CN203313097U - Large power photovoltaic power generation system - Google Patents

Abstract

The utility model discloses a high-power photovoltaic power generation system, which comprises a transformer, an inverter, N×M photovoltaic battery groups, conductors and N×M photovoltaic controllers, the output end of the transformer is connected to the power grid, and the input end is connected to the inverter. The output end of the inverter, the input end of each photovoltaic controller is connected to a photovoltaic battery group, and the output end is connected to the input end of the inverter through the conductor. The utility model uses a photovoltaic controller to realize MPPT control and Boost boost, which improves the power generation efficiency of the system and reduces the cost of the system.

Description

A high-power photovoltaic power generation system

technical field

The utility model relates to photovoltaic power generation technology, in particular to a high-power photovoltaic power generation system.

Background technique

As shown in Figure 1, the existing high-power photovoltaic grid-connected power generation system, such as a 1MW photovoltaic grid-connected power generation system, usually includes a grid-connected inverter, DC power distribution cabinet, combiner box, photovoltaic array, combiner box and multi-channel photovoltaic For array connection, the DC power distribution cabinet connects the DC cables output from the combiner box for confluence, and then connects them to the input of the grid-connected inverter for inversion and grid-connection. The output of the grid-connected inverter is connected to the grid through a box-type step-up.

In the existing grid-connected power generation system of this kind, the combiner box usually only serves as a confluence, without transforming the voltage and current. Considering safety factors, the operating voltage range of photovoltaic modules entering the combiner box and grid-connected inverter is 400VDC to 900VDC, and the open circuit voltage does not exceed 1000VDC. At this time, for the design of the inverter, if the three-phase full-bridge circuit shown in Figure 2 is used for one-stage conversion, for an input of 400VDC, only an AC voltage of about 270V can be output for grid connection. Due to the low voltage, the output current Large, such as the common 500kW photovoltaic inverter AC rated output current of more than 1000A, the cost of AC switches and IGBTs are high, and the line loss of copper bars and cables is large.

If the inverter system adopts the DC/DC boost first and then the three-phase full-bridge circuit for two-stage conversion as shown in Figure 3, the grid-connected AC voltage can be increased. A typical solution is DC/DC boost to about 600V, Then the DC/AC is converted to 380V AC voltage and connected to the grid, or the DC/DC is boosted to about 900V, and the corresponding DC/AC is converted to 620V AC voltage to be connected to the grid. Although this solution reduces the cost of the DC/AC conversion unit and the AC grid-connected side, it also improves the power generation efficiency of this part, but the conversion of the DC/DC part needs to increase losses and costs, resulting in the final overall power generation efficiency and cost. Compared with the scheme of Fig. 2, there is no great improvement.

For the grid-connected power generation system shown in Fig. 1, the inverter adopts the schemes of Fig. 2 and Fig. 3, but the problem of low power generation efficiency and high cost of the overall system is not improved.

Utility model content

The utility model aims at the above defects of the prior art, provides a high-power photovoltaic power generation system, changes the function of the combiner box, and proposes a high-power photovoltaic power generation system with higher power generation efficiency and cost performance.

The technical solution adopted by the utility model to solve the technical problem is: provide a high-power photovoltaic power generation system, including a transformer, an inverter and N×M photovoltaic cell groups, the output end of the transformer is connected to the power grid, and the input end is connected to the power grid. The output terminals of the inverter, N and M are both non-zero natural numbers, and N and M are not 1 at the same time, the system also includes conductors and N×M photovoltaic controllers, each input terminal of the photovoltaic controller A photovoltaic cell group is connected, and the output end is connected to the input end of the inverter through the conductor.

Preferably, each photovoltaic controller in the N×M photovoltaic controllers includes a plurality of DC/DCBoost boost circuits, and the input terminal of each DC/DC Boost boost circuit is connected to one of the corresponding photovoltaic cell groups The photovoltaic cells are connected, and the output ends of the multiple DC/DC Boost boost circuits form a positive output and a negative output after the positive and negative confluence; each photovoltaic controller also includes a circuit for each DC/DC Boost boost Maximum power point tracking control unit for maximum power point tracking.

Preferably, the N×M photovoltaic controllers are photovoltaic controllers whose output voltage is 0.7-1 times of the maximum input open-circuit voltage.

Preferably, the N photovoltaic controllers and the N photovoltaic battery groups are connected in parallel to form a photovoltaic group, and the output ends of the M photovoltaic groups are connected to the input ends of the inverter through the conductor.

Preferably, the system further includes a DC power distribution cabinet, the input end of the DC power distribution cabinet is connected to the output ends of the plurality of photovoltaic controllers through the conductor, and the output end is connected to the inverter input terminal.

