Anti-countercurrent photovoltaic grid-connected system

Abstract

The utility model discloses an anti-countercurrent photovoltaic grid-connected system, which comprises a photovoltaic assembly, a load, an energy storage battery, an inverter, a low-voltage bus tie switch, a first transformer for increasing low voltage to high voltage, a wire outlet switch, an anti-countercurrent device, a wire inlet switch and a second transformer for increasing high voltage to voltage required by a grid-connected system, the load is connected in parallel with the energy storage battery; the output end of the photovoltaic module is connected to one end of the low-voltage bus tie switch through the inverter, and the other end of the low-voltage bus tie switch is connected to a line between the first end of the load and the first end of the energy storage battery; the input end of the first transformer is electrically connected to a line between the second end of the load and the second end of the energy storage battery; the output end of the first transformer is electrically connected to the anti-reflux device through the outgoing line switch; the anti-backflow device is connected to the input end of the second transformer through the wire inlet switch, and the output end of the second transformer is connected to the power grid system. According to the utility model, the countercurrent risk of the photovoltaic grid-connected system can be further reduced.

Description

TECHNICAL FIELD

[0001] The utility model relates to photovoltaic grid-connected system technical field especially relates to a prevent reverse flow photovoltaic grid-connected system. BACKGROUND

[0002] In the domestic user side industrial and commercial photovoltaic energy storage comprehensive energy project, photovoltaic power station and energy storage power station are basically invested, constructed and operated by different capital parties, and the energy storage power station is required not to allow the discharge current to flow reversely to the grid when the system is discharged, so that the anti-reverse flow device is arranged. The anti-reverse flow device is usually installed in the transformer low-voltage side incoming line cabinet, and the photovoltaic power station and the energy storage power station grid-connected point are generally distributed on two different busbars of two transformer low-voltage sides.

[0003] However, when the anti-reverse flow device is installed in the transformer low-voltage side load incoming line cabinet of the energy storage power station grid-connected side, one of the transformers needs to be overhauled, in order to ensure the normal operation of the load at the lower end of the transformer during the overhaul, the factory will close the low-voltage side bus coupler switch, and simultaneously disconnect the transformer high-low voltage side switch, at this time the anti-reverse flow device is invalid. This installation scheme can only prevent reverse flow when the transformer is normally operated and the bus coupler switch is not closed; the anti-reverse flow meter can only detect the load power of the busbar, the anti-reverse flow meter adjusts the output power of the energy storage power station by measuring the positive and negative sequences of the current, this scheme suppresses the discharge power of the energy storage power station, and it is difficult to realize the maximum benefit of the operation of the energy storage power station; during the transformer operation and maintenance, the energy storage power station may discharge to the grid. In addition, in the prior art, the anti-reverse flow device is connected to the low-voltage intelligent electric meter, and the current sampling uses a secondary current transformer (CT), which has the problems of signal attenuation and complex wiring. UTILITY MODEL CONTENTS

[0004] The technical problem to be solved by the utility model lies in providing a kind of prevent reverse flow photovoltaic grid-connected system, which can further reduce the reverse flow risk of photovoltaic grid-connected system.

[0005] In order to solve the above technical problems, the utility model discloses a kind of prevent reverse flow photovoltaic grid-connected system, including photovoltaic module, load, energy storage battery, inverter, low-voltage bus coupler switch, first transformer that low voltage is raised to high voltage, outgoing line switch, anti-reverse flow device, incoming line switch, second transformer that high voltage is raised to the voltage required to be connected into grid system;

[0006] The load is connected in parallel with the energy storage battery;

[0007] The output end of the photovoltaic module is connected to one end of the low-voltage bus coupler switch through the inverter, and the other end of the low-voltage bus coupler switch is connected to the line between the first end of the load and the first end of the energy storage battery;

[0008] The input end of the first transformer is electrically connected to a line between the second end of the load and the second end of the energy storage battery;

[0009] The output end of the first transformer is electrically connected to the anti-backflow device through the outgoing line switch;

[0010] The anti-backflow device is connected to the input end of the second transformer through the incoming line switch, and the output end of the second transformer is connected to a power grid system.

