TWI713290B - With soft cut two-way power flow converter - Google Patents

Abstract

The present invention provides a two-way power flow converter with soft cut, which includes a first power terminal electrically connected to an AC device, a second power terminal electrically connected to the AC device, and a second power terminal electrically connected to the first power terminal and the AC device. The soft cut circuit of the second power terminal, a bidirectional switching circuit electrically connected to the soft cut circuit, a ripple circuit electrically connected to the bidirectional switch circuit, and a control unit electrically connected to the bidirectional switch circuit; wherein, the soft cut circuit It has a first capacitor and a first inductor connected in series, the bidirectional switching circuit has a first switch unit and a first clamp unit connected in parallel, and the other end of the first inductor is electrically connected to the first switch Unit, the other end of the first switch unit is electrically connected to the other end of the first capacitor; thereby, the first capacitor and the first inductor are generated before the control unit controls the first switch unit to be in the on state A first switch current makes the first switch unit to be in the on state before and after the time point, the voltage difference across the two ends of the first switch unit is approximately unchanged, so as to achieve the purpose of zero voltage soft cut conversion.

Description

With soft cut two-way power flow converter

The present invention relates to a two-way power flow converter, in particular to a soft-cutting two-way power flow converter with zero voltage switching.

At present, there are many kinds of AC-DC converters to integrate the electricity generated by solar energy or wind power into the general commercial power grid, and most of these AC-DC converters use semiconductor components as the switches required by the AC-DC converter. Therefore, these semiconductor components can be seen from the product of the current flowing through the semiconductor component and the voltage across the two terminals during the on and off transient period of the switch. When switching, the switching element is switched by non-zero voltage soft cut or non-zero current soft, so higher switching loss will be caused.

Furthermore, when applied to an AC-DC converter with a high step-up ratio, the duty cycle of the semiconductor device is usually adjusted to a maximum value to achieve the goal of a high step-up ratio, but such a driving method is not It is limited by the equivalent resistance of the inductor in the AC-DC converter, which limits its boost ratio. Therefore, how to improve the lack of prior art is a problem that the industry urgently wants to overcome.

The purpose of the present invention is to provide a two-way power flow converter, especially referring to A soft-cut bidirectional power flow converter for zero-voltage conversion.

To achieve the above object, the present invention provides a soft-cut bidirectional power flow converter, which includes: a first power terminal electrically connected to an AC device, a second power terminal electrically connected to the AC device, and an electrical connection The soft cutting circuit of the first power terminal and the second power terminal, a bidirectional switching circuit electrically connected to the soft cutting circuit, a ripple circuit electrically connected to the bidirectional switching circuit, and a control unit electrically connected to the bidirectional switching circuit The soft cut circuit includes a first capacitor, a second capacitor, a third capacitor, a fourth capacitor, a first inductor and a second inductor; wherein, one end of the first capacitor, the second capacitor One end of the first inductor and one end of the first inductor are electrically connected to the first power end; and one end of the third capacitor, one end of the fourth capacitor, and one end of the second inductor are electrically connected to the second power source. The two-way switching circuit includes a first switching unit, a second switching unit, a third switching unit, a fourth switching unit, a first clamping unit connected in parallel to the first switching unit, and a parallel connection The second clamping unit of the second switch unit, a third clamping unit connected in parallel to the third switch unit, and a fourth clamping unit connected in parallel to the fourth switch unit; wherein, the first switch unit is One end and one end of the second switch unit are electrically connected to the other end of the first inductor, and one end of the third switch unit and one end of the fourth switch unit are electrically connected to the other end of the second inductor; The ripple circuit includes a seventh capacitor having a first connection end and a second connection end, and the first connection end of the seventh capacitor is electrically connected to the other end of the first capacitor and the other end of the third capacitor , The other end of the first switch unit and the other end of the third switch unit; and the second connection end of the seventh capacitor is electrically connected to the other end of the second capacitor, the other end of the fourth capacitor, the The other end of the second switch unit and the other end of the fourth switch unit; thereby, the first capacitor and the first inductor will be at a resonance time until the control unit controls the first switch unit to be in the on state A first switching current is generated, and the first switching current causes the first switching unit to maintain a voltage difference across the first switching unit unchanged from the resonance time point to the on state.

