SVPWM modulation method for high power density three-phase Buck rectifier

Abstract

A SVPWM modulation method for a high power density three-phase Buck rectifier belongs to the field of power electronics technology and mainly solves the problems of input current distortion at sector switching and input phase voltage zero crossing and high voltage stress of the switch tube when traditional SVPWM is applied to a high power density three-phase Buck rectifier. The SVPWM method of the present invention changes the action sequence of the effective vector working mode and the selection of the zero vector working mode, effectively suppresses input current distortion, and clamps the voltage stress of the switch tube at the input filter capacitor voltage difference, reduces voltage stress, and reduces the difficulty of hardware selection. The present invention improves the input current quality and efficiency of the high power density three-phase Buck rectifier and has good engineering application prospects.

Description

Technical Field

[0001] The present invention belongs to the technical field of power electronics, and in particular relates to an SVPWM (Space Vector Pulse Width Modulation) modulation method with low input current THD and low voltage stress characteristics in high power density three-phase Buck rectifier applications. Background Art

[0002] With the rapid development of modern power electronics technology, especially in the fields of renewable energy, more electric aircraft and electric vehicles, the demand for three-phase PWM rectifiers is increasing. The three-phase Buck rectifier has gradually become a research hotspot for three-phase PWM rectifiers due to its simple structure, low starting current and high efficiency.

[0003] Since the driving signal of the three-phase Buck rectifier switch tube is three-valued logic, the SPWM (Sinusoidal Pulse Width Modulation) modulation method requires two-valued and three-valued logic conversion, which is difficult to implement in digital control, while the digital implementation of SVPWM is simple and more flexible. Therefore, the SVPWM modulation method is widely used in three-phase Buck rectifiers.

[0004] However, for three-phase Buck rectifiers using traditional SVPWM modulation, when switching between even sectors and odd sectors, the input current has sector switching distortion, and this distortion worsens with increasing frequency; when the phase voltage passes through zero, the duty cycle is extremely small and there is a loss of wave transmission, and the input current has zero-crossing distortion. In addition, in high-power density three-phase Buck rectifier applications, there is a parasitic capacitance (C ps , C ns ). When the switching frequency is too high, the parasitic capacitance becomes obvious, making the switch voltage stress of the traditional SVPWM method modulating the three-phase Buck rectifier high and related to the parasitic capacitance. The high voltage stress limits the selection of the switch tube and reduces the efficiency and stability of the system.

[0005] In response to the sector switching distortion of the input current, some scholars have proposed a low input current THD modulation method, which eliminates the irregular PWM wave during sector switching and reduces the input current THD. However, this method cannot solve the zero-crossing distortion of the input current when the input phase voltage passes through zero. And when applied to a high-power density three-phase Buck rectifier, this modulation method cannot solve the problem of high voltage stress of the switching device. In response to the problem of high voltage stress, some scholars have optimized the topology, but this method requires additional diodes, which increases the hardware cost.

[0006] The high power density of three-phase Buck rectifier is an inevitable trend in the context of high power, high efficiency and high density development of digital power supply. Therefore, it is very meaningful to propose an SVPWM modulation method with low input current THD and low voltage stress characteristics in high power density three-phase Buck rectifier applications. Summary of the invention

[0007] The present invention is used to solve the problems of input current sector switching distortion, zero-crossing distortion and high voltage stress of the switch tube in a high power density three-phase Buck rectifier adopting a traditional SVPWM modulation method.

