Flying capacitor control circuit and flying capacitor control system

Abstract

The invention relates to the technical field of photovoltaic inverter boost circuits, and discloses a flying capacitor control circuit and a flying capacitor control system, and the flying capacitor control circuit comprises an anti-reverse connection device group and a current limiting unit. Wherein one side of the anti-reverse-connection device group is connected in parallel with the two ends of the flying capacitor, the other side of the anti-reverse-connection device group is connected with one end of the current limiting unit, and the other end of the current limiting unit is connected to any point of a connecting line between the second capacitor and the third capacitor. Before the boost circuit is started, the flying capacitor is charged by using the current limiting unit; and after the boost circuit is started, the current limiting unit is used for carrying out current limiting on the pre-charging loop. The pre-charging circuit of the flying capacitor is optimized, and the pre-charging resistor and the current-limiting resistor are added, so that the diode is protected, and the over-current failure of the diode caused by frequent action is avoided.

Description

Technical Field

[0001] The present invention relates to the technical field of photovoltaic inverter boost circuits, and in particular to a flying capacitor control circuit and a flying capacitor control system. Background Art

[0002] The flying capacitor boost converter is a new type of high-voltage boost technology. Its core principle is to use the charging and discharging process of the capacitor to generate high-voltage pulses. This technology has the advantages of high output voltage, high efficiency, small size, and light weight. It is an important research direction in the future smart grid, aerospace and other fields. At present, the flying capacitor boost converter has been widely used in solar power generation, wind power generation, electric vehicles and other fields.

[0003] Existing boost circuits such as Figure 1 As shown, one end of the first inductor L1 is connected to one end of the first capacitor C1, the other end of the first inductor L1 is respectively connected to the first end of the first transistor Q1 and the anode of the third diode D3, the cathode of the third diode D3 is respectively connected to one end of the flying capacitor Cfly1 and the anode of the fourth diode D4, the cathode of the fourth diode D4 is connected to one end of the second capacitor C2, the second end of the first transistor Q1 is respectively connected to the other end of the flying capacitor Cfly1 and the first end of the second transistor Q2, the second end of the second transistor Q2 is respectively connected to the other end of the first capacitor C1 and the other end of the third capacitor C3, the control end of the first transistor Q1 and the control end of the second transistor Q2 are connected to the control signal, the first transistor Q1 is anti-parallel connected to the first diode D1, the second transistor Q2 is anti-parallel connected to the second diode D2, the other end of the second capacitor C2 is connected to one end of the third capacitor C3, the first capacitor C1 is connected in parallel to the output end of the photovoltaic panel, and the series branch of the second capacitor C2 and the third capacitor C3 is connected in parallel to the DC bus side.

[0004] like Figure 1 As shown in FIG. 1 , the boost circuit uses a boost IGBT module to achieve the purpose of boost control of the flying capacitor. However, since the pre-charge diodes D5 and D6 integrated in the boost IGBT module have relatively small specifications, after the flying capacitor is pre-charged and connected to the grid, the diodes D5 and D6 are easily over-current-failed due to frequent operation. Summary of the invention

[0005] In view of this, the present invention provides a flying capacitor control circuit and a photovoltaic inverter boost circuit to solve the problem of overcurrent failure caused by frequent operation of diodes in a boost IGBT module.

[0006] In a first aspect, the present invention provides a flying capacitor control circuit, which is applied to a boost circuit. The flying capacitor control circuit comprises: an anti-reverse connection device group and a current limiting unit, wherein:

[0007] One side of the anti-reverse connection device group is connected in parallel to both ends of the flying capacitor, the other side of the anti-reverse connection device group is connected to one end of the current limiting unit, and the other end of the current limiting unit is connected to any point of the connecting line between the second capacitor and the third capacitor;

[0008] Before the boost circuit is started, the flying capacitor is pre-charged by the current limiting unit; after the boost circuit is started, the current limiting unit is controlled to limit the current of the pre-charging loop.

[0009] The present invention provides a flying capacitor control circuit, which uses a current limiting unit to charge the flying capacitor before the boost circuit is started; and uses the current limiting unit to limit the current of the pre-charging circuit after the boost circuit is started. By optimizing the pre-charging circuit of the flying capacitor, increasing the pre-charging resistance and the current limiting resistance, the diode is protected and overcurrent failure caused by frequent operation of the diode is avoided.

[0010] In an optional implementation, the current limiting unit includes: a first resistor, a second resistor and a relay, wherein:

[0011] The moving contact of the relay is connected to the other side of the anti-reverse connection device group, the first static contact of the relay is connected to one end of the first resistor, the second static contact of the relay is connected to one end of the second resistor, the other end of the first resistor and the other end of the second resistor are connected and then connected to any point of the connecting line between the second capacitor and the third capacitor, and the resistance value of the first resistor is greater than the resistance value of the second resistor;

[0012] Before the boost circuit is started, the moving contact of the relay is controlled to be connected to the second static contact, and the flying capacitor is pre-charged through the second resistor; after the boost circuit is started, the moving contact of the relay is controlled to be connected to the first static contact, and the pre-charging circuit is current limited by the first resistor; finally, the pulses of the first transistor and the second transistor are controlled to adjust the voltage value of the flying capacitor.

[0013] Before the boost circuit is started, the flying capacitor is charged by a pre-charging resistor; after the boost circuit is started, the pre-charging circuit is current limited by a current limiting resistor, thereby protecting the diode and avoiding overcurrent failure caused by frequent operation of the diode.

[0014] In an optional embodiment,

[0015] When the boost circuit is a single-channel boost circuit, the anti-reverse connection device group includes: a first anti-reverse connection device and a second anti-reverse connection device, wherein one end of the first anti-reverse connection device is connected to one end of the flying capacitor, the other end of the first anti-reverse connection device is respectively connected to the moving contact of the relay and one end of the second anti-reverse connection device, and the other end of the second anti-reverse connection device is connected to the other end of the flying capacitor;

[0016] Or when the boost circuit is a multi-channel boost circuit, the anti-reverse connection device group includes: a plurality of first anti-reverse connection devices and a plurality of second anti-reverse connection devices, and for each boost circuit, a first anti-reverse connection device and a second anti-reverse connection device are correspondingly provided, wherein:

[0017] One end of each of the first anti-reverse polarity devices is connected to one end of the flying capacitor, the other end of each of the first anti-reverse polarity devices is respectively connected to the moving contact of the relay and one end of each of the second anti-reverse polarity devices, and the other end of each of the second anti-reverse polarity devices is connected to the other end of the flying capacitor.

[0018] In an optional implementation, the first anti-reverse connection device is a diode or a thyristor, and the second anti-reverse connection device is a diode or a thyristor.

