Noise suppression method and device for vehicle silicon carbide permanent magnet synchronous motor driving system

Abstract

The invention discloses a noise suppression method and device for a vehicle silicon carbide permanent magnet synchronous motor driving system, and the method comprises the following steps: S1, obtaining the quasi-duty ratios Da, Db and Dc of the current period of the permanent magnet synchronous motor driving system, and calculating the output average phase voltage of a three-phase inverter; s2, performing equivalence on circuits corresponding to eight switching states of the inverter by using a Thevenin equivalence principle according to the eight switching states of the inverter in the current switching period to obtain equivalent circuits; s3, the ripple current slope of each equivalent circuit is solved, and the phase current ripple peak value of the next period is predicted in combination with the duration of each switching state; and S4, comparing the predicted ripple current peak value with a ripple set value to obtain an updated switching period. According to the method, the switching frequency technology is changed by predicting the phase current ripple peak value of the next period, so that the purpose of suppressing system noise is achieved.

Description

Technical Field

[0001] The present invention belongs to the field of motor noise suppression, and in particular relates to a method for suppressing noise of a vehicle silicon carbide permanent magnet synchronous motor drive system. Background Art

[0002] With the rapid development of the new energy vehicle industry, the development goals of on-board motor drivers are gradually moving towards high efficiency, high power density, and high reliability. In order to meet the requirements of high power density, higher requirements are placed on the working switching frequency of the motor driver. As a third-generation semiconductor device, silicon carbide-based MOSFET (hereinafter referred to as SiC-based MOSFET, metal-oxide semiconductor field-effect transistor) is used in the existing technology to replace Si-based devices to work in a high switching frequency environment due to its high voltage resistance, high temperature resistance, and low loss. The drive is more miniaturized and lightweight. However, SiC-based MOSFET has key problems such as aggravated dead zone effect, high-frequency electromagnetic interference, and severe electromagnetic noise at high switching frequencies. Summary of the invention

[0003] The purpose of the present invention is to solve the problems of aggravated dead zone effect and severe high-frequency electromagnetic interference and electromagnetic noise in the prior art when using SiC-based MOSFET as a motor driver at a conventional high switching frequency.

[0004] To achieve the above object, the present invention provides the following technical solution: a method for suppressing noise in a vehicle silicon carbide permanent magnet synchronous motor drive system, comprising the following steps: S1: Get the quasi-duty ratio D of the current cycle of the permanent magnet synchronous motor drive system a , D b , D c , and calculate the average phase voltage U of the three-phase inverter output an , U bn , U cn : S2: The eight switching states of the inverter in the current switching cycle are equivalent to the circuits corresponding to the eight switching states of the inverter respectively by using the Thevenin equivalent principle to obtain an equivalent circuit; S3: Calculate the ripple current slope of each equivalent circuit, and then combine the duration of each switching state to predict the phase current ripple peak value of the next cycle; S4: Compare the predicted ripple current peak value with the ripple setting value to obtain an updated switching cycle: When the predicted ripple current peak value is greater than the ripple current limit value, the cycle time T can be reduced. s The switching frequency is changed to reduce the peak ripple current of the next cycle, thereby suppressing system noise.

[0005] Preferably, in step S1, the three-phase inverter outputs an average phase voltage U an , U bn , U cn for , U DC The bus voltage of the permanent magnet synchronous motor drive inverter.

[0006] Preferably, the method for predicting the phase current ripple peak value of the next cycle in step S3 is: obtaining the average phase voltage U according to the relationship between the current change rate and the voltage in the equivalent circuit an , U bn , U cn After the relationship between the ripple current slopes under different switching states of the three phases is calculated, the average phase voltage U an , U bn , U cn With bus voltage U DC The ripple current slope corresponding to each voltage vector is obtained by using the relationship between , and the ripple current turning point in the first half is calculated, combined with the central symmetry characteristics of SVPWM, to predict the ripple current change trend in the next cycle.

