Control method, system and device based on energy storage type flexible interconnection and medium

Abstract

The invention discloses a control method, system and device based on energy storage type flexible interconnection and a medium, and belongs to the technical field of power distribution network operation parameter control, and the method comprises the steps: detecting the operation state and operation parameters of a power distribution network; determining a target operation mode according to the operation state and the operation parameters; according to the target operation mode, selecting a corresponding capacitor voltage balance control strategy and executing a control mode corresponding to the capacitor voltage balance control strategy; and according to the capacitor voltage balance control strategy and the control mode, the operation state and the operation parameters of the power distribution network are adjusted. The method solves the problems that the prior art depends on a self power balance mechanism, is difficult to adapt to the working condition after new energy access and cannot stabilize power fluctuation through energy storage and release.

Description

Technical Field

[0001] This invention relates to the field of power distribution network operation parameter control technology, specifically to a control method, system, equipment, and medium based on energy storage-type flexible interconnection. Background Technology

[0002] In today's world of energy shortages and increasingly severe environmental pollution, fully developing and utilizing renewable energy is the optimal choice for solving energy and environmental problems. To promote the optimization and upgrading of the energy industry and achieve clean and low-carbon development, my country has vigorously developed various new energy power generation technologies in recent years, and the proportion of installed capacity from new energy sources has been continuously increasing. However, as the penetration rate of new energy in the power system continues to rise, the volatility and intermittency of new energy sources have adversely affected many aspects of power grid regulation, operation, and safety control. The occurrence of wind and solar power curtailment has greatly restricted the effective utilization rate of large-scale new energy power generation. my country's wind and solar power resources are mostly concentrated in remote inland areas, while the center of power load is mainly distributed in developed coastal areas. Coupled with the relatively lagging progress of my country's power grid construction, wind and solar power curtailment is particularly prominent in my country, resulting in a large amount of wind and solar resources being wasted every year. Data shows that in 2019, the wind curtailment volume in Xinjiang, Gansu, and Inner Mongolia was 6.61 TWh, 1.88 TWh, and 5.12 TWh respectively, accounting for 81% of the total wind curtailment volume. Meanwhile, the solar curtailment volume in Northwest China reached 4.02 TWh, accounting for 87% of the total solar curtailment volume. Traditional voltage regulation technologies are insufficient to meet the operational demands of new power systems, necessitating the use of power electronic converters and technologies to achieve flexible interconnection of the distribution network, thereby absorbing distributed renewable energy and improving power supply reliability.

[0003] Flexible multi-state switch (FMSS) is a power electronic device installed between two or more feeders in a distribution network. It can precisely regulate the active and reactive power between feeders. It adopts power electronic control technology and, compared with traditional tie switches, not only has two states, on and off, but also adds a continuously controllable power state. It has the advantages of flexible switching of operating modes, flexible and diverse control methods, fast response speed, flexible regulation methods, and high switching frequency. It has significant advantages in improving the absorption of distributed energy, balancing feeder loads, and improving power supply reliability.

[0004] However, traditional FMSS (Power Grid Switching System) mostly adopts a pure power conversion topology without integrating energy storage units, relying on the power grid's own power balancing mechanism. In terms of control strategy, it mainly focuses on the direct transmission control of AC and DC power, achieving voltage and current stability by adjusting the modulation coefficient. However, with the large-scale integration of distributed generation into the distribution network, the limitations of traditional FMSS have become increasingly apparent. Its application scenarios are mainly concentrated in situations with stable loads and fixed grid structures, making it difficult to adapt to the complex operating conditions after a high proportion of new energy sources are integrated. Simultaneously, traditional FMSS lacks energy storage capabilities, and cannot smooth power fluctuations through energy storage and release when facing intermittent power sources such as wind and solar power. When the output of distributed generation changes drastically, traditional FMSS can only perform power flow regulation through power conversion, failing to fundamentally solve the impact of power fluctuations on grid stability, resulting in large DC bus voltage fluctuations and affecting the power quality of the interconnected system.

[0005] Therefore, it is necessary to develop a new energy storage-type flexible interconnection switch topology. By integrating a battery energy storage unit into the SM module, it is possible to absorb excess power from new energy sources or release stored energy to supplement insufficient power in real time without affecting the normal operation of the system. At the same time, it provides reactive power support during faults, maintains DC voltage stability, improves the fault ride-through capability of the converter, and reduces the risk of converter shutdown due to voltage drops. Summary of the Invention

[0006] In view of the above-mentioned problems, the present invention is proposed.

[0007] Therefore, the technical problem solved by this invention is: to achieve control over the operating status of the distribution network through a control method based on energy storage-type flexible interconnection, and to further achieve control over the operating status of the distribution network by controlling the operating parameters of the distribution network.

