Light storage power supply control system and method

Abstract

The invention relates to the technical field of new energy power, in particular to a light storage power supply control system and method, and the system is used for the power supply of at least two loads. Comprising a photovoltaic power generation unit, an energy storage unit, an energy management system, a power grid bus, a photovoltaic bus, a first load branch and a second load branch. The first power supply branch is connected in series with a first controllable circuit breaker, and the second power supply branch is connected in series with a first anti-reflux device; the third power supply branch is connected in series with a second controllable circuit breaker, and the fourth power supply branch is connected in series with a second anti-reflux device. The invention aims to provide the optical storage power supply control system and the optical storage power supply control method, so that the problems of disturbance and protection reliability possibly existing during load grading power supply switching of an existing optical storage power supply system are solved, and the electric energy quality of switching of an unimportant load power supply loop is ensured.

Description

Technical Field

[0001] This invention relates to the field of new energy power technology, specifically to a photovoltaic power supply control system and method. Background Technology

[0002] In the industrial and commercial sectors, installing distributed renewable energy power generation systems such as photovoltaics and wind power has become a common choice to reduce electricity costs and carbon emissions. Under the "surplus electricity not fed into the grid" operating mode, where all generated electricity is consumed locally, industrial and commercial photovoltaic systems are often equipped with energy storage to improve self-consumption rates.

[0003] Commercial and industrial users often face the constraint of "not feeding surplus electricity into the grid" when installing photovoltaic (PV) systems. Existing solutions mostly rely on anti-reverse current devices and simple priority strategies to ensure power supply to critical loads and improve self-consumption. However, these solutions have significant drawbacks: First, when critical loads are operating under very light or no-load conditions, the PV bus forms a low-impedance path with the grid through a closed load switch, easily leading to power disturbances and frequent activation of anti-reverse current devices. Second, control relies entirely on a central energy management system; if communication is interrupted, the system may lose its core protection logic. Finally, existing solutions only focus on power distribution and do not utilize load switching capabilities to improve the power quality of critical buses.

[0004] Therefore, there is a need for an integrated solution that can operate stably, reliably, and intelligently under complex working conditions and abnormal situations. Summary of the Invention

[0005] The purpose of this invention is to provide a photovoltaic power supply control system and method to solve the problems of disturbance and protection reliability that may exist in the existing photovoltaic power supply system when switching power supply according to load grading, and to ensure the power quality when switching power supply circuits for non-critical loads.

[0006] To achieve the above objectives, the present invention provides a photovoltaic power supply control system for supplying power to at least two loads, wherein the power supply priority of the first load is higher than that of the second load; the system includes a photovoltaic power generation unit, an energy storage unit, an energy management system, a grid bus, a photovoltaic bus, a first load branch, and a second load branch. The first load branch is connected to the first load and includes a first power supply branch and a second power supply branch connected in parallel; a first controllable circuit breaker is connected in series on the first power supply branch and a first anti-reverse current device is connected in series on the second power supply branch. The second load branch is connected to the second load and includes a third power supply branch and a fourth power supply branch connected in parallel; a second controllable circuit breaker is connected in series on the third power supply branch, and a second anti-reverse current device is connected in series on the fourth power supply branch; The photovoltaic power generation unit is connected to the photovoltaic bus, and the energy storage unit is connected to the photovoltaic bus via a bidirectional converter; The first power supply branch and the third power supply branch are connected to the photovoltaic bus, and the second power supply branch and the fourth power supply branch are connected to the power grid bus; The energy management system is communicatively connected to the photovoltaic power generation unit, the energy storage unit, the first controllable circuit breaker, the second controllable circuit breaker, the first anti-backflow device, and the second anti-backflow device.

[0007] Preferably, the reverse current alarm signal output terminal of the first anti-reverse current device is electrically connected to the tripping drive terminal of the second controllable circuit breaker through an independent hardware interlocking circuit, so that the first anti-reverse current device can directly drive the second controllable circuit breaker to trip when it detects reverse current.

[0008] Preferably, it further includes metering devices disposed on the first power supply branch, the second power supply branch, the third power supply branch, the fourth power supply branch, the power supply branch between the photovoltaic power generation unit and the photovoltaic bus, and the power supply branch between the energy storage unit and the photovoltaic bus; the metering devices are communicatively connected to the energy management system.

[0009] Preferably, the photovoltaic-storage power supply control system is integrated into one grid-connected cabinet or distributed among multiple grid-connected cabinets.

[0010] Based on the above-mentioned photovoltaic-storage power supply control system, the present invention also provides a photovoltaic-storage power supply control method, which is executed by the energy management system and includes a basic operation mode and an optimized collaborative mode. The basic operating modes include: S1, First Priority: The power generated by the photovoltaic power generation unit is preferentially used for the first load; S2, Second Priority: After meeting the electricity demand of the first load, the surplus photovoltaic power is prioritized to charge the energy storage unit. S3, Third Priority: After the energy storage unit is fully charged, if there is still residual power, it is supplied to the second load; and during the supply process, it is monitored in real time. If the residual power is less than or equal to 0, the power supply to the second load is immediately stopped. The optimized collaborative mode includes at least one of the following: Mode A: When the real-time power of the first load is lower than the set threshold and the photovoltaic power generation unit has output, the power supply branch of the second load is used as an energy damper. By adjusting the power supply to the second load, the power detected by the first anti-reverse current device is kept to zero. Mode B: When the power quality index of the first load's access point is detected to exceed the set limit, an instruction that takes precedence over the third priority operation is generated and executed, and the instruction includes at least disconnecting the second controllable circuit breaker. Mode C: When the communication of the energy management system is interrupted, if the power generation of the photovoltaic power generation unit is detected to be greater than the power of the first load, the energy storage unit is controlled to stop discharging.

