A digital SPWM modulation method

Abstract

The application discloses a digital SPWM modulation method, comprising the following steps: 1) sampling a modulation wave to obtain a sampling value x As input data, the discrete lead transfer function is used to obtain the estimated value at the nearest peak of the lead; the modulation wave is sampled to obtain a sampling value; as input data, the discrete lag transfer function is used to obtain the estimated value at the nearest peak of the lag; 2) using the estimated values at the nearest peaks before and after the sampling value and the current sampling value, the intersection of the modulation wave and the carrier wave is solved by using the similar relationship of the triangle; 3) using the period of the carrier wave and the intersection relationship, the duty ratio in the carrier wave period is solved. The modulation method has small calculation amount compared with the natural sampling method and high accuracy compared with the symmetrical method.

Description

TECHNICAL FIELD

[0001] The present application relates to a kind of digital SPWM modulation methods, belong to power electronics and control technical field. BACKGROUND

[0002] Power electronics product needs pulse to control the on-off of IGBT when working, SPWM pulse width modulation technology is often used in pulse width modulation, there are generally natural sampling and symmetric sampling two ways, the high precision of SPWM (sine pulse width modulation) can make the output of inverter more approximate sine wave, with sine wave as modulating wave, isosceles triangle wave as carrier wave to compare, control the on-off of switching device at the natural intersection moment of two waveforms, this is natural sampling method.Its advantage is that the obtained SPWM waveform is closest to sine wave, but since the intersection of triangle wave and sine wave is arbitrary, the pulse center is not equidistant in a cycle, so the pulse width expression is a transcendental equation, calculation is complicated, difficult to real-time control.Therefore, symmetric sampling method is often used in engineering, the principle of this method is to obtain step wave by sampling sine wave with triangle wave as carrier wave, then control the on-off of switching device at the intersection moment of step wave and triangle wave, so as to realize SPWM modulation, but symmetric sampling method has larger error because the intersection of correct modulating wave and carrier wave cannot be obtained. SUMMARY

[0003] The technical problem to be solved by the present application is that power electronics product needs pulse to control the on-off of IGBT when working, pulse width modulation adopts natural sampling and symmetric sampling, the calculation amount of solving transcendental equation is larger when adopting natural sampling, and the error is larger when adopting symmetric sampling.

[0004] To solve the above technical problems, the present application provides a kind of digital SPWM modulation method, comprising:

[0005] 1) sampling modulating wave, obtaining sampling value x as input data, using the discrete lead transfer function tf1, to obtain the estimated value of the nearest peak in the lead;

[0006] Sampling modulating wave, obtaining sampling input x as input data, using the discrete lag transfer function tf2, to obtain the estimated value of the nearest peak in the lag;

[0007] 2) using the estimated value of the nearest peak before and after sampling value and the current sampling value, using triangle replacement method, using the similarity of triangle, to solve the intersection of modulating wave and carrier wave;

[0008] 3) using the period of carrier wave and the intersection relationship, to solve the duty cycle in the period of carrier wave.

[0009] In the aforementioned digital SPWM modulation method, in step 1), the lead transfer function is a SOGI-QSG type function. The input data is filtered using the lead transfer function, and an arbitrary lead angle is obtained according to the different carrier frequencies. The estimated value x1;

[0010] The complex frequency domain expression of the lead transfer function is:

[0011]

[0012] in, The lead transfer function is represented by k, and the closed-loop coefficient is represented by k. This indicates the resonant frequency of the SOGI-QSG. Let represent the complex variable of the Laplace transform.

[0013] In the aforementioned digital SPWM modulation method, the execution process of the lead transfer function in step 1) is as follows:

[0014] For the input signal x at the phase-locked angle Perform the abc-dq phase coordinate transformation below;

[0015] After the abc-dq phase coordinate transformation, the signal is in Perform dq-bac phase coordinate transformation;

[0016] The time-domain calculation formula for the lead transfer function is as follows:

[0017] .

[0018] In the aforementioned digital SPWM modulation method, in step 1), the hysteresis transfer function is a SOGI-QSG type function. The hysteresis transfer function filters the input data and simultaneously calculates arbitrary hysteresis angles based on different carrier frequencies. The estimated value x2, the complex frequency domain expression of the hysteresis transfer function is:

[0019]

[0020] in, The lag transfer function is represented by k, which represents the closed-loop coefficient. Let represent the resonant frequency of SOGI-QSG, and s represent the complex variable of the Laplace transform.