[0008] To address the aforementioned technical problems, this invention provides the following technical solution: a control method based on energy storage-type flexible interconnection, comprising the following steps: detecting the operating status and operating parameters of the distribution network; determining a target operating mode based on the operating status and operating parameters; selecting a corresponding capacitor voltage balance control strategy and executing the control method corresponding to the capacitor voltage balance control strategy based on the target operating mode; and adjusting the operating status and operating parameters of the distribution network according to the capacitor voltage balance control strategy and the control method.

[0009] As a preferred embodiment of the control method based on energy storage-type flexible interconnection described in this invention, the step of determining the target operating mode includes: determining whether the AC ports of the first converter and the second converter are both connected to the corresponding distribution network and are fault-free; when the AC ports are both connected and fault-free, the target operating mode is determined to be a flexible interconnection operating mode; when a fault is detected in the distribution network corresponding to one of the AC ports and the converter of that AC port is disconnected from the grid, the target operating mode is determined to be a load transfer operating mode; when a fault is detected in the distribution networks corresponding to two of the AC ports and the converters of both AC ports are disconnected from the grid, the target operating mode is determined to be an islanded operating mode; and real-time monitoring of the recovery status of the faulty distribution network, when the faulty distribution network is detected to have resumed normal power supply, switching to the corresponding target operating mode according to the recovered operating status.

[0010] As a preferred embodiment of the control method based on energy storage-type flexible interconnection described in this invention, the step of executing the corresponding control mode according to the capacitor voltage balance control strategy includes: when the target operating mode is determined to be the flexible interconnection operating mode, selecting the MMC-side control strategy; for the first converter in the flexible interconnection operating mode, selecting constant DC voltage control; for the second converter in the flexible interconnection operating mode, selecting constant active power control; when the target operating mode is determined to be the load transfer operating mode or the islanding operating mode, selecting the DC / DC-side control strategy; according to the DC / DC-side control strategy, selecting constant DC voltage control for the load transfer operating mode; and according to the DC / DC-side control strategy, selecting constant voltage and constant frequency control for the islanding operating mode. The beneficial effect of this preferred embodiment is that by binding the capacitor voltage balance control strategy with the operating mode, different types of control are applied to the power supply demand under corresponding fault scenarios to the distribution network operating parameters, achieving scenario-based adaptation of the control mode.

[0011] As a preferred embodiment of the control method based on energy storage-type flexible interconnection described in this invention, the MMC-side control strategy and the DC / DC-side control strategy include: power regulation and energy storage unit regulation; wherein, the power regulation adjusts the DC bus voltage by establishing a constraint relationship between AC power, DC power, and energy storage unit power; according to the constraint relationship, the third power port is indirectly controlled by directly regulating two controllable power ports among the three power ports, thereby maintaining the power balance of the three power ports; wherein, the energy storage unit regulation participates in the constant DC voltage control, constant active power control, and constant voltage and constant frequency control to control the DC bus voltage in the distribution network within a preset stable range. The beneficial effect of this preferred embodiment is that by constructing a control mechanism through the synergistic construction of power regulation and energy storage unit regulation, power balance is achieved through the power constraint relationship of the three ports, while allowing the energy storage unit to participate in the control, thus breaking through the regulation limitations of traditional converters.

[0012] As a preferred embodiment of the control method based on energy storage flexible interconnection described in this invention, the step of the energy storage unit participating in constant DC voltage control for adjustment includes: when the constant DC voltage control is in the MMC side control strategy; the first converter collects the actual value of the DC bus voltage and compares the actual value with the rated DC bus voltage to determine whether there is a DC bus voltage deviation; when the DC bus voltage deviation exists, the first converter adjusts its own first modulation coefficient to adjust the voltage and current of the DC bus voltage; when the DC bus voltage deviation still exists after the converter voltage adjustment, the energy storage unit performs charge and discharge adjustment on the voltage and current of the DC bus after the converter voltage adjustment through an equalization strategy; when the constant DC voltage control is in the DC / DC side control strategy; the energy storage unit performs charge and discharge adjustment on the voltage and current of the DC bus through the equalization strategy. The beneficial effects of this preferred implementation scheme are that it solves the DC bus voltage stability problem in different scenarios through hierarchical control and targeted strategies. In the flexible interconnection mode controlled by the MMC side, the voltage is initially regulated by the modulation coefficient of the first converter, and then the deviation is compensated by the charging and discharging of energy storage to improve the voltage control accuracy. In the fault scenario controlled by the DC / DC side, the voltage is directly regulated by energy storage combined with the equalization strategy to avoid the risk of converter regulation failure during the fault, and to ensure the continuity of load transfer and island power supply. As a preferred embodiment of the control method based on energy storage flexible interconnection described in this invention, the step of the energy storage unit participating in constant active power control includes: the second converter collecting its own actual active power on the AC side, comparing the actual active power with the rated active power, and determining whether there is a power deviation; when the power deviation exists, the second converter adjusts the AC power by adjusting the second modulation coefficient; when the power deviation still exists after the converter power adjustment, the energy storage unit performs charge and discharge regulation on the AC power after the converter power adjustment through the equalization strategy.