[0011] Preferably, in the basic operating mode, the power generation P0 of the photovoltaic power generation unit and the power P1 of the first load are acquired in real time; In step S1, it is determined whether the photovoltaic power generation meets the first load requirement; If P0≥P1, then the photovoltaic power generation unit supplies power to the first load and proceeds to step S2; If P0 < P1, the energy storage unit is controlled to discharge to make up for the power deficit of the first load; if the energy storage unit is still insufficient to make up for the power deficit of the first load after discharging, the power grid bus will supplement the power supply to the first load. In step S2, under the condition that P0≥P1, when the energy storage unit is rechargeable, it is controlled to charge at a power not greater than (P0-P1), and the remaining power P3 of the system after charging is calculated. In step S3, it is determined whether the remaining power P3 of the system is greater than 0; If so, the second controllable circuit breaker is closed to supply the remaining power P3 of the system to the second load; If not, or if the remaining power P3 of the system is not greater than 0 during the power supply process, the second controllable circuit breaker is immediately controlled to disconnect.

[0012] Preferably, in step S2, if the rate of change of power generation of the photovoltaic power generation unit exceeds the positive threshold and the state of charge of the energy storage unit is higher than the set high threshold, then step S2 is skipped, P3=P0-P1 is set, and step S3 is entered.

[0013] Preferably, in step S3, the power supplied to the second load does not exceed the smaller value between P3 and the real-time power P4 of the second load.

[0014] Preferably, in step S2, if the energy storage unit cannot be charged or is already full, then let P3 = P0 - P1.

[0015] Preferably, in the basic operating mode: When the first controllable circuit breaker is closed and the second controllable circuit breaker is open, if the first anti-reverse current device detects reverse current, it closes the second controllable circuit breaker, and the reverse current power is absorbed by the second load. When both the first and second controllable circuit breakers are closed, if the first anti-backflow device and / or the second anti-backflow device detects backflow, the energy management system will sequentially control the reduction of the energy storage unit output, the reduction of the photovoltaic power generation unit output, and the disconnection of the first and second controllable circuit breakers based on the backflow information.

[0016] Preferably, in Mode B, the power quality indicators include voltage sag, voltage surge, or harmonic content.

[0017] Preferably, after mode B is triggered and executed, when the power quality indicators return to normal, the method controls the system to return to the basic operating mode logic.

[0018] In summary, the technical effects achieved by this invention are as follows: Photovoltaic and energy storage capacity can be primarily configured based on the primary load, avoiding excessive investment for secondary loads and reducing initial costs. Through three-level priority scheduling, photovoltaic self-consumption is maximized, reducing electricity costs. The primary load enjoys triple power supply guarantees from photovoltaics, energy storage, and the grid. Through a dual mechanism of basic operation mode and optimized collaborative mode, it ensures absolute priority and zero backflow power supply to the primary load under any circumstances, resulting in high system robustness. The basic three-level priority logic is clear and reliable. Combined with three optimized collaborative modes, the system can intelligently cope with various complex boundary conditions such as no-load disturbances, power quality deterioration, and communication anomalies, achieving intelligent and adaptive power supply. Hardware modifications mainly involve adding a controllable circuit breaker, an anti-backflow device, and a hardware interlocking circuit. The cost is significantly lower than a solution using static transfer switches. The system can be integrated or distributed, making it easy to implement. Attached Figure Description

[0019] Figure 1 This is a connection diagram of the photovoltaic-storage power supply control system according to an embodiment of the present invention; Figure 2 This is a flowchart of the basic operation mode in the photovoltaic-storage power supply control method of the present invention. Figure 3 This is a flowchart of the optimized collaborative mode in the photovoltaic-storage power supply control method of the present invention.

[0020] The diagram is labeled as follows: 1. First load; 10. First load branch; 11. First power supply branch; 12. Second power supply branch; 2. Second load; 20. Second load branch; 21. Third power supply branch; 22. Fourth power supply branch; 3. Photovoltaic power generation unit; 4. Energy storage unit; 5. Power grid bus; 6. Photovoltaic bus; 71. First controllable circuit breaker; 72. Second controllable circuit breaker; 73. First anti-reverse current device; 74. Second anti-reverse current device; 75. Third controllable circuit breaker; 76. Fourth controllable circuit breaker. Detailed Implementation

[0021] The technical solutions in this embodiment will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0022] In the description of this invention, it should be noted that the terms "upper," "lower," "inner," "outer," "top / bottom," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing the invention and for simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on the invention. Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0023] In the description of this invention, it should be noted that, unless otherwise explicitly specified and limited, the terms "installed," "equipped with," "sleeved / connected," "connected," etc., should be interpreted broadly. For example, "connection" can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium; it can be a connection within two components. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0024] Currently, when industrial and commercial photovoltaic and energy storage systems are operating under extremely light or no-load conditions, the photovoltaic bus forms a low-impedance path with the grid through a closed load switch, which can easily lead to power disturbances and frequent activation of anti-reverse current devices. Control relies entirely on the central energy management system, and once communication is interrupted, the system may lose its core protection logic. It only focuses on power distribution and does not utilize load switching capabilities to improve the power quality of critical buses.

