Method and device for detecting open phase of permanent magnet synchronous motor, frequency converter and household appliance

Abstract

The application discloses a method and device for detecting open phase of a permanent magnet synchronous motor, a frequency converter and a household appliance, and belongs to the electronic technical field. The method comprises the following steps: in the case that a three-phase driving circuit supplies power to the permanent magnet synchronous motor, any phase bridge arm in the three-phase driving circuit is controlled to be turned off, so that the three-phase driving circuit is in a two-phase conduction state; in the case that the three-phase driving circuit is in the two-phase conduction state, it is determined whether the sampling current of a sampling resistor is zero current, and a sampling result is obtained; and the open phase state is determined according to the sampling result.

Description

Technical Field

[0001] This application belongs to the field of electronic technology, and in particular relates to a method, device, frequency converter and household appliance for detecting phase loss of a permanent magnet synchronous motor. Background Technology

[0002] When a permanent magnet synchronous motor experiences a phase loss fault (meaning at least one phase of the three-phase power supply is lost or disconnected), it can lead to a decrease in the motor's power performance, or even prevent the motor from rotating. In some cases, it can even cause excessive short-circuit current and burn out the motor. Currently, phase loss detection solutions for permanent magnet synchronous motors require additional hardware, increasing product costs, while low-cost solutions are often prone to errors and false alarms. Summary of the Invention

[0003] This application aims to solve at least one of the technical problems existing in the prior art. To this end, this application proposes a method, device, frequency converter, and household appliance for phase loss detection of a permanent magnet synchronous motor. By controlling the three-phase drive circuit to operate in a two-phase conducting state, and using a single resistor for current sampling, phase loss detection is achieved, resulting in high detection accuracy and low cost.

[0004] In a first aspect, this application provides a phase loss detection method for a permanent magnet synchronous motor, wherein the input terminal of the permanent magnet synchronous motor is electrically connected to the three-phase output side of a three-phase drive circuit, the DC side of the three-phase drive circuit is electrically connected to a bus, and a sampling resistor is provided on the bus.

[0005] Phase loss detection methods include:

[0006] When the three-phase drive circuit supplies power to the permanent magnet synchronous motor, control any one phase bridge arm in the three-phase drive circuit to turn off, so that the three-phase drive circuit is in a two-phase conduction state.

[0007] When the three-phase drive circuit is in a two-phase conducting state, determine whether the sampling current of the sampling resistor is zero to obtain the sampling result;

[0008] The phase loss status is determined based on the sampling results.

[0009] According to one embodiment of this application, the three-phase drive circuit supplies power to the permanent magnet synchronous motor in the stage when the permanent magnet synchronous motor is in the starting state;

[0010] Controlling any one phase bridge arm in the three-phase drive circuit to turn off, so that the three-phase drive circuit is in a two-phase conducting state, includes:

[0011] In the startup state, the three-phase drive circuit is controlled to achieve positioning and open-loop synchronous acceleration in a two-phase conduction mode, so that the three-phase drive circuit is in a two-phase conduction state.

[0012] The open-loop synchronous acceleration process also includes:

[0013] When the permanent magnet synchronous motor reaches the target synchronization state, the control three-phase drive circuit switches from two-phase conduction mode to three-phase conduction mode and enters closed-loop operation in three-phase conduction mode.

[0014] According to one embodiment of this application, a driving cycle of a two-phase conduction mode includes switching multiple conduction combination intervals, and the conduction phase combination portion between two adjacent conduction combination intervals is the same.

[0015] Determine whether the sampling current of the sampling resistor is zero to obtain the sampling results, including:

[0016] Within each conduction combination interval, obtain the sampling current of the sampling resistor;

[0017] When the sampling current is less than the first reference threshold, the sampling current is determined to be zero current; or when the sampling current is greater than or equal to the first reference threshold, the sampling current is determined to be non-zero current, so as to obtain the sampling results of each conduction combination interval.

[0018] According to one embodiment of this application, determining the phase loss state based on sampling results includes:

[0019] When at least one of the sampled currents corresponding to multiple conduction combination intervals is zero and at least one is non-zero, determine the first conduction phase combination of the zero-current conduction combination interval and the second conduction phase combination of the non-zero-current conduction combination interval.

[0020] The different phases in the first conducting phase combination that are combined with the second conducting phase combination are determined to be in a phase loss state.

[0021] According to one embodiment of this application, the three-phase drive circuit supplies power to the permanent magnet synchronous motor in the stage when the permanent magnet synchronous motor is in closed-loop operation.

[0022] Controlling any one phase bridge arm in the three-phase drive circuit to turn off, so that the three-phase drive circuit is in a two-phase conducting state, includes:

[0023] In closed-loop operation, the target phase bridge arm corresponding to the zero-crossing stage of the phase current in the three-phase drive circuit is turned off, so that the three-phase drive circuit is in a two-phase conduction state.

