Method and apparatus for pulse modulation of a three-phase inverter

Abstract

This exemplary embodiment provides a pulse modulation method and apparatus for a three-phase converter. The method includes: within one carrier cycle, changing the arrangement of SVPWM and DPWM, and through the ratio of SVPWM and DPWM, ensuring that the output current simultaneously meets the requirements of the switching frequency and the carrier frequency. Specifically, this includes determining the main resonant frequency point of the system; at f r ~1.5f r Selecting a suitable carrier frequency f s The carrier frequency f s Satisfy frequency multiplication n·f s (n = 1, 2, 3...) staggered from the main resonant frequency points; according to the carrier frequency f s and the switching frequency f r The relationship between SVPWM and DPWM is determined, and the final pulse sequence is arranged according to this relationship. This disclosure achieves control by changing the harmonic distribution of the supporting capacitor current without changing the IGBT switching frequency, eliminating the need for a low-inductance busbar and avoiding the resulting increase in system cost; furthermore, the impact on system losses and waveform quality is minimal as the switching frequency remains unchanged.

Description

Technical Field

[0001] Exemplary embodiments disclosed herein relate to the field of motor technology, and more particularly to a pulse modulation method and apparatus for a three-phase converter. Background Technology

[0002] In the fields of new energy power generation and motor drive control, three-phase PWM (Pulse Width Modulation) converters are the most common circuit topology. With the development of the industry, the power of converters is increasing, which also requires products with higher power density, reliability, and maintainability. As power increases, considering maintainability requirements, IGBTs are generally installed in several power units.

[0003] To suppress the overvoltage problem of IGBTs, a support capacitor is usually installed in each power unit. To prevent current resonance between the support capacitors of each power unit, the conventional method is to use a low-inductance busbar to connect the DC side of each power unit, but this results in higher product cost. Summary of the Invention

[0004] In view of this, the purpose of the exemplary embodiments of this disclosure is to propose a pulse modulation method and apparatus for a three-phase converter, which, while keeping the actual switching frequency of the IGBT unchanged, adjusts the frequency distribution of the higher-order current harmonics of the system by optimizing the PWM arrangement and adjusting the PWM carrier frequency, thereby avoiding the system resonance point problem.

[0005] To achieve the above objectives, an exemplary embodiment of this disclosure provides a pulse modulation method for a three-phase converter, comprising:

[0006] Within one carrier cycle, the arrangement of SVPWM and DPWM is changed, and the ratio of SVPWM to DPWM is adjusted to ensure that the output current simultaneously meets the requirements of the switching frequency and the carrier frequency.

[0007] In conjunction with the above description, in another possible implementation of the embodiments of this disclosure, changing the arrangement of SVPWM and DPWM includes:

[0008] Determining the system's main resonant frequency includes: adjusting the carrier frequency within a preset range, measuring the relationship between the phase capacitor current and the carrier frequency, and then determining the system's main resonant frequency. The preset range is a set value f. r ~1.5f r between;

[0009] In f r ~1.5f r Selecting a suitable carrier frequency f s The carrier frequency f sSatisfy frequency multiplication n·f s (n = 1, 2, 3...) to stagger the main resonant frequency points;

[0010] According to the carrier frequency f s and the switching frequency f r The relationship between SVPWM and DPWM is determined, and the final pulse sequence is arranged according to this relationship, including:

[0011] In response to SVPWM having a proportion of k1 and DPWM having a proportion of k2, and k1 + k2 = 1, when the carrier frequency is f s At that time, there were: Substituting k1 = 1 - k2 into the equation, we get the result. Right now: The arrangement of the SVPWM and the DPWM is determined based on the proportional relationship between k1 and k2.

[0012] In conjunction with the above description, in another possible implementation of the embodiments of this disclosure, the method further includes: determining a suitable The proportions should be taken as follows: (m, n = 0, 1, 2, 3, 4, 5), the carrier frequency calculated by rounding m and n is checked once in the relationship curve between capacitor current and carrier frequency, and the optimal k1 and k2 are selected.

[0013] In conjunction with the above description, in another possible implementation of the embodiments of this disclosure, determining the main resonant frequency of the system further includes:

[0014] The modulation method is selected as continuous SVPWM, and the carrier frequency is set to the design value f. r Furthermore, during continuous SVPWM modulation, the carrier frequency is equal to the switching frequency. Select a rated operating condition and measure the three-phase capacitor current value during steady-state operation.

