CN107994766B - Periodic Spread Spectrum PWM Control Method and Device Based on Ladder Wave Sequence - Google Patents

Abstract

The invention discloses a periodic spread spectrum PWM control method and device based on a ladder wave sequence, wherein the method includes: generating a ladder wave signal according to a ladder wave function; sampling the ladder wave signal to obtain a ladder wave sequence in a ladder wave distribution Obtain the disturbance frequency value according to the ladder wave sequence and the maximum frequency fluctuation; obtain the carrier signal with frequency change according to the reference switching frequency and the disturbance frequency value; generate the spread spectrum PWM control signal according to the comparison between the carrier signal and the modulation wave signal. This method can more effectively suppress the electromagnetic interference of power electronic converters. In terms of suppression effect, it can not only reduce the amplitude of switching frequency and its multiple sub-harmonics more significantly, but more importantly, only at the switching frequency and its multiple times There is an increase in the harmonic amplitude in a small range nearby, and the spectrum frequency expansion range is narrow, which avoids the generation of low-frequency noise and sub-harmonic noise, and can further improve the electromagnetic compatibility of the power electronic converter.

Description

Periodic Spread Spectrum PWM Control Method and Device Based on Ladder Wave Sequence

technical field

The present invention relates to the technical field of power electronics, in particular to a periodic spread spectrum PWM (Pulse Width Modulation, pulse width modulation) control method and device based on a ladder wave sequence.

Background technique

With the rapid development of power electronic technology, power electronic converters have been widely used in production and life. However, the problem of EMI (Electromagnetic Interference, electromagnetic interference) caused by high-frequency operation of switching devices in power electronic converters has also received widespread attention. Spread-spectrum PWM technology is a PWM technology for suppressing EMI of power electronic converters based on changing the switching frequency of power electronic converters. It can change the spectrum distribution of EMI and can effectively reduce the switching frequency of power electronic converters and its multiples. at the EMI peak.

In related technologies, spread-spectrum PWM is applied to suppress EMI of various types of power electronic converters, and the spread-spectrum PWM control of power electronic converters is realized by methods such as periodic spread-spectrum PWM, random spread-spectrum PWM, and chaotic spread-spectrum PWM. And analyze the mechanism of spread-spectrum PWM to suppress EMI, use analytical method, simulation and experiment to verify the effect of spread-spectrum PWM to suppress EMI. Traditional periodic spread spectrum PWM uses periodic functions such as triangle wave, sine wave, and square wave as modulation signals. By selecting modulation parameters, the sideband range can be limited, but the EMI peak suppression ability is not strong; random spread spectrum PWM and chaotic spread spectrum PWM are respectively Random signals and chaotic signals are used as modulation signals. Although they have a good effect on EMI peaks, random signals and chaotic signals have broadband white noise characteristics in the frequency domain, which continuously extend the sidebands to the entire frequency range and generate a large number of subharmonics. Waves and low-frequency harmonics, resulting in sub-harmonic noise and low-frequency noise, which is not conducive to the suppression of EMI in power electronic converters.

Contents of the invention

The present invention aims to solve one of the technical problems in the related art at least to a certain extent.

For this reason, an object of the present invention is to propose a periodic spread spectrum PWM control method based on a ladder wave sequence, which can more effectively suppress the electromagnetic interference of the power electronic converter, and in terms of the suppression effect, not only can the Reduce the amplitude of the switching frequency and its multiples, and more importantly, the harmonic amplitude increases only in a small range near the switching frequency and its multiples, and the spectrum frequency expansion range is narrow, avoiding low-frequency noise and sub-harmonics The generation of noise can further improve the electromagnetic compatibility of the power electronic converter.

Another object of the present invention is to propose a periodic spread spectrum PWM control device based on a ladder wave sequence.