[0019] In a second aspect, the present invention provides a flying capacitor control system, comprising a plurality of flying capacitor control circuits according to the first aspect or any corresponding embodiment thereof.

[0020] A flying capacitor control system provided by the present invention reduces the failure rate of the flying capacitor control circuit by optimizing the flying capacitor control circuit, thereby improving the reliability of the flying capacitor control system.

[0021] In a third aspect, the present invention provides a flying capacitor control circuit, which is applied to a boost circuit. The flying capacitor control circuit includes: an anti-reverse connection unit, a switch unit and a current limiting unit, wherein:

[0022] One end of the anti-reverse connection unit is connected to one end of the flying capacitor, the other end of the anti-reverse connection unit is connected to one end of the current limiting unit, the other end of the current limiting unit is connected to any point of the connecting line between the second capacitor and the third capacitor, one end of the switch unit is connected to the other end of the flying capacitor, and the other end of the switch unit is connected to any point of the connecting line between the second capacitor and the third capacitor;

[0023] Before the boost circuit is started, the flying capacitor is pre-charged by the current limiting unit, or the switch unit is controlled to be turned on to pre-charge the flying capacitor; after the boost circuit is started, the pre-charging loop is current limited by the current limiting unit, or the switch unit is controlled to be turned off to cut off the pre-charging loop.

[0024] The present invention provides a flying capacitor control circuit. By optimizing a pre-charging circuit of a flying capacitor, before a boost circuit is started, the flying capacitor is pre-charged through a current limiting unit, or a switch unit is controlled to be turned on to pre-charge the flying capacitor; after the boost circuit is started, the pre-charging circuit is current limited through the current limiting unit, or the switch unit is controlled to be turned off to cut off the pre-charging circuit, thereby protecting a diode and avoiding overcurrent failure of the diode due to frequent operation.

[0025] In an optional implementation, the current limiting unit includes a first resistor, a second resistor and a relay, wherein:

[0026] The moving contact of the relay is connected to the other end of the anti-reverse connection unit, the first static contact of the relay is connected to one end of the first resistor, the second static contact of the relay is connected to one end of the second resistor, the other end of the first resistor and the other end of the second resistor are connected and then connected to any point of the connecting line between the second capacitor and the third capacitor, and the resistance value of the first resistor is greater than the resistance value of the second resistor;

[0027] Before the boost circuit is started, the moving contact of the relay is controlled to be connected to the second static contact, and the flying capacitor is pre-charged through the second resistor; after the boost circuit is started, the moving contact of the relay is controlled to be connected to the first static contact, and the pre-charging circuit is current limited by the first resistor; finally, the pulses of the first transistor and the second transistor are controlled to adjust the voltage value of the flying capacitor.

[0028] In an optional embodiment,

[0029] When the boost circuit is a single-channel boost circuit, the anti-reverse connection unit includes: an anti-reverse connection device, and the switch unit includes: a switch device, wherein one end of the anti-reverse connection device is connected to one end of the flying capacitor, the other end of the anti-reverse connection device is connected to the moving contact of the relay, one end of the switch device is connected to the other end of the flying capacitor, and the other end of the switch device is connected to any point of the connecting line between the second capacitor and the third capacitor;

[0030] Or when the boost circuit is a multi-channel boost circuit, the anti-reverse connection unit includes: multiple anti-reverse connection devices, and the switch unit includes: multiple switch devices. For each boost circuit, an anti-reverse connection device and a switch device are correspondingly provided, wherein one end of each of the anti-reverse connection devices is connected to one end of the flying capacitor, the other end of each of the anti-reverse connection devices is connected to the moving contact of the relay, one end of each of the switch devices is connected to the other end of the flying capacitor, and the other end of each of the switch devices is connected to any point of the connecting line between the second capacitor and the third capacitor.

[0031] In an optional implementation, the anti-reverse connection device is a diode, and the switching device is a thyristor.

[0032] In a fourth aspect, the present invention provides a flying capacitor control system, comprising a plurality of flying capacitor control circuits according to the third aspect or any corresponding embodiment thereof.

[0033] A flying capacitor control system provided by the present invention reduces the failure rate of the flying capacitor control circuit by optimizing the flying capacitor control circuit, thereby improving the reliability of the flying capacitor control system. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] In order to more clearly illustrate the specific implementation methods of the present invention or the technical solutions in the prior art, the drawings required for use in the specific implementation methods or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are some implementation methods of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0035] Figure 1 Existing boost circuit diagram;

[0036] Figure 2 is a schematic diagram of a flying capacitor control circuit according to an embodiment of the present invention;

[0037] Figure 3 is another schematic diagram of a flying capacitor control circuit according to an embodiment of the present invention;

[0038] Figure 4 is another schematic diagram of a flying capacitor control circuit according to an embodiment of the present invention;

[0039] Figure 5 is another schematic diagram of a flying capacitor control circuit according to an embodiment of the present invention;

[0040] Figure 6 is another schematic diagram of a flying capacitor control circuit according to an embodiment of the present invention;

[0041] Figure 7 is another schematic diagram of a flying capacitor control circuit according to an embodiment of the present invention;

[0042] Figure 8 is another schematic diagram of a flying capacitor control circuit according to an embodiment of the present invention;

[0043] Fig. 9 is another schematic diagram of a flying capacitor control circuit according to an embodiment of the present invention;

[0044] Fig.10 is another schematic diagram of a flying capacitor control circuit according to an embodiment of the present invention;

[0045] Fig.11 is another schematic diagram of a flying capacitor control circuit according to an embodiment of the present invention;

[0046] Fig.12 is another schematic diagram of a flying capacitor control circuit according to an embodiment of the present invention;

[0047] Fig.13 is another schematic diagram of a flying capacitor control circuit according to an embodiment of the present invention;

[0048] Fig.14 is another schematic diagram of a flying capacitor control circuit according to an embodiment of the present invention;

[0049] Fig.15 is another schematic diagram of a flying capacitor control circuit according to an embodiment of the present invention;

[0050] Fig.16 is a schematic diagram of another flying capacitor control circuit according to an embodiment of the present invention. DETAILED DESCRIPTION

[0051] In order to make the purpose, technical solution and advantages of the embodiments of the present invention clearer, the technical solution in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative work are within the scope of protection of the present invention.

[0052] In the description of the present invention, it should be noted that, furthermore, the terms “first”, “second” and “third” are only used for descriptive purposes and cannot be understood as indicating or implying relative importance.

