Three-phase current sampling optimization method and system, detection control circuit and power device

Abstract

The invention relates to a three-phase current sampling optimization method and system, a detection control circuit and a power device, and belongs to the technical field of motor control. A plurality of sampling points and corresponding three-phase current values are obtained by taking a three-phase current pulse width midpoint as a starting point when a switch is switched on; and based on each sampling point moment and the corresponding three-phase current value, calculating to obtain an optimization coefficient corresponding to each phase current corresponding to each sampling point moment, then based on the optimization coefficient and each sampling point moment, calculating to obtain an optimal sampling point moment, and further obtaining an optimal three-phase current value. Compared with the prior art, the rotating speed of the motor does not need to be reduced, the optimal three-phase current value can be obtained, and therefore optimal control over the motor is achieved. The problems that in the prior art, the accurate motor load feedback three-phase current value cannot be obtained at the same time, and the motor performance is not affected are solved.

Description

Technical Field

[0001] The present invention relates to the technical field of motor control, and in particular to a three-phase current sampling optimization method, system, detection control circuit and power device. Background Art

[0002] In a power system using a three-phase AC motor, in order to obtain accurate load feedback of the three-phase current to achieve more accurate control of the motor, it is usually necessary to sample the three-phase current output by the motor load. Taking drones as an example, drones using three-phase AC motors usually integrate electronic speed regulators, in which the full-bridge circuit structure of the electronic speed regulator includes upper bridge arm and lower bridge arm circuits. The upper and lower bridge arms are alternately turned on and off to input PWM pulse drive signals respectively, thereby achieving control of the three-phase AC motor. Sampling the lower bridge arm to obtain the three-phase current of the motor load is a common practice in the industry, which has the advantages of low cost and low implementation difficulty.

[0003] Since the sampling circuit is usually grounded with the driver tube and is not isolated, the switching noise signal generated when the switch of the driver tube is turned on will affect the load feedback sampling data, making it impossible to confirm the optimal sampling three-phase current value, thereby making it difficult to optimally control the motor; among them, the impact on the lower bridge arm circuit of the drone electronic speed regulator is particularly serious. When the power of the PWM pulse drive signal output by the lower bridge arm is small, it is even impossible to obtain an accurate sampling value near the time when the switch is turned on, resulting in current loop oscillation.

[0004] In the prior art, the output power of the PWM pulse drive signal is generally limited so that the sampling load feedback moment is farther away from the switch-on moment, thereby obtaining an accurate sampling value. However, limiting the output power will limit the motor speed and affect the maneuverability. Therefore, how to obtain accurate motor load feedback three-phase current values ​​without affecting the motor performance has become a difficult problem in the industry. Summary of the invention

[0005] In view of the above analysis, the embodiments of the present invention aim to provide a three-phase current sampling optimization method, system, detection control circuit and power device to solve the problem in the prior art that it is impossible to obtain accurate motor load feedback three-phase current values ​​without affecting motor performance.

[0006] On the one hand, an embodiment of the present invention provides a three-phase current sampling optimization method, the method specifically comprising:

[0007] Taking the midpoint of the pulse width of the three-phase current when the switch is turned on as the starting point, continuous sampling is performed at a set time interval to obtain multiple sampling point moments and corresponding three-phase current values;

[0008] Based on the time of each sampling point and the corresponding three-phase current value, the optimization coefficient corresponding to each phase current corresponding to each sampling point time is calculated;

[0009] Calculate the optimal sampling point time based on the optimization coefficient and the sampling point time;

[0010] The optimal three-phase current value is obtained based on the optimal sampling point time correspondence.

[0011] The beneficial effects of the above technical solution are as follows: the midpoint of the three-phase current pulse width when the switch is turned on is used as the starting point, and the obtained sampling points and corresponding three-phase current values ​​are less affected by the switch than the sampling points and corresponding three-phase current values ​​at the instant of the switch being turned on, and the values ​​are more accurate; the optimization coefficient corresponding to each phase current at each sampling point is calculated based on the sampling point moment and the corresponding three-phase current value, which is based on the Newton interpolation method, combined with the three-phase current waveform characteristics to obtain the optimization coefficient corresponding to each phase current at each sampling point moment; then the optimal sampling point moment is calculated based on the optimization coefficient and each sampling point moment, and then the optimal three-phase current value is obtained. Compared with the prior art, there is no need to reduce the motor speed, and the optimal three-phase current value can be obtained to achieve optimal control of the motor.

