A power distribution station-oriented light-storage-load collaborative power supply recovery control device and method

Abstract

The application discloses a kind of light-storage-load collaborative power supply recovery control device and method for distribution station, it is related to electric power engineering and control automation technical field.The application is after power station power failure, central control equipment detects energy storage state of charge and terminal load power, when energy storage state of charge is greater than first threshold value, control network type energy storage system promotes voltage stability, and makes key load by hierarchical load switch and is incorporated;When energy storage state of charge is greater than or equal to second threshold value and load total power is less than preset output power, control net type photovoltaic system switches to load following mode, and does not satisfy then switches to maximum power tracking mode, and makes important load and is incorporated after stabilization;When energy storage state of charge is greater than third threshold value, ordinary load is incorporated, and the distribution station grid-connected operation of load level recovery power supply is realized.The application reduces distribution station grid-connected time, improves distribution station power supply recovery speed, simultaneously also avoids secondary power failure in the process of grid connection, improves security.

Description

Technical Field

[0001] This invention relates to the field of power engineering and control automation technology, and in particular to a photovoltaic-storage-load coordinated power supply restoration control device and method for power distribution substations. Background Technology

[0002] With the continuous increase in the penetration rate of renewable energy, substations, as the terminal link of the power system, occupy a crucial position. Furthermore, due to the frequent occurrence of extreme disasters, substations are highly susceptible to environmental factors that can affect the power supply to end users. Therefore, the complexity and vulnerability of substation operation are becoming increasingly prominent, and the power supply resilience of substations urgently needs to be enhanced. During the operation of the power system, when a substation is disconnected from the main grid due to a fault, a cascading problem can easily occur, leading to simultaneous power loss at multiple nodes and the lack of local restarting power. The traditional power restoration mode of emergency generator vehicles + manual inspection is limited by factors such as dispatch efficiency, road accessibility, and fuel replenishment, resulting in a significant increase in power restoration time and making it difficult to meet users' needs for continuous power supply.

[0003] To improve the recovery capability of substations after failures, existing technologies mainly focus on two directions: First, distribution network reconfiguration technology, which achieves load restoration of multi-node systems by adjusting the status of segment / tie switches in real time and optimizing the access range of distributed power sources. However, such methods are mostly designed for complex multi-node distribution networks and are not specific enough for single substations, making it difficult to adapt to the simplified topology scenarios of terminal substations. Second, mobile energy storage application technology, which provides emergency power supply by leveraging the plug-and-play characteristics of mobile energy storage. Although it has certain advantages over traditional diesel generators, power restoration depends on the on-site deployment of equipment, and the restoration speed has not been fundamentally improved.

[0004] With the advancement of technology and the accelerated construction of new power systems, distributed photovoltaic (PV) and energy storage systems (ESS) have become core technologies for improving power restoration capabilities after substation failures. However, the current application of PV and ESS in power restoration scenarios at terminal distribution substations (DS) still faces significant technical shortcomings. These shortcomings directly lead to existing solutions failing to balance restoration speed, equipment safety, and renewable energy utilization. Specific technical challenges are as follows: 1. In existing technologies, PV inverters mostly operate in maximum power point tracking (MPPT) mode, aiming only to maximize power generation, lacking dynamic coordination with energy storage status and load demand. When the substation is in islanded operation, if the PV output continuously exceeds the load consumption (such as during peak daytime PV generation or off-peak periods), the excess energy will be forcibly charged to the ESS (Energy Storage System). However, most ESS lack a real-time overcharge protection linkage mechanism, causing the SOC (State of Charge) to easily exceed the safety threshold (such as exceeding 90%), triggering the risk of battery thermal runaway, and even causing secondary power outages.

[0005] 2. After the substation is disconnected from the main grid, the PV trips due to loss of voltage support. At this time, the PLL integrator retains the integral value of the error before the power loss, instead of resetting it to zero. If not handled in time, this integral value will cause the PLL output to have a fixed deviation frequency, causing the PV output phase to continuously deviate from the true phase of the system (i.e., "cumulative integral error"). When the ESS rebuilds the voltage, the PV cannot reconnect to the grid due to the large phase difference, requiring manual intervention to reset the PLL, thus prolonging the recovery time. A similar situation occurred in an industrial park in Haining, Zhejiang Province, where the PV lost voltage and, due to a PLL failure, the grid connection restoration took more than 15 minutes. The accumulation of integral error hinders the reconnection of the substation to the grid, prolonging the substation's grid connection time; moreover, manual intervention and reset introduce errors. Under the urgent task of restoring power supply, the grid connection deviation caused by manual operation is further amplified. This not only fails to guarantee the rapid restoration of power supply and grid connection of the substation but also leads to a decrease in the accuracy of PV grid connection, delaying the substation's grid connection.

