A method, device and storage medium for estimating output torque of a three-phase motor

Abstract

The application discloses a kind of three-phase motor output torque estimation method, device and storage medium, method includes obtaining the first phase current and first bus voltage of last control cycle of inverter, and the second phase current and second bus voltage of current control cycle;According to the first phase current, first bus voltage, second phase current and second bus voltage, determine the three-phase output power of inverter in last control cycle;According to the duty ratio of three-phase PWM dead zone and three-phase current, determine the first output power of three-phase PWM under the action of dead zone in last control cycle;According to the motor efficiency characteristic diagram under rated voltage measured, combine voltage limit ellipse equation to carry out voltage proportional correction to motor speed, determine the motor efficiency under current bus voltage;According to the three-phase output power of inverter, first output power and motor efficiency, determine the output torque estimation value of three-phase motor.Using the above method, the high-precision estimation of three-phase motor output torque is realized.

Description

Technical Field

[0001] This invention relates to the technical field of three-phase drive motors, and more particularly to a method, apparatus, and storage medium for estimating the output torque of a three-phase motor. Background Technology

[0002] As the core component for output torque in electric vehicles, the drive motor is an effective means to estimate and monitor its output torque in real time to ensure the safe power output of electric vehicles. To achieve independent torque monitoring, the method of calculating the torque by calculating the three-phase output power is usually adopted. The traditional solution calculates the torque by acquiring the line voltage through hardware, which increases the hardware cost.

[0003] The existing method for calculating the output torque of a three-phase motor is to use three-phase PWM commands and actual acquired phase currents to calculate the three-phase output power. However, this method does not take into account the PWM output delay, PWM dead zone effect, and the need to estimate the average phase current during the actual discretization process. This results in low accuracy of the final output torque estimate, which can easily lead to mechanical vibration or system damage caused by torque runaway. Summary of the Invention

[0004] This invention provides a method, device, and storage medium for estimating the output torque of a three-phase motor. By combining the PWM output delay, PWM dead zone effect, and average phase current within the control cycle that occur during the discretization process, a high-precision estimate of the output torque of the three-phase motor is obtained, which effectively prevents mechanical vibration or system damage caused by torque runaway and improves the safety and reliability of the motor.

[0005] In a first aspect, the present invention provides a method for estimating the output torque of a three-phase motor, comprising:

[0006] Obtain the first phase current and first bus voltage of the inverter in the previous control cycle, and the second phase current and second bus voltage in the current control cycle;

[0007] The three-phase output power of the inverter in the previous control cycle is determined based on the first phase current, the first bus voltage, the second phase current, and the second bus voltage.

[0008] Based on the dead-time duty cycle and three-phase current of the three-phase PWM, determine the first output power of the three-phase PWM under the dead-time action in the previous control cycle;

[0009] Based on the measured motor efficiency characteristic diagram under rated voltage, and combined with the voltage limit ellipse equation, the motor speed is corrected by voltage ratio to determine the motor efficiency under the current bus voltage.

[0010] Based on the inverter's three-phase output power, first output power, and motor efficiency, determine the estimated output torque of the three-phase motor.

[0011] Optionally, based on the first phase current, the first bus voltage, the second phase current, and the second bus voltage, the three-phase output power of the inverter in the previous control cycle is determined, including:

[0012] Based on the first phase current and the second phase current, determine the average phase current of each phase of the inverter in the previous control cycle;

[0013] The average bus voltage of the inverter in the previous control cycle is determined based on the first bus voltage and the second bus voltage.

[0014] Based on the average phase current and average bus voltage of each phase, the three-phase output power of the inverter in the previous control cycle is determined according to the first calculation formula; the first calculation formula is: ,in, This is the three-phase output power. The average bus voltage, , and These refer to the duty cycle of the inverter's three-phase output. , and These are the average phase currents of the three phases, and n is the control period.

[0015] Optionally, based on the three-phase PWM dead-time duty cycle and three-phase current, determine the first output power of the three-phase PWM under dead-time operation in the previous control cycle, including:

[0016] Based on the three-phase PWM dead-time duty cycle and three-phase current, and using the second calculation formula, the first output power of the three-phase PWM under dead-time action in the previous control cycle is determined; the second calculation formula is: ,in, For the first output power, , and These are the dead-time duty cycles of the three-phase PWM. , and These are the average phase currents of the three phases. , and , respectively, are the sign functions of the three-phase average phase currents, and n is the control period.

[0017] Optionally, based on the inverter's three-phase output power, first output power, and motor efficiency, determine the estimated output torque of the three-phase motor, including:

[0018] The second output power of the inverter under dead zone is determined based on the three-phase output power and the first output power of the inverter.

[0019] The output power of the three-phase motor is determined based on the second output power and the motor efficiency.

[0020] Based on the output power of the three-phase motor, determine the initial estimated value of the output torque of the three-phase motor;

[0021] Based on the initial estimated value of the output torque of the three-phase motor, determine the estimated value of the output torque of the three-phase motor.

[0022] Optionally, based on the three-phase output power and the first output power of the inverter, the second output power of the inverter under dead-time action is determined, including:

[0023] Based on the inverter's three-phase output power and first output power, and using the third calculation formula, determine the inverter's second output power under dead-zone conditions; the third calculation formula is: ,in, For the second output power, This is the three-phase output power. denoted as the first output power, and n as the control cycle.

[0024] Optionally, the output power of the three-phase motor is determined based on the second output power and the motor efficiency, including:

[0025] Based on the second output power and motor efficiency, and using the fourth calculation formula, the output power of the three-phase motor is determined; the fourth calculation formula is: ,in, This refers to the output power of a three-phase motor. For the second output power, Let n be the motor efficiency and n be the control cycle.

[0026] Optionally, based on the output power of the three-phase motor, determine the initial estimated value of the output torque of the three-phase motor, including:

[0027] Based on the output power of the three-phase motor, and using the fifth calculation formula, determine the initial estimated value of the output torque of the three-phase motor; the fifth calculation formula is: ,in, This is the initial estimate of the output torque. denoted as the output power of the three-phase motor, n as the control cycle, and l as the motor speed.