[0015] Slowly reduce the carrier frequency and, under the same load conditions, measure the three-phase capacitor current value during operation at each frequency point under steady-state conditions.

[0016] Stop adjusting the carrier frequency when it drops to 0.5 times the design value;

[0017] Perform a spectral analysis on the capacitor current, plot the relationship curve between the capacitor current and the carrier frequency, and determine the main resonant frequency of the system based on this relationship curve.

[0018] In conjunction with the above description, in another possible implementation of the embodiments of this disclosure, the method further includes:

[0019] By arranging SVPWM and DPWM according to a certain pattern, the requirements of switching frequency and carrier frequency can be met simultaneously.

[0020] In a second aspect, an exemplary embodiment of the present invention also provides a three-phase converter pulse modulation device, comprising:

[0021] The arrangement unit is used to change the arrangement of SVPWM and DPWM within one carrier cycle;

[0022] The output unit is used to determine the ratio of SVPWM and DPWM obtained by arranging the units, so that the output current simultaneously meets the requirements of the switching frequency and the carrier frequency.

[0023] In conjunction with the above description, in another possible implementation of the embodiments of this disclosure, the arrangement unit is further used for:

[0024] The determination of a subunit, used to determine the main resonant frequency of the system, includes: adjusting the carrier frequency within a preset range, measuring the relationship between the phase capacitor current and the carrier frequency, and then determining the main resonant frequency of the system. The preset range is a set f... r ~1.5f r between;

[0025] Select sub-units for use in f r ~1.5f r Selecting a suitable carrier frequency f s The carrier frequency f s Satisfy frequency multiplication n·f s (n = 1, 2, 3...) to stagger the main resonant frequency points;

[0026] Arrangement determination subunits, used according to the carrier frequency f s and the switching frequency f r The relationship between SVPWM and DPWM is determined, and the final pulse sequence is arranged according to this relationship, including:

[0027] In response to SVPWM having a proportion of k1 and DPWM having a proportion of k2, and k1 + k2 = 1, when the carrier frequency is f s At that time, there were: Substituting k1 = 1 - k2 into the equation, we get the result. Right now: The arrangement of the SVPWM and the DPWM is determined based on the proportional relationship between k1 and k2.

[0028] In conjunction with the above description, in another possible implementation of the embodiments of this disclosure, the arrangement determination subunit is further configured to: determine suitable... The proportions should be taken as follows: (m, n = 0, 1, 2, 3, 4, 5), the carrier frequency calculated by rounding m and n is checked once in the relationship curve between capacitor current and carrier frequency, and the optimal k1 and k2 are selected.

[0029] In conjunction with the above description, in another possible implementation of the embodiments of this disclosure, the determining subunit is further configured to:

[0030] The modulation method is selected as continuous SVPWM, and the carrier frequency is set to the design value f. r Furthermore, during continuous SVPWM modulation, the carrier frequency is equal to the switching frequency. Select a rated operating condition and measure the three-phase capacitor current value during steady-state operation.

[0031] Slowly reduce the carrier frequency and, under the same load conditions, measure the three-phase capacitor current value during operation at each frequency point under steady-state conditions.

[0032] Stop adjusting the carrier frequency when it drops to 0.5 times the design value;

[0033] Perform a spectral analysis on the capacitor current, plot the relationship curve between the capacitor current and the carrier frequency, and determine the main resonant frequency of the system based on this relationship curve.

[0034] In conjunction with the above description, in another possible implementation of the embodiments of this disclosure, the arrangement unit is further used for:

[0035] By arranging SVPWM and DPWM according to a certain pattern, the requirements of switching frequency and carrier frequency can be met simultaneously.

[0036] As can be seen from the above, the three-phase converter pulse modulation method provided by the exemplary embodiments of this disclosure can achieve control by changing the harmonic distribution of the supporting capacitor current without changing the IGBT switching frequency. This eliminates the need to use a low-inductance busbar and avoids the resulting increase in system cost. In addition, the switching frequency remains unchanged, and the impact on system losses and waveform quality is minimal. Attached Figure Description

[0037] To more clearly illustrate the technical solutions in the exemplary embodiments of this disclosure or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only exemplary embodiments of this disclosure. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0038] Figure 1 A schematic diagram of a conventional three-phase PWM converter system as an exemplary embodiment of this disclosure;

[0039] Figure 2 This is a schematic diagram of a three-phase separate PMW converter system as an exemplary embodiment of the present disclosure;

