CN113992012A

CN113992012A - Suspension capacitive Boost circuit, inverter and grid-connected power generation system

Info

Publication number: CN113992012A
Application number: CN202111444891.6A
Authority: CN
Inventors: 何安然; 陈鹏; 孙帅; 颜世超; 孟鹏飞
Original assignee: Sungrow Power Supply Co Ltd
Current assignee: Sungrow Power Supply Co Ltd
Priority date: 2021-11-30
Filing date: 2021-11-30
Publication date: 2022-01-28
Anticipated expiration: 2041-11-30
Also published as: CN113992012B

Abstract

The invention provides a suspension capacitor type Boost circuit, an inverter and a grid-connected power generation system, wherein a first switch module and a second switch module are respectively arranged at two sides of a suspension capacitor in a main topology of the suspension capacitor type Boost circuit; when the first end and the second end of each switch module are connected, the suspension capacitor is connected between a connecting point of a branch where a rectifier diode is located in the main topology and a branch where an output capacitor is located and connecting points of two corresponding power tubes in the main topology, and therefore pre-charging of the suspension capacitor can be achieved; and in the case of the main topology, under the condition of active output, voltage sharing can be automatically realized by each rectifier diode. That is, the floating capacitor type Boost circuit can solve the problem of unbalanced voltage of the rectifier diode under the conditions of floating capacitor pre-charging and active output by fewer devices, and the scheme is simple and effective and has high reliability.

Description

Suspension capacitive Boost circuit, inverter and grid-connected power generation system

Technical Field

The invention relates to the technical field of power electronics, in particular to a suspension capacitor type Boost circuit, an inverter and a grid-connected power generation system.

Background

In a 1500V photovoltaic system, a three-level technology is generally adopted, and for a string converter, a front-stage Boost circuit of the string converter generally adopts a symmetrical three-level Boost or a suspension capacitive three-level Boost topology; compared with a symmetrical three-level Boost topology, the floating capacitive three-level Boost topology has the advantage of common input and output, and therefore the application of the topology is gradually increased.

At present, the difficulty of the application of the floating capacitor type three-level Boost topology is the problem of unbalanced voltage of a rectifier diode under the conditions of floating capacitor pre-charging and active output. For both of these problems, the existing solutions require more and complicated hardware circuits.

Disclosure of Invention

In view of the above, the present invention provides a floating capacitor type Boost circuit, an inverter and a grid-connected power generation system, so as to reduce the complexity of hardware circuits required to be added when solving the problem of unbalanced voltage of the rectifier diodes under the active conditions of the pre-charging and output of the floating capacitor.

In order to achieve the above purpose, the embodiments of the present invention provide the following technical solutions:

the invention provides a floating capacitor type Boost circuit, wherein two sides of a floating capacitor in a main topology are respectively provided with a corresponding switch module: a first switch module and a second switch module; each switch module is provided with a first end, a second end and a third end respectively; wherein the content of the first and second substances,

when each switch module is in a state that the first end is connected with the second end: the first end of the suspension capacitor is connected with a connection point of a branch where a rectifier diode is located in the main topology and a branch where an output capacitor is located through the corresponding first switch module; the second end of the floating capacitor is connected with the connection point of the two corresponding output capacitors in the main topology through the corresponding second switch module;

when each switch module is in a state that the first end is connected with the third end: the first end of the floating capacitor is connected with the connection point of the two corresponding rectifier diodes in the main topology through the corresponding first switch module; and the second end of the floating capacitor is connected with the connecting point of the two corresponding power tubes in the main topology through the corresponding second switch module.

Optionally, before the master topology is controlled to enter the working state, each switch module is controlled to switch itself from a state where the first end is connected to the second end to a state where the first end is connected to the third end.

Optionally, a current limiting resistor is further disposed between the second end of the second switch module and a connection point corresponding to the two output capacitors, for limiting current surge caused when the switch modules switch the connection state.

Optionally, each switch module is a single-pole double-throw switch, a fixed node of the single-pole double-throw switch serves as a first end of the corresponding switch module, a normally closed node of the single-pole double-throw switch serves as a second end of the corresponding switch module, and a normally open node of the single-pole double-throw switch serves as a third end of the corresponding switch module.

