Low-frequency ripple current suppression circuit and power supply system having low-frequency ripple current suppression function

Abstract

To provide a low-frequency ripple current suppression circuit.SOLUTION: This device is provided with a first boosting circuit 11 and a second boosting circuit 12. The first step-up circuit 11 has a first inductor L1, a first switch group S11 including a first switch S12 and a second switch S1, and a first capacitor C1. The second step-up circuit 12 has a second switch group L2 including a second inductor S21, a third switch S22, and a fourth switch S2, and a second capacitor C2. A low-frequency ripple current suppression circuit 10 receives a DC current idc having a ripple component Irip, and absorbs or suppresses the ripple component Irip by a first boosting circuit 11 and a second boosting circuit 12.SELECTED DRAWING: Figure 6

Description

[Technical Field]

[0001] The present invention relates to a current suppression circuit and a power supply system having a current suppression function, and more particularly to a low-frequency ripple current suppression circuit and a power supply system having a low-frequency ripple current suppression function. [Background technology]

[0002] With the growing awareness of environmental protection and green energy, the number of electric vehicles sold is doubling, and the demand for charging stations is also increasing. To achieve both overall power efficiency and charging quality to meet the charging demand of electric vehicles is a common goal for those skilled in the art. Summary of the Invention [Problem to be solved by the invention]

[0003] Therefore, in order to solve the problems and technical bottlenecks existing in the prior art, how to design a low-frequency ripple current suppression circuit and a power supply system equipped with a low-frequency ripple current suppression function is an important issue for the inventors of the present application. [Means for solving the problem]

[0004] One object of the present invention is to provide a low-frequency ripple current suppression circuit. The low-frequency ripple current suppression circuit includes a first boost circuit and a second boost circuit. The first boost circuit includes a first inductor, a first group of switches, and a first capacitor. The first inductor has a first end connected to the first DC side and a second end. The first group of switches includes a first switch having a first end connected to the second end of the first inductor and a second end connected to an equipotential node, and a second switch having a first end connected to the second end of the first inductor and a second end. The first capacitor has a first end connected to the second end of the second switch and a second end connected to the equipotential node. The second boost circuit includes a second inductor, a second group of switches, and a second capacitor. The second inductor has a first end connected to the second DC side and a second end. The second switch group includes a third switch having a first end connected to the second end of the second inductor and a second end connected to the equipotential node, and a fourth switch having a first end connected to the second end of the second inductor and a second end. The second capacitor has a first end connected to the second end of the fourth switch and a second end connected to the equipotential node. The low-frequency ripple current suppression circuit receives a DC current having a ripple component and absorbs or suppresses the ripple component using the first boost circuit and the second boost circuit.

[0005] Another object of the present invention is to provide a power supply system with a low-frequency ripple current suppression function. The power supply system with a low-frequency ripple current suppression function includes three single-phase AC / DC conversion circuits and a low-frequency ripple current suppression circuit. Each single-phase AC / DC conversion circuit is coupled between any two phases of a three-phase AC power supply or between each phase and a common connection point, and the output sides of these single-phase AC / DC conversion circuits are connected to an output node to output DC current. The low-frequency ripple current suppression circuit is connected to the output node. The low-frequency ripple current suppression circuit has a first boost circuit and a second boost circuit. The first boost circuit has a first inductor, a first group of switches, and a first capacitor, the first group of switches has a first switch and a second switch, the first inductor is connected to the first switch at a first common connection point, and the first inductor and the first switch are connected between the first DC side and the equipotential node, the second switch is connected in series with the first capacitor, and the second switch and the first capacitor are connected between the first common connection point and the equipotential node. The second boost circuit has a second inductor, a second group of switches, and a second capacitor, the second group of switches having a third switch and a fourth switch, the second inductor is connected to the third switch at a second common connection point, and the second inductor and the third switch are connected between the second DC side and the equipotential node, the fourth switch is connected in series with the second capacitor, and the fourth switch and the second capacitor are connected between the second common connection point and the equipotential node. [Effects of the Invention]

[0006] With the above-described configuration, the low-frequency ripple current suppression circuit and power supply system equipped with a low-frequency ripple current suppression function according to the present invention have the following characteristics and advantages: 1) by using a low-frequency ripple current suppression circuit, system efficiency can be maintained under light loads, and by removing the ripple component of the DC current, the output current flowing to the load can be a DC current that does not contain ripple components; and 2) a low-frequency ripple current suppression circuit can be realized with simple circuit design and control.

