阅读说明：本技术 滤波电容器的保护方法、保护系统及电机控制器 (Protection method and protection system of filter capacitor and motor controller ) 是由 孙可 王宇 黄宜坤 于 2019-10-08 设计创作，主要内容包括：本发明提供一种滤波电容器的保护方法、保护系统及电机控制器,通过物理建模的方法实时动态地获取滤波电容器的绝对温度,并根据获取的绝对温度值与设定的温度保护阈值之间的关系,控制电机控制器的输出能力,进而对滤波电容器进行过热保护。本发明通过物理建模的方法对滤波电容器进行保护,避免了温度传感器采集滤波电容器温度时因工况变化导致的绝对温度最大值的转移。同时,相对于传统的温度传感器测量,物理建模有较强的鲁棒性和一致性,可以有效的避免由于温度传感器特性不一致或寿命老化带来的温度测量数据的不准确性。另外,本发明提供的滤波电容器的保护方法可以替代温度传感器的使用,降低了生产成本。(The invention provides a protection method and a protection system of a filter capacitor and a motor controller. According to the invention, the filter capacitor is protected by a physical modeling method, and the transfer of the maximum absolute temperature value caused by working condition change when the temperature sensor collects the temperature of the filter capacitor is avoided. Meanwhile, compared with the traditional temperature sensor measurement, the physical modeling has stronger robustness and consistency, and the inaccuracy of temperature measurement data caused by inconsistent characteristics or aging of the temperature sensor can be effectively avoided. In addition, the protection method of the filter capacitor provided by the invention can replace a temperature sensor, so that the production cost is reduced.)

1. A method for protecting a filter capacitor from overheating in a motor controller, comprising:

collecting data information of the filter capacitor under various working conditions;

carrying out physical modeling on the data information to form a physical model corresponding to the working condition for acquiring the absolute temperature of the filter capacitor;

setting a temperature protection threshold value of the filter capacitor corresponding to the working condition;

acquiring input information under a certain working condition and inputting a physical model corresponding to the working condition to acquire the absolute temperature of the filter capacitor; and the number of the first and second groups,

and judging the magnitude relation between the absolute temperature of the filter capacitor and the temperature protection threshold value under the working condition, and controlling the output information of the motor controller according to the judgment result.

2. The filter capacitor protection method of claim 1, wherein the data information and the input information each comprise: the ripple current of the filter capacitor, the direct current on the direct current side and the water cooling temperature.

3. The filter capacitor protection method according to claim 2, wherein the process of obtaining the absolute temperature of the filter capacitor comprises:

acquiring ripple current of a filter capacitor and direct current of a direct current side under a certain working condition, and inputting a physical model corresponding to the working condition to acquire an absolute temperature rise value of the filter capacitor;

and acquiring the water cooling temperature, and calculating the absolute temperature of the filter capacitor according to the water cooling temperature and the absolute temperature rise value.

4. The filter capacitor protection method according to claim 3, wherein the water-cooling temperature is obtained by a water temperature sensor in a water-cooling system.

5. The filter capacitor protection method of claim 1, wherein the output information comprises: output power of the motor controller.

6. The filter capacitor protection method according to claim 5, wherein when the absolute temperature of the filter capacitor is lower than the temperature protection threshold, the output power of the motor controller is not limited; when the absolute temperature of the filter capacitor exceeds the temperature protection threshold, the motor controller correspondingly reduces the actual output power on the basis of the rated output power.

7. The filter capacitor protection method according to claim 6, wherein the temperature protection threshold includes an upper temperature protection threshold and a lower temperature protection threshold, and when the absolute temperature of the filter capacitor exceeds the lower temperature protection threshold and does not reach the upper temperature protection threshold, the output power of the motor controller decreases linearly, and when the absolute temperature of the filter capacitor reaches the upper temperature protection threshold, the output power of the motor controller is limited to 0.

