Method, system, device and storage medium for synchronous modulation of two-level inverter

Abstract

The application discloses a two-level inverter synchronous modulation method, system, device and storage medium, which is applied to the field of power electronics and comprises the following steps: determining positions of each sampling point and dividing sampling point types according to a carrier ratio, determining three-phase modulation waves of the positions of each sampling point in combination with modulation wave generation rules, determining carriers of the positions of each sampling point according to preset carrier generation rules, comparing the three-phase modulation waves with the carriers according to preset comparison rules, determining switch signals of the two-level inverter and controlling the two-level inverter, and the set modulation wave generation rules, carrier generation rules and comparison rules make the carrier frequency and the fundamental frequency synchronous, and make the output voltage of the two-level inverter satisfy three-phase symmetry, half-wave symmetry and quarter-cycle symmetry. The scheme of the application realizes a boundary sampling strategy based on a carrier, and the scheme can significantly reduce the calculation amount and is easy to apply.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of power electronics, in particular to a synchronous modulation method, system, device and storage medium of a two-level inverter. BACKGROUND

[0002] The main circuit topology of the two-level inverter is as shown in Figure 1 By controlling the turn-on and turn-off of each switching device, the two-level inverter can output two different level states, thereby accurately outputting the target voltage. Due to the advantages of fewer devices, simple structure, and convenient control, the two-level inverter has been widely used in wide-speed traction drive systems.

[0003] Wide-speed traction drive systems have the characteristic of wide frequency variation range, and the output carrier ratio varies greatly and mainly works in low carrier ratio conditions. The document "Improved Synchronous Carrier PWM Strategy for Three-Level Neutral-Point-Clamped Converters in Low Carrier Ratio Region" (Gao Zhan.[J].Transaction of Electrical Engineering, 2020, 35(18): 3894-3907.) points out that, in order to control the switching frequency and optimize the output performance, the inverter needs to use the synchronous modulation strategy with the carrier frequency varying synchronously with the fundamental frequency in low carrier ratio conditions.

[0004] The symmetry of the voltage waveform can eliminate specific harmonic components. The document "Synchronized SVPWM Algorithm for the Overmodulation Region of a Low Switching Frequency Medium-Voltage Three-Level VSI" (Beig A R.[J].IEEE Transactions on Industrial Electronics, 2012, 59(12): 4545-4554.) points out that, the three-phase symmetry of the voltage waveform can eliminate the three times frequency harmonics, the half-wave symmetry can eliminate the even harmonics, and the quarter cycle symmetry can eliminate the odd harmonics cosine terms. Therefore, in order to reduce the harmonic content, the output voltage waveform of the synchronous modulation strategy should satisfy the three-phase symmetry, half-wave symmetry and quarter cycle symmetry.

[0005] The document "Comparison of SVPWM Synchronous Modulation Strategies under Low Switching Frequency" (Wang Kun.[J].Proceedings of the Chinese Society of Electrical Engineering, 2015, 35(16): 4175-4183.) proposes a synchronous modulation strategy that satisfies the above symmetries of the output voltage waveform: boundary sampling strategy. The level states output by the two-level inverter from high to low are defined as P and N, Figure 2 is the space vector diagram of the two-level inverter. Assuming that the target voltage is located in the 90° to 150° phase angle region, based on Figure 2The spatial vector sequence of the boundary sampling strategy under different carrier ratios can be summarized in the following Table 1.

[0006] Table 1: Spatial vector sequence of the boundary sampling strategy under different carrier ratios

[0007]

[0008] Analyzing Table 1, the spatial vector sequence of the boundary sampling strategy has the following characteristics:

[0009] 1) The spatial vector sequence at 90°, 120° and the rest of the sampling points correspond to different three-phase action times. Among them, the spatial vector sequence at 90° corresponds to two-phase inaction and one-phase action twice. The spatial vector sequence at 120° corresponds to three-phase action once. The spatial vector sequence at the rest of the sampling points corresponds to one-phase inaction and two-phase action once.

[0010] 2) Under the same carrier ratio, the spatial vector sequence at different position sampling points uses different zero vector types. Taking carrier ratio 18 as an example, only NNN is used as the zero vector at 100°, while only PPP is used as the zero vector at 130°.

[0011] 3) Under different carrier ratios, the spatial vector sequence at the same region sampling point uses different zero vector types. Taking carrier ratios 15 and 18 as examples, in the 90° to 120° region, carrier ratio 15 only uses PPP as the zero vector, while carrier ratio 18 only uses NNN as the zero vector.

[0012] 4) Under different carrier ratios, the spatial vector sequence at the same position sampling point corresponds to different vector sequences. Taking carrier ratios 9 and 18 as examples, the spatial vector sequence of carrier ratio 9 at 110° is NNN→PNN→PPN, while the spatial vector sequence of carrier ratio 18 at 110° is PPN→PNN→NNN.

[0013] The boundary sampling strategy can make the voltage waveform satisfy synchronization, three-phase symmetry, half-wave symmetry and quarter-period symmetry. However, the boundary sampling strategy needs to calculate the action time of the spatial vector at each sampling point, that is, to calculate the action time of each switching state at each sampling point. This calculation is complex and inevitably has certain calculation errors, which is not conducive to engineering popularization and application.

[0014] In summary, how to more conveniently and effectively perform synchronous modulation of a two-level inverter and guarantee control performance is a technical problem that needs to be solved by those skilled in the art at present. SUMMARY

[0015] The application aims to provide a two-level inverter synchronous modulation method, system, device and storage medium, so as to conveniently and effectively perform two-level inverter synchronous modulation and guarantee control performance.

[0016] To solve the above technical problems, the application provides the following technical solutions.

[0017] A two-level inverter synchronous modulation method comprises the following steps:

[0018] According to a carrier ratio, each sampling point position is determined, and sampling point types are divided according to each sampling point position;

[0019] According to the sampling point types and modulation wave generation rules, three-phase modulation waves of each sampling point position are determined;

[0020] According to preset carrier generation rules, carriers of each sampling point position are determined;

[0021] According to preset comparison rules, the three-phase modulation waves and the carriers are compared to determine two-level inverter switching signals and perform two-level inverter control;

[0022] The modulation wave generation rules, the carrier generation rules and the comparison rules are set so that the carrier frequency is synchronized with the fundamental frequency, and the output voltage of the two-level inverter satisfies three-phase symmetry, half-wave symmetry and one-quarter cycle symmetry.

[0023] Preferably, the determination of each sampling point position according to the carrier ratio comprises the following steps:

[0024] Each sampling point position is determined by

[0025] Wherein, C is the carrier ratio, N is the sampling point number, X N is the position of the N+1th sampling point.

[0026] Preferably, the carrier ratio is set to an integer multiple of 3.