[0025] like Figure 1 As shown, to solve the above-mentioned technical problems, one embodiment of the present invention provides a photovoltaic-storage power supply control system for supplying power to at least two loads, wherein the power supply priority of the first load 1 is higher than that of the second load 2. The first load 1 is an important load, and its power supply needs must be guaranteed at all times, while the second load 2 is a non-important load, and can be supplied with power when the photovoltaic-storage power supply system has surplus power.

[0026] Specifically, it includes photovoltaic power generation unit 3, energy storage unit 4, energy management system (EMS) (not shown in the figure), power grid bus 5, photovoltaic bus 6, first load branch 10 and second load branch 20.

[0027] In this system, photovoltaic power generation unit 3, as a new energy power generation unit, is connected to photovoltaic bus 6 via first controllable circuit breaker 71. Energy storage unit 4 is connected to photovoltaic bus 6 via bidirectional converter PCS and then via second controllable circuit breaker 72. Therefore, the photovoltaic bus 6 stores the electricity generated by photovoltaic power generation unit 3. This electricity not only provides power to the first load 1 and the second load 2, but also charges energy storage unit 4. Energy storage unit 4 can receive the electricity generated by photovoltaic power generation unit 3 and also output electricity.

[0028] The first load branch 10 is connected to the first load 1 and provides power to the first load 1. It includes a first power supply branch 11 and a second power supply branch 12 connected in parallel. A first controllable circuit breaker 71 is connected in series on the first power supply branch 11, and a first anti-reverse current device 73 is connected in series on the second power supply branch 12.

[0029] Based on this, the first power supply branch 11 is connected to the photovoltaic bus 6, and the connection between the first load 1 and the photovoltaic bus 6 is completed by opening and closing the first controllable circuit breaker 71; the second power supply branch 12 is connected to the grid bus 5, and the grid bus 5 can supply power to the first load 1. At the same time, the first anti-reverse current device 73 on the second power supply branch 12 can prevent the power of the first load 1 from flowing back to the grid.

[0030] The second load branch 20 is connected to the second load 2 and provides power to the second load 2. It includes a third power supply branch 21 and a fourth power supply branch 22 connected in parallel. A second controllable circuit breaker 72 is connected in series on the third power supply branch 21, and a second anti-reverse current device 74 is connected in series on the fourth power supply branch 22.

[0031] Based on this, the third power supply branch 21 is connected to the photovoltaic bus 6. The second load 2 and the photovoltaic bus 6 are connected by opening and closing the second controllable circuit breaker. The fourth power supply branch 22 is connected to the grid bus 5. The grid bus 5 can supply power to the second load 2. At the same time, the second anti-reverse flow device 74 on the fourth power supply branch 22 can prevent the power of the second load 2 from flowing back to the grid.

[0032] In the first load branch 10 of the first load 1 and the second load branch 20 of the second load 2, the second power supply branch 12 also includes a normally closed third controllable circuit breaker 75 so that the power grid bus 5 provides power to the first load 1 according to the control logic; the fourth power supply branch 22 also includes a normally closed fourth controllable circuit breaker 76 so that the power grid bus 5 provides power to the second load 2 according to the control logic.

[0033] The Energy Management System (EMS) is communicatively connected to the photovoltaic power generation unit 3, the energy storage unit 4, the first controllable circuit breaker 71, the second controllable circuit breaker 72, the first anti-reverse current device 73, and the second anti-reverse current device 74. It is used to collect system operation data and execute control strategies. As the core of software control, the EMS needs to collect the operation data of the entire system before executing control strategies. Therefore, this embodiment also includes metering devices (not shown in the figure) installed on the first power supply branch 11, the second power supply branch 12, the third power supply branch 21, the fourth power supply branch 22, the power supply branch between the photovoltaic power generation unit 3 and the photovoltaic bus 6, and the power supply branch between the energy storage unit 4 and the photovoltaic bus 6. The metering devices are communicatively connected to the EMS and output system operation data to the EMS.

[0034] The aforementioned photovoltaic-storage power supply control system can be integrated into a single grid-connected cabinet or distributed across multiple grid-connected cabinets, depending on site requirements.

[0035] As can be seen from the above, the first load 1 and the second load 2 are similar in terms of the connection of the power supply branches. Since the first load 1 is an important load, its power supply needs must be guaranteed at all times, while the second load 2 is a non-critical load and can be supplied with power when the photovoltaic power storage system has surplus power. Therefore, this embodiment adopts different power supply modes and control logics for the first load 1 and the second load 2.

[0036] Based on the above-mentioned photovoltaic-storage power supply control system, this embodiment also provides a photovoltaic-storage power supply control method, which is executed by the energy management system (EMS) and includes a basic operation mode and an optimized collaborative mode.

