Anti-countercurrent control protection method and device for new energy power generation

Abstract

The invention relates to an anti-countercurrent control protection method and device for new energy power generation, and belongs to the technical field of new energy power generation. According to the invention, the problem of countercurrent of current flowing from a new energy system to a large power grid caused by instability of new energy power generation is solved. Cooperative control over a power generation unit, an energy storage unit and an electric vehicle charging and discharging unit in the new energy system is achieved by detecting the power and current size or direction of new energy power generation equipment, energy storage and electric vehicle charging and discharging in the new energy system, and anti-countercurrent protection of a large power grid is achieved under the condition that the influence on all parts of the new energy system is minimum. The operation stability of the new energy system is improved, and the negative influence of new energy system operation on a large power grid is reduced.

Description

Technical Field

[0001] This invention relates to a method and device for preventing backflow control and protection in new energy power generation, belonging to the field of new energy power generation technology. Background Technology

[0002] With the construction of new power systems, the installed capacity of new energy power generation, represented by photovoltaic and wind power, is increasing, and historically surpassed that of thermal power by the end of April 2025. In new energy power generation systems, the current flowing from the main power grid to the new energy power generation system is generally referred to as forward current. However, reverse current may also occur, with the current flowing from the new energy power generation system back to the main power grid. Reverse current can cause harmonic pollution to the main power grid, resulting in voltage fluctuations, reducing the power quality of the main power grid, and even damaging electrical equipment within the main power grid.

[0003] To prevent backflow, anti-backflow measures are necessary in the renewable energy generation sector. In renewable energy generation systems that include photovoltaic (PV) power generation, the output of the PV modules is connected in series with a MOSFET. The drain-source voltage of the MOSFET is measured in real time to detect backflow and cut off the backflow path. However, this control method is complex in terms of detection methods and control processes. Alternatively, a reverse power relay can be installed at the grid connection point to prevent backflow. When the reverse power relay detects reverse power, it directly disconnects the renewable energy system from the main grid, protecting the power quality of the main grid from the impact of renewable energy generation. However, this method has low control precision; even slight fluctuations can cause the reverse power relay to activate, leading to frequent tripping of the grid connection point switch and reducing system stability. Summary of the Invention

[0004] The purpose of this invention is to provide a method and device for anti-reverse current control and protection for new energy power generation, so as to solve the problems of low anti-reverse current control accuracy and low system stability caused by frequent operation of reverse power relays when new energy power generation is connected to the grid.

[0005] To achieve the above objectives, the present invention includes: The present invention provides a method for preventing reverse current control and protection in new energy power generation, comprising the following steps: 1) Obtain the power generation capacity of new energy sources and the load power of general loads in the new energy system; If the power generation of new energy sources is greater than the load power, then determine whether the energy storage system is fully charged. If yes, it is a; otherwise, it is b. If the power generation of new energy sources is less than the load power, then determine whether all new energy power generation equipment is in operation: if yes, it is c; otherwise, it is d. 2) Determine whether the electric vehicle connected to the new energy system is in a charging state; if yes, mark it as e; otherwise, mark it as f. 3) If a and e, then control the reduction of the output power of the new energy power generation system; if a current reverse current exceeding the threshold occurs, then control the new energy system to stop grid-connected operation. If a and f, then control the reduction of new energy power generation and the reduction of electric vehicle external discharge power. If current reverse flow exceeds the threshold, then control the new energy system to stop grid connection. If b and e, then control the increase of the charging power of the electric vehicle and control the charging of the energy storage system; If b and f, then control the charging of the energy storage system; If c and e, or if c and f, then control the grid-connected operation of the new energy system; If d and e, or if d and f, then control the unused portion of the new energy power generation equipment to generate electricity, either partially or entirely.

[0006] Further, in step 1), the power of the new energy generation equipment is obtained by the output power of the inverter on the branch where the new energy generation equipment is located; the power of the load is obtained by the output power of the rectifier on the branch where the general load is located.

[0007] Furthermore, in step 2), the direction of the inverter power on the branch where the charging pile connected to the electric vehicle is located is searched to determine whether the corresponding electric vehicle is in a charging state.

[0008] Furthermore, in step 3), the output power of the new energy power generation system is reduced by controlling the inverters on the branches where several new energy power generation devices are located to reduce their output power; and the power generation of new energy is reduced by shutting down some of the new energy power generation devices.

[0009] Furthermore, in step 3), the new energy system stops grid-connected operation by disconnecting the grid-connected switch, and the new energy system is connected to the grid by closing the grid-connected switch.