8. The method of claim 1, wherein the filter capacitor is a thin film capacitor.

9. The method of claim 8, wherein the filter capacitor is a polypropylene film capacitor.

10. A filter capacitor protection system for dynamically acquiring and protecting an absolute temperature of a filter capacitor in a motor controller in real time, comprising: an input module, an analysis module, a threshold setting module and an output module,

the input module is used for acquiring input information under a certain working condition and transmitting the input information to the analysis module;

the analysis module analyzes according to the input information to obtain the absolute temperature of the filter capacitor;

the threshold setting module is used for setting a temperature protection threshold corresponding to the working condition;

the output module judges the magnitude relation between the absolute temperature and the temperature protection threshold value and controls the output information of the motor controller according to the judgment result.

11. The filter capacitor protection system of claim 10, wherein the analysis module comprises physical models corresponding to different operating conditions of the filter capacitor, and the physical models are formed by physical modeling in a manner that specific input information is combined with calibration results.

12. The filter capacitor protection system of claim 10, wherein the input information comprises: the ripple current of the filter capacitor, the direct current on the direct current side and the water cooling temperature.

13. The filter capacitor protection system of claim 10, wherein the process of obtaining the absolute temperature of the filter capacitor comprises:

the method comprises the following steps that an input module obtains ripple current of a filter capacitor, direct current on a direct current side and water cooling temperature under a certain working condition, and the ripple current of the filter capacitor, the direct current on the direct current side and the water cooling temperature are input to an analysis module;

and the analysis module inputs the ripple current of the filter capacitor and the direct current of the direct current side into a physical model corresponding to the working condition so as to obtain an absolute temperature rise value of the filter capacitor, and the absolute temperature of the filter capacitor is calculated according to the water cooling temperature and the absolute temperature rise value.

14. The filter capacitor protection system of claim 12, wherein the water-cooled temperature is obtained by a water temperature sensor in a water-cooled system.

15. The filter capacitor protection system of claim 10, wherein the output information comprises: output power of the motor controller.

16. The filter capacitor protection system of claim 15, wherein the output module does not limit the output power of the motor controller when the absolute temperature of the filter capacitor is below the temperature protection threshold; when the absolute temperature of the filter capacitor exceeds the temperature protection threshold, the output module correspondingly reduces the actual output power on the basis of the rated output power of the motor controller.

17. The filter capacitor protection system of claim 16, wherein the temperature protection threshold comprises an upper temperature protection threshold and a lower temperature protection threshold, the output module controls the output power of the motor controller to decrease linearly when the absolute temperature of the filter capacitor exceeds the lower temperature protection threshold and does not reach the upper temperature protection threshold, and the output module limits the output power of the motor controller to 0 when the absolute temperature of the filter capacitor reaches the upper temperature protection threshold.

18. The filter capacitor protection system of claim 10, wherein the filter capacitor is a thin film capacitor.

19. The filter capacitor protection system of claim 10, wherein the filter capacitor is a polypropylene film capacitor.

20. A motor controller, comprising: a filter capacitor protection system for dynamically acquiring and protecting an absolute temperature of a filter capacitor in real time, comprising: the device comprises an input module, an analysis module, a threshold setting module and an output module, wherein the input module is used for acquiring input information under a certain working condition and transmitting the input information to the analysis module; the analysis module analyzes according to the input information to obtain the absolute temperature of the filter capacitor; the threshold setting module is used for setting a temperature protection threshold corresponding to the working condition; the output module judges the magnitude relation between the absolute temperature and the temperature protection threshold value and controls the output information of the motor controller according to the judgment result.

Technical Field

The invention relates to the technical field of electric vehicle control, in particular to a protection method and a protection system of a filter capacitor and a motor controller.

Background

Electric automobiles are widely considered as one of the main approaches to solve the problems of automobile exhaust pollution, petroleum energy shortage and the like, and along with the rapid development of electric automobiles, the requirements on the product performance, consistency and reliability of core parts of the electric automobiles are more and more important. The motor controller is used as a control unit of the power assembly of the electric automobile, and the performance of the product of the motor controller directly influences the performance index of the whole automobile. The current output capability of the motor controller is influenced by various factors, and from the viewpoint of the control machine, the heating of components is a factor which mainly limits the current capability output. Because components generate heat to different degrees during operation, the temperature rise of the components must be strictly limited in order to avoid thermal damage of the components and meet the service life of the controller, and therefore when the temperature reaches the upper limit value of a design index, the output capacity of the controller needs to be reduced.