[0037] like Figure 2 As shown, the basic operation mode includes three priority modes, divided into steps S1 to S3. During the entire basic operation mode, it is necessary to first obtain in real time the power generation P0 of photovoltaic power generation unit 3, the power P1 of the first load 1, the SOC status of energy storage unit 4, and the charging power P2. The basic operation mode specifically includes:

[0038] S1, First priority: The power generated by photovoltaic power generation unit 3 is preferentially used for the first load 1.

[0039] In this step, it is determined whether the power generation of the photovoltaic power generation unit 3 meets the requirements of the first load 1, that is, the power generation P0 of the photovoltaic power generation unit 3 and the power P1 of the first load 1 are first determined. If P0≥P1, it indicates that the photovoltaic power is sufficient or just enough to meet the first load 1. Then the first controllable circuit breaker 71 is closed, the photovoltaic power generation unit 3 supplies power to the first load 1, and the process proceeds to step S2. If P0 < P1, it indicates that the photovoltaic power is insufficient to meet the first load 1. Similarly, the first controllable circuit breaker 71 is closed, and the energy storage unit 4 is controlled to discharge to make up for the power deficit of the first load 1. If the energy storage unit 4 is still insufficient to make up for the power deficit of the first load 1 after discharging, the power deficit is supplemented by the grid bus 5 through the third controllable circuit breaker 75 to supply power to the first load 1.

[0040] During this process, the first controllable circuit breaker 71 on the first power supply branch 11 closes, realizing the connection between the first load 1 and the photovoltaic bus 6.

[0041] S2, Second Priority: After satisfying the electricity demand of the first load 1, the surplus photovoltaic power is prioritized to charge the energy storage unit 4.

[0042] In this step, under the condition that P0≥P1, when the energy storage unit 4 is rechargeable, it is controlled to charge at a power not greater than (P0-P1), and the remaining power P3 of the system after charging is calculated.

[0043] To determine whether the energy storage unit 4 is rechargeable, it is necessary to obtain the state of charge (SOC) of the energy storage unit 4 and to pre-set the charging conditions for the energy storage unit 4. For example, the SOC of the energy storage unit 4 when it starts charging is set to 0.7. That is, when the power generation P0 of the photovoltaic power generation unit 3 is greater than or equal to the power P1 of the first load 1 and the SOC of the energy storage unit 4 is less than 0.7, the photovoltaic power generation unit 3 charges the energy storage unit 4.

[0044] The charging power P2 of the energy storage unit 4 is set to be no greater than (P0-P1), and the remaining power P3 of the system after charging is calculated.

[0045] If the charging power P2 of energy storage unit 4 is less than (P0-P1), the remaining power of the system after charging is P3 = P0-P1-P2. If the charging power P2 of energy storage unit 4 is equal to (P0-P1), the remaining power of the system after charging is P3=0.

[0046] The above is the charging control logic for energy storage unit 4. The charging start condition for energy storage unit 4 is set. In order to improve the service life of energy storage unit 4, the charging stop condition for energy storage unit 4 also needs to be set, that is, energy storage unit 4 cannot be charged or is fully charged. At this time, P3=P0-P1.

[0047] In actual operation, there are also cases where the power generation rate of photovoltaic power generation unit 3 changes significantly, such as when the clouds disperse and the solar energy irradiating photovoltaic power generation unit 3 suddenly increases. In order to avoid the sudden increase in photovoltaic power generation affecting the entire system, this embodiment also adds grid protection measures. If the power generation rate of photovoltaic power generation unit 3 is detected to exceed the positive threshold and the state of charge (SOC) of energy storage unit 4 is higher than the set high threshold, then step S2 is skipped, P3 is set to P0-P1, and step S3 is entered.

[0048] S3, third priority: after the energy storage unit 4 is fully charged, if there is still residual power, it is supplied to the second load 2; and during the supply process, it is monitored in real time. If the residual power is not greater than 0, the power supply to the second load 2 is stopped immediately.

[0049] In this step, it is determined whether the remaining power P3 of the system is greater than 0; If so, the second controllable circuit breaker 72 is closed to supply the power of the remaining power P3 of the system to the second load 2; If not, or if the system's remaining power P3 ≤ 0 is detected during the power supply process, for example, a decrease in photovoltaic power generation or a sudden increase in the power P1 of the first load 1, the second controllable circuit breaker 72 will be immediately disconnected, and the energy storage charging power P2 will be adjusted.

[0050] It's acceptable that the power supplied to the second load 2 does not exceed the smaller of the system's remaining power P3 and the real-time power P4 of the second load 2. The system's remaining power P3 is the upper limit of the system's power supply capacity; the system cannot provide more power than its available capacity. Therefore, the power supplied to the second load 2 must never exceed the system's remaining power P3, otherwise it will violate power balance, leading to system instability or triggering protection. P4 is the actual power demand of the second load 2 at that moment; supplying power exceeding the load demand is invalid. If the second load 2 is a non-adjustable or constant power device, the excess power has nowhere to go, and the excess power may attempt to flow to the grid bus 5 through the fourth power supply branch 22, increasing the current flowing through the second anti-reverse current device 74, and even causing reverse current misjudgment or disturbance risk.

[0051] This protection logic ensures that the power supply to the first load 1 is not affected in any way. After the second controllable circuit breaker 72 is disconnected, the second load 2 is automatically powered by the power grid bus 5 through the fourth controllable circuit breaker 76 circuit, achieving seamless switching.

[0052] The above is the basic operating mode, which follows a strict three-level priority system. This part is the normal operating logic of the system, ensuring optimized operation most of the time.