[0012] Based on the further improvement of the above method, the set time interval is calculated by the following formula, which is specifically expressed as:

[0013] Where, T s is the set time interval, N is the number of sampling points, Pulse min is the minimum allowed pulse.

[0014] The beneficial effect of the above further improved solution is that the set time interval is calculated based on the set minimum allowable pulse, which can ensure that the three-phase current value can be sampled and obtained in each time interval.

[0015] Based on the further improvement of the above method, the optimization coefficient corresponding to each phase current corresponding to each sampling point time is calculated by Newton interpolation method based on each sampling point time and the corresponding three-phase current value.

[0016] The beneficial effect of the above-mentioned further improvement scheme is: in order to avoid the influence of switching noise on the sampled three-phase current, especially when the motor load power is small, the three-phase current of the motor load has not yet completely stabilized, and the three-phase current value directly sampled may be inaccurate; the expressions of each phase current corresponding to each sampling point of the three-phase current of the motor load are constructed by Newton interpolation, and then the optimization coefficients of each phase current corresponding to each sampling point are further derived, which helps to estimate the current of each phase corresponding to each sampling point as accurately as possible.

[0017] Based on the further improvement of the above method, the step of calculating the optimal sampling point time based on the optimization coefficient and the sampling point time specifically includes:

[0018] Substituting the optimization coefficient and the time of each sampling point into the interpolation expression of each phase current corresponding to the optimal sampling point;

[0019] The optimal time expression is obtained by adding the interpolation expressions of the phase currents corresponding to the optimal sampling points;

[0020] The time calculated and obtained when the optimal time expression is equal to 0 is used as the optimal sampling point time.

[0021] The beneficial effect of the above further improved solution is that the optimal sampling point moment can be calculated.

[0022] Based on the further improvement of the above method, when the optimal expression is equal to 0, there is no solution to the calculation, then the optimal expression is derived to obtain an updated optimal sampling point time expression;

[0023] The time obtained by calculating the updated optimal sampling point time expression equal to 0 is used as the optimal sampling point time.

[0024] The beneficial effect of the above further improved solution is that when the optimal expression is equal to 0 and there is no solution to be calculated, the optimal sampling point moment can be calculated by the above further improved solution.

[0025] Based on the further improvement of the above method, the interpolation expression of each phase current corresponding to the optimal sampling point is specifically expressed as:

[0026]

[0027] In the formula,

[0028] t is the optimal sampling point time,

[0029] t n is the nth sampling point moment,

[0030] I u (t), I v (t), I w (t) are the current values ​​of phase u, phase v and phase w corresponding to the optimal sampling point,

[0031] a n 、b n 、c n are respectively the optimization coefficients corresponding to the u-phase, v-phase and w-phase currents corresponding to the n-th sampling point, and n=0, 1, 2, ..., N-1.

[0032] The beneficial effect of the above further improved solution is that based on the Newton interpolation method and the sampling point moments and the optimization coefficient, an interpolation expression of each phase current corresponding to the optimal sampling point can be constructed for subsequent calculation of the optimal sampling point moment.

[0033] Based on a further improvement of the above method, the number N of sampling points is 2 or 3.

[0034] The beneficial effect of the above further improved scheme is that when the number of sampling points N is 2 or 3, the corresponding sampling point moments and the corresponding three-phase current values ​​obtained can meet the calculation accuracy of the optimal sampling point moments, and there is no need to collect too many sampling points to increase the amount of calculation and complexity.

[0035] On the other hand, an embodiment of the present invention provides a three-phase current sampling system, the system comprising a detection and sampling module, a processing and output module, wherein:

[0036] The detection and sampling module is used to take the detected three-phase current pulse width midpoint as the starting point, continuously sample at a set time interval to obtain three-phase current values ​​at multiple sampling points, and send them to the processing module;

[0037] The processing and output module calculates the optimization coefficient corresponding to each phase current at each sampling point based on the sampling point time and the corresponding three-phase current value, and then calculates the optimal sampling point time based on the optimization coefficient, each sampling point time and the corresponding three-phase current value, and obtains the optimal three-phase current value based on the optimal sampling point time and outputs it.