[0006] Furthermore, if the ESS is directly connected to the unloaded PCC at its rated voltage (1pu) during startup, the controller will detect that the actual voltage is much lower than the reference value and instruct the inverter to inject a large amount of capacitive reactive power. At the same time, the ESS's PI controller is prone to overshoot, causing a further surge in reactive power, triggering a momentary overvoltage in the PCC and causing a momentary voltage surge, which may lead to a secondary power outage.

[0007] Based on the above, existing methods for restoring power and achieving grid connection when a substation experiences a power outage or grid disconnection suffer from numerous problems, including a lack of solutions tailored to individual substations, low deployment efficiency and utilization in traditional energy-dependent scenarios, poor interoperability of equipment during grid connection restoration which may lead to secondary power outages, and low accuracy and efficiency in grid connection. Therefore, a safe and efficient technical solution for restoring power to a substation and achieving grid connection is urgently needed, addressing the pain points of existing technologies while promoting the development of power engineering and power control automation. Summary of the Invention

[0008] In view of this, the present invention provides a photovoltaic-storage-load coordinated power supply restoration control device and method for substations, which can reduce the time from the substation being disconnected from the main grid to the restoration of power supply and reconnection to the grid, improve the power supply restoration rate of substations, improve energy utilization, and eliminate the secondary power outage that may be caused by relying on traditional methods to restore power supply to substations, thereby improving grid connection security.

[0009] To achieve the above objectives, the present invention adopts the following technical solution: A photovoltaic-storage-load coordinated power supply restoration control device for substations, wherein the control device is installed between the substation and the terminal loads, including critical loads, important loads, and ordinary loads; The control devices include central control equipment, grid-connected energy storage system, grid-connected photovoltaic system, and graded load switches; The central control equipment is installed in the substation and is connected to the grid-type energy storage system, the grid-connected photovoltaic system and the graded load switch respectively. The grid-type energy storage system, the grid-connected photovoltaic system and the graded load switch are connected to each other through a common connection point. The graded load switch is connected to the terminal load. Before the power outage at the substation, the control device was operating normally; After a power outage at a substation: The central control equipment is used to detect the power of the grid-type energy storage system, obtain the energy storage state of charge, and acquire the terminal load power; When the energy storage state of charge is greater than the first threshold, the grid-type energy storage system is started linearly and ramped up according to the preset rate to increase the output voltage. When the output voltage of the grid-type energy storage system is stable, the critical load is connected through the graded load switch, while the important load and ordinary load are kept disconnected. The grid-type energy storage system supplies power to the critical load. The grid-connected photovoltaic system is dynamically controlled to switch modes based on the energy storage state of charge and the terminal load power. When the energy storage state of charge is greater than or equal to the second threshold and the current total load power is less than the preset output power, the grid-connected photovoltaic system is controlled to switch to load following mode. If the conditions are not met, it is switched to maximum power tracking mode. When the grid-connected photovoltaic system is stable, important loads are connected through graded load switches, while ordinary loads remain disconnected. The grid-connected energy storage system and the grid-connected photovoltaic system supply power to critical and important loads. When the state of charge of the energy storage exceeds the third threshold, ordinary loads are connected through the graded load switch. The grid-type energy storage system and the grid-connected photovoltaic system supply power to the terminal loads, thus restoring the power supply of the substation.

[0010] Optionally, the first threshold is 30%, the second threshold is the energy storage full threshold of the grid-type energy storage system, the third threshold is 50%, and the preset output power is the maximum output power of the grid-type photovoltaic system in maximum power point tracking mode.

[0011] The aforementioned device, optionally, is a grid-connected photovoltaic system, including: a grid-connected photovoltaic inverter, a photovoltaic array, a phase-locked loop module, an energy storage detector, and an active / reactive power controller.

[0012] Optionally, the phase-locked loop module of the aforementioned device is used to immediately lock out the grid-connected photovoltaic system to avoid the accumulation of integral errors when the power distribution station is de-energized and the grid-connected energy storage system loses voltage; and to immediately unlock the system when the output voltage of the grid-connected energy storage system stabilizes and critical loads are connected.

[0013] Optionally, the active / reactive power controller described above is used to suppress voltage fluctuations in grid-connected photovoltaic systems.

[0014] Optionally, when the grid-connected photovoltaic system is in load-following mode, the DC side tracks the load power through a PI controller, involving the following formula: ; In the formula, P pv_ref To match the DC-side output reference power of the grid-connected photovoltaic system, K P , K I For reference power PI controller proportional and integral coefficients, P pv_pu To match the per-unit value of the actual output power of the grid-connected photovoltaic system, P L This represents the current total load power. s For the Laplace operator; On the AC side, reactive power is adjusted by voltage deviation to suppress voltage fluctuations. The relevant formula is: ; In the formula, Q pv_ref To connect with the reactive power on the AC side of the grid-connected photovoltaic system, K Pq , K Iq These are the parameters for the reactive power PI controller. U dc_ref This is the DC voltage reference value. U dc_pu This is the actual per-unit value of the DC voltage.

