A method for detecting air compressor rotor stall

Abstract

The present invention provides an air compressor rotor stall detection method, comprising: in the window period of air compressor shutdown, controlling a motor control loop to be in a shutdown mode, in which the rotor angle in the motor control loop remains unchanged and the Q-axis target current is 0; using the Q-axis voltage in the current motor control loop as the target voltage; judging whether the target voltage satisfies a preset stall condition; if so, determining that the air compressor rotor has stalled; that is, keeping the rotor angle unchanged and giving the Q-axis target current as 0, and then determining whether the air compressor has stalled based on the target voltage, the unchanged rotor angle and the Q-axis target current being 0 do not affect the normal shutdown of the air compressor, and the rotor stalling moment can be accurately judged through a stall detection algorithm of the target voltage and the stall condition, thereby improving the detection accuracy, reducing the time interval between two starts, and improving the overall efficiency of the system, and the algorithm is simple and easy to promote and use.

Description

Technical Field

[0001] The present invention belongs to the technical field of motor detection, and more specifically, relates to a method for detecting the rotor stop of an air compressor. Background Art

[0002] In the field of hydrogen fuel cell air compressor controllers, a position sensorless FOC control algorithm is usually used to control the speed of the permanent magnet synchronous motor in the air compressor. The use of a position sensorless control algorithm can achieve rotor position estimation in the medium and high speed range, but when the air compressor speed is low, it is difficult for traditional estimation methods to accurately estimate the rotor position. Although the air compressor will not run in the low speed stage during normal operation, it is necessary to know when the air compressor rotor stops during the free stop stage after the air compressor is shut down. Only when the rotor stops can the next start be performed.

[0003] In the field of hydrogen fuel cell air compressor controllers, the permanent magnet synchronous motor is the core driving component of the air compressor, and the accuracy of its speed control is crucial to the performance of the entire system. At present, the industry generally adopts position sensorless and FOC (Field-Oriented Control) control algorithms to achieve effective control of the speed of permanent magnet synchronous motors. This algorithm can estimate the rotor position more accurately in the medium and high speed range, thereby ensuring the stable operation of the motor.

[0004] However, when the air compressor speed drops to the low speed range, the traditional position sensorless estimation method faces severe challenges and it is difficult to accurately estimate the rotor position. Although the air compressor will not run at a low speed for a long time under normal working conditions, it is a key issue to accurately judge when the rotor stops during the free stop phase after the air compressor is shut down. Because only when the rotor stops completely can the next startup be guaranteed to proceed smoothly.

[0005] At present, a delay judgment method is used to detect whether the rotor in the air compressor has stopped steadily. The delay judgment method is: when the air compressor controller reports shutdown, a fixed delay time is introduced. After the delay time is over, it is determined that the air compressor has stopped steadily.

[0006] However, for the delay judgment method, since it is impossible to accurately obtain the moment when the rotor stops in real time, and the mechanical properties of the air compressor may change over time, the only way is to extend the delay time to ensure that the rotor has stopped. This approach not only increases the time interval between two starts and reduces the overall efficiency of the system, but it is often difficult to find a safe and efficient delay time setting in actual applications. Summary of the invention

[0007] In view of this, the purpose of the present invention is to provide an air compressor rotor stall detection method, which is used to accurately determine the rotor stall moment through a stall detection algorithm based on Q-axis voltage and stall conditions without affecting the normal shutdown of the air compressor, thereby improving detection accuracy.

[0008] The present application discloses a method for detecting a rotor stall of an air compressor, comprising:

[0009] During the air compressor shutdown window, the motor control loop is controlled to be in shutdown mode, in which the rotor angle in the motor control loop remains unchanged and the Q-axis target current is 0;

[0010] Taking the Q-axis voltage in the current motor control loop as the target voltage;

[0011] Determine whether the target voltage meets a preset stopping condition; the preset stopping condition is to set a voltage range when the air compressor rotor stops;

[0012] If yes, make sure the air compressor rotor is stationary.

[0013] Optionally, the determining whether the target voltage satisfies a preset stabilization condition includes:

[0014] It is determined whether the target voltage satisfies a condition that it is less than a first threshold value and lasts for a first preset time.

[0015] Optionally, the first threshold value is 0.1% of the maximum output voltage of the motor of the air compressor; and / or, the first preset time is 1s.

[0016] Optionally, taking the Q-axis voltage in the current motor control loop as the target voltage includes:

[0017] The Q-axis voltage in the current motor control loop is processed by taking an absolute value to obtain a target voltage.

[0018] Optionally, determining whether the target voltage satisfies a preset stabilization condition includes:

[0019] It is determined whether the target voltage satisfies a condition that it is less than a second threshold and lasts for a second preset time.

[0020] Optionally, taking the Q-axis voltage in the current motor control loop as the target voltage includes:

[0021] Taking the Q-axis voltage in the current motor control loop as a reference, the amplitude of the Q-axis voltage within one sinusoidal cycle is selected as the target voltage.