[0008] The present invention adopts the following technical solutions to achieve the purpose:

[0009] A SVPWM modulation method for a high power density three-phase Buck rectifier, the method comprising: dividing a sector every 30° according to the magnitude relationship of the three-phase input phase voltages, with a total of twelve sectors; taking the point where the A-phase input voltage rises to a maximum value as the starting point, dividing sector 1, and arranging the other sectors in order of serial numbers;

[0010] In sectors 1 to 12, the working modes and working sequences of the three-phase bridge arm switches of the high power density three-phase Buck rectifier are as follows:

[0011] The working modes in sector 1 are: mode 110, mode 101, mode 010, and the working order in one switching cycle is: 010→110→101→010;

[0012] The working modes in sector 2 are: mode 011, mode 101, mode 010, and the working order in one switching cycle is: 010→011→101→010;

[0013] The working modes in sector 3 are: mode 011, mode 101, mode 100, and the working order in one switching cycle is: 100→011→101→100;

[0014] The working modes in sector 4 are: mode 011, mode 110, mode 100, and the working order in one switching cycle is: 100→011→110→100;

[0015] The working modes in sector 5 are: mode 011, mode 110, mode 001, and the working order in one switching cycle is: 001→011→110→001;

[0016] The working modes in sector 6 are: mode 110, mode 101, mode 001, and the working order in one switching cycle is: 001→110→101→001;

[0017] The working modes in sector 7 are: mode 110, mode 101, mode 010, and the working order in one switching cycle is: 010→110→101→010;

[0018] The working modes in sector 8 are: mode 101, mode 011, mode 010, and the working order in one switching cycle is: 010→101→011→010;

[0019] The working modes in sector 9 are: mode 101, mode 011, mode 100, and the working order in one switching cycle is: 100→101→011→100;

[0020] The working modes in sector 10 are: mode 011, mode 110, mode 100, and the working order in one switching cycle is: 100→011→110→100;

[0021] The working modes in sector 11 are: mode 011, mode 110, mode 001, and the working order in one switching cycle is: 001→011→110→001;

[0022] The working modes in sector 12 are: mode 110, mode 101, mode 001, and the working order in one switching cycle is: 001→110→101→001.

[0023] In summary, due to the adoption of this technical solution, the beneficial effects of the present invention are as follows:

[0024] The SVPWM modulation method of the present invention can effectively suppress the distortion of input current at sector switching and input phase voltage zero crossing without changing the hardware topology, and reduce the harmonic pollution to the system on the grid side by optimizing the modulation method only in software.

[0025] In addition, the method of the present invention pays special attention to the voltage stress problem of the switch tube, clamps the voltage stress of the switch tube at the voltage difference of the two-phase input filter capacitor, reduces the influence of the parasitic capacitance on the voltage stress of the switch tube, improves the efficiency of the system, and simplifies the difficulty of device selection. This is of great significance to the design of high power density three-phase Buck rectifier.

[0026] In general, the SVPWM modulation method of the present invention achieves the above advantages by changing the working mode sequence of the effective vector and selecting different zero vector working modes. This modulation method not only improves the quality of the input current, but also reduces the voltage stress of the switch tube, bringing technological progress to the design of high power density three-phase Buck rectifiers, has a wide range of engineering application prospects, and can meet the growing demand for high-performance and high-efficiency rectification solutions in the field of modern power electronics technology. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 This is a circuit topology diagram of a traditional three-phase Buck rectifier;

[0028] Figure 2 The circuit topology diagram of the high power density three-phase Buck rectifier;

[0029] Figure 3 It is a schematic diagram of sector division of 12-sector SVPWM modulation in the SVPWM method of the present invention;

[0030] Figure 4 It is the PWM sequence diagram of the traditional SVPWM modulation method in sectors 2 and 3;

[0031] Figure 5 The PWM sequence of the three-phase Buck rectifier in sectors 2 and 3 and the current and voltage waveforms of the input filter inductor using the traditional SVPWM modulation method are shown in the figure.