[0040] Figure 3 This is a schematic diagram of the internal equivalent circuit of the system in an exemplary embodiment of this disclosure;

[0041] Figure 4 This is a schematic diagram of the vector arrangement during SVPWM modulation in sector I, an exemplary embodiment of this disclosure;

[0042] Figure 5 This is a schematic diagram of various vector arrangements within a half-carrier period in sector I, an exemplary embodiment of this disclosure;

[0043] Figure 6 This is a schematic diagram of a method flow that exemplifies an embodiment of this disclosure;

[0044] Figure 7 This is a schematic diagram of the device structure of an exemplary embodiment of the present disclosure. Detailed Implementation

[0045] To make the objectives, technical solutions, and advantages of this disclosure clearer, the following detailed description is provided in conjunction with specific embodiments and the accompanying drawings.

[0046] It should be noted that, unless otherwise defined, the technical or scientific terms used in the exemplary embodiments of this disclosure should have the ordinary meaning understood by one of ordinary skill in the art to which this disclosure pertains. Words such as "comprising" or "including" mean that an element or object preceding the word encompasses the elements or objects listed following the word and their equivalents, without excluding other elements or objects. Words such as "connected" or "linked" are not limited to physical or mechanical connections, but can include electrical connections, whether direct or indirect.

[0047] Technical terms used in this disclosure:

[0048] Switching frequency: The number of times an electronic device turns on and off per second.

[0049] Carrier frequency: When a lower signal frequency is modulated to a relatively higher frequency, the higher frequency modulated by the lower frequency is called the carrier frequency. In PWM modulation, the pulse is generally generated by comparing the modulating wave and the triangular wave, and the carrier frequency refers to the frequency of the triangular wave.

[0050] SVPWM: Space Vector PWM technology is an advanced algorithm widely used in the field of variable frequency drives. Based on the switching mode of the inverter's main circuit, eight voltage space vectors can be obtained. The most significant characteristic of SVPWM is that it simultaneously contains two zero vectors, "000" and "111," with equal durations.

[0051] DPWM: Discontinuous PWM. In order to reduce losses while maintaining a fixed carrier frequency, only one phase is inactive during a certain carrier cycle. In terms of voltage vectors, this means that there is only one zero vector during half a carrier cycle.

[0052] Continuous PWM: Continuous modulation strategies include SPWM, SVPWM, etc., which are in contrast to the discontinuity of DPMW. It mainly refers to the zero vector containing two different states within half a carrier cycle.

[0053] The IGBT module system of the exemplary embodiment of the present invention has its basic parameters determined after the design is completed, such as its switching frequency. However, in some cases, the system becomes unstable when its inherent resonant frequency is reached, and the same situation exists at integer multiples of the resonant frequency. The purpose of the method of the present invention is to avoid the inherent resonant frequency of the system in order to avoid the occurrence of current resonance between the supporting capacitors of the power units that make up the system.

[0054] When a product exhibits resonance, in order to reduce the current in the supporting capacitor, it is necessary to avoid the resonant frequency point. There are two common methods: one is to redesign the DC bus structure and change the stray inductance parameters; the other is to change the switching frequency.

[0055] Changing the busbar structure to adjust the inductance generally requires a partial redesign of the product, which takes a long time. In addition, with the current conventional technical capabilities, it is not possible to accurately design stray parameters. Therefore, even if the busbar structure is redesigned, it may not achieve the optimal result.

[0056] Adjusting the switching frequency after the product design is completed can also bring a series of system problems. Lowering the switching frequency will reduce the quality of the output waveform; increasing the switching frequency will bring additional losses, and the previous design may not be able to meet the heat dissipation requirements.

[0057] The method proposed in this invention allows the system resonance point to be avoided by optimizing the PWM arrangement while keeping the switching frequency constant. The method of this invention does not require redesigning the system structure or heat dissipation; the goal can be achieved solely through software optimization.

[0058] A typical three-phase PWM converter system diagram is shown below. Figure 1 As shown, the supporting capacitor C_dc is shared when the power is low.

[0059] As the converter capacity increases, the number of capacitors and the weight of the heatsink also increase. Considering maintainability requirements, the IGBT module system is generally divided into several identical power units. A common partitioning method is as follows: Figure 2As shown, the IGBT module is divided into three identical power units according to the three output phases. The supporting capacitors are also evenly distributed among the power units, as shown in the diagram (C). a C b C c C a C b C c When placed separately, the equivalent impedance of the connecting busbar between them is L. a L b L c .