[0053] In the description of the present invention, it should be noted that, unless otherwise clearly specified and limited, the terms "installed", "connected", and "connected" should be understood in a broad sense, for example, it 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 it can be indirectly connected through an intermediate medium, it can also be the internal connection of two components, it can be a wireless connection, or it can be a wired connection. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0054] In addition, the technical features involved in the different embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0055] Example 1

[0056] The present invention provides a flying capacitor control circuit, which is applied to a boost circuit. Figure 2 As shown, the flying capacitor control circuit includes: an anti-reverse connection device group and a current limiting unit. One side of the anti-reverse connection device group is connected in parallel to both ends of the flying capacitor Cfly1, the other side of the anti-reverse connection device group is connected to one end of the current limiting unit, and the other end of the current limiting unit is connected to any point of the connecting line between the second capacitor C2 and the third capacitor C3.

[0057] Specifically, before the boost circuit is started, the flying capacitor Cfly1 is precharged by the current limiting unit. After the boost circuit is started, the current limiting unit is controlled to limit the current of the pre-charging circuit. At this time, the boost circuit does not work, the first transistor Q1 and the second transistor Q2 do not work, and the photovoltaic panel output terminal voltage PV1 pre-charges the flying capacitor Cfly1 through the path of L1→D3→Cfly1→anti-reverse device group→current limiting unit→BUSN. After the boost circuit is started, the current limiting unit is controlled to limit the current of the pre-charging circuit. At this time, the first transistor Q1 and the second transistor Q2 will be turned on alternately, and the photovoltaic panel output terminal voltage PV1 passes through L1→Q1→anti-reverse device group→current limiting unit→C3, and the pre-charging circuit is limited by the current limiting unit in this path. Finally, the pulses of the first transistor Q1 and the second transistor Q2 are controlled to adjust the voltage value of the flying capacitor Cfly1 so that the voltage value of the flying capacitor Cfly1 is greater than the half bus voltage.

[0058] A flying capacitor control circuit provided by the present invention includes: an anti-reverse connection device group and a current limiting unit. One side of the anti-reverse connection device group is connected in parallel to both ends of the flying capacitor Cfly1, the other side of the anti-reverse connection device group is connected to one end of the current limiting unit, and the other end of the current limiting unit is connected to any point of the connecting line between the second capacitor C2 and the third capacitor C3. Before the boost circuit is started, the flying capacitor is charged by the current limiting unit; after the boost circuit is started, the current limiting unit is used to limit the current of the pre-charging circuit. By optimizing the pre-charging circuit of the flying capacitor, increasing the pre-charging resistance and the current limiting resistance, the diode is protected and the diode is prevented from failing due to overcurrent caused by frequent operation.

[0059] In an optional embodiment, if Figure 3 As shown, the current limiting unit includes: a first resistor R1, a second resistor R2 and a relay K1. Among them, the moving contact 1 of the relay K1 is connected to the other side of the anti-reverse connection device group, the first static contact 2 of the relay K1 is connected to one end of the first resistor R1, the second static contact 3 of the relay K1 is connected to one end of the second resistor R2, the other end of the first resistor R1 and the other end of the second resistor R2 are connected and then connected to any point of the connecting line between the second capacitor C2 and the third capacitor C3, and the resistance value of the first resistor R1 is greater than the resistance value of the second resistor R2.

[0060] Specifically, before the boost circuit is started, the moving contact 1 of the control relay K1 is connected to the second static contact 3, and the flying capacitor Cfly1 is pre-charged through the second resistor R2. After the boost circuit is started, the moving contact of the control relay K1 is connected to the first static contact 2, and the pre-charging circuit is current limited by the first resistor R1. Finally, the pulses of the first transistor and the second transistor are controlled to adjust the voltage value of the flying capacitor Cfly1. Among them, the first resistor R1 is a large current limiting resistor, and the second resistor R2 is a small pre-charging resistor. Before the boost circuit is started, the flying capacitor is charged by the pre-charging resistor; after the boost circuit is started, the pre-charging circuit is current limited by the current limiting resistor, which protects the diode and avoids overcurrent failure caused by frequent operation of the diode.

[0061] In an optional embodiment, if Figure 4 As shown, when the boost circuit is a single-channel boost circuit, the anti-reverse connection device group includes: a first anti-reverse connection device and a second anti-reverse connection device. One end of the first anti-reverse connection device is connected to one end of the flying capacitor Cfly1, the other end of the first anti-reverse connection device is respectively connected to the moving contact 1 of the relay K1 and one end of the second anti-reverse connection device, and the other end of the second anti-reverse connection device is connected to the other end of the flying capacitor Cfly1.

[0062] Specifically, the first anti-reverse connection device is a diode or a thyristor, and the second anti-reverse connection device is a diode or a thyristor. Therefore, there are multiple combinations of the anti-reverse connection device group.

[0063] Combination method 1: When the first anti-reverse connection device is a diode D5 and the second anti-reverse connection device is a diode D6, the flying capacitor control circuit is as follows: Figure 5 In this pre-charging line optimization solution, compared with Figure 1 The existing scheme adds a first resistor R1, a second resistor R2 and a relay K1, wherein the first resistor R1 is a large current limiting resistor and the second resistor R2 is a small pre-charge resistor. Before the boost circuit is started, the moving contact 1 of the control relay K1 is connected to the second static contact 3, and the second resistor R2 is connected to the pre-charge circuit to pre-charge the flying capacitor Cfly1. At this time, the boost circuit does not work, the first transistor Q1 and the second transistor Q2 do not work, and the photovoltaic panel output terminal voltage PV1 pre-charges the flying capacitor Cfly1 through the path L1→D3→Cfly1→D6→R2→BUSN. After the boost circuit is started, the moving contact 1 of the control relay K1 is connected to the first static contact 2, and the first resistor R1 is connected to the pre-charge circuit to limit the current of the pre-charge circuit. At this time, the first transistor Q1 and the second transistor Q2 will be turned on alternately, and the photovoltaic panel output terminal voltage PV1 passes through L1→Q1→D6→R1→C3, and the pre-charge circuit is limited by the first resistor R1 in this path. Finally, the pulses of the first transistor Q1 and the second transistor Q2 are controlled to adjust the voltage value of the flying capacitor Cfly1 so that the flying capacitor voltage value is greater than the half bus voltage.