Optionally, each switch module includes two switch tubes;

one ends of the two switch tubes are connected and used as first ends of the corresponding switch modules;

and the other ends of the two switching tubes are respectively used as a second end and a third end of the corresponding switch module.

Optionally, when the capacitance value of the floating capacitor is less than or equal to 10% of the total capacitance value of the output capacitors connected in parallel when the first end and the second end of the switch modules at the two sides of the floating capacitor are connected.

Optionally, when the main topology is an n +1 level output topology, the number of the floating capacitors is n-1; n is an integer greater than 1.

Optionally, the master topology includes: the power supply comprises an input capacitor, an input inductor, n power tubes, n rectifier diodes, n output capacitors and n-1 suspension capacitors; wherein:

the input capacitor is arranged between two poles of the input end of the main topology;

the first end of the input inductor is connected with one pole of the input end of the main topology;

the second end of the input inductor is connected with the corresponding pole of the output end of the main topology sequentially through the rectifier diodes, and is also connected with the other pole of the input end and the other pole of the output end of the main topology sequentially through the power tubes;

each output capacitor is sequentially connected in series between two output end poles of the main topology;

and a corresponding suspension capacitor is respectively arranged between the connection point of two adjacent power tubes and the connection point of two corresponding adjacent rectifier diodes from the second end of the input inductor.

Optionally, the input inductor and each of the rectifier diodes are disposed on an anode branch of the main topology, and the main topology is a common-cathode topology; alternatively, the first and second electrodes may be,

the input inductor and each rectifier diode are arranged on a negative branch of the main topology, and the main topology is a common-anode topology.

The second aspect of the present invention also provides an inverter, comprising: the control module and the DC/AC conversion circuit and the at least one DC/DC conversion circuit controlled by the control module;

the output end of the DC/DC conversion circuit is connected in parallel with the direct current side of the DC/AC conversion circuit;

the DC/DC conversion circuit is a floating capacitor Boost circuit as described in any of the above paragraphs of the first aspect.

Optionally, the control module includes: a first control unit that controls the DC/AC conversion circuit, and a second control unit that controls the corresponding DC/DC conversion circuit;

the first control unit is in communication connection with the second control unit.

The third aspect of the present invention also provides a grid-connected power generation system, including: a DC/AC converter and at least one DC/DC converter;

the output end of the DC/DC converter is connected in parallel to the direct current side of the DC/AC converter;

a main circuit in the DC/DC converter is a floating capacitor type Boost circuit as described in any of the above paragraphs of the first aspect;

the DC/AC converter is communicatively coupled to the DC/DC converter.

The invention provides a suspension capacitor type Boost circuit, wherein a first switch module and a second switch module are respectively arranged at two sides of a suspension capacitor in a main topology; when the first end and the second end of each switch module are connected, the suspension capacitor is connected between a connecting point of a branch where a rectifier diode is located in the main topology and a branch where the output capacitor is located and connecting points of two corresponding power tubes in the main topology, and therefore pre-charging of the suspension capacitor can be achieved through the branch where the rectifier diode is located and input voltage of the main topology; in addition, under the condition that the output of the main topology is active, no path exists between the connection point of each rectifier diode and the connection point of each power tube, so that voltage equalization can be automatically realized by each rectifier diode, and the problem of unbalanced voltage of the rectifier diodes is avoided. In addition, when the first end and the third end of each switch module are connected, the suspension capacitor can be switched to the normal position in the main topology. Therefore, the floating capacitor type Boost circuit can solve the problem of unbalanced voltage of the rectifier diode under the conditions of floating capacitor pre-charging and active output by fewer devices, and is simple and effective in scheme and high in reliability.

Drawings

In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings to be used in the description of the embodiments or the prior art will be briefly introduced below, it is obvious that the drawings in the following description are only embodiments of the present invention, and for those skilled in the art, other drawings can be obtained according to the provided drawings without creative efforts.