[0022] Optionally, the determining whether the target voltage satisfies a preset stabilization condition includes:

[0023] It is determined whether the target voltage is less than a third threshold.

[0024] Optionally, the working process of the motor control loop includes:

[0025] Inputting the rotor angle into a first coordinate transformation method and a second coordinate transformation method; wherein the first coordinate transformation method is used to transform a three-phase coordinate system into a two-phase rotating coordinate system; and the second coordinate transformation method is used to transform a two-phase rotating coordinate system into a two-phase stationary coordinate system;

[0026] The three-phase current is converted into a D-axis current and a Q-axis current by using the first coordinate transformation method;

[0027] The negative D-axis current is summed with the positive D-axis target current, and then D-axis current PI control is performed to obtain the D-axis voltage;

[0028] The negative Q-axis current is summed with the positive Q-axis target current, and then Q-axis current PI control is performed to obtain the Q-axis voltage;

[0029] The D-axis voltage and the Q-axis voltage are converted into a first-axis static voltage and a second-axis static voltage by using the second coordinate transformation method;

[0030] The first axis static voltage and the second axis static voltage are subjected to space vector pulse width modulation to obtain a PWM signal for controlling a three-phase inverter of a motor of an air compressor.

[0031] Optionally, before controlling the motor control loop to be in shutdown mode during the air compressor shutdown window period, the method further includes:

[0032] When the air compressor operates normally, the motor control loop is controlled to be in a working mode; in the working mode, the three-phase current of the air compressor is processed using a rotor estimation method to obtain an estimated angle and an estimated speed;

[0033] Obtaining an estimated current based on the estimated speed and the target speed sent by the host computer;

[0034] The rotor angle in the motor control loop is controlled to be the estimated angle, and the target current in the motor control loop is controlled to be the estimated current.

[0035] Optionally, obtaining the estimated current according to the estimated speed and the target speed sent by the host computer includes:

[0036] Inputting the estimated speed to a negative input terminal of a summator, and inputting the target speed to a positive input terminal of the summator, to obtain a speed difference;

[0037] The speed difference is subjected to speed PI control to obtain the estimated current.

[0038] It can be seen from the above technical scheme that the present invention provides a method for detecting a rotor stop of an air compressor, comprising: in the window period of air compressor shutdown, controlling the motor control loop to be in shutdown mode, in which the rotor angle in the motor control loop remains unchanged and the Q-axis target current is 0; taking the Q-axis voltage in the current motor control loop as the target voltage; judging whether the target voltage satisfies the preset stop condition; if so, determining that the air compressor rotor has stopped; that is, in the window period after the air compressor is shut down, keeping the rotor angle unchanged and giving the Q-axis target current to 0, and then determining whether the air compressor has stopped based on the target voltage, the unchanged rotor angle and the Q-axis target current being 0 do not affect the normal shutdown of the air compressor, and the stop detection algorithm based on the target voltage and the stop condition can accurately judge the rotor stop moment, thereby improving the detection accuracy, reducing the time interval between two starts, and improving the overall efficiency of the system, and the algorithm is simple and easy to promote and use. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0040] Figure 1 A method for detecting a rotor stall of an air compressor is provided in an embodiment of the present invention;

[0041] Figure 2 It is a schematic diagram of the change of the Q-axis voltage value involved in a method for detecting the rotor stall of an air compressor provided by an embodiment of the present invention;

[0042] Figure 3 Schematic diagram of a motor control loop involved in a method for detecting a rotor stall of an air compressor provided in an embodiment of the present invention;

[0043] Figure 4 It is another schematic diagram of a motor control loop involved in a method for detecting a rotor stall of an air compressor provided in an embodiment of the present invention. DETAILED DESCRIPTION

[0044] In order to make the purpose, technical solution and advantages of the embodiments of the present invention clearer, the technical solution in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0045] In the present application, the term "comprises", "comprising" or any other variant thereof is intended to cover non-exclusive inclusion, so that the process, method, article or equipment including a series of elements includes not only those elements, but also includes other elements not explicitly listed, or also includes elements inherent to such process, method, article or equipment. In the absence of further restrictions, the elements defined by the sentence "comprising one..." do not exclude the existence of other identical elements in the process, method, article or equipment including the elements. In addition, the terms "first", "second", "third", "fourth", etc. (if any) in the specification and claims of the present application and the above-mentioned drawings are used to distinguish similar objects, and are not necessarily used to describe a specific order or sequence. It should be understood that the data used in this way can be interchangeable where appropriate, so that the embodiments of the present application described here can be implemented in an order other than those illustrated or described here, for example.

