency, an optimal switching frequency, and a maximum switching frequency of the inverter.

9. The method of any preceding claim, wherein the output filter is a sine filter.

10. A motor drive system comprising an inverter stage, a control module and an output filter, wherein the control module is configured to set parameters of the motor drive system according to a measured frequency performance of the motor drive system, wherein the frequency performance is measured in response to applying a small signal sweep to the motor drive system.

11. The motor drive system of claim 10, wherein the small signal frequency sweep is applied under control of the control module.

12. A motor drive system as claimed in claim 10 or claim 11, further comprising a cable connecting the output of the inverter stage to the motor.

13. A motor drive system according to any of claims 10 to 12, wherein the parameters include one or more of a minimum switching frequency, an optimum switching frequency and a maximum switching frequency of the inverter stage.

14. A motor drive system according to any one of claims 10 to 13, wherein the output filter is a sine filter.

15. A computer program product, comprising:

means for applying a small signal sweep to the motor drive system;

means for acquiring frequency response data in response to said frequency sweep to determine resonance in the motor drive system; and

means for setting parameters of the motor drive system based on the acquired frequency response data.

Technical Field

The invention relates to a method and a device for adapting a motor drive system.

Background

Fig. 1 is a block diagram of a system including an Adjustable Speed Drive (ASD), generally indicated by reference numeral 1. The system 1 includes an AC power source 2, an ASD 4, and a load 6 (such as a three-phase motor). The ASD 4 includes a rectifier 8, a DC link capacitor 10, an inverter 12, and a control module 14.

The output of the AC power source 2 is connected to the input of a rectifier 8. The output of the rectifier 8 provides DC power to an inverter 12. As described further below, the inverter 12 includes switching modules for converting the DC voltage to an AC voltage having a frequency and phase dependent upon the gate control signal. These gate control signals are typically provided by the control module 14. In this way, the frequency and phase to each input of the load 6 can be controlled.

The inverter 12 may generally be in bidirectional communication with the control module 14. The inverter 12 may monitor the current and voltage in each of the three connections to the load 6 (assuming a three-phase load is being driven) and may provide current and voltage data to the control module 14 (although it is not necessary to use both current and voltage sensors at all). The control module 14 may utilize the current and/or voltage data (when available) when generating the gate control signals required to operate the load as desired; another arrangement is to estimate the current and switching pattern from the plotted voltage-other control arrangements also exist.

Fig. 2 shows details of an exemplary embodiment of the inverter 12.

As shown in fig. 2, the inverter 12 includes first, second, and third high-side switching elements (T1, T2, and T3) and first, second, and third low-side switching elements (T4, T5, and T6). For example, each switching element may be an Insulated Gate Bipolar Transistor (IGBT) or a MOSFET transistor. Each switching element may be further associated with a respective freewheeling diode (D1-D6).

The exemplary inverter 12 shown in fig. 2 is a three-phase inverter that can be used to generate the following three outputs: u, V and W. These three phases of the inverter 12 provide three phases that are input to the load 6 in the system 1 described above. Of course, the inverter 12 may be modified to provide different numbers of outputs to drive different loads (such as loads having more or less than three phases).

Typically, the first high-side switching element T1 and the first low-side switching element T4 are connected together between the positive and negative DC terminals, with the midpoint of these switching elements providing a U-phase output. In a similar manner, the second high-side switching element T2 and the second low-side switching element T5 are generally connected together between the positive and negative DC terminals, with the midpoints of these switching elements providing a V-phase output. Further, the third high-side switching element T3 and the third low-side switching element T6 are typically connected together between the positive and negative DC terminals, with the midpoints of these switching elements providing a W-phase output.

The conventional inverter 12 described above is a 2-stage, 6-transistor inverter. As will be apparent to those skilled in the art, the principles of the present invention are applicable to different inverters, such as 3-stage inverters. The description of the inverter 12 is provided by way of example to help illustrate the principles of the present invention.

As described in detail below, the output of the inverter 12 may be filtered and may be transmitted along one or more cables. Such filtering and transmission affects the performance of the inverter in a manner that is detrimental to the performance of the inverter system.

The present invention seeks to address at least some of the problems outlined above.