[0015] Optionally, the preset rate of the aforementioned device is positively correlated with the short-term overvoltage tolerance value of the common connection point.

[0016] Optionally, the aforementioned device may monitor voltage fluctuations and frequency deviations at the point of common coupling when critical loads, important loads, and ordinary loads are connected.

[0017] A method for photovoltaic-storage-load coordinated power supply restoration control for substations, applied to the photovoltaic-storage-load coordinated power supply restoration control device for substations described in any of the above-mentioned embodiments, includes the following steps: S1. Status detection step: Obtain the energy storage charge status and terminal load power of the grid-type energy storage system after the power outage of the substation. S2, Energy storage start-up steps: When the energy storage state of charge is greater than the first threshold, the grid-type energy storage system is started up with a linear ramp to increase the voltage according to the preset rate control, and the voltage and frequency are monitored in real time. S3. Critical load connection procedure: When the voltage and frequency of the grid-type energy storage system are stable, critical loads are connected through graded load switches. S4. Photovoltaic grid connection steps: Dynamically control the mode switching of the grid-connected photovoltaic system according to the energy storage state of charge and the terminal load power. When the energy storage state of charge is greater than or equal to the second threshold and the current total load power is less than the preset output power, control the grid-connected photovoltaic system to switch to load following mode. If the conditions are not met, switch to maximum power point tracking mode. S5. Important load connection procedure: After the grid-connected photovoltaic system is stable, the important load is connected through the graded load switch. S6. Important load connection procedure: When the energy storage state of charge is greater than the third threshold, the ordinary load is connected through the graded load switch, and the power supply of the substation is fully restored.

[0018] As can be seen from the above technical solution, compared with the prior art, the present invention provides a photovoltaic-storage-load coordinated power supply restoration control device and method for power distribution substations, which has the following beneficial effects: (1) Orderly and efficient: The present invention has a fully automated phased grid restoration process without manual intervention or external equipment support, realizing the orderly connection of critical loads, important loads and ordinary loads. At the same time, the present invention controls the dynamic coordination of energy storage, photovoltaic and load systems through central control equipment, shortens the power supply restoration time and improves the restoration efficiency after grid outage. (2) Power supply is restored to stability: The grid-type energy storage system starts linearly and ramps up to avoid secondary power outages caused by instantaneous overvoltage due to direct grid connection, thus meeting the voltage quality requirements for islanded operation; at the same time, the central control equipment suppresses voltage fluctuations caused by load switching, photovoltaic grid connection and other operations through the power controller of the grid-connected photovoltaic system, so that the voltage changes at each stage are smooth and without sudden changes. (3) Accurate power supply restoration: After the power supply to the substation is cut off, the phase-locked loop is locked to clear the error integral value, so as to avoid the cumulative interference of the integral to the grid. The loop is unlocked after the grid-type energy storage system to be built establishes a stable voltage, so as to ensure that the photovoltaic grid is connected quickly and accurately. (4) Flexible control strategy: The linear ramp-up rate of the grid-type energy storage system to be constructed is flexibly adjusted according to the voltage withstand value of the point of common coupling, taking into account both safety and recovery efficiency; (5) Excellent engineering adaptability: The load classification access logic and control parameters (such as the various thresholds and PI controller parameters used as the basis for central control equipment control) can adapt to the differences in load composition of different substations. It does not need to rely on complex network reconstruction or external communication. It can be achieved through coordination by local central control equipment, resulting in low project implementation cost and high feasibility. Attached Figure Description

[0019] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on the provided drawings without creative effort.

[0020] Figure 1 This invention discloses a schematic diagram of a photovoltaic-storage-load coordinated power supply restoration control device for power distribution substations; Figure 2 This is a schematic diagram of the voltage ramp-up start-up control principle of a grid-type energy storage system disclosed in an embodiment of the present invention; Figure 3 This is a schematic diagram of the mode switching logic of a grid-connected photovoltaic system disclosed in an embodiment of the present invention; Figure 4 This is a timing diagram of substation grid connection restoration disclosed in an embodiment of the present invention; Figure 5 This is a schematic diagram of the power distribution station topology simulation model disclosed in an embodiment of the present invention; Figure 6 This is a schematic diagram of voltage fluctuations during the grid connection recovery process disclosed in an embodiment of the present invention; Figure 7 This is a schematic diagram of frequency fluctuations during the grid connection recovery process disclosed in an embodiment of the present invention; Figure 8 This is a graph showing the change in active power of each device during the grid restoration process disclosed in an embodiment of the present invention. Figure 9 This is a graph showing the change in SOC of energy storage during the grid connection recovery process disclosed in an embodiment of the present invention. Figure 10 This is a comparison curve of the change in energy storage SOC during the recovery process without coordinated control, as disclosed in an embodiment of the present invention. Figure 11 This is a comparison diagram of overvoltage levels at different preset rates disclosed in the embodiments of the present invention; Figure 12 This is a schematic diagram of the collaborative recovery control principle of the photovoltaic-storage-charge system disclosed in an embodiment of the present invention; Among them, 1-central control equipment, 2-grid-type energy storage system, 3-grid-connected photovoltaic system, and 4-tiered load switch. Detailed Implementation

