Distributed new energy power supply-energy storage isolated grid connection method

Abstract

The invention discloses a distributed new energy power supply-energy storage isolation type grid connection method, and belongs to the technical field of new energy storage grid connection, the distributed new energy power supply-energy storage isolation type grid connection method comprises a new energy power supply, the new energy power supply is connected with an energy storage battery pack, the energy storage battery pack is connected with a first switch, and the first switch is connected with a charging module; the energy storage battery is connected with an inversion module through a second switch. The output end of the inversion module is used for being connected with a power distribution network. The energy storage battery is connected with a battery management system, the battery management system is connected with a control module, the control module is connected with the charging module, and the control module is connected with the inversion module. By adopting the distributed new energy power supply-energy storage isolated grid-connected method, the new energy power supply is not directly connected to the power grid, but is isolated and then connected to the power grid through the separated charging / discharging process of the energy storage battery pack, so that the isolation and decoupling of the new energy power supply and the power grid are realized.

Description

Technical Field

[0001] The present invention belongs to the technical field of new energy storage grid-connected technology, and specifically relates to a distributed new energy power supply-energy storage isolated grid-connected method. Background Art

[0002] In response to the randomness, volatility, intermittency of distributed renewable energy and the drastic changes in power flow caused by transient weather changes, on-site energy storage is currently adopted. That is, distributed photovoltaics are directly connected to the grid through photovoltaic inverters, and wind power is directly connected to the grid through converters. Energy storage equipment is installed near the photovoltaic / wind power grid connection point, and the energy storage equipment is connected in parallel with wind power and photovoltaics on the distribution network.

[0003] However, even if distributed renewable energy sources are directly connected to the grid by means of on-site energy storage, the distribution network will find it difficult to cope with the impact of high-penetration distributed renewable energy generation. This is because due to the impact of instantaneous weather changes, the power generation of distributed renewable energy sources changes rapidly between 0-100%, and the action time of distribution network equipment and energy storage equipment is difficult to match such drastic changes and impacts of the flow; even if the energy storage is equipped to balance the power generation of renewable energy through charging and discharging, since the renewable energy power source and energy storage equipment are connected in parallel to the distribution network, the drastic changes in the flow on the connection line between the renewable energy power source and the energy storage equipment will simultaneously cause drastic changes in the flow of the main line of the distribution network connected to it, resulting in frequent fluctuations in the line power factor, over-compensation / under-compensation of the line reactive power, and fluctuations in the line voltage. Summary of the invention

[0004] The purpose of the present invention is to overcome the deficiencies of the prior art and to provide a distributed new energy power supply-energy storage isolated grid-connected method, which solves the problems in the above-mentioned background technology.

[0005] The purpose of the present invention is achieved as follows: a distributed new energy power supply-energy storage isolation type grid-connected method, which includes a new energy power supply, the new energy power supply is connected to an energy storage battery group, the energy storage battery group is connected to a first switch, the first switch is connected to a charging module, the energy storage battery is connected to an inverter module through a second switch, and the output end of the inverter module is used to connect to a power distribution network; the energy storage battery is connected to a battery management system, the battery management system is connected to a control module, and the control module is connected to the charging module, and the control module is connected to the inverter module. By adopting a distributed new energy power supply-energy storage isolation type grid-connected method, the new energy power supply is not directly connected to the power grid, but is isolated and connected to the power grid after being connected through the "separate charging / discharging process" of the energy storage battery group, thereby realizing isolation and decoupling of the new energy power supply from the power grid.

[0006] Furthermore, the new energy power source includes photovoltaics, the photovoltaics are connected to a DC-DC converter, the DC-DC converter is connected to the charging module, and is connected to the energy storage battery pack.

[0007] Furthermore, the new energy power source includes wind power, the wind power is connected to a converter, the converter is connected to the charging module, and is connected to the energy storage battery pack.

[0008] Furthermore, the energy storage battery pack includes battery pack A, battery pack B and battery pack C.