Fig. 1, fig. 2 and fig. 4 are schematic diagrams of three structures of a three-level floating capacitor type Boost circuit provided in the prior art respectively;

fig. 3 is a schematic voltage division diagram of a rectifier diode of a three-level floating capacitive Boost circuit provided in the prior art under the condition of active output;

fig. 5a is a schematic structural diagram of a three-level floating capacitor type Boost circuit according to an embodiment of the present invention;

fig. 5b and fig. 5c are two circuit diagrams of a three-level floating capacitor type Boost circuit according to an embodiment of the present invention;

fig. 6 is a circuit diagram of a four-level floating capacitor type Boost circuit according to an embodiment of the present invention;

fig. 7 is a circuit diagram of an n +1 level floating capacitor type Boost circuit according to an embodiment of the present invention;

fig. 8 is a schematic structural diagram of an inverter according to an embodiment of the present invention.

Detailed Description

The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.

In this application, the terms "comprises," "comprising," or any other variation thereof, are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements does not include only those elements but may include other elements not expressly listed or inherent to such process, method, article, or apparatus. Without further limitation, an element defined by the phrase "comprising an … …" does not exclude the presence of other identical elements in a process, method, article, or apparatus that comprises the element.

Fig. 1 shows a floating capacitive three-level Boost circuit, which specifically includes: an input capacitor Cin, an input inductor L, two power tubes T1 and T2, two rectifier diodes D1 and D2, two output capacitors C1 and C2 and a floating capacitor Cf; wherein:

the input capacitor Cin is arranged between two poles of the circuit input end; the first end of the input inductor L is connected with the positive electrode of the input end of the circuit; the second end of the input inductor L is connected with the anode of the output end of the circuit through rectifier diodes D1 and D2 in sequence, and is also connected with the cathode of the input end of the circuit and the cathode of the output end of the circuit through power tubes T1 and T2 in sequence; the output capacitors C1 and C2 are sequentially connected in series between two poles of the circuit output end; further, the floating capacitor Cf is provided between the connection point of the power tubes T1 and T2 and the connection point of the rectifier diodes D1 and D2.

Before the circuit works normally, because the power tubes T1 and T2 are not conducted, the floating capacitor Cf has no charging path, and automatic pre-charging cannot be realized; therefore, the prior art usually adds an extra soft start auxiliary circuit to precharge the floating capacitor Cf, as shown in fig. 2; the soft start auxiliary circuit usually requires more circuit devices and has a complicated circuit structure.

In addition, because the circuit has the function of boosting, the voltage at the output end of the circuit is higher than that at the input end of the circuit; under some conditions, the voltage at the input terminal may even be zero, for example, when the input terminal is disconnected, referring to fig. 3, since the voltages at the input capacitor Cin and the floating capacitor Cf are both 0V, the voltage borne by the rectifying diode D2 will be the entire output voltage Uout, and the voltage borne by the rectifying diode D1 is about 0V, so that the circuit has the problem of unbalanced rectifying diode voltage in the case of active output. The prior art generally needs to add an additional clamping circuit to realize the voltage clamping for the rectifying diode D2, as shown in fig. 4.

That is, in order to solve the problem of unbalanced voltage of the rectifier diode under the active conditions of the pre-charge and output of the floating capacitor in the prior art, corresponding devices need to be respectively arranged for implementation, that is, the soft start auxiliary circuit in fig. 2 and the clamping circuit in fig. 4 need to be added at the same time, the circuit structure is complex, and the cost is increased.

Therefore, the present invention provides a floating capacitor type Boost circuit to simultaneously solve the problem of unbalanced voltage of the rectifier diode under the conditions of floating capacitor pre-charging and active output, and reduce the complexity of the hardware circuit required to be increased.

Fig. 5a shows a floating capacitive three-level Boost circuit provided in this embodiment, which has a main topology specifically including: an input capacitor Cin, an input inductor L, two power tubes T1 and T2, two rectifier diodes D1 and D2, two output capacitors C1 and C2 and a floating capacitor Cf; wherein:

the input capacitor Cin is arranged between two poles of the input end of the main topology; the first end of the input inductor L is connected with the positive electrode of the input end of the main topology; the second end of the input inductor L is connected with the positive electrode of the output end of the main topology through rectifier diodes D1 and D2 in sequence, and is also connected with the negative electrode of the input end of the main topology and the negative electrode of the output end of the main topology through power tubes T1 and T2 in sequence; the output capacitors C1 and C2 are sequentially connected in series between the two poles of the output end of the main topology.