[0060] The switching action of an IGBT can be viewed as an excitation source of internal high-frequency current. Taking phase A as an example, the internal equivalent circuit is as follows: Figure 3 As shown, the system is a second-order circuit composed of inductors and capacitors, and there is a system resonance point.

[0061] When the excitation source is I a At that time, set It can be calculated that: At certain specific frequency points, Z O +Z Ca =0, which is the resonant frequency of the system. If the excitation source also has current in this frequency range, a large current will appear in the supporting capacitor.

[0062] The study "Research on Ripple Current of DC Bus Support Capacitor" analyzes the principle of capacitor current resonance caused by parameter mismatch between capacitor, connection impedance and switching frequency.

[0063] The system will have current harmonics distributed at integer multiples of the carrier frequency. Therefore, any frequency point that is an integer multiple of the carrier frequency may be a system resonant frequency point. When resonance occurs in the product, in order to reduce the current of the supporting capacitor, it is necessary to avoid the resonant frequency point. There are two common methods: one is to redesign the DC bus structure and change the stray inductance parameters; the other is to change the switching frequency.

[0064] Changing the busbar structure to adjust the inductance generally requires a partial redesign of the product, which takes a long time. In addition, with current conventional technology, it is not possible to accurately design stray parameters. Therefore, even if the busbar structure is redesigned, it may not be optimal.

[0065] Adjusting the switching frequency after the product design is completed can also bring a series of system problems. Lowering the switching frequency will reduce the quality of the output waveform; increasing the switching frequency will bring additional losses, and the previous design may not be able to meet the heat dissipation requirements.

[0066] The principles of modulation methods mainly include the following points:

[0067] The higher harmonics of the output current are distributed near integer multiples of the carrier frequency; when the carrier frequency is the same, the switching frequency of several general discontinuous PWM (DPWM) is only 2 / 3 of the switching frequency of continuous SVPWM.

[0068] Although modulation ratio and modulation method affect the output waveform quality, the most critical factor overall is the switching frequency of the IGBT.

[0069] Regarding PWM arrangement:

[0070] Taking sector I as an example, the data is analyzed. For sector I, Ua>Ub>Uc, therefore, if continuous SVPWM modulation is used, the vector arrangement within one carrier cycle is as follows: Figure 4 As shown.

[0071] The vectors are arranged according to half a carrier cycle. The vector arrangement of continuous SVPWM is as follows: Figure 5 As shown in a1 and a2.

[0072] Combination Figure 5 As shown, in sector I, for continuous SVPWM, the overall arrangement sequence is a1→a2→a1→a2→a1→a2→……

[0073] For DPWM0, the overall arrangement sequence is c1→c2→c1→c2→c1→c2→……

[0074] For DPWM2, the overall arrangement sequence is b1→b2→b1→b2→b1→b2→……

[0075] exist Figure 4 Based on this, by merging the zero vectors "000" and "111" and retaining only one zero vector, and arranging them according to half of the switch vector, we can obtain the following: Figure 5 There are four arrangement methods: b1, b2, c1, and c2.

[0076] Accordingly, this disclosure provides a pulse modulation method for a three-phase converter. By optimizing the PWM arrangement, the system resonance point can be avoided without changing the switching frequency. This method eliminates the need to redesign the system structure or heat dissipation. It is mainly used in scenarios where optimization of the three-phase converter is required. The basic idea is to achieve control by changing the harmonic distribution of the supporting capacitor current without changing the IGBT switching frequency. This eliminates the need to use a low-inductance busbar and avoids the resulting increase in system cost. In addition, since the switching frequency remains unchanged, the impact on system losses and waveform quality is minimal.

[0077] Combination Figure 6 The diagram shown is a basic schematic of the method flow of an exemplary embodiment of this disclosure, which basically includes the following steps:

[0078] In step 610, the system resonant frequency is measured;

[0079] In specific embodiments of this disclosure, the following are included:

[0080] The modulation method is selected as continuous SVPWM, and the carrier frequency is set to the design value f. r (When using continuous SVPWM modulation, the carrier frequency is equal to the switching frequency). Select a rated operating condition and measure the three-phase capacitor current value during steady-state operation.

[0081] Slowly reduce the carrier frequency and, under the same load conditions, measure the three-phase capacitor current value during operation at each frequency point under steady-state conditions.