The filter capacitor in the motor controller acts as a filter buffer for the dc side and also directly limits the continuous output capability of the motor controller. When the filter capacitor needs protection due to over-high temperature, the continuous output current of the motor controller needs to be reduced to prevent irreversible thermal damage of the filter capacitor. It is therefore important to protect the filter capacitor from overheating.

The common protection mode is that a temperature sensor is placed at a heating point of a component, and the controller is used for collecting temperature signals to realize the protection of the controller. However, there are two important disadvantages to this approach: firstly, the product cost can be directly increased by adding a physical temperature sensor, and the price of a common thermocouple is about 20-30 RMB; secondly, under the conditions that the capacitor is large in size, complex in structural material and variable in working environment, the highest temperature point in the filter capacitor is always changed continuously, and the highest temperature point cannot be accurately measured by a temperature sensor at a fixed position, so that the protection effect cannot be achieved.

Disclosure of Invention

The invention aims to provide a filter capacitor protection method, a filter capacitor protection system and a motor controller.

Another objective of the present invention is to provide a protection method, a protection system and a motor controller for a wave capacitor, which replace a temperature sensor to obtain the absolute temperature of a filter capacitor, so as to reduce the production cost and avoid the inaccuracy of temperature measurement data caused by the inconsistency of the characteristics of the temperature sensor or the aging of the lifetime of the temperature sensor.

In order to achieve the above object, the present invention provides a protection method for a filter capacitor, which is used for protecting the filter capacitor in a motor controller from overheating, and comprises:

collecting data information of the filter capacitor under various working conditions;

carrying out physical modeling on the data information, and forming a physical model corresponding to the working condition to obtain the absolute temperature of the filter capacitor;

setting a temperature protection threshold value of the filter capacitor corresponding to the working condition;

acquiring input information under a certain working condition, and inputting a physical model corresponding to the working condition for acquiring the absolute temperature of the filter capacitor; and the number of the first and second groups,

and judging the magnitude relation between the absolute temperature of the filter capacitor and the temperature protection threshold value under the working condition, and controlling the output information of the motor controller according to the judgment result.

Optionally, the data information and the input information both include: the ripple current of the filter capacitor, the direct current on the direct current side and the water cooling temperature.

Optionally, the process of obtaining the absolute temperature of the filter capacitor includes:

acquiring ripple current of a filter capacitor and direct current of a direct current side under a certain working condition, and inputting a physical model corresponding to the working condition to acquire an absolute temperature rise value of the filter capacitor;

and acquiring the water cooling temperature, and calculating the absolute temperature of the filter capacitor according to the water cooling temperature and the absolute temperature rise value.

Optionally, the water cooling temperature is obtained by a water temperature sensor in the water cooling system.

Optionally, the output information includes: output power of the motor controller.

Optionally, when the absolute temperature of the filter capacitor is lower than the temperature protection threshold, the output power of the motor controller is not limited; when the absolute temperature of the filter capacitor exceeds the temperature protection threshold, the motor controller correspondingly reduces the actual output power on the basis of the rated output power.

Optionally, the temperature protection threshold includes a temperature protection threshold upper limit and a temperature protection threshold lower limit, when the absolute temperature of the filter capacitor exceeds the temperature protection threshold lower limit and does not reach the temperature protection threshold upper limit, the output power of the motor controller is linearly reduced, and when the absolute temperature of the filter capacitor reaches the temperature protection threshold upper limit, the output power of the motor controller is limited to 0.

Optionally, the filter capacitor is a thin film capacitor.

Optionally, the filter capacitor is a polypropylene film capacitor.

Based on the same inventive concept, the invention also provides a protection system of the filter capacitor, which is used for dynamically acquiring the absolute temperature of the filter capacitor in the motor controller in real time and protecting the absolute temperature, and comprises the following steps: an input module, an analysis module, a threshold setting module and an output module,

the input module is used for acquiring input information under a certain working condition and transmitting the input information to the analysis module;

the analysis module analyzes according to the input information to obtain the absolute temperature of the filter capacitor;

the threshold setting module is used for setting a temperature protection threshold corresponding to the working condition;

the output module judges the magnitude relation between the absolute temperature and the temperature protection threshold value and controls the output information of the motor controller according to the judgment result.