[0021] 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.

[0022] In this application, relational terms such as "first" and "second" are used merely to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. The terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitation, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element.

[0023] See Figure 1 As shown, this invention discloses a photovoltaic-storage-load coordinated power supply restoration control device for substations. The control device is installed between the substation and the terminal loads, which include critical loads, important loads, and ordinary loads. The control device includes a central control device 1, a grid-type energy storage system 2, a grid-connected photovoltaic system 3, and a graded load switch 4. The central control device 1 is installed in the substation and is connected to the grid-type energy storage system 2, the grid-connected photovoltaic system 3, and the graded load switch 4. The grid-type energy storage system 2, the grid-connected photovoltaic system 3, and the graded load switch 4 are connected to each other through a point of common coupling (PCC). The graded load switch 4 is connected to the terminal loads.

[0024] Before the power outage at the substation, the control device was operating normally.

[0025] After the power supply to the substation is cut off: the central control device 1 is used to detect the power of the grid-type energy storage system 2, obtain the energy storage state of charge, and acquire the terminal load power.

[0026] The central control device 1 is also used to control the linear ramp start of the grid-type energy storage system 2 and increase the output voltage according to the preset rate when the energy storage state of charge is greater than the first threshold. When the output voltage of the grid-type energy storage system 2 is stable, the critical load is connected through the graded load switch 4, while the important load and ordinary load are kept disconnected, and the grid-type energy storage system 2 supplies power to the critical load.

[0027] The central control device 1 is also used to dynamically control the mode switching of the grid-connected photovoltaic system 3 according to the energy storage state of charge and the terminal load power. When the energy storage state of charge is greater than or equal to the second threshold and the current total load power is less than the preset output power, the central control device 1 controls the grid-connected photovoltaic system 3 to switch to the load following mode. If the conditions are not met, it switches to the maximum power tracking mode. When the grid-connected photovoltaic system 3 is stable, the important load is connected through the graded load switch 4, while the ordinary load remains disconnected. The grid-connected energy storage system 2 and the grid-connected photovoltaic system 3 supply power to the critical load and the important load.

[0028] The central control device 1 is also used to control the connection of ordinary loads through the graded load switch 4 when the energy storage state of charge is greater than the third threshold, so that the grid-type energy storage system 2 and the grid-connected photovoltaic system 3 can supply power to the terminal loads and realize the full restoration of power supply to the substation.

[0029] Furthermore, the first threshold is 30%, the second threshold is the energy storage full threshold of the grid-type energy storage system, the third threshold is 50%, and the preset output power is the maximum output power of the grid-connected photovoltaic system when it is in maximum power point tracking mode.

[0030] This invention addresses the current state of power restoration in substations by proposing the aforementioned photovoltaic-storage-load coordinated power restoration control device. It uses a closed-loop process of signal interaction, status judgment, and action execution as the operational basis for substation power restoration. The invention is further explained from three aspects: energy storage voltage ramp-up control, photovoltaic dual-mode switching coordinated control, and graded load orderly restoration control, as detailed below: 1. Energy storage voltage ramp start control Grid-based energy storage system 2 includes: a grid-based energy storage inverter, an energy storage battery pack, a PCC voltage sensor, and an energy storage circuit breaker. (Refer to...) Figure 2 The grid-type energy storage system 2 adopts a grid-type control mode and a V / f control strategy. Specifically, by adding voltage-frequency droop control to the grid-type energy storage inverter, the recovery speed of the inverter's start-up voltage control is limited, and then fine-tuning is made to achieve the V / f control strategy. As the main reference power source for the islanded system, the grid-type energy storage inverter can provide stable voltage and frequency support for power restoration. In addition, a linear voltage ramp start-up method is adopted to avoid instantaneous overvoltage caused by controller overshoot, thereby completely solving the voltage surge problem when energy storage is directly connected to the grid, laying a stable foundation for subsequent load and photovoltaic access.