Preferably, the system further includes M DC power distribution cabinets, the input end of each DC power distribution cabinet is connected to the output end of a photovoltaic group through the conductor, and the output end of each DC power distribution cabinet is connected to the The input terminal of the inverter.

Preferably, the conductor is a cable, a copper bar or a conductive aluminum bar.

Preferably, the length of the conductor is greater than or equal to 10 meters.

Preferably, each photovoltaic controller includes four DC/DC Boost circuits.

Preferably, each photovoltaic controller includes two DC/DC Boost circuits.

The high-power photovoltaic power generation system of the utility model has the following beneficial effects: the photovoltaic controller is used to realize MPPT control and Boost boost, and the input voltage of the inverter is increased due to the addition of a first-stage DC/DC Boost boost circuit. The grid-connected output voltage of the inverter is increased, so in the case of the same power, the current becomes smaller, which reduces the loss of the conductor, improves the system efficiency, and reduces the cost of the system cable; in addition, because the inverter The current and volume are reduced, so that high-power photovoltaic power generation systems (such as 1MW photovoltaic power generation systems) can use a single inverter, so that grid-connected transformers can use ordinary box-type transformers instead of the more expensive double-fission scheme; in addition , the maximum power point tracking (MPPT) function of photovoltaic modules is distributed to the photovoltaic controller, which can prevent the uneven loss caused by the inconsistency of radiation, temperature and other battery parameters; The difference is very large, and the distributed MPPT scheme can independently enhance and improve the performance of the battery panel, thereby improving the power generation efficiency of the system.

Description of drawings

Figure 1 is a schematic diagram of a traditional 1MW photovoltaic grid-connected power generation system;

Figure 2 is the main topology of a three-phase photovoltaic inverter with single-stage conversion;

Figure 3 is the main topology of the three-phase photovoltaic inverter with two-stage conversion;

Fig. 4 is a structural schematic diagram of the first embodiment of the high-power photovoltaic power generation system of the present invention;

Fig. 5 is the control schematic diagram of the first embodiment of the photovoltaic controller;

Fig. 6 is the control schematic diagram of the second embodiment of the photovoltaic controller;

Fig. 7 is the flow chart that photovoltaic controller carries out power control to inverter;

Fig. 8 is a schematic structural view of the second embodiment of the high-power photovoltaic power generation system of the present invention;

Fig. 9 is a schematic structural view of the third embodiment of the high-power photovoltaic power generation system of the present invention;

Fig. 10 is a schematic structural diagram of a fourth embodiment of the high-power photovoltaic power generation system of the present invention.

Detailed ways

Below in conjunction with accompanying drawing and embodiment the utility model is described further.

Fig. 4 is a schematic structural diagram of the first embodiment of the high-power photovoltaic power generation system 100 of the present invention. As shown in Fig. 4, in this embodiment, the system 100 includes a transformer 110, an inverter 120, and N×M photovoltaic A battery pack 130 , a conductor (not shown in the figure) and N×M photovoltaic controllers 140 . Wherein, both N and M are non-zero natural numbers, and N and M are not 1 at the same time. The output end of the transformer 110 is connected to the grid, the input end is connected to the output end of the inverter 120 , the input end of the photovoltaic controller 140 is connected to a photovoltaic cell group 130 , and the output end is connected to the input end of the inverter 120 through a conductor. Wherein, the conductor can be a cable, a copper row or a conductive aluminum row, and the length of the conductor is greater than or equal to 10 meters.

In this embodiment, the photovoltaic controller 140 can complete maximum power point tracking (MPPT), and has a DC/DC Boost function. In addition, the steady-state output voltage of the photovoltaic controller 140 is 0.7-1 times of its maximum input open-circuit voltage. Specifically, each photovoltaic controller 140 includes a plurality of independent DC/DC Boost boost circuits 141 and maximum power point tracking control unit 142 (ie, MPPT control unit 142), and the input terminals of each Boost boost circuit 141 correspond to A photovoltaic cell in the photovoltaic cell group 130 is connected, and the output terminals of all Boost booster circuits 141 form a positive output and a negative output 141 (that is, the output terminal of the photovoltaic controller 140) after the positive and negative confluence, which are used for conducting The body is connected to the inverter 120.

As shown in FIG. 5 , each photovoltaic controller 140 may include four independent DC/DC Boost boost circuits 141, and each DC/DC Boost boost circuit 141 has an independent MPPT function. The input end of each DC/DC Boost circuit 141 can be connected to a plurality of photovoltaic cells in a photovoltaic cell group 130, and at this time, each photovoltaic cell group 130 includes four photovoltaic cells. Compared with the photovoltaic controller that uses a single DC/DC Boost circuit inside, the advantage of using multiple DC/DC circuit schemes is that it can realize multiple sets of MPPT, thereby further improving power generation efficiency.