Optionally, the analysis module includes physical models corresponding to different working conditions of the filter capacitor, and the physical models are formed by performing physical modeling in a manner of combining specific input information and a calibration result.

Optionally, the input information includes: the ripple current of the filter capacitor, the direct current on the direct current side and the water cooling temperature.

Optionally, the process of obtaining the absolute temperature of the filter capacitor includes:

the method comprises the following steps that an input module obtains ripple current of a filter capacitor, direct current on a direct current side and water cooling temperature under a certain working condition, and inputs the ripple current of the filter capacitor, the direct current input on the direct current side and the water cooling temperature to an analysis module;

and the analysis module inputs the ripple current of the filter capacitor and the direct current of the direct current side into a physical model corresponding to the working condition so as to obtain an absolute temperature rise value of the filter capacitor, and the absolute temperature of the filter capacitor is calculated according to the water cooling temperature and the absolute temperature rise value.

Optionally, the water cooling temperature is obtained by a water temperature sensor in the electric water cooling system.

Optionally, the output information includes: output power of the motor controller.

Optionally, when the absolute temperature of the filter capacitor is lower than the temperature protection threshold, the output module does not limit the output power of the motor controller; when the absolute temperature of the filter capacitor exceeds the temperature protection threshold, the output module correspondingly reduces the actual output power on the basis of the rated output power of the motor controller.

Optionally, the temperature protection threshold includes a temperature protection threshold upper limit and a temperature protection threshold lower limit, and when the absolute temperature of the filter capacitor exceeds the temperature protection threshold lower limit and does not reach the temperature protection threshold upper limit, the output power of the output module control motor controller is linearly reduced, and when the absolute temperature of the filter capacitor reaches the temperature protection threshold upper limit, the output power of the output module limit motor controller is 0.

Optionally, the filter capacitor is a thin film capacitor.

Optionally, the filter capacitor is a polypropylene film capacitor.

Based on the same inventive concept, the present invention also provides a motor controller, comprising: a filter capacitor protection system for dynamically acquiring and protecting an absolute temperature of a filter capacitor in real time, comprising: the device comprises an input module, an analysis module, a threshold setting module and an output module, wherein the input module is used for acquiring input information under a certain working condition and transmitting the input information to the analysis module; the analysis module analyzes according to the input information to obtain the absolute temperature of the filter capacitor; the threshold setting module is used for setting a temperature protection threshold corresponding to the working condition; the output module judges the magnitude relation between the absolute temperature and the temperature protection threshold value and controls the output information of the motor controller according to the judgment result.

In summary, the protection method for the filter capacitor provided by the invention dynamically obtains the absolute temperature of the filter capacitor in real time through a physical modeling method, and controls the output capability of the motor controller according to the relationship between the obtained absolute temperature value of the filter capacitor and the set temperature protection threshold, so as to perform thermal protection on the filter capacitor. The filter capacitor is protected by a physical modeling method, and the influence of absolute temperature maximum value transfer of the filter capacitor caused by working condition change is avoided.

Meanwhile, compared with the absolute temperature of the filter capacitor obtained by the traditional temperature sensor, the physical modeling has stronger robustness and consistency, and the inaccuracy of temperature measurement data caused by the inconsistency of the characteristics of the temperature sensor or the aging of the service life of the temperature sensor can be effectively avoided. In addition, the protection method of the filter capacitor provided by the invention can effectively replace a temperature sensor, and the production cost is reduced.

Drawings

FIG. 1 is a flow chart of a filter capacitor protection method according to an embodiment of the present invention;

FIG. 2 is a schematic structural diagram of a filter capacitor according to an embodiment of the present invention;

FIG. 3 is a circuit design of a filter capacitor in a motor controller according to an embodiment of the present invention;

FIG. 4 is a block diagram of a filter capacitor absolute temperature acquisition process in an embodiment of the present invention;

FIG. 5 is a block diagram of the power output of a filter capacitor in an embodiment of the invention;

FIG. 6 is a block diagram of a filter capacitor protection system in an embodiment of the invention;

FIG. 7 is a graph of absolute temperature rise of a filter capacitor versus actual measured value over time in accordance with an embodiment of the present invention;

FIG. 8 is a graph of the error between the absolute temperature rise of the filter capacitor and the actual measured value over time for an embodiment of the present invention.

