Switching tube junction temperature detection method, motor controller, motor control system and medium

Abstract

The application discloses a kind of switch tube junction temperature detection method, motor controller, motor control system and medium, motor control system includes the three-phase inverter bridge of driving motor to work, method includes: determining the tube voltage drop and conduction current of at least one phase bridge arm in three-phase inverter bridge when lower tube is turned on;According to tube voltage drop and conduction current, determine the conduction resistance of at least one phase bridge arm when lower tube is turned on;According to conduction resistance, determine the junction temperature of at least one phase bridge arm when lower tube is turned on.The method is obtained by calculating conduction resistance according to tube voltage drop and conduction current, and the junction temperature of lower tube is determined based on conduction resistance, so that the junction temperature of lower tube obtained has higher accuracy.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of motor control, and in particular to a method for detecting junction temperature of a switching tube in a motor control system, a motor controller, a computer readable storage medium and a motor control system. BACKGROUND

[0002] In the field of household appliance motor control or the field of small and light electric vehicle control, etc., considering cost and space in all aspects, a motor controller is usually used to control a motor in a single-resistor current sampling mode, and a large number of discrete devices are used to implement switching devices. Among them, the conventional temperature protection method for discrete switching devices is usually to place a temperature resistor around the switching device to protect the temperature. Although this method provides temperature sensing capability, since the temperature resistor receives the space radiation temperature of the switching device, it is affected by the installation position of the temperature resistor, and the method has limited sensing capability for the internal temperature change of the switching device, which leads to inaccurate temperature detection of the switching device, and further affects the temperature protection of the switching device. SUMMARY

[0003] The present application aims to at least solve one of the technical problems in the related art. To this end, a first object of the present application is to provide a method for detecting junction temperature of a switching tube in a motor control system, by calculating the on-resistance according to the tube voltage drop and the on-current, and determining the tube junction temperature based on the on-resistance, so that the obtained tube junction temperature has high accuracy, thereby facilitating temperature protection of the switching device.

[0004] A second object of the present application is to provide a motor controller.

[0005] A third object of the present application is to provide a computer readable storage medium.

[0006] A fourth object of the present application is to provide a motor control system.

[0007] To achieve the above-mentioned objects, a first aspect of the present application provides a method for detecting junction temperature of a switching tube in a motor control system, the motor control system comprising a three-phase inverter bridge for driving a motor to work, the method comprising: determining a tube voltage drop and an on-current of a lower tube of at least one phase arm of the three-phase inverter bridge when the lower tube is on; determining an on-resistance of the lower tube of the at least one phase arm when the lower tube is on according to the tube voltage drop and the on-current; and determining a junction temperature of the lower tube of the at least one phase arm according to the on-resistance.

[0008] The method for detecting junction temperature of a switch tube in a motor control system according to an embodiment of the present application determines the voltage drop and the conduction current of the lower tube of at least one bridge arm in the three-phase inverter bridge, determines the conduction resistance of the lower tube of at least one bridge arm according to the voltage drop and the conduction current, and determines the junction temperature of the lower tube of at least one bridge arm according to the conduction resistance, so that the obtained junction temperature of the lower tube has high accuracy, thereby facilitating temperature protection of the switch device.

[0009] According to an embodiment of the present application, the determination of the voltage drop and the conduction current of the lower tube of at least one bridge arm in the three-phase inverter bridge includes: determining the sampling time of the voltage drop and the sampling time of the phase current of the motor according to the conduction sequence of the switch tube in the three-phase inverter bridge; performing voltage sampling and current sampling at the sampling time of the voltage drop and the sampling time of the phase current of the motor respectively to obtain the voltage drop and the conduction current of the lower tube of at least one bridge arm; and determining the conduction current of the lower tube of at least one bridge arm according to the at least one phase current of the motor.

[0010] According to an embodiment of the present application, when a single resistor is used to detect the phase current of the motor, the determination of the sampling time of the voltage drop and the sampling time of the phase current of the motor according to the conduction sequence of the switch tube in the three-phase inverter bridge includes: determining the first sampling window time, the second sampling window time and the third sampling window time according to the conduction sequence of the switch tube in the three-phase inverter bridge, wherein the first sampling window time is the time from the start of the conduction of the lower tubes of the three bridge arms in the three-phase inverter bridge to the conduction of the upper tube of any bridge arm in the three-phase inverter bridge, the second sampling window time is the time from the start of the conduction of the upper tube of any bridge arm in the three-phase inverter bridge after a first preset time to the conduction of the upper tube of the next bridge arm in the three-phase inverter bridge, and the third sampling window time is the time from the start of the conduction of the upper tube of the next bridge arm in the three-phase inverter bridge after a first preset time to the conduction of the upper tube of the last bridge arm in the three-phase inverter bridge; at least two of the first sampling window time, the second sampling window time and the third sampling window time are used as the sampling time of the voltage drop and the sampling time of the phase current, or the third sampling window time is used as the sampling time of the voltage drop and the sampling time of the phase current.

[0011] According to an embodiment of the present application, when the first sampling window time, the second sampling window time and the third sampling window time are all used as the sampling time of the voltage drop and the sampling time of the phase current, the voltage drop and the conduction current of the lower tube of each bridge arm in the three-phase inverter bridge are determined.

[0012] According to one embodiment of the present application, the method for determining the tube voltage drop and the conduction current of the lower tube of each phase arm in a three-phase inverter bridge comprises: obtaining the tube voltage drop of the lower tube of each phase arm in a first sampling window time; obtaining the U-phase current and the tube voltage drop of the lower tube of the U-phase arm and the tube voltage drop of the lower tube of the W-phase arm in a second sampling window time; obtaining the W-phase current or the U-phase current and the tube voltage drop of the lower tube of the W-phase arm or the tube voltage drop of the lower tube of the U-phase arm in a third sampling window time; determining the V-phase current according to the U-phase current and the W-phase current, or determining the W-phase current according to the U-phase current and the V-phase current; and determining the conduction current of the lower tube of each phase arm according to the U-phase current, the W-phase current and the V-phase current.

[0013] According to one embodiment of the present application, the method for determining the tube voltage drop and the conduction current of the lower tube of each phase arm in a three-phase inverter bridge comprises: obtaining the tube voltage drop of the lower tube of each phase arm in a first sampling window time; obtaining the V-phase current and the tube voltage drop of the lower tube of the U-phase arm and the tube voltage drop of the lower tube of the W-phase arm in a second sampling window time; obtaining the W-phase current or the U-phase current and the tube voltage drop of the lower tube of the W-phase arm or the tube voltage drop of the lower tube of the U-phase arm in a third sampling window time; determining the U-phase current according to the V-phase current and the W-phase current, or determining the W-phase current according to the V-phase current and the U-phase current; and determining the conduction current of the lower tube of each phase arm according to the U-phase current, the W-phase current and the V-phase current.

[0014] According to one embodiment of the present application, the method for determining the tube voltage drop and the conduction current of the lower tube of each phase arm in a three-phase inverter bridge comprises: obtaining the tube voltage drop of the lower tube of each phase arm in a first sampling window time; obtaining the W-phase current and the tube voltage drop of the lower tube of the U-phase arm and the tube voltage drop of the lower tube of the V-phase arm in a second sampling window time; obtaining the U-phase current or the V-phase current and the tube voltage drop of the lower tube of the U-phase arm or the tube voltage drop of the lower tube of the V-phase arm in a third sampling window time; determining the V-phase current according to the W-phase current and the U-phase current, or determining the U-phase current according to the W-phase current and the V-phase current; and determining the conduction current of the lower tube of each phase arm according to the U-phase current, the W-phase current and the V-phase current.

[0015] According to one embodiment of the present application, after the junction temperature of the lower tube is determined, the method further comprises: performing instantaneous over-temperature protection and inverse time overload protection according to the junction temperature of the lower tube.

[0016] According to one embodiment of the present application, the instantaneous over-temperature protection performed according to the junction temperature of the lower tube comprises: when the junction temperature of the lower tube is greater than a preset maximum protection temperature, controlling the three-phase inverter bridge to stop output.

[0017] According to one embodiment of the present application, the inverse time overload protection is performed according to the lower tube junction temperature, comprising: determining an inverse time protection curve, and performing overload protection timing according to the relationship between the lower tube junction temperature and the inverse time protection curve; when the timing time arrives, controlling the three-phase inverter bridge to stop outputting.

[0018] According to one embodiment of the present application, the timing time is inversely related to the lower tube junction temperature.

[0019] To achieve the above object, the second aspect of the present application provides a motor controller, comprising a memory, a processor, and a switch tube junction temperature detection program stored in the memory and executable on the processor, wherein when the processor executes the switch tube junction temperature detection program, the above-mentioned switch tube junction temperature detection method in the motor control system is implemented.

[0020] According to the motor controller of the embodiment of the present application, based on the above-mentioned switch tube junction temperature detection method in the motor control system, the on-resistance is calculated according to the tube voltage drop and the on-current, and the lower tube junction temperature is determined based on the on-resistance, so that the obtained lower tube junction temperature has high accuracy, thereby facilitating temperature protection of the switching device.

[0021] To achieve the above object, the third aspect of the present application provides a computer readable storage medium, which stores a switch tube junction temperature detection program in the motor control system, and when the switch tube junction temperature detection program in the motor control system is executed by a processor, the above-mentioned switch tube junction temperature detection method in the motor control system is implemented.