[0027] Preferably, the division of sampling point types according to each sampling point position comprises the following steps:

[0028] When the sampling point position is 30°, 90°, 150°, 210°, 270° or 330°, the sampling point is regarded as a first-type sampling point;

[0029] When the sampling point position is 0°, 60°, 120°, 180°, 240° or 300°, the sampling point is regarded as a second-type sampling point;

[0030] ​When the sampling point is located within the interval (90°, 120°), or within the interval (120°, 150°), or within the interval (210°, 240°), or within the interval (240°, 270°), or within the interval (330°, 0°), or within the interval (0°, 30°), the sampling point is designated as a third type of sampling point.

[0031] When the sampling point is located within the interval (150°, 180°), or within the interval (180°, 210°), or within the interval (270°, 300°), or within the interval (300°, 330°), or within the interval (30°, 60°), or within the interval (60°, 90°), the sampling point is designated as a fourth type of sampling point.

[0032] The step of determining the three-phase modulated wave at each sampling point position according to the sampling point type and modulation wave generation rule includes:

[0033] According to the preset modulation wave generation rules, two sets of three-phase modulation waves are set for each first-type sampling point, and one set of three-phase modulation waves is set for each second-type sampling point, each third-type sampling point, and each fourth-type sampling point.

[0034] Preferably, the step of setting two sets of three-phase modulation waves for each first-type sampling point according to a preset modulation wave generation rule, and setting one set of three-phase modulation waves for each second-type sampling point, each third-type sampling point, and each fourth-type sampling point, includes:

[0035] For the first type of sampling point, when the sampling point position is 30°, set S mbp =S m S mbn =-S m Set S map S man S mcp and S mcn All are U;

[0036] When the sampling point position is 90°, set S map =S m S man =-S m Set S mbp S mbn S mcp and S mcn All are 0;

[0037] When the sampling point position is 150°, set S mcp =S m S mcn =-S m Set Smap , S man , S mbp , S mbn are all U;

[0038] When the sampling point position is 210°, set S mbp = S m , S mbn = -S m , set S map , S man , S mcp , and S mcn are all 0;

[0039] When the sampling point position is 270°, set S map = S m , S man = -S m , set S mbp , S mbn , S mcp , and S mcn are all U;

[0040] When the sampling point position is 330°, set S mcp = S m , S mcn = -S m , set S map , S man , S mbp , and S mbn are all 0;

[0041] wherein S map and S man respectively represent the first group of modulation waves and the second group of modulation waves of the A phase, S mbp and S mbn respectively represent the first group of modulation waves and the second group of modulation waves of the B phase, S mcp and S mcn respectively represent the first group of modulation waves and the second group of modulation waves of the C phase, U is the sine wave amplitude value, S m represents a modulation wave variable, and the calculation method of S m is as follows:

[0042]

[0043] wherein S max and S min are respectively the current maximum value of the three-phase sine wave and the current minimum value of the three-phase sine wave;

[0044] For any one second type sampling point, the three-phase modulation wave set is represented as:

[0045]

[0046] For any one third type sampling point, the three-phase modulation wave set is represented as:

[0047]

[0048] For any one fourth type sampling point, the three-phase modulation wave set is represented as:

[0049]

[0050] Wherein, S ma , S mb and S mc represent the modulation wave of A phase, B phase and C phase respectively, S a , S b and S c represent the sine wave of A phase, B phase and C phase respectively.

[0051] Preferably, the carrier wave at each sampling point position is determined according to the preset carrier generation rule, comprising:

[0052] For the first type sampling point:

[0053] When C / 2 or (C+1) / 2 is odd, the carrier direction at the 30°, 150° and 270° sampling point positions is set as the downward direction, and the carrier direction at the 90°, 210° and 330° sampling point positions is set as the upward direction;

[0054] When C / 2 or (C+1) / 2 is even, the carrier direction at the 30°, 150° and 270° sampling point positions is set as the upward direction, and the carrier direction at the 90°, 210° and 330° sampling point positions is set as the downward direction;

[0055] For the second type sampling point, the third type sampling point and the fourth type sampling point:

[0056] When C / 2 is odd, the carrier direction at the 0°, 120° and 240° sampling point positions is set as the downward direction, and the carrier direction at the 60°, 180° and 300° sampling point positions is set as the upward direction, and the carrier direction at any one of the remaining sampling point positions is opposite to the carrier direction at the previous sampling point position of the sampling point position;

[0057] When C / 2 is even, the carrier direction at the 0°, 120° and 240° sampling point positions is set as the upward direction, and the carrier direction at the 60°, 180° and 300° sampling point positions is set as the downward direction, and the carrier direction at any one of the remaining sampling point positions is opposite to the carrier direction at the previous sampling point position of the sampling point position;

[0058] When (C+1) / 2 is odd, set the carrier direction at the nearest sampling point position of 0°, 120° and 240° as descending direction, and set the carrier direction at the nearest sampling point position of 60°, 180° and 300° as ascending direction, and the carrier direction at any other sampling point position is opposite to the carrier direction at the previous sampling point position of the sampling point position;

[0059] When (C+1) / 2 is even, set the carrier direction at the nearest sampling point position of 0°, 120° and 240° as ascending direction, and set the carrier direction at the nearest sampling point position of 60°, 180° and 300° as descending direction, and the carrier direction at any other sampling point position is opposite to the carrier direction at the previous sampling point position of the sampling point position;

[0060] For any one sampling point position, when the carrier direction at the sampling point position is ascending direction, the triangular carrier value at the sampling point position is When the carrier direction at the sampling point position is descending direction, the triangular carrier value at the sampling point position is

[0061] Wherein, Carr is the triangular carrier value, C is the carrier ratio, N is the sampling point number, X N is the position of the N+1th sampling point, θ is the phase angle.

[0062] Preferably, the comparison of the three-phase modulation wave and the carrier wave according to the preset comparison rule, the determination of the switching signal of the two-level inverter and the control of the two-level inverter, comprises:

[0063] For the first type of sampling point:

[0064] When S map and S man are not equal, if S map >Carr and S man Carr are both established, control the upper bridge arm switching tube of phase A to be turned on and the lower bridge arm switching tube of phase A to be turned off; if S map >Carr and S man Carr are not both established, control the upper bridge arm switching tube of phase A to be turned off and the lower bridge arm switching tube of phase A to be turned on;

[0065] When S map and S man are equal, if S map =U, control the upper bridge arm switching tube of phase A to be turned on and the lower bridge arm switching tube of phase A to be turned off; if S map =0, control the upper bridge arm switching tube of phase A to be turned off and the lower bridge arm switching tube of phase A to be turned on;

[0066] When S mbp and S mbn are not equal, if S mbp >Carr and S mbn Carr are both true, the upper bridge arm switch of phase B is turned on and the lower bridge arm switch of phase B is turned off; if S mbp >Carr and S mbn Carr are not both true, the upper bridge arm switch of phase B is turned off and the lower bridge arm switch of phase B is turned on;

[0067] When S mbp and S mbn are equal, if S mbp =U, the upper bridge arm switch of phase B is turned on and the lower bridge arm switch of phase B is turned off; if S mbp =0, the upper bridge arm switch of phase B is turned off and the lower bridge arm switch of phase B is turned on;

