A method and system for continuous overmodulation control of multiphase motors based on current feedback

Abstract

This application relates to a continuous overmodulation control method and system for multiphase motors based on current feedback, belonging to the field of overmodulation technology. The method employs the following technical solution: The motor load rate is calculated in real-time based on the collected motor current; based on the motor load rate, the current operating condition is determined, and the maximum allowable modulation ratio under the current operating condition is calculated; wherein the current operating condition includes at least light-load and heavy-load operating conditions; the maximum modulation ratio is used as an upper limit value, and the received modulation ratio command is limited to a range not exceeding the upper limit value to calculate the final modulation ratio; the switching action of the power electronic switching device is controlled by the final modulation ratio. This application achieves a smooth transition in overmodulation technology, achieving an adaptive balance between improving voltage utilization and suppressing current harmonics.

Description

Technical Field

[0001] This application relates to the field of overmodulation technology, and in particular to a method and system for continuous overmodulation control of a multiphase motor based on current feedback. Background Technology

[0002] Voltage source inverters, as the core power conversion unit of modern power electronic drive systems, generally employ a three-phase bridge structure composed of fully controlled switching devices (such as insulated gate bipolar transistors (IGBTs) or metal-oxide-semiconductor field-effect transistors (MOSFETs)). These power devices use pulse width modulation (PWM) technology to convert the DC bus voltage into the three-phase AC power required to drive AC motors (such as permanent magnet synchronous motors and induction motors). Overmodulation technology is a key means to improve the utilization rate of the DC bus voltage and expand the constant power operating range of the motor. It increases the fundamental amplitude of the output voltage by making the modulation index (M) break through the linear limitation of sinusoidal PWM (SPWM).

[0003] Traditional overmodulation schemes typically employ a segmented implementation strategy, which divides the entire modulation range (0 < M ≤ M_max) into several fixed intervals such as the SPWM linear region, the overmodulation region, and the square wave region, and uses different switching time calculation logic in each interval, switching between intervals through a preset fixed modulation ratio threshold (e.g., M = 1.0).

[0004] However, this overmodulation strategy based on fixed thresholds and segmented logic poses a serious challenge to the power electronic switching devices (such as IGBT / MOSFET chips and modules) that make up the inverter in practical applications, such as: Fixed-threshold overmodulation strategies cannot adapt to changes in motor load. Under heavy-load conditions, if fixed-threshold overmodulation based on light-load optimization is still used, it may lead to increased output current harmonics, causing a simultaneous increase in IGBT / MOSFET conduction and switching losses. This additional loss is directly converted into heat, causing a significant increase and drastic fluctuation in the junction temperature of the power module. The increase in junction temperature not only reduces system efficiency but is also a major cause of device performance degradation (such as parameter drift) and eventual thermal breakdown, placing excessive demands on the design of the heat dissipation system, thus requiring improvement. Summary of the Invention

[0005] To address the technical problem that overmodulation strategies with fixed thresholds cannot adapt to changes in motor load, this application provides a continuous overmodulation control method and system for multiphase motors based on current feedback.

[0006] In a first aspect, this application provides a continuous overmodulation control method for a multiphase motor based on current feedback, employing the following technical solution: The motor load rate is calculated in real time based on the real-time collected motor current. Based on the motor load rate, the current operating condition is determined, and the maximum allowable modulation ratio under the current operating condition is calculated; wherein, the current operating condition includes at least light load operating condition and heavy load operating condition; The maximum modulation ratio is used as an upper limit value, and the received modulation ratio command is limited to a range not exceeding the upper limit value to calculate the final modulation ratio. The switching action of the power electronic switching device is controlled by the final modulation ratio.

[0007] By adopting the above technical solution and dynamically limiting the modulation ratio according to the load current, the sharp increase in IGBT / MOSFET conduction and switching losses due to improper overmodulation depth under heavy load and high current conditions is fundamentally avoided. This directly optimizes the junction temperature of the power chip, preventing it from being damaged by overheating, and improves the long-term reliability and lifespan of the components, meeting the requirements of "component manufacturing" for high-reliability applications. It ensures that the system can operate at its optimal or near-optimal state under different loads, achieving an adaptive balance between improving voltage utilization and suppressing current harmonics.

[0008] Optionally, controlling the switching action of the power electronic switching device through the final modulation ratio includes: The basic switching time is calculated based on the final modulation ratio using a preset algorithm. The dynamic adjustment coefficient C is calculated in real time based on the error between the motor command current and the actual current. Based on the dynamic adjustment coefficient C and the preset correction formula, the basic switching time is corrected to obtain the adaptive switching time. The adaptive switching time is sent to the inverter's PWM generator to generate corresponding drive pulses to control the switching on and off of the power electronic switching devices.

[0009] By adopting the above technical solution, the closed-loop correction mechanism can quickly suppress current overshoot, thereby actively smoothing the switching process of IGBT / MOSFET and suppressing di / dt and dv / dt caused by drastic current changes. This directly reduces the peak electrical stress and switching losses experienced by the switching device at each turn-on and turn-off moment, which is crucial for protecting the fragile chip gate oxide layer and extending device lifespan.

[0010] Optionally, the preset algorithm is the SPWM algorithm; or the preset algorithm is a combination of the SPWM algorithm and the overmodulation algorithm. The method of controlling the switching action of the power electronic switching device through the final modulation ratio further includes: When the preset algorithm is a combination of SPWM algorithm and overmodulation algorithm, the first switching time and the second switching time are calculated by SPWM algorithm and overmodulation algorithm respectively. The weighting factor is calculated based on the final modulation ratio. Based on the weighting factor, the first switching time and the second switching time are fused to obtain the adaptive switching time. The step of fusing the first switching time and the second switching time to obtain the adaptive switching time also includes: The first switching time and the second switching time are corrected using the dynamic adjustment coefficient.