[0028] Optionally, based on the initial estimated value of the three-phase motor's output torque, determine the estimated value of the three-phase motor's output torque, including:

[0029] After removing high-frequency components from the initial estimated output torque of the three-phase motor, the estimated output torque of the three-phase motor is obtained; ;in, To discretize the sampling time, This is the initial estimate of the output torque. The time constant of the low-pass filter. The first two values ​​represent the estimated output torque of the three-phase motor, and n represents the control cycle.

[0030] Secondly, the present invention provides a device for estimating the output torque of a three-phase motor, comprising:

[0031] The electrical signal acquisition module is used to acquire the first phase current and the first bus voltage of the inverter in the previous control cycle, as well as the second phase current and the second bus voltage in the current control cycle.

[0032] The first calculation module is used to determine the three-phase output power of the inverter in the previous control cycle based on the first phase current, the first bus voltage, the second phase current, and the second bus voltage.

[0033] The second calculation module is used to determine the first output power of the three-phase PWM under dead-time action in the previous control cycle based on the three-phase PWM dead-time duty cycle and the three-phase current.

[0034] The third calculation module is used to determine the motor efficiency under the current bus voltage by performing voltage proportional correction on the motor speed based on the measured motor efficiency characteristic diagram under the rated voltage and the voltage limit ellipse equation.

[0035] The fourth calculation module is used to determine the estimated output torque of the three-phase motor based on the inverter's three-phase output power, first output power, and motor efficiency.

[0036] Thirdly, the present invention provides a computer-readable storage medium storing computer instructions that, when executed by a processor, implement the above-described method for estimating the output torque of a three-phase motor.

[0037] The technical solution of this invention obtains the first phase current and first bus voltage of the inverter in the previous control cycle, and the second phase current and second bus voltage in the current control cycle; determines the three-phase output power of the inverter in the previous control cycle based on the first phase current, first bus voltage, second phase current, and second bus voltage; determines the first output power of the three-phase PWM under dead-time in the previous control cycle based on the three-phase PWM dead-time duty cycle and three-phase current; determines the motor efficiency under the current bus voltage by applying voltage proportional correction to the motor speed based on the measured motor efficiency characteristic diagram at rated voltage and the voltage limit ellipse equation; and determines the estimated output torque of the three-phase motor based on the three-phase output power, first output power, and motor efficiency. Using the above method, combined with the PWM output delay, PWM dead-time effect, and average phase current within the control cycle that occur during discretization, a high-precision estimate of the three-phase motor output torque is obtained, effectively preventing mechanical jitter or system damage caused by torque runaway, and improving the safety and reliability of the motor.

[0038] It should be understood that the description in this section is not intended to identify key or essential features of the embodiments of the present invention, nor is it intended to limit the scope of the invention. Other features of the invention will become readily apparent from the following description. Attached Figure Description

[0039] To more clearly illustrate the technical solutions in the embodiments of the present invention, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0040] Figure 1 This is a flowchart of a method for estimating the output torque of a three-phase motor provided in an embodiment of the present invention;

[0041] Figure 2 A flowchart illustrating another method for estimating the output torque of a three-phase motor provided in an embodiment of the present invention;

[0042] Figure 3 A timing diagram of an ideal three-phase PWM output corresponding to a certain voltage space vector, provided for an embodiment of the present invention;

[0043] Figure 4 for Figure 3 Timing diagram of the PWM output of the upper and lower bridge arms of the three-phase inverter after the introduction of dead time;

[0044] Figure 5 This is a schematic diagram of a device for estimating the output torque of a three-phase motor, provided in an embodiment of the present invention. Detailed Implementation

[0045] To enable those skilled in the art to better understand the present invention, the technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort should fall within the scope of protection of the present invention.

[0046] It should be noted that the terms "first," "second," etc., in the specification, claims, and accompanying drawings of this invention are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that such data can be interchanged where appropriate so that the embodiments of the invention described herein can be implemented in orders other than those illustrated or described herein. Furthermore, the terms "comprising" and "having," and any variations thereof, are intended to cover non-exclusive inclusion; for example, a process, method, system, product, or apparatus that comprises a series of steps or units is not necessarily limited to those steps or units explicitly listed, but may include other steps or units not explicitly listed or inherent to such processes, methods, products, or apparatus.

[0047] In one embodiment, Figure 1 This is a flowchart illustrating a method for estimating the output torque of a three-phase motor according to an embodiment of the present invention. This embodiment is applicable to situations where the estimated output torque value is calculated considering the PWM output delay, PWM dead zone effect, and average phase current value within the control cycle that occur during the discretization process, achieving high-precision estimation. This method can be executed by a three-phase motor output torque estimation device, which can be implemented in hardware and / or software and can be configured in an electronic device. Figure 1 As shown, the method includes:

[0048] S110: Obtain the first phase current and first bus voltage of the inverter in the previous control cycle, as well as the second phase current and second bus voltage in the current control cycle.

[0049] The first phase current and the first bus voltage refer to the instantaneous values ​​of the three-phase motor current and the DC-side bus voltage obtained from the sampling in the previous control cycle (at time k-1). The second phase current and the second bus voltage refer to the instantaneous values ​​of the three-phase current and the bus voltage obtained in real time in the current control cycle (at time k).