Different from the prior art, two switch modules are respectively arranged on two sides of the floating capacitor Cf: a first switch module and a second switch module, as shown in fig. 5 a; each switch module is provided with a first end, a second end and a third end respectively; the first end of the switch can be selectively connected with the second end or the third end. Each switch module may be a single-pole double-throw switch (as shown in fig. 5 b), or may be two switch tubes connected at one end (as shown in fig. 5 c).

Taking the single-pole double-throw switch shown in fig. 5b as an example, the fixed node serves as the first end of the corresponding switch module, the normally-closed node serves as the second end of the corresponding switch module, and the normally-open node serves as the third end of the corresponding switch module. As shown in fig. 5b, the two switch modules, i.e., the first single pole double throw switch S1 and the second single pole double throw switch S2; the first end of the floating capacitor Cf is connected with a connection point of a rectifier diode D2 and an output capacitor C1 through a fixed node and a normally closed node 1 of a first single-pole double-throw switch S1; the first end of the floating capacitor Cf is also connected with the connection point of a rectifier diode D1 and D2 through a fixed node and a normally open node 2 of a first single-pole double-throw switch S1; the second end of the floating capacitor Cf is connected with the connection point of the output capacitor C1 and C2 through the fixed node of the second single-pole double-throw switch S2 and the normally closed node 1; the second end of the floating capacitor Cf is also connected with the connection point of the power tube T1 and T2 through the fixed node of the second single-pole double-throw switch S2 and the normally open node 2.

When the fixed nodes of the two single-pole double-throw switches are connected with the normally-open node 2, the floating capacitor Cf is connected between the connection point of the power tubes T1 and T2 and the connection point of the rectifier diodes D1 and D2, the main topology is equivalent to the structure shown in figure 1, and the normal boosting function of the main topology can be realized. When the fixed nodes of the two single pole double throw switches are connected to the normally closed node 1, the floating capacitor Cf is connected in parallel with the output capacitor C1.

The circuit has the following two application cases:

(1) when the circuit is completely powered off, when voltage is applied to the input side, the circuit automatically charges output capacitors C1 and C2, and simultaneously automatically pre-charges the floating capacitor Cf to half bus voltage; when the floating capacitor Cf is properly designed, for example, its capacitance is less than or equal to 10% of the capacitance of the output capacitor C1, the effect of the divided electric quantity on the output capacitors C1 and C2 is small, and the bias voltage on the output capacitors C1 and C2 is negligible. When the circuit is ready to enter the working state, the two single-pole double-throw switches S1 and S2 are switched from the normally closed node 1 to the normally open node 2, and the topological structure is converted. In the switching process, since the voltage drop of the rectifier diode D2 in the forward conduction state is negligible, the

nodes

1 and 2 of the first single-pole double-throw switch S1 are at the same potential; the two power transistors T1 and T2 are voltage-sharing, and the voltage at the connection point is also half bus voltage, so

nodes

1 and 2 of the second single-pole double-throw switch S2 are also equipotential.

(2) When the input side of the circuit is out of power and voltage is applied to the output side, voltage sharing of the rectifier diodes D1 and D2 can be automatically realized due to the fact that connection between the middle points of the rectifier diodes D1 and D2 and the middle points of the power tubes T1 and T2 is cut off, and the whole output bus voltage Uout is borne. Moreover, in a photovoltaic application scenario, the output of the photovoltaic string is powered on the premise that the circuit operates, so that the input side of the circuit is necessarily powered, at this time, the power tubes T1 and T2 bear input voltage, and the rectifier diodes D1 and D2 bear the difference Uout-Uin between the input voltage Uin and the output voltage Uout (the input voltage is smaller than the output voltage); before the circuit enters a working state, the two single-pole double-throw switches S1 and S2 are switched from the normally closed node 1 to the normally open node 2, so that the conversion of a topological structure is realized; at this time, the voltage transformation of the

nodes

1 and 2 of the two single-pole double-throw switches S1 and S2 is only half (Uout-Uin)/2 of the input and output voltage difference, the voltage change is not large, and the device type selection of the single-pole device switches S1 and S2 is facilitated.

According to the three-level suspension capacitor type Boost circuit provided by the embodiment, the two single-pole double-throw switches S1 and S2 are introduced to the two ends of the suspension capacitor Cf, so that the decoupling of the suspension capacitor Cf and a main topology is realized, and the pre-charging of the suspension capacitor Cf is automatically realized in a default state. And only need increase two single-pole double-throw switches can solve three level suspension electric capacity type Boost circuit's suspension electric capacity Cf charge problem and output under the active condition the problem that rectifier diode withstand voltage is uneven simultaneously, the scheme is simple effective, and the reliability is high.

