CN211860010U - A photovoltaic power generation system with an isolated MPPT combiner box - Google Patents

Abstract

The utility model discloses a photovoltaic power generation system with isolated form MPPT collection flow box belongs to photovoltaic power generation technical field. The photovoltaic modules are connected in series to form a photovoltaic subunit string, the photovoltaic subunit string is connected with an isolated MPPT (maximum power point tracking) combiner box, and the output sides of all the isolated MPPT combiner boxes are connected in parallel and then connected to an inverter; the isolated MPPT combiner box comprises an input circuit group, a direct current bus and a control and drive module; the input circuit group comprises a plurality of MPPT and isolation modules, the input sides of the MPPT and isolation modules are connected with the photovoltaic sub-group in series, and the output sides of the MPPT and isolation modules are connected with the direct-current busbar after being connected in series. The installation mode and the wiring mode of the photovoltaic module array are not changed, particularly the maximum voltage to earth of the photovoltaic module is not improved, the direct-current voltage-withstanding grade of the modules in the photovoltaic group substrings is not improved, and the line loss and the cable consumption of the output side of the isolation type MPPT combiner box can be obviously reduced; the MPPT tracking accuracy of the system can still be kept at the photovoltaic group cascade of the conventional voltage level.

Description

A photovoltaic power generation system with an isolated MPPT combiner box

technical field

The utility model belongs to the technical field of photovoltaic power generation, in particular to a photovoltaic power generation system with an isolated MPPT combiner box.

Background technique

Increasing the DC voltage level of photovoltaic systems helps reduce line losses and system costs. Conventional photovoltaic systems can obtain large DC voltage levels by connecting modules in series, such as 1000V or 1500V DC voltage, but while obtaining 1000V DC voltage and 1500V DC voltage, the PV modules in the string are required to have 1000V or 1500V insulation resistance at the same time. pressure level. Since there are currently no photovoltaic modules with a withstand voltage above 1500V, and no relevant technical standards, the development of photovoltaic systems to higher DC voltage levels is limited.

At the same time, when the withstand voltage level of photovoltaic modules meets the high-voltage requirements, obtaining a better DC bus voltage means that more photovoltaic modules need to be connected in series, and more series connection means a greater probability of series mismatch, which is not conducive to Increase in system power.

SUMMARY OF THE INVENTION

In order to solve the above-mentioned existing problems, the purpose of the present utility model is to provide a photovoltaic power generation system with an isolated MPPT combiner box, without changing the installation method and wiring method of the photovoltaic module array, especially without increasing the maximum pair of connected photovoltaic modules. The ground voltage, and will not increase the DC withstand voltage level of the components in the sub-string of the photovoltaic group, can significantly reduce the line loss and cable consumption on the output side of the isolated MPPT combiner box; the MPPT tracking accuracy of the system can still be maintained at the photovoltaic level of the conventional voltage level. String level.

The utility model is realized through the following technical solutions:

The utility model discloses a photovoltaic power generation system with an isolated MPPT combiner box. A plurality of photovoltaic modules are connected in series to form a photovoltaic sub-string, and a plurality of photovoltaic sub-strings are connected with an isolated MPPT combiner box. The side is connected in parallel to the DC side of the inverter of the photovoltaic power generation system;

The isolated MPPT combiner box includes an input circuit group, a DC busbar, and a control and drive module; the output sides of several input circuit groups are connected in parallel with the DC busbar, and the DC busbar is connected to the output side of the isolated MPPT combiner box; control and The drive module is connected with the input circuit group;

The input circuit group includes several MPPTs and isolation modules, the input sides of the MPPTs and the isolation modules are connected in series with the photovoltaic subgroups, and the output sides of the several MPPTs and the isolation modules are connected in series with the DC busbar.

Preferably, the MPPT and the isolation module include an access terminal, an MPPT circuit and an isolation circuit that are connected in sequence; the access terminal is connected to the photovoltaic sub-group in series, and the isolation circuit is connected to the output side of the MPPT and the isolation module; the MPPT circuit and the isolation circuit are respectively connected to Control and drive module connections.

Further preferably, a fuse is connected between the access terminal and the MPPT circuit.

Preferably, an anti-reverse diode is connected in series between the positive output side of the input circuit group and the DC busbar.

Preferably, a DC circuit breaker is connected in series between the DC busbar and the output side of the isolated MPPT combiner box.

Preferably, a lightning protection grounder is connected in parallel between the DC busbar and the output side of the isolated MPPT combiner box.

Preferably, the number of MPPTs and isolation modules in the input circuit group is greater than or equal to 2.