[0009] Furthermore, the first switch includes a switch K11 and a switch K12, K11 and K12 are a linked switch group, switch K11 is used to connect to the positive pole of battery pack A, B or C, and switch K12 is used to connect to the negative pole of battery pack A, B or C; the second switch includes a switch K21 and a switch K22, K21 and K22 are a linked switch group, switch K21 is used to connect to the positive pole of battery pack A, B or C, and switch K22 is used to connect to the negative pole of battery pack A, B or C.

[0010] Furthermore, the first switch and the second switch are both mechanical knife switches, contact switches or power electronic IGBT solid-state switches, or a combination of the three.

[0011] Furthermore, the battery management system is used to monitor the parameters of the battery voltage, current and temperature, and calculate and analyze the remaining battery capacity of the battery.

[0012] Furthermore, the control module is used to manage the operation of the charging module, control the connection and disconnection of the linkage switch, manage the operation of the inverter module, receive and process feedback information from the battery management system, manage the battery management system, control the charging and discharging of the energy storage battery pack, and receive dispatch instructions from the power grid.

[0013] Furthermore, the energy storage battery pack jointly determines charging parameters and switching according to the power generation power and energy of the new energy power source and the battery status parameters fed back by the battery management system; the discharge process of the energy storage battery pack is determined by the control module according to the scheduling instructions and the battery status parameters fed back by the battery management system.

[0014] The beneficial effects of the present invention are as follows: conventional energy storage batteries are installed in parallel near the photovoltaic / wind power grid connection point, which only absorbs the power generation and discharge of new energy, and has no isolation and decoupling effect; and the drastic change in the size of the current on the connection line between the new energy power source and the energy storage device will simultaneously cause the drastic change in the current of the main line of the distribution network connected thereto, resulting in frequent fluctuations in the line power factor, over-compensation / under-compensation of the line reactive power, and line voltage fluctuations.

[0015] The technical solution of the present invention is different from the traditional photovoltaic / wind power + energy storage grid-connected structure. The new energy power source is not directly connected to the grid, but is connected to the grid after being isolated and decoupled by the energy storage battery group. Since the energy storage battery group is composed of multiple battery groups, the charging and discharging of the multiple battery groups are carried out independently, so that the energy storage battery group plays a smoothing and filtering role similar to that of a capacitor, realizes the decoupling and isolation of new energy and the grid, and ensures the safe and stable operation of the distribution network. It is achieved that: on the power supply side, the transient overvoltage phenomenon caused by the change of the power factor of the distribution network caused by the instantaneous drastic change of the new energy grid-connected power due to weather changes is greatly reduced, and the impact of new energy power generation on the grid is alleviated; on the load side, the distribution network can directly dispatch the discharge interface of the energy storage battery group, and does not directly dispatch the new energy power source, thereby resolving the problem that the existing distribution network dispatching mode is difficult to effectively dispatch large-scale new energy power stations, enhancing the stability of the grid and improving the quality of electric energy. Give full play to the role of energy storage batteries in the new energy grid-connected link, reduce the phenomenon of "building but not using" due to the failure of new energy distribution storage to comply with the grid operation mechanism, improve the phenomenon of wind abandonment and light abandonment, and increase the investment income of new energy. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 is a schematic diagram of the wind power structure of the present invention; Figure 2 It is a schematic diagram of the photovoltaic structure of the present invention. DETAILED DESCRIPTION

[0017] The present invention is further described in detail below in conjunction with the accompanying drawings. It should be pointed out that it is only for the purpose of more clearly describing and explaining the present invention. Example 1

[0018] like Figure 1 and 2 As shown, this embodiment discloses a distributed new energy power supply-energy storage isolation type grid-connected method, which includes a new energy power supply, the new energy power supply is connected to an energy storage battery group, the energy storage battery group is connected to a first switch, the first switch is connected to a charging module, the energy storage battery is connected to an inverter module through a second switch, and the output end of the inverter module is used to connect to the power distribution network; the energy storage battery is connected to a battery management system, the battery management system is connected to a control module, and the control module is connected to the charging module, and the control module is connected to the inverter module. By adopting a distributed new energy power supply-energy storage isolation type grid-connected method, the new energy power supply is not directly connected to the power grid, but is isolated and connected to the power grid after being isolated through the "separate charging / discharging process" of the energy storage battery group, so as to achieve isolation and decoupling between the new energy power supply and the power grid. The new energy power supply includes wind power, the wind power is connected to a converter, the converter is connected to the charging module, and is connected to the energy storage battery group.