[0021] In the aforementioned digital SPWM modulation method, the execution process of the hysteresis transfer function is as follows:

[0022] For the input signal x at the phase-locked angle Perform the abc-dq phase coordinate transformation below;

[0023] The abc-dq phase coordinate transformed signal is subjected to dq-bac phase coordinate transformation. The abc-dq phase coordinate transformed signal is subjected to dq-bac phase coordinate transformation.

[0024] The time domain calculation formula of the lag transfer function is:

[0025]

[0026] The lead transfer function and the lag transfer function are subjected to bilinear transformation on the estimated parameters after parameter estimation at any angle, and the parameter discretization processing is completed, which is used in a digital controller.

[0027] The aforementioned digital SPWM modulation method, in step 2), in the triangular replacement method, the arc between the modulation wave and the carrier intersection is replaced by a straight line BCD at a high carrier frequency, thereby constructing triangle ABC and triangle DCF, A point is the positive half cycle peak value of the carrier, B point is the intersection point of the modulation wave when the vertical line of A point is drawn to the time axis, C point is the intersection point of the modulation wave and the carrier, D point is the intersection point of the modulation wave and the time axis, E point is the negative half cycle peak value of the carrier, F point is the intersection point of the time axis when the vertical line of C point is drawn to the time axis, G point is the intersection point formed by the parallel line of B point to the time axis and AE;

[0028] The on length of PWM is DF, and the off length of PWM is BG. The arc BCD is replaced by a straight line BCD at a high carrier frequency, and the effective high and low pulse time of PWM is obtained according to the relationship of triangle, wherein the height coordinate of B point is x1, which is the previous input, and the height coordinate of D point is x, which is the current sampling input.

[0029] There is a triangle , and , which obtains:

[0030] (2)

[0031] (3)

[0032] According to the relationship of the relationship formula (2) and (3), formula (4) can be obtained:

[0033] (4).

[0034] The aforementioned digital SPWM modulation method, in step 3), AB=1–x1, ED=1 + x, BG+DF= / 2, is the carrier cycle, and the high level time t DF in the corresponding half cycle is obtained, and the calculation result is shown in formula (5):

[0035] (5)

[0036] The modulated wave intersects the carrier wave at point H, where the height coordinate of point H is x2. Similarly, the high-level time on the right side of the sample can be calculated:

[0037] (6)

[0038] The high-level time for the entire cycle is:

[0039] (7)

[0040] The duration of the low level within the cycle is determined as follows:

[0041] (8)

[0042] Within one PWM cycle Ts, the PWM wave is maintained for t sequentially. L1 The duration of the low level, t H The duration of the high level and t L2 The duration of the low level, where t L1 t H t L2 They are respectively:

[0043]

[0044]

[0045]

[0046] Find t L1 , t H , t L2 The actual value is the high and low level time within the carrier period, where x is the sampling input of the current modulated wave, and x1 is the lead time calculated by the lead transfer function. The leading estimate of the angle, where x2 is the lag calculated using the leading transfer function. The lagged estimate of the angle, t L1 For the first low-level period, t H For the high-level time, t L2 This is the second low-level period.

[0047] In the aforementioned digital SPWM modulation method, in step 3), based on the obtained high-level time and low-level time, a digital period register is used to determine the relationship between the value of the period register and the high and low-level times by increasing the value of the register, thereby generating corresponding high and low pulses and completing the modulation.

[0048] In the aforementioned digital SPWM modulation method, in step 3), when the per-unit value t of the period counter is less than t... L1The output is low when t is greater than t. L1 And less than t L1 + t H The output is high, and t is greater than t. L1 + t H And if it is less than Ts, it is a low level, thus completing the modulation.

[0049] A computer device / apparatus / system includes a memory, a processor, and a computer program stored in the memory, wherein the processor executes the computer program to implement the steps of the above-described method.

[0050] A computer-readable storage medium having a computer program / instructions stored thereon, which, when executed by a processor, implement the steps of the above-described method.