[0011] By adopting the above technical solution, the weighted fusion technology completely eliminates the voltage and current jumps caused by sudden changes in switching logic at traditional fixed threshold switching points. This shockless switching ensures that IGBT / MOSFET always operate within their safe operating area (SOA), avoiding catastrophic failures such as device avalanche breakdown or latch-up effects caused by single or multiple switching shocks. It is a core protection measure for component reliability.

[0012] Optionally, the method further includes: The rate of change of the motor phase current is monitored in real time. If the absolute value of the rate of change exceeds a preset safety threshold, a buffering mechanism is triggered to slow down the rate of change of the weighting factor α and extend the transition time.

[0013] By adopting the above technical solution, this mechanism acts as a "safety valve" to cope with unforeseen abnormal situations in the control loop (such as sudden load changes). By actively intervening in the evolution rate of the switching timing, it directly prevents extreme rate-of-change events that could damage the IGBT chip, greatly enhancing the system's robustness and fault tolerance under complex operating conditions, and providing ultimate protection for the safety of power electronic components.

[0014] Optionally, the real-time monitoring of the rate of change of the motor phase current, if the absolute value of the rate of change exceeds a preset safety threshold, triggers a buffering mechanism to slow down the rate of change of the weighting factor α and extend the transition time, including: Based on the current operating status of the motor and the trend of the modulation ratio command, the first adjustment trajectory of the weighting factor α is predicted; The inverter's output voltage utilization rate η is calculated in real time, and the first adjustment trajectory is dynamically corrected with the goal of approximating the optimal voltage utilization rate, thereby generating a second adjustment trajectory with weight factor α. The change in the second adjustment trajectory control weight factor α is used to achieve smooth switching; and during the switching process, the rate of change of the motor phase current is monitored in real time. If the absolute value of the rate of change of the motor phase current exceeds a preset safety threshold, a buffering mechanism is triggered. The buffering mechanism extends the transition time by covering the second adjustment trajectory and forcibly reducing the rate of change of the weighting factor α.

[0015] By adopting the above technical solutions and combining prediction with real-time optimization, the switching process achieves dual optimization in both the time dimension (early intervention) and the performance dimension (voltage utilization). This maximizes the inverter's voltage output potential while ensuring absolute smoothness. Specifically, predictive control avoids switching at the peak of current and voltage stress, proactively arranging the switching transients of IGBT / MOSFETs at the most moderate operating points, significantly reducing switching losses and the risk of turn-off overvoltage. Voltage utilization optimization ensures that, under the same DC bus voltage, the current stress on power devices is reduced, or that the junction temperature of the chip is better controlled at the same output power. The dual-layer protection architecture provides both forward-looking optimization and real-time hard protection for the safe operating area (SOA) of the IGBT module, directly improving the reliability and lifespan of the components.

[0016] Optionally, the real-time calculation of the dynamic adjustment coefficient C includes: The rate of change of the final modulation ratio is calculated in real time, and the rate of change of the final modulation ratio is multiplied by a preset feedforward gain coefficient to obtain the feedforward correction amount. The feedback correction amount is calculated by the PI controller based on the error between the commanded motor current and the actual current. The dynamic adjustment coefficient C is calculated based on the feedforward correction and the feedback correction.

[0017] By adopting the above technical solution, the error between the actual current and the command current is used as feedback, while the modulation ratio command change is tracked simultaneously. The rate of change of the modulation ratio command is used as the feedforward quantity. The dynamic adjustment coefficient C is generated by the "feedforward + feedback" composite, which greatly reduces the hysteresis and overshoot of current tracking, making the dynamic response of the overmodulation process faster and smoother. This effectively solves the inherent hysteresis problem of pure current error feedback control. Specifically, by suppressing current overshoot in advance, the problem of excessive current stress caused by instantaneous current spikes in IGBTs / MOSFETs is directly avoided, protecting the safe operating area (SOA) of the device. Smoother current transition means that the switching transient process of the IGBT is more controllable, reducing the degree of hard switching under high voltage and high current conditions, and helping to reduce switching losses. The reduction of current stress and switching losses directly translates into a reduction in the heat generated by the power chip, which is beneficial for controlling the junction temperature and improving the long-term reliability and lifespan of the components.

[0018] Optionally, determining the current operating condition based on the motor load rate and calculating the maximum allowable modulation ratio under the current operating condition includes: The motor load rate is compared with a preset load rate threshold. Based on the comparison result, the current operating condition is determined, and the maximum allowable modulation ratio under the current operating condition is calculated. The method further includes: The stator resistance of the motor is identified in real time to obtain the identified value of the stator resistance. The load rate threshold is dynamically adjusted according to the ratio of the identified value of the stator resistance to the preset rated stator resistance value.

[0019] By adopting the above technical solution, this solution enables the overmodulation control system to possess the ability to "learn" and "evolve," automatically compensating for parameter drift caused by motor temperature rise and aging. It ensures that the overmodulation strategy remains within the optimal or safe range throughout the entire product lifecycle, solving the pain point of fixed-parameter control systems becoming "less accurate with use." Specifically, by identifying increased motor resistance (indicating increased heating) and preemptively limiting the overmodulation depth, it effectively prevents the motor from operating under high-temperature, high-loss conditions. This indirectly protects the IGBT / MOSFETs that power it, preventing their junction temperature from rising and conduction losses from driving an overheated motor. This solution treats the motor and inverter as a complete system for collaborative protection. Through indirect sensing and proactive control of the motor's thermal state, it avoids the risk of insulation aging and performance degradation caused by overheating in the entire drive system (including the motor and IGBT modules), significantly improving the overall reliability and lifespan of the system.