[0013] As a preferred embodiment of the control method based on energy storage flexible interconnection described in this invention, the step of the energy storage unit participating in constant voltage and constant frequency control includes: the first converter and the second converter collecting a first voltage, a first frequency, and a second voltage and a second frequency, respectively comparing the first voltage and the second voltage with the rated voltage, and respectively comparing the first frequency and the second frequency with the rated frequency, to determine whether there is a voltage deviation or a frequency deviation; when the voltage deviation or frequency deviation exists, the converter adjusts the voltage deviation or frequency deviation by adjusting the switching state of the DC / DC converter; when the voltage deviation or frequency deviation still exists after the converter adjustment, the energy storage unit performs charge and discharge adjustment on the voltage deviation or frequency deviation after the converter adjustment through the equalization strategy.

[0014] This invention provides a control system based on energy storage-type flexible interconnection.

[0015] To address the aforementioned technical problems, the present invention further provides the following technical solution: a control system based on energy storage-type flexible interconnection, comprising: a detection module for detecting the operating status and operating parameters of the distribution network; a target operating mode determination module for determining a target operating mode based on the operating status and the operating parameters; a control mode execution module for selecting a corresponding capacitor voltage balance control strategy and executing the control mode corresponding to the capacitor voltage balance control strategy based on the target operating mode; and an adjustment control module for adjusting the operating status and operating parameters of the distribution network according to the capacitor voltage balance control strategy and the control mode.

[0016] The present invention provides a computer device, including a memory and a processor, wherein the memory stores a computer program, and the processor executes the computer program to implement the steps of the control method based on energy storage flexible interconnection.

[0017] The present invention provides a computer-readable storage medium having a computer program stored thereon, characterized in that the computer program, when executed by a processor, implements the steps of the control method based on energy storage flexible interconnection.

[0018] The beneficial effects of this invention are as follows: By adapting control logic to different scenarios, the operating mode and control strategy are adapted. For flexible interconnection, load transfer, and islanding scenarios, control strategies are implemented on the MMC side or DC / DC side, respectively. Three control methods—constant DC voltage control, constant active power control, and constant voltage / constant frequency control—are used, switching according to the distribution network fault state and power supply demand, thus improving the system's adaptability to complex power grid environments. Through the synergy of converter regulation and energy storage unit regulation, the energy storage unit participates in all three control methods. Combined with port power constraints, this enables control of distribution network operating parameters, ensuring the safe operation of the distribution network. In energy storage unit regulation, a balancing strategy avoids power distribution deviations caused by uneven energy storage capacity, extending the lifespan of the energy storage unit while ensuring stable output during regulation, thereby improving the reliability of the distribution network power supply. Attached Figure Description

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

[0020] Figure 1 The present invention provides an overall flowchart of a control method based on energy storage flexible interconnection according to an embodiment of the present invention.

[0021] Figure 2 This is a schematic diagram of an SM module for a control method based on energy storage flexible interconnection, provided as an embodiment of the present invention.

[0022] Figure 3 This is a schematic diagram illustrating the adjustment of AC power in an energy storage unit implementing an equalization strategy according to a control method based on energy storage flexible interconnection, provided as an embodiment of the present invention.

[0023] Figure 4 This is a schematic diagram illustrating the adjustment of DC power in an energy storage unit implementing an equalization strategy according to a control method based on energy storage flexible interconnection, provided as an embodiment of the present invention. Detailed Implementation

[0024] To make the above-mentioned objects, features, and advantages of the present invention more apparent and understandable, specific embodiments of the present invention will be described in detail below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of them. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort should fall within the protection scope of the present invention.

[0025] Example 1, referring to Figure 1 This is the first embodiment of the present invention, which provides a control method based on energy storage-type flexible interconnection, including: S100: Detects the operating status and parameters of the power distribution network.

[0026] S200: Determine the target operating mode based on the operating status and operating parameters.

[0027] S300: Based on the target operating mode, select the corresponding capacitor voltage balance control strategy and execute the control method corresponding to the capacitor voltage balance control strategy.

[0028] S400: Adjusts the operating status and parameters of the distribution network according to the capacitor voltage balance control strategy and control method.

[0029] It should be noted that existing flexible multi-state switches mostly adopt pure power conversion topologies, relying on the power grid's own power balance mechanism. In terms of control strategy, they mainly rely on the direct transmission control of AC and DC power, which is difficult to adapt to the complex operating conditions after the integration of new energy sources. In addition, existing flexible multi-state switches do not have energy storage capabilities and cannot smooth out power fluctuations through energy storage and release.