[0022] According to the computer readable storage medium of the embodiment of the present application, based on the above-mentioned switch tube junction temperature detection method in the motor control system, the on-resistance is calculated according to the tube voltage drop and the on-current, and the lower tube junction temperature is determined based on the on-resistance, so that the obtained lower tube junction temperature has high accuracy, thereby facilitating temperature protection of the switching device.

[0023] To achieve the above object, the fourth aspect of the present application provides a motor control system, comprising: a motor; a three-phase inverter bridge connected between DC buses and driving the motor to work; a current detection unit arranged corresponding to the negative pole of the DC bus, used for detecting the DC bus current; a first voltage detection unit arranged corresponding to the lower tube of the U-phase bridge arm of the three-phase inverter bridge, used for detecting the voltage drop of the lower tube of the U-phase bridge arm; a second voltage detection unit arranged corresponding to the lower tube of the V-phase bridge arm of the three-phase inverter bridge, used for detecting the voltage drop of the lower tube of the V-phase bridge arm; a third voltage detection unit arranged corresponding to the lower tube of the W-phase bridge arm of the three-phase inverter bridge, used for detecting the voltage drop of the lower tube of the W-phase bridge arm; and a control unit, used for determining the conduction current of the lower tube of at least one phase bridge arm of the three-phase inverter bridge when the lower tube is turned on according to the DC bus current, obtaining the tube voltage drop of the lower tube of at least one phase bridge arm of the three-phase inverter bridge when the lower tube is turned on, and determining the conduction resistance of the lower tube of at least one phase bridge arm when the lower tube is turned on according to the tube voltage drop and the conduction current, and determining the junction temperature of the lower tube of at least one phase bridge arm according to the conduction resistance.

[0024] According to the motor control system of the embodiment of the present application, the control unit determines the conduction current of the lower tube of at least one phase bridge arm of the three-phase inverter bridge when the lower tube is turned on according to the DC bus current, obtains the tube voltage drop of the lower tube of at least one phase bridge arm of the three-phase inverter bridge when the lower tube is turned on, and determines the conduction resistance of the lower tube of at least one phase bridge arm when the lower tube is turned on according to the tube voltage drop and the conduction current, and determines the junction temperature of the lower tube of at least one phase bridge arm according to the conduction resistance, so that the obtained junction temperature of the lower tube has higher accuracy, thereby facilitating temperature protection of the switching device.

[0025] Additional aspects and advantages of the present application will be made apparent from the following description. BRIEF DESCRIPTION OF DRAWINGS

[0026] Figure 1 Structure diagram of the motor control system according to one embodiment of the present application;

[0027] Figure 2 Flow diagram of the switching tube junction temperature detection method according to one embodiment of the present application;

[0028] Figure 3 Relationship curve between the conduction resistance and the junction temperature of the switching tube according to one embodiment of the present application;

[0029] Figure 4 Acquisition flow diagram of the conduction current of the switching tube according to one embodiment of the present application;

[0030] Figure 5a Sampling diagram of the tube voltage drop and the phase current of the lower tube according to the first embodiment of the present application;

[0031] Figure 5b This is a schematic diagram of the sampling of the tube voltage drop and phase current of the lower tube according to the second embodiment of the present invention;

[0032] Figure 5c This is a schematic diagram of the sampling of the tube voltage drop and phase current of the lower tube according to the third embodiment of the present invention;

[0033] Figure 6 This is a graph of the inverse time protection curve according to an embodiment of the present invention. Detailed Implementation

[0034] Embodiments of the present invention are described in detail below, examples of which are illustrated in the accompanying drawings, wherein the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary and intended to explain the present invention, and should not be construed as limiting the present invention.

[0035] In an embodiment of the present invention, the motor control system may include a three-phase inverter bridge, which is used to drive the motor to work.

[0036] Specifically, refer to Figure 1 As shown, the three-phase inverter bridge includes a U-phase bridge arm, a V-phase bridge arm, and a W-phase bridge arm. The U-phase bridge arm includes an upper tube VT1 and a lower tube VT4, the V-phase bridge arm includes an upper tube VT3 and a lower tube VT6, and the W-phase bridge arm includes an upper tube VT5 and a lower tube VT2. The upper transistor VT1 has its first end connected to the positive terminal of the DC bus, the lower transistor VT4 has its first end connected to the second end of the upper transistor VT1, and the second end of the lower transistor VT4 is connected to the negative terminal of the DC bus; the upper transistor VT3 has its first end connected to the positive terminal of the DC bus, the lower transistor VT6 has its first end connected to the second end of the upper transistor VT3, and the second end of the lower transistor VT6 is connected to the negative terminal of the DC bus; the upper transistor VT5 has its first end connected to the positive terminal of the DC bus, the lower transistor VT2 has its first end connected to the second end of the upper transistor VT5, and the second end of the lower transistor VT2 is connected to the negative terminal of the DC bus; the control terminals of the upper transistor VT1, lower transistor VT4, upper transistor VT3, lower transistor VT6, upper transistor VT5, and lower transistor VT2 are respectively connected to a control unit. The control unit may include a microcontroller with memory, a DSP (Digital Signal Processing), or other control devices. This control unit controls the six switching transistors to turn on or off, thereby converting the DC power on the DC bus into AC power, which is then supplied to downstream loads such as motors to enable the motors to operate. The source of DC power can be a battery or AC power rectified; there are no specific restrictions here. A DC bus capacitor is installed between the positive and negative terminals of the DC bus for energy storage and voltage regulation.

[0037] When the control unit controls the six switching transistors to turn on or off for operation, the six switching transistors generate heat, causing their temperatures to rise. In severe cases, this can damage the switching transistors. Therefore, in related technologies, a temperature resistor is placed around the six switching transistors for temperature protection. Although this method provides temperature sensing capability, it is limited in its ability to sense internal temperature changes of the switching transistors because the temperature resistor receives the ambient radiant temperature of the switching transistors. This leads to inaccurate temperature detection and consequently affects the temperature protection of the switching transistors. Based on this, this application provides a switching transistor junction temperature detection method. This method can accurately obtain the junction temperature of the lower transistor, which is beneficial for temperature protection of the switching transistors.

[0038] Figure 2 This is a schematic flowchart of a switching transistor junction temperature detection method according to an embodiment of the present invention. (Reference) Figure 2 As shown, the method for detecting the junction temperature of a switching transistor may include the following steps:

[0039] Step S10: Determine the tube voltage drop and conduction current when the lower tube of at least one phase arm of the three-phase inverter bridge is turned on.

[0040] It should be noted that the transistor voltage drop refers to the voltage difference between the first and second terminals of the switching transistor when it is turned on, and the conduction current refers to the current flowing through the switching transistor when it is turned on. For example... Figure 1 As shown, the voltage drop across the lower transistor VT4 is the voltage difference between its first and second terminals when it is turned on, and the conduction current of the lower transistor VT4 is the current flowing through it when it is turned on; the voltage drop across the lower transistor VT6 is the voltage difference between its first and second terminals when it is turned on, and the conduction current of the lower transistor VT6 is the current flowing through it when it is turned on; the voltage drop across the lower transistor VT2 is the voltage difference between its first and second terminals when it is turned on, and the conduction current of the lower transistor VT2 is the current flowing through it when it is turned on.

[0041] To determine the voltage drop across the lower tube when it is conducting, a voltage detection unit can be set up for each lower tube to detect the voltage drop across that lower tube when it is conducting. For example... Figure 1 As shown, a first voltage detection unit can be set for the lower transistor VT4 to detect the voltage drop of the lower transistor VT4; a second voltage detection unit can be set for the lower transistor VT6 to detect the voltage drop of the lower transistor VT6; and a third voltage detection unit can be set for the lower transistor VT2 to detect the voltage drop of the lower transistor VT2.

[0042] In determining the conduction current of the lower tube, a current detection unit can be arranged on the DC bus, the DC bus current is detected through the current detection unit, and the corresponding conduction current is obtained through the DC bus current. As shown in Figure 1 , a current sampling resistor and a current detection unit can be arranged on the negative electrode of the DC bus, and the DC bus current is obtained by sampling through the current sampling resistor and the current detection unit. Since the DC bus current is related to the conduction current of the lower tube, the conduction current of the lower tube VT4, VT6 and VT2 can be obtained based on the DC bus current. For example, the conduction current of part of the switch tubes in the lower tube VT4, VT6 and VT2 can be directly obtained based on the loop current direction during conduction, and the conduction current of other switch tubes can be obtained based on the single-resistor current reconstruction mode, so that it is not necessary to arrange a current sampling resistor and a current detection unit for each lower tube, which is beneficial to reduce the cost and space occupation.

[0043] Step S20, determining the conduction resistance of the lower tube of the at least one phase bridge arm during conduction according to the tube voltage drop and the conduction current.

[0044] Specifically, when the tube voltage drop and the conduction current of the switch tube are obtained, a resistance can be calculated based on the relationship between voltage and current, and the resistance is the conduction resistance of the switch tube during conduction. As shown in Figure 1 , after obtaining the tube voltage drop and the conduction current of the lower tube VT4, the conduction resistance of the lower tube VT4 can be calculated; after obtaining the tube voltage drop and the conduction current of the lower tube VT6, the conduction resistance of the lower tube VT6 can be calculated; and after obtaining the tube voltage drop and the conduction current of the lower tube VT2, the conduction resistance of the lower tube VT2 can be calculated. The calculation can be obtained by the following formula (1):

[0045]

[0046] , R dson-real is the conduction resistance, V ds is the tube voltage drop, and I is the conduction current.