[0011] As an optional implementation, at least two groups of the load and the energy storage battery are in parallel connection, and at least two low-voltage main connection switches and two first transformers are provided;

[0012] The inverter has at least two output ends, each of which is connected to the input end of the second transformer through a low-voltage main connection switch, a group of the load and the energy storage battery in parallel connection, and a first transformer through an outgoing line switch.

[0013] As another optional implementation, the incoming line switch is provided with a current transformer.

[0014] As another optional implementation, the anti-backflow device comprises an anti-backflow meter and an anti-backflow controller, the anti-backflow meter is a high-voltage meter, and the high-voltage meter sends current direction information to the anti-backflow controller based on the current transformer.

[0015] As another optional implementation, the first transformer is 400V to 10kV.

[0016] As another optional implementation, the outgoing line switch and the incoming line switch both support at least 10kV voltage.

[0017] As another optional implementation, the second transformer is 10kV to 35kV.

[0018] As another optional implementation, the anti-backflow controller is in communication connection with an energy management system (EMS) of the energy storage battery, the anti-backflow controller transmits current direction information to the energy management system (EMS) in real time, and the energy management system (EMS) dynamically adjusts charging and discharging power of the energy storage battery based on the current direction information and load demand.

[0019] As another optional implementation, the energy storage battery is composed of at least two groups of lithium batteries in parallel connection, each group of lithium batteries is connected with a battery management system (BMS) in series, and each BMS is connected with the energy management system (EMS) through a CAN bus.

[0020] Compared with the prior art, the embodiment of the utility model has the following beneficial effects:

[0021] The anti-backflow device is arranged at the high-voltage side (10kV) after voltage boosting and directly connected to the front of the second transformer of the power grid system, so that the power consumption demand of the entire photovoltaic plant area can be monitored in real time, and the current direction can be accurately detected; when the discharge power of the energy storage power station exceeds the load demand, the anti-backflow device quickly identifies the backflow signal through the current transformer of the high-voltage side, so that the power is dynamically adjusted through the energy storage EMS subsequently, and the backflow risk caused by transformer maintenance or the closing of the bus coupler switch is effectively avoided; at the same time, the independent grid connection point design of photovoltaic and energy storage (respectively located at the low-voltage sides of different transformers) ensures that the energy storage power station can still supply power to other loads through the bus coupler switch during transformer maintenance, and the system operation flexibility and income stability are significantly improved. BRIEF DESCRIPTION OF DRAWINGS

[0022] In order to make the personnel in the art better understand the technical scheme of the present application, the technical scheme in the embodiments of the present application will be described clearly and completely below with reference to the drawings of the embodiments of the present application. Obviously, the described embodiments are only some of the embodiments of the present application, not all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor fall within the scope of protection of the present application.

[0023] Fig. 1 is a structural schematic diagram of an anti-backflow photovoltaic grid-connected system disclosed by the embodiments of the present application;

[0024] Fig. 2 is a partial structural schematic diagram of an anti-backflow photovoltaic grid-connected system disclosed by the embodiments of the present application. DETAILED DESCRIPTION

[0025] In order to make the personnel in the art better understand the technical scheme of the present application, the technical scheme in the embodiments of the present application will be described clearly and completely below with reference to the drawings of the embodiments of the present application. Obviously, the described embodiments are only some of the embodiments of the present application, not all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor fall within the scope of protection of the present application.

[0026] Referring to Figs. 1-2 The embodiments of the present application disclose an anti-backflow photovoltaic grid-connected system, which comprises a photovoltaic assembly 1, a load 4, an energy storage battery 5, an inverter 2, a low-voltage bus coupler switch 3, a first transformer 6 for raising low voltage to high voltage, an outgoing line switch 7, an anti-backflow device 8, an incoming line switch 9, and a second transformer 10 for raising high voltage to the required voltage of grid connection 11.

[0027] The load 4 is connected in parallel with the energy storage battery 5.