Disclosure of Invention

The invention provides a method, comprising: applying a small signal sweep to a motor drive system, wherein the motor drive system includes an inverter, an output filter (such as a sine filter), and a motor (and typically also a rectifier and a DC link stage, the motor drive system may also include one or more cables and may include multiple motors); acquiring frequency response data in response to said frequency sweep in order to determine (electrical) resonances in the motor drive system; and setting parameters (such as an optimum switching frequency and/or a maximum switching frequency of the inverter of the motor drive system) according to the acquired frequency response data.

The invention also provides a motor drive system comprising an inverter stage, a control module (and typically a rectifier stage and a DC link stage) and an output filter (and possibly one or more motors), wherein the control module is configured to set parameters of the motor drive system (such as an optimum switching frequency and/or a maximum switching frequency of the inverter of the motor drive system) in dependence on a measured frequency performance of the motor drive system, wherein the frequency performance is measured in response to applying a small signal frequency sweep to the motor drive system (which frequency sweep may be applied under the control of the control module). One or more cables may be provided to connect the output of the inverter stage to one or more motors. In such an arrangement, the frequency performance of the system may include the performance of the cable connection(s) and motor(s).

The present invention yet further provides a computer program (or computer program product) comprising: code (or some other means) for applying a small signal sweep to a motor drive system (where the motor drive system includes an inverter, an output filter, and a motor); code (or some other means) for acquiring frequency response data in response to said frequency sweep in order to determine (electrical) resonances in the motor drive system; and code (or some other means) for setting parameters of the motor drive system in accordance with the acquired frequency response data.

Applying a small signal sweep may include applying a low voltage amplitude signal (typically only a few volts, such as 5V RMS) to the motor over a certain frequency range (e.g., 300Hz to 5000 Hz).

The acquired frequency response data may include current data as a function of frequency generated by the applied frequency sweep.

In one form of the invention, applying the small-signal frequency sweep includes applying a plurality of small-signal frequency sweeps at different DC offset levels (by applying a DC magnetization pulse (or level)), and acquiring frequency response data includes acquiring frequency response data for each of the plurality of small-signal frequency sweeps.

The invention may further comprise applying a (varying level) DC magnetization pulse and repeating the frequency sweep applying step and the frequency response data acquisition step. A plurality of DC magnetization pulses may be applied, and applying the DC magnetization pulses may include incrementing the DC magnetization pulses.

The invention may include repeating the sweep frequency application and frequency response data acquisition (and possibly parameter setting steps) periodically (e.g., weekly or monthly). The invention may further include determining whether a change in the frequency response data indicates a significant performance change (and if so, issuing an alarm).

Drawings

The invention will now be described in further detail with reference to the following schematic illustrations, in which:

fig. 1 shows an inverter drive system;

FIG. 2 illustrates an exemplary inverter;

FIG. 3 illustrates a highly schematic motor drive system in accordance with an aspect of the present invention;

FIG. 4 is a flow chart illustrating an algorithm for exemplary use of the system according to the present invention;

FIGS. 5-7 show graphs of a test application of the present invention; and is

Fig. 8 is a flow chart illustrating an algorithm used in accordance with an example of the present invention.

Detailed Description

Fig. 3 illustrates a motor drive system, generally indicated by reference numeral 20, in accordance with an aspect of the present invention.

The motor drive system 20 includes the AC power supply 2 and an Adjustable Speed Drive (ASD)4 described above. An output filter 22, typically a sine filter, is provided to filter the output of the ASD 4. As shown in fig. 3, the exemplary system 20 includes a first cable 24 connecting the output of the filter 22 to a first motor 26 and a second cable 25 connecting the output of the filter 22 to a second motor 27. The particular arrangement shown in fig. 3 is not necessary for all embodiments of the invention. For example, more motors may be arranged in parallel. Further, a single motor may be provided (and thus a single cable may be provided) (e.g., cable 25 and motor 27 omitted).

There are many reasons why a sine filter, such as filter 22, may be provided in motor drive system 20. In some motor drive systems, longer motor cables may be required, which may require the use of a sine filter. Other possible reasons for requiring a sine filter include low audible noise requirements or the use of motor insulation that cannot withstand PWM voltages. In order to obtain reliable operation of the system 20, the combination of the converter, filter and motor should be matched together. There are many reasons why this may be difficult to achieve in practice.