[0031] Startup logic of grid-type energy storage system 2: After receiving the start signal, grid-type energy storage system 2 is controlled by central control device 1, and the voltage reference value U at the output terminal of grid-type energy storage inverter is adjusted according to the PCC voltage detected by the PCC voltage sensor. ba_refThe voltage linearly increases from 0 to 1 pu, ensuring that the instantaneous energy storage output voltage is consistent with the PCC voltage, thus avoiding voltage over-limit caused by the injection of a large amount of capacitive reactive power.

[0032] Adjustable ramp rate: The preset rate can be flexibly set according to the PCC's overvoltage tolerance and recovery speed requirements. If the PCC has high short-term overvoltage tolerance, the ramp rate can be increased to shorten the voltage settling time.

[0033] Furthermore, the preset rate is positively correlated with the short-term overvoltage tolerance value of the common connection point.

[0034] 2. Photovoltaic dual-mode switching coordinated control

[0035] The grid-connected photovoltaic system 3 includes: a grid-connected photovoltaic inverter, a photovoltaic array, a phase-locked loop module, an energy storage detector, and an active / reactive power controller. The photovoltaic inverter adopts a grid-connected control mode, dynamically switching between Maximum Power Point Tracking (MPPT) mode and Load Following (LF) mode based on the energy storage state of charge (SOC) and load power demand.

[0036] The grid-connected photovoltaic system 3 adds a voltage outer loop and reactive power regulation loop. It uses an active / reactive power controller to suppress voltage fluctuations during power restoration. Furthermore, when a power outage at the substation causes photovoltaic voltage loss, the phase-locked loop (PLL) module immediately locks the PLL to prevent the accumulation of integral errors and ensure rapid and accurate grid connection of the photovoltaic system. The PLL is a closed-loop electronic system based on feedback control that dynamically adjusts the frequency and phase of the output signal to maintain precise synchronization with the input reference signal.

[0037] Furthermore, the phase-locked loop module is used to immediately lock out the grid-connected photovoltaic system to avoid the accumulation of integral errors when the power distribution station is de-energized and the grid-connected energy storage system loses voltage; and to immediately unlock the system when the output voltage of the grid-connected energy storage system stabilizes and critical loads are connected.

[0038] Furthermore, the active / reactive power controller is used to suppress voltage fluctuations in grid-connected photovoltaic systems.

[0039] Reference Figure 3 The mode switching of the grid-connected photovoltaic system is achieved through a mode switching signal. S t Triggered, switches to LF mode when the following conditions are met; otherwise, runs in MPPT mode: ; In the formula, S et For the energy storage full charging threshold, Ppv_max To achieve the maximum output power of a grid-connected photovoltaic system in 3 MPPT mode, P L This represents the current total load power.

[0040] Furthermore, when the grid-connected photovoltaic system 3 is in load-following mode, the DC side tracks the load power through a PI controller, involving the following formula: ; In the formula, P pv_ref To match the DC-side output reference power of the grid-connected photovoltaic system, K P , K I For reference power PI controller proportional and integral coefficients, P pv_pu To match the per-unit value of the actual output power of the grid-connected photovoltaic system, s For the Laplace operator.

[0041] On the AC side, reactive power is adjusted by voltage deviation to suppress voltage fluctuations. The relevant formula is: ; In the formula, Q pv_ref To connect with the reactive power on the AC side of the grid-connected photovoltaic system, K Pq , K Iq These are the parameters for the reactive power PI controller. U dc_ref This is the DC voltage reference value. U dc_pu This is the actual per-unit value of the DC voltage.

[0042] 3. Tiered load recovery control

[0043] According to demand and importance, loads are classified into critical loads, important loads, and ordinary loads. Critical loads are those whose power outage would directly threaten personal safety, trigger social crises, or major safety accidents. Examples include operating rooms, fire emergency equipment, and central control centers. Important loads whose power outage would cause significant economic losses or paralysis of public services. Examples include emergency lighting and elevators in shopping malls, ticketing systems in high-speed rail stations, and assembly line equipment in factories. Ordinary loads whose power outage only affects local use and has no significant social or economic impact, such as residential electricity, warehouse lifting equipment, and shopping mall billboards. This invention prioritizes the power supply to critical loads from the perspective of load importance, achieving orderly grid connection of tiered loads.

[0044] During the orderly grid connection process, the central control device 1 connects different levels of loads in stages based on the energy storage SOC status and system voltage / frequency stability criteria; and after each stage of load connection, it monitors the PCC voltage fluctuation (ΔU≤0.07 pu) and frequency deviation (Δf≤0.02 Hz) in real time to ensure system stability.

[0045] Furthermore, the central control equipment monitors voltage fluctuations and frequency deviations at the point of common coupling when critical loads, important loads, and ordinary loads are connected.