[0010] The present invention provides an anti-reverse flow control and protection device for new energy power generation, comprising a processor, wherein the processor executes a computer program to implement the following method steps: 1) Obtain the power generation capacity of new energy sources and the load power of general loads in the new energy system; If the power generation of new energy sources is greater than the load power, then determine whether the energy storage system is fully charged. If yes, it is a; otherwise, it is b. If the power generation of new energy sources is less than the load power, then determine whether all new energy power generation equipment is in operation: if yes, it is c; otherwise, it is d. 2) Determine whether the electric vehicle connected to the new energy system is in a charging state; if yes, mark it as e; otherwise, mark it as f. 3) If a and e, then control the reduction of the output power of the new energy power generation system; if a current reverse current exceeding the threshold occurs, then control the new energy system to stop grid-connected operation. If a and f, then control the reduction of new energy power generation and the reduction of electric vehicle external discharge power. If current reverse flow exceeds the threshold, then control the new energy system to stop grid connection. If b and e, then control the increase of the charging power of the electric vehicle and control the charging of the energy storage system; If b and f, then control the charging of the energy storage system; If c and e, or if c and f, then control the grid-connected operation of the new energy system; If d and e, or if d and f, then control the unused portion of the new energy power generation equipment to generate electricity, either partially or entirely.

[0011] Further, in step 1), the power of the new energy generation equipment is obtained by the output power of the inverter on the branch where the new energy generation equipment is located; the power of the load is obtained by the output power of the rectifier on the branch where the general load is located.

[0012] Furthermore, in step 2), the direction of the inverter power on the branch where the charging pile connected to the electric vehicle is located is searched to determine whether the corresponding electric vehicle is in a charging state.

[0013] Furthermore, in step 3), the output power of the new energy power generation system is reduced by controlling the inverters on the branches where several new energy power generation devices are located to reduce their output power; and the power generation of new energy is reduced by shutting down some of the new energy power generation devices.

[0014] Furthermore, in step 3), the new energy system stops grid-connected operation by disconnecting the grid-connected switch, and the new energy system is connected to the grid by closing the grid-connected switch.

[0015] The beneficial effects of this invention are as follows: The method and apparatus of this invention solve the problem of reverse current flow from the renewable energy generation system to the main power grid caused by the instability of renewable energy generation. By installing anti-reverse current control and protection devices and implementing anti-reverse current control and protection methods at the grid connection point of a renewable energy system containing renewable energy generation equipment, energy storage, and electric vehicle charging and discharging, coordinated control of the power generation unit, energy storage unit, and electric vehicle charging and discharging unit within the system is achieved. This enables anti-reverse current protection of the main power grid with minimal impact on each part of the renewable energy system, improves the operational stability of the renewable energy system, and reduces the negative impact of renewable energy generation and operation on the main power grid. Attached Figure Description

[0016] Figure 1 This is a schematic diagram of the configuration of the new energy system to which this invention applies; Figure 2 This is a flowchart of an anti-reverse flow control and protection method for new energy power generation according to the present invention. Detailed Implementation

[0017] To make the objectives, technical solutions, and advantages of the present invention clearer, the present invention will be further described in detail below with reference to the accompanying drawings and embodiments.

[0018] This invention discloses an anti-reverse current control and protection method for new energy power generation, which addresses the negative impacts of reverse current on power grids, such as power quality degradation. The main concept is as follows: The reverse current control and protection device of this invention for new energy power generation is installed at the grid connection point. After the device is powered on, it collects analog quantities such as voltage and current at the grid connection point through voltage transformers (TV) and current transformers (TA) installed at the grid connection point, monitors the voltage and current at the grid connection point in real time, and further calculates the amplitude and direction of the power at the grid connection point. The device of this invention communicates with the inverter in the new energy power generation system through a communication line to obtain the inverter's output power and can also send control commands to the inverter.

[0019] The device internally determines the power generation capacity of the new energy system and the power of the internal general load, thereby determining the conditions for the next step.

[0020] When the power generation of the new energy system is greater than the power of the general load, the status of the energy storage system is further determined; when the power generation of the new energy system is less than the power of the general load, the status of the new energy power generation is further determined.

[0021] Based on the energy storage status within the system, the charging and discharging status of electric vehicles can be further determined; based on the input status of new energy power generation within the system, the charging and discharging status of electric vehicles can be further determined.

[0022] Based on the charging and discharging status of electric vehicles, anti-reverse current control and protection are achieved through an anti-reverse current device to avoid negative impacts of reverse current on the power grid.