Further, the fourth capacitor and the second inductor will generate a second switching current before the control unit controls the fourth switching unit to be on at another resonance time point, and the second switching current will cause the The fourth switch unit maintains a voltage difference across the fourth switch unit unchanged from another resonance time point to the on state.

Further, the capacitance difference between the first capacitor and the second capacitor is greater than or equal to 0, but less than or equal to 10%.

Further, before the control unit controls the fourth switching unit to be in the on state at the resonance time point, the fourth capacitor and the second inductor generate a second switching current.

Further, at the resonance time point until the first switch unit and the fourth switch unit are in the conducting state, the current value of the first switch current of the first switch unit and the second switch of the fourth switch unit The current value of the current is different.

Further, the bidirectional switching circuit includes a fifth switch unit, a sixth switch unit, a fifth clamping unit connected in parallel to the fifth switch unit, and a sixth clamping unit connected in parallel to the sixth switch unit; Wherein, one end of the fifth switch unit and one end of the sixth switch unit are electrically connected to a third power terminal electrically connected to the AC device.

Further, the flexible cutting circuit is provided with a fifth capacitor, a sixth capacitor, and a third inductor; wherein, one end of the fifth capacitor, one end of the sixth capacitor, and one end of the third inductor are connected in common Connect the third power terminal.

Further, the first connection end of the seventh capacitor is electrically connected to the other end of the fifth capacitor and the other end of the fifth switch unit, and the second connection end of the seventh capacitor is electrically connected to Connect the other end of the sixth capacitor and the other end of the sixth switch unit.

Further, the first capacitor and the first inductor form a first resonance frequency, and the first resonance frequency is less than a switching frequency of the first switch unit and greater than zero.

Therefore, the present invention has the following beneficial effects compared with the prior art: the present invention is based on the fact that the first switch unit, the second switch unit, the third switch unit, the fourth switch unit, the fifth switch unit, and the sixth switch unit are in the on-state. , The capacitor and inductor connected in series will resonate to generate a first switching current or a second switching current, and make the first switching unit, the second switching unit, the third switching unit, the fourth switching unit, and the The fifth switch unit and the sixth switch unit maintain the voltage difference between the two ends of the switch unit approximately unchanged before and when it is turned on, thereby achieving zero-voltage flexible switching, thereby reducing the switching loss of the switching unit.

100‧‧‧Soft-cut two-way power flow converter

10: The first power terminal

20: The second power terminal

30: Third power terminal

40: Soft cut circuit

41: The first capacitor

42: second capacitor

43: third capacitor

44: The fourth capacitor

45: Fifth capacitor

46: sixth capacitor

47: The first inductor

48: second inductor

49: third inductor

50: Two-way switching circuit

51: The first switch unit

511: first clamping unit

52: The second switch unit

521: second clamping unit

53: The third switch unit

531: Third Clamping Unit

54: The fourth switch unit

541: Fourth Clamping Unit

55: Fifth switch unit

551: Fifth Clamping Unit

56: The sixth switch unit

561: Sixth Clamping Unit

60: Ripple circuit

61: First connection

62: second connection end

63: seventh capacitor

70: control unit

Ia: first switching current

Fa: first resonance frequency

Ib: second switching current

Fb: second resonance frequency

Fp‧‧‧Switching frequency

TR‧‧‧Resonance time point

T0‧‧‧on time point

200‧‧‧AC device

300‧‧‧DC device

a, b, c, d‧‧‧endpoint

Figure 1 is a block diagram of the circuit of the present invention.

Figure 2 is a schematic diagram of the circuit structure of the present invention.

Figure 3-1 is a schematic diagram of the operations before the first switching element and the sixth switching element of the present invention are turned on.

Figure 3-2 is a schematic diagram of the actions of the first switching element and the sixth switching element of the present invention when they are turned on.

Figure 4-1 is a simulation experiment result of the conduction period and the change of the switching current through the terminal a of the first switching element and the terminal c through the sixth switching element during operation of the present invention.

Figure 4-2 shows the results of the measurement experiment of the switching timing of the first switching element and the first switching current through the terminal a of the first switching element of the present invention.