[0047] Step S30, determining the junction temperature of the lower tube of the at least one phase bridge arm according to the conduction resistance.

[0048] Specifically, after obtaining the conduction resistance of the switch tube, the junction temperature of the switch tube can be obtained based on the relationship between the conduction resistance and the junction temperature of the switch tube. Specifically, the relationship curve between the standard conduction resistance of the selected switch tube and the PN junction temperature of the device can be obtained first (as shown in Figure 3 ), and then the corresponding curve is converted into computer data table values and saved to the aforementioned memory, which can be obtained by table lookup in actual application. As shown in Figure 1 , after obtaining the conduction resistance of the lower tube VT4, the junction temperature of the lower tube VT4 can be obtained based on Figure 3The on-resistance and junction temperature characteristic curve shown is used to obtain the junction temperature of the lower transistor VT4 by table lookup or the like; after the on-resistance of the lower transistor VT6 is obtained, the junction temperature of the lower transistor VT6 can be obtained based on Figure 3 The on-resistance and junction temperature characteristic curve shown is used to obtain the junction temperature of the lower transistor VT6 by table lookup or the like; after the on-resistance of the lower transistor VT2 is obtained, the junction temperature of the lower transistor VT2 can be obtained based on Figure 3 The on-resistance and junction temperature characteristic curve shown is used to obtain the junction temperature of the lower transistor VT2 by table lookup or the like.

[0049] In the above embodiments, by obtaining the internal resistance voltage, i.e., the voltage drop of the transistor, and the on-current when the transistor is turned on, and by calculating the on-resistance of the transistor based on the on-current and the voltage drop, the junction temperature of the transistor can be accurately obtained by table lookup or the like based on the on-resistance, which can quickly respond to the internal temperature of the transistor compared to the junction temperature of the transistor obtained indirectly based on the space temperature radiation through the temperature resistance arranged aside, thereby facilitating accurate and reliable temperature protection of the transistor, and the method is simple and easy to implement in engineering applications.

[0050] In some embodiments of the present application, with reference to Figure 4 As shown, the foregoing step S10 can specifically include:

[0051] Step S11, determining the sampling time of the voltage drop and the sampling time of the phase current of the motor according to the on-time sequence of the transistors in the three-phase inverter bridge.

[0052] Specifically, the on-time sequence of the transistors determines the on-sequence of the transistors, and therefore the sampling time of the voltage drop and the sampling time of the phase current can be determined based on the on-time sequence.

[0053] In some embodiments of the present application, when a single resistance is used to detect the phase current of the motor, step S11 can specifically include: determining the first sampling window time, the second sampling window time and the third sampling window time according to the on-time sequence of the transistors in the three-phase inverter bridge. The first sampling window time is the time from when the lower transistors of the three-phase bridge arms are all turned on to when the upper transistor of any one of the three-phase bridge arms is turned on, the second sampling window time is the time from when the upper transistor of any one of the three-phase bridge arms is turned on and delayed for a first preset time to when the upper transistor of the next one of the three-phase bridge arms is turned on, and the third sampling window time is the time from when the upper transistor of the next one of the three-phase bridge arms is turned on and delayed for a first preset time to when the upper transistor of the last one of the three-phase bridge arms is turned on; at least two of the three sampling window times are used as the sampling time of the voltage drop and the sampling time of the phase current, or the third sampling window time is used as the sampling time of the voltage drop and the sampling time of the phase current.

[0054] Specifically, with reference to Figure 5aAs shown, corresponding to different PWM (Pulse Width Modulation) voltage vector moments U, PWM V, and PWM W, after avoiding current fluctuations caused by switching signal triggering, different acquisition signal moments appear. At the bottom of the triangular wave, the triangular wave timer will experience an underflow interrupt. At this time, PWM U, PWM V, and PWM W are all 0, the upper transistors VT1, VT3, and VT5 of the three-phase bridge arm are all off, and the lower transistors VT4, VT6, and VT2 of the three-phase bridge arm are all on. From this moment until any first turned-on upper transistor turns on (at... Figure 5a In the example shown, the upper tube VT1 of the U-phase bridge arm is the first upper tube to be turned on, and Ta is the turn-on time of the upper tube VT1 of the U-phase bridge arm. The time between these two points is the first sampling window time Ts1. The first sampling window time Ts1 = Ta - T. Since the sampling window time is timed by another timer, the initial time T = 0, that is, Ts1 = Ta.

[0055] After the first sampling window time Ts1 ends, the turn-on voltage vector changes. After avoiding the current fluctuation caused by the switching signal trigger, a second sampling window time Ts2 appears. This second sampling window time Ts2 is from the turn-on of any first turned-on upper transistor (in... Figure 5a In the example shown, the upper tube VT1 of the U-phase bridge arm is the first upper tube to be turned on, and after a first preset time Tdelay, the conduction begins until the second upper tube is turned on (in...). Figure 5a In the example shown, the upper tube VT3 of the V-phase bridge arm is the second upper tube to be turned on, and Tb is the time when the upper tube VT3 of the V-phase bridge arm is turned on. The second sampling window time Ts2 = Tb - Ta - Tdelay.

[0056] After the second sampling window time Ts2 ends, the turn-on voltage vector changes. After avoiding the current fluctuation caused by the switching signal trigger, a third sampling window time Ts3 occurs. This third sampling window time Ts3 is from the turn-on of the second turned-on upper transistor (in... Figure 5a In the example shown, the upper tube VT3 of the V-phase bridge arm is the second upper tube to be turned on, and the process begins after a first preset time Tdelay, until the last upper tube is turned on (in...). Figure 5a In the example shown, the upper tube VT5 of the W phase bridge arm is the last upper tube to be turned on, and Tc is the time when the upper tube VT5 of the W phase bridge arm is turned on. The third sampling window time Ts3 = Tc - Tb - Tdelay.

[0057] After the sampling window times Ts1, Ts2 and Ts3 are determined, two or three of the sampling window times (such as the sampling window times Ts1, Ts2 and Ts3, or the sampling window times Ts2 and Ts3, etc.) can be taken as the tube voltage drop sampling time and the phase current sampling time; or only the sampling window time Ts3 can be taken as the tube voltage drop sampling time and the phase current sampling time.

[0058] Step S12, voltage sampling and current sampling are respectively performed at the tube voltage drop sampling time and the phase current sampling time to obtain the tube voltage drop of the lower tube of the at least one phase bridge arm and the at least one phase current of the motor.

[0059] Specifically, after the tube voltage drop sampling time and the phase current sampling time are determined, voltage sampling can be performed at the tube voltage drop sampling time, and current sampling can be performed at the phase current sampling time. Figure 1 In the example shown, the voltage detection unit is correspondingly arranged at the two ends of the lower tube, and thus the tube voltage drop of the corresponding lower tube is obtained through voltage sampling; meanwhile, current sampling is performed at the phase current sampling time, and the current detection unit is correspondingly arranged at the negative pole of the DC bus, and thus the DC bus current is obtained through current sampling. Figure 1 In the example shown, the current detection unit is correspondingly arranged at the negative pole of the DC bus, and the sampled current is the DC bus current. Since the DC bus current is related to the phase current, which is determined by the conduction timing, that is, determined by the sector where the voltage vector is located, the corresponding phase current can be obtained based on the sector where the voltage vector is located after the DC bus current is sampled, for example, Table 1 shows the sector where the voltage vector is located, and the phase current corresponding to the DC bus current:

[0060] Table 1

[0061]

[0062]

[0063] In Table 1, UH represents the upper tube conduction of the U-phase bridge arm, VH represents the upper tube conduction of the V-phase bridge arm, and WH represents the upper tube conduction of the W-phase bridge arm, “1” represents conduction, and “0” represents disconnection. Idc is the DC bus current, Iu is the U-phase current, Iv is the V-phase current, and Iw is the W-phase current.

[0064] Step S13, determining the conduction current of the lower tube of the at least one phase bridge arm according to the at least one phase current of the motor.

[0065] Specifically, when a single resistor is used for phase current detection, two of the three phase currents of the motor can be obtained based on the sampled DC bus current through Table 1, and the third phase current can be calculated based on the single-resistor current reconstruction technology, that is, calculated according to the formula Iu+Iv+Iw=0, and then the conduction current of the lower tube can be obtained based on the phase current.

[0066] It should be noted that when the aforementioned sampling window times Ts1, Ts2, and Ts3 are used as the sampling times for tube voltage drop and phase current, the tube voltage drop and conduction current of the lower tube of each phase bridge arm can be determined based on the sampling results.

[0067] As a first example, determining the tube voltage drop and conduction current when the lower tube of each phase bridge arm is turned on includes: obtaining the tube voltage drop when the lower tube of each phase bridge arm is turned on during a first sampling window; obtaining the U-phase current and the tube voltage drop when the lower tube of the V-phase bridge arm and the lower tube voltage drop when the lower tube of the W-phase bridge arm is turned on during a second sampling window; obtaining the W-phase current or the V-phase current and the tube voltage drop when the lower tube of the W-phase bridge arm or the lower tube voltage drop when the lower tube of the V-phase bridge arm is turned on during a third sampling window; determining the V-phase current based on the U-phase current and the W-phase current, or determining the W-phase current based on the U-phase current and the V-phase current; and determining the conduction current when the lower tube of each phase bridge arm is turned on based on the U-phase current, the W-phase current, and the V-phase current.