[0046] The embodiment of the present application discloses a method for detecting the rotor standing still of an air compressor, so as to solve the problem in the prior art that, since it is impossible to accurately obtain the moment when the rotor stands still in real time and the mechanical properties of the air compressor may change over time, the only way to ensure that the rotor has stood still is to extend the delay time. This approach not only increases the time interval between two starts and reduces the overall efficiency of the system, but also it is often difficult to find a delay time setting that is both safe and efficient in practical applications.

[0047] See also Figure 1 The air compressor rotor stall detection method comprises:

[0048] S101. During the air compressor shutdown window, the motor control loop is controlled to be in shutdown mode. In the shutdown mode, the rotor angle in the motor control loop remains unchanged and the Q-axis target current is 0.

[0049] That is to say, when the air compressor is shut down, the motor control loop is controlled to be in shutdown mode, so that the motor control loop adopts the control strategy corresponding to the shutdown mode until the air compressor rotor stops. In shutdown mode, the rotor angle in the motor control loop is a set value, such as 0, and of course it can be other values, which will not be repeated here.

[0050] There is no position sensor in this air compressor, and its specific structure will not be described in detail here.

[0051] The motor control loop, also known as the motor control loop, is a closed-loop control system. It measures the actual output of the motor (such as speed, position, etc.), feeds the measurement result back to the controller, compares it with the set value, and calculates the error signal. Then, the controller corrects the motor input signal according to the error signal so that the motor output is close to the set value, thereby achieving precise control.

[0052] It should be noted that the rotor angle can act on the first coordinate transformation method and the second coordinate transformation method in the motor control loop; wherein the first coordinate transformation method is used to transform the three-phase coordinate system into a two-phase rotating coordinate system; the second coordinate transformation method is used to transform the two-phase rotating coordinate system into a two-phase stationary coordinate system.

[0053] That is to say, the first coordinate transformation method transforms the three-phase coordinate system corresponding to the three-phase current received by the motor into a two-phase rotating coordinate system based on the rotor angle, and obtains the Q-axis current and D-axis current of the motor; the second coordinate transformation method transforms the two-phase rotating coordinate system corresponding to the D-axis voltage and the Q-axis voltage into a two-phase stationary coordinate system based on the rotor angle, and obtains the first-axis stationary voltage and the second-axis stationary voltage.

[0054] It should be noted that the air compressor is provided with a motor, which has components such as a stator and a rotor. The air compressor rotor, the motor rotor, etc. are the same component.

[0055] S102 : Taking the Q-axis voltage in the current motor control loop as the target voltage.

[0056] It should be noted that the Q-axis voltage in the motor control loop is related to the difference between the Q-axis target current and the Q-axis actual current. Specifically, the difference between the Q-axis target current and the Q-axis actual current is PI controlled to obtain the Q-axis voltage.

[0057] The Q-axis voltage can be directly used as the target voltage to execute subsequent steps, or the Q-axis voltage can be processed accordingly to obtain the target voltage; for example, taking the absolute value, taking the periodic amplitude, etc., which will not be described here one by one.

[0058] S103: Determine whether the target voltage meets a preset stopping condition.

[0059] It should be noted that when the air compressor is shut down, the motor will stop running and may reverse to consume the internal pressure of the machine body. At the same time, the electrical parameters of the motor will gradually decrease during the shutdown process. In the daily maintenance and care of the air compressor, the operation and electrical parameters of the motor should be checked regularly to ensure its normal operation and extend its service life.

[0060] That is to say, after the air compressor is shut down and before it stops, there is a back electromotive force, so the Q-axis voltage will produce a disturbance that is consistent with the trend of the back electromotive force; when the air compressor stops, the disturbance of the Q-axis voltage disappears, and by judging the AC disturbance in the Q-axis voltage, it can be known whether the air compressor controller has stopped. Figure 2 As shown in the figure, when the speed gradually decreases from 5000rpm, the Q-axis voltage always has an AC jitter. When the speed drops to 0, the AC jitter disappears; that is, the Q-axis voltage fluctuates around 0, and the amplitude of the Q-axis voltage gradually decreases.

[0061] In addition, it can be seen from the above description that the target voltage is related to the Q-axis voltage, that is, the target voltage changes with the Q-axis voltage.

[0062] Therefore, a stopping condition can be pre-configured so that when the target voltage meets the stopping condition, it can be determined that the air compressor rotor has stopped; the stopping condition can be that the target voltage is less than a threshold value within a preset time, that is, close to 0; of course, the stopping condition can also be other situations.

[0063] If the target voltage meets the preset stopping condition, step S104 is executed.

[0064] S104, confirm that the air compressor rotor is stationary.

[0065] That is to say, when the Q-axis voltage meets the stopping condition, it can be determined that the air compressor rotor is stopped.

