A high voltage reduction ratio single-stage three-phase current mode PWM rectifier and a modulation method thereof

Abstract

The application discloses a high-voltage-reduction-ratio single-stage three-phase current-mode PWM rectifier, which comprises an AC side filter module, a three-phase rectifier bridge module and a DC side switching inductor module which are sequentially connected. p 、 The DC side switching inductor module comprises an inductor L n , an inductor L n , a diode D7 and a diode D8; the anode of the diode D7 is connected with one end of the inductor L n , the other end of the inductor L p is connected to the anode of the diode D8; the cathode of the diode D8 is connected with one end of the inductor L p , the other end of the inductor L p is connected to the cathode of the diode D7, the intersection of the cathode of the diode D7 and the inductor L n and the intersection of the anode of the diode D8 and the inductor L are respectively connected to the two ends of the output side of the three-phase rectifier bridge module. The rectifier utilizes the DC side switching inductor module and the modulation strategy, so that the zero vector state is divided into two parts, the lower output voltage is realized, the high-voltage-reduction ratio is obtained, the influence of the extreme duty cycle of the switching tube on the system performance is effectively reduced, and the stability and reliability of the system are enhanced.

Description

Technical Field

[0001] This invention relates to the field of rectifiers, and more specifically to a high buck ratio single-stage three-phase current-mode PWM rectifier and its modulation method. Background Technology

[0002] Currently, three-phase PWM rectifiers are mainly divided into two categories: three-phase current-source PWM rectifiers and three-phase voltage-source PWM rectifiers. Three-phase voltage-source PWM rectifiers are boost converters, offering advantages such as stable output voltage and high energy conversion efficiency; three-phase current-source PWM rectifiers are buck converters, offering advantages such as sinusoidal grid-side current and high reliability. Both types of converters have promising development prospects in fields such as electric vehicle battery chargers, battery charging and discharging devices, and water electrolysis for hydrogen production.

[0003] With the development of the power electronics industry, research on three-phase buck converters, characterized by high step-down ratio and high reliability, has gradually become a hot topic. However, in applications requiring high step-down ratio and low-voltage, high-current operation, traditional three-phase PWM rectifiers still suffer from the following drawbacks: First, to obtain a lower output voltage, the switching transistors of traditional three-phase current-source PWM rectifiers will operate at extreme duty cycles, resulting in extremely high current stress on the transistors and reverse recovery issues in the diodes, thus affecting the rectifier's regulation capability and efficiency. Second, although three-phase voltage-source PWM rectifiers have a simple structure and boost function, reducing the output voltage typically requires additional cascaded buck DC / DC converters. For example, patent publication number CN117175943A discloses a novel negative voltage output soft-switching high buck ratio converter, which includes a PWM module and a closed-loop control module. The closed-loop control module also includes a PI controller and a DC / DC converter. The PWM module is used to receive control signals and adjust the duty cycle to convert them into drive signals. The DC / DC converter receives the drive signals and then performs voltage conversion. Although it can improve the buck ratio and adjust the duty cycle to a certain extent, it still adopts a structure in which the DC / DC converter is connected after the PWM module, which increases the manufacturing cost of the system and increases the loss. Summary of the Invention

[0004] The problem this invention aims to solve is how to achieve a high buck ratio in a three-phase current-source PWM rectifier while improving the extreme duty cycle of its switching transistors.

[0005] The present invention solves the above problems through the following technical means: a high step-down ratio single-stage three-phase current-type PWM rectifier, comprising an AC side filter module, a three-phase rectifier bridge module, and a DC side switching inductor module connected in sequence;

[0006] The DC-side switching inductor module includes an inductor. L p ,inductanceL n ,diode D 7 and diodes D 8; the diode D 7 Anode and Inductance L n One end is connected to the inductor. L n The other end is connected to a diode. D The anode of 8; the diode D The cathode of 8 is connected to the inductor. L p One end of the inductor L p The other end is connected to a diode. D 7 cathode, diode D 7 Cathode and Inductor L p Connection points and diodes D 8. Anode and Inductance L n The connection points are respectively connected to the two ends of the output side of the three-phase rectifier bridge module.

[0007] Preferably, the three-phase rectifier bridge module includes three-phase bridge arms: A Mutually, B phase and C Each phase bridge arm includes an upper bridge arm and a lower bridge arm, and each upper bridge arm and lower bridge arm is controlled by a switching transistor. Q i and a diode D i Composed of series connections.