Preferably, a current limiting resistor R is further provided between the normally closed contact of the second single-pole double-throw switch S2 and the connection point of the output capacitors C1 and C2, for limiting current surge caused when the respective single-pole double-throw switches are switched to the connection state.

It should be noted that fig. 5a to 5c only illustrate a three-level floating capacitor type Boost circuit, but the solution provided by the present application is not limited to a three-level circuit, and is also applicable to other multi-level circuits, such as a five-level circuit, a seven-level circuit, and the like. Taking an example that the switch module includes a single-pole double-throw switch, fig. 6 is a four-level floating capacitive Boost circuit, fig. 7 is an n + 1-level floating capacitive Boost circuit, and n is an integer greater than 1; the main topologies all include: an input capacitor Cin, an input inductor L, n power tubes (such as T1, T2 and T3 shown in FIG. 6 and T1, T2 and T3 … Tn shown in FIG. 7), n rectifier diodes (such as D1, D2 and D3 shown in FIG. 6 and D1, D2 and D3 … Dn shown in FIG. 7), n output capacitors (such as C1, C2 and C3 shown in FIG. 6 and C1, C2 and C3 … Cn shown in FIG. 7) and n-1 floating capacitors Cf; wherein:

the input capacitor Cin is arranged between two poles of the input end of the main topology; the first end of the input inductor L is connected with one pole of the input end of the main topology; the second end of the input inductor L is connected with the corresponding pole of the output end of the main topology through each rectifier diode in sequence, and is also connected with the other pole of the input end and the other pole of the output end of the main topology through each power tube in sequence; and each output capacitor is sequentially connected in series between the two output ends of the main topology. Starting from the second end of the input inductor L, a corresponding suspension capacitor Cf is respectively arranged between the connecting point of two adjacent power tubes and the connecting point of two corresponding adjacent rectifier diodes; for example, a floating capacitor Cf is arranged between a connection point of the power tubes T1 and T2 and a connection point of the corresponding rectifier diodes D1 and D2; a floating capacitor Cf is also arranged between the connection point of the power tubes T2 and T3 and the connection point of the corresponding rectifier diodes D2 and D3.

When n is 2, the floating capacitive Boost circuit is a three-level circuit; when n is 3, the floating capacitive Boost circuit is a four-level circuit; and so on.

No matter what value of n is, two sides of each floating capacitor Cf in the main topology are respectively provided with a corresponding single-pole double-throw switch: a first single pole double throw switch S1 and a second single pole double throw switch S2; for each floating capacitor Cf, there are:

the first end of the floating capacitor Cf is connected with a connecting point of a branch where a rectifier diode is located and a branch where an output capacitor is located in the main topology through a fixed node and a normally closed node 1 of a corresponding first single-pole double-throw switch S1; the first end of the floating capacitor Cf is also connected to the connection point of the corresponding two rectifier diodes in the main topology through the fixed node and the normally open node 2 of the corresponding first single-pole double-throw switch S1.

The second end of the floating capacitor Cf is connected with the connecting point of two corresponding output capacitors in the main topology through the fixed node and the normally closed node 1 of the corresponding second single-pole double-throw switch S2; and the second end of the floating capacitor Cf is also connected with the connecting point of two corresponding power tubes in the main topology through the fixed node and the normally open node 2 of the corresponding second single-pole double-throw switch S2.

Optionally, when the capacitance value of each floating capacitor Cf is less than or equal to 10% of the total capacitance value of the output capacitor connected in parallel when the fixed node of the single-pole double-throw switch on both sides of the floating capacitor Cf is connected with the normally closed node. For example, from the second end of the input inductor L, the capacitance value of the first floating capacitor Cf is less than or equal to 10% of the capacitance value of the output capacitor C1, the capacitance value of the second floating capacitor Cf is less than or equal to 10% of the total capacitance value of the output capacitors C1 and C2, the capacitance value of the third floating capacitor Cf is less than or equal to 10% of the total capacitance value of the output capacitors C1, C2, and C3, and so on, and description thereof is omitted.