In order to achieve the above object, an embodiment of the present invention proposes a periodic spread spectrum PWM control method based on a ladder wave sequence, including the following steps: generating a ladder wave signal according to a ladder wave function; sampling the ladder wave signal to obtain A ladder wave sequence with a ladder wave distribution; a disturbance frequency value is obtained according to the ladder wave sequence and the maximum frequency fluctuation; a carrier signal with a frequency change is obtained according to the reference switching frequency and the disturbance frequency value; according to the carrier signal and the modulation The wave signal is compared to generate a spread spectrum PWM control signal.

The periodic spread spectrum PWM control method based on the step wave sequence in the embodiment of the present invention can obtain the step wave sequence by sampling the step wave signal, thereby obtaining the disturbance frequency value according to the step wave sequence and the maximum frequency fluctuation, and according to the reference switching frequency and The carrier signal with frequency change is obtained by perturbing the frequency value, and the spread spectrum PWM control signal is generated by comparing the carrier signal and the modulating wave signal, which can more effectively suppress the electromagnetic interference of the power electronic converter. Reduce the amplitude of the switching frequency and its multiples, and more importantly, the harmonic amplitude increases only in a small range near the switching frequency and its multiples, and the spectrum frequency expansion range is narrow, avoiding low-frequency noise and sub-harmonics The generation of noise can further improve the electromagnetic compatibility of the power electronic converter.

In addition, the periodic spread spectrum PWM control method based on the ladder wave sequence according to the above-mentioned embodiments of the present invention may also have the following additional technical features:

Further, in one embodiment of the present invention, the mathematical expression of the step wave signal is:

Among them, A ₁ , A ₂ , and N are parameters of the step wave function.

Further, in one embodiment of the present invention, the parameters of the step wave function are restricted according to the following formula, so that the value range of the step wave sequence is (-1, 1), the formula is:

Among them, f _m is the frequency of the staircase wave signal.

Further, in one embodiment of the present invention, the frequency of the carrier signal is represented by the following formula, and its value changes within a preset range.

f _c = f _r + x _i ·Δf, x _i ∈ (-1,1), i=1,2,...,

Among them, f _c is the frequency of the chaotic carrier signal, f _r is the reference carrier frequency, Δf is the maximum frequency fluctuation value, and _xi is the ladder wave sequence.

Further, in an embodiment of the present invention, the parameters A1 and A2 of the step wave function are obtained according to the parameters of the power electronic converter to achieve an optimal electromagnetic interference suppression effect.

In order to achieve the above object, another embodiment of the present invention proposes a periodic spread spectrum PWM control device based on a ladder wave sequence, including: a first generation module for generating a ladder wave signal according to a ladder wave function; an acquisition module for The step wave signal is sampled to obtain a step wave sequence in a step wave distribution; the first acquisition module is used to obtain a disturbance frequency value according to the step wave sequence and the maximum frequency fluctuation; the second acquisition module is used to obtain a disturbance frequency value according to A frequency-changing carrier signal is obtained from the reference switching frequency and the disturbance frequency value; a second generating module is configured to generate a spread-spectrum PWM control signal according to the comparison between the carrier signal and the modulation wave signal.

The periodic spread spectrum PWM control device based on the step wave sequence in the embodiment of the present invention can obtain the step wave sequence by sampling the step wave signal, thereby obtaining the disturbance frequency value according to the step wave sequence and the maximum frequency fluctuation, and according to the reference switching frequency and The carrier signal with frequency change is obtained by perturbing the frequency value, and the spread spectrum PWM control signal is generated by comparing the carrier signal and the modulating wave signal, which can more effectively suppress the electromagnetic interference of the power electronic converter. Reduce the amplitude of the switching frequency and its multiples, and more importantly, the harmonic amplitude increases only in a small range near the switching frequency and its multiples, and the spectrum frequency expansion range is narrow, avoiding low-frequency noise and sub-harmonics The generation of noise can further improve the electromagnetic compatibility of the power electronic converter.

In addition, the periodic spread spectrum PWM control device based on the ladder wave sequence according to the above-mentioned embodiments of the present invention may also have the following additional technical features:

Further, in one embodiment of the present invention, the mathematical expression of the step wave signal is:

Among them, A ₁ , A ₂ , and N are parameters of the step wave function.

