High step-down ratio single-stage three-phase current type PWM rectifier and modulation strategy thereof

Abstract

The invention discloses a single-stage three-phase current type PWM rectifier with a high step-down ratio. The single-stage three-phase current type PWM rectifier comprises an alternating-current side filtering module, a three-phase rectifier bridge module and a direct-current side switch inductance module which are connected in sequence, the direct current side switch inductance module comprises an inductor Lp, an inductor Ln, a diode D7 and a diode D8; the anode of the diode D7 is connected with one end of the inductor Ln, and the other end of the inductor Ln is connected to the anode of the diode D8; the cathode of the diode D8 is connected to one end of the inductor Lp, the other end of the inductor Lp is connected to the cathode of the diode D7, and the intersection point of the cathode of the diode D7 and the inductor Lp and the intersection point of the anode of the diode D8 and the inductor Ln are connected to the two ends of the output side of the three-phase rectifier bridge module respectively. According to the rectifier, a zero vector state is divided into two parts by utilizing the direct current side switch inductance module and a modulation strategy, so that lower output voltage can be realized, a high step-down ratio can be obtained, the influence of an extreme duty ratio of a switch tube on system performance can be effectively reduced, and the stability and the reliability of a system are enhanced.

Description

Technical Field

[0001] The invention relates to the field of rectifiers, and in particular to a high step-down ratio single-stage three-phase current-type PWM rectifier and a modulation strategy thereof. Background Art

[0002] At present, three-phase PWM rectifiers are mainly divided into two categories: three-phase current-type PWM rectifiers and three-phase voltage-type PWM rectifiers. Among them, the three-phase voltage-type PWM rectifier is a boost converter with the advantages of stable output voltage and high energy conversion rate; the three-phase current-type PWM rectifier is a buck converter with the advantages of sinusoidal grid-side current and high reliability. Both of the above converters have good development prospects in the fields of electric vehicle battery chargers, battery charging and discharging devices, and water electrolysis for hydrogen production.

[0003] With the development of the power electronics industry, the research on three-phase buck converters with high step-down ratio and high reliability has gradually become a hot topic. In situations where a high step-down ratio, low voltage and high current are required, the traditional three-phase PWM rectifier still has the following defects: First, if you want to obtain a lower output voltage, the switch tube of the traditional three-phase current-type PWM rectifier will work at an extreme duty cycle, causing the switch tube to be subjected to extremely high current stress, and the diode will have a reverse recovery problem, which will affect the rectifier's regulation ability and efficiency; second, although the three-phase voltage-type PWM rectifier has a simple structure and a boost function, to reduce the output voltage, an additional cascaded buck DC / DC converter is usually required. For example, the patent publication number is: CN117175943A, which discloses a new type of negative voltage output soft switch high step-down ratio converter, including a PWM module and a closed-loop control module. The closed-loop control module also includes a PI controller, a DC / DC converter, etc. The PWM module is used to receive a control signal and adjust the duty cycle to convert it into a drive signal. The DC / DC converter receives the drive signal and then performs voltage conversion. Although it can improve the step-down 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 to be solved by the present invention is how to enable a three-phase current-source PWM rectifier to achieve a high step-down ratio while improving the extreme duty cycle of its switch tube.

[0005] The present invention solves the above problems by 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 switch inductor module, which are connected in sequence;

[0006] The DC side switch inductor module includes an inductor L p 、Inductance L n, diode D7 and diode D8; the anode of the diode D7 and the inductor L n One end of the inductor L n The other end is connected to the anode of the diode D8; the cathode of the diode D8 is connected to the inductor L p One end of the inductor L p The other end is connected to the cathode of diode D7, and the cathode of diode D7 is connected to the inductor L p The intersection point of the connection and the anode of diode D8 and inductor L n The intersection points of the connections are 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: phase A, phase B and phase C, each phase bridge arm includes an upper bridge arm and a lower bridge arm, each upper bridge arm and lower bridge arm is composed of a switch tube Q i and a diode D i Series composition.