[0051] The beneficial effects achieved by this invention are as follows: The digital SPWM modulation method proposed in this invention utilizes the lead and lag transfer functions and the approximate trigonometric relationship to solve for the estimated values ​​of arbitrary lead and lag angles, and then solves for the approximate intersection point of the modulated wave and the carrier wave, thereby obtaining the high and low level times of the pulse width. Compared with the symmetrical method, this improves the accuracy of pulse width modulation and makes the output waveform closer to a sine wave.

[0052] The present invention discloses a digital SPWM modulation method, wherein the SOGI-QSG type cycle extension transfer function can filter the modulated wave and estimate the lead and lag parameters at any angle. This type of transfer function can adjust the parameters according to different carrier frequencies during use, which is highly flexible and can reduce the amount of engineering calculations and avoid the problem of solving transcendental equations. Attached Figure Description

[0053] Figure 1 This is a flowchart illustrating the implementation of a digital SPWM modulation method in Embodiment 1 of the present invention;

[0054] Figure 2 This is a diagram showing the carrier wave and modulation wave relationship in a digital SPWM modulation method according to Embodiment 1 of the present invention.

[0055] Figure 3 This is a schematic diagram illustrating the equivalent calculation of a digital SPWM modulation method in Embodiment 1 of the present invention;

[0056] Figure 4 This is an input-output diagram of the lead transfer function of a digital SPWM modulation method in Embodiment 1 of the present invention;

[0057] Figure 5 The input-output diagram is shown for the hysteresis transfer function of a digital SPWM modulation method in Embodiment 1 of the present invention.

[0058] Figure 6A pulse waveform diagram generated by a digital SPWM modulation method in Embodiment 1 of the present application. DETAILED DESCRIPTION

[0059] The present application is further described below in conjunction with the accompanying drawings. The following embodiments are only used to more clearly illustrate the technical solutions of the present application, and cannot be used to limit the protection scope of the present application.

[0060] Embodiment 1

[0061] The present embodiment provides a digital SPWM modulation method, comprising:

[0062] 1) Sampling the modulation wave to obtain a sampling value x as input data, and using a discretized lead transfer function tf1 to obtain an estimated value at a nearest peak value in the lead;

[0063] Sampling the modulation wave to obtain a sampling value x as input data, and using a discretized lag transfer function tf2 to obtain an estimated value at a nearest peak value in the lag;

[0064] The lead transfer function is a SOGI-QSG type function, and the data lag in the lead is determined by a carrier period Angular graphical representation.

[0065] In step 1), the lead transfer function is a SOGI-QSG type function, and the SOGI-QSG (second-order generalized integrator quadrature signal generator, SOGI-QSG) algorithm is a phase-locked loop algorithm based on three-phase signals. The input data is filtered by using the lead transfer function, and according to the difference of the carrier frequency, the estimated value of the lead at any angle is obtained, as shown in , the lead estimated value x1 is obtained; Figure 4

[0066] The complex frequency domain expression of the lead transfer function is:

[0067]

[0068] Among them, represents the lead transfer function, k represents the closed loop coefficient, represents the resonant frequency of SOGI-QSG, represents the complex variable of Laplace transform.

[0069] The execution process of the lead transfer function is:

[0070] The input signal x is subjected to abc-dq coordinate transformation at the phase-locked angle . ​

[0071] After the abc-dq phase coordinate transformation, the signal is in Perform dq-bac phase coordinate transformation.

[0072] The time-domain calculation formula for the lead transfer function is as follows:

[0073]

[0074] The hysteresis transfer function is a SOGI-QSG type function. This hysteresis transfer function can filter the input data and can also determine arbitrary hysteresis angles based on different carrier frequencies. The estimated value, such as Figure 5 As shown, the lag estimate x2 is obtained, and the complex frequency domain expression of the lag transfer function is:

[0075]

[0076] in, The lag transfer function is represented by k, which represents the closed-loop coefficient. Let represent the resonant frequency of SOGI-QSG, and s represent the complex variable of the Laplace transform.

[0077] The execution process of the hysteresis transfer function is as follows:

[0078] For the input signal x at the phase-locked angle Perform the abc-dq phase coordinate transformation below;

[0079] After the abc-dq phase coordinate transformation, the signal is in Perform dq-bac phase coordinate transformation.

[0080] The time-domain calculation formula for the hysteresis transfer function is as follows:

[0081]

[0082] After estimating the parameters at any angle, the lead transfer function and lag transfer function need to undergo a bilinear transformation to discretize the estimated parameters for use in digital controllers.