[0068] When S mcp and S mcn are not equal, if S mcp >Carr and S mcp Carr are both true, the upper bridge arm switch of phase C is turned on and the lower bridge arm switch of phase C is turned off; if S mcp >Carr and S mcp Carr are not both true, the upper bridge arm switch of phase C is turned off and the lower bridge arm switch of phase C is turned on;

[0069] When S mcp and S mcn are equal, if S mcp =U, the upper bridge arm switch of phase C is turned on and the lower bridge arm switch of phase C is turned off; if S mcp =0, the upper bridge arm switch of phase C is turned off and the lower bridge arm switch of phase C is turned on;

[0070] For the second type of sampling point, the third type of sampling point and the fourth type of sampling point:

[0071] When S ma >Carr is true, the upper bridge arm switch of phase A is turned on and the lower bridge arm switch of phase A is turned off; when S ma >Carr is not true, the upper bridge arm switch of phase A is turned off and the lower bridge arm switch of phase A is turned on;

[0072] When S mb >Carr is true, the upper bridge arm switch of phase B is turned on and the lower bridge arm switch of phase B is turned off; when S mb >Carr is not true, the upper bridge arm switch of phase B is turned off and the lower bridge arm switch of phase B is turned on;

[0073] When S mc >When Carr is established, the upper arm switch of phase C is turned on, and the lower arm switch of phase C is turned off. When S mc >When Carr is not established, the upper arm switch of phase C is turned off and the lower arm switch of phase C is turned on.

[0074] A synchronous modulation system for a two-level inverter, comprising:

[0075] The sampling point location determination module is used to determine the location of each sampling point based on the carrier ratio, and to classify the sampling point type based on the location of each sampling point.

[0076] The modulation wave generation module is used to determine the three-phase modulation wave at each sampling point position according to the sampling point type and the modulation wave generation rule.

[0077] The carrier generation module is used to determine the carrier at each sampling point position according to the preset carrier generation rules;

[0078] The switching signal determination module is used to compare the three-phase modulation wave with the carrier wave according to a preset comparison rule, determine the switching signal of the two-level inverter, and control the two-level inverter.

[0079] The modulation wave generation rule, the carrier generation rule, and the comparison rule set therein ensure that the carrier frequency is synchronized with the fundamental frequency, and that the output voltage of the two-level inverter satisfies three-phase symmetry, half-wave symmetry, and quarter-cycle symmetry.

[0080] A synchronous modulation device for a two-level inverter includes:

[0081] Memory, used to store computer programs;

[0082] A processor for executing the computer program to implement the steps of the synchronous modulation method for a two-level inverter as described above.

[0083] A computer-readable storage medium storing a computer program that, when executed by a processor, implements the steps of the synchronous modulation method for a two-level inverter as described above.

[0084] The present invention provides a boundary sampling strategy for a two-level inverter based on a carrier wave. Specifically, the scheme first determines the location and type of each sampling point according to the carrier ratio. Then, according to a preset modulation wave generation rule, the three-phase modulation wave at each sampling point location is determined. Next, according to a preset carrier wave generation rule, the carrier wave at each sampling point location is determined. Finally, based on the comparison between the three-phase modulation wave and the carrier wave, the switching signal of the two-level inverter is determined, and synchronous modulation of the two-level inverter is performed. The modulation wave generation rule, carrier wave generation rule, and comparison rule settings in this application ensure that the two-level inverter satisfies synchronous modulation, thereby achieving precise control of the switching frequency. Furthermore, the output voltage satisfies three-phase symmetry, half-wave symmetry, and quarter-cycle symmetry, effectively eliminating specific harmonic components in the line voltage. That is, the scheme in this application is equivalent to using a boundary sampling strategy. Since this application determines the switching signal of the two-level inverter by generating and comparing the three-phase modulation wave and the carrier wave, it does not require setting a space vector sequence and calculating the action time as in traditional boundary sampling strategies. Therefore, the computational load can be significantly reduced, making it easier to implement in engineering applications. Attached Figure Description

[0085] To more clearly illustrate the technical solutions in the embodiments of the present invention 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 some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0086] Figure 1 This is a schematic diagram of the main circuit topology of a two-level inverter.

[0087] Figure 2 A spatial vector diagram of a two-level inverter;

[0088] Figure 3 This is a flowchart illustrating the implementation of a synchronous modulation method for a two-level inverter in this invention.

[0089] Figure 4 This is a schematic diagram of simulation results for a scenario with a fundamental frequency of 20Hz, a modulation ratio of 0.3, and a carrier ratio of 24.

[0090] Figure 5 This is a schematic diagram of simulation results for a scenario with a fundamental frequency of 25Hz, a modulation ratio of 0.4, and a carrier ratio of 21.

[0091] Figure 6 This is a schematic diagram of the simulation results for a scenario with a fundamental frequency of 40Hz, a modulation ratio of 0.5, and a carrier ratio of 18.

[0092] Figure 7 Fig. 4 is a schematic diagram of simulation results of a two-level inverter in a case of a fundamental frequency of 50 Hz, a modulation ratio of 0.6, and a carrier ratio of 15;

[0093] Figure 8 Fig. 5 is a schematic diagram of simulation results of a two-level inverter in a case of a fundamental frequency of 64 Hz, a modulation ratio of 0.7, and a carrier ratio of 12;

[0094] Figure 9 Fig. 6 is a schematic diagram of simulation results of a two-level inverter in a case of a fundamental frequency of 80 Hz, a modulation ratio of 0.8, and a carrier ratio of 9;

[0095] Figure 10 Fig. 7 is a schematic diagram of simulation results of a two-level inverter in a case of a fundamental frequency of 100 Hz, a modulation ratio of 0.9, and a carrier ratio of 6;

[0096] Figure 11 Fig. 8 is a schematic diagram of simulation results of a two-level inverter in a case of a fundamental frequency of 125 Hz, a modulation ratio of 1, and a carrier ratio of 3;

[0097] Figure 12 Fig. 9 is a schematic diagram of a structure of a synchronous modulation system of a two-level inverter. DETAILED DESCRIPTION

[0098] The core of the present application is to provide a synchronous modulation method of a two-level inverter, output voltage waveforms satisfying synchronization, three-phase symmetry, half-wave symmetry, and quarter-period symmetry, so as to realize accurate control of a switching frequency, effectively eliminate specific harmonic components in line voltage, and the scheme of the present application can significantly reduce the amount of calculation, and is easier to realize engineering application.

[0099] In order for those skilled in the art to better understand the present application, the present application will be further described in detail below in combination with the drawings and specific embodiments. Obviously, the described embodiments are only some of the embodiments of the present application, not all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor fall within the scope of protection of the present application.

[0100] Reference should be made to Figure 3 , Figure 3 Fig. 10 is a flowchart of an embodiment of a synchronous modulation method of a two-level inverter, which can include the following steps:

[0101] Step S301: determining each sampling point position according to a carrier ratio, and dividing sampling point types according to each sampling point position.