It should be further noted that fig. 5a to fig. 7 all show common-negative electrode topologies as examples, and input inductors L and respective rectifier diodes thereof are all disposed on a positive electrode branch of the main topology; in practical application, the dual topology, that is, the common-anode topology, the input inductor L and each rectifier diode are all disposed on the negative branch of the main topology, and corresponding single-pole double-throw switches may also be disposed on both sides of each floating capacitor Cf, all within the protection scope of the present application.

In the floating capacitive Boost circuit provided by this embodiment, two sides of the floating capacitor Cf in the main topology are respectively provided with a first single-pole double-throw switch S1 and a second single-pole double-throw switch S2; when the fixed node of each single-pole double-throw switch is connected with the normally closed contact, the floating capacitor Cf is connected between the connecting point of the branch where the rectifying diode is located and the branch where the output capacitor is located in the main topology and the connecting point of the two corresponding power tubes in the main topology, and therefore the pre-charging of the floating capacitor Cf can be achieved through the branch where the rectifying diode is located and the input voltage of the main topology; in addition, under the condition that the output of the main topology is active, no path exists between the connection point of each rectifier diode and the connection point of each power tube, so that voltage equalization can be automatically realized by each rectifier diode, and the problem of unbalanced voltage of the rectifier diodes is avoided. In addition, when the fixed node of each single-pole double-throw switch is connected with the normally open contact, the floating capacitor Cf can be switched to the normal position in the main topology. Therefore, the floating capacitor type Boost circuit can solve the problem of unbalanced voltage of the rectifier diode under the conditions of pre-charging and active output of the floating capacitor Cf by fewer devices, and is simple and effective in scheme and high in reliability.

In practical application, before the main topology of the suspension capacitance type Boost circuit is controlled to enter a working state, each single-pole double-throw switch is controlled to switch the state of the single-pole double-throw switch from the state of connecting a fixed node with a normally closed node 1 to the state of connecting the fixed node with a normally open node 2, and the main topology can be enabled to carry out boosting work normally.

In addition, each switch module in the floating capacitor type Boost circuit is not limited to the single-pole double-throw switch shown in fig. 5b, fig. 6 and fig. 7, and may also include two switch tubes; one end of each of the two switching tubes is connected to serve as a first end of the corresponding switching module; and the other ends of the two switching tubes are respectively used as the second end and the third end of the corresponding switching module. The implementation form of the two switching tubes is not particularly limited, and is determined according to the application environment, and both are within the protection scope of the present application. The automatic control of the switch modules can be realized through the control module in the equipment where the circuit is positioned.

Another embodiment of the present invention also provides an inverter, as shown in fig. 8, including: the control module 10 and the DC/AC converting circuit 22 and at least one DC/DC converting circuit 21 (a plurality of them are shown in the figure) controlled by the control module; wherein, the output end of each DC/DC conversion circuit 21 is connected in parallel to the DC side of the DC/AC conversion circuit 22; each DC/DC conversion circuit 21 is a floating capacitor type Boost circuit as described in any of the above embodiments. The specific structure and the working principle of the floating capacitive Boost circuit can be obtained by referring to the above embodiments, and are not described in detail herein.

In practical applications, the control module 10 may include: a first control unit controlling the DC/AC conversion circuit, and a second control unit controlling the corresponding DC/DC conversion circuit;

the first control unit is in communication connection with the second control unit. The inverter can be used as a string type inverter of a grid-connected power generation system, and is connected to the grid after inverting the electric energy generated by a photovoltaic string.

Another embodiment of the present invention further provides a grid-connected power generation system, including: a DC/AC converter and at least one DC/DC converter; the output end of the DC/DC converter is connected in parallel with the direct current side of the DC/AC converter; the input end of the DC/DC converter is respectively connected with corresponding photovoltaic group strings in the photovoltaic array; a main circuit in the DC/DC converter is a floating capacitive Boost circuit as described in any one of the embodiments above; the specific structure and the working principle of the floating capacitive Boost circuit can be obtained by referring to the above embodiments, and are not described in detail herein. The DC/AC converter and the DC/DC converter are in communication connection, can be respectively arranged at a long distance, and can also be used for carrying out inversion and grid connection on electric energy generated by each photovoltaic group string.