[0023] Implementation method of anti-reverse flow control and protection device for new energy power generation: The present invention provides an anti-reverse flow control and protection device for new energy power generation, applicable to, for example... Figure 1 The illustrated new energy system includes photovoltaic panels 1 and wind turbine generators 2, which serve as new energy power generation equipment. All the new energy power generation equipment constitutes the new energy power generation system. It also includes, for example, an energy storage system 3 that can use electrochemical energy storage, several charging piles 4 for charging new energy vehicles, and general loads 5 in the new energy system. The general loads 5 in the new energy system include DC loads such as lighting, cooling fans, and liquid-cooled water pumps, and can also be used for the excitation of DC motors for wind power generation.

[0024] The wind power station unit 2 uses a DC generator. Therefore, both the photovoltaic panel 1 and the wind power station unit 2 are connected to the new energy system bus 8 through their respective inverters 6 and branch transformers 7 to supply power to the new energy system bus 8.

[0025] The energy storage system 3 is also connected to the new energy system bus 8 via the converter 9 and the branch transformer 7. It can supply power to the new energy bus 8 or serve as a load for the new energy system bus 8 to store power to the energy storage system 3. Therefore, the converter 9 connected to the energy storage system 3 is a bidirectional converter, which can operate in rectification mode (charging the energy storage system 3) or inverter mode (discharging the energy storage system 3 to supply power to the new energy system bus 8).

[0026] The new energy system bus 8 is also connected to the charging pile 4 via branch transformer 7 and converter 9 to supply power to the charging pile 4 for charging the electric vehicle 11. Meanwhile, the charging pile 4 is a bidirectional charging pile (with V2G, Vehicle-to-Grid functionality), which can use the electric vehicle's power battery as an energy storage medium when necessary, drawing power from it to supply the new energy system bus 8. Therefore, the converter 9 connected to the charging pile 4 is also a bidirectional converter, capable of operating in rectification mode (supplying power to the charging pile 4) or inverter mode (supplying power to the new energy system bus 8).

[0027] The new energy system bus 8 is also connected to the general load 5 in the new energy system through the branch transformer 7 and rectifier 10, and supplies power to the general load 5.

[0028] The inverters 6, converters 9 and rectifiers 10 are connected to the corresponding branch transformers 7 on their respective lines by a first circuit breaker 12; each branch transformer 7 and the new energy system bus 8 are also connected to a second circuit breaker 13.

[0029] The new energy system bus 8 is connected to the main power grid 15 through the main transformer 14. A third circuit breaker 16 is installed between the new energy system bus 8 and the main transformer 14, and a fourth circuit breaker 17 is installed between the main transformer 14 and the main power grid 15.

[0030] The anti-reverse current control and protection device 18 of this invention for new energy power generation is installed at the grid connection point between the new energy system and the main power grid. The grid connection point is specifically located between the main transformer 14 and the third circuit breaker 16. The anti-reverse current control and protection device 18 monitors the grid connection point current through a current transformer TA and the grid connection point voltage through a voltage transformer TV. It also connects to each inverter 6, converter 9, and rectifier 10 in the new energy system via wired or wireless communication to obtain the output power of the corresponding inverters, rectifiers, and converters (including the output power direction or operating mode of converter 9) to obtain the corresponding power of the new energy power generation equipment, energy storage system 3, charging pile 4, and general load 5 of the new energy system. Power includes positive power and negative power. Positive power is considered as the power generated to supply power to the new energy system; negative power is considered as the load, which is the power consumed from the new energy system.

[0031] The anti-reverse flow control and protection device 18 also controls each inverter 6, converter 9 and rectifier 10 in the new energy system through wired or wireless communication to adjust the output power of inverter 6 and rectifier 10, and also controls the power direction (i.e. the working mode, whether it is working in rectification mode or inverter mode) and output power of converter 9.

[0032] The anti-backflow control and protection device 18 also communicates with the energy storage system 3 via wired or wireless means to obtain the power of the energy storage system.

[0033] The anti-backflow control and protection device 18 consists of an LCD display, an operation keypad, an analog quantity acquisition circuit, a digital quantity acquisition circuit, a communication circuit, and a tripping circuit for driving the switch to trip. The device can acquire the voltage, current, and frequency at the grid connection point to monitor the amplitude and direction of the current and power at the grid connection point in real time, and trips the grid connection point switch upon tripping. The operation keypad allows setting the anti-backflow protection setting value.

[0034] The anti-reverse flow control and protection device 18 for new energy power generation of the present invention also executes the following protection logic to implement the anti-reverse flow control and protection method for new energy power generation of the present invention.