[0102] Specifically, the carrier ratio can be preset and input into the controller as an input quantity, and the scheme of the application is executed by the controller. The scheme of the application satisfies the synchronization of the carrier frequency and the fundamental frequency, that is, in the process of controlling the two-level inverter, the ratio of the carrier frequency to the fundamental frequency is constant, that is, the carrier ratio is constant. Therefore, when the fundamental frequency changes, the carrier frequency determined in the subsequent operation will change synchronously to ensure that the carrier ratio is constant.

[0103] The positions of the sampling points can be determined according to the carrier ratio. Specifically, in one specific embodiment of the application, the determination of the positions of the sampling points according to the carrier ratio described in step S301 can specifically include:

[0104] The positions of the sampling points are determined.

[0105] Wherein, C is the carrier ratio, N is the sampling point number, is an integer, the value range is 0 to 2C-1, X N is the position of the N+1th sampling point. For example, when the carrier ratio is 9, there are 18 sampling points in one sampling period.

[0106] After the positions of the sampling points are determined, the types of the sampling points can be divided according to the positions of the sampling points. That is, in the scheme of the application, the types of the sampling points can be divided according to the positions of the sampling points, and then the corresponding three-phase modulation waves are determined for the sampling points of different types.

[0107] Step S302: determining the three-phase modulation waves of the positions of the sampling points according to the types of the sampling points and the modulation wave generation rules.

[0108] In the scheme of the application, the types of the sampling points can be divided according to the positions of the sampling points, and then the corresponding three-phase modulation waves are determined for the sampling points of different types. The specific way of the preset modulation wave generation rule can be set according to the actual situation, but it can be understood that, in order to be equivalent to the boundary sampling strategy, the modulation wave generation rule, the carrier generation rule and the comparison rule need to be able to make the output voltage waveform of the two-level inverter satisfy synchronization, three-phase symmetry, half-wave symmetry and quarter-cycle symmetry.

[0109] In one specific embodiment of the application, the division of the types of the sampling points according to the positions of the sampling points described in step S301 can specifically include:

[0110] When the position of the sampling point is 30°, 90°, 150°, 210°, 270° or 330°, the sampling point is taken as the first type of sampling point;

[0111] ​When the sampling point position is 0°, 60°, 120°, 180°, 240° or 300°, the sampling point is taken as a second type sampling point;

[0112] When the sampling point position is in the interval (90°, 120°), or in the interval (120°, 150°), or in the interval (210°, 240°), or in the interval (240°, 270°), or in the interval (330°, 0°), or in the interval (0°, 30°), the sampling point is taken as a third type sampling point;

[0113] When the sampling point position is in the interval (150°, 180°), or in the interval (180°, 210°), or in the interval (270°, 300°), or in the interval (300°, 330°), or in the interval (30°, 60°), or in the interval (60°, 90°), the sampling point is taken as a fourth type sampling point;

[0114] Correspondingly, the step S302 can specifically include: setting 2 groups of three-phase modulation waves for each first type sampling point, setting 1 group of three-phase modulation wave for each second type sampling point, each third type sampling point and each fourth type sampling point according to the preset modulation wave generation rule.

[0115] The sampling point position is the phase angle position of the sampling point. In this embodiment, the sampling points with the phase angle positions of 30°, 90°, 150°, 210°, 270° and 330° are divided into first type sampling points. The sampling points with the phase angle positions of 0°, 60°, 120°, 180°, 240° and 300° are divided into second type sampling points. The sampling points with the phase angle positions in the range of 90° to 150°, 210° to 270° and 330° to 30°, and excluding the first type and second type sampling points, are taken as third type sampling points. The sampling points with the phase angle positions in the range of 150° to 210°, 270° to 330° and 30° to 90°, and excluding the first type and second type sampling points, are taken as fourth type sampling points.

[0116] For the first type sampling point, two modulation waves are set, that is, 2 groups of three-phase modulation waves are set, and other types of sampling points are set with single modulation wave.

[0117] In a specific embodiment of the present application, according to the preset modulation wave generation rule, 2 groups of three-phase modulation waves are set for each first type sampling point, and 1 group of three-phase modulation wave is set for each second type sampling point, each third type sampling point and each fourth type sampling point, which can specifically include:

[0118] For the first type sampling point, when the sampling point position is 30°, S mbp = Sm S mbn =-S m Set S map S man S mcp and S mcn All are U;

[0119] When the sampling point position is 90°, set S map =S m S man =-S m Set S mbp S mbn S mcp and S mcn All are 0;

[0120] When the sampling point position is 150°, set S mcp =S m S mcn =-S m Set S map S man S mbp and S mbn All are U;

[0121] When the sampling point position is 210°, set S mbp =S m S mbn =-S m Set S map S man S mcp and S mcn All are 0;

[0122] When the sampling point position is 270°, set S map =S m S man =-S m Set S mbp S mbn S mcp and S mcn All are U;

[0123] When the sampling point position is 330°, set S mcp =S m S mcn =-S m Set S map S man S mbp and S mbn All are 0.

[0124] Among them, S map and Sman respectively represent the first and second group of modulation waves of phase A, S mbp and S mbn respectively represent the first and second group of modulation waves of phase B, S mcp and S mcn respectively represent the first and second group of modulation waves of phase C, U is the sine wave amplitude, S m represents the modulation wave variable, or called double modulation wave variable, and S m is calculated as follows:

[0125]

[0126] wherein S max and S min are the current maximum and minimum of three-phase sine wave, i.e. S max and S min are variables, related to the current sampling point position.

[0127] And for any one second type sampling point, the set three-phase modulation wave can be expressed as:

[0128]

[0129] For any one third type sampling point, the set three-phase modulation wave is expressed as:

[0130]

[0131] For any one fourth type sampling point, the set three-phase modulation wave is expressed as:

[0132]

[0133] wherein S ma , S mb and S mc represent the modulation wave of phase A, B and C, i.e. single modulation wave of phase A, B and C, S a , S b and S c represent the sine wave of phase A, B and C, similar to S max and S min , S a , S b and S c are variables, related to the current sampling point position. In actual application, the output voltage of two-level inverter can be detected in real time or periodically, so as to obtain the sine wave amplitude U and phase angle θ, and then the three-phase sine wave S a , S b and Sc .

[0134] Step S303: determining the carrier of each sampling point position according to a preset carrier generation rule.

[0135] After the three-phase modulation wave of each sampling point position is determined according to the preset modulation wave generation rule, the carrier can be determined according to the preset carrier generation rule. Specifically, the carrier direction of each sampling point position can be determined first, and then the corresponding carrier waveform is determined according to the different directions. As described above, the modulation wave generation rule, the carrier generation rule and the comparison rule are set to make the carrier frequency and the fundamental frequency synchronous, and the output voltage of the two-level inverter is three-phase symmetrical, half-wave symmetrical and quarter-cycle symmetrical.