Figure 5 is a schematic structural diagram of another embodiment of the present invention.

Fig. 6-1 is a schematic diagram of the operation before the first switching element and the fourth switching element of the present invention are turned on.

Figure 6-2 is a schematic diagram of the actions of the first switching element and the fourth switching element of the present invention when they are turned on.

Here are a few preferred implementation aspects of the technical features and operation methods of this application, which will be described in conjunction with the illustrations for review and reference. Furthermore, the figures in the present invention are not necessarily drawn according to the actual scale for the convenience of explanation, and the proportions in the figures are not used to limit the scope of the present invention.

Regarding the technology of the present invention, please refer to Figures 1 to 2. One end of the present invention is a soft-cut bidirectional power flow converter 100 that is electrically connected to a three-phase AC device 200 and the other end is electrically connected to a constant Power flow device 300, by which the soft-cut bidirectional power flow converter 100 converts the DC power from the DC device 300 into the AC power required by the AC device 200, or vice versa to convert the AC power from the AC device 200 It is the DC power required by the DC device 300 and achieves zero-voltage soft-cutting during power conversion. The soft-cutting bidirectional power flow converter 100 mainly includes a first power terminal 10 and a second power terminal 20 , A third power terminal 30, a soft cut circuit 40, a bidirectional switching circuit 50, a ripple circuit 60 and a control unit 70, and the first power terminal 10, the second power terminal 20 and the third power The terminal 30 is electrically connected to the AC device 200, and in this embodiment, the DC device 300 can be a load, a battery, or a power generating device; wherein, the AC device 200 can be a three-phase AC device or a power generator as described in this embodiment. Generally single-phase AC power supply is not limited to this.

The soft cut circuit 40 includes a first capacitor 41, a second capacitor 42, a third capacitor 43, a fourth capacitor 44, a fifth capacitor 45, a sixth capacitor 46, and a first inductor 47 , A second inductor 48 and a third inductor 49; wherein, one end of the first capacitor 41, one end of the second capacitor 42 and one end of the first inductor 47 are electrically connected together At the first power terminal 10, one terminal of the third capacitor 43, one terminal of the fourth capacitor 44, and one terminal of the second inductor 48 are electrically connected to the second power terminal 20, one terminal of the fifth capacitor 45 One end of the sixth capacitor 46 and one end of the third inductor 49 are electrically connected to the third power terminal 30. In this embodiment, the difference in capacitance between the first capacitor 41 and the second capacitor 42 is greater than Or equal to 0, but less than or equal to 10%, that is to say, the first capacitor 41 and the second capacitor 42, the third capacitor 43 and the fourth capacitor 44, the upper and lower arms of the soft cut circuit 40 The capacitance difference between the fifth capacitor 45 and the sixth capacitor 46 may be between 0% and 10%.

The bidirectional switching circuit 50 includes a first switch unit 51, a second switch unit 52, a third switch unit 53, a fourth switch unit 54, a fifth switch unit 55, a sixth switch unit 56, A first clamping unit 511 connected in parallel to the first switch unit 51, a second clamping unit 521 connected in parallel to the second switch unit 52, and a third clamping unit 531 connected in parallel to the third switch unit 53 A fourth clamping unit 541 connected in parallel to the fourth switch unit 54, a fifth clamping unit 551 connected in parallel to the fifth switch unit 55, and a sixth clamping unit connected in parallel to the sixth switch unit 56 561; wherein one end of the first switch unit 51 and one end of the second switch unit 52 are electrically connected to the other end of the first inductor 47; one end of the third switch unit 53 and the fourth switch unit 54 One end is electrically connected to the other end of the second inductor 48; one end of the fifth switch unit 55 and one end of the sixth switch unit 56 are electrically connected to the other end of the third inductor 49; and this embodiment In the example, the first clamping unit 511, the second clamping unit 521, the third clamping unit 531, the fourth clamping unit 541, the fifth clamping unit 551, and the sixth clamping unit 561 are The clamping voltage of the diode is approximately 0.5V to 0.7V; and the first switch unit 51, the second switch unit 52, the third switch unit 53, the fourth switch unit 54, the fifth switch unit The switch unit 55 and the sixth switch unit 56 are Insulated Gate Bipolar Transistor (IGBT) in this embodiment, but not limited to this.