There are many parameters that affect the operation of the system 20. One parameter is the combination of the resonant frequency of the output filter 22 and the cable and motor impedance. The resonant frequency depends, among other things, on the length of the motor cable(s) and the motor impedance(s), which may vary greatly depending on the type of motor.

A particular problem arises in the case where different entities provide different elements of the system 20. For example, it is known to the end user that the result of providing the output filter 22 is: it is difficult for the supplier of ASD 4 to provide the system 20 with the appropriate control parameters.

One particular situation where the resonant frequency may vary significantly is a multiple motor installation (where one output filter powers many motors) where the number of motors used varies over time.

Figure 4 is a flow chart showing an algorithm, generally indicated by reference numeral 40, demonstrating an exemplary use of the system of the present invention.

The algorithm 40 begins with a step 42 of applying a DC magnetization pulse (or level) to the motor(s). One purpose of the DC magnetization pulse is to prevent the rotor from rotating during the adaptation process.

Next, in step 44, a frequency sweep of low voltage amplitude (typically only a few volts) is applied to the motor(s) over a specified frequency range (e.g., 300Hz to 5000 Hz). The current resulting from the applied frequency sweep is then measured.

Next, in step 46, resonances in the system 20 are identified. The detected resonance is an electrical resonance in the system 20.

Figure 5 shows a graph of a test application of the present invention generally indicated by reference numeral 60. The test was performed using a 500V driver and a 15A filter. A frequency sweep from 100Hz to 2kHz was performed with 5V RMS voltage. The current clearly peaks at the resonant frequency, allowing the resonant frequency to be detected (step 46 of the algorithm 40).

In the event that a resonant frequency in the system is detected, the algorithm 40 moves to step 48 where it is determined whether testing has been performed at all desired DC magnetizing trunks. This step allows repeating steps 42 to 46 for different levels of DC magnetization to check how the saturation of the inductor can affect the resonant frequency.

If it is determined in step 48 that algorithm 40 has not been applied at all desired DC magnetization levels, the DC magnetization levels are incremented (in step 50) and algorithm 40 returns to step 42. If it is determined in step 48 that the algorithm 40 has been applied at all desired DC magnetization levels, the algorithm 40 moves to step 52.

Fig. 6 shows a graph, generally indicated by reference numeral 70, of an exemplary application of the plurality of frequency sweep steps 44 at different DC magnetization levels. Graph 70 shows the current output of five different instances of sweep step 44, generally indicated by reference numerals 71 to 75.

The current output curve 71 is at a low DC magnetization level. The graph shows the measured current plotted on the y-axis and the time plotted on the x-axis. The frequency applied during the frequency sweep step 44 increases with time such that the frequency of the signal output by the ASD 4 is lowest at the beginning of the curve 71 (time t ═ 0) and highest at the end of the curve 71 (time t ═ 200 ms).

Each of the current curves 72 to 75 shows the measured current in response to successively higher DC magnetization levels.

As is clearly visible in the graph 70, each of the current curves 71 to 75 shows a similar resonant response, wherein the resonant current occurs at approximately 75 ms. Thus, at time t of 75ms, the frequency output of the ASD 4 of the motor drive system 20 has the electrical resonant frequency of the system 20.

Fig. 7 shows a graph, generally indicated by reference numeral 80, of another exemplary application of the plurality of frequency sweep steps 44 at different DC magnetization levels. Graph 80 shows the current output of five different instances of sweep step 44, generally indicated by reference numerals 81 to 85.

The current output curve 81 is at a low DC magnetization level and is therefore similar to the current output curve 71 described above. As with curve 71, current output curve 81 shows that the resonant current occurs at approximately 75 ms. Thus, at time t 75ms, the frequency output of the ASD 4 has the electrical resonant frequency of the system 20.

Graph 80 differs from graph 70 in the effect of increasing the DC magnetization level. In graph 70, each of the current output curves 71 through 75 shows a similar resonant response. In graph 80, as the DC magnetization level increases (as shown by current output curves 82-85), the resonant frequency changes, as does the magnitude of the measured current, such that at the highest DC magnetization level (indicated by current output curve 85), the resonant frequency is at about 90 ms.