[0082] Stop adjusting the carrier frequency when it drops to 0.5 times the design value.

[0083] In step 620, the carrier frequency is determined;

[0084] In f r ~1.5f r Selecting a suitable carrier frequency f s , making its frequency multiplied by n·f s (n = 1, 2, 3...) can all be well staggered at the resonant frequency points, while ensuring a certain margin.

[0085] In step 630, the pulse arrangement is determined;

[0086] According to the carrier frequency f s and switching frequency f r The relationship between SVPWM and DPWM is determined to establish the ratio between them, and the final pulse sequence arrangement is determined accordingly.

[0087] Let the SVPWM proportion be k1 and the DPWM proportion be k2, then we have k1 + k2 = 1, when the carrier frequency is f. s At that time, there were: Substituting k1 = 1 - k2 into the equation, we get the result. Right now:

[0088] Choose the appropriate The ratio is generally taken as follows: (m, n = 0, 1, 2, 3, 4, 5), the carrier frequency calculated by rounding m and n is then checked again on the relationship curve between capacitor current and carrier frequency, and the optimal one is selected.

[0089] Taking sector I in the voltage space vector as an example, the data is analyzed. For sector I, the switching combinations corresponding to the non-zero vector combinations are Ua>Ub>Uc. Therefore, if continuous SVPWM modulation is used, the vector arrangement within one carrier cycle is as shown in Figure 4.

[0090] For example, if the switching frequency of an IGBT is 3kHz based on its heat dissipation design, and the optimal carrier frequency is 3.6kHz, then k2 = 0.5 can be calculated. That is, the duration of continuous SVPWM and DPWM is 1:1. In addition, the switching process of continuous SVPWM and DPWM should keep the number of flipped phases as small as possible. For example, b2 or c2 can be connected after a1, and b1 or c1 can be connected after a21.

[0091] The 1:1 pulse arrangement sequence mentioned above can be selected as: a1→a2→c1→c2→a1→a2→c1→c2→……, or according to the half-wave alternation, it can be selected as: a1→c2→a1→c2→a1→c2→…….

[0092] The method disclosed herein determines the system resonant frequency point by adjusting the carrier frequency within a certain range and measuring the relationship between the phase capacitor current and the carrier frequency, and within f r ~1.5f r A suitable carrier frequency point is selected between the two frequencies, so that its doubling point avoids the system resonant frequency point and leaves a certain margin. By arranging SVPWM and DPWM according to a certain rule, the requirements of switching frequency and carrier frequency are met at the same time.

[0093] The method disclosed herein utilizes SVPWM and DPWM arranged according to a certain pattern to simultaneously meet the requirements of switching frequency and carrier frequency; that is, within one carrier cycle, the ratio of the combination of two modulation methods with different switching frequencies is used to meet the requirements. The selection of SVPWM, the DPWM method, and its arrangement can all be changed to achieve the same effect. For example, a 1:1 pulse arrangement sequence, when selected as a1→a2→c1→c2→a1→a2→c1→c2→… and a1→c2→a1→c2→a1→c2→…, can both achieve the effect of staggering the main resonant frequency points.

[0094] The method of this invention is applicable to both back-to-back converter systems and non-back-to-back converter systems. By changing the harmonic distribution of the supporting capacitor current without altering the IGBT switching frequency, overall control is achieved, thus eliminating the need for a dedicated low-inductance busbar and reducing system cost. Furthermore, since the switching frequency remains unchanged, the impact on system losses and waveform quality is minimal.

[0095] Based on the same inventive concept, corresponding to the methods of any of the above embodiments, this disclosure also provides a three-phase converter pulse modulation device.

[0096] refer to Figure 7 The three-phase converter pulse modulation device includes:

[0097] The arrangement unit 710 is used to change the arrangement of SVPWM and DPWM within one carrier cycle;

[0098] The output unit 720 is used to obtain the ratio of SVPWM and DPWM through the arrangement of units, so that the output current can simultaneously meet the requirements of the switching frequency and the carrier frequency.

