Bus current estimation method and device of synchronous motor, equipment and storage medium

Abstract

The invention provides a bus current estimation method and device of a synchronous motor, equipment and a storage medium. The bus current estimation method comprises the steps of obtaining a corresponding three-phase current sampling value of the synchronous motor in a current control period; the target action duration corresponding to each phase of the synchronous motor in the current control period is obtained; wherein the target action duration corresponding to each phase is calculated in the previous control period of the synchronous motor; and according to the current control period, the three-phase current sampling value and the target action duration corresponding to each phase, calculating to obtain the bus current of the synchronous motor in the current control period. Through the mode, the actual action time of each phase corresponds to the corresponding current sampling value, and the bus current is obtained through calculation on the basis, so that the bus current value is accurate, and estimation precision reduction caused by period lag of the algorithm execution time and the action time is avoided.

Description

Technical Field

[0001] This application mainly relates to the technical field of motors, and particularly to a method, device, equipment, and storage medium for estimating the bus current of a synchronous motor. Background Art

[0002] The bus current of a motor is an important physical quantity used to judge the operating state of the motor, such as to judge whether the motor is overcurrent, idling, or blocked. Generally, field-oriented control of a permanent magnet synchronous motor requires detecting three-phase currents. If the bus current needs to be detected, an additional bus current sampling circuit or bus current sensor is required, which increases the hardware cost. Therefore, indirectly estimating the bus current has broad application prospects. Summary of the Invention

[0003] The main purpose of this application is to provide a method, device, equipment, and storage medium for estimating the bus current of a synchronous motor to solve the problem of insufficient accuracy in estimating the bus current during the operation of the motor, and to improve the accuracy of bus current estimation by changing the calculation method.

[0004] This application provides a method for estimating the bus current. The method for estimating the bus current includes: obtaining the three-phase current sampling values corresponding to the synchronous motor in the current control period; and obtaining the target action duration corresponding to each phase of the synchronous motor in the current control period; wherein, the target action duration corresponding to each phase is calculated in the previous control period of the synchronous motor; and calculating the bus current of the synchronous motor in the current control period according to the current control period, the three-phase current sampling values, and the target action duration corresponding to each phase.

[0005] In an embodiment, the three-phase current sampling values include a first-phase current sampling value, a second-phase current sampling value, and a third-phase current sampling value. Calculating the bus current of the synchronous motor in the current control period according to the current control period, the three-phase current sampling values, and the action duration corresponding to each phase includes: calculating the product of the first-phase current sampling value and the action duration corresponding to the first phase to obtain a first value; calculating the product of the second-phase current sampling value and the action duration corresponding to the second phase to obtain a second value; calculating the product of the third-phase current sampling value and the action duration corresponding to the third phase to obtain a third value; and using the sum of the first value, the second value, and the third value, and dividing it by the current control period to obtain the bus current of the synchronous motor in the current control period.

[0006] In one embodiment, obtaining the three-phase current sampling values corresponding to the synchronous motor in the current control period includes: obtaining the three-phase current sampling values corresponding to the synchronous motor in the current control period, and the three-phase current sampling values corresponding to the synchronous motor in the previous control period; calculating an average current sampling value based on the three-phase current sampling values corresponding to the current control period and the three-phase current sampling values corresponding to the previous control period, and using the average current sampling value as the three-phase current sampling values.

[0007] In one embodiment, the three-phase current sampling values include a first-phase current sampling value, a second-phase current sampling value, and a third-phase current sampling value. Calculating an average current sampling value based on the three-phase current sampling values corresponding to the current control period and the three-phase current sampling values corresponding to the previous control period includes: calculating the average value of the first-phase current sampling value corresponding to the current control period and the first-phase current sampling value corresponding to the previous control period to obtain a first-phase average current sampling value; calculating the average value of the second-phase current sampling value corresponding to the current control period and the second-phase current sampling value corresponding to the previous control period to obtain a second-phase average current sampling value; calculating the average value of the third-phase current sampling value corresponding to the current control period and the third-phase current sampling value corresponding to the previous control period to obtain a third-phase average current sampling value.

[0008] In one embodiment, calculating an average current sampling value based on the three-phase current sampling values corresponding to the current control period and the three-phase current sampling values corresponding to the previous control period includes: respectively integrating each phase current sampling value in the three-phase current sampling values in the current control period to obtain an integrated current sampling value for each phase; calculating the average current sampling value corresponding to each phase based on the current control period and the integrated current sampling value for each phase.

[0009] In one embodiment, obtaining the target action duration corresponding to each phase of the synchronous motor in the current control period includes: obtaining the theoretical action duration corresponding to each phase of the synchronous motor in the current control period; obtaining the dead-time action duration corresponding to each phase of the synchronous motor in the current control period; calculating the target action duration corresponding to each phase of the synchronous motor in the current control period based on the theoretical action duration and the dead-time action duration.