[0008] Preferably, the AC-side filtering module includes three filtering inductors: L a , L b , L c The filter inductor L a , L b , L c The input terminals are connected to the three phases of the three-phase power supply respectively; the filter inductor L a The other end and A Phase bridge arm connection, connection point located at A Between the upper and lower bridge arms, the filter inductor L b The other end and B Phase bridge arm connection, connection point located at B Between the upper and lower bridge arms, the filter inductorL c The other end and C Phase bridge arm connection, connection point located at C Between the upper and lower bridge arms.

[0009] Preferably, the AC side filtering module further includes three filtering capacitors: C a , C b , C c Filter capacitor C a , C b , C c One end is connected to the filter capacitor. C a The other end is connected to the filter inductor L a The output terminal, filter capacitor C b The other end is connected to the filter inductor. L b The output terminal, filter capacitor C c The other end is connected to the filter inductor L c The output terminal.

[0010] The three filter capacitors in this invention C a , C b , C c and three filter inductors L a , L b , L c The composition LC The filter is used to filter out current ripple on the AC side.

[0011] The present invention also provides a modulation method for the above-mentioned high buck ratio single-stage three-phase current-source PWM rectifier, the modulation method comprising: modulating the rectifier using twelve-sector SVPWM modulation.

[0012] Preferably, based on the relative relationship of the three-phase input voltages, one voltage input cycle is divided into 12 sectors. When the three-phase input voltages meet the following conditions... v a >0> v b > v cThe time is defined as the first sector, where v a express A Phase input voltage, v b express B Phase input voltage, v c express C Three-phase input voltage; when the three-phase input voltage satisfies v a > v b >0> v c The second sector is defined as the time when the three-phase input voltage satisfies... v b > v a >0> v c The third sector is defined as the three-phase input voltage when it satisfies the following conditions. v b >0> v a > v c The fourth sector is defined as the three-phase input voltage when it satisfies the following conditions. v b >0> v c > v a The fifth sector is defined as the time when the three-phase input voltage satisfies... v b > v c >0> v a The time is defined as the sixth sector; when the three-phase input voltage satisfies v c > v b >0> v a The term is defined as the seventh sector; when the three-phase input voltage satisfies... v c >0> v b > v a The term is defined as the eighth sector; when the three-phase input voltage satisfies... v c >0> v a > v b The term is defined as the ninth sector; when the three-phase input voltage satisfies... v c > va >0> v b The time is defined as the tenth sector; when the three-phase input voltage satisfies v a > v c >0> v b The time is defined as the eleventh sector; when the three-phase input voltage satisfies v a >0> v c > v b It is defined as the twelfth sector.

[0013] Preferably, based on the on / off status of each switch and diode on the three-phase bridge arm in the second sector, the bridge arm has four different operating modes; when the second sector is in operating mode one, A upper bridge arm and C The lower bridge arm is conducting. A Lower bridge arm, B upper and lower bridge arms, C The upper bridge arm is turned off; when the second sector is in operating mode two, B upper bridge arm and C The lower bridge arm is conducting. A upper and lower bridge arms, B Lower bridge arm and C The upper bridge arm is turned off; when the second sector is in operating mode three, B The upper and lower bridge arms are conducting. A upper and lower bridge arms C The upper and lower bridge arms are turned off; when the second sector is in operating mode four, A upper and lower bridge arms, B upper and lower bridge arms C Both upper and lower bridge arms are shut down.

[0014] Preferably, when the bridge arm is in different operating modes, different current vectors are generated, and the current vectors include non-zero vectors and zero vectors; within each sector, the switching state of the switching transistor is composed of a combination of a non-zero vector state and a zero vector state, wherein the non-zero vector state includes a non-zero vector one state and a non-zero vector two state;

[0015] The zero vector state includes zero vector state one and zero vector state two. When both the upper and lower arms of a certain phase bridge arm are turned on, and the upper and lower arms of the remaining bridge arms are turned off, this zero vector state is called zero vector state one. When all the upper and lower arms of all bridge arms are turned off, the diodes... D 7. D When 8 is turned on, the zero vector state is called the zero vector two state.

[0016] Preferably, the duty cycle of the non-zero vector-1 state is set to... D a The duty cycle of the non-zero vector in two states is D b The duty cycle of the zero vector in state one is D d The duty cycle of the zero vector in two states is D e The four duty cycles mentioned satisfy: D a + D b + D d + D e =1.