[0032] Figure 6 The current path schematic diagram of the SVPWM method of the present invention in the working mode 011 of sector 2; in the figure, path 1 provides energy for the load, and paths 2 and 3 provide loops for the parasitic capacitance and the difference between the upper and lower inductor currents;

[0033] Figure 7 Schematic diagram of current path of the SVPWM method of the present invention in the working mode 101 of sector 2; in the figure, path 1 provides energy for the load, and paths 2 and 3 provide loops for the difference between the parasitic capacitance and the upper and lower inductor currents;

[0034] Figure 8 Schematic diagram of current path of the SVPWM method of the present invention in working mode 010 in sector 2; in the figure, path 1 provides energy for the load, and paths 2 and 3 provide loops for the difference between the parasitic capacitance and the upper and lower inductor currents;

[0035] Fig. 9 The schematic diagram of the working modes and sequence of the 12 sectors of the SVPWM modulation method of the present invention;

[0036] Fig.10 PWM sequence diagram of the SVPWM method of the present invention in sector 1;

[0037] Fig.11 PWM sequence diagram of the SVPWM method of the present invention in sector 2;

[0038] Fig.12 PWM sequence diagram of the SVPWM method of the present invention in sector 3;

[0039] Fig.13PWM sequence diagram of the SVPWM method of the present invention in sector 4;

[0040] Fig.14 PWM sequence diagram of the SVPWM method of the present invention in sector 5;

[0041] Fig.15 PWM sequence diagram of the SVPWM method of the present invention in sector 6;

[0042] Fig.16 PWM sequence diagram of the SVPWM method of the present invention in sector 7;

[0043] Fig.17 PWM sequence diagram of the SVPWM method of the present invention in sector 8;

[0044] Fig.18 PWM sequence diagram of the SVPWM method of the present invention in sector 9;

[0045] Fig.19 PWM sequence diagram of the SVPWM method of the present invention in sector 10;

[0046] Fig. 20 PWM sequence diagram of the SVPWM method of the present invention in sector 11;

[0047] Fig.21 PWM sequence diagram of the SVPWM method of the present invention in sector 12;

[0048] Fig. 22 Schematic diagram of input current waveform of high power density three-phase Buck rectifier in traditional SVPWM method;

[0049] Fig.23 Schematic diagram of input current waveform of high power density three-phase Buck rectifier in SVPWM method of the present invention;

[0050] Fig.24 The switch tube Q of the high power density three-phase Buck rectifier in the traditional SVPWM method is 2 Schematic diagram of voltage stress;

[0051] Fig.25 The switch tube Q of the high power density three-phase Buck rectifier in the SVPWM method of the present invention is 2 Schematic diagram of voltage stress;

[0052] Fig.26 A schematic diagram of the upper and lower inductor currents and their difference in the high power density three-phase Buck rectifier in the traditional SVPWM method;

[0053] Fig. 27Schematic diagram of the upper and lower inductor currents and their difference of the high power density three-phase Buck rectifier in the SVPWM method of the present invention. DETAILED DESCRIPTION

[0054] 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, not all of the embodiments. Generally, the components of the embodiments of the present invention described and shown in the drawings here can be arranged and designed in various different configurations.

[0055] Therefore, the following detailed description of the embodiments of the present invention provided in the accompanying drawings is not intended to limit the scope of the invention claimed for protection, but merely represents selected embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0056] Example

[0057] like Figure 1 As shown, the main components of the traditional three-phase Buck rectifier include: input filter L x and C x (x=a,b,c), three-phase six-switch bridge arm Q 1 ~Q 6 and D 1 ~D 6 , freewheeling diode D F , output filter L o and C o Each phase bridge arm consists of a MOSFET and a diode in series to ensure the unidirectional flow of the bridge arm current.

[0058] like Figure 2 As shown in the figure, in order to suppress the influence of common-mode current on input current and improve the power density of the rectifier, the common-mode capacitor C p , C n It is connected to the neutral points M and N of the input filter capacitor to form a common-mode filter. Its neutral line MN is designed as a shielding layer to block the electrical interference between the main circuit and the control circuit. Due to the existence of the output common-mode filter and the shielding layer, compared with the traditional three-phase Buck rectifier, a parasitic capacitor C is formed between the main circuit and the shielding layer of the high-power density three-phase Buck rectifier. ps ,C ns .