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

[0009] Preferably, 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 of the filter capacitor C a The other end is connected to the filter inductor L a At the output end, the filter capacitor C b The other end of the filter inductor L b At the output end, the filter capacitor C c The other end is connected to the filter inductor L c The output terminal.

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

[0011] The present invention also provides a modulation strategy applied to the above-mentioned high step-down ratio single-stage three-phase current-source PWM rectifier, and the modulation strategy includes: using twelve-sector SVPWM modulation to modulate the rectifier.

[0012] Preferably, according to the relative relationship of the three-phase input voltage, a voltage input cycle is divided into 12 sectors. When the three-phase input voltage satisfies v a >0>v b >v c The first sector is defined as v a Indicates the A phase input voltage, v b Indicates the B phase input voltage, v c Indicates the C phase input voltage; when the three-phase input voltage meets v a >v b >0>v c It is defined as the second sector; when the three-phase input voltage meets v b >v a >0>v c It is defined as the third sector; when the three-phase input voltage meets v b >0>v a >v c It is defined as the fourth sector; when the three-phase input voltage meets v b >0>v c >v a It is defined as the fifth sector; when the three-phase input voltage meets v b >v c >0>v a It is defined as the sixth sector; when the three-phase input voltage meets v c >v b >0>v a It is defined as the seventh sector; when the three-phase input voltage meets v c >0>v b >v a It is defined as the eighth sector; when the three-phase input voltage meets v c >0>v a >v b It is defined as the ninth sector; when the three-phase input voltage meets v c >v a >0>v b It is defined as the tenth sector; when the three-phase input voltage meets v a >vc >0>v b It is defined as the eleventh sector; when the three-phase input voltage meets v a >0>v c >v b It is defined as the twelfth sector.

[0013] Preferably, according to the on and off conditions of each switch tube and diode on the three-phase bridge arm in the second sector, the bridge arm has four different working modes; when the second sector is in working mode one, the upper bridge arm of phase A and the lower bridge arm of phase C are turned on, and the lower bridge arm of phase A, the upper and lower bridge arms of phase B, and the upper bridge arm of phase C are turned off; when the second sector is in working mode two, the upper bridge arm of phase B and the lower bridge arm of phase C are turned on, and the upper and lower bridge arms of phase A, the lower bridge arm of phase B, and the upper bridge arm of phase C are turned off; when the second sector is in working mode three, the upper and lower bridge arms of phase B are turned on, and the upper and lower bridge arms of phase A and the upper and lower bridge arms of phase C are turned off; when the second sector is in working mode four, the upper and lower bridge arms of phase A, the upper and lower bridge arms of phase B, and the upper and lower bridge arms of phase C are all turned off.

[0014] Preferably, when the bridge arm is in different working modes, different current vectors are generated, and the current vectors include non-zero vectors and zero vectors; in each sector, the switching state of the switch tube is composed of a non-zero vector state and a zero vector state, wherein the non-zero vector state includes a non-zero vector state 1 and a non-zero vector state 2;

[0015] The zero vector state includes a zero vector state one and a zero vector state two. When the upper and lower bridge arm switches of a certain phase bridge arm are turned on and the upper and lower bridge arms of the remaining bridge arms are turned off, the zero vector state is called the zero vector state one. When the upper and lower bridge arms of all bridge arms are turned off and diodes D7 and D8 are turned on, the zero vector state is called the zero vector state two.