[0010] In one embodiment, according to the theoretical action duration and the dead - zone action duration, calculating the target action duration corresponding to each phase of the synchronous motor in the current control cycle includes: for any phase current, in response to the current direction of any phase current being the positive direction, subtracting the dead - zone action duration from the theoretical action duration to obtain the target action duration of any phase current; wherein, the positive direction indicates that the current flows into the synchronous motor; for any phase current, in response to the current direction of any phase current being the negative direction, adding the dead - zone action duration to the theoretical action duration to obtain the target action duration of any phase current; wherein, the negative direction indicates that the current flows out of the synchronous motor.

[0011] To solve the above problems, the present application also provides a bus - bar current estimation device, which includes: a sampling module that acquires the three - phase current sampling values corresponding to the synchronous motor in the current control cycle; a calculation module coupled to the sampling module, and the calculation module calculates in the previous control cycle of the synchronous motor to obtain the target action duration corresponding to each phase of the synchronous motor in the current control cycle; and, based on the current control cycle, the three - phase current sampling values, and the target action duration corresponding to each phase, calculates the bus - bar current of the synchronous motor in the current control cycle.

[0012] To solve the above problems, the present application also provides a bus - bar current estimation device, which includes: a memory; a processor connected to the memory, and the processor is configured to execute the bus - bar current estimation method described in any one of the above - mentioned embodiments.

[0013] To solve the above problems, the present application also provides a computer - readable storage medium, which stores computer - executable instructions. When the computer - executable instructions are executed by a processor, they are used to implement the bus - bar current estimation method described in any one of the above - mentioned embodiments.

[0014] Through the bus - bar current estimation method provided by the present application, combining the current control cycle, the three - phase current sampling values, and the target action duration corresponding to each phase, an estimated value of the bus - bar current is calculated. On this basis, by corresponding the timing of the action duration of each phase and the current sampling value, the accuracy of the bus - bar current estimation is improved, so as to avoid the reduction of the estimation accuracy caused by the cycle lag between the algorithm execution time and the action time. Description of the Drawings

[0015] To more clearly illustrate the technical solutions in the embodiments of the present application, the following will briefly introduce the drawings required for the description of the embodiments. Obviously, the following drawings are only some embodiments of the present application. For those of ordinary skill in the art, without creative efforts, other drawings can be obtained based on these drawings. Among them:

[0016] Figure 1 It is a schematic diagram of the step flow of an embodiment of the bus current estimation method provided by this application;

[0017] Figure 2 It is a spatial vector distribution diagram of an embodiment of the vector correspondence relationship provided by this application;

[0018] Figure 3 It is a schematic diagram of the combined action of effective vectors and zero vectors in an embodiment of the bus current estimation method provided by this application;

[0019] Figure 4 It is a schematic diagram of the relationship between effective vectors, zero vectors and duty ratios of each phase in an embodiment of the bus current estimation method provided by this application;

[0020] Figure 5 It is Figure 1 a schematic diagram of the sub-step flow of step S30 in

[0021] Figure 6 It is a logical schematic diagram of an embodiment of the execution timing of the control algorithm provided by this application;

[0022] Figure 7 It is a schematic diagram of the change of sampled current provided by this application;

[0023] Figure 8 It is Figure 1 a schematic diagram of the sub-step flow of step S10 in

[0024] Figure 9 It is Figure 8 a schematic diagram of the first sub-step flow of step S12 in

[0025] Figure 10 It is Figure 8 a schematic diagram of the second sub-step flow of step S12 in

[0026] Figure 11 It is an oscillogram of an embodiment of the U phase and its corresponding PWM drive signal provided by this application;

[0027] Figure 12 It is a dead-time duty ratio relationship diagram of an embodiment of the dead-time compensation provided by this application;

[0028] Figure 13a and Figure 13b It is a schematic diagram of the current flow direction within the dead time in a single bridge arm provided by this application;

[0029] Figure 14 It is a schematic diagram of the structure of an embodiment of the bus current estimation device provided by this application;

[0030] Figure 15 It is a schematic diagram of the structure of an embodiment of the bus current estimation device provided by this application;

[0031] Figure 16 It is a schematic structural diagram of an embodiment of a computer-readable storage medium provided by this application.

[0032] Reference numerals in the drawings:

[0033] 100, bus current estimation device; 110, sampling module; 120, calculation module; 200, bus current estimation device; 210, memory; 220, processor; 300, computer-readable storage medium; 310, computer-executable instructions. Detailed implementation manners

[0034] Next, the technical solutions in the embodiments of this application will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of this application. It can be understood that the specific embodiments described herein are only used to explain this application, rather than limiting this application. Additionally, it should be noted that for the sake of description, only parts related to this application rather than all structures are shown in the accompanying drawings. Based on the embodiments in this application, all other embodiments obtained by those of ordinary skill in the art without creative efforts belong to the scope of protection of this application.