[0064] Combination method 2: When the first anti-reverse connection device is a diode D5 and the second anti-reverse connection device is a thyristor SCR, the flying capacitor control circuit is as follows: Figure 6 This pre-charging circuit optimization solution is Figure 5On the basis of the scheme, the diode D6 is replaced with a thyristor SCR, and the SCR is kept in a normally open state. Before the boost circuit is started, the moving contact 1 of the control relay K1 is connected to the second static contact 3, and the second resistor R2 is connected to the pre-charging circuit to pre-charge the flying capacitor Cfly1. At this time, the boost circuit does not work, the first transistor Q1 and the second transistor Q2 do not work, and the photovoltaic panel output terminal voltage PV1 pre-charges the flying capacitor Cfly1 through the path of L1→D3→Cfly1→SCR→R2→BUSN. After the boost circuit is started, the moving contact 1 of the control relay K1 is connected to the first static contact 2, and the first resistor R1 is connected to the pre-charging circuit to limit the current of the pre-charging circuit. At this time, the first transistor Q1 and the second transistor Q2 will be turned on alternately, and the photovoltaic panel output terminal voltage PV1 passes through L1→Q1→SCR→R1→C3, and the pre-charging circuit is limited by the first resistor R1 in this path. Finally, the pulses of the first transistor Q1 and the second transistor Q2 are controlled to adjust the voltage value of the flying capacitor Cfly1 so that the flying capacitor voltage value is greater than the half bus voltage.

[0065] Combination method 3: When the first anti-reverse connection device is a thyristor SCR and the second anti-reverse connection device is a diode D6, the flying capacitor control circuit is as follows: Figure 7 This pre-charging circuit optimization solution is Figure 5 On the basis of the scheme, the diode D5 is replaced with a thyristor SCR, and the SCR is kept in a normally open state. Before the boost circuit is started, the moving contact 1 of the control relay K1 is connected to the second static contact 3, and the second resistor R2 is connected to the pre-charging circuit to pre-charge the flying capacitor Cfly1. At this time, the boost circuit does not work, the first transistor Q1 and the second transistor Q2 do not work, and the photovoltaic panel output terminal voltage PV1 pre-charges the flying capacitor Cfly1 through the L1→D3→Cfly1→D6→R2→BUSN path. After the boost circuit is started, the moving contact 1 of the control relay K1 is connected to the first static contact 2, and the first resistor R1 is connected to the pre-charging circuit to limit the current of the pre-charging circuit. At this time, the first transistor Q1 and the second transistor Q2 will be turned on alternately, and the photovoltaic panel output terminal voltage PV1 passes through L1→Q1→D6→R1→C3, and the pre-charging circuit is limited by the first resistor R1 in this path. Finally, the pulses of the first transistor Q1 and the second transistor Q2 are controlled to adjust the voltage value of the flying capacitor Cfly1 so that the flying capacitor voltage value is greater than the half bus voltage.

[0066] In an optional embodiment, when the boost circuit is a multi-channel boost circuit, the anti-reverse connection device group includes: a plurality of first anti-reverse connection devices and a plurality of second anti-reverse connection devices, and a first anti-reverse connection device and a second anti-reverse connection device are correspondingly provided for each boost circuit. Among them, one end of each first anti-reverse connection device is connected to one end of the flying capacitor Cfly1, and the other end of each first anti-reverse connection device is respectively connected to the moving contact of the relay K1 and one end of each second anti-reverse connection device, and the other end of each second anti-reverse connection device is connected to the other end of the flying capacitor Cfly1.

[0067] Specifically, the first anti-reverse connection device is a diode or a thyristor, and the second anti-reverse connection device is a diode or a thyristor. Therefore, when the boost circuit is a multi-channel boost circuit, there are also multiple combinations of the anti-reverse connection device group.

[0068] Combination method 1: When the first anti-reverse connection device is a diode D5 and the second anti-reverse connection device is a diode D6, the flying capacitor control circuit is as follows: Figure 8 As shown. For each boost circuit, a diode D5 and a diode D6 are set accordingly. In this pre-charge circuit optimization scheme, compared with the existing scheme, the first resistor R1, the second resistor R2 and the relay K1 are added, wherein the first resistor R1 is a large current limiting resistor, and the second resistor R2 is a small pre-charge resistor. For the unstarted boost circuit, before the boost circuit is started, the moving contact 1 of the control relay K1 is connected to the second static contact 3, and the second resistor R2 is connected to the pre-charge circuit to pre-charge the flying capacitor Cfly1. At this time, the boost circuit does not work, the first transistor Q1 and the second transistor Q2 do not work, and the photovoltaic panel output terminal voltage PV1 pre-charges the flying capacitor Cfly1 through the L1→D3→Cfly1→D6→R2→BUSN path. After the boost circuit is started, the moving contact 1 of the control relay K1 is connected to the first static contact 2, and the first resistor R1 is connected to the pre-charge circuit. At this time, the first transistor Q1 and the second transistor Q2 are turned on alternately, and the photovoltaic panel output voltage PV1 passes through L1→Q1→D6→R1→C3. In this path, the pre-charging circuit is limited by the first resistor R1. Finally, the pulses of the first transistor Q1 and the second transistor Q2 are controlled to adjust the voltage value of the flying capacitor Cfly1 so that the flying capacitor voltage value is greater than the half bus voltage.

[0069] Further, when one group of photovoltaic panels is shaded, the output voltage PV1 of the photovoltaic panel is low and does not reach the grid voltage, and the other groups of photovoltaic panels have started to be connected to the grid, the BUS voltage will increase. At this time, the BUS terminal voltage can be used to reversely precharge the boost circuit that is not connected to the grid, and the output voltage of the photovoltaic panel group is promptly increased to the grid voltage. For the unstarted boost circuit, before the boost circuit is started, the moving contact 1 of the control relay K1 is connected to the second static contact 3, and the second resistor R2 is connected to the pre-charge circuit to pre-charge the flying capacitor Cfly1. At this time, the boost circuit does not work, the first transistor Q1 and the second transistor Q2 do not work, and the voltage at BUSN pre-charges the flying capacitor Cfly1 through the path of R2→D5→Cfly1→D1→L1→C1. After the boost circuit is started, the moving contact 1 of the control relay K1 is connected to the first static contact 2, and the first resistor R1 is connected to the pre-charge circuit to limit the current of the pre-charge circuit. At this time, the first transistor Q1 and the second transistor Q2 are turned on alternately, and the voltage at BUSN passes through R1→D5→Cfly1→Q2. In this path, the pre-charging circuit is limited by the first resistor R1. Finally, the pulses of the first transistor Q1 and the second transistor Q2 are controlled to adjust the voltage value of the flying capacitor Cfly1 so that the flying capacitor voltage value is greater than the half bus voltage.

