A "replace cutting with adjusting" power balance control method and system suitable for terminal power supply micro-grid

Abstract

A power balance strategy method and system suitable for terminal power supply micro-grid "adjustment instead of switching", the method comprising: collecting real-time operation data, including: active power output of each photovoltaic power generation unit, current output and maximum chargeable power of energy storage device, and active power of tie line between micro-grid and large grid; when detecting grid-connected to off-grid event, taking the active power of tie line as the system power surplus amount to be balanced after grid-connected to off-grid; executing the priority control strategy of "adjustment instead of switching"; monitoring the frequency and voltage of off-grid micro-grid, and when they are stable in the safe range, gradually canceling the down-regulation instruction of photovoltaic output and the forced charging instruction of energy storage, so as to make the system return to the off-grid optimal operation state. The application preferentially utilizes the rapid power regulation capability of photovoltaic, realizes smooth transition of the grid-connected to off-grid process, and only assists with the minimum rapid removal when the power surplus is too large, so as to achieve the purpose of "protecting load, cutting source less" and maximizing the consumption of new energy.

Description

Technical Field

[0001] This invention belongs to the field of automatic control technology for power grid safety and stability. More specifically, it relates to a power balance control method and system for microgrids during the transition from grid connection to off-grid operation, which is particularly suitable for end-point power supply microgrids with high photovoltaic penetration. Background Technology

[0002] With the large-scale integration of distributed renewable energy sources, especially photovoltaic power generation, the application of end-point power supply microgrids is becoming increasingly widespread. The core requirement of this type of microgrid is "load protection and minimal power cut-off," that is, under any operating condition, prioritizing the power supply to critical loads and maximizing the utilization of local renewable energy sources.

[0003] When a main grid fails and a microgrid switches from grid-connected to off-grid operation, if the photovoltaic (PV) system is generating at its peak, a severe power surplus will occur within the microgrid. This will cause a sharp spike in system frequency and voltage, potentially triggering protection devices (such as over-frequency and over-voltage protection) to disconnect power sources or loads, or even damaging equipment. Traditional microgrid stabilization systems often employ a passive "shutdown" control mode to address such issues, directly and quickly disconnecting some PV power generation units to eliminate the power surplus. While this approach is direct and effective, it violates the principles of "maximizing renewable energy utilization" and "minimizing power disconnection," reducing the microgrid's power supply reliability and renewable energy utilization rate.

[0004] Furthermore, photovoltaic inverters typically possess LVRT (Low Voltage Ride Through) capability, enabling them to maintain grid connection for a period of time during sudden voltage drops. How to coordinate the rapid regulation capabilities of photovoltaics with necessary disconnection measures to achieve a smooth and rapid power balance during the grid-to-off switching process is a problem that urgently needs to be solved in current technology. Summary of the Invention

[0005] To address the shortcomings of existing technologies, this invention provides a power balance control method and system that utilizes "adjustment instead of switching," resolving the problem of low renewable energy absorption and reduced power supply reliability caused by the forced large-scale disconnection of photovoltaic power sources due to power surplus during the grid-to-off-grid transition of microgrids. The power balance control method prioritizes the rapid power regulation capability of photovoltaics to achieve a smooth transition during the grid-to-off process, only supplementing with minimal rapid disconnection when the power surplus is excessive, thereby achieving the goal of "preserving load, minimizing power source disconnection," and maximizing the absorption of renewable energy.

[0006] The present invention adopts the following technical solution.

[0007] The first aspect of the present invention provides a "regulation-based" power balance control method suitable for end-point power supply microgrids, comprising the following steps: Real-time acquisition of operational data from microgrid systems; When a grid-connected to off-grid event is detected, the power surplus of the microgrid system that needs to be absorbed internally by the microgrid system is calculated based on the aforementioned operational data. P surplus ; Implement a priority control strategy to prioritize the use of the maximum absorbable power of energy storage devices to absorb the power surplus of the microgrid system. P surplus If there is a portion of power exceeding the maximum absorbable power of the energy storage device and reducing the photovoltaic output is sufficient to absorb it, the photovoltaic output should be reduced first. If there is a portion of power exceeding the maximum absorbable power and reducing the photovoltaic output is insufficient to completely absorb it, one photovoltaic collector line should be disconnected, and the remaining photovoltaic power generation units should absorb the remaining portion.

[0008] Preferably, the real-time acquisition of the microgrid system's operating data includes: Active power output of each photovoltaic power generation unit P pv,i Adjustable power output P pv,reg,i Current output of energy storage device P ESS_now Maximum rechargeable power of energy storage device P ESS_nc And the active power of the interconnection lines between the microgrid system and the main grid. P tie The maximum rechargeable power of the energy storage device P ESS_nc The value is positive, indicating the current output of the energy storage device. P ESS_now >0 indicates discharge. P ESS_now <0 indicates charging.