Detailed Description

The present invention will be described in detail with reference to the accompanying drawings in order to make the objects and features of the present invention more comprehensible, however, the present invention may be realized in various forms and should not be limited to the embodiments described above. Furthermore, it will be understood that each block of the block diagrams and/or flowchart illustrations, and combinations of blocks in the block diagrams and/or flowchart illustrations, can be implemented by special purpose hardware-based systems that perform the specified functions or acts, or combinations of special purpose hardware and computer program instructions. It is well known to those skilled in the art that implementation by hardware, by software, and by a combination of software and hardware are equivalent.

Referring to fig. 1, the present invention provides a protection method for a filter capacitor, which is used to protect the filter capacitor in a motor controller from overheating, and includes the following steps:

s01: collecting data information of the filter capacitor under various working conditions;

s02: carrying out physical modeling on the data information to form a physical model corresponding to the working condition for acquiring the absolute temperature of the filter capacitor;

s03: setting a temperature protection threshold value of the filter capacitor corresponding to the working condition;

s04: acquiring input information under a certain working condition and inputting a physical model corresponding to the working condition to acquire the absolute temperature of the filter capacitor;

s05: and judging the magnitude relation between the absolute temperature of the filter capacitor and the corresponding temperature protection threshold value, and controlling the output information of the motor controller according to the judgment result.

The protection method of the filter capacitor provided by the invention is described below by taking the filter capacitor in the motor controller as an example, wherein the filter capacitor is a thin film capacitor. As shown in fig. 2, the basic structure of the filter capacitor includes: the capacitor comprises a shell (not shown in the figure), a positive copper bar 11, a negative copper bar 12, insulating paper 13 and a capacitor core 10, wherein one end of the capacitor core 10 is connected with the positive copper bar 11, the other end of the capacitor core is connected with the negative copper bar 12, the insulating paper 13 is arranged between the two layers of copper bars, and the capacitor core 10, the positive copper bar 11, the insulating paper 13 and the negative copper bar 12 are wrapped by the shell; and pins 14 are arranged on the two layers of copper bars and extend to the outside of the shell. It can be seen that, the inside multiple material substance that contains of filter capacitor, the heat conduction electric conduction characteristic of different materials is all different, and filter capacitor is bulky, is the square shape in certain space, and the inside hot spot of filter capacitor can change along with the change of operating mode under the operating condition.

The principle of the internal heating of the filter capacitor is that in a working state, alternating current flows through the capacitor, different materials have different impedance characteristics, power loss is generated after the current flows, and heat is generated when the current acts on thermal resistance. The basic thermal principle is shown in formula (1), where Δ T is the temperature rise of a filter capacitor at a certain node, P is the power loss, and R is_cIs the thermal resistance of the corresponding node. Therefore, the equivalent current flowing through the filter capacitor body is calculated and can be used for representing the power loss condition of the filter capacitor.

ΔT＝P·R_c(1)

Fig. 3 is a schematic circuit diagram of a filter Capacitor in a motor controller, which can visually see an equivalent Current of a Direct Current Capacitor (DC Cap) and a Direct Current on an incoming line sideThe relation between the current and the input current of the inverter can obtain the equivalent current I of the filter capacitor by the known technology of a three-phase inverter system_capThe calculation formula of (2):

wherein, I_{inv_rms}Is the ripple current; i is_phaIs the phase current; m is a modulation degree;

is a power factor.

Because the internal material and the shape of the filter capacitor are complex, accurate impedance parameters are difficult to obtain, and meanwhile, only ripple current flows inside the filter capacitor when the filter capacitor works, and the flow path of equivalent ripple current is clear, so that the ripple current of the filter capacitor is directly used as equivalent input of loss.

Referring to fig. 3, it can be seen that the connection position of the filter capacitor on the hardware circuit is directly connected to the dc side, and since the filter capacitor structure includes conductive copper bars at two ends, the current on the dc side flows through the copper bars, and further generates a certain amount of heat. The heat generated on the copper bar can directly influence the heat effect of the internal material of the capacitor. Therefore, the magnitude of the current on the dc side also affects the capacitor heat transfer to some extent, and should be used as input information.