[0050] Specifically, based on the characteristics of the discrete control of the inverter, the actual output duty cycle of the current phase current sampling control cycle is generally the output of the duty cycle of the previous current sampling control cycle. Therefore, introducing cross-cycle data is to more accurately reconstruct the average output power of the previous cycle in the discrete digital control system and eliminate the error caused by sampling delay. In this embodiment, to more accurately estimate the three-phase output power of the inverter, it is necessary to obtain the first phase current and the first bus voltage in the previous control cycle, as well as the second phase current and the second bus voltage in the current control cycle, so as to determine the three-phase output power based on the electrical signals in the two control cycles under discrete conditions. In specific implementation, various embodiments can be used to obtain the above parameters, such as triggering the double buffer register to read at the center moment of the PWM carrier, using a hardware sample-and-hold circuit to lock the signal of the previous cycle, or fitting the value of the previous cycle from the current and historical data using a software linear interpolation algorithm. The specific method can be determined according to the actual situation and is not limited here. This cross-cycle data acquisition mechanism breaks through the limitations of traditional single-point sampling. By utilizing the ideas of difference or averaging on the time series, it provides a high-fidelity data foundation for the subsequent accurate reconstruction of the output power in the previous cycle, effectively solving the problem of data asynchrony caused by the execution time of the control algorithm.

[0051] S120. Determine the three-phase output power of the inverter in the previous control cycle based on the first phase current, the first bus voltage, the second phase current, and the second bus voltage.

[0052] Among them, the three-phase output power refers to the total instantaneous electrical power (including the active part of the active and reactive components) output by the inverter AC side to the motor in the previous control cycle. It is used as a reference value for energy input and represents the total energy rate actually delivered by the power supply to the motor drive system.

[0053] Specifically, after obtaining the first-phase current, first bus voltage, second-phase current, and second bus voltage, the three-phase output power of the inverter in the previous control cycle is determined based on these parameters. Specific determination methods may include, but are not limited to, averaging the phase currents and bus voltages separately and then substituting them into a preset formula for output power; the instantaneous value product method can also be used, directly calculating the sum of the products of the three-phase voltages and currents and performing a moving average filter; or the fundamental frequency extraction method can be used, extracting the fundamental components of the voltage and current through low-pass filtering or FFT to calculate the output power, thereby filtering out high-frequency switching noise interference. The specific method can be determined according to the actual situation and is not limited here.

[0054] S130. Based on the three-phase PWM dead-time duty cycle and the three-phase current, determine the first output power of the three-phase PWM under dead-time action in the previous control cycle.

[0055] Dead zone refers to the artificially inserted waiting time in the same bridge arm of an inverter (such as a three-phase motor driver) during which the upper and lower power switches (such as IGBTs or MOSFETs) are simultaneously turned off to prevent a "shoot-through" short circuit due to turn-off delay when switching states. During this extremely short time (usually on the order of microseconds), the bridge arm does not output active voltage, and current flows only through the freewheeling diode. The dead zone duty cycle of a three-phase PWM refers to the proportion of the non-conducting time artificially inserted to prevent shoot-through short circuits between the upper and lower bridge arms of the inverter to the entire PWM cycle. The first output power refers to the power loss value caused by the dead zone effect (i.e., the power lost due to the output voltage drop caused by the dead zone). Its function is to quantify the energy loss caused by non-ideal switching characteristics so as to remove this part of invalid energy from the total output power and ensure that the subsequent calculations are the effective power that actually acts on the motor.

[0056] Specifically, when calculating the first output power under dead-zone conditions, the first output power of the three-phase PWM under dead-zone conditions in the previous control cycle is calculated using a preset formula based on the obtained three-phase PWM dead-zone duty cycle and three-phase current. Alternatively, an analytical calculation method can be used, based on a preset dead-zone time constant, current bus voltage, and current direction (sign function), to directly calculate the average voltage drop caused by the dead-zone, and then multiply it by the current to obtain the power loss. A lookup table method can also be used, where dead-zone losses are measured beforehand under different current amplitudes and bus voltages, and a three-dimensional lookup table is established for direct indexing during runtime. Another method is model estimation, where an equivalent circuit model including the switching transistor on-state voltage drop and dead-zone time is established, and the power loss of each phase is calculated in real-time and accumulated. The specific method can be determined based on actual conditions and is not limited here.

[0057] S140. Based on the measured motor efficiency characteristic diagram under rated voltage, and combined with the voltage limit ellipse equation, the motor speed is corrected by voltage ratio to determine the motor efficiency under the current bus voltage.

[0058] Among them, the motor efficiency characteristic map refers to a two-dimensional or three-dimensional map of the motor's efficiency as a function of speed and torque, measured through bench testing under rated bus voltage. The voltage limit ellipse equation describes the trajectory boundary of the motor stator voltage vector endpoints in the dq coordinate system under a specific bus voltage limit, reflecting the motor's maximum output capability (field weakening limit). Voltage proportional correction refers to the mathematical process of mapping the efficiency characteristics under rated voltage to the current actual bus voltage using the principle of similarity. Its purpose is to solve the problem that a fixed efficiency map cannot adapt to battery voltage fluctuations (such as SOC changes), achieving accurate efficiency prediction across the entire voltage range.

[0059] Specifically, utilizing the motor similarity law and voltage limit theory, it is assumed that when the magnetic circuit is not saturated and the control strategy is consistent, the rotational speed and voltage are linearly proportional. The algorithm first calculates the current actual rotational speed based on the ratio of the current bus voltage to the rated voltage, obtaining the "equivalent speed"; then, it uses this equivalent speed to query the efficiency map under the rated voltage; finally, it combines the voltage limit ellipse to determine whether the current operating point has entered the deep field weakening region. If it is in the region, an additional iron loss correction coefficient is introduced.

[0060] In this embodiment, the calculation process of motor efficiency under the current bus voltage is first based on the full-condition efficiency Map obtained through bench testing under the rated bus voltage Un (with torque command trq and speed l as inputs). Then, under the condition of high-speed steady state and neglecting resistance voltage drop, the constraint relationship between voltage and speed is established using the voltage limit ellipse equation in the dq coordinate system, that is... When the actual bus voltage Udc deviates from the rated bus voltage Un (i.e., Udc ≠ Un), in order to reuse the rated efficiency Map, a voltage proportional correction method is adopted, and the current actual speed l[l-1] is adjusted according to... The proportional conversion is used to obtain the equivalent speed, and then combined with the torque command trq[n-2] from the previous control cycle as an index to look up a lookup table (LUT), thereby dynamically obtaining the accurate motor efficiency value under the current non-rated voltage condition. ,Right now LUT stands for lookup table function.

