Power factor correction circuit and charger

Abstract

The invention discloses a power factor correction circuit and a charger, and relates to the technical field of new energy automobiles, a mode switching module, a first compensation switch and a first compensation capacitor are arranged in the power factor correction circuit, and when it is detected that a power supply connected with the mode switching module is a single-phase alternating current power supply, the first compensation switch and the first compensation capacitor are switched on and switched off. Controlling the mode switching module to enter a single-phase charging state, connecting a single-phase alternating current power supply to the three-phase bridge rectifier module, and controlling the first compensation switch to be closed, so that the three-phase bridge rectifier module works in the single-phase charging mode; and harmonic compensation is carried out on the output current of the three-phase bridge rectifier module through the first compensation capacitor and the rectifier bridge arm connected with the third alternating current end. According to the invention, the technical problem of how to reduce the second harmonic current in the output current of the PFC converter of the vehicle-mounted charger and ensure the power density of the PFC converter is solved.

Description

Technical Field

[0001] The present application relates to the technical field of new energy vehicles, and in particular to a power factor correction circuit and a charger. Background Art

[0002] The development trend of on-board chargers is to have the functions of single-phase charging, single-phase inverter, three-phase charging and three-phase discharge at the same time. Generally, a two-stage rectifier circuit is used, which combines a front-stage PFC (Power Factor Correction) converter with a rear-stage DC / DC converter. When the on-board charger works in single-phase charging mode, the instantaneous output power of the front-stage PFC converter pulsates at twice the power frequency, which will cause the presence of secondary harmonic current in the output current of the PFC converter.

[0003] In the related art, the second harmonic current is reduced by increasing the bus capacitance of the on-board charger, but the increase in the volume of the bus capacitance will lead to a decrease in the power density of the PFC converter. Therefore, how to reduce the second harmonic current in the output current of the on-board charger PFC converter and ensure the power density of the PFC converter needs to be solved urgently. Summary of the invention

[0004] The main purpose of this application is to propose a power factor correction circuit and a charger, aiming to solve the technical problem of how to reduce the secondary harmonic current in the output current of the PFC converter of the on-board charger and ensure the power density of the PFC converter.

[0005] To achieve the above object, the present application proposes a power factor correction circuit, which includes a mode switching module, a three-phase bridge rectifier module, a main control module, a first bus capacitor and a second bus capacitor connected in series, and a first compensation switch and a first compensation capacitor connected in series;

[0006] The three-phase bridge rectifier module includes a first AC end, a second AC end, a third AC end, a first DC end and a second DC end; the mode switching module is connected to the main control module, the first AC end, the second AC end and the third AC end respectively; the first compensation switch is also connected to the main control module, one end of the first compensation switch and the first compensation capacitor connected in series is connected to the third AC end, and the other end of the first compensation switch and the first compensation capacitor connected in series is connected to the second DC end; the common point of the first bus capacitor and the second bus capacitor forms a capacitor midpoint, one end of the first bus capacitor and the second bus capacitor connected in series is connected to the first DC end, and the other end of the first bus capacitor and the second bus capacitor connected in series is connected to the second DC end;

[0007] The main control module is used to control the mode switching module to enter a single-phase charging state when it is detected that the power supply connected to the mode switching module is a single-phase AC power supply, so that the live wire of the single-phase AC power supply is connected to the first AC terminal and the second AC terminal respectively, and the neutral line of the single-phase AC power supply is connected to the midpoint of the capacitor, and control the first compensation switch to be closed, so as to perform harmonic compensation on the output current of the three-phase bridge rectifier module through the first compensation capacitor and the target rectifier bridge arm connected to the third AC terminal.

[0008] In one embodiment, the target rectifier bridge arm includes an upper bridge switch tube and a lower bridge switch tube connected in series, and the wave generation timing of the upper bridge switch tube is complementary to the wave generation timing of the lower bridge switch tube;

[0009] The main control module is also used to control the duty cycle of the upper bridge switch tube to be greater than the duty cycle of the lower bridge switch tube when it is detected that the output current is greater than the reference current, and to control the duty cycle of the upper bridge switch tube to be less than the duty cycle of the lower bridge switch tube when the output current is less than the reference current.

[0010] In one embodiment, the main control module is also used to control the duty cycle of the upper bridge switch tube to be greater than the duty cycle of the lower bridge switch tube when it is detected that the output voltage of the three-phase bridge rectifier module is greater than the reference voltage, and to control the duty cycle of the upper bridge switch tube to be less than the duty cycle of the lower bridge switch tube when the output voltage is less than the reference voltage.

[0011] In one embodiment, the main control module is also used to control the mode switching module to enter a three-phase state when it is detected that the power supply is a three-phase AC power supply, so that the first phase output of the three-phase AC power supply is connected to the first AC end, the second phase output of the three-phase AC power supply is connected to the second AC end, the third phase output of the three-phase AC power supply is connected to the third AC end, and the neutral line of the three-phase AC power supply is connected to the midpoint of the capacitor, and the first compensation switch is controlled to be disconnected so that the three-phase bridge rectifier module performs power factor correction.

[0012] In one embodiment, the main control module is also used to control the mode switching module to enter a single-phase inverter state when it is detected that the load connected to the three-phase bridge rectifier module is a single-phase AC load, so that the first AC terminal and the second AC terminal are both connected to the positive electrode of the load, and the third AC terminal and the midpoint of the capacitor are both connected to the negative electrode of the load, and the first compensation switch is controlled to be disconnected so that the three-phase bridge rectifier module performs single-phase inversion.