As shown in FIG. 6, each photovoltaic controller 140 may also include two independent DC/DC Boost boost circuits 141, and each DC/DC Boost boost circuit 141 has an independent MPPT function. Likewise, the input section of each DC/DCBoost booster circuit 141 is connected to a plurality of photovoltaic cells in a photovoltaic cell group 130 . Compared with the photovoltaic controller shown in FIG. 5 , the photovoltaic controller is smaller in size, lighter in weight, more convenient for maintenance, and can realize natural cooling.

In the above two embodiments of the photovoltaic controller 140, the photovoltaic controller 140 can realize the maximum power point tracking (MPPT) function, complete the grid connection with the inverter 120, stabilize the DC bus voltage of the inverter 120 and control the inverter The inverter 120 performs the function of controlling reactive power. The flow of power control of the inverter 120 by the photovoltaic controller 140 is shown in Figure 7. In the figure, Udcref is the given bus voltage, which determines the DC bus voltage and photovoltaic control of the inverter 120. The output voltage of the inverter 140, Qref is a reactive power reference, which determines the amount of reactive power output by the inverter 120 to the grid.

For high-power photovoltaic power generation systems, the maximum output open-circuit voltage of photovoltaic modules is generally designed to be 1000Vdc, and the corresponding MPPT voltage range is about 400Vdc-900Vdc. In the present utility model, if the semiconductor device of the DC/DC Boost boost circuit 141 selects a 1200V withstand voltage grade, then the steady-state output voltage of the DC/DC Boost boost circuit 141 is designed to be about 850VDC, which is 1.1 times more than 850VDC (that is, 935VDC) to prevent overvoltage from damaging the semiconductor, and the rated grid-connected output voltage of the corresponding 1MW DC/AC inverter 120 is 560Vac. If the semiconductor device of the DC/DC Boost circuit 141 is selected with a withstand voltage level of 1700V, then the steady-state output voltage of the DC/DC Boost circuit 141 can be designed to be about 1000VDC, and if it exceeds 1200VDC, wave sealing protection will be performed, corresponding to 1MWDC/AC The rated grid-connected output voltage of the inverter 120 is 690Vac.

In other embodiments of the high-power photovoltaic power generation system 100 of the present utility model, the connection of N photovoltaic controllers 140 and N photovoltaic battery groups 130 can also be connected in parallel to form a photovoltaic group, then there are M photovoltaic groups The output end of the inverter 120 is connected to the input end of the inverter 120 through a conductor.

In the high-power photovoltaic power generation system 100 of the present utility model, a DC/DC Boost boost circuit is added to increase the input voltage of the inverter 120 to above 850VDC, and at the same time, the grid-connected output voltage of the inverter 120 can be increased by The 270Vac is increased to above 560Vac, so that the current will become smaller under the same power due to the voltage increase, so that the cost of the inverter 120 can be reduced to half of the original. In addition, when both the DC side voltage and the AC side voltage are increased, the current will become smaller under the same power, which will lead to a decrease in the loss of the conductor and improve the system efficiency. Furthermore, after both the voltage on the DC side and the voltage on the AC side are increased, under the same power condition, the current will be reduced and the cost of the system cable will be reduced. In addition, since the current and volume of the inverter 120 are reduced, a single inverter can be used in a 1MW system, so that the grid-connected transformer 110 can use a common box-type transformer instead of a more expensive dual-fission solution. In addition, distributing the maximum power point tracking (MPPT) function of photovoltaic modules to the photovoltaic controller 140 can prevent uneven losses caused by inconsistencies in radiation, temperature and other battery parameters. This is due to the following two reasons: First, the internal chaos of the centralized MPPT stays at the local highest point when performing power configuration, and is set at the suboptimal point of the voltage; second, under abnormal conditions, the voltage point difference of the MPPT may Very large, beyond the working range and voltage range of the centralized MPPT. Due to the large differences between the panels, the distributed MPPT scheme can independently enhance and improve the performance of the panels, thereby improving the power generation efficiency of the system.

Fig. 8 is a schematic structural diagram of the second embodiment of the high-power photovoltaic power generation system 100 of the present invention. The difference between this embodiment and the first embodiment of the system 100 is that in this embodiment, the system 100 also includes a DC power distribution cabinet 150 , the input end of the DC power distribution cabinet 150 is connected to the output ends of multiple photovoltaic controllers 140 through conductors, and the output end of the DC power distribution cabinet 150 is connected to the input end of the inverter 120 . In this embodiment, the output of the photovoltaic controller 140 is connected to the inverter 120 after passing through the DC power distribution cabinet 150 .