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

[0017] Preferably, the non-zero vector-state duty cycle Where M is the modulation index, v a is the A phase input voltage, V m is the peak value of the three-phase input phase voltage; non-zero vector two-state duty cycle where v b is the B phase input voltage; zero vector two-state duty cycle De =1-MD, where D is a given duty cycle, and D<1-M;

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

[0019] The formula obtained from the volt-second balance and D a , D b With D e Combining the formula

[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, uses a small number of components, and reduces material costs;

[0022] (2) By combining the DC side switching inductor module and the modulation strategy of the rectifier in the rectifier of the present invention, compared with the traditional three-phase PWM rectifier, the zero vector state of the rectifier of the present invention is divided into two parts: zero vector state 1 and zero vector state 2, thereby achieving a lower output voltage, that is, a high step-down ratio can be obtained; the zero vector state 1 and the zero vector state 2 each correspond to a duty cycle, which can effectively reduce the influence of the extreme duty cycle of the switch tube on the system performance, thereby enhancing the stability and reliability of the system. BRIEF DESCRIPTION OF THE DRAWINGS

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

[0024] Figure 2 The sector division diagram of the topological three-phase input voltage of the embodiment of the present invention;

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

[0026] Figure 4 The working mode 1 of the topology during sector 2 of the embodiment of the present invention;

[0027] Figure 5 This is the working mode 2 of the topology during sector 2 of the embodiment of the present invention;

[0028] Figure 6 This is working mode 3 of the topology during sector 2 of the embodiment of the present invention;

[0029] Figure 7 This is working mode 4 of the topology during sector 2 of the embodiment of the present invention;

[0030] Figure 8 The table of action time duty ratios of vectors in different sectors of topology according to an embodiment of the present invention;

[0031] Fig. 9 A comparison diagram of the voltage conversion ratio between a conventional three-phase current PWM rectifier and the topology of an embodiment of the present invention;

[0032] Fig.10 The topology input voltage waveform and output voltage waveform of the embodiment of the present invention;

[0033] Fig.11 The topological input current waveform of the embodiment of the present invention;

[0034] Fig.12 This is the inductor current waveform of the DC side topology of the embodiment of the present invention. DETAILED DESCRIPTION

[0035] In order to make the purpose, technical solution and advantages of the embodiments of the present invention clearer, the technical solution in the embodiments of the present invention will be clearly and completely described below in combination with the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. 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.

[0036] Example 1

[0037] like Figure 1 As shown, a high step-down ratio single-stage three-phase current-source PWM rectifier topology structure based on a switching inductor in this embodiment includes an AC side filter module, a three-phase rectifier bridge module, and a DC side switching inductor module, which are connected in sequence;

[0038] The three-phase rectifier bridge is composed of three groups of bridge arms, namely, the A-phase bridge arm, the B-phase bridge arm and the C-phase bridge arm. Each phase bridge arm includes an upper bridge arm and a lower bridge arm. Each upper bridge arm and the lower bridge arm are composed of a switch tube Q i and a diode D i They are connected in series to realize the conversion of three-phase AC to DC.

[0039] Specifically, the upper bridge arm of phase A is composed of a switch tube Q1 and a diode D1 connected in series, the lower bridge arm of phase A is composed of a switch tube Q4 and a diode D4 connected in series, the upper bridge arm of phase B is composed of a switch tube Q3 and a diode D3 connected in series, the lower bridge arm of phase B is composed of a switch tube Q6 and a diode D6 connected in series, the upper bridge arm of phase C is composed of a switch tube Q5 and a diode D5 connected in series, and the lower bridge arm of phase C is composed of a switch tube Q2 and a diode D2 connected in series; the diodes connected in series on the bridge arms play a role in preventing reverse current from flowing in the circuit.

[0040] The AC side filter module includes three filter inductors: L a , L b , L c , the filter inductor L a , L b , L c The input end is connected to the three phases of the three-phase power supply respectively; the filter inductor L a The other end is connected to the A-phase bridge arm, and the connection point is located between the upper bridge arm and the lower bridge arm of the A-phase. The filter inductor L b The other end is connected to the B-phase bridge arm, and the connection point is located between the upper bridge arm and the lower bridge arm of the B-phase. The filter inductor L c The other end is connected to the C-phase bridge arm, and the connection point is located between the upper bridge arm and the lower bridge arm of the C-phase. 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 of the filter capacitor C a The other end is connected to the filter inductor L a At the output end, the filter capacitor C b The other end is connected to the filter inductor L b At the output end, the filter capacitor C c The other end is connected to the filter inductor L c The output terminal of the three filter capacitors C a , C b , C c And three filter inductors L a , L b , L c The LC filter formed is used to filter out the current ripple on the AC side.