[0013] In one embodiment, the mode switching module includes a first input terminal, a second input terminal, a third input terminal, a fourth input terminal, a first output terminal, a second output terminal, and a third output terminal;

[0014] The first output terminal is connected to the second AC terminal, the second output terminal is connected to the third AC terminal, and the third output terminal is connected to the midpoint of the capacitor;

[0015] A main control module, for controlling the first input terminal to be connected to the first output terminal, and controlling the second input terminal, the third input terminal, the fourth input terminal, the second output terminal and the third output terminal to be suspended, so that the mode switching module enters a single-phase charging state when detecting that the power source is a single-phase AC power source;

[0016] Or, a main control module, for controlling the first input terminal, the fourth input terminal and the third output terminal to be suspended, controlling the second input terminal to be connected to the first output terminal, and controlling the third input terminal to be connected to the second output terminal, when detecting that the power supply is a three-phase AC power supply, so that the mode switching module enters a three-phase state;

[0017] Or, a main control module is used to control the first input terminal to be connected to the first output terminal, control the second input terminal to be suspended, control the third input terminal to be connected to the second output terminal, and control the fourth input terminal to be connected to the third output terminal when it is detected that the load connected to the three-phase bridge rectifier module is a single-phase AC load, so that the mode switching module enters a single-phase inverter state.

[0018] In one embodiment, the mode switching module includes a first switch, a second switch and a third switch;

[0019] The first switch includes three connection terminals, the first connection terminal of the first switch is connected to the first AC terminal, and the third connection terminal of the first switch is connected to the second AC terminal; the second switch and the third switch each include two connection terminals, the first connection terminal of the second switch is connected to the first connection terminal of the third switch, the second connection terminal of the second switch is connected to the third AC terminal, and the second connection terminal of the third switch is connected to the midpoint of the capacitor;

[0020] A main control module, for controlling the first connection end of the first switch and the third connection end of the first switch to be closed, controlling the second connection end of the first switch to be suspended, and controlling the second switch and the third switch to be disconnected, so that the mode switching module enters a single-phase charging state when detecting that the power source is a single-phase AC power source;

[0021] Or, a main control module is used to control the first connection end of the first switch to be suspended, control the second connection end of the first switch to be closed with the third connection end of the first switch, control the second switch to be closed, and control the third switch to be opened, so that the mode switching module enters a three-phase state when it is detected that the power supply is a three-phase AC power supply;

[0022] Or, a main control module is used to control the first connection end of the first switch and the third connection end of the first switch to be closed, control the second connection end of the first switch to be suspended, and control the second switch and the third switch to be closed when it is detected that the load connected to the three-phase bridge rectifier module is a single-phase AC load, so that the mode switching module enters a single-phase inverter state.

[0023] The present application also proposes a charger, the charger comprising:

[0024] A power factor correction circuit as described above;

[0025] A DC / DC converter in parallel with a power factor correction circuit.

[0026] In one embodiment, the DC / DC converter includes a first switch tube and a second switch tube connected in series, and the power factor correction circuit includes a first bus capacitor and a second bus capacitor connected in series;

[0027] The charger also includes a midpoint compensation circuit;

[0028] The midpoint compensation circuit is respectively connected to the common point of the first switch tube and the second switch tube and the midpoint of the first bus capacitor and the second bus capacitor, and is used for harmonic compensation of the midpoint of the capacitor.

[0029] In one embodiment, the midpoint compensation circuit includes a second compensation switch and a second compensation capacitor connected in series, one end of the second compensation switch and the second compensation capacitor connected in series is connected to the common point of the first switch tube and the second switch tube, and the other end of the second compensation switch and the second compensation capacitor connected in series is connected to the midpoint of the capacitor.

[0030] One or more technical solutions proposed in this application have at least the following technical effects:

[0031] The technical solution of the present application is to set a mode switching module, a first compensation switch and a first compensation capacitor in a power factor correction circuit. When it is detected that the power supply connected to the mode switching module is a single-phase AC power supply, the mode switching module is controlled to enter a single-phase charging state, the single-phase AC power supply is connected to a three-phase bridge rectifier module, and the first compensation switch is controlled to be closed, so that when the three-phase bridge rectifier module operates in a single-phase charging mode, the output current of the three-phase bridge rectifier module is harmonically compensated through the first compensation capacitor and the rectifier bridge arm connected to the third AC end.

[0032] Therefore, the present application forms a second harmonic current compensator through the newly added second compensation capacitor and the idle rectifier bridge arm in the three-phase bridge rectifier module to perform harmonic compensation on the output current of the three-phase bridge rectifier module. Since the second compensation capacitor and the idle rectifier bridge arm are combined to absorb current ripple or compensate for current ripple, the capacitance of the second compensation capacitor does not need to be too large and the volume is small. Compared with directly increasing the bus capacitance to perform harmonic compensation on the output current of the three-phase bridge rectifier module, the volume of the power factor correction circuit is reduced, the power density of the PFC converter is guaranteed, and the technical problem of how to reduce the second harmonic current in the output current of the PFC converter of the on-board charger and ensure the power density of the PFC converter is solved. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on the structures shown in these drawings without paying any creative work.

[0034] Figure 1 A circuit schematic diagram of a first embodiment of a power factor correction circuit provided in the present application;

[0035] Figure 2 A circuit schematic diagram of a second embodiment of a power factor correction circuit provided in the present application;

[0036] Figure 3 A control strategy block diagram of a power factor correction circuit provided in this application;

[0037] Figure 4 An exemplary control timing diagram of a power factor correction circuit provided in the present application;

[0038] Figure 5 for Figure 1 A first equivalent circuit schematic diagram of a power factor correction circuit;

[0039] Figure 6 for Figure 1 A second equivalent circuit schematic diagram of a power factor correction circuit;

[0040] Figure 7 for Figure 1 The third equivalent circuit schematic diagram of the power factor correction circuit;

[0041] Figure 8 for Figure 1 A fourth equivalent circuit schematic diagram of a power factor correction circuit;

[0042] Fig. 9 Output current waveform diagram of the power factor correction circuit provided in this application;

[0043] Fig.10 A circuit diagram of the first embodiment of the charger provided in this application;

[0044] Fig.11 A circuit diagram of the second embodiment of the charger provided in this application;

[0045] Fig.12 A circuit diagram of the third embodiment of the charger provided in this application;

[0046] Fig.13 for Fig.12The circuit diagram of the medium-sized charger working in single-phase inverter mode;

[0047] Fig.14 for Fig.12 Circuit diagram of the medium-sized charger working in single-phase charging mode.