[0038] The beneficial effects of the above technical solution are as follows: the system structure composed of the detection and sampling module and the processing and output module is simple, wherein the detection and sampling module is used to take the detected midpoint of the three-phase current pulse width as the starting point, and continuously sample at time intervals to obtain three-phase current values ​​at multiple sampling points. Compared with the prior art, the sampled three-phase current values ​​are less affected by switching noise; the processing and output module calculates in sequence based on each sampling point moment and the corresponding three-phase current value and finally obtains the processing process of the optimal sampling point moment accurately, with a small amount of calculation and easy implementation.

[0039] The embodiment of the present invention further provides a three-phase current detection control circuit, the control circuit includes a power switch circuit, a current detection amplifier circuit, and a controller circuit, wherein:

[0040] The current detection amplifier circuit detects the three-phase current of the motor and amplifies it to obtain a simulated three-phase current signal and outputs it to the controller circuit;

[0041] The controller circuit includes an analog-to-digital conversion circuit, a sampling signal processing module, a motor control module, and SVPWM, wherein:

[0042] The digital-to-analog conversion circuit takes the pulse width midpoint of the analog three-phase current signal as the starting point, and continuously samples at set time intervals to obtain multiple sampling point moments and corresponding three-phase current values;

[0043] The sampling signal processing module calculates the optimization coefficient corresponding to each phase current corresponding to each sampling point time based on each sampling point time and the corresponding digital three-phase current signal, and then calculates the optimal sampling point time based on the optimization coefficient and each sampling point time, and then obtains the optimal three-phase current signal corresponding to the optimal sampling point time and outputs it;

[0044] The motor control module calculates and outputs an output voltage based on the optimal three-phase current signal;

[0045] The SVPWM calculates a PWM driving signal based on the output voltage and outputs the PWM driving signal to the power switch circuit;

[0046] The power switch circuit amplifies the power of the PWM drive signal and then outputs it.

[0047] The beneficial effects of the above technical solution are as follows: the circuit structure is simple, can be applied to various application scenarios of three-phase current sampling control, and can achieve faster implementation than the existing technology, as well as optimal control of the motor.

[0048] An embodiment of the present invention further provides a power device, which includes a motor and a three-phase current detection control circuit provided by an embodiment of the present invention.

[0049] The beneficial effects of the above technical solution are as follows: it can achieve optimized power output.

[0050] In the present invention, the above-mentioned technical solutions can also be combined with each other to achieve more preferred combination solutions. Other features and advantages of the present invention will be described in the subsequent description, and some advantages can become obvious from the description, or can be understood by practicing the present invention. The purpose and other advantages of the present invention can be realized and obtained through the contents particularly pointed out in the description and the drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0051] The accompanying drawings are only used for the purpose of illustrating specific embodiments and are not to be considered as limiting the present invention. In the entire drawings, the same reference symbols represent the same components;

[0052] Figure 1 This is a flow chart of the method of Example 1 of the present invention;

[0053] Figure 2 This is a schematic diagram of interpolating sampling points in Example 1 of the present invention;

[0054] Figure 3 It is a current waveform diagram obtained by sampling in the prior art;

[0055] Figure 4 This is a current waveform diagram obtained by sampling in Example 1 of the present invention;

[0056] Figure 5 This is a schematic diagram of a circuit for lower bridge arm sampling according to Embodiment 3 of the present invention;

[0057] Figure 6 FIG. 3 is a circuit diagram of embodiment 3 of the present invention applied to output phase sampling.

[0058] Reference numerals:

[0059] 1-controller circuit; 2-power switch circuit; 3-motor; 4-current detection amplifier circuit; 5-analog-to-digital conversion circuit; 6-sampling signal processing module; 7-motor control module; 8-SVPWM. DETAILED DESCRIPTION

[0060] The preferred embodiments of the present invention are described in detail below in conjunction with the accompanying drawings, wherein the accompanying drawings constitute a part of this application and are used together with the embodiments of the present invention to illustrate the principles of the present invention, but are not used to limit the scope of the present invention.