[0009] Preferably, when a grid-connected to off-grid event is detected, the power surplus of the microgrid system that needs to be absorbed internally by the microgrid system is calculated based on the operating data. P surplus include: When a large power grid fault or an event requiring active disconnection is detected, the disconnection control is triggered and switched. At the moment of control activation, the tie-line power... P tie The active power of the tie line drops instantaneously to 0 before being disconnected from the network. P tie As a power surplus of microgrid systems that needs to be balanced after being transferred from grid to off-grid, P surplus ,Right now P surplus = P tie .

[0010] Preferably, the maximum absorbable power of the energy storage device is used to absorb the power surplus of the microgrid system. P surplus include: Maximum rechargeable power of energy storage devices P ESS_nc With current output P ESS_now Summation to calculate the maximum absorbable power of the energy storage device. P ESS_max_charge ; Determine the power surplus of a microgrid system P surplus With the maximum absorbable power of the energy storage device P ESS_max_charge The size relationship, if P surplus ≤ P ESS_max_charge The main approach is to reduce the power of energy storage, and increase the charging power of energy storage devices to balance the power surplus of the microgrid system. P surplus .

[0011] Preferably, if there is a portion of power exceeding the maximum absorbable power of the energy storage device and reducing the photovoltaic output is sufficient to absorb it, the photovoltaic output should be reduced first; if there is a portion of power exceeding the maximum absorbable power and reducing the photovoltaic output is insufficient to completely absorb it, one photovoltaic collector line is selected for disconnection, and the remaining photovoltaic power generation units absorb the remaining portion, including: like P surplus > P ESS_max_charge Then, by combining the reduction of photovoltaic power and the reduction of energy storage, a grid-type ESS can be constructed to absorb the maximum power. P ESS_max_charge The microgrid system has a power surplus during operation. P surplus Exceeding the maximum absorbable power of a mesh-type ESS P ESS_max_charge Part of the photovoltaic demand reduction P need , According to the photovoltaic demand reduction P need With the active power output of each photovoltaic power collector P pv,i Adjustable power output P pv,reg,i Determine whether some photovoltaic (PV) power generation units need to be disconnected. If necessary, select and execute the disconnection operation of one PV collector line, and implement power reduction control on at least one remaining PV collector line to jointly balance the power surplus of the microgrid system. Psurplus .

[0012] Preferably, the minimum active power output of the photovoltaic collector is obtained by comparing the output of all photovoltaic power generation units laterally. P pv_min ; Comparing the required reduction in photovoltaic power generation P need Minimum active power output of all photovoltaic collectors P pv_min ; like P need < P pv_min If no photovoltaic collector disconnection operation is performed, the microgrid system will have a power surplus. P surplus The balance is achieved entirely by adjusting the energy storage charging power and the photovoltaic output reduction. Specifically, only the power of the photovoltaic collector line with the lowest active power output needs to be reduced to achieve the required photovoltaic power reduction. P need ; like P need ≥ P pv_min Then select the current active power output that is less than and closest to the required reduction in photovoltaic power output. P need The photovoltaic collector wires are disconnected. After disconnecting one photovoltaic collector wire, the remaining power that needs to be balanced by the output of the photovoltaic collector is calculated, and the balance is achieved by reducing the output of one or more photovoltaic collector wires that have not been disconnected.

[0013] Preferably, the control method further includes: monitoring the frequency and voltage of the microgrid after it is off-grid, and gradually releasing the commands to reduce photovoltaic output and force charge the energy storage after they stabilize within a safe range, so that the system can be restored to the optimal off-grid operating state.

[0014] Preferably, during the transition from parallel to off-grid, the microgrid frequency is continuously monitored. f and voltage U If the microgrid frequency f and voltage U Once suppressed and stabilized within a safe range, the commands to reduce photovoltaic output and the commands to force charging energy storage are gradually lifted, guiding each photovoltaic power generation unit and energy storage device to gradually recover to its optimal output point according to the new operating conditions after off-grid operation.

