Three-level inverter control method, device, storage medium and new energy vehicle

Abstract

The application discloses a three-level inverter control method, device, storage medium and new energy vehicle, and relates to the technical field of new energy vehicles. The method comprises the following steps: acquiring the rotating speed and actual torque of a motor; if it is determined that the motor enters a locked-rotor working condition according to the rotating speed and the actual torque, injecting a pulse-vibration common-mode voltage into an original PWM control signal of a three-level inverter to generate a PWM wave signal, and controlling the working of the three-level inverter based on the PWM wave signal; wherein the PWM wave signal is used to control different part power devices of the three-level inverter to alternately bear phase currents without changing the actual torque and phase current amplitude of the motor. In this way, the application controls the different part power devices of the three-level inverter to alternately bear the phase currents, realizes the thermal load balance of the power devices in the locked-rotor working condition, and thus improves the locked-rotor capacity of the electric drive system.

Description

Technical Field

[0001] This application relates to the field of new energy vehicle technology, and in particular to a three-level inverter control method, device, storage medium, and new energy vehicle. Background Technology

[0002] Driven by the need for shorter charging times and increased electric drive power in new energy vehicles, electric drive systems with voltage levels exceeding 1200V are being developed. The topology of three-level inverters makes the withstand voltage stress of power devices half that of two-level inverters, leading mainstream automakers to begin applying three-level inverters to electric drives.

[0003] However, existing three-level inverter topologies still have significant limitations in practical applications. The conduction state of their power devices is highly correlated with the output duty cycle: when the duty cycle is positive, a specific group of power devices is continuously conducting; when the duty cycle is negative, another group of power devices takes over the conduction task. Under normal motor rotation conditions, as the rotor position changes, the power devices of each bridge arm can alternately share the current, achieving a relatively balanced heat distribution. However, under stall conditions, because the motor's mechanical angle remains stationary, the corresponding voltage space vector distribution is fixed, causing the inverter output duty cycle to remain constant at a positive or negative value. This state results in the stall current being continuously conducted by a single group of power devices for a long time, causing severe heat accumulation in those devices, while other power devices remain idle. This extreme concentration of heat load greatly limits the motor system's continuous stall capability and overall reliability.

[0004] The above content is only used to help understand the technical solution of this application and does not represent an admission that the above content is prior art. Summary of the Invention

[0005] The main objective of this application is to provide a three-level inverter control method, which aims to solve the technical problem that in existing three-level inverters, severe heat accumulation in some power devices under motor stall conditions limits the motor's stall capability.

[0006] To achieve the above objectives, the three-level inverter control method proposed in this application is applied to a new energy vehicle electric drive system, which includes a motor and a three-level inverter for driving the motor. The method includes: Obtain the motor's rotational speed and actual torque; If the motor is determined to be in a stalled state based on the speed and actual torque, a pulsed common-mode voltage injection is performed on the original PWM control signal of the three-level inverter to generate a PWM wave signal, and the operation of the three-level inverter is controlled based on the PWM wave signal; wherein, the PWM wave signal is used to control different power devices of the three-level inverter to alternately bear the phase current without changing the actual torque and phase current amplitude of the motor.

[0007] In one embodiment, the method further includes, prior to pulsating common-mode voltage injection: Based on the direct-axis voltage and quadrature-axis voltage under the current stall condition, calculate the stator phase voltage amplitude of the motor under the current stall condition; Obtain the DC bus voltage of the three-level inverter, and calculate the maximum common-mode voltage duty cycle that can be injected under the current voltage space based on the stator phase voltage amplitude and the DC bus voltage; The pulsed common-mode voltage is generated based on the maximum common-mode voltage duty cycle allowed to be injected in the current voltage space and the current square wave frequency.

[0008] In one embodiment, the formula for calculating the stator phase voltage amplitude includes: ; in, The stator phase voltage amplitude, The direct-axis voltage, The quadrature-axis voltage; and / or The formula for calculating the maximum common-mode voltage duty cycle allowed to be injected under the current voltage space includes: ; in, This represents the stator phase voltage amplitude under the current stalled rotor condition. The DC bus voltage This is the maximum common-mode voltage duty cycle that can be injected under the current voltage space.

[0009] In one embodiment, before calculating the stator phase voltage amplitude of the motor under the current stall condition based on the direct-axis voltage and quadrature-axis voltage under the current stall condition, the method further includes: The direct-axis current, quadrature-axis current, and offline parameters of the motor under the current stall condition are obtained, and the direct-axis voltage and quadrature-axis voltage are determined based on the direct-axis current, the quadrature-axis current, and the offline parameters of the motor. The offline parameters of the motor include electrical angular velocity, equivalent direct-axis inductance, equivalent quadrature-axis inductance, equivalent rotor permanent magnet flux linkage, and stator phase resistance.