And after the structure of the filter capacitor is fixed, the thermal resistance parameter as the inherent characteristic parameter will not be changed, and the thermal characteristic can be regarded as the specific performance under the input of a certain working condition. Therefore, on the basis of basic analysis and equivalence, the capacitor is protected by adopting a physical modeling method, the core is to observe the hottest point of a capacitor core in the filter capacitor under the current working condition, and then the power output is limited by utilizing a temperature protection threshold value, so that the protection of the capacitor is realized.

Firstly, data information of the filter capacitor under various working conditions is collected. The data information includes the above-mentioned nano-ripple current and DC side of the filter capacitorThe direct current of course also includes the types of filter capacitors corresponding to different working conditions, the specific connection mode of the filter capacitors on a hardware circuit, the setting of other operating parameters, and the like. And then, carrying out physical modeling on the data information to form a physical model corresponding to the working condition so as to obtain the absolute temperature of the filter capacitor under the working condition. In the embodiment, a mode of combining specific data information and a calibration result is adopted to complete mathematical observation of absolute temperature and temperature of the filter capacitor, then physical models corresponding to different working conditions are constructed according to the mathematical observation result, a basic structure block diagram of the physical models is shown in FIG. 4, I_capFor filtering capacitor ripple current, I_dcDirect side direct current, Δ T_capThe method includes the steps that the absolute temperature rise value of a filter capacitor is obtained, wherein the ripple current of the filter capacitor and the direct-current side direct current of the filter capacitor are key data information for constructing a physical model, data information is collected through thermal calibration of a single sample, then physical modeling is carried out on collected data, corresponding to the corresponding physical model under the same working condition of the same product, and when input information (the ripple current I of the filter capacitor) is input into the corresponding physical model_capAnd DC side DC I_dc) And outputting the absolute temperature rise value delta T of the filter capacitor under the working condition through the operation of a physical model_cap。

Obtaining the absolute temperature rise value delta T of the filter capacitor under a certain working condition_capThen, the absolute temperature rise value Δ T_capThe temperature change value of a certain node of the filter capacitor under the working condition is dynamically changed, and therefore, the delta T is obtained_capThen, the absolute temperature rise value delta T is also required to be measured through a low-pass filter_capPerforming corresponding modulation and smoothing delta T_capAnd suppressing interfering signals so that the absolute temperature rise value Δ T_capThe dynamic rising trend is stable, and the low-pass filter can be a first-order low-pass filter (PT1) for example.

The absolute temperature rise value delta T of the filter capacitor under a certain working condition can be obtained_capHowever, the greater reference to temperature protection of the filter capacitor is filteringWave capacitor temperature absolute temperature T_fTherefore, the temperature T of the water cooling in the filter capacitor application also needs to be considered₀. The block diagram of the scheme structure is shown in fig. 5. As shown in fig. 2, the water cooling facility 15 is generally disposed below the copper bars of the smoothing capacitor, wherein the water cooling temperature T₀The acquisition of the temperature of the water cooling system can be obtained through a motor controller or a water temperature sensor in the water cooling system of the whole vehicle, or can also be obtained through an estimation system of the temperature of the water cooling system by the motor controller. Obtaining the Water-Cooling temperature T₀Then, according to the water-cooling temperature T₀And the absolute temperature rise value Delta T_capCalculating the absolute temperature T of the filter capacitor_f。

Then, setting the temperature protection threshold T of the filter capacitor corresponding to the corresponding working condition_p. When the absolute temperature T of the filter capacitor_fDoes not reach the set temperature protection threshold value T_pWhen the absolute temperature T of the filter capacitor is not limited, the output information of the motor controller is not limited_fReach the set temperature protection threshold value T_pWhen the absolute temperature T of the filter capacitor is higher than the reference value, the output information of the motor controller is correspondingly limited, for example, the actual output power is correspondingly reduced on the basis of the original rated output power, and further, the absolute temperature T of the filter capacitor is obtained_fExceeding a set temperature protection threshold T_pWithin a certain range, the output information of the motor controller correspondingly reduces the actual output power according to the exceeding temperature, for example, the actual output power can be increased with the exceeding T_pIs linearly decreased when T is exceeded_pWhen the temperature of the motor reaches a certain node, the output limit of the motor controller is 0, so that the purpose of overheat protection of the filter capacitor is achieved.