[0015] The second aspect of the present invention provides a "regulation-based power balance control system" suitable for end-point power supply microgrids, which operates a "regulation-based power balance control method" suitable for end-point power supply microgrids according to the first aspect, including: a data acquisition module, a decision calculation module, and a control execution module; The data acquisition module is used to acquire real-time operational data; The decision calculation module is used to calculate the power surplus of the microgrid system when the parallel-to-disconnection event is triggered. P surplus Maximum absorbable power of energy storage device P ESS_max_charge and photovoltaic power demand reduction P need Determine the power surplus of the microgrid system P surplus With the maximum absorbable power of the energy storage device P ESS_max_charge The size relationship, if P surplus ≤ P ESS_max_charge The main approach is to reduce the power of energy storage, and increase the charging power of energy storage devices to balance the power surplus of the microgrid system. P surplus ;like P surplus > P ESS_max_charge Therefore, by combining the reduction of photovoltaic (PV) and energy storage, power balance needs to be achieved by adjusting the charging capacity of energy storage and the output of PV. If necessary, power balance can be maintained by cutting off some PV units. Among these measures, the energy storage device should operate at its maximum absorbable power. P ESS_max_charge Run; generate control sequences; The control execution module is used to send the control command sequence to the circuit breakers of the photovoltaic inverter, energy storage converter, and photovoltaic power collection line.

[0016] Preferably, the decision calculation module compares the output of all photovoltaic power generation units horizontally to obtain the minimum active power output of the photovoltaic collector line. P pv_min ; Comparing the required reduction in photovoltaic power generation P need Minimum active power output of all photovoltaic collectors P pv_min ; like P need < P pv_min If no photovoltaic collector disconnection operation is performed, the microgrid system will have a power surplus. P surplusThe balance is achieved entirely by adjusting the energy storage charging power and the photovoltaic output reduction. Specifically, only the power of the photovoltaic collector line with the lowest active power output needs to be reduced to achieve the required photovoltaic power reduction. P need ; like P need ≥ P pv_min Then select the current active power output that is less than and closest to the required reduction in photovoltaic power output. P need The photovoltaic collector wires are disconnected. After disconnecting one photovoltaic collector wire, the remaining power that needs to be balanced by the output of the photovoltaic collector is calculated, and the balance is achieved by reducing the output of one or more photovoltaic collector wires that have not been disconnected.

[0017] Compared with the prior art, the beneficial effects of the present invention include at least the following: 1. Precise control and minimal cut-off: By introducing photovoltaic demand reduction. P need The calculation and comparison logic with the minimum photovoltaic collector power enables precise decision-making, from "whether to cut" to "how much to cut" and "which line to cut". This ensures that under any circumstances, the amount of photovoltaic power cut is the minimum required to meet power balance conditions, and may even completely avoid cutting, resolving the problem solely through adjustments.

[0018] 2. Smooth transition: By prioritizing and quickly reducing photovoltaic output instead of directly cutting it off, the power surge during the grid-to-offline transition is greatly smoothed out, effectively suppressing frequency and voltage spikes, avoiding equipment damage due to overfrequency and overvoltage, and achieving a "seamless" transition from grid connection to off-grid.

[0019] 3. Maximize absorption: This invention abandons the traditional "source cut-off to protect grid" approach and implements "source adjustment to protect grid", which maximizes the on-grid operation of photovoltaic power sources and significantly improves the renewable energy absorption rate under off-grid operation conditions after a fault.

[0020] 4. Adapting to core needs: It perfectly meets the core operational needs of end-point supply-guarantee microgrids, namely "ensuring load and minimizing power cut-offs". While ensuring uninterrupted power supply to important loads, it optimizes power supply-side control and enhances the microgrid's autonomy and power supply reliability. Attached Figure Description

[0021] Figure 1 This is a flowchart of a "disruption-based" power balance control method for end-point power supply microgrids provided in accordance with an embodiment of the present invention; Figure 2 This is a flowchart of the photovoltaic switching logic judgment sub-process provided according to an embodiment of the present invention. Detailed Implementation

[0022] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions of this invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of this invention. The described embodiments are merely some embodiments of this invention, and not all embodiments. Based on the spirit of this invention, all other embodiments obtained by those skilled in the art without creative effort are within the protection scope of this invention.

[0023] A power balance control method using "adjustment instead of tripping" is proposed for end-point power supply microgrids. The microgrid comprises multiple photovoltaic power generation units, energy storage devices, and local loads. The control method is executed by the microgrid's stability control system. P pv,i Indicates photovoltaic collector wire i The active power output corresponds to the active power output of a single photovoltaic power generation unit or unit group. For ease of explanation, we will take the active power output corresponding to a single photovoltaic power generation unit as an example, namely... P pv,i It also indicates that the first i The active power output of each photovoltaic power generation unit, namely i =1,2,……, N , N This represents the total number of photovoltaic power generation units. N Greater than or equal to 2. If one photovoltaic collector line corresponds to a unit group, the unit group can be equivalent to one photovoltaic power generation unit. Preferably, but not limitingly, the energy storage device is a grid-type Energy Storage System (ESS).