[0024] According to one embodiment of this application, determining whether the sampling current of the sampling resistor is zero and obtaining the sampling result includes:

[0025] During the zero-crossing phase, when both phases are conducting, the sampling current of the sampling resistor is obtained;

[0026] When the sampling current is less than the second reference threshold, the sampling current is determined to be zero current; when the sampling current is greater than or equal to the second reference threshold, the sampling current is determined to be non-zero current, so as to obtain the sampling results corresponding to multiple zero-crossing stages.

[0027] According to one embodiment of this application, determining the phase loss state based on sampling results includes:

[0028] When the sampling current corresponding to multiple zero-crossing stages is at least zero and at least non-zero, determine the third conduction phase combination of the zero-crossing stage with zero current and the fourth conduction phase combination of the zero-crossing stage with non-zero current.

[0029] The different phases in the third conducting phase combination that are combined with the fourth conducting phase combination are determined to be in a phase loss state.

[0030] Secondly, this application provides a control device for a permanent magnet synchronous motor, wherein the input terminal of the permanent magnet synchronous motor is electrically connected to the three-phase output side of the three-phase drive circuit, the DC side of the three-phase drive circuit is electrically connected to the bus, and a sampling resistor is provided on the bus.

[0031] The control device includes:

[0032] The drive unit is used to control any one phase bridge arm in the three-phase drive circuit to turn off when the three-phase drive circuit supplies power to the permanent magnet synchronous motor, so that the three-phase drive circuit is in a two-phase conducting state.

[0033] The detection unit is used to determine whether the sampling current of the sampling resistor is zero when the three-phase drive circuit is in a two-phase conducting state, and to obtain the sampling result.

[0034] The analysis unit is used to determine the phase loss status based on the sampling results.

[0035] Thirdly, this application provides a frequency converter, including a controller and a bus, a three-phase drive circuit and a permanent magnet synchronous motor connected in sequence. A sampling resistor is provided on the bus. The controller is electrically connected to the sampling resistor and the three-phase drive circuit respectively, and is configured to implement the aforementioned phase loss detection method.

[0036] Fourthly, this application provides a household appliance, including the frequency converter according to the foregoing.

[0037] According to the permanent magnet synchronous motor phase loss detection method, device, frequency converter and household appliance of this application, by controlling the conduction mode of the three-phase drive circuit, it is made to operate in a two-phase conduction state. At this time, the current is sampled by a single resistor on the bus, and the phase loss detection is realized based on whether the sampled current is zero. The detection accuracy is high, and it does not involve hardware changes and has low cost.

[0038] Additional aspects and advantages of this application will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of this application. Attached Figure Description

[0039] The above and / or additional aspects and advantages of this application will become apparent and readily understood from the description of the embodiments taken in conjunction with the following drawings, in which:

[0040] Figure 1 This is a schematic diagram of the motor circuit provided in an embodiment of this application;

[0041] Figure 2 This is a schematic flowchart of the phase loss detection method for a permanent magnet synchronous motor provided in the embodiments of this application;

[0042] Figure 3 This is a current waveform diagram of a permanent magnet synchronous motor in the starting state provided in the embodiments of this application;

[0043] Figure 4 This is a schematic diagram of the conduction signal combination of the three-phase drive circuit provided in the embodiments of this application;

[0044] Figures 5 to 10 This is a schematic diagram of the conduction state of the three-phase drive circuit provided in the embodiments of this application;

[0045] Figure 11 This is a current waveform diagram of a permanent magnet synchronous motor in closed-loop operation provided in an embodiment of this application;

[0046] Figure 12 This is a structural diagram of the control device for the permanent magnet synchronous motor provided in the embodiments of this application.

[0047] Figure label:

[0048] Three-phase drive circuit 100, current detection circuit 200, PWM drive circuit 300, capacitor C1, permanent magnet synchronous motor M, control device 10, drive unit 11, detection unit 12, analysis unit 13. Detailed Implementation

[0049] The technical solutions of the embodiments of this application will be clearly described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of this application. All other embodiments obtained by those skilled in the art based on the embodiments of this application are within the scope of protection of this application.

[0050] The terms "first," "second," etc., used in the specification and claims of this application are used to distinguish similar objects and not to describe a specific order or sequence. It should be understood that such use of data can be interchanged where appropriate so that embodiments of this application can be implemented in orders other than those illustrated or described herein, and the objects distinguished by "first," "second," etc., are generally of the same class and the number of objects is not limited; for example, a first object can be one or more. Furthermore, in the specification and claims, "and / or" indicates at least one of the connected objects, and the character " / " generally indicates that the preceding and following objects are in an "or" relationship.