[0061] Embodiment 1:

[0062] A specific embodiment of the present invention discloses a three-phase current sampling optimization method, such as Figure 1 shown.

[0063] The method specifically comprises:

[0064] Taking the midpoint of the pulse width of the three-phase current when the switch is turned on as the starting point, continuous sampling is performed at a set time interval to obtain multiple sampling point moments and corresponding three-phase current values;

[0065] Based on the time of each sampling point and the corresponding three-phase current value, the optimization coefficient corresponding to each phase current corresponding to each sampling point time is calculated;

[0066] Calculate the optimal sampling point time based on the optimization coefficient and the sampling point time;

[0067] The optimal three-phase current value is obtained based on the optimal sampling point time correspondence.

[0068] In order to achieve optimal control of the three-phase AC motor, the output load of the three-phase AC motor needs to be periodically sampled to obtain the three-phase current value of the load feedback, and the PWM pulse drive signal to be output in the next cycle is calculated based on the three-phase current value of the load feedback. Based on the working principle of the three-phase AC motor, each time it is turned on, it is necessary to ensure that there is current passing through in order to collect the three-phase current value of the load feedback. Therefore, the minimum allowable pulse needs to be set. The set minimum allowable pulse is the output pulse time corresponding to the minimum PWM pulse drive signal with current passing through when turned on. It may vary based on hardware differences and is generally 2-3us.

[0069] Each time the switch is turned on, the following steps are performed:

[0070] Step 1: Taking the midpoint of the pulse width of the three-phase current when the switch is turned on as the starting point, continuous sampling is performed at a set time interval to obtain multiple sampling point moments and corresponding three-phase current values.

[0071] When the switch is turned on, the switching noise will cause the three-phase current instantaneously output to the load to be distorted and unable to reflect the actual load feedback three-phase current value. The distortion will become smaller as the switch is turned on for a longer time. Therefore, the sampling point obtained by taking the midpoint of the pulse width of the three-phase current when the switch is turned on as the starting point is optimal.

[0072] Furthermore, the set time interval is calculated by the following formula, which is specifically expressed as:

[0073] Where, T s is the set time interval, N is the number of sampling points, Pulse min is the minimum allowed pulse.

[0074] Specifically, the set time interval is set based on the set minimum allowable pulse because the set minimum allowable pulse is the shortest on-time. The set time interval obtained on this basis aims to ensure that the sampling points starting from the midpoint of the pulse width of the three-phase current when the switch is turned on are all within the switch on pulse, that is, the sampling points are all valid and can be used for subsequent optimization calculations. Then, step 1 is executed to obtain multiple sampling point moments and corresponding three-phase current values.

[0075] Next, step 2 is performed: based on the time of each sampling point and the corresponding three-phase current value, the optimization coefficient corresponding to each phase current corresponding to each sampling point time is calculated.

[0076] When the switch is turned on, affected by the switching noise, the three-phase current signals of each sampling point are not completely stable and cannot reflect the true situation of the load feedback three-phase current. Since the current waveform of the three-phase current after the switch is turned on shows a sine wave or cosine wave trend change, in order to find the optimal sampling point time based on the sampling point time and the corresponding three-phase current value, the Newton interpolation method is used to estimate the three-phase current value of each sampling point to first obtain the optimization coefficient corresponding to each phase current corresponding to each sampling point time.

[0077] Furthermore, based on the time of each sampling point and the corresponding three-phase current value, the optimization coefficient corresponding to each phase current corresponding to each sampling point time is calculated by Newton interpolation method.