[0035] A. The anti-reverse current control and protection device for new energy power generation of the present invention has a customizable anti-reverse current protection setting value (e.g., V2G reverse grid current setting value). When the new energy power generation obtained through communication is greater than the load power (i.e., the load size of the general load 5 in the new energy system), the energy storage system 3 is fully charged, and the electric vehicle 18 is charging, the device reduces the output power of the inverter 6 of the corresponding branch of the new energy power generation system. If the value of the current flowing back into the main grid 15 at the grid connection point exceeds the anti-reverse current protection setting value (V2G reverse grid current setting value), the anti-reverse current control and protection device trips the grid connection switch (including the third circuit breaker 16 and / or the fourth circuit breaker 17).

[0036] B. The anti-reverse current control and protection device for new energy power generation of the present invention, when the new energy power generation obtained through communication is greater than the general load power, the energy storage system 3 is in a fully charged state, and the electric vehicle 11 is in a discharging state, cuts off a portion of the new energy power generation equipment and limits the reverse current fed into the grid by the V2G charging pile 4. If the value of the current flowing back into the main grid exceeds the anti-reverse current protection setting (V2G reverse current setting), the anti-reverse current control and protection device trips the grid connection switch.

[0037] C. When the new energy power generation obtained through communication is greater than the general load power, the energy storage system 3 is not fully charged, and the electric vehicle 11 is charging, the anti-reverse current control and protection device of the present invention controls the charging pile 4 to prioritize the charging of the electric vehicle 11. The anti-reverse current control and protection device controls the closing of the energy storage switch (the first circuit breaker 12 and / or the second circuit breaker 13 of the branch where the energy storage system 3 is located) to charge the energy storage system 3 for standby and absorb the excess power generated in the new energy system.

[0038] D. When the new energy power generation obtained through communication is greater than the general load power, the energy storage system 3 is not fully charged, or the electric vehicle 11 is in a discharging state, the anti-reverse current control and protection device of the present invention controls the closing of the energy storage switch to absorb the excess power generated in the new energy system.

[0039] E. The anti-reverse flow control and protection device for new energy power generation of the present invention closes the grid connection switch when the new energy power generation obtained through communication is less than the general load power, all new energy power generation equipment is put into operation, and electric vehicle 11 is in charging state, so that the new energy system is connected to the grid and supplies power to electric vehicle 11 or general load 5 through the large power grid 15.

[0040] F. The anti-reverse flow control and protection device for new energy power generation of the present invention, when the new energy power generation obtained through communication is less than the general load power, when all new energy power generation equipment is in operation, and when the electric vehicle 11 is in a discharge state, the discharge power of the electric vehicle 11 is used to supply power to the general load 5, and the grid connection switch is closed, and the large power grid 15 provides the missing power.

[0041] G. The anti-reverse current control and protection device for new energy power generation of the present invention, when the new energy power generation obtained through communication is less than the general load power, the new energy power generation equipment is not fully engaged, or the electric vehicle 11 is in a charging state, closes part or all of the new energy power generation switches of the unengaged part (the first circuit breaker 12 and / or the second circuit breaker 13 on the branch corresponding to the new energy power generation equipment), and engages part or all of the unengaged part of the new energy power generation equipment.

[0042] H. The anti-reverse flow control and protection device for new energy power generation of the present invention, when the new energy power generation obtained through communication is less than the general load power, the new energy power generation equipment is not fully engaged, or the electric vehicle 11 is in a discharge state, the discharge power of the electric vehicle 11 is used to supply power to the general load 5, closes the switch of some or all of the unengaged new energy power generation, and engages some or all of the unengaged new energy power generation equipment.

[0043] The anti-reverse current control and protection device 18 for new energy power generation of the present invention performs the following steps to implement the anti-reverse current control and protection method for new energy power generation of the present invention: Figure 2 As shown, the details are as follows: 1) The anti-reverse flow control and protection device 18 obtains the power of the new energy generation system through the inverter 6 of the corresponding branch of the new energy power generation system, and also obtains the load power of the general load through the rectifier 10 of the branch where the general load 5 is located. 1.1) If the power generation of new energy is greater than the load power, then it also communicates with the energy storage system 3 to determine whether the energy storage system is fully charged; 1.2) If the power generation of new energy is less than the load power, the inverters 6 of each branch of the new energy power generation system are used to determine whether all new energy power generation equipment is in operation.