[0010] In one embodiment, the formula for calculating the direct-axis voltage includes: ; in, The direct-axis voltage, This represents the direct-axis current under the current stall condition. The stator phase resistance. The electric angular velocity under the current stall condition. The equivalent quadrature-axis inductance under the current stall condition, The quadrature-axis current under the current stall condition; and / or The formula for calculating the quadrature-axis voltage includes: ; in, The quadrature-axis voltage, This represents the quadrature-axis current under the current stall condition. The stator phase resistance. The electric angular velocity under the current stall condition. This is the equivalent direct-axis inductance under the current stall condition. This represents the direct-axis current under the current stall condition. This refers to the equivalent rotor permanent magnet flux linkage under the current stall condition.

[0011] In one embodiment, determining that the motor has entered a stall condition based on the rotational speed and the torque includes: When the absolute value of the rotational speed is less than a preset rotational speed threshold for a first duration exceeding a first preset time threshold, and the absolute value of the actual torque is greater than a preset torque threshold for a second duration exceeding a second preset time threshold, the motor is determined to have entered a stall condition.

[0012] In one embodiment, before generating the pulsed common-mode voltage based on the maximum common-mode voltage duty cycle allowed to be injected in the current voltage space and the current square wave frequency, the method further includes: The thermal time constant of the power device of the three-level inverter is obtained, and the current square wave frequency is determined based on the thermal time constant of the power device of the three-level inverter.

[0013] This application also proposes a storage medium, which is a computer-readable storage medium, on which a computer program is stored, and when the computer program is executed by a processor, it implements the steps of the three-level inverter control method described above.

[0014] This application also proposes a three-level inverter control device, the device comprising: a memory, a processor, and a computer program stored in the memory and executable on the processor, the computer program being configured to implement the steps of the three-level inverter control method described above.

[0015] This application also proposes a new energy vehicle, including an electric motor and a three-level inverter for driving the electric motor, as well as a three-level inverter control device as described above.

[0016] This application employs a three-level inverter control method applied to a new energy vehicle electric drive system. The new energy vehicle electric drive system includes a motor and a three-level inverter for driving the motor. The method includes: acquiring the motor's rotational speed and actual torque; if the motor is determined to be in a stalled state based on the rotational speed and actual torque, then injecting pulsed common-mode voltage into the original PWM control signal of the three-level inverter to generate a PWM wave signal, and controlling the operation of the three-level inverter based on the PWM wave signal; wherein the PWM wave signal is used to control different power devices of the three-level inverter to alternately bear the phase current without changing the actual torque and phase current amplitude of the motor. Thus, this application achieves thermal load balancing of the power devices under stalled conditions by controlling different power devices of the three-level inverter to alternately bear the phase current, thereby improving the stall capability of the electric drive system. Attached Figure Description

[0017] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on the structures shown in these drawings without creative effort.

[0018] Figure 1 A schematic diagram of the structure of the first embodiment of the three-level inverter control method provided in this application; Figure 2 A schematic diagram of the structure of the second embodiment of the three-level inverter control method provided in this application; Figure 3 This is a schematic diagram of the structure of the third embodiment of the three-level inverter control method provided in this application; Figure 4 A PWM waveform generation diagram for a three-level inverter control method according to an embodiment of this application; Figure 5 An electronic circuit diagram of a three-level inverter according to an embodiment provided in this application; Figure 6 A three-phase duty cycle waveform after pulsed common-mode voltage injection is provided in an embodiment of this application; Figure 7 A waveform diagram of the upper and lower bridge internal transistors after pulsed common-mode voltage injection according to an embodiment provided in this application; Figure 8 This application provides the waveforms of the upper and lower bridge internal transistor currents and phase currents after the injection of pulsed common-mode voltages of different amplitudes; Figure 9 A schematic diagram of the structure of a three-level inverter control device according to an embodiment of this application.

[0019] The realization of the purpose, functional features and advantages of this application will be further explained in conjunction with the embodiments and with reference to the accompanying drawings. Detailed Implementation

[0020] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of this application, and not all of the embodiments. Based on the embodiments of this application, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of this application.

[0021] It should be noted that all directional indicators (such as up, down, left, right, front, back, etc.) in the embodiments of this application are only used to explain the relative positional relationship and movement of each component in a certain specific posture (as shown in the figure). If the specific posture changes, the directional indicator will also change accordingly.