9 is a schematic structural diagram of the third embodiment of the high-power photovoltaic power generation system 100 of the present invention. The difference between this embodiment and the second embodiment of the system 100 is that in this embodiment, N photovoltaic controllers 140 and N The photovoltaic cell groups 130 are connected in parallel to form a photovoltaic group. The outputs of M photovoltaic groups are sent to the input end of the DC power distribution cabinet 150 through M independent conductors (such as M pairs of cables) over a long distance, and then passed through the DC power distribution cabinet. The converging current of the cabinet 150 is sent to the inverter 120, and the inverter 120 converts it into alternating current after DC/AC inversion and is connected to the grid with the transformer 110.

Fig. 10 is a schematic structural diagram of a fourth embodiment of a high-power photovoltaic power generation system 100 of the present invention. The difference between this embodiment and the first embodiment of the system 100 is that in this embodiment, the system 100 also includes M DC power distribution The cabinet 150, the N photovoltaic controllers 140 and the N photovoltaic battery groups 130 are connected in parallel to form a photovoltaic group. In this embodiment, the input end of each DC power distribution cabinet 150 is connected to the output end of a photovoltaic group (that is, the output end of the photovoltaic controller 140 ) through a conductor, and the output end of each DC power distribution cabinet 150 is connected to the inverter The input terminal of the transformer 120. For example, N=8 and M=2 can be taken. At this time, there are 2 DC power distribution cabinets 150 in total, and the input end of each DC power distribution cabinet 150 is connected to the output of 8 photovoltaic groups. The outputs of the 16 photovoltaic controllers 140 are sequentially connected to 16 circuit breaker switches inside the two DC power distribution cabinets 150 through 16 pairs of independent conductors, and the output of the DC power distribution cabinet 150 is connected to the input of the inverter 120, through Control of each breaker switch allows for independent maintenance and repair of each photovoltaic controller 140 .

The above descriptions are only preferred embodiments of the utility model, and are not intended to limit the utility model. For those skilled in the art, the utility model can have various modifications and changes. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present utility model shall be included within the scope of the claims of the present utility model.

Claims (10)

1. a high-power photovoltaic electricity generation system (100), comprise transformer (110), inverter (120) and N * M photovoltaic cell group (130), the output of described transformer (110) connects electrical network, the output of the input described inverter of link (120), N and M are the non-zero natural number, and when N is different with M, be 1, it is characterized in that, described system (100) also comprises electric conductor and N * M photovoltaic controller (140), each input of photovoltaic controller (140) connects a photovoltaic cell group (130), output connects the input of described inverter (120) by described electric conductor.

2. high-power photovoltaic electricity generation system according to claim 1 (100), it is characterized in that, each photovoltaic controller (140) in described N * M photovoltaic controller (140) comprises a plurality of DC/DCBoost booster circuits (141), the input of each DC/DC Boost booster circuit (141) connects with a photovoltaic cell in corresponding photovoltaic cell group (130), and the output of described a plurality of DC/DC Boost booster circuits (141) is exported by the positive and negative anodal output in rear formation one road and the negative pole of confluxing; Each photovoltaic controller (140) also comprises for each DC/DC Boost booster circuit (141) being carried out to the maximum power point tracking unit (142) of maximum power point tracking.

3. high-power photovoltaic electricity generation system according to claim 2 (100), is characterized in that, described N * M photovoltaic controller (140) is the photovoltaic controller (140) of 0.7～1 times of maximum input pull-down voltage for output voltage.

4. high-power photovoltaic electricity generation system according to claim 1 (100), it is characterized in that, after the connecting overall parallel connection of N photovoltaic controller (140) and N photovoltaic cell group (130), form a photovoltaic grouping, the output of M photovoltaic grouping connects the input of described inverter (120) by described electric conductor.

5. according to the described high-power photovoltaic electricity generation system of any one in claim 1-4 (100), it is characterized in that, described system (100) also comprises a DC power distribution cabinet (150), and the input of a described DC power distribution cabinet (150) is by the input that described electric conductor is connected with the output of described a plurality of photovoltaic controllers (140), output connects described inverter (120).

6. high-power photovoltaic electricity generation system according to claim 4 (100), it is characterized in that, described system (100) also comprises M DC power distribution cabinet (150), the input of each DC power distribution cabinet (150) is connected with the output of a photovoltaic grouping by described electric conductor, and the output of each DC power distribution cabinet (150) connects the input of described inverter (120).

7. high-power photovoltaic electricity generation system according to claim 1 (100), is characterized in that, described electric conductor is cable, copper bar or electroconductive aluminium strip.

8. high-power photovoltaic electricity generation system according to claim 7 (100), is characterized in that, the length of described electric conductor is more than or equal to 10 meters.

9. high-power photovoltaic electricity generation system according to claim 2 (100), is characterized in that, each photovoltaic controller (140) comprises four DC/DC Boost booster circuits (141).

10. high-power photovoltaic electricity generation system according to claim 2 (100), is characterized in that, each photovoltaic controller (140) comprises two DC/DC Boost booster circuits (141).

Images