[0019] For better effect, the energy storage battery pack includes battery pack A, battery pack B and battery pack C. The first switch includes switch K11 and switch K12, K11 and K12 are a linkage switch group, switch K11 is used to connect to the positive electrode of battery pack A, B or C, and switch K12 is used to connect to the negative electrode of battery pack A, B or C; the second switch includes switch K21 and switch K22, K21 and K22 are a linkage switch group, switch K21 is used to connect to the positive electrode of battery pack A, B or C, and switch K22 is used to connect to the negative electrode of battery pack A, B or C.

[0020] For better effect, the first switch and the second switch are both mechanical knife switches, contact switches or power electronic IGBT solid-state switches, or a combination of the three. The battery management system is used to monitor the parameters of the voltage, current and temperature of the battery, and calculate and analyze the remaining battery capacity of the battery. The control module is used to manage the operation of the charging module, control the connection and disconnection of the linkage switch, manage the operation of the inverter module, receive and process feedback information from the battery management system, manage the battery management system, control the charging and discharging of the energy storage battery pack, and receive dispatch instructions from the power grid.

[0021] The energy storage battery pack jointly determines charging parameters and switching according to the power generation power and energy of the new energy power source and the battery status parameters fed back by the battery management system; the discharge process of the energy storage battery pack is determined by the control module according to the scheduling instructions and the battery status parameters fed back by the battery management system. Example 2

[0022] like Figure 1 and 2 As shown, this embodiment discloses a distributed new energy power supply-energy storage isolated grid-connected method, which includes a new energy power supply, the new energy power supply is connected to an energy storage battery group, the energy storage battery group is connected to a first switch, the first switch is connected to a charging module, the energy storage battery is connected to an inverter module through a second switch, and the output end of the inverter module is used to connect to a power distribution network; the energy storage battery is connected to a battery management system, the battery management system is connected to a control module, and the control module is connected to the charging module, and the control module is connected to the inverter module. The new energy power supply includes photovoltaics, the photovoltaics are connected to a DC-DC converter, the DC-DC converter is connected to the charging module, and is connected to the energy storage battery group.

[0023] The electricity generated by photovoltaics enters the charging module after DC / DC conversion; the charging module is connected to the energy storage battery group through the first switch K11 and K12; the energy storage battery group is connected to the inverter module through the second switch K21 and K22; the inverter module is connected to the distribution network. The energy storage battery group includes three battery groups: battery group A, battery group B, and battery group C.

[0024] The first switch includes switches K11 and K12. Switch K11 can be connected to the positive pole of battery pack A, B or C, and switch K12 can be connected to the negative pole of battery pack A, B or C. The second switch includes switches K21 and K22. Switch K21 can be connected to the positive pole of battery pack A, B or C, and switch K22 can be connected to the negative pole of battery pack A, B or C. When the linkage switch is working, switches K11 and K12 of the first switch can only be connected to the positive pole and negative pole of the same battery pack at the same time, and K11 and K12 are connected and disconnected at the same time, and cannot act alone; switches K21 and K22 of the second switch can also only be connected to the positive pole and negative pole of the same battery pack at the same time, and K21 and K22 are connected and disconnected at the same time, and cannot act alone. And the first switch and the second switch cannot be connected to the same battery pack at the same time. (That is, when K11 is connected to the positive pole of battery pack A, K12 can only be connected to the negative pole of battery pack A; and at this time, K11 cannot be connected to the positive pole of battery pack B or C at the same time, and K12 cannot be connected to the negative pole of battery pack B or C at the same time).