[0017] Preferably, the non-zero vector-state duty cycle ,in M In order to adjust the system, v a for A Phase input voltage, V m Peak values ​​of three-phase input phase voltages; non-zero vector two-state duty cycle. ,in v b for B Phase input voltage; zero vector two-state duty cycle ,in D Given a duty cycle, and D <1- M ;

[0018] According to the volt-second balance: ,in v ac The output voltage of the non-zero vector one-state three-phase rectifier bridge module. v bc The output voltage of the non-zero vector two-state three-phase rectifier bridge module. V o For output voltage, D d The duty cycle of a zero vector in state 1;

[0019] The formula obtained from the volt-second balance and D a , D b and D e The formula is obtained by combining the formulas. .

[0020] Compared with the prior art, the advantages of the present invention are:

[0021] (1) The rectifier of the present invention adopts a single-stage topology structure, which uses fewer components and reduces material costs;

[0022] (2) Combining the DC-side switching inductor module and the modulation method of the rectifier in this invention, the zero vector state of the rectifier in this invention is divided into two parts compared with the traditional three-phase PWM rectifier: zero vector state one and zero vector state two, thereby achieving a lower output voltage, i.e., a high step-down ratio; each of the zero vector state one and zero vector state two corresponds to a duty cycle, which can effectively reduce the impact of the extreme duty cycle of the switching transistor on the system performance and enhance the stability and reliability of the system. Attached Figure Description

[0023] Figure 1 This is a circuit diagram of a high step-down ratio single-stage three-phase current-source PWM rectifier provided in an embodiment of the present invention;

[0024] Figure 2 This is a sector diagram of the three-phase input voltage of the topology in an embodiment of the present invention;

[0025] Figure 3 This is a schematic diagram of the topology driven during sector 2 in an embodiment of the present invention;

[0026] Figure 4 This is the first operating mode of the topology in sector 2 according to an embodiment of the present invention;

[0027] Figure 5 This is the second operating mode of the topology in sector 2 of this embodiment of the invention;

[0028] Figure 6 This is the third operating mode of the topology in sector 2 of this embodiment of the invention;

[0029] Figure 7 This is the fourth operating mode of the topology in sector 2 of this embodiment of the invention;

[0030] Figure 8 This is a table showing the duty cycle of vectors in different sectors of the topology in embodiments of the present invention;

[0031] Figure 9 This is a comparison chart of the voltage conversion ratio between a traditional three-phase current PWM rectifier and the topology of this invention embodiment;

[0032] Figure 10 The above describes the input voltage waveform and output voltage waveform of the topology in an embodiment of the present invention.

[0033] Figure 11 The input current waveform is shown in the topology of this embodiment of the invention.

[0034] Figure 12The waveform of the DC-side inductor current in an embodiment of the present invention is shown. Detailed Implementation

[0035] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0036] Example 1

[0037] like Figure 1 As shown, this embodiment presents a high buck ratio single-stage three-phase current-mode PWM rectifier topology based on a switched inductor, which includes an AC side filter module, a three-phase rectifier bridge module, and a DC side switched inductor module connected in sequence.

[0038] The three-phase rectifier bridge consists of three sets of bridge arms, namely... A Bridge arm, B Phase bridge arm and C Phase bridge arm, each phase bridge arm includes an upper bridge arm and a lower bridge arm, and each upper bridge arm and lower bridge arm is controlled by a switching transistor. Q i and a diode D i They are connected in series to achieve the conversion of three-phase alternating current to direct current.

[0039] Specifically, A The upper bridge arm is composed of switching transistors Q 1 and diode D 1. Series connection, A The lower bridge arm is composed of a switching transistor. Q 4 and diodes D Composed of 4 series, B The upper bridge arm is composed of switching transistors Q 3 and diodes D Composed of 3 series, B The lower bridge arm is composed of a switching transistor. Q 6 and diodes D Composed of 6 series, C The upper bridge arm is composed of switching transistors Q 5 and diodes D Composed of 5 series connections, C The lower bridge arm is composed of a switching transistor. Q 2 and diode D 2. Series connection; the diodes connected in series on the bridge arm play the role of preventing reverse current flow in the circuit.

[0040] The AC-side filtering module includes three filtering inductors: L a , L b , L c The filter inductor L a , L b , L c The input terminals are connected to the three phases of the three-phase power supply respectively; the filter inductor L a The other end and A Phase bridge arm connection, connection point located at A Between the upper and lower bridge arms, the filter inductor L b The other end and B Phase bridge arm connection, connection point located at B Between the upper and lower bridge arms, the filter inductor L c The other end and C Phase bridge arm connection, connection point located at C Between the upper and lower bridge arms. The AC side filter module also includes three filter capacitors: C a , C b , C c Filter capacitor C a , C b , C c One end is connected to the filter capacitor. C a The other end is connected to the filter inductor L a The output terminal, filter capacitor C b The other end is connected to the filter inductor L b The output terminal, filter capacitor C c The other end is connected to the filter inductor L c The output terminal. Three filter capacitors. C a , C b , C c and three filter inductors L a , L b, L c The composition LC The filter is used to filter out current ripple on the AC side.