[0020] Secondly, this application provides a multiphase motor continuous overmodulation control system based on current feedback, including, The motor operation status monitoring module is used to calculate the motor load rate in real time based on the real-time collected motor current. The operating condition and modulation ratio determination module is used to determine the current operating condition based on the motor load rate and calculate the maximum allowable modulation ratio under the current operating condition; wherein, the current operating condition includes at least light load operating condition and heavy load operating condition; The final modulation ratio control module is used to use the maximum modulation ratio as an upper limit value to limit the received modulation ratio command to a range not exceeding the upper limit value in order to calculate the final modulation ratio, and control the switching action of the power electronic switching device through the final modulation ratio.

[0021] Thirdly, this application provides a multiphase motor continuous overmodulation control device based on current feedback, including a memory and a processor, wherein the memory stores a computer program that can be loaded by the processor and executed as described in any of the first aspects.

[0022] Fourthly, this application provides a computer-readable storage medium storing a computer program that can be loaded by a processor and executed as described in any of the first aspects.

[0023] In summary, this application includes at least one of the following beneficial technical effects: This application effectively solves the problem of uneven transition in existing overmodulation technology. Through continuous dynamic partitioning and seamless switching logic, it avoids step changes in voltage and current, reduces motor speed fluctuations and torque impacts to a certain extent, and improves operational stability. Furthermore, dynamic boundary adjustment based on current feedback and adaptive allocation of switching time enhance the adaptability to changes in motor parameters (such as resistance changes caused by temperature). While ensuring current stability, it effectively improves voltage utilization, reduces harmonic content, and adapts to the full operating conditions of multiphase motors. Attached Figure Description

[0024] 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.

[0025] Figure 1 This is a flowchart illustrating the continuous overmodulation control method for a multiphase motor based on current feedback disclosed in an embodiment of this application.

[0026] Figure 2 This is a structural block diagram of a multiphase motor continuous overmodulation control system based on current feedback disclosed in an embodiment of this application.

[0027] Explanation of reference numerals in the attached figures: 201, Motor operation status monitoring module; 202, Operating condition and modulation ratio determination module; 203, Final modulation ratio control module; 2031, Switching time adaptive correction unit; 2032, Overmodulation control unit; 2033, Switching time gradual change control unit. Detailed Implementation

[0028] The following is in conjunction with the appendix Figure 1-2 This application will be described in further detail.

[0029] This application discloses a multiphase motor continuous overmodulation control method based on current feedback (hereinafter referred to as the modulation control method). The execution entity is a multiphase motor continuous overmodulation control system based on current feedback (hereinafter referred to as the modulation control system), specifically executed by the inverter's digital signal processor (DSP) or microcontroller (MCU). The modulation control system acquires the three-phase currents (Iu, Iv, Iw) of the motor in real time, and after Clarke and Park transformations, obtains the AC and DC axis currents (Id, Iq) used for feedback. Simultaneously, the modulation control system also receives command currents (Id_ref, Iq_ref) and modulation ratio commands (Mcmd) from the upper-level speed or torque controller. The following will combine... Figure 1 This section elaborates on the specific execution process of the modulation control system for the modulation control method.

[0030] S101, calculates the motor load rate in real time based on the real-time collected motor current; S102, based on the motor load rate, determine the current operating condition and calculate the maximum allowable modulation ratio under the current operating condition; wherein, the current operating condition includes at least light load condition and heavy load condition; S103, using the maximum modulation ratio as the upper limit, limits the received modulation ratio command to a range not exceeding the upper limit to calculate the final modulation ratio, and controls the switching action of the power electronic switching device through the final modulation ratio.

[0031] S103, "controlling the switching action of the power electronic switching device through the final modulation ratio," specifically includes the following sub-steps: S1031 uses a preset algorithm to calculate the basic switching time based on the final modulation ratio.

[0032] S1032, based on the error between the motor command current and the actual current, calculates the dynamic adjustment coefficient C in real time; specifically, the calculation of the dynamic adjustment coefficient C includes: calculating the rate of change of the final modulation ratio in real time, multiplying the rate of change of the final modulation ratio by the preset feedforward gain coefficient to obtain the feedforward correction amount; calculating the feedback correction amount through the PI controller based on the error between the motor command current and the actual current; and calculating the dynamic adjustment coefficient C based on the feedforward correction amount and the feedback correction amount.

[0033] S1033, based on the dynamic adjustment coefficient C and the preset correction formula, the basic switching time is corrected to obtain the adaptive switching time; The preset algorithm is the SPWM algorithm; or the preset algorithm is a combination of the SPWM algorithm and the overmodulation algorithm. S1034, when the preset algorithm is a combination of SPWM algorithm and overmodulation algorithm, the first switching time and the second switching time are calculated by using SPWM algorithm and overmodulation algorithm respectively; the weighting factor is calculated according to the final modulation ratio; and the first switching time and the second switching time are fused together based on the weighting factor to obtain the adaptive switching time. The phrase "the adaptive switching time is obtained by fusing the first switching time and the second switching time" in S1034 may also include: The first and second switching times are corrected using dynamic adjustment coefficients.

[0034] S1035 sends the adaptive switching time to the inverter's PWM generator to generate corresponding drive pulses to control the turn-on and turn-off of power electronic switching devices.

[0035] S104 monitors the rate of change of the motor phase current in real time. If the absolute value of the rate of change exceeds the preset safety threshold, a buffering mechanism is triggered to slow down the rate of change of the weighting factor α and extend the transition time.