[0066] It should be noted that the low-speed estimation algorithm is to try to use a position sensorless rotor position estimation algorithm to estimate the rotor position in the low-speed stage, so as to indirectly determine whether the air compressor has stopped steadily. As for the low-speed estimation algorithm, although it can theoretically solve the problem of rotor position estimation in the low-speed stage, the algorithm is not yet mature and is relatively complicated to implement. More importantly, in the current application scenario, we do not need to know the specific position information of the rotor, but only need to determine whether it has stopped steadily. Therefore, the low-speed estimation algorithm is too complicated and not direct enough to meet this requirement.

[0067] In the embodiment of the present application, during the window period of air compressor shutdown, the motor control loop is controlled to be in shutdown mode, in which the rotor angle in the motor control loop remains unchanged and the Q-axis target current is 0; the Q-axis voltage in the current motor control loop is used as the target voltage; it is determined whether the target voltage meets the preset stopping condition; if so, it is determined that the air compressor rotor has stopped; that is, during the window period after the air compressor is shut down, the rotor angle is kept unchanged and the Q-axis target current is given to be 0, and then whether the air compressor has stopped is determined based on the target voltage. The unchanged rotor angle and the Q-axis target current of 0 do not affect the normal shutdown of the air compressor, and the stopping detection algorithm based on the target voltage and stopping condition can accurately determine the rotor stopping moment, thereby improving the detection accuracy, reducing the time interval between two starts, and improving the overall efficiency of the system. The algorithm is simple and easy to promote and use.

[0068] Optionally, determining whether the target voltage satisfies a preset stop condition includes:

[0069] It is determined whether the target voltage satisfies a condition that it is less than a first threshold value and lasts for a first preset time.

[0070] At this time, the Q-axis voltage in the current motor control loop can be directly used as the target voltage.

[0071] Since the Q-axis voltage always has an AC jitter, when the speed drops to 0, the AC jitter disappears; that is, the Q-axis voltage fluctuates around 0, and the amplitude of the Q-axis voltage gradually decreases.

[0072] Therefore, when setting the first threshold, it is also necessary to set the duration to avoid misjudgment.

[0073] That is to say, the stopping condition is that the Q-axis voltage is less than the first threshold and lasts for a first preset time.

[0074] Specifically, when the Q-axis voltage Vq is less than the first threshold Vend and lasts for 1s, it can be determined that the rotor has stopped, where 1s is an empirical value. When the air compressor stops, the theoretical value of Vq should be 0V. Considering the detection error Vend, it can be set to Vmax*0.1%, where Vmax is the maximum output voltage of the motor.

[0075] In motor control, the Q-axis voltage (also called the quadrature-axis voltage) is usually used to control the torque and speed of the motor. When it is necessary to determine whether the motor has reached a stable state, the change in the Q-axis voltage can be monitored. Specifically, if the Q-axis voltage gradually decreases and stabilizes at a lower level (i.e., less than a preset first threshold), and this stable state lasts for a period of time (i.e., a first preset time), it can be considered that the motor has met the stable state condition.

[0076] Determine the duration: if the Q-axis voltage is less than the first threshold, the timing starts, and only when the Q-axis voltage remains below this level for a first preset time, is it considered that the motor meets the stopping condition.

[0077] The first preset time needs to be set according to the characteristics of the motor and the application scenario. If the preset time is too short, it may lead to misjudgment; if the preset time is too long, it may delay the judgment of the stable state.

[0078] Specifically, the first preset time may be 1s, and of course may be other values, which will not be elaborated here one by one. It depends on the actual situation and is within the protection scope of this application.

[0079] The setting of the first threshold value also needs to be determined according to the characteristics of the motor and the control requirements. If it is set too high, the motor may be misjudged as stopped before it reaches a truly stopped state; if it is set too low, the risk of misjudgment may increase.

[0080] Specifically, the first threshold value may be 0.1% of the maximum output voltage of the motor, and may be other values, which will not be elaborated here. It depends on the actual situation and is within the protection scope of this application.

[0081] Optionally, the above step S102, taking the Q-axis voltage in the current motor control loop as the target voltage, includes:

[0082] The absolute value of the Q-axis voltage in the current motor control loop is taken to obtain the target voltage.

[0083] That is to say, the Q-axis voltage value with direction may be used for judgment, or the absolute value without direction may be used for judgment.

[0084] When using the absolute value of the Q-axis voltage for judgment, the focus is on the magnitude of the voltage, regardless of its positive or negative direction. This judgment method is suitable for application scenarios that are insensitive to the direction of the voltage and only care about whether the voltage value drops below a certain level. When the stopping condition of the motor mainly depends on the value of the Q-axis voltage, it is more appropriate to use absolute value judgment. For example, when judging whether the motor has stopped running or reached a certain stable operating state, you may only care about whether the Q-axis voltage has dropped below a preset threshold, regardless of its positive or negative direction.