The ripple circuit 60 includes a seventh capacitor 63 having a first connection terminal 61 and a second connection terminal 62; wherein, the first connection terminal 61 of the seventh capacitor 63 is electrically connected to the first capacitor 41 The other end of the third capacitor 43, the other end of the fifth capacitor 45, the other end of the first switch unit 51, the other end of the third switch unit 53, and the other end of the fifth switch unit 55 And the second connecting end 62 of the seventh capacitor 63 is electrically connected to the other end of the second capacitor 42, the other end of the fourth capacitor 44, the other end of the sixth capacitor 46, the second switch unit 52 The other end of the fourth switch unit 54 and the other end of the sixth switch unit 56.

The control unit 70 respectively controls the first switch unit 51, the second switch unit 52, the third switch unit 53, the fourth switch unit 54, the fifth switch unit 55, and the sixth switch that are electrically connected. Unit 56.

Wherein, the control unit 70 controls the first switch unit 51 and the sixth switch unit 56 to be in the conducting state. The start time is a conducting time T0, and the first capacitor 41 and the first inductor 47 will have a resonance time. From point TR to the control unit 70 controlling the first switching unit 51 to generate a first switching current Ia before the on-state, that is, the first switching current Ia will be generated before the on-time point T0; the sixth capacitor 56 and The third inductor 49 will also generate a second switching current Ib from the resonance time TR to before the control unit 70 controls the sixth switch unit 56 to be in the on state; the first switching current Ia causes the first switch From the resonance time point TR to the first switch unit being in the conducting state of the unit 51, a voltage difference between the two ends of the first switch unit 51 remains unchanged, that is, the two ends of the first switch unit 51 are in conduction. The voltage difference before and after the change is approximately zero, and zero-voltage soft cut conversion is achieved. For example, the first switch unit 51 of this embodiment is an IGBT transistor, so the voltage difference of Vce remains unchanged before and after the on-time T0; The second switching current Ib will make the sixth switch When the switch unit 56 is in the on state from the resonance time point TR to the sixth switch unit 56, the other voltage difference across the voltage across the sixth switch unit 56 remains unchanged, that is, the voltage across both ends of the sixth switch unit 56 remains unchanged. The change of the voltage difference before and after the turn-on is also approximately zero. For example, the sixth switch unit 56 of this embodiment is an IGBT transistor, so the voltage difference of Vce remains unchanged before and after the turn-on time T0; in addition, the first switch The current value of the first switching current Ia of the unit 51 and the current value of the second switching current Ib of the sixth switching unit 56 may be the same or different from the resonance time point TR to the turn-on time point T0 , Not limited to this; In addition, the first capacitor 41 and the first inductor 47 form a first resonant frequency fa, the first resonant frequency fa is less than a switching frequency fp of the first switch unit 51, but not This is the limit; in addition, the second capacitor 42 and the first inductor 47 will also form the resonant first resonant frequency fa, so that the first switch unit 51 has the first resonant frequency fa when the AC power is in different half-wave periods A resonant frequency fa causes the first clamping unit 511 to generate the first switching current Ia before the first switching unit 51 is turned on. In this embodiment, the AC device 200 is a three-phase AC device, so the AC When the power is in different half-wave periods, the operation modes of the second switch unit 52, the third switch unit 53, the fourth switch unit 54, the fifth switch unit 55, and the sixth switch unit 56 are the same as those of the aforementioned first switch unit. The switching unit 51 has the same operating modes in different half-wave periods corresponding to the AC power, so it will not be repeated.