[0022] Furthermore, the use of terms such as "first" and "second" in this application is for descriptive purposes only and should not be construed as indicating or implying their relative importance or implicitly specifying the number of technical features indicated. Therefore, a feature defined as "first" or "second" may explicitly or implicitly include at least one of that feature. Additionally, the technical solutions of the various embodiments can be combined with each other, but only on the basis of being achievable by those skilled in the art. When the combination of technical solutions is contradictory or impossible to implement, such a combination of technical solutions should be considered non-existent and not within the scope of protection claimed in this application.

[0023] The existing three-level inverter topology still has significant limitations in practical applications. The conduction state of its power devices is highly correlated with the output duty cycle: when the duty cycle is positive, a specific group of power devices is continuously conducting; when the duty cycle is negative, another group of power devices takes over the conduction task. Under normal motor rotation conditions, as the rotor position changes, the power devices of each bridge arm can alternately share the current, achieving a relatively balanced heat distribution. However, under stall conditions, because the motor's mechanical angle remains stationary, the corresponding voltage space vector distribution is fixed, causing the inverter output duty cycle to remain constant at a positive or negative value. This state results in the stall current being continuously conducted by a single group of power devices for a long time, causing severe heat accumulation in those devices, while other power devices remain idle. This extreme concentration of heat load greatly limits the motor system's continuous stall capability and overall reliability.

[0024] This application proposes a three-level inverter control method.

[0025] Please see Figure 1 In the first embodiment of this application, the three-level inverter control method is applied to a new energy vehicle electric drive system. The new energy vehicle electric drive system includes a motor and a three-level inverter for driving the motor. The method includes steps S10 to S20: Step S10: Obtain the motor speed and actual torque.

[0026] It should be noted that the motor speed can be measured directly through the sensors inside the motor, and the actual torque can be obtained by looking up a table (current-torque table) based on the direct-axis current or quadrature-axis current obtained from the three-phase current conversion; or the motor's three-phase current, three-phase voltage, and DC bus voltage can be collected in real time, and the motor speed and actual torque can be calculated by combining the motor's physical model. There are no restrictions here.

[0027] Step S20: If the motor is determined to be in stall condition based on the rotational speed and actual torque, then the original PWM control signal of the three-level inverter is injected with pulsed common-mode voltage to generate a PWM wave signal, and the operation of the three-level inverter is controlled based on the PWM wave signal; wherein, the PWM wave signal is used to control the different power devices of the three-level inverter to alternately bear the phase current without changing the actual torque and phase current amplitude of the motor.

[0028] It should be noted that a three-level inverter is a high-performance power conversion topology. Compared to the traditional two-level structure, its output voltage waveform is closer to a sine wave, and its harmonic losses are lower, but its control logic is more complex. Stalled rotor operation refers to the operating state where the motor still needs to output a specific target torque even when its speed is zero or extremely low (such as vehicle starting or parking on a slope). Pulsating common-mode voltage injection refers to superimposing a zero-sequence voltage component of a specific frequency and amplitude onto the original three-phase modulation wave while keeping the motor line voltage (i.e., the effective voltage that determines torque) constant. This changes the potential distribution of the three-phase bridge arms relative to the neutral point, but does not affect the electromagnetic torque output of the motor itself.

[0029] It should be noted that this three-level inverter control method can be applied to all three-level inverters in which only a portion of the power devices bear the phase current under stall conditions, and there are no restrictions here.

[0030] Please see Figure 5 , Figure 5 An electronic circuit diagram of a three-level inverter according to an embodiment of this application is provided. The three-level inverter includes three-phase bridge arms UVW. (As shown...) Figure 5 As shown, taking phase U as an example, V1 is its upper bridge external transistor, V2 is its upper bridge internal transistor, V3 is its lower bridge internal transistor, and V4 is its lower bridge external transistor. Under normal motor rotation conditions, V1 and V3 of the three-level inverter are complementaryly turned on, and V2 and V4 are complementaryly turned on. When the duty cycle is in the positive half-wave, V1 and V3 switch their states according to the duty cycle, with the upper bridge internal transistor V2 continuously conducting and the lower bridge external transistor V4 continuously turning off, and the current in the positive half-wave is completely conducted by the upper bridge internal transistor V2. When the duty cycle is in the negative half-wave, V2 and V4 switch their states according to the duty cycle, with the lower bridge internal transistor V3 continuously conducting and the upper bridge external transistor V1 continuously turning off. Under stall conditions, when considering stall, the upper bridge inner tube V2 or the lower bridge inner tube V3 will be continuously conducting at any random angle. At this time, the phase current is entirely borne by the upper bridge inner tube V2 or the lower bridge inner tube V3 alone, resulting in large conduction losses of the inner tube, severe heat generation, triggering junction temperature drop and power reduction, which leads to a decrease in the stall capability of the motor.