[0059] Depend on Figure 1 and Figure 2From the topology, it can be seen that whether the switch tube in the bridge arm of the three-phase Buck rectifier is turned on requires two conditions: whether the MOSFET has a driving signal; whether the series diode withstands the forward voltage drop. There are two driving modes for the switch tube of the three-phase Buck rectifier: redundant driving mode and independent driving mode. In the redundant driving mode, the switch tube Q in each sector 1 ~Q 6 All are assigned PWM drive signals, but the drive signals of the upper and lower switch tubes of each phase bridge arm are the same, so only three PWM drive signals need to be configured; in independent drive mode, the drive signals of the upper and lower switch tubes of each phase bridge arm are different, so six PWM drive signals need to be configured. Therefore, the implementation of redundant drive mode is simpler and more meaningful in engineering practice. The SVPWM modulation of the present invention adopts redundant drive mode.

[0060] like Figure 3 As shown, the twelve-sector SVPWM modulation of the present invention takes the point where the input voltage of phase A rises to the maximum value as the starting point, and divides a sector every 30°. In each sector, the conduction and shutdown of the corresponding switch tube are controlled according to the working mode to achieve input current following input voltage.

[0061] The working mode in each sector of the SVPWM modulation method represents the on and off status of the switch tube of each phase, where "1" means that the upper and lower switch tubes of the corresponding bridge arm are configured with drive signals at the same time, and "0" means that the upper and lower switch tubes of the corresponding bridge arm are turned off at the same time.

[0062] In this embodiment, according to the on and off conditions of the switch tubes of the corresponding bridge arms, it can be deduced that the SVPWM modulation method of the present invention has seven working modes: working mode 101, working mode 011, working mode 110, working mode 000, working mode 100, working mode 010, and working mode 001. Among them, in working modes 101, 011, and 110, the input end provides energy to the output end, which is an effective vector working mode. In working modes 000, 100, 010, and 001, the output inductor provides energy to the output end, which is a zero vector working mode.

[0063] The situations of the 12 sectors of the SVPWM modulation method can be analyzed by analogy. Therefore, sector 2 is selected to analyze how to solve the distortion of the input current at the zero crossing of the input phase voltage and how to reduce the voltage stress of the switch tube when the high power density three-phase Buck rectifier adopts the SVPWM modulation method of the present invention; sector 2 switching to sector 3 is selected as an example to analyze how to solve the distortion of the input current at the sector switching.

[0064] like Figure 4 As shown, the three working modes of the traditional SVPWM modulation method in a switching cycle in sector 2 are: working mode 101, working mode 011, and working mode 000. Figure 3 , at the beginning of sector 2, the B-phase input voltage passes through zero, the duty cycle of the B-phase switch tube is extremely small, that is, the action time of the working mode 011 is extremely short, there is a situation where the duty cycle is lost, and the input current has zero-crossing distortion. The three modes of the SVPWM modulation method of the present invention in a switching cycle in sector 2 are: working mode 011, working mode 101, and working mode 010. The zero-vector working mode is changed from the working mode 000 of the traditional modulation method to the working mode 010, that is, the zero-vector working mode in which all the switch tubes are turned off is changed to the long-on of the upper and lower switch tubes of the B phase, which increases the conduction time of the B-phase switch tube, avoids the situation where the duty cycle is lost due to extremely small duty cycle, and eliminates the distortion of the input current at the zero-crossing of the input phase voltage.

[0065] like Figure 5 As shown in FIG. 1 , the PWM sequence of the traditional SVPWM modulation method at the switching point between sectors 2 and 3 is shown. It can be found that due to the inconsistency in the working mode sequence of sectors 2 and 3, two working modes 101 appear continuously at the sector switching point, which causes the B-phase input filter capacitor to be continuously charged, and the input filter inductor current i b Rapidly decreases, distortion occurs; the input filter capacitor of phase A continues to discharge, and the input filter inductor current i a Rapidly increases and distortion occurs; the C-phase input filter capacitor voltage is not affected by the continuous action of the working mode 101, and the input filter inductor current i c There is no distortion.

