Hierarchical control method and hierarchical control device for optical storage and charging direct current micro-grid

Abstract

The application provides a layered control method and device for a photovoltaic energy storage and charging direct-current micro-grid, which comprises the following steps: a cloud platform performs real-time monitoring and scheduling on the photovoltaic energy storage and charging direct-current micro-grid; when the voltage change rate of a direct-current bus is less than gamma, an edge controller controls the power of DC / DC of the photovoltaic energy storage and charging direct-current micro-grid according to the scheduling issued by the cloud platform, so that the power of photovoltaic, energy storage and load of the direct-current micro-grid is balanced; when the voltage change rate of the direct-current bus is greater than gamma or the voltage of the direct-current bus is in a first protection voltage range, an end device controls the power of the photovoltaic energy storage and charging direct-current micro-grid, so as to suppress the voltage fluctuation of the direct-current bus. The layered control of 'cloud-edge-end cooperation' is adopted, different control modes and control levels are adopted according to different working conditions, the direct-current bus power fluctuation can be quickly, safely and flexibly absorbed, the power quality is improved, and the system safety is ensured.

Description

Technical Field

[0001] This invention relates to the field of new energy technology, specifically to a hierarchical control method and a hierarchical control system for a photovoltaic-storage-charging DC microgrid. Background Technology

[0002] Currently, most photovoltaic-storage-charging DC microgrids adopt bidirectional VSC (Voltage Source Converter) connections to the power grid. Power shortfalls caused by large load fluctuations are shared by the AC distribution network and the photovoltaic-storage devices. This type of DC bus microgrid connects photovoltaics, energy storage, and loads via a DC bus, eliminating multiple AC-DC conversion processes and making the energy conversion process simple and efficient.

[0003] However, the above method has the following technical problems:

[0004] When the DC bus voltage fluctuates drastically, the inertial compensation strategy needs to be sent to the control center of the photovoltaic-storage charging station to control the discharge of photovoltaic and energy storage, i.e., V2G (Vehicle-to-Grid) reverse discharge, to smooth out the bus voltage fluctuations. The operation path is: obtain control strategy—control center sends it—DC / DC (direct current / direct current) execution. However, in actual operation, completing this set of compensation operations takes several seconds. In a rapidly changing DC bus microgrid, a response time of several seconds may cause equipment to trigger protection shutdown or even damage under extreme power surge conditions, leading to system paralysis. Summary of the Invention

[0005] To solve the above-mentioned technical problems, the first objective of this invention is to propose a hierarchical control method for a photovoltaic-storage-charging DC microgrid.

[0006] The second objective of this invention is to propose a hierarchical control system for a photovoltaic-storage-charging DC microgrid.

[0007] The technical solution adopted in this invention is as follows:

[0008] An embodiment of the first aspect of the present invention proposes a hierarchical control method for a photovoltaic-storage-charging DC microgrid, comprising the following steps: a cloud platform performs real-time monitoring and scheduling of the photovoltaic-storage-charging DC microgrid based on big data; when the DC bus voltage change rate is less than or equal to a first threshold γ, an edge controller performs power control on the DC / DC converter of the photovoltaic-storage-charging DC microgrid according to the schedule issued by the cloud platform, so as to balance the power of photovoltaic, energy storage and load in the photovoltaic-storage-charging DC microgrid; when the DC bus voltage change rate is greater than the first threshold γ or the DC bus voltage is within a first protection voltage range, end devices perform power regulation on the photovoltaic-storage-charging DC microgrid to smooth DC bus voltage fluctuations, wherein the end devices include: photovoltaic DC / DC converters and energy storage DC / DC converters.

[0009] The hierarchical control method for photovoltaic-storage-charging DC microgrids proposed in this invention may also have the following additional technical features:

[0010] According to one embodiment of the present invention, the edge controller performs power control on the DC / DC converter of the photovoltaic-storage-charging DC microgrid according to the schedule issued by the cloud platform. Specifically, the edge controller obtains the power of the gate meter and determines whether the photovoltaic-storage-charging DC microgrid is in an overcapacity state based on the power of the gate meter. The power of the gate meter includes: load power P. Load Photovoltaic power P PV and energy storage power P ES In the supercapacity state, P exists ES +P Load -P PV >P 超 P 超 An upper limit is set to prevent overcapacity. If the photovoltaic-storage-charging DC microgrid exceeds its capacity, the edge controller controls the microgrid to enter an overcapacity prevention mode. If the microgrid does not exceed its capacity, the edge controller further determines whether the microgrid is in a reverse current state based on the power measured at the gateway. In the reverse current state, P... ES +P Load -P PV <P 逆 P 逆 A lower limit is set to prevent reverse current. If the photovoltaic-storage-charging DC microgrid is in the reverse current state, the edge controller controls the photovoltaic-storage-charging DC microgrid to enter the anti-reverse current mode. If the photovoltaic-storage-charging DC microgrid is not in the reverse current state, the edge controller controls the photovoltaic-storage-charging DC microgrid to enter the energy balance mode.

[0011] According to one embodiment of the present invention, the edge controller controls the photovoltaic-storage-charging DC microgrid to enter the overcapacity protection mode, specifically including: acquiring the energy storage power P ES Determine whether P exists. ES >0; if P exists ESIf the value is greater than 0, the edge controller adjusts the energy storage DC / DC converter to increase the energy storage charging power P. ES =0; detect load power P Load If P Load ≤P 超 Then the edge controller controls the photovoltaic-storage-charging DC microgrid to enter energy balance mode; if P Load >P 超 The edge controller then adjusts the load power P. Load , making P Load =P 超 +P PV The edge controller determines whether the cloud platform has issued a dynamic capacity expansion strategy. If the cloud platform has not issued a dynamic capacity expansion strategy, the edge controller controls the photovoltaic-storage-charging DC microgrid to enter energy balance mode. If the cloud platform has issued the dynamic capacity expansion strategy, the edge controller controls the energy storage to discharge, thereby adjusting the energy storage power to P. ES =P 超 +P PV -P Load And determine (P) 超 +P PV -P Load If the energy storage power limit is exceeded, the edge controller controls the energy storage to maintain the maximum discharge power and reduces the load power P. Load To P Load =P 超 +P PV -P ES If P exists ES If ≤0, then the edge controller controls the load power P. Load Reduce to P Load =P 超 +P PV -P ES It also controls the photovoltaic-storage-charging DC microgrid to enter energy balance mode.