[0007] For a better understanding of the techniques, means and advantages for achieving the specified objects of the present invention, reference should be made to the following detailed description of the invention and the accompanying drawings, from which the objects, features and characteristics of the present invention can be more specifically and profoundly understood, but the accompanying drawings are not intended to limit the present invention and are provided for reference and explanation only. [Brief explanation of the drawings]

[0008] [Figure 1] 1 is a circuit block diagram of a first embodiment of a plurality of single-phase AC / DC conversion circuits according to the present invention. [Figure 2] FIG. 4 is a circuit block diagram of a second embodiment of a plurality of single-phase AC / DC conversion circuits according to the present invention. [Figure 3] FIG. 1 is a circuit block diagram of power supply using three sets of single-phase AC / DC conversion circuits of the present invention. [Figure 4] FIG. 2 is a circuit block diagram of power supply using two sets of single-phase AC / DC conversion circuits of the present invention. [Figure 5] 1 is a circuit block diagram of power supply using a set of single-phase AC / DC conversion circuits of the present invention. [Figure 6] 1 is a circuit diagram of a low-frequency ripple current suppression circuit according to the present invention; [Figure 7] 1 is a circuit block diagram of a power supply system having a low-frequency ripple current suppression function according to the present invention; [Figure 8] 1 is a circuit block diagram showing the operation of a power supply system having a low-frequency ripple current suppression function according to the present invention; DETAILED DESCRIPTION OF THE INVENTION

[0009] The technical contents and detailed description of the present invention will be described below with reference to the accompanying drawings.

[0010] The present invention will be described below with reference to specific embodiments, and those skilled in the art will be able to easily understand other advantages and effects of the present invention from the contents disclosed herein. The present invention may be embodied or applied in other specific examples, and various modifications and changes may be made to the details described herein based on different perspectives and applications without departing from the spirit of the present invention.

[0011] The structures, ratios, sizes, number of components, etc. shown in the drawings attached to this specification are all provided to supplement the contents disclosed in this specification so that those skilled in the art can easily understand and grasp them, and are not intended to limit the implementation of the present invention, so they have no technical significance. Modifications to the structure, changes in ratios, or adjustments to the size within the scope that does not impair the effects and purpose of the present invention are considered to be within the scope covered by the technical contents disclosed in this specification.

[0012] Fig. 1 is a circuit block diagram of a first embodiment of a plurality of single-phase AC / DC conversion circuits according to the present invention. Fig. 1 shows a charging system using a three-phase power supply, which is composed of three single-phase AC / DC conversion circuits 100-1, 100-2, and 100-3. The three single-phase AC / DC conversion circuits 100-1, 100-2, and 100-3 are each connected between two different lines of a three-phase AC power supply. For example, the first single-phase AC / DC conversion circuit 100-1 is connected to the R-phase and S-phase AC power of the three-phase AC power supply, the second single-phase AC / DC conversion circuit 100-2 is connected to the S-phase and T-phase AC power of the three-phase AC power supply, and the third single-phase AC / DC conversion circuit 100-3 is connected to the T-phase and R-phase AC power of the three-phase AC power supply. In the embodiment shown in Fig. 1, the three single-phase isolated AC / DC conversion circuits are delta-connected (Δ-connected) to the three-phase AC power supply. Each single-phase isolated AC / DC conversion circuit includes rectifier circuits 101-1, 101-2, and 101-3 and single-phase isolated power factor correction circuits 102-1, 102-2, and 102-3. Specifically, the first single-phase AC / DC conversion circuit 100-1 includes a first rectifier circuit 101-1 and a first single-phase isolated power factor correction circuit 102-1, the second single-phase AC / DC conversion circuit 100-2 includes a second rectifier circuit 101-2 and a second single-phase isolated power factor correction circuit 102-2, and the third single-phase AC / DC conversion circuit 100-3 includes a third rectifier circuit 101-3 and a third single-phase isolated power factor correction circuit 102-3.