[0078] Specifically, the optimization coefficient corresponding to each phase current corresponding to each sampling moment can be obtained based on the Newton interpolation method. Taking the u-phase current as an example, the standard expression of the Newton interpolation method is specifically expressed as:

[0079] I u (t)=a0+a1(t-t0)+a2(t-t0)(t-t1)+a n (t-t0)(t-t1)…(tt n-1 ),

[0080] Where t is the optimal sampling point time, t n is the nth sampling point, a n is the optimization coefficient corresponding to the u-phase current at the nth sampling point, n=0, 1, 2, ..., N-1,

[0081] Then, based on the Newton interpolation transformation, we can get I u (t) The corresponding optimization coefficient a n The expression transformation form is specifically expressed as the following expression:

[0082]

[0083] In the formula, u[n], v[n], and w[n] are the current values ​​of phase u, phase v, and phase w corresponding to the nth sampling point, respectively. The Newton interpolation method is iteratively derived layer by layer based on the difference quotient algorithm, that is, based on the above formula, the optimization coefficient a0 when n=0 is the sampling current value u[0] at time t0; when n=1, the difference quotient from time t1 to time t0 is calculated based on u[0] and u[1] to obtain the optimization coefficient a1 at time t1. When calculating the optimization coefficient at the next moment, it is an iterative calculation based on the calculation result of the previous moment. By analogy, based on the derivation and transformation of each order expression, the optimization coefficient a corresponding to u[n] is obtained. n ;

[0084] Similarly, based on Newton interpolation method, we can transform v[n] to obtain the optimization coefficient b n , the optimization coefficient c corresponding to w[n] n .

[0085] Step 3: Calculate the optimal sampling point time based on the optimization coefficient and the sampling point times.

[0086] Furthermore, the step of calculating the optimal sampling point time based on the optimization coefficient and the sampling point times specifically includes:

[0087] Substituting the optimization coefficient and the time of each sampling point into the interpolation expression of each phase current corresponding to the optimal sampling point;

[0088] The optimal time expression is obtained by adding the interpolation expressions of the phase currents corresponding to the optimal sampling points;

[0089] The time calculated and obtained when the optimal time expression is equal to 0 is used as the optimal sampling point time.

[0090] Based on the principle of three-phase AC motor, when the sum of the three-phase currents at the same sampling point is 0, the power supply is stable and the three-phase currents are symmetrical with each other. Therefore, the sum of the estimated three-phase current values ​​obtained by interpolating each sampling point based on the Newton interpolation method is 0, and the corresponding three-phase current value can be considered to be closest to the true value. Based on the corresponding optimization coefficient at each sampling point, the interpolation expression of each phase current of the optimal sampling point can be derived.

[0091] Furthermore, the interpolation expression of each phase current corresponding to the optimal sampling point is specifically expressed as:

[0092]

[0093] In the formula, I u (t), I v (t), I w (t) are the current values ​​of phase u, phase v, and phase w corresponding to the optimal sampling point, respectively, n 、b n 、c n are respectively the optimization coefficients corresponding to the u-phase, v-phase and w-phase currents corresponding to the n-th sampling point, and n=0, 1, 2, ..., N-1.

[0094] Based on the principle of three-phase AC motor, I u (t)+I v (t)+I w(t)=0, substituting the interpolation expressions of the phase currents corresponding to the optimal sampling point into the optimal sampling point can construct a one-variable equation with the optimal sampling point time t as the only unknown quantity, and further solving the one-variable equation to obtain t is the optimal sampling point time.

[0095] In actual situations, due to the influence of switching noise and sampling accuracy, the three-phase current values ​​corresponding to each sampling point have errors, which may cause the one-variable equation to have no solution. Further, when the optimal expression is equal to 0, the calculation has no solution, and the optimal expression is derived to obtain an updated optimal sampling point time expression;

[0096] The time obtained by calculating the updated optimal sampling point time expression equal to 0 is used as the optimal sampling point time.

[0097] Specifically, the number of sampling points and the polynomial order used by the Newton interpolation method satisfy n = N + 1. Theoretically, the more sampling points there are, the more polynomial orders Newton interpolation method uses, and the more accurate the calculation results are, but it will lead to a surge in the amount of calculation.

[0098] Furthermore, the number N of sampling points is 2 or 3.

[0099] Specifically, the number of sampling points N of 2 or 3 can already meet the minimum sampling accuracy requirement, and the resulting amount of computation is within an acceptable range, without causing delays and other problems due to a surge in the amount of computation.

[0100] Step 4: Obtain the optimal three-phase current value based on the optimal sampling point time.

[0101] Specifically, the optimal sampling point time t obtained by executing step 3 is substituted into the interpolation expressions of each phase current corresponding to the optimal sampling point, and the optimal three-phase current value can be calculated.