Further, in one embodiment of the present invention, the first generation module is further configured to limit the parameters of the staircase wave signal by the following formula, so that the value range of the staircase wave sequence is (-1,1 ), the formula is:

Among them, f _m is the frequency of the staircase wave signal.

Further, in one embodiment of the present invention, the frequency of the carrier signal is represented by the following formula, and its value changes within a preset range.

f _c = f _r + x _i ·Δf, x _i ∈ (-1,1), i=1,2,...,

Among them, f _c is the frequency of the chaotic carrier signal, f _r is the reference carrier frequency, Δf is the maximum frequency fluctuation value, and _xi is the ladder wave sequence.

Further, in an embodiment of the present invention, the parameters A1 and A2 of the step wave function are obtained according to the parameters of the power electronic converter to achieve an optimal electromagnetic interference suppression effect.

Additional aspects and advantages of the invention will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention.

Description of drawings

The above and/or additional aspects and advantages of the present invention will become apparent and easy to understand from the following description of the embodiments in conjunction with the accompanying drawings, wherein:

1 is a flow chart of a periodic spread spectrum PWM control method based on a ladder wave sequence according to an embodiment of the present invention;

FIG. 2 is a schematic diagram of a ladder wave signal according to an embodiment of the present invention;

FIG. 3 is a schematic diagram of a ladder wave modulation signal according to an embodiment of the present invention;

Fig. 4 is the flow chart of the periodic spread spectrum PWM control method based on the ladder wave sequence according to a specific embodiment of the present invention;

5 is a schematic diagram of a Boost converter topology and an EMI interference path thereof according to an embodiment of the present invention;

6 is a schematic diagram of the V _ds spectrum of the Boost converter under different control modes according to an embodiment of the present invention;

7 is a schematic diagram of the V _ds spectrum of the Boost converter under different control modes according to another embodiment of the present invention;

8 is a schematic diagram of the V _ds spectrum of the Boost converter under different control modes according to another embodiment of the present invention;

FIG. 9 is a schematic structural diagram of a periodic spread spectrum PWM control device based on a staircase wave sequence according to an embodiment of the present invention.

Detailed ways

Embodiments of the present invention are described in detail below, examples of which are shown in the drawings, wherein the same or similar reference numerals designate the same or similar elements or elements having the same or similar functions throughout. The embodiments described below by referring to the figures are exemplary and are intended to explain the present invention and should not be construed as limiting the present invention.

Before introducing the periodic spread-spectrum PWM control method and device based on the ladder wave sequence in the embodiment of the present invention, let us briefly introduce the traditional spread-spectrum PWM implementation method.

For the spread-spectrum PWM control of the power electronic converter, its switching frequency is no longer a constant value, but changes within a certain range, and the switching frequency f _s can be expressed by formula (1).

f _c ＝f _r +x _i ·Δf,x _i ∈(-1,1),i=1,2,... (1)

Among them, f _r is the reference switching frequency, Δf is the switching frequency fluctuation range, and _xi is the modulation signal sequence. By superimposing a disturbance frequency value on the basis of the reference switching frequency, the switching frequency can be changed within a certain range. In spread spectrum PWM control, the modulation signal usually adopts periodic signal (sine wave signal, triangular wave signal, square wave signal, etc.), random signal, chaotic signal (logistic mapping, tent mapping, chebyshev mapping, etc.).

According to the PWM control principle of the power electronic converter, the control signal of the switching device is generated by comparing the modulation wave signal with the carrier signal. The device works, so as to realize the spread spectrum PWM control.

The following describes the periodic spread spectrum PWM control method and device based on the ladder wave sequence according to the embodiments of the present invention with reference to the accompanying drawings. method.

FIG. 1 is a flowchart of a periodic spread spectrum PWM control method based on a staircase wave sequence according to an embodiment of the present invention.

As shown in Figure 1, the periodic spread spectrum PWM control method based on the ladder wave sequence comprises the following steps:

In step S101, a staircase wave signal is generated according to a staircase wave function.