[0035] The terms "first", "second", etc. in this application are used to distinguish different objects, rather than to describe a specific order. In addition, the terms "including" and "having" and any variations thereof are intended to cover non-exclusive inclusion. For example, a process, method, system, product, or device that includes a series of steps or units is not limited to the listed steps or units, but optionally further includes unlisted steps or units, or optionally further includes other steps or units inherent to these processes, methods, products, or devices.

[0036] Referring to "embodiments" herein means that specific features, structures, or characteristics described in conjunction with the embodiments can be included in at least one embodiment of this application. The phrase appears in various positions in the specification does not necessarily refer to the same embodiment, nor is it an independent or alternative embodiment mutually exclusive with other embodiments. Those skilled in the art explicitly and implicitly understand that the embodiments described herein can be combined with other embodiments.

[0037] Permanent Magnet Synchronous Motors (PMSMs) are widely used in various industrial control fields due to their advantages of high power density, low loss, and reliability. Currently, the control method of PMSMs mainly uses Field Oriented Control (FOC) to complete the closed-loop control of torque and speed. To achieve closed-loop control, it is necessary to detect the motor phase current in real time.

[0038] The scheme for estimating the bus current using the three-phase current of the motor needs to directly or indirectly use the three-phase voltage and three-phase current of the motor. Therefore, the accuracy of the phase voltage or phase current will directly affect the accuracy of the bus current estimation. The factors affecting the accuracy of the phase voltage include the dead-time effect, inverter non-linearity, etc., and the factors affecting the accuracy of the phase current include the accuracy of the current sensor, hardware current noise, etc. Based on the above problems and factors, the present application provides a method, device, equipment, and storage medium for estimating the bus current of a synchronous motor to solve the above problems and improve the accuracy of the bus current estimation.

[0039] Refer to Figure 1 as shown in Figure 1 FIG. 8 is a schematic flowchart of the steps of an embodiment of the bus current estimation method provided by the present application; the bus current estimation method includes the following steps:

[0040] Step S10: Obtain the three-phase current sampling values corresponding to the synchronous motor in the current control cycle.

[0041] According to the hardware setting position of the current sensor, the motor phase current sampling scheme can generally be divided into three types: arm sampling, phase line sampling, and bus sampling. Among them, the bus sampling scheme is to connect a current sensor in series at the high-voltage input ground end. Since there is a direct connection between the bus current and the three-phase current of the motor, the motor phase current can be captured in the bus current by dynamically setting the sampling point in the main control chip. For this scheme, obtaining the bus current only requires simple low-pass filtering of the output result of the current sensor and then sampling. For the arm sampling and phase line sampling schemes, there is no current sensor on the bus, so the bus current can only be reconstructed using the sampled three-phase current.

[0042] Therefore, on the premise of considering the above reasons, the bus current is estimated by calculating the time sequence of the phase current and the phase voltage.

[0043] It can be understood that in a FOC control system using Space Vector Pulse Width Modulation (SVPWM), defining the upper bridge arm conducting and the lower bridge arm turning off as 0, and the upper bridge arm turning off and the lower bridge arm conducting as 1, there are eight vectors, namely 111 (u7), 000 (u0), 001 (u1), 010 (u2), 011 (u3), 100 (u4), 101 (u5), 110 (u6), and their vector correspondence is as Figure 2 shown in Figure 2 FIG. 24 is a space vector distribution diagram of an embodiment of the vector correspondence provided by the present application. Among them, u7 and u0 are called zero vectors, u x, where \(x = 1\sim6\), is called the effective vector. Among them, FOC (Field-Oriented Control) is a high-performance control technology used to control AC motors (such as permanent magnet synchronous motors PMSM and induction motors IM). Its core idea is to decompose the three-phase current of the motor into a magnetic field component (excitation component) and a torque component through coordinate transformation, so as to achieve precise control of the motor, similar to the control method of DC motors.

[0044] Combined with Figure 3 as shown in Figure 3 is a schematic diagram of the combined action of the effective vector and the zero vector in an embodiment of the bus current estimation method provided by this application; among them, the combined action of the effective vector and the zero vector is a PWM cycle, \(u\) x and \(u\) y respectively represent two effective vectors acting in a cycle. When the effective vector acts, the motor phase current will flow between the motor and the bus, and when the zero vector acts, the motor phase current will only flow between the motor and the inverter switching devices. Therefore, the relationship between the bus current and the three-phase current in a PWM cycle is the weighted average sum of the phase currents generated under the action of the effective vector according to the action time. The specific calculation method is as follows:

[0045] The relationship between the effective vector, the zero vector and the duty ratio of each phase in a PWM cycle is as Figure 4 shown in Figure 4 is a schematic diagram of the relationship between the effective vector, the zero vector and the duty ratio of each phase in an embodiment of the bus current estimation method provided by this application; among them, let \(T\) pwm , \(T\) u , \(T\) v , \(T\) w , \(T_0\), \(T_7\) respectively represent the PWM cycle time, the action time of phase U, the action time of phase V, the action time of phase W, the action time of \(u\) o vector, the action time of \(u_7\) vector, \(T\) x , \(T\) y respectively represent the action time of the first effective vector and the action time of the second effective vector. Use \(I\) x , \(I\) y to represent the current generated by the action of the first effective vector and the current generated by the action of the second effective vector respectively. Among them, the first phase is represented by \(u\), the second phase is represented by \(v\), and the third phase is represented by \(w\).

[0046] It can be understood that according to the volt-second equivalence principle, the calculation expression of the average value of the bus current in a PWM cycle is:

[0047]

[0048] In a PWM cycle, the weighted average sum of the action times corresponding to the three-phase currents is:

[0049]

[0050] Because,

[0051]

[0052] Then, Equation (2) can be expanded as:

[0053]

[0054] Because, I u + I v + I w = 0, I u + I v = -I w Therefore, Equation (4) can be simplified to:

[0055]

[0056] Wherein, is the three-phase average current, is the bus current, and Equation (5) and Equation (1) also satisfy I x = I u , I y = -I w , I x and I y are actually corresponding phase currents related to the acting voltage vector. According to the sector voltage vector correspondence described by Figure 4 , the phase current values are summarized in Table 1 below. Table 1 is a table showing the relationship between the current generated by the effective vector action in each sector provided by this application and the phase current;

[0057]

[0058] It can be concluded from the above derivation that the bus current can be estimated using the three-phase current by Equation (2), that is, by dividing the sum of the first value, the second value, and the third value by the current control period, the bus current of the synchronous motor in the current control period is obtained. At the same time, it can also be seen that the accuracy of the phase current and the accuracy of the acting time directly determine the accuracy of the bus current estimation.

[0059] Step S20: Obtain the target acting duration corresponding to each phase of the synchronous motor in the current control period; wherein, the target acting duration corresponding to each phase is calculated in the previous control period of the synchronous motor.

[0060] It can be understood that during the execution of the motor action, since the chip calculation and execution require a certain amount of time, there will be a certain execution lag during the process of applying the calculated value to the inverter. For example, the action execution lags behind by one control cycle. Therefore, after considering the corresponding relationship of the time sequence, the actual target action duration is calculated by obtaining the synchronous motor in different control cycles.

[0061] Step S30: Calculate the bus current of the synchronous motor in the current control cycle according to the current control cycle, the three-phase current sampling values, and the target action duration corresponding to each phase.

[0062] Through the above bus current estimation method, combined with the current control cycle, the three-phase current sampling values, and the target action duration corresponding to each phase, the estimated value of the bus current is calculated. On this basis, by corresponding the time sequence of the action duration and current sampling value of each phase, the accuracy of the bus current estimation is improved, so as to avoid the reduction of the estimation accuracy caused by the cycle lag between the algorithm execution time and the action time.

[0063] Therefore, combined with the above embodiments and their explanations, the above solution estimates the bus current by using the three-phase current in combination with the action time in terms of time sequence correspondence, as follows:

[0064] In one embodiment, refer to Figure 5 as shown, Figure 5 is Figure 1 the schematic diagram of the sub-step flow of step S30 in

[0065] Step S310: Calculate the product of the first-phase current sampling value and the action duration corresponding to the first phase to obtain the first value.

[0066] Step S311: Calculate the product of the second-phase current sampling value and the action duration corresponding to the second phase to obtain the second value.

[0067] Step S312: Calculate the product of the third-phase current sampling value and the action duration corresponding to the third phase to obtain the third value.

[0068] Step S313: Divide the sum of the first value, the second value, and the third value by the current control cycle to obtain the bus current of the synchronous motor in the current control cycle.

[0069] It can be understood that in the above embodiment solution, considering the above lag problem, a time sequence correspondence solution is proposed, combined with Figure 6As shown Figure 6 is a logical schematic diagram of an embodiment of the execution timing of the control algorithm provided by this application; where T pwm represents the PWM cycle time, and T uvw represents the three-phase action time, and I uvw represents the three-phase current sampling value. Task represents the motor control algorithm execution task. In Task, the required three-phase action time will be calculated. Let (k) represent the current cycle and (k + 1) represent the next cycle. Since the chip algorithm execution takes time, the three-phase action time calculated at the (k) moment can only be applied to the inverter at the (k + 1) moment, resulting in a one-cycle lag. Because the motor phase voltage changes sinusoidally, there will be a difference in the action time between two cycles. As the rotational speed increases, this difference will be gradually amplified. Ignoring this difference will reduce the accuracy of the bus current estimation. For the voltage action T uvw (k) at time (k), the current generated is reflected in the cycle from (k) to (k + 1). It can be understood that since the action time for different phases needs to be calculated, during the calculation process, usually the moment of the previous control cycle, that is, (k - 1), can be used to calculate the action time of the current (k) cycle. However, for the sake of easy understanding in the description, it is described as the current control cycle and the next control cycle. Therefore, in the subsequent calculation process, for the calculation of the cycle time, for the previous control cycle, the current control cycle, and the next control cycle, they can be adjusted with each other according to different understandings.