The physical model corresponding to the working condition is established and the temperature protection threshold value T is set_pWhen the input information under a certain working condition is obtained, the physical model corresponding to the working condition is input to obtain the absolute temperature T of the filter capacitor_f。

Then, the absolute temperature T of the filter capacitor is judged_fWith corresponding temperature protection threshold T_pThe magnitude relationship between them; finally, according to the judgmentThe break result controls the output information of the motor controller. The output information includes output current, output voltage, and the like, and preferably, the output power of the motor controller is used in this embodiment. When the absolute temperature T of the filter capacitor_fBelow the temperature protection threshold T_pWhen the motor is started, the output power of the motor controller is not limited; when the absolute temperature T of the filter capacitor_fExceeding the temperature protection threshold T_pAnd meanwhile, the motor controller correspondingly reduces the actual output power on the basis of the original output power.

Illustratively, the temperature protection threshold T_pIncluding an upper temperature protection threshold T_p1And lower temperature protection threshold T_p2When the absolute temperature T of the filter capacitor_fExceeds the lower temperature protection threshold T_p2And does not reach the upper limit T of the temperature protection threshold value_p1When the absolute temperature T of the filter capacitor is lower than the reference temperature T, the output power of the motor controller is linearly reduced_fReaching the upper temperature protection threshold T_p1At this time, the output power of the motor controller is limited to 0.

FIG. 7 is a diagram illustrating an absolute temperature rise value Δ T of the filter capacitor obtained in the present embodiment_capFig. 8 is a relationship between an error between an absolute temperature rise value of the filter capacitor obtained in the present embodiment and an actual measurement value and time. Referring to fig. 7 and 8, it can be seen; under a certain working condition, the absolute temperature rise value delta T of the filter capacitor obtained by the embodiment₁And the actual measured value DeltaT₂The high consistency is kept, and in the whole dynamic process, the absolute temperature rise value Delta T of the filter capacitor acquired by the embodiment₁And the actual measured value DeltaT₂The error of the filter capacitor protection method is basically within 2 ℃, and the high estimation precision is achieved, so that the effectiveness of the filter capacitor protection method provided by the embodiment is proved.

In the protection method for the filter capacitor provided in this embodiment, the filter capacitor is a polypropylene film capacitor, and the application environment and the product are mainly based on a motor controller, but the protection method is also applicable to other types of capacitors, and meanwhile, not only is the product limited to the motor controller, but also the filter capacitor used on the dc side in an inverter system can be protected and designed by using a similar scheme.

Referring to fig. 6, based on the same inventive concept, an embodiment of the present invention further provides a protection system 100 for a filter capacitor, for dynamically obtaining an absolute temperature of the filter capacitor in a motor controller in real time and protecting the absolute temperature, including: an input module 101, an analysis module 102, a threshold setting module 103 and an output module 104,

the input module 101 is configured to obtain input information under a certain working condition and transmit the input information to the analysis module;

the analysis module 102 performs analysis according to the input information to obtain the absolute temperature T of the filter capacitor_f；

The threshold setting module 103 is used for setting a temperature protection threshold T corresponding to a working condition_p；

The output module 104 determines the absolute temperature T_fAnd the temperature protection threshold T_pAnd controlling the output information of the motor controller according to the judgment result.

Specifically, the analysis module 102 includes physical models corresponding to different working conditions of the filter capacitor, and the physical models are formed by performing physical modeling in a manner of combining specific input data information and calibration results. The input information comprises ripple current Icap of a filter capacitor and direct current I at a direct current side_dcAnd water cooling temperature T₀The method also includes the types of the filter capacitors corresponding to different working conditions, the specific connection mode of the filter capacitors on the hardware circuit, the setting of other operation parameters, and the like. Wherein the absolute temperature T of the filter capacitor is obtained_fThe process comprises the following steps:

the input module 101 obtains the ripple current I of the filter capacitor under a certain condition_capDirect current I at the direct current side_dcAnd water cooling temperature T₀And the ripple current I of the filter capacitor is measured_capDirect current I at the direct current side_dcAnd water cooling temperature T₀Input to the analysis module 102.