[0036] In implementation, firstly, the modulation control system is used to dynamically set the safe operating boundary of the modulation ratio based on the actual load of the motor. The specific implementation scheme is as follows: S11, the modulation control system calculates the effective value Irms of the three-phase current based on the real-time acquired motor three-phase current. Where T is one power cycle, and in actual digital implementation, it can be discretized using a sliding window or the root mean square algorithm of the cycle. Then, the load factor K = Irms / In is calculated, where In is the rated current of the motor, which is a fixed parameter pre-stored in the controller.

[0037] S12, the modulation control system calculates the maximum allowable modulation ratio Mmax_limit under the current operating condition based on a pre-built lookup table or piecewise function Mmax_limit=f(K) and the load rate K calculated above. Specifically, the piecewise function Mmax_limit=f(K) is as follows: When K < x1 (e.g., x1 = 0.3), it is determined to be light load, and the output Mmax_limit = Mmax (Mmax ​​is the maximum modulation ratio corresponding to square wave modulation). When K≥x2 (e.g., x2=0.8), it is determined to be overloaded, and Mmax_limit= Mheavy is output, where Mheavy is a conservative value less than Mmax (e.g., Mheavy=1.1). When x1≤K<x2, the output Mmax_limit is linearly or non-linearly interpolated between Mheavy and Mmax to achieve a smooth transition.

[0038] S13, the modulation control system then executes the operation Mfinal=min(Mcmd, Mmax_limit) based on the calculated Mmax_limit and the modulation ratio command Mcmd issued from the upper layer, and outputs the final modulation ratio M after load adaptive limiting for subsequent calculations. final .

[0039] Next, the modulation and control system introduces current closed-loop fine-tuning based on the basic switching time calculation to optimize dynamic performance. The specific implementation scheme is as follows: S21, based on the final modulation ratio M calculated above. final And the electrical angle θ, using the SPWM algorithm, the base switching time t1 is calculated. For one phase of a three-phase inverter (taking phase U as an example), its reference voltage signal is Uref_base=M final ×sin(θ). The corresponding base switching time t1 can be calculated within one carrier period Ts using the formula t1=(1+Uref_base)×Ts / 2.

[0040] S22, based on the command current Iq_ref (taking the torque current component as an example) and the actual feedback current Iq, calculate the current error e(t) = Iq_ref − Iq, and send the error signal to a digital PI controller, outputting ΔCpi = Kp × e(t) + Ki × ∫e(t) dt. Here, Kp and Ki are the proportional and integral gains after engineering tuning, a set of fixed values ​​determined after engineering debugging. In other embodiments, to ensure optimal performance of the modulation control system under different operating conditions, Ki and Kp can be adjusted online according to the modulation ratio M or load rate K. For example, under light load, a higher Kp can be set for fast response; under heavy load, a lower Kp can be set for stability.

[0041] Then, based on the current time and previous times, the final modulation ratio M is calculated for each control cycle. final Calculate the modulation ratio change rate dM / dt = [M] final (k)- M final [(k-1)] / Ts; where k is the current control cycle and Ts is the duration of the control cycle.

[0042] Then, based on the preset feedforward gain coefficient K ffThis coefficient can be determined through theoretical analysis (such as system modeling) or experimental debugging. Its dimensions are used to convert the modulation ratio change rate into a correction amount for the adjustment coefficient C. Finally, the feedforward quantity is superimposed with the output of the PI controller to generate a dynamic adjustment coefficient C = 1 + ΔC for correcting the switching time; ΔC = ΔCpi + K ff ×dM / dt.

[0043] Correspondingly, when the modulation ratio command increases rapidly (dM / dt > 0), it is assumed that the upper-level controller requires a rapid increase in the inverter output voltage, which will increase the current command and pose a risk of overshoot. In this case, the feedforward quantity K... ff ×dM / dt is a positive number, which ensures that C > 1.0 before the current error e(t) increases significantly. This makes the subsequent correction of the switching time t1' more conservative, suppressing the current surge that may be caused by a sudden voltage rise. When the modulation ratio command decreases rapidly (dM / dt < 0), it is assumed that the upper controller requires the inverter output voltage to decelerate. At this time, the feedforward quantity K... ff When ×dM / dt is negative, C < 1.0 will be made earlier, thus causing the subsequent switching time t1' to change in the direction of decreasing earlier. This allows the inverter output voltage to drop earlier, thereby helping the actual current to follow the command current drop more quickly and avoiding tailing.

[0044] S23, the modulation control system calculates the adaptive switching time t1'=C×t1 using the correction formula based on the basic switching time t1 calculated above and the dynamic adjustment parameter C.

[0045] As discussed above, the adaptive switching time t1' obtained is based on a correction of the base switching time t1 calculated by a single algorithm (i.e., the SPWM algorithm). Furthermore, when the modulation control system runs two algorithms (such as the SPWM algorithm and the overmodulation algorithm) in parallel to calculate the base switching time t1, this application proposes setting a weighting factor α to combine the calculation results of these two algorithms to obtain the final adaptive switching time. (Since this adaptive switching time is calculated based on the premise of two parallel algorithms, to distinguish it from the adaptive switching time t' calculated by the single algorithm mentioned above, this adaptive switching time will be referred to as T below.) final The specific implementation plan is as follows: S31, The modulation control system is used to base the modulation ratio M final The electrical angle θ is used to calculate the first switching time T in parallel using the SWPM algorithm. SPWM The second switching time T is calculated using modulation algorithms (including but not limited to the arcsine function-based correction method, the third harmonic injection method, and the two-phase modulation method). OvermodIt should be noted that since the techniques for calculating the switching time using the SWPM algorithm and the overmodulation algorithm are common knowledge and existing technology in this field, they will not be elaborated on here.