Please refer to Figures 3-1 to 4-2 again. The bidirectional switching circuit 50 of the present invention is a three-phase power full-wave bridge circuit. Therefore, when the AC device 200 provides power to the DC device 300. The DC device 300 of this embodiment is a load. When the first power terminal 10 of the AC device 200 receives positive half-cycle AC power for power flow conversion, the first switch unit 51 is electrically connected to the A capacitor 41 and the first inductor 47 resonate and generate the first switching current Ia from the resonance time point TR to the control unit 70 before the first switching unit 51 is turned on, that is, at the resonance time point During the period from TR to the on-time point T0 when the first switch unit 51 is in the on state, the first switch current Ia flows through the first clamp after the first capacitor 41 passes through the first inductor 47 The unit 511 forms a loop, and measures the voltage difference between the terminal a and the terminal b of the first switch unit 51. At this time, the first clamping unit 511 is in a conducting state. The first switch unit 51 is an IGBT transistor, so the voltage difference between the two ends of the first switch unit 51, that is, Vce is the voltage across the diode of the first clamping unit 511, and the voltage difference is about Between 0.5 volt and 0.7 volt, but the first switch unit 51 is still in a non-conducting state during the period from the resonance time point TR to the conduction time point T0.

Please refer to FIG. 4-2. When the control unit 70 controls the first switch unit 51 to be in a conducting state, that is, when the conducting time point T0 starts, the first clamping unit 511 will be in a non-conducting state. The clamping voltage of the first switch unit 51 is provided so that the voltage across the two terminals of the first switch unit 51 at the time point of the on-time T0 is still between 0.5 volts and 0.7 volts, so the first switch unit 51 The voltage difference (Vce) between the two terminals of the terminal a and the terminal b does not change. The change of the voltage difference between the two terminals of the first switch unit 51 is substantially zero, so the first switch unit 51 is in the on state The voltage difference (Vce) between the terminal a and the terminal b of the two terminals in the front and the conducting state will be approximately the same and will not change, so that the first switch unit 51 is switched from the non-conducting state to the conducting state The effect of zero-voltage soft-cutting can be achieved, and the sixth capacitor 46 and the third inductor 49 that are electrically connected to the sixth switch unit 56 will also resonate from the resonance time point TR to the conduction time point T0. The second switching current Ib is generated during the period of, and the second switching current Ib flows through the sixth clamping unit 561 from the sixth capacitor 46 through the third inductor 49 to form a loop, and the sixth switch is measured The voltage difference between the terminal c and the terminal d at both ends of the unit 56. At this time, the sixth clamping unit 561 is in a conducting state. The sixth switching unit 56 of this embodiment is an IGBT transistor, so The voltage difference between the end point c and the end point d of the sixth switch unit 56 is the voltage across the diode of the sixth clamp unit 561, and the voltage difference is about 0.5 volts. To 0.7 volts, but the sixth switch unit 56 is still in the off state, that is, the non-conducting state, from the resonance time point TR to the conduction time point T0; when the control unit 70 controls the sixth switch unit When 56 is in the conducting state, the sixth switch unit 56 will also operate in the same mode as the first switch unit 51, so that the sixth clamping unit 561 will be in a non-conducting state and provide the sixth switch unit 56 with a clamping voltage so that The voltage across the two ends of the sixth switch unit 56 is 0.5V to 0.7V across the diode of the sixth clamping unit. Therefore, the sixth switch unit 56 has two ends across before and during the on state. The voltage difference Vce will be approximately the same without any change, so that when the sixth switch unit 56 is switched from the non-conducting state to the conducting state, the zero-voltage soft cut can be achieved, because the bidirectional switching circuit 50 in this embodiment is three Phase bridge rectification design, so at the turn-on time T0, the first switch unit 51 and the sixth switch unit 56 will be in a conductive state, and the first switch unit 51 is an IGBT transistor, and defines the first switch unit 51 The reference current direction of a switch unit 51 is the direction from the end point a to the end point b, and the measured end point a is the current value of the first switch current Ia, so the first switch current Ia is conducted in the first switch unit 51 Will be equal to the Ice current of the first switch unit 51 (the Ice current is the current flowing from the collector to the emitter); please refer to Figure 4-2. At the resonance time TR, the first capacitor 41 and the first An inductor 47 generates the first switching current Ia that turns on the first clamping unit 511 due to resonance. Therefore, between the resonance time point TR and the conduction time point T0, there will be a Measured to the value of the voltage difference across the two ends of the first clamping unit 511, and the value of the voltage difference between the two ends of the first clamping unit 511 will be equivalent to the value of Vce across the first switching unit 51 (The voltage difference between the collector and the emitter); and the first switching current Ia opposite to the reference current direction can be measured at the terminal a or the terminal b; when the first switching unit 51 is in the conduction time Point T0 is on At this time, the control unit 70 controls the first switch unit 51 to be in the on state and makes the Vge voltage high. At this time, the voltage difference between the terminal a and the terminal b before and after the on-time point T0 can be seen There is substantially no change as at the resonance time point TR, that is, the change in the voltage difference between the end point a and the end point b is approximately zero; and the first switching current Ia is at the end of the on-time point T0. Point a or end point b is measured to measure the Ice current of the first switch unit 51 in the same direction as the reference current. Therefore, the first switch unit 51, the sixth switch unit 56 and the DC device 300 form a loop, so the measurement results of the sixth switch unit 56 at the end points c and d will be the same as the first switch unit 51 are the same, so they will not be repeated; at the same time, the second switch unit 52, the third switch unit 53, the fourth switch unit 54 and the fifth switch unit 55 in this embodiment have the same operating principles as the first switch The unit 54 is the same as the sixth switch unit 56, and only has a difference in timing, so it will not be repeated. In this embodiment, because the first clamping unit 511 and the sixth clamping unit 561 are diodes, the clamping voltage is about 0.5V to 0.7V, but it is not limited thereto.