[0068] Specifically, refer to Figure 5a As shown, within the first sampling window time Ts1, since the lower tubes VT4, VT6 and VT2 of the three-phase bridge arm are all turned on, the tube voltage drops of the lower tubes VT4, VT6 and VT2 can be collected simultaneously to obtain the tube voltage drops Vdsu, Vdsv and Vdsw. At the same time, the DC bus current Idc is 0 and the corresponding motor phase current is 0.

[0069] Within the second sampling window time Ts2, since the upper tube of one phase of the three-phase bridge arm is in a conducting state, and the lower tubes of the other two phases are in a conducting state, there is current in the DC bus. At this time, the phase current of the phase containing the upper tube can be obtained by sampling the DC bus current Idc, and the tube voltage drop of the lower tube can also be sampled. Figure 5a As shown, during the second sampling window time Ts2, the upper tube VT1 of the U-phase bridge arm is in the conducting state. Therefore, the U-phase current Iu can be obtained by sampling the DC bus current Idc. At the same time, the tube voltage drops Vdsv and Vdsw of the lower tubes VT6 and VT2 can be obtained by voltage sampling.

[0070] Within the third sampling window time Ts3, since the upper transistors of two phases of the three-phase bridge arm are in the conducting state, and the lower transistor of the other phase is in the conducting state, there is current in the DC bus. At this time, the phase current of the phase containing the lower transistor can be obtained by sampling the DC bus current Idc, and the transistor voltage drop of the lower transistor can also be sampled. Figure 5aAs shown, in the third sampling window time Ts3, the upper tube VT1 of the U-phase bridge arm and the upper tube VT3 of the V-phase bridge arm are both in the conducting state, so that the W-phase current Iw can be obtained by sampling the DC bus current Idc, and the tube voltage drop Vdsw of the lower tube VT2 can be obtained by voltage sampling; or, in the third sampling window time Ts3, the upper tube VT1 of the U-phase bridge arm and the upper tube VT5 of the W-phase bridge arm are both in the conducting state (not shown in the figure), so that the V-phase current IV can be obtained by sampling the DC bus current Idc, and the tube voltage drop Vdsv of the lower tube VT6 can be obtained by voltage sampling. That is, the second upper tube that is turned on can be the V-phase or the W-phase, and the corresponding phase current and tube voltage drop are different when different phases are turned on.

[0071] It should be noted that when the tube voltage drop sampling of the three lower tubes cannot be completed due to the short first sampling window time Ts1, the tube voltage drop sampling of the corresponding lower tube when turned on can be dispersed at the time of other vector occurrence according to the three-phase PWM turn-on relationship, i.e., the vector state. For example, the tube voltage drop Vdsu of the lower tube VT4 can be sampled in the first sampling window time Ts1, the tube voltage drop Vdsv of the lower tube VT6 can be sampled in the second sampling window time Ts2, and the tube voltage drop Vdsw of the lower tube VT2 can be sampled in the third sampling window time Ts3; or, the tube voltage drop Vdsu of the lower tube VT4 can be sampled in the first sampling window time Ts1, the tube voltage drop Vdsw of the lower tube VT2 can be sampled in the second sampling window time Ts2, and the tube voltage drop Vdsv of the lower tube VT6 can be sampled in the third sampling window time Ts3. Thus, the tube voltage drop of each lower tube can be obtained.

[0072] When the U-phase current Iu and the V-phase current Iv are obtained by the foregoing manner, the W-phase current Iw can be calculated based on the sum of the three-phase currents being zero, and when the U-phase current Iu and the W-phase current Iw are obtained by the foregoing manner, the V-phase current Iv can be calculated based on the sum of the three-phase currents being zero. After obtaining the U-phase current Iu, the V-phase current Iv, and the W-phase current Iw, the conducting current of the lower tube VT4 is Iu, the conducting current of the lower tube VT6 is Iv, and the conducting current of the lower tube VT2 is Iw.

[0073] As a second example, determining the voltage drop and conduction current of the lower tube of each phase bridge arm when it is turned on includes: obtaining the voltage drop of the lower tube of each phase bridge arm when it is turned on during a first sampling window; obtaining the V-phase current and the voltage drop of the lower tube of the U-phase bridge arm and the lower tube of the W-phase bridge arm when they are turned on during a second sampling window; obtaining the W-phase current or the U-phase current and the voltage drop of the lower tube of the W-phase bridge arm or the lower tube of the U-phase bridge arm when they are turned on during a third sampling window; determining the U-phase current based on the V-phase current and the W-phase current, or determining the W-phase current based on the V-phase current and the U-phase current; and determining the conduction current of each phase bridge arm when it is turned on based on the U-phase current, the W-phase current, and the V-phase current.

[0074] Specifically, refer to Figure 5b As shown, during the first sampling window time Ts1, since the lower transistors VT4, VT6, and VT2 of the three-phase bridge arm are all conducting, the voltage drops of VT4, VT6, and VT2 can be simultaneously sampled to obtain the voltage drops Vdsu, Vdsv, and Vdsw. At the same time, the DC bus current Idc is 0, and the corresponding motor phase current is 0. During the second sampling window time Ts2, the upper transistor VT3 of the V-phase bridge arm is conducting. Therefore, the V-phase current Iv can be obtained by sampling the DC bus current Idc, and the voltage drops Vdsu and Vdsw of the lower transistors VT4 and VT2 can be obtained by voltage sampling. During the third sampling window time Ts3, both the upper transistor VT1 of the U-phase bridge arm and the upper transistor VT3 of the V-phase bridge arm are in the on state. Therefore, the W-phase current Iw can be obtained by sampling the DC bus current Idc, and the voltage drop Vdsw of the lower transistor VT2 can be obtained by voltage sampling. Alternatively, during the third sampling window time Ts3, both the upper transistor VT3 of the V-phase bridge arm and the upper transistor VT5 of the W-phase bridge arm are in the on state (not shown in the figure). Therefore, the U-phase current Iu can be obtained by sampling the DC bus current Idc, and the voltage drop Vdsu of the lower transistor VT4 can be obtained by voltage sampling.

[0075] It should be noted that when the sampling of the tube voltage drop of the three lower tubes cannot be completed due to the short first sampling window time Ts1, the tube voltage drop sampling of the lower tube at the turn-on time of the corresponding vector can be performed at the time of occurrence of other vectors. For example, the tube voltage drop Vdsv of the lower tube VT6 can be sampled in the first sampling window time Ts1, the tube voltage drop Vdsu of the lower tube VT4 can be sampled in the second sampling window time Ts2, and the tube voltage drop Vdsw of the lower tube VT2 can be sampled in the third sampling window time Ts3; or the tube voltage drop Vdsv of the lower tube VT6 can be sampled in the first sampling window time Ts1, the tube voltage drop Vdsw of the lower tube VT2 can be sampled in the second sampling window time Ts2, and the tube voltage drop Vdsu of the lower tube VT4 can be sampled in the third sampling window time Ts3. Thus, the tube voltage drop of each lower tube is obtained.

[0076] When the V-phase current Iv and the W-phase current Iw are obtained by the foregoing manner, the U-phase current Iu can be calculated based on the sum of the three-phase currents being zero, and when the V-phase current Iv and the U-phase current Iu are obtained by the foregoing manner, the W-phase current Iw can be calculated based on the sum of the three-phase currents being zero. After the U-phase current Iu, the V-phase current Iv and the W-phase current Iw are obtained, the conduction current of the lower tube VT4 is Iv, the conduction current of the lower tube VT6 is Iv, and the conduction current of the lower tube VT2 is Iw.

[0077] As a third example, determining the tube voltage drop and the conduction current of the lower tube of each phase bridge arm includes: obtaining the tube voltage drop of the lower tube of each phase bridge arm in a first sampling window time; obtaining the W-phase current in a second sampling window time, and obtaining the tube voltage drop of the lower tube of the U-phase bridge arm and the tube voltage drop of the lower tube of the V-phase bridge arm; obtaining the U-phase current or the V-phase current in a third sampling window time, and obtaining the tube voltage drop of the lower tube of the U-phase bridge arm or the tube voltage drop of the lower tube of the V-phase bridge arm; determining the V-phase current according to the W-phase current and the U-phase current, or determining the U-phase current according to the W-phase current and the V-phase current; and determining the conduction current of the lower tube of each phase bridge arm according to the U-phase current, the W-phase current and the V-phase current.

[0078] Specifically, referring to Figure 5cAs shown, in the first sampling window time Ts1, since the lower tubes VT4, VT6 and VT2 of the three-phase bridge arm are all turned on, the tube voltage drops of the lower tubes VT4, VT6 and VT2 can be collected simultaneously to obtain the tube voltage drops Vdsu, Vdsv and Vdsw, while the DC bus current Idc is 0, and the phase current of the corresponding motor is 0. In the second sampling window time Ts2, the upper tube VT5 of the W-phase bridge arm is in the conducting state, so the W-phase current Iw can be obtained by sampling the DC bus current Idc, and the tube voltage drops Vdsu and Vdsv of the lower tubes VT4 and VT6 can be obtained by voltage sampling. In the third sampling window time Ts3, the upper tube VT3 of the V-phase bridge arm and the upper tube VT5 of the W-phase bridge arm are both in the conducting state, so the U-phase current Iu can be obtained by sampling the DC bus current Idc, and the tube voltage drop Vdsu of the lower tube VT4 can be obtained by voltage sampling; or, in the third sampling window time Ts3, the upper tube VT1 of the U-phase bridge arm and the upper tube VT5 of the W-phase bridge arm are both in the conducting state (not shown in the figure), so the V-phase current Iv can be obtained by sampling the DC bus current Idc, and the tube voltage drop Vdsv of the lower tube VT6 can be obtained by voltage sampling.