[0013] FIG. 2 is a circuit block diagram of a second embodiment of multiple single-phase AC / DC conversion circuits of the present invention. In contrast to the embodiment shown in FIG. 1, in the embodiment of FIG. 2, three single-phase isolated AC / DC conversion circuits are configured in a star connection (Y connection) with respect to a three-phase AC power source. Whether the configuration is a delta connection or a star connection, it is possible to sufficiently supply the power required for full load or heavy load. FIG. 3 is a circuit block diagram of power supply using three single-phase AC / DC conversion circuits of the present invention. In a three-phase balanced power supply, by converting a three-phase AC power source using three single-phase isolated AC / DC conversion circuits, it is possible to obtain a DC (output) current i with sufficiently suppressed ripple components as the current required for charging. dc load (e.g., the battery V of an electric vehicle) BAT ) can be supplied to

[0014] However, when the charging load decreases (for example, to 2 / 3 load output), in order to maintain system efficiency, one set of single-phase isolated AC / DC conversion circuits is usually turned off and the load is charged with a low output power, which is so-called phase shedding power supply. However, in this operating mode, due to the asymmetric three-phase power supply, the DC output terminal contains harmonic AC components equivalent to more than twice the line frequency (commercial power frequency such as 50 Hz or 60 Hz), and as shown in Figure 4, the DC (output) current i dc This generates a ripple component in the load, which affects the quality of power supply to the load and even the life of the load. If the charging load is further reduced (for example, to 1 / 3 load output), or if charging is performed with a light load, the second set of single-phase isolated AC / DC conversion circuits is further turned off, but as shown in Figure 5, the DC (output) current i dc The ripple component occurring in the

[0015] 1 and 2 further include first filter capacitors 103-1, 103-2, and 103-3 and second filter capacitors 104-1, 104-2, and 104-3. For example, the first single-phase AC / DC conversion circuit 100-1 includes a first filter capacitor 103-1 and a second filter capacitor 104-1, which are connected to the input and output sides of the first single-phase isolated power factor correction circuit 102-1, respectively. Unlike electrolytic capacitors used in general PFC circuits, these filter capacitors have high capacitance and are large in size because their purpose is to filter harmonic AC components equivalent to more than twice the line frequency output from the single-phase AC / DC conversion circuit.

[0016] In contrast, the three single-phase AC / DC conversion circuits 100-1, 100-2, and 100-3 of the present invention are each powered by two different lines of a three-phase AC power supply. The output ripples of each conversion circuit are configured to be out of phase with each other. Therefore, harmonic components equivalent to twice the line frequency cancel each other out in the total output, eliminating the need for additional filtering. Specifically, the first filter capacitor 103-1 and the second filter capacitor 104-1 of the first single-phase AC / DC conversion circuit 100-1 are high-frequency filter capacitors whose primary purpose is to filter high-frequency noise generated by the high-frequency switching of the power electronics high-frequency switching elements in the first single-phase AC / DC conversion circuit 100-1. Therefore, the first filter capacitor 103-1 and the second filter capacitor 104-1 can be realized as small-capacitance, compact capacitor components. The filter capacitors of the second single-phase AC / DC conversion circuit 100-2 and the third single-phase AC / DC conversion circuit 100-3 have similar characteristics, and therefore detailed description thereof will not be repeated here.

[0017] Therefore, in consideration of the above-mentioned problem that the ripple component of the DC (output) current affects the load when one or two sets of single-phase isolated converters are turned off to improve system efficiency under light load charging conditions, the present invention proposes a low-frequency ripple current suppression circuit and a power supply system equipped with a low-frequency ripple current suppression function, which will be described in detail below.

[0018] Figure 6 is a circuit diagram of a low-frequency ripple current suppression circuit of the present invention. As shown in Figure 6, the low-frequency ripple current suppression circuit 10 includes a first boost circuit 11 and a second boost circuit 12. The first boost circuit 11 includes a first inductor L1, a first switch group S1, and a first capacitor C1. The second boost circuit 12 includes a second inductor L2, a second switch group S2, and a second capacitor C2.

[0019] The first inductor L1 has a first end connected to the first DC side DC1 and a second end. The first switch group S1 includes a first switch S11 and the second switch S 12 The first switch S 11 has a first end connected to the second end of the first inductor L1 (i.e., the first common connection point) and a second end connected to the equipotential node O. 12 The first capacitor C1 has a first end connected to the second end of the first inductor L1 and a second end connected to the second switch S 12 and a second end connected to the equipotential node O.