[0136] The triangular carrier is commonly used, so in one specific embodiment of the application, step S303 can specifically include:

[0137] For the first type of sampling point:

[0138] When C / 2 or (C+1) / 2 is odd, the carrier direction of the 30°, 150° and 270° sampling point positions is set to the downward direction, and the carrier direction of the 90°, 210° and 330° sampling point positions is set to the upward direction;

[0139] When C / 2 or (C+1) / 2 is even, the carrier direction of the 30°, 150° and 270° sampling point positions is set to the upward direction, and the carrier direction of the 90°, 210° and 330° sampling point positions is set to the downward direction.

[0140] It can be seen that the above is for the first type of sampling point, and the directions of each sampling point in the first type of sampling point are set according to the different C.

[0141] And for the second type of sampling point, the third type of sampling point and the fourth type of sampling point, specifically:

[0142] When C / 2 is odd, the carrier direction of the 0°, 120° and 240° sampling point positions is set to the downward direction, and the carrier direction of the 60°, 180° and 300° sampling point positions is set to the upward direction, and the carrier direction of the remaining sampling point positions is set according to the rule that the carrier direction of the previous sampling point position is opposite to the carrier direction of the previous sampling point position, that is, the carrier direction of any one of the remaining sampling point positions is opposite to the carrier direction of the previous sampling point position of the sampling point position;

[0143] When C / 2 is even, the carrier directions at the 0°, 120° and 240° sampling point positions are set as upward directions, the carrier directions at the 60°, 180° and 300° sampling point positions are set as downward directions, and the carrier direction at any one of the remaining sampling point positions is opposite to the carrier direction at the previous sampling point position of the sampling point position.

[0144] When (C+1) / 2 is odd, the carrier directions at the nearest sampling point positions of 0°, 120° and 240° are set as downward directions, the carrier directions at the nearest sampling point positions of 60°, 180° and 300° are set as upward directions, and the carrier direction at any one of the remaining sampling point positions is opposite to the carrier direction at the previous sampling point position of the sampling point position.

[0145] When (C+1) / 2 is even, the carrier directions at the nearest sampling point positions of 0°, 120° and 240° are set as upward directions, the carrier directions at the nearest sampling point positions of 60°, 180° and 300° are set as downward directions, and the carrier direction at any one of the remaining sampling point positions is opposite to the carrier direction at the previous sampling point position of the sampling point position.

[0146] After the carrier directions of the sampling point positions are obtained, for any one of the sampling point positions, when the carrier direction at the sampling point position is an upward direction, the triangular carrier value at the sampling point position is when the carrier direction at the sampling point position is a downward direction, the triangular carrier value at the sampling point position is wherein, Carr is the triangular carrier value, U is the amplitude of the sine wave, C is the carrier ratio, N is the sampling point number, X N is the position of the N+1th sampling point, and θ is the phase angle.

[0147] Step S304: comparing the three-phase modulation wave with the carrier wave according to a preset comparison rule, determining the switching signal of the two-level inverter and performing control on the two-level inverter.

[0148] The switching signal can be obtained by comparing the three-phase modulation wave with the carrier wave. The subsequent Figures 4 to 11 of the present application shows the modulation wave of one phase in the three phases.

[0149] In one specific embodiment of the present application, step S304 can include:

[0150] For the first type of sampling point:

[0151] When S map and S man are not equal, if S map >Carr and S manIf Carr is true, the upper arm switch of phase A is turned on, and the lower arm switch of phase A is turned off. The other cases are the opposite, i.e., if S... map >Carr and S man If Carr is not met, the upper arm switch of phase A is turned off and the lower arm switch of phase A is turned on.

[0152] When S map and S man When they are equal, if S map =U, controls the upper arm switch of phase A to turn on and the lower arm switch of phase A to turn off; if S map =0, the upper arm switch of phase A is turned off, and the lower arm switch of phase A is turned on;

[0153] When S mbp and S mbn If they are not equal, if S mbp >Carr and S mbn If both Carr and S are true, the upper arm switch of phase B is turned on and the lower arm switch of phase B is turned off; if S mbp >Carr and S mbn When Carr is not fully established, the upper arm switch of phase B is turned off and the lower arm switch of phase B is turned on.

[0154] When S mbp and S mbn When they are equal, if S mbp =U, controls the upper arm switch of phase B to turn on and the lower arm switch of phase B to turn off; if S mbp =0, control the upper arm switch of phase B to turn off, and the lower arm switch of phase B to turn on;

[0155] When S mcp and S mcn If they are not equal, if S mcp >Carr and S mcp <If Carr is true, the upper arm switch of phase C is turned on, and the lower arm switch of phase C is turned off; if S mcp >Carr and S mcp When Carr is not fully established, the upper arm switch of phase C is turned off and the lower arm switch of phase C is turned on.

[0156] When S mcp and S mcn When they are equal, if S mcp =U, controls the upper arm switch of phase C to turn on and the lower arm switch of phase C to turn off; if S mcp =0, controls the upper arm switch of phase C to turn off and the lower arm switch of phase C to turn on.

[0157] As can be seen, the above describes the comparison method between the dual-modulated wave and the carrier wave, that is, the comparison method between the two sets of three-phase modulated waves and the triangular carrier wave after setting two sets of three-phase modulated waves for each first-type sampling point.

[0158] The comparison method between the single-modulated wave and the carrier wave, specifically for the second, third, and fourth types of sampling points, is as follows:

[0159] When S ma >When Carr is established, the upper arm switch of phase A is turned on, and the lower arm switch of phase A is turned off. When S ma >When Carr is not established, the upper arm switch of phase A is turned off and the lower arm switch of phase A is turned on.

[0160] When S mb >When Carr is established, the upper arm switch of phase B is turned on, and the lower arm switch of phase B is turned off. When S mb >When Carr is not established, the upper arm switch of phase B is turned off and the lower arm switch of phase B is turned on.

[0161] When S mc >When Carr is established, the upper arm switch of phase C is turned on, and the lower arm switch of phase C is turned off. When S mc >When Carr is not established, the upper arm switch of phase C is turned off and the lower arm switch of phase C is turned on.

[0162] In this application, the carrier ratio can be set to an integer multiple of 3. Compared with some traditional solutions that only allow the carrier ratio to be set to an odd or even multiple of 3, this application has a higher degree of flexibility.

[0163] The technical scheme provided by the embodiment of the application implements a boundary sampling strategy of a two-level inverter based on a carrier. Specifically, in the scheme of the application, the positions of the sampling points are determined according to the carrier ratio and are classified, then the three-phase modulation waves at the positions of the sampling points are determined according to a modulation wave generation rule, the carriers at the positions of the sampling points are determined according to a preset carrier generation rule, and finally the switching signals of the two-level inverter are determined according to the comparison between the three-phase modulation waves and the carriers, and the two-level inverter is synchronously modulated. The settings of the modulation wave generation rule, the carrier generation rule and the comparison rule make the two-level inverter meet the synchronous modulation, thereby achieving accurate control of the switching frequency. Moreover, the output voltage meets the three-phase symmetry, half-wave symmetry and quarter-period symmetry, thereby effectively eliminating specific harmonic components in the line voltage. That is, the scheme of the application is equivalent to the boundary sampling strategy. Since the scheme of the application determines the switching signals of the two-level inverter by generating the three-phase modulation waves and the carriers and comparing them, it does not need to set the space vector sequence and calculate the action time as in the traditional boundary sampling strategy, and therefore can significantly reduce the calculation amount and is easier to implement in engineering applications.