[0083] The modulated wave is a single-phase signal; a three-phase signal is constructed using the time delay method, i.e., through... Input generation and Using the SOGI_QSG method, input as The axis is generated by constructing the transfer function using SOGI_QSG. Axis data, then using triangular relationships and , The value completes the construction of the lead transfer function and the lag transfer function.

[0084] 2) Using the estimated value of the nearest peak before and after the sampling value and the current sampling value, the intersection point of the modulating wave and the carrier wave is solved by using the triangle replacement method and the similarity of the triangle.

[0085] In the triangle replacement method, the arc between the intersection of the modulating wave and the carrier wave is replaced by a straight line BCD at a high carrier frequency, thereby constructing triangles ABC and DCF for calculation, avoiding solving transcendental equations. Point A is the positive half-cycle peak value of the carrier wave, point B is the intersection of the vertical line from point A to the time axis and the modulating wave, point C is the intersection of the modulating wave and the carrier wave, point D is the intersection of the modulating wave and the time axis, point E is the negative half-cycle peak value of the carrier wave, point F is the intersection of the vertical line from point C to the time axis and the time axis, and point G is the intersection of the parallel line from point B to the time axis and AE.

[0086] Figure 2 For the image composed of the triangular carrier wave and the modulating wave, in order to calculate more intuitively, the enlarged image is as shown in Figure 3 The on length of the PWM is DF, and the off length of the PWM is BG. Here, at a high carrier frequency, a replacement is made by replacing the arc BCD with a straight line BCD, so that the effective high and low pulse time of the PWM can be obtained according to the relationship of the triangle, wherein the height coordinate of point B is x1, which is the previous input, and the height coordinate of point D is x, which is the current sampling input.

[0087] As can be seen from Figure 3 , there are triangles , and , so we can get:

[0088] (2)

[0089] (3)

[0090] According to the relationship between the relationship formulas (2) and (3), formula (4) can be obtained:

[0091] (4).

[0092] 3) Using the period of the carrier wave and the intersection relationship, the duty cycle within the carrier wave period is solved.

[0093] From AB = 1 - x1, ED = 1 + x, BG + DF = / 2, is the carrier wave period, so the high level time t DF within the corresponding half cycle can be obtained, and the calculation result is as shown in formula (5):

[0094] (5)

[0095] To determine the PWM duty cycle over the entire sampling period, the data to the right of the input data x is analyzed, such as... Figure 3 As shown, the modulated wave intersects the carrier wave at point H, where the height coordinate of point H is x2. Similarly, the high-level time on the right side of the sample can be calculated:

[0096] (6)

[0097] From the above, we can know that the high-level time of the entire cycle is:

[0098] (7)

[0099] This also allows us to determine the duration of the low level within the period:

[0100] (8)

[0101] Within one PWM cycle Ts, the PWM wave is maintained for t sequentially. L1 The duration of the low level, t H The duration of the high level and t L2 The duration of the low level, where t L1 t H t L2 They are respectively:

[0102]

[0103]

[0104]

[0105] Find t L1 , t H , t L2 The actual value is the high and low level time within the carrier period, where x is the sampling input of the current modulated wave, and x1 is the lead time calculated by the lead transfer function. The leading estimate of the angle, where x2 is the lag calculated using the leading transfer function. The lagged estimate of the angle, t L1 For the first low-level period, t H For the high-level time, t L2 This is the second low-level period.

[0106] A computer device / apparatus / system includes a memory, a processor, and a computer program stored in the memory, wherein the processor executes the computer program to implement the steps of the above-described method.

[0107] A computer readable storage medium having stored thereon computer programs / instructions which, when executed by a processor, implement the steps of the above method.

[0108] Embodiment 2

[0109] On the basis of embodiment 1, according to the obtained high level time and low level time, the corresponding high and low pulses are generated by loading, i.e. increasing, the value of the register, judging the size relationship between the value of the register and the high and low level time, and completing the modulation.

[0110] When the period of the period counter t is less than t L1 , the output is low, t is greater than t L1 and less than t L1 + t H , the output is high, t is greater than t L1 + t H and less than Ts, the output is low, and the waveform in the period is as shown in Figure 6 , and the processing mode in other periods is the same, so as to complete the modulation.