Wherein, in one embodiment of the present invention, the mathematical expression of the step wave signal is:

Among them, A ₁ , A ₂ , and N are parameters of the step wave function.

It can be understood that in the above formula parameters, N can determine the number of steps of f(x), and the number of generated step waves is 2N+2, N=1,2,3,..., A ₁ and A ₂ Determine the height and width of each step wave; for the step wave signal whose intermediate value is located at the coordinate origin, its general mathematical expression is shown in formula (2).

In the formula, N, M=1, 2, 3,..., N determines the number of steps when f(x) is positive, M determines the number of steps when f(x) is negative, A ₁ and A ₂ determines the height and width of each staircase wave.

Optionally, according to the value range of xi in formula (1): x _i ∈ (-1,1), N=M should be taken, so formula (2) can be rewritten as:

In formula (3), N determines the number of steps in the overall step wave signal. If N=3, the generated staircase wave signal is shown in Figure 2.

Further, in one embodiment of the present invention, the parameters of the step wave function are restricted according to the following formula, so that the value range of the step wave sequence is (-1, 1), the formula is:

Among them, f _m is the frequency of the staircase wave signal.

It can be understood that if the signal shown in Figure 2 is used in the spread spectrum PWM control of the power electronic converter, the parameters of the step wave function need to be limited as follows:

Among them, f _m is defined as the frequency of the ladder wave signal, that is, the frequency of the modulation signal in the ladder wave spread spectrum PWM control. Then in actual control, the waveform of the step wave modulation signal is shown in Figure 3.

In step S102, the step wave signal is sampled to obtain a step wave sequence in a step wave distribution.

In step S103, the disturbance frequency value is obtained according to the staircase wave sequence and the maximum frequency fluctuation.

In step S104, a frequency-changing carrier signal is obtained according to the reference switching frequency and the disturbance frequency value.

In step S105, a spread-spectrum PWM control signal is generated according to the comparison between the carrier signal and the modulated wave signal.

Further, in an embodiment of the present invention, the frequency of the carrier signal is represented by the following formula, and its value changes within a preset range.

f _c = f _r + x _i ·Δf, x _i ∈ (-1,1), i=1,2,...,

Among them, f _c is the frequency of the chaotic carrier signal, f _r is the reference carrier frequency, Δf is the maximum frequency fluctuation value, and _xi is the ladder wave sequence.

Further, in an embodiment of the present invention, the parameters A1 and A2 of the step wave function are obtained according to the parameters of the power electronic converter to achieve an optimal electromagnetic interference suppression effect.

It can be understood that the selection of the parameters A ₁ , A ₂ , and N values of the ladder wave function has a great influence on the effect of the spread-spectrum PWM control to suppress the power electronic converter, and it is necessary to select the parameter A ₁ reasonably for the applied power electronic converter , A ₂ , N value in order to achieve the best electromagnetic interference suppression effect.

Specifically, for step-wave spread-spectrum PWM, x _i in formula (1) can be generated by a step-wave signal. Among them, the flow chart of the implementation principle of step wave spread spectrum PWM is shown in Figure 4. The method of the embodiment of the present invention first generates a step wave signal according to the step wave formula; secondly, the step wave signal is sampled to obtain sequence values in a step wave distribution , so as to replace x _i in formula (1); use formula (1) again to generate a carrier signal whose frequency changes within a certain range and compare it with the modulating wave to generate a spread-spectrum PWM control signal, and then control the switching device of the power electronic converter. Off, in order to realize the step wave spread spectrum PWM control of the power electronic converter.

For example, in order to analyze the effect of step-wave spread-spectrum PWM control on suppressing EMI of power electronic converters, the embodiment of the present invention takes a commonly used Boost converter as an example, and applies step-wave spread-spectrum PWM to the control of Boost converters, The topology diagram of the Boost converter is shown in Figure 5.