[0051] In related technologies, one method for detecting phase loss in permanent magnet synchronous motors is to add current sensors to the three phase lines of the motor to determine if a phase is missing, or to add an additional phase loss detection circuit. However, this method increases the product cost. Another method is to use a single resistor to sample and reconstruct the current, then compare the magnitudes of the currents in each phase to determine if a phase is missing. This method, because it relies on current reconstruction, is often prone to errors and false alarms.

[0052] Therefore, this application proposes a phase loss detection method, device, frequency converter, and household appliance for permanent magnet synchronous motors. By controlling the conduction mode of the three-phase drive circuit, it is made to operate in a two-phase conduction state. At this time, a single resistor on the bus is used for current sampling, and phase loss detection is achieved based on whether the sampled current is zero. The detection accuracy is high, and it does not involve hardware changes and has low cost.

[0053] The following description, in conjunction with the accompanying drawings, details the phase loss detection method, device, frequency converter, and household appliance for permanent magnet synchronous motors provided in this application, through specific embodiments and application scenarios.

[0054] Reference Figure 1 , Figure 1 A motor circuit is shown. The input terminal of the permanent magnet synchronous motor M is electrically connected to the three-phase output side of the three-phase drive circuit 100. The DC side of the three-phase drive circuit 100 is electrically connected to the bus Bus. A capacitor C1 is connected between the positive bus Bus+ and the negative bus Bus-. A sampling resistor R is provided on the negative bus Bus-, and the sampling resistor R is connected to the current detection circuit 200. Of course, the sampling resistor R can also be set to the positive bus Bus+.

[0055] The three-phase drive circuit 100 may include six switching transistors, with each pair of transistors connected in series to form U-phase, V-phase, and W-phase bridge arms. The control terminal of each switching transistor is connected to a PWM (Pulse Width Modulation) drive circuit 300. The PWM drive circuit 300 transmits PWM signals through the control terminals of each switching transistor to control the on / off state of each transistor, achieving voltage and current modulation. Switches connected to the positive bus (Bus+) can serve as the upper bridge arm, and those connected to the negative bus (Bus-) can serve as the lower bridge arm. The PWM signals of the upper and lower bridge arms within the same phase are complementary.

[0056] The switching transistor can be a MOSFET (Metal-Oxide-Semiconductor Field-Effect Transistor) or an IGBT (Insulated-Gate Bipolar Transistor), etc.

[0057] In addition, the motor circuit also includes a control circuit (not shown in the figure), which is connected to the current detection circuit 200 and the PWM drive circuit 300 respectively. The control circuit receives the detection signal fed back by the current detection circuit 200 to determine the current detection result, and can control the PWM drive circuit 300 accordingly.

[0058] The following is Figure 1 Based on the motor circuit shown, the phase loss detection method for permanent magnet synchronous motor proposed in this application will be explained.

[0059] Reference Figure 2 , Figure 2 A phase loss detection process for a permanent magnet synchronous motor is illustrated, and one embodiment of this application proposes a phase loss detection method. In this embodiment, the phase loss detection method includes steps 10, 20, and 30.

[0060] Step 10: When the three-phase drive circuit 100 supplies power to the permanent magnet synchronous motor M, control any one phase bridge arm in the three-phase drive circuit 100 to turn off, so that the three-phase drive circuit 100 is in a two-phase conducting state.

[0061] Step 20: With the three-phase drive circuit 100 in a two-phase conducting state, determine whether the sampling current of the sampling resistor R is zero and obtain the sampling result;

[0062] Step 30: Determine the phase loss status based on the sampling results.

[0063] It should be noted that the execution entity of the phase loss detection method in this embodiment can be the aforementioned control circuit or controller. The controller may include an integrated control circuit, current detection circuit 200, and PWM drive circuit 300. The following description uses the control circuit as an example.

[0064] The permanent magnet synchronous motor M is powered by a three-phase power supply, including phase U, phase V, and phase W. During normal power supply, current flows into the permanent magnet synchronous motor M from at least one phase and flows out from the remaining phases. For example, current flows into the permanent magnet synchronous motor M from phase U and flows out from phases V and W.

[0065] In this embodiment, the three-phase drive circuit 100 is put into a two-phase conduction state by turning off any one phase bridge arm. For example, the PWM drive circuit 300 sends a turn-off signal to two switches in one phase, and simultaneously sends a conduction signal to one upper bridge arm and one lower bridge arm in the other two phases. In the two-phase conduction state, the current of the permanent magnet synchronous motor M flows in from one phase and flows out from one phase.

[0066] The current detection circuit 200 samples the sampling resistor R. When the three-phase drive circuit 100 is in a two-phase conducting state, it feeds back the detection information to the control circuit. The control circuit determines the sampling result based on the received detection information. For example, the current detection circuit 200 compares the sampled signal with a reference signal. If the current value represented by the sampled signal is less than the reference threshold, it determines that the sampled current is zero and sends a first signal to the control circuit; or if the current value represented by the sampled signal is greater than or equal to the reference threshold, it determines that the sampled current is not zero and sends a second signal to the control circuit. The control circuit determines whether the sampled current is zero based on the received first or second signal.