[0007] Preferably, the method for obtaining the updated switching period in step S4 is: The peak value of the three-phase phase current ripple current is expressed as:

[0008]

[0009] , where Ix_A and Iy_A represent the turning points of the ripple current ripple of the A-phase inductor in the x-direction and y-direction, Ix_B and Iy_B represent the turning points of the ripple current ripple of the B-phase inductor in the x-direction and y-direction, and Ix_C and Iy_C represent the turning points of the ripple current ripple of the C-phase inductor in the x-direction and y-direction. At this time, take the maximum value of the ripple current of the three-phase current:

[0010] After obtaining the peak value of the three-phase ripple current of the next cycle, take the maximum ripple current I ripple_MAX , and then according to the expected value of ripple current I ripple_required , reference period T sn , and the updated switching period T s As shown below:

[0011] A device for suppressing noise of a vehicle silicon carbide permanent magnet synchronous motor drive system, comprising: The average phase voltage acquisition unit is used to obtain the quasi-duty ratio D of the current cycle of the permanent magnet synchronous motor drive system. a , D b , D c , and according to the quasi-duty cycle D a , D b , D c And the bus voltage of the permanent magnet synchronous motor drive inverter is calculated to obtain the average phase voltage U of the three-phase inverter output an , U bn , U cn ; The equivalent circuit unit is used to use the Thevenin equivalent principle to respectively perform equivalent circuits corresponding to the eight switching states of the inverter in the current switching cycle, and obtain the corresponding equivalent circuits; the ripple current slope unit is used to calculate the ripple current slope of each equivalent circuit, and then combine the duration of each switching state to predict the phase current ripple peak value of the next cycle; The switching cycle updating unit is used to compare the predicted ripple current peak value with the ripple setting value to obtain an updated switching cycle; wherein, when the predicted ripple current peak value is greater than the ripple current limit value, the cycle time T is reduced. s The switching frequency is changed to reduce the peak ripple current of the next cycle, thereby suppressing system noise.

[0012] The present invention has the following beneficial effects: The present invention provides a noise suppression method for a vehicle silicon carbide permanent magnet synchronous motor drive system, which achieves the purpose of suppressing system noise by changing the switching frequency technology by predicting the phase current ripple peak value of the next cycle, and this functional method does not require the addition of additional equipment and is suitable for all vehicle permanent magnet synchronous motor drive platforms. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings required for use in the embodiments will be briefly introduced below. It should be understood that the following drawings only show certain embodiments of the present invention and therefore should not be regarded as limiting the scope. For a technician in this field, other related drawings can be obtained based on these drawings without paying any creative work.

[0014] Figure 1 It is a schematic diagram of the process of the automotive silicon carbide permanent magnet synchronous motor drive system based on current prediction of the present invention; FIG. 2 (a) to FIG. 2 (h) are eight switch vector equivalent circuits and corresponding equivalent circuits provided by the present invention; Figure 3 is the slope of the corresponding three-phase current under the action of the eight switching vectors of the present invention; Figure 4 is the trajectory of the single-phase current ripple within one switching cycle of the present invention; Figure 5 is the prediction result of the phase current ripple current peak value of the present invention; FIG6 (1) is an FFT analysis diagram of the present invention at a fixed switching frequency; Figure 6 (2) is a comparison diagram of variable frequency FFT analysis based on current ripple prediction; Figure 7 It is a schematic diagram of a vehicle silicon carbide permanent magnet synchronous motor drive device based on current prediction of the present invention. DETAILED DESCRIPTION

[0015] In order to make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, rather than all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by the first technician in the field without making creative work belong to the scope of protection of the present invention. Therefore, the following detailed description of the embodiments of the present invention provided in the drawings is not intended to limit the scope of the invention claimed for protection, but merely represents the selected embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by the first technician in the field without making creative work belong to the scope of protection of the present invention.

[0016] In the description of the present invention, it should be understood that the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", "clockwise", "counterclockwise" and the like indicate orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the referred device or element must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as a limitation on the present invention.

[0017] In addition, the terms "first" and "second" are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined as "first" and "second" may explicitly or implicitly include one or more of the features. In the description of the present invention, the meaning of "plurality" is two or more, unless otherwise clearly and specifically defined.