[0164] In actual applications, a two-level inverter model can be built by means of software such as PSIM, and the effectiveness of the scheme of the application can be verified by simulation. For example, in a specific case, the simulation conditions can be set as follows: the DC side voltage is 3300V, the simulation step is 1μs, the output power factor is 0.8, the carrier ratios are set to 24, 21, 18, 15, 12, 9, 6 and 3 respectively, the modulation ratios are set to 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9 and 1 respectively, the fundamental frequencies are set to 20Hz, 25Hz, 40Hz, 50Hz, 64Hz, 80Hz, 100Hz and 125Hz respectively, and the carrier frequencies are set according to the carrier ratios and the fundamental frequencies to achieve synchronous modulation.

[0165] Reference can be made to Figure 4 Fig. 1 is a schematic diagram of the simulation results for the case of a fundamental frequency of 20Hz, a modulation ratio of 0.3 and a carrier ratio of 24, from top to bottom being the schematic diagrams of the modulation wave and the triangular carrier, the phase voltage, the line voltage and the line voltage harmonic amplitude. It can be seen from Fig. 1 that, when the carrier ratio is 24, the scheme of the application can directly obtain the switching signals of the two-level inverter by using the double modulation wave or the single modulation wave and the triangular carrier of a specific direction, and equivalently implement the boundary sampling strategy synchronous 17 times modulation. The scheme of the application does not need to calculate the space vector action time, and is very convenient to implement. Moreover, the scheme of the application can eliminate the harmonic components of the multiples of 3, even times and fractional times in the line voltage, and the corresponding voltage waveform meets the synchronization, three-phase symmetry, half-wave symmetry and quarter-period symmetry. The carrier ratio 24 is an even multiple of 3, and therefore the scheme of the application can optimize the output harmonic performance of the two-level inverter at the even multiple carrier ratios of 3. Figure 4 It can be seen that, when the carrier ratio is 24, the scheme of the application can directly obtain the switching signals of the two-level inverter by using the double modulation wave or the single modulation wave and the triangular carrier of a specific direction, and equivalently implement the boundary sampling strategy synchronous 17 times modulation. The scheme of the application does not need to calculate the space vector action time, and is very convenient to implement. Moreover, the scheme of the application can eliminate the harmonic components of the multiples of 3, even times and fractional times in the line voltage, and the corresponding voltage waveform meets the synchronization, three-phase symmetry, half-wave symmetry and quarter-period symmetry. The carrier ratio 24 is an even multiple of 3, and therefore the scheme of the application can optimize the output harmonic performance of the two-level inverter at the even multiple carrier ratios of 3.

[0166] Reference can be made to Figure 5 Fig. 6 is a schematic diagram of simulation results of the application when the fundamental frequency is 25 Hz, the modulation ratio is 0.4, and the carrier ratio is 21. From top to bottom, the schematic diagram is of the modulation wave and the triangular carrier, the phase voltage, the line voltage, and the line voltage harmonic amplitude, respectively. It can be seen that when the carrier ratio is 21, the application can directly obtain the switching signal of the two-level inverter by using the double modulation wave or the single modulation wave and the triangular carrier of a specific direction, and equivalently implement the boundary sampling strategy synchronous 15 modulation. The application does not need to calculate the space vector action time, and the implementation is very convenient. Moreover, the application can eliminate the 3 multiple, even and fractional harmonic components in the line voltage, and the corresponding voltage waveform satisfies the synchronization, three-phase symmetry, half-wave symmetry and quarter-cycle symmetry. The carrier ratio 24 is an odd multiple of 3, so the application can optimize the output harmonic performance of the two-level inverter under the odd multiple carrier ratio of 3 Figure 5

[0167] Fig. 7 is a schematic diagram of simulation results of the application when the fundamental frequency is 40 Hz, the modulation ratio is 0.5, and the carrier ratio is 18, Figure 6 Fig. 8 is a schematic diagram of simulation results of the application when the fundamental frequency is 50 Hz, the modulation ratio is 0.6, and the carrier ratio is 15, Figure 7 Fig. 9 is a schematic diagram of simulation results of the application when the fundamental frequency is 64 Hz, the modulation ratio is 0.7, and the carrier ratio is 12, Figure 8 Fig. 10 is a schematic diagram of simulation results of the application when the fundamental frequency is 80 Hz, the modulation ratio is 0.8, and the carrier ratio is 9, Figure 9 Fig. 11 is a schematic diagram of simulation results of the application when the fundamental frequency is 100 Hz, the modulation ratio is 0.9, and the carrier ratio is 6, Figure 10 Fig. 12 is a schematic diagram of simulation results of the application when the fundamental frequency is 125 Hz, the modulation ratio is 1, and the carrier ratio is 3, Figure 11 Fig. 12 is a schematic diagram of simulation results of the application when the fundamental frequency is 125 Hz, the modulation ratio is 1, and the carrier ratio is 3, Figures 6 to 11 Fig. 12 is a schematic diagram of simulation results of the application when the fundamental frequency is 125 Hz, the modulation ratio is 1, and the carrier ratio is 3,

[0168] In addition, from Figures 4 to 11It can be seen that by controlling the carrier ratio, the number of synchronous modulation of the scheme can be controlled, thereby realizing accurate control of the switching frequency. When the carrier ratio is an integer multiple of 3, the scheme can effectively eliminate specific harmonic components in the line voltage under different modulation ratios and fundamental frequencies, and has superior robustness.

[0169] Corresponding to the above method embodiments, the embodiments of the application also provide a synchronous modulation system of a two-level inverter, which can be mutually corresponding with the above.

[0170] Referring to Figure 12 Fig. 1 shows a structure schematic diagram of a synchronous modulation system of a two-level inverter in the application, which comprises:

[0171] A sampling point position determination module 201 is configured to determine various sampling point positions according to a carrier ratio, and divide sampling point types according to the various sampling point positions;

[0172] A modulation wave generation module 202 is configured to determine three-phase modulation waves of the various sampling point positions according to sampling point types and modulation wave generation rules;

[0173] A carrier generation module 203 is configured to determine carriers of the various sampling point positions according to preset carrier generation rules;

[0174] A switching signal determination module 204 is configured to compare the three-phase modulation waves with the carriers according to preset comparison rules, determine switching signals of the two-level inverter, and control the two-level inverter;

[0175] The modulation wave generation rules, the carrier generation rules, and the comparison rules are configured to synchronize the carrier frequency with the fundamental frequency, and make the output voltage of the two-level inverter satisfy three-phase symmetry, half-wave symmetry, and quarter-cycle symmetry.