[0067] Understandably, if the sampled current is zero when two phases are conducting, it indicates that at least one of the conducting phases is missing. Therefore, by combining various combinations of two-phase conduction states, it is possible to determine which phase is missing. The reference threshold can be the minimum operating current of the permanent magnet synchronous motor M; if the sampled current is less than this minimum operating current, it can be determined that the sampled current is zero.

[0068] As an example, if the sampling current is zero when phases U and V are conducting, it indicates that at least one of phases U and V is missing a phase; if the sampling current is not zero when phases U and W are conducting, it indicates that phases U and W are not missing a phase; thus, it can be concluded that phase V is missing a phase.

[0069] It is understandable that this implementation method judges the phase loss based on whether the sampling current is zero. The information of whether the sampling current is zero is easy to obtain and is not prone to error, thereby improving the accuracy of phase loss detection.

[0070] In some embodiments, the three-phase drive circuit 100 supplies power to the permanent magnet synchronous motor M, including the stage when the permanent magnet synchronous motor M is in the start-up state; controlling any one phase bridge arm of the three-phase drive circuit 100 to turn off, so that the three-phase drive circuit 100 is in a two-phase conducting state, including: in the start-up state, controlling the three-phase drive circuit 100 to achieve positioning and open-loop synchronous acceleration in a two-phase conducting mode, so that the three-phase drive circuit 100 is in a two-phase conducting state.

[0071] like Figure 3 As shown, Figure 3 A current waveform diagram of a permanent magnet synchronous motor in the startup state is shown. In this embodiment, the permanent magnet synchronous motor M achieves positioning and open-loop synchronous acceleration in a two-phase conduction mode during startup. Positioning refers to determining the relative position of the rotor and stator magnetic field through accurate rotor position detection during the startup process of the permanent magnet synchronous motor M. Open-loop synchronous acceleration refers to gradually accelerating the motor at a preset rate through the control system during the startup process of the permanent magnet synchronous motor M.

[0072] In two-phase conduction mode, only two phases of the three-phase drive circuit 100 are conducting. This reduces the current surge during the initial startup of the permanent magnet synchronous motor M. Since the motor rotor is stationary, the back electromotive force of the motor is almost zero. At this time, the two-phase conduction can prevent excessive current from flowing into the permanent magnet synchronous motor M, thus achieving the protection purpose.

[0073] In this embodiment, after controlling the three-phase drive circuit 100 to achieve positioning and open-loop synchronous acceleration in two-phase conduction mode, the method further includes: during the open-loop synchronous acceleration process, controlling the three-phase drive circuit 100 to switch from two-phase conduction mode to three-phase conduction mode and enter closed-loop operation state in three-phase conduction mode.

[0074] As an example, the open-loop synchronous acceleration process also includes: when the permanent magnet synchronous motor M reaches the target synchronization state, controlling the three-phase drive circuit 100 to switch from two-phase conduction mode to three-phase conduction mode, and entering the closed-loop operation state in three-phase conduction mode.

[0075] Three-phase conduction mode refers to the simultaneous flow of current through the U, V, and W phases of the permanent magnet synchronous motor M. The target synchronization state refers to the permanent magnet synchronous motor M's rotational speed approaching the synchronous speed, and the angular difference between the rotor and the rotating magnetic field approaching the threshold. At this point, during the later stages of open-loop synchronous acceleration, the stator magnetic field speed is close to synchronous with the rotor. The three-phase drive circuit 100 is then switched to three-phase conduction mode to provide more current and torque to maintain acceleration, achieving synchronization under three-phase power drive and completing the startup. After startup, the three-phase drive circuit 100 continues to operate in three-phase conduction mode.

[0076] In some embodiments, a driving cycle of a two-phase conduction mode includes switching multiple conduction combination intervals, wherein the conduction phase combination portion is the same between two adjacent conduction combination intervals.

[0077] Reference Figure 4 , Figure 4 This diagram illustrates a combination of conduction signals during a drive cycle in a two-phase conduction mode. As an example, the conduction phase signal is activated at a high level, and the conduction signal combination intervals during the drive cycle include G1, G2, G3, G4, G5, and G6. In interval G1, the upper arm of phase U and the lower arm of phase V are activated; in interval G2, the upper arm of phase U and the lower arm of phase W are activated; in interval G3, the upper arm of phase V and the lower arm of phase W are activated; in interval G4, the upper arm of phase V and the lower arm of phase U are activated; in interval G5, the upper arm of phase W and the lower arm of phase U are activated; and in interval G6, the upper arm of phase W and the lower arm of phase V are activated.