[0041] The DC-side switching inductor module consists of an inductor. L p ,inductance L n ,diode D 7 and diodes D Composed of 8 components, diodes D The anode of 7 is connected to the inductor L n On the right side, diode D The cathode of 7 is connected to the inductor L p On the left side, diode D The anode of 8 is connected to the inductor L n On the left side, diode D The cathode of 8 is connected to the inductor L p On the right side, diode D 7 and inductance L n The intersection and diode on the right side D 8 and inductance L p The intersections on the right are connected to the two ends of the output capacitor, and the diode... D 7 and inductance L p The intersection and diode on the left side D 8 and inductance L n The intersections on the left are connected to the two ends of the output side of the three-phase rectifier bridge module.

[0042] The output terminal and output capacitor of the DC-side switching inductor module C Connect the two ends of 0, capacitor C 0 and load R L in parallel.

[0043] The high step-down ratio single-stage three-phase current-mode PWM rectifier of the present invention adopts a single-stage topology, with a simple circuit structure, fewer components, and low material cost.

[0044] Example 2

[0045] Corresponding to Embodiment 1 of the present invention, this embodiment provides a modulation method for a high buck ratio single-stage three-phase current-source PWM rectifier, the modulation method comprising:

[0046] See Figure 2In this embodiment, a twelve-sector SVPWM modulation is used to modulate the high buck ratio single-stage three-phase current-type PWM rectifier. The voltage within one input cycle of the rectifier is divided into twelve sectors. Specifically, when the three-phase input voltage meets the following conditions... v a >0> v b > v c The time is defined as the first sector, where v a express A Phase input voltage, v b express B Phase input voltage, v c express C Three-phase input voltage; when the three-phase input voltage satisfies v a > v b >0> v c The second sector is defined as the time when the three-phase input voltage satisfies... v b > v a >0> v c The third sector is defined as the three-phase input voltage when it satisfies the following conditions. v b >0> v a > v c The fourth sector is defined as the three-phase input voltage when it satisfies the following conditions. v b >0> v c > v a The fifth sector is defined as the time when the three-phase input voltage satisfies... v b > v c >0> v a The time is defined as the sixth sector; when the three-phase input voltage satisfies v c > v b >0> v a The term is defined as the seventh sector; when the three-phase input voltage satisfies... v c >0> v b > va The term is defined as the eighth sector; when the three-phase input voltage satisfies... v c >0> v a > v b The term is defined as the ninth sector; when the three-phase input voltage satisfies... v c > v a >0> v b The time is defined as the tenth sector; when the three-phase input voltage satisfies v a > v c >0> v b The time is defined as the eleventh sector; when the three-phase input voltage satisfies v a >0> v c > v b The time is defined as the twelfth sector, where each sector corresponds to two specific non-zero current vectors and two zero vectors.

[0047] This embodiment uses the second sector ( v a > v b >0> v c The following explanation will be given using an example:

[0048] See Figure 3 This refers to the on / off state of each switch on the three-phase bridge arm in the topology of this invention during the second sector. The on / off state of the switches on the same bridge arm is always the same. During the second sector, the bridge arm has four different operating modes, specifically:

[0049] See Figure 4 During mode one, A Phase upper bridge arm (consisting of switching transistors) Q 1 and diode D 1. Composed in series) and C The lower bridge arm (composed of the switching transistor) Q 2 and diode D (2-unit series connection) When the diode is turned on, the other four bridge arms are turned off. At this time, the diode... D 7 and diodes D 8. The transistor is cut off when it withstands reverse voltage, and current flows through the switching transistor. Q 1. Diode D 1. Inductor L p Load end, inductorL n ,diode D 2 and switching transistor Q 2. Inductance L p and L n Series charging;

[0050] See Figure 5 During mode two, B Phase upper bridge arm (consisting of switching transistors) Q 3 and diodes D (3 series) and C The lower bridge arm (composed of the switching transistor) Q 2 and diode D (2-unit series connection) When the diode is turned on, the other four bridge arms are turned off. At this time, the diode... D 7 and diodes D 8. The transistor is cut off when it withstands reverse voltage, and current flows through the switching transistor. Q 3. Diode D 3. Inductance L p Load end, inductor L n ,diode D 2 and switching transistor Q 2. Inductance L p and L n Still connected in series for charging;