[0085] When using non-absolute values ​​for judgment, both the magnitude and direction of the Q-axis voltage are considered. This judgment method is suitable for application scenarios that require precise control of the direction and magnitude of the voltage, such as vector control. When the motor control strategy needs to accurately consider the direction of the Q-axis voltage, it is more appropriate to use non-absolute value judgment. For example, in vector control, the torque and speed of the motor need to be adjusted according to the direction of the Q-axis voltage to achieve precise control.

[0086] In summary, whether to use the absolute value or non-absolute value of the Q-axis voltage to judge the stopping condition mainly depends on the motor control strategy, application scenario and the requirement for the accuracy of the judgment result. In practical applications, the appropriate judgment method should be selected according to the specific situation.

[0087] Optionally, when the absolute value of the Q-axis voltage in the current motor control loop is taken to obtain the target voltage, the above step S103, determining whether the target voltage meets the preset stopping condition, includes:

[0088] It is determined whether the target voltage satisfies a condition that it is less than a second threshold value and lasts for a second preset time.

[0089] The judgment here is similar to the above judgment process, except that the second threshold and the second preset time are used here.

[0090] The second threshold value and the first threshold value may be the same or different, which is not limited here and may be determined according to the actual situation and is within the protection scope of this application.

[0091] The second preset time is different from the first preset time, but it is worth noting that when the Q-axis voltage is directly used as the target voltage, the duration of the negative half-axis needs to be considered, while when the absolute value of the Q-axis voltage is used as the target voltage, there is no need to consider the positive and negative half-axes, that is, there is no need to consider the duration of the negative half-axis; therefore, the second preset time may be less than the first preset time.

[0092] Optionally, the above step S102, taking the Q-axis voltage in the current motor control loop as the target voltage, includes:

[0093] Taking the Q-axis voltage in the current motor control loop as a reference, the amplitude of the Q-axis voltage within one sinusoidal cycle is selected as the target voltage.

[0094] That is to say, the amplitude of the Q-axis voltage in a sinusoidal cycle is used as the target voltage. Since the Q-axis voltage changes in the positive and negative half cycles are generally similar, the amplitude of the Q-axis voltage in a half cycle can also be used as the target voltage. For example, the amplitude of the Q-axis voltage in a positive half cycle is used as the target voltage, or the amplitude of the Q-axis voltage in a negative half cycle is used as the target voltage.

[0095] Of course, the sine cycle can also be replaced by a third preset time; that is, the above step S102, taking the Q-axis voltage in the current motor control loop as the target voltage, includes: taking the Q-axis voltage in the current motor control loop as a reference, selecting the amplitude of the Q-axis voltage within the third preset time as the target voltage. The third preset time can be the aforementioned sine cycle; it can also be a sine half cycle, and of course it can also be other situations, which will not be repeated here.

[0096] Optionally, when the Q-axis voltage in the current motor control loop is used as a reference and the amplitude of the Q-axis voltage within one sinusoidal cycle is selected as the target voltage, the above step S103, determining whether the target voltage meets the preset stabilization condition, includes:

[0097] It is determined whether the target voltage is less than a third threshold.

[0098] like Figure 2 As shown, in the process of the speed gradually decreasing from 5000rpm, the Q-axis voltage always has an AC jitter, and when the speed drops to 0, the AC jitter disappears; that is, the amplitude of the Q-axis voltage gradually decreases with the speed or time within a sinusoidal period, and when the speed drops to 0, the amplitude of the Q-axis voltage is less than the third threshold.

[0099] It should be noted that the amplitude of the Q-axis voltage within the sinusoidal period is unidirectionally decreasing, and the Q-axis voltage changes sinusoidally, and the absolute value of the Q-axis voltage is a sine wave after taking the absolute value, that is, it only changes in the positive half axis; therefore, when using the amplitude of the Q-axis voltage within the sinusoidal period to make a judgment, there is no need to judge whether it lasts for a specific time.

[0100] When the sinusoidal period is replaced by the third preset time, the specific process of determining whether the target voltage satisfies the preset stabilization condition may also be determining whether the target voltage is less than the third threshold value.

[0101] Optional, such as Figure 3 As shown, in any of the above embodiments, the control process of the motor control loop includes:

[0102] (1) Change the rotor angle (such as Figure 3 θ) is input into the first coordinate transformation method (such as Figure 3 abc toDQ as shown) and the second coordinate transformation method (such as Figure 3 dq to αβ shown); wherein the first coordinate transformation method is used to transform the three-phase coordinate system into the two-phase rotating coordinate system; the second coordinate transformation method is used to transform the two-phase rotating coordinate system into the two-phase stationary coordinate system.

[0103] The first coordinate transformation method is abc to DQ; that is, transforming from a three-phase coordinate system (ABC coordinate system) to a two-phase rotating coordinate system (DQ coordinate system). In a three-phase AC system, three phases a, b, c (or A, B, C) are usually used to represent current or voltage. These three phases are 120 degrees electrical angle apart in space and are a common coordinate system in the field of motors and power electronics. Two-phase rotating coordinate system (DQ): The DQ coordinate system is a coordinate system that rotates with the rotor, in which the D axis (direct axis) is consistent with the direction of the rotor flux, and the Q axis (cross axis) is perpendicular to the D axis. This coordinate system can greatly simplify the mathematical analysis of the motor model.

