CN215300582U - Photovoltaic inverter and photovoltaic inverter system - Google Patents

Abstract

The utility model discloses a photovoltaic inverter and a photovoltaic inverter system. The photovoltaic inverter comprises a DC-DC conversion unit, a DC-LINK capacitor bank and a DC-AC conversion unit which are connected in sequence. The photovoltaic inverter It also has a PV input terminal for connecting the photovoltaic strings. The photovoltaic inverter also includes a string detection device for detecting whether the connected photovoltaic strings are reversely connected. The string detection device includes: a current detection unit, which is used for It is used to detect the current of the PV input terminal and output the detection signal; the comparator unit is used to compare the voltage value of the detection signal with the reference voltage, and output a signal indicating the reverse connection of the string when the set condition is met; and the power storage unit , which is used for powering the current detection unit and the comparator unit; the photovoltaic inverter includes: a first charging unit, which is used for charging the power storage unit. The PV inverter can accurately detect the reverse connection of PV strings when it is not connected to the grid power supply or when all strings are reversely connected.

Description

A photovoltaic inverter and photovoltaic inverter system

technical field

The utility model belongs to the field of photovoltaic inverters, and relates to a photovoltaic inverter and a photovoltaic inverter system.

Background technique

Photovoltaic inverter, as a core device that converts direct current provided by solar modules into alternating current for civil or industrial use, plays an increasingly important role in the field of new energy. In recent years, with the planning of carbon peaking and carbon neutrality, green energy has ushered in an explosive development. The installed capacity of photovoltaic module machine power generation systems has become larger and larger, and it has become the main force of green energy at present. Since photovoltaic modules often encounter the problem of reverse connection of photovoltaic panel strings (hereinafter referred to as "PV strings") during the construction and installation of PV modules, how to efficiently and quickly identify reversely connected strings and issue an alarm to guide installers in a timely manner It is of great practical significance to carry out connection adjustment and maintenance. However, the current PV string reverse connection detection technology uses a current sensor to collect the input current of the string to determine whether it is reversely connected. When all PV strings are reversely connected and not connected to the power grid, the reverse connection cannot be accurately detected. .

Utility model content

In view of the above technical problems, one object of the present invention is to provide a photovoltaic inverter and a photovoltaic inverter system, which can accurately reverse the connection of PV strings when not connected to the grid power supply or when all strings are reversely connected situation to be detected.

The utility model adopts the following technical solutions:

A photovoltaic inverter includes a DC-DC conversion unit, a DC-LINK capacitor bank and a DC-AC conversion unit connected in sequence, the photovoltaic inverter also has a PV input terminal for connecting a photovoltaic group string, the The photovoltaic inverter also includes a string detection device for detecting whether the connected photovoltaic strings are reversely connected, the string detection device is connected between the PV input end and the DC-DC conversion unit, so The group string detection device includes:

a current detection unit, which is used for detecting the current of the PV input terminal and outputting a detection signal;

a comparator unit, the input terminal of which is connected to the output terminal of the current detection unit, and is used for comparing the voltage value of the detection signal with the reference voltage. When the set condition is satisfied, the output of the comparator unit indicates that the series is reversed signal; and

a power storage unit, which is respectively connected to the current detection unit and the comparator unit to supply power to the current detection unit and the comparator unit;

The photovoltaic inverter includes:

The first charging unit is used for charging the power storage unit, the input end of the first charging unit is connected to the DC-LINK capacitor bank, and the output end is connected to the power storage unit.

Preferably, the string detection device further includes a second charging unit for charging the power storage unit, the input end of the second charging unit is connected to the AC side of the DC-AC conversion unit, and the output end is connected to the AC side of the DC-AC conversion unit. Connect the power storage unit.

Preferably, the photovoltaic inverter further includes a control unit, and the output end of the comparator unit is connected to the control unit.

Preferably, the string detection device further includes an alarm unit, the alarm unit is connected to the output end of the comparator unit, and the power energy storage unit is connected to the alarm unit to supply power. Through the introduction of the alarm unit, the great convenience of installation and maintenance is realized, which has important display significance.

Preferably, the alarm unit includes a status indicator light.

Preferably, the non-inverting input terminal of the comparator unit is connected to the reference voltage, and the inverting input terminal is connected to the output terminal of the current detection unit.

Preferably, the photovoltaic inverter includes multiple groups of PV input terminals and multiple string detection devices, each group of PV input terminals is used to connect to one PV string, and each group of PV input terminals is respectively associated with a corresponding string detection device device connection, and the output ends of the first charging unit are respectively connected with the power energy storage units of the string detection devices.

Preferably, the setting condition is: the voltage value of the detection signal is smaller than the reference voltage.

Preferably, the power storage unit is a super capacitor.