[0030] Therefore, addressing the problems of existing technologies relying on their own power balancing mechanisms, difficulty adapting to operating conditions after the integration of new energy sources, and inability to smooth power fluctuations through energy storage and release, this invention constructs a control method based on energy storage-type flexible interconnection through steps S100-S400. First, the operating status and operating parameters of the distribution network are detected; second, the target operating mode is determined based on the operating status and operating parameters; then, according to the target operating mode, the corresponding capacitor voltage balance control strategy is selected and the control method corresponding to the capacitor voltage balance control strategy is executed; finally, the operating status and operating parameters of the distribution network are adjusted according to the capacitor voltage balance control strategy and control method.

[0031] Example 2, refer to Figures 1 to 4 This is the second embodiment of the present invention, which provides a control method based on energy storage flexible interconnection.

[0032] In this embodiment of the invention, in step S100, the operating status and operating parameters of the power distribution network are detected.

[0033] Specifically, detecting the operating status of the distribution network includes the distribution network topology connection status, load and power supply fluctuation status, and fault warning status.

[0034] Furthermore, the operating parameters of the distribution network include the three-phase bus voltage, line current, system frequency, active power, and reactive power on the distribution network side.

[0035] It should be noted that the first converter and the second converter are two main converters, each corresponding to a distribution network. The first converter and the second converter are distinguished by their labels.

[0036] In this embodiment of the invention, in step S200, the target operating mode is determined based on the operating status and operating parameters.

[0037] It should be noted that the determination is based on whether the AC ports of the first converter and the second converter are both connected to the corresponding distribution network and are fault-free.

[0038] Specifically, the circuit breaker and disconnector at the AC port are monitored for their open / closed status signals. If the circuit breaker is closed, the connection is maintained. Faults are identified by monitoring fault characteristics such as short circuits and grounding.

[0039] Furthermore, if all communication ports remain connected and without faults, the target operating mode is determined to be the flexible interconnection operating mode.

[0040] Furthermore, when a fault is detected in the distribution network corresponding to an AC port and the converter of that AC port is disconnected from the grid, the target operating mode is determined to be the load transfer operating mode.

[0041] Furthermore, when a fault is detected in the distribution network corresponding to both AC ports and the converters of both AC ports are disconnected from the grid, the target operating mode is determined to be islanded operating mode.

[0042] It should be noted that the recovery status of the faulty distribution network is monitored in real time. When the faulty distribution network is detected to have resumed normal power supply, the system switches to the corresponding target operating mode based on the restored operating status.

[0043] In this embodiment of the invention, in step S300, a corresponding capacitor voltage balance control strategy is selected according to the target operating mode, and the control method corresponding to the capacitor voltage balance control strategy is executed.

[0044] Specifically, when the target operating mode is determined to be a flexible interconnected operating mode, the MMC-side control strategy is selected; Furthermore, for the first converter operating in the flexible interconnection mode, constant DC voltage control is selected; for the second converter operating in the flexible interconnection mode, constant active power control is selected.

[0045] Specifically, when the target operating mode is determined to be load transfer operating mode or islanded operating mode, the DC / DC side control strategy is selected; Furthermore, based on the DC / DC side control strategy, constant DC voltage control is selected for the load transfer operation mode; based on the DC / DC side control strategy, constant voltage and constant frequency control is selected for the islanded operation mode.

[0046] It should be noted that both the MMC-side control strategy and the DC / DC-side control strategy include power regulation and energy storage unit regulation.

[0047] Among them, the power regulation adjusts the DC bus voltage by establishing a constraint relationship between AC power, DC power and energy storage unit power, and according to the constraint relationship, the third power port is indirectly controlled by directly adjusting two controllable power ports among the three power ports, so as to keep the power of the three power ports in balance.

[0048] Among them, the energy storage unit regulation participates in constant DC voltage control, constant active power control and constant voltage and frequency control to control the DC bus voltage in the distribution network within a preset stable range.

[0049] It should be noted that the preset stability range is set to 5%.

[0050] In one possible implementation, power regulation can also be achieved through power droop characteristics. Specifically, the actual active power and reactive power of the AC port, the actual power of the DC port, and the actual charging and discharging power of the energy storage unit are collected, and these actual powers are compared with their respective rated powers to obtain the deviation. Based on a preset droop curve, power adjustment commands for each port are generated and transmitted to the control units of the DC / DC converter and the MMC converter. By switching the converter switching states, the AC output power and DC bus power are adjusted.

[0051] In another possible implementation, power regulation can also be replaced by impedance matching. Specifically, according to the total power demand of the system, the power command is allocated to the AC port, DC port and energy storage unit according to a preset ratio. By collecting the actual power of each port and comparing it with the allocated command power, the deviation value is determined. Based on the deviation value, the AC power is adjusted through the MMC converter, and then the DC power is corrected through the DC / DC converter.

[0052] It should be noted that when a fault occurs in the distribution network corresponding to the first converter, the AC power can be expressed as: ; In the formula, and These are the dq-axis components of the positive-sequence AC voltage and positive-sequence current in a positively rotating coordinate system. and The negative sequence voltage and negative sequence current are respectively in the anti-phase synchronous rotating coordinate system. Axial components; For AC power, For alternating active power; For AC reactive power; and The AC grid voltage and current are respectively in the stationary coordinate system. Quantity.