[0104] The abc to DQ transformation is a series of mathematical operations to transform the current or voltage components in the three-phase coordinate system into the two-phase rotating coordinate system. This transformation usually includes the Clarke transformation and the Park transformation: Clarke transformation: First, the current or voltage components in the three-phase coordinate system are transformed into the two-phase stationary coordinate system (α-β coordinate system). This transformation is usually called the Clarke transformation or the 3 / 2 transformation. Park transformation: Then, the components in the two-phase stationary coordinate system are transformed into the two-phase rotating coordinate system. This transformation is usually called the Park transformation.

[0105] The abc to DQ transformation is widely used in motor control, power electronics, and power system analysis. Through this transformation, the complex motor model can be simplified into a mathematical model that is easier to analyze, thereby achieving precise control of the motor. In addition, in power electronic converters, this transformation can achieve decoupling control of current or voltage, improving system stability and performance.

[0106] The second coordinate transformation method is dq to αβ, that is, transforming from a two-phase rotating coordinate system to a two-phase stationary coordinate system. This transformation is also widely used in the fields of motor control, power electronics, and power systems.

[0107] In a two-phase rotating coordinate system, the D axis is usually consistent with the direction of the rotor flux, the Q axis is perpendicular to the D axis, and the coordinate system rotates with the rotor. In a two-phase stationary coordinate system, the α axis and the β axis are fixed and do not rotate with the rotor. Therefore, the dq to αβ transformation is actually the transformation of the current or voltage component in the rotating coordinate system to the stationary coordinate system.

[0108] In motor control, the current command in the rotating coordinate system can be transformed into the stationary coordinate system through dq to αβ transformation, so as to achieve precise control of the motor. This helps to simplify the control algorithm and improve the stability and performance of the system.

[0109] (2) Use the first coordinate transformation method to transform the three-phase current (such as Figure 3ia, ib, ic) shown in the figure are converted into D-axis current (such as Figure 3 ID) and Q-axis current (as shown Figure 3 shown in Figure 1).

[0110] The accuracy of coordinate transformation is crucial to the performance of motor control. Therefore, when performing coordinate transformation, it is necessary to ensure the correctness of the transformation matrix and the accuracy of the transformation parameters.

[0111] (3) Negative D-axis current and positive D-axis target current (such as Figure 3 IDRef) shown in the figure is summed and then D-axis current PI control is performed (such as Figure 3 D-axis control PI shown in the figure), and obtain the D-axis voltage (such as Figure 3 The negative Q-axis current and the positive Q-axis target current (such as Figure 3 The IDRef shown in the figure is summed and then Q-axis current PI control is performed (such as Figure 3 Q-axis control PI shown in the figure) to obtain the Q-axis voltage (such as Figure 3 Vd shown).

[0112] The parameters of the PI controller (such as the proportional coefficient and the integral coefficient) need to be debugged and optimized according to the characteristics of the motor and the control requirements. The specific debugging and optimization process is not described here. It depends on the actual situation and is within the scope of protection of this application.

[0113] (4) Use the second coordinate transformation method to convert the D-axis voltage and Q-axis voltage into the first-axis static voltage (such as Figure 3 Vα shown and the second axis static voltage (as Figure 3 Vβ shown).

[0114] The first axis is the α axis, and the second axis is the β axis.

[0115] (5) Performing space vector pulse width modulation on the first axis static voltage and the second axis static voltage to obtain a PWM signal for controlling the three-phase inverter of the motor (such as Figure 3 PwmA, PwmB and PwmC shown).

[0116] The α-axis voltage (Vα) and the β-axis voltage (Vβ) are subjected to space vector pulse width modulation to obtain the PWM signal used to control the three-phase inverter of the motor. SVPWM is an efficient modulation method that decomposes and synthesizes the voltage vector on the α-β plane to produce the inverter switching state that is closest to the ideal voltage waveform.

[0117] The implementation of SVPWM may also need to consider factors such as the switching frequency, dead time, harmonic suppression, etc. of the inverter, which will not be elaborated here one by one. It depends on the actual situation and is within the scope of protection of this application.

[0118] In the control loop, SVPWM is an important modulation technology, which is widely used in fields such as motor control. The following is a detailed explanation of SVPWM in the control loop:

[0119] The basic principle of SVPWM is to use the ideal stator flux circle of a three-phase symmetrical motor when powered by a three-phase symmetrical sinusoidal voltage as a reference standard, and to form a PWM wave by appropriately switching different switching modes of the three-phase inverter. The specific working principle and working process of SVPWM will not be described in detail here.