[0020] The second inductor L2 has a first end connected to the second DC side DC2 and a second end. The second switch group S2 includes a third switch S 21 and the fourth switch S 22 and a third switch S 21 has a first end connected to the second end of the second inductor L2 (i.e., the second common connection point) and a second end connected to the equipotential node O. 22 The second capacitor C2 has a first end connected to the second end of the second inductor L2 and a second end connected to the fourth switch S 22 and a second end connected to the equipotential node O.

[0021] The low-frequency ripple current suppression circuit 10 suppresses the ripple component I rip DC current i dc and the first boost circuit 11 and the second boost circuit 12 generate a ripple component I rip Therefore, the circuit configuration design of the low-frequency ripple current suppression circuit 10 described above absorbs the DC current i dc Ripple component I rip It is possible to remove

[0022] The low-frequency ripple current suppression circuit 10 is composed of two boost circuits (i.e., the first boost circuit 11 and the second boost circuit 12), and the first capacitor C1 and the second capacitor C2 absorb and smooth the energy of the low-frequency ripple component, respectively. Therefore, from the standpoint of voltage resistance and capacitance, the first capacitor C1 and the second capacitor C2 have a wider and more flexible range of specification selection, and it is possible to select, for example, capacitor components with a lower voltage resistance or a wider range of capacitance.

[0023] The low-frequency ripple current suppression circuit 10 further includes a filter circuit 13. The filter circuit 13 includes a first filter capacitor C f1 and the second filter capacitor C f2 The first filter capacitor C f1 has a first end connected to the first DC side DC1 and a second end connected to the equipotential node O. The second filter capacitor C f2 has a first end connected to the second DC side DC2 and a second end connected to the equipotential node O.

[0024] The first filter capacitor C f1 and the second filter capacitor C f2 is the first switch S1 of the first switch group S1. 11 and a second switch S 12 , and the third switch S of the second switch group S2 21 and a fourth switch S 22 The first filter capacitor C is a high-frequency filter capacitor for filtering high-frequency noise generated by the switching of the f1 and the second filter capacitor C f2 can be realized as a capacitor component with a small capacitance and a small size.

[0025] As mentioned above, the DC current i dc Ripple component I ripIn order to eliminate this, the first switch group S1 of the first booster circuit 11 and the second switch group S2 of the second booster circuit 12 are controlled as follows. 11 and a second switch S 12 and the third switch S of the second switch group S2. 21 and a fourth switch S 22 It should be noted that the controller or control unit is not separately shown in the drawings, since it can be controlled by control signals generated in the controller or control unit.

[0026] The control signal generated by the controller controls the first switch S1 of the first switch group S1. 11 and the second switch S 12 That is, the first switch S 11 When the second switch S 12 is turned off, and conversely, the first switch S 11 When the second switch S 12 Furthermore, the control signal generated by the controller controls the third switch S2 of the second switch group S2 to be turned on. 21 and the fourth switch S 22 In other words, the third switch S 21 When the fourth switch S 22 is turned off, and conversely, the third switch S 21 When the fourth switch S 22 is turned on.

[0027] In one embodiment, the first switch S1 of the first group of switches S1 11 and the third switch S of the second switch group S2 21 are turned on / off synchronously. That is, the first switch S 11 is turned on to turn on the second switch S 12 When the third switch S 21 is turned on and the fourth switch S 22is turned off, and conversely, the first switch S 11 is turned off and the second switch S 12 When the third switch S 21 is turned off and the fourth switch S 22 is turned on.

[0028] In another embodiment, the first switch S1 of the first group of switches S1 11 and the third switch S of the second switch group S2 21 In the previous embodiment, the first switch S 11 and the third switch S 21 are turned on / off synchronously, whereas in this embodiment, the first switch S 11 and the third switch S 21 are not controlled synchronously, and there is a time difference (phase difference) between the controls of the two. For example, the first switch S 11 is turned on to turn on the second switch S 12 When the third switch S 21 is turned on and the fourth switch S 22 is turned off, and conversely, the first switch S 11 is turned off and the second switch S 12 When the third switch S is turned on, the third switch S 21 is turned off and the fourth switch S 22 In this case, the DC current i dc Ripple component I rip can be eliminated.