[0176] Corresponding to the above method and system embodiments, the embodiments of the application also provide a synchronous modulation device of a two-level inverter and a computer readable storage medium, which can be mutually corresponding with the above. The computer readable storage medium stores a computer program, and the computer program is executed by a processor to realize the steps of the synchronous modulation method of the two-level inverter in any of the above embodiments. The computer readable storage medium mentioned herein includes a random access memory (RAM), a memory, a read-only memory (ROM), an electrically programmable ROM, an electrically erasable programmable ROM, a register, a hard disk, a removable disk, a CD-ROM, or any other form of storage medium known in the technical field.

[0177] The synchronous modulation device of the two-level inverter can comprise:

[0178] A memory is configured to store a computer program;

[0179] a processor configured to execute computer program to implement the steps of the method for synchronous modulation of a two-level inverter according to any one of the preceding embodiments.

[0180] It should also be noted that, in the specification, relational terms such as first and second, and the like, can be used solely to distinguish one entity or action from another entity or action without necessarily implying any actual relationship or order between such entities or actions. Moreover, the terms "comprises", "comprising", or any other variations thereof, are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements does not include only those elements but can include other elements not expressly listed or inherent to such process, method, article, or apparatus. Without further limitation, an element preceded by "comprises... a" does not, without more constraints, foreclose the existence of additional identical elements in the process, method, article, or apparatus that comprises the element.

[0181] Those skilled in the art will further appreciate that the units and algorithm steps of the examples described in connection with the embodiments disclosed herein can be implemented in electronic hardware, computer software, or any combination thereof. To clearly illustrate the interchangeability of hardware and software, various examples have been described generally in terms of their functionality without reference to the corresponding structure. Whether such functionality is implemented in hardware or software depends on the particular application and design constraints imposed on the overall architecture. Skilled persons can implement the described functionality in varying ways for each particular application, but such implementation should not be construed to depart from the scope of the present application.

[0182] The principles and implementation modes of the present application are described by using specific examples in the specification, and the above description of the examples is only used to help understand the technical solutions and core ideas of the present application. It should be noted that, for ordinary skilled persons in the art, without departing from the principles of the present application, a number of improvements and modifications can be made to the present application, and these improvements and modifications also fall within the protection scope of the present application.

Claims

1. A synchronous modulation method for a two-level inverter, characterized in that, include: The location of each sampling point is determined based on the carrier ratio, and the sampling point type is classified according to the location of each sampling point; According to the sampling point type and modulation wave generation rule, determine the three-phase modulation wave at each sampling point position; According to the preset carrier generation rules, determine the carrier at each sampling point position; According to the preset comparison rules, the three-phase modulated wave is compared with the carrier wave to determine the switching signal of the two-level inverter and control the two-level inverter. The modulation wave generation rule, the carrier generation rule, and the comparison rule set therein ensure that the carrier frequency is synchronized with the fundamental frequency, and that the output voltage of the two-level inverter satisfies three-phase symmetry, half-wave symmetry, and quarter-cycle symmetry. The process of determining the position of each sampling point based on the carrier ratio includes: pass The locations of each sampling point were determined; Where C is the carrier ratio, N is the sampling point number, and X N This represents the position of the (N+1)th sampling point; The carrier ratio is set to an integer multiple of 3; The classification of sampling point types based on the location of each sampling point includes: When the sampling point is located at 30°, 90°, 150°, 210°, 270° or 330°, the sampling point is regarded as the first type of sampling point; When the sampling point is located at 0°, 60°, 120°, 180°, 240° or 300°, the sampling point is designated as a second type of sampling point. When the sampling point is located within the interval (90°, 120°), or within the interval (120°, 150°), or within the interval (210°, 240°), or within the interval (240°, 270°), or within the interval (330°, 0°), or within the interval (0°, 30°), the sampling point is designated as a third type of sampling point. When the sampling point is located within the interval (150°, 180°), or within the interval (180°, 210°), or within the interval (270°, 300°), or within the interval (300°, 330°), or within the interval (30°, 60°), or within the interval (60°, 90°), the sampling point is designated as a fourth type of sampling point. The step of determining the three-phase modulated wave at each sampling point position according to the sampling point type and modulation wave generation rule includes: According to the preset modulation wave generation rules, two sets of three-phase modulation waves are set for each first-type sampling point, and one set of three-phase modulation waves is set for each second-type sampling point, each third-type sampling point, and each fourth-type sampling point.

2. The synchronous modulation method for a two-level inverter according to claim 1, characterized in that, According to the preset modulation wave generation rules, two sets of three-phase modulation waves are set for each first-type sampling point, and one set of three-phase modulation waves is set for each second-type, third-type, and fourth-type sampling point, including: For the first type of sampling point, when the sampling point position is 30°, set S mbp =S m S mbn =−S m Set S map S man S mcp and S mcn All are U; When the sampling point position is 90°, set S map =S m S man =−S m Set S mbp S mbn S mcp and S mcn All are 0; When the sampling point position is 150°, set S mcp =S m S mcn =−S m Set S map S man S mbp and S mbn All are U; When the sampling point position is 210°, set S mbp =S m S mbn =−S m Set S map S man S mcp and S mcn All are 0; When the sampling point position is 270°, set S map =S m S man =−S m Set S mbp S mbn S mcp and S mcn All are U; When the sampling point position is 330°, set S mcp =S m S mcn =−S m Set S map S man S mbp and S mbn All are 0; Among them, S map and S man S represents the first and second modulating waves of phase A, respectively. mbp and S mbn S represents the first and second modulating waves of phase B, respectively. mcp and S mcn These represent the first and second modulating waves of phase C, respectively, where U is the amplitude of the sine wave, and S... m Represents the modulated wave variable, and S m The calculation method is as follows: ； Among them, S max and S min These are the current maximum and minimum values ​​of the three-phase sine wave, respectively. For any one second-type sampling point, the set three-phase modulated wave is represented as: ； For any one third-type sampling point, the set three-phase modulated wave is represented as: ； For any one fourth-type sampling point, the set three-phase modulated wave is represented as: ； Among them, S ma S mb and S mc S represents the modulation waves of phases A, B, and C, respectively. a S b and S c These represent the sine waves of phase A, phase B, and phase C, respectively.