[0053] Furthermore, the formula for AC power is expanded into real and imaginary parts, specifically expressed as follows: ; In the formula, and These are the DC components of the AC active and reactive power, respectively. and These are the sinusoidal components of active and reactive power, respectively. and These are the cosine components of the active and reactive power of the AC circuit, respectively.

[0054] In this embodiment of the invention, in step S400, the operating status and operating parameters of the distribution network are adjusted according to the capacitor voltage balance control strategy and control method.

[0055] It should be noted that the control methods include constant DC voltage control, constant active power control, and constant voltage and constant frequency control.

[0056] When performing constant DC voltage control, it is necessary to determine whether the control strategy is on the MMC side or the DC / DC side.

[0057] When the constant DC voltage control is in the MMC side control strategy, the first converter collects the actual value of the DC bus voltage and compares the actual value with the rated DC bus voltage to determine whether there is a DC bus voltage deviation. When the DC bus voltage deviation exists, the first converter adjusts its own first modulation coefficient to regulate the voltage and current of the DC bus. When the DC bus voltage deviation still exists after the converter voltage regulation, the energy storage unit uses an equalization strategy to regulate the voltage and current of the DC bus after the converter voltage regulation.

[0058] It should be noted that the first modulation coefficient and the second adjustment coefficient are only used to distinguish different control strategies, and their meanings are the same as the actual values.

[0059] When the constant DC voltage control is in the DC / DC side control strategy, the energy storage unit regulates the voltage and current of the DC bus through a balancing strategy.

[0060] During constant active power control, the second converter collects its own actual active power on the AC side and compares it with the rated active power to determine if there is a power deviation. When a power deviation exists, the second converter adjusts the second modulation coefficient to regulate the AC power. If the power deviation still exists after the converter power regulation, the energy storage unit uses an equalization strategy to regulate the charging and discharging of the AC power after the converter power regulation.

[0061] In one possible implementation, constant active power control can also be replaced by a PI controller. The second converter collects its own actual active power on the AC side and inputs the difference between the actual active power and the rated active power into the PI controller. The PI controller calculates and outputs a control signal based on the magnitude and direction of the deviation and transmits it to the control unit of the converter. The control unit then changes the phase difference between the AC voltage and current output by the converter to regulate the AC power.

[0062] In another possible implementation, constant active power control can also be replaced by model prediction. By constructing a mathematical model of power transmission on the AC side of the second converter, the second converter collects the actual active power and the rated active power, substitutes the deviation into the model, predicts the power change at the next moment under different control parameters, and selects and outputs the control parameters that minimize the power deviation.

[0063] During constant voltage and frequency control, the first and second converters collect the first voltage and first frequency, and the second voltage and second frequency, respectively. They then compare the first voltage and second voltage with the rated voltage, and the first frequency and second frequency with the rated frequency to determine whether there is a voltage deviation or frequency deviation. When a voltage deviation or frequency deviation exists, the converter adjusts the voltage deviation or frequency deviation by adjusting the switching state of the DC / DC converter. If the voltage deviation or frequency deviation still exists after the converter adjustment, the energy storage unit uses a balancing strategy to charge and discharge adjust the voltage deviation or frequency deviation after the converter adjustment.

[0064] In one possible implementation, constant voltage and frequency control can also be replaced by a PID controller. After the first and second converters acquire the actual voltage and frequency, the deviations from the rated values ​​are input to their respective PID controllers. The PID controllers output control signals according to the corresponding proportional gain through integral and derivative operations. These control signals act on the DC / DC converter, changing its switching state to adjust the output voltage and frequency.

[0065] In another possible implementation, constant voltage and frequency control can be replaced by constant voltage and frequency adjustment with droop control. The first converter and the second converter respectively collect their corresponding first voltage, first frequency and second voltage and second frequency. After comparing these actual values ​​with the rated voltage and rated frequency to obtain the deviation, they generate control commands according to the preset droop characteristic curve. The commands are transmitted to the control unit of the DC / DC converter. The control unit adjusts the deviation by adjusting the output voltage amplitude and frequency of the converter.

[0066] It should be noted that the first voltage and the first frequency are the voltage and frequency of the first converter itself; the second voltage and the second frequency are the voltage and frequency of the second converter itself.

[0067] It should be noted that all energy storage units participate in DC voltage control, constant active power control, and constant voltage and frequency control.

[0068] Among them, the energy storage units all adopted a balancing strategy when participating in the control. The balancing strategy is operated by monitoring the power of the energy storage units.