[0029] Furthermore, there are different implementations for selecting the first switch group S1 and the second switch group S2. In one embodiment, as shown in FIG. 11 and the second switch S 12 , and the third switch S of the second switch group S2 21 and the fourth switch S 22are transistors. Therefore, the control signals generated by the controller described above can perform corresponding on / off control for all switches, thereby achieving the effect of synchronous rectification.

[0030] In another embodiment, not shown, the first switch S1 of the first switch group S1 11 and the third switch S of the second switch group S2 21 is a transistor, and the second switch S of the first switch group S1 12 and the fourth switch S of the second switch group S2 22 is a diode. Therefore, the first switch S1 of the first switch group S1 is turned on and off by the control signal generated by the controller. 11 and the third switch S of the second switch group S2 21 It is possible to perform corresponding on / off control for each.

[0031] 7 is a circuit block diagram of a power supply system having a low-frequency ripple current suppression function according to the present invention. The power supply system having a low-frequency ripple current suppression function (hereinafter referred to as the power supply system) includes three single-phase AC / DC conversion circuits 100-1, 100-2, and 100-3 (also see FIG. 3), namely, a first single-phase AC / DC conversion circuit 100-1, a second single-phase AC / DC conversion circuit 100-2, and a third single-phase AC / DC conversion circuit 100-3. The single-phase AC / DC conversion circuits 100-1, 100-2, and 100-3 are connected in correspondence with the AC voltages Vin_R, Vin_S, and Vin_T of the respective phases of the three-phase AC power supply (not limited to the delta-connected configuration of FIG. 1 or the star-connected configuration of FIG. 2). That is, the single-phase AC / DC conversion circuits 100-1, 100-2, and 100-3 are connected in correspondence with two different lines of the three-phase AC power supply or between each phase and a common connection point, and the output sides of the three single-phase AC / DC conversion circuits 100-1, 100-2, and 100-3 are connected to an output node N O is connected to the DC current i dc Output.

[0032] The power supply system further includes a low-frequency ripple current suppression circuit 10. The low-frequency ripple current suppression circuit 10 has already been described in detail above, and therefore will not be described again here. The input side of the low-frequency ripple current suppression circuit 10, i.e., the first DC side DC1, is connected to the output node N O , the output DC current i of the three single-phase AC / DC conversion circuits 100-1, 100-2, and 100-3 is dc Receive.

[0033] As shown in FIG. 7, taking the case where two pairs of single-phase isolated AC / DC conversion circuits (i.e., the second single-phase AC / DC conversion circuit 100-2 and the third single-phase AC / DC conversion circuit 100-3) are turned off as an example, the DC current i dc Ripple component I rip From the matters described in FIG. 5, in the case of the operation shown in FIG. 7, the DC current i dc Ripple component I rip It is clear that is large.

[0034] Output node N O Output DC current i from dc (i.e., the combined output current of the three single-phase AC / DC conversion circuits) flows into the first DC side DC1 and is subjected to high-frequency filtering by the filter circuit 13, so that the filtered output DC current i dc flows into the first boost circuit 11 and the second boost circuit 12. As described above, the DC current i dc Regarding the first switch S1 of the first switch group S1, 11 Turn on the second switch S 12 By turning off the ripple component I rip the first switch S 11 The current flows through the first inductor L1 to store energy, and then the first switch S1 of the first switch group S1 11 and turn off the second switch S 12 By turning on the first inductor L1, the energy stored in the first inductor L1 is transferred to the second switch S12 The voltage is discharged to the first capacitor C1 via

[0035] Similarly, the third switch S2 of the second switch group S2 21 Turn on the fourth switch S 22 By turning off the ripple component I rip the third switch S 21 The current flows through the second inductor L2 to store energy, and then the third switch S of the second switch group S2 21 Turn off the fourth switch S 22 By turning on the fourth switch S, the energy stored in the second inductor L2 is transferred to the 22 In this way, the ripple component Irip of the DC current idc is absorbed by the first boost circuit 11 and the second boost circuit 12, so the output current Idc flowing to the load is rip It becomes a direct current that does not have

[0036] 8 is a circuit block diagram showing the operation of a power supply system having a low-frequency ripple current suppression function of the present invention. This power supply system is used to charge a load 20, which may be, but is not limited to, an electric vehicle (EV). The low-frequency ripple current suppression circuit 10 is electrically connected between these single-phase AC / DC conversion circuits 100-1, 100-2, 100-3 and the load 20, and supplies a DC current i dc Ripple component I rip In order to remove (absorb) the output current I dc is the ripple component I rip It becomes a direct current that does not have