[0025] When the system is working, battery packs A, B, and C are charged and discharged in turn. For example, (1) at a certain moment, the first switch is connected to battery pack A (i.e., switch K11 is connected to the positive pole of battery pack A, and switch K12 is connected to the negative pole of battery pack A), battery pack A is in a charging state, and the photovoltaic power is charging battery pack A; at the same time, the second switch is connected to battery pack B (i.e., switch K21 is connected to the positive pole of battery pack B, and switch K22 is connected to the negative pole of battery pack B), battery pack B is in a half-full state, battery pack B is discharging, and the discharged power is connected to the grid after being inverted by the inverter module; battery pack C is in a fully charged state and is on standby. (2) After running for a period of time, battery pack B is fully discharged, and battery pack A is not fully charged, then the state of the first switch remains unchanged, and battery pack A continues to charge; the second switch is disconnected from battery pack B and connected to battery pack C, battery pack C starts to discharge, and battery pack B is on standby. (3) After a period of continuous operation, battery pack A is fully charged, but battery pack C is not fully discharged. The second switch remains in the same state, and battery pack C continues to discharge. The first switch is disconnected from battery pack A and connected to battery pack B, and battery pack B starts to charge while battery pack A is on standby. In this way, battery packs A, B, and C are charged and discharged in turn, so that the energy storage battery pack can be charged by new energy sources and discharged by the grid at the same time.

[0026] The battery pack must be three or more groups. One or two groups cannot achieve the above functions. This is because ① the generation of new energy is random, and the load connected to the distribution network side is also random. The "source and load" fluctuate at both ends, and there is a mismatch between the time and amount of power generation and power consumption; in this state, if there are only two battery packs a and b, due to the uncertainty of charging and discharging speed, it is difficult to achieve a matching state where battery pack a is fully charged and battery pack b is just empty, resulting in the battery pack being unable to continue charging to absorb the power generated by new energy or being unable to continue discharging to provide the power required by the load; ② the switch immediately switches from charging battery pack a and discharging battery pack b to charging battery pack a and discharging battery pack a, which is difficult to control and causes great damage to the battery; therefore, a third battery pack must be used as a capacity buffer and backup.

[0027] Switch K can be a common mechanical knife switch, contact switch or solid-state switch such as power electronic IGBT, or a combination of the three. BMS is a battery management system that can monitor basic parameters such as battery voltage, current, temperature, and calculate and analyze the battery's SOC (remaining battery capacity). The control module manages the work of the charging module, controls the connection and disconnection of the linkage switch, manages the work of the inverter module, receives and processes feedback information from the BMS, manages the BMS, and controls the charging and discharging of the battery pack. The control module can receive dispatch instructions from the power grid.

[0028] The charging process of the battery pack is determined by the control module based on the power and energy of the new energy source and the battery status parameters fed back by the BMS. The discharge process of the battery pack is determined by the control module based on the dispatching instructions and the battery status parameters fed back by the BMS. Traditional energy storage batteries are installed in parallel near the photovoltaic / wind power grid connection point, which only absorbs new energy power generation and discharges, without isolation and decoupling. In addition, the drastic changes in the flow on the connection line between the new energy source and the energy storage device will simultaneously cause drastic changes in the flow of the main line of the distribution network connected to it, resulting in frequent fluctuations in the line power factor, over-compensation / under-compensation of the line reactive power, and line voltage fluctuations.