[0048] The realization of the purpose, functional features and advantages of this application will be further explained in conjunction with embodiments and with reference to the accompanying drawings. DETAILED DESCRIPTION

[0049] The following will be combined with the drawings in the embodiments of the present application to clearly and completely describe the technical solutions in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of this application.

[0050] It should be noted that in this application, the terms "include", "comprises" or any other variations thereof are intended to cover non-exclusive inclusion, so that a device or system including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such a device or system. In the absence of more restrictions, an element defined by the sentence "includes..." does not exclude the existence of other identical elements in the device or system including the element.

[0051] In this application, unless otherwise clearly specified and limited, the terms "connection", "fixation", etc. should be understood in a broad sense. For example, "connection" can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium, it can be the internal connection of two elements or the interaction relationship between two elements, unless otherwise clearly defined. For ordinary technicians in this field, the specific meanings of the above terms in this application can be understood according to specific circumstances.

[0052] In this application, if there are descriptions involving "first", "second", etc., the descriptions of "first", "second", etc. are only used for descriptive purposes and cannot be understood as indicating or implying their relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined as "first" or "second" may explicitly or implicitly include at least one of the features.

[0053] In the present application, the suffixes such as "module", "component" or "unit" used to represent elements are used only to facilitate the description of the present application and have no specific meaning in themselves. Therefore, "module", "component" or "unit" can be used in a mixed manner. For those of ordinary skill in the art, the specific meanings of the above terms in the present application can be understood according to the specific circumstances. In addition, the technical solutions of the various embodiments can be combined with each other, but they must be based on the ability of those of ordinary skill in the art to implement them. When the combination of technical solutions is contradictory or cannot be implemented, it should be deemed that such combination of technical solutions does not exist and is not within the scope of protection required by the present application.

[0054] The development trend of on-board chargers is to have the functions of single-phase charging, single-phase inverter, three-phase charging and three-phase discharge at the same time. Generally, a two-stage rectifier circuit is used, which combines a front-stage PFC (Power Factor Correction) converter with a rear-stage DC / DC converter. When the on-board charger works in single-phase charging mode, the instantaneous output power of the front-stage PFC converter pulsates at twice the power frequency, which will cause the presence of secondary harmonic current in the output current of the PFC converter.

[0055] In the related art, the second harmonic current is reduced by increasing the bus capacitance of the on-board charger, but the increase in the volume of the bus capacitance will lead to a decrease in the power density of the PFC converter. Therefore, how to reduce the second harmonic current in the output current of the on-board charger PFC converter and ensure the power density of the PFC converter needs to be solved urgently.

[0056] In addition, under the condition of the same capacitance, using electrolytic capacitors as bus capacitors will also reduce the volume of bus capacitors, but if there is secondary harmonic current in the output current of the PFC converter, the service life of the electrolytic capacitor will be short, usually only 3000 to 5000 hours, and the service life of the electrolytic capacitor will be shortened by half for every 10°C increase in operating temperature. Therefore, if electrolytic capacitors are used as bus capacitors, the reliability and service life of the on-board charger will also be restricted.

[0057] In order to solve the above technical problems, the present application proposes a power factor correction circuit and a charger.

[0058] See also Figure 1 , an embodiment of the present application provides a power factor correction circuit, the power factor correction circuit comprising a mode switching module, a three-phase bridge rectifier module, a main control module, a first bus capacitor C1 and a second bus capacitor C2 connected in series, and a first compensation switch S4 and a first compensation capacitor C3 connected in series;

[0059] The three-phase bridge rectifier module includes a first AC end, a second AC end, a third AC end, a first DC end and a second DC end; the mode switching module is connected to the main control module, the first AC end, the second AC end and the third AC end respectively; the first compensation switch S4 is also connected to the main control module, one end of the first compensation switch S4 and the first compensation capacitor C3 connected in series is connected to the third AC end, and the other end of the first compensation switch S4 and the first compensation capacitor C3 connected in series is connected to the second DC end; the common point of the first bus capacitor C1 and the second bus capacitor C2 forms a capacitor midpoint, one end of the first bus capacitor C1 and the second bus capacitor C2 connected in series is connected to the first DC end, and the other end of the first bus capacitor C1 and the second bus capacitor C2 connected in series is connected to the second DC end;

[0060] The main control module is used to control the mode switching module to enter a single-phase charging state when it is detected that the power supply connected to the mode switching module is a single-phase AC power supply, so that the live wire of the single-phase AC power supply is connected to the first AC terminal and the second AC terminal respectively, and the neutral line of the single-phase AC power supply is connected to the midpoint of the capacitor, and control the first compensation switch to be closed, so as to output the output current I of the three-phase bridge rectifier module through the first compensation capacitor C3 and the target rectifier bridge arm connected to the third AC terminal. bus Perform harmonic compensation.

[0061] It should be noted that the AC end of the three-phase bridge rectifier module can be connected to an external AC power supply and powered by the external AC power supply. The external AC power supply can be a single-phase AC power supply or a three-phase AC power supply. The AC end of the three-phase bridge rectifier module can also be connected to a load, and the three-phase bridge rectifier module can invert the output voltage of the energy storage battery connected to the DC end to power the load. Correspondingly, the working mode of the three-phase bridge rectifier module may include a single-phase charging mode, a single-phase inverter mode, a three-phase rectification mode, and a three-phase inverter mode. Among them, the mode switching module can enter different working states according to the working mode of the three-phase bridge rectifier module to switch the working mode of the three-phase bridge rectifier module. Among them, the working state of the mode switching module may include a single-phase charging state, a single-phase inverter state, and a three-phase state.