[0070] The corresponding step S313: Using the sum of the first value, the second value, and the third value, and dividing it by the current control cycle, the specific formula for the bus current of the synchronous motor in the current control cycle is:

[0071]

[0072] where, is the bus current, I u (k + 1) is the first-phase current, I v (k + 1) is the second-phase current, I w (k + 1) is the third-phase current, T u (k) is the first-phase control time, T v (k) is the second-phase control time, T w (k) is the third-phase control time, (k) represents the current control cycle, (k + 1) represents the next control cycle, and T pwm is a PWM control cycle.

[0073] In the above manner, the timing relationship between the phase current and the phase voltage is strictly analyzed according to the PWM control period, so that the phase current used in the calculation is the phase voltage that generates the current, ensuring the accuracy of the instantaneous bus current reconstruction.

[0074] For current fitting:

[0075] As Figure 7 shown, Figure 7 is a schematic diagram of the change in the sampled current provided by this application; in a PWM cycle, under the action of a fixed phase voltage, the motor current gradually changes. Therefore, there is a large difference between I(k) and I(k + 1), and this difference will also be amplified as the rotational speed increases. At this time, using I(k + 1) to represent the bus current value in the (k) cycle is obviously too large, and relatively, I(k) is too small. Therefore, in order to better fit the average value of the bus current in the (k) cycle, the two-point averaging method is used here to obtain the average value of the phase current period for estimating the bus current. The average value calculation method is as described in the following embodiments. In one embodiment, as Figure 8 shown, Figure 8 is Figure 1 a schematic diagram of the sub-step process of step S10 in

[0076] Step S11: Obtain the three-phase current sampled values corresponding to the synchronous motor in the current control cycle, and the three-phase current sampled values corresponding to the synchronous motor in the previous control cycle;

[0077] Step S12: Calculate the average current sampled value according to the three-phase current sampled values corresponding to the current control cycle and the three-phase current sampled values corresponding to the previous control cycle, and use the average current sampled value as the three-phase current sampled value.

[0078] Generally, the calculation of the average current in the PWM cycle can be further implemented as the following embodiment scheme:

[0079] In one embodiment, as Figure 9 shown, Figure 9 is Figure 8 a schematic diagram of the first sub-step process of step S12 in

[0080] Step S120: Integrate each phase current sampled value in the three-phase current sampled values in the current control cycle to obtain each phase integrated current sampled value.

[0081] Step S121: Calculate the average current sampled value corresponding to each phase according to the current control cycle and each phase integrated current sampled value.

[0082]

[0083] Among them, I uave is the first-phase average current, T pwm is the control period, t(k - 1) is the start time of the previous control period, t(k) is the start time of the current control period, I u (t) is the first-phase current of the current control period, (k) represents the current control period, and (k - 1) represents the previous control period.

[0084] By the above method, analyze the change trend of the phase current in the PWM period, and calculate the average current in an integral way to improve the accuracy of the average value of the bus current.

[0085] However, in the actual process, since the control system, digital implementation, etc. are discrete and cannot be continuously integrated, an approximate scheme is considered. Since the PWM period is very short and the change of the current in one PWM period is considered linear, the method of averaging two points is used to calculate the integral result.

[0086] Based on the above scheme, a two-point averaging method is proposed to calculate the average value of the current in this period to improve the accuracy of the average value of the bus current.

[0087] Among them, the calculation of the two-point average current sampling value includes:

[0088]

[0089] Among them, I ave represents the sampling value of the average current of any one phase.

[0090] In an embodiment, as Figure 10 shown, Figure 10 is Figure 8 the schematic flow diagram of the second sub-step of step S12 in ; among them, the three-phase current sampling values include the first-phase current sampling value, the second-phase current sampling value, and the third-phase current sampling value. The average current sampling value is calculated according to the three-phase current sampling values corresponding to the current control period and the three-phase current sampling values corresponding to the previous control period, and includes the following sub-steps:

[0091] Step S122: Calculate the average value of the first-phase current sampling value corresponding to the current control period and the first-phase current sampling value corresponding to the previous control period to obtain the first-phase average current sampling value.