[0079] It should be noted that when the first sampling window time Ts1 is too short to complete the tube voltage drop sampling of the three lower tubes, the tube voltage drop sampling of the corresponding lower tube at the opening time can be dispersed at other vector occurrence times according to the three-phase PWM opening relationship, i.e., the vector state. For example, the tube voltage drop Vdsw of the lower tube VT2 can be sampled in the first sampling window time Ts1, the tube voltage drop Vdsv of the lower tube VT6 can be sampled in the second sampling window time Ts2, and the tube voltage drop Vdsu of the lower tube VT4 can be sampled in the third sampling window time Ts3; or, the tube voltage drop Vdsw of the lower tube VT2 can be sampled in the first sampling window time Ts1, the tube voltage drop Vdsu of the lower tube VT4 can be sampled in the second sampling window time Ts2, and the tube voltage drop Vdsv of the lower tube VT6 can be sampled in the third sampling window time Ts3. Thus, the tube voltage drops of each lower tube can be obtained.

[0080] When the U-phase current Iu and the W-phase current Iw are obtained by the foregoing manner, the V-phase current Iv can be calculated based on the sum of the three-phase currents being zero, and when the V-phase current Iv and the W-phase current Iw are obtained by the foregoing manner, the U-phase current Iu can be calculated based on the sum of the three-phase currents being zero. After obtaining the U-phase current Iu, the V-phase current Iv and the W-phase current Iw, the conducting current of the lower tube VT4 is Iu, the conducting current of the lower tube VT6 is Iv, and the conducting current of the lower tube VT2 is Iw.

[0081] Table 2 shows the relationship table of the sector where the voltage vector is located, the phase current corresponding to the DC bus current, and the tube voltage drop sampling of the lower tube that can be performed:

[0082] Table 2

[0083]

[0084]

[0085] It should be noted that when the foregoing third sampling window time Ts3 is taken as the tube voltage drop sampling moment and the phase current sampling moment, based on the sampling results, the tube voltage drop and the conduction current of the lower tube of one phase in the three phases can be determined. As shown in Figure 5a and Figure 5b , the tube voltage drop Vdsw and the conduction current of the lower tube VT2 of the W-phase bridge arm can be determined; as shown in Figure 5c , the tube voltage drop Vdsu and the conduction current of the lower tube VT4 of the U-phase bridge arm can be determined; and so on.

[0086] Next, a specific example is used to illustrate the process of obtaining the junction temperature of the lower tube.

[0087] Specifically, taking the first switching cycle shown in Figure 5a as an example, three sampling window times Ts1, Ts2 and Ts3 can be calculated based on the conduction timing first, where Ts1 = Ta-T, Ta is the conduction moment of the upper tube VT1 of the U-phase bridge arm, since the sampling window time is timed by another timer, therefore the initial time T = 0, that is, Ts1 = Ta; Ts2 = Tb-Ta-Tdelay, Tb is the conduction moment of the upper tube VT3 of the V-phase bridge arm, and Tdelay is the first preset time; Ts3 = Tb-Ta-Tdelay, Tc is the conduction moment of the upper tube VT5 of the W-phase bridge arm.

[0088] When the timer of the triangular wave overflows, i.e. PWM overflow interrupt starts, the first sampling window time Ts1 is entered, at this time the timing time of the sampling timer is set as Ta+Tdelay, and the sampling timer is started (the counting pulse of the sampling timer can be of the same frequency as the PWM pulse), and the sampling of the voltage drop of the lower tube is started, so as to sample the voltage drop of one or more lower tubes, for example, the voltage drops of the lower tubes VT4, VT6 and VT2 are sampled to obtain the voltage drops Vdsu, Vdsv and Vdsw, and are saved. When the timing time of the sampling timer reaches Ta+Tdelay, the second sampling window time Ts2 is entered, at this time the timing time of the sampling timer is set as Ts2+Tdelay, and the sampling timer is started, and the sampling of the voltage drops of the lower tubes VT6 and VT2 and the sampling of the DC bus current Idc are started, so as to obtain the voltage drops Vdsv and Vdsw of the lower tubes VT6 and VT2 and the U-phase current Iu, and save them. When the timing time of the sampling timer reaches Ts2+Tdelay, the third sampling window time Ts3 is entered, at this time the sampling of the voltage drop of the lower tube VT2 and the sampling of the DC bus current Idc are started, so as to obtain the voltage drop Vdsw of the lower tube VT2 and the W-phase current Iw, and save them. Thus, the sampling in a whole switching period is completed, and then the V-phase current Iv can be calculated according to Iu+Iv+Iw=0, so as to obtain the voltage drops Vdsu, Vdsv and Vdsw of the three lower tubes VT4, VT6 and VT2 when they are turned on, and the turn-on currents Iu, Iv and Iw, and then the turn-on resistances of the three lower tubes VT4, VT6 and VT2 are calculated according to the formula (1), and the junction temperatures of the three lower tubes VT4, VT6 and VT2 are obtained by looking up the table based on the turn-on resistances and the preset relationship curve between the turn-on resistances and the junction temperatures matched with the types of the lower tubes, thus the detection of the junction temperatures of the lower tubes in a period is completed.

[0089] It should be noted that the junction temperature detection processes of other switching periods are the same as that of the first switching period, which will not be described here in detail.

[0090] In the above embodiment, in the motor control process, the turn-on sequence is used to calculate the sampling window time in different voltage vector times, and the currents of the corresponding phases and the voltage drops of the lower tubes are sampled in the sampling window times, and the three-phase currents are restored in the case of single-resistance current sampling according to the characteristic that the phase currents are zero, and then the turn-on currents of the lower tubes are obtained according to the three-phase currents, and then the turn-on resistances are calculated according to the turn-on currents and the voltage drops, and the junction temperatures of the lower tubes are obtained according to the turn-on resistances and the relationship curve between the turn-on resistances and the junction temperatures. Since the current sampling period is short, the temperature change of the switching tube can be responded at high speed, so as to overcome the problems of slow response, poor precision and low reliability in the indirect acquisition of the junction temperature of the switching tube through the by-temperature resistance, and has high engineering application value.

[0091] It should be noted that, in order to comprehensively protect each switch tube, in the foregoing example, a corresponding voltage sampling unit is arranged for each lower tube, the tube voltage drop of the lower tube is sampled through the voltage sampling unit, and then the conduction resistance of each lower tube is obtained based on the tube voltage drop of each lower tube, and then the junction temperature of the lower tube is obtained, and the sampling form is not limited to the tube voltage drop sampling of all lower tubes, and the junction temperature of all lower tubes can also be determined by sampling the tube voltage drop of one lower tube or the tube voltage drop of two lower tubes to reduce the cost.

[0092] In some embodiments of the present application, after the lower tube junction temperature is determined, the switch tube junction temperature detection method can further include: performing inverse-time overload protection and / or instantaneous over-temperature protection according to the lower tube junction temperature.

[0093] It should be noted that the instantaneous over-temperature protection refers to a protection that is immediately performed when the junction temperature of the switch tube meets the over-temperature protection condition; the inverse-time overload protection refers to a protection that has different action time limits when the junction temperature of the switch tube meets the overload protection condition, wherein the higher the junction temperature, the shorter the action time limit, and the lower the junction temperature, the longer the action time limit. After the lower tube junction temperature is obtained, inverse-time overload protection and / or instantaneous over-temperature protection can be performed based on the lower tube junction temperature, and preferably both protections are performed at the same time.

[0094] In some embodiments, performing instantaneous over-temperature protection according to the lower tube junction temperature can include: when the lower tube junction temperature is greater than a preset maximum protection temperature (the preset maximum protection temperature can be set according to actual conditions, and can be determined according to the model of the switch tube), controlling the three-phase inverter bridge to stop outputting.

[0095] Specifically, after the lower tube junction temperature is obtained by the foregoing method, it is judged whether the lower tube junction temperature meets the over-temperature protection condition, such as whether the lower tube junction temperature is greater than or equal to the preset maximum protection temperature Tmax. If the lower tube junction temperature is greater than or equal to the preset maximum protection temperature Tmax, it means that the current junction temperature has reached the temperature limit that the switch tube can withstand, and if the switch tube continues to work, it may cause damage to the switch tube, at which time a protection action is immediately performed, that is, the control signal such as the PWM signal of the switch tube of the three-phase inverter bridge is immediately turned off to stop driving the switch tube to work, so that the three-phase inverter bridge stops working, thereby realizing instantaneous over-temperature protection of the three-phase inverter bridge, and over-temperature alarm can also be performed at the same time.

[0096] In some embodiments, performing inverse-time overload protection according to the lower tube junction temperature can include: determining an inverse-time protection curve, and performing overload protection timing according to the relationship between the lower tube junction temperature and the inverse-time protection curve; when the timing time arrives, controlling the three-phase inverter bridge to stop outputting. The timing time is inversely related to the lower tube junction temperature, that is, the higher the lower tube junction temperature, the shorter the timing time, and the lower the lower tube junction temperature, the longer the timing time.