[0111] In the embodiment, a commonly used level converter is adopted, and the control object is the on-off of IGBT, and the specific implementation method is as shown in Figure 1 The digital SPWM modulation method of the embodiment comprises a sampling module for sampling a modulation wave, the sampling mode is generally peak value sampling, comprises a lead transfer function for solving the estimated value of the sampling value leading the nearest peak value, and comprises a lag transfer function for solving the estimated value of the sampling value lagging the nearest peak value; the lead estimated value, the lag estimated value and the current sampling value are brought into the calculation formula derived by the application, to solve the high and low level time t L1 , t H , t L2 in the carrier period, and then the high and low levels are generated according to the relationship between the value of the digital period register and the high and low level time, and the modulation is completed.

[0112] The digital SPWM modulation method of the application can avoid solving transcendental equations in the modulation calculation, and reduce the calculation time. The SOGI-QSG type cycle extension transfer function can be used for filtering the modulation wave, and the lead and lag parameter estimation of any angle can be performed, the transfer function can be adjusted according to different carrier frequencies when used, and has high engineering value. The intersection of the modulation wave and the carrier is solved according to the relationship of similar triangles, and then the high and low level time in the carrier period is derived, and the precision of the pulse width modulation is improved compared with the symmetric method.

[0113] Those skilled in the art will appreciate that embodiments of the application can be readily used as software, hardware, or a combination of software and hardware. In one

[0114] The computer program instructions can also be loaded onto a computer or other programmable data processing apparatus to cause a series of operational steps to be performed on the computer or other programmable apparatus to produce a computer-implemented process such that the instructions which execute on the computer or other programmable apparatus provide steps for implementing the functions specified in the flowchart block or blocks. Figure 1 one or more flowcharts and / or blocks in the flowcharts and / or a combination of flowcharts and / or blocks in the flowcharts can be implemented by computer program instructions. Figure 1 means for carrying out functions specified in the flowchart block or blocks.

[0115] These computer program instructions can also be stored in a computer-readable memory that can direct a computer or other programmable data processing apparatus to function in a particular manner, such that the instructions stored in the computer-readable memory produce an article of manufacture including instructions which implement the function specified in the flowchart block or blocks. Figure 1 one or more flowcharts and / or blocks in the flowcharts and / or a combination of flowcharts and / or blocks in the flowcharts can be implemented by computer program instructions. Figure 1 means for carrying out functions specified in the flowchart block or blocks.

[0116] These computer program instructions can also be loaded onto a computer or other programmable data processing apparatus to cause a series of operational steps to be performed on the computer or other programmable apparatus to produce a computer-implemented process such that the instructions which execute on the computer or other programmable apparatus provide steps for implementing the functions specified in the flowchart block or blocks. Figure 1 one or more flowcharts and / or blocks in the flowcharts and / or a combination of flowcharts and / or blocks in the flowcharts can be implemented by computer program instructions. ​ means for carrying out functions specified in the flowchart block or blocks.

[0117] The embodiments of the application described above are intended to be merely exemplary and those skilled in the art will recognize that many changes can be made to the specific embodiments described which will fall within the scope of the present application as defined by the claims below.