[0070] Combination method 2: When the first anti-reverse connection device is a diode D5 and the second anti-reverse connection device is a thyristor SCR, the flying capacitor control circuit is as follows: Fig. 9 As shown in the figure. For each boost circuit, a diode D5 and a thyristor SCR are set accordingly. This pre-charge circuit optimization solution is based on Figure 8On the basis of the scheme, the diode D6 is replaced with a thyristor SCR, and the SCR is kept in a normally open state. For the unstarted boost circuit, before the boost circuit is started, the moving contact 1 of the control relay K1 is connected to the second static contact 3, and the second resistor R2 is connected to the pre-charging circuit to pre-charge the flying capacitor Cfly1. At this time, the boost circuit does not work, the first transistor Q1 and the second transistor Q2 do not work, and the photovoltaic panel output terminal voltage PV1 pre-charges the flying capacitor Cfly1 through the L1→D3→Cfly1→SCR→R2→BUSN path. After the boost circuit is started, the moving contact 1 of the control relay K1 is connected to the first static contact 2, and the first resistor R1 is connected to the pre-charging circuit. At this time, the first transistor Q1 and the second transistor Q2 will be turned on alternately, and the photovoltaic panel output terminal voltage PV1 passes through L1→Q1→SCR→R1→C3, and the pre-charging circuit is limited by the first resistor R1 in this path. Finally, the pulses of the first transistor Q1 and the second transistor Q2 are controlled to adjust the voltage value of the flying capacitor Cfly1 so that the flying capacitor voltage value is greater than the half bus voltage.

[0071] Further, when one group of photovoltaic panels is shaded, the output voltage PV1 of the photovoltaic panel is low and does not reach the grid voltage, and the other groups of photovoltaic panels have started to be connected to the grid, the BUS voltage will increase. At this time, the BUS terminal voltage can be used to reversely precharge the boost circuit that is not connected to the grid, and the output voltage of the photovoltaic panel group is promptly increased to the grid voltage. For the unstarted boost circuit, before the boost circuit is started, the moving contact 1 of the control relay K1 is connected to the second static contact 3, and the second resistor R2 is connected to the pre-charge circuit to pre-charge the flying capacitor Cfly1. At this time, the boost circuit does not work, the first transistor Q1 and the second transistor Q2 do not work, and the voltage at BUSN pre-charges the flying capacitor Cfly1 through the path of R2→D5→Cfly1→D1→L1→C1. After the boost circuit is started, the moving contact 1 of the control relay K1 is connected to the first static contact 2, and the first resistor R1 is connected to the pre-charge circuit to limit the current of the pre-charge circuit. At this time, the first transistor Q1 and the second transistor Q2 are turned on alternately, and the voltage at BUSN passes through R1→D5→Cfly1→Q2. In this path, the pre-charging circuit is limited by the first resistor R1. Finally, the pulses of the first transistor Q1 and the second transistor Q2 are controlled to adjust the voltage value of the flying capacitor Cfly1 so that the flying capacitor voltage value is greater than the half bus voltage.

[0072] Combination method three: When the first anti-reverse connection device is a thyristor SCR and the second anti-reverse connection device is a diode D5, the flying capacitor control circuit is as follows: Fig.10As shown in the figure. For each boost circuit, a diode D6 and a thyristor SCR are set accordingly. This pre-charge circuit optimization solution is based on Figure 8 On the basis of the scheme, the diode D5 is replaced with a thyristor SCR, and the SCR is kept in a normally open state. For the unstarted boost circuit, before the boost circuit is started, the moving contact 1 of the control relay K1 is connected to the second static contact 3, and the second resistor R2 is connected to the pre-charging circuit to pre-charge the flying capacitor Cfly1. At this time, the boost circuit does not work, the first transistor Q1 and the second transistor Q2 do not work, and the photovoltaic panel output terminal voltage PV1 pre-charges the flying capacitor Cfly1 through the L1→D3→Cfly1→D6→R2→BUSN path. After the boost circuit is started, the moving contact 1 of the control relay K1 is connected to the first static contact 2, and the first resistor R1 is connected to the pre-charging circuit. At this time, the first transistor Q1 and the second transistor Q2 will be turned on alternately, and the photovoltaic panel output terminal voltage PV1 passes through L1→Q1→D6→R1→C3, and the pre-charging circuit is limited by the first resistor R1 in this path. Finally, the pulses of the first transistor Q1 and the second transistor Q2 are controlled to adjust the voltage value of the flying capacitor Cfly1 so that the flying capacitor voltage value is greater than the half bus voltage.

[0073] Furthermore, when one group of photovoltaic panels is shaded, the output voltage PV1 of the photovoltaic panel is low and does not reach the grid voltage, and the BUS voltage will increase after the other groups of photovoltaic panels have started to be connected to the grid. At this time, the BUS terminal voltage can be used to reversely precharge the boost circuit that is not connected to the grid, and the output voltage of the photovoltaic panel group is promptly increased to the grid voltage. For the unstarted boost circuit, before the boost circuit is started, the moving contact 1 of the control relay K1 is connected to the second static contact 3, and the second resistor R2 is connected to the pre-charge circuit to pre-charge the flying capacitor Cfly1. At this time, the boost circuit does not work, the first transistor Q1 and the second transistor Q2 do not work, and the voltage at BUSN pre-charges the flying capacitor Cfly1 through the R2→SCR→Cfly1→D1→L1→C1 path. After the boost circuit is started, the moving contact 1 of the control relay K1 is connected to the first static contact 2, and the first resistor R1 is connected to the pre-charge circuit to limit the current of the pre-charge circuit. At this time, the first transistor Q1 and the second transistor Q2 are turned on alternately, and the voltage at BUSN passes through R1→SCR→Cfly1→Q2. In this path, the pre-charging circuit is limited by the first resistor R1. Finally, the pulses of the first transistor Q1 and the second transistor Q2 are controlled to adjust the voltage value of the flying capacitor Cfly1 so that the flying capacitor voltage value is greater than the half bus voltage.

[0074] The present invention provides a flying capacitor control system, comprising a plurality of Figure 2-Figure 10 A flying capacitor control circuit as shown in any of the accompanying drawings.

[0075] Specifically, the working process of the flying capacitor control circuit in the flying capacitor control system refers to the above-mentioned embodiment 1, which will not be described in detail here.

[0076] A flying capacitor control system provided by the present invention reduces the failure rate of the flying capacitor control circuit by optimizing the flying capacitor control circuit, thereby improving the reliability of the flying capacitor control system.

[0077] Example 2

[0078] The present invention provides a flying capacitor control circuit, which is applied to a boost circuit, such as Fig.11 and Fig.12 As shown, the flying capacitor control circuit includes: an anti-reverse connection unit, a switch unit and a current limiting unit. Among them, one end of the anti-reverse connection unit is connected to one end of the flying capacitor Cfly1, the other end of the anti-reverse connection unit is connected to one end of the current limiting unit, the other end of the current limiting unit is connected to any point of the connecting line between the second capacitor C2 and the third capacitor C3, one end of the switch unit is connected to the other end of the flying capacitor Cfly1, and the other end of the switch unit is connected to any point of the connecting line between the second capacitor C2 and the third capacitor C3.