[0061] S150. Based on the inverter's three-phase output power, first output power, and motor efficiency, determine the estimated output torque of the three-phase motor.

[0062] The output torque estimate refers to the final calculated mechanical torque at the motor shaft end. It serves as a feedback or monitoring value for the control system, enabling high-precision torque closed-loop control, fault diagnosis, and energy efficiency optimization.

[0063] Specifically, after determining the inverter's three-phase output power, first output power, and motor efficiency, the estimated output torque of the three-phase motor can be calculated based on these parameters. The calculation methods can include, but are not limited to, direct algebraic operations, substituting the scalar values ​​obtained in the previous steps into the formula for real-time calculation; recursive filtering estimation, using the calculated instantaneous torque as an observation value and inputting it into a Kalman filter or low-pass filter, combining it with the motor's moment of inertia model to output a smoothed torque estimate to suppress noise; or using a lookup table method, using the calculated effective input power and current speed as indexes to directly read the corresponding torque value from a pre-generated "power-speed-torque" three-dimensional mapping table to reduce online floating-point computation.

[0064] The technical solution of this invention obtains the first phase current and first bus voltage of the inverter in the previous control cycle, and the second phase current and second bus voltage in the current control cycle; determines the three-phase output power of the inverter in the previous control cycle based on the first phase current, first bus voltage, second phase current, and second bus voltage; determines the first output power of the three-phase PWM under dead-time in the previous control cycle based on the three-phase PWM dead-time duty cycle and three-phase current; determines the motor efficiency under the current bus voltage by applying voltage proportional correction to the motor speed based on the measured motor efficiency characteristic diagram at rated voltage and the voltage limit ellipse equation; and determines the estimated output torque of the three-phase motor based on the three-phase output power, first output power, and motor efficiency. Using the above method, combined with the PWM output delay, PWM dead-time effect, and average phase current within the control cycle that occur during discretization, a high-precision estimate of the three-phase motor output torque is obtained, effectively preventing mechanical jitter or system damage caused by torque runaway, and improving the safety and reliability of the motor.

[0065] In another specific embodiment, Figure 2 A flowchart illustrating another method for estimating the output torque of a three-phase motor provided in an embodiment of the present invention. Figure 3 This is a timing diagram illustrating an ideal three-phase PWM output corresponding to a certain voltage space vector, provided by an embodiment of the present invention. Figure 4 for Figure 3 The timing diagram of the PWM output of the upper and lower bridge arms of the inverter after introducing the dead time is shown in this embodiment. This embodiment refines the specific implementation of S120 in the above embodiment, which determines the three-phase output power of the inverter in the previous control cycle based on the first phase current, the first bus voltage, the second phase current, and the second bus voltage, as follows:

[0066] Based on the first phase current and the second phase current, determine the average phase current of each phase of the inverter in the previous control cycle;

[0067] The average bus voltage of the inverter in the previous control cycle is determined based on the first bus voltage and the second bus voltage.

[0068] Based on the average phase current and average bus voltage of each phase, the three-phase output power of the inverter in the previous control cycle is determined according to the first calculation formula; the first calculation formula is: ,in, This is the three-phase output power. The average bus voltage, , and These refer to the duty cycle of the inverter's three-phase output. , and These are the average phase currents of the three phases, and n is the control period.

[0069] Furthermore, the specific implementation method for S130 in the above embodiment, which determines the first output power of the three-phase PWM under dead-time action in the previous control cycle based on the three-phase PWM dead-time duty cycle and three-phase current, is refined as follows:

[0070] Based on the three-phase PWM dead-time duty cycle and three-phase current, and using the second calculation formula, the first output power of the three-phase PWM under dead-time action in the previous control cycle is determined; the second calculation formula is: ,in, For the first output power, , and These are the dead-time duty cycles of the three-phase PWM. , and These are the average phase currents of the three phases. , and , respectively, are the sign functions of the three-phase average phase currents, and n is the control period.

[0071] Furthermore, the specific implementation method for determining the estimated output torque of the three-phase motor based on the three-phase output power, the first output power, and the motor efficiency in S150 of the above embodiment is refined as follows:

[0072] The second output power of the inverter under dead zone is determined based on the three-phase output power and the first output power of the inverter.

[0073] The output power of the three-phase motor is determined based on the second output power and the motor efficiency.

[0074] Based on the output power of the three-phase motor, determine the initial estimated value of the output torque of the three-phase motor;

[0075] Based on the initial estimated value of the output torque of the three-phase motor, determine the estimated value of the output torque of the three-phase motor.

[0076] For details not covered in this embodiment, please refer to the above embodiments, which will not be repeated here.

[0077] refer to Figures 2 to 4 As shown, the method includes:

[0078] S210: Obtain the first phase current and first bus voltage of the inverter in the previous control cycle, and the second phase current and second bus voltage in the current control cycle.

[0079] S220. Based on the first phase current and the second phase current, determine the average phase current of each phase of the inverter in the previous control cycle.

[0080] The average phase current refers to the average current value of the previous cycle calculated from the phase current values ​​of the two control cycles. Its purpose is to eliminate random noise and phase deviation from single-point sampling, and to use smoother data to represent the actual current level in the cycle, thereby improving the accuracy of power calculation.

[0081] Specifically, when calculating the average phase current, the linear interpolation or trapezoidal integral principle of discrete signals is used to perform an arithmetic average or weighted average of the current sample values ​​from two adjacent control cycles, thereby approximating the continuously changing effective current value in the previous control cycle. In this embodiment, according to the calculation formula... , This is the sampled value of the phase current from the previous control cycle, i.e., the first phase current. The current is the sampled phase current value for the current control cycle, i.e., the second phase current. Substituting the phase currents sampled in two adjacent control cycles into the above calculation formula yields the average phase current. It should be noted that the average phase current includes the average of the three-phase currents; similarly, the obtained phase current is also the three-phase current (i.e., the average phase current). , , The average current of each phase needs to be calculated separately according to the above formula.