[0041] The DC side switch inductor module consists of an inductor L p 、Inductance L n , diode D7 and diode D8, the anode of diode D7 is connected to the inductor L n On the right side, the cathode of diode D7 is connected to the inductor L pOn the left side, the anode of diode D8 is connected to the inductor L n On the left side, the cathode of diode D8 is connected to the inductor L p On the right side, diode D7 and inductor L n The intersection point on the right and the diode D8 and inductor L p The intersection on the right is connected to the two ends of the output capacitor, the diode D7 and the inductor L p The intersection point on the left and the diode D8 and inductor L n The intersection points on the left are respectively connected to the two ends of the output side of the three-phase rectifier bridge module.

[0042] The output end of the DC side switch inductor module is connected to the two ends of the output capacitor C0, and the capacitor C0 and the load R L in parallel.

[0043] The high step-down ratio single-stage three-phase current-type PWM rectifier of the present invention adopts a single-stage topological structure, has a simple circuit structure, uses a small number of components, and has low material cost.

[0044] Example 2

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

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

[0047] In this embodiment, the second sector (v a >v b >0>v c ) as an example to explain the following:

[0048] See also Figure 3 , is the on and off status of each switch tube on the three-phase bridge arm in the topology of the present invention during the second sector. The on and off status of the upper and lower switches of the same bridge arm are always the same. During the second sector, the bridge arm has four different working modes, specifically:

[0049] See also Figure 4 During mode 1, the upper bridge arm of phase A (consisting of switch tube Q1 and diode D1 in series) and the lower bridge arm of phase C (consisting of switch tube Q2 and diode D2 in series) are turned on, and the other four bridge arms are turned off. At this time, diodes D7 and D8 are cut off due to reverse voltage, and the current flows through switch tube Q1, diode D1, and inductor L. p , load end, inductor L n , diode D2 and switch tube Q2, inductor L p and L n Series charging;

[0050] See also Figure 5During mode 2, the upper bridge arm of phase B (consisting of switch tube Q3 and diode D3 in series) and the lower bridge arm of phase C (consisting of switch tube Q2 and diode D2 in series) are turned on, and the other four bridge arms are turned off. At this time, diodes D7 and D8 are cut off due to reverse voltage, and the current flows through switch tube Q3, diode D3, and inductor L. p , load end, inductor L n , diode D2 and switch tube Q2, inductor L p and L n Still charging in series;

[0051] See also Figure 6 During mode 3, the upper bridge arm of phase B (consisting of switch tube Q3 and diode D3 in series) and the lower bridge arm of phase B (consisting of switch tube Q6 and diode D6 in series) are turned on, and the other four bridge arms are turned off. At this time, diodes D7 and D8 are cut off due to reverse voltage, and the current flows through switch tube Q3, diode D3, and inductor L. p , load end, inductor L n , diode D6 and switch tube Q6, forming a freewheeling circuit in the direct-through state, and the inductor L p and L n Series discharge;

[0052] See also Figure 7 During mode 4, all six bridge arms are in the off state, diodes D7 and D8 are turned on by the forward voltage, and the current flows through the inductor L p , diode D7, inductor L n , diode D8 and the load end form a freewheeling circuit, and the inductor L p and L n Parallel discharge.

[0053] It should be noted that the conduction of the bridge arm and the conduction of the switch tube are not the same concept. The conduction or shutdown of the bridge arm is jointly controlled by the state of the switch tube and the diode. For example: when the switch tube Q1 and the diode D1 of the upper bridge arm of phase A are both turned on, the upper bridge arm of phase A is turned on. When only one of the switch tube Q1 and the diode D1 is turned on or both are turned off, the upper bridge arm of phase A is turned off.