[0078] Reference Figures 5 to 10 , Figures 5 to 10 Each conduction state is shown. Within the G1 interval, the corresponding conduction states are as follows: Figure 5 As shown; within the G2 interval, the corresponding conduction states are as follows: Figure 6 As shown; within the G3 interval, the corresponding conduction states are as follows: Figure 7 As shown; within the G4 interval, the corresponding conduction states are as follows: Figure 8 As shown; within the G5 interval, the corresponding conduction states are as follows: Figure 9 As shown; within the G6 interval, the corresponding conduction states are as follows: Figure 10 As shown.

[0079] In this embodiment, determining whether the sampling current of the sampling resistor R is zero and obtaining the sampling result includes: acquiring the sampling current of the sampling resistor R within each conduction combination interval; determining that the sampling current is zero when the sampling current is less than a first reference threshold, or determining that the sampling current is non-zero when the sampling current is greater than or equal to the first reference threshold, so as to obtain the sampling result of each conduction combination interval.

[0080] The first reference threshold can be the minimum operating current of the permanent magnet synchronous motor M. If the sampled current is less than the minimum operating current, the sampled current can be determined to be zero.

[0081] It should be noted that the sampling window for sampling the sampling resistor R is larger than the reference sampling threshold to ensure that the current tends to stabilize during sampling. For example, a combination of conduction signals with a PWM signal duty cycle greater than the reference duty cycle can be selected for detection. Alternatively, sampling can be performed after a reference time has elapsed following the switching of the conduction signal combination interval.

[0082] Understandably, when the three-phase drive circuit 100 is in two-phase conduction mode, the current in multiple conduction signal combination intervals can be detected, such as intervals G1, G2, G3, G4, G5, and G6. Alternatively, the current in each interval can be detected over multiple drive cycles to obtain more sampling results and improve the accuracy of phase loss detection.

[0083] In some embodiments, determining the phase loss state based on the sampling results includes: when at least one of the sampled currents corresponding to multiple conduction combination intervals is zero current and at least one is not zero current, determining the first conduction phase combination of the zero current conduction combination interval and the second conduction phase combination of the non-zero current conduction combination interval; and determining the different phases in the first conduction phase combination that are different from the second conduction phase combination as the phase loss state.

[0084] As an example, if the sampling current corresponding to interval G1 is zero, then the first conducting phase combination is phase U and phase V. If the sampling current corresponding to interval G2 is non-zero, then the second conducting phase combination is phase U and phase W. Therefore, based on the sampling results of interval G1, it can be known that at least one of phases U and V is missing. Based on the sampling results of interval G2, it can be known that neither phase U nor phase W is missing, thus it can be concluded that phase V is missing.

[0085] If the sampling currents corresponding to intervals G1 and G2 are both zero, it indicates that phase U is missing, phases V and W are missing, or all phases are missing. In this case, other intervals can be used for judgment. For example, if the sampling currents corresponding to interval G3 are not zero, it indicates that phases V and W are not missing, thus it can be determined that phase U is missing.

[0086] In some embodiments, the three-phase drive circuit 100 supplies power to the permanent magnet synchronous motor M, including when the permanent magnet synchronous motor M is in a closed-loop operation state; controlling any phase bridge arm in the three-phase drive circuit 100 to turn off, so that the three-phase drive circuit 100 is in a two-phase conduction state, includes: in the closed-loop operation state, controlling the target phase bridge arm corresponding to the zero-crossing stage of the phase current in the three-phase drive circuit 100 to turn off, so that the three-phase drive circuit 100 is in a two-phase conduction state.

[0087] In this embodiment, the permanent magnet synchronous motor M is in closed-loop operation, that is, in normal operation, and may be used to drive a corresponding load. In this state, by turning off one phase arm, the three-phase drive circuit 100 is temporarily in a two-phase conducting state. Furthermore, since the current of the turned-off phase is at zero crossing, the impact on the operation of the permanent magnet synchronous motor M is relatively small.

[0088] Reference Figure 11 , Figure 11The diagram shows the current waveform of a permanent magnet synchronous motor M under closed-loop operation. As an example, at point ①, the W-phase current is at zero-crossing; at this time, the upper and lower bridge arms of phase W are turned off, forming a waveform as shown below. Figure 5 The conduction state is shown; at point ②, the V-phase current is in the zero-crossing stage, at which point the upper and lower arms of the V-phase are turned off, forming a state as shown. Figure 6 The conduction state is shown; at point ③, the U-phase current is in the zero-crossing stage, at which point the upper and lower bridge arms of the U-phase are turned off, forming a state as shown. Figure 7 The conduction state is shown; at point ④, the W-phase current is in the zero-crossing stage, at which point the upper and lower bridge arms of the W-phase are turned off, forming a state as shown. Figure 8 The conduction state is shown; at point ⑤, the V-phase current is in the zero-crossing stage, at which point the upper and lower arms of the V-phase are turned off, forming a state as shown. Figure 9 The conduction state is shown; at point ⑥, the U-phase current is in the zero-crossing stage, at which point the upper and lower bridge arms of the U-phase are turned off, forming a state as shown. Figure 10 The indicated conduction state.