Please refer to FIG. 6 to FIG. 7-2 again, which is another embodiment of the present invention. The main difference is that the AC device 200 uses single-phase AC power. Therefore, there is the first power terminal 10 Is electrically connected to the second power terminal 20 and the AC device 200; and the soft cut circuit 40 includes the first capacitor 41, the second capacitor 42, the third capacitor 43, the fourth capacitor 44, and the An inductor 47 and the second inductor 48; wherein one end of the first capacitor 41, one end of the second capacitor 42 and one end of the first inductor 47 are electrically connected to the first power terminal 10; One end of the three capacitors 43, one end of the fourth capacitor 44, and one end of the second inductor 48 are electrically connected to the second power terminal 20; and the two-way switching circuit 50 is a single-phase full-wave bridge rectifier circuit, so The two-way switching circuit 50 includes the first switch unit 51, the second switch unit 52, a third switch unit 53, a fourth switch unit 54, and a parallel connection to the first switch unit The first clamping unit 511 of 51, a second clamping unit 521 connected in parallel to the second switch unit 52, a third clamping unit 531 connected in parallel to the third switch unit 53, and a fourth switch connected in parallel The fourth clamping unit 541 of the unit 54; wherein one end of the first switch unit 51 and one end of the second switch unit 52 are electrically connected to the other end of the first inductor 47; the third switch unit 53 One end and one end of the fourth switch unit 54 are electrically connected to the other end of the second inductor 48. The rest of the circuit structure and driving mode are substantially the same as the embodiment of the present invention in which the AC device 200 is a three-phase AC power source. Repeat it again.

In summary, the present invention is based on the first switch unit 51, the second switch unit 52, the third switch unit 53, the fourth switch unit 54, the fifth switch unit 55, and the sixth switch unit 56 Before turning on, make the first capacitor 41, a second capacitor 42, a third capacitor 43, a fourth capacitor 44, a fifth capacitor 45, a sixth capacitor 46, a first inductor 47, a second capacitor The inductor 48 and a third inductor 49 will resonate to generate the first switch current Ia and the second switch current Ib, and make the first switch unit 51, the second switch unit 52, and the third switch unit 53 , The voltage difference across the voltage across the fourth switch unit 54, the fifth switch unit 55 and the sixth switch unit 56 is substantially unchanged before and during the conduction, thereby achieving the effect of zero voltage soft cutting, and then Reduce the switching loss of the switch unit.

The content of the present invention has been described in detail above, but the above are only the preferred embodiments of the present invention, and should not be used to limit the scope of implementation of the present invention, that is, all equivalent changes and Modifications should still fall within the scope of the patent of the present invention.