[0053] The control method provided in this embodiment is also subject to the relevant regulations of "surplus power not being fed into the grid". Therefore, this embodiment also needs to monitor the reverse current status of the two anti-reverse current devices at all times throughout the entire basic operation mode. Since the first load 1 is an important load, the power supply of the first load 1 must be guaranteed first. Therefore, the first controllable circuit breaker 71 is in a closed state during this process. Only when the photovoltaic power generation unit 3 simultaneously satisfies the first load 1 and the energy storage unit 4 and there is still surplus power will the second controllable circuit breaker 72 close to supply power to the second load 2.

[0054] Therefore, backflow prevention monitoring is divided into two states: When the first controllable circuit breaker 71 is closed and the second controllable circuit breaker 72 is open, the second load 2 is powered by the grid bus 5, and there is no reverse current. The energy management system (EMS) only needs to monitor the first anti-reverse current device 73, reducing the processing and response speed of the second anti-reverse current device 74 and reducing the burden on the energy management system (EMS). If the first anti-reverse current device 73 detects reverse current, it indicates that the photovoltaic output still has a surplus after supplying the first load 1 and is not being effectively utilized. The second controllable circuit breaker 72 is then closed, and the second load 2 absorbs the reverse current power. At this time, the electrical energy generated by the photovoltaic power generation unit 3 will flow back to the grid bus 5 through the second controllable circuit breaker 72. Both the first anti-reverse current device 73 and the second anti-reverse current device 74 may have reverse current, and the system enters the second state.

[0055] When both the first controllable circuit breaker 71 and the second controllable circuit breaker 72 are closed, if the first anti-reverse current device 73 and / or the second anti-reverse current device 74 detects reverse current, the energy management system (EMS) will control the reduction of the output of the energy storage unit 4 and the photovoltaic power generation unit 3 in sequence according to the reverse current information, until there is no reverse current in the two anti-reverse current devices. If there is still reverse current after reducing the output of the energy storage unit 4 and the photovoltaic power generation unit 3, the first controllable circuit breaker 71 and the second controllable circuit breaker 72 will be disconnected to ensure that the surplus power is not connected to the grid.

[0056] In addition to the basic operating mode, this embodiment also provides an optimized collaborative mode to deal with abnormal situations such as no-load of the first load 1, power quality changes of the power output of the grid bus 5, and disconnection of the energy management system EMS.

[0057] like Figure 3 As shown, specifically, optimized collaboration modes include at least one of the following: Mode A: When the real-time power of the first load 1 is lower than the set threshold and the photovoltaic power generation unit 3 has output, the power supply branch of the second load 2 is used as an energy damper. By adjusting the power supply to the second load 2, the power detected by the first anti-reverse current device 73 is kept to zero.

[0058] When the first load 1 is close to no load, the first load branch 10 is a low impedance path, and the photovoltaic bus 6 will cause a parallel disturbance to the power grid through the low impedance path.

[0059] In this mode, the system may not completely follow the passive control logic of the basic operation mode. The energy management system (EMS) closes the second controllable circuit breaker 72 and uses the second load branch 20 as an active and controllable energy damper to adjust the on / off state and power of the second controllable circuit breaker 72, so that the power flowing through the first anti-reverse current device 73 is always stable within a narrow positive and negative band near zero. The second load 2 is used to absorb the small amount of power that may be generated by photovoltaic fluctuations and attempt to flow to the grid bus 5, thereby actively eliminating the risk of reverse current, rather than waiting to detect reverse current before protection.

[0060] It's acceptable. The Energy Management System (EMS) sets a virtual load for the first load branch 10. When the power P1 of the first load is detected to be less than the virtual load, and the photovoltaic system is outputting power, the EMS actively controls the bidirectional converter PCS or a reserved low-power resistor load to ensure that the power flowing from the photovoltaic bus 6 to the first load branch 10 is at least the virtual load, ensuring the absolute reliability and speed of the reverse current protection, while not wasting photovoltaic energy.

[0061] Mode B: When the power quality index of the first load's access point is detected to exceed the set limit, an instruction that takes precedence over the third priority operation is generated and executed. The instruction includes at least disconnecting the second controllable circuit breaker 72.

[0062] When the power supply to the connection point of the first load 1, i.e. the second power supply branch 12, is abnormal, including voltage dips, voltage spikes, or the presence of harmonics, Mode B can proactively improve the power quality on the second power supply branch 12 of the first load 1 by utilizing the power supply flexibility of the second load 2, while ensuring that the power supply to the first load 1 is not affected.

[0063] To enable the operation of Mode B, a power quality monitoring unit (not shown in the figure) needs to be added to the system circuit structure.

[0064] The power quality monitoring unit is installed at the power supply inlet of the first load 1. When a brief voltage drop or harmonic exceedance is detected in the first load branch 10, even if it is currently in the third priority and P3>0, the energy management system (EMS) can instantly command the second controllable circuit breaker 72 to trip.

[0065] Mode B utilizes the grid's support capacity to help the voltage of the first load branch 10 recover more quickly by suddenly removing a load point that might exacerbate voltage problems. After Mode B is triggered and executed, when the power quality indicators return to normal, it re-evaluates whether to close the second controllable circuit breaker 72 and returns to the basic operating mode logic.