The analysis module 102 converts the ripple current I_capA direct current I on the direct side_dcInputting a physical model corresponding to the working condition to obtain an absolute temperature rise value delta T of the filter capacitor_capAccording to the water cooling temperature T₀And the absolute temperature rise value Delta T_capCalculating the absolute temperature T of the filter capacitor_f。

In addition, when Δ T is acquired_capThen, the absolute temperature rise value delta T is also required to be measured through a low-pass filter_capPerforming corresponding modulation and smoothing delta T_capAnd suppressing interfering signals so that the absolute temperature rise value Δ T_capThe low-pass filter is a first-order low-pass filter (PT1), for example, and has a stable dynamic trend.

The threshold setting module 103 may be set according to specific operating conditions, which may be directly obtained through the input module 101 or indirectly obtained from the analysis module 102.

The output module 104 is used for outputting the absolute temperature T_fAnd the temperature protection threshold T_pThe magnitude relation between the output current and the output voltage controls the output information of the motor controller, and the output information comprises the output current, the output voltage and the like. When the absolute temperature T of the filter capacitor_fBelow the temperature protection threshold T_pWhen the motor is started, the output power of the motor controller is not limited; when the absolute temperature T of the filter capacitor_fExceeding the temperature protection threshold T_pAnd meanwhile, the motor controller correspondingly reduces the actual output power on the basis of the original output power. Illustratively, the temperature protection threshold T_pIncluding an upper temperature protection threshold T_p1And lower temperature protection threshold T_p2When the absolute temperature T of the filter capacitor_fExceeds the lower temperature protection threshold T_p2And does not reach the upper limit T of the temperature protection threshold value_p1When the absolute temperature T of the filter capacitor is lower than the reference temperature T, the output power of the motor controller is linearly reduced_fReaching the upper temperature protection threshold T_p1At this time, the output power of the motor controller is limited to 0.

In the protection system of the filter capacitor provided by this embodiment, the filter capacitor is a polypropylene film capacitor and is mainly applied to a motor controller, but the protection system of the filter capacitor is also applicable to other types of capacitors, and meanwhile, the protection system of the filter capacitor is not limited to a motor controller product, and in an inverter system, the filter capacitor used on the dc side can be protected by using a similar protection system.

Based on the same inventive concept, an embodiment of the present invention further provides a motor controller, including: a filter capacitor protection system for dynamically acquiring and protecting an absolute temperature of a filter capacitor in real time, comprising: the device comprises an input module, an analysis module, a threshold setting module and an output module, wherein the input module is used for acquiring input information under a certain working condition and transmitting the input information to the analysis module; the analysis module analyzes according to the input information to obtain the absolute temperature of the filter capacitor; the threshold setting module is used for setting a temperature protection threshold corresponding to the working condition; the output module judges the magnitude relation between the absolute temperature and the temperature protection threshold value and controls the output information of the motor controller according to the judgment result.

In summary, according to the protection method, the protection system and the motor controller for the filter capacitor provided by the invention, the absolute temperature of the filter capacitor is dynamically obtained in real time by a physical modeling method, and the output capability of the motor controller is controlled according to the relation between the obtained absolute temperature value of the filter capacitor and the set temperature protection threshold, so as to perform overheat protection on the filter capacitor. The invention protects the filter capacitor by a physical modeling method, and avoids the influence of hot spot (maximum value of absolute temperature) transfer caused by working condition change of the filter capacitor.

Meanwhile, compared with the absolute temperature (hot spot) of the filter capacitor obtained by the traditional temperature sensor, the physical modeling has stronger robustness and consistency, and the inaccuracy of temperature measurement data caused by the inconsistency of the characteristics of the temperature sensor or the aging of the service life of the temperature sensor can be effectively avoided. In addition, the protection method of the filter capacitor provided by the invention can effectively replace a temperature sensor, and the production cost is reduced.

It will be apparent to those skilled in the art that various changes and modifications may be made in the invention without departing from the spirit and scope of the invention. Thus, if such modifications and variations of the present invention fall within the scope of the claims of the present invention and their equivalents, the present invention is also intended to include such modifications and variations.