[0051] See Figure 6 During mode three, B Phase upper bridge arm (consisting of switching transistors) Q 3 and diodes D (3 series) and B The lower bridge arm (composed of the switching transistor) Q 6 and diodes D The diode (composed of 6 series arms) is turned on, while the other four bridge arms are turned off. D 7 and diodes D 8. The transistor is cut off when it withstands reverse voltage, and current flows through the switching transistor. Q 3. Diode D 3. Inductance L p Load end, inductor L n ,diode D 6 and switching transistors Q 6. Forming a freewheeling circuit in a direct-flow state, inductor L p and L n Series discharge;

[0052] See Figure 7 During mode four, all six bridge arms are in the off state, and the diodes... D 7 and diodes D 8. When subjected to a positive voltage, the inductor conducts, and current flows through it. L p ,diode D 7. Inductance L n ,diode D 8 and the load terminal form a freewheeling circuit, inductor L p and L n Parallel discharge.

[0053] It should be noted that bridge arm conduction and switching transistor conduction are not the same concept. Bridge arm conduction or cutoff is jointly controlled by the states of the switching transistor and diode. For example: when A Switching transistor of upper bridge arm Q 1 and diode D When all 1 are conducting, A Phase upper bridge arm conducts, switching transistor Q 1 and diode D 1. When only one is on or both are off, A The bridge arm is shut off.

[0054] Different current vectors can be generated depending on the different combinations of switching transistors and diodes on the three-phase bridge arms of the rectifier. Within each sector, the switching state of the switching transistor is composed of a combination of non-zero vector states and zero vector states.

[0055] In a traditional three-phase current-source PWM rectifier, the switching states of the MOSFETs include a non-zero vector one state, a non-zero vector two state, and a zero vector state. The non-zero vector one and non-zero vector two states of this invention are consistent with those of a traditional three-phase current-source rectifier. The difference is that the zero vector state during operation in this invention is divided into two parts: zero vector one state and zero vector two state. In this case, both the upper and lower arms of a certain phase bridge arm are conducting, and the inductor... L p and L n During series discharge, it is called the zero vector one state, where all bridge arms are turned off and the freewheeling diode... D 7. D 8 conducts, inductor L p and L n The parallel discharge is called the zero vector two state.

[0056] Make the inductor L p and Ln The inductance value L When all bridge arms are turned off, the freewheeling diode... D 7. D 8 conducts, inductor L p and L n Parallel connection, that is, when entering the zero vector two state, the total inductance is At this time, the total inductance on the DC side changes from 2 L Descending to L / 2, the total inductance value changes within one operating cycle.

[0057] Adjustment system M Combined with the three-phase input voltage, the duty cycle of the three-phase reference vector in different sectors can be obtained. In this embodiment, the duty cycle is given. D Its value is less than 1- M And with a certain margin. Combined with Figure 8 This table shows the vector action time duty cycle of the topology in different sectors in this embodiment. I 1 indicates the switching transistor Q 1. Q 2. The non-zero current vector corresponding to when the circuit is turned on; I 2 indicates the switching transistor. Q 2. Q 3. The non-zero current vector corresponding to when the circuit is turned on; I 3 indicates the switching transistor. Q 3. Q 4. The non-zero current vector corresponding to the conduction state; I 4 indicates the switching transistor. Q 4. Q 5. The non-zero current vector corresponding to when the circuit is turned on; I 5 indicates the switching transistor. Q 5. Q 6. The non-zero current vector corresponding to when the circuit is turned on; I 6 indicates a switching transistor Q 6. Q 1. The non-zero current vector corresponding to when the circuit is turned on; I 01 This represents the zero vector corresponding to when the upper and lower bridge arms in phase are conducting. I 02 Indicates diode D 7 and D The zero vector corresponding to when 8 is on and all other devices are off. I 02 The duty cycle of the action is always 1- M - D .

[0058] For the DC-side inductor of a traditional three-phase current-source PWM rectifier Lp Analysis: Let the duty cycle of the non-zero vector in state one be... D a The duty cycle of the non-zero vector in two states is D b The duty cycle of the zero vector state is D c , D a + D b + D c =1, v ac The output voltage of the non-zero vector one-state three-phase rectifier bridge module. v bc The output voltage of the non-zero vector two-state three-phase rectifier bridge module. V o For output voltage, V m The peak value of the three-phase input phase voltage is given, where the relationship between the duty cycle and the modulation index is as follows:

[0059] (1)

[0060] (2)

[0061] According to the volt-second balance, we can obtain:

[0062] (3)