[0082] S230. Determine the average bus voltage of the inverter in the previous control cycle based on the first bus voltage and the second bus voltage.

[0083] The average bus voltage is an equivalent voltage value that characterizes the DC power supply capacity in the previous control cycle. Its function is to serve as a voltage reference in power calculation and to offset the impact of instantaneous voltage jumps caused by bus capacitor charging and discharging or grid fluctuations on power estimation.

[0084] Specifically, this step is also based on the principle of time-domain discretization. By averaging the sampling points of two adjacent bus voltages across cycles, the average DC bus voltage in the previous cycle is reconstructed and calculated. This can be achieved by directly taking the arithmetic mean of the voltage values ​​at two different times to filter out high-frequency measurement noise. In this embodiment, the calculation formula can be used... , This is the bus voltage sample value from the previous control cycle, i.e., the first bus voltage. The current control cycle bus voltage sample value is the second bus voltage. Substituting the bus voltages collected in two adjacent control cycles into the above calculation formula, the average bus voltage can be obtained.

[0085] S240. Based on the average phase current and average bus voltage of each phase, and using the first calculation formula, determine the three-phase output power of the inverter in the previous control cycle.

[0086] The first calculation formula is: ,in, This is the three-phase output power. The average bus voltage, , and These refer to the duty cycle of the inverter's three-phase output. , and These are the average phase currents of the three phases, and n is the control period.

[0087] Specifically, when calculating the three-phase output power of the inverter in the previous control cycle, based on the average phase current and average bus voltage of each phase determined above, and using the first calculation formula... Average bus voltage and three-phase average phase current , and The duty cycle of the inverter's three-phase output is obtained through the above calculations. , and Can be done in advance according to Figure 3 The three-phase output power can be obtained or calculated, where dyc[n] can be calculated based on the period of the previous control cycle (i.e., FOC[n-1]), and so on, dyc[n-2] can be calculated based on the period of the previous three control cycles (i.e., FOC[n-3]). After substituting the determined parameters into the first calculation formula, the three-phase output power can be calculated. .

[0088] It should be noted that the first calculation formula is based on the three-phase output power of the inverter under ideal conditions, combined with discretized control. The derivation process for the three-phase output power of the inverter under ideal conditions is briefly explained here. (Reference) Figure 3 For each phase, the upward pulse is the upper bridge arm, and the downward pulse is the lower bridge arm. This indicates that all three lower bridge arms are closed simultaneously. This indicates that all three upper bridge arms are closed simultaneously, therefore , When in operation, the inverter output voltage is 0 and the output power is also 0.

[0089] When in operation, the negative voltage of the neutral point of the three-phase motor relative to the high voltage is: The percentage of the duration of action is The sum of the three-phase power of U, V, and W is:

[0090] ;

[0091] When in operation, the negative voltage of the motor neutral point relative to the high voltage is: The percentage of the duration of action is The sum of the three-phase power of U, V, and W is:

[0092] ;

[0093] Therefore, the three-phase output power (i.e., the sum of the three-phase power) is:

[0094] ;

[0095] in, Bus voltage , , The duty cycle of the inverter's three-phase output. , , This refers to the three-phase output current of the inverter.

[0096] S250. Based on the three-phase PWM dead-time duty cycle and three-phase current, and using the second calculation formula, determine the first output power of the three-phase PWM under dead-time action in the previous control cycle.

[0097] The second calculation formula is as follows: ,in, For the first output power, , and These are the dead-time duty cycles of the three-phase PWM. , and These are the average phase currents of the three phases. , and , respectively, are the sign functions of the three-phase average phase currents, and n is the control period.

[0098] Specifically, when calculating the first output power of the three-phase PWM under dead-time in the previous control cycle, based on the average phase current and average bus voltage of each phase determined above, and using the second calculation formula... Average bus voltage and three-phase average phase current , and The three-phase PWM dead-time duty cycle of the inverter was obtained through the above calculations. , and Can be done in advance according to Figure 4 Obtained or calculated , and These are the sign functions of the three-phase average phase currents, which can be determined in advance. By substituting the determined parameters into the second calculation formula, the first output power of the three-phase PWM under dead-time can be calculated. .

[0099] It should be noted that the actual derivation process of the first output power of three-phase PWM under dead-time conditions is briefly explained here. (Reference) Figure 4 , Figure 4 for Figure 3 The timing diagram of the PWM output of the upper and lower bridge arms of the inverter after introducing the dead time, at which point the polarity of the three-phase current is... When the current is positive, the dead time only affects the rising edge of the upper bridge arm PWM; when the current is negative, the dead time only affects the rising edge of the lower bridge arm PWM. Figure 4 In the diagram, PWM_U, PWM_V, and PWM_W represent the PWM drive signal waveforms of the three phases U, V, and W, respectively (high level indicates the upper transistor is on, low level indicates the lower transistor is on); dycU, dycV, and dycW represent the ideal duty cycle of the three phases (i.e., the theoretical on-state ratio calculated by the controller), corresponding to the "effective high-level width" marked in the green solid box. dycDT is the dead time, marked in the red dashed box. It is a safety interval time of "both transistors are off" forcibly inserted when switching between the upper and lower bridge arms to prevent the inverter from burning out due to the simultaneous conduction of the upper and lower transistors caused by the delay of the switching devices; dycU / V / W-dycDT should be understood as the effective starting point from the beginning point to the end of the first dead time. U0~U7 represent the eight basic voltage vector states in space vector modulation: U0 and U7 are zero vectors (all three phases are on or all three phases are off); U1~U6 are six non-zero effective vectors (e.g., U1=100, indicating that the upper transistor of phase U is on, and the lower transistors of phases V and W are on).