For Boost converters, the main component of EMI is conducted EMI. Conducted EMI can be divided into common-mode EMI and differential-mode EMI according to its interference path. The interference path is shown in Figure 5. According to the generation mechanism of common-mode EMI and differential-mode EMI, the gate-source voltage V _ds of switching device Q is the main electromagnetic interference source of Boost converter. During the turn-on and turn-off process of the switching device, V _ds is a pulsating voltage, which forms an interference current through the boost converter inductance, voltage source, line and parasitic parameters, thereby generating common-mode EMI and differential-mode EMI, common-mode EMI and differential-mode EMI Ultimately, it is jointly determined by the interference source and the interference path impedance. Since the mechanism of spread-spectrum PWM control to suppress EMI of power electronic converters is to improve the spectrum distribution of electromagnetic interference sources, in the Boost converter shown in Figure 5, spread-spectrum PWM control can change the spectrum distribution of EMI source voltage V _ds , so this The method of the embodiment of the invention will only analyze the frequency spectrum of the voltage V _ds below.

The method of the embodiment of the present invention utilizes Matlab/Simulink to set up the Boost simulation circuit under the control of the spread-spectrum PWM, and Table 1 is the simulation parameter table of the Boost converter system.

Table 1

parameter value Input voltage 20V power 120W The output voltage 50V Reference switching frequency F_r 20kHz Maximum frequency disturbance △f 1kHz

According to formula (3), step wave modulation signals with different step numbers and different frequencies can be generated. At the same time, in order to illustrate the effectiveness of step wave spread-spectrum PWM control for suppressing EMI, the method of the embodiment of the present invention respectively combines step wave spread-spectrum PWM with traditional constant Frequency PWM, triangular-wave spread-spectrum PWM, and chaotic spread-spectrum PWM are compared. In addition, the impact of step-wave spread-spectrum PWM on the frequency spectrum of the Boost converter is analyzed when the number of steps is different.

Firstly, the comparison between ladder wave spread spectrum PWM and traditional fixed frequency PWM and triangular wave spread spectrum PWM is introduced.

Set N=14 in formula (3), so that a step wave with a step number of 30 can be generated as a step wave modulation signal and applied to the control of the Boost converter. The triangular wave spread spectrum PWM uses a triangular wave signal. It should be noted that the frequencies of the triangular wave signal and the ladder wave signal are the same.

Using simulation to measure the V _ds of the Boost converter under the control of fixed frequency PWM, triangular wave spread spectrum PWM and ladder wave spread spectrum PWM. The V _ds spectrum diagram of the Boost converter under the three control modes is shown in Fig. 6(a), and its enlarged diagram at 0-50kHz is shown in Fig. 6(b).

As shown in Figure 6, compared with the Boost converter under the control of fixed-frequency PWM, the triangular wave spread PWM and ladder wave spread PWM can reduce the switching frequency and its multiple times. Harmonic peak, and the spreading width of the two is basically the same, but under the control of ladder wave spreading PWM, the amplitude of switching frequency and its multiple sub-harmonic is lower. At 20kHz, the amplitude under constant frequency PWM control is 144.5dBμV, the amplitude is 130dBμV under the control of triangular wave spread spectrum PWM, and the amplitude is 127dBμV under the control of fixed frequency PWM, which shows that the effect of ladder wave spread spectrum PWM on improving V _ds spectrum is better.

The second is the comparison between ladder wave spread spectrum PWM and traditional fixed frequency PWM and chaotic spread spectrum PWM.

Also set N=14 in the formula (3), so as to generate a step wave with a step number of 30 as a step wave modulation signal and apply it to the control of the Boost converter. Chaotic spread spectrum PWM control adopts Logistic chaotic mapping, and its expression is shown in formula (5):

ξ _i = μξ _i-1 (1-ξ _i-1 ), ξ _i ∈ (0, 1), i = 1, 2,... (5)

When the parameter μ = 4 and the initial condition ξ = 0.6, the Logistic chaos map will be in a chaotic state. Apply this map to formula (1) to realize chaotic spread spectrum PWM control.

The V _ds of the Boost converter under the control of fixed-frequency PWM, chaotic spread-spectrum PWM and step-wave spread-spectrum PWM are measured by simulation. The V _ds spectrum diagram of the Boost converter under the three control modes is shown in Fig. 7(a), among them, the enlarged diagram at 0-50kHz is shown in Fig. 7(b).