[0063] From equations (1), (2), and (3), we can obtain:

[0064] (4)

[0065] DC-side inductor of the topology in the embodiment of the present invention L p Analysis: Let the duty cycle of the non-zero vector in state one be... D a The duty cycle of the non-zero vector in two states is D b The duty cycle of the zero vector in state one is D d The duty cycle of the zero vector in two states is D e , D a + D b + D e + D d =1, v acThe output voltage of the non-zero vector one-state three-phase rectifier bridge module. v bc The output voltage of the non-zero vector two-state three-phase rectifier bridge module. V 0 represents the output voltage. V m The peak value of the three-phase input phase voltage is given, where the relationship between the duty cycle and the modulation index is as follows:

[0066] (5)

[0067] (6)

[0068] (7)

[0069] According to the volt-second balance, we can conclude that:

[0070] (8)

[0071] From equations (5), (6), (7), and (8), we can obtain:

[0072] (9)

[0073] Comparing equations (4) and (9), it can be seen that, under the same input voltage, the output voltage of the topology in this embodiment is 2- lower than that of a conventional three-phase current-type PWM rectifier. M - D The step-down ratio of the topology of this invention is higher than that of the traditional three-phase current-source PWM rectifier.

[0074] See Figure 9 This is a comparison diagram of the voltage conversion ratio of a traditional three-phase current-source PWM rectifier and the topology of this invention. Let... V o / V m For voltage conversion ratio, by Figure 9 It can be seen that, under the same input voltage, the voltage conversion ratio of the topology of the present invention is less than that of the traditional three-phase current-type PWM rectifier.

[0075] This embodiment further performs open-loop simulation under the following conditions: effective value of three-phase input phase voltage is 220V, switching frequency is 50kHz, output power is 1.5kW, and given duty cycle. D The value is 0.1, and the simulation results are analyzed as follows:

[0076] See Figure 10Figure 1 shows the input voltage waveform and output waveform of the topology in this embodiment of the invention. As shown, the output voltage is 239V, and the calculated voltage conversion ratio is 0.7681. Under the same input conditions, the output voltage of the three-phase current-type PWM rectifier is 300V, and the calculated voltage conversion ratio is 0.9642. The simulation results show that the topology in this embodiment has a lower voltage conversion ratio.

[0077] See Figure 11 and Figure 12 The waveforms are the input current waveform and the DC-side inductor current waveform of the topology in this embodiment, respectively. It can be observed that the sinusoidal nature of the input current is good and the inductor current waveform is continuous.

[0078] Compared to traditional three-phase current-mode PWM rectifiers, this invention achieves a lower output voltage under the same input conditions. It optimizes the voltage gain from the topology, effectively improving the buck ratio and mitigating the impact of extreme duty cycles of the switching transistors on system performance, thus enhancing system stability and reliability. Furthermore, this invention performs better under high-voltage input and low-voltage high-current output conditions, effectively solving the problems of traditional rectifiers under high buck ratio conditions.