[0028] The output end of the photovoltaic assembly 1 is connected to one end of a low-voltage bus coupler 3 through the inverter 2, and the other end of the low-voltage bus coupler 3 is connected to a line between a first end of the load 4 and a first end of the energy storage battery 5;

[0029] The input end of the first transformer 6 is electrically connected to a line between a second end of the load 4 and a second end of the energy storage battery 5;

[0030] The output end of the first transformer 6 is electrically connected to the anti-backflow device 8 through the outgoing line switch 7;

[0031] The anti-backflow device 8 is connected to the input end of the second transformer 10 through the incoming line switch 9, and the output end of the second transformer 10 is connected to a power grid system 11.

[0032] In the embodiment of the utility model, the anti-backflow device 8 is arranged on the high-voltage side (10kV) after voltage boosting and directly connected to the second transformer 10 of the power grid system 11, so that the electricity load demand of the whole photovoltaic plant area can be monitored in real time, and the current direction can be accurately detected; when the discharge power of the energy storage power station exceeds the demand of the load 4, the anti-backflow device 8 quickly identifies the backflow signal through the current transformer of the high-voltage side, so that the power can be dynamically adjusted through the energy storage EMS subsequently, and the backflow risk caused by transformer maintenance or bus coupler closing is effectively avoided; at the same time, the independent grid connection point design of photovoltaic and energy storage (respectively located on the low-voltage side of different transformers) ensures that the energy storage power station can still supply power to other loads 4 through the bus coupler during transformer maintenance, and the system operation flexibility and income stability are significantly improved.

[0033] In an optional embodiment, there are at least two groups of parallel structures of the load 4 and the energy storage battery 5, at least two low-voltage bus couplers 3 and two first transformers 6;

[0034] The inverter 2 has at least two output ends, each of which is connected to the input end of the second transformer 10 through one low-voltage bus coupler 3, one group of parallel structures of the load 4 and the energy storage battery 5 and one first transformer 6 through the outgoing line switch 7.

[0035] In the embodiment, through the parallel structure of multiple groups of loads 4 and energy storage and independent transformer channels, the system can flexibly expand the energy storage capacity and meet the demand of different loads 4. When one transformer is under maintenance, other channels can still operate independently after the bus coupler is closed, the energy storage power station can supply power to the whole plant load 4 across the transformer, and the system paralysis caused by single-point failure is avoided. In addition, the redundant design of multiple inverter 2 output ends improves the photovoltaic power generation consumption capacity and ensures that the anti-backflow function can still be maintained under complex working conditions.

[0036] In yet another optional embodiment, the incoming line switch 9 is correspondingly provided with a current transformer.

[0037] Installation in switch cabinet: The current transformer is usually integrated with the switch in the switch cabinet for measurement and protection functions. For example, a current transformer for metering can be installed on the upper end of the main switch for electric energy metering.

[0038] In this embodiment, the current transformer is provided on the high-voltage side incoming line switch 9 to directly collect the full-system current data of the power grid access point, solving the problem of limited detection range on the traditional low-voltage side. The high-precision measurement capability of the high-voltage current transformer can capture tiny reverse current signals in real time, ensuring the timeliness and accuracy of the reverse current prevention control and avoiding the risk of grid penalties due to detection delay.

[0039] In yet another optional embodiment, the reverse current prevention device 8 includes a reverse current prevention metering electric meter and a reverse current prevention controller, and the reverse current prevention metering electric meter is a high-voltage electric meter that sends current direction information to the reverse current prevention controller based on the current transformer.

[0040] In this embodiment, a high-voltage smart meter is used in series in the primary metering loop, eliminating the need for secondary CT equipment, simplifying the installation process, and reducing hardware costs by more than 30%. The reverse current prevention metering electric meter directly obtains high-voltage side current direction information, and through the reverse current prevention controller and the energy storage EMS linkage, it realizes millisecond-level power regulation response, with system stability improved by more than 40%, especially suitable for high-proportion new energy access scenarios.

[0041] In yet another optional embodiment, the first transformer 6 is 400V to 10kV. The first transformer 6 is designed as a 400V / 10kV standard industrial voltage level, which is compatible with existing low-voltage grid-connected interfaces of distributed photovoltaic / energy storage and meets the high-voltage reverse current detection requirements.