3. The synchronous modulation method for a two-level inverter according to claim 2, characterized in that, The step of determining the carrier at each sampling point position according to a preset carrier generation rule includes: For the first type of sampling points: When C / 2 or (C+1) / 2 is odd, the carrier direction at the sampling points of 30°, 150° and 270° is set as the falling direction, and the carrier direction at the sampling points of 90°, 210° and 330° is set as the rising direction. When C / 2 or (C+1) / 2 is even, the carrier direction at the sampling points of 30°, 150° and 270° is set as the rising direction, and the carrier direction at the sampling points of 90°, 210° and 330° is set as the falling direction. For the second, third, and fourth types of sampling points: When C / 2 is odd, the carrier direction at the sampling points of 0°, 120° and 240° is set as the falling direction, and the carrier direction at the sampling points of 60°, 180° and 300° is set as the rising direction. The carrier direction at any other sampling point is opposite to the carrier direction at the previous sampling point. When C / 2 is even, the carrier direction at the sampling point positions of 0°, 120° and 240° is set as the rising direction, and the carrier direction at the sampling point positions of 60°, 180° and 300° is set as the falling direction. The carrier direction at any other sampling point position is opposite to the carrier direction at the previous sampling point position. When (C+1) / 2 is odd, the carrier direction at the nearest sampling point positions of 0°, 120° and 240° is set as the falling direction, and the carrier direction at the nearest sampling point positions of 60°, 180° and 300° is set as the rising direction. The carrier direction at any other sampling point position is opposite to the carrier direction at the previous sampling point position. When (C+1) / 2 is even, the carrier direction at the nearest sampling point position of 0°, 120° and 240° is set as the rising direction, and the carrier direction at the nearest sampling point position of 60°, 180° and 300° is set as the falling direction. The carrier direction at any other sampling point position is opposite to the carrier direction at the previous sampling point position. For any given sampling point, when the carrier direction at that sampling point is upward, the triangular carrier value at that sampling point is... When the carrier direction at the sampling point is downward, the triangular carrier value at that sampling point is... ; Where Carr is the triangular carrier value, C is the carrier ratio, N is the sampling point number, and X is the carrier ratio. N The position of the (N+1)th sampling point It is the phase angle.

4. The synchronous modulation method for a two-level inverter according to claim 3, characterized in that, The step of comparing the three-phase modulated wave with the carrier wave according to a preset comparison rule to determine the switching signal of the two-level inverter and control the two-level inverter includes: For the first type of sampling points: When S map and S man If they are not equal, if S map >Carr and S man <If Carr is true, the upper arm switch of phase A is turned on, and the lower arm switch of phase A is turned off; if S map >Carr and S man When Carr is not fully established, the upper arm switch of phase A is turned off and the lower arm switch of phase A is turned on. When S map and S man When they are equal, if S map =U, controls the upper arm switch of phase A to turn on and the lower arm switch of phase A to turn off; if S map =0, control the upper arm switch of phase A to turn off, and the lower arm switch of phase A to turn on; When S mbp and S mbn If they are not equal, if S mbp >Carr and S mbn If both Carr and S are true, the upper arm switch of phase B is turned on and the lower arm switch of phase B is turned off; if S mbp >Carr and S mbn When Carr is not fully established, the upper arm switch of phase B is turned off and the lower arm switch of phase B is turned on. When S mbp and S mbn When they are equal, if S mbp =U, controls the upper bridge arm switch of phase B to turn on and the lower bridge arm switch of phase B to turn off; if S mbp =0, control the upper arm switch of phase B to turn off, and the lower arm switch of phase B to turn on; When S mcp and S mcn If they are not equal, if S mcp >Carr and S mcp <If Carr is true, the upper arm switch of phase C is turned on, and the lower arm switch of phase C is turned off; if S mcp >Carr and S mcp When Carr is not fully established, the upper arm switch of phase C is turned off and the lower arm switch of phase C is turned on. When S mcp and S mcn When they are equal, if S mcp =U, controls the upper arm switch of phase C to turn on and the lower arm switch of phase C to turn off; if S mcp =0, control the upper arm switch of phase C to turn off, and the lower arm switch of phase C to turn on; For the second, third, and fourth types of sampling points: When S ma >When Carr is established, the upper arm switch of phase A is turned on, and the lower arm switch of phase A is turned off. When S ma >When Carr is not established, the upper arm switch of phase A is turned off and the lower arm switch of phase A is turned on. When S mb >When Carr is established, the upper arm switch of phase B is turned on, and the lower arm switch of phase B is turned off. When S mb >When Carr is not established, the upper arm switch of phase B is turned off and the lower arm switch of phase B is turned on. When S mc >When Carr is established, the upper arm switch of phase C is turned on, and the lower arm switch of phase C is turned off. When S mc >When Carr is not established, the upper arm switch of phase C is turned off and the lower arm switch of phase C is turned on.

5. A synchronous modulation system for a two-level inverter, characterized in that, include: The sampling point location determination module is used to determine the location of each sampling point based on the carrier ratio, and to classify the sampling point type based on the location of each sampling point. The modulation wave generation module is used to determine the three-phase modulation wave at each sampling point position according to the sampling point type and the modulation wave generation rule. The carrier generation module is used to determine the carrier at each sampling point position according to the preset carrier generation rules; The switching signal determination module is used to compare the three-phase modulation wave with the carrier wave according to a preset comparison rule, determine the switching signal of the two-level inverter, and control the two-level inverter. The modulation wave generation rule, the carrier generation rule, and the comparison rule set therein ensure that the carrier frequency is synchronized with the fundamental frequency, and that the output voltage of the two-level inverter satisfies three-phase symmetry, half-wave symmetry, and quarter-cycle symmetry. The location of each sampling point is determined based on the carrier ratio, including: pass The locations of each sampling point were determined; Where C is the carrier ratio, N is the sampling point number, and X N This represents the position of the (N+1)th sampling point; The carrier ratio is set to an integer multiple of 3; Sampling point types are categorized based on their location, including: When the sampling point is located at 30°, 90°, 150°, 210°, 270° or 330°, the sampling point is regarded as the first type of sampling point; When the sampling point is located at 0°, 60°, 120°, 180°, 240° or 300°, the sampling point is designated as a second type of sampling point. When the sampling point is located within the interval (90°, 120°), or within the interval (120°, 150°), or within the interval (210°, 240°), or within the interval (240°, 270°), or within the interval (330°, 0°), or within the interval (0°, 30°), the sampling point is designated as a third type of sampling point. When the sampling point is located within the interval (150°, 180°), or within the interval (180°, 210°), or within the interval (270°, 300°), or within the interval (300°, 330°), or within the interval (30°, 60°), or within the interval (60°, 90°), the sampling point is designated as a fourth type of sampling point. The step of determining the three-phase modulated wave at each sampling point position according to the sampling point type and modulation wave generation rule includes: According to the preset modulation wave generation rules, two sets of three-phase modulation waves are set for each first-type sampling point, and one set of three-phase modulation waves is set for each second-type sampling point, each third-type sampling point, and each fourth-type sampling point.

6. A synchronous modulation device for a two-level inverter, characterized in that, include: Memory, used to store computer programs; A processor for executing the computer program to implement the steps of the synchronous modulation method for a two-level inverter as described in any one of claims 1 to 4.

7. A computer-readable storage medium, characterized in that, The computer-readable storage medium stores a computer program that, when executed by a processor, implements the steps of the synchronous modulation method for a two-level inverter as described in any one of claims 1 to 4.

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