[0066] Mode C: When the communication of the energy management system (EMS) is interrupted, if the power generation of the photovoltaic power generation unit 3 is detected to be greater than the power of the first load 1, the energy storage unit 4 is controlled to stop discharging.

[0067] When the uplink communication of the Energy Management System (EMS) is completely interrupted, priority power supply to the first load 1 must be maintained, and uncontrolled reverse current must be prevented. In Mode C, the reverse current alarm signal output terminal of the first anti-reverse current device 73 is electrically connected to the tripping drive terminal of the second controllable circuit breaker 72 through an independent hardware interlocking circuit (not shown in the figure), so that the first anti-reverse current device 73 can directly drive the second controllable circuit breaker 72 to trip when reverse current is detected.

[0068] A hard-wired direct connection, bypassing the Energy Management System (EMS), is added between the first anti-reverse current device 73 and the second controllable circuit breaker 72 in the hardware interlocking circuit. The hardware interlocking circuit continuously receives reverse current signals from the first anti-reverse current device 73. These signals are not transmitted through the communication network. If any current flowing to the grid bus 5 is detected at the first anti-reverse current device 73, indicating a reverse current tendency in the first load branch 10, the hardware interlocking circuit immediately trips the second controllable circuit breaker 72, regardless of whether an instruction is received from the EMS.

[0069] A communication interruption means that the Energy Management System (EMS) cannot obtain complete real-time system status and cannot ensure precise and reliable power control of energy storage unit 4. Continuing to operate in the basic mode, with incomplete information and an unreliable control link, could increase the risk of system power imbalance or control conflicts. Therefore, if the photovoltaic power exceeds the power of the first load 1 during a communication interruption, discharging automatically stops, avoiding complex management of the dynamic charging and discharging of energy storage unit 4 during communication anomalies.

[0070] Throughout the process, the first anti-backflow device 73 and the second anti-backflow device 74 continuously monitor their respective circuits to ensure that no power is fed back to the grid bus 5 under any circumstances. The third controllable circuit breaker 75 and the fourth controllable circuit breaker 76 remain closed at all times, providing backup power from the grid to the first load 1 and the second load 2, ensuring the continuity of power supply to the system under any mode switching.

[0071] The hardware interlocking circuit does not rely on any communication and can directly cut off non-critical loads when reverse current is detected. This ensures that even if communication is interrupted, the system can still reliably prevent reverse current and absolutely prioritize power supply to the first load 1.

[0072] In summary, the technical effects achieved by the technical solution provided in this embodiment are as follows: Through three-level fixed priority control of two loads and energy storage unit 4, it is ensured that the power generated and stored by new energy sources is prioritized and directed to the first load 1 with the highest value. The first load 1 always has triple power supply guarantee from photovoltaic power generation unit 3, energy storage unit 4 and grid bus 5. When the photovoltaic output drops sharply or the first load 1 increases suddenly, the energy management system EMS can cut off the power supply to the second load 2 in milliseconds to ensure that the power supply to the first load 1 is absolutely unaffected. Since the second load 2 is normally guaranteed by the power grid and is only used when there is a large surplus of photovoltaic power, the installed capacity of the photovoltaic power generation system can be configured mainly based on the power demand of the first load 1, avoiding over-sizing of capacity to meet all loads, effectively reducing the initial investment cost. Moreover, the hardware modification only requires adding an electric operating mechanism to the circuit breaker and adding an anti-reverse current device, which is significantly cheaper than the solution that adopts STS for all loads. The dual anti-reverse current device on the grid side ensures that power is not fed back under any circumstances. Simultaneously, it employs a dual protection path of software control by the Energy Management System (EMS) and hardware control through hard-wired interlocking. Even if the EMS completely fails, the hard-wired interlocking acts as a last line of defense, implementing the core principles of anti-reverse current and prioritizing the protection of the first load (Load 1), and instantly isolating the second load (Load 2) to protect Load 1. This significantly improves the overall safety and reliability of the system. This design is not obvious and is highly practical. By introducing an adaptive bypass judgment based on the photovoltaic power change rate and the energy storage SOC, the system can dynamically fine-tune the fixed priority strategy according to the real-time status. When the energy storage is nearly full and the photovoltaic power increases sharply, the surplus power can be directly guided to non-critical loads for immediate consumption. Compared with forcibly charging the high SOC energy storage, this can better protect the battery life and improve the instantaneous consumption efficiency. By using energy damping control, the risk of system oscillation under no-load boundary conditions of the first load 1 is resolved, and the second load 2 is transformed into a system stabilizer, thereby improving the completeness and robustness of the technical solution.

[0073] The following is a detailed explanation using the power supply of critical and non-critical loads in a factory as an example: A factory has a production line and other critical loads with a power consumption of 200kW, while non-critical loads such as office air conditioning and lighting have a power consumption of 100kW. The proposed solution utilizes a 250kW photovoltaic system and 500kWh energy storage.

[0074] Case 1: On a sunny midday, the photovoltaic output is 300kW. The system first uses 200kW to power the production line, and then uses 50kW to charge the energy storage. At this time, P3 = P0 - P1 - P2 = 50kW. Since P3 > 0, the system closes the second controllable circuit breaker 72, supplying the remaining 50kW of photovoltaic power to non-critical loads. The remaining 50kW for non-critical loads is supplemented by the grid. In this scenario, the photovoltaic power is fully utilized.