[0089] In some embodiments, determining whether the sampling current of the sampling resistor is zero current and obtaining the sampling result includes: acquiring the sampling current of the sampling resistor in the two-phase conduction state during the zero-crossing phase; determining that the sampling current is zero current when the sampling current is less than a second reference threshold, or determining that the sampling current is non-zero current when the sampling current is greater than or equal to the second reference threshold, so as to obtain the sampling results corresponding to multiple zero-crossing phases.

[0090] The second reference threshold can be the minimum operating current of the permanent magnet synchronous motor M. If the sampled current is less than this minimum operating current, the sampled current can be determined to be zero. The sampling window for sampling the sampling resistor R is larger than the reference sampling threshold to ensure that the current tends to stabilize during sampling. For example, after turning off a certain phase bridge arm, sampling is performed after a reference time.

[0091] As an example, the permanent magnet synchronous motor M can be set with multiple detection cycles during operation, such as setting a detection cycle at certain time intervals (3 hours, 5 hours or 10 hours, etc.); or setting the detection cycle according to natural time (such as 8 o'clock or 20 o'clock, etc.); or it can also be set according to historical operation records before the high load operation period.

[0092] Within a detection cycle, the current in the sampling resistor R is sampled when the phase current of each phase is at its zero-crossing stage, and the sampling result is obtained. For example, the detection cycle may include at least one detection process as described in ① to ⑥ above. This allows for the acquisition of more sampling results and improves detection accuracy.

[0093] In some embodiments, determining the phase loss state based on the sampling results includes: when at least one of the sampled currents corresponding to multiple zero-crossing stages is zero current and at least one is not zero current, determining the third conducting phase combination of the zero-crossing stage with zero current and the fourth conducting phase combination of the zero-crossing stage with non-zero current; and determining the different phases in the third conducting phase combination that are different from the fourth conducting phase combination as the phase loss state.

[0094] As an example, if the sampling current at point ① is zero, then the first conducting phase combination is phase U and phase V. If the sampling current at point ② is non-zero, then the second conducting phase combination is phase U and phase W. Therefore, based on the sampling result at point ①, it can be known that at least one of phases U and V is missing. Based on the sampling result at point ②, it can be known that phases U and W are not missing, thus it can be concluded that phase V is missing.

[0095] If the sampling currents at points ① and ② are both zero, it indicates that phase U is missing, phases V and W are missing, or all phases are missing. In this case, other intervals can be considered for judgment. For example, if the sampling currents at point ③ are not zero, it indicates that phases V and W are not missing, thus confirming that phase U is missing.

[0096] Reference Figure 12 , Figure 12 The structure of a control device for a permanent magnet synchronous motor is shown. An embodiment of this application also proposes a control device for a permanent magnet synchronous motor. In this embodiment, the control device 10 includes a drive unit 11, a detection unit 12, and an analysis unit 13. The drive unit 11 is used to control any one phase bridge arm of the three-phase drive circuit 100 to turn off when the three-phase drive circuit 100 supplies power to the permanent magnet synchronous motor M, so that the three-phase drive circuit 100 is in a two-phase conducting state. The detection unit 12 is used to determine whether the sampling current of the sampling resistor R is zero current when the three-phase drive circuit 100 is in a two-phase conducting state, and obtain the sampling result. The analysis unit 13 is used to determine the phase loss state based on the sampling result.

[0097] Understandably, if the sampled current is zero when two phases are conducting, it indicates that at least one of the conducting phases is missing. Therefore, by combining various combinations of two-phase conduction states, it is possible to determine which phase is missing. The reference threshold can be the minimum operating current of the permanent magnet synchronous motor M; if the sampled current is less than this minimum operating current, it can be determined that the sampled current is zero.

[0098] As an example, if the sampling current is zero when phases U and V are conducting, it indicates that at least one of phases U and V is missing a phase; if the sampling current is not zero when phases U and W are conducting, it indicates that phases U and W are not missing a phase; thus, it can be concluded that phase V is missing a phase.

[0099] In some embodiments, the three-phase drive circuit 100 supplies power to the permanent magnet synchronous motor M in the stage where the permanent magnet synchronous motor M is in the starting state; the drive unit 11 is also used to control the three-phase drive circuit 100 to achieve positioning and open-loop synchronous acceleration in the starting state, so that the three-phase drive circuit is in the two-phase conducting state.

[0100] In some embodiments, a driving cycle of the two-phase conduction mode includes multiple switching conduction combination intervals, and the conduction phase combination portion between two adjacent conduction combination intervals is the same; the detection unit 12 is further configured to acquire the sampling current of the sampling resistor in each conduction combination interval; determine that the sampling current is zero current when the sampling current is less than a first reference threshold, or determine that the sampling current is non-zero current when the sampling current is greater than or equal to the first reference threshold, so as to obtain the sampling result of each conduction combination interval.