[0012] According to one embodiment of the present invention, the edge controller controls the photovoltaic-storage-charging DC microgrid to enter the anti-reverse current mode, specifically including: acquiring the energy storage power P ES Determine whether P exists. ES >0; if P exists ES If the value is greater than 0, the edge controller adjusts the energy storage power P. ES , making P ES =P PV -P Load +P 逆 And determine (P) PV -P Load +P 逆 ) Does it exceed the energy storage power limit? If it does not exceed the energy storage power limit, the edge controller adjusts the energy storage DC / DC to make PES =P PV -P Load +P 逆 If the energy storage power limit is exceeded, the edge controller maintains the energy storage DC / DC power at the extreme value and adjusts the photovoltaic DC / DC to keep the photovoltaic power P constant. PV Adjust to P PV =P ES +P Load -P 逆 If P exists ES ≤0, determine if P exists. PV ≤P Load -P 逆 If P exists PV ≤P Load -P 逆 Then the edge controller controls the photovoltaic-storage-charging DC microgrid to enter energy balance mode; if P PV >P Load -P 逆 Then the edge controller adjusts the photovoltaic power P PV =P Load -P 逆 The system determines whether the cloud platform has a green energy consumption strategy set. If the cloud platform has not set a green energy consumption strategy, the edge controller controls the photovoltaic-storage-charging DC microgrid to enter energy balance mode. If the cloud platform has set a green energy consumption strategy, the edge controller controls the energy storage charging and adjusts the energy storage power P. ES Adjust to P ES =P 逆 +P PV -P Load and judgment (P) 逆 +P PV -P Load Whether it exceeds the energy storage power limit; if (P 逆 +P PV -P Load If the energy storage power exceeds the limit, the edge controller will control the energy storage to maintain the maximum charging power and reduce the photovoltaic power P. PV To P PV =P ES +P Load -P 逆 Afterwards, the photovoltaic-storage-charging DC microgrid is controlled to enter the energy balance mode.

[0013] According to one embodiment of the present invention, an edge controller controls a photovoltaic-storage-charging DC microgrid to enter an energy balance mode, specifically including: if the photovoltaic system is operating in MPPT (Maximum Power Point Tracking) mode, and the energy storage is in charging mode, and the load power is constant, the edge controller adjusts the energy storage charging power according to the power fluctuation of the photovoltaic system and the power supply demand of the load. When the energy storage SOC reaches the upper limit, the photovoltaic system is limited to 0 power, and the energy storage switches to discharge mode to supply power to the load; if the photovoltaic system is operating in MPPT mode, and the energy storage is in discharge mode, and the load power is constant, the edge controller adjusts the energy storage discharge power according to the power fluctuation of the photovoltaic system and the power supply demand of the load. When the energy storage SOC reaches the lower limit, the energy storage system is limited to 0 power, and some loads are shut down; if the photovoltaic system is operating in MPPT mode, and the energy storage is in charging mode, and there is no load power, the edge controller controls the energy storage to absorb photovoltaic green electricity. When the energy storage SOC reaches the upper limit, the photovoltaic system is limited to zero power.

[0014] According to one embodiment of the present invention, the terminal device performs power regulation on the photovoltaic-storage-charging DC microgrid according to the schedule issued by the cloud platform. Specifically, this includes: when the photovoltaic system is operating in MPPT mode and the energy storage system is in charging mode, if the load power increases and the rate of change is greater than a second threshold, the energy storage DC / DC converter reduces its charging power within a set time to match the bus voltage until zero power; when the photovoltaic system is operating in MPPT mode and the energy storage system is in discharging mode, if the load power decreases and the rate of change is greater than a third threshold, the energy storage DC / DC converter reduces its discharging power within a set time to match the bus voltage until zero power; when the photovoltaic system is operating in MPPT mode and the energy storage system is in discharging mode, and the load power is constant, if the photovoltaic power increases and the rate of change is greater than a fourth threshold, the energy storage DC / DC converter reduces its discharging power within a set time to match the bus voltage until zero power. The photovoltaic (PV) power is adjusted according to the bus voltage until zero power is reached. When the PV is operating in MPPT mode and the energy storage is in charging mode, with a constant load, if the PV power increases and the rate of change is greater than the fourth threshold, the energy storage DC / DC will increase the charging power within a set time until the maximum power is reached. The PV DC / DC will then switch the PV to constant voltage mode within a set time, reducing the PV output. When the PV is operating in MPPT mode and the energy storage is in discharging mode, with a constant load power, if the PV power decreases and the rate of change is greater than the fifth threshold, the energy storage DC / DC will increase the discharging power within a set time until the maximum power is reached. When the PV is operating in MPPT mode and the energy storage is in charging mode, with a constant load power, if the PV power decreases and the rate of change is greater than the fifth threshold, the energy storage DC / DC will decrease the charging power within a set time until zero power is reached.

[0015] According to one embodiment of the present invention, the power regulation of the photovoltaic-storage-charging DC microgrid by the terminal device further includes: when the bus voltage is within the second protection voltage range, the photovoltaic DC / DC and energy storage DC / DC controllers trigger shutdown protection within a set time.

[0016] According to an embodiment of the present invention, the hierarchical control method of the above-mentioned photovoltaic-storage-charging DC microgrid further includes: the cloud platform establishing a DC / DC droop control strategy in the photovoltaic-storage-charging DC microgrid to provide virtual inertia for the system, wherein the droop control strategy adopts a combination of hyperbolic function and exponential function to enable adaptive adjustment of virtual inertia.

[0017] According to one embodiment of the present invention, the virtual inertia is adaptively adjusted using the following formula:

[0018]

[0019] Wherein, ΔU ref U is the droop intercept adjustment amount. ref_max and U ref_min The vertical intercepts U of the curves are respectively ref The maximum and minimum values ​​of U ref0 U is the initial intercept of the sag curve, k1 and k2 are the first virtual inertia adjustment parameter and the second virtual inertia adjustment parameter, respectively. dc This is the DC side voltage value.

[0020] According to one embodiment of the present invention, the photovoltaic-storage-charging DC microgrid is connected to the AC power grid through a phase-shifting transformer.

[0021] A second aspect of the present invention proposes a hierarchical control system for a photovoltaic-storage-charging DC microgrid, comprising: a cloud platform for real-time monitoring, data display, and scheduling of the photovoltaic-storage-charging DC microgrid based on big data; an edge controller for power control of the DC / DC converter of the photovoltaic-storage-charging DC microgrid according to a schedule issued by the cloud platform when the DC bus voltage change rate is less than or equal to a first threshold γ, so as to balance the power of the photovoltaic, energy storage, and load of the photovoltaic-storage-charging DC microgrid; and end devices, including a photovoltaic DC / DC converter and an energy storage DC / DC converter, for power regulation of the photovoltaic-storage-charging DC microgrid when the DC bus voltage change rate is greater than the first threshold γ or the DC bus voltage is within a first protection voltage range, so as to smooth DC bus voltage fluctuations.

[0022] The beneficial effects of this invention are:

[0023] This invention adopts a hierarchical control system of "cloud-edge-device collaboration". Different control modes and control levels are used according to different operating conditions to ensure that the system can quickly adjust the power supply with a millisecond-level response speed when there are sudden power changes. It can quickly, safely and flexibly absorb DC bus power fluctuations, improve power quality and ensure system safety.