[0046] Reference Figure 4 The horizontal axis indicates the time change, and the specific process of orderly recovery of graded loads is as follows: 1) Normal operation phase: The substation maintains connection with the main grid, and the grid-connected energy storage system 2 and the grid-connected photovoltaic system 3 operate in the conventional mode to provide stable power supply to the terminal load. The substation is in normal grid-connected operation. 2) Fault Triggering and Total Shutdown Phase: All circuit breakers in the substation trip, and the photovoltaic phase-locked loop is locked; 3) Energy storage start-up preparation stage: Detect the remaining power of the grid-type energy storage system 2. When SOC > 30%, the condition is met. Based on ramp control, start the voltage at a rate of 1 pu / s and linearly increase the output voltage from 0. 4) Critical load recovery phase: After voltage and frequency stabilize, critical loads are connected; 5) Grid-connected photovoltaic stage: Unlock the photovoltaic PLL and connect the grid-connected photovoltaic system 3 to the system. The grid-connected photovoltaic system 3 switches between MPPT and LF according to the energy storage SOC status and the current total load power. 6) Restoration of critical loads: After the photovoltaic system is connected to the grid and stabilized, critical loads are restored; 7) Normal load restoration: To ensure the priority power supply rights of critical and important loads, normal loads will only be connected in batches when the energy storage SOC is ≥ 50%.

[0047] Figure 4 In China, energy storage black start refers to the process by which, after a power system outage due to a fault, the entire power grid is in a "black" state. Without relying on external power sources, the system gradually restores power to the plant and starts the main generating units through its internal power sources with self-starting capabilities, thus restoring power supply to the entire grid.

[0048] The present invention also discloses the following specific embodiments to verify the effectiveness of the technical solutions disclosed in the present invention. A simulation model is built on the PSCAD / EMTDC platform, such as... Figure 5 As shown, it includes a 100 kW photovoltaic array, a 250 kW energy storage system, a 25 kW critical load, a 75 kW important load, and a 250 kW general load.

[0049] like Figure 7 As shown, the horizontal axis represents time and the vertical axis represents power. In this embodiment, a fully automated phased recovery is adopted without manual intervention or external equipment support, achieving energy storage startup within 30 seconds, restoration of critical load power supply within 9 seconds, and completion of all load access within 21 seconds.

[0050] Compared to existing power distribution network reconfiguration technologies (which are mostly designed for multi-node systems and have poor adaptability to single power distribution stations) and fixed energy storage solutions without coordinated control, this invention reduces the power restoration time after a power distribution station failure from minutes to seconds, improves the restoration efficiency by more than 80%, and significantly reduces power outage losses for users.

[0051] The embodiments disclosed in this invention not only have high grid-connection recovery efficiency but also excellent stability, with minimal voltage and frequency fluctuations during operation. (Refer to...) Figure 6 As shown, the grid-connected energy storage system adopts a 1 pu / s voltage ramp start-up to avoid instantaneous overvoltage caused by direct grid connection (the instantaneous overvoltage reaches 1.5 pu and lasts for about 50 ms without ramp control). In this embodiment of the invention, the voltage fluctuation of the PCC is always controlled within ±0.07 pu, meeting the voltage quality requirements for islanded operation. The grid-connected photovoltaic system further suppresses voltage fluctuations caused by load switching, photovoltaic grid connection, and other operations through voltage outer loop reactive power regulation, making the voltage changes at each stage smooth and without abrupt changes. (Refer to...) Figure 8 As shown, during the grid connection process, the PCC frequency maintained a system frequency deviation of ≤±0.02 Hz throughout the process, with no frequency drift or instability, ensuring that all terminal loads could operate normally.

[0052] Reference Figure 10 Without coordinated control, the energy storage SOC will continuously exceed the threshold limit. To avoid damage from overcharging, in this embodiment of the invention, the grid-connected photovoltaic system dynamically switches its operating mode based on the energy storage SOC and load demand, referring to... Figure 9 and combined Figure 10 It can be seen that when the energy storage SOC is greater than 90% and the photovoltaic output is greater than the load, the photovoltaic system can automatically switch to LF mode to limit the output power (such as only outputting 25 kW to match the critical load) and avoid overcharging of the energy storage.

[0053] Reference Figure 11 In this embodiment of the invention, the preset rate used to control the linear ramp start-up of the grid-type energy storage system can be flexibly adjusted: when the PCC short-term overvoltage tolerance is high, the preset rate can be set to 10 pu / s to shorten the voltage settling time by 0.08 seconds; when the system is sensitive to overvoltage, the rate of 1 pu / s is maintained to reserve engineering error redundancy, taking into account both safety and recovery efficiency.