[0099] In conjunction with the above description, in another possible implementation of the embodiments of this disclosure, the arrangement unit is further used for:

[0100] The determination of a subunit, used to determine the main resonant frequency of the system, includes: adjusting the carrier frequency within a preset range, measuring the relationship between the phase capacitor current and the carrier frequency, and then determining the main resonant frequency of the system. The preset range is a set f... r ~1.5f r between;

[0101] Select sub-units for use in f r ~1.5f r Selecting a suitable carrier frequency f s The carrier frequency f s Satisfy frequency multiplication n·f s (n = 1, 2, 3...) to stagger the main resonant frequency points;

[0102] Arrangement determination subunits, used according to the carrier frequency f s and the switching frequency f r The relationship between SVPWM and DPWM is determined, and the final pulse sequence is arranged according to this relationship, including:

[0103] In response to SVPWM having a proportion of k1 and DPWM having a proportion of k2, and k1 + k2 = 1, when the carrier frequency is f s At that time, there were: Substituting k1 = 1 - k2 into the equation, we get the result. Right now: The arrangement of the SVPWM and the DPWM is determined based on the proportional relationship between k1 and k2.

[0104] In conjunction with the above description, in another possible implementation of the embodiments of this disclosure, the arrangement determination subunit is further configured to: determine suitable... The proportions should be taken as follows: (m, n = 0, 1, 2, 3, 4, 5), the carrier frequency calculated by rounding m and n is checked once in the relationship curve between capacitor current and carrier frequency, and the optimal k1 and k2 are selected.

[0105] In conjunction with the above description, in another possible implementation of the embodiments of this disclosure, the determining subunit is further configured to:

[0106] The modulation method is selected as continuous SVPWM, and the carrier frequency is set to the design value f. r Furthermore, during continuous SVPWM modulation, the carrier frequency is equal to the switching frequency. Select a rated operating condition and measure the three-phase capacitor current value during steady-state operation.

[0107] Slowly reduce the carrier frequency and, under the same load conditions, measure the three-phase capacitor current value during operation at each frequency point under steady-state conditions.

[0108] Stop adjusting the carrier frequency when it drops to 0.5 times the design value;

[0109] Perform a spectral analysis on the capacitor current, plot the relationship curve between the capacitor current and the carrier frequency, and determine the main resonant frequency of the system based on this relationship curve.

[0110] In conjunction with the above description, in another possible implementation of the embodiments of this disclosure, the arrangement unit is further used for:

[0111] By arranging SVPWM and DPWM according to a certain pattern, the requirements of switching frequency and carrier frequency can be met simultaneously.

[0112] For ease of description, the above apparatus is described in terms of its functions, divided into various modules. Of course, in implementing this disclosure, the functions of each module can be implemented in one or more software and / or hardware.

[0113] The three-phase converter pulse modulation device of the above embodiments is used to implement the corresponding three-phase converter pulse modulation method in any of the foregoing embodiments, and has the beneficial effects of the corresponding method embodiments, which will not be repeated here.

[0114] Those skilled in the art should understand that the discussion of any of the above embodiments is merely exemplary and is not intended to imply that the scope of this disclosure (including the claims) is limited to these examples; within the framework of this disclosure, the technical features of the above embodiments or different embodiments can also be combined, the steps can be implemented in any order, and there are many other variations of different aspects of the exemplary embodiments of this disclosure as described above, which are not provided in detail for the sake of brevity.

[0115] Additionally, to simplify the description and discussion, and to avoid obscuring the exemplary embodiments of this disclosure, the well-known power / ground connections to the integrated circuit (IC) chip and other components may or may not be shown in the provided drawings. Furthermore, the apparatus may be shown in block diagram form to avoid obscuring the exemplary embodiments of this disclosure, and this also takes into account the fact that the details of implementation of these block diagram apparatuses are highly dependent on the platform on which the exemplary embodiments of this disclosure will be implemented (i.e., these details should be fully understood by those skilled in the art). While specific details (e.g., circuitry) have been set forth to describe exemplary embodiments of this disclosure, it will be apparent to those skilled in the art that the exemplary embodiments of this disclosure can be implemented without these specific details or with variations thereof. Therefore, these descriptions should be considered illustrative rather than restrictive.

[0116] Although this disclosure has been described in conjunction with specific embodiments thereof, many substitutions, modifications and variations of these embodiments will be apparent to those skilled in the art from the foregoing description.

[0117] The exemplary embodiments disclosed herein are intended to cover all such substitutions, modifications, and variations that fall within the broad scope of the appended claims. Therefore, any omissions, modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the exemplary embodiments disclosed herein should be included within the scope of protection of this disclosure.