[0066] The working order of the SVPWM modulation method of the present invention in one switching cycle in sector 2 is: 010→011→101→010; the working order in one switching cycle in sector 3 is: 100→011→101→100, and the effective vector working mode action order of the SVPWM modulation method of the present invention is consistent in sectors 2 and 3. Compared with the traditional SVPWM modulation method, the SVPWM method of the present invention changes the PWM sequence of sector 2 to avoid the continuous action of the working mode 101, suppresses the input current distortion at the sector switching point, and improves the input current quality.

[0067] like Figure 6 As shown, in working mode 011, the upper bridge arm Q of phase B 3 , D 3 , C phase lower bridge arm Q 2 , D 2 There are three loops in the three-phase Buck rectifier. Path 1 provides energy to the load. The DC link current flows out from phase B and passes through the phase B input filter, diode D 3 , switch tube Q 3 , DC link inductance L p 、Load R L , DC link inductance Ln 、Diode D 2 , switch tube Q 2 , C-phase input filter, flows back to the input side. Paths 2 and 3 are the difference between the upper and lower inductor currents Δi pn The parasitic capacitance provides a loop, and part of the difference between the upper and lower inductor currents passes through L p , Common mode filter capacitor C p , parasitic capacitance C ps , switch tube Q 3 The other part of the difference between the upper and lower inductor currents passes through the common mode filter capacitor C n , parasitic capacitance C ns , switch tube Q 2 In this working mode, the switch tube Q 2 The switch tube Q 2 The voltage stress is 0, and the conventional SVPWM modulation is consistent with the modulation method of the present invention.

[0068] like Figure 7 As shown, in working mode 101, the upper bridge arm Q of phase A 1 , D 1 , C phase lower bridge arm Q 2 , D 2 There are three loops in the three-phase Buck rectifier. Path 1 provides energy to the load. The DC link current flows out from phase A and passes through the phase A input filter, diode D 1 , switch tube Q 1 , DC link inductance L p 、Load R L , DC link inductance L n 、Diode D 2 , switch tube Q 2 , C-phase input filter, flows back to the input side. Paths 2 and 3 are the difference between the upper and lower inductor currents Δi pn The parasitic capacitance provides a loop, and part of the difference between the upper and lower inductor currents passes through L p , Common mode filter capacitor C p , parasitic capacitance C ps , switch tube Q 1 The other part of the difference between the upper and lower inductor currents passes through the common mode filter capacitor C n , parasitic capacitance C ns , switch tube Q 2 In this working mode, the switch tube Q 2 The switch tube Q 2 The voltage stress is 0, and the conventional SVPWM modulation is consistent with the modulation method of the present invention.

[0069] like Figure 8As shown, in working mode 010, the upper bridge arm Q of phase B 3 , D 3 , B phase lower bridge arm Q 6 , D 6 The remaining bridge arms are in the disconnected state. There are three loops in the three-phase Buck rectifier. Path 1 is the output inductor freewheeling loop, which consists of the freewheeling diode, L p , R L , L n Paths 2 and 3 are the difference between the upper and lower inductor currents Δi pn The parasitic capacitance provides a loop, and part of the difference between the upper and lower inductor currents passes through L p , Common mode filter capacitor C p , parasitic capacitance C ps , switch tube Q 3 The other part of the difference between the upper and lower inductor currents passes through the common mode filter capacitor C n , parasitic capacitance C ns , switch tube Q 6 In this working mode, the switch tube Q 2 Disconnect, at this time the switch tube Q 2 The voltage stress is V Cb -V Cc In traditional SVPWM modulation, the working mode at this stage is 000, and the switch tube Q 2 The voltage stress and parasitic capacitance C ns The capacitance is inversely related, and the voltage stress is uncontrollable and high. Compared with the traditional SVPWM, the SVPWM modulation method in the present invention switches the switch tube Q 2 The voltage stress of the switch tube is clamped at the voltage difference of the input filter capacitor, which greatly reduces the voltage stress of the switch tube. 2 The voltage stress is 430V. The SVPWM modulation method of the present invention is adopted. The switch tube Q 2 The voltage stress is 250V.