Compared with the prior art, the utility model has the following beneficial technical effects:

The utility model discloses a photovoltaic power generation system with an isolated MPPT combiner box. The photovoltaic components are not directly connected in series to form a group string, but a photovoltaic sub-string is formed by connecting several photovoltaic components in series, and several photovoltaic sub-strings are connected to one Isolated MPPT combiner box, the isolation controller is connected in parallel to the inverter of the photovoltaic power generation system. The isolated MPPT combiner box does not change the installation method and wiring method of the photovoltaic module array, especially does not increase the maximum ground voltage of the connected photovoltaic modules, and does not increase the DC withstand voltage level of the components in the photovoltaic sub-strings. The series connection of the sub-strings through the isolated MPPT combiner box can achieve a multiple increase of the DC voltage level, which can significantly reduce the line loss and cable consumption on the output side of the isolated MPPT combiner box. At the same time, since each photovoltaic sub-string independently performs maximum power point tracking, the MPPT tracking accuracy of the system can still be maintained at the photovoltaic string level of the conventional voltage level.

Further, the MPPT circuit in the MPPT and the isolation module performs maximum power point tracking on the connected photovoltaic substring, and the isolation circuit realizes the voltage isolation on the input and output sides.

Further, the fuse can be cut off when the current is too large to ensure the normal operation of the system.

Further, the anti-reverse diode can prevent the current from flowing backward and ensure the normal operation of the system.

Further, the DC circuit breaker can be individually cut off when components in the circuit fail or leak, without affecting the normal operation of the entire combiner box.

Further, the lightning protection grounding device is used to prevent lightning strikes and static electricity hazards, and to improve the safety and stability of the system.

Description of drawings

Fig. 1 is the structural principle schematic diagram of the isolation type MPPT combiner box of the present invention;

Fig. 2 is the structural representation of MPPT and isolation module of the present invention;

3 is a schematic structural diagram of an input circuit group of the present invention;

4 is a schematic diagram of the overall structure of a photovoltaic power generation system with an isolated MPPT combiner box of the present invention.

In the figure: 1 is photovoltaic module, 2 is isolated MPPT combiner box, 21 is input circuit group, 211 is MPPT and isolation module, 2111 is access terminal, 2112 is fuse, 2113 is MPPT circuit, 2114 is isolation circuit, 22 is a DC busbar, 23 is a control and drive module, 24 is an anti-reverse diode, 25 is a lightning protection grounder, 26 is a DC circuit breaker, and 3 is an inverter.

Detailed ways

Below in conjunction with the accompanying drawings and specific embodiments, the present utility model is described in further detail, and its content is to explain rather than limit the present utility model:

As shown in Figure 1, the isolated MPPT combiner box 2 includes an input circuit group 21, a DC busbar 22, and a control and drive module; the output sides of several input circuit groups 21 are connected in parallel with the DC busbar 22, and the positive pole of the input circuit group 21 outputs An anti-reverse diode 24 is connected in series between the DC busbar 22 and the DC busbar 22; The lightning grounder 25 is connected with a DC circuit breaker 26 in series.

As shown in FIG. 3, the input circuit group 21 includes several MPPTs and isolation modules 211. The input sides of the MPPTs and the isolation modules 211 are connected to the photovoltaic sub-strings, and the output sides of two or more adjacent MPPTs and the isolation modules 211 are connected in series. Then connect with the DC bus bar 22 .

As shown in FIG. 2 , the MPPT and isolation module 211 includes an access terminal 2111 , an MPPT circuit 2113 and an isolation circuit 2114 connected in sequence; the access terminal 2111 is connected to the photovoltaic sub-string, and the isolation circuit 2114 is connected to the output side of the MPPT and the isolation module 211 . ; The MPPT circuit 2113 and the isolation circuit 2114 are connected to the control and drive module 23 respectively.

The positive and negative poles of each photovoltaic substring are introduced into the MPPT circuit 2113 through a set of access terminals 2111 of the MPPT and isolation module 211. After the MPPT circuit 2113 performs maximum power tracking on the photovoltaic substring, its output end is connected to the isolation circuit 2114 to isolate the The function of the circuit 2114 is to electrically isolate the ground voltage of the output terminal from the ground voltage of the input terminal; two or more adjacent MPPT and isolation modules 211 are connected in series at the output side and an anti-reverse diode 26 is connected in series at the positive pole. An input circuit group 21 is formed, and its positive and negative output terminals are connected to the positive and negative DC busbars 22 of the isolated MPPT combiner box 2, and finally output through the DC circuit breaker 26 and the lightning protection grounder 25, and the output voltage at this time has increased. is N*V, where V is the PV string voltage on the input side, and N is the number of MPPTs and isolation modules 211 connected in series with each other. The control and driving module 23 provides driving control of the MPPT circuit 2113 and the isolation circuit 2114, as well as collecting and transmitting electrical signals to the upper stage. For example, if the voltage level of a single photovoltaic sub-string connected is 1000V, then two or three photovoltaic sub-strings are connected in series through the MPPT circuit 2113 and the isolation circuit 2114 and then connected to the DC busbar 22, the isolated MPPT The voltage level of the DC busbar 22 (output) of the combiner box 2 becomes 2000V or 3000V, and the maximum voltage to the ground of the output side electrode of the isolated MPPT combiner box 2 will be 2000V or 3000V. However, due to the electrical isolation between the input side and the output side of the isolated MPPT combiner box 2, the maximum voltage to ground at the electrode terminals of each PV sub-string is still maintained at 1000V, that is, the withstand voltage strength of the PV module 1 is required to be the same as the DC system voltage. Level up and up.