[0018] In the present invention, unless otherwise clearly specified and limited, the terms "installed", "connected", "connected", "fixed" and the like should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium, it can be the internal connection of two elements or the interaction relationship between two elements. For those skilled in the art, the specific meanings of the above terms in the present invention can be understood according to the specific circumstances.

[0019] In the present invention, unless otherwise clearly specified and limited, a first feature being "above" or "below" a second feature may include that the first and second features are in direct contact, or may include that the first and second features are not in direct contact but are in contact through another feature between them. Moreover, a first feature being "above", "above" and "above" a second feature includes that the first feature is directly above and obliquely above the second feature, or simply indicates that the first feature is higher in level than the second feature. A first feature being "below", "below" and "below" a second feature includes that the first feature is directly below and obliquely below the second feature, or simply indicates that the first feature is lower in level than the second feature.

[0020] Example The following are only preferred implementations of the present invention. The protection scope of the present invention is not limited to the following embodiments. All technical solutions under the concept of the present invention belong to the protection scope of the present invention.

[0021] Reference Manual Attached Figure 1 The present invention provides a method for driving a vehicle silicon carbide permanent magnet synchronous motor based on current prediction, which can be executed by a silicon carbide permanent magnet synchronous motor drive controller, and in particular, by one or more processors in the silicon carbide permanent magnet synchronous motor drive controller to implement the following steps: S1: Get the quasi-duty ratio D of the current cycle of the permanent magnet synchronous motor drive system a , D b , D c , and calculate the average phase voltage U of the three-phase inverter output an , U bn , U cn : , U DC The bus voltage of the permanent magnet synchronous motor drive inverter; S2: The 8 switching states of the inverter in the current switching cycle, see the appendix of the manual. Figure 3, using the Thevenin equivalent principle, the circuits corresponding to the eight switching states of the inverter are equivalent to obtain equivalent circuits, see Figures 2 (a) to 2 (h) of the specification. In SVPWM, the switching state of the inverter is realized by controlling the switching elements of the three phases. If the on state of each power switch device on the bridge arm is represented by "1" and the off state is represented by "0", there are eight combinations of the switching states of the six power switch devices in the upper and lower bridge arms of the inverter, corresponding to the eight switching modes of the inverter. The eight switching modes are (000), (100), (110), (010), (011), (001), (101), and (111). Among them, (000) and (111) are two zero vectors; Figure 2 (a) is the equivalent circuit of the present invention in the (000) switching mode, Figure 2 (b) is the equivalent circuit of the present invention in the (001) switching mode, Figure 2 (c) is the equivalent circuit of the present invention in the (010) switching mode, Figure 2 (d) is the equivalent circuit of the present invention in the (011) switching mode, Figure 2 (e) is the equivalent circuit of the present invention in the (100) switching mode, Figure 2 (f) is the equivalent circuit of the present invention in the (101) switching mode, Figure 2 (g) is the equivalent circuit of the present invention in the (110) switching mode, and Figure 2 (h) is the equivalent circuit of the present invention in the (111) switching mode.

[0022] S3: Calculate the ripple current slope of each equivalent circuit, and then combine the duration of each switching state to predict the phase current ripple peak value of the next cycle: For an inductor, the relationship between the rate of change of current and voltage is:

[0023] Among them, V L is the voltage across the inductor, L is the inductance, is the rate of change of the inductor current.

[0024] In a three-phase inverter, the voltage V of the A-phase inductor is La Determined by the difference between the inverter output voltage and the load voltage, the calculation formula for the A-phase inductor voltage is as follows:

[0025] The load voltage u load Usually the three-phase voltage u of the inverter an ,u bn ,u cn Ideally, the three-phase voltage is symmetrical, so the load voltage can be approximated by the average voltage of phases B and C:

[0026] Therefore, the A phase inductor voltage VLa It can be expressed as:

[0027] Substituting the above formula into the basic formula of inductor current change rate

[0028] have to

[0029] Simplifying the above formula, we get

[0030] In a three-phase inverter system, considering the structure and control strategy of the inverter, there is usually a scaling factor used to adjust the calculation of the current change rate to take into account the symmetry of the system and the working mode of the inverter. Substituting the scaling factor 3 / 2 into the above formula, the calculation formula for the A-phase inductor current ripple is as follows:

[0031] By using symmetry to generalize, the calculation formula for the inductor current ripple of phase B and C is as follows:

[0032]

[0033] At the same time, U an , U bn , U cn The formula is as follows:

[0034] Define the inverter quasi duty cycle as D x * (x=A,B,C) (i.e., the quasi-duty cycle of the inverter is determined by phases A, B, and C), and 0≤D x *≤1.