100‧‧‧Soft-cut two-way power flow converter

40‧‧‧Soft cut circuit

50‧‧‧Bidirectional switching circuit

60‧‧‧Ripple circuit

70‧‧‧Control Unit

200‧‧‧AC device

300‧‧‧DC device

Claims (8)

A soft-cut bidirectional power flow converter. One end is electrically connected to an AC device, and the other end is electrically connected to DC devices for power conversion. It includes: a first power terminal electrically connected to the AC device; Connect the second power terminal of the AC device; a soft-cut circuit including a first capacitor, a second capacitor, a third capacitor, a fourth capacitor, a first inductor and a second inductor; wherein , One end of the first capacitor, one end of the second capacitor, and one end of the first inductor are electrically connected to the first power end; and one end of the third capacitor, one end of the fourth capacitor and the second One end of the inductor is electrically connected to the second power end; a bidirectional switching circuit includes a first switch unit, a second switch unit, a third switch unit, a fourth switch unit, and a parallel connection to the The first clamping unit of the first switch unit, a second clamping unit connected in parallel to the second switch unit, a third clamping unit connected in parallel to the third switch unit, and a parallel connection to the fourth switch unit A fourth clamping unit; wherein one end of the first switch unit and one end of the second switch unit are electrically connected to the other end of the first inductor; one end of the third switch unit and the fourth switch unit One end is commonly electrically connected to the other end of the second inductor; a ripple circuit includes a seventh capacitor having a first connection end and a second connection end; wherein, the first connection of the seventh capacitor The other end of the first capacitor, the other end of the third capacitor, the other end of the first switch unit and the other end of the third switch unit are electrically connected; the second connection end of the seventh capacitor is electrically connected The other end of the second capacitor, the other end of the fourth capacitor, the other end of the second switch unit, and the other end of the fourth switch unit; and a control unit that respectively controls the electrically connected first switch units , The second switch unit, the third switch unit, and the fourth switch unit; Wherein, the first capacitor and the first inductor generate a first switching current at a resonance time point until the control unit controls the first switching unit to be in the on state; wherein, the first switching current causes the second A switch unit maintains a voltage difference across the first switch unit unchanged from the resonance time point to the on-state; wherein, the fourth capacitor and the second inductor will reach the control unit at another resonance time point A second switching current is generated before controlling the fourth switching unit to be in the on state, and the second switching current causes the fourth switching unit to maintain a voltage across the fourth switching unit from another resonance time point to the on state The difference remains the same. The soft-cut bidirectional power flow converter described in item 1 of the scope of patent application, wherein the difference in capacitance between the first capacitor and the second capacitor is greater than or equal to 0 but less than or equal to 10%. The soft-cut bidirectional power flow converter described in the first item of the scope of patent application, wherein, at the resonance time point to the control unit controlling the fourth switch unit to be in the on state, the fourth capacitor and the second inductor The converter generates a second switching current. The soft-cut bidirectional power flow converter according to item 3 of the scope of patent application, wherein, at the resonance time point until the first switching unit and the fourth switching unit are in the conducting state, the first switching unit The current value of the first switch current is different from the current value of the second switch current of the fourth switch unit. The soft-cutting two-way power flow converter described in item 1 of the scope of patent application, wherein the two-way switching circuit further includes a fifth switch unit, a sixth switch unit, and a fifth switch unit connected in parallel to the fifth switch unit A clamping unit and a sixth clamping unit connected in parallel to the sixth switch unit; one end of the fifth switch unit and one end of the sixth switch unit are both electrically connected to an electrical connection Connect the third power terminal of the AC device. The soft-cutting bidirectional power flow converter described in item 5 of the scope of patent application, wherein the soft-cutting circuit is provided with a fifth capacitor, a sixth capacitor and a third inductor; one end of the fifth capacitor, the One end of the sixth capacitor and one end of the third inductor are electrically connected to the third power end. The soft-cut bidirectional power flow converter according to item 5 of the scope of patent application, wherein the first connection end of the seventh capacitor is electrically connected to the other end of the fifth capacitor and the other end of the fifth switch unit; The second connection end of the seventh capacitor is electrically connected to the other end of the sixth capacitor and the other end of the sixth switch unit. The soft-cut bidirectional power flow converter according to the first item of the scope of patent application, wherein the first capacitor and the first inductor form a first resonant frequency, and the first resonant frequency is less than that of the first switching unit A switching frequency and greater than zero.

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