[0024] This invention uses a phase-shifting transformer connected to the AC power grid. Through cloud-edge-terminal collaborative control, the microgrid can locally absorb bus voltage fluctuations caused by various reasons, without feeding the fluctuations back to the main grid. Moreover, the microgrid can operate independently and will not affect the stability of the AC power grid when connected to the grid. Attached Figure Description

[0025] Figure 1 This is a flowchart of a hierarchical control method for a photovoltaic-storage-charging DC microgrid according to an embodiment of the present invention;

[0026] Figure 2 This is a schematic diagram of the architecture of a photovoltaic-storage-charging DC microgrid according to an embodiment of the present invention;

[0027] Figure 3 This is a control flowchart of an edge controller according to an embodiment of the present invention;

[0028] Figure 4 This is a flowchart of the overcapacity prevention mode according to an embodiment of the present invention;

[0029] Figure 5 This is a flowchart of the anti-backflow mode according to an embodiment of the present invention;

[0030] Figure 6 This is a flowchart of an energy balance mode according to an embodiment of the present invention;

[0031] Figure 7 This is a control flowchart of an end device according to an embodiment of the present invention;

[0032] Figure 8 This is a virtual inertia control architecture diagram of a photovoltaic-storage-charging DC microgrid according to an embodiment of the present invention;

[0033] Figure 9 This is a schematic diagram of virtual inertia droop control for a photovoltaic-storage-charging DC microgrid according to an embodiment of the present invention. Detailed Implementation

[0034] The technical solutions of the embodiments of the present invention 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. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0035] Figure 1 This is a flowchart of a hierarchical control method for a photovoltaic-storage-charging DC microgrid according to an embodiment of the present invention. Figure 2 This is a schematic diagram of the architecture of a photovoltaic-storage-charging DC microgrid according to an embodiment of the present invention. Wherein, as... Figure 2 As shown, a photovoltaic-storage-charging DC microgrid can include: a cloud platform, an edge controller, and end devices. The end devices mainly include: photovoltaic DC / DC converters, photovoltaic combiner cabinets and photovoltaic modules, energy storage cabinets and energy storage DC / DC converters, phase-shifting transformers, rectifier cabinets, and loads, etc. The loads can be charging piles. The end devices can also include: smart meters, switches, and other equipment. The end devices can perform data acquisition and reporting, and coordinated control of current and voltage.

[0036] like Figure 1 As shown, the hierarchical control method for a photovoltaic-storage-charging DC microgrid includes the following steps:

[0037] S1, the cloud platform uses big data to monitor and schedule the photovoltaic-storage-charging DC microgrid in real time.

[0038] Specifically, the cloud platform uses big data to predict the electricity consumption of the load and the power supply of new energy sources, provides users with scheduling predictions, formulates and issues schedules according to different strategies, and performs real-time monitoring, diagnosis and alarm, panoramic analysis and orderly management of the photovoltaic, energy storage, charging and load in the microgrid system.

[0039] S2, when the DC bus voltage change rate is less than or equal to the first threshold γ, the edge controller performs power control on the DC / DC converter of the photovoltaic-storage-charging DC microgrid according to the schedule issued by the cloud platform, so as to balance the power of photovoltaic, energy storage and load in the photovoltaic-storage-charging DC microgrid.

[0040] Specifically, the edge controller, based on a locally deployed energy management system, collects and uploads the operating status and data of local devices, including the real-time SOC (State of Charge) of the battery, the maximum allowable charge / discharge power, and the maximum allowable boost / buck power of the DC / DC device. The edge controller can issue device start-up commands and power control commands, match the power balance between photovoltaics, energy storage, and loads, and receive and execute schedules issued by the cloud platform.

[0041] S3, when the DC bus voltage change rate is greater than the first threshold γ or the DC bus voltage is within the first protection voltage range, the end equipment performs local DC / DC regulation of the power of the photovoltaic-storage-charging DC microgrid to smooth the DC bus voltage fluctuation. The end equipment includes: photovoltaic DC / DC and energy storage DC / DC.

[0042] In a specific embodiment of the present invention, the first threshold γ and the first protection voltage range are preset in advance according to the actual situation. For example, the first protection voltage can be (630V, 660V) and (850V, 870V).

[0043] Specifically, the cloud platform uses big data to predict load power consumption and renewable energy power supply, providing users with scheduling forecasts. It then formulates schedules based on different strategies and distributes them to edge controllers or end devices. When the DC bus microgrid power fluctuation is small, the microgrid is in a state of basic energy balance. At this time, the edge controller performs system power control, executes the schedules issued by the cloud platform, and sends power adjustment commands to the local DC / DC converter to regulate the power of photovoltaics, energy storage, and loads. This balances the power of photovoltaics, energy storage, and loads in the photovoltaic-energy storage-charging DC microgrid, reducing the burden on the local DC / DC converter and lowering the capacity of end devices. However, when the DC bus microgrid power fluctuation is large, or when the DC bus voltage enters the 630-660V or 850-870V range, the DC bus voltage fluctuates drastically, and the microgrid is in a state of energy imbalance. In this case, the local end devices autonomously adjust the power based on the actual situation, prioritizing equipment protection. This rapidly adjusts the power of photovoltaics or energy storage, smooths out bus voltage fluctuations, and quickly responds to avoid equipment damage. Therefore, by adopting a hierarchical control system of "cloud-edge-device collaboration", different regulation modes and control levels are used according to different operating conditions to ensure that the system can quickly regulate the power fluctuations with a millisecond-level response speed. This can quickly, safely and flexibly absorb DC bus power fluctuations, improve power quality, and ensure system safety.

[0044] According to one embodiment of the present invention, such as Figure 3 As shown, the edge controller performs power control on the DC / DC converter of the photovoltaic-storage-charging DC microgrid according to the schedule issued by the cloud platform, specifically including:

[0045] S21, the edge controller obtains the power from the gateway meter and determines whether the photovoltaic-storage-charging DC microgrid is in an overcapacity state based on the gateway meter power. The gateway meter power includes: load power P. Load Photovoltaic power P PV and energy storage power P ES P exists in the overcapacity state. ES +P Load -P PV >P 超 P 超 An upper limit is set to prevent exceeding the capacity.

[0046] S22, if the photovoltaic-storage-charging DC microgrid exceeds its capacity, the edge controller will control the photovoltaic-storage-charging DC microgrid to enter the overcapacity protection mode.

[0047] S23, if the photovoltaic-storage-charging DC microgrid is not overcapacitated, the edge controller further determines whether the photovoltaic-storage-charging DC microgrid is in a reverse current state based on the power meter reading at the gateway. In the reverse current state, P exists. ES +P Load -P PV <P 逆 , for P 逆 A lower limit is set to prevent backflow.

[0048] S24, if the photovoltaic-storage-charging DC microgrid is in the reverse current state, the edge controller controls the photovoltaic-storage-charging DC microgrid to enter the anti-reverse current mode.

[0049] S25. If the photovoltaic-storage-charging DC microgrid is not in a reverse current state, the edge controller controls the photovoltaic-storage-charging DC microgrid to enter the energy balance mode.

[0050] In other words, if P ES +P Load -P PV >P 超 This is not true; further judgment is needed regarding P. ES +P Load -P PV <P 逆 Whether it is true, if P ES +P Load -P PV <P 逆 If the condition is met, it is determined whether the photovoltaic-storage-charging DC microgrid is in a reverse flow state, and the edge controller controls the photovoltaic-storage-charging DC microgrid to enter the energy balance mode.