[0062] It is understandable that the three-phase bridge rectifier module may include a first rectifier bridge arm, a second rectifier bridge arm and a third rectifier bridge arm. Figure 1As shown, the first rectifier bridge arm includes a first inductor L1 and an upper bridge switch tube Q1 and a lower bridge switch tube Q2 connected in series, the second rectifier bridge arm includes a second inductor L2 and an upper bridge switch tube Q3 and a lower bridge switch tube Q4 connected in series, and the third rectifier bridge arm includes a third inductor L3 and an upper bridge switch tube Q5 and a lower bridge switch tube Q6 connected in series. The target rectifier bridge arm is the third rectifier bridge arm. The first end of the first inductor L1, the first end of the second inductor L2 and the first end of the third inductor L3 are respectively the first AC end, the second AC end and the third AC end of the three-phase bridge rectifier module, the second end of the first inductor L1 is connected to the common connection point of the upper bridge switch tube Q1 and the lower bridge switch tube Q2 connected in series, the second end of the second inductor L2 is connected to the common connection point of the upper bridge switch tube Q3 and the lower bridge switch tube Q4 connected in series, and the second end of the third inductor L3 is connected to the common connection point of the upper bridge switch tube Q5 and the lower bridge switch tube Q6 connected in series. The upper bridge switch tube Q1 and the lower bridge switch tube Q2 connected in series, the upper bridge switch tube Q3 and the lower bridge switch tube Q4 connected in series, and the upper bridge switch tube Q5 and the lower bridge switch tube Q6 connected in series are connected in parallel to form the first DC end and the second DC end of the three-phase bridge rectifier module. Among them, the upper bridge switch tube Q1, the lower bridge switch tube Q2, the upper bridge switch tube Q3, the lower bridge switch tube Q4, the upper bridge switch tube and the lower bridge switch tube Q6 can all be MOS tubes.

[0063] In a specific implementation, when the main control module detects that the single-phase AC power supply is supplying power to the three-phase bridge rectifier module, the main control module controls the mode switching module to enter a single-phase charging state, so that the live wire of the single-phase AC power supply is connected to the first AC end and the second AC end of the three-phase bridge rectifier module, and the neutral line of the single-phase AC power supply is connected to the midpoint of the capacitor. At the same time, the main control module also controls the first rectifier bridge arm and the second rectifier bridge arm in the three-phase bridge rectifier module to perform the rectification function to achieve power factor correction. At this time, the main control module also controls the first compensation switch S4 to close, so that the first compensation capacitor C3 combines with the third rectifier bridge arm to form a second harmonic compensator, generating a power frequency compensation current to compensate for the output current I of the first rectifier bridge arm and the second rectifier bridge arm. bus The power frequency ripple in the DC end of the three-phase bridge rectifier module makes the output current of the DC end of the three-phase bridge rectifier module free of power frequency ripple. The DC end of the three-phase bridge rectifier module can use a first bus capacitor and a second bus capacitor with a smaller capacity to reduce the output current I bus Filtering is performed to reduce the volume of the bus capacitor and ensure the power density of the PFC converter.

[0064] In addition, it is understandable that Figure 1 and Figure 2 As shown, the positions of the first compensation switch S4 and the first compensation capacitor C3 can be exchanged.

[0065] In a feasible implementation manner, the target rectifier bridge arm includes an upper bridge switch tube Q5 and a lower bridge switch tube Q6 connected in series, and the wave generation timing of the upper bridge switch tube Q5 is complementary to the wave generation timing of the lower bridge switch tube Q6;

[0066] The main control module is also used to detect the output current I bus Greater than the reference current I ref In the case of , the duty cycle of the upper bridge switch Q5 is controlled to be greater than the duty cycle of the lower bridge switch Q6. bus Less than the reference current I ref In this case, the duty cycle of the upper bridge switch tube Q5 is controlled to be smaller than the duty cycle of the lower bridge switch tube Q6.

[0067] It should be noted that the reference current I ref It can be determined based on the theoretical output current of the three-phase bridge rectifier module working in single-phase charging mode. The three-phase bridge rectifier module works in single-phase charging mode, and the power frequency ripple in the output current can be determined based on the reference current I ref With the output current I bus The magnitude of the power frequency compensation current can be adjusted by controlling the duty cycle of the upper bridge switch tube Q5 and the duty cycle of the lower bridge switch tube Q6. Therefore, the main control module can also collect the output current I of the three-phase bridge rectifier module. bus , the output current I bus With reference current I ref By comparison, the duty cycle of the upper bridge switch tube Q5 and the duty cycle of the lower bridge switch tube Q6 are determined to adjust the power frequency compensation current. Figure 3 As shown, the main control module may include a ripple controller, which may be configured to generate a ripple current according to a reference current I ref With the output current I bus The current difference between them determines the duty cycle of the upper bridge switch tube Q5 and the duty cycle of the lower bridge switch tube Q6.

[0068] It is understandable that if Figure 1 As shown, the second harmonic compensator composed of the first compensation capacitor C3 and the third rectifier bridge arm is a Buck-Boost bidirectional converter, including two working modes: buck mode and boost mode. bus Greater than the reference current I ref In the case of , the Buck-Boost bidirectional converter works in buck mode to absorb the power frequency ripple. At this time, it is necessary to control the duty cycle of the upper bridge switch Q5 to be greater than the duty cycle of the lower bridge switch Q6; when the output current I bus Less than the reference current I refIn this case, the Buck-Boost bidirectional converter works in boost mode, releasing energy to compensate for the power frequency ripple. At this time, it is necessary to control the duty cycle of the upper bridge switch tube Q5 to be smaller than the duty cycle of the lower bridge switch tube Q6.