[0069] In one possible implementation, the balancing strategy can also be replaced by voltage feedback from the SM module. Specifically, by collecting the terminal voltage of the battery in each SM module, the average voltage value is calculated from the battery terminal voltages of all SM modules. Then, the actual voltage of each SM module is compared with the average voltage to determine whether there is a voltage deviation. If there is a deviation, the control signal is transmitted to the bidirectional DC / DC converter in the SM module. By adjusting the converter, the charging and discharging current of the battery is changed to achieve power balancing.

[0070] In another possible implementation, the balancing strategy can also be replaced by coordinating the temperature and power of the SM module. Specifically, the power value of the energy storage unit of each SM module battery is collected in real time, the deviation between the power of each SM module energy storage unit and the average power of the energy storage unit is calculated, and the charging and discharging time is adjusted by controlling the DC / DC converter according to the magnitude of the deviation.

[0071] It should be noted that the energy storage unit is integrated in the SM module, and the SM modules are connected in series to form a bridge arm. The bridge arms are combined to construct the first converter and the second converter.

[0072] The average electricity consumption of the entire energy storage system is specifically represented as follows: ; In the formula, for Phase battery load status, , for Battery load status of the upper and lower bridge arms, for Mutually Bridge arm Battery load status of each SM module for Mutually Arm battery load status. If all battery capacities are equal, then each battery should have equal power when all battery storage units are balanced; however, if there are differences in battery capacity, then battery capacity must be taken into account in power allocation, that is, battery power should be allocated according to the proportion of battery capacity.

[0073] Furthermore, the total capacity of each battery phase is defined. and the total capacity of the bridge arm battery for: ; ; In the formula, Let p be the total reference power of the energy storage units in the k-th phase arm, p and n be the power distribution nodes, and N be the total number of SM modules under the node. Let be the battery capacity of the i-th SM module in the j-th phase bridge arm.

[0074] Furthermore, the specific manifestation of distributing the total battery power to each phase is as follows: ; In the formula, Let be the reference value of the active power of a certain SM module energy storage unit in the k-th phase bridge arm. The total reference power of the energy storage units in the k-th phase bridge arm is given. For three-phase bridge arms ( Mutually, phase and Sum the reference values ​​of the total reactive power of the k-th phase bridge arm (phase ) Reference value for the total active power of the energy storage unit Furthermore, the total power of the upper and lower arms of each phase is also distributed according to this principle, specifically as follows: ; In the formula, Let be the reference value of the active power of a certain SM module energy storage unit under the j-th power distribution node of the k-th phase bridge arm. This is the reference value for the total reactive power of the energy storage unit at the j-th power distribution node in the k-th phase bridge arm. Let be the reference value for the total reactive power of the energy storage unit in the k-th phase bridge arm. This is the reference value for the total active power of the energy storage unit in the k-th phase bridge arm.

[0075] Furthermore, the total power of the bridge arm is allocated to each SM module battery pack according to the battery capacity, specifically in the following form: ; In the formula, The reference value for the active power of the energy storage unit of the i-th SM module in the j-th power distribution node of the k-th phase bridge arm. The reactive power reference value for the energy storage unit of the i-th SM module in the j-th power distribution node of the k-th phase bridge arm. This is the reference value for the total reactive power of the energy storage unit at the j-th power distribution node in the k-th phase bridge arm. This is the reference value for the total active power of the energy storage unit at the j-th power distribution node of the k-th phase bridge arm.

[0076] Furthermore, taking the phase-to-phase energy storage unit balancing strategy as an example, in order to achieve the balancing of phase-to-phase energy storage units, the average energy storage unit capacity of the system is used as the command value, and the difference between it and the average energy storage unit capacity of each phase is adjusted through an adjustment coefficient. Obtain the power adjustment component for balancing energy storage units. ,like Figure 3 , This determines the rate at which the energy storage unit's charge is balanced. Ultimately, considering the differences in battery capacity, the battery power command for each SM module in the energy storage unit's charge balancing is: ; In the formula, The reference value for the active power of the energy storage unit of the i-th SM module in the j-th power distribution node of the k-th phase bridge arm. The reactive power reference value for the energy storage unit of the i-th SM module in the j-th power distribution node of the k-th phase bridge arm. This is the reference value for the total reactive power of the energy storage unit at the j-th power distribution node in the k-th phase bridge arm. Let be the reference value for the total reactive power of the energy storage unit in the k-th phase bridge arm. For three-phase bridge arms ( Mutually phase and Sum the reference values ​​of the total reactive power of the k-th phase bridge arm (phase ) This is a reference value for the total active power of the energy storage unit. This represents the active power correction for the energy storage unit in the k-th phase bridge arm. This represents the active power correction for the energy storage unit at the j-th power distribution node in the k-th phase bridge arm. This is the active power correction amount for the energy storage unit of the i-th SM module in the j-th power distribution node of the k-th phase bridge arm.

