CN209963748U

CN209963748U - Photovoltaic grid-connected inverter

Info

Publication number: CN209963748U
Application number: CN201920587759.2U
Authority: CN
Inventors: 熊新; 曾建友; 朱成林
Original assignee: Shenzhen Hewang Technology Co Ltd
Current assignee: Shenzhen Hewang Technology Co Ltd
Priority date: 2019-04-26
Filing date: 2019-04-26
Publication date: 2020-01-17
Anticipated expiration: 2029-04-26

Abstract

The application discloses a photovoltaic grid-connected inverter, which comprises a photovoltaic component, an inverter circuit connected between a positive electrode output end and a negative electrode output end of the photovoltaic component, and a grid-connected switch connected in series at the output end of the inverter circuit; the photovoltaic grid-connected inverter is characterized by further comprising a first fuse connected in series with the positive electrode output end of the photovoltaic assembly and/or a second fuse connected in series with the negative electrode output end of the photovoltaic assembly. The photovoltaic module is characterized in that a first fuse is connected in series with the positive electrode output end of the photovoltaic module and/or a second fuse is connected in series with the negative electrode output end of the photovoltaic module; the problem that the photovoltaic grid-connected inverter is damaged after the ground insulation fault of the PV assembly occurs in the operation process of the photovoltaic grid-connected inverter is solved; the service life of the product is prolonged.

Description

Photovoltaic grid-connected inverter

Technical Field

The application relates to the technical field of power electronics, in particular to a photovoltaic grid-connected inverter.

Background

The existing non-isolated photovoltaic inverter applied to a TN system power grid (N-line grounding system) cannot operate under the grounding condition of a PV assembly, and if the machine normally operates, the grounding fault of the PV assembly occurs, the inverter can be damaged.

Fig. 1 is a schematic diagram of a two-stage photovoltaic inverter circuit, and fig. 2 is a schematic diagram of a negative electrode ground of the two-stage photovoltaic inverter circuit. As shown in fig. 2, if the inverter grid-connected switches K1 and K2 are closed, a large current flows through the body diode of the switching tube Q2 during the negative half cycle of the grid, and although the inverter sends out a command to open K1 and K2 after detecting the hardware overcurrent, since the relay response time is in the millisecond level, the inductor current is enough to damage the body diode of Q2 before the relay is completely opened, thereby causing the damage of the inverter. Fig. 3 is another circuit diagram of a two-stage photovoltaic inverter, which also has similar problems. Other circuits, such as: three-phase string inverters, concentrated inverters, etc., also suffer from similar problems.

The prior art typically addresses the above problems: before the inverter is started, detecting the insulation resistance of the PV assembly to the ground; if the abnormal insulation resistance is detected, the inverter does not run and is started, namely K1 and K2 are in an off state, no current flows through a body diode of Q2, and the inverter is protected. However, if the PV module fails to insulate the ground during the operation of the inverter, the inverter may be damaged.

SUMMERY OF THE UTILITY MODEL

In view of this, an object of the present application is to provide a photovoltaic grid-connected inverter, so as to solve the problem that the photovoltaic grid-connected inverter is damaged after a ground insulation fault of a PV module occurs in an operation process of the photovoltaic grid-connected inverter.

The technical scheme adopted by the application for solving the technical problems is as follows:

according to one aspect of the application, a photovoltaic grid-connected inverter is provided, which comprises a photovoltaic component, an inverter circuit connected between a positive output end and a negative output end of the photovoltaic component, and a grid-connected switch connected in series at an output end of the inverter circuit; the photovoltaic grid-connected inverter also comprises a first fuse connected in series with the positive output end of the photovoltaic component and/or a second fuse connected in series with the negative output end of the photovoltaic component.

In a possible embodiment, the inverter circuit comprises a dc bus capacitor and a switching tube circuit connected in sequence between the positive output end and the negative output end of the photovoltaic module.

In one possible embodiment, the inverter circuit further comprises a boost circuit connected between the positive output terminal and the negative output terminal of the photovoltaic module;

the booster circuit is arranged between the photovoltaic module and the direct current bus capacitor.

In one possible embodiment, the switching tube circuit is a single-phase full-bridge switching tube circuit or an H6 topology switching tube circuit.

In a possible embodiment, the first fuse is arranged between the photovoltaic module and the dc bus capacitor or between the dc bus capacitor and the switching tube circuit;

the second fuse is arranged between the photovoltaic module and the direct current bus capacitor or between the direct current bus capacitor and the switch tube circuit.