[0035]

[0036] The calculation formula of the A-phase inductor current ripple slope can be deduced as follows:

[0037] Then the phase current ripple of phase A can be obtained, see the formula as follows:

[0038] By analogy, the ripple current slope corresponding to each voltage vector can be obtained. Figure 3 The slope of the current corresponding to the three-phase inverter in state 8 is shown in the appendix of the manual. Figure 4, predicting the ripple current turning points Ix and Iy of the next cycle through the ripple current slope; Assuming the ripple current slope of interval 1 of the seven-segment SVPWM is K1, and the ripple current slope of interval 2 is K2, the expressions of Ix and Iy are:

[0039] Wherein, T0 represents the action time when the switch state is off, and T1 represents the action time when the switch state is on.

[0040] The trajectory of the single-phase current ripple in a switching cycle is obtained through the center-symmetric seven-segment SVPWM algorithm. Common SVPWM implementations include center-symmetric seven-segment SVPWM and five-segment SVPWM. By adopting the center-symmetric seven-segment SVPWM algorithm, the trajectory of the single-phase current ripple in a switching cycle can be obtained. Center symmetry means that in the switching cycle, the zero vector is symmetrically distributed before and after the non-zero vector. This arrangement can effectively reduce the number of voltage jumps in each switching cycle, making the current change smoother, thereby tracking the change trajectory of the single-phase current ripple in the entire switching cycle; S4: Compare the predicted ripple current peak value with the ripple set value to obtain the updated switching cycle: the peak value of the ripple current of phase A I ripple_AMAX It is expressed as:

[0041]

[0042]

[0043] At this time, the peak value of the ripple current of the three-phase current is:

[0044] After obtaining the peak value of the three-phase ripple current of the next cycle, take the maximum ripple current I ripple_MAX , and then according to the expected value of ripple current I ripple_required , and the reference period T sn , then the updated switching period T s As shown below:

[0045] When the predicted ripple current peak value is greater than the ripple current limit value, the cycle time T s The switching frequency is changed to reduce the peak ripple current of the next cycle, thereby suppressing system noise.

[0046] Refer to Figure 6 of the specification, where Figure 6 (1) is a comparison diagram of the present invention at a fixed switching frequency and Figure 6 (2) is a comparison diagram of the frequency conversion FFT analysis based on current ripple prediction; phase current FFT analysis based on the frequency conversion strategy based on ripple current peak prediction, and phase current PSD analysis. By comparing Figure 6 (1) and Figure 6 (2), it can be seen that the frequency conversion strategy based on ripple current peak prediction has better performance in suppressing harmonic content, better harmonic peak suppression effect in the power spectrum, stronger continuous distribution of the power spectrum, and better performance in improving electromagnetic noise.

[0047] Reference Manual Attached Figure 7 The second embodiment of the present invention further provides a vehicle-based silicon carbide permanent magnet synchronous motor drive device based on current prediction, which includes: The duty cycle acquisition unit 210 is used to acquire the quasi duty cycle D of the permanent magnet synchronous motor drive system in the current cycle. a , D b , D c , and calculate the average phase voltage output by the three-phase inverter; An equivalent circuit unit 220 is used to obtain equivalent circuits corresponding to eight switching states of the inverter; The ripple current slope unit 230 calculates the ripple current slope of each equivalent circuit, and then combines the duration of each switching state to predict the phase current ripple peak value of the next cycle; The switching period updating unit 240 compares the predicted ripple current peak value with the ripple setting value to obtain an updated switching period.