[0037] Furthermore, the number of single-phase AC / DC conversion circuits to be turned off among these single-phase AC / DC conversion circuits 100-1, 100-2, and 100-3 can be determined according to the power supply demand of the load 20, thereby improving the system power supply efficiency. Therefore, the power supply system includes a power supply controller 30 for receiving information about the load 20. Taking an electric vehicle as an example of the load 20, the power supply controller 30 receives a load information signal S LD Therefore, the power supply controller 30 receives the charging information required by the electric vehicle as the load information signal S LD When the charge information required by the load 20 is acquired based on the CAD1 ,S CAD2 ,S CAD3 and can control the disabling or enabling of these single-phase AC / DC conversion circuits 100-1, 100-2, and 100-3. When this charging information indicates light load power supply, as shown in Fig. 8, the power supply controller 30 turns off the second single-phase AC / DC conversion circuit 100-2 and the third single-phase AC / DC conversion circuit 100-3, and supplies power only from the first single-phase AC / DC conversion circuit 100-1.

[0038] The power supply controller 30 outputs a switch control signal S for controlling the first switch group S1 of the first boost circuit 11 and the second switch group S2 of the second boost circuit 12. CRC By supplying the DC current i dc Ripple component I rip The output current I dc Ripple component I rip It can also be a direct current that does not have

[0039] In summary, the present invention has the following features and advantages:

[0040] 1) By using a low-frequency ripple current suppression circuit, it is possible to maintain system efficiency under light loads, and by removing the ripple component of the DC current, it is possible to make the output current flowing to the load a DC current that does not contain ripple components.

[0041] 2) A low-frequency ripple current suppression circuit can be realized through simple circuit design and control.

[0042] The above is merely a detailed description and drawings of preferred specific embodiments of the present invention, and is not intended to limit the present invention, and the features of the present invention are not limited thereto. The scope of the present invention shall be determined in accordance with the following claims, and similar embodiments that do not deviate from the spirit of the claims of the present invention shall be encompassed within the scope of the present invention, and changes and modifications that can be easily thought up by those skilled in the art shall be encompassed within the scope of the claims of the present invention. [Explanation of symbols]

[0043] 10 Low-frequency ripple current suppression circuit 100-1, 100-2, 100-3 Single-phase AC / DC conversion circuit 101-1, 101-2, 101-3 Rectifier circuit 102-1, 102-2, 102-3 Single-phase isolated power factor correction circuit Vin_R,Vin_S,Vin_T 3-phase AC power 11 First booster circuit L1 First inductor S1 First switch group S 11 First Switch S 12 Second Switch C1 First capacitor 12 Second boost circuit L2 Second inductor S2 Second switch group S 21 Third Switch S 22 The fourth switch C2 Second capacitor C f1 First filter capacitor C f2 Second Filter Capacitor O Equipotential Node 13 Filter Circuit 20 Load 30 Power Controller idc direct current I rip Ripple component I dc Output Current N O Output node DC1 First DC side DC2 Second DC side V BAT Battery S LD Load information signal S CAD1 ,S CAD2 ,S CAD3 Conversion circuit control signal S CRC Switch Control Signal

Claims

1. A low-frequency ripple current suppression circuit, comprising a first boost circuit and a second boost circuit; The first boost circuit comprises: a first inductor having a first end connected to the first DC side and a second end; a first switch group including a first switch having a first end connected to the second end of the first inductor and a second end connected to an equipotential node, and a second switch having a first end connected to the second end of the first inductor and a second end; a first capacitor having a first end connected to the second end of the second switch and a second end connected to the equipotential node; The second boost circuit comprises: a second inductor having a first end connected to the second DC side and a second end; a second switch group including a third switch having a first end connected to the second end of the second inductor and a second end connected to the equipotential node, and a fourth switch having a first end connected to the second end of the second inductor and a second end; a second capacitor having a first end connected to the second end of the fourth switch and a second end connected to the equipotential node; and A low-frequency ripple current suppression circuit receives a DC current having a ripple component, and absorbs or suppresses the ripple component by means of the first boost circuit and the second boost circuit.