[0079] Specifically, in this pre-charge circuit optimization scheme, two flying capacitor control circuits can be designed according to the different layout positions of the anti-reverse connection unit and the switch unit. When the anti-reverse connection unit is located above the flying capacitor Cfly1 and the switch unit is located below the flying capacitor Cfly1, the following design is used: Fig.11 When the switch unit is located above the flying capacitor Cfly1 and the anti-reverse connection unit is located below the flying capacitor Cfly1, the following design is made: Fig.12 The flying capacitor control circuit shown.

[0080] like Fig.11 As shown, before the boost circuit is started, the switch unit is controlled to be turned on to pre-charge the flying capacitor Cfly1. At this time, the boost circuit does not work, the first transistor Q1 and the second transistor Q2 do not work, and the photovoltaic panel output terminal voltage PV1 pre-charges the flying capacitor Cfly1 through the L1→D3→Cfly1→switch unit→BUSN path. After the boost circuit is started, the switch unit is controlled to be turned off to cut off the pre-charging loop. Finally, the pulses of the first transistor Q1 and the second transistor Q2 are controlled to adjust the voltage value of the flying capacitor Cfly1 so that the flying capacitor voltage value is greater than the half bus voltage.

[0081] like Fig.12As shown, before the boost circuit is started, the flying capacitor Cfly1 is precharged through the current limiting unit. At this time, the boost circuit does not work, the first transistor Q1 and the second transistor Q2 do not work, and the photovoltaic panel output terminal voltage PV1 precharges the flying capacitor Cfly1 through the path of L1→D3→Cfly1→anti-reverse connection unit→current limiting unit→BUSN. After the boost circuit is started, the pre-charging circuit is current limited by the current limiting unit. At this time, the first transistor Q1 and the second transistor Q2 will be turned on alternately, and the photovoltaic panel output terminal voltage PV1 passes through L1→Q1→anti-reverse connection unit→current limiting unit→C3, and the pre-charging circuit is current limited by the current limiting unit in this path. Finally, the pulses of the first transistor Q1 and the second transistor Q2 are controlled to adjust the voltage value of the flying capacitor Cfly1 so that the flying capacitor voltage value is greater than the half bus voltage.

[0082] The present invention provides a flying capacitor control circuit. By optimizing a pre-charging circuit of a flying capacitor, before a boost circuit is started, the flying capacitor is pre-charged through a current limiting unit, or a switch unit is controlled to be turned on to pre-charge the flying capacitor; after the boost circuit is started, the pre-charging circuit is current limited through the current limiting unit, or the switch unit is controlled to be turned off to cut off the pre-charging circuit, thereby protecting a diode and avoiding overcurrent failure of the diode due to frequent operation.

[0083] In an optional embodiment, if Fig.13 and Fig.14 As shown, the current limiting unit includes a first resistor R1, a second resistor R2 and a relay K1. Among them, the moving contact 1 of the relay K1 is connected to the other end of the anti-reverse connection unit, the first static contact 2 of the relay K1 is connected to one end of the first resistor R1, the second static contact 3 of the relay K1 is connected to one end of the second resistor R2, the other end of the first resistor R1 and the other end of the second resistor R2 are connected and then connected to any point of the connecting line between the second capacitor C2 and the third capacitor C3, and the resistance value of the first resistor R1 is greater than the resistance value of the second resistor R2.

[0084] Specifically, in Fig.13 In the example, the reverse connection protection unit is diode D5. Fig.14 In the example, the reverse connection protection unit is diode D6. Fig.13 and Fig.14As shown, before the boost circuit is started, the moving contact of the control relay K1 is connected to the second static contact 3, and the flying capacitor Cfly1 is pre-charged through the second resistor R2; after the boost circuit is started, the moving contact of the control relay K1 is connected to the first static contact 2, and the first resistor R1 is used to limit the current of the pre-charging circuit; finally, the pulses of the first transistor and the second transistor are controlled to adjust the voltage value of the flying capacitor Cfly1. Among them, the first resistor R1 is a large current limiting resistor, and the second resistor R2 is a small pre-charging resistor.

[0085] In an optional embodiment, if Fig.13 and Fig.14 As shown, when the boost circuit is a single-channel boost circuit, the anti-reverse connection unit includes: an anti-reverse connection device, and the switch unit includes: a switch device. Among them, one end of the anti-reverse connection device is connected to one end of the flying capacitor Cfly1, the other end of the anti-reverse connection device is connected to the moving contact of the relay K1, one end of the switch device is connected to the other end of the flying capacitor Cfly1, and the other end of the switch device is connected to any point of the connecting line between the second capacitor C2 and the third capacitor C3.

[0086] Specifically, the reverse connection protection device is a diode, and the switch device is a thyristor. When the diode is located above the flying capacitor Cfly1 and the switch device is located below the flying capacitor Cfly1, the design is as follows: Fig.13 When the switch device is located above the flying capacitor Cfly1 and the anti-reverse connection unit is located below the flying capacitor Cfly1, the design is as follows Fig.14 The flying capacitor control circuit shown.

[0087] like Fig.13 As shown, the diode D5 is located above the flying capacitor Cfly1, and the thyristor SCR is located below the flying capacitor Cfly1. Before the boost circuit is started, the thyristor SCR is controlled to be turned on to pre-charge the flying capacitor Cfly1. At this time, the boost circuit does not work, the first transistor Q1 and the second transistor Q2 do not work, and the photovoltaic panel output terminal voltage PV1 pre-charges the flying capacitor Cfly1 through the L1→D3→Cfly1→SCR→BUSN path. After the boost circuit is started, the thyristor SCR is controlled to be turned off to cut off the pre-charging circuit. Finally, the pulses of the first transistor Q1 and the second transistor Q2 are controlled to adjust the voltage value of the flying capacitor Cfly1 so that the flying capacitor voltage value is greater than the half bus voltage.