[0100] When the U-phase dead zone acts alone, the voltage change at the U-phase input terminal is: This results in a change in the U-phase voltage of The voltage changes of phase V and phase W are Output power of a three-phase motor under the sole action of the U-phase dead zone for:

[0101] ;

[0102] When the V-phase dead zone acts alone, the change in voltage at the V-phase input terminal is: This results in a change in the voltage of phase V of... The voltage changes of phases U and W are Output power of a three-phase motor under the sole action of the V-phase dead zone for:

[0103] ;

[0104] When the dead zone of phase W acts alone, the voltage change at the input terminal of phase W is: This results in a change in the voltage of phase W of phase W. The voltage changes of phases U and V are The output power of a three-phase motor under the sole action of the W-phase dead zone for:

[0105] ;

[0106] The calculation method for the first output power of a three-phase motor after considering the discretization delay is as follows:

[0107] .

[0108] S260. Based on the measured motor efficiency characteristic diagram under rated voltage, and combined with the voltage limit ellipse equation, the motor speed is corrected by voltage ratio to determine the motor efficiency under the current bus voltage.

[0109] S270. Determine the second output power of the inverter under dead zone based on the three-phase output power and the first output power of the inverter.

[0110] This step can be further broken down as follows: Based on the inverter's three-phase output power and first output power, and using the third calculation formula, determine the inverter's second output power under dead-zone conditions; the third calculation formula is: ,in, For the second output power, This is the three-phase output power. denoted as the first output power, and n as the control cycle.

[0111] The second output power refers to the inverter output power after taking into account the effects of dead zone, which is the effective electrical power actually applied to the motor stator winding. Its function is to act as an energy bridge connecting the inverter side and the motor side, ensuring that subsequent efficiency calculations and torque estimations are based on the actual motor input energy, rather than the total output energy including losses.

[0112] Specifically, the second output power of the inverter after considering the effects of dead time can be calculated using the third formula. Among them, the three-phase output power and first output power Both parameters can be obtained through the above calculation process. Therefore, by inputting the two parameters into the third calculation formula, the second output power of the inverter under dead-zone conditions can be obtained. .

[0113] S280. Determine the output power of the three-phase motor based on the second output power and the motor efficiency.

[0114] This step can be further broken down as follows: Based on the second output power and motor efficiency, and using the fourth calculation formula, determine the output power of the three-phase motor; the fourth calculation formula is: ,in, This refers to the output power of a three-phase motor. For the second output power, Let n be the motor efficiency and n be the control cycle.

[0115] Specifically, after calculating the second output power, based on the motor efficiency and the second output power, and using the fourth calculation formula... Second output power and motor efficiency All of these parameters are obtained through the above calculations. Therefore, by substituting these parameters into the fourth calculation formula, the output power of the three-phase motor can be obtained. .

[0116] S290. Determine the initial estimated value of the output torque of the three-phase motor based on the output power of the three-phase motor.

[0117] This step can be further broken down as follows: Based on the output power of the three-phase motor, and using the fifth calculation formula, determine the initial estimated value of the output torque of the three-phase motor; the fifth calculation formula is: ,in, This is the initial estimate of the output torque. denoted as the output power of the three-phase motor, n as the control cycle, and l as the motor speed.

[0118] Specifically, after calculating the output power of the three-phase motor, based on the output power of the three-phase motor, the fifth calculation formula is used. The output power of a three-phase motor The motor speed *l* is obtained in advance through the above calculations. Therefore, by substituting the above parameters into the fifth calculation formula, the initial estimated value of the output torque of the three-phase motor can be obtained. .

[0119] S300. Determine the estimated output torque of the three-phase motor based on the initial estimated output torque value.

[0120] This step can be further broken down as follows: High-frequency components are removed from the initial estimated output torque of the three-phase motor to obtain the estimated output torque value of the three-phase motor; the estimated output torque value... ;in, To discretize the sampling time, This is the initial estimate of the output torque. The time constant of the low-pass filter. The first two values ​​represent the estimated output torque of the three-phase motor, and n represents the control cycle.

[0121] Specifically, after calculating the initial estimated value of the output torque of the three-phase motor, a low-pass filter is applied to the original estimated value of the output torque to eliminate high-frequency components, thus obtaining the estimated output torque value of the three-phase motor. Based on the order of the low-pass filter, the estimated output torque value can be obtained according to the formula... We obtain, where the discretization sampling time and the time constant of the low-pass filter This information is obtained or calculated in advance, for example, when selecting a first-order low-pass filter, based on torque response time performance indicators. The time constant of the first-order low-pass filter can be obtained as follows: The first two estimated values ​​of the output torque of the three-phase motor The output torque of the three-phase motor can be estimated by substituting the parameters into the calculation formula described above. .

[0122] The technical solution of this invention involves determining the average phase current of each phase of the inverter in the previous control cycle based on the first phase current and the second phase current; determining the average bus voltage of the inverter in the previous control cycle based on the first bus voltage and the second bus voltage; determining the three-phase output power of the inverter in the previous control cycle based on the average phase current and the average bus voltage using a first calculation formula; determining the first output power of the three-phase PWM under dead-time operation in the previous control cycle based on the three-phase PWM dead-time duty cycle and the three-phase current using a second calculation formula; determining the second output power of the inverter under dead-time operation based on the three-phase output power and the first output power; determining the output power of the three-phase motor based on the second output power and the motor efficiency; determining the initial estimated value of the output torque of the three-phase motor based on the output power of the three-phase motor; and determining the estimated value of the output torque of the three-phase motor based on the initial estimated value of the output torque of the three-phase motor. Using the above method, high-precision calculation of the estimated value of the output torque of the three-phase motor is achieved, improving the safety and reliability of the drive motor.

[0123] Based on the same inventive concept Figure 5 This is a schematic diagram of a three-phase motor output torque estimation device provided in an embodiment of the present invention, with reference to... Figure 5 As shown, the device includes:

[0124] The electrical signal acquisition module 110 is used to acquire the first phase current and the first bus voltage of the inverter in the previous control cycle, as well as the second phase current and the second bus voltage in the current control cycle.