The embodiments in the present specification are described in a progressive manner, and the same and similar parts among the embodiments are referred to each other, and each embodiment focuses on the differences from the other embodiments. In particular, the system or system embodiments are substantially similar to the method embodiments and therefore are described in a relatively simple manner, and reference may be made to some of the descriptions of the method embodiments for related points. The above-described system and system embodiments are only illustrative, wherein the units described as separate parts may or may not be physically separate, and the parts displayed as units may or may not be physical units, may be located in one place, or may be distributed on a plurality of network units. Some or all of the modules may be selected according to actual needs to achieve the purpose of the solution of the present embodiment. One of ordinary skill in the art can understand and implement it without inventive effort.

Those of skill would further appreciate that the various illustrative elements and algorithm steps described in connection with the embodiments disclosed herein may be implemented as electronic hardware, computer software, or combinations of both, and that the various illustrative components and steps have been described above generally in terms of their functionality in order to clearly illustrate this interchangeability of hardware and software. Whether such functionality is implemented as hardware or software depends upon the particular application and design constraints imposed on the implementation. Skilled artisans may implement the described functionality in varying ways for each particular application, but such implementation decisions should not be interpreted as causing a departure from the scope of the present invention.

In the above description of the disclosed embodiments, the features described in the embodiments in this specification may be replaced or combined with each other to enable those skilled in the art to make or use the invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the generic principles defined herein may be applied to other embodiments without departing from the spirit or scope of the invention. Thus, the present invention is not intended to be limited to the embodiments shown herein but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. The utility model provides a suspension electric capacity type Boost circuit which characterized in that, the suspension electric capacity both sides in its main topology are provided with corresponding switch module respectively: a first switch module and a second switch module; each switch module is provided with a first end, a second end and a third end respectively; wherein the content of the first and second substances,

2. The floating capacitor Boost circuit of claim 1, wherein each switch module is controlled to switch itself from a state in which the first terminal is connected to the second terminal to a state in which the first terminal is connected to the third terminal before the main topology is controlled to enter the operating state.

3. The floating capacitor Boost circuit of claim 1, wherein a current limiting resistor is further disposed between the second end of the second switch module and a connection point corresponding to the two output capacitors, for limiting a current surge caused when each switch module switches the connection state.

4. The floating capacitance type Boost circuit of claim 1, wherein each switch module is a single-pole double-throw switch, a fixed node of the single-pole double-throw switch is used as a first end of the corresponding switch module, a normally closed node of the single-pole double-throw switch is used as a second end of the corresponding switch module, and a normally open node of the single-pole double-throw switch is used as a third end of the corresponding switch module.

5. The floating capacitive Boost circuit of claim 1, wherein each switch module comprises two switch tubes;

6. The floating capacitive Boost circuit of any of claims 1 to 5, wherein the capacitance of the floating capacitor is less than or equal to 10% of the total capacitance of the output capacitors connected in parallel when the first and second terminals of the two-sided switch modules are connected.

7. The floating capacitive Boost circuit according to any of claims 1 to 5, wherein when the main topology is an n +1 level output topology, the number of the floating capacitors is n-1; n is an integer greater than 1.

8. The suspended capacitive Boost circuit of claim 7, wherein the primary topology comprises: the power supply comprises an input capacitor, an input inductor, n power tubes, n rectifier diodes, n output capacitors and n-1 suspension capacitors; wherein:

9. The floating capacitance Boost circuit of claim 8, wherein the input inductor and each of the rectifier diodes are disposed on a positive branch of the main topology, the main topology being a common-negative topology; alternatively, the first and second electrodes may be,

10. An inverter, comprising: the control module and the DC/AC conversion circuit and the at least one DC/DC conversion circuit controlled by the control module;

the DC/DC conversion circuit is the floating capacitance type Boost circuit according to any one of claims 1 to 9.

11. The inverter of claim 10, wherein the control module comprises: a first control unit that controls the DC/AC conversion circuit, and a second control unit that controls the corresponding DC/DC conversion circuit;

12. A grid-connected power generation system, comprising: a DC/AC converter and at least one DC/DC converter;

a main circuit in the DC/DC converter is a suspension capacitance type Boost circuit according to any one of claims 1 to 9;

the DC/AC converter is communicatively coupled to the DC/DC converter.