[0070] Combined with the above description, by analogy with sectors 2 and 3, the working modes of the remaining sectors can be derived; Fig. 9 The working modes and the working order of the SVPWM modulation method of the present invention in sectors 1 to 12 are as follows:

[0071] See also Fig.10 In sector 1, the working modes of the three-phase bridge arm switch tube are: mode 110, mode 101, mode 010, and the working order in one switching cycle is: 010→110→101→010.

[0072] See also Fig.11In sector 2, the working modes of the three-phase bridge arm switch tube are: mode 011, mode 101, mode 010, and the working order in one switching cycle is: 010→011→101→010.

[0073] See also Fig.12 In sector 3, the working modes of the three-phase bridge arm switch tube are: mode 011, mode 101, mode 100, and the working order in one switching cycle is: 100→011→101→100.

[0074] See also Fig.13 In sector 4, the working modes of the three-phase bridge arm switch tube are: mode 011, mode 110, mode 100, and the working order in one switching cycle is: 100→011→110→100.

[0075] See also Fig.14 In sector 5, the working modes of the three-phase bridge arm switch tube are: mode 011, mode 110, mode 001, and the working order in one switching cycle is: 001→011→110→001.

[0076] See also Fig.15 In sector 6, the working modes of the three-phase bridge arm switch tube are: mode 110, mode 101, mode 001, and the working order in one switching cycle is: 001→110→101→001.

[0077] See also Fig.16 In sector 7, the working modes of the three-phase bridge arm switch tube are: mode 110, mode 101, mode 010, and the working order in one switching cycle is: 010→110→101→010.

[0078] See also Fig.17 In sector 8, the working modes of the three-phase bridge arm switch tube are: mode 101, mode 011, mode 010, and the working order in one switching cycle is: 010→101→011→010.

[0079] See also Fig.18 In sector 9, the working modes of the three-phase bridge arm switch tube are: mode 101, mode 011, mode 100, and the working order in one switching cycle is: 100→101→011→100.

[0080] See also Fig.19 In sector 10, the working modes of the three-phase bridge arm switch tube are: mode 011, mode 110, mode 100, and the working order in one switching cycle is: 100→011→110→100.

[0081] See also Fig. 20In sector 11, the working modes of the three-phase bridge arm switch tube are: mode 011, mode 110, mode 001, and the working order in one switching cycle is: 001→011→110→001.

[0082] See also Fig.21 In sector 12, the working modes of the three-phase bridge arm switch tube are: mode 110, mode 101, mode 001, and the working order in one switching cycle is: 001→110→101→001.

[0083] At the end of this embodiment, simulation results of the method of this embodiment and the traditional method are presented to intuitively introduce the advantages of the method of this embodiment.

[0084] contrast Fig. 22 and Fig.23 It can be seen that compared with the traditional SVPWM modulation method, the SVPWM modulation of the present invention can effectively suppress the distortion of the input current at the sector switching and the input phase voltage zero crossing point, improve the input current DC, and reduce the input current THD from 3.6% to 1.55%.

[0085] contrast Fig.24 and Fig.25 It can be seen that compared with the traditional SVPWM modulation method, the SVPWM modulation method of the present invention clamps the voltage stress of the switch tube at the voltage difference between the two-phase input filter capacitors, and no longer has any effect on the parasitic capacitor C ps , C ns The voltage stress is reduced from 430V to 250V, which reduces the difficulty of device selection and improves system efficiency.

[0086] contrast Fig.26 and Fig. 27 It can be seen that compared with the traditional SVPWM modulation method, the SVPWM modulation method of the present invention reduces the ripple of the output side inductor current and the difference between the upper and lower inductor currents. The inductor current ripple is reduced from 2.4A to 1.9A, and the difference is reduced from 1.5A to 1A. This is conducive to the improvement of input current quality and the design of output inductance.