[0125] The first calculation module 120 is used to determine the three-phase output power of the inverter in the previous control cycle based on the first phase current, the first bus voltage, the second phase current, and the second bus voltage.

[0126] The second calculation module 130 is used to determine the first output power of the three-phase PWM under dead time action in the previous control cycle based on the three-phase PWM dead time duty cycle and the three-phase current.

[0127] The third calculation module 140 is used to determine the motor efficiency under the current bus voltage by performing voltage proportional correction on the motor speed based on the measured motor efficiency characteristic diagram under the rated voltage and the voltage limit ellipse equation.

[0128] The fourth calculation module 150 is used to determine the estimated output torque of the three-phase motor based on the inverter's three-phase output power, the first output power, and the motor efficiency.

[0129] The three-phase motor output torque estimation device provided in this embodiment of the invention can execute the three-phase motor output torque estimation method provided in any embodiment of the invention, and has the corresponding functional modules and beneficial effects of the method.

[0130] Optionally, the first calculation module 120 can also be configured to: determine the average phase current of each phase of the inverter in the previous control cycle based on the first phase current and the second phase current; determine the average bus voltage of the inverter in the previous control cycle based on the first bus voltage and the second bus voltage; and determine the three-phase output power of the inverter in the previous control cycle based on the average phase current and the average bus voltage, using a first calculation formula; the first calculation formula is: ,in, This is the three-phase output power. The average bus voltage, , and These refer to the duty cycle of the inverter's three-phase output. , and These are the average phase currents of the three phases, and n is the control period.

[0131] Optionally, the second calculation module 130 can also be configured to: determine the first output power of the three-phase PWM under dead-time operation in the previous control cycle based on the three-phase PWM dead-time duty cycle and the three-phase current, using a second calculation formula; the second calculation formula is: ,in, For the first output power, , and These are the dead-time duty cycles of the three-phase PWM. , and These are the average phase currents of the three phases. , and , respectively, are the sign functions of the three-phase average phase currents, and n is the control period.

[0132] Optionally, the fourth calculation module 150 can also be configured to: determine the second output power of the inverter under dead zone based on the three-phase output power and the first output power of the inverter; determine the output power of the three-phase motor based on the second output power and the motor efficiency; determine the initial estimated value of the output torque of the three-phase motor based on the output power of the three-phase motor; and determine the estimated value of the output torque of the three-phase motor based on the initial estimated value of the output torque of the three-phase motor.

[0133] Optionally, the fourth calculation module 150 can also be configured to: determine the second output power of the inverter under dead-zone action based on the three-phase output power and the first output power of the inverter, using a third calculation formula; the third calculation formula is: ,in, For the second output power, This is the three-phase output power. denoted as the first output power, and n as the control cycle.

[0134] Optionally, the fourth calculation module 150 can also be configured to: determine the output power of the three-phase motor based on the second output power and the motor efficiency, using a fourth calculation formula; the fourth calculation formula is: ,in, This refers to the output power of a three-phase motor. For the second output power, Let n be the motor efficiency and n be the control cycle.

[0135] Optionally, the fourth calculation module 150 can also be configured to: determine the initial estimated value of the output torque of the three-phase motor based on the output power of the three-phase motor and the fifth calculation formula; the fifth calculation formula is: ,in, This is the initial estimate of the output torque. denoted as the output power of the three-phase motor, n as the control cycle, and l as the motor speed.

[0136] Optionally, the fourth calculation module 150 can also be configured to: remove high-frequency components from the initial estimated value of the output torque of the three-phase motor to obtain the estimated value of the output torque of the three-phase motor; the estimated value of the output torque ;in, To discretize the sampling time, This is the initial estimate of the output torque. The time constant of the low-pass filter. The first two values ​​represent the estimated output torque of the three-phase motor, and n represents the control cycle.

[0137] Based on the same inventive concept, the present invention provides a computer-readable storage medium storing computer instructions that are used to cause a processor to execute the above-described method for estimating the output torque of a three-phase motor.

[0138] In the context of this invention, a computer-readable storage medium can be a tangible medium that may contain or store a computer program for use by or in conjunction with an instruction execution system, apparatus, or device. A computer-readable storage medium may include, but is not limited to, electronic, magnetic, optical, electromagnetic, infrared, or semiconductor systems, apparatus, or devices, or any suitable combination thereof. Alternatively, a computer-readable storage medium may be a machine-readable signal medium. More specific examples of machine-readable storage media include electrical connections based on 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 fibers, portable compact disk read-only memory (CD-ROM), optical storage devices, magnetic storage devices, or any suitable combination thereof.

[0139] To provide interaction with a user, the systems and techniques described herein can be implemented on an electronic device having: a display device (e.g., a CRT (cathode ray tube) or LCD (liquid crystal display) monitor) for displaying information to the user; and a keyboard and pointing device (e.g., a mouse or trackball) through which the user provides input to the electronic device. Other types of devices can also be used to provide interaction with the user; for example, feedback provided to the user can be any form of sensory feedback (e.g., visual feedback, auditory feedback, or tactile feedback); and input from the user can be received in any form (including sound input, voice input, or tactile input).

[0140] The systems and technologies described herein can be implemented in computing systems that include backend components (e.g., as data servers), or middleware components (e.g., application servers), or frontend components (e.g., user computers with graphical user interfaces or web browsers through which users can interact with implementations of the systems and technologies described herein), or any combination of such backend, middleware, or frontend components. The components of the system can be interconnected via digital data communication of any form or medium (e.g., communication networks). Examples of communication networks include local area networks (LANs), wide area networks (WANs), blockchain networks, and the Internet.

[0141] A computing system can include clients and servers. Clients and servers are generally located far apart and typically interact through communication networks. The client-server relationship is created by computer programs running on the respective computers and having a client-server relationship with each other. The server can be a cloud server, also known as a cloud computing server or cloud host, which is a hosting product within the cloud computing service system to address the shortcomings of traditional physical hosts and VPS services, such as high management difficulty and weak business scalability.