[0051] The specific control strategies for the overcapacity prevention mode, the backflow prevention mode, and the energy balance mode are described below with reference to specific embodiments.

[0052] In one specific embodiment of the present invention, such as Figure 4 As shown, the edge controller controls the photovoltaic-storage-charging DC microgrid to enter the overcapacity protection mode, specifically including:

[0053] S221, Obtain the energy storage power P ES Determine whether P exists. ES >0.

[0054] S222, if P exists ES If the value is greater than 0, the edge controller adjusts the energy storage DC / DC converter to increase the energy storage charging power P. ES It is 0.

[0055] S223, detect load power P Load If P Load ≤P 超 Then the edge controller controls the photovoltaic-storage-charging DC microgrid to enter the energy balance mode.

[0056] S224, if P Load >P 超 The edge controller then adjusts the load power P. Load , making P Load =P 超 +P PV .

[0057] S225, the edge controller determines whether the cloud platform issues a dynamic capacity expansion policy.

[0058] S226 If the cloud platform does not issue a dynamic capacity expansion strategy, the edge controller will control the photovoltaic-storage-charging DC microgrid to enter the energy balance mode.

[0059] S227, If the cloud platform issues a dynamic capacity expansion strategy, the edge controller controls the energy storage discharge to adjust the energy storage power so that P ES =P 超 +P PV -P Load And determine (P) 超 +P PV -P Load Whether it exceeds the energy storage power limit.

[0060] S228, if the energy storage power limit is exceeded, the edge controller controls the energy storage to maintain the maximum discharge power and reduces the load power P. Load To P Load =P 超 +P PV -P ES .

[0061] S229, if P exists ES If ≤0, then the edge controller controls the load power P. Loa Reduce to P Load =P 超 +P PV -P ES It also controls the photovoltaic-storage-charging DC microgrid to enter energy balance mode.

[0062] Specifically, is the photovoltaic-storage-charging DC microgrid in an overcapacity state? If P ES <0, reduce load power, let P Load =P 超 +P PV -P ES If the overcapacity prevention is successful, exit the overcapacity prevention mode and enter the energy balance mode.

[0063] If P ES >0, the edge controller adjusts the energy storage charging power to P. ES =0, at this time the load power is detected, if P Load ≤P 超 If P is successful, the overcapacity prevention mode is completed, and the system exits the overcapacity prevention mode and enters the energy balance mode. Load >P 超 Then adjust the load power P Load , let P Load =P 超 +P PV At this point, the cloud platform determines whether the dynamic capacity expansion strategy has been triggered. If the dynamic capacity expansion strategy is not triggered, the over-capacity protection is successful, and the system exits the over-capacity protection mode and enters the energy balance mode. If the cloud platform determines that the dynamic capacity expansion strategy has been triggered, the edge controller controls the energy storage to discharge, adjusting the energy storage power to P. ES =P 超 +P PV -P Load If P at this time 超 +P PV -P Load If the energy storage power limit has been exceeded, the energy storage will maintain its maximum discharge power while reducing the load power to P. Load =P 超 +P PV -P ES .

[0064] According to one embodiment of the present invention, such as Figure 5 As shown, the edge controller controls the photovoltaic-storage-charging DC microgrid to enter the anti-reverse current mode, specifically including:

[0065] S241, Obtain energy storage power P ES Determine whether P exists. ES >0.

[0066] S242, if P exists ES If the value is greater than 0, the edge controller adjusts the energy storage power P. ES , making P ES =P PV -P Load +P 逆 And determine (P) PV -P Load +P 逆 Whether it exceeds the energy storage power limit.

[0067] S243, if the energy storage power limit is not exceeded, the edge controller adjusts the energy storage DC / DC converter to make P ES =P PV -P Load +P 逆 .

[0068] S244, if the energy storage power limit is exceeded, the edge controller maintains the energy storage DC / DC power at the extreme value and adjusts the photovoltaic DC / DC to keep the photovoltaic power P constant. PV Adjust to P PV =P ES +P Load -P 逆 .

[0069] S245, if P exists ES ≤0, determine if P exists. PV ≤P Load -P 逆 .

[0070] S246, if P exists PV ≤P Load -P 逆 Then the edge controller controls the photovoltaic-storage-charging DC microgrid to enter the energy balance mode.

[0071] Specifically, if P PV ≤P Load -P 逆 If the anti-backflow mode is successfully completed, the anti-backflow mode will be exited and the energy balance mode will be entered.

[0072] S247, if P PV >P Load -P 逆 The edge controller then adjusts the photovoltaic power P. PV =P Load -P 逆 And determine whether the cloud platform has set a green electricity consumption strategy.

[0073] S248 If the cloud platform does not set a green electricity consumption strategy, the edge controller will control the photovoltaic-storage-charging DC microgrid to enter the energy balance mode.

[0074] S249, If the cloud platform has set a green electricity consumption strategy, the edge controller controls the charging of the energy storage and adjusts the energy storage power P. ES Adjust to P ES =P 逆 +P PV -P Load and judgment (P) 逆 +P PV -P Load Whether it exceeds the energy storage power limit.

[0075] S2410, if (P) 逆 +P PV -P Load If the energy storage power exceeds the limit, the edge controller will control the energy storage to maintain the maximum charging power and reduce the photovoltaic power P.PV To P PV =P ES +P Load -P 逆 Afterwards, the photovoltaic-storage-charging DC microgrid is controlled to enter the energy balance mode.

[0076] Specifically, reduce photovoltaic power P PV To P PV =P ES +P Load -P 逆 At this point, the anti-backflow mode is successfully completed, and the anti-backflow mode is exited, entering the energy balance mode.

[0077] According to one embodiment of the present invention, such as Figure 6 As shown, the edge controller controls the photovoltaic-storage-charging DC microgrid to enter the energy balance mode, specifically including:

[0078] S251 If the photovoltaic is operating in MPPT mode and the energy storage is in charging mode, and the load power is constant, the edge controller adjusts the energy storage charging power according to the power fluctuation of the matching photovoltaic and the power supply demand of the load. When the energy storage SOC reaches the upper limit, the photovoltaic is limited to 0 power and the energy storage switches to discharge mode to supply power to the load.

[0079] S252 If the photovoltaic is operating in MPPT mode and the energy storage is in discharge mode, and the load power is constant, the edge controller adjusts the energy storage discharge power according to the power fluctuation of the photovoltaic and the power supply demand of the load. When the energy storage SOC reaches the lower limit, the energy storage is limited to 0 power and some loads are shut down.

[0080] S253 If the photovoltaic is operating in MPPT mode and the energy storage is in charging mode with no load power, the edge controller controls the energy storage to consume photovoltaic green electricity. When the energy storage SOC reaches the upper limit, the photovoltaic is limited to zero power.

[0081] The normal operating range of the bus voltage is 660-850V. When the bus voltage fluctuates drastically, with the rate of change exceeding the threshold γ, or when the bus voltage enters the 630-660V or 850-870V range, the end-device DC / DC converter performs system power control to stabilize the voltage. The following describes, with specific examples, how the end-device regulates the power of the photovoltaic-storage-charging DC microgrid according to the schedule issued by the cloud platform.