[0077] It should be noted that the specific forms of regulation performed by the energy storage unit in the processing are as follows: ; In the formula, It is a three-phase AC voltage. To obtain phase information for the phase-locked loop, and These are the DC side voltage and current, respectively. and These are the reference values ​​for active power and reactive power on the AC side, respectively. and These are the positive-sequence and negative-sequence components of the grid voltage, respectively. For power adjustment components.

[0078] In summary, this invention adapts operating modes and control strategies through control logic and scenario adaptation. For flexible interconnection, load transfer, and islanding scenarios, it employs either MMC-side or DC / DC-side control strategies, respectively, and utilizes three control methods: constant DC voltage control, constant active power control, and constant voltage / constant frequency control. These methods switch according to the distribution network fault state and power supply demand, enhancing the system's adaptability to complex grid environments. Through the synergy of converter regulation and energy storage unit regulation, the energy storage unit participates in all three control methods. Combined with port power constraints, this achieves control over distribution network operating parameters, ensuring the safe operation of the distribution network. During energy storage unit regulation, a balancing strategy avoids power distribution deviations caused by uneven energy storage capacity, extending the lifespan of the energy storage unit while ensuring stable output during regulation, thus improving the reliability of the distribution network.

[0079] Example 3 is the third embodiment of the present invention. This embodiment provides a control system based on energy storage-type flexible interconnection, including: The detection module detects the operating status and parameters of the power distribution network.

[0080] The target operating mode determination module determines the target operating mode based on the operating status and operating parameters.

[0081] The control mode execution module selects the corresponding capacitor voltage balance control strategy and executes the control mode corresponding to the capacitor voltage balance control strategy according to the target operating mode.

[0082] The adjustment and control module adjusts the operating status and parameters of the distribution network according to the capacitor voltage balance control strategy and control mode.

[0083] Example 4, the fourth embodiment of the present invention, differs from the previous three embodiments in that: if the function is implemented as a software functional unit and sold or used as an independent product, it can be stored in a computer-readable storage medium. Based on this understanding, the technical solution of the present invention, or the part that contributes to the prior art, or a part of the technical solution, can be embodied in the form of a software product. This computer software product is stored in a storage medium and includes several instructions to cause a computer device (which may be a personal computer, server, or network device, etc.) to execute all or part of the steps of the methods described in the various embodiments of the present invention. The aforementioned storage medium includes various media capable of storing program code, such as USB flash drives, portable hard drives, read-only memory (ROM), random access memory (RAM), magnetic disks, or optical disks.

[0084] The logic and / or steps represented in the flowchart or otherwise described herein, for example, can be considered as a sequenced list of executable instructions for implementing logical functions, and can be embodied in any computer-readable medium for use by, or in conjunction with, an instruction execution system, apparatus, or device (such as a computer-based system, a processor-including system, or other system that can fetch and execute instructions from, an instruction execution system, apparatus, or device). For the purposes of this specification, "computer-readable medium" can be any means that can contain, store, communicate, propagate, or transmit programs for use by, or in conjunction with, an instruction execution system, apparatus, or device.

[0085] More specific examples of computer-readable media (a non-exhaustive list) include: electrical connections (electronic devices) having one or more wires, portable computer disk drives (magnetic devices), random access memory (RAM), read-only memory (ROM), erasable and editable read-only memory (EPROM or flash memory), fiber optic devices, and portable optical disc read-only memory (CDROM). Furthermore, computer-readable media can even be paper or other suitable media on which the program can be printed, because the program can be obtained electronically, for example, by optically scanning the paper or other medium, followed by editing, interpreting, or otherwise processing as necessary, and then stored in computer memory.

[0086] It should be understood that various parts of the present invention can be implemented in hardware, software, firmware, or a combination of all three. In the above embodiments, multiple steps or methods can be implemented in software or firmware stored in memory and executed by a suitable instruction execution system. For example, if implemented in hardware, as in another embodiment, it can be implemented using any one or a combination of the following techniques known in the art: discrete logic circuits having logic gates for implementing logical functions on data signals, application-specific integrated circuits (ASICs) having suitable combinational logic gates, programmable gate arrays (PGAs), field-programmable gate arrays (FPGAs), etc.

[0087] 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 preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the spirit and scope of the technical solutions of the present invention, and all such modifications or substitutions should be covered within the scope of the claims of the present invention.

Claims

1. A control method based on energy storage-type flexible interconnection, characterized in that: include, Detect the operating status and parameters of the power distribution network; Based on the operating status and the operating parameters, determine the target operating mode; Based on the target operating mode, select the corresponding capacitor voltage balance control strategy and execute the control method corresponding to the capacitor voltage balance control strategy. The operating status and operating parameters of the power distribution network are adjusted according to the capacitor voltage balance control strategy and the control method.