[0142] It should be understood that the various forms of processes shown above can be used, with steps reordered, added, or deleted. For example, the steps described in this invention can be executed in parallel, sequentially, or in different orders, as long as the desired result of the technical solution of this invention can be achieved, and this is not limited herein.

[0143] The specific embodiments described above do not constitute a limitation on the scope of protection of this invention. Those skilled in the art should understand that various modifications, combinations, sub-combinations, and substitutions can be made according to design requirements and other factors. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of this invention should be included within the scope of protection of this invention.

Claims

1. A method for estimating the output torque of a three-phase motor, characterized in that, include: Obtain the first phase current and first bus voltage of the inverter in the previous control cycle, and the second phase current and second bus voltage in the current control cycle; The three-phase output power of the inverter in the previous control cycle is determined based on the first phase current, the first bus voltage, the second phase current, and the second bus voltage. Based on the three-phase PWM dead-time duty cycle and the three-phase current, determine the first output power of the three-phase PWM under dead-time action in the previous control cycle; Based on the measured motor efficiency characteristic diagram under rated voltage, and combined with the voltage limit ellipse equation, the motor speed is corrected by voltage ratio to determine the motor efficiency under the current bus voltage. The estimated output torque of the three-phase motor is determined based on the three-phase output power of the inverter, the first output power, and the motor efficiency.

2. The estimation method according to claim 1, characterized in that, Based on the first phase current, the first bus voltage, the second phase current, and the second bus voltage, the three-phase output power of the inverter in the previous control cycle is determined, including: Based on the first phase current and the second phase current, determine the average phase current of each phase of the inverter in the previous control cycle; The average bus voltage of the inverter in the previous control cycle is determined based on the first bus voltage and the second bus voltage. Based on the average phase current and average bus voltage of each phase, the three-phase output power of the inverter in the previous control cycle is determined according to the first calculation formula; the first calculation formula is: ,in, The three-phase output power, The average bus voltage is... , and These refer to the duty cycle of the inverter's three-phase output. , and These are the average phase currents of the three phases, and n is the control period.

3. The estimation method according to claim 1, characterized in that, Based on the three-phase PWM dead-time duty cycle and three-phase current, determine the first output power of the three-phase PWM under dead-time action in the previous control cycle, including: Based on the three-phase PWM dead-time duty cycle and three-phase current, and using the second calculation formula, the first output power of the three-phase PWM under dead-time operation in the previous control cycle is determined; the second calculation formula is: ,in, For the first output power, , and These are the dead-time duty cycles of the three-phase PWM, , and These are the average phase currents of the three phases. , and , respectively, are the sign functions of the three-phase average phase currents, and n is the control period.

4. The estimation method according to claim 1, characterized in that, Based on the three-phase output power of the inverter, the first output power, and the motor efficiency, the estimated output torque of the three-phase motor is determined, including: Based on the three-phase output power of the inverter and the first output power, determine the second output power of the inverter under dead zone action; The output power of the three-phase motor is determined based on the second output power and the motor efficiency. Based on the output power of the three-phase motor, determine the initial estimated value of the output torque of the three-phase motor; Based on the initial estimated value of the output torque of the three-phase motor, the estimated value of the output torque of the three-phase motor is determined.

5. The estimation method according to claim 4, characterized in that, Based on the three-phase output power of the inverter and the first output power, the second output power of the inverter under dead-zone conditions is determined, including: Based on the three-phase output power of the inverter and the first output power, the second output power of the inverter under dead-zone conditions is determined using a third calculation formula; the third calculation formula is: ,in, This is the second output power. The three-phase output power, Let n be the first output power, and n be the control period.

6. The estimation method according to claim 4, characterized in that, Determining the output power of the three-phase motor based on the second output power and the motor efficiency includes: Based on the second output power and the motor efficiency, the output power of the three-phase motor is determined using a fourth calculation formula; the fourth calculation formula is: ,in, The output power of the three-phase motor is... This is the second output power. Let n be the motor efficiency, and n be the control cycle.

7. The estimation method according to claim 4, characterized in that, Based on the output power of the three-phase motor, determine the initial estimated value of the output torque of the three-phase motor, including: Based on the output power of the three-phase motor, and using the fifth calculation formula, the initial estimated value of the output torque of the three-phase motor is determined; the fifth calculation formula is: ,in, This is the initial estimated value of the output torque. Let n be the output power of the three-phase motor, n be the control cycle, and l be the motor speed.

8. The estimation method according to claim 4, characterized in that, Based on the initial estimated value of the output torque of the three-phase motor, the estimated value of the output torque of the three-phase motor is determined, including: By removing the high-frequency components from the initial estimated output torque value of the three-phase motor, the estimated output torque value of the three-phase motor is obtained; the estimated output torque value ;in, To discretize the sampling time, This is the initial estimated value of the output torque. The time constant of the low-pass filter. The output torque of the three-phase motor mentioned in the previous two measurements is estimated, and n is the control cycle.

9. A device for estimating the output torque of a three-phase motor, characterized in that, include: The electrical signal acquisition module is used to acquire the first phase current and the first bus voltage of the inverter in the previous control cycle, as well as the second phase current and the second bus voltage in the current control cycle. The first calculation module is used to determine the three-phase output power of the inverter in the previous control cycle based on the first phase current, the first bus voltage, the second phase current, and the second bus voltage. The second calculation module is used to determine the first output power of the three-phase PWM under dead zone action in the previous control cycle based on the three-phase PWM dead zone duty cycle and the three-phase current. The third calculation module is used to determine the motor efficiency under the current bus voltage by performing voltage proportional correction on the motor speed based on the measured motor efficiency characteristic diagram under the rated voltage and the voltage limit ellipse equation. The fourth calculation module is used to determine the estimated output torque of the three-phase motor based on the three-phase output power of the inverter, the first output power, and the motor efficiency.

10. A computer-readable storage medium, characterized in that, The computer-readable storage medium stores computer instructions that, when executed by a processor, implement the method for estimating the output torque of a three-phase motor as described in any one of claims 1-8.

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