[0031] In this embodiment, a PWM signal is generated by injecting pulsed common-mode voltage into the original PWM control signal of the three-level inverter. The phase current under stall condition is alternately shared by different power devices of the three-level inverter, so as to effectively reduce the heat generation of the power devices and improve the stall capability of the motor.

[0032] Specifically, please refer to Figure 4 , Figure 4This document presents a diagram illustrating the PWM signal generation method for a three-level inverter control method according to an embodiment of this application. It should be noted that the original PWM control signal includes the duty cycles of the U-phase, V-phase, and W-phase. The three-phase duty cycles are generated using a Field-Oriented Control (FOC) algorithm. The algorithm first acquires the three-phase current of the motor and, combined with the current electrical angle, decouples the originally complexly coupled AC current into two independent DC currents through coordinate transformation: one specifically responsible for generating the magnetic field, and the other specifically responsible for generating torque. Next, based on the input torque command, the algorithm calculates the required voltage for the motor at that moment through closed-loop control. Finally, using the DC bus voltage as a reference, the algorithm translates the target voltage into the required conduction time ratios for each of the U, V, and W phases using SVPWM (Space Vector Pulse Width Modulation) technology, i.e., the UVW three-phase duty cycles, to accurately respond to the torque command. Simultaneously, a stall condition is determined. If the motor is determined to be in stall condition based on the speed and actual torque, the switch is switched to pulsed common-mode voltage mode. Pulsed common-mode voltage is injected into the original PWM control signal of the three-level inverter to generate a PWM wave signal. The operation of the three-level inverter is then controlled based on this PWM wave signal. The PWM wave signal is used to control different power devices in the three-level inverter to alternately handle the phase current without changing the actual torque and phase current amplitude of the motor. For example, corresponding to... Figure 5 The three-level inverter shown generates 12 PWM waveform signals, which control the switching states of the 12 transistors in the UVW three-phase bridge arm respectively.

[0033] It should be noted that, in one exemplary embodiment, the continuous conduction current of the upper bridge transistor is switched to alternating conduction of the upper and lower bridge transistors by injecting a DC common-mode voltage, but the phase current amplitude remains unchanged, i.e., the actual torque remains unchanged. However, considering the midpoint voltage offset problem of the three-level inverter, if a DC common-mode voltage is continuously injected, it will generate a continuous zero-sequence current with a non-zero average value, causing the midpoint voltage to offset. Excessive midpoint voltage offset can lead to power device withstand voltage failure, current runaway, and other problems. In this embodiment, to avoid midpoint voltage offset, a pulsed common-mode voltage injection method is used to switch the continuous conduction current of the upper bridge transistor to alternating conduction of the upper and lower bridge transistors.

[0034] Please see Figure 6 , Figure 6 The waveform of the three-phase duty cycle (PWM signal) after pulsed common-mode voltage injection is shown in one embodiment of this application. Before pulsed common-mode voltage injection, the three-phase duty cycle is a DC wave; after pulsed common-mode voltage injection, the three-phase duty cycle becomes a pulsed square wave. Please refer to... Figure 7 , Figure 7This embodiment provides a waveform diagram of the current in the upper and lower bridge inner tubes after pulsed common-mode voltage injection. Taking the U-phase bridge arm as an example, the phase current amplitude remains unchanged before and after injection. Before injection, the phase current is completely conducted by the upper bridge inner tube V2. After injection, the phase current is intermittently conducted by the upper bridge inner tube V2. During the off-phase phase of the upper bridge inner tube, the current is conducted by the lower bridge inner tube V3, which can effectively alleviate problems such as high upper bridge losses and severe heat generation. Thus, this embodiment can distribute a portion of the current that is only conducted by the upper bridge inner tube to the lower bridge inner tube by alternating conduction of the upper and lower bridge inner tubes, thereby changing the continuous conduction current of the upper bridge inner tube into an intermittent conduction current, thereby reducing its conduction losses, reducing junction temperature, and improving the stall capability of the motor.

[0035] In this embodiment, the motor's speed and actual torque are acquired in real time. Once the motor enters a stall condition (where the speed is extremely low but the actual torque is relatively high), the injection mode is immediately triggered. At this time, a pulsed common-mode voltage injection is performed on the original PWM control signal (i.e., the three-phase duty cycle). Without changing the motor's phase current amplitude and output torque, the duty cycle of the upper and lower bridge arms of the three-phase inverter fluctuates frequently between positive and negative values. This alters the current flow path between the power devices inside the inverter, activating power devices that were previously idle due to a fixed duty cycle and intermittently turning on those that were previously continuously conducting. Thus, this embodiment achieves thermal load balancing of the power devices under stall conditions by controlling different parts of the three-level inverter to alternately bear the phase current, thereby improving the stall capability of the electric drive system.