[0024] Step 1: Collect real-time operating data of the microgrid system, including the active power output of each photovoltaic power generation unit. P pv,i Adjustable power reduction P pv,reg,i Current output of ESS network P ESS_now Maximum rechargeable power of grid-type ESS P ESS_nc And the active power of the interconnection lines between the microgrid system and the main grid. P tie Among them, the maximum rechargeable power of the grid-type ESS P ESS_nc The current output of the network-type ESS is positive. P ESS_now >0 indicates discharge. P ESS_now <0 indicates charging.

[0025] It is understandable that the active power output represents the current photovoltaic power generation capacity, and the adjustable power output represents how much more power can be reduced. If the photovoltaic power output can be reduced to the limit of 0, then the adjustable power output is the same as the active power output, which is usually the same value.

[0026] Step 2: Grid-to-Off Connection Triggering and Power Surplus Calculation: When a grid-to-off connection event is detected, such as, but not limited to, a large grid fault or an event requiring active grid disconnection, the grid-to-off connection control is triggered. At the instant of control, the tie-line power... P tie The active power of the tie line drops instantaneously to 0 before being disconnected from the network. P tie As a power surplus of microgrid systems that needs to be balanced after being transferred from grid to off-grid, P surplus ,Right now P surplus = P tie After being transferred, the microgrid system has a power surplus. P surplus It needs to be absorbed internally by the microgrid system.

[0027] Step 3: Implement a priority control strategy of "adjustment instead of switching", prioritizing the use of the maximum absorbable power of energy storage devices to absorb the power surplus of the microgrid system. P surplus If there is power exceeding the maximum absorbable power of the energy storage device and reducing the photovoltaic output is sufficient to absorb it, the photovoltaic output should be reduced first. If there is power exceeding the maximum absorbable power and reducing the photovoltaic output is insufficient to completely absorb it, one photovoltaic collector should be disconnected, and the remaining photovoltaic power generation units should absorb the remaining portion. Preferably, but not limitingly, step 3 specifically includes: Step 3.1: Maximum rechargeable power of grid-connected ESS P ESS_nc With current output P ESS_now Summation to calculate the maximum absorbable power of the mesh-type ESS. P ESS_max_charge It can be expressed by the following formula: P ESS_max_charge = P ESS_nc + P ESS_now ; In the formula: P ESS_max_charge The maximum power that a grid-type ESS can absorb is P ESS_nc This represents the maximum rechargeable power of a grid-connected ESS. P ESS_now It contributes to the current construction of network-type ESS.

[0028] Step 3.2: Determine the power surplus of the microgrid system P surplus Maximum absorbable power of mesh-type ESS P ESS_max_charge The size relationship, if P surplus ≤ P ESS_max_charge If so, the main approach will be to reduce energy storage, and step 3.3 will continue; if P surplus > P ESS_max_charge If the photovoltaic and energy storage settings are adjusted, then proceed to step 3.4.

[0029] Step 3.3: Power balance is achieved entirely by mobilizing the charging capacity of energy storage, i.e., the grid-type ESS increases the charging power to balance the power surplus of the microgrid system. P surplus Then proceed to step 4.

[0030] Step 3.4: Power balance needs to be achieved by mobilizing energy storage charging capacity in conjunction with adjusting photovoltaic output. If necessary, power balance can be maintained by disconnecting some photovoltaic units. Among these, the maximum absorbable power is achieved by using a grid-type ESS. P ESS_max_charge The microgrid system has a power surplus during operation. P surplus Exceeding the maximum absorbable power of a mesh-type ESS P ESS_max_charge Part of the photovoltaic demand reduction P need It can be expressed by the following formula: P need = P surplus P ESS_max_charge In the formula: P need The amount of photovoltaic power needs to be reduced. P surplus For the power surplus of the microgrid system, P ESS_max_charge For network type ESS Maximum absorbable power.

[0031] According to the photovoltaic demand reductionP need With the active power output of each photovoltaic power collector P pv,i Adjustable power output P pv,reg,i Determine whether some photovoltaic (PV) power generation units need to be disconnected. If necessary, select and execute the disconnection operation of one PV collector line, and implement power reduction control on at least one remaining PV collector line to jointly balance the power surplus of the microgrid system. P surplus .

[0032] Further preferred, but not limiting, step 3.4 specifically includes: Step 3.4.1: Compare the output of all photovoltaic power generation units horizontally to obtain the minimum active power output of the photovoltaic collector line, expressed by the following formula: P pv_min = min( P pv,1 , P pv,2 , ……, P pv,N ) In the formula: P pv_min This represents the minimum active power output of all photovoltaic collectors. P pv,i For the first i The active power output of a photovoltaic power generation unit, i.e., the photovoltaic collector wire i Those who have made contributions i =1,2,……, N , N This represents the total number of photovoltaic power generation units.