[0042] In yet another optional embodiment, the outgoing line switch 7 and the incoming line switch 9 both support at least 10kV voltage.

[0043] In yet another optional embodiment, the second transformer 10 is 10kV to 35kV.

[0044] In yet another optional embodiment, the reverse current prevention controller is in communication connection with the energy management system EMS of the energy storage battery 5, the reverse current prevention controller transmits current direction information to the energy management system EMS in real time, and the energy management system EMS dynamically adjusts the charge and discharge power of the energy storage battery 5 based on the current direction information and the load 4 demand.

[0045] In yet another optional embodiment, the energy storage battery 5 is composed of at least two groups of lithium batteries in parallel, each group of lithium batteries is connected with a battery management system BMS in series, and each BMS is connected with the energy management system EMS through a CAN bus.

[0046] The embodiments of the utility model discloses the only for the utility model preferred embodiment, only for the description of the technical scheme of the utility model, and not to its limit, although the utility model has been explained in detail with reference to the foregoing embodiment, the ordinary skill of the art should understand, still can modify the technical scheme recorded in the foregoing each item embodiment, or equivalent replacement is carried out to part of technical features, and these modifications or replacements, do not make the essence of corresponding technical scheme deviate from the spirit and scope of the utility model each item embodiment technical scheme.

Claims

1. A reverse current protection photovoltaic grid connected system, characterized in that, The photovoltaic assembly, the load, the energy storage battery, the inverter, the low-voltage bus coupler, the first transformer, the outgoing switch, the anti-backflow device, the incoming switch, and the second transformer; The load and the energy storage battery are connected in parallel; An output end of the photovoltaic assembly is connected to one end of the low-voltage bus coupler through the inverter, and the other end of the low-voltage bus coupler is connected to a line between a first end of the load and a first end of the energy storage battery; An input end of the first transformer is electrically connected to a line between a second end of the load and a second end of the energy storage battery; An output end of the first transformer is electrically connected to the anti-backflow device through the outgoing switch; The anti-backflow device is connected to an input end of the second transformer through the incoming switch, and an output end of the second transformer is connected to a power grid system.

2. The anti-reflective photovoltaic grid-tie system of claim 1, wherein, There are at least two groups of parallel structures of the load and the energy storage battery, at least two low-voltage bus couplers, and two first transformers; The inverter has at least two output ends, each of which is connected to the input end of the second transformer through a low-voltage bus coupler, a parallel structure of the load and the energy storage battery, and a first transformer in sequence.

3. The anti-reflective photovoltaic grid-tie system of claim 1, wherein, The incoming switch is provided with a current transformer.

4. The anti-reflective photovoltaic grid-tie system of claim 3, wherein, The anti-backflow device includes an anti-backflow metering electric meter and an anti-backflow controller, the anti-backflow metering electric meter is a high-voltage electric meter, and the high-voltage electric meter sends current direction information to the anti-backflow controller based on the current transformer.

5. The anti-reflective photovoltaic grid-tie system of claim 1, wherein, The first transformer is 400V to 10kV.

6. The anti-reflective photovoltaic grid-tie system of claim 1, wherein, The outgoing switch and the incoming switch both support at least 10kV voltage.

7. The anti-reflective photovoltaic grid-tie system of claim 1, wherein, The second transformer is 10kV to 35kV.

8. The anti-reflective photovoltaic grid-tie system of claim 4, wherein, The anti-backflow controller is communicatively connected to an energy management system (EMS) of the energy storage battery, the anti-backflow controller transmits current direction information to the energy management system (EMS) in real time, and the energy management system (EMS) dynamically adjusts the charging and discharging power of the energy storage battery based on the current direction information and load demand.

9. The anti-reflective photovoltaic grid-tie system of claim 8, wherein, The energy storage battery is composed of at least two groups of parallel lithium batteries, each group of lithium batteries is connected in series with a battery management system (BMS), and each BMS is connected to the energy management system (EMS) through a CAN bus.

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