[0097] Specifically, the inverse time protection curve can be determined according to the temperature characteristic point of the switch tube, for example, three alarm temperatures of a first alarm temperature Twarning1, a second alarm temperature Twarning2 and a third alarm temperature Twarning3 can be set based on the temperature characteristic point, the timing time corresponding to the first alarm temperature Twarning1 is 1 minute, the timing time corresponding to the second alarm temperature Twarning2 is 10 seconds, and the timing time corresponding to the third alarm temperature Twarning3 is 1 second, the timing time between the first alarm temperature Twarning1 and the second alarm temperature Twarning2 is less than 1 minute and greater than 10 seconds, the timing time between the second alarm temperature Twarning2 and the third alarm temperature Twarning3 is less than 10 seconds and greater than 1 second, and finally the inverse time protection curve as shown in FIG. 2 is formed. Figure 6

[0098] After obtaining the lower tube junction temperature Tj in the foregoing manner, the lower tube junction temperature Tj is judged, when the obtained lower tube junction temperature Tj is equal to the first alarm temperature Twarning1 in the inverse time protection curve, the overload protection timing of 1 minute is started, when the timing time reaches 1 minute, the protection action is performed, that is, the three-phase inverter bridge is controlled to be inoperative, and overload alarm reminding can also be performed.

[0099] When the obtained lower tube junction temperature Tj is greater than the first alarm temperature Twarning1 and less than the second alarm temperature Twarning2 in the inverse time protection curve, the corresponding timing time is obtained according to the lower tube junction temperature by table lookup (the inverse time protection curve can be converted into a relationship data table of lower tube junction temperature and timing time in advance, and the corresponding timing time is obtained by table lookup), the timing time is less than 1 minute and greater than 10 seconds, and the overload protection timing is started based on the timing time, when the timing time reaches, the protection action is performed, that is, the three-phase inverter bridge is controlled to be inoperative, and overload alarm reminding can also be performed.

[0100] When the obtained lower tube junction temperature Tj is equal to the second alarm temperature Twarning2, the overload protection timing of 10 seconds is started, when the timing time reaches 10 seconds, the protection action is performed, that is, the three-phase inverter bridge is controlled to be inoperative, and overload alarm reminding can also be performed.

[0101] ​When the obtained lower tube junction temperature Tj is greater than the second alarm temperature Twarning2 and less than the third alarm temperature Twarning3 in the inverse time protection curve, a corresponding timing time is obtained according to the lower tube junction temperature through a table lookup mode according to the inverse time protection curve, the timing time is less than 10 seconds and greater than 1 second, and an overload protection timing is started based on the timing time, and when the timing time reaches, a protection action is performed, that is, the three-phase inverter bridge is controlled to be inoperable, and an overload alarm reminder can also be performed.

[0102] When the obtained lower tube temperature Tj is equal to the third alarm temperature Twarning3, an overload protection timing of 1 second is started, and when the timing time reaches 1 second, a protection action is performed, that is, the three-phase inverter bridge is controlled to be inoperable, and an overload alarm reminder can also be performed.

[0103] It should be noted that if the lower tube temperature is not in the overload temperature range, that is, between the first alarm temperature Twarning1 and the third alarm temperature Twarning3, no protection action is performed, that is, after determining the time to temperature overload protection according to the obtained lower tube temperature and each alarm temperature, when the temperature is always in the overload temperature range and the delay time reaches, the overload protection is performed, and an overload alarm reminder can also be performed. In addition, the maximum alarm temperature corresponding to the inverse time overload protection is less than the preset maximum protection temperature corresponding to the instantaneous over-temperature protection, such as the third alarm temperature Twarning3 being less than the preset maximum protection temperature Tmax. It can be understood that the instantaneous over-temperature protection can also be regarded as a special case of the inverse time overload protection, and the corresponding timing time is 0 seconds.

[0104] It should be noted that in some embodiments, after obtaining the junction temperature of the lower tube, the junction temperature is also filtered, and then temperature protection is performed based on the junction temperature. Specifically, in actual application, due to the complex electromagnetic environment of the application itself, there may be signal noise and other interference burrs from space radiation and line conduction in the process of collecting tube voltage drop signals and motor phase current signals, which causes the junction temperature data to fluctuate up and down within a certain range. In order to ensure that the temperature protection action runs stably within the inverse time protection curve, that is, the protection value needs to be reasonably filtered, therefore, after obtaining the junction temperature of the lower tube, the junction temperature is also filtered, and then temperature protection is performed based on the junction temperature.

[0105] As a specific example, still taking Figure 5aThe example shown is an example. After obtaining the junction temperature of each lower tube VT4, VT6 and VT2, the junction temperature of each lower tube VT4, VT6 and VT2 is compared with the preset maximum protection temperature Tmax, and if the junction temperature of any one of the lower tubes VT4, VT6 and VT2 is greater than or equal to the preset maximum protection temperature Tmax, a protection action is immediately performed, that is, the three-phase inverter bridge is controlled to stop working, and an over-temperature alarm is given; and if the junction temperature of each lower tube VT4, VT6 and VT2 is less than the preset maximum protection temperature Tmax, overload protection is performed on each lower tube based on the inverse time protection curve. For example, when the junction temperature of the lower tube VT4 is equal to the first alarm temperature Twarning1, a 1-minute overload protection timing is started, and when the timing time reaches 1 minute, a protection action is performed, that is, the three-phase inverter bridge is controlled to stop working, and an overload alarm is given; when the junction temperature of the lower tube VT4 is greater than the first alarm temperature Twarning1 and less than the second alarm temperature Twarning2, the corresponding timing time is obtained by table lookup based on the inverse time protection curve, and when the timing time is reached, a protection action is performed and an overload alarm is given; and so on, which will not be listed here.

[0106] In the above embodiment, after obtaining the junction temperature of the lower tube, the inverse time overload protection and the instantaneous overload protection, that is, the highest temperature instantaneous protection, are performed based on the junction temperature, which can effectively avoid damage of the three-phase inverter bridge due to excessive temperature, and realize reliable temperature protection of the three-phase inverter bridge.

[0107] In summary, according to the switch tube junction temperature detection method of the embodiment of the present application, the current time-sharing sampling technology is used to share the temperature detection and protection of multiple phases at the same time, which has the characteristics of fast and efficient detection of the internal temperature, that is, the junction temperature, of each lower tube, small temperature deviation and fast reaction speed, overcomes the problems of slow reaction, poor precision and low reliability in indirectly obtaining the junction temperature of the switch tube through the by-temperature resistance, and has the advantages of simple method, easy implementation and high engineering application value.

[0108] In some embodiments of the present application, a motor controller is provided, which includes a processor, a memory, and a switch tube junction temperature detection program stored in the memory and executable on the processor. When the processor executes the program, the switch tube junction temperature detection method described above is realized.

[0109] The motor controller according to the embodiment of the present application, based on the foregoing switch tube junction temperature detection method, shares the temperature detection and protection of multiple phases at the same time through the current time-sharing sampling technology, has the characteristics of fast and efficient detection of the internal temperature, i.e. the junction temperature, of each lower tube, has small temperature deviation and fast reaction speed, overcomes the problems of slow reaction, poor precision and low reliability in indirectly obtaining the junction temperature of the switch tube through the by-located temperature resistance, and has simple method, easy implementation and high engineering application value.

[0110] In some embodiments of the present application, a computer readable storage medium is provided, which stores a switch tube junction temperature detection program, and the program is executed by a processor to implement the foregoing switch tube junction temperature detection method.

[0111] The computer readable storage medium according to the embodiment of the present application, based on the foregoing switch tube junction temperature detection method, shares the temperature detection and protection of multiple phases at the same time through the current time-sharing sampling technology, has the characteristics of fast and efficient detection of the internal temperature, i.e. the junction temperature, of each lower tube, has small temperature deviation and fast reaction speed, overcomes the problems of slow reaction, poor precision and low reliability in indirectly obtaining the junction temperature of the switch tube through the by-located temperature resistance, and has simple method, easy implementation and high engineering application value.

[0112] In some embodiments of the present application, a motor control system is also provided, as shown in Figure 1 , the motor control system comprises a motor (not shown in the figure), a three-phase inverter bridge 10, a current detection unit 20, a first voltage detection unit 30, a second voltage detection unit 40, a third voltage detection unit 50 and a control unit (not specifically shown in the figure).

[0113] The three-phase inverter bridge 10 is connected between the DC bus and drives the motor to work; the current detection unit 20 is arranged corresponding to the negative pole of the DC bus and is used for detecting the DC bus current; the first voltage detection unit 30 is arranged corresponding to the lower tube of the U-phase bridge arm in the three-phase inverter bridge 10 and is used for detecting the voltage drop of the lower tube of the U-phase bridge arm, i.e. the voltage drop of the lower tube VT4; the second voltage detection unit 40 is arranged corresponding to the lower tube of the V-phase bridge arm in the three-phase inverter bridge 10 and is used for detecting the voltage drop of the lower tube of the V-phase bridge arm, i.e. the voltage drop of the lower tube VT6; the third voltage detection unit 50 is arranged corresponding to the lower tube of the W-phase bridge arm in the three-phase inverter bridge 10 and is used for detecting the voltage drop of the lower tube of the W-phase bridge arm, i.e. the voltage drop of the lower tube VT2; the control unit is used for determining the conduction current of the lower tube of at least one phase bridge arm when the lower tube is turned on, obtaining the tube voltage drop of the lower tube of at least one phase bridge arm when the lower tube is turned on, determining the conduction resistance of the lower tube of at least one phase bridge arm when the lower tube is turned on according to the tube voltage drop and the conduction current, and determining the junction temperature of the lower tube of at least one phase bridge arm according to the conduction resistance.