[0079] The above embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit it. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A high step-down ratio single-stage three-phase current-source PWM rectifier, characterized in that, It includes an AC-side filter module, a three-phase rectifier bridge module, and a DC-side switching inductor module, which are connected in sequence. The DC-side switching inductor module includes an inductor. L p ,inductance L n ,diode D 7 and diodes D 8; the diode D 7 Anode and Inductance L n One end is connected to the inductor. L n The other end is connected to a diode. D The anode of 8; the diode D The cathode of 8 is connected to the inductor. L p One end of the inductor L p The other end is connected to a diode. D 7 cathode, diode D 7 Cathode and Inductor L p Connection points and diodes D 8. Anode and Inductance L n The connection points are respectively connected to the two ends of the output side of the three-phase rectifier bridge module; The three-phase rectifier bridge module includes three-phase bridge arms: A Mutually, B phase and C Each phase bridge arm includes an upper bridge arm and a lower bridge arm, and each upper bridge arm and lower bridge arm is controlled by a switching transistor. Q i and a diode D i Composed of series connections; The modulation method of the high step-down ratio single-stage three-phase current-source PWM rectifier is as follows: The rectifier is modulated using twelve-sector SVPWM modulation; based on the relative relationship of the three-phase input voltages, one voltage input cycle is divided into 12 sectors, when the three-phase input voltages meet the following conditions... v a >0> v b > v c The time is defined as the first sector, where v a express A Phase input voltage, v b express B Phase input voltage, v c express C Phase input voltage; when the three-phase input voltage satisfies v a > v b >0> v c The second sector is defined as the time when the three-phase input voltage satisfies... v b > v a >0> v c The third sector is defined as the three-phase input voltage when it satisfies the following conditions. v b >0> v a > v c The fourth sector is defined as the three-phase input voltage when it satisfies the following conditions. v b >0> v c > v a The fifth sector is defined as the time when the three-phase input voltage satisfies... v b > v c >0> v a The time is defined as the sixth sector; when the three-phase input voltage satisfies v c > v b >0> v a The term is defined as the seventh sector; when the three-phase input voltage satisfies... v c >0> v b > v a The term is defined as the eighth sector; when the three-phase input voltage satisfies... v c >0> v a > v b The term is defined as the ninth sector; when the three-phase input voltage satisfies... v c > v a >0> v b The time is defined as the tenth sector; when the three-phase input voltage satisfies v a > v c >0> v b The time is defined as the eleventh sector; when the three-phase input voltage satisfies v a >0> v c > v b The time is defined as the twelfth sector; Based on the on / off status of each switch and diode on the three-phase bridge arm in the second sector, the bridge arm exists in four different operating modes; when the second sector is in operating mode one... A upper bridge arm and C The lower bridge arm is conducting. A Lower bridge arm, B upper and lower bridge arms, C Phase upper bridge arm shut off; At this time, the diode D 7 and diodes D 8. The transistor is cut off when it withstands reverse voltage, and current flows through the switching transistor. Q 1. Diode D 1. Inductor L p Load end, inductor L n ,diode D 2 and switching transistor Q 2. Inductance L p and L n Series charging; when the second sector is in operating mode two, B upper bridge arm and C The lower bridge arm is conducting. A upper and lower bridge arms, B Lower bridge arm and C Phase upper bridge arm shut off; At this time, the diode D 7 and diodes D 8. The transistor is cut off when it withstands reverse voltage, and current flows through the switching transistor. Q 3. Diode D 3. Inductance L p Load end, inductor L n ,diode D 2 and switching transistor Q 2. Inductance L p and L n Still connected in series for charging; when the second sector is in operating mode three, B The upper and lower bridge arms are conducting. A upper and lower bridge arms C The upper and lower bridge arms are turned off; at this time, the diode... D 7 and diodes D 8. The transistor is cut off when it withstands reverse voltage, and current flows through the switching transistor. Q 3. Diode D 3. Inductance L p Load end, inductor L n ,diode D 6 and switching transistor Q 6. Forming a freewheeling circuit in a direct-flow state, inductor L p and L n Series discharge; the second sector is in operating mode four. A upper and lower bridge arms, B upper and lower bridge arms C Both upper and lower bridge arms are turned off, diode D 7 and diodes D 8. When subjected to a positive voltage, the inductor conducts, and current flows through it. L p ,diode D 7. Inductance L n ,diode D 8 and the load terminal form a freewheeling circuit, inductor L p and L n Parallel discharge.

2. The high step-down ratio single-stage three-phase current-source PWM rectifier according to claim 1, characterized in that, The AC-side filtering module includes three filtering inductors: L a , L b , L c The filter inductor L a , L b , L c The input terminals are connected to the three phases of the three-phase power supply respectively; the filter inductor L a The other end and A Phase bridge arm connection, connection point located at A Between the upper and lower bridge arms, the filter inductor L b The other end and B Phase bridge arm connection, connection point located at B Between the upper and lower bridge arms, the filter inductor L c The other end and C Phase bridge arm connection, connection point located at C Between the upper and lower bridge arms.

3. A high step-down ratio single-stage three-phase current-source PWM rectifier according to claim 2, characterized in that, The AC side filtering module also includes three filtering capacitors: C a , C b , C c Filter capacitor C a , C b , C c One end is connected to the filter capacitor. C a The other end is connected to the filter inductor L a The output terminal, filter capacitor C b The other end is connected to the filter inductor L b The output terminal, filter capacitor C c The other end is connected to the filter inductor L c The output terminal.