[0044] 2) The anti-reverse current control and protection device 18 determines the charging status of the electric vehicle 11 corresponding to the charging pile 4 in the new energy system (i.e., the working status of the electric vehicle connected to the new energy system, including charging and external discharge; in this embodiment, the connected electric vehicle only works in these two states, and there is no state where the connected electric vehicle is neither charging nor discharging). If it is in the charging state, the corresponding electric vehicle 11 is charging and replenishing energy; if it is not in the charging state, it means that the corresponding charging pile 4 is working in V2G mode, and the power battery of the electric vehicle 11 is discharging externally as a power source. 2.1) If the energy storage system in 1.1) is fully charged, the converter 9 on the branch where the charging pile 4 is located will also determine whether the electric vehicle 11 corresponding to the charging pile 4 in the new energy system is charging. 2.2) If the energy storage system in 1.1) is not fully charged, the converter 9 on the branch where the charging pile 4 is located will also determine whether the electric vehicle 11 corresponding to the charging pile 4 in the new energy system is charging. 2.3) If all the new energy power generation equipment in 1.2) is put into operation, the converter 9 on the branch where the charging pile 4 is located will also determine whether the electric vehicle 11 corresponding to the charging pile 4 in the new energy system is in a charging state. 2.4) If not all of the new energy power generation equipment in 1.2) is put into operation, the converter 9 on the branch where the charging pile 4 is located can also be used to determine whether the electric vehicle 11 corresponding to the charging pile 4 in the new energy system is in a charging state.

[0045] 3) The anti-backflow control and protection device 18 executes the corresponding strategy based on the judgment results of 2.1) to 2.4) to realize the backflow protection control of the new energy system; 3.1) If the charging status of electric vehicle 11 is determined to be yes in 2.1), that is, the electric vehicle consumes power while charging. At this time, the new energy power generation is used for general load 5 and electric vehicle 11 charging. The energy storage system is fully charged and cannot consume the stored excess power. Then the anti-reverse current control protection device 18 controls the inverter 6 corresponding to the new energy power generation system to reduce the output power of inverter 6. If the value of the current flowing back into the main grid 15 exceeds the anti-reverse current protection setting (or the V2G back-feeding grid current setting), the anti-reverse current control protection device 18 trips the grid connection point switch (including the third circuit breaker 16 and / or the fourth circuit breaker 17).

[0046] 3.2) If the charging status of electric vehicle 11 is determined to be no in 2.1), that is, the electric vehicle is discharging and generating power, the new energy system is in a relatively saturated extreme state, and neither the energy storage system nor the charging pile can consume power, and the reverse current phenomenon is very likely to occur; then the anti-reverse current control and protection device 18 cuts off a part of the new energy power generation equipment, that is, reduces the power generation of new energy, and at the same time limits the current of charging pile 4 fed back to the main grid 15 in V2G mode. If the value of the current flowing back into the main grid exceeds the anti-reverse current protection setting (or the V2G back grid current setting), the anti-reverse current control and protection device 18 trips the grid connection point switch.

[0047] 3.3) If the charging status of electric vehicle 11 is determined to be yes in 2.2), that is, the electric vehicle consumes power for charging, the energy storage system 3 in the energy system can also consume power to store electrical energy at this time; then the anti-reverse current control protection device 18 controls the output power of the converter 9 in the branch where the charging pile 4 is located, and the new energy power generation is given priority to the charging of electric vehicle. At the same time, the anti-reverse current control protection device 18 controls the closing of the energy storage switch (the first circuit breaker 12 and / or the second circuit breaker 13 in the branch where the energy storage system 3 is located) to charge the energy storage system 3 for standby and absorb the excess power generation of new energy.

[0048] 3.4) If the charging status of electric vehicle 11 is determined to be no in 2.2), that is, the electric vehicle discharges and generates power, the energy storage system 3 in the energy system can consume power to store electrical energy; then the anti-reverse current control protection device 18 controls the closing of the energy storage switch to charge the energy storage system 3 for standby and absorb excess generated power.

[0049] 3.5) If the charging status of electric vehicle 11 is determined to be yes in 2.3), that is, the electric vehicle consumes power for charging, and the power generation of new energy is insufficient for the current state of the new energy system, then the anti-reverse current control protection device 18 closes the grid connection point switch (including the third circuit breaker 16 and / or the fourth circuit breaker 17), the new energy system is connected to the grid, and the large power grid 15 charges electric vehicle 11 or supplies power to general load 5.

[0050] 3.6) If the charging status of electric vehicle 11 is not determined in 2.3), that is, the electric vehicle discharges and generates power, the power generation of the new energy system is insufficient for the current state of the new energy system. The discharge power of the electric vehicle is used to supply power to the general load 5 in the new energy system. Then the anti-reverse current control protection device 18 closes the grid connection point switch and uses the large power grid 15 to supplement the power gap.