[0092] Step S123: Calculate the average value of the second-phase current sampling value corresponding to the current control period and the second-phase current sampling value corresponding to the previous control period to obtain the second-phase average current sampling value.

[0093] Step S124: Calculate the average value of the third-phase current sampling value corresponding to the current control period and the third-phase current sampling value corresponding to the previous control period to obtain the third-phase average current sampling value.

[0094] Combined with the above embodiments, corresponding to formula (7), the average current sampling value corresponding to each phase is calculated by using the current control period and the integral current sampling value of each phase. On the basis of combining the solution of this embodiment, the estimation of the bus current is as follows:

[0095]

[0096] Wherein, is the bus current, T pwm is the control period, t(k + 1) is the start time of the next control period, t(k) is the start time of the current control period, I u is the first-phase current, I v is the second-phase current, I w is the third-phase current, T u is the first-phase control time, T v is the second-phase control time, T w is the third-phase control time, (k) represents the current control period, and (k + 1) represents the next control period.

[0097] For the two-point average calculation method, corresponding to formula (8), the phase current period average value obtained is used to estimate the bus current, and its calculation formula is as follows:

[0098]

[0099] Wherein, is the bus current, I u (k + 1) is the first-phase current, I v (k + 1) is the second-phase current, I w (k + 1) is the third-phase current, T u (k) is the first-phase control time, T v (k) is the second-phase control time, T w (k) is the third-phase control time, (k) represents the current control period, (k + 1) represents the next control period, T pwm is the control period.

[0100] It can be understood that referring to Figure 11 as shown, Figure 11It is an oscillogram of an embodiment of the U phase and its corresponding PWM drive signal provided by this application; among them, taking the U phase of the motor and its corresponding PWM drive signal as an example, at this time, the U phase current frequency is 750 Hz, the PWM switching frequency is 10 kHz, and there are approximately 13 PWM cycles in one current cycle. The periods k-1 and k are marked in the figure, and the corresponding U phase action times are Tu(k-1) and Tu(k) respectively. Usually, current sampling is performed at the 0 vector in motor control, so the corresponding U phase sampled currents in the current cycle are Iu(k-1) and Iu(k) respectively. In the k-1 cycle, the U phase current rapidly changes from Iu(k-1) to Iu(k), while Tu(k-1) and Tu(k) change little. If Iu(k) is directly used as the U phase current in the k-1 cycle to estimate the bus current, it will bring a large error. Therefore, through the above method, a current fitting strategy is introduced. At this time, Ia = Tu(k-1)*(Iu(k)+Iu(k-1)) / 2. The average processing of the current makes the current calculation in the k-1 cycle more accurate, thereby obtaining a more accurate bus current estimate.

[0101] Regarding dead-time compensation:

[0102] Among them, the dead time refers to when driving power electronic converters such as inverters and rectifiers, the switching tubes of the same bridge arm cannot be turned on simultaneously, which will cause a short-circuit phenomenon, burn out power electrical devices, etc., resulting in economic losses and safety hazards. And any solid-state power switching tube has a certain on and off time. To ensure that the upper and lower switching tubes of the same bridge arm do not cause a through-fault, usually, the rising edge (or falling edge) of the ideal PWM drive signal is delayed by a period of time Td (referred to as the dead time). The dead time is a measure taken to ensure the safe and reliable operation of the switching device.

[0103] In one embodiment, obtaining the target action duration corresponding to each phase of the synchronous motor in the current control cycle includes: obtaining the theoretical action duration corresponding to each phase of the synchronous motor in the current control cycle; obtaining the dead-time action duration corresponding to each phase of the synchronous motor in the current control cycle; and calculating the target action duration corresponding to each phase of the synchronous motor in the current control cycle according to the theoretical action duration and the dead-time action duration.

[0104] It can be understood that in order to prevent the switching device from being through, the complementary PWM signals applied to a pair of bridge arms in the inverter system need to add a dead time at the edge to achieve that when one switching tube is turned on or off, the signal side of the other switching tube is in the off state, as Figure 12 shown Figure 12 It is a dead-time duty ratio relationship diagram of an embodiment of dead-time compensation provided by this application; among them, the shaded part represents adding a dead time T d . The PWM cycle time is represented by T pwmIndicates, T set Indicates the calculated action time, T real Indicates the actual output PWM action application after subtracting the dead time, that is, satisfying T real = T set - T d .

[0105] In one embodiment, according to the theoretical action duration and the dead-time action duration, the calculated target action duration corresponding to each phase of the synchronous motor in the current control period includes: for any phase current, in response to the current direction of any phase current being the positive direction, subtracting the dead-time duration from the theoretical action duration to obtain the target action duration of any phase current; wherein, the positive direction indicates that the current flows into the synchronous motor; for any phase current, in response to the current direction of any phase current being the negative direction, adding the dead-time duration to the theoretical action duration to obtain the target action duration of any phase current; wherein, the negative direction indicates that the current flows out of the synchronous motor.