[0114] According to one embodiment of the present application, the control unit is specifically configured to: determine the sampling time of the tube voltage drop and the sampling time of the phase current of the motor according to the conduction sequence of the switch tube in the three-phase inverter bridge; perform voltage sampling and current sampling at the sampling time of the tube voltage drop and the sampling time of the phase current of the motor respectively, to obtain the tube voltage drop of the lower tube conduction time of at least one phase arm and the at least one phase current of the motor; and determine the conduction current of the lower tube conduction time of at least one phase arm according to the at least one phase current of the motor.

[0115] According to one embodiment of the present application, the control unit is specifically configured to: determine the first sampling window time, the second sampling window time and the third sampling window time according to the conduction sequence of the switch tube in the three-phase inverter bridge, wherein the first sampling window time is the time from the start of the lower tube conduction of the three-phase arm to the upper tube conduction time of any one phase arm in the three-phase arm, the second sampling window time is the time from the start of the upper tube conduction of any one phase arm in the three-phase arm after a first preset time to the upper tube conduction time of the next phase arm in the three-phase arm, and the third sampling window time is the time from the start of the upper tube conduction of the next phase arm in the three-phase arm after a first preset time to the upper tube conduction time of the last phase arm in the three-phase arm; use at least two of the first sampling window time, the second sampling window time and the third sampling window time as the sampling time of the tube voltage drop and the sampling time of the phase current, or use the third sampling window time as the sampling time of the tube voltage drop and the sampling time of the phase current.

[0116] According to one embodiment of the present application, when the control unit uses the first sampling window time, the second sampling window time and the third sampling window time as the sampling time of the tube voltage drop and the sampling time of the phase current, the control unit determines the tube voltage drop and the conduction current of the lower tube conduction time of each phase arm in the three-phase inverter bridge.

[0117] According to one embodiment of the present application, the control unit is specifically configured to: obtain the tube voltage drop of the lower tube conduction time of each phase arm in the first sampling window time; obtain the U-phase current, the tube voltage drop of the lower tube conduction time of the V-phase arm and the tube voltage drop of the lower tube conduction time of the W-phase arm in the second sampling window time; obtain the W-phase current or the V-phase current and the tube voltage drop of the lower tube conduction time of the W-phase arm or the tube voltage drop of the lower tube conduction time of the V-phase arm in the third sampling window time; determine the V-phase current according to the U-phase current and the W-phase current, or determine the W-phase current according to the U-phase current and the V-phase current; and determine the conduction current of the lower tube conduction time of each phase arm according to the U-phase current, the W-phase current and the V-phase current.

[0118] According to another embodiment of the present application, the control unit is specifically configured to: obtain the voltage drop of the lower tube of each phase bridge arm when the lower tube is turned on within a first sampling window time; obtain the V-phase current, and obtain the voltage drop of the lower tube of the U-phase bridge arm and the voltage drop of the lower tube of the W-phase bridge arm within a second sampling window time; obtain the W-phase current or the U-phase current, and obtain the voltage drop of the lower tube of the W-phase bridge arm or the voltage drop of the lower tube of the U-phase bridge arm within a third sampling window time; determine the U-phase current according to the V-phase current and the W-phase current, or determine the W-phase current according to the V-phase current and the U-phase current; and determine the conduction current of the lower tube of each phase bridge arm according to the U-phase current, the W-phase current and the V-phase current.

[0119] According to another embodiment of the present application, the control unit is specifically configured to: obtain the voltage drop of the lower tube of each phase bridge arm when the lower tube is turned on within a first sampling window time; obtain the W-phase current, and obtain the voltage drop of the lower tube of the U-phase bridge arm and the voltage drop of the lower tube of the V-phase bridge arm within a second sampling window time; obtain the U-phase current or the V-phase current, and obtain the voltage drop of the lower tube of the U-phase bridge arm or the voltage drop of the lower tube of the V-phase bridge arm within a third sampling window time; determine the V-phase current according to the W-phase current and the U-phase current, or determine the U-phase current according to the W-phase current and the V-phase current; and determine the conduction current of the lower tube of each phase bridge arm according to the U-phase current, the W-phase current and the V-phase current.

[0120] According to an embodiment of the present application, the control unit is further configured to: perform instantaneous over-temperature protection and inverse-time overload protection according to the junction temperature of the lower tube.

[0121] According to an embodiment of the present application, the control unit is specifically configured to: control the three-phase inverter bridge to stop output when the junction temperature of the lower tube is greater than a preset maximum protection temperature.

[0122] According to an embodiment of the present application, the control unit is specifically configured to: determine an inverse-time protection curve, and perform overload protection timing according to the relationship between the junction temperature of the lower tube and the inverse-time protection curve; and control the three-phase inverter bridge to stop output when the timing time arrives.

[0123] According to an embodiment of the present application, the timing time is inversely related to the junction temperature of the lower tube.

[0124] It should be noted that the description of the motor control system of the present application can refer to the description of the switching tube junction temperature detection method in the present application, and will not be repeated here.

[0125] The motor control system according to the embodiment of the present application shares the temperature detection and protection of multiple phases at the same time through the current time-sharing sampling technology, has the characteristics of fast and efficient detection of the internal temperature, i.e. the junction temperature, of each lower tube, has the characteristics of small temperature deviation and fast reaction speed, overcomes the problems of slow reaction, poor precision and low reliability in the indirect acquisition of the junction temperature of the switching tube through the by-located temperature resistance, and has a simple method, easy implementation and high engineering application value.

[0126] It should be noted that the logic and / or steps represented in the flowcharts or otherwise described herein, for example, can be considered as a list of executable instructions for implementing logic functions, and can be embodied in any computer-readable medium for use by or in connection with an instruction execution system, apparatus or device, such as a computer-based system, a system including a processor or other system that can fetch the instructions from the instruction execution system, apparatus or device and execute the instructions, or in conjunction with these instruction execution systems, apparatus or devices. For the purpose of this specification, "computer-readable medium" can be any device that can contain, store, communicate, propagate or transport a program for use by or in connection with an instruction execution system, apparatus or device, or in conjunction with these instruction execution systems, apparatus or devices. More specific examples (non-exhaustive list) of computer-readable medium include the following: electrical connections having one or more wires (electronic devices), portable computer diskette (magnetic devices), random access memory (RAM), read-only memory (ROM), erasable programmable read-only memory (EPROM or flash memory), fiber optic devices, and portable compact disc read-only memory (CDROM). In addition, the computer-readable medium can even be paper or other suitable medium on which the program can be printed, as the program can be electronically obtained, for example, by optical scanning of the paper or other medium, followed by electronic conversion, interpretation or processing, if necessary, in other suitable manner, and then stored in a computer memory.

[0127] It should be understood that parts of the present application can be realized in hardware, software, firmware or a combination thereof. In the above-described embodiments, a plurality of steps or methods can be realized by software or firmware stored in a memory and executed by a suitable instruction execution system. For example, if realized in hardware, and as in another embodiment, any one or a combination of the following technologies known in the art can be used: discrete logic circuit with logic gate circuit for implementing logic functions on data signals, application specific integrated circuit with suitable combination logic gate circuit, programmable gate array (PGA), field programmable gate array (FPGA), etc.

[0128] In the description of the specification, the description of the terms "one embodiment", "some embodiments", "an example", "a specific example", or "some examples" etc. means that the specific features, structures, materials or characteristics described in connection with the embodiment or example are included in at least one embodiment or example of the present application. In the specification, the illustrative description of the above terms does not necessarily mean the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described can be combined in any one or more embodiments or examples in a suitable manner.

[0129] In addition, the terms "first", "second" are only for descriptive purposes, and cannot be understood as indicating or implying relative importance or implicitly indicating the number of the technical features indicated. Therefore, the features defined with "first", "second" can explicitly or implicitly include at least one of the features. In the description of the present application, the meaning of "a plurality of" is at least two, for example, two, three, etc., unless otherwise explicitly specified and limited.

[0130] In the present application, unless otherwise explicitly specified and limited, the terms "mounting", "connection", "connection", "fixing" and other terms should be understood in a broad sense, for example, can be fixedly connected, can also be detachably connected, or integrated; can be mechanically connected, can also be electrically connected; can be directly connected, can also be indirectly connected through an intermediate medium, can be the internal communication of two elements or the interaction relationship between two elements, unless otherwise explicitly limited. For those skilled in the art, the specific meaning of the above terms in the present application can be understood according to the specific circumstances.

[0131] Although the embodiments of the present application have been shown and described above, it can be understood that the above embodiments are exemplary and cannot be understood as limiting the present application, and those skilled in the art can make changes, modifications, replacements and variations to the above embodiments within the scope of the present application.