[0036] Please see Figure 2 Based on the first embodiment, in the second embodiment of this application, before pulsed common-mode voltage injection, the three-level inverter control method further includes steps S01 to S03: Step S01: Based on the direct-axis voltage and quadrature-axis voltage under the current stall condition, calculate the stator phase voltage amplitude of the motor under the current stall condition.

[0037] It should be noted that the current methods for obtaining the direct-axis voltage and quadrature-axis voltage under stall conditions include any of the following: Directly obtain the direct-axis voltage component and quadrature-axis voltage component of the current loop output; Alternatively, it can be calculated based on the motor's offline parameters and the actual output current under the current stall condition.

[0038] In one embodiment, prior to step S01, the three-level inverter control method further includes step S001: Step S001: Obtain the direct-axis current, quadrature-axis current, and offline parameters of the motor under the current stall condition, and determine the direct-axis voltage and quadrature-axis voltage based on the direct-axis current, quadrature-axis current, and offline parameters of the motor; wherein, the offline parameters of the motor include electrical angular velocity, equivalent direct-axis inductance, equivalent quadrature-axis inductance, equivalent rotor permanent magnet flux linkage, and stator phase resistance.

[0039] The formula for calculating the direct-axis voltage may include: ; in, It is the direct-axis voltage. This represents the direct-axis current under the current stall condition. Stator phase resistance, The electric angular velocity under the current stall condition. The equivalent quadrature-axis inductance under the current stall condition, This represents the quadrature-axis current under the current stall condition.

[0040] The formula for calculating the quadrature-axis voltage includes: ; in, It is the quadrature axis voltage. This represents the quadrature-axis current under the current stall condition. Stator phase resistance, The electric angular velocity under the current stall condition. This is the equivalent direct-axis inductance under the current stall condition. This represents the direct-axis current under the current stall condition. This refers to the equivalent rotor permanent magnet flux linkage under the current stall condition.

[0041] In this step, the formula for calculating the stator phase voltage amplitude may include: ; in, This refers to the stator phase voltage amplitude. It is the direct-axis voltage. It is the quadrature-axis voltage.

[0042] Step S02: Obtain the DC bus voltage of the three-level inverter, and calculate the maximum common-mode voltage duty cycle that can be injected under the current voltage space based on the stator phase voltage amplitude and the DC bus voltage.

[0043] In another embodiment, the formula for calculating the maximum common-mode voltage duty cycle allowed to be injected in the current voltage space includes: ; in, This represents the stator phase voltage amplitude under the current stalled rotor condition. DC bus voltage, This represents the maximum common-mode voltage duty cycle that can be injected under the current voltage space.

[0044] Step S03: Generate a pulsed common-mode voltage based on the maximum allowable common-mode voltage duty cycle and the current square wave frequency under the current voltage space.

[0045] In another embodiment, prior to step S03, the three-level inverter control method further includes step S031: Obtain the thermal time constant of the power devices of the three-level inverter, and determine the current square wave frequency based on the thermal time constant of the power devices of the three-level inverter.

[0046] It's important to note that the thermal time constant of a power device is a core parameter describing its internal dynamic response to heat transfer. Defined as the product of thermal resistance and thermal capacity, it characterizes the time required for the junction temperature to rise to a steady-state value after a constant power is applied, or the time required to cool back to its initial temperature after power is turned off. Understandably, a lower injected square wave frequency, meaning a longer continuous current conduction time for the power device, is detrimental to reducing junction temperature. Therefore, the frequency of the injected pulsating common-mode voltage can be set to be no less than the natural frequency corresponding to the thermal time constant of the power device. Taking an IGBT power device as an example, since its thermal time constant is no less than 10ms, meaning its natural frequency is 100Hz, the current square wave frequency can be set to 500Hz. This optimizes the thermal reliability of the power device and improves its thermal management performance.

[0047] In this embodiment, to ensure the safety and effectiveness of pulsed common-mode voltage injection and prevent overmodulation or voltage saturation in the inverter, the maximum allowable common-mode voltage duty cycle under the current voltage space is calculated using the direct-axis voltage, quadrature-axis voltage, and DC bus voltage. Based on this maximum allowable common-mode voltage duty cycle and the current square wave frequency, a pulsed common-mode voltage is generated. The square wave frequency of the pulsed common-mode voltage is set sufficiently high, such as 500Hz, meaning the sign of the injected voltage is switched every 1 millisecond. This results in shorter periods of continuous phase current borne by different power devices, leading to better optimization of device heating and reducing the likelihood of midpoint voltage shift.