[0054] and Figure 1Corresponding to the photovoltaic-storage-load coordinated power supply restoration control device for power distribution substations shown, this invention also discloses a photovoltaic-storage-load coordinated power supply restoration control method for power distribution substations, applied to... Figure 1 The illustrated power restoration control device for a power distribution substation, comprising the following steps: S1. Status detection step: Obtain the energy storage charge status and terminal load power of the grid-type energy storage system after the power outage of the substation. S2, Energy storage startup steps: When the energy storage state of charge is greater than the first threshold, the grid-type energy storage system is started up with a linear ramp to increase the voltage according to the preset rate control, and the voltage and frequency are monitored in real time. S3. Critical load connection procedure: When the voltage and frequency of the grid-type energy storage system are stable, critical loads are connected through graded load switches. S4. Photovoltaic grid connection steps: Dynamically control the mode switching of the grid-connected photovoltaic system according to the energy storage state of charge and the terminal load power. When the energy storage state of charge is greater than or equal to the second threshold and the current total load power is less than the preset output power, control the grid-connected photovoltaic system to switch to load following mode. If the conditions are not met, switch to maximum power point tracking mode. S5. Important load connection procedure: After the grid-connected photovoltaic system is stable, the important load is connected through the graded load switch. S6. Important load connection procedure: When the energy storage state of charge is greater than the third threshold, the ordinary load is connected through the graded load switch, and the power supply of the substation is fully restored.

[0055] The control method proposed in this invention is implemented as follows: Figure 12 As shown, it comprises three core modules: voltage control for the energy storage GFM inverter (Grid-Forming Inverter), power control for the photovoltaic GFL inverter (Grid-Following Inverter), and hierarchical load orderly access control. The core logic is as follows: by adding a voltage-frequency droop stage to the voltage control of the energy storage GFM inverter, the output voltage of the energy storage dynamically adjusts with changes in the system frequency; the photovoltaic GFL inverter senses the system power balance status by monitoring changes in the PCC voltage; and by further adding a load following controller based on a PI controller to the photovoltaic inverter power controller, coordinated power restoration of photovoltaic-energy storage-load is achieved after a substation fault.

[0056] Each core component forms an electrical closed loop through the PCC (Power Control Center). Energy storage serves as the core for voltage / frequency support, while photovoltaics acts as a power regulation unit. Loads are connected in an orderly manner according to priority. The central control center coordinates the interaction of control signals, enabling real-time detection of load power and energy storage capacity, as well as controlling whether the photovoltaic mode switches. When the energy storage is fully charged, the central control center sends a mode switching command to the photovoltaic module to switch to LF mode, and simultaneously sends the collected load power to the photovoltaic module to track the load power output. When the energy storage is not fully charged, it sends an MPPT (Multi-Level Photovoltaic) mode operation command to the photovoltaic module, forming a closed-loop architecture of perception-decision-control.

[0057] The specific process of the closed-loop architecture is as follows: the substation is disconnected from the main grid → the central control system triggers a fault response (tripping load, blocking photovoltaic PLL) → the energy storage ramp is started and the drooping link is activated → the critical load is connected → the photovoltaic system is unlocked and connected to the grid and the output is adjusted through the PI controller → the important load is connected → the ordinary load is connected after the energy storage SOC reaches the standard → the system operates stably.

[0058] This invention ensures system frequency stability through a voltage-frequency droop circuit, achieves dynamic matching between photovoltaics and loads through a PI controller, and avoids power surges through tiered access. Ultimately, it achieves full load recovery within 21 seconds, simultaneously improving photovoltaic utilization. The system voltage fluctuation is ≤ ±0.07 pu, the frequency deviation is ≤ ±0.02 Hz, and there is no risk of overvoltage, overcharging, or secondary power outages.

[0059] The above description of the disclosed embodiments enables those skilled in the art to make or use the invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the invention. Therefore, the invention is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A photovoltaic-storage-load coordinated power supply restoration control device for substations, characterized in that, The control device is installed between the substation and the terminal loads, which include critical loads, important loads, and ordinary loads. The control devices include: central control equipment, grid-connected energy storage system, grid-connected photovoltaic system, and graded load switches; The central control equipment is installed in the substation and is connected to the grid-type energy storage system, the grid-connected photovoltaic system and the graded load switch respectively. The grid-type energy storage system, the grid-connected photovoltaic system and the graded load switch are connected to each other through a common connection point. The graded load switch is connected to the terminal load. Before the power outage at the substation, the control device was operating normally; After a power outage at a substation: The central control equipment is used to detect the power of the grid-type energy storage system, obtain the energy storage state of charge, and acquire the terminal load power; When the energy storage state of charge is greater than the first threshold, the grid-type energy storage system is started linearly and ramped up according to the preset rate to increase the output voltage. When the output voltage of the grid-type energy storage system is stable, the critical load is connected through the graded load switch, while the important load and ordinary load are kept disconnected. The grid-type energy storage system supplies power to the critical load. The grid-connected photovoltaic system is dynamically controlled to switch modes based on the energy storage state of charge and the terminal load power. When the energy storage state of charge is greater than or equal to the second threshold and the current total load power is less than the preset output power, the grid-connected photovoltaic system is controlled to switch to load following mode. If the conditions are not met, it is switched to maximum power tracking mode. When the grid-connected photovoltaic system is stable, important loads are connected through graded load switches, while ordinary loads remain disconnected. The grid-connected energy storage system and the grid-connected photovoltaic system supply power to critical and important loads. When the state of charge of the energy storage exceeds the third threshold, ordinary loads are connected through the graded load switch. The grid-type energy storage system and the grid-connected photovoltaic system supply power to the terminal loads, thus restoring the power supply of the substation.