[0101] In some embodiments, the analysis unit 13 is further configured to determine the first conducting phase combination of the conducting phase combination interval with zero current and the second conducting phase combination of the conducting phase combination interval with non-zero current when the sampled current corresponding to the multiple conducting phase combination intervals is at least zero current and at least non-zero current; and to determine the different phases in the first conducting phase combination that are related to the second conducting phase combination as a phase loss state.

[0102] In some embodiments, the drive unit 11 is further configured to control the three-phase drive circuit to switch from two-phase conduction mode to three-phase conduction mode during open-loop synchronous acceleration, and to enter closed-loop operation state in three-phase conduction mode.

[0103] In some embodiments, the three-phase drive circuit 100 supplies power to the permanent magnet synchronous motor M in the stage where the permanent magnet synchronous motor M is in closed-loop operation; the drive unit 11 is also used to control the target phase bridge arm corresponding to the zero-crossing stage of the phase current in the three-phase drive circuit 100 to turn off in the closed-loop operation state, so that the three-phase drive circuit 100 is in a two-phase conduction state.

[0104] In some embodiments, the detection unit 12 is further configured to acquire the sampling current of the sampling resistor in the two-phase conduction state during the zero-crossing phase; determine that the sampling current is zero current when the sampling current is less than the second reference threshold, or determine that the sampling current is non-zero current when the sampling current is greater than or equal to the second reference threshold, so as to obtain the sampling results corresponding to multiple zero-crossing phases.

[0105] In some embodiments, the analysis unit 13 is further configured to determine the third conducting phase combination of the zero-current zero-crossing stage and the fourth conducting phase combination of the non-zero-current zero-crossing stage when at least one of the sampled currents corresponding to the multiple zero-crossing stages is zero and at least one is not zero; and to determine the different phases in the third conducting phase combination that are different from the fourth conducting phase combination as a phase loss state.

[0106] One embodiment of this application also provides a frequency converter, a frequency converter controller, and a bus, a three-phase drive circuit 100, and a permanent magnet synchronous motor M connected in sequence. A sampling resistor R is provided on the bus. The frequency converter includes, as shown below... Figure 1 The motor circuit shown has a controller (not shown) electrically connected to the sampling resistor R and the three-phase drive circuit 100, and is configured to implement the phase loss detection method described above. The specific structure of the motor circuit and the specific process of the phase loss detection method can be found in the aforementioned embodiments, and will not be repeated here.

[0107] One embodiment of this application also provides a household appliance, including the inverter according to the foregoing.

[0108] As an example, household appliances may include air conditioners or refrigerators. The specific structure and function of the frequency converter can be referred to in the foregoing embodiments, and will not be repeated here.

[0109] It should be noted that, in this document, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitations, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes that element. Furthermore, it should be noted that the scope of the methods and apparatuses in the embodiments of this application is not limited to performing functions in the order shown or discussed, but may also include performing functions substantially simultaneously or in the reverse order, depending on the functions involved. For example, the described methods may be performed in a different order than described, and various steps may be added, omitted, or combined. Additionally, features described with reference to certain examples may be combined in other examples.

[0110] Through the above description of the embodiments, those skilled in the art can clearly understand that the methods of the above embodiments can be implemented by means of software plus necessary general-purpose hardware platforms. Of course, they can also be implemented by hardware, but in many cases the former is a better implementation method. Based on this understanding, the technical solution of this application, in essence, or the part that contributes to the prior art, can be embodied in the form of a computer software product. This computer software product is stored in a storage medium (such as ROM / RAM, magnetic disk, optical disk) and includes several instructions to cause a terminal (which may be a mobile phone, computer, server, or network device, etc.) to execute the methods described in the various embodiments of this application.

[0111] The embodiments of this application have been described above with reference to the accompanying drawings. However, this application is not limited to the specific embodiments described above. The specific embodiments described above are merely illustrative and not restrictive. Those skilled in the art can make many other forms under the guidance of this application without departing from the spirit and scope of the claims, and all of these forms are within the protection scope of this application.

[0112] In the description of this specification, the references to terms such as "one embodiment," "some embodiments," "illustrative embodiment," "example," "specific example," or "some examples," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of this application. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0113] Although embodiments of this application have been shown and described, those skilled in the art will understand that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of this application, the scope of which is defined by the claims and their equivalents.

Claims

1. A method for detecting phase loss in a permanent magnet synchronous motor, characterized in that, The input terminal of the permanent magnet synchronous motor is electrically connected to the three-phase output side of the three-phase drive circuit, the DC side of the three-phase drive circuit is electrically connected to the bus, and a sampling resistor is provided on the bus. The phase loss detection method includes: When the three-phase drive circuit supplies power to the permanent magnet synchronous motor, control any one phase bridge arm of the three-phase drive circuit to turn off, so that the three-phase drive circuit is in a two-phase conduction state. When the three-phase drive circuit is in a two-phase conducting state, determine whether the sampling current of the sampling resistor is zero current to obtain the sampling result; The phase loss state is determined based on the sampling results.