[0029] The technical solution of the present invention is different from the traditional photovoltaic / wind power + energy storage grid-connected structure. The new energy power source is not directly connected to the grid, but is connected to the grid after being isolated and decoupled by the energy storage battery group. Since the energy storage battery group is composed of multiple battery groups, the charging and discharging of the multiple battery groups are carried out independently, so that the energy storage battery group plays a smoothing and filtering role similar to that of a capacitor, realizes the decoupling and isolation of new energy and the grid, and ensures the safe and stable operation of the distribution network. It is achieved that: the role of energy storage batteries in the new energy grid-connected link is fully utilized, the phenomenon of "building but not using" due to the non-compliance of the new energy distribution storage with the grid operation mechanism is reduced, the phenomenon of wind and light abandonment is improved, and the investment income of new energy is increased. On the power supply side, the transient overvoltage phenomenon caused by the change of the power factor of the distribution network caused by the instantaneous drastic change of the new energy grid-connected power due to weather changes is greatly reduced, and the impact of new energy power generation on the grid is alleviated; on the load side, the distribution network can directly dispatch the discharge interface of the energy storage battery group instead of directly dispatching the new energy power source, thereby resolving the problem that the existing distribution network dispatching mode is difficult to effectively dispatch large-scale new energy power stations, enhancing the stability of the grid and improving the quality of electric energy.

[0030] The above are only preferred specific implementation modes of the present invention, but the protection scope of the present invention is not limited thereto. Any technician familiar with the technical field can make equivalent replacements or changes according to the technical solutions and concepts of the present invention within the technical scope disclosed by the present invention, which should be covered by the protection scope of the present invention.

Claims

1. A distributed new energy power supply-energy storage isolated grid-connected method, characterized by: It includes a new energy power supply, which is connected to an energy storage battery group, which is connected to a first switch, which is connected to a charging module, and the energy storage battery is connected to an inverter module via a second switch, and the output end of the inverter module is used to connect to a power distribution network; the energy storage battery is connected to a battery management system, which is connected to a control module, and the control module is connected to the charging module, and the control module is connected to the inverter module.

2. The distributed new energy power supply-energy storage isolated grid-connected method according to claim 1 is characterized in that: The new energy power source includes photovoltaics, the photovoltaics are connected to a DC-DC converter, the DC-DC converter is connected to the charging module, and is connected to the energy storage battery pack.

3. The distributed new energy power supply-energy storage isolated grid-connected method according to claim 1 is characterized in that: The new energy power source includes wind power, the wind power is connected to a converter, the converter is connected to the charging module, and is connected to the energy storage battery pack.

4. The distributed new energy power supply-energy storage isolated grid-connected method according to claim 2 or 3, characterized in that: The energy storage battery pack includes battery pack A, battery pack B and battery pack C.

5. The distributed new energy power supply-energy storage isolated grid-connected method according to claim 4 is characterized in that: The first switch includes a switch K11 and a switch K12, K11 and K12 are a linked switch group, switch K11 is used to connect to the positive pole of battery pack A, B or C, and switch K12 is used to connect to the negative pole of battery pack A, B or C; the second switch includes a switch K21 and a switch K22, K21 and K22 are a linked switch group, switch K21 is used to connect to the positive pole of battery pack A, B or C, and switch K22 is used to connect to the negative pole of battery pack A, B or C.

6. The distributed new energy power supply-energy storage isolated grid-connected method according to claim 1, characterized in that: The first switch and the second switch are both mechanical knife switches, contact switches or power electronic IGBT solid-state switches, or a combination of the three.

7. The distributed new energy power supply-energy storage isolated grid-connected method according to claim 1, characterized in that: The battery management system is used to monitor the parameters of the battery voltage, current and temperature, and calculate and analyze the remaining battery capacity of the battery.

8. The distributed new energy power supply-energy storage isolated grid-connected method according to claim 1, characterized in that: The control module is used to manage the operation of the charging module, control the connection and disconnection of the linkage switch, manage the operation of the inverter module, receive and process feedback information from the battery management system, manage the battery management system, control the charging and discharging of the energy storage battery pack, and receive dispatch instructions from the power grid.

9. The distributed new energy power supply-energy storage isolated grid-connected method according to claim 8, characterized in that: The energy storage battery pack jointly determines charging parameters and switching according to the power generation power and energy of the new energy power source and the battery status parameters fed back by the battery management system; the discharge process of the energy storage battery pack is determined by the control module according to the scheduling instructions and the battery status parameters fed back by the battery management system.

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