As shown in FIG. 4, the photovoltaic power generation system of the present invention has an isolated MPPT combiner box. Several photovoltaic modules 1 are connected in series to form photovoltaic sub-strings, and several photovoltaic sub-strings are connected to the isolated MPPT combiner box 2. All isolated MPPT combiner boxes The output side of 2 is connected in parallel to the inverter 3 of the photovoltaic power generation system. The conventional PV strings with the PV substring voltage level of 1000V or 1500V before the isolated MPPT combiner box 2 are boosted to above 2000V-3000V after being boosted in series inside the isolated MPPT combiner box 2. The DC collecting cables at the rear of the isolated MPPT combiner box 2 all use 2000V or 3000V withstand voltage specifications. The outputs of a plurality of isolated MPPT combiner boxes 2 are connected in parallel on the DC side of the inverter 3, and are connected to the grid after being inverted by the inverter 3.

It should be noted that the above is only one of the embodiments of the present invention, and the equivalent changes made by the system described in the present invention are all included in the protection scope of the present invention. Those skilled in the art to which the present invention pertains can substitute the specific examples described in a similar manner, as long as they do not deviate from the structure of the present invention or go beyond the scope defined by the claims, they all belong to the protection scope of the present invention.

Claims (7)

1. A photovoltaic power generation system with an isolated MPPT combiner box is characterized in that a plurality of photovoltaic modules (1) are connected in series to form a photovoltaic subgroup string, the photovoltaic subgroup string is connected with an isolated MPPT combiner box (2), and the output sides of all the isolated MPPT combiner boxes (2) are connected in parallel and then connected to the direct current side of an inverter (3) of the photovoltaic power generation system;

the isolated MPPT bus box (2) comprises an input circuit group (21), a direct current bus (22) and a control and drive module (23); the output sides of the plurality of input circuit groups (21) are connected in parallel and then are connected with a direct current bus (22), and the direct current bus (22) is connected with the output side of the isolated MPPT combiner box (2); the control and drive module (23) is connected with the input circuit group (21);

the input circuit group (21) comprises a plurality of MPPT and isolation modules (211), the input sides of the MPPT and isolation modules (211) are connected with the photovoltaic sub-group in series, and the output sides of the MPPT and isolation modules (211) are connected with the direct-current busbar (22) after being connected in series.

2. The photovoltaic power generation system with the isolated MPPT combiner box of claim 1, wherein the MPPT and isolation module (211) includes an access terminal (2111), an MPPT circuit (2113) and an isolation circuit (2114) connected in sequence; the access terminal (2111) is connected with the photovoltaic subgroup string, and the isolation circuit (2114) is connected with the MPPT and the output side of the isolation module (211); the MPPT circuit (2113) and the isolation circuit (2114) are respectively connected with the control and drive module (23).

3. The photovoltaic power generation system with isolated MPPT combiner box of claim 2, wherein a fuse (2112) is connected between the access terminal (2111) and the MPPT circuit (2113).

4. The photovoltaic power generation system with the isolated MPPT combiner box of claim 1, wherein an anti-reflection diode (24) is connected in series between the positive output side of the input circuit group (21) and the DC bus bar (22).

5. The photovoltaic power generation system with the isolated MPPT combiner box of claim 1, characterized in that a DC breaker (26) is connected in series between the DC busbar (22) and the output side of the isolated MPPT combiner box (2).

6. The photovoltaic power generation system with the isolated MPPT combiner box of claim 1, characterized in that a lightning protection earth (25) is connected in parallel between the DC busbar (22) and the output side of the isolated MPPT combiner box (2).

7. The photovoltaic power generation system with the isolated MPPT combiner box of claim 1, wherein the number of MPPT and isolation modules (211) in the input circuit group (21) is greater than or equal to 2.

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