[0051] 3.7) If the charging status of electric vehicle 11 is determined to be yes in 2.4), that is, the electric vehicle is consuming power while charging. At this time, the power generation of new energy is insufficient for the current state of the new energy system, and the new energy power generation is not fully put into operation. Then, the anti-reverse current control protection device 18 closes the switch of some or all of the new energy power generation of the unoperated part, puts into operation some or all of the new energy power generation equipment of the unoperated part, that is, increases the power generation of new energy.

[0052] 3.8) If the charging status of electric vehicle 11 is not determined in 2.4), that is, the electric vehicle discharges and generates power, the power generation of new energy is insufficient for the current state of the new energy system, and the new energy power generation equipment is not fully put into operation. The discharge power of electric vehicle is used to supply power to the general load 5 in the new energy system. Then the anti-reverse current control protection device 18 closes the switch of some or all of the unused new energy power generation equipment, puts into operation some or all of the unused new energy power generation equipment, that is, increases the power generation of new energy.

[0053] Implementation method of anti-reverse flow control and protection method for new energy power generation: The reverse current control and protection method for new energy power generation of the present invention is applicable to, for example, Figure 1 The illustrated new energy scenario includes photovoltaic panels 1 (as part of a new energy power generation system), wind turbine generators 2, an energy storage system 3 (which may employ electrochemical energy storage), several charging piles 4 (for charging new energy vehicles), and general loads 5 within the new energy system. The general loads 5 in the new energy system include DC loads such as lighting, cooling fans, and liquid-cooled water pumps, and can also be used for the excitation of DC motors in wind power generation.

[0054] The wind power station unit 2 uses a DC generator. Therefore, both the photovoltaic panel 1 and the wind power station unit 2 are connected to the new energy system bus 8 through their respective inverters 6 and branch transformers 7 to supply power to the new energy system bus 8.

[0055] The energy storage system 3 is also connected to the new energy system bus 8 via the converter 9 and the branch transformer 7. It can supply power to the new energy bus 8 or serve as a load for the new energy system bus 8 to store power to the energy storage system 3. Therefore, the converter 9 connected to the energy storage system 3 is a bidirectional converter, which can operate in rectification mode (charging the energy storage system 3) or inverter mode (discharging the energy storage system 3 to supply power to the new energy system bus 8).

[0056] The new energy system bus 8 is also connected to the charging pile 4 via branch transformer 7 and converter 9 to supply power to the charging pile 4 for charging the electric vehicle 11. Meanwhile, the charging pile 4 is a bidirectional charging pile (with V2G, Vehicle-to-Grid functionality), which can use the electric vehicle's power battery as an energy storage medium when necessary, drawing power from it to supply the new energy system bus 8. Therefore, the converter 9 connected to the charging pile 4 is also a bidirectional converter, capable of operating in rectification mode (supplying power to the charging pile 4) or inverter mode (supplying power to the new energy system bus 8).

[0057] The new energy system bus 8 is also connected to the general load 5 in the new energy system through the branch transformer 7 and rectifier 10, and supplies power to the general load 5.

[0058] The inverters 6, converters 9 and rectifiers 10 are connected to the corresponding branch transformers 7 on their respective lines by a first circuit breaker 12; each branch transformer 7 and the new energy system bus 8 are also connected to a second circuit breaker 13.

[0059] The new energy system bus 8 is connected to the main power grid 15 through the main transformer 14. A third circuit breaker 16 is installed between the new energy system bus 8 and the main transformer 14, and a fourth circuit breaker 17 is installed between the main transformer 14 and the main power grid 15. The third circuit breaker 16 and the fourth circuit breaker 17 can be used as grid connection switches.

[0060] like Figure 2 As shown, a method for preventing reverse current flow control and protection in new energy power generation according to the present invention includes the following steps: 1) Obtain the power generation capacity of new energy sources and the load power of general loads in the new energy system; 1.1) If the power generation of new energy sources is greater than the load power, then determine whether the energy storage system is fully charged; 1.2) If the power generation of new energy sources is less than the load power, then determine whether all new energy power generation equipment is in operation.

[0061] 2) Determine the charging status of the electric vehicle 11 corresponding to the charging pile 4 in the new energy system. If it is in a charging state, the electric vehicle 11 is charging and replenishing energy. If it is not in a charging state, it means that the corresponding charging pile 4 is working in V2G mode and the power battery of the electric vehicle 11 is discharging to the outside as a power source. 2.1) If the energy storage system in 1.1) is fully charged, then it is also determined whether the electric vehicle 11 corresponding to the charging pile 4 in the new energy system is in a charging state; 2.2) If the energy storage system in 1.1) is not fully charged, also determine whether the electric vehicle 11 corresponding to the charging pile 4 in the new energy system is charging. 2.3) If all the new energy power generation equipment in 1.2) is put into operation, then it is also necessary to determine whether the electric vehicle 11 corresponding to the charging pile 4 in the new energy system is in a charging state; 2.4) If not all of the new energy power generation equipment in 1.2) is put into operation, it is also necessary to determine whether the electric vehicle 11 corresponding to the charging pile 4 in the new energy system is in a charging state.