[0120] Of course, the motor control loop may also include steps such as measurement and feedback of the rotor angle, sampling of the current and voltage, and adjustment of the PI controller parameters, which will not be described in detail here.

[0121] In summary, the motor control loop is a complex system involving multiple steps and parameters. Through precise control and modulation, efficient, stable and reliable operation of the motor can be achieved.

[0122] That is, according to Figure 3As shown in the control block diagram, the rotor angle = 0 is input into the abc to DQ and dq to αβ modules respectively; the other input of the abc to DQ module is the three-phase current (Ia, Ib, Ic), and the output of the abc to DQ module is ID and IQ; ID is transmitted to the negative input terminal of the first adder, the D-axis target current value is transmitted to the positive input terminal of the first adder, and the output terminal of the first adder is connected to the D-axis current PI module; the D-axis current PI module outputs Vd; IQ is transmitted to the negative input terminal of the second adder, and the Q-axis target current value (Q-axis target current value = 0) is transmitted to the positive input terminal of the second adder; the output terminal of the second adder is connected to the Q-axis current PI module; the Q-axis current PI module outputs Vq; the other input of the dq to αβ module receives Vq and Vd respectively, and the dq to The αβ module outputs Vα and Vβ to the SVPMW module, and the SVPMW module outputs PwmA, PwmB, and PwmC; PwmA, PwmB, and PwmC are respectively the A-phase PWM signal, the B-phase PWM signal, and the C-phase PWM signal of the three-phase inverter of the motor; the steady stop detection module detects and outputs a determination signal stopFlg based on Vq; specifically, the steady stop detection module directly uses the current Q-axis voltage as the target voltage, and then determines whether the Q-axis voltage Vq is less than the first threshold value and lasts for the first preset time; or, the steady stop detection module uses the absolute value of the current Q-axis voltage as the target voltage, and determines whether the Q-axis voltage |Vq| is less than the second threshold value and lasts for the second preset time; or, the steady stop detection module uses the current Q-axis voltage as a reference, selects the Q-axis voltage within one sinusoidal cycle as the target voltage, and determines whether the amplitude of the Q-axis voltage Vd within one sinusoidal cycle is less than the third threshold value; the first threshold, the second threshold, and the third threshold may be the same or different, and are not specifically limited here.

[0123] Optionally, in any of the above embodiments, before the above step S101, during the window period of air compressor shutdown, controlling the motor control loop to be in shutdown mode, the process further includes:

[0124] First, when the air compressor operates normally, the control motor control loop is in working mode; in the working mode, the rotor estimation method is used to process the three-phase current of the air compressor to obtain the estimated angle and estimated speed; secondly, the estimated current is obtained based on the estimated speed and the target speed sent by the host computer; finally, the rotor angle in the control motor control loop is the estimated angle, and the target current in the control motor control loop is the estimated current.

[0125] That is, the rotor angle in the motor control loop is obtained by using the rotor position estimation method, and the Q-axis target current in the motor control loop is calculated by using the rotor speed obtained by the rotor position estimation method.

[0126] Specifically, this estimation method is performed based on three-phase current data, and can estimate the estimated rotation angle and estimated rotation speed of the rotor, and then control the rotor angle in the motor control loop to be the estimated angle.

[0127] Then the Q-axis target current is not directly obtained by the rotor position estimation method, but depends on the estimated speed obtained by the rotor position estimation method. Specifically, the estimated speed is first obtained by the rotor position estimation method, and then the estimated current is determined based on the estimated speed; for example, the estimated current is obtained based on the estimated speed and the target speed sent by the host computer; and then the target current in the motor control loop is controlled to be the estimated current.

[0128] Optionally, the estimated current is obtained based on the estimated speed and the target speed sent by the host computer, including:

[0129] First, the estimated speed is input to the negative input terminal of the summer, and the target speed is input to the positive input terminal of the summer to obtain a speed difference; then, the speed difference is subjected to speed PI control to obtain an estimated current.

[0130] Through this process, the air compressor motor control loop can achieve precise control of the rotor position and speed, thereby ensuring the stable operation of the air compressor.

[0131] That is to say, Figure 4 As shown, when the air compressor is operating normally, the rotor speed (such as Figure 4 The speed shown in the figure is calculated by the rotor position estimator (rotor position estimation method), and the target speed (such as Figure 4 The SpeedRef shown in the figure is sent by the host computer, and the speed error (SpeedRef - Speed) is used as the input of the speed PI control loop. The output of the speed PI control loop is the Q-axis current target value. The Q-axis current PI control loop controls the motor speed by adjusting the Q-axis current.

[0132] That is to say, after the air compressor starts to initialize, the air compressor operates normally, and the control motor control loop is in working mode. In this working mode, the rotor estimation method is used to estimate the estimated rotation angle and the estimated speed; and the estimated current is obtained based on the estimated speed and the target speed; the rotor angle in the control motor control loop is the estimated angle, and the target current in the control motor control loop is the estimated current.