[0082] According to one embodiment of the present invention, such as Figure 7 As shown, the terminal equipment performs power regulation on the photovoltaic-storage-charging DC microgrid according to the schedule issued by the cloud platform, specifically including:

[0083] S31, the photovoltaic is operating in MPPT mode and the energy storage is in charging mode. If the load power increases and the rate of change is greater than the second threshold, the energy storage DC / DC will reduce the charging power within a set time to match the bus voltage until zero power.

[0084] The time setting can be 100ms.

[0085] S32, when the photovoltaic is operating in MPPT mode and the energy storage is in discharge mode, if the load power decreases and the rate of change is greater than the third threshold, the energy storage DC / DC will reduce the discharge power within a set time to match the bus voltage until zero power.

[0086] S33, the photovoltaic works in MPPT mode and the energy storage is in discharge mode, the load power is constant. If the photovoltaic power increases and the rate of change is greater than the fourth threshold, the energy storage DC / DC will reduce the discharge power within a set time to match the bus voltage until zero power.

[0087] Specifically, the photovoltaic system operates in MPPT mode, the energy storage system is in discharge mode, the load is constant, and the photovoltaic power suddenly increases, causing the bus voltage to rise rapidly. The energy storage DC / DC converter reduces the discharge power within 100ms to match the bus voltage until the power reaches 0.

[0088] S34, the photovoltaic works in MPPT mode and the energy storage is in charging mode, the load is constant. If the photovoltaic power increases and the rate of change is greater than the fourth threshold, the energy storage DC / DC will increase the charging power within a set time until the maximum power. The photovoltaic DC / DC will switch the photovoltaic to constant voltage mode within a set time and reduce the photovoltaic output.

[0089] Specifically, the photovoltaic system operates in MPPT mode, the energy storage system is in charging mode, the load is constant, and the photovoltaic power suddenly increases, causing the bus voltage to rise rapidly. The energy storage DC / DC increases the charging power within 100ms until it reaches the maximum power. Within 100ms, the photovoltaic DC / DC switches the photovoltaic system to constant voltage mode to reduce the photovoltaic output.

[0090] S35, the photovoltaic works in MPPT mode and the energy storage is in discharge mode, the load power is constant. If the photovoltaic power decreases and the rate of change is greater than the fifth threshold, the energy storage DC / DC will increase the discharge power within a set time until the maximum power.

[0091] Specifically, the photovoltaic system operates in MPPT mode, the energy storage system is in discharge mode, the load is constant, the photovoltaic power suddenly decreases, causing the bus voltage to drop rapidly, and the energy storage DC / DC increases the discharge power within 100ms until it reaches the maximum power.

[0092] S36, the photovoltaic works in MPPT mode and the energy storage is in charging mode, the load power is constant. If the photovoltaic power decreases and the rate of change is greater than the fifth threshold, the energy storage DC / DC will reduce the charging power within a set time until the power is zero.

[0093] Specifically, the photovoltaic system operates in MPPT mode, the energy storage system is in charging mode, the load is constant, and a sudden drop in photovoltaic power causes a rapid drop in bus voltage. The energy storage DC / DC converter then reduces its charging power to zero within 100ms.

[0094] According to one embodiment of the present invention, such as Figure 7 As shown, the hierarchical control method of the photovoltaic-storage-charging DC microgrid described above may also include: S37, when the bus voltage is within the second protection voltage range, the photovoltaic DC / DC and energy storage DC / DC controls trigger shutdown protection within a set time.

[0095] Specifically, if the bus voltage continues to change and the photovoltaic-storage voltage exceeds the protection voltage range (below 630V or above 870V), the system enters a shutdown protection mode. The photovoltaic and storage DC / DC converters will trigger shutdown protection within 100ms. During shutdown protection, when the bus voltage recovers from below 630V to between 630-660V, or from above 870V to between 850-870V, the DC / DC converter is in a protective shutdown state and does not accept commands from the energy management system. When the bus voltage further recovers to the normal operating voltage of 660-850V, the photovoltaic-storage DC / DC converter enters a restart standby state and can perform voltage regulation according to commands from the energy management system.

[0096] In summary, the hierarchical control method employed in this invention allows for control at the "edge" level by the energy management system when DC bus voltage fluctuations are small, reducing the workload of the local DC / DC converter and allowing for a reduction in DC / DC equipment capacity, thus offering economic flexibility. When fluctuations are large, the local DC / DC converter directly controls the photovoltaic and energy storage systems according to the control strategy, providing rapid response with millisecond-level reaction speeds, thereby ensuring the safety of the equipment and system. In extreme cases such as excessive microgrid voltage changes, the local DC / DC converter quickly responds and automatically shuts down. Once the bus voltage returns to normal, the energy management system coordinates the photovoltaic and load power, determining that it is safe to start before issuing a command to the DC / DC converter to start, thus ensuring equipment safety.

[0097] like Figure 2 As shown, the photovoltaic-storage-charging DC microgrid of the present invention is connected to the AC power grid through a phase-shifting transformer. Through cloud-edge-end collaborative control, the microgrid itself can work with the photovoltaic and energy storage to absorb the fluctuations locally caused by various reasons, without feeding the fluctuations back to the main power grid. Moreover, the microgrid can operate independently and will not affect the stability of the AC power grid when connected to the grid.

[0098] Understandably, this solution employs different control modes and levels at the cloud-edge-device level based on varying operating conditions to quickly, safely, and flexibly absorb DC bus power fluctuations. The control logic under different operating conditions was explained above. In actual operation, regardless of whether the control mode is from the cloud platform, edge controller, or end device, commands are sent to the end devices, which then receive and execute the commands. The difference lies in the timing of the DC bus microgrid power fluctuations. When the DC bus microgrid power fluctuations are small, the edge controller issues commands based on different operating conditions to reduce the local DC / DC load and decrease the end device capacity. Conversely, when the DC bus microgrid power fluctuations are large, the end devices directly control the system locally for rapid response and to prevent equipment damage.

[0099] Specifically, in the control algorithm, in order to solve the low inertia problem of DC microgrids and improve the stability of bus voltage, the angular frequency, electromagnetic power and virtual moment of inertia of the virtual synchronous machine in the AC system are compared with the DC voltage, DC current and virtual inertia coefficient in the DC system, respectively. This releases the potential inertia of the DC microgrid. In essence, it virtualizes an equivalent capacitance on the DC side of the grid with a value much larger than the actual capacitance to enhance the system inertia, so that the system has sufficient ability to suppress bus voltage fluctuations.

[0100] By establishing a droop control strategy for the DC / DC converter in the energy storage system, the rapid charging and discharging of the photovoltaic energy storage device by the DC / DC converter can be flexibly controlled, providing virtual inertia for the system, delaying the deviation time of the DC bus voltage, reducing the rate of voltage drop, providing strong support for the dispatching of the DC distribution network system, and comprehensively improving the power quality of the DC distribution network.