[0062] 3) Based on the judgment results of 2.1) to 2.4), execute the corresponding strategy to realize the reverse current protection control of the new energy system; 3.1) If the charging status of electric vehicle 11 is determined to be yes in 2.1), that is, the electric vehicle consumes power while charging. At this time, the new energy power generation is used for general load 5 and electric vehicle 11 charging. The energy storage system is fully charged and cannot consume or store excess power. Then control the new energy power generation system to reduce the output power. If the value of the current flowing back into the main grid 15 exceeds the anti-reverse current protection setting (or the V2G reverse grid current setting), then control the tripping of the new energy system grid connection point switch (including the third circuit breaker 16 and / or the fourth circuit breaker 17).

[0063] 3.2) If the charging status of electric vehicle 11 is not determined in 2.1), that is, the electric vehicle is discharging and generating power, the new energy system is in a relatively saturated extreme state, and neither the energy storage system nor the charging pile can consume power, and the reverse current phenomenon is very likely to occur; then a part of the new energy power generation equipment is cut off, that is, the power generation of new energy is reduced, and the current of charging pile 4 fed back to the main grid 15 in V2G mode is limited. If the value of the current flowing back into the main grid exceeds the anti-reverse current protection setting (or the V2G reverse grid current setting), then the new energy system grid connection point switch is tripped.

[0064] 3.3) If the charging status of electric vehicle 11 is determined to be yes in 2.2), that is, the electric vehicle consumes power for charging, the energy storage system 3 in the energy system can also consume power to store electrical energy; then control to increase the output power of charging pile 4, so that as much of the new energy power generation is used for electric vehicle charging, and at the same time charge the energy storage system 3 for backup, absorbing the excess power generation of new energy.

[0065] 3.4) If the charging status of electric vehicle 11 is determined to be no in 2.2), that is, the electric vehicle discharges and generates power, the energy storage system 3 in the energy system can consume power to store electrical energy; then control the charging of the energy storage system 3 for backup, and absorb the excess generated power.

[0066] 3.5) If the charging status of electric vehicle 11 is determined to be yes in 2.3), that is, the power consumed by electric vehicle charging is insufficient for the current state of the new energy system, then close the grid connection point switch of the new energy system, that is, control the grid connection operation of the new energy system, and the large power grid 15 charges electric vehicle 11 or supplies power to general load 5.

[0067] 3.6) If the charging status of electric vehicle 11 is not determined in 2.3), that is, the electric vehicle discharges and generates power, the power generation of the new energy system is insufficient for the current state of the new energy system. The discharge power of the electric vehicle is used to supply power to the general load 5 in the new energy system. Then close the grid connection point switch of the new energy system and use the large power grid 15 to supplement the power gap.

[0068] 3.7) If the charging status of electric vehicle 11 is determined to be yes in 2.4), that is, the charging power of electric vehicle is insufficient for the current state of the new energy system, and the new energy power generation equipment is not fully put into operation, then the part or all of the part of the new energy power generation equipment that is not put into operation will be put into operation to generate electricity, that is, to increase the power generation of new energy.

[0069] 3.8) If the charging status of electric vehicle 11 is not determined in 2.4), that is, the electric vehicle discharges and generates power, the power generation of the new energy system is insufficient at this time, and the new energy power generation equipment is not fully put into operation. The discharge power of the electric vehicle is used to supply power to the general load 5 in the new energy system. Then, the part or all of the part of the new energy power generation equipment that is not put into operation will be put into operation to generate power, that is, the power generation of the new energy system will be increased.

[0070] This invention solves the problem of reverse current flow from the renewable energy system to the main power grid caused by the instability of renewable energy power generation. By installing anti-reverse current control and protection devices and implementing anti-reverse current control and protection methods at the grid connection point of renewable energy systems containing renewable energy power generation equipment, energy storage, and electric vehicle charging and discharging, coordinated control of the power generation units, energy storage units, and electric vehicle charging and discharging units within the system is achieved. This enables anti-reverse current protection of the main power grid with minimal impact on each part of the renewable energy system, improves the operational stability of the renewable energy system, and reduces the negative impact of renewable energy power generation on the main power grid.