[0033] Step 3.4.2: Compare the required reduction amount of photovoltaic power. P need Minimum active power output of all photovoltaic collectors P pv_min ,like P need < P pv_min If no photovoltaic collector disconnection operation is performed, the microgrid system will have a power surplus. P surplus The balance is achieved entirely by adjusting the energy storage charging power and the photovoltaic output reduction. Specifically, only the power of the photovoltaic collector line with the lowest active power output needs to be reduced to achieve the required photovoltaic power reduction. P need Then continue with step 4; if Pneed ≥ P pv_min Continue with step 3.4.3.

[0034] Step 3.4.3: Select the current active power output that is less than and closest to the required photovoltaic power reduction. P need The photovoltaic collector wire is disconnected, as expressed by the following formula: P pv_cut = max{ P pv,j | P need - P pv,j >0, j =1,2,……, N} In the formula: P pv_cut For the active power output of the disconnected photovoltaic power collectors, P pv,j For the first j The active power output of a photovoltaic power generation unit, i.e., the photovoltaic collector wire j Those who have made contributions j =1,2,……, N , N This represents the total number of photovoltaic power generation units.

[0035] P need The amount of photovoltaic power needs to be reduced.

[0036] Step 3.4.4: After disconnecting one photovoltaic collector wire, calculate the remaining power that needs to be balanced by reducing the output of the photovoltaic collector wire. This balance is achieved by reducing the output of one or more of the remaining photovoltaic collector wires, as expressed by the following formula: P adjust = P need P pv_cut In the formula: P adjust Reduce total output for at least one uncut photovoltaic collector.

[0037] Step 4: Dynamic monitoring and recovery, including: continuous monitoring of microgrid frequency during the transition from parallel to off-grid operation. f and voltage U If the microgrid frequency f and voltageU Once suppressed and stabilized within a safe range, the commands to reduce photovoltaic output and the commands to force charge energy storage are gradually lifted. This guides each photovoltaic power generation unit and grid-connected ESS to gradually recover to the optimal output point based on the new operating conditions after off-grid operation, such as but not limited to load changes and energy storage status, thereby maximizing the absorption of new energy sources.

[0038] Embodiment 2 of the present invention provides a "regulation-based power balance control system" suitable for end-point power supply microgrids, which executes the "regulation-based power balance control method" suitable for end-point power supply microgrids according to Embodiment 1, including: a data acquisition module, a decision calculation module and a control execution module.

[0039] The data acquisition module is used to acquire real-time operating data, including: the active power output of each photovoltaic power generation unit. P pv,i Adjustable power output P pv,reg,i Current output of ESS network P ESS_now Maximum rechargeable power of grid-type ESS P ESS_nc And the active power of the interconnection lines between the microgrid system and the main grid. P tie microgrid frequency f and voltage U ; The decision calculation module is used to calculate the power surplus of the microgrid system when the parallel-to-disconnection event is triggered. P surplus Maximum absorbable power of mesh-type ESS P ESS_max_charge and photovoltaic power demand reduction P need Determine the power surplus of the microgrid system P surplus Maximum absorbable power of mesh-type ESS P ESS_max_charge The size relationship, if P surplus ≤ P ESS_max_charge The main approach is to reduce the energy storage capacity, while grid-connected ESS (Energy Storage System) increases charging power to balance the power surplus of the microgrid system. P surplus ;like P surplus > P ESS_max_chargeTherefore, by combining the reduction of photovoltaic (PV) and energy storage (ESD) power, power balance needs to be achieved by adjusting the charging capacity of ESD power storage in conjunction with adjusting PV output. If necessary, power balance can be maintained by disconnecting some PV units. Among these, the maximum absorbable power of a grid-type ESS is [the key factor]. P ESS_max_charge Run; generate control sequences; The control execution module is used to send the control command sequence to the circuit breakers of the photovoltaic inverter, energy storage converter, and photovoltaic power collection line; The status monitoring module is used to monitor and transition the dynamic response of the system in real time during the transition period, and feed it back to the decision calculation module to achieve closed-loop control.