[0054] Different current vectors can be generated according to the different combination states of the switch tubes and diodes on the three-phase bridge arm of the rectifier. In each sector, the switching state of the switch tube is a combination of a non-zero vector state and a zero vector state.

[0055] The switching states of the MOS tube in the traditional three-phase current-type PWM rectifier include a non-zero vector state 1, a non-zero vector state 2 and a zero vector state. The non-zero vector state 1 and the non-zero vector state 2 of the present invention are consistent with those of the traditional three-phase current-type rectifier. The difference is that the zero vector state of the present invention during operation is divided into two parts: zero vector state 1 and zero vector state 2. Among them, the upper and lower bridge arms of a certain phase are both turned on, and the inductor L p With L n The series discharge is called the zero vector state, all bridge arms are turned off, freewheeling diodes D7 and D8 are turned on, and the inductor L p and L n The parallel discharge is called the zero vector two state.

[0056] Let the inductance L p and L n The inductance value is L. When all bridge arms are turned off, the freewheeling diodes D7 and D8 are turned on, and the inductance L p and L n When connected in parallel, that is, when entering the zero vector 2 state, the total inductance At this time, the total inductance value of the DC side drops from 2L to L / 2, and the total inductance value changes within one operating cycle.

[0057] The modulation index M combined with the three-phase input voltage can obtain the action time duty ratio of the three-phase reference vector in different sectors. In this embodiment, the duty ratio D is given, and its value is less than 1-M, and a certain margin is left. Figure 8 , is a table of the vector action time duty cycle of the topology of this embodiment in different sectors, I1 represents the non-zero current vector corresponding to when the switches Q1 and Q2 are turned on; I2 represents the non-zero current vector corresponding to when the switches Q2 and Q3 are turned on; I3 represents the non-zero current vector corresponding to when the switches Q3 and Q4 are turned on; I4 represents the non-zero current vector corresponding to when the switches Q4 and Q5 are turned on; I5 represents the non-zero current vector corresponding to when the switches Q5 and Q6 are turned on; I6 represents the non-zero current vector corresponding to when the switches Q6 and Q1 are turned on; I 01 Indicates the zero vector corresponding to the conduction of the upper and lower bridge arms in the same phase; I 02 It represents the zero vector when diodes D7 and D8 are turned on and the other devices are turned off. 02 The action time duty cycle is always 1-MD.

[0058] The DC side inductor L of the traditional three-phase current-source PWM rectifier p Analysis: Assume that the duty cycle of a non-zero vector state is D a , the duty cycle of the non-zero vector two state is D b , the duty cycle of the zero vector state is D c , D a +D b +D c=1,v ac is the output voltage of the three-phase rectifier bridge module in a non-zero vector state, v bc is the non-zero vector two-state three-phase rectifier bridge module output voltage, V o is the output voltage, V m is the peak value of the three-phase input phase voltage, where the relationship between the duty cycle and the modulation index is:

[0059]

[0060] According to the volt-second balance, we can get:

[0061]

[0062] From formula (1), formula (2) and formula (3), we can get:

[0063]

[0064] The DC side inductor L of the topology of the embodiment of the present invention p Analysis: Assume that the duty cycle of a non-zero vector state is D a , the duty cycle of the non-zero vector two state is D b , the duty cycle of the zero vector state is D d , the zero vector two-state duty cycle is D e , D a +D b +D e +D d =1,v ac is the output voltage of the three-phase rectifier bridge module in a non-zero vector state, v bc is the output voltage of the non-zero vector two-state three-phase rectifier bridge module, V0 is the output voltage, V m is the peak value of the three-phase input phase voltage, where the relationship between the duty cycle and the modulation index is:

[0065]

[0066] D e =1-MD (7)

[0067] According to the volt-second balance, we can get:

[0068]

[0069] From equation (5), equation (6), equation (7) and equation (8), we can get:

[0070]

[0071] By comparing equation (4) with equation (9), it can be seen that, under the condition of equal input voltage, the output voltage of the topology of the embodiment of the present invention is reduced by 2-MD times compared with the output voltage of the traditional three-phase current-type PWM rectifier, that is, the step-down ratio of the topology of the present invention is higher than that of the traditional three-phase current-type PWM rectifier.