[0069] In a feasible implementation manner, the main control module is also used to detect the output voltage V of the three-phase bridge rectifier module. bus Greater than the reference voltage V ref In the case of , the duty cycle of the upper bridge switch Q5 is controlled to be greater than the duty cycle of the lower bridge switch Q6. bus Less than the reference voltage V ref In this case, the duty cycle of the upper bridge switch tube Q5 is controlled to be smaller than the duty cycle of the lower bridge switch tube Q6.

[0070] It should be noted that the reference voltage V ref It can be determined based on the theoretical output voltage of the three-phase bridge rectifier module working in single-phase charging mode. The main control module can also collect the output voltage V of the three-phase bridge rectifier module. bus , the output voltage V bus With reference voltage V ref By comparison, the duty cycle of the upper bridge switch tube Q5 and the duty cycle of the lower bridge switch tube Q6 are determined to adjust the power frequency compensation current. Figure 3 As shown, the ripple controller can be based on the reference voltage V ref With output voltage V bus The voltage difference between them determines the duty cycle of the upper bridge switch tube Q5 and the duty cycle of the lower bridge switch tube Q6.

[0071] like Figure 4 As shown, the output voltage V bus Greater than the reference voltage V ref In the case of , the Buck-Boost bidirectional converter works in buck mode to absorb the power frequency ripple. At this time, it is necessary to control the duty cycle of the upper bridge switch Q5 to be greater than the duty cycle of the lower bridge switch Q6. bus Less than the reference voltage V ref In this case, the Buck-Boost bidirectional converter works in boost mode, releasing energy to compensate for the power frequency ripple. At this time, it is necessary to control the duty cycle of the upper bridge switch tube Q5 to be smaller than the duty cycle of the lower bridge switch tube Q6.

[0072] In the specific implementation, the Buck-Boost bidirectional converter works in buck mode, such as Figure 5 As shown, t 1 -t 2 At this moment, Q5 is turned on, Q6 is turned off, and capacitor C3 absorbs energy; Figure 6 As shown, t 2 -t 3At this moment, Q5 is turned off, Q6 is turned on, and the inductor L3 continues to flow. The Buck-Boost bidirectional converter works in boost mode. Figure 7 As shown, t 5 -t 6 At the moment Q5 is turned off, Q6 is turned on, and the current of inductor L3 increases; Figure 8 As shown, t 6 -t 7 At this moment, Q5 is turned on and Q6 is turned off. The current of inductor L3 is released to the DC end of the three-phase bridge rectifier module through Q5 to compensate for the power frequency ripple in the output current. Fig. 9 As shown, the output current I bus After compensation, the second harmonic current flowing into the subsequent stage is reduced.

[0073] In a feasible implementation manner, the main control module is also used to control the mode switching module to enter a three-phase state when it is detected that the power supply is a three-phase AC power supply, so that the first phase output of the three-phase AC power supply is connected to the first AC end, the second phase output of the three-phase AC power supply is connected to the second AC end, the third phase output of the three-phase AC power supply is connected to the third AC end, and the neutral line of the three-phase AC power supply is connected to the midpoint of the capacitor, and the first compensation switch S4 is controlled to be disconnected so that the three-phase bridge rectifier module performs power factor correction.

[0074] It should be noted that when the main control module detects that the three-phase AC power supply is supplying power to the three-phase bridge rectifier module, the main control module controls the mode switching module to enter the three-phase state, so that the first phase output A of the three-phase AC power supply is connected to the first AC end of the three-phase bridge rectifier module, the second phase output B of the three-phase AC power supply is connected to the second AC end of the three-phase bridge rectifier module, the third phase output C of the three-phase AC power supply is connected to the third AC end of the three-phase bridge rectifier module, and the neutral line N of the three-phase AC power supply is connected to the midpoint of the capacitor. At the same time, the main control module also controls the three rectifier bridge arms of the three-phase bridge rectifier module to rectify the three-phase AC power supply after the first compensation switch S4 is disconnected, and realizes power factor correction.

[0075] It can be understood that when the main control module detects that the load connected to the AC end of the three-phase bridge rectifier module is a three-phase AC load, the control mode switching module enters a three-phase state, and after controlling the first compensation switch S4 to disconnect, it also controls the three rectifier bridge arms of the three-phase bridge rectifier module to perform three-phase inversion on the output current of the energy storage battery connected to the three-phase bridge rectifier module to supply power to the three-phase AC load.

[0076] In a feasible implementation manner, the main control module is also used to control the mode switching module to enter a single-phase inversion state when it is detected that the load connected to the three-phase bridge rectifier module is a single-phase AC load, so that the first AC terminal and the second AC terminal are both connected to the positive pole of the load, and the third AC terminal and the midpoint of the capacitor are both connected to the negative pole of the load, and the first compensation switch S4 is controlled to be disconnected, so that the three-phase bridge rectifier module performs single-phase inversion.

[0077] It should be noted that when the main control module detects that the load connected to the three-phase bridge rectifier module is a single-phase AC load, the main control module controls the mode switching module to enter a single-phase inverter state, so that the first AC end and the second AC end of the three-phase bridge rectifier module are both connected to the positive electrode of the load, and the third AC end of the three-phase bridge rectifier module and the midpoint of the PFC capacitor are both connected to the negative electrode of the load. At the same time, after the main control module controls the first compensation switch S4 to be disconnected, it also controls the three-phase bridge rectifier module to perform single-phase inversion on the output current of the energy storage battery connected to the three-phase bridge rectifier module to supply power to the single-phase AC load.