The different frequency responses shown in graph 80 are caused by and can be used to measure the effects of saturation of inductors in motor drive system 20.

In step 52 of the algorithm 40, a number of variables of the system are determined or defined. These variables may include one or more of a minimum switching frequency, an optimal switching frequency, and a maximum switching frequency of system 20. These variables may also include parameters for controlling the set to ensure stable operation for this particular system resonant frequency. This should have better dynamic performance in applications requiring a sine filter.

In one form of the invention, the optimum switching frequency of the system 20 may be set to a predetermined multiple of the resonant frequency detected during step 46 of the algorithm 40. For example, a frequency three times the resonance frequency may be set. In the example described above with reference to fig. 6, at time t of 75ms shown in fig. 6, the frequency may be three times the frequency of the motor system. In the example described above with reference to fig. 7, at time t-90 ms, the frequency may be three times the frequency of the motor system, such that the effect of saturation of the inductance in the motor system 20 is taken into account. Therefore, it may be advantageous if the instance of the frequency sweep step 44 occurs within a range of DC magnetization levels that can reasonably be expected to occur during operation of the motor system 20.

The sweep step 44 may also be performed during normal operation, depending on the possible performance of the drive (e.g., current sampling, frequency switching rate).

A simple version of the algorithm 40 may be implemented without DC magnetization (i.e., omitting steps 42, 48, and 50 of the algorithm 40). If the voltage amplitude is low enough and starts at a very high frequency (possibly above 300Hz), the rotor is likely not to rotate. Another option is to use an asymmetric AC voltage that does not cause the motor to rotate.

In the above system 20, the output of the output filter 22 is connected to the input of one or more motors. This is not essential to all forms of the invention. For example, a transformer (typically a step-up transformer) may be provided between the output filter and the motor. In such embodiments, DC magnetization may not be used, but the frequency sweep steps described herein may still be performed.

The algorithm 40 (or a variant thereof, e.g., omitting the DC magnetization step) may be repeated at time intervals to detect whether the preferred system variable (as set at step 52) changes over time. This not only allows the variables to vary with changes in system performance, but can also be used to detect changes in system performance and can, for example, provide early warning of potential failure of components such as filter components that may occur, for example, due to aging.

Fig. 8 is a flow chart illustrating an algorithm, generally indicated by reference numeral 90, in accordance with an exemplary use of the present invention.

The algorithm 90 begins at step 92 with storing the raw parameters of the system 20. Such parameters may be set in step 52 of algorithm 40, but this is not required. Such original parameters may be factory set parameters, for example.

Next, the algorithm 90 moves to step 94 where new parameters are set. Step 94 may implement the algorithm 40 described above (or a variation of this algorithm).

After step 94, it is determined in step 96 whether the parameters have changed from the previous parameters, and if so, the algorithm moves to step 99 where an alarm is issued. If the parameter has not deviated from the previous parameter (or is within an acceptable tolerance), the algorithm 90 moves to step 98. In step 96, parameters may be considered changed, for example, if they have changed by a predetermined amount or percentage.

In step 98, the algorithm 90 waits for the next test period before repeating steps 94 and 96. The delay period may be, for example, one week or one month, but of course any period may be chosen. Further, the period may be variable (e.g., depending on the life of system 20). Step 98 may be implemented as an interrupt in a number of different ways, for example.

As described above, step 96 may determine the difference between the measured variable (in the example of step 52 of algorithm 40) and the original parameter (set in step 92 of algorithm 90). This is not necessary. For example, step 96 may determine the difference between the measured variables in two different instances of step 52. For example, a more complex arrangement would compare the measured variable to the original parameter and previously measured variables to obtain an indication of how the determined variable has changed over time.

The embodiments of the invention described above are provided by way of example only. Those skilled in the art will appreciate that many modifications, variations, and substitutions can be made without departing from the scope of the invention. For example, the principles of the present invention are not limited to use with a motor drive system of the form shown in FIG. 1. The appended claims are intended to cover all such modifications, changes, and substitutions as fall within the true spirit and scope of the invention.