[0088] like Fig.14As shown, the thyristor SCR is located above the flying capacitor Cfly1, and the diode D5 is located below the flying capacitor Cfly1. Before the boost circuit is started, the moving contact 1 of the control relay K1 is connected to the second static contact 3, and the second resistor R2 is connected to the pre-charging circuit to pre-charge the flying capacitor Cfly1. At this time, the boost circuit does not work, the first transistor Q1 and the second transistor Q2 do not work, and the photovoltaic panel output terminal voltage PV1 pre-charges the flying capacitor Cfly1 through the path L1→D3→Cfly1→D6→R2→BUSN. After the boost circuit is started, the moving contact 1 of the control relay K1 is connected to the first static contact 2, and the first resistor R1 is connected to the pre-charging circuit to limit the current of the pre-charging circuit. At this time, the first transistor Q1 and the second transistor Q2 will be turned on alternately, and the photovoltaic panel output terminal voltage PV1 passes through L1→Q1→D6→R1→C3, and the pre-charging circuit is limited by the first resistor R1 in this path. Finally, the pulses of the first transistor Q1 and the second transistor Q2 are controlled to adjust the voltage value of the flying capacitor Cfly1 so that the flying capacitor voltage value is greater than the half bus voltage.

[0089] In an optional embodiment, when the boost circuit is a multi-channel boost circuit, the anti-reverse connection unit includes: a plurality of anti-reverse connection devices, and the switch unit includes: a plurality of switch devices. For each boost circuit, an anti-reverse connection device and a switch device are correspondingly provided, wherein one end of each anti-reverse connection device is connected to one end of the flying capacitor Cfly1, the other end of each anti-reverse connection device is connected to the moving contact of the relay K1, one end of each switch device is connected to the other end of the flying capacitor Cfly1, and the other end of each switch device is connected to any point of the connecting line between the second capacitor C2 and the third capacitor C3.

[0090] Specifically, the reverse connection protection device is a diode, and the switch device is a thyristor. For each boost circuit, when the diode is located above the flying capacitor Cfly1 and the switch device is located below the flying capacitor Cfly1, the following design is performed: Fig.15 For each boost circuit, when the switch device is located above the flying capacitor Cfly1 and the anti-reverse connection unit is located below the flying capacitor Cfly1, the following design is performed: Fig.16 The flying capacitor control circuit shown.

[0091] like Fig.15As shown, for each boost circuit, the diode D5 is located above the flying capacitor Cfly1, and the thyristor SCR is located below the flying capacitor Cfly1. For the unstarted boost circuit, the thyristor SCR is controlled to be turned on to pre-charge the flying capacitor Cfly1. At this time, the boost circuit does not work, the first transistor Q1 and the second transistor Q2 do not work, and the photovoltaic panel output terminal voltage PV1 pre-charges the flying capacitor Cfly1 through the L1→D3→Cfly1→SCR→BUSN path. After the boost circuit is started, the thyristor SCR is controlled to be turned off and the pre-charging circuit is cut off. Finally, the pulses of the first transistor Q1 and the second transistor Q2 are controlled to adjust the voltage value of the flying capacitor Cfly1 so that the flying capacitor voltage value is greater than the half bus voltage.

[0092] Further, when one group of photovoltaic panels is shaded, the output voltage PV1 of the photovoltaic panel is low and does not reach the grid voltage, and the other groups of photovoltaic panels have started to be connected to the grid, the BUS voltage will increase. At this time, the BUS terminal voltage can be used to reversely precharge the boost circuit that is not connected to the grid, and the output voltage of the photovoltaic panel group is promptly increased to the grid voltage. For the unstarted boost circuit, before the boost circuit is started, the moving contact 1 of the control relay K1 is connected to the second static contact 3, and the second resistor R2 is connected to the pre-charge circuit to pre-charge the flying capacitor Cfly1. At this time, the boost circuit does not work, the first transistor Q1 and the second transistor Q2 do not work, and the voltage at BUSN pre-charges the flying capacitor Cfly1 through the path of R2→D5→Cfly1→D1→L1→C1. After the boost circuit is started, the moving contact 1 of the control relay K1 is connected to the first static contact 2, and the first resistor R1 is connected to the pre-charge circuit to limit the current of the pre-charge circuit. At this time, the first transistor Q1 and the second transistor Q2 are turned on alternately, and the voltage at BUSN passes through R1→D5→Cfly1→Q2. In this path, the pre-charging circuit is limited by the first resistor R1. Finally, the pulses of the first transistor Q1 and the second transistor Q2 are controlled to adjust the voltage value of the flying capacitor Cfly1 so that the flying capacitor voltage value is greater than the half bus voltage.

[0093] like Fig.16As shown, for each boost circuit, the thyristor SCR is located above the flying capacitor Cfly1, and the diode D5 is located below the flying capacitor Cfly1. For the unstarted boost circuit, the moving contact 1 of the control relay K1 is connected to the second static contact 3, and the second resistor R2 is connected to the pre-charging circuit to pre-charge the flying capacitor Cfly1. At this time, the boost circuit does not work, the first transistor Q1 and the second transistor Q2 do not work, and the photovoltaic panel output terminal voltage PV1 pre-charges the flying capacitor Cfly1 through the L1→D3→Cfly1→D5→R2→BUSN path. After the boost circuit is started, the moving contact 1 of the control relay K1 is connected to the first static contact 2, and the first resistor R1 is connected to the pre-charging circuit to limit the current of the pre-charging circuit. At this time, the first transistor Q1 and the second transistor Q2 will be turned on alternately, and the photovoltaic panel output terminal voltage PV1 passes through L1→Q1→D5→R1→C3, and the pre-charging circuit is limited by the first resistor R1 in this path. Finally, the pulses of the first transistor Q1 and the second transistor Q2 are controlled to adjust the voltage value of the flying capacitor Cfly1 so that the flying capacitor voltage value is greater than the half bus voltage.

[0094] Furthermore, when one group of photovoltaic panels is shaded, resulting in a low output voltage PV1 of the photovoltaic panel that does not reach the grid-connected voltage, and the other groups of photovoltaic panels have already started to be connected to the grid, the BUS voltage will increase. At this time, the BUS terminal voltage can be used to reversely precharge the boost circuit that is not connected to the grid, and the output voltage of the photovoltaic panel group can be timely increased to the grid-connected voltage. For the unstarted boost circuit, before the boost circuit is started, the thyristor SCR is controlled to be turned on. At this time, the boost circuit does not work, the first transistor Q1 and the second transistor Q2 do not work, and the voltage at BUSN precharges the flying capacitor Cfly1 through the path of SCR→Cfly1→D1→L1→C1. After the boost circuit is started, the thyristor SCR is controlled to be closed and the pre-charging circuit is cut off. Finally, the pulses of the first transistor Q1 and the second transistor Q2 are controlled to adjust the voltage value of the flying capacitor Cfly1 so that the flying capacitor voltage value is greater than the half bus voltage.

[0095] The present invention provides a flying capacitor control system, comprising a plurality of Figure 11-Figure 16 A flying capacitor control circuit as shown in any of the accompanying drawings.