2. a first filter capacitor having a first end connected to the first DC side and a second end connected to the equipotential node; 2. The low-frequency ripple current suppression circuit of claim 1, further comprising: a filter circuit having a second filter capacitor having a first end connected to the second DC side and a second end connected to the equipotential node.

3. 2. The low-frequency ripple current suppression circuit according to claim 1, wherein the first switch and the second switch of the first switch group are turned on / off synchronously and complementarily, and the third switch and the fourth switch of the second switch group are turned on / off synchronously and complementarily.

4. 2. The low-frequency ripple current suppression circuit of claim 1, wherein the first switch and the second switch of the first group of switches and the third switch and the fourth switch of the second group of switches are transistors.

5. 2. The low-frequency ripple current suppression circuit of claim 1, wherein the first switch of the first group of switches and the third switch of the second group of switches are transistors, and the second switch of the first group of switches and the fourth switch of the second group of switches are diodes.

6. 2. The low-frequency ripple current suppression circuit according to claim 1, wherein the first switch of the first group of switches and the third switch of the second group of switches are turned on / off in synchronization with each other.

7. 2. The low-frequency ripple current suppression circuit according to claim 1, wherein the first switch of the first group of switches and the third switch of the second group of switches are turned on / off asynchronously.

8. A power supply system with a low-frequency ripple current suppression function, comprising: three single-phase AC / DC conversion circuits; and a low-frequency ripple current suppression circuit; each of the single-phase AC / DC conversion circuits is connected between two different lines of a three-phase AC power supply or between each phase and a common connection point, and the output side of each of the single-phase AC / DC conversion circuits is connected to an output node to output a DC current; the low-frequency ripple current suppression circuit is connected to the output node; a first boost circuit having a first inductor, a first group of switches, and a first capacitor, wherein the first group of switches has a first switch and a second switch, the first inductor is connected to the first switch at a first common connection point, and the first inductor and the first switch are connected between a first DC side and an equipotential node, the second switch is connected in series with the first capacitor, and the second switch and the first capacitor are connected between the first common connection point and the equipotential node; a second boost circuit having a second inductor, a second group of switches, and a second capacitor, wherein the second group of switches has a third switch and a fourth switch, the second inductor is connected to the third switch at a second common connection point, and the second inductor and the third switch are connected between a second DC side and the equipotential node, the fourth switch is connected in series with the second capacitor, and the fourth switch and the second capacitor are connected between the second common connection point and the equipotential node.

9. the first inductor has a first end connected to the first DC side and a second end, the first switch has a first end connected to the second end of the first inductor and a second end connected to the equipotential node, the second switch has a first end connected to the second end of the first inductor and a second end, and the first capacitor has a first end connected to the second end of the second switch and a second end connected to the equipotential node, 9. The power supply system with a low-frequency ripple current suppression function according to claim 8, wherein the second inductor has a first end connected to the second DC side and a second end, the third switch has a first end connected to the second end of the second inductor and a second end connected to the equipotential node, the fourth switch has a first end connected to the second end of the second inductor and a second end, and the second capacitor has a first end connected to the second end of the fourth switch and a second end connected to the equipotential node.

10. 9. The power supply system with low-frequency ripple current suppression function according to claim 8, wherein the single-phase AC / DC conversion circuits can be partially turned off as the load supplied by the single-phase AC / DC conversion circuits decreases.

11. a power supply controller that receives information about the load; 11. The power supply system with a low-frequency ripple current suppression function according to claim 10, wherein the power supply controller is configured to turn off some of the single-phase AC / DC conversion circuits and control the low-frequency ripple current suppression circuit based on a reduced state of the load.

12. 9. The power supply system with a low-frequency ripple current suppression function according to claim 8, wherein the single-phase AC / DC conversion circuit is for charging a battery of an electric vehicle.

13. 9. The power supply system with a low-frequency ripple current suppression function according to claim 8, wherein the single-phase AC / DC conversion circuits form a delta-connected configuration or a star-connected configuration.

14. 9. The power supply system with a low-frequency ripple current suppression function according to claim 8, wherein the first switch and the second switch of the first switch group are turned on / off synchronously and complementarily, and the third switch and the fourth switch of the second switch group are turned on / off synchronously and complementarily.

15. 9. The power supply system having a low-frequency ripple current suppression function according to claim 8, wherein the first switch of the first switch group and the third switch of the second switch group are turned on / off in synchronization with each other.

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