In one possible embodiment, the inverter circuit is a three-phase inverter circuit.

In one possible embodiment, the photovoltaic module comprises a plurality of photovoltaic sub-modules connected in parallel.

According to the photovoltaic grid-connected inverter, the first fuse is connected to the positive electrode output end of the photovoltaic assembly in series, and/or the second fuse is connected to the negative electrode output end of the photovoltaic assembly in series; the problem that the photovoltaic grid-connected inverter is damaged after the ground insulation fault of the PV assembly occurs in the operation process of the photovoltaic grid-connected inverter is solved; the service life of the product is prolonged.

Drawings

Fig. 1 is a schematic circuit diagram of a conventional two-stage photovoltaic inverter;

fig. 2 is a schematic diagram of a negative ground of a conventional two-stage photovoltaic inverter circuit;

fig. 3 is another circuit schematic diagram of a conventional two-stage photovoltaic inverter;

fig. 4 is a schematic structural diagram of a photovoltaic grid-connected inverter according to an embodiment of the present application;

fig. 5 is a schematic structural diagram of an inverter circuit in the photovoltaic grid-connected inverter according to the embodiment of the present application;

fig. 6 is another schematic structural diagram of an inverter circuit in the photovoltaic grid-connected inverter according to the embodiment of the present application;

fig. 7 is another schematic structural diagram of the photovoltaic grid-connected inverter according to the embodiment of the present application;

fig. 8 is a schematic diagram of a single-pole single-phase photovoltaic inverter photovoltaic module PV + ground fault according to an embodiment of the present application;

fig. 9 is a PV-ground fault schematic diagram of a single-pole single-phase photovoltaic inverter photovoltaic module according to an embodiment of the present application;

fig. 10 is a schematic diagram of a two-stage multi-inverter PV module to ground fault according to an embodiment of the present disclosure.

The implementation, functional features and advantages of the objectives of the present application will be further explained with reference to the accompanying drawings.

Detailed Description

In order to make the technical problems, technical solutions and advantageous effects to be solved by the present application clearer and clearer, the present application is further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the present application and are not intended to limit the present application.

In the description of the present application, it is to be understood that the terms "central", "upper", "lower", and "upper" are used herein,

The directional or positional relationships indicated by "front", "rear", "left", "right", etc., are based on the directional or positional relationships shown in the drawings and are only for convenience of describing the present application and for simplicity of description, and do not indicate or imply that the device or element referred to must have a particular orientation, be constructed and operated in a particular orientation, and therefore should not be construed as limiting the present application. Furthermore, the terms "first" and "second" are used for descriptive purposes only and are not to be construed as indicating or implying relative importance.

As shown in fig. 4, the embodiment of the present application provides a photovoltaic grid-connected inverter, which includes a photovoltaic module PV1, an inverter circuit T1 connected between a positive output terminal PV + and a negative output terminal PV-of the photovoltaic module PV1, and a grid-connected switch (shown as K1 and K2 in the figure) connected in series at an output terminal of the inverter circuit T1; the photovoltaic grid-connected inverter also comprises a first fuse F1 connected in series with a positive output end PV + of the photovoltaic module PV1 and/or a second fuse F2 connected in series with a negative output end PV-of the photovoltaic module PV 1.

As will be understood from fig. 5, in one embodiment, the inverter circuit T1 includes a dc bus capacitor C1 and a switching tube circuit (a switching tube circuit composed of Q1-Q4 in the drawing) connected between the positive output terminal and the negative output terminal of the photovoltaic module PV 1.

As will be understood from fig. 5, in one embodiment, the inverter circuit T1 further includes a voltage boosting circuit (a voltage boosting circuit composed of Q5 and D1 in the figure) connected between the positive output terminal and the negative output terminal of the photovoltaic module;

the boost circuit is arranged between the photovoltaic module PV1 and the DC bus capacitor.

As will be understood with reference to fig. 6, in one embodiment, the switching tube circuit is a single-phase full-bridge switching tube circuit or an H6 topology switching tube circuit. The switching tube circuit in fig. 5 is a single-phase full-bridge switching tube circuit, and the switching tube circuit in fig. 6 is an H6 topology switching tube circuit (composed of Q1-Q6, and D1-D2).