[0106] Because the inductor current is continuous, although the PWM turn-on signal is not applied during the dead time, due to the existence of the freewheeling diode of the switching device, the corresponding switch is in an equivalent conduction state. Therefore, even if there is a dead-time deviation of T d between the applied PWM signal and the given value, this value cannot be directly subtracted from T set , but the action time needs to be recalculated according to the freewheeling diode state in the current period. Taking a bridge arm as an example, the current flow direction during the dead time is as shown in Figure 13a and Figure 13b ; Figure 13a and Figure 13b are the schematic diagrams of the current flow direction during the dead time in the single bridge arm provided by the present application; wherein, the current flowing into the motor is defined as the positive current as shown in Figure 13a , and the flowing out is the negative current as shown in Figure 13b . (That is, corresponding to the positive direction and the negative direction in the above embodiment) When the current is positive, during the dead time, the current uses the diode D2 of the lower tube of the bridge arm to freewheel, and at this time the application time T apply = T set - T d ; when the current is negative, during the dead time, the current uses the diode D1 of the upper tube of the bridge arm to freewheel, and at this time the application time T apply = T set + T d . Recalculate the bus current using the action time after dead-time compensation as follows:

[0107]

[0108] Among them, corresponding to the above embodiment, T apply is the target action duration, T setis the theoretical operating duration, T d is the dead-time operating duration.

[0109] Regarding the dead-time compensation scheme mentioned above, in other embodiments, the phase voltage of the motor can also be directly sampled by setting up a motor phase voltage sampling circuit to avoid the problem of reduced estimation accuracy caused by errors in the phase voltage used when estimating the bus current. The proposed current fitting scheme is a rough average current estimation method. For the accurate average current in the PWM cycle, especially the average value of the bus current under the action of the effective vector, a more accurate average current can be calculated by continuously sampling using a high-sampling-rate ADC (Analog to Digital Converter), thereby improving the estimation accuracy of the bus current.

[0110] Through the above method, dead-time compensation is introduced to improve the accuracy of phase voltage reconstruction in the no-phase-voltage sampling system, thereby improving the accuracy of bus current estimation. Among them, according to the introduced dead-time compensation scheme and combined with other schemes in the above embodiments, the estimation accuracy of the bus current is further improved.

[0111] To solve the above problems, the present application also provides a bus current estimation device 100, as Figure 14 shown, Figure 14 is a schematic structural diagram of an embodiment of the bus current estimation device 100 provided by the present application; the bus current estimation device 100 includes: a sampling module 110, and the sampling module 110 obtains the three-phase current sampling values corresponding to the synchronous motor in the current control cycle; a calculation module 120, the calculation module 120 is coupled to the sampling module 110, and the calculation module 120 calculates through the previous control cycle of the synchronous motor to obtain the target action duration corresponding to each phase of the synchronous motor in the current control cycle; and, according to the current control cycle, the three-phase current sampling values and the target action duration corresponding to each phase, the bus current of the synchronous motor in the current control cycle is calculated.

[0112] To solve the above problems, the present application also provides a bus current estimation device 200, as Figure 15 shown, Figure 15 is a schematic structural diagram of an embodiment of the bus current estimation device 200 provided by the present application; the bus current estimation device 200 includes: a memory 210; a processor 220, connected to the memory 210, and the processor 220 is configured to execute the bus current estimation method described in any one of the above embodiments.

[0113] To solve the above problems, the present application also provides a computer-readable storage medium 300, as Figure 16 shown, Figure 16It is a schematic structural diagram of an embodiment of the computer-readable storage medium 300 provided by the present application; the computer-readable storage medium 300 stores computer-executable instructions 310, and when the computer-executable instructions 310 are executed by the processor 220, they are used to implement the bus current estimation method described in any one of the above embodiments.

[0114] In the above manner, by obtaining the current sampling value of each phase and the corresponding action duration of each phase, the bus current value is obtained through calculation. Through current fitting, timing correspondence, and dead-time compensation, the accuracy of calculating the bus current value is improved, and the influence of low accuracy of the bus current estimation caused by problems such as the accuracy of the phase voltage or phase current and the corresponding action duration is avoided.

[0115] The above has introduced the embodiments of the present application in detail. Specific examples are used in this article to elaborate on the principle and implementation manner of the present application. The description of the above embodiments is only used to help understand the method and its core idea of the present application; at the same time, for those skilled in the art, according to the idea of the present application, there will be changes in the specific implementation manner and application scope. In summary, the content of this specification should not be construed as a limitation to the present application.