[0040] Preferably, but not limitingly, the decision calculation module compares the output of all photovoltaic power generation units horizontally to obtain the minimum active power output of the photovoltaic collector line. P pv_min ; Comparing the required reduction in photovoltaic power generation P need Minimum active power output of all photovoltaic collectors P pv_min ; like P need < P pv_min If no photovoltaic collector disconnection operation is performed, the microgrid system will have a power surplus. P surplus The balance is achieved entirely by adjusting the energy storage charging power and the photovoltaic output reduction. Specifically, only the power of the photovoltaic collector line with the lowest active power output needs to be reduced to achieve the required photovoltaic power reduction. P need ; like P need ≥ P pv_min Then select the current active power output that is less than and closest to the required reduction in photovoltaic power output. P need The photovoltaic collector wires are disconnected. After disconnecting one photovoltaic collector wire, the remaining power that needs to be balanced by the output of the photovoltaic collector is calculated, and the balance is achieved by reducing the output of one or more photovoltaic collector wires that have not been disconnected.

[0041] To more clearly illustrate the outstanding substantive features of this invention and the significant progress it brings to the prior art, an application example of implementing this invention is described below.

[0042] Application Example 1: The end-side power supply guarantee microgrid of this application example includes two photovoltaic collection lines, namely a first photovoltaic collection line PV1 and a second photovoltaic collection line PV2, a set of grid-forming ESS, and local loads. When operating in grid-connected mode, with high photovoltaic power output, power is transmitted to the main grid through the tie line P tie = 50MW, that is, the microgrid has a power surplus of 50MW. The grid-forming ESS is currently in a floating charge state, P now = 5MW, is in a charging state, and has a maximum chargeable power P nc =30MW.

[0043] Event trigger: A fault occurs in the main grid, and off-grid operation is required immediately.

[0044] Calculation and judgment: After switching from grid-connected to off-grid operation, the power surplus of the microgrid system P surplus =50MW. The grid-forming ESS maximum absorbable power P ESS_max_charge = P nc + P now =30-5=25MW. Since 50MW>25MW, it is necessary to select one photovoltaic collection line whose current active power output is less than and closest to the required photovoltaic power reduction amount P need to perform a disconnection operation.

[0045] Calculate the required photovoltaic power reduction amount: P need =50 25=25MW.

[0046] Selection, disconnection and regulation: The data acquisition module obtains that the current output of the first photovoltaic collection line PV1 is 32MW, and the current output of the second photovoltaic collection line PV2 is 28MW.

[0047] Comparison: P need (25MW)<min(PV1, PV2)=28MW, the power surplus of the microgrid system P surplus is completely balanced by adjusting the charging power of the energy storage and reducing the photovoltaic power output, only the power of the second photovoltaic collection line needs to be reduced to achieve the required photovoltaic power reduction amount P need .

[0048] Execution: Do not disconnect any photovoltaic collection lines. The control instruction is: a )Instruct the grid-forming ESS Charge at maximum capacity (25) MW ).

[0049] (b) Instruct the first photovoltaic collector PV1 and the second photovoltaic collector PV2 to rapidly reduce their output, with a total reduction of Pneed = 25MW. For example, instruct the first photovoltaic collector PV1 to reduce its output by 25MW, while the second photovoltaic collector PV2 maintains its original output.

[0050] Result: The system achieved balance by "fully charging the energy storage + reducing the photovoltaic power by 25MW", thus preserving all photovoltaic power.

[0051] Application Example 2: Compared with Application Example 1, other conditions remain unchanged in Application Example 2. Assume the power transmission capacity at the time of grid connection is... P tie = 80MW. P surplus =80MW. P surplus (80MW)>( P nc + P now With a capacity of 25MW, combining the reduction of photovoltaic (PV) and energy storage, select and execute the disconnection operation of one PV collector line, and implement power reduction control on at least one remaining PV collector line to jointly balance the power surplus of the microgrid system. P surplus， Reduced demand P need =80 25 = 55MW.

[0052] Compare: P need (55MW)>min(PV1,PV2)=28MW.

[0053] Selection: Select a current active power output that is less than and closest to the required photovoltaic power reduction. P need The photovoltaic power collectors were disconnected. Both the first photovoltaic power collector PV1 (32MW) and the second photovoltaic power collector PV2 (28MW) have a combined capacity of less than 55MW, with the first photovoltaic power collector PV1 being closer to 32MW. The first photovoltaic power collector PV1 was disconnected.

[0054] Adjustment: After disconnecting the first photovoltaic collector PV1, the remaining power that needs to be balanced is P adjust = P need P pv_cut =55 32 = 23MW. This remaining capacity is achieved by reducing the output of the second photovoltaic collector PV2 by 23MW.