[0048] The above embodiments are only for illustrating the technical concept and features of the present invention, and their purpose is to enable people familiar with the technology to understand the content of the present invention and implement it accordingly, and they cannot be used to limit the protection scope of the present invention. Any equivalent changes or modifications made according to the spirit of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for suppressing noise in a vehicle silicon carbide permanent magnet synchronous motor drive system, characterized in that: The steps include: S1: Get the quasi-duty ratio D of the current cycle of the permanent magnet synchronous motor drive system a , D b , D c , and according to the quasi-duty cycle D a , D b , D c And the bus voltage of the permanent magnet synchronous motor drive inverter is calculated to obtain the average phase voltage U of the three-phase inverter output an , U bn , U cn : S2: for the eight switching states of the inverter in the current switching cycle, the circuits corresponding to the eight switching states of the inverter are respectively equivalent using the Thevenin equivalent principle to obtain corresponding equivalent circuits; S3: Calculate the ripple current slope of each equivalent circuit, and then combine the duration of each switching state to predict the phase current ripple peak value of the next cycle; S4: Compare the predicted ripple current peak value with the ripple set value to obtain an updated switching cycle; wherein, when the predicted ripple current peak value is greater than the ripple current limit value, the switching frequency is changed by reducing the switching cycle to reduce the ripple current peak value of the next cycle, thereby achieving the purpose of suppressing system noise.

2. The method for suppressing noise of a vehicle silicon carbide permanent magnet synchronous motor drive system according to claim 1, characterized in that: In step S1, the three-phase inverter outputs an average phase voltage U an , U bn , U cn for , U DC The bus voltage of the permanent magnet synchronous motor drive inverter.

3. The method for suppressing noise of a vehicle silicon carbide permanent magnet synchronous motor drive system according to claim 1, characterized in that: The method for predicting the phase current ripple peak value of the next cycle in step S3 is: obtaining the average phase voltage U according to the relationship between the current change rate and the voltage in the equivalent circuit. an , U bn , U cn After the relationship between the ripple current slopes under different switching states of the three phases is calculated, the average phase voltage U an , U bn , U cn With bus voltage U DC The ripple current slope corresponding to each voltage vector is obtained by using the relationship between , and the ripple current turning point in the first half is calculated, combined with the central symmetry characteristics of SVPWM, to predict the ripple current change trend in the next cycle.

4. The method for suppressing noise of a vehicle silicon carbide permanent magnet synchronous motor drive system according to claim 1, characterized in that: In step S4: The peak value of the three-phase phase current ripple current is expressed as: , where Ix_A and Iy_A represent the turning points of the ripple current ripple of the A-phase inductor in the x-direction and y-direction, Ix_B and Iy_B represent the turning points of the ripple current ripple of the B-phase inductor in the x-direction and y-direction, and Ix_C and Iy_C represent the turning points of the ripple current ripple of the C-phase inductor in the x-direction and y-direction. At this time, take the maximum value of the ripple current of the three-phase current: After obtaining the peak value of the three-phase ripple current of the next cycle, take the maximum ripple current I ripple_MAX , and then according to the expected value of ripple current I ripple_required , reference period T sn , get the updated switching period T s As shown below: 。 5. A device for suppressing noise in a vehicle silicon carbide permanent magnet synchronous motor drive system, characterized in that: include: The average phase voltage acquisition unit is used to obtain the quasi-duty ratio D of the current cycle of the permanent magnet synchronous motor drive system. a , D b , D c , and according to the quasi-duty cycle D a , D b , D c And the bus voltage of the permanent magnet synchronous motor drive inverter is calculated to obtain the average phase voltage U of the three-phase inverter output an , U bn , U cn ; The equivalent circuit unit is used to use the Thevenin equivalent principle to respectively perform equivalent circuits corresponding to the eight switching states of the inverter in the current switching cycle, and obtain the corresponding equivalent circuits; the ripple current slope unit is used to calculate the ripple current slope of each equivalent circuit, and then combine the duration of each switching state to predict the phase current ripple peak value of the next cycle; The switching cycle updating unit is used to compare the predicted ripple current peak value with the ripple setting value to obtain an updated switching cycle; wherein, when the predicted ripple current peak value is greater than the ripple current limit value, the cycle time T is reduced. s The switching frequency is changed to reduce the peak ripple current of the next cycle, thereby suppressing system noise.

Images