[0102] Figure 2 : A schematic diagram of interpolating sampling points in this embodiment is shown in FIG. 1 , wherein the long dashed line represents the change trend of the three-phase current corresponding to each sampling point, that is, the real current value collected. Affected by the switching noise, the real current value fluctuates irregularly and the change trend deviates; the short dashed line represents the change trend of each interpolation current obtained based on the Newton interpolation method. It can be seen that the change trend of the interpolation current is a regular curve that conforms to the ideal state of the three-phase current.

[0103] In this embodiment, the midpoint of the three-phase current pulse width when the switch is turned on is used as the starting point, and the obtained sampling points and corresponding three-phase current values ​​are less affected by the switch than the sampling points and corresponding three-phase current values ​​at the instant of the switch being turned on, and the values ​​are more accurate; the optimization coefficients corresponding to the currents of each phase at each sampling point are calculated based on the sampling point moments and the corresponding three-phase current values, which is based on the Newton interpolation method, combined with the principle of three-phase AC motors and the characteristics of three-phase current waveforms to obtain the optimization coefficients corresponding to the currents of each phase at each sampling point moment; then, the optimal sampling point moment is calculated based on the optimization coefficients and the sampling point moments, and then the optimal three-phase current value is obtained. Compared with the prior art, there is no need to reduce the motor speed, and the optimal three-phase current value can be obtained to achieve optimal control of the motor.

[0104] Figure 3 The figure shows the variation curve of the three-phase current value collected in the prior art, and it can be seen that the fluctuation is extremely severe; Figure 4 The three-phase current value change curve collected by the present embodiment shown in the figure shows a curve change with minimal fluctuation that is significantly better than the prior art, and the trend of the collected current is clearly discernible, showing a very good effect.

[0105] Embodiment 2:

[0106] The second embodiment of the present invention discloses a three-phase current sampling system, which includes a detection and sampling module and a processing and output module, wherein:

[0107] The detection and sampling module is used to take the detected three-phase current pulse width midpoint as the starting point, continuously sample at a set time interval to obtain three-phase current values ​​at multiple sampling points, and send them to the processing module;

[0108] The processing and output module calculates the optimization coefficient corresponding to each phase current at each sampling point based on the sampling point time and the corresponding three-phase current value, and then calculates the optimal sampling point time based on the optimization coefficient, each sampling point time and the corresponding three-phase current value, and obtains the optimal three-phase current value based on the optimal sampling point time and outputs it.

[0109] Embodiment 2 includes all the technical features of Embodiment 1.

[0110] Specifically, the system structure of this embodiment composed of the detection and sampling module and the processing and output module is simple, wherein the detection and sampling module is used to take the detected midpoint of the three-phase current pulse width as the starting point, and continuously sample at time intervals to obtain three-phase current values ​​at multiple sampling points. Compared with the prior art, the sampled three-phase current values ​​are less affected by switching noise; the processing and output module calculates in sequence based on each sampling point moment and the corresponding three-phase current value and finally obtains the processing process of the optimal sampling point moment, which is accurate, has a small amount of calculation, and is easy to implement.

[0111] Embodiment 3:

[0112] A third embodiment of the present invention discloses a three-phase current detection control circuit, the control circuit comprising a power switch circuit (2), a current detection amplifier circuit (4), and a controller circuit (1), wherein:

[0113] The current detection amplifier circuit (4) detects the three-phase current of the motor (3), amplifies it, obtains a simulated three-phase current signal, and outputs it to the controller circuit (1);

[0114] The controller circuit (1) comprises an analog-to-digital conversion circuit (5), a sampling signal processing module (6), a motor control module (7), and a SVPWM (8), wherein:

[0115] The digital-to-analog conversion circuit (5) takes the pulse width midpoint of the analog three-phase current signal as the starting point, and continuously samples at a set time interval to obtain a plurality of sampling point moments and corresponding three-phase current values;

[0116] The sampling signal processing module (6) calculates the optimization coefficient corresponding to each phase current corresponding to each sampling point time based on each sampling point time and the corresponding digital three-phase current signal, then calculates the optimal sampling point time based on the optimization coefficient and each sampling point time, and then obtains the optimal three-phase current signal corresponding to the optimal sampling point time and outputs it;

[0117] The motor control module (7) calculates and outputs an output voltage based on the optimal three-phase current signal;

[0118] The SVPWM (8) calculates a PWM drive signal based on the output voltage and outputs the signal to the power switch circuit (2);

[0119] The power switch circuit (2) amplifies the power of the PWM drive signal and then outputs it.