[0078] In a feasible implementation, the mode switching module may include a first input terminal, a second input terminal, a third input terminal, a fourth input terminal, a first output terminal, a second output terminal and a third output terminal;

[0079] The first output terminal is connected to the second AC terminal, the second output terminal is connected to the third AC terminal, and the third output terminal is connected to the midpoint of the capacitor;

[0080] A main control module, for controlling the first input terminal to be connected to the first output terminal, and controlling the second input terminal, the third input terminal, the fourth input terminal, the second output terminal and the third output terminal to be suspended, so that the mode switching module enters a single-phase charging state when detecting that the power source is a single-phase AC power source;

[0081] Or, a main control module, for controlling the first input terminal, the fourth input terminal and the third output terminal to be suspended, controlling the second input terminal to be connected to the first output terminal, and controlling the third input terminal to be connected to the second output terminal, when detecting that the power supply is a three-phase AC power supply, so that the mode switching module enters a three-phase state;

[0082] Or, a main control module is used to control the first input terminal to be connected to the first output terminal, control the second input terminal to be suspended, control the third input terminal to be connected to the second output terminal, and control the fourth input terminal to be connected to the third output terminal when it is detected that the load connected to the three-phase bridge rectifier module is a single-phase AC load, so that the mode switching module enters a single-phase inverter state.

[0083] It should be noted that the mode switching module may include multiple input terminals and multiple output terminals. By switching different input terminals to be directly connected or disconnected with the output terminals, different working states can be switched to connect different power sources or loads to the three-phase bridge rectifier module. The mode switching module may be implemented by a switch, a relay, etc.

[0084] In a feasible implementation, the mode switching module may include a first switch S2, a second switch S3, and a third switch S4;

[0085] The first switch S1 may include three connection terminals, the first connection terminal of the first switch S1 is connected to the first AC terminal, and the third connection terminal of the first switch S1 is connected to the second AC terminal; the second switch S2 and the third switch S3 may each include two connection terminals, the first connection terminal of the second switch S2 is connected to the first connection terminal of the third switch S3, the second connection terminal of the second switch S2 is connected to the third AC terminal, and the second connection terminal of the third switch S3 is connected to the midpoint of the capacitor;

[0086] The main control module is used to control the first connection end of the first switch S1 and the third connection end of the first switch S1 to be closed, control the second connection end of the first switch S1 to be suspended, and control the second switch S2 and the third switch S3 to be disconnected, so that the mode switching module enters a single-phase charging state when it is detected that the power supply is a single-phase AC power supply;

[0087] Or, a main control module is used to control the first connection end of the first switch S1 to be suspended, control the second connection end of the first switch S1 and the third connection end of the first switch S1 to be closed, control the second switch S2 to be closed, and control the third switch S3 to be opened, so that the mode switching module enters a three-phase state when it is detected that the power supply is a three-phase AC power supply;

[0088] Or, a main control module is used to control the first connection end of the first switch S1 and the third connection end of the first switch S1 to be closed, control the second connection end of the first switch S1 to be suspended, and control the second switch S2 and the third switch S3 to be closed when it is detected that the load connected to the three-phase bridge rectifier module is a single-phase AC load, so that the mode switching module enters a single-phase inverter state.

[0089] It should be noted that if Figure 1 , Figure 2 , Fig.10 , Fig.11 , Fig.12 and Fig.13 As shown, the mode switching module may include a first switch S2, a second switch S2 and a third switch S3. The main control module realizes the working state switching of the mode switching module and the working mode switching of the three-phase bridge rectifier module by controlling the opening and closing of the first switch S2, the second switch S2 and the third switch S3.

[0090] Therefore, this embodiment provides a power factor correction circuit, which forms a second harmonic current compensator by adding a second compensation capacitor and an idle rectifier bridge arm in the three-phase bridge rectifier module to perform harmonic compensation on the output current of the three-phase bridge rectifier module. Since the second compensation capacitor and the idle rectifier bridge arm are combined to absorb current ripple or compensate current ripple, the capacitance of the second compensation capacitor does not need to be too large and the volume is small. Compared with directly increasing the bus capacitance to perform harmonic compensation on the output current of the three-phase bridge rectifier module, the volume of the power factor correction circuit is reduced, the power density of the PFC converter is guaranteed, and the technical problem of how to reduce the second harmonic current in the output current of the vehicle charger PFC converter and ensure the power density of the PFC converter is solved. In addition, after the second harmonic current in the output current of the PFC converter is compensated in this embodiment, there is no second harmonic current in the output current of the three-phase bridge rectifier module. Therefore, the bus capacitor of the PFC can use an electrolytic capacitor or a non-electrolytic capacitor, which increases the selection of the bus capacitor.

[0091] In addition, the embodiment of the present application further provides a charger, which may include:

[0092] A power factor correction circuit as described above;

[0093] A DC / DC converter in parallel with a power factor correction circuit.

[0094] It should be noted that if Fig.10 and Fig.11 As shown, the DC / DC converter can be connected in parallel with the first DC terminal and the second DC terminal of the three-phase bridge rectifier module. At this time, the neutral line N of the power supply can be connected to the DC / DC converter.

[0095] It can be understood that the specific structure of the power factor correction circuit refers to the above-mentioned embodiments. Since the transient detection device of the power device adopts all the technical solutions of all the above-mentioned embodiments, it at least has all the beneficial effects brought by the technical solutions of the above-mentioned embodiments, which will not be described one by one here.

[0096] In a feasible implementation manner, the DC / DC converter includes a first switch tube Q7 and a second switch tube Q8 connected in series, and the power factor correction circuit includes a first bus capacitor C1 and a second bus capacitor C2 connected in series;

[0097] The charger may further include a midpoint compensation circuit;

[0098] The midpoint compensation circuit is respectively connected to the common point of the first switch tube Q7 and the second switch tube Q8 and the midpoint of the first bus capacitor C1 and the second bus capacitor C2 for harmonic compensation of the midpoint of the capacitor.