[0046] S32, the modulation control system is used to adjust the modulation ratio M according to... final The mapping yields a weighting factor α, and the mapping relationship is determined by a predefined continuous function, for example: When M final ≤M low When α = 1.0; When M final ≥M high When α = 0.0; When M low ≤M final ≤M high When, α = (M high - M final ) / (M high - M low Alternatively, a sigmoid function can be used to achieve a smoother transition.

[0047] Among them, [M low M high The value is within a small neighborhood of the SPWM and overmodulation threshold X (for example, when X=1, the corresponding neighborhood can be [0.95, 1.05], i.e., M). low =0.95, M high =1.05).

[0048] S33, the modulation control system is used to adjust according to M final T SPWM T Overmod The final switching time T is calculated using the weighting factor α and the real-time phase current I. final =α×T SPWM +(1-α)×T Overmod .

[0049] In a preferred embodiment of the present invention, the adaptive correction step (i.e., S23) and the seamless switching step (S32) can work together. Specifically, after executing S31 to obtain the first switching time T, SPWM Second switching time T Overmod Afterwards, and before executing S32, based on the steps described in S23, the dynamic adjustment coefficient C can be used to correct them respectively to obtain the corrected first switching time Tspwm' (where Tspwm'=C×T SPWM ) and the corrected second switching time Tovermod' (where, Tovermod' = C × T OvermodThen, based on Tspwm' and Tovermod', S32 and S33 are performed to calculate T. final =α×Tspwm'+(1-α)×Tovermod'.

[0050] The modulation control system is also used to sample the phase current using a high-precision ADC in each PWM cycle, and calculate the current change rate di / dt = [I(k)−I(k−1)] / Ts in real time, where k is the current sampling time and T_s is the sampling period. Furthermore, when |di / dt| exceeds a preset threshold D... max If the value is 50 A / ms, a buffering mechanism is triggered. This buffering mechanism temporarily modifies the update rate of the weighting factor α. For example, it makes the weighting factor remain unchanged or only allows it to change slowly over the next N carrier cycles, thereby actively prolonging the transition process and avoiding shocks. Specifically, a preset, fixed and extremely small rate of change increment Δα_slow (e.g., 0.01 / cycle) is used as the only legal control variable, forcing the weighting factor to change slowly according to the law α(k+1) = α(k) ± Δα_slow until |di / dt| falls back below the safe threshold.

[0051] The modulation control system is used for the final seamless synthesis and secure monitoring of the switching time T. final This signal is directly fed into the DSP's PWM generator to generate pulse signals that drive the inverter's power switching transistors. In summary, this achieves smooth, adaptive, and highly reliable operation across all operating conditions during the overmodulation process.

[0052] Optionally, S104 specifically includes the following steps: Based on the current operating status of the motor and the trend of the modulation ratio command, the first adjustment trajectory of the weighting factor α is predicted; The inverter's output voltage utilization rate η is calculated in real time, and the first adjustment trajectory is dynamically corrected with the goal of approximating the optimal voltage utilization rate, thereby generating a second adjustment trajectory with weight factor α. The second adjustment trajectory control weight factor α is changed to achieve smooth switching; and the rate of change of motor phase current is monitored in real time during the switching process. If the absolute value of the rate of change of the motor phase current exceeds the preset safety threshold, the buffer mechanism is triggered. The buffer mechanism extends the transition time by overriding the second adjustment trajectory and forcibly reducing the rate of change of the weight factor α.

[0053] In implementation, the modulation and control system is specifically used to execute the following scheme: S41: Real-time detection of motor speed ω, acquisition of real-time AC and DC axis currents (Id, Iq), and the modulation ratio command sequence M_cmd(k), M_cmd(k+1)... issued by the upper-level controller (such as the speed loop PI controller) for the next few control cycles. It should be noted that when the upper-level controller calculates in the current control cycle k, its internal algorithm generates an output queue of estimates (i.e., the modulation ratio command sequence for the next few control cycles). For example, assuming the speed loop controller cycle is much longer than the current loop / modulation cycle, at time k, the speed loop outputs M_cmd(k), and it is assumed that in the next few fast modulation cycles, this command will either remain unchanged or be linearly extrapolated according to its trend (e.g., M_cmd(k) - M_cmd(k-1)), ultimately obtaining the estimated values ​​of M_cmd(k+1), M_cmd(k+2)..., and this modulation ratio command sequence is only used in this prediction.

[0054] S42: Using the built-in motor mathematical model (including parameters such as stator resistance Rs, inductance Ld / Lq, and back EMF constant Ke), based on the data obtained in S41, forward calculations are performed to predict the waveform of the future motor back EMF and the zero-crossing time of the phase current, generating the first adjustment trajectory α_base(t). This trajectory ensures that the core change process of the weights (such as α from 0.9 to 0.1) is completed as close as possible to the predicted current zero-crossing point, thereby taking advantage of the natural advantage that di / dt is almost zero when the current naturally crosses zero to avoid impact.