[0120] Embodiment 3 includes all the technical features of Embodiment 2.

[0121] Figure 5 , Figure 6 Two specific implementation examples of this embodiment are shown in FIG. Figure 5 An implementation example of this embodiment applied to lower bridge arm sampling is shown in FIG.

[0122] Specifically, the current detection amplifier circuit (4) is connected to the lower bridge arm resistor in the power switch circuit (2) to detect the three-phase current of the motor (3) when the power switch circuit (2) is turned on, and amplifies the current to obtain a simulated three-phase current signal and outputs it to the controller circuit (3);

[0123] The controller circuit (1) is specifically an MCU, and specifically comprises the analog-to-digital conversion circuit (5), the sampling signal processing module (6), the motor control module (7), and the SVPWM (8), wherein the analog three-phase current signal obtained by the current detection amplifier circuit (4) is output to the analog-to-digital conversion circuit (5); the digital-to-analog conversion circuit (5) takes the pulse width midpoint of the analog three-phase current signal as the starting point, continuously samples at a set time interval to obtain a plurality of sampling point moments and corresponding three-phase current values, and outputs them to the sampling signal processing module (6); the sampling signal processing module (6) calculates the optimization coefficient corresponding to each phase current corresponding to each sampling point moment based on each sampling point moment and the corresponding digital three-phase current signal, and then calculates the optimal sampling point moment based on the optimization coefficient and each sampling point moment, and then obtains the optimal three-phase current value corresponding to the optimal sampling point moment. The current signal is outputted. It can be seen that the optimal three-phase current value has been obtained after being processed by the sampling signal processing module (6) and outputted to the motor control module (7); the motor control module (7) calculates the output voltage based on the optimal three-phase current signal and outputs it to the SVPWM (8); the SVPWM (8) calculates the PWM drive signal based on the output voltage. In order to ensure that the sampling current can still be obtained when the output pulse of the lower bridge arm is too low, the SVPWM also detects the PWM drive signal. When the PWM drive signal is less than the set minimum allowable pulse, the SVPWM sets the PWM drive signal to the minimum allowable pulse before outputting it to the power switch circuit (2); the power switch circuit (2) amplifies the PWM drive signal, then turns on the switch and outputs the PWM drive signal to the motor (3) for operation.

[0124] Figure 6 FIG. 4 shows an implementation example of this embodiment applied to output phase sampling, wherein the difference is that Figure 6 The current detection amplifier circuit (4) is connected to the load line of the motor (3) for sampling, and the rest of the implementation process is the same as Figure 5 The example is consistent with the above.

[0125] It should be noted that Figure 5 , Figure 6 The examples are only used to illustrate the principles of this embodiment and are not used to limit the specific implementation methods and scope of the technical solutions of this embodiment.

[0126] The circuit structure of this embodiment is simple, and can be applied to various application scenarios of three-phase current sampling control. It can also achieve faster implementation and optimal control of the motor compared to the prior art.

[0127] Embodiment 4:

[0128] The fourth embodiment of the present invention discloses a power device, which includes a motor and a three-phase current detection control circuit disclosed in the third embodiment.

[0129] Those skilled in the art will appreciate that all or part of the processes of the above-mentioned embodiments can be implemented by instructing related hardware through a computer program, and the program can be stored in a computer-readable storage medium, wherein the computer-readable storage medium is a disk, an optical disk, a read-only storage memory, or a random access memory, etc.

[0130] The above description is only a preferred specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Any changes or substitutions that can be easily conceived by any technician familiar with the technical field within the technical scope disclosed by the present invention should be covered within the protection scope of the present invention.