[0099] It should be noted that the charger may be an onboard charger of an electric vehicle. Fig.12 , Fig.13 and Fig.14 As shown, the charger may further include a midpoint compensation circuit. When the charger operates in SVPWM modulation (Space Vector Pulse Width Modulation), the midpoint compensation circuit can reduce the current ripple at the midpoint of the capacitor and improve the EMC (Electromagnetic Compatibility) effect of the charger.

[0100] In a feasible embodiment, the midpoint compensation circuit includes a second compensation switch S5 and a second compensation capacitor C4 connected in series, one end of the second compensation switch S5 and the second compensation capacitor C4 connected in series is connected to the common point of the first switch tube Q7 and the second switch tube Q8, and the other end of the second compensation switch S5 and the second compensation capacitor C4 connected in series is connected to the midpoint of the capacitor.

[0101] It should be noted that if Fig.12 , Fig.13 and Fig.14 As shown, the positions of the second compensation switch S5 and the second compensation capacitor C4 in the midpoint compensation circuit can be exchanged.

[0102] It is understandable that if Fig.12 As shown, when the main control module detects that the power supply connected to the three-phase bridge rectifier module is a three-phase AC power supply, the first connection end of the first switch S1 is controlled to be suspended, the second connection end of the first switch S1 is controlled to be closed with the third connection end of the first switch S1, the second switch S2 is controlled to be closed, and the third switch S3 is controlled to be disconnected, so that the mode switching module enters a three-phase state, the first phase output A of the three-phase AC power supply is connected to the first AC end of the three-phase bridge rectifier module, the second phase output B of the three-phase AC power supply is connected to the second AC end of the three-phase bridge rectifier module, the third phase output C of the three-phase AC power supply is connected to the third AC end of the three-phase bridge rectifier module, and the neutral line N of the three-phase AC power supply is connected to the midpoint of the capacitor, and the first compensation switch S4 is controlled to be disconnected, so that the three-phase bridge rectifier module performs power factor correction.

[0103] like Fig.13As shown, when the main control module detects that the load connected to the three-phase bridge rectifier module is a single-phase AC load, the first connection end of the first switch S1 and the third connection end of the first switch S1 are controlled to be closed, the second connection end of the first switch S1 is controlled to be suspended, and the second switch S2 and the third switch S3 are controlled to be closed, so that the mode switching module enters a single-phase inverter state, the first AC end of the three-phase bridge rectifier module and the second AC end of the three-phase bridge rectifier module are both connected to the positive electrode of the single-phase AC load, and the third AC end of the three-phase bridge rectifier module and the midpoint of the capacitor are both connected to the negative electrode of the three-phase AC load, and the first compensation switch S4 is controlled to be disconnected, so that the three-phase bridge rectifier module performs single-phase inverter.

[0104] like Fig.14 As shown, when the main control module detects that the power supply connected to the three-phase bridge rectifier module is a single-phase AC power supply, the first connection end of the first switch S1 and the third connection end of the first switch S3 are controlled to be closed, the second connection end of the first switch S1 is controlled to be suspended, and the second switch S2 and the third switch S3 are controlled to be disconnected, so that the mode switching module enters a single-phase charging state, the live wire of the single-phase AC power supply is connected to the first AC end and the second AC end, the neutral line of the single-phase AC power supply is connected to the midpoint of the capacitor, and the first compensation switch S4 is controlled to be closed, so as to perform harmonic compensation on the output current of the three-phase bridge rectifier module through the first compensation capacitor C3 and the third rectifier bridge arm connected to the third AC end.

[0105] Therefore, this embodiment provides a charger, which forms a secondary harmonic current compensator through a newly added second compensation capacitor and an idle rectifier bridge arm in the three-phase bridge rectifier module to perform harmonic compensation on the output current of the three-phase bridge rectifier module. Since the second compensation capacitor and the idle rectifier bridge arm are combined to absorb current ripple or compensate current ripple, the capacitance of the second compensation capacitor does not need to be too large and the volume is small. Compared with directly increasing the bus capacitance to perform harmonic compensation on the output current of the three-phase bridge rectifier module, the volume of the power factor correction circuit is reduced, the power density of the PFC converter is guaranteed, and the technical problem of how to reduce the secondary harmonic current in the output current of the PFC converter of the on-board charger and ensure the power density of the PFC converter is solved.

[0106] The above description is only an exemplary implementation of the present application and does not limit the patent scope of the present application. All equivalent structural changes made by using the contents of the present application specification and drawings under the technical concept of the present application, or directly / indirectly applied in other related technical fields are included in the patent protection scope of the present application.

Claims

1. A power factor correction circuit, characterized in that: The power factor correction circuit includes a mode switching module, a three-phase bridge rectifier module, a main control module, a first bus capacitor and a second bus capacitor connected in series, and a first compensation switch and a first compensation capacitor connected in series; The three-phase bridge rectifier module includes a first AC end, a second AC end, a third AC end, a first DC end and a second DC end; the mode switching module is connected to the main control module, the first AC end, the second AC end and the third AC end respectively; the first compensation switch is also connected to the main control module, one end of the first compensation switch and the first compensation capacitor connected in series is connected to the third AC end, and the other end of the first compensation switch and the first compensation capacitor connected in series is connected to the second DC end; the common point of the first bus capacitor and the second bus capacitor forms a capacitor midpoint, one end of the first bus capacitor and the second bus capacitor connected in series is connected to the first DC end, and the other end of the first bus capacitor and the second bus capacitor connected in series is connected to the second DC end; The main control module is used to control the mode switching module to enter a single-phase charging state when it is detected that the power supply connected to the mode switching module is a single-phase AC power supply, so that the live wire of the single-phase AC power supply is respectively connected to the first AC terminal and the second AC terminal, and the neutral line of the single-phase AC power supply is connected to the midpoint of the capacitor, and control the first compensation switch to be closed, so as to perform harmonic compensation on the output current of the three-phase bridge rectifier module through the first compensation capacitor and the target rectifier bridge arm connected to the third AC terminal.