[0075] This scenario represents the daily operation scenario based on the basic operating mode.

[0076] Case 2: When the photovoltaic system is blocked by clouds, the photovoltaic output drops sharply from 300kW to 180kW. At this time, P0 < P1. Under the first priority, the energy storage unit 4 immediately discharges 20kW to make up for the 200kW shortfall of the important load. P3 becomes 0, and the energy management system (EMS) immediately disconnects the second controllable circuit breaker 72. All non-critical loads are switched to grid power, and the power supply to the production line is not affected in any way.

[0077] This scenario is a special operating scenario based on the basic operating mode.

[0078] Case 3: On cloudy or rainy days, the photovoltaic output is 0, the production line is powered by energy storage and / or the grid, and non-critical loads are powered entirely by the grid.

[0079] This scenario is a special operating scenario two based on the basic operating mode.

[0080] Case 4: The production line suddenly increases by 50kW, for example, when the equipment starts up. The energy management system (EMS) detects that P3 has become 50kW and sends a trip command to the second controllable circuit breaker 72 within 15 milliseconds. The second controllable circuit breaker 72 opens, and non-critical loads are smoothly switched to grid power. The power supply of the production line is not affected by any voltage fluctuations.

[0081] This scenario is a special operating scenario three based on the basic operating mode.

[0082] Case 5: When the first anti-backflow device 73 detects a slight backflow trend, its hardware interlocking circuit immediately controls the second controllable circuit breaker 72 to trip instantly. This action does not rely on the energy management system (EMS) and is a pure hardware action. The response time can be within 10 milliseconds, forming a fast and reliable protection barrier.

[0083] This situation is an anti-backflow scenario in the basic operating mode.

[0084] Case 6: During evening or weekend shutdowns, when the production line stops and the Energy Management System (EMS) detects P1≈0 for more than 10 minutes, the system enters no-load mode. First, the EMS instructs the bidirectional converter PCS of energy storage unit 4 to generate a 5kW virtual load current drawing power from the photovoltaic bus 6. This current flows through the first controllable circuit breaker 71, the production line wiring, and the first anti-reverse current device 73, establishing a small positive current measurement at the first anti-reverse current device 73 to ensure the monitoring loop is effective. Simultaneously, based on the reading from the first anti-reverse current device 73, the EMS fine-tunes the switching and conduction power of the second controllable circuit breaker 72, ensuring that the power consumed by non-critical loads precisely offsets any potential surplus caused by photovoltaic fluctuations. This keeps the net power flowing to the grid bus 5 within ±1kW, perfectly damping photovoltaic fluctuations.

[0085] This scenario represents Scenario A in the optimized collaboration mode.

[0086] Case 7: The start-up of a large motor in the factory caused a voltage drop on the grid bus 5. The power quality detection unit detected this event. Even though the photovoltaic system still had a surplus, the energy management system (EMS) ignored the current state of supplying power to non-critical loads and immediately disconnected the second controllable circuit breaker 72, removing the non-critical loads. This helped to reduce the impact of the disturbance on the grid bus 5 on the local bus. At the same time, the rapid response of the energy storage supported the bus voltage of the critical loads, reducing the sudden load on the grid bus 5. By utilizing the instantaneous support capability of the grid, the voltage of the production line bus was restored more quickly. Once the voltage of the grid bus 5 stabilized, the energy management system (EMS) reclosed the second controllable circuit breaker 72.

[0087] This scenario describes the optimization of Mode B within the collaborative model.

[0088] Case 8: EMS communication network failure, local hardware interlocking circuit takes over. Since there is no reverse current on the non-critical load side, the state of the second controllable circuit breaker 72 is determined by the command of the final energy management system (EMS). The local controller of energy storage unit 4 is in standby mode because it detects no photovoltaic power. The entire system operates safely and stably without central control, and critical loads are reliably powered by the grid.

[0089] At this time, a drop in grid voltage may lead to a relative overcapacity of photovoltaic power output, resulting in a tendency for reverse current to flow back to the grid along the path of important loads.

[0090] The first anti-backflow device 73 detects the backflow tendency, and the hardware interlocking circuit directly connects the tripping circuit of the second controllable circuit breaker 72. Without the participation of the energy management system (EMS), the second controllable circuit breaker 72 is physically forced to trip, ensuring that energy is prioritized for maintaining the local system.

[0091] At the same time, the energy storage unit automatically stops discharging.

[0092] This scenario represents the optimization of Mode C within the collaborative model.

[0093] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and inventive concept of the present invention, should be covered within the scope of protection of the present invention.

Claims

1. A photovoltaic-storage power supply control system, characterized in that: Power is supplied for at least two loads, and the power supply priority of the first load is higher than that of the second load; It includes a photovoltaic power generation unit, an energy storage unit, an energy management system, a power grid bus, a photovoltaic bus, a first load branch, and a second load branch; The first load branch is connected to the first load and includes a first power supply branch and a second power supply branch connected in parallel; a first controllable circuit breaker is connected in series on the first power supply branch and a first anti-reverse current device is connected in series on the second power supply branch; The second load branch is connected to the second load and includes a third power supply branch and a fourth power supply branch connected in parallel; a second controllable circuit breaker is connected in series on the third power supply branch, and a second anti-reverse current device is connected in series on the fourth power supply branch; The photovoltaic power generation unit is connected to the photovoltaic bus, and the energy storage unit is connected to the photovoltaic bus via a bidirectional converter; The first power supply branch and the third power supply branch are connected to the photovoltaic bus, and the second power supply branch and the fourth power supply branch are connected to the power grid bus; The energy management system is communicatively connected to the photovoltaic power generation unit, the energy storage unit, the first controllable circuit breaker, the second controllable circuit breaker, the first anti-backflow device, and the second anti-backflow device.