Claims

1. A digital SPWM modulation method, characterized by, The method comprises: 1) sampling the modulated wave to obtain sampling value x as input data, and using a discretized lead transfer function tf1 to obtain the estimated value at the nearest peak in the lead; sampling the modulated wave to obtain sampling value x as input data, and using a discretized lag transfer function tf2 to obtain the estimated value at the nearest peak in the lag; 2) using the estimated values at the nearest peaks before and after the sampling value and the current sampling value, using the triangular replacement method, using the similarity of triangles to solve the intersection point of the modulated wave and the carrier wave; 3) using the period of the carrier wave and the intersection point relationship to solve the duty cycle in the carrier wave period. In step 2), in the triangular replacement method, the arc between the intersection of the modulated wave and the carrier wave is replaced by a straight line BCD at a high carrier frequency, thereby constructing triangles ABC and DCF, A is the positive half-cycle peak value of the carrier wave, B is the intersection point of the vertical line of A on the time axis and the modulated wave, C is the intersection point of the modulated wave and the carrier wave, D is the intersection point of the modulated wave and the time axis, E is the negative half-cycle peak value of the carrier wave, F is the intersection point of the vertical line of C on the time axis and the time axis, and G is the intersection point formed by the parallel line of B on the time axis and AE; The on length of PWM is DF, and the off length of PWM is BG. The arc BCD is replaced by a straight line BCD at a high carrier frequency, and the effective high and low pulse time of PMW is obtained according to the relationship of triangles, wherein the height coordinate of B is x1, which is the previous input, and the height coordinate of D is x, which is the current sampling input; There is a triangle , and , resulting in: (2) (3) According to the relationship of formulas (2) and (3), formula (4) is obtained: (4)； In step 3), AB = 1 - x1, ED = 1 + x, BG + DF = 1 + x1 / 2, is the carrier cycle, then the high level time t DF in the corresponding half cycle is obtained, and the calculation result is shown in formula (5): (5) The modulated wave intersects with the carrier wave at H point, and the height coordinate of H point is x2. Similarly, the high level time on the right side of the sampling is calculated: (6) The high level time in the whole period is: (7) The low level duration in the period is obtained: (8) The PWM wave maintains low level for t L1 , high level for t H , low level for t L2 , and high level for t L1 , t H , and t L2 , respectively, in a PWM cycle Ts ； ； ； Find t L1 , t H , t L2 The actual value is the high and low level time within the carrier period, where x is the sampling input of the current modulated wave, and x1 is the lead time calculated by the lead transfer function. The leading estimate of the angle, where x2 is the lag calculated using the leading transfer function. The lagged estimate of the angle, t L1 For the first low-level period, t H For the high-level time, t L2 This is the second low-level period.

2. A digital SPWM modulation method according to claim 1, characterized in that, In step 1), the lead transfer function is a SOGI-QSG type function, the input data is filtered by using the lead transfer function, and the estimated value x1 of the lead angle is calculated according to the difference of the carrier frequency . The complex frequency domain expression of the lead transfer function is: ； wherein, represents a lead transfer function, k represents a closed loop coefficient, represents a resonance frequency of the SOGI-QSG, represents a complex variable of the Laplace transform.

3. A digital SPWM modulation method according to claim 2, characterized in that, In step 1), the execution process of the lead transfer function is: The input signal x is subjected to an abc-dq coordinate transformation at the phase-locked angle θp The abc-dq phase coordinate transformed signal is subjected to dq-bac phase coordinate transformation. The abc-dq phase coordinate transformed signal is subjected to dq-bac phase coordinate transformation. The time domain calculation formula of the lead transfer function is: 。 4. The digital SPWM modulation method according to claim 1, wherein, In step 1), the lag transfer function is a SOGI-QSG type function, the lag transfer function filters the input data, and simultaneously calculates the estimated value x2 of the lag arbitrary angle according to the difference of the carrier frequency The complex frequency domain expression of the lag transfer function is: ； wherein, represents a lag transfer function, k represents a closed loop coefficient, represents a resonant frequency of the SOGI-QSG, s represents a complex variable of the Laplace transform.

5. A digital SPWM modulation method according to claim 4, characterized in that, The execution process of the lag transfer function is: The input signal x is subjected to an abc-dq phase coordinate transformation at the phase-locked angle θp The abc-dq phase coordinate transformed signal is subjected to dq-bac phase coordinate transformation. The abc-dq phase coordinate transformed signal is subjected to dq-bac phase coordinate transformation. The time domain calculation formula of the lag transfer function is: ； The lead transfer function and the lag transfer function are used for parameter discretization processing after parameter estimation of any angle.

6. The method of claim 1, wherein, In step 3), according to the obtained high level time and low level time, the corresponding high and low pulses are generated by using the digital period register and judging the size relationship between the value of the period register and the high and low level time through the increase of the value of the register, and the modulation is completed.

7. The method of claim 1, wherein, In step 3), when the value of the period counter t is less than t L1 , t is greater than t L1 and less than t L1 + t H , t is greater than t L1 + t H and less than Ts, the output is low, and the modulation is completed.

8. A computer apparatus comprising a memory, a processor, and a computer program stored on the memory, wherein the computer program, when executed by the processor, causes the processor to perform the method of any one of claims 1 to 7. The processor executes the computer program to realize the steps of the method of claim 1.

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