Claims

1. A method for preventing reverse current control and protection in new energy power generation, characterized in that, Includes the following steps: 1) Obtain the power generation capacity of new energy sources and the load power of general loads in the new energy system; If the power generation of new energy sources is greater than the load power, then determine whether the energy storage system is fully charged. If yes, it is a; otherwise, it is b. If the power generation of new energy sources is less than the load power, then determine whether all new energy power generation equipment is in operation: if yes, it is c; otherwise, it is d. 2) Determine whether the electric vehicle connected to the new energy system is in a charging state; if yes, mark it as e; otherwise, mark it as f. 3) If a and e, then control the reduction of the output power of the new energy power generation system; if a current reverse current exceeding the threshold occurs, then control the new energy system to stop grid-connected operation. If a and f, then control the reduction of new energy power generation and the reduction of electric vehicle external discharge power. If current reverse flow exceeds the threshold, then control the new energy system to stop grid connection. If b and e, then control the increase of the charging power of the electric vehicle and control the charging of the energy storage system; If b and f, then control the charging of the energy storage system; If c and e, or if c and f, then control the grid-connected operation of the new energy system; If d and e, or if d and f, then control the unused portion of the new energy power generation equipment to generate electricity, either partially or entirely.

2. The anti-reverse flow control and protection method for new energy power generation according to claim 1, characterized in that, In step 1), the power of the new energy generation equipment is obtained by the output power of the inverter on the branch where the new energy power generation equipment is located; the power of the load is obtained by the output power of the rectifier on the branch where the general load is located.

3. The anti-reverse flow control and protection method for new energy power generation according to claim 1, characterized in that, In step 2), the direction of the inverter power on the branch where the electric vehicle is connected to the charging pile is searched to determine whether the corresponding electric vehicle is in a charging state.

4. The anti-reverse flow control and protection method for new energy power generation according to claim 1, characterized in that, In step 3), the output power of the new energy power generation system is reduced by controlling the inverters on the branches where several new energy power generation devices are located to reduce their output power; the output power of the new energy power generation system is reduced by shutting down some of the new energy power generation devices.

5. The anti-reverse flow control and protection method for new energy power generation according to claim 1, characterized in that, In step 3), the new energy system stops grid-connected operation by disconnecting the grid-connected switch, and the new energy system resumes grid-connected operation by closing the grid-connected switch.

6. A reverse current control and protection device for new energy power generation, characterized in that, Includes a processor that executes a computer program to implement the steps of the following method: 1) Obtain the power generation capacity of new energy sources and the load power of general loads in the new energy system; If the power generation of new energy sources is greater than the load power, then determine whether the energy storage system is fully charged. If yes, it is a; otherwise, it is b. If the power generation of new energy sources is less than the load power, then determine whether all new energy power generation equipment is in operation: if yes, it is c; otherwise, it is d. 2) Determine whether the electric vehicle connected to the new energy system is in a charging state; if yes, mark it as e; otherwise, mark it as f. 3) If a and e, then control the reduction of the output power of the new energy power generation system; if a current reverse current exceeding the threshold occurs, then control the new energy system to stop grid-connected operation. If a and f, then control the reduction of new energy power generation and the reduction of electric vehicle external discharge power. If current reverse flow exceeds the threshold, then control the new energy system to stop grid connection. If b and e, then control the increase of the charging power of the electric vehicle and control the charging of the energy storage system; If b and f, then control the charging of the energy storage system; If c and e, or if c and f, then control the grid-connected operation of the new energy system; If d and e, or if d and f, then control the unused portion of the new energy power generation equipment to generate electricity, either partially or entirely.

7. The anti-reverse flow control and protection device for new energy power generation according to claim 6, characterized in that, In step 1), the power of the new energy generation equipment is obtained by the output power of the inverter on the branch where the new energy power generation equipment is located; the power of the load is obtained by the output power of the rectifier on the branch where the general load is located.

8. The anti-reverse flow control and protection device for new energy power generation according to claim 6, characterized in that, In step 2), the direction of the inverter power on the branch where the electric vehicle is connected to the charging pile is searched to determine whether the corresponding electric vehicle is in a charging state.

9. The anti-reverse flow control and protection device for new energy power generation according to claim 6, characterized in that, In step 3), the output power of the new energy power generation system is reduced by controlling the inverters on the branches where several new energy power generation devices are located to reduce their output power; the output power of the new energy power generation system is reduced by shutting down some of the new energy power generation devices.

10. The anti-reverse flow control and protection device for new energy power generation according to claim 6, characterized in that, In step 3), the new energy system stops grid-connected operation by disconnecting the grid-connected switch, and the new energy system resumes grid-connected operation by closing the grid-connected switch.

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