Claims

1. A method for detecting the junction temperature of a switching transistor in a motor control system, characterized in that, The motor control system includes a three-phase inverter bridge for driving the motor, and the method includes: Determine the voltage drop and conduction current of at least one phase arm of the three-phase inverter bridge when the lower tube is turned on; The on-resistance when the lower tube of at least one phase bridge arm is turned on is determined based on the tube voltage drop and the on-current. The lower junction temperature of the at least one phase bridge arm is determined based on the on-resistance. Determining the voltage drop and on-current of the lower transistor in at least one phase arm of the three-phase inverter bridge when it is turned on includes: The sampling time of the tube voltage drop and the sampling time of the motor phase current are determined based on the conduction sequence of the switching tubes in the three-phase inverter bridge. Voltage sampling and current sampling are performed at the sampling time of the tube voltage drop and the sampling time of the motor phase current, respectively, to obtain the tube voltage drop when the lower tube of the at least one phase bridge arm is turned on and the phase current of the at least one phase of the motor. The conduction current when the lower tube of the at least one phase bridge arm is turned on is determined based on the phase current of at least one phase of the motor. When using a single resistor for motor phase current detection, the sampling time for the voltage drop of the transistor and the sampling time for the motor phase current are determined based on the conduction sequence of the switching transistors in the three-phase inverter bridge, including: The first sampling window time, the second sampling window time, and the third sampling window time are determined based on the conduction timing of the switching transistors in the three-phase inverter bridge. The first sampling window time is the time from when all the lower transistors of the three-phase bridge arms in the three-phase inverter bridge are turned on until when the upper transistor of any one phase bridge arm in the three-phase inverter bridge is turned on. The second sampling window time is the time from when the upper transistor of any one phase bridge arm in the three-phase inverter bridge is turned on and delayed by a first preset time until when the upper transistor of the next phase bridge arm in the three-phase inverter bridge is turned on. The third sampling window time is the time from when the upper transistor of the next phase bridge arm in the three-phase inverter bridge is turned on and delayed by a first preset time until when the upper transistor of the last phase bridge arm in the three-phase inverter bridge is turned on. At least two of the first sampling window time, the second sampling window time, and the third sampling window time are used as the sampling time for the tube voltage drop and the sampling time for the phase current, or the third sampling window time is used as the sampling time for the tube voltage drop and the sampling time for the phase current.

2. The method according to claim 1, characterized in that, By using the first sampling window time, the second sampling window time, and the third sampling window time as the sampling time for the tube voltage drop and the phase current, the tube voltage drop and conduction current of each phase arm in the three-phase inverter bridge when the lower tube is turned on are determined.

3. The method according to claim 2, characterized in that, Determining the voltage drop and conduction current of the lower transistor in each phase arm of the three-phase inverter bridge when it is turned on includes: Within the first sampling window time, the tube voltage drop when the lower tube of each phase bridge arm is turned on is obtained; During the second sampling window, the U-phase current is obtained, and the voltage drop across the lower tube of the V-phase bridge arm and the voltage drop across the lower tube of the W-phase bridge arm are obtained when the lower tube is turned on. During the third sampling window, the W-phase current or V-phase current is obtained, and the voltage drop across the lower tube of the W-phase bridge arm or the voltage drop across the lower tube of the V-phase bridge arm when it is turned on is obtained. The V-phase current is determined based on the U-phase current and the W-phase current, or the W-phase current is determined based on the U-phase current and the V-phase current. The conduction current when the lower tube of each phase bridge arm is turned on is determined based on the U-phase current, the W-phase current, and the V-phase current.

4. The method according to claim 2, characterized in that, Determining the voltage drop and conduction current of the lower transistor in each phase arm of the three-phase inverter bridge when it is turned on includes: Within the first sampling window time, the tube voltage drop when the lower tube of each phase bridge arm is turned on is obtained; During the second sampling window, the V-phase current is obtained, and the voltage drop across the U-phase bridge arm when the lower tube is turned on and the voltage drop across the W-phase bridge arm when the lower tube is turned on are obtained. During the third sampling window, the W-phase current or U-phase current is obtained, and the voltage drop across the lower tube of the W-phase bridge arm or the voltage drop across the lower tube of the U-phase bridge arm when it is turned on is obtained. The U-phase current is determined based on the V-phase current and the W-phase current, or the W-phase current is determined based on the V-phase current and the U-phase current. The conduction current when the lower tube of each phase bridge arm is turned on is determined based on the U-phase current, the W-phase current, and the V-phase current.

5. The method according to claim 2, characterized in that, Determining the voltage drop and conduction current of the lower transistor in each phase arm of the three-phase inverter bridge when it is turned on includes: Within the first sampling window time, the tube voltage drop when the lower tube of each phase bridge arm is turned on is obtained; During the second sampling window, the W-phase current is obtained, and the voltage drop across the U-phase bridge arm when the lower tube is turned on and the voltage drop across the V-phase bridge arm when the lower tube is turned on are obtained. During the third sampling window, the U-phase current or V-phase current is obtained, and the voltage drop across the lower tube of the U-phase bridge arm or the voltage drop across the lower tube of the V-phase bridge arm when it is turned on is obtained. The V-phase current is determined based on the W-phase current and the U-phase current, or the U-phase current is determined based on the W-phase current and the V-phase current. The conduction current when the lower tube of each phase bridge arm is turned on is determined based on the U-phase current, the W-phase current, and the V-phase current.

6. The method according to any one of claims 1-5, characterized in that, After determining the junction temperature of the lower tube, the method further includes: Instantaneous over-temperature protection and inverse-time overload protection are performed based on the lower tube junction temperature.

7. The method according to claim 6, characterized in that, Instantaneous over-temperature protection based on the lower tube junction temperature includes: When the junction temperature of the lower tube exceeds the preset maximum protection temperature, the three-phase inverter bridge is controlled to stop outputting.

8. The method according to claim 6, characterized in that, Inverse-time overload protection based on the lower tube junction temperature includes: Determine the inverse time protection curve and perform overload protection timing based on the relationship between the lower tube junction temperature and the inverse time protection curve; When the timer expires, the three-phase inverter bridge is controlled to stop outputting.

9. The method according to claim 8, characterized in that, The timing interval is inversely correlated with the junction temperature of the lower tube.

10. A motor controller, characterized in that, The method includes a memory, a processor, and a switching transistor junction temperature detection program stored in the memory and executable on the processor. When the processor executes the switching transistor junction temperature detection program, it implements the switching transistor junction temperature detection method in the motor control system according to any one of claims 1-9.

11. A computer-readable storage medium, characterized in that, It stores a junction temperature detection program for a switching transistor in a motor control system. When the processor executes the junction temperature detection program for a switching transistor in a motor control system, it implements the junction temperature detection method for a switching transistor in a motor control system according to any one of claims 1-9.

12. A motor control system, characterized in that, include: Electric motor; A three-phase inverter bridge is connected between DC buses and drives the motor to work. A current detection unit is provided, which is set to the negative terminal of the DC bus and is used to detect the DC bus current. The first voltage detection unit is configured on the lower tube of the U-phase bridge arm in the three-phase inverter bridge to detect the voltage drop of the lower tube of the U-phase bridge arm. The second voltage detection unit is configured on the lower tube of the V-phase bridge arm in the three-phase inverter bridge to detect the voltage drop of the lower tube of the V-phase bridge arm. The third voltage detection unit is set on the lower tube of the W-phase bridge arm in the three-phase inverter bridge to detect the voltage drop of the lower tube of the W-phase bridge arm. The control unit is configured to determine the conduction current when the lower tube of at least one phase arm of the three-phase inverter bridge is turned on based on the DC bus current, and to obtain the tube voltage drop when the lower tube of at least one phase arm of the three-phase inverter bridge is turned on, and to determine the conduction resistance when the lower tube of at least one phase arm is turned on based on the tube voltage drop and the conduction current, and to determine the junction temperature of the lower tube of at least one phase arm based on the conduction resistance. Determining the voltage drop and on-state current of the lower transistor of at least one phase arm in the three-phase inverter bridge when it is turned on includes: determining the sampling time of the voltage drop and the sampling time of the phase current of the motor according to the turn-on sequence of the switching transistors in the three-phase inverter bridge; performing voltage sampling and current sampling at the sampling time of the voltage drop and the sampling time of the phase current of the motor respectively to obtain the voltage drop and the phase current of at least one phase of the motor when the lower transistor of the at least one phase arm is turned on; and determining the on-state current of the lower transistor of the at least one phase arm when it is turned on based on the phase current of the at least one phase of the motor. When using a single resistor for motor phase current detection, the sampling time of the transistor voltage drop and the sampling time of the motor phase current are determined according to the conduction sequence of the switching transistors in the three-phase inverter bridge. This includes determining a first sampling window time, a second sampling window time, and a third sampling window time based on the conduction sequence of the switching transistors in the three-phase inverter bridge. The first sampling window time is the time from when all the lower transistors of the three phase arms of the three-phase inverter bridge are turned on until the upper transistor of any one phase arm of the three-phase inverter bridge is turned on. The second sampling window time is the time from when the upper transistor of any one phase arm of the three-phase inverter bridge is turned on. The third sampling window time is the time from the start of the conduction and delay of a first preset time until the upper tube of the next phase arm of the three-phase inverter bridge is turned on. The third sampling window time is the time from the start of the conduction and delay of a first preset time of the upper tube of the next phase arm of the three-phase inverter bridge until the upper tube of the last phase arm of the three-phase inverter bridge is turned on. At least two of the first sampling window time, the second sampling window time and the third sampling window time are used as the sampling time of the tube voltage drop and the sampling time of the phase current, or the third sampling window time is used as the sampling time of the tube voltage drop and the sampling time of the phase current.

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