Claims

1. A method for estimating the bus current of a synchronous motor, characterized in that The bus current estimation method includes: Obtaining the three-phase current sampling values corresponding to the synchronous motor in the current control period; And obtaining the target action duration corresponding to each phase of the synchronous motor in the current control period; wherein, the target action duration corresponding to each phase is calculated in the previous control period of the synchronous motor; Calculating the bus current of the synchronous motor in the current control period according to the current control period, the three-phase current sampling values and the target action duration corresponding to each phase.

2. The busbar current estimation method according to claim 1, wherein The three-phase current sampling values include a first-phase current sampling value, a second-phase current sampling value and a third-phase current sampling value. Calculating the bus current of the synchronous motor in the current control period according to the current control period, the three-phase current sampling values and the action duration corresponding to each phase includes: Calculating the product of the first-phase current sampling value and the action duration corresponding to the first phase to obtain a first value; Calculating the product of the second-phase current sampling value and the action duration corresponding to the second phase to obtain a second value; Calculating the product of the third-phase current sampling value and the action duration corresponding to the third phase to obtain a third value; Dividing the sum of the first value, the second value and the third value by the current control period to obtain the bus current of the synchronous motor in the current control period.

3. The busbar current estimation method according to claim 1, wherein The obtaining the three-phase current sampling values corresponding to the synchronous motor in the current control period includes: Obtaining the three-phase current sampling values corresponding to the synchronous motor in the current control period, and the three-phase current sampling values corresponding to the synchronous motor in the previous control period; Calculating an average current sampling value according to the three-phase current sampling values corresponding to the current control period and the three-phase current sampling values corresponding to the previous control period, and using the average current sampling value as the three-phase current sampling values.

4. The busbar current estimation method according to claim 3, characterized in that, The three-phase current sampling values include a first-phase current sampling value, a second-phase current sampling value and a third-phase current sampling value. Calculating an average current sampling value according to the three-phase current sampling values corresponding to the current control period and the three-phase current sampling values corresponding to the previous control period includes: Calculating the average value of the first-phase current sampling value corresponding to the current control period and the first-phase current sampling value corresponding to the previous control period to obtain a first-phase average current sampling value; Calculating the average value of the second-phase current sampling value corresponding to the current control period and the second-phase current sampling value corresponding to the previous control period to obtain a second-phase average current sampling value; Calculating the average value of the third-phase current sampling value corresponding to the current control period and the third-phase current sampling value corresponding to the previous control period to obtain a third-phase average current sampling value.

5. The method for estimating busbar current according to claim 3, wherein Calculating an average current sampling value according to the three-phase current sampling values corresponding to the current control period and the three-phase current sampling values corresponding to the previous control period includes: Integrate each phase current sampling value in the three-phase current sampling values within the current control period to obtain each phase integrated current sampling value; Calculate the average current sampling value corresponding to each phase according to the current control period and each phase integrated current sampling value.

6. The busbar current estimation method according to any one of claims 1-5, characterized in that The obtaining the target action duration corresponding to each phase of the synchronous motor at the current control period includes: Obtain the theoretical action duration corresponding to each phase of the synchronous motor at the current control period; Obtain the dead-time action duration corresponding to each phase of the synchronous motor at the current control period; According to the theoretical action duration and the dead-time action duration, calculate the target action duration corresponding to each phase of the synchronous motor at the current control period.

7. The busbar current estimation method according to claim 6, characterized in that, The calculating the target action duration corresponding to each phase of the synchronous motor at the current control period according to the theoretical action duration and the dead-time action duration includes: For any phase current, in response to the current direction of the any phase current being the positive direction, subtract the dead-time action duration from the theoretical action duration to obtain the target action duration of the any phase current; wherein, the positive direction indicates that the current flows into the synchronous motor; For any phase current, in response to the current direction of the any phase current being the negative direction, add the dead-time action duration to the theoretical action duration to obtain the target action duration of the any phase current; wherein, the negative direction indicates that the current flows out of the synchronous motor.

8. A busbar current estimation device for a synchronous motor, characterized in that, The bus current estimation device includes: A sampling module, which obtains the three-phase current sampling values corresponding to the synchronous motor at the current control period; A calculation module, which is coupled to the sampling module. The calculation module calculates in the previous control period of the synchronous motor to obtain the target action duration corresponding to each phase of the synchronous motor at the current control period; and, according to the current control period, the three-phase current sampling values and the target action duration corresponding to each phase, calculates the bus current of the synchronous motor at the current control period.

9. A busbar current estimation device for a synchronous motor, characterized in that, The bus current estimation device includes: A memory; A processor, connected to the memory, and the processor is configured to execute the bus current estimation method according to any one of claims 1-7.

10. A computer-readable storage medium, characterized in that, The computer-readable storage medium stores computer-executable instructions, and when the computer-executable instructions are executed by a processor, they are used to implement the bus current estimation method according to any one of claims 1-7.

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