Claims

1. A three-phase current sampling optimization method, characterized in that: The method specifically comprises: Taking the midpoint of the pulse width of the three-phase current when the switch is turned on as the starting point, continuous sampling is performed at a set time interval to obtain multiple sampling point moments and corresponding three-phase current values; Based on the time of each sampling point and the corresponding three-phase current value, the optimization coefficient corresponding to each phase current corresponding to each sampling point time is calculated; Calculate the optimal sampling point time based on the optimization coefficient and the sampling point time; The optimal three-phase current value is obtained based on the optimal sampling point time correspondence.

2. A three-phase current sampling optimization method according to claim 1, characterized in that: The set time interval is calculated by the following formula, which is specifically expressed as: Where, T s is the set time interval, N is the number of sampling points, Pulse min is the minimum allowed pulse.

3. A three-phase current sampling optimization method according to claim 1, characterized in that: Based on the time of each sampling point and the corresponding three-phase current value, the optimization coefficient corresponding to each phase current corresponding to each sampling point time is calculated by Newton interpolation method.

4. A three-phase current sampling optimization method according to claim 1, characterized in that: The step of calculating the optimal sampling point time based on the optimization coefficient and the sampling point times specifically includes: Substituting the optimization coefficient and the time of each sampling point into the interpolation expression of each phase current corresponding to the optimal sampling point; The optimal time expression is obtained by adding the interpolation expressions of the phase currents corresponding to the optimal sampling points; The time calculated and obtained when the optimal time expression is equal to 0 is used as the optimal sampling point time.

5. A three-phase current sampling optimization method according to claim 4, characterized in that: When the optimal expression is equal to 0, there is no solution to the calculation, then the optimal expression is derived to obtain an updated optimal sampling point time expression; The time obtained by calculating the updated optimal sampling point time expression equal to 0 is used as the optimal sampling point time.

6. A three-phase current sampling optimization method according to claim 4, characterized in that: The interpolation expression of each phase current corresponding to the optimal sampling point is specifically expressed as: In the formula, t is the optimal sampling point time, t n is the nth sampling point moment, I u (t), I v (t), I w (t) are the current values ​​of phase u, phase v and phase w corresponding to the optimal sampling point, a n , b n 、c n are respectively the optimization coefficients corresponding to the u-phase, v-phase and w-phase currents corresponding to the n-th sampling point, and n=0, 1, 2, ..., N-1.

7. A three-phase current sampling optimization method according to any one of claims 1 to 6, characterized in that: The number N of sampling points is 2 or 3.

8. A three-phase current sampling system, characterized in that: The system includes a detection and sampling module and a processing and output module, wherein: The detection and sampling module is used to take the detected three-phase current pulse width midpoint as the starting point, continuously sample at a set time interval to obtain three-phase current values ​​at multiple sampling points, and send them to the processing module; The processing and output module calculates the optimization coefficient corresponding to each phase current at each sampling point based on the sampling point time and the corresponding three-phase current value, and then calculates the optimal sampling point time based on the optimization coefficient, each sampling point time and the corresponding three-phase current value, and obtains the optimal three-phase current value based on the optimal sampling point time and outputs it.

9. A detection control circuit, characterized in that: The control circuit includes a power switch circuit, a current detection amplifier circuit, and a controller circuit, wherein: The current detection amplifier circuit detects the three-phase current of the motor and amplifies it to obtain a simulated three-phase current signal and outputs it to the controller circuit; The controller circuit includes an analog-to-digital conversion circuit, a sampling signal processing module, a motor control module, and SVPWM, wherein: The digital-to-analog conversion circuit takes the pulse width midpoint of the analog three-phase current signal as the starting point, and continuously samples at set time intervals to obtain multiple sampling point moments and corresponding three-phase current values; The sampling signal processing module calculates the optimization coefficient corresponding to each phase current corresponding to each sampling point time based on each sampling point time and the corresponding digital three-phase current signal, and then calculates the optimal sampling point time based on the optimization coefficient and each sampling point time, and then obtains the optimal three-phase current signal corresponding to the optimal sampling point time and outputs it; The motor control module calculates and outputs an output voltage based on the optimal three-phase current signal; The SVPWM calculates a PWM driving signal based on the output voltage and outputs the PWM driving signal to the power switch circuit; The power switch circuit amplifies the power of the PWM drive signal and then outputs it.

10. A power device, characterized in that: The power device includes a motor and a three-phase current detection control circuit as described in claim 9.

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