[0048] In this embodiment, please refer to Figure 8 , Figure 8 The diagram illustrates the current waveforms and phase current waveforms of the upper and lower bridge transistors after injection of pulsed common-mode voltages of different amplitudes, as provided in this application. When the amplitude of the pulsed common-mode voltage is injected at the maximum common-mode voltage duty cycle, the upper bridge transistor can have current flowing through the lower bridge transistor for nearly half the time. Thus, this embodiment can effectively alleviate problems such as high upper bridge losses and severe heat generation.

[0049] Please see Figure 3 Based on the first embodiment, in the three embodiments of this application, determining whether the motor enters the stall condition based on the rotational speed and torque includes step S21: When the absolute value of the rotational speed is less than the preset rotational speed threshold for a first duration exceeding the first preset time threshold, and the absolute value of the actual torque is greater than the preset torque threshold for a second duration exceeding the second preset time threshold, the motor is determined to have entered a stall condition.

[0050] In this embodiment, a preset torque threshold is set to be greater than or equal to the motor's continuous torque capability. Considering that the motor also has a small speed in stall conditions, the preset speed threshold can be set to a value greater than or equal to zero, for example, the speed threshold can be set to 200 rpm, and the first preset time threshold and / or the second preset time threshold can be set to 0.5s. After determining that a stall condition has been entered, a pulsed common-mode voltage is injected into the original PWM control signal to generate a PWM wave signal. When the above-mentioned conditions for entering a stall condition are no longer met (i.e., the absolute value of the speed rises back to the preset speed threshold or above, or the absolute value of the actual torque falls to the preset torque threshold or below, or the absolute value of the speed being less than the preset speed threshold does not exceed the first preset time threshold and / or the absolute value of the actual torque being greater than the preset torque threshold for a second duration does not exceed the second preset time threshold), the stall condition is exited, and the pulsed common-mode voltage injection function is immediately turned off. In this way, stall conditions can be accurately and reliably identified, eliminating misjudgments of stall conditions caused by normal start-up and instantaneous impact.

[0051] It should be noted that the above examples are only for understanding this application and do not constitute a limitation on the three-level inverter control method of this application. Any simple modifications based on this technical concept are within the protection scope of this application.

[0052] This application provides a three-level inverter control device, which includes: at least one processor; and a memory communicatively connected to the at least one processor; wherein the memory stores instructions executable by the at least one processor, and the instructions are executed by the at least one processor to enable the at least one processor to perform the three-level inverter control method in the above embodiment 1.

[0053] The following is for reference. Figure 9This document illustrates a structural schematic diagram of a three-level inverter control device suitable for implementing embodiments of this application. The three-level inverter control device in the embodiments of this application may include, but is not limited to, mobile terminals such as mobile phones, laptops, digital radio receivers, PDAs (Personal Digital Assistants), PADs (Portable Application Description), PMPs (Portable Media Players), in-vehicle terminals (e.g., in-vehicle navigation terminals), and fixed terminals such as digital TVs and desktop computers. Figure 9 The three-level inverter control device shown is merely an example and should not impose any limitations on the functionality and scope of use of the embodiments of this application.

[0054] like Figure 9 As shown, the three-level inverter control device may include a processing unit 1001 (e.g., a central processing unit, a graphics processing unit, etc.), which can perform various appropriate actions and processes according to a program stored in a read-only memory (ROM) 1002 or a program loaded from a storage device 1003 into a random access memory (RAM) 1004. The RAM 1004 also stores various programs and data required for the operation of the three-level inverter control device. The processing unit 1001, ROM 1002, and RAM 1004 are interconnected via a bus 1005. An input / output (I / O) interface 1006 is also connected to the bus. Typically, the following systems can be connected to I / O interface 1006: input devices 1007 including, for example, touchscreens, touchpads, keyboards, mice, image sensors, microphones, accelerometers, gyroscopes, etc.; output devices 1008 including, for example, liquid crystal displays (LCDs), speakers, vibrators, etc.; storage devices 1003 including, for example, magnetic tapes, hard disks, etc.; and communication devices 1009. Communication device 1009 allows the three-level inverter control device to communicate wirelessly or wiredly with other devices to exchange data. Although a three-level inverter control device with various systems is shown in the figure, it should be understood that it is not required to implement or possess all the systems shown. More or fewer systems can be implemented alternatively.

[0055] Specifically, according to the embodiments disclosed in this application, the processes described above with reference to the flowcharts can be implemented as computer software programs. For example, embodiments disclosed in this application include a computer program product comprising a computer program carried on a computer-readable medium, the computer program containing program code for performing the methods shown in the flowcharts. In such embodiments, the computer program can be downloaded and installed from a network via a communication device, or installed from storage device 1003, or installed from ROM 1002. When the computer program is executed by processing device 1001, it performs the functions defined in the methods of the embodiments disclosed in this application.