As shown in Figure 7, compared with the Boost converter under constant frequency PWM control, chaotic spread spectrum PWM can also reduce the harmonic peak value of the switching frequency and its multiple times, but under the control of chaotic spread spectrum PWM, the reduction At the same time as the peak value of the switching frequency and its multiple sub-harmonics, large-scale, high-amplitude sub-harmonics will be generated around the switching frequency and its multiples. There is an increase in the harmonic amplitude in the small frequency band near the frequency and its multiples, and at 20kHz, the amplitude under the control of chaotic spread spectrum PWM is 136dBμV, which is 9dBμV higher than that under the control of ladder wave spread spectrum PWM. In summary, compared with chaotic spread-spectrum PWM, step-wave spread-spectrum PWM has a better effect on suppressing EMI.

The last one is the comparison of step wave spread spectrum PWM control when the number of steps is different.

Set N=14 and N=19 in the formula (3) respectively, so as to generate a step wave with a step number of 30 and a step number of 40 as a step wave modulation signal, apply it to the control of the Boost converter, and then compare the step number effect on the spectrum distribution.

The simulation result is shown in Figure 8(a), and its enlarged view at 0-50kHz is shown in Figure 8(b). From the figure, it can be seen that when the number of steps increases, the peak value of the switching frequency and its multiple sub-harmonic The suppression effect is better, at 20kHz, when N=19, the amplitude under step wave spread spectrum PWM control is 124dBμV, which is 3dBμV lower than that when N=14.

According to the periodic spread spectrum PWM control method based on the step wave sequence proposed in the embodiment of the present invention, the step wave sequence can be obtained by sampling the step wave signal, so as to obtain the disturbance frequency value according to the step wave sequence and the maximum frequency fluctuation, and according to the reference switch Frequency and disturbance frequency value to obtain the carrier signal with frequency change, to generate a spread spectrum PWM control signal by comparing the carrier signal and the modulation wave signal, which can more effectively suppress the electromagnetic interference of the power electronic converter. In terms of suppression effect, not only can the The reduction of switching frequency and its multiple harmonic amplitude, more importantly, the harmonic amplitude increase only in a small range near the switching frequency and its multiple times, the spectrum frequency expansion range is narrow, avoiding low-frequency noise and sub-harmonic The generation of wave noise can further improve the electromagnetic compatibility of power electronic converters.

Next, the periodic spread spectrum PWM control device based on the ladder wave sequence proposed according to the embodiment of the present invention will be described with reference to the accompanying drawings.

FIG. 9 is a schematic structural diagram of a periodic spread spectrum PWM control device based on a staircase wave sequence according to an embodiment of the present invention.

As shown in FIG. 9 , the step-wave sequence-based periodic spread spectrum PWM control device 10 includes: a first generation module 100 , an acquisition module 200 , a first acquisition module 300 , a second acquisition module 400 and a second generation module 500 .

Wherein, the first generating module 100 is used for generating a staircase wave signal according to a staircase wave function. The acquisition module 200 is used to sample the staircase wave signal to obtain a staircase wave sequence in a staircase wave distribution. The first acquisition module 300 is used to obtain the disturbance frequency value according to the ladder wave sequence and the maximum frequency fluctuation. The second obtaining module 400 is used to obtain the carrier signal with frequency change according to the reference switching frequency and the disturbance frequency value. The second generating module 500 is used for generating a spread-spectrum PWM control signal according to the comparison between the carrier signal and the modulating wave signal. The device 10 of the embodiment of the present invention can generate a spread-spectrum PWM control signal according to the comparison between the carrier signal and the modulating wave signal, which can more effectively suppress the electromagnetic interference of the power electronic converter. In terms of suppression effect, it can not only reduce the switching frequency and The amplitude of its multiple sub-harmonics, more importantly, the harmonic amplitude increases only in a small range near the switching frequency and its multiples, and the spectrum frequency expansion range is narrow, avoiding the generation of low-frequency noise and sub-harmonic noise. The electromagnetic compatibility of the power electronic converter can be further improved.