[0055] Result: The system achieved balance by "disconnecting the first photovoltaic collector PV1 (32MW) + fully charging the energy storage (25MW) + reducing the second photovoltaic collector PV2 (23MW)". Compared with the traditional approach of disconnecting all or blindly disconnecting, this strategy minimizes the disconnection (disconnecting only one line) when necessary, and is supplemented by fine-tuning.

[0056] It is worth noting that in the embodiments of the present invention, the steps plus numbers are merely an expression for clearly describing the specific implementation of the "adjustment instead of cutting" power balance control method applicable to end-point power supply microgrids, rather than an absolute restriction on the order of the steps. Under the guidance of the core concept of the present invention, changing the order of these steps to achieve the same or similar technical effects all fall within the scope of the present invention.

[0057] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit it. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that modifications or equivalent substitutions can still be made to the specific implementation of the present invention. Any modifications or equivalent substitutions that do not depart from the spirit and scope of the present invention should be covered within the protection scope of the claims of the present invention.

Claims

1. A power balance control method for end-point power supply microgrids that uses "adjustment instead of tripping" to achieve power balance, characterized in that: Includes the following steps: Real-time acquisition of operational data from microgrid systems; When a grid-connected to off-grid event is detected, the power surplus of the microgrid system that needs to be absorbed internally by the microgrid system is calculated based on the aforementioned operational data. P surplus ; Implement a priority control strategy to prioritize the use of the maximum absorbable power of energy storage devices to absorb the power surplus of the microgrid system. P surplus If there is a portion of power exceeding the maximum absorbable power of the energy storage device and reducing the photovoltaic output is sufficient to absorb it, the photovoltaic output should be reduced first. If there is a portion of power exceeding the maximum absorbable power and reducing the photovoltaic output is insufficient to completely absorb it, one photovoltaic collector line should be disconnected, and the remaining photovoltaic power generation units should absorb the remaining portion.

2. The "adjustment-instead-of-switching" power balance control method for end-point power supply microgrids according to claim 1, characterized in that: The real-time acquisition of microgrid system operation data includes: Active power output of each photovoltaic power generation unit P pv,i Adjustable power output P pv,reg,i Current output of energy storage device P ESS_now Maximum rechargeable power of energy storage device P ESS_nc And the active power of the interconnection lines between the microgrid system and the main grid. P tie The maximum rechargeable power of the energy storage device P ESS_nc The value is positive, indicating the current output of the energy storage device. P ESS_now >0 indicates discharge. P ESS_now <0 indicates charging.

3. The "adjustment-instead-of-switching" power balance control method for end-point power supply microgrids according to claim 1, characterized in that: When a grid-connected to off-grid event is detected, the power surplus of the microgrid system that needs to be absorbed internally by the microgrid system is calculated based on the operational data. P surplus include: When a large power grid fault or an event requiring active grid disconnection is detected, the disconnection control is triggered and switched. At the moment of control activation, the tie-line power... P tie The active power of the tie line drops instantaneously to 0 before being disconnected from the network. P tie As a power surplus of microgrid systems that needs to be balanced after being transferred from grid to off-grid, P surplus ,Right now P surplus = P tie .

4. A power balance control method for end-point power supply microgrids according to any one of claims 1 to 3, characterized in that: The maximum absorbable power of the energy storage device is preferentially used to absorb the power surplus of the microgrid system. P surplus include: Maximum rechargeable power of energy storage devices P ESS_nc With current output P ESS_now Summation to calculate the maximum absorbable power of the energy storage device. P ESS_max_charge ; Determine the power surplus of a microgrid system P surplus With the maximum absorbable power of the energy storage device P ESS_max_charge The size relationship, if P surplus ≤ P ESS_max_charge The main approach is to reduce the power of energy storage, and increase the charging power of energy storage devices to balance the power surplus of the microgrid system. P surplus .

5. The "adjustment-instead-of-switching" power balance control method for end-point power supply microgrids according to claim 4, characterized in that: If there is a portion of power exceeding the maximum absorbable power of the energy storage device and reducing the photovoltaic output is sufficient to absorb it, the photovoltaic output should be reduced first; if there is a portion of power exceeding the maximum absorbable power and reducing the photovoltaic output is insufficient to completely absorb it, one photovoltaic collector line should be disconnected, and the remaining photovoltaic power generation units should absorb the remaining portion, including: like P surplus > P ESS_max_charge Then, by combining the reduction of photovoltaic power and the reduction of energy storage, a grid-type ESS can be constructed to absorb the maximum power. P ESS_max_charge The microgrid system has a power surplus during operation. P surplus Exceeding the maximum absorbable power of a mesh-type ESS P ESS_max_charge Part of the photovoltaic demand reduction P need , According to the photovoltaic demand reduction P need With the active power output of each photovoltaic power collector P pv,i Adjustable power output P pv,reg,i Determine whether some photovoltaic (PV) power generation units need to be disconnected. If necessary, select and execute the disconnection operation of one PV collector line, and implement power reduction control on at least one remaining PV collector line to jointly balance the power surplus of the microgrid system. P surplus .