The utility model also adopts the following technical solutions:

A photovoltaic inverter system includes a photovoltaic string and a photovoltaic inverter, the photovoltaic inverter adopts the photovoltaic inverter as described above, and the output end of the photovoltaic string is directly connected to the photovoltaic inverter the PV input of the device.

The utility model adopts the above scheme, and has the following advantages compared with the prior art:

In a photovoltaic inverter and a photovoltaic inverter system of the present invention, a group string detection device is integrated into the photovoltaic inverter, and the group string detection unit includes a power supply energy storage unit capable of supplying power for the group string detection unit, which can realize full-scale operation. The function of intelligently detecting the reverse connection of the PV strings when the PV string is reversed or all PV strings is reversed, effectively solves the difficulty of reverse connection of the PV strings in the actual installation and application, and can be realized without connecting to the power grid, effectively ensuring the installation and maintenance. convenience and safety.

Description of drawings

In order to illustrate the technical solutions of the present invention more clearly, the following briefly introduces the drawings used in the description of the embodiments. Obviously, the drawings in the following description are only some embodiments of the present invention. For those of ordinary skill in the art, other drawings can also be obtained from these drawings without any creative effort.

FIG. 1 is a circuit diagram of a photovoltaic inverter and a photovoltaic inverter system according to an embodiment;

FIG. 2 is a circuit diagram of a string detection device.

in,

1. Photovoltaic string; 2. String detection device; 3. DC-DC conversion unit; 4. DC-LINK capacitor bank; 5. DC-AC conversion unit; 6. First charging unit; 7. Second charging unit 8. Control unit; 9. Power grid; 10. Photovoltaic inverter; 11. Current detection unit; 12. Comparator unit; 13. Power storage unit; 14. Alarm unit.

Detailed ways

The preferred embodiments of the present invention are described in detail below with reference to the accompanying drawings, so that the advantages and features of the present invention can be more easily understood by those skilled in the art. It should be noted here that the description of these embodiments is used to help the understanding of the present invention, but does not constitute a limitation of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative work fall within the protection scope of the present invention.

As shown in FIG. 1 , this embodiment provides a photovoltaic inverter 10 , which includes a string detection device 2 , a DC-DC conversion unit 3 , a DC-LINK capacitor bank 4 , and a DC-AC conversion unit 5 , which are connected in sequence. The input terminal of the string detection device 2 is connected to the PV input terminals PV+ and PV- to detect whether the connected PV strings are reversely connected. There are multiple groups of PV input terminals PV+ and PV-, and there are also multiple string detection devices 2. Each group of PV input terminals PV+ and PV- is used to connect one PV string 1. PV string 1 is grounded. The input terminals PV+ and PV- are respectively connected with a corresponding string detection device 2 . The output terminal of the string detection device 2 is connected to the DC-DC conversion unit 3, and the power output from the PV input terminals PV+ and PV- is connected to the DC-DC conversion unit 3 via the string detection device 2. The electrical energy can supply power to the DC-LINK capacitor group 4 .

The photovoltaic inverter 10 further includes: a first charging unit 6 , a second charging unit 7 and a control unit 8 . The first charging unit 6 is used for charging the power energy storage unit 13. The input end of the first charging unit 6 is connected to the DC-LINK capacitor group 4, and the output end is connected to the power energy storage unit 13. The output end is also connected to the DC-AC conversion unit 5 to supply power thereto, and the first charging unit 6 specifically includes a switching power supply DC-SPS. The second charging unit 7 is also used for charging the power storage unit 13 , the input end of the second charging unit 7 is connected to the AC side of the DC-AC conversion unit 5 , and the second charging unit 7 specifically includes a switching power supply AC-SPS. The first charging unit 6 and the output terminals of each string detection device 2 are respectively connected to the control unit 8, and the DC-DC conversion unit 3 and the DC-AC conversion unit 5 are respectively connected to the control unit 8 for signal transmission. Both the unit 6 and the second charging unit 7 can supply power to the control unit 8 .