[0055] The specific implementation logic is as follows: At time k, Id(k), Iq(k), θ(k) (i.e., the electrical angle at time k), and ωe(k) (i.e., the electrical angular velocity at time k) are measured; assuming that ωe and Vd, Vq (determined by M_cmd and the angle) remain constant over a very short time interval Ts (one PWM cycle), we can predict the current at time k+1: Id(k+1) = Id(k) + Ts * [ (Vd(k) - Rs*Id(k) + ωe(k)*Lq*Iq(k)) / Ld ]; Iq(k+1) = Iq(k) + Ts * [ (Vq(k) - Rs*Iq(k) - ωe(k)*Ld*Id(k) - ωe(k)*λpm) / Lq ]; Then, the predicted Id(k+1) and Iq(k+1) are transformed into the three-phase stationary coordinate system ABC by the inverse Park transformation based on the predicted electrical angle θ(k+1)=θ(k)+ ωe(k)*Ts, to obtain the predicted phase currents Ia(k+1), Ib(k+1), and Ic(k+1). Then, analyze the predicted waveforms of Ia(k+1), Ib(k+1), and Ic(k+1) to determine their sign change trends. For example, if Ia(k) is positive and Ia(k+1) is negative, and their changes are continuous, then a zero-crossing point can be predicted between time k and k+1. A more precise zero-crossing point time can be estimated using linear interpolation. Then, using the estimated zero-crossing point time T_zero as the center, extend the time window by a specified duration ΔT to obtain the zero-crossing time window [T_zero-ΔT, T_zero+ΔT]. Then, plan the weight factor α to change from its initial value (referred to as α_start) to its target value (referred to as α_end) within the zero-crossing time window. If the time interval corresponding to this change process of the weight factor α is defined as [t_start, t_end], then t_start = T_zero – ΔT, t_end = T_zero + ΔT.

[0056] The formula for calculating α_start is as described above, which is M calculated based on the current PWM cycle. final When M final ≤M low When M, α_start = 1.0; when M final ≥M high When M is at 0, α_start = 0.0; when M is at 0, α_start = 0.0. low ≤M final ≤M high At that time, α_start = (M high -M final ) / (M high - M low ); α_end is the opposite of α_start, if the prediction shows M final It will continue to increase during the zero-point time window and eventually stabilize at M. high (For example, 1.1) above, then α_end = 0.0; if the prediction shows M final It will continue to decrease during the zero-point time window and eventually stabilize at Ml. ow Below (e.g., 0.9), α_end = 1.0; Finally, the first adjustment trajectory is obtained using linear programming: α_base(t) = α_start + (α_end - α_start) * (t - t_start) / (2 * ΔT).

[0057] S43: Extract the fundamental voltage amplitude V1_actual from the sampled voltage using low-pass filtering or Fast Fourier Transform (FFT), obtain the current DC bus voltage Vdc, calculate the real-time voltage utilization rate η = V1_actual / (Vdc × 0.612), and compare it with a desired voltage utilization rate curve η_ref. Here, η_ref is a preset ideal curve, representing the modulation ratio M. final The function, depending on the overmodulation algorithm used (such as an arcsine-based algorithm), can accurately calculate, under ideal conditions, the modulation ratio M for each modulation ratio M. final The corresponding theoretical voltage utilization rate η_theoretical. This η_theoretical - M final The curve is the most direct η_ref; in other embodiments, η_ref can also be obtained by implementing a lookup table, such as in bench testing, where precise measurements are taken to record different M values ​​under optimal switching timing. final The corresponding maximum achievable η is used to form an η_ref lookup table, and then based on the current M... final The corresponding η_ref is obtained by looking up the table.

[0058] During the comparison process, if the voltage utilization rate η is less than η_ref and continues for a specified duration, and the current error is less than the preset error, a correction amount Δα_rate is generated (at this time, Δα_rate>0). If the voltage utilization rate η changes drastically (e.g., the rate of change of voltage utilization rate η dη / dt = [η(k) - η(k-1)] / T_s exceeds the preset rate of change threshold), a correction amount Δα_rate is generated (at this time, Δα_rate = min(Δα_rate,0) is forced, i.e., Δα_rate≤0), and finally the second adjustment trajectory α_final(t)=α_base(t)+∫Δα_rate dt is generated.

[0059] The correction amount Δα_rate is generated through a dedicated PI controller. This is achieved by comparing the voltage utilization rate η with the voltage utilization rate curve η_ref, calculating the error e_η(t) = η_ref(t) - η(t), and then using the formula Δα_rate = Kp_η×e_η(t) + Ki_η×∫e_η(t)dt to obtain Δα_rate. Δα_rate is then limited, for example, by limiting it to -0.05 ≤ Δα_rate ≤ +0.05, to prevent overly aggressive correction. When η is lower than η_ref, e_η(t) > 0, resulting in a positive Δα_rate output, accelerating the change in α. When η is higher than η_ref, e_η(t) ≤ 0, resulting in a zero or negative Δα_rate output, slowing down or maintaining the change in α.

[0060] It should be noted here that when the triggering condition of the buffering mechanism is met, the buffering mechanism is executed until |di / dt| falls back below the safety threshold, and then the weight factor α is intelligently adjusted according to the adjustment scheme.

[0061] Optionally, S102 specifically includes: comparing the motor load rate with a preset load rate threshold, determining the current operating condition based on the comparison result, and calculating the maximum allowable modulation ratio under the current operating condition; Corresponding modulation control methods also include: The stator resistance of the motor is identified in real time to obtain the identified value of the stator resistance. The load rate threshold is dynamically adjusted based on the ratio of the identified value of the stator resistance to the preset rated stator resistance value.

[0062] In implementation, the modulation control system is used to first perform initialization operations: read the preset motor rated resistance Rso, q-axis inductance Lq and forget factor λ (usually taken as 0.99), set Rs_hat = Rs0 (that is, to realize the initialization of the stator resistance identification value, the initial value is Rs0), and set P = 100000 (a very large initial value, such as 100,000, to ensure that the algorithm starts quickly). Then, every control cycle k, the following calculations are performed sequentially: S51: Read the current d-axis voltage Vd, d-axis current Id, q-axis current Iq, and electric angular velocity ωe from memory; calculate the intermediate variable Y = Vd + ωe × Lq × Iq; S52: Calculate the gain K' = (P × Id) / (λ + Id × P × Id); S53: Calculate the prediction error E=Y-Id×Rs0; S54: Update the stator resistance identification value: Updated Rs_hat = Rs_hat at the current time + K' × E; S55: Update intermediate variable P: Updated P = (1 - K' × Id) × P / λ at the current time.