[0133] After the air compressor is shut down, it is in the shutdown window period, and the motor control loop is in shutdown mode. In this shutdown mode, the rotation angle in the motor control loop remains unchanged and the Q-axis current target value is 0; and whether it is stopped steadily is detected based on the Q-axis voltage.

[0134] The present application's air compressor can relatively accurately determine the rotor stopping moment during the low speed stage without the need for complex estimation methods.

[0135] The features described in the various embodiments in this specification can be replaced or combined with each other, and the same or similar parts between the various embodiments can be referenced to each other. Each embodiment focuses on the differences from other embodiments.

[0136] The above description of the disclosed embodiments enables one skilled in the art to implement or use the present invention. Various modifications to these embodiments will be apparent to one skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention will not be limited to the embodiments shown herein, but rather to the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A method for detecting the rotor stall of an air compressor, characterized in that: include: During the air compressor shutdown window, the motor control loop is controlled to be in shutdown mode, in which the rotor angle in the motor control loop remains unchanged and the Q-axis target current is 0; Taking the Q-axis voltage in the current motor control loop as the target voltage; Determine whether the target voltage meets a preset stopping condition; the preset stopping condition is to set a voltage range when the air compressor rotor stops; If yes, make sure the air compressor rotor is stopped.

2. The air compressor rotor stall detection method according to claim 1, characterized in that: The determining whether the target voltage satisfies a preset stabilization condition includes: It is determined whether the target voltage satisfies a condition that it is less than a first threshold value and lasts for a first preset time.

3. The air compressor rotor stall detection method according to claim 2, characterized in that: The first threshold value is 0.1% of the maximum output voltage of the motor of the air compressor; and / or the first preset time is 1s.

4. The air compressor rotor stall detection method according to claim 1, characterized in that: The method of using the Q-axis voltage in the current motor control loop as the target voltage includes: The Q-axis voltage in the current motor control loop is processed by taking an absolute value to obtain a target voltage.

5. The air compressor rotor stall detection method according to claim 4, characterized in that: Determining whether the target voltage satisfies a preset stopping condition includes: It is determined whether the target voltage satisfies a condition that it is less than a second threshold and lasts for a second preset time.

6. The method for detecting the air compressor rotor stall according to claim 1, characterized in that: The Q-axis voltage in the current motor control loop is used as the target voltage, including: Taking the Q-axis voltage in the current motor control loop as a reference, the amplitude of the Q-axis voltage within one sinusoidal cycle is selected as the target voltage.

7. The method for detecting the air compressor rotor stalling according to claim 6, characterized in that: The determining whether the target voltage satisfies a preset stabilization condition includes: It is determined whether the target voltage is less than a third threshold.

8. The method for detecting the air compressor rotor being stationary according to any one of claims 1 to 7, characterized in that: The working process of the motor control loop includes: Inputting the rotor angle into a first coordinate transformation method and a second coordinate transformation method; wherein the first coordinate transformation method is used to transform a three-phase coordinate system into a two-phase rotating coordinate system; and the second coordinate transformation method is used to transform a two-phase rotating coordinate system into a two-phase stationary coordinate system; The three-phase current is converted into a D-axis current and a Q-axis current by using the first coordinate transformation method; The negative D-axis current is summed with the positive D-axis target current, and then D-axis current PI control is performed to obtain the D-axis voltage; The negative Q-axis current is summed with the positive Q-axis target current, and then Q-axis current PI control is performed to obtain the Q-axis voltage; The D-axis voltage and the Q-axis voltage are converted into a first-axis static voltage and a second-axis static voltage by using the second coordinate transformation method; The first axis static voltage and the second axis static voltage are subjected to space vector pulse width modulation to obtain a PWM signal for controlling a three-phase inverter of a motor of an air compressor.

9. The method for detecting the air compressor rotor being stationary according to any one of claims 1 to 7, characterized in that: During the air compressor shutdown window period, before controlling the motor control loop to be in shutdown mode, the method further includes: When the air compressor operates normally, the motor control loop is controlled to be in a working mode; in the working mode, the three-phase current of the air compressor is processed using a rotor estimation method to obtain an estimated angle and an estimated speed; Obtaining an estimated current based on the estimated speed and the target speed sent by the host computer; The rotor angle in the motor control loop is controlled to be the estimated angle, and the target current in the motor control loop is controlled to be the estimated current.

10. The air compressor rotor stall detection method according to claim 9, characterized in that: According to the estimated speed and the target speed sent by the host computer, the estimated current includes: Inputting the estimated speed to a negative input terminal of a summator, and inputting the target speed to a positive input terminal of the summator, to obtain a speed difference; The speed difference is subjected to speed PI control to obtain the estimated current.

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