[0101] In photovoltaic (PV) systems, the operating mode is dynamically adjusted based on the DC bus voltage and the State of Charge (SOC) of the energy storage system. To ensure the energy storage system functions effectively when microgrid power changes, the SOC is defined within a reasonable range. min ≤SOC≤SOC max ).

[0102] When the State of Charge (SOC) reaches the lower limit of the battery capacity. min When, that is, SOC = SOC min The energy storage system shuts down after discharging all its power. If the DC bus voltage U dc When the voltage is below its normal range, the photovoltaic system operates in MPPT mode, rapidly boosting the DC bus voltage with maximum power output. Once the bus voltage Udc returns to its normal range, the photovoltaic system switches to constant voltage mode. When SOC... min <SOC<SOC max When, if the DC bus voltage U dcWhen the voltage is below its normal range, the photovoltaic system operates in constant voltage mode, increasing the output power by increasing the photovoltaic output voltage reference value in constant voltage mode until the bus voltage returns to the normal range. When the State of Charge (SOC) reaches the upper limit of the power capacity... max When, that is, SOC = SOC max The energy storage system is shut down because it is fully charged. If the DC bus voltage U dc When the voltage is above its normal range, the photovoltaic system operates in constant voltage mode, reducing the output power by lowering the reference value of the photovoltaic output reference voltage in constant voltage mode until the bus voltage returns to the normal range.

[0103] The formula for calculating the inertial time constant of a DC microgrid is:

[0104]

[0105] In the formula, H dmg The inertial time constant of the DC microgrid is represented by W. ei Represented as parallel capacitor C i Stored energy; S Nci C i The capacity base value; U dc is the DC side voltage value, and n is a positive integer.

[0106] according to Figure 8 When the DC microgrid is disturbed, the energy storage system, based on virtual inertia hierarchical control, rapidly charges and discharges to provide inertia for the system, virtually creating a large capacitor, C, on the DC side. vir The power relationship on the DC capacitor side of the DC microgrid can be obtained as follows:

[0107]

[0108] In the formula, P PV P ES P Load These represent the photovoltaic output power, the energy storage output power under virtual inertial hierarchical control, and the power required by the load, respectively; C is the actual DC-side capacitance value.

[0109] U dc When kept constant, P PV +P ES =P Load Established.

[0110] Therefore, after adding virtual inertial hierarchical control, the total capacitance on the DC side increases to (C+C). vir At this point, the system's inertial time constant becomes:

[0111] When the energy storage system adopts droop control based on PU characteristics, the following formula applies:

[0112]

[0113] In the formula, U dc_ref U is the reference value for the control voltage of the DC / DC converter in the energy storage system. ref The y-intercept represents the droop curve; 1 / k is the droop coefficient.

[0114] like Figure 9 As shown in the figure, assuming a is the initial operating point of the system, when the load power increases to P... b When the DC bus voltage is detected to be lower than the expected value, the control curve is shifted upward to point c, the vertical intercept increases, the reference voltage of the energy storage system's DC / DC equipment increases, and the output current of the DC / DC equipment increases to support the bus voltage; when the load power drops to P... d When the DC bus voltage is detected to be higher than the expected value, the control curve is shifted downward to point e, the vertical intercept decreases, the reference voltage of the DC / DC device of the energy storage system decreases, the output current of the DC / DC device decreases or even becomes negative, and the energy storage system charges to store the system's redundant power.

[0115] Furthermore, let the droop intercept adjustment amount ΔU ref and du dc / dt combined, making it follow du dc / dt changes; when du dc When / dt is positive, decrease U ref To prevent the voltage from increasing further, U should be increased if necessary. ref Therefore, we can conclude that: In the formula, U ref0 k is the initial intercept of the sag curve. d To adjust the parameters, and k d >0.

[0116] Combining the two equations above, we get:

[0117] Combining the definition of droop control, we get:

[0118] The left side of the equation above represents the power of the virtual capacitor added to the energy storage DC / DC converter after droop control, i.e.:

[0119] Eliminate du on both sides dc / dt yields the expression for calculating the virtual capacitance:

[0120] In this invention, an algorithm combining hyperbolic and exponential functions is used to achieve adaptive adjustment of virtual inertia, meeting practical and flexible requirements. When the voltage change rate is small, the virtual capacitor participates in the work more quickly, shortening the duration of transient fluctuations in DC bus voltage; when the voltage change rate is large, it ensures that the virtual capacitor provides virtual inertial support to the DC microgrid to the maximum extent.

[0121] The adaptive adjustment algorithm for virtual inertia is as follows:

[0122]

[0123] Wherein, ΔU ref U is the droop intercept adjustment amount. ref_max and U ref_min The vertical intercepts U of the curves are respectively ref The maximum and minimum values ​​of U ref0 U is the initial intercept of the sag curve, k1 and k2 are the first virtual inertia adjustment parameter and the second virtual inertia adjustment parameter, respectively. dc This is the DC side voltage value.

[0124] Draw a secant line through the origin to represent the virtual capacitance of the curve obtained from the adaptive algorithm described above. By utilizing the properties of hyperbolic and exponential functions, the magnitude of the provided virtual inertia can be effectively adjusted adaptively.

[0125] In summary, the hierarchical control method for the photovoltaic-storage-charging DC microgrid according to embodiments of the present invention adopts a "cloud-edge-end collaborative" hierarchical control, employing different regulation modes and control levels according to different operating conditions. This ensures rapid regulation with millisecond-level response speed during power surges, enabling fast, safe, and flexible absorption of DC bus power fluctuations, improving power quality, and guaranteeing system safety. By using a phase-shifting transformer connected to the AC grid and through cloud-edge-end collaborative control, the microgrid itself can coordinate with photovoltaic and energy storage to locally absorb bus voltage fluctuations caused by various reasons, without feeding the fluctuations back to the main grid. Furthermore, the microgrid can operate independently and will not affect the stability of the AC grid when connected to the grid.

[0126] Furthermore, this invention also proposes a hierarchical control system for a photovoltaic-storage-charging DC microgrid. Since the system embodiment of this invention is the same as the method embodiment described above, details not disclosed in the system embodiment can be found in the method embodiment described above, and will not be repeated here.

[0127] like Figure 2 As shown, the hierarchical control system of the photovoltaic-storage-charging DC microgrid according to an embodiment of the present invention includes: a cloud platform, an edge controller, and end devices.

[0128] The cloud platform is used for real-time monitoring and scheduling of the photovoltaic-storage-charging DC microgrid based on big data; the edge controller is used to control the power of the DC / DC converter of the photovoltaic-storage-charging DC microgrid according to the schedule issued by the cloud platform when the DC bus voltage change rate is less than or equal to the first threshold γ, so as to balance the power of photovoltaic, energy storage and load in the photovoltaic-storage-charging DC microgrid; the end devices include photovoltaic DC / DC and energy storage DC / DC, which are used to regulate the power of the photovoltaic-storage-charging DC microgrid when the DC bus voltage change rate is greater than the first threshold γ or the DC bus voltage is within the first protection voltage range, so as to smooth the DC bus voltage fluctuation.