Further, in one embodiment of the present invention, the mathematical expression of the step wave signal is:

Among them, A ₁ , A ₂ , and N are parameters of the step wave function.

Further, in one embodiment of the present invention, the first generation module 100 is also used to limit the parameters of the step wave function by the following formula, so that the value range of the step wave sequence is (-1, 1), the formula for:

Among them, f _m is the frequency of the staircase wave signal.

Further, in an embodiment of the present invention, the frequency of the carrier signal is represented by the following formula, and its value changes within a preset range.

f _c = f _r + x _i ·Δf, x _i ∈ (-1,1), i=1,2,...,

Among them, f _c is the frequency of the chaotic carrier signal, f _r is the reference carrier frequency, Δf is the maximum frequency fluctuation value, and _xi is the ladder wave sequence.

Further, in an embodiment of the present invention, the parameters A1 and A2 of the step wave function are obtained according to the parameters of the power electronic converter to achieve an optimal electromagnetic interference suppression effect.

It should be noted that, the foregoing explanations on the embodiment of the periodic spread spectrum PWM control method based on the staircase wave sequence are also applicable to the periodic spread spectrum PWM control device based on the staircase wave sequence in this embodiment, and will not be repeated here.

According to the periodic spread spectrum PWM control device based on the step wave sequence proposed in the embodiment of the present invention, the step wave sequence can be obtained by sampling the step wave signal, thereby obtaining the disturbance frequency value according to the step wave sequence and the maximum frequency fluctuation, and according to the reference switch Frequency and disturbance frequency value to obtain the carrier signal with frequency change, to generate a spread spectrum PWM control signal by comparing the carrier signal and the modulation wave signal, which can more effectively suppress the electromagnetic interference of the power electronic converter. In terms of suppression effect, not only can the The reduction of switching frequency and its multiple harmonic amplitude, more importantly, the harmonic amplitude increase only in a small range near the switching frequency and its multiple times, the spectrum frequency expansion range is narrow, avoiding low-frequency noise and sub-harmonic The generation of wave noise can further improve the electromagnetic compatibility of power electronic converters.

In describing the present invention, it should be understood that the terms "center", "longitudinal", "transverse", "length", "width", "thickness", "upper", "lower", "front", " Back", "Left", "Right", "Vertical", "Horizontal", "Top", "Bottom", "Inner", "Outer", "Clockwise", "Counterclockwise", "Axial", The orientation or positional relationship indicated by "radial", "circumferential", etc. is based on the orientation or positional relationship shown in the drawings, and is only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying the referred device or element Must be in a particular orientation, be constructed in a particular orientation, and operate in a particular orientation, and therefore should not be construed as limiting the invention.

In addition, the terms "first" and "second" are used for descriptive purposes only, and cannot be interpreted as indicating or implying relative importance or implicitly specifying the quantity of indicated technical features. Thus, the features defined as "first" and "second" may explicitly or implicitly include at least one of these features. In the description of the present invention, "plurality" means at least two, such as two, three, etc., unless otherwise specifically defined.

In the present invention, unless otherwise clearly specified and limited, terms such as "installation", "connection", "connection" and "fixation" should be understood in a broad sense, for example, it can be a fixed connection or a detachable connection , or integrated; it may be mechanically connected or electrically connected; it may be directly connected or indirectly connected through an intermediary, and it may be the internal communication of two components or the interaction relationship between two components, unless otherwise specified limit. Those of ordinary skill in the art can understand the specific meanings of the above terms in the present invention according to specific situations.

In the present invention, unless otherwise clearly specified and limited, the first feature may be in direct contact with the first feature or the first and second feature indirectly through an intermediary. touch. Moreover, "above", "above" and "above" the first feature on the second feature may mean that the first feature is directly above or obliquely above the second feature, or simply means that the first feature is higher in level than the second feature. "Below", "beneath" and "beneath" the first feature may mean that the first feature is directly below or obliquely below the second feature, or simply means that the first feature is less horizontally than the second feature.