Claims

1. A SVPWM modulation method for a high power density three-phase Buck rectifier, characterized in that: According to the magnitude relationship of the three-phase input phase voltage, a sector is divided every 30°, with a total of twelve sectors; the point where the A-phase input voltage rises to the maximum value is used as the starting point to divide sector 1, and the other sectors are arranged in sequence; In sectors 1 to 12, the working modes and working sequences of the three-phase bridge arm switches of the high power density three-phase Buck rectifier are as follows: The working modes in sector 1 are: mode 110, mode 101, mode 010, and the working order in one switching cycle is: 010→110→101→010; The working modes in sector 2 are: mode 011, mode 101, mode 010, and the working order in one switching cycle is: 010→011→101→010; The working modes in sector 3 are: mode 011, mode 101, mode 100, and the working order in one switching cycle is: 100→011→101→100; The working modes in sector 4 are: mode 011, mode 110, mode 100, and the working order in one switching cycle is: 100→011→110→100; The working modes in sector 5 are: mode 011, mode 110, mode 001, and the working order in one switching cycle is: 001→011→110→001; The working modes in sector 6 are: mode 110, mode 101, mode 001, and the working order in one switching cycle is: 001→110→101→001; The working modes in sector 7 are: mode 110, mode 101, mode 010, and the working order in one switching cycle is: 010→110→101→010; The working modes in sector 8 are: mode 101, mode 011, mode 010, and the working order in one switching cycle is: 010→101→011→010; The working modes in sector 9 are: mode 101, mode 011, mode 100, and the working order in one switching cycle is: 100→101→011→100; The working modes in sector 10 are: mode 011, mode 110, mode 100, and the working order in one switching cycle is: 100→011→110→100; The working modes in sector 11 are: mode 011, mode 110, mode 001, and the working order in one switching cycle is: 001→011→110→001; The working modes in sector 12 are: mode 110, mode 101, mode 001, and the working order in one switching cycle is: 001→110→101→001.

2. The high power density three-phase Buck rectifier SVPWM modulation method according to claim 1, characterized in that: The topology of the high power density three-phase Buck rectifier is composed of a three-phase input filter, a three-phase six-switch bridge arm, a freewheeling diode, and an output filter, wherein each phase bridge arm is composed of a switch tube and a diode in series; the topology of the high power density three-phase Buck rectifier also includes a common mode capacitor C p , C n ; Common mode capacitance C p , C n The neutral points M and N of the input filter capacitor are connected to form a common-mode filter, and the neutral line MN is designed as a shielding layer to shield the interference between the main circuit and the control circuit; the common-mode filter and the shielding layer form a parasitic capacitor C between the main circuit and the shielding layer of the high-power density three-phase Buck rectifier. ps , C ns .

3. The high power density three-phase Buck rectifier SVPWM modulation method according to claim 1, characterized in that: The driving mode of the three-phase six-bridge arm of the high power density three-phase Buck rectifier is a redundant driving mode, the upper and lower switch tube driving signals of each phase bridge arm are the same, and the six switch tubes are correspondingly configured with three PWM driving signals.

4. The high power density three-phase Buck rectifier SVPWM modulation method according to claim 3 is characterized in that: Whether the switch is turned on requires the following conditions to be met at the same time: whether the switch is equipped with a driving signal; and whether the diode connected in series with it is subject to a forward voltage.

5. The high power density three-phase Buck rectifier SVPWM modulation method according to claim 4, characterized in that: "1" in the SVPWM modulation method represents that the upper and lower switch tubes of the corresponding phase are both configured with a conduction drive signal, and "0" represents that the upper and lower switch tubes of the corresponding phase are both turned off; according to the state of the switch tube, there are seven working modes in the SVPWM modulation method: 101, 011, 110, 000, 100, 010, 001, among which the working modes 101, 011, 110 are effective vector working modes, and the working modes 000, 100, 010, 001 are zero vector working modes.

6. The high power density three-phase Buck rectifier SVPWM modulation method according to claim 5, characterized in that: The SVPWM modulation method exchanges the action order of the effective vector working mode and the selection of the zero vector working mode. The zero vector working mode is selected as a certain phase bridge arm is long-on.

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