[0129] The hierarchical control system of the photovoltaic-storage-charging DC microgrid according to an embodiment of the present invention adopts a "cloud-edge-end collaborative" hierarchical control. Different regulation modes and control levels are used according to different operating conditions to ensure that the microgrid can quickly regulate the power supply with a millisecond-level response speed during power surges. It can quickly, safely, and flexibly absorb DC bus power fluctuations, improve power quality, and ensure system safety. The microgrid is connected to the AC grid using a phase-shifting transformer. Through cloud-edge-end collaborative control, the microgrid itself can coordinate with the photovoltaic and storage systems to absorb the bus voltage fluctuations caused by various reasons locally, without feeding the fluctuations back to the main grid. Moreover, the microgrid can operate independently and will not affect the stability of the AC grid when connected to the grid.

[0130] In the description of this invention, references to terms such as "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the invention. In this specification, illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Any process or method description in the flowcharts or otherwise herein can be understood as representing a module, segment, or portion of code comprising one or more executable instructions for implementing custom logical functions or processes, and the scope of preferred embodiments of the invention includes additional implementations in which functions may be performed not in the order shown or discussed, including substantially simultaneously or in reverse order according to the functions involved, as should be understood by those skilled in the art to which embodiments of the invention pertain.

[0131] The logic and / or steps represented in the flowchart or otherwise described herein, for example, can be considered as a sequenced list of executable instructions for implementing logical functions, and can be embodied in any computer-readable medium for use by, or in conjunction with, an instruction execution system, apparatus, or device (such as a computer-based system, a processor-included system, or other system that can fetch and execute instructions from, an instruction execution system, apparatus, or device). For the purposes of this specification, "computer-readable medium" can be any means that can contain, store, communicate, propagate, or transmit programs for use by, or in conjunction with, an instruction execution system, apparatus, or device. More specific examples (a non-exhaustive list) of computer-readable media include: an electrical connection having one or more wires (electronic device), a portable computer disk drive (magnetic device), random access memory (RAM), read-only memory (ROM), erasable and editable read-only memory (EPROM or flash memory), fiber optic devices, and portable optical disc read-only memory (CDROM). Alternatively, the computer-readable medium may be paper or other suitable media on which the program can be printed, since the program can be obtained electronically, for example, by optically scanning the paper or other medium, followed by editing, interpreting, or otherwise processing as necessary, and then stored in a computer memory.

[0132] Those skilled in the art will understand that all or part of the steps of the methods in the above embodiments can be implemented by a program instructing related hardware. The program can be stored in a computer-readable storage medium, and when executed, the program includes one or a combination of the steps of the method embodiments.

[0133] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A hierarchical control method for a photovoltaic-storage-charging DC microgrid, characterized in that, Includes the following steps: The cloud platform uses big data to monitor and schedule the photovoltaic-storage-charging DC microgrid in real time. When the DC bus voltage change rate is less than or equal to the first threshold γ, the edge controller performs power control on the DC / DC converter of the photovoltaic-storage-charging DC microgrid according to the schedule issued by the cloud platform, so as to balance the power of photovoltaic, energy storage and load in the photovoltaic-storage-charging DC microgrid. When the DC bus voltage change rate is greater than the first threshold γ or the DC bus voltage is within the first protection voltage range, the terminal equipment performs power regulation on the photovoltaic-storage-charging DC microgrid to smooth DC bus voltage fluctuations. The terminal equipment includes: photovoltaic DC / DC and energy storage DC / DC. The cloud platform establishes a DC / DC droop control strategy in the photovoltaic-storage-charging DC microgrid to provide virtual inertia for the system. The droop control strategy uses a combination of hyperbolic and exponential functions to enable adaptive adjustment of the virtual inertia. The edge controller performs power control on the DC / DC converter of the photovoltaic-storage-charging DC microgrid according to the schedule issued by the cloud platform, specifically including: The edge controller acquires the power from the gateway meter and determines whether the photovoltaic-storage-charging DC microgrid is in an overcapacity state based on the gateway meter power. The gateway meter power includes: load power P. Load Photovoltaic power P PV and energy storage power P ES In the supercapacity state, P exists ES +P Load -P PV >P 超 P 超 An upper limit is set to prevent overcapacity; If the photovoltaic-storage-charging DC microgrid exceeds its capacity, the edge controller will control the photovoltaic-storage-charging DC microgrid to enter the overcapacity protection mode. If the photovoltaic-storage-charging DC microgrid is not overcapacitated, the edge controller further determines whether the photovoltaic-storage-charging DC microgrid is in a reverse current state based on the power measured at the gateway. In the reverse current state, P exists. ES +P Load -P PV <P 逆 P 逆 A lower limit is set to prevent backflow; If the photovoltaic-storage-charging DC microgrid is in the reverse current state, the edge controller controls the photovoltaic-storage-charging DC microgrid to enter the anti-reverse current mode; If the photovoltaic-storage-charging DC microgrid is not in the reverse flow state, the edge controller controls the photovoltaic-storage-charging DC microgrid to enter the energy balance mode.

2. The hierarchical control method for a photovoltaic-storage-charging DC microgrid according to claim 1, characterized in that, The edge controller controls the photovoltaic-storage-charging DC microgrid to enter overcapacity protection mode, specifically including: Obtain energy storage power P ES Determine whether P exists. ES >0; If P exists ES If the value is greater than 0, the edge controller adjusts the energy storage DC / DC converter to increase the energy storage charging power P. ES =0; Detect load power P Load If P Load ≤P 超 Then the edge controller controls the photovoltaic-storage-charging DC microgrid to enter the energy balance mode; If P Load >P 超 The edge controller then adjusts the load power P. Load , making P Load =P 超 +P PV ; The edge controller determines whether the cloud platform has issued a dynamic capacity expansion policy; If the cloud platform does not issue a dynamic capacity expansion strategy, the edge controller will control the photovoltaic-storage-charging DC microgrid to enter the energy balance mode. If the cloud platform issues the aforementioned dynamic capacity expansion strategy, the edge controller controls the energy storage discharge to adjust the energy storage power so that P ES =P 超 +P PV -P Load And determine (P) 超 +P PV -P Load Does it exceed the energy storage power limit? If the energy storage power limit is exceeded, the edge controller controls the energy storage to maintain the maximum discharge power and reduces the load power P. Load To P Load =P 超 +P PV -P ES ; If P exists ES If ≤0, then the edge controller controls the load power P. Load Reduce to P Load =P 超 +P PV -P ES It also controls the photovoltaic-storage-charging DC microgrid to enter energy balance mode.