2. The power factor correction circuit according to claim 1, characterized in that: The target rectifier bridge arm comprises an upper bridge switch tube and a lower bridge switch tube connected in series, and the wave generation timing of the upper bridge switch tube is complementary to the wave generation timing of the lower bridge switch tube; The main control module is also used to control the duty cycle of the upper bridge switch tube to be greater than the duty cycle of the lower bridge switch tube when it is detected that the output current is greater than the reference current, and to control the duty cycle of the upper bridge switch tube to be less than the duty cycle of the lower bridge switch tube when the output current is less than the reference current.

3. The power factor correction circuit according to claim 2, characterized in that: The main control module is also used to control the duty cycle of the upper bridge switch tube to be greater than the duty cycle of the lower bridge switch tube when it is detected that the output voltage of the three-phase bridge rectifier module is greater than the reference voltage, and to control the duty cycle of the upper bridge switch tube to be less than the duty cycle of the lower bridge switch tube when the output voltage is less than the reference voltage.

4. The power factor correction circuit according to claim 1, characterized in that: The main control module is also used to control the mode switching module to enter a three-phase state when it is detected that the power supply is a three-phase AC power supply, so that the first phase output of the three-phase AC power supply is connected to the first AC end, the second phase output of the three-phase AC power supply is connected to the second AC end, the third phase output of the three-phase AC power supply is connected to the third AC end, and the neutral line of the three-phase AC power supply is connected to the midpoint of the capacitor, and the first compensation switch is controlled to be disconnected so that the three-phase bridge rectifier module performs power factor correction.

5. The power factor correction circuit according to claim 1, characterized in that: The main control module is also used to control the mode switching module to enter a single-phase inverter state when it is detected that the load connected to the three-phase bridge rectifier module is a single-phase AC load, so that the first AC end and the second AC end are both connected to the positive electrode of the load, and the third AC end and the midpoint of the capacitor are both connected to the negative electrode of the load, and control the first compensation switch to be disconnected so that the three-phase bridge rectifier module performs single-phase inversion.

6. The power factor correction circuit according to any one of claims 1 to 5, characterized in that: The mode switching module includes a first input terminal, a second input terminal, a third input terminal, a fourth input terminal, a first output terminal, a second output terminal and a third output terminal; The first output terminal is connected to the second AC terminal, the second output terminal is connected to the third AC terminal, and the third output terminal is connected to the midpoint of the capacitor; The main control module is used to control the first input end to be connected to the first output end, and control the second input end, the third input end, the fourth input end, the second output end, and the third output end to be suspended when detecting that the power source is the single-phase AC power source, so that the mode switching module enters the single-phase charging state; Or, the main control module is used to control the first input terminal, the fourth input terminal and the third output terminal to be suspended, control the second input terminal to be connected to the first output terminal, and control the third input terminal to be connected to the second output terminal when detecting that the power supply is a three-phase AC power supply, so that the mode switching module enters the three-phase state; Or, the main control module is used to control the first input terminal to be connected to the first output terminal, control the second input terminal to be suspended, control the third input terminal to be connected to the second output terminal, and control the fourth input terminal to be connected to the third output terminal when it is detected that the load connected to the three-phase bridge rectifier module is a single-phase AC load, so that the mode switching module enters the single-phase inversion state.

7. The power factor correction circuit according to any one of claims 1 to 5, characterized in that: The mode switching module includes a first switch, a second switch and a third switch; The first switch includes three connection terminals, a first connection terminal of the first switch is connected to the first AC terminal, and a third connection terminal of the first switch is connected to the second AC terminal; the second switch and the third switch each include two connection terminals, a first connection terminal of the second switch is connected to the first connection terminal of the third switch, a second connection terminal of the second switch is connected to the third AC terminal, and a second connection terminal of the third switch is connected to the midpoint of the capacitor; The main control module is used to control the first connection end of the first switch and the third connection end of the first switch to be closed, control the second connection end of the first switch to be suspended, and control the second switch and the third switch to be disconnected, so that the mode switching module enters the single-phase charging state when detecting that the power source is the single-phase AC power source; Or, the main control module is used to control the first connection end of the first switch to be suspended, control the second connection end of the first switch to be closed with the third connection end of the first switch, control the second switch to be closed, and control the third switch to be opened, so that the mode switching module enters the three-phase state when it is detected that the power supply is a three-phase AC power supply; Alternatively, the main control module is used to control the first connection end of the first switch and the third connection end of the first switch to be closed, control the second connection end of the first switch to be suspended, and control both the second switch and the third switch to be closed when it is detected that the load connected to the three-phase bridge rectifier module is a single-phase AC load, so that the mode switching module enters the single-phase inverter state.

8. A charger, characterized in that: The charger comprises: The power factor correction circuit according to any one of claims 1 to 7; A DC / DC converter is connected in parallel with the power factor correction circuit.

9. The charger according to claim 8, characterized in that: The DC / DC converter includes a first switch tube and a second switch tube connected in series, and the power factor correction circuit includes a first bus capacitor and a second bus capacitor connected in series; The charger also includes a midpoint compensation circuit; The midpoint compensation circuit is respectively connected to the common point of the first switch tube and the second switch tube and the midpoint of the capacitors of the first bus capacitor and the second bus capacitor, and is used to perform harmonic compensation on the midpoint of the capacitor.

10. The charger according to claim 9, characterized in that: The midpoint compensation circuit includes a second compensation switch and a second compensation capacitor connected in series, one end of the second compensation switch and the second compensation capacitor connected in series is connected to the common point of the first switch tube and the second switch tube, and the other end of the second compensation switch and the second compensation capacitor connected in series is connected to the midpoint of the capacitor.

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