As shown in FIG. 2 , each string detection device 2 includes: a current detection unit 11 , which is used to detect the currents of PV input terminals PV+ and PV- and output detection signals, and the current detection unit 11 outputs Vout and is connected to the control unit 8. It is used for the detection of string current and the judgment of abnormality; the input end of the comparator unit 12 is connected to the output end of the current detection unit 11, and is used to compare the voltage value of the detection signal with the reference voltage. When the voltage of the detection signal is When the value is less than the reference voltage, the comparator unit 12 outputs a signal indicating the reverse connection of the string. Specifically, in this embodiment, the non-inverting input terminal of the comparator unit 12 is connected to the reference voltage, and the inverting input terminal and the output of the current detection unit 11 The power storage unit 13 is connected to the current detection unit 11 and the comparator unit 12 to supply power to the current detection unit 11 and the comparator unit 12. Specifically in this embodiment, the power storage unit 13 is a super capacitor, The output terminals of the first charging unit 6 are respectively connected to the power storage units 13 of each string detection device 2 , and the output terminals of the second charging unit 7 are connected to the power storage units 13 ; the alarm unit 14 , and the output of the comparator unit 12 . The alarm unit 14 includes a status indicator, the status indicator can receive the enable signal output from the comparator to give an alarm, that is, the indicator is on. The photovoltaic inverter 10 further includes a voltage input terminal Vcc, which is connected to the power storage unit 13 , the current detection unit 11 and the alarm unit 14 respectively, and supplies power to the power storage unit 13 , the current detection unit 11 and the alarm unit 14 . Both the first charging unit 6 and the second charging unit 7 can supply power to the string detection device 2 .

The present embodiment also adopts the following technical solutions:

As shown in FIG. 1, a photovoltaic inverter system includes a photovoltaic string 1 and a photovoltaic inverter. The photovoltaic inverter adopts the photovoltaic inverter 10 as described above, and the output end of the photovoltaic string is directly connected to the photovoltaic The PV input terminals PV+ and PV- of the inverter 10, and the PV input terminals PV+ and PV- have multiple groups, and the string detection device 2 also has multiple groups. Each group of PV input terminals PV+ and PV- is used to connect to a photovoltaic channel. In the string, each group of PV input terminals PV+ and PV- are respectively connected with a corresponding string detection device 2, and each group of PV input terminals PV+ and PV- are grounded respectively. The AC side of the DC-AC conversion unit 5 is connected to the power grid 9 , the DC-LINK capacitor bank 4 can convert the direct current into alternating current through the DC-AC conversion unit 5 and connect it to the power grid 9 , and the electric energy of the power grid 9 can be supplied to the second charging unit 7 synchronously .

The present embodiment also adopts the following technical solutions:

A control method for a photovoltaic inverter, implemented based on a photovoltaic inverter, the photovoltaic inverter is the photovoltaic inverter 10 as described above, and the control method includes the following steps:

When part of the PV strings 1 are reversely connected, usually in maintenance or repair conditions, and the DC-SPS unit does not work (the voltage of the strings that are not reversely connected is lower than the working voltage of the DC-SPS unit), the string detection device 2 Powered by the power storage unit 13, the output signal Vout of the current detection unit 11 is compared with the reference voltage Vref by the comparator unit 12. If Vout<Vref, the comparator unit 12 outputs a signal indicating the reverse connection of the series, and the comparator unit 12 will output an enable signal to make the alarm unit 14 connected to it to give an alarm (such as a status light indication);

When part of the PV strings 1 are reversely connected, usually under maintenance or repair conditions, and the DC-SPS unit is working (the voltage of the string that is not reversely connected is higher than the working voltage of the DC-SPS unit), the string detection device 2 Powered by the DC-SPS unit, the output signal Vout of the current detection unit 11 is compared with the reference voltage Vref through the comparator unit 12. If Vout<Vref, the comparator unit 12 outputs a signal indicating the reverse connection of the series, and the comparator The unit 12 will output an enable signal to make the alarm unit 14 connected to it give an alarm (such as the status light indication), and the control unit 8 will also detect the abnormal information of the string current and send the string reverse connection information to the host computer of the inverter monitoring, etc.;

When all PV strings 1 are reversely connected, at this time, the PV inverter 10 is usually not connected to the grid, and the AC-SPS unit does not work (the inverter grid is not connected or there is no AC-SPS unit), the The string detection device 2 is powered by the power storage unit 13, and the output signal Vout of the current detection unit 11 is compared with the reference voltage Vref through the comparator unit 12. If Vout<Vref, the output of the comparator unit 12 indicates that the string is inverted. the connected signal, the comparator will output an enable signal to make the alarm unit 14 connected to it to give an alarm (such as a status light indication);

When all PV strings 1 are reversely connected, at this time, the PV inverter 10 is usually connected to the grid, the AC-SPS unit works (the inverter is connected to the grid), and the string detection device 2 is controlled by the AC-SPS unit. Power supply, the output signal Vout of the current detection unit 11 is compared with the reference voltage Vref by the comparator unit 12. If Vout<Vref, the comparator unit 12 outputs a signal indicating the reverse connection of the series, and the comparator outputs an enable signal The alarm unit 14 connected to it will give an alarm (eg, the status light indicates), and the control unit 8 will also detect the abnormal information of the string current and send the string reverse connection information to the inverter host computer for monitoring and so on.