[0056] The three-level inverter control device provided in this application, employing the three-level inverter control method described in the above embodiments, can solve the technical problem that existing three-level inverters experience severe heat accumulation in some power devices under motor stall conditions, thereby limiting the motor's stall capability. Compared with the prior art, the beneficial effects of the three-level inverter control device provided in this application are the same as those of the three-level inverter control method provided in the above embodiments, and other technical features of this three-level inverter control device are the same as those disclosed in the previous embodiment method, and will not be repeated here.

[0057] It should be understood that the various parts disclosed in this application can be implemented using hardware, software, firmware, or a combination thereof. In the description of the above embodiments, specific features, structures, materials, or characteristics can be combined in any suitable manner in one or more embodiments or examples.

[0058] The above description is merely a specific embodiment of this application, but the scope of protection of this application is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in this application should be included within the scope of protection of this application. Therefore, the scope of protection of this application should be determined by the scope of the claims.

[0059] This application provides a computer-readable storage medium having computer-readable program instructions (i.e., a computer program) stored thereon, the computer-readable program instructions being used to execute the three-level inverter control method in the above embodiments.

[0060] The computer-readable storage medium provided in this application may be, for example, a USB flash drive, but is not limited to, electrical, magnetic, optical, electromagnetic, infrared, or semiconductor systems, devices, or any combination thereof. More specific examples of computer-readable storage media may include, but are not limited to: electrical connections having one or more wires, portable computer disks, hard disks, random access memory (RAM), read-only memory (ROM), erasable programmable read-only memory (EPROM or flash memory), optical fiber, portable compact disk read-only memory (CD-ROM), optical storage devices, magnetic storage devices, or any suitable combination thereof. In this embodiment, the computer-readable storage medium may be any tangible medium containing or storing a program that can be used by or in conjunction with an instruction execution system, system, or device. The program code contained on the computer-readable storage medium may be transmitted using any suitable medium, including but not limited to: wires, optical cables, RF (Radio Frequency), etc., or any suitable combination thereof.

[0061] The aforementioned computer-readable storage medium may be included in the three-level inverter control device; or it may exist independently and not assembled into the three-level inverter control device.

[0062] The aforementioned computer-readable storage medium carries one or more programs that, when executed by the three-level inverter control device, cause the three-level inverter control device to: Obtain the motor's speed and actual torque; If the motor is determined to be in a stalled state based on the speed and actual torque, a pulsed common-mode voltage injection is performed on the original PWM control signal of the three-level inverter to generate a PWM wave signal, and the operation of the three-level inverter is controlled based on the PWM wave signal. The PWM wave signal is used to control the different power devices of the three-level inverter to alternately bear the phase current without changing the actual torque and phase current amplitude of the motor.

[0063] Computer program code for performing the operations of this application can be written in one or more programming languages ​​or a combination thereof, including object-oriented programming languages ​​such as Java, Smalltalk, and C++, and conventional procedural programming languages ​​such as the "C" language or similar programming languages. The program code can be executed entirely on the user's computer, partially on the user's computer, as a standalone software package, partially on the user's computer and partially on a remote computer, or entirely on a remote computer or server. In cases involving remote computers, the remote computer can be connected to the user's computer via any type of network—including a Local Area Network (LAN) or a Wide Area Network (WAN)—or can be connected to an external computer (e.g., via the Internet using an Internet service provider).

[0064] The flowcharts and block diagrams in the accompanying drawings illustrate the architecture, functionality, and operation of possible implementations of systems, methods, and computer program products according to various embodiments of this application. In this regard, each block in a flowchart or block diagram may represent a module, segment, or portion of code containing one or more executable instructions for implementing a specified logical function. It should also be noted that in some alternative implementations, the functions indicated in the blocks may occur in a different order than those indicated in the drawings. For example, two consecutively indicated blocks may actually be executed substantially in parallel, and they may sometimes be executed in reverse order, depending on the functions involved. It should also be noted that each block in the block diagrams and / or flowcharts, and combinations of blocks in the block diagrams and / or flowcharts, can be implemented using a dedicated hardware-based system that performs the specified function or operation, or using a combination of dedicated hardware and computer instructions.

[0065] The modules described in the embodiments of this application can be implemented in software or hardware. The names of the modules do not necessarily limit the functionality of the unit itself.

[0066] The readable storage medium provided in this application is a computer-readable storage medium that stores computer-readable program instructions (i.e., a computer program) for executing the above-described three-level inverter control method. This solves the technical problem that in existing three-level inverters, severe heat accumulation in some power devices limits the motor's stall capability under motor stall conditions. Compared with the prior art, the beneficial effects of the computer-readable storage medium provided in this application are the same as those of the three-level inverter control method provided in the above embodiments, and will not be repeated here.