3. The hierarchical control method for a photovoltaic-storage-charging DC microgrid according to claim 1, characterized in that, The edge controller controls the photovoltaic-storage-charging DC microgrid to enter anti-reverse current mode, specifically including: Obtain energy storage power P ES Determine whether P exists. ES >0; If P exists ES If the value is greater than 0, the edge controller adjusts the energy storage power P. ES , making P ES =P PV -P Load +P 逆 And determine (P) PV -P Load +P 逆 Does it exceed the energy storage power limit? If the energy storage power limit is not exceeded, the edge controller adjusts the energy storage DC / DC converter to make P ES =P PV -P Load +P 逆 ; If the energy storage power limit is exceeded, the edge controller maintains the energy storage DC / DC power at the extreme value and adjusts the photovoltaic DC / DC to keep the photovoltaic power P constant. PV Adjust to P PV =P ES +P Load -P 逆 ; If P exists ES ≤0, determine if P exists. PV ≤P Load -P 逆 ; If P exists PV ≤P Load -P 逆 Then the edge controller controls the photovoltaic-storage-charging DC microgrid to enter the energy balance mode; If P PV >P Load -P 逆 Then the edge controller adjusts the photovoltaic power P PV =P Load -P 逆 And determine whether the cloud platform has set a green electricity consumption strategy; If the cloud platform does not set a green electricity consumption strategy, the edge controller will control the photovoltaic-storage-charging DC microgrid to enter the energy balance mode; If the cloud platform has already set up a green energy consumption strategy, the edge controller will control the charging of the energy storage and adjust the energy storage power P. ES Adjust to P ES =P 逆 +P PV -P Load and judgment (P) 逆 +P PV -P Load Does it exceed the energy storage power limit? If (P) 逆 +P PV -P Load If the energy storage power exceeds the limit, the edge controller will control the energy storage to maintain the maximum charging power and reduce the photovoltaic power P. PV To P PV =P ES +P Load -P 逆 Afterwards, the photovoltaic-storage-charging DC microgrid is controlled to enter the energy balance mode.

4. The hierarchical control method for a photovoltaic-storage-charging DC microgrid according to claim 1, characterized in that, The edge controller controls the photovoltaic-storage-charging DC microgrid to enter energy balance mode, specifically including: If the photovoltaic (PV) operates in MPPT mode and the energy storage is in charging mode, and the load power is constant, the edge controller adjusts the energy storage charging power according to the power fluctuation of the matching PV and the power supply demand of the load. When the energy storage SOC reaches the upper limit, the PV is limited to 0 power, and the energy storage switches to discharge mode to supply power to the load. If the photovoltaic system operates in MPPT mode and the energy storage is in discharge mode, and the load power is constant, the edge controller adjusts the energy storage discharge power according to the power fluctuation of the photovoltaic system and the power supply demand of the load. When the energy storage SOC reaches the lower limit, the energy storage is limited to 0 power and some loads are shut down. If the photovoltaic system operates in MPPT mode and the energy storage is in charging mode with no load power, the edge controller controls the energy storage to consume the photovoltaic green electricity. When the energy storage SOC reaches the upper limit, the photovoltaic power is limited to zero.

5. The hierarchical control method for a photovoltaic-storage-charging DC microgrid according to claim 1, characterized in that, The terminal equipment performs power regulation on the photovoltaic-storage-charging DC microgrid according to the schedule issued by the cloud platform, specifically including: The photovoltaic system operates in MPPT mode and the energy storage system is in charging mode. If the load power increases and the rate of change is greater than the second threshold, the energy storage DC / DC will reduce the charging power within a set time to match the bus voltage until the power is zero. When the photovoltaic system is operating in MPPT mode and the energy storage system is in discharge mode, if the load power decreases and the rate of change is greater than the third threshold, the energy storage DC / DC will reduce the discharge power within a set time to match the bus voltage until the power is zero. The photovoltaic system operates in MPPT mode and the energy storage system is in discharge mode. The load power is constant. If the photovoltaic power increases and the rate of change is greater than the fourth threshold, the energy storage DC / DC will reduce the discharge power within a set time to match the bus voltage until the power is zero. The photovoltaic system operates in MPPT mode and the energy storage system is in charging mode. The load is constant. If the photovoltaic power increases and the rate of change is greater than the fourth threshold, the energy storage DC / DC will increase the charging power within a set time until the maximum power is reached. The photovoltaic DC / DC will switch the photovoltaic system to constant voltage mode within a set time and reduce the photovoltaic output. The photovoltaic system operates in MPPT mode and the energy storage system is in discharge mode. The load power is constant. If the photovoltaic power decreases and the rate of change is greater than the fifth threshold, the energy storage DC / DC will increase the discharge power within a set time until the maximum power is reached. The photovoltaic system operates in MPPT mode and the energy storage system is in charging mode. The load power is constant. If the photovoltaic power decreases and the rate of change is greater than the fifth threshold, the energy storage DC / DC will reduce the charging power within a set time until the power is zero.

6. The hierarchical control method for a photovoltaic-storage-charging DC microgrid according to claim 5, characterized in that, The terminal equipment performs power regulation on the photovoltaic-storage-charging DC microgrid, and also includes: When the bus voltage is within the second protection voltage range, the photovoltaic DC / DC and energy storage DC / DC controllers will trigger shutdown protection within a set time.

7. The hierarchical control method for a photovoltaic-storage-charging DC microgrid according to any one of claims 1-6, characterized in that, The photovoltaic-storage-charging DC microgrid is connected to the AC power grid via a phase-shifting transformer.

8. A hierarchical control system for a photovoltaic-storage-charging DC microgrid, characterized in that, include: The cloud platform is used for real-time monitoring and scheduling of photovoltaic-storage-charging DC microgrids based on big data. An edge controller is used to control the power of the DC / DC converter of the photovoltaic-storage-charging DC microgrid according to the schedule issued by the cloud platform when the DC bus voltage change rate is less than or equal to a first threshold γ, so as to balance the power of photovoltaic, energy storage and load in the photovoltaic-storage-charging DC microgrid. The terminal equipment includes a photovoltaic DC / DC converter and an energy storage DC / DC converter. The terminal equipment is used to perform power regulation on the photovoltaic-storage-charging DC microgrid when the DC bus voltage change rate is greater than the first threshold γ or the DC bus voltage is within the first protection voltage range, so as to smooth the DC bus voltage fluctuation. The cloud platform is also used to: establish a DC / DC droop control strategy in a photovoltaic-storage-charging DC microgrid to provide virtual inertia for the system, wherein the droop control strategy uses a combination of hyperbolic and exponential functions to enable adaptive adjustment of the virtual inertia; The edge controller is specifically used for: acquiring the power of the gateway meter, and determining whether the photovoltaic-storage-charging DC microgrid is in an overcapacity state based on the gateway meter power. The gateway meter power includes: load power P. Load Photovoltaic power P PV and energy storage power P ES In the supercapacity state, P exists ES +P Load -P PV >P 超 P 超 An upper limit is set to prevent overcapacity. If the photovoltaic-storage-charging DC microgrid exceeds its capacity, the edge controller controls the microgrid to enter an overcapacity prevention mode. If the microgrid does not exceed its capacity, the edge controller further determines whether the microgrid is in a reverse current state based on the power measured at the gateway. In the reverse current state, P... ES +P Load -P PV <P 逆 P 逆 A lower limit is set to prevent reverse current. If the photovoltaic-storage-charging DC microgrid is in the reverse current state, the edge controller controls the photovoltaic-storage-charging DC microgrid to enter the anti-reverse current mode. If the photovoltaic-storage-charging DC microgrid is not in the reverse current state, the edge controller controls the photovoltaic-storage-charging DC microgrid to enter the energy balance mode.

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