Claims

1. A method of pulse modulation of a three-phase inverter, characterized in that, include: Within one carrier cycle, the arrangement of SVPWM and DPWM is changed, and the ratio of SVPWM to DPWM is adjusted to ensure that the output current simultaneously meets the requirements of the switching frequency and the carrier frequency. The change in the arrangement of SVPWM and DPWM includes: According to carrier frequency and switching frequency The relationship between SVPWM and DPWM is determined, and the final pulse sequence is arranged according to this relationship, including: Response to SVPWM ratio is DPWM accounts for 1% ,and When the carrier frequency is At that time, there were: ,Will Substituting, we get ,Right now: ,according to and The proportional relationship between them determines the arrangement of the SVPWM and the DPWM.

2. The method according to claim 1, characterized in that, The change in the arrangement of SVPWM and DPWM also includes: Determining the system's main resonant frequency includes: adjusting the carrier frequency within a preset range, measuring the relationship between the phase capacitor current and the carrier frequency, and then determining the system's main resonant frequency. The preset range is a set range. ~ between; exist ~ Selecting a suitable carrier frequency The carrier frequency Satisfy frequency (n=1, 2, 3...) to stagger the main resonant frequency points.

3. The method according to claim 2, characterized in that, The method further includes: determining a suitable The proportions should be taken as follows: (m, n = 0, 1, 2, 3, 4, 5), the carrier frequency calculated by rounding m and n is checked once on the relationship curve between capacitor current and carrier frequency, and the optimal one is selected. and .

4. The method according to claim 2, characterized in that, Determining the main resonant frequency point of the system further includes: The modulation method is selected as continuous SVPWM, and the carrier frequency is set to the design value. Furthermore, during continuous SVPWM modulation, the carrier frequency is equal to the switching frequency. Select a rated operating condition and measure the three-phase capacitor current value during steady-state operation. Slowly reduce the carrier frequency and, under the same load conditions, measure the three-phase capacitor current value during operation at each frequency point under steady-state conditions. Stop adjusting the carrier frequency when it drops to 0.5 times the design value; Perform a spectral analysis on the capacitor current, plot the relationship curve between the capacitor current and the carrier frequency, and determine the main resonant frequency of the system based on this relationship curve.

5. A pulse modulation device for a three-phase converter, characterized in that, include: The arrangement unit is used to change the arrangement of SVPWM and DPWM within one carrier cycle; The arrangement unit includes an arrangement determination subunit, used to determine the arrangement based on the carrier frequency. and switching frequency The relationship between SVPWM and DPWM is determined, and the final pulse sequence is arranged according to this relationship, including: Response to SVPWM ratio is DPWM accounts for 1% ,and When the carrier frequency is At that time, there were: ,Will Substituting, we get ,Right now: ,according to and The proportional relationship between them determines the arrangement of the SVPWM and the DPWM; The output unit is used to determine the ratio of SVPWM and DPWM obtained by arranging the units, so that the output current simultaneously meets the requirements of the switching frequency and the carrier frequency.

6. The apparatus according to claim 5, characterized in that, The arrangement unit also includes: The determination of a subunit, used to determine the main resonant frequency of the system, includes: adjusting the carrier frequency within a preset range, measuring the relationship between the phase capacitor current and the carrier frequency, and then determining the main resonant frequency of the system. The preset range is a set range. ~ between; Select sub-units for use in ~ Selecting a suitable carrier frequency The carrier frequency Satisfy frequency (n=1, 2, 3...) to stagger the main resonant frequency points.

7. The apparatus according to claim 6, characterized in that, The arrangement determination subunit is also used to: determine suitable... The proportions should be taken as follows: (m, n = 0, 1, 2, 3, 4, 5), the carrier frequency calculated by rounding m and n is checked once on the relationship curve between capacitor current and carrier frequency, and the optimal one is selected. and .

8. The apparatus according to claim 6, characterized in that, The determining subunit is also used for: The modulation method is selected as continuous SVPWM, and the carrier frequency is set to the design value. Furthermore, during continuous SVPWM modulation, the carrier frequency is equal to the switching frequency. Select a rated operating condition and measure the three-phase capacitor current value during steady-state operation. Slowly reduce the carrier frequency and, under the same load conditions, measure the three-phase capacitor current value during operation at each frequency point under steady-state conditions. Stop adjusting the carrier frequency when it drops to 0.5 times the design value; Perform a spectral analysis on the capacitor current, plot the relationship curve between the capacitor current and the carrier frequency, and determine the main resonant frequency of the system based on this relationship curve.

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