[0096] Specifically, the working process of the flying capacitor control circuit in the flying capacitor control system refers to the above-mentioned embodiment 2, which will not be described in detail here.

[0097] A flying capacitor control system provided by the present invention reduces the failure rate of the flying capacitor control circuit by optimizing the flying capacitor control circuit, thereby improving the reliability of the flying capacitor control system.

[0098] Although the embodiments of the present invention have been described in conjunction with the accompanying drawings, those skilled in the art may make various modifications and variations without departing from the spirit and scope of the present invention, and such modifications and variations are all within the scope defined by the appended claims.

Claims

1. A flying capacitor control circuit, characterized in that: Applied to boost circuit, the flying capacitor control circuit includes: an anti-reverse connection device group and a current limiting unit, wherein: One side of the anti-reverse connection device group is connected in parallel to both ends of the flying capacitor, the other side of the anti-reverse connection device group is connected to one end of the current limiting unit, and the other end of the current limiting unit is connected to any point of the connecting line between the second capacitor and the third capacitor; Before the boost circuit is started, the flying capacitor is pre-charged by the current limiting unit; after the boost circuit is started, the current limiting unit is controlled to limit the current of the pre-charging loop.

2. The flying capacitor control circuit according to claim 1, characterized in that: The current limiting unit includes: a first resistor, a second resistor and a relay, wherein: The moving contact of the relay is connected to the other side of the anti-reverse connection device group, the first static contact of the relay is connected to one end of the first resistor, the second static contact of the relay is connected to one end of the second resistor, the other end of the first resistor and the other end of the second resistor are connected and then connected to any point of the connecting line between the second capacitor and the third capacitor, and the resistance value of the first resistor is greater than the resistance value of the second resistor; Before the boost circuit is started, the moving contact of the relay is controlled to be connected to the second static contact, and the flying capacitor is pre-charged through the second resistor; after the boost circuit is started, the moving contact of the relay is controlled to be connected to the first static contact, and the pre-charging circuit is current limited by the first resistor; finally, the pulses of the first transistor and the second transistor are controlled to adjust the voltage value of the flying capacitor.

3. The flying capacitor control circuit according to claim 2, characterized in that: When the boost circuit is a single-channel boost circuit, the anti-reverse connection device group includes: a first anti-reverse connection device and a second anti-reverse connection device, wherein one end of the first anti-reverse connection device is connected to one end of the flying capacitor, the other end of the first anti-reverse connection device is respectively connected to the moving contact of the relay and one end of the second anti-reverse connection device, and the other end of the second anti-reverse connection device is connected to the other end of the flying capacitor; Or when the boost circuit is a multi-channel boost circuit, the anti-reverse connection device group includes: a plurality of first anti-reverse connection devices and a plurality of second anti-reverse connection devices, and for each boost circuit, a first anti-reverse connection device and a second anti-reverse connection device are correspondingly provided, wherein: One end of each of the first anti-reverse polarity devices is connected to one end of the flying capacitor, the other end of each of the first anti-reverse polarity devices is respectively connected to the moving contact of the relay and one end of each of the second anti-reverse polarity devices, and the other end of each of the second anti-reverse polarity devices is connected to the other end of the flying capacitor.

4. The flying capacitor control circuit according to claim 3, characterized in that: The first anti-reverse connection device is a diode or a thyristor, and the second anti-reverse connection device is a diode or a thyristor.

5. A flying capacitor control system, characterized in that: The invention comprises a plurality of flying capacitor control circuits as described in any one of claims 1 to 4.

6. A flying capacitor control circuit, characterized in that: Applied to a boost circuit, the flying capacitor control circuit includes: an anti-reverse connection unit, a switch unit and a current limiting unit, wherein: One end of the anti-reverse connection unit is connected to one end of the flying capacitor, the other end of the anti-reverse connection unit is connected to one end of the current limiting unit, the other end of the current limiting unit is connected to any point of the connecting line between the second capacitor and the third capacitor, one end of the switch unit is connected to the other end of the flying capacitor, and the other end of the switch unit is connected to any point of the connecting line between the second capacitor and the third capacitor; Before the boost circuit is started, the flying capacitor is pre-charged by the current limiting unit, or the switch unit is controlled to be turned on to pre-charge the flying capacitor; after the boost circuit is started, the pre-charging loop is current limited by the current limiting unit, or the switch unit is controlled to be turned off to cut off the pre-charging loop.

7. The flying capacitor control circuit according to claim 6, characterized in that: The current limiting unit includes a first resistor, a second resistor and a relay, wherein: The moving contact of the relay is connected to the other end of the anti-reverse connection unit, the first static contact of the relay is connected to one end of the first resistor, the second static contact of the relay is connected to one end of the second resistor, the other end of the first resistor and the other end of the second resistor are connected and then connected to any point of the connecting line between the second capacitor and the third capacitor, and the resistance value of the first resistor is greater than the resistance value of the second resistor; Before the boost circuit is started, the moving contact of the relay is controlled to be connected to the second static contact, and the flying capacitor is pre-charged through the second resistor; after the boost circuit is started, the moving contact of the relay is controlled to be connected to the first static contact, and the pre-charging circuit is current limited by the first resistor; finally, the pulses of the first transistor and the second transistor are controlled to adjust the voltage value of the flying capacitor.

8. The flying capacitor control circuit according to claim 7, characterized in that: When the boost circuit is a single-channel boost circuit, the anti-reverse connection unit includes: an anti-reverse connection device, and the switch unit includes: a switch device, wherein one end of the anti-reverse connection device is connected to one end of the flying capacitor, the other end of the anti-reverse connection device is connected to the moving contact of the relay, one end of the switch device is connected to the other end of the flying capacitor, and the other end of the switch device is connected to any point of the connecting line between the second capacitor and the third capacitor; Or when the boost circuit is a multi-channel boost circuit, the anti-reverse connection unit includes: multiple anti-reverse connection devices, and the switch unit includes: multiple switch devices. For each boost circuit, an anti-reverse connection device and a switch device are correspondingly provided, wherein one end of each of the anti-reverse connection devices is connected to one end of the flying capacitor, the other end of each of the anti-reverse connection devices is connected to the moving contact of the relay, one end of each of the switch devices is connected to the other end of the flying capacitor, and the other end of each of the switch devices is connected to any point of the connecting line between the second capacitor and the third capacitor.

9. The flying capacitor control circuit according to claim 8, characterized in that: The anti-reverse connection device is a diode, and the switch device is a thyristor.

10. A flying capacitor control system, characterized in that: It comprises a plurality of flying capacitor control circuits as described in any one of claims 6 to 9.

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