[0063] The latest calculated Rs_hat is used as the identification value of the stator resistance for this cycle and stored in memory; in the next control cycle k+1, the above calculation steps S51, S52, S53, S54, and S55 are repeated to update the resistance identification value Rs_hat.

[0064] Then, each time the modulation control system obtains the stator resistance identification value Rs_hat during each update, it calculates the resistance change rate kR = Rs_hat / Rso based on Rs_hat and the preset motor rated resistance Rso, and then adjusts the load rate thresholds x1 and x2 according to the resistance change rate. The adjusted x1 = preset initial value x1 / kR; the adjusted x2 = preset initial value x2 / Rs_hat; the principle here is explained as follows: the resistance is increased by k. R This means that, under the same Irms, the actual heat load (proportional to Irms²Rs) increases by k. R Therefore, to protect the motor and inverter, the current threshold for judging "light load" and "heavy load" should be reduced accordingly to 1 / kR of the original value. For example, if the resistance increases by 20% (kR=1.2), then the original heavy load threshold x2 should be corrected to x2 / 1.2, and the system will judge the heavy load condition earlier, thus limiting the upper limit of the modulation ratio earlier.

[0065] This application also discloses a continuous overmodulation control system for a multiphase motor based on current feedback. (Refer to...) Figure 2 ,include: The motor operation status monitoring module 201 is used to calculate the motor load rate in real time based on the motor current collected in real time. The operating condition and modulation ratio determination module 202 is used to determine the current operating condition based on the motor load rate and calculate the maximum allowable modulation ratio under the current operating condition; wherein, the current operating condition includes at least light load condition and heavy load condition; The final modulation ratio control module 203 is used to use the maximum modulation ratio as the upper limit value to limit the received modulation ratio command to a range not exceeding the upper limit value in order to calculate the final modulation ratio, and control the switching action of the power electronic switching device through the final modulation ratio.

[0066] Optionally, the final modulation ratio control module 203 includes a switching time adaptive correction unit 2031, which is used to calculate the basic switching time based on the final modulation ratio using a preset algorithm; calculate the dynamic adjustment coefficient C in real time according to the error between the motor command current and the actual current; and correct the basic switching time according to the dynamic adjustment coefficient C and the preset correction formula to obtain the adaptive switching time. The final modulation ratio control module 203 also includes an overmodulation control unit 2032, which is used to send the adaptive switching time to the inverter's PWM generator to generate corresponding drive pulses and control the power electronic switching devices to turn on and off. Optionally, the final modulation ratio control module 203 further includes a switching time gradual control unit 2033, which is used to calculate the first switching time and the second switching time respectively using the SPWM algorithm and the overmodulation algorithm when the preset algorithm is a combination of the SPWM algorithm and the overmodulation algorithm; calculate the weight factor according to the final modulation ratio; and calculate the adaptive switching time by fusing the first switching time and the second switching time based on the weight factor. The switching time adaptive correction unit 2031 is also used to correct the first switching time and the second switching time using a dynamic adjustment coefficient.

[0067] Optionally, a weighting factor intelligent control module is also included, which is used to monitor the rate of change of the motor phase current in real time. If the absolute value of the rate of change exceeds the preset safety threshold, a buffering mechanism is triggered to slow down the rate of change of the weighting factor α and extend the transition time.

[0068] Optionally, the intelligent control module for weighting factors is also used to predict the first adjustment trajectory of weighting factor α based on the current operating state of the motor and the trend of the modulation ratio command; calculate the output voltage utilization rate η of the inverter in real time, and dynamically correct the first adjustment trajectory with the goal of approximating the optimal voltage utilization rate to generate the second adjustment trajectory of weighting factor α; control the change of weighting factor α according to the second adjustment trajectory to achieve smooth switching; and monitor the rate of change of motor phase current in real time during the switching process; if the absolute value of the rate of change of motor phase current exceeds the preset safety threshold, a buffer mechanism is triggered, which extends the transition time by covering the second adjustment trajectory and forcibly reducing the rate of change of weighting factor α.

[0069] Optionally, the switching time adaptive correction unit 2031 is also used to calculate the rate of change of the final modulation ratio in real time, multiply the rate of change of the final modulation ratio by a preset feedforward gain coefficient to obtain the feedforward correction amount; calculate the feedback correction amount by the PI controller based on the error between the motor command current and the actual current; and calculate the dynamic adjustment coefficient C based on the feedforward correction amount and the feedback correction amount.

[0070] Optionally, the operating condition and modulation ratio determination module 202 is also used to compare the motor load rate with a preset load rate threshold, determine the current operating condition based on the comparison result, and calculate the maximum allowable modulation ratio under the current operating condition; It also includes a load rate threshold adjustment module, which is used to identify the stator resistance of the motor in real time to obtain the identified value of the stator resistance, and dynamically adjust the load rate threshold according to the ratio of the identified value of the stator resistance to the preset rated stator resistance value.

[0071] This application also discloses a multiphase motor continuous overmodulation control device based on current feedback. The multiphase motor continuous overmodulation control device based on current feedback includes a memory and a processor. The memory stores a computer program that can be loaded by the processor and executed as described above for the multiphase motor continuous overmodulation control method based on current feedback.