In this embodiment, the first fuse F1 is disposed between the photovoltaic module and the dc bus capacitor or between the dc bus capacitor and the switch tube circuit;

the second fuse F2 is disposed between the photovoltaic module and the DC bus capacitor or between the DC bus capacitor and the switch tube circuit.

Referring to fig. 7, in one embodiment, the inverter circuit T1 is a three-phase inverter circuit. Correspondingly, the grid-connected switch connected in series at the output end of the inverter circuit T1 is K1-K3.

In one embodiment, the photovoltaic module comprises a plurality of photovoltaic sub-modules connected in parallel. As shown in fig. 10, the photovoltaic module is composed of PV1, PV2, PV3 connected in parallel.

For a better understanding of the present embodiment, the following description of the ground fault of the photovoltaic module is made in conjunction with fig. 8-10:

as shown in fig. 8, for a single-pole single-phase photovoltaic inverter (the switching tube circuit is a single-phase full-bridge switching tube circuit and has no booster circuit), in the operation process of the machine, if a module PV + ground insulation short-circuit fault occurs, a large current flows through the body diode of the switching tube Q1 and the fuse F1 during the positive half cycle of the power grid, and since the i2t of the fuse F1 is far smaller than the IGBT body diode i2t, the fuse F1 fuses before the body diode is damaged, so as to cut off the current loop, thereby realizing the self-protection of the machine and avoiding the occurrence of a machine explosion.

As shown in fig. 9, for the single-pole single-phase photovoltaic inverter, if a PV-to-ground insulation short-circuit fault occurs during the operation of the machine, a large current flows through the body diode of the switching tube Q2 and the fuse F2 during the negative half cycle of the power grid, and at this time, the fuse F2 fuses before the body diode is damaged, so as to cut off the current loop, thereby realizing the self-protection of the machine.

For a two-stage topology (the switching tube circuit is a single-phase full-bridge switching tube circuit and is provided with a booster circuit, for example, as shown in fig. 5), if a PV + ground short circuit fault occurs during operation, due to the action of a diode D1 of the booster circuit, a large current does not occur in a body diode of a Q1, the inverter judges that an RCD leakage current is too large or an insulation impedance is abnormal, and even if a hardware overcurrent fault occurs, the inverter is stopped immediately at the moment, so that the protection of the inverter is realized. The positive electrode does not need to be re-fused. The PV-to-ground short fault is similar to that described above.

As shown in fig. 10, in an inverter in which two or more stages of two or more strings of cells share one boost circuit, in order to avoid the battery panel failure caused by the reverse polarity of the battery string, a fuse is mounted on the positive electrode of the battery string inside the inverter, and if the positive fuse is placed on the negative electrode of the input battery string, the inverter can be protected without increasing other costs when the ground insulation failure occurs in the PV module during normal operation of the machine.

The preferred embodiments of the present application have been described above with reference to the accompanying drawings, and are not intended to limit the scope of the claims of the application accordingly. Any modifications, equivalents and improvements which may occur to those skilled in the art without departing from the scope and spirit of the present application are intended to be within the scope of the claims of the present application.

Claims

1. A photovoltaic grid-connected inverter comprises a photovoltaic component, an inverter circuit connected between a positive output end and a negative output end of the photovoltaic component, and a grid-connected switch connected in series at the output end of the inverter circuit; the photovoltaic grid-connected inverter is characterized by further comprising a first fuse connected in series with the positive electrode output end of the photovoltaic assembly and/or a second fuse connected in series with the negative electrode output end of the photovoltaic assembly.

2. The grid-connected photovoltaic inverter according to claim 1, wherein the inverter circuit comprises a dc bus capacitor and a switching tube circuit connected in sequence between the positive output terminal and the negative output terminal of the photovoltaic module.

3. The pv grid-connected inverter according to claim 2, wherein the inverter circuit further comprises a boost circuit connected between the positive output terminal and the negative output terminal of the pv module;

4. The grid-connected photovoltaic inverter according to claim 2, wherein the switching tube circuit is a single-phase full-bridge switching tube circuit or an H6 topology switching tube circuit.

5. The grid-connected photovoltaic inverter according to claim 2, wherein the first fuse is provided between the photovoltaic module and the dc bus capacitor or between the dc bus capacitor and the switching tube circuit;

6. The grid-connected photovoltaic inverter according to claim 1, wherein the inverter circuit is a three-phase inverter circuit.

7. The pv grid-connected inverter according to claim 1, wherein the pv module comprises a plurality of pv subassemblies connected in parallel.