2. The photovoltaic-storage-load coordinated power supply restoration control device for substations according to claim 1, characterized in that, The first threshold is 30%, the second threshold is the energy storage full threshold of the grid-type energy storage system, the third threshold is 50%, and the preset output power is the maximum output power of the grid-connected photovoltaic system when it is in maximum power point tracking mode.

3. The photovoltaic-storage-load coordinated power supply restoration control device for substations according to claim 1, characterized in that, Grid-connected photovoltaic systems include: grid-connected photovoltaic inverters, photovoltaic arrays, phase-locked loop modules, energy storage detectors, and active / reactive power controllers.

4. The photovoltaic-storage-load coordinated power supply restoration control device for substations according to claim 3, characterized in that, The phase-locked loop module is used to immediately lock out the grid-connected photovoltaic system to avoid the accumulation of integral errors when the power distribution station is de-energized and the grid-connected energy storage system loses voltage; and to immediately unlock the system when the output voltage of the grid-connected energy storage system stabilizes and a critical load is connected.

5. A photovoltaic-storage-load coordinated power supply restoration control device for substations according to claim 3, characterized in that, Active / reactive power controllers are used to suppress voltage fluctuations in grid-connected photovoltaic systems.

6. The photovoltaic-storage-load coordinated power supply restoration control device for substations according to claim 1, characterized in that, When a grid-connected photovoltaic system is in load-following mode, the DC side tracks the load power through a PI controller, involving the following formula: ； In the formula, P pv_ref To match the DC-side output reference power of the grid-connected photovoltaic system, K P , K I For reference power PI controller proportional and integral coefficients, P pv_pu To match the per-unit value of the actual output power of the grid-connected photovoltaic system, P L This represents the current total load power. s For the Laplace operator; On the AC side, reactive power is adjusted by voltage deviation to suppress voltage fluctuations. The relevant formula is: ； In the formula, Q pv_ref To connect with the reactive power on the AC side of the grid-connected photovoltaic system, K Pq , K Iq These are the parameters for the reactive power PI controller. U dc_ref This is the DC voltage reference value. U dc_pu This is the actual per-unit value of the DC voltage.

7. A photovoltaic-storage-load coordinated power supply restoration control device for substations according to claim 1, characterized in that, The preset rate is positively correlated with the short-term overvoltage tolerance value of the common connection point.

8. A photovoltaic-storage-load coordinated power supply restoration control device for substations according to claim 1, characterized in that, When critical loads, important loads, and ordinary loads are connected, the central control equipment monitors voltage fluctuations and frequency deviations at the point of common coupling.

9. A method for photovoltaic-storage-load coordinated power supply restoration control in substations, characterized in that, The photovoltaic-storage-load coordinated power supply restoration control device for substations, as described in any one of claims 1-8, comprises the following steps: S1. Status detection step: Obtain the energy storage charge status and terminal load power of the grid-type energy storage system after the power outage of the substation. S2, Energy storage start-up steps: When the energy storage state of charge is greater than the first threshold, the grid-type energy storage system is started up with a linear ramp to increase the voltage according to the preset rate control, and the voltage and frequency are monitored in real time. S3. Critical load connection procedure: When the voltage and frequency of the grid-type energy storage system are stable, critical loads are connected through graded load switches. S4. Photovoltaic grid connection steps: Dynamically control the mode switching of the grid-connected photovoltaic system according to the energy storage state of charge and the terminal load power. When the energy storage state of charge is greater than or equal to the second threshold and the current total load power is less than the preset output power, control the grid-connected photovoltaic system to switch to load following mode. If the conditions are not met, switch to maximum power point tracking mode. S5. Important load connection procedure: After the grid-connected photovoltaic system is stable, the important load is connected through the graded load switch. S6. Important load connection procedure: When the energy storage state of charge is greater than the third threshold, the ordinary load is connected through the graded load switch, and the power supply of the substation is fully restored.

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