[0072] This application also discloses a computer-readable storage medium that stores a computer program that can be loaded by a processor and executed as described above for a multiphase motor continuous overmodulation control method based on current feedback. The computer-readable storage medium includes, for example, various media capable of storing program code, such as a USB flash drive, a portable hard drive, a read-only memory (ROM), a random access memory (RAM), a magnetic disk, or an optical disk.

[0073] It should be noted that in this paper, relational terms such as first and second are used only to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations.

[0074] The above embodiments are only used to illustrate the technical solutions of this application, and are not intended to limit the scope of protection of the application. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. Based on these embodiments, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

Claims

1. A continuous overmodulation control method for a multiphase motor based on current feedback, characterized in that, include: The motor load rate is calculated in real time based on the real-time collected motor current. Based on the motor load rate, the current operating condition is determined, and the maximum allowable modulation ratio under the current operating condition is calculated; wherein, the current operating condition includes at least light load operating condition and heavy load operating condition; The maximum modulation ratio is used as the upper limit value, and the received modulation ratio command is limited to a range not exceeding the upper limit value to calculate the final modulation ratio. The switching action of the power electronic switching device is controlled by the final modulation ratio. The method of controlling the switching action of the power electronic switching device through the final modulation ratio includes: The basic switching time is calculated based on the final modulation ratio using a preset algorithm. The dynamic adjustment coefficient C is calculated in real time based on the error between the motor command current and the actual current. Based on the dynamic adjustment coefficient C and the preset correction formula, the basic switching time is corrected to obtain the adaptive switching time. The adaptive switching time is sent to the inverter's PWM generator to generate corresponding drive pulses to control the power electronic switching devices to turn on and off. The preset algorithm is the SPWM algorithm; or the preset algorithm is a combination of the SPWM algorithm and the overmodulation algorithm. The method of controlling the switching action of the power electronic switching device through the final modulation ratio further includes: When the preset algorithm is a combination of SPWM algorithm and overmodulation algorithm, the first switching time and the second switching time are calculated by SPWM algorithm and overmodulation algorithm respectively. The weighting factor is calculated based on the final modulation ratio. Based on the weighting factor, the first switching time and the second switching time are fused to obtain the adaptive switching time. The step of fusing the first switching time and the second switching time to obtain the adaptive switching time also includes: The first switching time and the second switching time are corrected using the aforementioned dynamic adjustment coefficient; The real-time calculation of the dynamic adjustment coefficient C includes: The rate of change of the final modulation ratio is calculated in real time, and the rate of change of the final modulation ratio is multiplied by a preset feedforward gain coefficient to obtain the feedforward correction amount. The feedback correction amount is calculated by the PI controller based on the error between the commanded motor current and the actual current. The dynamic adjustment coefficient C is calculated based on the feedforward correction and the feedback correction.

2. The multiphase motor continuous overmodulation control method based on current feedback according to claim 1, characterized in that, The method further includes: The rate of change of the motor phase current is monitored in real time. If the absolute value of the rate of change exceeds a preset safety threshold, a buffering mechanism is triggered to slow down the rate of change of the weighting factor α and extend the transition time.

3. The multiphase motor continuous overmodulation control method based on current feedback according to claim 2, characterized in that, The real-time monitoring of the rate of change of the motor phase current, if the absolute value of the rate of change exceeds a preset safety threshold, triggers a buffering mechanism to slow down the rate of change of the weighting factor α and extend the transition time, including: Based on the current operating status of the motor and the trend of the modulation ratio command, the first adjustment trajectory of the weighting factor α is predicted; The inverter's output voltage utilization rate η is calculated in real time, and the first adjustment trajectory is dynamically corrected with the goal of approximating the optimal voltage utilization rate, thereby generating a second adjustment trajectory with weight factor α. The change in the second adjustment trajectory control weight factor α is used to achieve smooth switching; and during the switching process, the rate of change of the motor phase current is monitored in real time. If the absolute value of the rate of change of the motor phase current exceeds a preset safety threshold, a buffering mechanism is triggered. The buffering mechanism extends the transition time by covering the second adjustment trajectory and forcibly reducing the rate of change of the weighting factor α.

4. The multiphase motor continuous overmodulation control method based on current feedback according to claim 1, characterized in that, The step of determining the current operating condition based on the motor load rate and calculating the maximum allowable modulation ratio under the current operating condition includes: The motor load rate is compared with a preset load rate threshold. Based on the comparison result, the current operating condition is determined, and the maximum allowable modulation ratio under the current operating condition is calculated. The method further includes: The stator resistance of the motor is identified in real time to obtain the identified value of the stator resistance. The load rate threshold is dynamically adjusted according to the ratio of the identified value of the stator resistance to the preset rated stator resistance value.

5. A multiphase motor continuous overmodulation control system based on current feedback, applied to the multiphase motor continuous overmodulation control method based on current feedback as described in claim 1, characterized in that, include, The motor operation status monitoring module (201) is used to calculate the motor load rate in real time based on the motor current collected in real time. The operating condition and modulation ratio determination module (202) is used to determine the current operating condition based on the motor load rate and calculate the maximum allowable modulation ratio under the current operating condition; wherein, the current operating condition includes at least light load operating condition and heavy load operating condition; The final modulation ratio control module (203) is used to use the maximum modulation ratio as the upper limit value, and to limit the received modulation ratio command to a range not exceeding the upper limit value in order to calculate the final modulation ratio, and to control the switching action of the power electronic switching device through the final modulation ratio.

6. A multiphase motor continuous overmodulation control device based on current feedback, characterized in that, It includes a memory and a processor, wherein the memory stores a computer program that can be loaded by the processor and executed as described in any one of claims 1 to 4.

7. A computer-readable storage medium, characterized in that, The computer program is stored that can be loaded by a processor and executed as described in any one of claims 1 to 4.

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