2. The control method based on energy storage flexible interconnection as described in claim 1, characterized in that: The steps to determine the target operating mode include: Determine whether the AC ports of the first converter and the second converter are both connected to the corresponding distribution network and are fault-free; When all the AC ports remain connected and without fault, the target operating mode is determined to be the flexible interconnection operating mode. When a fault is detected in the distribution network corresponding to an AC port and the converter of the AC port is disconnected from the grid, the target operating mode is determined to be the load transfer operating mode. When it is detected that the distribution network corresponding to both AC ports has failed and the converters of both AC ports have gone offline, the target operating mode is determined to be the islanding operating mode. The system monitors the recovery status of the faulty distribution network in real time. When the faulty distribution network is detected to have resumed normal power supply, the system switches to the corresponding target operating mode based on the restored operating status.

3. The control method based on energy storage flexible interconnection as described in claim 2, characterized in that: The steps for executing the corresponding control method according to the capacitor voltage balance control strategy include: When the target operating mode is determined to be the flexible interconnection operating mode, the MMC-side control strategy is selected; For the first converter in the flexible interconnection operation mode, constant DC voltage control is selected; For the second converter in the flexible interconnection operation mode, constant active power control is selected; When the target operating mode is determined to be the load transfer operating mode or the islanding operating mode, the DC / DC side control strategy is selected. Based on the DC / DC side control strategy, constant DC voltage control is selected for the load transfer operation mode; Based on the DC / DC side control strategy, constant voltage and constant frequency control is selected for the islanded operation mode.

4. The control method based on energy storage flexible interconnection as described in claim 3, characterized in that: The MMC-side control strategy and the DC / DC-side control strategy include: Power regulation and energy storage unit regulation; The power regulation adjusts the DC bus voltage by establishing a constraint relationship between AC power, DC power, and energy storage unit power. Based on the aforementioned constraint relationship, the power of the third power port can be indirectly controlled by directly adjusting two of the three power ports, thereby maintaining a balance among the three power ports. The energy storage unit regulates the DC bus voltage in the distribution network within a preset stable range by participating in the constant DC voltage control, constant active power control, and constant voltage and frequency control.

5. The control method based on energy storage flexible interconnection as described in claim 4, characterized in that: The steps for the energy storage unit to participate in constant DC voltage control for regulation include: When the constant DC voltage control is in the MMC-side control strategy; The first converter acquires the actual value of the DC bus voltage and compares the actual value with the rated DC bus voltage to determine whether there is a DC bus voltage deviation. When the DC bus voltage deviation exists, the first converter adjusts its own first modulation coefficient to regulate the voltage and current of the DC bus; When the DC bus voltage deviation still exists after voltage regulation by the converter, the energy storage unit uses a balancing strategy to charge and discharge the voltage and current of the DC bus after voltage regulation by the converter. When the constant DC voltage control is in the DC / DC side control strategy; The energy storage unit regulates the voltage and current of the DC bus through the equalization strategy.

6. The control method based on energy storage flexible interconnection as described in claim 5, characterized in that: The steps for the energy storage unit to participate in constant active power control for regulation include: The second converter collects its own actual active power on the AC side, compares the actual active power with the rated active power, and determines whether there is a power deviation. When the power deviation exists, the second converter adjusts the second modulation coefficient to regulate the AC power. When the power deviation still exists after the power adjustment by the converter, the energy storage unit performs the charging and discharging adjustment on the AC power after the power adjustment by the converter through the equalization strategy.

7. The control method based on energy storage flexible interconnection as described in claim 6, characterized in that: The steps for the energy storage unit to participate in constant voltage and constant frequency control for regulation include: The first converter and the second converter collect a first voltage and a first frequency, and a second voltage and a second frequency, respectively, and compare the first voltage and the second voltage with the rated voltage, and compare the first frequency and the second frequency with the rated frequency, respectively, to determine whether there is a voltage deviation and a frequency deviation. When the voltage or frequency deviation exists, the voltage or frequency deviation is adjusted by regulating the switching state of the DC / DC converter. When the voltage or frequency deviation still exists after adjustment by the converter, the energy storage unit performs charge and discharge regulation on the voltage or frequency deviation after adjustment by the converter through the equalization strategy.

8. A control system based on energy storage flexible interconnection, employing the control method based on energy storage flexible interconnection as described in any one of claims 1 to 7, characterized in that, include: The detection module detects the operating status and parameters of the power distribution network; The target operating mode determination module determines the target operating mode based on the operating status and the operating parameters; The control mode execution module selects the corresponding capacitor voltage balance control strategy according to the target operating mode and executes the control mode corresponding to the capacitor voltage balance control strategy. The adjustment and control module adjusts the operating status and operating parameters of the distribution network according to the capacitor voltage balance control strategy and the control method.

9. A computer device comprising a memory and a processor, wherein the memory stores a computer program, characterized in that, When the processor executes the computer program, it implements the steps of the control method based on energy storage flexible interconnection as described in any one of claims 1 to 7.

10. A computer-readable storage medium having a computer program stored thereon, characterized in that, When the computer program is executed by the processor, it implements the steps of the control method based on energy storage flexible interconnection as described in any one of claims 1 to 7.

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