A photovoltaic inverter and a photovoltaic inverter system provided by this embodiment include a string detection device 2 connected between the PV input terminal PV+ and PV- and the DC-DC conversion unit 3, and the string detection device 2 is integrated In the photovoltaic inverter 10, the output signal of the current detection unit 11 in the string detection device 2 is compared with the reference voltage, and the comparator unit 12 can output a signal indicating the reverse connection of the string to the alarm unit 14 for alarming according to the comparison result. It can realize the detection of the reverse connection of the photovoltaic string 1 under the full working conditions of the inverter (maintenance or repair stage, installation stage); and, except for the reverse connection of some photovoltaic strings 1, the photovoltaic inverter 10 can also It is detected that all PV strings 1 are reversely connected; at the same time, since the current detection unit 11 can be powered by the power storage unit 13, no matter whether the inverter is connected to the grid, or whether the first charging unit 6, the second charging unit 7 Whether it is working normally, the photovoltaic inverter system can intelligently identify and detect the reverse connection of photovoltaic string 1, and give an alarm by the way of indicator light. The photovoltaic inverter system not only effectively solves the problem of how to detect whether the photovoltaic string 1 is reversely connected, but also can intelligently identify and alarm quickly and accurately without connecting to the grid power supply and all strings are reversely connected , which greatly guarantees the convenience and effectiveness of the application. The introduction of the alarm unit 14 effectively guarantees the convenience and safety of installation and maintenance, and has important display significance. The control method of a photovoltaic inverter provided in this embodiment can realize the function of intelligently detecting reverse connection of the photovoltaic strings under all operating conditions or when all photovoltaic strings 1 are reversely connected, and effectively solve the practical installation and application of photovoltaic strings 1 The difficulty of reverse connection of the middle outgoing line can be detected without being connected to the power grid, which effectively ensures the convenience and safety of installation and maintenance.

The above-mentioned embodiment is only to illustrate the technical concept and characteristics of the present invention, and is a preferred embodiment. The scope of protection of the utility model. All equivalent transformations or modifications made according to the spirit of the present invention shall be included within the protection scope of the present invention.

Claims (10)

1. A photovoltaic inverter comprising a DC-DC conversion unit, a DC-LINK capacitor bank and a DC-AC conversion unit connected in sequence, said photovoltaic inverter further having a PV input for connecting a string of photovoltaic banks, characterized in that said photovoltaic inverter further comprises a string detection device for detecting whether an accessed string of photovoltaic banks is connected in reverse, said string detection device being connected between said PV input and said DC-DC conversion unit, said string detection device comprising:

the current detection unit is used for detecting the current of the PV input end and outputting a detection signal;

the input end of the comparator unit is connected with the output end of the current detection unit and is used for comparing the voltage value of the detection signal with a reference voltage, and the comparator unit outputs a signal representing that the group is in reverse connection when a set condition is met; and

The power supply energy storage unit is respectively connected with the current detection unit and the comparator unit to supply power to the current detection unit and the comparator unit;

the photovoltaic inverter includes:

the first charging unit is used for charging the power supply energy storage unit, the input end of the first charging unit is connected with the DC-LINK capacitor bank, and the output end of the first charging unit is connected with the power supply energy storage unit.

2. The pv inverter of claim 1, wherein the string detection device further comprises a second charging unit for charging the power storage unit, an input of the second charging unit is connected to the AC side of the DC-AC conversion unit, and an output of the second charging unit is connected to the power storage unit.

3. The pv inverter of claim 1, further comprising a control unit, wherein the output of the comparator unit is connected to the control unit.

4. The pv inverter of claim 1 wherein the string detection device further comprises an alarm unit, the alarm unit being connected to an output of the comparator unit, the power storage unit being connected to the alarm unit to provide power thereto.

5. The photovoltaic inverter of claim 4, wherein the alert unit comprises a status indicator light.

6. The pv inverter of claim 1, wherein the comparator unit has a non-inverting input connected to the reference voltage and an inverting input connected to the output of the current detection unit.

7. The PV inverter of claim 1, wherein the PV inverter comprises a plurality of PV input terminals and a plurality of string detection devices, each PV input terminal is configured to access a string of PV strings, each PV input terminal is connected to a corresponding string detection device, and the output terminal of the first charging unit is connected to the power storage unit of each string detection device.

8. The photovoltaic inverter according to claim 1, wherein the set condition is: the voltage value of the detection signal is smaller than the reference voltage.

9. The photovoltaic inverter of claim 1, wherein the power storage unit is a super capacitor.

10. A PV inverter system comprising a string of PV strings and a PV inverter, wherein the PV inverter employs the PV inverter of any of claims 1 to 9, and wherein the output of the string of PV strings is directly connected to the PV input of the PV inverter.

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