[0072] See also Fig. 9 , is a comparison diagram of the voltage conversion ratio between the conventional three-phase current-source PWM rectifier and the topology of the embodiment of the present invention, assuming that V o / V m is the voltage conversion ratio, given by Fig. 9 It can be seen that, under the condition of the same input voltage, the voltage conversion ratio of the topology of the embodiment of the present invention is smaller than the voltage conversion ratio of the traditional three-phase current-source PWM rectifier.

[0073] This embodiment further performs an open-loop simulation, and the simulation conditions are as follows: the effective value of the three-phase input phase voltage is 220V, the switching frequency is 50kHz, the output power is 1.5kW, and the given duty cycle D is 0.1. The simulation results are analyzed as follows:

[0074] See also Fig.10 , are the input voltage waveform and output waveform of the topology of the embodiment of the present invention. As shown in the figure, the output voltage value 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. It can be verified from the above simulation that the topology of this embodiment has a lower voltage conversion ratio.

[0075] See also Fig.11 and Fig.12 , which are respectively the input current waveform and the DC side inductor current waveform of the topology of this embodiment. It can be observed that the input current has good sinusoidality and the inductor current waveform is continuous.

[0076] Compared with the traditional three-phase current-type PWM rectifier, the present invention can achieve a lower output voltage under the same input conditions, optimizes the voltage gain from the topological structure, can effectively improve the step-down ratio, and effectively reduce the influence of the extreme duty cycle of the switch tube on the system performance, thereby enhancing the stability and reliability of the system. In addition, the present invention performs better under the conditions of high voltage input and low voltage and high current output, and can effectively solve the problems existing in traditional rectifiers under high step-down ratio conditions.

[0077] The above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit the same. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that the technical solutions described in the aforementioned embodiments may still be modified, or some of the technical features may be replaced by equivalents. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions 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 switch inductor module and they are connected in sequence; The DC side switch inductor module includes an inductor L p 、Inductance L n , diode D7 and diode D8; the anode of the diode D7 and the inductor L n One end of the inductor L n The other end is connected to the anode of the diode D8; the cathode of the diode D8 is connected to the inductor L p One end of the inductor L p The other end is connected to the cathode of diode D7, and the cathode of diode D7 is connected to the inductor L p The intersection point of the connection and the anode of diode D8 and inductor L n The intersection points of the connections are connected to the two ends of the output side of the three-phase rectifier bridge module.

2. A high step-down ratio single-stage three-phase current-source PWM rectifier according to claim 1, characterized in that: The three-phase rectifier bridge module includes three-phase bridge arms: phase A, phase B and phase C. Each phase bridge arm includes an upper bridge arm and a lower bridge arm. Each upper bridge arm and lower bridge arm is composed of a switch tube Q i and a diode D i Series composition.

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

4. A high step-down ratio single-stage three-phase current-source PWM rectifier according to claim 3, characterized in that: 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 of the filter capacitor C a The other end is connected to the filter inductor L a At the output end, the filter capacitor C b The other end is connected to the filter inductor L b At the output end, the filter capacitor C c The other end is connected to the filter inductor L c The output terminal.

5. The modulation strategy of the high step-down ratio single-stage three-phase current source PWM rectifier according to any one of claims 1 to 4, characterized in that: The rectifier is modulated using twelve-sector SVPWM modulation.