6. The "adjustment-instead-of-switching" power balance control method for end-point power supply microgrids according to claim 5, characterized in that: By comparing the output of all photovoltaic power generation units horizontally, the minimum active power output of the photovoltaic collector wire is obtained. P pv_min ; Comparing the required reduction amount of photovoltaic power P need Minimum active power output of all photovoltaic collectors P pv_min ; like P need < P pv_min If no photovoltaic collector disconnection operation is performed, the microgrid system will have a power surplus. P surplus The balance is achieved entirely by adjusting the energy storage charging power and the photovoltaic output reduction. Specifically, only the power of the photovoltaic collector line with the lowest active power output needs to be reduced to achieve the required photovoltaic power reduction. P need ; like P need ≥ P pv_min Then select the current active power output that is less than and closest to the required reduction in photovoltaic power output. P need The photovoltaic collector wires are disconnected. After disconnecting one photovoltaic collector wire, the remaining power that needs to be balanced by the output of the photovoltaic collector is calculated, and the balance is achieved by reducing the output of one or more photovoltaic collector wires that have not been disconnected.

7. A power balance control method for end-point power supply microgrids according to any one of claims 1 to 3, characterized in that: The control method further includes: monitoring the frequency and voltage of the microgrid after it is off-grid, and gradually releasing the commands to reduce photovoltaic output and force charge the energy storage after it stabilizes within a safe range, so that the system can be restored to the optimal off-grid operating state.

8. The "adjustment-instead-of-switching" power balance control method for end-point power supply microgrids according to claim 7, characterized in that: During the transition from grid connection to off-grid, the microgrid frequency is continuously monitored. f and voltage U If the microgrid frequency f and voltage U Once suppressed and stabilized within a safe range, the commands to reduce photovoltaic output and the commands to force charging energy storage are gradually lifted, guiding each photovoltaic power generation unit and energy storage device to gradually recover to its optimal output point according to the new operating conditions after off-grid operation.

9. A "regulation-based power balancing control system" suitable for end-point power supply microgrids, operating a "regulation-based power balancing control method" suitable for end-point power supply microgrids according to any one of claims 1 to 8, characterized in that, include: Data acquisition module, decision calculation module, and control execution module; The data acquisition module is used to acquire real-time operational data; The decision calculation module is used to calculate the power surplus of the microgrid system when the parallel-to-disconnection event is triggered. P surplus Maximum absorbable power of energy storage device P ESS_max_charge and photovoltaic power demand reduction P need Determine the power surplus of the microgrid system P surplus With the maximum absorbable power of the energy storage device P ESS_max_charge The size relationship, if P surplus ≤ P ESS_max_charge The main approach is to reduce the power of energy storage, and increase the charging power of energy storage devices to balance the power surplus of the microgrid system. P surplus ;like P surplus > P ESS_max_charge Therefore, by combining the reduction of photovoltaic (PV) and energy storage, power balance needs to be achieved by adjusting the charging capacity of energy storage and the output of PV. If necessary, power balance can be maintained by cutting off some PV units. Among these measures, the energy storage device should operate at its maximum absorbable power. P ESS_max_charge Run; generate control command sequence; The control execution module is used to send the control command sequence to the circuit breakers of the photovoltaic inverter, energy storage converter, and photovoltaic power collection line.

10. A power balance control system for end-point power supply microgrids according to claim 9, characterized in that: The decision calculation module compares the output of all photovoltaic power generation units horizontally to obtain the minimum active power output of the photovoltaic collector line. P pv_min ; Comparing the required reduction amount of photovoltaic power P need Minimum active power output of all photovoltaic collectors P pv_min ; like P need < P pv_min If no photovoltaic collector disconnection operation is performed, the microgrid system will have a power surplus. P surplus The balance is achieved entirely by adjusting the energy storage charging power and the photovoltaic output reduction. Specifically, only the power of the photovoltaic collector line with the lowest active power output needs to be reduced to achieve the required photovoltaic power reduction. P need ; like P need ≥ P pv_min Then select the current active power output that is less than and closest to the required reduction in photovoltaic power output. P need The photovoltaic collector wires are disconnected. After disconnecting one photovoltaic collector wire, the remaining power that needs to be balanced by the output of the photovoltaic collector is calculated, and the balance is achieved by reducing the output of one or more photovoltaic collector wires that have not been disconnected.

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