[0067] The above description is merely an exemplary embodiment of this application and does not limit the patent scope of this application. Any equivalent structural transformations made based on the technical concept of this application and the contents of the specification and drawings of this application, or direct / indirect applications in other related technical fields, are included within the patent protection scope of this application.

Claims

1. A three-level inverter control method, characterized in that, An application to an electric drive system for new energy vehicles, the electric drive system including a motor and a three-level inverter for driving the motor, the method comprising: Obtain the motor's rotational speed and actual torque; If the motor is determined to be in a stalled state based on the speed and actual torque, a pulsed common-mode voltage injection is performed on the original PWM control signal of the three-level inverter to generate a PWM wave signal, and the operation of the three-level inverter is controlled based on the PWM wave signal; wherein, the PWM wave signal is used to control different power devices of the three-level inverter to alternately bear the phase current without changing the actual torque and phase current amplitude of the motor.

2. The three-level inverter control method as described in claim 1, characterized in that, Prior to pulsed common-mode voltage injection, the method further includes: Based on the direct-axis voltage and quadrature-axis voltage under the current stall condition, calculate the stator phase voltage amplitude of the motor under the current stall condition; Obtain the DC bus voltage of the three-level inverter, and calculate the maximum common-mode voltage duty cycle that can be injected under the current voltage space based on the stator phase voltage amplitude and the DC bus voltage; The pulsed common-mode voltage is generated based on the maximum common-mode voltage duty cycle allowed to be injected in the current voltage space and the current square wave frequency.

3. The three-level inverter control method as described in claim 2, characterized in that, The formula for calculating the stator phase voltage amplitude includes: ； in, The stator phase voltage amplitude, The direct-axis voltage, The quadrature-axis voltage; and / or The formula for calculating the maximum common-mode voltage duty cycle allowed to be injected under the current voltage space includes: ； in, This represents the stator phase voltage amplitude under the current stalled rotor condition. The DC bus voltage This is the maximum common-mode voltage duty cycle that can be injected under the current voltage space.

4. The three-level inverter control method as described in claim 2, characterized in that, Before calculating the stator phase voltage amplitude of the motor under the current locked-rotor condition based on the direct-axis voltage and quadrature-axis voltage, the method further includes: The direct-axis current, quadrature-axis current, and offline parameters of the motor under the current stall condition are obtained, and the direct-axis voltage and quadrature-axis voltage are determined based on the direct-axis current, the quadrature-axis current, and the offline parameters of the motor. The offline parameters of the motor include electrical angular velocity, equivalent direct-axis inductance, equivalent quadrature-axis inductance, equivalent rotor permanent magnet flux linkage, and stator phase resistance.

5. The three-level inverter control method as described in claim 4, characterized in that, The formula for calculating the direct-axis voltage includes: ； in, The direct-axis voltage, This represents the direct-axis current under the current stall condition. The stator phase resistance. The electric angular velocity under the current stall condition. The equivalent quadrature-axis inductance under the current stall condition, The quadrature-axis current under the current stall condition; and / or The formula for calculating the quadrature-axis voltage includes: ； in, The quadrature-axis voltage, This represents the quadrature-axis current under the current stall condition. The stator phase resistance. The electric angular velocity under the current stall condition. This is the equivalent direct-axis inductance under the current stall condition. This represents the direct-axis current under the current stall condition. This refers to the equivalent rotor permanent magnet flux linkage under the current stall condition.

6. The three-level inverter control method as described in claim 1, characterized in that, The step of determining whether the motor enters a stall condition based on the rotational speed and the torque includes: When the absolute value of the rotational speed is less than a preset rotational speed threshold for a first duration exceeding a first preset time threshold, and the absolute value of the actual torque is greater than a preset torque threshold for a second duration exceeding a second preset time threshold, the motor is determined to have entered a stall condition.

7. The three-level inverter control method as described in claim 2, characterized in that, Before generating the pulsed common-mode voltage based on the maximum common-mode voltage duty cycle allowed to be injected in the current voltage space and the current square wave frequency, the method further includes: The thermal time constant of the power device of the three-level inverter is obtained, and the current square wave frequency is determined based on the thermal time constant of the power device of the three-level inverter.

8. A storage medium, characterized in that, The storage medium is a computer-readable storage medium, and a computer program is stored on the storage medium. When the computer program is executed by a processor, it implements the steps of the three-level inverter control method as described in any one of claims 1 to 7.

9. A three-level inverter control device, characterized in that, The device includes: a memory, a processor, and a computer program stored in the memory and executable on the processor, the computer program being configured to implement the steps of the three-level inverter control method as described in any one of claims 1 to 7.

10. A new energy vehicle, characterized in that, It includes a motor and a three-level inverter for driving the motor, as well as a three-level inverter control device as described in claim 9.

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