6. The modulation strategy according to claim 5, characterized in that: According to the relative relationship of the three-phase input voltage, a voltage input cycle is divided into 12 sectors. When the three-phase input voltage meets v a >0>v b >v c The first sector is defined as v a Indicates the A phase input voltage, v b Indicates the B phase input voltage, v c Indicates the C phase input voltage; when the three-phase input voltage meets v a >v b >0>v c It is defined as the second sector; when the three-phase input voltage meets v b >v a >0>v c It is defined as the third sector; when the three-phase input voltage meets v b >0>v a >v c It is defined as the fourth sector; when the three-phase input voltage meets v b >0>v c >v a It is defined as the fifth sector; when the three-phase input voltage meets v b >v c >0>v a It is defined as the sixth sector; when the three-phase input voltage meets v c >v b >0>v a It is defined as the seventh sector; when the three-phase input voltage meets v c >0>v b >v a It is defined as the eighth sector; when the three-phase input voltage meets v c >0>v a >v b It is defined as the ninth sector; when the three-phase input voltage meets v c >v a >0>v b It is defined as the tenth sector; when the three-phase input voltage meets v a >v c >0>v b It is defined as the eleventh sector; when the three-phase input voltage meets v a >0>v c >v b It is defined as the twelfth sector.

7. The modulation strategy according to claim 6, characterized in that: According to the on and off conditions of each switch tube and diode on the three-phase bridge arm in the second sector, the bridge arm has four different working modes; when the second sector is in working mode one, the upper bridge arm of phase A and the lower bridge arm of phase C are turned on, and the lower bridge arm of phase A, the upper and lower bridge arms of phase B, and the upper bridge arm of phase C are turned off; when the second sector is in working mode two, the upper bridge arm of phase B and the lower bridge arm of phase C are turned on, and the upper and lower bridge arms of phase A, the lower bridge arm of phase B, and the upper bridge arm of phase C are turned off; when the second sector is in working mode three, the upper and lower bridge arms of phase B are turned on, and the upper and lower bridge arms of phase A and the upper and lower bridge arms of phase C are turned off; when the second sector is in working mode four, the upper and lower bridge arms of phase A, the upper and lower bridge arms of phase B, and the upper and lower bridge arms of phase C are all turned off.

8. The modulation strategy according to claim 6, characterized in that: When the bridge arm is in different working modes, different current vectors are generated. In each sector, the switching state of the switch tube is composed of a non-zero vector state and a zero vector state, wherein the non-zero vector state includes a non-zero vector state 1 and a non-zero vector state 2. The zero vector state includes a zero vector state one and a zero vector state two. When the upper and lower bridge arm switches of a certain phase bridge arm are turned on and the upper and lower bridge arms of the remaining bridge arms are turned off, the zero vector state is called the zero vector state one. When the upper and lower bridge arms of all bridge arms are turned off and diodes D7 and D8 are turned on, the zero vector state is called the zero vector state two.

9. The modulation strategy according to claim 8, characterized in that: Set the non-zero vector state duty cycle to D a , the duty cycle of the non-zero vector two states is D b , the duty cycle of the zero vector state is D d , the zero vector two-state duty cycle is D e , the four duty ratios satisfy: D a +D b +D d +D e =1.

10. The modulation strategy according to claim 9, characterized in that: The non-zero vector-state duty cycle Where M is the modulation index, v a is the A phase input voltage, V m is the peak value of the three-phase input phase voltage; non-zero vector two-state duty cycle where v b is the B phase input voltage; Zero vector two-state duty cycle D e =1-MD, where D is a given duty cycle, and D<1-M; According to the volt-second balance: where v ac is the output voltage of the three-phase rectifier bridge module in a non-zero vector state, v bc is the non-zero vector two-state three-phase rectifier bridge module output voltage, V o is the output voltage, D d is the zero vector one state duty cycle; The formula obtained from the volt-second balance and D a , D b With D e Combining the formula

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