2. The photovoltaic-storage power supply control system according to claim 1, characterized in that: The reverse current alarm signal output terminal of the first anti-reverse current device is electrically connected to the tripping drive terminal of the second controllable circuit breaker through an independent hardware interlocking circuit, so that the first anti-reverse current device can directly drive the second controllable circuit breaker to trip when it detects reverse current.

3. The photovoltaic-storage power supply control system according to claim 1 or 2, characterized in that: It also includes metering devices installed on the first power supply branch, the second power supply branch, the third power supply branch, the fourth power supply branch, the power supply branch between the photovoltaic power generation unit and the photovoltaic bus, and the power supply branch between the energy storage unit and the photovoltaic bus; the metering devices are communicatively connected to the energy management system.

4. The photovoltaic-storage power supply control system according to claim 1 or 2, characterized in that: The photovoltaic-storage power supply control system is integrated into one grid-connected cabinet or distributed among multiple grid-connected cabinets.

5. A control method based on the photovoltaic-storage power supply control system of claim 1 or 2, executed by the energy management system, characterized in that: This includes basic operating modes and optimized collaborative modes; The basic operating modes include: S1, First Priority: The power generated by the photovoltaic power generation unit is preferentially used for the first load; S2, Second Priority: After meeting the electricity demand of the first load, the surplus photovoltaic power is prioritized to charge the energy storage unit. S3, Third Priority: After the energy storage unit is fully charged, if there is still residual power, it is supplied to the second load; and during the supply process, it is monitored in real time. If the residual power is less than or equal to 0, the power supply to the second load is immediately stopped. The optimized collaborative mode includes at least one of the following: Mode A: When the real-time power of the first load is lower than the set threshold and the photovoltaic power generation unit has output, the power supply branch of the second load is used as an energy damper. By adjusting the power supply to the second load, the power detected by the first anti-reverse current device is kept to zero. Mode B: When the power quality index of the first load's access point is detected to exceed the set limit, an instruction that takes precedence over the third priority operation is generated and executed, and the instruction includes at least disconnecting the second controllable circuit breaker. Mode C: When the communication of the energy management system is interrupted, if the power generation of the photovoltaic power generation unit is detected to be greater than the power of the first load, the energy storage unit is controlled to stop discharging.

6. The control method according to claim 5, characterized in that: In the basic operating mode, the power generation P0 of the photovoltaic power generation unit and the power P1 of the first load are acquired in real time. In step S1, it is determined whether the photovoltaic power generation meets the first load requirement; If P0≥P1, then the photovoltaic power generation unit supplies power to the first load and proceeds to step S2; If P0 < P1, the energy storage unit is controlled to discharge to make up for the power deficit of the first load; if the energy storage unit is still insufficient to make up for the power deficit of the first load after discharging, the power grid bus will supplement the power supply to the first load. In step S2, under the condition that P0≥P1, when the energy storage unit is rechargeable, it is controlled to charge at a power not greater than (P0-P1), and the remaining power P3 of the system after charging is calculated. In step S3, it is determined whether the remaining power P3 of the system is greater than 0; If so, the second controllable circuit breaker is closed to supply the remaining power P3 of the system to the second load; If not, or if the remaining power P3 of the system is not greater than 0 during the power supply process, the second controllable circuit breaker is immediately controlled to disconnect.

7. The control method according to claim 6, characterized in that: In step S2, if the rate of change of power generation of the photovoltaic power generation unit exceeds the positive threshold and the state of charge of the energy storage unit is higher than the set high threshold, then step S2 is skipped, P3=P0-P1 is set, and step S3 is entered.

8. The control method according to claim 6, characterized in that: In step S3, the power supplied to the second load does not exceed the smaller of P3 and the real-time power P4 of the second load.

9. The control method according to claim 6, characterized in that: In step S2, if the energy storage unit cannot be charged or is already full, then let P3 = P0 - P1.

10. The control method according to claim 5, characterized in that: In the basic operating mode: When the first controllable circuit breaker is closed and the second controllable circuit breaker is open, if the first anti-reverse current device detects reverse current, it closes the second controllable circuit breaker, and the reverse current power is absorbed by the second load. When both the first and second controllable circuit breakers are closed, if the first anti-backflow device and / or the second anti-backflow device detects backflow, the energy management system will sequentially control the reduction of the energy storage unit output, the reduction of the photovoltaic power generation unit output, and the disconnection of the first and second controllable circuit breakers based on the backflow information.

11. The control method according to claim 5, characterized in that: In Mode B, the power quality indicators include voltage sag, voltage surge, or harmonic content.

12. The control method according to claim 5, characterized in that: After mode B is triggered and executed, when the power quality indicators return to normal, the method controls the system to return to the basic operating mode logic.

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