2. The phase loss detection method according to claim 1, characterized in that, The three-phase drive circuit supplies power to the permanent magnet synchronous motor, including when the permanent magnet synchronous motor is in the starting state; The step of controlling any one phase bridge arm of the three-phase drive circuit to turn off, so that the three-phase drive circuit is in a two-phase conducting state, includes: In the startup state, the three-phase drive circuit is controlled to achieve positioning and open-loop synchronous acceleration in a two-phase conduction mode, so that the three-phase drive circuit is in a two-phase conduction state. The open-loop synchronous acceleration process also includes: When the permanent magnet synchronous motor reaches the target synchronization state, the three-phase drive circuit is controlled to switch from the two-phase conduction mode to the three-phase conduction mode, and enters the closed-loop operation state in the three-phase conduction mode.

3. The phase loss detection method according to claim 2, characterized in that, One driving cycle of the two-phase conduction mode includes multiple switching conduction combination intervals, and the conduction phase combination portion is the same between two adjacent conduction combination intervals. The step of determining whether the sampling current of the sampling resistor is zero, and obtaining the sampling result, includes: Within each of the aforementioned conduction combination intervals, the sampling current of the sampling resistor is obtained; When the sampling current is less than the first reference threshold, the sampling current is determined to be zero current; or when the sampling current is greater than or equal to the first reference threshold, the sampling current is determined to be non-zero current, so as to obtain the sampling results of each of the conduction combination intervals.

4. The phase loss detection method according to claim 3, characterized in that, Determining the phase loss state based on the sampling results includes: If at least one of the sampled currents corresponding to multiple conduction combination intervals is zero and at least one is not zero, determine the first conduction phase combination of the conduction combination interval with zero current and the second conduction phase combination of the conduction combination interval with non-zero current. The different phases in the first conducting phase combination that are in the second conducting phase combination are determined to be in a phase loss state.

5. The phase loss detection method according to any one of claims 1-4, characterized in that, The three-phase drive circuit supplies power to the permanent magnet synchronous motor during the period when the permanent magnet synchronous motor is in closed-loop operation. The step of controlling any one phase bridge arm of the three-phase drive circuit to turn off, so that the three-phase drive circuit is in a two-phase conducting state, includes: In the closed-loop operation state, the target phase bridge arm corresponding to the zero-crossing stage of the phase current in the three-phase drive circuit is turned off, so that the three-phase drive circuit is in a two-phase conduction state.

6. The phase loss detection method according to claim 5, characterized in that, The step of determining whether the sampling current of the sampling resistor is zero, and obtaining the sampling result, includes: During the zero-crossing phase, in the two-phase conduction state, the sampling current of the sampling resistor is obtained; When the sampling current is less than the second reference threshold, the sampling current is determined to be zero current; or when the sampling current is greater than or equal to the second reference threshold, the sampling current is determined to be non-zero current, so as to obtain sampling results corresponding to multiple zero-crossing stages.

7. The phase loss detection method according to claim 6, characterized in that, Determining the phase loss state based on the sampling results includes: In the case where at least one of the sampled currents corresponding to the multiple zero-crossing stages is zero current and at least one is not zero current, the third conduction phase combination of the zero-crossing stage with zero current and the fourth conduction phase combination of the zero-crossing stage with non-zero current are determined. The different phases in the third conducting phase combination that are combined with the fourth conducting phase combination are determined to be in a phase loss state.

8. A control device for a permanent magnet synchronous motor, characterized in that, The input terminal of the permanent magnet synchronous motor is electrically connected to the three-phase output side of the three-phase drive circuit, the DC side of the three-phase drive circuit is electrically connected to the bus, and a sampling resistor is provided on the bus. The control device includes: The drive unit is used to control any one phase bridge arm of the three-phase drive circuit to turn off when the three-phase drive circuit supplies power to the permanent magnet synchronous motor, so that the three-phase drive circuit is in a two-phase conduction state. The detection unit is used to determine whether the sampling current of the sampling resistor is zero when the three-phase drive circuit is in a two-phase conducting state, and to obtain the sampling result; An analysis unit is used to determine the phase loss state based on the sampling results.

9. A frequency converter, characterized in that, The device includes a controller and a busbar, a three-phase drive circuit, and a permanent magnet synchronous motor connected in sequence. A sampling resistor is provided on the busbar. The controller is electrically connected to the sampling resistor and the three-phase drive circuit, and is configured to implement the phase loss detection method according to any one of claims 1-7.

10. A household appliance, characterized in that, Including the frequency converter according to claim 9.

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