4. A modulation method for a high buck ratio single-stage three-phase current-source PWM rectifier, characterized in that, Based on any one of claims 1-3, a high step-down ratio single-stage three-phase current-type PWM rectifier is provided, wherein the rectifier is modulated using twelve-sector SVPWM modulation; according to the relative relationship of the three-phase input voltages, one voltage input cycle is divided into 12 sectors, and when the three-phase input voltages meet the requirements... v a >0> v b > v c The time is defined as the first sector, where v a express A Phase input voltage, v b express B Phase input voltage, v c express C Phase input voltage; when the three-phase input voltage satisfies v a > v b >0> v c The second sector is defined as the time when the three-phase input voltage satisfies... v b > v a >0> v c The third sector is defined as the three-phase input voltage when it satisfies the following conditions. v b >0> v a > v c The fourth sector is defined as the three-phase input voltage when it satisfies the following conditions. v b >0> v c > v a The fifth sector is defined as the time when the three-phase input voltage satisfies... v b > v c >0> v a The time is defined as the sixth sector; when the three-phase input voltage satisfies v c > v b >0> v a The term is defined as the seventh sector; when the three-phase input voltage satisfies... v c >0> v b > v a The term is defined as the eighth sector; when the three-phase input voltage satisfies... v c >0> v a > v b The term is defined as the ninth sector; when the three-phase input voltage satisfies... v c > v a >0> v b The time is defined as the tenth sector; when the three-phase input voltage satisfies v a > v c >0> v b The time is defined as the eleventh sector; when the three-phase input voltage satisfies v a >0> v c > v b The time is defined as the twelfth sector; Based on the on / off status of each switch and diode on the three-phase bridge arm in the second sector, the bridge arm exists in four different operating modes; when the second sector is in operating mode one... A upper bridge arm and C The lower bridge arm is conducting. A Lower bridge arm, B upper and lower bridge arms, C Phase upper bridge arm shut off; At this time, the diode D 7 and diodes D 8. The transistor is cut off when it withstands reverse voltage, and current flows through the switching transistor. Q 1. Diode D 1. Inductor L p Load end, inductor L n ,diode D 2 and switching transistor Q 2. Inductance L p and L n Series charging; when the second sector is in operating mode two, B upper bridge arm and C The lower bridge arm is conducting. A upper and lower bridge arms, B Lower bridge arm and C Phase upper bridge arm shut off; At this time, the diode D 7 and diodes D 8. The transistor is cut off when it withstands reverse voltage, and current flows through the switching transistor. Q 3. Diode D 3. Inductance L p Load end, inductor L n ,diode D 2 and switching transistor Q 2. Inductance L p and L n Still connected in series for charging; when the second sector is in operating mode three, B The upper and lower bridge arms are conducting. A upper and lower bridge arms C The upper and lower bridge arms are turned off; at this time, the diode... D 7 and diodes D 8. The transistor is cut off when it withstands reverse voltage, and current flows through the switching transistor. Q 3. Diode D 3. Inductance L p Load end, inductor L n ,diode D 6 and switching transistor Q 6. Forming a freewheeling circuit in a direct-flow state, inductor L p and L n Series discharge; the second sector is in operating mode four. A upper and lower bridge arms, B upper and lower bridge arms C Both upper and lower bridge arms are turned off, diode D 7 and diodes D 8. When subjected to a positive voltage, the inductor conducts, and current flows through it. L p ,diode D 7. Inductance L n ,diode D 8 and the load terminal form a freewheeling circuit, inductor L p and L n Parallel discharge.

5. The modulation method according to claim 4, characterized in that, When the bridge arm is in different operating modes, it generates different current vectors. In each sector, the switching state of the switching transistor is composed of a combination of non-zero vector state and zero vector state. Among them, the non-zero vector state includes non-zero vector state one and non-zero vector state two. Zero vector states include zero vector state one and zero vector state two. Zero vector state one occurs when both upper and lower bridge arm switches of a certain phase bridge arm are on, and the upper and lower bridge arms of the remaining bridge arms are off. When all upper and lower bridge arms are off, the diodes... D 7. D When 8 is turned on, the zero vector state is called the zero vector two state.

6. The modulation method according to claim 5, characterized in that, The duty cycle of the non-zero vector-1 state is set as follows: D a The duty cycle of the non-zero vector in two states is D b The duty cycle of the zero vector in state one is D d The duty cycle of the zero vector in two states is D e The four duty cycles mentioned satisfy: D a + D b + D d + D e =1.

7. The modulation method according to claim 6, characterized in that, The non-zero vector-state duty cycle ,in M In order to adjust the system, v a for A Phase input voltage, V m Peak values ​​of three-phase input phase voltages; non-zero vector two-state duty cycle. ,in v b for B Phase input voltage; Zero vector two-state duty cycle ,in D Given a duty cycle, and D <1- M ; According to the volt-second balance: ,in v ac The output voltage of the non-zero vector one-state three-phase rectifier bridge module. v bc The output voltage of the non-zero vector two-state three-phase rectifier bridge module. V o For output voltage, D d The duty cycle of a zero vector in state 1; The formula obtained from the volt-second balance and D a , D b and D e The formula is obtained by combining the formulas. .

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