In the description of this specification, descriptions referring to the terms "one embodiment", "some embodiments", "example", "specific examples", or "some examples" mean that specific features described in connection with the embodiment or example , structure, material or characteristic is included in at least one embodiment or example of the present invention. In this specification, the schematic representations of the above terms are not necessarily directed to the same embodiment or example. Furthermore, the described specific features, structures, materials or characteristics may be combined in any suitable manner in any one or more embodiments or examples. In addition, those skilled in the art can combine and combine different embodiments or examples and features of different embodiments or examples described in this specification without conflicting with each other.

Although the embodiments of the present invention have been shown and described above, it can be understood that the above embodiments are exemplary and should not be construed as limiting the present invention, and those skilled in the art can make the above-mentioned The embodiments are subject to changes, modifications, substitutions and variations.

Claims (6)

1. A periodic spread spectrum PWM control method based on ladder wave sequence, is characterized in that, comprises the following steps: Generate a staircase wave signal according to the staircase wave function; Sampling the ladder wave signal to obtain a ladder wave sequence in a ladder wave distribution; obtaining a disturbance frequency value according to the ladder wave sequence and the maximum frequency fluctuation; Obtaining a frequency-varying carrier signal according to the reference switching frequency and the disturbance frequency value; and generating a spread spectrum PWM control signal according to the comparison between the carrier signal and the modulating wave signal; Wherein, the mathematical expression of described step wave signal is: Among them, A ₁ , A ₂ , N are the parameters of the step wave function; The parameters of the step wave function are limited according to the following formula, so that the value range of the step wave sequence is (-1, 1), the formula is: (2N+1)A ₂ =2 Among them, f _m is the frequency of the staircase wave signal. 2. the periodic spread-spectrum PWM control method based on step wave sequence according to claim 1, is characterized in that, the frequency of described carrier signal is expressed with following formula, and its value changes within preset range: f _c = f _r + x _i ·Δf, x _i ∈ (-1,1), i=1,2,..., Among them, f _c is the frequency of the chaotic carrier signal, f _r is the reference carrier frequency, Δf is the maximum frequency fluctuation value, and _xi is the ladder wave sequence. 3. the periodic spread spectrum PWM control method based on step wave sequence according to claim 1, is characterized in that, obtains the parameter A1 of described step wave function according to the parameter of power electronic converter, A2 to reach optimal electromagnetic interference Inhibitory effect. 4. A periodic spread spectrum PWM control device based on a ladder wave sequence, characterized in that it comprises: The first generating module is used to generate a ladder wave signal according to the ladder wave function; An acquisition module, configured to sample the ladder wave signal to obtain a ladder wave sequence in a ladder wave distribution; The first acquisition module is used to obtain the disturbance frequency value according to the ladder wave sequence and the maximum frequency fluctuation; The second acquisition module is used to obtain a carrier signal with a frequency change according to the reference switching frequency and the disturbance frequency value; and The second generation module is used to generate a spread-spectrum PWM control signal according to the comparison between the carrier signal and the modulation wave signal; Wherein, the mathematical expression of the step wave signal is: Among them, A ₁ , A ₂ , N are the parameters of the step wave function; The first generation module is also used to limit the parameters of the step wave function by the following formula, the formula is: (2N+1)A ₂ =2 Among them, f _m is the frequency of the staircase wave signal. 5. the periodic spread spectrum PWM control device based on step wave sequence according to claim 4, is characterized in that, the frequency of described carrier signal is represented by following formula, and its value changes within preset range: f _c = f _r + x _i ·Δf, x _i ∈ (-1,1), i=1,2,..., Among them, f _c is the frequency of the chaotic carrier signal, f _r is the reference carrier frequency, Δf is the maximum frequency fluctuation value, and _xi is the ladder wave sequence. 6. the periodic spread spectrum PWM control device based on the step wave sequence according to claim 4, is characterized in that, obtains the parameter A1 of described step wave function according to the parameter of power electronic converter, A2 to reach optimal electromagnetic interference Inhibitory effect.